Current knowledge of CYP2S1 in endogenous function is largely related to eicosanoids metabolism, and some of its metabolic products have been identified, including 12-HHT, 5-oxo-eicosatetraenoic acid (5-oxoETE), 12-oxoETE, 15-oxoETE, etc.12 Some of them have been demonstrated to be involved in tumor progression, such as 12-HHT and 5-oxoETE,33,34 as supported by our data that CYP2S1 knockdown in BCPAP and 8505C cells dramatically reduced 12-HHT levels, and the restoration of 12-HHT could partially reverse inhibitory effect of CYP2S1 knockdown in cell viability. This evidence concerns the gene CYP2S1 and neoplasm.