A preliminary investigation demonstrating the effect of quercetin on the expression of genes related to cell-cycle arrest, apoptosis and xenobiotic metabolism in human CO115 colon-adenocarcinoma cells using DNA microarray

The role of the natural dietary flavonoid chemical quercetin (an antioxidant) in the prevention and treatment of colon cancer is receiving a great deal of attention. However, little is known about the molecular mechanisms of action of this flavonoid. In the present study, whole genome DNA microarrays were used to evaluate the effect of quercetin on gene expression in the CO115 colon-adenocarcinoma cell line with the completely deleted chromosome 18 harbouring the SMAD4 tumour-suppressor gene related to colon carcinogenesis. The study demonstrated that quercetin, widely present in fruit and vegetables, inhibited the growth of CO115 cells at 100 microM concentration in both the G(1)/S and the G(2)/M phases by modulating cell-cycle and apoptosis-related genes. Differential changes in accumulation of transcripts analysed for cells treated with 100 microM quercetin for 24 and 48 h in three independent repeated experiments revealed 5060-7000 differentially expressed genes. This means that quercetin probably does have a broad modulatory effect on gene expression in colon cancer. Out of these differentially expressed genes, the expression of 35 and 23 unique set of genes involved in cell-cycle control, apoptosis and xenobiotic metabolism were significantly altered after 24 and 48 h quercetin treatment respectively. Our results represent a novel aspect of the biological profile of quercetin that induces cell-cycle arrest through modulation of cell-cycle-related and apoptosis genes. The present study demonstrates a new step in elucidating the underlying molecular mechanisms of the antitumour action of quercetin, which could become a chemopreventive or chemotherapeutic agent for colon cancer.

[Asymptomatic ischemia following myocardial infarct]

To assess the incidence of silent ischemia after myocardial infarction, a prospective series of 100 consecutive patients was studied 5 weeks after the acute event. Objective evaluation of myocardial ischemia included a 9-lead ECG, thallium-201 scintigraphy and radionuclide ventriculography, each at rest and during symptom-limited bicycle ergometry. Diagnostic criteria were ECG: greater than or equal to 1 mm horizontal or downsloping ST depression or greater than or equal to 1 mm ST elevation; thallium scintigraphy: a clearly reversible perfusion defect at rest, detectable only after exercise; radionuclide ventriculography: an exercise-induced decrease in global LVEF greater than or equal to 5% and/or in anyone regional EF greater than or equal to 14%. Presence of ischemia was assumed if at least 2 of 3 objective ischemic signs were found. This was the case in 28 of 100 patients. During exercise, 15 of 100 patients complained of chest pain, but only 8 (54%) had objective evidence of ischemia. Thus, silent ischemia was demonstrated in 20 of 100 patients. The sensitivity of both nuclear cardiology procedures was markedly superior to that of the ECG in diagnosing post-myocardial ischemia.