“…In that regard, GPX1, GPX3, and GPX7 expression were found to be decreased [ 144 , 240 , 241 , 242 , 243 ] in tumor tissues, while the expression of GPX2 and GPX4 was found to be upregulated [ 144 , 146 , 244 , 245 , 246 , 247 ]. In addition, GSTA1, GSTM1, and GSTZ1 are reported to be downregulated in tumor tissue and can correlate with a poor prognosis [ 63 , 248 , 249 , 250 , 251 ], while GSTT1, GSTO1, and GSTK1 are mostly reported to be upregulated in tumor tissue compared to the normal surrounding tissue [ 252 , 253 ]. The expression level of GSTP1 in tumor tissue is controversial [ 144 , 253 , 254 , 255 ], and its involvement in tumorigenesis could at least in part depend on its hypermethylation [ 256 , 257 , 258 , 259 , 260 ].…”