Abstract 1: Interaction of prostate cancer cells with tumor microenvironment promotes EMT and DTCs activation

Abstract Metastasis causes high mortality in malignancies, which includes prostate cancer (PCa), breast cancer, lung cancer and other cancer types. PCa cells, for example, frequently metastasize to bone resulting in a mixture of osteoblastic and osteolytic lesions. There are currently no effective treatments proven to cure PCa skeletal metastases. Accumulating data has suggested that cancer cells undergo epithelial-to-mesenchymal transition (EMT) to initiate tumor progression. Recent evidence has addressed a link between EMT and activation of disseminated tumor cells (DTCs) that are located in bone marrow and called “sleeping cells” when they are inactive state. However, there is lack of studies regarding direct evidence of localized PCa cells occurring EMT and DTCs activation when tumor cells interact with microenvironment. In this study, we first generated luciferase labeled PCa cells (PC3-luc and C4-2B-luc), and implanted the cells subcutaneously into nude mice. Tumor growth was monitored by in vivo bioluminescense imaging and tumor volume was measured twice a week. We found that tumor volumes were at heterogeneous levels. Then, the tumors were removed, exercised, and digested ex vivo to generate single cell suspension (we named the cells as PC3-lucsc and C4-2B-lucsc), and the cells were subcutaneously re-injected into nude mice. We observed those cells grew faster than that of parental cells and enhanced neo-vessel formation. We compared the differences of gene and protein expressions between PC3-lucand PC3-lucsc cells and found that hallmarkers of EMT, for example vimentin, slug and ZEB2 were expressed at higher levels in PC3-lucsc compared to PC3-luccells. Accordingly, production of E-cadherin and β-catenin was significantly decreased in PC3-lucsc cells. Angiogenesis markers, including VEGFR2, VEGFR3, MCP-3, MCP-4, I-TAC, I309, uPAR, GCP-2 and GROα, were also increased in PC3-lucsc cells using antibody array. Interestingly, CCL2 was significantly increased in PC3-lucsc cells comparing to the parental cells. We finally flushed out bone marrow and we were able to detect DTCs by RT-PCR and successfully isolated DTCs by Magnetic Activated Cell Sorting (MACS), in addition to confirmation of DTCs by immunohistochemical staining. This is the first report showing that interaction of PCa cells with tumor microenvironment promotes EMT and DTCs activation. The current study may provide potential therapeutic targets and diagnostic markers in PCa progression. Supported by NSF projects 81171993 and 81272415; NSF key project 81130046. Citation Format: Junlin Shi, Yudui Xia, Qiong Song, Xiaolin Zhou, Atsushi Mizokami, Evan Keller, Jian Zhang, Yi Lu. Interaction of prostate cancer cells with tumor microenvironment promotes EMT and DTCs activation. abstract. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1. doi:10.1158/1538-7445.AM2014-1