ABCC5 and pachyonychia congenita: (25) found that leptin attenuated the cytotoxic effects of 5-fluorouracil (5-FU) on PC by increasing the expression of Notch signaling pathway transcription factors and eliciting increased expression of the drug efflux proteins ABCC5 and ABCC11, of which 5-FU retards chemoresistance precisely by decreasing ABCC5 and ABCC11, suggesting that the therapeutic sensitivity of 5-FU in PC patients could be strengthened clinically by targeting the leptin/Notch axis (Table 1).