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Background and purpose: Colorectal cancer is one of the most common digestive system malignancies, and chemotherapy for colorectal cancer and drug resistance have always been concerns. 5-fluorouracil (5-FU) is the first-line chemotherapy drug for colorectal cancer, and its efficacy is often affected by drug resistance or adverse reactions. Dihydropyrimidine dehydrogenase (DPD) is a key rate-limiting enzyme in 5-FU metabolism, and its expression or degradation may be a factor affecting the efficacy of 5-FU. Autophagy is an important pathway of intracellular protein metabolism, and its role in chemotherapy-induced cell death or proliferation inhibition is still controversial. This study aimed to investigate the role of autophagy in colorectal cancer chemotherapy and the mechanism by which autophagy affects 5-FU drug resistance. Methods: Human colon cancer HCT-8, COLO205, LOVO and SW480 cell lines were cultured in vitro to observe the effect of DPD expression on 5-FU sensitivity. 5-FU sensitive cells were screened by drug sensitivity test. The expression of DPD, the level of autophagy and the expressions of microtubule-associated protein light chain 3 (LC3) and P62 in 5-FU-sensitive cell lines and their corresponding drug-resistant cell lines were detected. The effect of autophagy on the expression of DPD and the biological behavior and chemotherapy resistance of tumor cells were observed. UbiBrowser database screening and co-inmunoprecipitationn (Co-IP) experiment were used to verify the E3 ligase in the process of DPD degradation, and to investigate the molecular mechanism of reversing 5-FU resistance caused by autophagy degradation of DPD. Results: The COLO205 cell line had the highest DPD expression and was the most resistant to 5-FU, while the HCT-8 cell line had the lowest DPD expression and was the most sensitive to 5-FU. Compared with HCT-8/5-FU cells, HCT-8/FU-resistant cells expressed higher levels of DPD and lower levels of basal autophagy. Rapamycin (RAPA)-mediated autophagy activation enhanced the autophagy level, decreased the expression of DPD, and decreased cell proliferation, invasion and 5-FU resistance. The inhibition of autophagy mediated by 3-Methyladenine (3-MA) and hydroxychloroquine (HCQ) attenuated the autophagy level, increased the expression of DPD, and enhanced the drug resistance of 5-FU. The inhibitory effect of 5-FU combined with autophagy activator was much stronger compared with 5-FU alone or combined with autophagy inhibitor. The degradation of DPD required the participation of complete autophagic flow, among which the formation of autophagic lysosomes was one of the key steps of DPD degradation, however a single autophagosome could not degrade DPD. E3 ligase NEDD4 co-immunoprecipitated with DPD and P62 proteins in HCT-8/5-FU cells and played a role in autophagic degradation of DPD. Conclusion: The involvement of autophagy in DPD degradation affects the sensitivity of colorectal cancer cells to chemotherapy drugs. Activation of autophagy can promote the degradation of DPD and inhibit the catabolism of 5-FU, which may be a new way to reverse 5-FU resistance in colorectal cancer.

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Background and purpose: Colorectal cancer is one of the most common malignancies. The efficacy of 5-fluorouracil (5-FU) in the treatment of colorectal cancer is often affected by drug resistance or toxic side effects. Dihydropyrimidine dehydrogenase (DPD) is the key enzyme in the metabolism of 5-FU, and the expression or degradation rate of 5-FU may be a factor affecting the efficacy of 5-FU. Autophagy is an important pathway of intracellular protein degradation. This study aimed to detect the expression of microtubule-associated protein light chain 3 (LC3), P62 and DPD in colorectal cancer, and to explore their correlation and clinical significance, so as to provide a new way to reverse 5-FU resistance. Methods: Immunohistochemical envision method was used to detect the expressions of LC3, p62 and DPD in 157 colorectal cancer paraffin tissues archived by Department of Pathology, Binzhou Medical University Hospital from 2013 to 2014. Western blot and real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR) were used to detect the expressions of LC3, p62 and DPD in 44 colorectal cancer fresh tissues received by Department of Pathology, Binzhou Medical University Hospital in 2020. The correlation and clinical significance were analyzed. Results: The expressions of LC3, P62 and DPD were significantly higher in colorectal carcinoma than in normal tissues (P0.05). The expression of P62 was positively correlated with T stage and lymph node metastasis. The expression of LC3 was positively correlated with tumor size and T stage. The protein expression of DPD was closely related to histological type (P

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shandong Medical Journal is the property of Shandong Medical Health Newspapers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)