For instance, expression of COX3 subunit of CcO is lower than normal in colon adenomas [78], while COX4 subunit isoform 1 (COX4-1) is overexpressed in glioblastoma (GBM) cells, and its upregulation is linked to the development of temozolomide (TMZ) chemoresistance in GBM cells [79]. Here, COX4I1 is linked to glioblastoma.