Neo-angiogenesis and the premalignant micro-circulatory augmentation of early colon carcinogenesis.

Spectroscopic techniques have demonstrated that in the microscopically normal mucosa, there is an increase in mucosal micro-circulation in patients harboring neoplasia elsewhere in the colon (i.e. marker of field carcinogenesis). However, the physiological and molecular basis of this early increase in blood supply (EIBS) has not been elucidated. We, therefore, investigated the microvessel density (MVD) and angiogenic gene expression in the premalignant colonic mucosa from the well-validated azoxymethane (AOM)-treated rat experimental model of colon carcinogenesis. Fisher 344 rats were treated with AOM (15 mg/kg i.p.) or saline and euthanized 14 weeks later (a time-point that precedes carcinoma development). Colon sections were studied for MVD via immunohistochemical assessment for CD31 and location was compared with optical assessment of mucosal hemoglobin with low-coherence enhanced backscattering spectroscopy (LEBS). Finally, we performed a pilot real-time PCR angiogenesis microarray (84 genes) from the microscopically normal colonic mucosa of AOM and age-matched saline treated rats. AOM treatment increased MVD in both the mucosa and submucosa of the rats (125% increase in mucosa; p<0.007, and 96% increase in submucosa; p<0.02) but the increase was most pronounced at the cryptal base consistent with the LEBS data showing maximal hemoglobin augmentation at 200-225 μm depth. Microarray analysis showed striking dysregulation of angiogenic and anti-angiogenic factors. We demonstrate, for the first time, that neo-angiogenesis occurs in the microscopically normal colonic mucosa and was accentuated at the bottom of the crypt. This finding has potential implications as a biomarker for risk-stratification and target for chemoprevention.