Tumor-stroma interaction in a “vicious cycle” manner promotes prostate cancer progression

1031 Reciprocal interactions between prostate cancer and stromal cells permanently altered genotypes and behaviors of human prostate cancer cells in vivo or in vitro. The purposes of this study are: 1) to determine cellular interaction between prostate cancer and prostate or bone stromal cells induce reciprocal changes and promote cancer progression in a “vicious cycle” manner; and 2) to validate genes of tumor-associated stroma after co-culture that may be mimicked clinical specimens by LCM or stromal fibroblasts from malignant human prostate gland. Osteosarcoma cell line, MG63, was co-cultured under 3-D rotary wall vessel (RWV) with LNCaP or its lineage-derived androgen-independent C4-2 cell. The differentially regulated genes in MG63 after co-culture with LNCaP (MGLN) or C4-2 (MGC4-2) were compared with stromal fibroblasts harvested from benign (Pt-N) and malignant (Pt-C) portions of the prostate gland from a patient. In addition, we also conducted comparative studies on chromosome, gene expression and behavioral of these stromal fibroblasts as well as induce prostate cancer growth in athymic mice and validation of the gene expression by microarray and qRT-PCR. Cytogenetic analysis showed non-random permanent genetic changes occurred in MGLN and MGC4-2 compared to its parental MG63 cells (MGRWV). Gross morphology and growth rate differences were also observed in MGC4-2. Co-inoculation of MGC4-2 with C4-2Luc (stably tagged with luciferase) cells in vivo resulted in over 10-fold stimulated growth of C4-2 tumors, increased angiogenesis and serum PSA than MGLN. Remarkably, the behaviorally altered MGC4-2 mimicked the Pt-C but not Pt-N. In five of the mice no tumor was readily detectable in Pt-N/ C4-2Luc and the average serum PSA concentration was 2.1 ng/ml. However, all mice inoculated with Pt-C/ C4-2Luc formed tumors with an average PSA concentration of 466.5 ng/ ml. Relative luciferase activity (RLU) of the tissue specimens inoculated with Pt-C/ C4-2Luc and Pt-N/ C4-2Luc chimera was 78,470 and 193 RLU, respectively. Gene expression profiles among MG63, MGLN and MGC4-2 revealed overexpression of the extracellular matrix proteins versican, tenascin, osteonectin and pro-collagen 1, in MGC4-2 compared to MGRWV. In addition, microarray and qRT-PCR confirmed following genes to be overexpressed, cellular retinoic acid binding protein 2 and keratin 18 and the other genes to be underexpressed, proliferation-associated 2G4 and a selenium binding protein 1, IGFBP7 and IL8, in Pt-C and MGC4-2 when compared to Pt-N and MGLN. We demonstrated the plasticity of prostate cancer as well as bone stromal cells which are subjected to modification, both genetically and phenotypically, after cellular interaction in vitro under 3-D and as chimeric tumors in vivo. We propose the interaction between tumor and stroma creates a “vicious cycle” ultimately leads to increased prostate cancer growth, invasion and metastasis.