Furthermore, Cx43 signal seemed to be inversely and significantly correlated with breast cancer subtype aggressiveness, being the lowest in the most serious subtype triple negative (ER, PR and HER2 negative), slightly higher in non-luminal HER2+ (ER and PR negative, HER2 positive) and luminal B HER2- (ER and/or PR positive, HER2 negative), and the highest in luminal B HER2+ (ER and/or PR positive, HER2 positive) and in the better-prognosis luminal A (ER and/or PR positive, HER2 negative). This evidence concerns the gene ESR1 and breast cancer.