Metabolic dysfunction and metformin modify plasma extracellular vesicle signaling to prostate cancer cells

Type 2 diabetes (T2D) is associated with altered outcomes in established prostate cancer, but the underlying mechanisms remain unclear. We examined whether whole-body metabolic state and systemic metformin treatment are associated with changes in circulating plasma extracellular vesicle (EV) signaling to prostate cancer cells. Plasma EV-derived miRNAs were profiled in six T2D and six non-diabetic (ND) donors, selected mimics were tested in DU145 cells for effects on transcription of ZEB1, a master regulator of tumor progression. Recipient cell transcriptional responses to human EV-enriched fractions were also assessed by RNA sequencing using six T2D and two ND donors. DU145 cells were also transfected with plasma EV-derived RNA from high fat diet (HFD)-fed mice with or without metformin treatment. Human miRNA profiling identified miR-192-5p, miR-106b-5p, and miR-29b-3p as candidates with greater than two-fold elevation and nominal P<0.05; none of the 84 assayed miRNAs remained significant after multiple-testing correction. Synthetic miR-192-5p and miR-106b-3p mimics increased ZEB1, whereas miR-29b-3p had no effect on ZEB1. T2D donor EV exposure was associated with broad range of aggressive responses, including cytoskeletal, extracellular matrix, mitotic, and RHO-GTPase-related pathways. Mouse EV-derived RNA from metformin-treated HFD mice induced lower DU145 migration than RNA from untreated HFD mice (12.23% versus 20.25% mean membrane coverage; n=3 mice/group; Welch P=0.0246). Matrigel invasion analysis showed less invasion for HFD+metformin than HFD alone (4.89% versus 7.89%; n=3 mice/group; Welch P=0.0302). These findings support a strong association between abnormal systemic metabolism and circulating EV signaling to drive prostate cancer progression, together with a metformin-driven reduction in the tumor progression activity of plasma EV-derived RNA. The responsible RNA species and molecular mechanisms will be central to future research.