Abstract 4344: Cd146 modulates the malignant phenotype in human prostate cancer

Abstract

Abstract Prostate Cancer (PCa) is the most frequent cancer in males and the second leading cause of death from cancer in men. When PCa progress from androgen-responsive to castration resistance, the formation of incurable metastases, mainly in the bone, is almost inevitable. Therefore, understanding the factors that regulate homing and survival of metastatic cancer cells in the bone is important for the identification of new therapeutic targets. High CD146 expression has been measured in the stroma of lytic and blastic lesions in preclinical models of PCa bone metastasis. The objective of this study is to characterize the role of CD146 in the maintenance of the aggressive and invasive phenotype in human PCa. We used shRNAs to knockdown the expression of CD146 in the lytic PC-3M-Pro4Luc2dTomato and in the blastic C4-2BdTomato PCa cell lines. We validated the knockdown at protein level and tested the effect with functional assays such as migration, proliferation. We used RT-qPCR to test CD146 knockdown on EMT markers. We measured the effect of the knockdown on the maintenance of cancer stem/progenitor-like cells by ALDEFLUOR assay. CD146 knockdown reduced proliferation in PC-3M-Pro4Luc2dTomato PCa cells and resulted in increased E-Cadherin expression. Conversely, no effect on proliferation was measured on C4-2BdTomato cells. It has been described that metastatic human PCa cells target the hematopoietic stem cell (HSC) niche in the bone marrow at the level of an “endosteal/osteoblast” niche and a “vascular/perivascular” niche. We optimized an in vitro model of “osteoblast niche” to study the behavior of prostate cancer cells upon co-culture with osteoblasts and to measure the resulting effects on cancer stem/progenitor-like markers. Our results showed that CD146 is required for the osteoblast-mediated induction of ALDH activity on PCa cells and CD146 knockdown prevented the increase in the size of the ALDHhigh subpopulation in the tumor cells, mediated by human osteoblasts. Additionally, CD146 knockdown in PCa cells co-cultured with osteoblast, reduced the amount of CD146 expressed by osteoblasts compared to non-targeted control. Finally, we showed that CD146 is significantly increased in the highly metastatic ALDHhigh cells and identified a new subset of ALDHhigh / CD146high cells which could be depleted upon CD146 knockdown. In Conclusion, we detected a novel subset of ALDHhigh/CD146high cells and found that CD146 influences the maintenance of an aggressive-mesenchymal phenotype in human PCa. Therefore, CD146 represents a promising molecule to modulate the behavior of aggressive PCa cells. Note: This abstract was not presented at the meeting. Citation Format: Eugenio Zoni, Letizia Astrologo, Janine Melsen, Sofia Karkampouna, Irena Klima, Joël Grosjean, Peter C. Gray, Gabri van der Pluijm, Marco G. Cecchini, Marianna Kruithof-de Julio, George N. Thalmann. Cd146 modulates the malignant phenotype in human prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4344. doi:10.1158/1538-7445.AM2017-4344