Breast cancer (BC) is the most prevalent type of cancer among women with triple negative breast cancer (TNBC) accounting for 15% of BC. The majority of BCs are hormone sensitive, TNBC, a more aggressive subtype is characterized by its negative expression of ER and PR, and lack of Her2/NEU amplification. Due to its receptor status, TNBC lacks targeted therapy. FK228 (Romidepsin), a class I and II histone deacetylase inhibitor (HDACi) has been approved by the FDA for the treatment of PTCL (peripheral T-cell lymphoma) and is a promising drug for TNBC treatment. FK228 mechanism of action was through cell cycle arrest and apoptosis (1,2). FK228 specifically targets the enzymes HDACs 1 and 2, tumor suppressor and other proteins thereby exerting epigenetic changes on cancer cells resulting in anti-tumor activity. To assess the role of HDACi, TNBC cell lines were treated with FK228 and Panobinostat (LBH, a panHDACi) and analyzed for suppression of cell cycle genes. Similar to PTCL, TNBC cell lines showed an increase in cell cycle arrest genes such as p21 and others subsequent to treatment with both drugs. Using PCR and crystal violet we identified changes in morphology and migration in 2k1, MDA-MB 231 and HS-578t cell lines treated with FK228 under in-vitro conditions. Further studies show a reversal of the epithelial to mesenchymal transition (EMT) in FK228 treated cells; specifically in key EMT genes CDH1 and ZEB2, both directly linked to HDAC1/2 activity. Similar results were replicated in 3D culture mammospheres. We are also further studying the effects of HDACi in vivo using PDXs (patient derived xenografts) in mouse models; the PDX is either injected as cells or implanted directly in the mammary pad. The PDX model is an excellent translational tool used to monitor growth patterns and recurrence, study metastasis and drug response. Thus far, the TU-BcX-2O0 PDX in vivo model demonstrated growth suppression in tumor growth with FK228 treatment. We are also studying FK228 in models TU-BX-4IC, 4M4 and 4QX. Metastasis in the models is monitored by H&E staining lung and liver tissue for further staining and analysis; we are also using IVIS imaging in an in vivo model consisting of GFP/luciferase transfected breast cancer cells MDA-MB-231 and SUM-159 to monitor both the proliferation and spread of disease in mice. Ultimately we aim to characterize the pathways altered by FK228 and the involvement of HDACs in tumorigenesis, metastasis and resistance within TNBC. References: 1.Gisselbrecht, Christian, and David Sibon. “New Perspectives in the Therapeutic Approach of Peripheral T-Cell Lymphoma.” Current Opinion in Oncology, vol. 30, no. 5, 2018, pp. 285-291., doi:10.1097/cco.0000000000000469.2.Yang, L. P. (2011). Romidepsin. Drugs, 71(11), 1469-1480. doi:10.2165/11207170-000000000-00000 Citation Format: Madlin Alzoubi, Khoa Nguyen, Hope Burks, Katherine Hebert, Thomas Cheng, Margarite Matossian, Maryl Wright, Bridgette Collins-Burow, Matthew Burow. The response of histone deacetylase inhibitors in triple negative breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-05-07.

Background Triple-negative breast cancers (TNBCs) are clinically aggressive subtypes of breast cancer. TNBC is difficult to treat with targeted agents due to the lack of commonly targeted therapies within this subtype. Androgen receptor (AR) has been detected in 12–55% of TNBCs. AR stimulates breast tumor growth in the absence of estrogen receptor (ER), and it has become an emerging molecular target in TNBC treatment. Methods Ceritinib is a small molecule inhibitor of tyrosine kinase and it is used in the therapy of non-small lung cancer patients. Enzalutamide is a small molecule compound targeting the androgen receptor and it is used to treat prostate cancer. Combination therapy of these drugs were investigated using AR positive breast cancer mouse xenograft models. Also, combination treatment of ceritinib and paclitaxel investigated using AR − and AR low mouse xenograft and patient derived xenograft models. Results We screened 133 FDA approved drugs that have a therapeutic effect of AR + TNBC cells. From the screen, we identified two drugs, ceritinib and crizotinib. Since ceritinib has a well- defined role in androgen independent AR signaling pathways, we further investigated the effect of ceritinib. Ceritinib treatment inhibited RTK/ACK/AR pathway and other downstream pathways in AR + TNBC cells. The combination of ceritinib and enzalutamide showed a robust inhibitory effect on cell growth of AR + TNBC cells in vitro and in vivo. Interestingly Ceritinib inhibits FAK-YB-1 signaling pathway that leads to paclitaxel resistance in all types of TNBC cells. The combination of paclitaxel and ceritinib showed drastic inhibition of tumor growth compared to a single drug alone. Conclusions To improve the response of AR antagonist in AR positive TNBC, we designed a novel combinational strategy comprised of enzalutamide and ceritinib to treat AR + TNBC tumors through the dual blockade of androgen-dependent and androgen-independent AR signaling pathways. Furthermore, we introduced a novel therapeutic combination of ceritinib and paclitaxel for AR negative or AR-low TNBCs and this combination inhibited tumor growth to a great extent. All agents used in our study are FDA-approved, and thus the proposed combination therapy will likely be useful in the clinic.

Liver kinase B1 (LKB1) is a potent tumor suppressor that regulates cellular energy balance and metabolism as an upstream kinase of the AMP-activated protein kinase (AMPK) pathway. LKB1 regulates cancer cell invasion and metastasis in multiple cancer types, including breast cancer. In this study, we evaluated LKB1’s role as a regulator of the tumor microenvironment (TME). This was achieved by seeding the MDA-MB-231-LKB1 overexpressing cell line onto adipose and tumor scaffolds, followed by the evaluation of tumor matrix-induced tumorigenesis and metastasis. Results demonstrated that the presence of tumor matrix enhanced tumorigenesis in both MDA-MB-231 and MDA-MB-231-LKB1 cell lines. Metastasis was increased in both MDA-MB-231 and -LKB1 cells seeded on the tumor scaffold. Endpoint analysis of tumor and adipose scaffolds revealed LKB1-mediated tumor microenvironment remodeling as evident through altered matrix protein production. The proteomic analysis determined that LKB1 overexpression preferentially decreased all major and minor fibril collagens (collagens I, III, V, and XI). In addition, proteins observed to be absent in tumor scaffolds in the LKB1 overexpressing cell line included those associated with the adipose matrix (COL6A2) and regulators of adipogenesis (IL17RB and IGFBP4), suggesting a role for LKB1 in tumor-mediated adipogenesis. Histological analysis of MDA-MB-231-LKB1-seeded tumors demonstrated decreased total fibril collagen and indicated decreased stromal cell presence. In accordance with this, in vitro condition medium studies demonstrated that the MDA-MB-231-LKB1 secretome inhibited adipogenesis of adipose-derived stem cells. Taken together, these data demonstrate a role for LKB1 in regulating the tumor microenvironment through fibril matrix remodeling and suppression of adipogenesis.

OBJECTIVES/GOALS: In triple negative breast cancer (TNBC), obesity is associated with poor outcomes. Adipose stem cells (ASCs) from obese patients (obASCs) secrete higher levels of adipokines compared to ASCs from lean individuals. Leptin, one of these adipokines, has been implicated in many cancers. This study seeks to examine the role of leptin signaling in TNBC. METHODS/STUDY POPULATION: Previous work in conjunction with a collaborating lab has shown that leptin signaling promotes metastasis and increased expression of epithelial-mesenchymal transition (EMT) markers in triple negative breast cancer cell lines. This project expands upon this work through using both patient-derived cell lines and and patient-derived xenografts (PDX), and examines the role of leptin signaling both in vitro and in vivo. To determine the effects of obesity upon a PDX model of TNBC, a high fat diet was used to induce obesity in vivo. A pharmacological inhibitor of the leptin receptor was used to test the requirement for leptin signaling both in vivo and in vitro. RESULTS/ANTICIPATED RESULTS: Exposure to conditioned media harvested from obASCs increased the percentage of TNBC cells that expressed cancer stem cell markers, whereas exposure to an inhibitor of the leptin receptor decreased the percentage of cells with cancer stem cell markers. PDX tumors implanted into mice with diet-induced obesity had an increased volume compared to tumors implanted into lean controls. Further analysis will be conducted on metastasis, circulating tumor cells, and survival in both lean and obese mice. DISCUSSION/SIGNIFICANCE: Understanding the complex signaling events in the obese tumor microenvironment is essential, as these molecular differences may contribute to different outcomes for obese and lean individuals with triple negative breast cancer. Therefore, study of the crosstalk between obASCs and TNBC cells is critical.

Triple-negative breast cancer (TNBC) is an aggressive, heterogenous disease that lacks approved targeted therapeutics. Due to the complexity of tumor microenvironment (TME) interactions in TNBC, it is crucial to identify therapeutic targets that regulate the extracellular matrix (ECM). Traditional 2D TNBC models do not accurately mimic the cell-matrix interactions and structural matrix proteins that are key in maintaining the unique TME in individual patient tumors. Here, we introduce our decellularized TNBC patient-derived xenograft (PDX) models to address this gap in knowledge. Utilizing our decellularized models, we can investigate the unique ECM composition and cell-matrix interactions in PDX models from understudied patients with diverse clinical presentations. We can also use our decellularized tumor scaffolds as drug testing models. We utilize our tissue decellularization method on PDX tumor scaffolds derived from two of our established TNBC PDX models (TU-BcX-56S and TU-BcX-4QX). Decellularization of tumor scaffolds was confirmed by DNA quantification and histological analysis (H&E, Masson’s Trichrome, and Movat’s staining). MDA-MB-231 cells expressing GFP and luciferase were seeded onto scaffolds and treated with 100nM of Paclitaxel, a microtubule-stabilizing cytotoxic chemotherapeutic, or DMSO for 48 hours. Concordantly, cells in 2D culture were treated with 100nM of Paclitaxel or DMSO for 48 hours. Using the IVIS imaging system, we measured the bioluminescence of cells on our seeded scaffolds before treatment and at 24 and 48 hours after treatment. Cells in 2D culture showed a significant decrease in bioluminescent signal (p-value < 0.05) in the Paclitaxel group compared to the DMSO group at 48 hours. Cells seeded on TU-BcX-56S scaffold also showed a significant decrease in bioluminescent signal (p-value < 0.05) in the Paclitaxel group compared to the DMSO group at 48 hours. Interestingly, cells seeded on TU-BcX-4QX scaffold showed a decrease in bioluminescence in both the treatment and control groups at 24 and 48 hours, albeit there was no significant difference. Using qPCR, we investigated scaffold regulation of ECM gene composition in our treatment and control groups. These results demonstrate that the unique ECM composition and architecture of these scaffolds are important drivers of cell behavior. Here, we demonstrate that our decellularized PDX tumor scaffold models can be used as drug testing platforms. Furthermore, our models recapitulate key structural matrix proteins in the TNBC TME, can be used to investigate ECM onco-architecture and composition, and can be used in therapeutic discovery research. Citation Format: Maryl Wright, Khoa Nguyen, Elizabeth Martin, Melyssa Bratton, Bridgette Collins-Burow, Matthew Burow. Utilizing decellularized triple-negative breast cancer patient-derived tumor models as drug testing platforms [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3831.

Abstract There is a critical need to develop methods for efficient testing of drug efficacy in patient-derived tumor samples to discover new therapeutics. Two-dimensional (2D) cell culture remains the primary method of drug screening, despite being considered less physiologically relevant than three-dimensional (3D) culture. Increased complexity and technical challenges of 3D systems have limited its widespread adoption as a primary screening method. In this study, we demonstrate methods for increased throughput, imaging and automation in 3D assays that are suitable for compound screening using patient-derived samples. In addition, we show analysis approaches and descriptors that allow gain more information about disease phenotypes and compound effects. We measured responses to drug treatment in 3D tumoroids for cytotoxicity and altered morphology. Tumoroids were formed from primary cells isolated from a patient-derived tumor explant, TU-BcX-4IC, that represents metaplastic breast cancer with a triple-negative subtype and treated with 165 compounds, of approved cancer drugs, at multiple concentrations. We characterize multiple quantitative descriptors for tumor phenotypes and compound effects. Cell Painting method was used for 3D tumoroids for evaluation of phenotypic effects. Eight compounds were detected that demonstrated effects at low concentrations (10nM), including romidepsin, trametinib, bortezomib, carfilzomib, panobinostat, which will be further investigated as potential drug candidates.

Mitogen Activated Protein (MAP) kinases are a category of serine/threonine kinases that have been demonstrated to regulate intracellular events including stress responses, developmental processes, and cancer progression Although many MAP kinases have been extensively studied in various disease processes, MAP3K19 is an understudied kinase whose activities have been linked to lung disease and fibroblast development. In this manuscript, we use bioinformatics databases starBase, GEPIA, and KMPlotter, to establish baseline expressions of MAP3K19 in different tissue types and its correlation with patient survival in different cancers.

Abstract Triple negative breast cancer (TNBC) is an aggressive and difficult-to-treat subtype of breast cancer that typically exhibits rapid growth rates, high rates of metastasis, and resistance to commonly used oncological drugs. Historically, cell lines have been utilized in order to study TNBC; recently, however, patient derived xenografts (PDX) models have evolved as the new standard that offers a translational approach to the research and subsequent treatment of breast cancer. Here, we characterize two novel PDX models for TNBC: TU-BcX-4QA and TU-BcX-4QAN. The former derived from a biopsy specimen prior to any therapies, and the latter derived from a mastectomy of the same patient after three rounds of AC-T therapy (doxorubicin and cyclophosphamide followed by paclitaxel). In establishing a treatment naïve and post-neoadjuvant therapy PDX model pair, we created a prime model that examines the effects of chemotherapy on tumor heterogeneity, clonal selection, and the overall characteristics of a tumor. Furthermore, we examined the evolution of the characteristics of the post-neoadjuvant therapy PDX model after continual passaging within the SCID/Beige murine models. Through serial implantation in SCID/Beige murine models for tissue propagation, we observed that TU-BcX-4QAN consistently had a higher tumor growth rate and a smaller number of metastatic lesions that developed on the lungs and liver in comparison to the TU-BcX-4QA model. In treating the tumor derived cell lines with NCI-approved oncological drugs, we distinguished the variations in their responses to various, commonly used therapies, and determined that TU-BcX-4QAN had a more resistant profile. Using qRT-PCR, we further discovered the differences between the two models in their contrasting gene expression; preliminary data indicates an increase in certain mesenchymal genes (CDH2, VIM, and ZEB2), a decrease in cell cycle genes (p21, p53), and an increase in proliferation genes (MK167) in TU-BcX-4QAN compared to TU-BcX-4QA. Additionally, serial passages are correlated with a decrease trend in human gene expression within TU-BcX-4QAN. This suggest that treatment can select for certain cancer cells within the primary tumor that allows for the growth of a different tumor altogether and illustrates both the advantages and limitations of the TU-BcX-4QA andTU-BcX-4QAN model pair in translational research. Citation Format: Gabrielle Olivia Windsor, Margarite Matossian, Maryl Wright, Steven Elliott, Khoa Nguyen, Bridgette Collins-Burow, Matthew Burow. Treatment naïve patient-derived xenograft model compared to the post-neoadjuvant model from the same patient diagnosed with triple negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-47.

Abstract Triple negative breast cancer (TNBC) is an aggressive disease with poor prognoses, partly due to the lack of clinically approved targeted therapeutics. The mechanisms underlying the process of drug resistance in TNBC remain elusive, prompting the need for the identification of kinase targets. Our lab previously found that liver kinase B1 (LKB1) overexpression inhibits the migratory phenotype and pathways involved in EMT of TNBC. However, the specific mechanisms in which LKB1 suppresses TNBC metastasis have not been fully elucidated. We believe that overexpression of LKB1 inhibits the migratory axis by inhibiting ECM remodeling that promotes invasion in TNBC. Here we utilize our novel decellularized patient-derived xenograft (PDX) TNBC model, TU-BcX-2K1 (“2K1”) tumor scaffold, to test this hypothesis. We seeded MDA-MB-231-LKB1 overexpressed and MDA-MB-231-vector cells onto decellularized 2K1 PDX tumor scaffold or decellularized adipose tissue (“AT”) and implanted our model into SCID/beige mice. Results demonstrated that tumor matrix enhanced cancer cell growth in both MDA-MB-231-vector and -LKB1 cell lines. LKB1 on adipose scaffold did not have tumor formation. These data suggest a novel microenvironment dependent function of LKB1. We compared the number of metastases in the lungs and livers excised from mice in each group. There were significantly more lung metastases in the 2K1+MDA-MB-231-vector group than in the AT+MDA-MB-231-vector group (p-value = 0.0144). There were slightly more lung metastases in the AT-MDA-MB-231-LKB1 group than in the 2K1+MDA-MB-231-LKB1 group, albeit not significantly. There were more liver metastases in the 2K1+MDA-MB-231-vector group than in the AT+MDA-MB-231-vector group, albeit not significantly. There were also more liver metastases in the 2K1+MDA-MB-231-LKB1 group than in the AT+MDA-MB-231-LKB1 group; however, there was no significance. LKB1 appeared to inhibit stromal remodeling in tumor, evident from decreased collagen composition and stromal cell infiltration. In vitro validation of this demonstrated that LKB1 secretome was able to inhibit adipogenesis of stem cells. To further test LKB1's role in stromal remodeling, we performed an in vivo experiment co-injecting MDA-MB-231-LKB1 and MDA-MB-231-vector cells with ASCs into SCID/beige mice. MDA-MB-231-LKB1 tumors grew significantly slower than MDA-MB-231-vector tumors (p-value = 0.0097). There was no significant difference in tumor growth in the MDA-MB-231-LKB1+ASCs and MDA-MB-231-vector+ASCs groups. We compared differences in the number of lung and liver metastases in each group. We investigated stromal remodeling in tumors in each group. Our data show how the ECM alters cancer cell response, inducing LKB1 overexpressed cells to become more aggressive. The data presented here will help elucidate the cell-matrix interactions that are vital in migration and invasion in TNBC. Citation Format: Maryl Wright, Margarite Matossian, Madlin Alzoubi, Conner King, Steven Elliott, Melyssa Bratton, Elizabeth Martin, Bridgette Collins-Burow, Matthew Burow. Utilizing a decellularized PDX tumor matrix model to investigate LKB1 regulation of ECM remodeling in TNBC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 80.

Obesity rates are climbing, representing a confounding and contributing factor to many disease states, including cancer. With respect to breast cancer, obesity plays a prominent role in the etiology of this disease, with certain subtypes such as triple-negative breast cancer having a strong correlation between obesity and poor outcomes. Therefore, it is critical to examine the obesity-related alterations to the normal stroma and the tumor microenvironment (TME). Adipocytes and adipose stem cells (ASCs) are major components of breast tissue stroma that have essential functions in both physiological and pathological states, including energy storage and metabolic homeostasis, physical support of breast epithelial cells, and directing inflammatory and wound healing responses through secreted factors. However, these processes can become dysregulated in both metabolic disorders, such as obesity and also in the context of breast cancer. Given the well-established obesity-neoplasia axis, it is critical to understand how interactions between different cell types in the tumor microenvironment, including adipocytes and ASCs, govern carcinogenesis, tumorigenesis, and ultimately metastasis. ASCs and adipocytes have multifactorial roles in cancer progression; however, due to the plastic nature of these cells, they also have a role in regenerative medicine, making them promising tools for tissue engineering. At the physiological level, the interactions between obesity and breast cancer have been examined; here, we will delineate the mechanisms that regulate ASCs and adipocytes in these different contexts through interactions between cancer cells, immune cells, and other cell types present in the tumor microenvironment. We will define the current state of understanding of how adipocytes and ASCs contribute to tumor progression through their role in the tumor microenvironment and how this is altered in the context of obesity. We will also introduce recent developments in utilizing adipocytes and ASCs in novel approaches to breast reconstruction and regenerative medicine.

PURPOSE:Breast cancer remains a prominent global disease affecting women worldwide despite the emergence of novel therapeutic regimens. Metastasis is responsible for most cancer-related deaths, and acquisition of a mesenchymal and migratory cancer cell phenotypes contributes to this devastating disease. The utilization of kinase targets in drug discovery have revolutionized the field of cancer research but despite impressive advancements in kinase-targeting drugs, a large portion of the human kinome remains understudied in cancer. NEK5, a member of the Never-in-mitosis kinase family, is an example of such an understudied kinase. Here, we characterized the function of NEK5 in breast cancer. METHODS:Stably overexpressing NEK5 cell lines (MCF7) and shRNA knockdown cell lines (MDA-MB-231, TU-BcX-4IC) were utilized. Cell morphology changes were evaluated using immunofluorescence and quantification of cytoskeletal components. Cell proliferation was assessed by Ki-67 staining and transwell migration assays tested cell migration capabilities. In vivo experiments with murine models were necessary to demonstrate NEK5 function in breast cancer tumor growth and metastasis. RESULTS:NEK5 activation altered breast cancer cell morphology and promoted cell migration independent of effects on cell proliferation. NEK5 overexpression or knockdown does not alter tumor growth kinetics but promotes or suppresses metastatic potential in a cell type-specific manner, respectively. CONCLUSION:While NEK5 activity modulated cytoskeletal changes and cell motility, NEK5 activity affected cell seeding capabilities but not metastatic colonization or proliferation in vivo. Here we characterized NEK5 function in breast cancer systems and we implicate NEK5 in regulating specific steps of metastatic progression.

Abstract Triple negative breast cancer (TNBC) is an aggressive and heterogeneous disease with poorer prognoses compared to other breast cancer (BC) subtypes. This is due, in part, to the lack of clinically approved targeted therapeutics. The mechanisms underlying the process of recurrence in TNBC remain elusive. Traditional 2D BC models do not accurately mimic the cell-matrix interactions and extracellular matrix (ECM) composition that are vital to maintaining the tumor microenvironment and are unique to individual patient tumors. Here we introduce and utilize our novel decellularized patient-derived xenograft (PDX) TNBC model, TU-BcX-4IC (“4IC”), to address this knowledge discrepancy. In this study, we seeded TU-BcX-4IC PDX-derived cells onto TU-BcX-4IC PDX decellularized tumor scaffold (“4IC + 4IC scaffold”) and implanted our model into SCID/beige mice. Concordantly, mice were inoculated with TU-BcX-4IC cells mixed with Matrigel and PBS (“4IC + Matrigel”), or PBS alone (“4IC + PBS”). We demonstrate that our decellularized model, along with the injected cells, can form tumors in vivo. We also show that the “4IC + 4IC scaffold” model retains aberrant mitotic figures seen in the original 4IC PDX. However, due to inconsistent tumor growth in the experimental group, optimization of cell seeding onto our decellularized scaffold model is needed to produce consistent tumor propagation in vivo. We compared the number and area of metastases in the lungs and livers excised from the mice. The area and number of lung metastases were lower in mice implanted with “4IC + 4IC scaffold,” albeit not significantly. There was little difference in the area of liver metastases in all groups. The number of liver metastases was lower in the “4IC + Matrigel” and “4IC + 4IC scaffold” groups; however, there was no significance. All groups had a greater propensity to metastasize to the livers. We also compared differences in human and mouse ECM gene expression amongst all groups. Our decellularized scaffold model can be used as a platform to evaluate ECM onco-architecture and composition. The data presented here will help enhance our understanding of the breast tumor microenvironment and elucidate the mechanisms underlying tumorigenesis and recurrence in TNBC. Citation Format: Maryl Wright, Margarite Matossian, Connor King, Khoa Nguyen, Steven Elliott, Madlin Alzoubi, Elizabeth Martin, Bridgette Collins-Burow, Matthew Burow. Utilizing a decellularized patient-derived xenograft tumor model for the evaluation of triple negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-01-16.

Abstract Triple-negative breast cancers (TNBCs) constitute approximately 12% of all breast cancer cases and are approximately twice as prevalent in African-American populations. Louisiana has a high proportion of African-American residents (32.3% in 2017), and New Orleans has among the highest incidences of TNBC in the country. Louisiana patients also have a high incidence of co-morbidities that affect breast cancer biology and outcomes, including type 2 diabetes and obesity. TNBCs have an aggressive clinical presentation due to high rates of metastasis, recurrence and chemoresistance. There are currently no clinically approved targeted therapies for TNBC; cytotoxic chemotherapy is the first-line treatment for TNBC, and recurrent, chemoresistant cancers are usually fatal. TNBCs are molecularly heterogeneous, consisting of at least four molecular subgroups, and immunologically heterogeneous. Both molecular and immunologic properties are associated with clinical outcomes and are seriously understudied in patients under-represented in biomedical research. Patient-derived xenografts (PDXs), as well as patient-derived organoids (PDO), are currently the best model for translational oncology therapeutic research because they accurately recapitulate the complex architecture and heterogenous genetic and molecular composition of solid cancers. To date, the majority of TNBC research has been based on Caucasian patients, although incidence rates of TNBC are higher in African-American cohorts. Our collaborative team aims to overcome this obstacle by establishing and characterizing TNBC PDX models that represent this understudied cohort. We currently have ten TNBC PDX models representing different patient ethnicities, responsiveness to chemotherapies, as well as different TNBC molecular subtypes and metastatic behavior. We dissect and evaluate the various individual components (tumor cell biology, stroma, immune, extracellular matrix) of TNBC tumors. We utilize these models in vivo, ex vivo and in vitro to examine how unique kinases and targeted inhibitors affect the distinct tumor characteristics. In addition to in vivo treatment studies, we generated cell lines and PDOs and we utilize novel techniques such as tissue decellularization to examine extracellular matrix components. We also analyze mechanistically relevant transcript (qRT-PCR) and protein (Western blot, immunohistochemistry) expression patterns that are unique to each PDX model to evaluate the effects of targeted therapies. We work with surrounding laboratories in the greater New Orleans area (Tulane, LSU, Xavier) that are also focused on therapeutic discovery of TNBC in a collaborative effort to provide translational models for their projects. Our aim is to leverage novel PDX models from understudied patients with a range of clinical and molecular presentations to guide the selection of therapeutically targetable pathways and therapeutic agents in specific molecular subtypes of TNBC. Citation Format: Margarite D. Matossian, Steven Elliott, Hope E. Burks, Maryl Wright, Rachel A. Sabol, Van T. Hoang, Deniz A. Ucar, Alex Alfortish, Jovanny Zabaleta, Fokhrul Hossain, Tiffany Chang, Henri Wathieu, Nicholas Pashos, Bruce Bunnell, Krzysztof Moroz, Arnold Zea, Adam Riker, Steven D. Jones, Elizabeth C. Martin, Lucio Miele, Bridgette M. Collins-Burow, Matthew E. Burow. Applications of patient-derived triple-negative breast cancer xenografts that represent understudied patients in Louisiana in targeted therapeutic research [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr C110.

Triple negative breast cancers (TNBCs) are a clinically and biologically aggressive breast cancer (BC) subtype; TNBC tumors have higher rates of metastasis, relapse and acquired/inherent drug resistance. Incidence and mortality rates of TNBC are stratified based on patient ethnicity - patients with African ancestry have higher mortality rates and diagnoses of invasive cancers compared to patients representing other ethnicities. Louisiana has a high proportion of African-American residents (32.7% in 2018), and New Orleans has among the highest incidences of TNBC in the country. Many of our patients present with TNBC tumors that are partially or completely resistant to neoadjuvant chemotherapies. There are currently no clinically approved targeted therapies for TNBC. Current therapeutic discovery focused TNBC research does not aptly address the knowledge gap regarding ethnic disparity in TNBC incidence/mortality rates and TNBC biology. To date, most TNBC-related research and knowledge has been acquired from Caucasian patients, although patients with African and Hispanic ancestries represent the majority of TNBC cases. Patient-derived xenografts (PDXs) are extensively used in BC research, as they mimic complex microanatomy, oncoarchitecture, and cell-cell/cell-stroma interactions of tumors. Here, we demonstrated the unique composition of PDX tumors is not dramatically affected by serial transplantation in mice, based on molecular phenotypes (examined using qRT-PCR and RNA sequencing) and the oncoarchitecture of the extracellular matrix (based on cryogenic scanning electron microscopy). Using these models in basic research facilitates translation of laboratory findings to the clinical setting, and dramatically enhanced drug discovery research. We have established over twelve TNBC PDX models, 90% of which represent patients of African ancestry, and most of which are resistant to neoadjuvant regimens. We focus on dissecting and evaluating kinase inhibitor/targeted drug response to various individual components (tumor cell biology, stroma, immune, extracellular matrix) of chemotherapy resistant TNBC tumors. Histone deacetylase inhibitors (DACi) are a promising therapeutic agent in TNBC systems; they have been shown to suppress tumorigenesis and metastasis in TNBC through suppression of the mesenchymal phenotype in cell line-based studies. In this study we utilized various TNBC PDX models (TU-BcX-2K1, -2O0, 4IC, -4M4, -4QAN, -4QX) to assess these findings in more translational systems. Interestingly, we showed that DACi effect on tumorigenesis and metastasis varied depending on specific TNBC PDXs utilized. These data implicate specific genes/signaling pathways exist in individual patient tumors that can predict tumor responsiveness to DACi. Preliminary data using the NCI oncology drug set implicated the MEK1/2 pathway contributed to sensitization of TNBC cells. Furthermore, we found a disconnect in gene expressions that were previously shown to be affected by DACi therapy (CDH1, VIM, ZEB1, ZEB2) in various derivations of PDX models (cells, PDX-Os, ex vivo, in vivo). These findings demonstrate that testing various derivations of PDX models is crucial to parsing out specific mechanisms of targeted therapies. Our methods presented here to assess targeted drug response and drug resistance using PDX models can be applied to any area of cancer research and is not limited to breast cancer. Citation Format: Margarite Matossian, Steven Elliott, Maryl Wright, Tiffany Chang, Madlin Alzoubi, Henri Wathieu, Rachel Sabol, Alex Alfortish, Hope Burks, Van Hoang, Deniz Ucar, Gabrielle Windsor, Thomas Yan, Jovanny Zabaleta, Fokhrul Hossain, Bruce Bunnell, Krzysztof Moroz, Arnold Zea, Adam Riker, Steven Jones, Elizabeth Martin, Lucio Miele, Bridgette Collins-Burow, Matthew Burow. Effect of histone deacetylase inhibitors on patient-derived neoadjuvant chemotherapy resistant triple negative breast cancer xenografts that represent understudied patients [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-03-17.

Conventional mitogen-activated protein kinase (MAPK) family members regulate diverse cellular processes involved in tumor initiation and progression, yet the role of ERK5 in cancer biology is not fully understood. Triple-negative breast cancer (TNBC) presents a clinical challenge due to the aggressive nature of the disease and a lack of targeted therapies. ERK5 signaling contributes to drug resistance and metastatic progression through distinct mechanisms, including activation of epithelial-to-mesenchymal transition (EMT). More recently a role for ERK5 in regulation of the extracellular matrix (ECM) has been proposed, and here we investigated the necessity of ERK5 in TNBC tumor formation. Depletion of ERK5 expression using the CRISPR/Cas9 system in MDA-MB-231 and Hs-578T cells resulted in loss of mesenchymal features, as observed through gene expression profile and cell morphology, and suppressed TNBC cell migration. In vivo xenograft experiments revealed ERK5 knockout disrupted tumor growth kinetics, which was restored using high concentration Matrigel™ and ERK5-ko reduced expression of the angiogenesis marker CD31. These findings implicated a role for ERK5 in the extracellular matrix (ECM) and matrix integrity. RNA-sequencing analyses demonstrated downregulation of matrix-associated genes, integrins, and pro-angiogenic factors in ERK5-ko cells. Tissue decellularization combined with cryo-SEM and interrogation of biomechanical properties revealed that ERK5-ko resulted in loss of key ECM fiber alignment and mechanosensing capabilities in breast cancer xenografts compared to parental wild-type cells. In this study, we identified a novel role for ERK5 in tumor growth kinetics through modulation of the ECM and angiogenesis axis in breast cancer.

Despite a decline in overall incidence rates for cancer in the past decade, due in part to impressive advancements in both diagnosis and treatment, breast cancer (BC) remains the leading cause of cancer-related deaths in women. BC alone accounts for ∼30% of all new cancer diagnoses in women worldwide. Triple-negative BC (TNBC), defined as having no expression of the estrogen or progesterone receptors and no amplification of the HER2 receptor, is a subtype of BC that does not benefit from the use of estrogen receptor-targeting or HER2-targeting therapies. Differences in socioeconomic factors and cell intrinsic and extrinsic characteristics have been demonstrated in Black and White TNBC patient tumors. The emergence of patient-derived xenograft (PDX) models as a surrogate, translational, and functional representation of the patient with TNBC has led to the advances in drug discovery and testing of novel targeted approaches and combination therapies. However, current established TNBC PDX models fail to represent the diverse patient population and, most importantly, the specific ethnic patient populations that have higher rates of incidence and mortality. The primary aim of this review is to emphasize the importance of using clinically relevant translatable tumor models that reflect TNBC human tumor biology and heterogeneity in high-risk patient populations. The focus is to highlight the complexity of BC as it specifically relates to the management of TNBC in Black women. We discuss the importance of utilizing PDX models to study the extracellular matrix (ECM), and the distinct differences in ECM composition and biophysical properties in Black and White women. Finally, we demonstrate the crucial importance of PDX models toward novel drug discovery in this patient population.

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.