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 myeloid cell leukemia 1 (MCL-1) protein degradation. However, the detailed mechanism remains to be further elucidated. We found that clitocine upregulates the expression of F-box and WD repeat domain containing 7 (FBXW7), a ubiquitin ligase involved in the MCL-1 degradation. Transcriptome sequencing analysis revealed that clitocine significantly inhibits the cyclic adenosine monophosphate (cAMP) and extracellular regulated protein kinases (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. A 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 knockout of the adenosine receptor A2B and Br-cAMP treatment can effectively attenuate the function of clitocine in vitro and in vivo. This study clarified that clitocine enhanced the drug sensitivity of colon cancer cells by promoting FBXW7-mediated MCL-1 degradation via inhibiting the A2B/cAMP/ERK axis, providing further knowledge of the clinical application for clitocine.NEW & NOTEWORTHY Our study found that clitocine enhances the drug sensitivity of colon cancer cells by promoting FBXW7-mediated MCL-1 degradation via inhibiting the A2B/cAMP/ERK axis.

Analysis of Plasma EBV-DNA and Soluble Checkpoint Proteins in Nasopharyngeal Carcinoma Patients after Definitive Intensity-Modulated Radiotherapy.

BACKGROUND: Tumor immunotherapy and immunological checkpoint-related proteins are research hotspots. Intensity-modulated radiotherapy (IMRT) is the main treatment for nasopharyngeal carcinoma (NPC). Hence, the evaluation of its effect is very important. The aim of this study was to assess the relationship between the concentrations of soluble checkpoint proteins, plasma EBV-DNA, and cytokines in NPC patients treated with IMRT. METHODS: In this study, the plasma samples of 37 NPC patients and 40 healthy controls were collected. Luminex MAGPIX was used to detect the concentrations of 32 plasma targets, including soluble programmed cell death 1 (sPD-1). RT-qPCR was used to measure EBV-DNA. RESULTS: The concentrations of 33 plasma targets were detected in NPC patients before and after IMRT to explore the changes after IMRT. The results showed that IMRT could increase the expression of sPD-1 and significantly reduce the level of EBV-DNA in the plasma of NPC patients. The expression level of sPD-1 in TNM I/II patients was significantly higher than that in III/IV patients. Besides, the concentrations of 12 other targets were significantly different after IMRT, including LAG-3, PD-L1, TIM-3, IFN-γ, IL-12p70, IL-1ß, IL-5, IL-6, TNF-α, IL-10, IL-17A, and IL-22. High sPD-1 patients had longer survival than those with low sPD-1. Also, patients with lower EBV-DNA and TNM grades I and II/III had longer survival than those with higher EBV-DNA or TNM IV. CONCLUSIONS: This study demonstrated that the concentration of sPD-1 was significantly increased and EBV-DNA was significantly reduced in the NPC patients after IMRT. Plasma EBV-DNA level was a highly specific and sensitive biomarker for NPC diagnosis. Both sPD-1 expression and EBV-DNA concentration in plasma were related to the survival of patients.