M. Montagnani Marelli

Luteinizing hormone-releasing hormone agonists interfere with the mitogenic activity of the insulin-like growth factor system in androgen-independent prostate cancer cells

We have previously shown that LHRH agonists exert a direct and specific inhibitory action on the proliferation of the androgen-independent DU 145 prostate cancer cell line; however, the cellular mechanisms mediating this antiproliferative action are not well defined. It is well known that the insulin-like growth factor (IGF) system plays a crucial role in the local regulation of the growth of androgen-independent prostate cancer. The present experiments were performed to evaluate whether LHRH agonists might exert their antimitogenic effect by interfering with the activity of the locally expressed IGF system. To this purpose, the effects of the LHRH agonist Zoladex (LHRH-A) on 1) the mitogenic action of IGF-I, 2) the tyrosine phosphorylation of type 1 IGF-I receptor (IGF-IR), 3) the concentration of IGF-IR, and 4) the secretion of IGF-binding protein-3 were studied. The results obtained show that in DU 145 cells, LHRH-A 1) counteracts the mitogenic action of IGF-I in a dose-dependent manner, 2) prevents th...

Growth-Inhibitory Activity of Melatonin on Human Androgen-Independent DU 145 Prostate Cancer Cells

The pineal hormone melatonin has been shown to exert a direct oncostatic activity on neoplastic cells, particularly from breast cancer. In the present study, we evaluated the effects of melatonin on the proliferation and on the cell cycle distribution of human androgen‐independent DU 145 prostate cancer cells. Experiments were also performed to gain insights into the possible mechanism of action of the hormone.

PO-078 Role of the ER stress-autophagy axis and mitochondrial metabolism reprogramming in the apoptosis induced by δ-TOCOTRIENOL in prostate cancer

Introduction Castration resistant prostate cancer (CRPC) is an aggressive tumour with still limited therapeutic outcomes. Tocotrienols (TT), vitamin E derivatives, were reported to exert anticancer activity in different tumours. The aim of this study was to assess the effects of δ-TT on human CRPC cells growth and the molecular mechanisms associated with its activity. Material and methods In human normal prostate (RWPE-1) and CRPC (PC3 and DU145) cell lines the effect of δ-TT on cell viability was evaluated by MTT assay; in PC3 and DU145 cells Trypan blue exclusion and colony formation assays were also performed. The expression of apoptosis-, ER stress- and autophagy-related proteins was analysed by Western blot and immunofluorescence assays, and the cytotoxic effect of δ-TT was also assessed using specific inhibitors of these pathways. The effect on mitochondrial metabolism was evaluated analysing the expression of the OXPHOS complexes (Western blot), the mitochondrial activity and mass (flow cytometry), the oxygen consumption (Clark-type oxygen electrode) and the ATP production (colorimetric assay). Results and discussions We demonstrated that δ-TT exerts a cytotoxic effect on PC3 and DU145 but not on RWPE-1 cells. In particular, δ-TT induces caspase 3 and PARP cleavage and cytochrome c release from mitochondria, and its cytotoxic effect is partially blocked by co-treatment with the pan-caspase inhibitor z-VAD-FMK, confirming that δ-TT exerts a pro-apoptotic effect on CRPC cells. We also observed that δ-TT significantly increases the expression of ER stress (BiP, IRE1α, PERK, pEIF2α, ATF4 and CHOP) and autophagy mediators (LC3-II and p62). Using the ER stress inhibitors salubrinal and 4-phenylbutyrate (4-PBA) and the autophagic flux inhibitors 3-methyladenine and chloroquine, we confirmed that the effect of δ-TT is mediated by both these mechanisms. In addition, treatment with salubrinal or 4-PBA impairs δ-TT-induced LC3-II expression, demonstrating that this compound triggers the ER stress-autophagy axis. Finally, we observed that δ-TT severely alters mitochondrial metabolism: the expression of the OXPHOS protein complexes, the mitochondrial activity/mass ratio, the oxygen consumption and the ATP production were significantly reduced after δ-TT treatment. Conclusion These results demonstrate that δ-TT exerts a selective pro-apoptotic effect on human CRPC cells through the activation of the ER stress-autophagy axis and the rewiring of mitochondrial metabolism.