Clitocine enhances the drug sensitivity of colon cancer cells by promoting FBXW7-mediated MCL-1 degradation via inhibiting the A2B/cAMP/ERK axis

Chemotherapy resistance to colon cancer is an unavoidable obstacle in the clinical management of the disease. Clitocine, an adenosine analog, played a significant role in the chemosensitivity of human colon cancer cells by promoting MCL-1 protein degradation. However, the detailed mechanism remains to be further elucidated. We found that clitocine up-regulates the expression of FBXW7, a ubiquitin ligase involved in the MCL-1 degradation. Transcriptome sequencing analysis revealed that clitocine significantly inhibits the cAMP and ERK downstream signaling pathways in colon cancer cells, thereby enhancing FBXW7 expression and subsequently promoting the ubiquitination degradation of MCL-1 protein. We verified that clitocine regulated intracellular cAMP levels by competitive binding with the adenosine receptor A2B. Molecular docking assay also verified the binding relationship. By decreasing intracellular cAMP levels, clitocine blocks the activation of downstream signaling pathways, which ultimately enhances the drug sensitivity of colon cancer cells through increased FBXW7 expression due to the inhibition of its promoter DNA methylation. Both knock-out of adenosine receptor A2B and Br-cAMP treatment can effectively attenuate the function of clitocine