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The tumor cell defense response to ionizing radiation involves a temporary arrest at the cell cycle G2 checkpoint, which is activated by a signaling cascade initiated by the ATM kinase response to DNA damage, ultimately leading to the outcome of further cell survival if the DNA is properly repaired. The inhibitory targeting of the checkpoint kinase signaling elicited by ATM may define a biologically based strategy to override the G2 phase delay that prevents mitotic entry after DNA damage, thereby increasing the probability of mitotic cell death following exposure to ionizing radiation.Breast carcinoma cell lines with intact or defective function of the tumor-suppressor protein BRCA1 were exposed to ionizing radiation in the absence or presence of a specific inhibitor (UCN-01) of the checkpoint kinase CHK1, and the response profiles of cell cycle distribution and G2 phase regulatory factors, as well as the efficiency of clonogenic regrowth, were analyzed.The radiation-induced G2 phase accumulation was preceded by a transient down-regulation of the G2 phase-specific polo-like kinase-1 and cyclin B1, which required intact function of both BRCA1 and CHK1. The concomitant treatment with UCN-01 seemed to amplify the cytotoxic effect of ionizing radiation on clonogenic regrowth.The effector mechanism of DNA damage on cell cycle gene regulation signals through the checkpoint kinase network. Among molecular cell cycle-targeted drugs currently in pipeline for testing in early phase clinical trials, CHK1 inhibitors may have therapeutic potential as radiosensitizers. [Copyright &y& Elsevier]

Objectives: To assess health-related quality of life (HRQoL) with first-line pembrolizumab, pembrolizumab-chemotherapy, or cetuximab-chemotherapy in recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC) in the phase 3 KEYNOTE-048 trial (NCT02358031).Materials and Methods: HRQoL was measured using the European Organisation for Research and Treatment of Cancer 30-question quality-of-life (EORTC QLQ-C30), the EORTC 35-question quality-of-life head and neck cancer-specific module (EORTC QLQ-H&N35), and the EuroQol 5-dimension 3-level instruments (EQ-5D-3L). Secondary endpoints included mean change from baseline in EORTC QLQ-C30 global health status/quality of life (GHS/QoL) at week 15 and time to deterioration (TTD) in EORTC QLQ-C30 GHS/QoL and EORTC QLQ-H&N35 pain and swallowing.Results: Of 882 enrolled participants, 844 received ≥ 1 dose of study treatment and completed ≥ 1 HRQoL assessment; adherence was ≥ 79% at week 15 across treatment groups. At week 15, EORTC QLQ-C30 GHS/QoL scores remained stable; no clinically meaningful between-group differences were observed (least squares mean difference, pembrolizumab vs cetuximab-chemotherapy, 0.24; 95% CI, -3.34 to 3.82; pembrolizumab-chemotherapy vs cetuximab-chemotherapy, 0.40; 95% CI, -3.46 to 4.26). Median TTD in EORTC QLQ-C30 GHS/QoL and EORTC QLQ-H&N35 pain and swallowing scores was not reached over 51 weeks across groups, showing stable HRQoL. TTD was similar between groups for EORTC QLQ-C30 GHS/QoL (pembrolizumab vs cetuximab-chemotherapy: HR, 1.38; 95% CI, 0.95-2.00; pembrolizumab-chemotherapy vs cetuximab-chemotherapy: HR, 1.37; 95% CI, 0.94-2.00), as was TTD in EORTC QLQ-H&N35 pain and swallowing scores.Conclusions: Pembrolizumab monotherapy and pembrolizumab-chemotherapy extended OS while maintaining HRQoL, further supporting first-line use for R/M HNSCC. [ABSTRACT FROM AUTHOR]

Abstract: A senescence-like growth arrest succeeded by recovery of proliferative capacity was observed in MCF-7 breast tumor cells exposed to fractionated radiation, 5×2Gy. Exposure to EB 1089, an analog of the steroid hormone 1α, 25 dihydroxycholecalciferol (1α, 25 dihydroxy Vitamin D3; calcitriol), prior to irradiation promoted cell death and delayed both the development of a senescent phenotype and the recovery of proliferative capacity. EB 1089 also reduced clonogenic survival over and above that produced by fractionated radiation alone and further conferred susceptibility to apoptosis in MCF-7 cells exposed to radiation. In contrast, EB 1089 failed to enhance the response to radiation (or to promote apoptosis) in normal breast epithelial cells or BJ fibroblast cells. EB 1089 treatment and fractionated radiation additively promoted ceramide generation and suppressed expression of polo-like kinase 1. Taken together, these data indicate that EB 1089 (and 1α, 25 dihydroxycholecalciferol or its analogs) could selectively enhance breast tumor cell sensitivity to radiation through the promotion of cell death, in part through the generation of ceramide and the suppression of polo-like kinase. [Copyright &y& Elsevier]