Characterization of the Potential Cytotoxicity of Isolated from Colorectal Cancer Patients against a Normal Human Fibroblast Model.

Colorectal cancer is one of the most common types of cancer worldwide, with a multifactorial digestive pathology. Evidence has suggested that gut microbial dysbiosis is connected to the development of colorectal cancer by generating cancer cell-conducive microenvironments. Nevertheless, the relationship between colorectal cancer pathogenesis and microorganisms has not been fully clarified to date. Here, we addressed this issue and determined the cancer-causing potential of the culture filtrate and proteins of on healthy cells. In this study, the culture filtrate and total proteins of isolated from patients with colorectal cancer were investigated to determine their cytotoxic effects against the normal human fibroblast PCS-201-012 cell model. As a result of the isolation procedure, three different strains (named , , and ) were obtained from biopsy samples. Their 16S rRNA gene sequences were submitted to the GenBank database under the accession numbers MK156319, MK156320, and MK156321, respectively. The WST-8 and hemolysis tests were performed to examine the exacerbating effect of these strains on normal cells. The apoptosis-inducing ability of the isolated strains was characterized based on a combination of several techniques: determination of caspase-3 activity, JC-1 mitochondrial assay, and flow cytometry-based FITC-Annexin-V/PI double staining. Moreover, the expression profiles of four candidate genes (APC, SMAD, KRAS, TP53), which play important roles in the development of colorectal cancer, were analyzed by the qRT-PCR method. Cell biology experiments demonstrated that the culture filtrate and proteins of the related strains clearly cause cell death in normal human fibroblasts due to increased inflammatory response and necrosis. Furthermore, the culture filtrates and proteins led to a decrease in the expression of tumor suppressor genes , , and and an increase in the expression of the oncogene, emphasizing the tumorigenicity of the strains in colorectal cancer. These results revealed that strains are capable of triggering cytotoxicity in normal human fibroblast cells.