GLUTAMINE MODULATES PHENOTYPE AND STIMULATES PROLIFERATION IN HUMAN COLON-CANCER CELL-LINES

Glutamine supplementation has been advocated for patients requiring pa renteral nutritional support. However, the direct effect of glutamine on neoplastic cells is poorly understood. We therefore investigated th e effects of glutamine on the proliferation, differentiation, and cell -matrix interactions of two human colon carcinoma cell lines (Caco-2 a nd SW620) adapted to glutamine-free media. Doubling times were calcula ted by logarithmic transformation of serial cell counts. Alkaline phos phatase, cathepsin C (dipeptidyl peptidase), lactase, and isomaltase e xpression (markers of differentiation) were assayed by digestion of sy nthetic substrates. Adhesion to matrix proteins was assessed by colori metric quantitation of toluidine blue staining of adherent cells. Surf ace expression of Caco-2 receptors for matrix proteins (integrins) was studied by biotinylation and immunoprecipitation with specific antibo dies. Glutamine (1-10 mM) dose-dependently stimulated Caco-2 prolifera tion on all matrices studied with maximal effect at 7 mM. For instance , Caco-2 doubling time on collagen IV decreased by 57 +/- 0.2% (SE) (P < 0.001). Glutamine inhibited the expression of all four digestive en zy?mes with maximal inhibition ranging from 10 to 40% (P < 0.05 for al l). Adhesion to matrix proteins was markedly diminished (51 +/- 1%, P < 0.01) by glutamine (5 mM) treatment, correlating with decreased alph a 2 and beta 1 integrin subunit surface expression. Glutamine had simi lar effects on SW620 cells, stimulating proliferation, inhibiting dige stive enzyme expression, and diminishing both adhesion and integrin su rface expression. Glutamine supplementation modulates the phenotype of at least two human colon carcinoma cell lines, increasing proliferati on, decreasing differentiation, and decreasing adhesion to matrix prot eins in association with decreased integrin expression. Although the m echanisms of these effects await elucidation, such characteristics wou ld appear to predict more aggressive tumor behavior and raise the poss ibility that nutritional supplementation with glutamine may be deleter ious in patients with cancer.