Jacob Vargas

Introduction. Colorectal cancer is identified as the third most common cancer and fourth most common cause of cancer-related death in individuals with most cases detected in women and in western countries.¹ Patients typically present with rectal bleeding, microcytic anemia, altered bowel habits, and chronic abdominal pain.² Clinical diagnosis of colorectal cancer is achieved through colonoscopy-guided biopsy and diagnostic staging.² The likelihood of metastases is less than 10% for stage I, 10% to 20% for stage II, and 25% to 50% for stage III colorectal cancer.² The median survival is approximately 30 months for patients who receive treatment for metastatic colorectal cancer, while those who do not have a median survival of 6-12 months.² The VEGF-C/VEGFR3 pathway is the main inducer of lymphatic endothelial cell proliferation, migration, and survival and is known to be overexpressed in colorectal cancer-associated endothelial and macrophage cells.³ Researchers have determined that lymphatic vessels are key routes for metastatic spread because they allow for tumor cell dissemination with each additional vessel leading to a 1.45x increase in the risk of metastasis.³ The purpose of this study was to observe the factors contributing to the overexpression of VEGF-C in colorectal cancer cells focusing on its regulation by miR-182-5p, cancer-associated exosomes, and the involvement of lipopolysaccharide. Methods. Mice tumor models, colorectal cancer cell lines and patient blood samples were utilized in experiments. Immunohistochemistry, qRT-PCR and western blot analysis were used to analyze expression of VEGF-C and VEGFR in control samples and those treated with lipopolysaccharide and cancer exosomes as well as expression of miR-182-5p. Wound healing, transwell migration and invasion, and colony formation assays were used to observe tumor cell motility and proliferation. Results. Overexpression of VEGF-C led to increases in tumor density, size and metastasis and vice versa when VEGFR3 is blocked.^4,5 Colorectal cancer cells were shown to possess significant downregulation of miR-182-5p but its transfection into cells led to suppression of VEGF-C.⁶ Cancer exosomes were found to re-educate macrophages to overexpress VEGF-C through expression of IRF-2.⁷ Lastly, increased concentration of lipopolysaccharide affected expression of VEGF-C to promote motility but not proliferation.⁸ Conclusions. Studies confirmed that overexpression or blockage of the VEGF-C/VEGFR3 pathway correlated with the rate of growth and metastasis of colorectal cancer cells in tumor models. Loss of the regulation by miR-182-5p, macrophage re-education by cancer exosomes, and increases in lipopolysaccharide concentration were also confirmed as mechanisms causing overexpression of VEGF-C in tumor cells leading to increased migration and proliferation.

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