Growth hormone affects gene expression and proliferation in human prostate cancer cells

Summary We previously showed that growth hormone (GH) receptors (GHR) are expressed in the most commonly studied human prostate cancer (PCa) cell lines and that GHR isoforms undergo differential, cell‐type‐specific hormonal regulation. We now report that human GH (hGH) can stimulate/modulate insulin‐like growth factor (IGF) and β‐oestradiol (E2) receptor (ERβ) gene expressions in these cells and interact with IGF‐I and E2 to stimulate androgen‐dependent LNCaP cell proliferation. We observed a cell type‐dependent, differential regulation of IGF axis gene expression by GH: IGF‐I was stimulated in the androgen‐dependent LNCaP cells; IGF‐II was stimulated in androgen‐insensitive (AI) PC3 cells; the IGF‐I cognate receptor, IGF‐IR, was stimulated in LNCaP cells, but inhibited in PC3 cells; IGF‐IIR was stimulated in both LNCaP and PC3 cells. GH also stimulated ERβ gene expression in LNCaP and PC3 cells, but had little or no effect on any of those genes in AI DU145 cells. The potent androgen analogue, mibolerone, also stimulated IGF‐I, IGF‐IR and ERβ, but reduced IGF‐IIR mRNAs in LNCaP cells. Furthermore, triiodothyronine (T3) and E2 also stimulated the expression of those four genes in LNCaP cells, but co‐administration of GH had almost no effect. Finally, we also studied the effects of GH, IGF‐I and E2, alone or in combination, on LNCaP cell proliferation. Importantly, we demonstrated, for the first time, that although GH and IGF‐I alone had no effect on LNCaP cell proliferation, concomitant administration for 96 h revealed a permissive role of GH on IGF‐I‐induced proliferation. GH also appeared to exert a synergistic effect on E2‐stimulated LNCaP cell proliferation. Taken together, these findings indicate that GH via GHRs, most likely in concert with gonadal steroids, T3, IGF system axis and probably other hormones and growth factors, potentially plays an important role in the mechanisms underlying tumour cell growth in PCa.