Radiosensitizing effects of miR-18a-5p on lung cancer stem-like cells via downregulating both ATM and HIF-1α

Long noncoding RNA GAS5 modulates α-Solanine-induced radiosensitivity by negatively regulating miR-18a in human prostate cancer cells

Radiotherapy is an adjuvant treatment of surgery in prostate cancer, while radioresistance has been the challenge of treatment. It has been reported that α-Solanine exhibits anti-cancer activity and enhances the chemo- and radio-sensitivity in several human cancers, whereas the role of α-Solanine on radiosensitivity to PCa remains to be uncovered yet. We found α-Solanine decreased cell viability in human PCa cells rather than normal prostate epithelial cells in vitro. Functional experiments showed that cell viability and colonies formation were declined & apoptosis rate and DNA double strand breaks (DSBs) marker γ-H2AX expressions were elevated by α-Solanine in PCa cells treated with X-ray irradiation, compared with X-ray irradiation treatment only. GAS5 was down-regulated & miR-18a was up-regulated in PCa cells, which was reversed in the presence of α-Solanine. Effects of ectopic GAS5 on inhibiting cell viability and survival & promoting apoptosis and DNA damage were reversed by miR-18a overexpression in PCa cells. Moreover, GAS5 regulated miR-18a expression by target binding during α-Solanine treatment. Collectively, α-Solanine suppresses cell proliferation and promotes radiosensitivity through up-regulating GAS5/miR-18a pathway in PCa. Our results provide a novel mechanism of α-Solanine treatment in human prostate cancer and help to develop a new approach to sensitizing radioresistant prostate cancer cells by targeting GAS5/miR-18a.

Radiosensitizing effects of miR-18a-5p on lung cancer stem-like cells via downregulating both ATM and HIF-1α

Lung cancer is one of the main causes of cancer mortality globally. Most patients received radiotherapy during the course of disease. However, radioresistance generally occurs in the majority of these patients, leading to poor curative effect, and the underlying mechanism remains unclear. In the present study, miR-18a-5p expression was downregulated in irradiated lung cancer cells. Overexpression of miR-18a-5p increased the radiosensitivity of lung cancer cells and inhibited the growth of A549 xenografts after radiation exposure. Dual luciferase report system and miR-18a-5p overexpression identified ataxia telangiectasia mutated (ATM) and hypoxia inducible factor 1 alpha (HIF-1α) as the targets of miR-18a-5p. The mRNA and protein expressions of ATM and HIF-1α were dramatically downregulated by miR-18a-5p in vitro and in vivo. Clinically, plasma miR-18a-5p expression was significantly higher in radiosensitive than in radioresistant group (P < .001). The cutoff value of miR-18a-5p >2.28 was obtained from receiver operating characteristic (ROC) curve. The objective response rate (ORR) was significantly higher in miR-18a-5p-high group than in miR-18a-5p-low group (P < .001). A tendency demonstrated that the median local progression-free survival (PFS) from radiotherapy was longer in miR-18a-5p-high than in miR-18a-5p-low group (P = .082). The median overall survival (OS) from radiotherapy was numerically longer in miR-18a-5p-high than in miR-18a-5p-low group (P = .281). The sensitivity and specificity of plasma miR-18a-5p to predict radiosensitivity was 87% and 95%, respectively. Collectively, these results indicate that miR-18a-5p increases the radiosensitivity in lung cancer cells and CD133+ stem-like cells via downregulating ATM and HIF-1α expressions. Plasma miR-18a-5p would be an available indicator of radiosensitivity in lung cancer patients.