ABCB1 and breast cancer: Our results support the findings of previous reports of in vitro exosomal transfer of MDR1/P-gp mRNA and protein from doxorubicin resistant human osteosarcoma (Torreggiani et al. 2016), docetaxel resistant prostate cancer (Corcoran et al. 2012), and breast cancer (Lv et al. 2014) cells to their sensitive counterparts as well as in vivo data showing intercellular transfer of P-gp in tumor cells (Levchenko et al. 2005).