Does glutamine supplementation increase radioresistance in squamous cell carcinoma of the cervix?

Objective, Glutamine is proposed to protect bowel from radiation. However, glutamine may decrease cancer's radiosensitivity. We evaluate glutamine's e ffect on the growth rate and radiosensitivity of two cervical carcinoma cel l lines in vitro. Methods. HeLa and CaSki cells were seeded at 3000 cells/well in glutamine-f ree medium. An increasing amount of glutamine (0.4, 10, and 20 mM) was adde d to the respective plates, incubated, and irradiated with a single fractio n of 0.5, 1, 3, and 6 Gy, Using a growth inhibition assay and photometric a nalysis, the viable cells were counted on day 8. Cell counts represent a me an +/- standard deviation from six experiments and are expressed in 10(3) c ells. Analysis of variance was performed. Results. In nonirradiated HeLa plates, absence of glutamine results in 5.7 +/- 1.2 cells/well, Addition of glutamine at 0.4, 10, and 20 mM to nonirrad iated cells significantly (P < 0.0001) increased growth to 79.1 +/- 10.0, 1 22.5 +/- 9.0, and 114.3 +/- 13.9 cells/well, respectively. In culture plate s irradiated with 6 Gy, HeLa cells supplemented with 0.4, 10, and 20 mM of glutamine showed lower cell counts (P < 0.008). A similar significant growt h suppression at 6 Gy in comparison to 0.5, 1, and 3 Gy was observed (P < 0 .01), CaSki cells showed similar patterns. Conclusions. Growth of HeLa and CaSki cells in vitro requires a minimum of 0.4 mM of glutamine in the medium. Supraphysiologic glutamine concentration does not increase tumor growth or radioresistance. Glutamine should be eva luated further as a potential bowel radioprotector, (C) 1998 Academic Press .