Estimation of Radiation-Induced Interphase Cell Death in Cultures of Human Tumor Material and in Cell Lines

Abstract

A short-term assay method able to estimate the radiation response of human cancer tissue samples would be of great advantage to the individualization of radiotherapy in cancer patients. However, the effect of radiation on [ 3 H]thymidine incorporation by proliferating cells reflects a composite of cell cycle arrest and induced cell death pathways. Here we consider whether it is feasible to correct for cell cycle effects based on comparison of the effects of radiation and the mitotic inhibitor paclitaxel on [ 3 H]thymidine incorporation. Sixty-two short-term (7-day) cultures of human tumor tissue from 61 patients with melanoma, gynecological cancer, brain cancer, and head and neck cancer, as well as 18 5-day cultures of low passage human tumor cell lines, were irradiated at doses from 2 to 9 Gy, or exposed to paclitaxel (200 nM). [ 3 H]Thymidine incorporation was measured at the end of the incubation. Cell cycle times could be estimated from the paclitaxel data and were 2.7 to 18.6 days for melanomas, 2.5 to >40 days for carcinomas, 3.9 to 39 days for brain tumors, and 1.1 to 3.8 days for cell lines. The effects of radiation on [ 3 H]thymidine incorporation varied widely (0-97% and 0-99% inhibition for 2 and 9 Gy, respectively), and in 23 of the clinical samples, but in none of the cell lines, radiation caused significantly greater inhibition of 3 H]thymidine incorporation than paclitaxel (p < 0.05). We argue that that these differences reflect radiation-induced cell loss from G 1 phase and/or S phase. Responses of short-term cultures of clinical tumor material to radiation, with appropriate correction for cell cycle effects, might have the potential to provide information on radiation-induced cell death in individual patients.

Derivation of Breast Cancer Cell Lines Under Physiological (5%) Oxygen Concentrations

“…As described previously ( 8 ), tumor tissue taken from four patients undergoing surgery for breast cancer was sent to the histopathologist immediately after surgery, where a portion was placed into growth medium without serum for laboratory studies. Formal consent was obtained from all patients, using guidelines approved by the Northern A Health and Disability Ethics Committee.…”

“…The difference raises the question of whether the oxygen concentration in air, for instance by generating increased reactive oxygen species (ROS), might modulate signaling pathways in “regular” cell culture conditions and thus alter responses to therapeutic agents ( 3 , 4 ). In our previous studies, human melanoma specimens were cultured in an atmosphere of 5% O 2 , 5% CO 2 , 90% N 2 to minimize oxygen-mediated damage ( 5 ) and in subsequent studies, these conditions were used in the development of more than 100 melanoma lines ( 6 , 7 ) and more than 50 carcinoma lines ( 8 ). In this report, we describe four human breast cancer cell lines that were developed under these conditions, to ascertain whether their properties, including receptor status, signaling pathway utilization, mutations and drug responses, were comparable to those of established cell lines.…”