ABCB1 and cancer: At the same time, TNT formation between cancer cell lines and primary cancer cells derived from ovarian, breast, pancreatic, prostate and colon cancer was demonstrated and proposed to play an important role in cancer cell pathogenesis and invasion [4], achieved e.g. by an intercellular transfer of functional P-glycoprotein, a drug efflux pump mediating multi-drug resistance [67,68], or oncogenic microRNAs [69].