PCDH17 increases the sensitivity of colorectal cancer to 5-fluorouracil treatment by inducing apoptosis and autophagic cell death

5-Fluorouracil(5-FU)is known as a first-line chemotherapeutic agent against colorectal cancer(CRC),but drug resistance occurs frequently and significantly limits its clinical success.Our previous study showed that the protocadherin 17(PCDH17)gene was frequently methylated and functioned as a tumor suppressor in CRC.However,the relationship between PCDH17 and 5-FU resistance in CRC remains unclear.Here,we revealed that PCDH17 was more highly expressed in 5-FU-sensitive CRC tissues than in 5-FU-resistant CRC tissues,and high expression of PCDH17 was correlated with high BECN1 expression.Moreover,this expression profile contributed to superior prognosis and increased survival in CRC patients.Restoring PCDH17 expression augmented the 5-FU sensitivity of CRC in vitro and in vivo by promoting apoptosis and autophagic cell death.Furthermore,autophagy played a dominant role in PCDH17-induced cell death,as an autophagy inhibitor blocked cell death to a greater extent than the pancaspase inhibitor Z-VAD-FMK.PCDH17 inhibition by siRNA decreased the autophagy response and 5-FU sensitivity.Mechanistically,we showed that c-Jun NH2-terminal kinase(JNK)activation was a key determinant in PCDH17-induced autophagy.The compound SP600125,an inhibitor of JNK,suppressed autophagy and 5-FU-induced cell death in PCDH17-reexpressing CRC cells.Taken together,our findings suggest for the first time that PCDH17 increases the sensitivity of CRC to 5-FU treatment by inducing apoptosis and JNK-dependent autophagic cell death.PCDH17 may be a potential prognostic marker for predicting 5-FU sensitivity in CRC patients.