Int J Biol Sci 2018; 14(9):1054-1066. doi:10.7150/ijbs.25349 This issue Cite
Research Paper
1. Labortaory of Cancer Biology, Key Laboratory of Biotherapy in Zhejiang, Sir Runrun Shaw hospital, Medical School of Zhejiang University, China
2. Department of Medical Oncology, Sir Runrun Shaw hospital, Medical School of Zhejiang University, China
3. Pathology Center, Shanghai General Hospital, Medical School of Shanghai Jiaotong University
4. Department of Molecular Cell Biology and Toxicology, School of Public Health, Nanjing Medical University, Nanjing, China
5. Department of Preventive Medicine and Public Health Laboratory Science, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, China
Chemotherapy is one of the most important approaches for the treatment of various cancers. However, tumor cells often develop resistance to chemotherapeutic drugs. The tumor microenvironment reconstituted by various cytokines secreted from immune cells was recently found to play important roles in affecting therapeutic response of tumor cells. Herein, we reported that tumor cells can secrete autocrine cytokines to confer chemoresistance by inactivating proapoptotic autophagy. Through cytokine screening, we found that drug resistant cancer cells secreted more CCL2 than drug sensitive cells. Such secreted CCL2 could not only maintain chemoresistance in drug-resistant cancer cells but also confer drug resistance to drug-sensitive cancer cells. CCL2 attenuated drug-induced cytotoxicity by activating PI3K-Akt-mTOR signaling to inhibit proapoptotic autophagy and increase SQSTM1 expression. CCL2 expression in primary carcinoma tissues also correlated well with SQSTM1 expression. Either CCL2 knock-down or autophagy induction successfully reversed drug resistance of tumor cells. Moreover, increased expression of SQSTM1 in turn activated CCL2 transcription via NF-κB signal pathway, representing a positive feedback loop to maintain drug resistance. Therefore, our results provided a new insight to understand drug resistance, and indicated the potential value of CCL2 as a biomarker and intervention target for chemotherapy resistance.
Keywords: CCL2, drug resistance, apoptosis, autophagy, gastric cancer