OBJECTIVETo investigate the effect of infiltrating mast cells on neuroendocrine differentiation (NED) and docetaxel sensitivity of prostate cancer (PCa) cells in vitro.

METHODSHuman PCa cell lines (LNCaP and C4-2) were co-cultured with human mast cell line (HMC-1) in Transwell chambers. Androgen receptor (AR) was silenced in C4-2 cells using sh-AR lentivirus, and p21 was knocked down and overexpressed by transfecting C4-2 cells with pLKO.1-sh-p21 and pCMV-p21, respectively. The morphological changes of LNCaP and C4-2 cells were observed. MTT assay and colony formation assay were used to assess the proliferation of LNCaP and C4-2 cells. CCK8 assay was used to detect the cell viability of C4-2 cells following docetaxel trreatment. RT-qPCR and Western blotting were performed to determine the mRNA and protein expressions of neuroendocrine markers, AR and p21 in the cells.

RESULTSCo-culture with HMC-1 cells enhanced the neuroendocrine phenotypes, inhibited the proliferation and up-regulated the expression of p21 in LNCaP and C4-2 cells. P21 positively regulated NED through a non-AR-dependent signaling pathway, while p21 knockdown partially reversed NED promoted by the mast cells. PCa cells co-cultured with HMC-1 cells showed increased resistance to docetaxel, and silencing p21 partially reversed docetaxel resistance in PCa cells.

CONCLUSIONInfiltrating mast cells up-regulates p21 to promote NED and increase docetaxel resistance in PCa cells in vitro.