To understand the role of H2S in tumor oncogenesis and progression, it is essential to analyze the interaction between the enzymes that synthesize H2S (such as CBS, CSE, 3-MST, and CARS) and those that catabolize H2S (including enzymes involved in sulfide oxidation processes like SQOR, hETHE.1, TST, SUOX/SO, and CcO, as well as enzymes involved in sulfide methylation processes: TMT, TEMT). Here, SQOR is linked to neoplasm.