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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Cell Separation, Cell Survival, Dose-Response Relationship, Radiation, Female, Fibroblasts, Flow Cytometry, G2 Phase, Humans, Radiation Tolerance, Tumor Stem Cell Assay, Uterine Cervical Neoplasms.
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Is low-dose hyper-radiosensitivity a common effect in normal asynchronous and G2-phase fibroblasts of cancer patients? Context: In our previous study, using the micronucleus assay, a low-dose hyper-radiosensitivity (HRS)-like phenomenon was observed for normal fibroblasts of 2 of the 40 cancer patients investigated. In this article we report, for the first time, the survival response of primary fibroblasts from 25 of these patients to low-dose irradiation and answer the question regarding the effect of G2-phase enrichment on HRS elicitation. The clonogenic survival of asynchronous as well as G2-phase enriched fibroblast populations was measured. Separation of G2-phase cells and precise cell counting was performed using a fluorescence-activated cell sorter. Sorted and plated cells were irradiated with single doses (0.1-4 Gy) of 6-MV x-rays. For each patient, at least 4 independent experiments were performed, and the induced-repair model was fitted over the whole data set to confirm the presence of HRS effect. The HRS response was demonstrated for the asynchronous and G2-phase enriched cell populations of 4 patients. For the rest of patients, HRS was not defined in either of the 2 fibroblast populations. Thus, G2-phase enrichment had no effect on HRS elicitation.
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The fact that low-dose hyper-radiosensitivity is not a common effect in normal human fibroblasts implies that HRS may be of little consequence in late-responding connective tissues with regard to radiation fibrosis. Final Decision: no