ABCB1 and breast carcinoma: Despite possible diffusion of the chemotherapeutic agent between cancer cells, it has been observed that TNTs could increase chemoresistance in cancer cells by permitting P-glycoprotein (encoded by the multidrug resistance gene-1, MDR1) transfer between the Michigan Cancer Foundation-7 (MCF-7) breast cancer cells, a phenomenon which can also occur through exosomes [50].