Marine cyanobacteria have gained momentum in recent years as a source of novel bioactive small molecules. This paper describes the structure elucidation and pharmacological evaluation of two new (veraguamide O (1) and veraguamide P (2)) and one known (veraguamide C (3)) analogs isolated from a cyanobacterial collection made in the Las Perlas Archipelago of Panama. We hypothesized that these compounds would be cytotoxic in cancer cell lines. The compounds were screened against HEK-293, estrogen receptor positive (MCF-7), and triple-negative breast cancer (MDA-MB-231) cells as well as against a broad panel of membrane-bound receptors. The planar structures were determined based on NMR and MS data along with a comparison to previously isolated veraguamide analogs. Phylogenetic analysis of the collection suggests it to be an Okeania sp., a similar species to the cyanobacterium reported to produce other veraguamides. Veraguamide O shows no cytotoxicity (greater than 100 μM) against ER-positive cells (MCF-7) with 13 μM IC50 against MDA-MB-231 TNBC cells. Interestingly, these compounds show affinity for the sigma2/TMEM-97 receptor, making them potential leads for the development of non-toxic sigma 2 targeting ligands.

Abstract Introduction Nicotine addiction remains a primary health concern as tobacco smoking remains the number one cause of preventable death in America. At the same time, America is still facing the threat of the opioid epidemic. While the prevalence of smoking combustible cigarettes or electronic nicotine delivery systems in the United States varies between 12% and 35%, the smoking rates among the opioid use dependent (OUD) population is 74%–97%. We examined changes in brain reward mechanisms in which co-use of nicotine and opioids may result in enhanced reward and reinforcement. Aims and Methods Adult male and female α4-mCherryα6-GFP mice (C57BL/6J) were used in conditioned place preference (CPP) and microscopy assays to examine reward-related behavior and nicotinic acetylcholine receptor (nAChR) upregulation following treatments with saline, nicotine, morphine, or nicotine plus morphine. Following this, separate mice were trained in e-Vape self-administration assays to examine morphine’s impact on nicotine reinforcement. Results We observed that nicotine and morphine coexposure in a CPP assay did not produce enhanced reward-related behavior when compared with nicotine or morphine alone. In parallel we observed coexposure reduced nicotine-induced upregulation of nAChRs on ventral tegmental area dopamine and GABA neurons. Additionally, we observed that concurrent morphine exposure reduced nicotine (plus menthol) vapor self-administration in male and female mice. Conclusions While nicotine use is high among OUD individuals, our CPP assays suggest coexposure not only fails to enhance reward-related behavior but also reduces nicotine-induced changes in ventral tegmental area neurobiology. Our self-administration assays suggest that morphine exposure during nicotine acquisition reduces nicotine reinforcement-related behavior. Implications While some may postulate that the co-use of opioids and nicotine may be driven by reward-related mechanisms, our data indicate that opioid exposure may hinder nicotine intake due to reduced upregulation of nAChRs critical for nicotine reward and reinforcement. Thus, the high co-use in OUD individuals may be a result of other mechanisms and this warrants further investigations into nicotine and opioid co-use.

The epithelial to mesenchymal transition (EMT) is characterized by a loss of cell polarity, a decrease in the epithelial cell marker E-cadherin, and an increase in mesenchymal markers including the zinc-finger E-box bind-ing homeobox (ZEB1). The EMT is also associated with an increase in cell migration and anchorage-independent growth. Induction of a reversal of the EMT, a mesenchymal to epithelial transition (MET), is an emerging strategy being explored to attenuate the metastatic potential of aggressive cancer types, such as triple-negative breast can-cers (TNBCs) and tamoxifen-resistant (TAMR) ER-positive breast cancers, which have a mesenchymal phenotype. Patients with these aggressive cancers have poor prognoses, quick relapse, and resistance to most chemother-apeutic drugs. Overexpression of extracellular signal-regulated kinase (ERK) 1/2 and ERK5 is associated with poor patient survival in breast cancer. Moreover, TNBC and tamoxifen resistant cancers are unresponsive to most targeted clinical therapies and there is a dire need for alternative therapies. In the current study, we found that MAPK3, MAPK1, and MAPK7 gene expression correlated with EMT mark-ers and poor overall survival in breast cancer patients using publicly available datasets. The effect of ERK1/2 and ERK5 pathway inhibition on MET was evaluated in MDA-MB-231, BT-549 TNBC cells, and tamoxifen-resistant MCF-7 breast cancer cells. Moreover, TU-BcX-4IC patient-derived primary TNBC cells were included to enhance the translational relevance of our study. We evaluated the effect of pharmacological inhibitors and lentivirus-induced activation or inhibition of the MEK1/2-ERK1/2 and MEK5-ERK5 pathways on cell morphology, E-cadherin, vimentin and ZEB1 expression. Additionally, the effects of pharmacological inhibition of trametinib and XMD8-92 on nuclear localization of ERK1/2 and ERK5, cell migration, proliferation, and spheroid formation were evaluated. Novel compounds that target the MEK1/2 and MEK5 pathways were used in combination with the AKT inhibitor ipatasertib to understand cell-specific responses to kinase inhibition. The results from this study will aid in the design of innovative therapeutic strategies that target cancer metastases.

OBJECTIVE To evaluate the outcomes of excision and primary anastomosis (EPA) for radiation-associated bulbomembranous stenoses using a multi-institutional analysis. The treatment of radiation-associated urethral stenosis is typically complex owing to the adverse impact of radiation on adjacent tissue. METHODS An IRB-approved multi-institutional retrospective review was performed on patients who underwent EPA for bulbomembranous urethral stenosis following prostate radiotherapy. Preoperative patient demographics, operative technique, and postoperative outcomes were abstracted from 1/2007-6/2018. Success was defined as voiding per urethra without the need for endoscopic treatment and a minimum follow-up of 12 months. RESULTS One hundred and thirty-seven patients from 10 centers met study criteria with a mean age of 69.3 years (50-86), stenosis length of 2.3 cm (1-5) and an 86.9% (119/137) success rate at a mean follow-up 32.3 months (12-118). Univariate Cox regression analysis identified increasing patient age (P = .02), stricture length (P<.0001) and combined modality radiotherapy (P = .004) as factors associated with stricture recurrence while body mass index (P = .79), diabetes (P = .93), smoking (P =.62), failed endoscopic treatment (P = .08) and gracilis muscle use (P = .25) were not. On multivariate analysis, increasing patient age (H.R.1.09, 95%CI 1.01-1.16; P = .02) and stenosis length (H.R.2.62, 95%CI 1.49-4.60; P = .001) remained associated with recurrence. Subsequent artificial urinary sphincter was performed in 30 men (21.9%), of which 25 required a transcorporal cuff and 5 developed cuff erosion. CONCLUSIONS EPA for radiation-associated urethral stenosis effectively provides unobstructed instrumentationfree voiding. However, increasing stenosis length and age are independently associated with surgical failure. Patients should be counseled that further surgery for incontinence may be necessary. (C) 2021 Elsevier Inc.

Triple-negative breast cancer (TNBC) presents a clinical challenge due to the aggressive nature of the disease and a lack of targeted therapies. Constitutive activation of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway has been linked to chemoresistance and metastatic progression through distinct mechanisms, including activation of epithelial-to-mesenchymal transition (EMT) when cells adopt a motile and invasive phenotype through loss of epithelial markers (CDH1), and acquisition of mesenchymal markers (VIM, CDH2). Although MAPK/ERK1/2 kinase inhibitors (MEKi) are useful antitumor agents in a clinical setting, including the Food and Drug Administration (FDA)-approved MEK1,2 dual inhibitors cobimetinib and trametinib, there are limitations to their clinical utility, primarily adaptation of the BRAF pathway and ocular toxicities. The MEK5 (HGNC: MAP2K5) pathway has important roles in metastatic progression of various cancer types, including those of the prostate, colon, bone and breast, and elevated levels of ERK5 expression in breast carcinomas are linked to a worse prognoses in TNBC patients. The purpose of this study is to explore MEK5 regulation of the EMT axis and to evaluate a novel pan-MEK inhibitor on clinically aggressive TNBC cells. Our results show a distinction between the MEK1/2 and MEK5 cascades in maintenance of the mesenchymal phenotype, suggesting that the MEK5 pathway may be necessary and sufficient in EMT regulation while MEK1/2 signaling further sustains the mesenchymal state of TNBC cells. Furthermore, additive effects on MET induction are evident through the inhibition of both MEK1/2 and MEK5. Taken together, these data demonstrate the need for a better understanding of the individual roles of MEK1/2 and MEK5 signaling in breast cancer and provide a rationale for the combined targeting of these pathways to circumvent compensatory signaling and subsequent therapeutic resistance.

Abstract Extracellular signal-regulated kinase (ERK) 5, a member of mitogen activated protein kinase (MAPK) family, is an emerging target in cancer therapeutics. Activation of ERK5 via overexpression induces EMT and hormone-independent growth of breast cancer. EMT leads to the loss of cell polarity, downregulation of E-cadherin, and upregulation of mesenchymal markers snail, zinc-finger E-box binding homeobox (ZEB1), and vimentin. EMT is also associated with drug resistance. Although ERK1/2 and ERK5 activation is known to mediate EMT, the effect of ERK1/2 and ERK5 inhibition on mesenchymal to epithelial transition (MET), the reverse of EMT, is poorly understood in cancer.Triple negative breast cancer (TNBC) cells have a mesenchymal phenotype and show poor sensitivity to chemotherapy agents. The loss of estrogen, progesterone hormone receptors and human epidermal growth factor receptors (HER2) contributes to the aggressive state of the disease and lack of targeted therapy. Activation of the intracellular signaling pathways such as the MAPK pathway mediates tumorigenesis in TNBCs. MEK1/2 inhibitors have been successful clinical drug candidates; however, there is emerging evidence that the activation of the MEK5-ERK5 pathway mediates resistance to the MEK1/2 inhibitors in several BRAF and KRAS-mutant cancers. The effect of MEK1/2 inhibition on MEK5-mediated EMT, cell survival, and migration in TNBC is less well understood. Therefore, we hypothesize that dual inhibition of the ERK1/2 and ERK5 pathways is a relevant strategy to target TNBCs.In the present study, the effect of dual ERK1/2 and ERK5 inhibition on MET, cell viability, migration, and anchorage-independent growth was evaluated in TNBC. ERK1/2 and ERK5 activities were modulated via pharmacological inhibitors and molecular tools. Cell morphology and protein expression of EMT markers E-cadherin, ZEB1, snail, and vimentin were evaluated. XMD8-92, an ERK5 inhibitor was found to synergize with doxorubicin in lung and cervical cancer cells. Therefore, the effect of dual ERK1/2 and ERK5 on doxorubicin sensitivity was evaluated. Citation Format: Akshita Bhatt, Thomas Wright, Van Barnes, Suravi Chakrabarty, Patrick Flaherty, Matthew Burow, Jane Cavanaugh. Targeting the ERK5 and ERK1/2 pathways simultaneously induces mesenchymal to epithelial transition in TNBC [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5042.

Background: Melatonin-tamoxifen drug conjugate linked with a 5-carbon chain (C5) exhibited uterus protection in female mice, which did not occur when the same doses of unlinked melatonin and tamoxifen were co-administered. Anti-cancer actions of C5 and 4 others, with varying carbon lengths (C2, C4, C9, C15), were further tested in phenotypically diverse breast cancer (BC) cell lines—MCF-7(ER+/PR+), MMC(HER2+) and triple negatives(MDA-MB-231 and BT-549) in terms of cell viability and migration. In all BC lines, C4 and C5 exhibited superior potency and efficacy compared to C2, C9, C15 and unlinked melatonin and tamoxifen or 4-OH-tamoxifen controls. In this study, C4 and C5 were further tested for their anti-cancer effects in tamoxifen-resistant MCF-7 cells(TamR-MCF-7); their pharmacokinetic parameters were assessed in vitro and in vivo; and the mechanisms underlying C4- and C5-mediated anti-cancer actions were also determined by use of inhibitors against MEK1/2, MEK5 or PI3 kinase and western blot analysis. Results: C4 and C5 exhibited similar potency (TamR-MCF-7 IC50 = 4.22µM and 7.21µM; MCF-7 IC50 = 3.62nM and 440mM) and efficacy (TamR-MCF-7 = 83% and 81% inhibition; MCF-7= 71% and 90% inhibition) to inhibit TamR-MCF-7 cell viability as they did in MCF-7 cells. Regarding metabolism, C4 and C5 displayed similar CYP-mediated pharmacokinetic profiles as tamoxifen in both mouse and human liver microsomes where 40% loss of tamoxifen, C4 or C5 occurred by 10 min in mouse vs. 20 min in human. In vivo, the Tmax for C5 (oral) was 24h compared to 0.5h for C4 (oral) resulting in lower Cmax (8.9 ng/mL) and AUC0-24 (1.6 hr.ng/mL) for C5 compared to C4 (Cmax =102.6 ng/mL and AUC0-24 =143.7 hr.ng/mL) and lower oral bioavailability (0.11%) for C5 compared to C4 (4.52%). Regarding mechanisms, the effect of C4- or C5-mediated protein modulation was “context-specific” dependent upon BC phenotype (i.e., ER+, HER2+ or ER-/PR-/HER2-); the number of carbons linking melatonin to tamoxifen (i.e., 4 carbons for C4 or 5 carbons for C5); and the concentration (i.e., 1nM or 10µM) of C4 or C5 tested. For MCF-7, MMC and MDA- MB-231 cells, inhibition of MEK1/2, MEK5 and PI3K enhanced but did not block C4’s or C5’s anti-cancer actions; while for BT-549 cells, Bix02189 blocked C5’s effects. Also, in MCF-7 cells, pERK1/2, NF-κB and Runx2 were significantly modulated by C4 or C5; for MMCs, C4 and C5 modulated NF-κB and β1-integrin expression; for MDA-MB-231, MEK1/2 and MEK5 played a more central role possibly through co-modulation of NF-κB; and for BT-549, C5-mediated effects on pERK5 or PI3K-dependent regulation of pERK1/2 may underlie its anti-cancer actions. Conclusions: Melatonin-tamoxifen drug conjugates (C4 and C5) may be superior to tamoxifen therapy alone in a variety of cancers, including TamR BC. Citation Format: Mahmud Hasan, Thomas D. Wright, Saugat Adhikari, Mohamed A. Marzouk, Alaina Pericoloso, Kelsey Murgas, Miranda Burgman, Benton P. Miller, Ulrike Holzgrabe, Darius P. Zlotos, Robert E. Stratford, Paula A. Witt-Enderby. Melatonin-tamoxifen drug conjugates: Mechanism against breast cancer cells, and pharmacokinetic assessment in female mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3893.

Triple negative breast cancer is characterized by the loss of hormone receptors and lack of targeted therapy. Most invasive cancers, including triple negative (TNBC) breast cancer have a mesenchymal phenotype, which is associated with increased chemoresistance. Activation of the MEK1/2 and MEK5 pathways plays a crucial role in the activation of the epithelial to mesenchymal transition program and increases the survival, proliferation, and migration of the cancer cells. Disruption of actin skeleton via ras and src mediated activation of extracellular regulated kinase 1/2 (ERK1/2) and ERK5 is reported, indicating their role in oncogenic transformation. Moreover, inhibition of either pathway results in a compensatory increase in the PI3K/AKT pathway. These crosstalk mechanisms are involved in mediating therapeutic drug resistance. MDA-MB-231, a BRAF and KRAS mutant TNBC cell line has more than 90% of high CD44+/CD24-/low stem cell population, and high ERK5 and ERK1/2 expression; hence it was used as the model for our experiments. Moreover, MDA-MB-231-ERK5-KO cells were utilized to confirm the mechanism of action. To target TNBC, known inhibitors of the MEK1/2 pathway: trametinib, an FDA approved drug for BRAF mutant melanoma, VX-11-e, an ERK2 inhibitor, and XMD-8-92, an ERK5 inhibitor were used in combination with the chemotherapeutic drugs paclitaxel and doxorubicin to examine cell viability. We have shown that dual inhibition of the ERK5 and AKT signaling pathways synergistically reduces TNBC cell viability and enhances sensitivity of the cells to paclitaxel. A series of novel quinazoline derivatives was generated to dually target the ERK5 and the AKT pathway. The effect of novel quinazolines on cell viability in combination with the chemotherapeutic agent paclitaxel was examined in the TNBC cells and some encouraging results were obtained. The overall significance of this research is to enhance the anti-cancer activity of chemotherapeutic agents and reduce off-target toxicity by dose-reduction strategy. Citation Format: Akshita B. Bhatt, Thomas D. Wright, Saloni Patel, Suravi Chakrabarty, Van Barnes, Matthew Burow, Patrick T. Flaherty, Jane Cavanaugh. Inhibition of the MAPK pathways enhances the sensitivity of triple negative breast cancer cells to chemotherapeutic drugs [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B078. doi:10.1158/1535-7163.TARG-19-B078

Triple-negative breast cancers (TNBCs) represent 15% to 20% of all breast cancers and are often associated with poor prognosis. The lack of targeted therapies for TNBCs contributes to higher mortality rates. Aberrations in the phosphoinositide-3-kinase (PI3K) and mitogen-activated protein kinase pathways have been linked to increased breast cancer proliferation and survival. It has been proposed that these survival characteristics are enhanced through compensatory signaling and crosstalk mechanisms. While the crosstalk between PI3K and extracellular signal-regulated kinase 1/2 (ERK1/2) pathways has been characterized in several systems, new evidence suggests that MEK5/ERK5 signaling is a key component in the proliferation and survival of several aggressive cancers. In this study, we examined the effects of dual inhibition of PI3K/protein kinase B (Akt) and MEK5/ERK5 in the MDA-MB-231, BT-549, and MDA-MB-468 TNBC cell lines. We used the Akt inhibitor ipatasertib, ERK5 inhibitors XMD8-92 and AX15836, and the novel MEK5 inhibitor SC-1-181 to investigate the effects of dual inhibition. Our results indicated that dual inhibition of PI3K/Akt and MEK5/ERK5 signaling was more effective at reducing the proliferation and survival of TNBCs than single inhibition of either pathway alone. In particular, a loss of Bad phosphorylation at two distinct sites was observed with dual inhibition. Furthermore, the inhibition of both pathways led to p21 restoration, decreased cell proliferation, and induced apoptosis. In addition, the dual inhibition strategy was determined to be synergistic in MDA-MB-231 and BT-549 cells and was relatively nontoxic in the nonneoplastic MCF-10 cell line. In summary, the results from this study provide a unique prospective into the utility of a novel dual inhibition strategy for targeting TNBCs.

Abstract The organization of cell cytoskeleton is altered in events of epithelial to mesenchymal transition (EMT), promotion of cell motility, and cancer metastases. EMT is associated with decreased cell-cell adhesion, downregulation of epithelial markers like E-Cadherin, cytokeratins, and occludins, and upregulation of mesenchymal markers such as N-cadherin, vimentin, and various transcription factors such as slug and ZEB. Epithelial to mesenchymal transition is also a consequence of drug resistance and is responsible for cancer metastases. Triple negative breast cancer is highly aggressive cancer and patients show poor prognosis and disease-free survival due to the lack of targeted therapy. Mitogen activated protein kinase pathway, including extracellular activated kinase ERK1/2 and ERK5, and phosphoinositide 3-kinase (PI3K) pathway are known to alter the cytoskeleton through the downstream activation of oncogenes such as FRA-1 and loss of focal adhesions. Of these pathways, the MEK5-ERK5 pathway is understudied in triple negative breast cancer TNBC, and there are few research tools available to selectively inhibit this pathway. The diphenylamine analogs were derived from the parent molecule Mekinist, a FDA approved MEK1/2 inhibitor for melanoma, and modified to gain selectivity towards MEK5. SC-1-151, a type-III allosteric inhibitor of MEK5 is a dual MEK1/2 (98.6%) and MEK5 (59%) inhibitor; the molecule inhibits cell viability and colony formation, and attenuates tumor growth. SC-1-151 was serendipitously identified as a mesenchymal to epithelial transition activator in TNBC cell line MDA-MB-231. E-cadherin protein expression and cell morphology were examined to study MET after the treatment of MDA-MB-231 cells with different structural analogs of SC-1-151 after treatment for 5 days. The compound was further found to induce E-cadherin expression and epithelial phenotype in tamoxifen resistant estrogen positive MCF-7 cell line that underwent EMT. The compound is identified to promote this activity by targeting at least the ERK-FRA1-ZEB1 axis. Alkyl or N-Methyl piperazine substituents on the amide of ring 1 produced similar result as SC-1-151, and substituting the amide group with acid or ester also induced MET. In contrast, ortho-fluoro, para-iodo functional groups of the arene ring 2, when replaced with a meta-bromo substituent did not induce MET. We aim to test the compounds on EGF treated MDA-MB-468 cells to observe the attenuation of EGF induced EMT. Future studies will be performed to determine the specific protein interactions of the promising compounds. Citation Format: Bhatt AB, Wright TD, Anna K, Gupta M, Chakrabarty S, Flaherty PT, Hoang V, Burow M, Cavanaugh JE. Study of diphenylamine analogs as inducers of mesenchymal to epithelial transition in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-08-07.

Epithelial to mesenchymal transition (EMT) is a cellular program that converts non-motile epithelial cells into invasive mesenchymal cells. EMT is implicated in cancer metastasis, chemo-resistance, cancer progression, and generation of cancer stem cells (CSCs). Inducing mesenchymal to epithelial transition (MET), the reverse phenomenon of EMT, is proposed as a novel strategy to target triple negative and tamoxifen-resistant breast cancer. Triple negative breast cancer (TNBC) is characterized by the loss of hormone receptors, a highly invasive mesenchymal phenotype, and a lack of targeted therapy. Estrogen receptor-positive breast cancer can be targeted by tamoxifen, an ER antagonist. However, these cells undergo EMT over the course of treatment and develop resistance. Thus, there is an urgent need to develop therapeutic interventions to target these aggressive cancers. In this study, we examined the role of novel diphenylamine analogs in converting the mesenchymal phenotype of MDA-MB-231 TNBC cells to a lesser aggressive epithelial phenotype. Using analog-based drug design, a series of diphenylamine analogs were synthesized and initially evaluated for their effect on E-cadherin protein expression and changes incell morphology, which was quantified by measuring the spindle index (SI) value. Selected compound 1 from this series increases the expression of E-cadherin, a primary marker for epithelial cells, and decreases the mesenchymal markers SOX2, ZEB1, Snail, and vimentin. The increase in epithelial markers and the decrease in mesenchymal markers are consistent with a phenotypic switch from spindle-like morphology to cobblestone-like morphology. Furthermore, Compound 1 decreases spheroid viability, cell migration, and cell proliferation in triple negative BT-549 and tamoxifen-resistant MCF-7 breast cancer cells.

Epithelial to mesenchymal transition is an important cellular adaptation that helps cancer cells acquire a spindle-like phenotype from a cuboidal phenotype, degrade the extracellular matrix, invade the neighboring tissues, and metastasize to other organs and form secondary tumor. Cellular plasticity is governed by growth factors that act in a paracrine manner to activate downstream oncogenes and regulate the activity of epigenetic factors, which facilitate phenotypic switch from epithelial to mesenchymal, ultimately leading to increased cell migration and invasion. The intracellular phosphorylation cascade that is downstream of growth factor receptors plays an important role in transmitting the signal from the extracellular environment into the nucleus, thereby completing the loop required to elicit a cellular response. Triple negative breast cancer (TNBC), characterized by loss of hormone receptors is a highly aggressive form of cancer and patients show poor prognosis and disease-free survival due to lack of targeted therapy. In contrast, estrogen positive breast cancer can be targeted by estrogen receptor antagonists or CDK4/6 inhibitors, but drug resistance and relapse is often associated with epithelial to mesenchymal transition and poor patient outcome. Hence, targeting the mesenchymal phenotype with small molecule inhibitors is an emerging strategy to attenuate the invasive and aggressive nature of cancer cells. The MEK5-ERK5 pathway is understudied in triple negative breast cancer and there are few research tools available to selectively inhibit this pathway. Diphenylamine derivatives, synthesized as putative MEK5 inhibitors from parent MEK1/2 inhibitor trametinib, are effective in inducing mesenchymal to epithelial transition in MDA-MB-231 triple negative breast cancer cells, as indicated by an increase in E-cadherin expression, which is a marker of epithelial phenotype, and a decrease in spindle index, an important cell shape determinant. Compound 1, a dual MEK1/2 (98%) and MEK5 (59%) inhibitor was further characterized in functional assays; Compound 1 was found to significantly inhibit cell viability, proliferation, migration, spheroid viability, and colony formation in MDA-MB-231 cells. Compound 1 is effective in reversing the mesenchymal phenotype of MDA-MB-231, BT-549, and tamoxifen resistant-MCF-7 breast cancer cells. Signaling crosstalk and drug resistance in cancer limits the applicability of monotherapy. Our current work is focused on treating diverse breast cancer cells with combination of novel compound 1 and paclitaxel, ipatasertib, JQ-1, and LBH589 to induce synthetic lethality at lower concentration, restore drug sensitivity, and enhance selectivity. Citation Format: Akshita B. Bhatt, Thomas D. Wright, Katie Anna, Mohit Gupta, Suravi Chakrabarty, Van Hoang, Matthew Burow, Patrick T. Flaherty, Jane E. Cavanaugh. Novel diphenylamine analogs induce mesenchymal to epithelial transition and enhance the sensitivity of breast cancer cells to conventional chemotherapeutic agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1879.

Tamoxifen is used to prevent and treat estrogen receptor-positive (ER+) breast cancer (BC); however, its chronic use can increase uterine cancer risk and induce tamoxifen resistance. Novel melatonin-tamoxifen drug conjugates may be promising to treat BC and may help offset the adverse effects of tamoxifen usage alone due to the presence of melatonin. We synthesized and screened five drug conjugates (C2, C4, C5, C9, and C15 linked) for their effects on BC cell (MCF-7, tamoxifen-resistant MCF-7, mouse mammary carcinoma, MDA-MB-231, and BT-549) viability, migration, and binding affinity to melatonin receptor 1 (MT1R) and estrogen receptor 1 (ESR1). C4 and C5 demonstrated the most favorable pharmacological characteristics with respect to binding profiles (affinity for ESR1 and MT1R) and their potency/efficacy to inhibit BC cell viability and migration in four phenotypically diverse invasive ductal BC cell lines. C4 and C5 were further assessed for their actions against tamoxifen-resistant MCF-7 cells and a patient-derived xenograft triple-negative BC cell line (TU-BcX-4IC) and for their mechanisms of action using selective mitogen-activated protein kinase kinase MEK1/2, MEK5, and phosphoinositide 3-kinase (PI3K) inhibitors. C4 and C5 inhibited tamoxifen-resistant MCF-7 cells with equal potency (IC50 = 4-8 μM) and efficacy (∼90% inhibition of viability and migration) but demonstrated increased potency (IC50 = 80-211 μM) and efficacy (∼140% inhibition) to inhibit migration versus cell viability (IC50 = 181-304 mM; efficacy ∼80% inhibition) in TU-BcX-4IC cells. Unique pharmacokinetic profiles were observed, with C4 having greater bioavailability than C5. Further assessment of C4 and C5 demonstrates that they create novel pharmacophores within each BC cell that is context specific and involves MEK1/2/pERK1/2, MEK5/pERK5, PI3K, and nuclear factor κB. These melatonin-tamoxifen drug conjugates show promise as novel anticancer drugs and further preclinical and clinical evaluation is warranted.

Abstract Triple negative breast cancer (TNBC) is a molecularly heterogeneous, clinically aggressive disease group that is highly prevalent among African-Americans and younger patients. Standard chemo/radio therapy often produces clinical responses, but recurrence and metastasis are unfortunately common. Metastatic disease is generally incurable. Chemo/radiotherapy has been shown to induce EMT and enrich a chemo-resistant cancer stem-like cell (CSC) population in TNBC. CSCs are thought to drive disease recurrence. Notch signaling is critical for maintenance of TNBC CSC. Expression of Notch1 and its ligand Jagged1 are correlated with poor prognosis. Efforts to pharmacologically target Notch with Gamma Secretase Inhibitors (GSIs) have been impaired by the systemic toxicity of the GSIs, and by the fact that Notch1 also plays a key role in anti-tumor adaptive immunity. Therapeutic agents that indirectly and selectively target Notch signaling in breast cancer cells would be a potentially attractive strategy. However, no such agents have been identified to date. We have found that the MAPK5-ERK5 kinase pathway, which contains at least two druggable targets, functions as a master regulator of Notch signaling in TNBC cells. ERK5 knockout TNBC cells have dramatically decreased expression of Notch receptors, ligands and transcriptional targets. In vivo, these cells form barely detectable tumors that do not metastasize and express lower levels of Notch1 and its ligand Jagged1. Using in silico screening, we identified a class of compounds that selectively target MAP2K5 (MEK5) and decrease the phosphorylation of MAPK7 (ERK5). We selected compound SC-181 for further study. Consistent with ERK5KO cells, pharmacological suppression of ERK5 phosphorylation with SC-181 decreased Notch1 and Jagged1 mRNAs and proteins. SC-181 reversed EMT and reduced the CD44hi/CD24lo CSC population in TNBC cells, but had no effect on T-cell proliferation. SC-181 decreased the number and size of mammospheres in a concentration-dependent manner. Overexpression of the Notch1 intracellular domain (N1IC) in ERK5KO cells rescues their phenotype, dramatically increasing the CSC fraction and promoting EMT. Our results suggest that targeting the MEK5-ERK5 pathway is a promising new strategy to selectively modulate Notch signaling in TNBC CSC without compromising tumor immunity. Citation Format: Ucar DA, Matossian MD, Hoang-Barnes VT, Hossain FM, Gupta M, Burks HE, Wright TD, Cavanaugh J, Flaherty P, Burow ME, Miele L. A novel druggable target upstream of Notch: MEK5/ERK5 signaling regulates Jagged-1 and Notch1 expression in triple negative breast cancer stem cells [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-03-04.

Abstract Triple negative breast cancer (TNBC) is a molecularly heterogeneous, clinically aggressive disease group that is highly prevalent among African-Americans and younger patients. Standard chemo/radio therapy often produces clinical responses, but recurrence and metastasis are unfortunately common. Metastatic disease is generally incurable. Chemo/radiotherapy has been shown to induce EMT and enrich a chemo-resistant cancer stem cell-like (CSC) population in TNBC. CSCs are thought to drive disease recurrence. Notch signaling, particularly Notch1, is critical for maintenance of TNBC CSC. Expression of Notch1 and its ligand Jagged1 are correlated with poor prognosis. Efforts to pharmacologically target Notch directly have been impaired by the systemic toxicity of the Gamma Secretase Inhibitors (GSI) used, and by the fact that Notch1 also plays a key role in anti-tumor adaptive immunity. Therapeutic agents that target Notch signaling in breast cancer cells indirectly and selectively are a potentially attractive strategy. However, no such target has been identified to date. We have found that the MAPK5-ERK5 kinase pathway, which contains at least two druggable targets, functions as a master regulator of Notch signaling in TNBC cells. ERK5 knockout TNBC cells have dramatically decreased expression of Notch receptors, ligands and targets. In vivo, these cells form barely detectable tumors that do not metastasize and express lower levels of Notch1 and its ligand Jagged1. Using in silico screening method, we have identified a small molecule compound that targets MAP2K5 (MEK5) and decreases phosphorylation of MAPK7 (ERK5). Expression of ERK5 is associated with poor prognosis in TNBC. Consistent with ERK5KO cells, suppression of ERK5 phosphorylation decreased the amount of Notch1 and Jagged1 protein and mRNAs. More importantly, a selective MEK5 inhibitor, SC-181, reversed EMT and reduced the CD44hi/CD24lo CSC population in TNBC cells without suppressing T-cell proliferation. Treatment with nanomolar concentration of this compound decreased the number and size of mammospheres in a dose- dependent manner. Our preliminary results suggest that targeting the MEK5-ERK5 pathway is a promising strategy to selectively target Notch signaling in TNBC CSC without systemic Notch inhibition. Citation Format: Deniz A. Ucar-Bilyeu, Margarite D. MATOSSIAN, VAN Hoang Barnes, Fokhrul M. Hossain, Mohit Gupta, HOPE E. BURKS, THOMAS D. WRIGHT, Jane Cavanaugh, Patrick Flaherty, Matthew E. Burow, Lucio Miele. Targeting notch one notch above [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 967.

Background: A dual melatonin and tamoxifen hybrid ligand (HL) was developed and shown to display uterine protective actions while co-administration of the same doses of melatonin and tamoxifen unlinked increased uterine weight (US Patent 8785501). The anti-cancer actions of this HL (C5) and 4 others (C2, C4, C9 and C15)—which differed only in their number of carbon linkers—were further tested in 5 phenotypically diverse breast cancer (BC) cell lines—MCF-7 (ER+/PR+), tamoxifen resistant MCF-7 (TamR), MMC (HER2+) and triple negatives (MDA-MB-231 with a raf-1 mutation and BT549 with PTEN mutation) for their effects on cell proliferation, migration, protein expression and binding affinity to melatonin receptors (MT1Rs) and estrogen receptors (ERs). Analysis of HL effects on pERK1/2, pERK5, NF-kB, Runx2, and β1-integrin expression in each BC line and use of the MEK1/2 inhibitor (PD98059) or the MEK5 inhibitor (Bix02189) in the presence of the HLs helped elucidate their mechanism of action. Also, we determined the pharmacokinetic parameters of C4 and C5 HL using both in vitro and in vivo models. Results: All HLs demonstrated concentration-dependent inhibition of 2-[125I]-melatonin binding to MT1Rs, whereas C5 HL also showed equal binding affinity like melatonin. Only C4 and C5 HLs demonstrated equal affinity as tamoxifen or 4-OH-tamoxifen to ERs, and no concentration dependent inhibition of [125I]-estradiol/[3H]-estradiol binding occurred for C2, C9, and C15 HLs. All HLs were screened for their effects on BC cell proliferation and migration and it was determined that C4 and C5 demonstrated superior potency and efficacy compared to the other HLs (C2, C9, C15) and to co-exposure to melatonin and tamoxifen or 4-OH-tamoxifen (unlinked) for all BC cell lines including TamR MCF-7 cells. Acute (15 min) exposure to C4 and C5 HL increased pERK1/2 activity in MCF-7 cells and C5 HL increased NF-КB protein expression in MCF-7 and MDA-231 cells vs vehicle. Inhibition of MEK1/2 or MEK5 alone inhibited MMC, MDA-231 and BT549 cell migration. The addition of PD98059 enhanced C4-mediated inhibition of MCF-7 and BT549 cell proliferation and enhanced C5-mediated inhibition of MCF-7 cell proliferation and migration and BT549 cell migration. The addition of Bix02189 enhanced C4-mediated inhibition of MMC and BT549 cell proliferation and enhanced C5-mediated inhibition of MCF-7 and BT549 cell migration. Co-administration of Bix02189 and C4 HL blocked MDA-231 cell migration. C4 and C5 HLs displayed similar CYP-mediated loss profiles as tamoxifen in both mouse and human liver microsomes; including, the rate of metabolism being faster in mice vs human. Moreover, C4 HL showed better oral bioavailability than C5 HL in C57BL/6J female mice. Conclusions: Novel melatonin-tamoxifen HLs linked by 4 or 5 carbons show promise as anti-cancer drugs in phenotypically diverse BCs including triple negative and tamoxifen resistant and may display less uterotropic effects. Citation Format: Mahmud Hasan, Mohamed Akmal Marzouk, Saugat Adhikari, Thomas Wright, Benton Miller, Brianna Peckich, Spencer Yingling, Robert Stratford, Darius Zlotos, Jane Cavanaugh, Paula Witt-Enderby. Melatonin-tamoxifen hybrid ligands and their effects on breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3915.

Many receptor‐mediated cellular processes progress through mitogen‐activated protein kinase (MAPK) signaling pathways, which are initiated by activation of a surface receptor and ultimately lead to a change in cell physiology. Previous research has shown that the influence of melatonin on osteoblast activity is mediated in part through MAPK/ERK kinases (MEK) 1/2 and MEK5. Here we explore the possible effects of MEK 1/2 and MEK5 disruption on the skeletal structure in rodents with diurnal melatonin rhythms. To investigate the influence of MAPK signaling on bone mineral density and trabecular bone phenotypes, one group of SCID mice (SC; n = 4) was injected daily for a period of 30 days with a dual MEK1/2 and MEK5 inhibitor, SC‐1‐151. A second control group (n = 4) was injected daily with DMSO vehicle for the same period. At the end of the experimental period mice were euthanized, and tibiae were dissected free of soft tissues and fixed in formalin. Tibia were scanned at 9.61 μm 3 voxel size for subsequent morphometric analyses. Regions of interest were identified on the scans and then analyzed for trabecular thickness (Tb.Th), trabecular spacing (Tb.Sp), bone volume fraction (BV/TV), and cortical bone mineral density (BMD) using ImageJ software. Resulting bone phenotypes were analyzed using Bayesian linear models. We found that the SC group showed credibly decreased BV/TV compared to the DMSO controls (Pr[SC < DMSO] = 0.83). However, comparisons of Tb.Th, Tb.Sp, and BMD indicated minimal credible differences between the SC and DMSO treatment groups. Overall, our results suggest that, while previous research has shown that disruption of the MAPK signaling pathway may have a negative effect on osteoblast activity, these effects may result in only subtle changes for trabecular bone phenotypes and no change in cortical bone mineralization. This project provides preliminary results for a larger‐scale project investigating the role of melatonin, MEK1/2, and MEK5 in bone formation. Support or Funding Information Research support: University of Missouri School of Medicine, National Institute of Arthritis and Musculoskeletal and Skin Diseases This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Abstract Triple negative breast cancer (TNBC) is characterized by the loss of hormone receptors and high invasive potential. TNBC cells express high levels of the mesenchymal markers vimentin, fibronectin, N-cadherin, and cadherin11, which are involved in cell invasion and metastasis, and low levels of the epithelial markers E-cadherin, occludins and cytokeratins, which are involved in cellular contact and stability of the cell membrane. Mitogen activated protein kinases, including ERK5 and ERK1/2 are important pro-survival proteins and are known to be upregulated in most cancers. Of these pathways, the MEK5-ERK5 pathway is understudied in triple negative breast cancer, and there are few research tools available to selectively inhibit this pathway. The diphenylamine moiety was derived from the parent molecule Trametinib, a FDA approved MEK1/2 inhibitor for melanoma. Structural modifications were made on the lead molecule to gain selectivity towards MEK. SC-1-151, one of the compounds from this diphenylamine series was identified as a dual MEK1/2 (98.6% inhibition) and MEK5 (59% inhibition) inhibitor. Additionally, we have shown that SC-1-151 attenuates tumor growth in severe combined immunodeficient (SCID) xenograft mice and causes a mesenchymal to epithelial transition (MET) in MDA-MB-231 TNBC cells. The goal of this research is to determine the structural features of diphenylamines that are responsible for MET. E-cadherin and cadherin-11 protein expression and cell morphology were examined to study MET after the treatment of MDA-MB-231 cells with different structural analogs of SC-1-151 for 5 days. Alkyl or N-Methyl piperazine substituents on the amide of ring 1 produced similar result as SC-1-151, and substituting the amide group with acid or ester also induced MET. In contrast, ortho-fluoro, para-iodo functional groups of the arene ring 2, when replaced with a meta-bromo substituent did not induce MET. Therefore, our data suggest the necessary functional groups for inducing MET include the hydrogen atom on the amine linkage, and the iodine atom on the arene ring 2. Future studies will be performed to determine the specific protein interactions of the promising compounds. Citation Format: Akshita B. Bhatt, Thomas D. Wright, Katie Anna, Mohit Gupta, Patrick Flaherty, Van Hoang, Matthew Burow, Jane E. Cavanaugh. Structure-activity relationship of diphenylamine derivatives to target epithelial to mesenchymal transition in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4204.