CMTM7 and breast carcinoma: Furthermore, BSP sequencing was performed to detect the methylation status of CMTM7 promoter in breast cancer cell lines and tissues, and hypermethylation status of the CMTM7 promoter was detected in low CMTM7 mRNA-expressing breast cancer tissues and cell lines (Fig. 2F, G), indicating a negative association between the CMTM7 expression level and the methylation status of its CpG island in breast cancer.