NF-κB in the Radiation Response of A549 Non-Small Cell Lung Cancer Cells to X-rays and Carbon Ions under Hypoxia.

Cellular hypoxia, detectable in up to 80% of non-small cell lung carcinoma (NSCLC) tumors, is a known cause of radioresistance. High linear energy transfer (LET) particle radiation might be effective in the treatment of hypoxic solid tumors, including NSCLC. Cellular hypoxia can activate nuclear factor κB (NF-κB), which can modulate radioresistance by influencing cancer cell survival. The effect of high-LET radiation on NF-κB activation in hypoxic NSCLC cells is unclear. Therefore, we compared the effect of low (X-rays)- and high (12C)-LET radiation on NF-κB responsive genes' upregulation, as well as its target cytokines' synthesis in normoxic and hypoxic A549 NSCLC cells. The cells were incubated under normoxia (20% O2) or hypoxia (1% O2) for 48 h, followed by irradiation with 8 Gy X-rays or 12C ions, maintaining the oxygen conditions until fixation or lysis. Regulation of NF-κB responsive genes was evaluated by mRNA sequencing. Secretion of NF-κB target cytokines, IL-6 and IL-8, was quantified by ELISA. A greater fold change increase in expression of NF-κB target genes in A549 cells following exposure to 12C ions compared to X-rays was observed, regardless of oxygenation status. These genes regulate cell migration, cell cycle, and cell survival. A greater number of NF-κB target genes was activated under hypoxia, regardless of irradiation status. These genes regulate cell migration, survival, proliferation, and inflammation. X-ray exposure under hypoxia additionally upregulated NF-κB target genes modulating immunosurveillance and epithelial-mesenchymal transition (EMT). Increased IL-6 and IL-8 secretion under hypoxia confirmed NF-κB-mediated expression of pro-inflammatory genes. Therefore, radiotherapy, particularly with X-rays, may increase tumor invasiveness in surviving hypoxic A549 cells.

Hypersensitivity and Induced Radioresistance in Chinese Hamster Cells Exposed to Radiations with Different LET Values.

We study the impact of radiation LET on manifestation of HRS/IRR response in Chinese hamster cells ovary cells exposed to radiations used in radiotherapy. Earlier we have investigated this response to carbon ions (455 MeV/amu) in the pristine Bragg curve plateau and behind the Bragg peak, 60Co γ-rays, and 14.5 MeV neutrons. Now we present results of cytogenetic metaphase analysis in plateau-phase CHO-K1 cells irradiated with scanning beam protons (83 MeV) at doses < 1 Gy and additional data for 14.5 MeV neutrons. Dose curves for frequency of total chromosome aberrations (CA, protons), paired fragments (protons, neutrons), aberrant cells (neutrons) had typical HRS/IRR structure: HRS region (up to 0.1 and 0.15 Gy), IRR region (0.1−0.6 Gy and 0.15−0.35 Gy) for protons and neutrons, respectively, and regular dose dependence. Taken together with previous results, the data show that LET increase shifts the HRS upper border (from 0.08−0.1 Gy for γ-rays, protons and plateau carbons to 0.12−0.15 Gy for "tail" carbons and neutrons). The IRR regions shortens (0.52−0.4 γ-rays and protons, 0.25 plateau carbons, 0.2 Gy "tail" carbons and neutrons). CA level of IRR increases by 1.5−2.5 times for carbons as compared to γ-rays and protons. Outside HRS/IRR the yield of CA also enhanced with LET increase. The results obtained for different LET radiations suggest that CHO-K1 cells with G1-like CA manifested the general feature of the HRS/IRR phenomena.

Low-dose fractionated radiation and chemotherapy prior to definitive chemoradiation in locally advanced carcinoma of the uterine cervix: Results of a prospective phase II clinical trial.

BACKGROUND: We investigated the feasibility of neoadjuvant low-dose radiation and chemotherapy with paclitaxel and carboplatin (LDCRT) before radical chemoradiation (CRT) and assessed the feasibility, efficacy, and response rate to such a regimen. METHODS: This is a single-arm phase II trial of 24 patients, with locally advanced squamous cell carcinoma of the cervix (stage IIB-IIIB). Patients received low-dose fractionated radiotherapy, carboplatin (AUC×5) and paclitaxel (175 mg/m(2)), three weekly for two cycles followed by CRT. The primary end point was overall and disease-free survival. RESULTS: Mean age of the patients at diagnosis was 50 years; Radiological complete or partial response rate was 40% and 60%, respectively, post-LDCRT. The median follow-up was 30 months (24-36 months). Both overall and progression-free survivals at 2.5 years were 84%. Grade 3/4 toxicities were 24% hematological toxicity during LDCRT and 46% during CRT (hematological: 42%, non-hematological: 4%). CONCLUSION: A good response rate is achieved by low-dose radiation and chemotherapy with carboplatin and paclitaxel followed by radical CRT. This treatment regimen is feasible and effective as evidenced by the acceptable toxicity and 84% local control at 2.5 years.

Radiation-responsive scintillating nanotheranostics for reduced hypoxic radioresistance under ROS/NO-mediated tumor microenvironment regulation.

Hypoxia-induced radioresistance is the primary reason for failure of tumor radiotherapy (RT). Changes within the irradiated tumor microenvironment (TME) including oxygen, reactive oxygen species (ROS) and nitric oxide (NO) are closely related to radioresistance. Therefore, there is an urgent need to develop new approaches for overcoming hypoxic radioresistance by incorporating TME regulation into current radiotherapeutic strategies. METHODS: Herein, we explored a radiation-responsive nanotheranostic system to enhance RT effects on hypoxic tumors by multi-way therapeutic effects. This system was developed by loading S-nitrosothiol groups (SNO, a NO donor) and indocyanine green (ICG, a photosensitizer) onto mesoporous silica shells of Eu3+-doped NaGdF4 scintillating nanocrystals (NSC). RESULTS: Under X-ray radiation, this system can increase the local dosage by high-Z elements, promote ROS generation by X-ray-induced photodynamic therapy, and produce high levels of NO to enhance tumor-killing effects and improve hypoxia via NO-induced vasodilation. In vitro and in vivo studies revealed that this combined strategy can greatly reinforce DNA damage and apoptosis of hypoxic tumor cells, while significantly suppressing tumor growth, improving tumor hypoxia and promoting p53 up-regulation and HIF1α down-regulation. In addition, this system showed pronounced tumor contrast performance in T1-weighted magnetic resonance imaging and computed tomography. CONCLUSION: This work demonstrates the great potential of scintillating nanotheranostics for multimodal imaging-guided X-ray radiation-triggered tumor combined therapy to overcome radioresistance.

ATR signaling cooperates with ATM in the mechanism of low dose hypersensitivity induced by carbon ion beam.

Little work has been done on the mechanism of low dose hyper-radiosensitivity (HRS) and later appeared radioresistance (termed induced radioresistance (IRR)) after irradiation with medium and high linear energy transfer (LET) particles. The aim of this study was to find out whether ATR pathway is involved in the mechanism of HRS induced by high LET radiation. GM0639 cells and two ATM deficient/mutant cells, AT5BIVA and AT2KY were irradiated by carbon ion beam. Thymidine block technique was developed to enrich the G2-phase population. Radiation induced early G2/M checkpoint was quantitatively assess with dual-parameter flow cytometry by detecting the cells positive for phospho-histone H3. The involvement of ATR pathway in HRS/IRR response was detected with pretreatment of specific inhibitors prior to carbon ion beam. The link between the early G2/M checkpoint and HRS/IRR under carbon ion beam was first confirmed in GM0639 cells, through the enrichment of cell population in G2-phase or with Aurora kinase inhibitor that attenuates the transition from G2 to M phase. Interestingly, the early G2/M arrest could still be observed in ATM deficient/mutant cells with an effect of ATR signaling, which was discovered to function in an LET-dependent manner, even as low as 0.2Gy for carbon ion radiation. The involvement of ATR pathway in heavy particles induced HRS/IRR was determined with the specific ATR inhibitor in GM0639 cells, which affected the HRS/IRR occurrence similarly as ATM inhibitor. These data demonstrate that ATR pathway may cooperate with ATM in the mechanism of low dose hypersensitivity induced by carbon ion beam.

Low doses of radiation are protective in vitro and in vivo: evolutionary origins.

Research reports using cells from bacteria, yeast, alga, nematodes, fish, plants, insects, amphibians, birds and mammals, including wild deer, rodents or humans show non-linear radio-adaptive processes in response to low doses of low LET radiation. Low doses increased cellular DNA double-strand break repair capacity, reduced the risk of cell death, reduced radiation or chemically-induced chromosomal aberrations and mutations, and reduced spontaneous or radiation-induced malignant transformation in vitro. In animals, a single low, whole body dose of low LET radiation, increased cancer latency and restored a portion of the life that would have been lost due to either spontaneous or radiation-induced cancer in the absence of the low dose. In genetically normal fetal mice, a prior low dose protected against radiation-induced birth defects. In genetically normal adult-male mice, a low dose prior to a high dose protected the offspring of the mice from heritable mutations produced by the large dose. The results show that low doses of low-LET radiation induce protective effects and that these induced responses have been tightly conserved throughout evolution, suggesting that they are basic responses critical to life. The results also argue strongly that the assumption of a linear increase in risk with increasing dose in humans is unlikely to be correct, and that low doses actually reduce risk.