Abstract
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 (CK1α) in the regulation of autophagy, we tested the combined effect of 5-FU and CK1α inhibitor (D4476) on HCT116 cells as a model of MSI-H colorectal cancer. To achieve this goal, the gene expression of Beclin1 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 D1 and c-myc). Hence, our data indicates that targeting of CK1α 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 CK1α inhibitor.Graphic abstract
Highlights
Colorectal cancer (CRC) is among the most common and lethal cancers worldwide (Blondy et al 2020; Mokarram et al 2017)
Several well-known mechanisms may contribute to drug resistance in cancer, such as apoptosis inhibition (Qie and Diehl 2016), drug inactivation (Mansoori et al 2017), multi-drug resistance (MDR) via different ATP-binding cassette (ABC) transporters (e.g., ABCB1, ABCG2, ABCB4, ABCC15, ABCC10, and ABCG4) (Fletcher et al 2016), cell cycle modulators (e.g., c-myc and cyclin D1) (Christowitz et al 2019), and the autophagy pathway (Desantis et al 2018; Hombach-Klonisch et al 2018)
In this study, combined 5-FU/D4476 decreased ABCG2, cyclin D1 and c-myc gene expression and increased the levels of autophagy markers including LC3-II, p62 and Beclin1 compared with the 5-FU alone in HCT116 human CRC cells
Summary
Colorectal cancer (CRC) is among the most common and lethal cancers worldwide (Blondy et al 2020; Mokarram et al 2017). Surgery is commonly used as the primary treatment for CRC, but chemotherapy is used as an adjunct therapy to reduce the risk of recurrence of stages 1 and 2 cancers after surgery (Reima et al 2020). FOLFOX is a neoadjuvant chemotherapy for patients with advanced or metastatic disease including Oxaliplatin, Leucovorin, and Fluorouracil sequential therapy (Symonds and Cohen 2019). FOLFOX is generally more effective as compared to fluorouracil/Leucovorin for patients with stage III colon cancer (Rebuzzi et al 2020). The adjuvant therapy with oxaliplatin or irinotecan may potentially overcome 5-FU resistance, in some cases (Douillard et al 2000; Longley et al 2003). More effective combined therapeutic strategies involving adjuvant medications to ameliorate mechanism involved in resistance to chemotherapy are being sough. Several well-known mechanisms may contribute to drug resistance in cancer, such as apoptosis inhibition (Qie and Diehl 2016), drug inactivation (Mansoori et al 2017), multi-drug resistance (MDR) via different ATP-binding cassette (ABC) transporters (e.g., ABCB1, ABCG2, ABCB4, ABCC15, ABCC10, and ABCG4) (Fletcher et al 2016), cell cycle modulators (e.g., c-myc and cyclin D1) (Christowitz et al 2019), and the autophagy pathway (Desantis et al 2018; Hombach-Klonisch et al 2018)
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