PGP and colonic neoplasm: The p-glycoproteins (P-gp) also called multi-drug resistance proteins are involved in the efflux of PARPi (Figure 1, step A, arrow #11), because P-gp inhibitors prevent the decrease of PARPi in HCT116 colon cancer cells (Oplustilova et al., 2012) and re-sensitize PARPi-resistant BRCA-1 deficient cells to PARPi (Rottenberg et al., 2008).