De novo steroidogenesis in prostate cancer cells is increased by insulin-like growth factor II. (#204)
Insulin-like growth factor II (IGF II) has been postulated to increase growth and aggressiveness of many cancers, including prostate cancer (CaP). We investigated the role of IGF II in de novo steroidogenesis in prostate cancer cells, a major pathway for reactivation of androgen pathways and CaP progression. IGF II but not IGF II receptor mRNA expression was increased in patient samples during progression to castrate resistant prostate cancer (CRPC), as was immunoreactivity to insulin receptor (INSR) and IGF I receptor (IGF-IR) antibodies. Treatment of androgen receptor (AR) positive CaP cell lines LNCaP and 22RV1 with IGF II for 48hr resulted in increased expression of steroidogenic enzymes at the protein and mRNA levels, including steroid acute regulatory protein (StAR), cytochrome p450 family member (CYP)17A1, aldo-keto reductase family member (AKR)3B, and hydroxysteroid dehydrogenase (HSD)17B3. IGF II treatment resulted in increased steady state steroid levels and increased de novo steroidogenesis and increased AR activation as demonstrated by PSA mRNA induction. Inhibition of IGF-IR / INSR signalling axis attenuated the effects of IGF II on steroid hormone synthesis. We present a potential mechanism for prostatic IGF II contributing to CaP progression by inducing steroidogenesis, and that the IGF II signalling and related pathways present attractive targets for CaP therapy.