Extracellular vesicles (EVs) are increasingly recognized as critical mediators of intercellular communication, not least during cellular stress or therapy. While EV signalling is well-studied in various tissues, its role in the prepubertal testicular environment is not well understood. Chemotherapy, commonly used in paediatric oncology, poses a significant risk to spermatogonial stem cells (SSCs) and may affect long-term fertility in cancer survivors. The role of EVs in chemotherapy-induced testicular damage in these patients is unknown and may be important for developing new fertility preservation methods. Immortalised murine Sertoli (TM4) and spermatogonial (GC1-spg) cell lines were used to investigate cisplatin-induced changes in EV biogenesis, release, and function in an in vitro model of the prepubertal testicular microenvironment. Our findings indicate that cisplatin significantly increases EV secretion and internalisation by recipient cells. Notably, EVs from cisplatin-exposed Sertoli cells exhibit a novel pro-apoptotic phenotype when co-cultured with chemotherapy-naïve Sertoli cells. Proteomic profiling of these EVs shows enrichment of apoptosis-regulatory proteins including caspases, activating Caspase-3/7 in recipient Sertoli cells. Conversely, germ cells exposed to Sertoli cell-derived EVs displayed reduced levels of apoptosis as well as a chemoprotective role to germ cells undergoing treatment with cisplatin. These findings indicate a dual role for Sertoli cell-derived EVs in mediating (1) apoptosis in Sertoli cells and (2) protection of germ cells following cisplatin exposure. The presence of pro-apoptotic molecules, especially caspases, in chemotherapy-induced Sertoli cell EVs provides mechanism for the induction of somatic cell apoptosis. Furthermore, their protective effects on germ cells demonstrate the complexity of EV-mediated signalling between testicular cell types. Manipulating EV biogenesis and cargo loading could be a promising approach to reduce chemotherapy-related gonadotoxicity and preserve fertility in childhood cancer patients.

Immunofluorescence (IF) staining represents a convenient and cost-effective approach to analysing single extracellular vesicles (EVs) and identifying subpopulations with specific roles or biological functions. However, the application of the method is challenged by the weak and unstable signals generated by the low abundant markers carried by the vesicles. In this study, we report the development of an IF strategy based on tyramide signal amplification (TSA) that employs tyramide probes for signal enhancement. The technique is first validated on glioblastoma circulating tumour cells (GBM CTCs) and systematically compared with conventional approaches using fluorescently labelled primary and secondary antibodies. Thereafter, the proposed method is adapted, tested and optimised for the multiplexed fluorescent staining of single EVs isolated from the parental GBM CTCs. The results demonstrate specific staining of single EVs by the developed TSA method, highlighting its advantages of amplified (>6×) signal intensities, more stable signals and broader (∼3×) signal dynamic ranges as compared to the conventional fluorescence methods. The developed protocol also supports multiplexing by incorporating a quenching buffer between the different staining colours. Finally, the protocol demonstrates its applicability to CTCs and EVs derived from plasma samples of GBM patients, with easy adaptation to other cancers or proteins of interest.

Measuring virus in biofluids is complicated by confounding biomolecules coisolated with viral nucleic acids. To address this, we developed an affinity-based microfluidic device for specific capture of intact severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Our approach used an engineered angiotensin-converting enzyme 2 to capture intact virus from plasma and other complex biofluids. Our device leverages a staggered herringbone pattern, nanoparticle surface coating, and processing conditions to achieve detection of as few as 3 viral copies per milliliter. We further validated our microfluidic assay on 103 plasma, 36 saliva, and 29 stool samples collected from unique patients with COVID-19, showing SARS-CoV-2 detection in 72% of plasma samples. Longitudinal monitoring in the plasma revealed our device’s capacity for ultrasensitive detection of active viral infections over time. Our technology can be adapted to target other viruses using relevant cell entry molecules for affinity capture. This versatility underscores the potential for widespread application in viral load monitoring and disease management.

Background: Vascular cell adhesion molecule-1 (VCAM-1+) endothelial cell-derived extracellular vesicles (EC-EVs) are augmented in cardiovascular disease, where they can signal the deployment of immune cells from the splenic reserve. Endothelial cells in culture activated with pro-inflammatory tumor necrosis factor-α (TNF-a) also release VCAM-1+ EC-EVs. However, isolating VCAM-1+ EC-EVs from conditioned cell culture media for subsequent in-depth analysis remains challenging. Aim: We utilized the extracellular vesicles (EV) microfluidics herringbone chip (EVHB-Chip), coated with anti-VCAM-1 antibodies, for selective capture of VCAM-1+ cells and EC-EVs. Methods and Results: Engineered EA.hy926 endothelial cells overexpressing VCAM-1 (P < 0.001 versus control) showed increased binding to the VCAM-1- EVHB-Chip versus an IgG device. TNF-α-stimulated human umbilical cord vein endothelial cells (HUVECs) exhibited elevated VCAM-1 protein levels (P < 0.001) and preferential binding to the VCAM-1- EVHB-Chip versus the IgG device. HUVECs stimulated with TNF-α showed differential gene expression of intercellular adhesion molecule-1 (ICAM-1) (P < 0.001) and VCAM-1 (P < 0.001) by digital droplet PCR versus control cells. HUVEC-derived EC-EVs were positive for CD9, CD63, HSP70, and ALIX and had a modal size of 83.5 nm. Control and TNF-α-stimulated HUVEC-derived EC-EV cultures were captured on the VCAM-1- EVHB-Chip, demonstrating selective capture. VCAM-1+ EC-EV were significantly enriched for ICAM-1 (P < 0.001) mRNA transcripts. Conclusion: This study presents a novel approach using the EVHB-Chip, coated with anti-VCAM-1 antibodies and digital droplet PCR for the study of VCAM-1+ EC-EVs. Isolation of VCAM-1+ EC-EV from heterogeneous sources such as conditioned cell culture media holds promise for subsequent detailed characterization, and may facilitate the study of VCAM-1+ EC-EVs in cardiovascular and metabolic diseases, for disease monitoring and therapeutic insights.

Supplementary Tables 1 and 2, Figures S1-16. Supplementary Table 1: Gene lists from DAVID analysis of genes downregulated in RKIP derived TAMs with a Benjamini p-value < 0.5 Supplementary Table 2: Gene lists from DAVID analysis of genes upregulated in RKIP+CCRL5 derived (rescue) TAMs with a Benjamini p-value < 0.5 Figure S1: Immunoblot validation of RKIP expression in 1833 (BM1), MDA-MB-436, and 4T1.2 cells Figure S2: A schematic describing the method used for RNAseq analysis to compare metastatic BM1 with non-metastatic BM1+RKIP Figure S3: Tumor growth in orthotopic xenograft BM1 tumors, significance compared using a 2-way ANOVA. Figure S4: GO categories enriched in BM1+RKIP tumors from RNAseq analysis. Figure S5: Quantile-quantile plots for all stromal cell types tested between metastatic BM1 and non-metastatic BM1+RKIP tumors. Figure S6: Relative TAM infiltration in MDA-MD-436 tumors determined by %pos staining cells for F4/80. Figure S7: Flow cytometric analysis to determine the purity and heterogeneity of BM1 isolated TAMs. Figure S8: CCL5 levels measured by ELISA from BM1 cells in culture. Figure S9: CCL5 expression by qRT-PCR of MDA-MD-436 and 4T1.2 overexpressing RKIP. Figure S10?: RKIP and CCL5 immunoblotts from 1833 (BM1) tumors overexpressing the vectors shown. Figure S11: Tumor growth, tumor weight, and correlation between tumor weight and TAM infiltration in BM1 tumors treated with the CCR5 inhibitor Maraviroc. Figure S12: Invasion assay for BM1 cells overexpressing RKIP, CCL5, or both. Figure S13: Images of Raybiotech L308 arrays. Figure S14: Gene expression data of TAM secreted factors in human patient data sets. Figure S15: Correlation between CCL5 and TAM secreted factors in human patient data sets. Figure S16: Heatmap identifying data sets where breast cancer metastasis free survival is significantly stratified by classifier

Extracellular vesicles (EVs) are small, lipid-bilayer-bound particles released by cells that can contain important bioactive molecules, including lipids, RNAs, and proteins. Once released in the extracellular environment, EVs can act as messengers locally as well as to distant tissues to coordinate tissue homeostasis and systemic responses. There is a growing interest in not only understanding the physiology of EVs as signaling particles but also leveraging them as minimally invasive diagnostic and prognostic biomarkers (e.g., they can be found in biofluids) and drug-delivery vehicles. On October 30-November 2, 2022, researchers in the EV field convened for the Keystone symposium "Exosomes, Microvesicles, and Other Extracellular Vesicles" to discuss developing standardized language and methodology, new data on the basic biology of EVs and potential clinical utility, as well as novel technologies to isolate and characterize EVs.

Microfluidic devices have been used for decades to isolate cells, viruses, and proteins using on-chip immunoaffinity capture using biotinylated antibodies, proteins, or aptamers. To accomplish this, the inner surface is modified to present binding moieties for the desired analyte. While this approach is successful in research settings, it is challenging to scale many surface modification strategies. Traditional polydimethylsiloxane (PDMS) devices can be effectively functionalized using silane-based methods; however, it requires high labor hours, equipment, and hazardous chemicals. Manufacture of microfluidic devices using plastics, including cyclic olefin copolymer (COC), allows chips to be mass produced, but most functionalization methods used with PDMS are not compatible with plastic. Herein, this work demonstrates how to deposit biotin onto the surface of a plastic microfluidic chips using aryl-diazonium. This method chemically bonds biotin to the surface, allowing for the addition of streptavidin nanoparticles to the surface. Nanoparticles increase the surface area of the chip and allow for proper capture moiety orientation. This process is faster, can be performed outside of a fume hood, is very cost-effective using readily available laboratory equipment, and demonstrates higher rates of capture. Additionally, this method allows for more rapid and scalable production of devices, including for diagnostic testing.

Aberrant expression of viral-like repeat elements is a common feature of epithelial cancers, and the substantial diversity of repeat species provides a distinct view of the cancer transcriptome. Repeatome profiling across ovarian, pancreatic, and colorectal cell lines identifies distinct clustering independent of tissue origin that is seen with coding gene analysis. Deeper analysis of ovarian cancer cell lines demonstrated that human satellite II (HSATII) satellite repeat expression was highly associated with epithelial-mesenchymal transition (EMT) and anticorrelated with IFN-response genes indicative of a more aggressive phenotype. SATII expression — and its correlation with EMT and anticorrelation with IFN-response genes — was also found in ovarian cancer RNA-Seq data and was associated with significantly shorter survival in a second independent cohort of patients with ovarian cancer. Repeat RNAs were enriched in tumor-derived extracellular vesicles capable of stimulating monocyte-derived macrophages, demonstrating a mechanism that alters the tumor microenvironment with these viral-like sequences. Targeting of HSATII with antisense locked nucleic acids stimulated IFN response and induced MHC I expression in ovarian cancer cell lines, highlighting a potential strategy of modulating the repeatome to reestablish antitumor cell immune surveillance.

Purpose: To understand how tumor cells alter macrophage biology once they are recruited to triple-negative breast cancer (TNBC) tumors by CCL5. Method: Mouse bone marrow derived macrophage (BMDMs) were isolated and treated with recombinant CCL5 protein alone, with tumor cell conditioned media, or with tumor extracellular vesicles (EVs). Media from these tumor EV-educated macrophages (TEMs) was then used to determine how these macrophages affect TNBC invasion. To understand the mechanism, we assayed the cytokine secretion from these macrophages to determine how they impact tumor cell invasion. Tumor CCL5 expression was varied in tumors to determine its role in regulating macrophage biology through EVs. Results: Tumor EVs are a necessary component for programming naïve macrophages toward a pro-metastatic phenotype. CCL5 expression in the tumor cells regulates both EV biogenesis/secretion/cargo and macrophage EV-education toward a pro-metastatic phenotype. Analysis of the tumor EV-educated macrophages (TEMs) showed secretion of a variety of factors including CXCL1, CTLA-4, IFNG, OPN, HGF, TGFB, and CCL19 capable of remodeling the surrounding tumor stroma and immune infiltrate. Injection of tumor cells with macrophages educated by metastatic tumor cell EVs into mice increased tumor metastasis to the lung. Conclusion: These results demonstrate that tumor-derived EVs are key mediators of macrophage education and likely play a more complex role in modulating tumor therapeutic response by regulating the tumor immune infiltrate.

Extracellular vesicles (EVs) have emerged as promising candidates in biomarker discovery and diagnostics. Protected by the lipid bilayer, the molecular content of EVs in diverse biofluids are protected from RNases and proteases in the surrounding environment that may rapidly degrade targets of interests. Nonetheless, cryopreservation of EV-containing samples to -80°C may expose the lipid bilayer to physical and biological stressors which may result in cryoinjury and contribute to changes in EV yield, function, or molecular cargo. In the present work, we systematically evaluate the effect of cryopreservation at -80°C for a relatively short duration of storage (up to 12 days) on plasma- and media-derived EV particle count and/or RNA yield/quality, as compared to paired fresh controls. On average, we found that the plasma-derived EV concentration of stored samples decreased to 23% of fresh samples. Further, this significant decrease in EV particle count was matched with a corresponding significant decrease in RNA yield whereby plasma-derived stored samples contained only 47–52% of the total RNA from fresh samples, depending on the extraction method used. Similarly, media-derived EVs showed a statistically significant decrease in RNA yield whereby stored samples were 58% of the total RNA from fresh samples. In contrast, we did not obtain clear evidence of decreased RNA quality through analysis of RNA traces. These results suggest that samples stored for up to 12 days can indeed produce high-quality RNA; however, we note that when directly comparing fresh versus cryopreserved samples without cryoprotective agents there are significant losses in total RNA. Finally, we demonstrate that the addition of the commonly used cryoprotectant agent, DMSO, alongside greater control of the rate of cooling/warming, can rescue EVs from damaging ice formation and improve RNA yield.

Circulating tumor cell (CTC)-based liquid biopsies provide unique opportunities for cancer diagnostics, treatment selection, and response monitoring, but even with advanced microfluidic technologies for rare cell detection the very low number of CTCs in standard 10-mL peripheral blood samples limits their clinical utility. Clinical leukapheresis can concentrate mononuclear cells from almost the entire blood volume, but such large numbers and concentrations of cells are incompatible with current rare cell enrichment technologies. Here, we describe an ultrahigh-throughput microfluidic chip, LPCTC-iChip, that rapidly sorts through an entire leukapheresis product of over 6 billion nucleated cells, increasing CTC isolation capacity by two orders of magnitude (86% recovery with 105 enrichment). Using soft iron-filled channels to act as magnetic microlenses, we intensify the field gradient within sorting channels. Increasing magnetic fields applied to inertially focused streams of cells effectively deplete massive numbers of magnetically labeled leukocytes within microfluidic channels. The negative depletion of antibody-tagged leukocytes enables isolation of potentially viable CTCs without bias for expression of specific tumor epitopes, making this platform applicable to all solid tumors. Thus, the initial enrichment by routine leukapheresis of mononuclear cells from very large blood volumes, followed by rapid flow, high-gradient magnetic sorting of untagged CTCs, provides a technology for noninvasive isolation of cancer cells in sufficient numbers for multiple clinical and experimental applications.

Mitochondrial metabolism is an attractive target for cancer therapy 1 , 2 . Reprogramming metabolic pathways could improve the ability of metabolic inhibitors to suppress cancers with limited treatment options, such as triple-negative breast cancer (TNBC) 1 , 3 . Here we show that BTB and CNC homology1 (BACH1) 4 , a haem-binding transcription factor that is increased in expression in tumours from patients with TNBC, targets mitochondrial metabolism. BACH1 decreases glucose utilization in the tricarboxylic acid cycle and negatively regulates transcription of electron transport chain (ETC) genes. BACH1 depletion by shRNA or degradation by hemin sensitizes cells to ETC inhibitors such as metformin 5 , 6 , suppressing growth of both cell line and patient-derived tumour xenografts. Expression of a haem-resistant BACH1 mutant in cells that express a short hairpin RNA for BACH1 rescues the BACH1 phenotype and restores metformin resistance in hemin-treated cells and tumours 7 . Finally, BACH1 gene expression inversely correlates with ETC gene expression in tumours from patients with breast cancer and in other tumour types, which highlights the clinical relevance of our findings. This study demonstrates that mitochondrial metabolism can be exploited by targeting BACH1 to sensitize breast cancer and potentially other tumour tissues to mitochondrial inhibitors.

Oxidative phosphorylation is an attractive target for cancer therapy. Reprogramming metabolic pathways by promoting oxidative phosphorylation could improve the ability of metabolic inhibitors to suppress cancers with limited treatment options like triple negative breast cancer (TNBC). Here we show that BACH1, a heme-binding transcription factor whose expression is enriched in patients with TNBC, inhibits oxidative phosphorylation through direct transcriptional regulation of electron transport chain (ETC) gene expression. Treatment of cells with hemin, which induces BACH1 degradation, mimics BACH1 depletion with shRNA. Pretreatment of TNBC tumors with BACH1 shRNA or hemin overcame resistance to metformin, an anti-diabetic drug, and abolished the growth of both cell line and patient-derived tumor xenografts. BACH1 gene expression inversely correlated with ETC gene expression in breast cancer patients as well as other tumor types, highlighting the clinical relevance. This study demonstrates that oxidative phosphorylation represents an Achilles heel that can be exploited through targeting BACH1 to sensitize breast cancer and potentially other tumor tissues to mitochondrial inhibitors. Citation Format: Jiyoung Lee, Ali Yesilkanal, Casey Frankenberger, Mohamad Elbaz, Daniel Rabe, Jielin Yan, Felicia Rustandy, Peter Hart, Christie Kang, Elizabeth Grossman, Jason Locasale, Daniel Nomura, Marcelo Bonini, Marsha Rosner. Effective combination therapy for breast cancer targeting BACH1 and mitochondrial metabolism [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 5497.

Abstract Clear cell renal cell carcinoma (ccRCC) is the most prevalent form of kidney cancer and is frequently associated with loss of von Hippel Lindau (VHL) gene function, resulting in the aberrant accumulation of the hypoxia inducible factor-alpha subunit (HIF-α), which contributes to tumor growth, angiogenesis, and metastasis. Recent studies suggest that this normoxic stabilization of HIF-1α is not sufficient to reproduce tumorigenesis, and HIF-1α is thought to act as a tumor suppressor in ccRCC. Conversely, HIF-2α acts as an oncogene, turning on transcription of a large number of HIF-regulated genes, and upregulation of HIF-2α is often associated with poor prognosis. To this end, two HIF-2α selective inhibitors are currently in clinical trials for RCC. To isolate additional HIF-2α selective compounds for use as research tools and drug development leads, a cell-based high-throughput screen (HTS) of the NCI Natural Products Repository was performed. Stably transformed clones of the human ccRCC-derived cell line 786-0 expressing a luciferase reporter construct downstream of the human vascular endothelial growth factor (VEGF) gene promoter were used to identify natural product samples with inhibitory activity and minimal cellular toxicity. HTS leads were chromatographically separated into component structures yielding ~40 pure compounds with micromolar or submicromolar IC50 values, >80% inhibition, and <10% cell toxicity. These hits were then screened for their ability to inhibit VEGF-A protein secretion by VHL- and HIF1A-negative 786-0 cells, and several compounds showed >90% inhibition of VEGF secretion at micromolar doses under normoxic conditions. Patterns of mRNA expression of HIF-1α, HIF-2α, and several HIF target genes in cell lines engineered to express either HIF alone or both were studied to help identify HIF-2α-selective inhibitors. Several lead compounds reduced VEGF transcription and secretion, and downregulated HIF-2α target genes. To further characterize the HTS leads, ICM-Pro protein/small-molecule docking software was used to dock the ligands of interest to high-resolution HIF-2α and HIF-1α 3D structures. The HIF-2α selective inhibitor currently undergoing clinical investigation, PT2385, has been found to bind directly to a hydrophobic pocket of the HIF-2α:ARNT dimerization. Using the PT2385 binding mode as a benchmark, docking studies of the HTS leads were performed and the results have been linked to empirical data in an effort to explain selectivity for HIF-2α over HIF-1α, reveal key favorable interactions between the protein and ligand, define mode of action, and aid in future drug development studies. Citation Format: Molly M. Lee, Daniel C. Rabe, Tawnya C. McKee, Girma M. Woldemichael, James R. Vasselli, James B. McMahon, W. Marston Linehan, Donald P. Bottaro. The identification and development of selective natural product inhibitors of hypoxia inducible factor-2α for the treatment of renal cell carcinoma [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A127.

Abstract Metastatic progression of tumors is the major cause of death in patients with triple-negative breast cancer (TNBC). However, since metastasis is a multistep process, unraveling its complexity is a major challenge. One effective way of tackling this question is to study natural blockers of the metastatic process, metastasis suppressors, and identify the mechanisms by which they regulate metastasis. Raf kinase inhibitory protein (RKIP), a protein that regulates kinase activity, is a suppressor of TNBC metastasis. Although RKIP inhibits the activity of key kinases such as Raf-1, GRK2, NIK/IKK in cultured cells, the kinase targets of RKIP in tumors are not known. To address this question, we used a mass spectrometry approach involving inhibitor-conjugated beads to identify kinases that are downregulated by RKIP in human TNBC xenograft tumors. Our results identified a network of stress kinases targeted by RKIP, including kinases that have not been previously reported as RKIP targets. In order to unravel the effect of this stress network on metastatic gene expression, we investigated genes that correlate with RKIP expression in TCGA breast cancer patient data set. We identified prometastatic genes such as APC and DOCK4 as novel RKIP targets in in vitro and in vivo models of TNBC. We also demonstrated these genes are downstream of the RKIP-stress network. Finally, by using a high-throughput invasion assay, we developed a low-dose multidrug cocktail of small-molecule kinase inhibitors that mimic RKIP's antimetastatic role in TNBCs. Elucidating RKIP function at a systems level reveals the interplay between key metastatic signaling cascades, particularly in relation to cell motility and invasion. Our findings suggest that the low-dose multidrug combination that targets a network of stress kinases is a viable antimetastatic therapy for TNBC patients. Citation Format: Ali Ekrem Yesilkanal, Daniel C. Rabe, Payal Tiwari, Casey Frankenberger, Gary L. Johnson, Marsha Rosner. A novel approach for antimetastatic therapies against TNBC utilizing a physiologic suppressor [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 4179.

Summary Triple-negative breast cancers (TNBC) are highly infiltrated by tumor-associated macrophages (TAMs) that promote tumor growth, survival, metastasis and therapeutic resistance. Although cytokines such as CCL5 have been implicated in TAM recruitment to TNBC tumors, the mechanism by which tumor cells educate TAMs is not understood. Here we show that tumor EVs are both necessary and sufficient for programming TAMs toward a pro-metastatic phenotype. The mechanism involves CCL5 regulation of tumor extracellular vesicles (EVs), which activate TLR2 and TLR3, leading to secretion of a common set of cytokines that further stimulate tumor cell invasion and metastasis as well as alter the tumor microenvironment. Cytokine expression is significantly correlated to CCL5 expression and up-regulated in TNBC patient tumors. These results demonstrate for the first time that tumor EVs are key mediators of TAM education, phenocopy the pro-metastatic and drug resistant state of the tumors to TAMs, and illustrate the potential clinical relevance of these findings to TNBC patients. Highlights Tumor extracellular vesicles (EVs) are required for pro-metastatic programming of tumor-associated macrophages (TAMs) Tumor CCL5 and macrophage TLR signaling mediate tumor EV programming of TAMs in TNBCs Tumor EVs mediate drug resistance in TAMs and alter recruitment of regulatory T-cells. Cytokines expressed by EV-educated TAMs are enriched and correlate with CCL5 in human TNBC patients. eTOC Chemokines such as CCL5 recruit tumor-associated macrophages (TAMs) that are required for metastasis, but TAM programming is not understood. Rabe et al. show that tumor extracellular vesicles (EVs) are required for programming TAMs via Toll-like Receptors (TLRs) to phenocopy the tumor, rewire the microenvironment, drive metastasis and promote immune cell evasion.

Abstract Metastatic progression of tumors is the major cause of death in patients with triple negative breast cancer (TNBC), the most aggressive subtype of breast cancer. However, since metastasis is a multi-step process, unraveling its complexity is a major challenge. One effective way of tackling this question is to study natural blockers of the metastatic process, metastasis suppressors, and identify the mechanisms by which they regulate metastasis. Raf kinase inhibitory protein (RKIP), a protein that regulates kinase activity, is a suppressor of TNBC metastasis. Although RKIP inhibits the activity of key kinases such as Raf-1, GRK2, NIK/IKK in cultured cells, the kinase targets of RKIP in tumors are not known. To address this question, we used a mass spectrometry approach involving inhibitor-conjugated beads to identify kinases that are down-regulated by RKIP in human TNBC xenograft tumors. Our results identified novel targets of RKIP whose kinase activity is either down-regulated or up-regulated by RKIP. We used bioinformatics analysis to build RKIP-regulated signaling networks based upon RKIP-induced changes in kinase activity and related gene expression. Elucidating RKIP function at a systems level reveals the interplay between key metastatic signaling cascades, particularly in relation to cell migration and invasion, and can potentially identify novel anti-metastatic target combinations in TNBCs. Citation Format: Ali E. Yesilkanal, Casey Frankenberger, Daniel C. Rabe, Gary L. Johnson, Marsha Rosner. Elucidating metastatic signaling networks in TNBC by investigating RKIP-regulated kinome. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1620.

ObjectiveTo measure Met protein content in prostate biopsies guided by fused magnetic resonance and ultrasound imaging, and to measure soluble Met (sMet) protein concentration in plasma samples from patients presenting evidence of prostate cancer.Patients and Methods345 patients had plasma samples drawn prior to image-guided biopsy of the prostate. Of these, 32% had benign biopsies. Of the 236 that were positive for prostate adenocarcinoma (PCa), 132 treated by total prostatectomy had Gleason scores of 6 (17%), 7, (55%), 8 (16%), or 9-10 (12%). 23% had evidence of local invasion. Plasma samples were also obtained from 80 healthy volunteers. Tissue Met and plasma sMet were measured by two-site immunoassay; values were compared among clinically defined groups using non-parametric statistical tests to determine significant differences or correlations.ResultsPCa tumor Met correlated significantly with plasma sMet, but median values were similar among benign and malignant groups. Median plasma sMet values were also similar among those groups, although both medians were significantly above normal. Median Met content in primary PCa tumors and sMet concentrations were independent of Gleason score, final pathologic stage and age.ConclusionPlasma sMet is not predictive of PCa or its severity in patients with organ-confined or locally invasive disease. Quantitative analysis of Met protein content and activation state in PCa tumor biopsy samples was highly feasible and may have value in follow-up to genomic and/or transcriptomic-based screens that show evidence of oncogenically relevant MET gene features that occur at relatively low frequency in non-metastatic PCa.