IFITM2 and breast cancer: In addition, a negative correlation between IFITM2 and ESR1 gene expression in the Luminal A subtype of cancer patients was seen, indicating that ER expression is not important for interferon action; however, there was a positive correlation between IFITM2 gene expression and positive ER status in breast cancer patients, showing the importance of ER status as a complementary marker for the immune system for future treatment.