The IGF network with its main receptors IGF receptor 1 (IGF1R) and
insulin receptor (INSR) is of major importance for
cancer initiation and progression. To date, clinical studies targeting this network were disappointing and call for thorough analysis of the IGF network in
cancer models. We highlight the oncogenic effects controlled by IGF1R and INSR in
prostate cancer cells and show similarities as well as differences after receptor knockdown (KD). In PC3
prostate cancer cells stably transduced with inducible short hairpin RNAs, targeting IGF1R or INSR attenuated cell growth and proliferation ultimately driving cells into apoptosis. IGF1R KD triggered rapid and strong antiproliferative and proapoptotic responses, whereas these effects were less pronounced and delayed after INSR KD. Down-regulation of the antiapoptotic
proteins myeloid cell leukemia-1 and
survivin was observed in both KDs, whereas IGF1R KD also attenuated expression of prosurvival
proteins B cell lymphoma-2 and
B cell lymphoma-xL. Receptor KD induced cell death involved autophagy in particular upon IGF1R KD; however, no difference in mitochondrial energy metabolism was observed. In a mouse xenograft model, induction of IGF1R or INSR KD after
tumor establishment eradicated most of the
tumors. After 20 days of receptor KD,
tumor cells were found only in 1/14 IGF1R and 3/14 INSR KD
tumor remnants. Collectively, our data underline the oncogenic functions of IGF1R and INSR in
prostate cancer namely growth, proliferation, and survival in vitro as well as in vivo and identify myeloid cell leukemia-1 and
survivin as important mediators of inhibitory and apoptotic effects.