Predominance of Infection With Blastocystis hominis in Patients With Colorectal Cancer and Its Association With High Mucin Content, Infiltration of Inflammatory Cells and Elevated Serum Tumor Necrosis Factor α

Abstract

Background Blastocystis hominis is a unicellular protozoan parasite with a worldwide distribution. It was hypothesized that the infection with B. hominis plays a role in the pathogenesis of colorectal cancer in humans. Objective We aimed to test this hypothesis in a 1-year study using patients from Saudi Arabia with colorectal cancer. Subjects and Methods Colorectal cancer patients with various stages were enrolled in the study as cases (n = 75) along with a noncolorectal cancer patients as controls (n = 25). All participants in the study were subjected to history taking and investigated for B. hominis infection by microscopy and molecular-based tests applied to their fecal samples. Also, the tumor necrosis factor α in serum collected from both patients and controls was calculated in our study. Results The B. hominis were identified more in cases (20/75; 26.6%) than in controls (2/25; 8%), with significant difference (P < 0.05). Marked inflammatory cells infiltrate and mucin contents were demonstrated more in colorectal cancer patients infected with B. hominis, particularly those with stage 3 and stage 4 cancers. In patients with stage 4 colorectal cancer, there was a significantly higher level of mucin content and serum level of tumor necrosis factor α compared with colorectal cancer patients with less advanced stages (P < 0.05). In colorectal cancer cases, a statistically significant higher serum level of tumor necrosis factor α was observed compared with the controls (P < 0.05). Conclusions The findings of our study support the hypothesis that the infection with B. hominis has a possible role in the pathogenesis of colorectal cancer because it increases inflammatory cells infiltration and proinflammatory cytokines (tumor necrosis factor α) in the study's setting. This possibility demands future cohort prospective studies to prove whether the infection induces the colonic tissue to form a tumor or exacerbates the existing tumor. After this, we suggest that the study's population be screened for B. hominis, especially those suffering from colorectal cancers.