Gamma radiation-induced apoptosis, G2 delay, and the risk of salivary and thyroid carcinomas - A preliminary report

Background. While radiation has been the only well-established risk factor for salivary and thyroid cancers, the exact mechanisms remain unknown. We hypothesized that individuals with altered apoptotic response to γ irradiation may be susceptible to salivary and thyroid cancers. Methods. We tested our hypothesis in a pilot case-control study of 29 patients with neoplasms of the salivary and thyroid glands and 29 cancer-free control subjects. Patients and control subjects were matched on age, sex, and ethnicity. In vitro γ radiation-induced apoptosis in lymphocytes was quantified utilizing the TUNEL assay and flow cytometry, Results. The mean apoptotic capacity was 13.55 ± 10.54 for control subjects, 5.75 ± 4.96 for patients with salivary gland carcinomas (p = .003), and 6.87 ± 4.45 for patients with thyroid carcinomas (p = .006). These differences were associated with a 10-fold increased risk of salivary gland carcinoma (odds ratio [OR] = 10.71; 95% confidence interval [CI], 1.21-94.86) and a four-fold increased risk of thyroid carcinoma (OR = 3.93; 95% CI, 0.90-17.08). Conclusions. Our data suggests that γ radiation-induced apoptosis may serve as a biomarker of genetic susceptibility to salivary and thyroid carcinoma, and further confirmatory studies with larger sample size are warranted.