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Purpose: Clinical outcomes for advanced malignant melanoma (MM) are often poor due to tumor invasiveness, metastasis, recurrence, and multidrug resistance., Methods: We investigated whether apoptosis, cell cycle regulation, oxidative status, and redox balance were altered by changes in the expression of the long noncoding RNA, growth arrest-specific transcript 5 (GAS5), in MM cells., Results: Analysis of clinical samples from MM patients showed that the rate of reduced GAS5 expression, relative to that in adjacent noncancerous tissues, was significantly lower for tumors from patients with advanced disease (76.6%, P < 0.001), as evidenced by larger tumor size, higher TNM stage, and higher incidences of ulceration and metastasis (P < 0.001 for all). Cell culture experiments showed that siRNA-mediated knockdown of GAS5 increased the viability of A375-GAS5si cells. Flow cytometry and western blotting showed that GAS5 knockdown increased MM cell proliferation by inducing G1/S cell cycle progression through increases in Cyclin D1, CDK4, and p27 expression (P < 0.05 for all) and by inhibiting apoptosis through an increase in Bcl-2 expression (P < 0.001). Knockdown of GAS5 also increased levels of superoxide anion (P < 0.01), NADP + (P < 0.001), and oxidized glutathiones (P < 0.01) through increases in NOX4 expression (P < 0.001), G6PD expression (P < 0.01), and NOX activity (P < 0.05), and RNA co-immunoprecipitation showed that GAS5 induced these changes through a physical interaction between GAS5 and the G6PD protein., Conclusions: Our findings show GAS5 contributes to regulation of the apoptosis, cell cycle, homeostasis of reactive oxygen species, and redox balance in MM cells, and suggest that reduced GAS5 expression contributes to disease progression in MM patients.