Casein Kinase-1-Alpha Inhibitor (D4476) Sensitizes Microsatellite Instable Colorectal Cancer Cells to 5-Fluorouracil via Authophagy Flux Inhibition

Adjuvant chemotherapy with 5-fluorouracil (5-FU) does not improve survival of patients suffering from a form of colorectal cancer (CRC) characterized by high level of microsatellite instability (MSI-H). Given the importance of autophagy and multi-drug-resistant (MDR) proteins in chemotherapy resistance, as well as the role of casein kinase 1-alpha (CK1 alpha) in the regulation of autophagy, we tested the combined effect of 5-FU and CK1 alpha inhibitor (D4476) on HCT116 cells as a model of MSI-H colorectal cancer. To achieve this goal, the gene expression of Beclinl and MDR genes, ABCG2 and ABCC3 were analyzed using quantitative real-time polymerase chain reaction. We used immunoblotting to measure autophagy flux (LC3, p62) and flow cytometry to detect apoptosis. Our findings showed that combination treatment with 5-FU and D4476 inhibited autophagy flux. Moreover, 5-FU and D4476 combination therapy induced G2, S and G1 phase arrests and it depleted mRNA of both cell proliferation-related genes and MDR-related genes (ABCG2, cyclin DI and c-myc). Hence, our data indicates that targeting of CK1 alpha may increase the sensitivity of HCT116 cells to 5-FU. To our knowledge, this is the first description of sensitization of CRC cells to 5-FU chemotherapy by CK1 alpha inhibitor.

Automated summary

The study demonstrates that the combination of 5-FU and CK1 alpha inhibitor D4476 increases the sensitivity of HCT116 cells to 5-FU chemotherapy by inhibiting autophagy flux, inducing cell cycle arrest, and affecting gene expression related to cell proliferation and multidrug resistance. This novel approach suggests a potential strategy to enhance the efficacy of 5-FU treatment in colorectal cancer with high microsatellite instability.