Hypoxia inducible factor-1α (HIF-1α) is a critical transcriptional factor for the response of cells to hypoxic microenvironment and its expression induces resistance of hypoxic non-small-cell lung cancer (NSCLC) cells to radiotherapy. This study investigated how the activation of HIF-1α/B-cell lymphoma 2 (BCL-2) signaling under normoxic conditions impacted radiosensitivity of NSCLC cells. The recombinant pcDNA3.0-EGFP plasmids with wild-type or mutant HIF-1α complementary DNA (cDNA) were transfected into H1299 cells, an NSCLC cell line, establishing two H1299 sublines with high expression of HIF-1α. Compared with the levels of HIF-1α and BCL-2 proteins in non-transfected cells, increased levels of both proteins were found in transfected cells. Moreover, the expression of HIF-1α in non-transfected cells induced by chloride cobalt (CoCl2), a commonly used mimetic hypoxia reagent, was concomitant with the enhancement of BCL-2 expression. Conversely, reduction of HIF-1α expression by an inhibitor decreased the levels of BCL-2 proteins. The results revealed that the stabilization and expression of HIF-1α promoted the accumulation of BCL-2 proteins in H1299 cells. Subsequent experiments showed that intracellular HIF-1α/BCL-2 signaling was triggered in a normoxic environment after H1299 cells were exposed to irradiation, causing an elevated radioresistance. In contrast, blockage of HIF-1α/BCL-2 signaling leads to an elevated radiosensitivity. Proliferation of cells assay showed that, under normoxic conditions, population doubling times (PDTs) of irradiated cells were prolonged by suppression of HIF-1α/BCL-2 signaling. It is, therefore, indicated that HIF-1α/BCL-2 signaling activated by ionizing radiation reduces the radiosensitivity of H1299 cells independent of the hypoxic environment.

中文翻译：

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低氧诱导因子-1α/ B细胞淋巴瘤2信号影响常氧环境中H1299非小细胞肺癌细胞的放射敏感性。

低氧诱导因子-1α（HIF-1α）是细胞对低氧微环境反应的关键转录因子，其表达诱导低氧非小细胞肺癌（NSCLC）细胞对放疗的耐药性。这项研究调查了常氧条件下HIF-1α/ B细胞淋巴瘤2（BCL-2）信号的激活如何影响NSCLC细胞的放射敏感性。将具有野生型或突变型HIF-1α互补DNA（cDNA）的重组pcDNA3.0-EGFP质粒转染到NSCLC细胞系H1299细胞中，建立了两个HIF-1α高表达的H1299亚系。与未转染细胞中的HIF-1α和BCL-2蛋白水平相比，在转染细胞中两种蛋白的水平均升高。此外，HIF-1α在氯化钴（CoCl2）诱导的未转染细胞中的表达，常用的模拟低氧试剂与BCL-2表达的增强同时发生。相反，抑制剂降低HIF-1α表达可降低BCL-2蛋白的水平。结果表明，HIF-1α的稳定和表达促进了H1299细胞中BCL-2蛋白的积累。随后的实验表明，在暴露于H1299细胞后，在常氧环境中会触发细胞内HIF-1α/ BCL-2信号传导，从而导致放射抵抗力升高。相反，HIF-1α/ BCL-2信号传导受阻会导致放射敏感性升高。细胞增殖试验表明，在常氧条件下，通过抑制HIF-1α/ BCL-2信号传导，可以延长辐照细胞的群体倍增时间（PDT）。因此，