Interestingly, very high levels of CMTM6 mRNA and protein expression were detected in the trastuzumab-resistant JIMT-1 (HER2+) BC cells while relatively lower levels of CMTM6 expression were observed in the trastuzumab-sensitive SKBR3 and BT474 BC cells, suggesting that up-regulated CMTM6 expression may be associated with trastuzumab resistance in HER2+ BC. This evidence concerns the gene CMTM6 and breast cancer.