miR-340 improves the efficiency of p53 gene therapy in metastatic prostate cancer cells through downregulation of MDM2

Despite current standard treatments such as chemotherapy, radiotherapy, and hormone therapy, the five-year survival rate for patients with metastatic castration-resistant prostate cancer (mCRPC) remains about 50%. While p53 gene therapy has been widely investigated in cancer research, its clinical efficacy is limited by tumor evasion mechanisms, including the upregulation of p53 negative regulators, such as MDM2. This study aims to evaluate the impact of miR-340-mediated downregulation of MDM2 on the therapeutic efficacy of p53 gene therapy in p53 non-expressing PC3 cells. Lentiviral vectors, produced using HEK293T cells, were employed to generate scramble, miR-340-overexpressing, p53-overexpressing, and co-overexpressing PC3 cells. Quantitative polymerase chain reaction (qPCR) was used to determine the expression of p53, MDM2, p21, VEGF, and miR-340. Cell viability, apoptosis, necrosis, cell cycle alterations, cellular migration, proliferation in 2D/3D culture, and HUVECs’ angiogenic potential were assessed in vitro. Additionally, the efficacy of radiotherapy and docetaxel chemotherapy was evaluated through MTT, flow cytometry, and colony formation assay. miR-340 reduced MDM2 mRNA expression by 66% compared to the scramble control and by 45% compared to p53-overexpressing PC3 cells. miR-340 also decreased MDM2 protein expression by 30% compared to both the scramble control and p53-overexpressing PC3 cells. In PC3 cells co-expressing miR-340 and p53, miR-340 induced a 21-fold increase in p21 mRNA levels and a 58.8% increase in p53 protein expression relative to p53-overexpressing cells. Moreover, miR-340/p53 gene therapy effectively inhibited cell proliferation, migration, and angiogenic potential of PC3 cells, without markedly affecting apoptosis rates. Interestingly, this combined gene therapy substantially enhanced the therapeutic response to radiotherapy and low-dose docetaxel chemotherapy. In conclusion, miR-340 can enhance the efficacy of p53 gene therapy and holds promise for the management of mCRPC.