Combined low initial DNA damage and high radiation-induced apoptosis confers clinical resistance to long-term toxicity in breast cancer patients treated with high-dose radiotherapy

Abstract

BackgroundEither higher levels of initial DNA damage or lower levels of radiation-induced apoptosis in peripheral blood lymphocytes have been associated to increased risk for develop late radiation-induced toxicity. It has been recently published that these two predictive tests are inversely related. The aim of the present study was to investigate the combined role of both tests in relation to clinical radiation-induced toxicity in a set of breast cancer patients treated with high dose hyperfractionated radical radiotherapy.MethodsPeripheral blood lymphocytes were taken from 26 consecutive patients with locally advanced breast carcinoma treated with high-dose hyperfractioned radical radiotherapy. Acute and late cutaneous and subcutaneous toxicity was evaluated using the Radiation Therapy Oncology Group morbidity scoring schema. The mean follow-up of survivors (n = 13) was 197.23 months. Radiosensitivity of lymphocytes was quantified as the initial number of DNA double-strand breaks induced per Gy and per DNA unit (200 Mbp). Radiation-induced apoptosis (RIA) at 1, 2 and 8 Gy was measured by flow cytometry using annexin V/propidium iodide.ResultsMean DSB/Gy/DNA unit obtained was 1.70 ± 0.83 (range 0.63-4.08; median, 1.46). Radiation-induced apoptosis increased with radiation dose (median 12.36, 17.79 and 24.83 for 1, 2, and 8 Gy respectively). We observed that those "expected resistant patients" (DSB values lower than 1.78 DSB/Gy per 200 Mbp and RIA values over 9.58, 14.40 or 24.83 for 1, 2 and 8 Gy respectively) were at low risk of suffer severe subcutaneous late toxicity (HR 0.223, 95%CI 0.073-0.678, P = 0.008; HR 0.206, 95%CI 0.063-0.677, P = 0.009; HR 0.239, 95%CI 0.062-0.929, P = 0.039, for RIA at 1, 2 and 8 Gy respectively) in multivariate analysis.ConclusionsA radiation-resistant profile is proposed, where those patients who presented lower levels of initial DNA damage and higher levels of radiation induced apoptosis were at low risk of suffer severe subcutaneous late toxicity after clinical treatment at high radiation doses in our series. However, due to the small sample size, other prospective studies with higher number of patients are needed to validate these results.

Radiogenomics: A systems biology approach to understanding genetic risk factors for radiotherapy toxicity?

“…A subsequent smaller study (n=16) using fresh lymphocytes from breast RT patients and a fluorescence-labelled inhibitor of caspases (FLICA) to detect apoptosis also found no difference in mean apoptotic fractions (190). Although not all studies were able to show a significant association of lymphocyte apoptosis with normal-tissue reaction, three studies in which associations with late reactions were significant showed a consistent negative correlation between the frequency of apoptosis and the risk of late reaction (194, 212, 213) while increased early cell death correlated with early toxicity (194, 196, 212). A large multicentre prospective validation study of the RILA assay in breast and prostate patients is currently undertaken as part of the EU-funded REQUITE project (214) initiated by the RGC.…”

“…An early study found increased apoptosis in breast cancer patients relative to controls but no significant difference between patients with and without late reaction after RT (207). Enhanced apoptosis detected by Annexin V was found to be associated with resistance to late toxicity in 26 breast cancer RT patients (194). A recent study tested early death of lymphocytes by staining with trypan blue 4h after irradiation with 2 Gy and found a significant association with early toxicity grade (196).…”

Radioprotective effects of genistein on HL-7702 cells via the inhibition of apoptosis and DNA damage

“…However, in addition to killing cancer cells, ionizing radiation causes damage to normal tissues and cells [1], which may cause serious adverse reactions, such as diarrhea, abdominal pain, nausea, vomiting and bleeding, among others [2][3][4].…”

Radiosensitivity in breast cancer assessed by the histone γ-H2AX and 53BP1 foci

“…But the difference was not confirmed when γ-H2AX foci were counted by fluorescence microscopy. A series of studies [18-24] used histone γ-H2AX as a marker to predict the toxicity in normal tissue during radiotherapy of tumor patients, however, with contradictory outcomes. Thus, some of the quoted studies [19,21-23] revealed no correlation between either acute or late side effects of radiation therapy (RT) and expression of histone γ-H2AX.…”