Anti-Outer membrane protein C antibodies in colorectal neoplasia

Sporadic colorectal cancer (CRC) represents an enormous problem worldwide. Large intestinal microbiota play an important role in the colorectal carcinogenesis. The aim of the study was to investigate anti-Outer membrane protein C (anti-OmpC) antibodies, aimed at porin C, which is embedded in the outer membrane of gram-negative bacteria, in patients with colorectal adenoma (CRA), CRC and controls. The study included 22 patients with CRA (11 men, 11 women, aged 26-79, mean 65 ± 12), 11 patients with CRC (9 men, 2 women, aged 50-83, mean 66 ± 11) and 45 controls, blood donors (24 men, 21 women, aged 20-58, mean 38 ± 10). Serum anti-OmpC antibodies were investigated by means of ELISA. Values of 0-20 U/mL were considered to be negative; values >25 U/mL were assessed as positive. A total of 9/11 (82 %) patients with CRC had positive anti-OmpC antibodies. Anti-OmpC antibodies were negative or grey-zone in 37/45 (82 %) controls. Serum anti-OmpC were found to be significantly higher in patients with CRC (median 42.4, interquartile range (IQR) 22.2) compared to controls (median 18.3, IQR 12.4), p < 0.001. No statistically significant difference in anti-OmpC was found between controls (median 18.3, IQR 12.4) and CRA patients (median 17.7, IQR 16.5), p = 0.326. Anti-OmpC were significantly higher in patients with CRC (median 42.4, IQR 22.2) compared to patients with CRA (median 17.7, IQR 16.5), p = 0.011. Positivity of anti-OmpC antibodies was found in patients with CRC, which supports the contribution of gram-negative large intestinal microbiota to the pathogenesis of CRC.