G2 checkpoint control and G2 chromosomal radiosensitivity in cancer survivors and their families

摘要

Significant inter-individual variation in G2 chromosomal radiosensitivity, measured as radiation-induced chromatid-type aberrations in the subsequent metaphase, has been reported in peripheral blood lymphocytes of both healthy individuals and a range of cancer patients. One possible explanation for this variation is that it is driven, at least in part, by the efficiency of G2–M checkpoint control. The hypothesis tested in the current analysis is that increased G2 chromosomal radiosensitivity is facilitated by a less efficient G2–M checkpoint. The study groups comprised 23 childhood and adolescent cancer survivors, their 23 partners and 38 of their offspring (Group 1) and 29 childhood and young adult cancer survivors (Group 2). Following exposure to 0.5 Gy of 300 kV X-rays, lymphocyte cultures were assessed for both G2 checkpoint delay and G2 chromosomal radiosensitivity. In Group 1, the extent of G2 checkpoint delay was measured by mitotic inhibition. No statistically significant differences in G2 checkpoint delay were observed between the cancer survivors (P = 0.660) or offspring (P = 0.171) and the partner control group nor was there any significant relationship between G2 checkpoint delay and G2 chromosomal radiosensitivity in the cancer survivors (P = 0.751), the partners (P = 0.634), the offspring (P = 0.824) or Group 1 taken as a whole (P = 0.379). For Group 2, G2 checkpoint delay was assessed with an assay utilising premature chromosome condensation to distinguish cell cycle stage. No significant relationship between G2 checkpoint delay and G2 chromosomal radiosensitivity was found (P = 0.284). Thus, this study does not support a relationship between G2–M checkpoint efficiency and variation in G2 chromosomal radiosensitivity.