L-arginase from Streptomyces diastaticus MAM5 as a potential therapeutic agent in breast cancer: Purification, characterization, G1 phase arrest and autophagy induction

Abstract

Targeting cancer metabolic processes has increased interest over the last century. Cancer cells have an enhanced proliferation rate that requires high quantities of amino acids, including arginine. Therefore, arginine deprivation by L-arginase impairs tumor growth resulting in cell death. In the present study, L-arginine amidinohydrolase (L-arginase) from Streptomyces diastaticus was purified successfully by heat treatment, ethanol precipitation, and Sephadex G75–120 column. The molecular mass of the purified enzyme was 39 kDa. It showed maximum activity at pH 9.0 and a temperature of 50 °C. Moreover, the enzyme stability was observed at temperatures up to 50 °C and a pH range of 7.5 to 9.0. Then, the potential cytotoxicity of L-arginase was examined. L-arginase has an IC50 value of 595 μg/ml for MCF-7 (breast adenocarcinoma cells), 915 μg/ml for HepG2 (hepatocellular carcinoma cells), and 1200 μg/ml for SW620 cells (colorectal carcinoma cells) at 72 h post-treatment. Noteworthy, MCF-7 showed the lowest IC50 value of arginase treatment, therefore was further investigated for the underlying cytotoxic mechanisms using flow cytometric analysis of cell-cycle distribution, apoptosis, and autophagy. Moreover, SI values indicating a high selective cytotoxicity of arginase toward MCF-7 cells. L-arginase induced significant cell cycle arrest at the G1 phase, and no apparent apoptosis was detected. Interestingly, arginine deprivation by arginase leads to a prominent activation of autophagy in the apoptosis defected MCF-7 cells. Moreover, treatment with arginase significantly attenuated MCF-7 cell migration compared with control medium-treated cells. Collectively, L-arginase might potentially be involved in treating breast cancer.