Combination therapy with β-carotene+5-FU to overcome uL3-mediated drug resistance in p53 deleted colon cancer cells

Colon cancer is one of the leading causes of cancer-related death worldwide [1]. Despite recent therapeutic advancements, resistance to 5-Fluorouracil (5-FU) remains a major obstacle to the successful treatments of this disease. We have identified ribosomal protein uL3 as a key player in the cell response to 5-FU [2]. Loss of uL3 is associated to 5-FU chemoresistance, alteration in cell motility, epithelial-mesenchymal transition and autophagy [3-5]. Natural products, like carotenoids, have shown the ability to enhance the response of cytotoxic drugs to cancer cells and may provide a safer choice to defeat chemoresistance in cancer [6]. Through the analysis of a cohort of 594 colorectal patients, we found a correlation between uL3 expression and both progression-free survival and response to 5-FU treatments. uL3 low transcriptional state was found to be associated with increased expression of specific ABC/MDR genes. By using a model of 5-FU resistant colon cancer cells p53 deleted and stably silenced of uL3 we have also investigated the effect of novel combination therapy based on β-carotene plus 5-FU. Our results indicated that this treatment may overcome 5-FU chemoresistance inducing a G2/M cell cycle arrest associated with induction of apoptosis in 2D and 3D cell culture models. Furthermore, the combined treatment significantly reduced the expression levels of analyzed ABC/MDR genes. In conclusion, our data reveal that 5-FU in combination with β-carotene may provide a more effective therapeutic approach to treat colon cancers lacking functional p53 and characterized by low expression levels of uL3. References 1. Dekker et al. Colorectal cancer. Lancet. 2019 Oct 19;394(10207):1467-1480. doi: 10.1016/S0140-6736(19)32319-0. PMID: 31631858. 2. Pagliara et al. 5-FU targets rpL3 to induce mitochondrial apoptosis via cystathionine-β-synthase in colon cancer cells lacking p53. Oncotarget. 2016 Aug 2;7(31):50333-50348. doi: 10.18632/oncotarget.10385. PMID: 27385096; PMCID: PMC5226586. 3. Russo et al. Role of uL3 in Multidrug Resistance in p53-Mutated Lung Cancer Cells. Int J Mol Sci. 2017 Mar 3;18(3):547. doi: 10.3390/ijms18030547. PMID: 28273808; PMCID: PMC5372563. 4. Pecoraro et al. Ribosomal protein uL3 targets E2F1 and Cyclin D1 in cancer cell response to nucleolar stress. Sci Rep. 2019 Oct 28;9(1):15431. doi: 10.1038/s41598-019-51723-7. PMID: 31659203; PMCID: PMC6817900. 5. Pecoraro et al. Role of uL3 in the Crosstalk between Nucleolar Stress and Autophagy in Colon Cancer Cells. Int J Mol Sci. 2020 Mar 20;21(6):2143. doi: 10.3390/ijms21062143. PMID: 32244996; PMCID: PMC7139652. 6. Saini et al. Dietary carotenoids in cancer chemoprevention and chemotherapy: A review of emerging evidence. Pharmacol Res. 2020 Jul; 157:104830. doi: 10.1016/j.phrs.2020.104830. Epub 2020 Apr 25. PMID: 32344050.