MPST and cancer: However, 7 out of 8 cancer cell lines expressed significantly high CBS, though the other H2S producing enzyme 3-mercaptopyruvate sulfurtransferase (MPST) and cystathionine gamma-lyase (CSE) did not reveal any significant difference with OSE (Fig. 1D), while 6 out of 8 cancer cell lines expressed significantly high SREBP1 or SREBP2 (Fig. 1D).