The tumor microenvironment of prostate cancer (PCa) plays an important role in disease progression, responsiveness to therapy, or inversely restraint of tumor growth. PCa cell evolution including loss of androgen receptor dependency is associated with intratumor heterogeneity, generating progressive PCa cell subclones. The tumor stroma of PCa contains multiple functionally different populations of fibroblasts that regulate PCa cell progression, e.g., cancer-promoting or cancer-restraining. Fibroblasts secret a number of growth factors, cytokines, the ECM molecules, and miRNAs in a cellular characteristic-specific manner. Thus, we hypothesize that diversity of fibroblasts may induce heterogenous PCa cell progression. To investigate the heterotypical communications between PCa cells and fibroblasts, we used 3 subclones of androgen-sensitive LNCaP cells and 4 patient-derived fibroblasts. Androgen-low-sensitive E9 and F10 cells were obtained from the parental androgen-sensitive LNCaP cell population through use of a limiting dilution method in regular culture condition. In contrast, androgen-insensitive AIDL cells were established from LNCaP cells by continuous passaging under hormone-depleted condition. Commercially available normal human prostate stromal cells (PrSC) was purchased from Lonza Group Ltd. Three original fibroblasts pcPrFs (-M5, -M28, -M31) were isolated from needle biopsy samples of patients with advanced PCa. To examine the effects of fibroblasts on cancer-related gene expression in PCa cells, in vitro co-culture experiment was performed using cell culture insert. In all PCa cells, LNCaP and its subclones, expressions of NFKB1, SRC, and MYC mRNA were not dramatically changed by co-culturing with 3 PCa patient-derived fibroblasts. Only in LNCaP cells, however, they were uniformly down-regulated by co-culturing with PrSC. Only in LNCaP cells, expression of CDH2 mRNA was up-regulated by co-culturing with pcPrF-M5 and pcPrF-M28. In all PCa cells, expression of NKX3-1 mRNA was uniformly up-regulated by co-culturing with pcPrF-M28 and pcPrF-M31. In LNCaP, E9, and F10 cells but not in AIDL cells, expression of GSTP1 mRNA was uniformly up-regulated by co-culturing with pcPrF-M31. Cell growth of LNCaP cells was not remarkably affected by co-culturing with pcPrF-M28 and pcPrF-M31. The heterogeneous stromal compartment in PCa tissues contains multiple functionally different populations of fibroblasts that are also associated with intratumor heterogeneity. Our data showed that up-regulations of NKX3-1 and GSTP1 mRNA expression by co-culturing with pcPrF-M28 and pcPrF-M31 were commonly observed in LNCaP subclones differing in androgen sensitivity. This result suggests that certain fibroblasts may restrain PCa cell progression by up-regulations of tumor suppressor gene expression even in progressive poorly differentiated PCa cells.

Citation Format: Kenichiro Ishii, Chise Matsuda, Yasuhisa Nakagawa, Taku Shirai, Yoshifumi Hirokawa, Takeshi Sasaki, Kazuhiro Iguchi, Masatoshi Watanabe. Progressive prostate cancer LNCaP subclones partially retain regressive communications with patient-derived fibroblasts [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 3163.