Association of Dietary Factors and Microbiome Imbalance with Tumor-Related Genes Expression in Colorectal Cancer Patients

Abstract

Background: The global incidence of colorectal cancer (CRC) has been rising in low-income countries and has become a global health concern. The etiology of the disease has been linked to several factors, including the gut microbiome, intestinal permeability, inflammation, and oxidative stress, all of which are significantly influenced by lifestyle, including diet. The relationship between gut microbiota imbalance and increased intestinal permeability has been demonstrated to alter oxidative stress and inflammation. These alterations affect the expression patterns of important genes involved in CRC development. This study assessed differences in the composition and diversity of the gut microbiome between CRC patients and healthy controls. The genes Adenomatous Polyposis Coli (APC), Kirsten rat sarcoma viral oncogene homolog (KRAS), and mutS homolog 6 (MSH6) protein expression patterns were evaluated, and their association with dietary factors and microbial signatures was investigated. The study also demonstrated the association of intestinal permeability, inflammation, and oxidative stress with CRC, using intestinal fatty acid binding protein (iFABP), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β), and malondialdehyde (MDA) levels, respectively, as surrogate markers. Methods: 16S rRNA sequencing was employed to identify microbial signatures in stool samples from CRC and non-CRC participants. Real-time quantitative PCR was used to evaluate Escherichia coli with the polyketide synthase (E. coli +pks), Fusobacterium nucleatum with the Fusobacterium adhesin A (F. nucleatum+FadA), and Bacteroides fragilis with the Bacteroides fragilis toxin (B. fragilis+bft) genes in fecal samples. The protein expression levels of APC, KRAS, and MSH6 in colorectal tumors and normal tissues were determined using immunohistochemistry, followed by APC and KRAS gene mRNA quantification using RT- qPCR. iFABP, TNF-α, IL-1β, and MDA in serum samples were measured using an appropriate enzyme-linked immunosorbent assay (ELISA). A well-structured food frequency questionnaire was used to collect data on the nutritional status of study participants. Results: A greater relative abundance of CRC- associated bacterial genera was observed in the fecal samples of CRC patients compared to the non-CRC group. Participants with F. nucleatum were about five times at risk of CRC than those without F. nucleatum. KRAS protein was greatly expressed in the CRC tissues compared to the non-CRC tissues, while APC and MSH6 proteins were highly expressed in the non-CRC tissues than in the CRC tissues. Similarly, KRAS mRNA expression was markedly elevated in the CRC tissues compared to the non-CRC tissues. Interestingly, mRNA expression for APC was elevated in the CRC tissues compared to the healthy control tissues. Decreased APC protein expression was associated with frequent consumption of red and processed meat, whereas decreased KRAS protein expression was associated with frequent consumption of fruits and vegetables. Lastly, increased levels of serum iFABP, TNF-α, IL-1β, and MDA were observed in the CRC patients than in the non-CRC controls. Levels of iFABP (OR = 1.108, 95% CI: 1.01 – 1.22, p = 0.036), TNF-α (OR = 1.139, 95% CI: 1.02 – 1.28, p = 0.026), and MDA (OR = 1.048, 95% CI: 1.01 – 1.09, p = 0.022) were reported as independent risk factors for CRC. Conclusion: The study showed gut dysbiosis in CRC patients and an association of F. nucleatum with CRC. KRAS oncogene protein expression in CRC patients was inversely associated with fruit and vegetable intake. APC protein expression was shown to be lowered in people who frequently consumed red and processed meat. Serum MDA, TNF-α, and iFABP levels were identified as independent predictors of CRC in multivariable analysis.