Indeed, paclitaxel had no effect on the invasion of P-gp (+)/PrPC (−) and P-gp (−)/PrPC (+) cells, confirming that this drug promotes the invasion in multidrug-resistant (MDR) breast cancer cells through a mechanism that involves the interaction of P-gp with PrPC [58] (Figure 3). The gene discussed is PGP; the disease is breast cancer.