Silencing of heat shock protein 27 increases the radiosensitivity of non-small cell lung carcinoma cells

Radiotherapy is a useful treatment for malignant tumors, including lung carcinoma; however, non-small cell lung carcinoma (NSCLC) is frequently insensitive to radiation. It has been reported that heat shock protein 27 (HSPB1) is a radioresistance-associated protein in nasopharyngeal carcinoma. In the present study, the role of HSPB1 in NSCLC cells induced by irradiation was investigated. The viability of cells was determined by a Cell Counting Kit-8 assay. The apoptotic activity, cell cycle distribution and mitochondrial membrane potential (MMP) of cells were evaluated via flow cytometry. Reverse transcription-quantitative polymerase chain reaction and western blot analyses were employed to measure the expression of various genes and proteins. It was observed that knockdown of HSPB1 with small interfering RNA (si-HSPB1) markedly decreased the viability of A549 NSCLC cells and induced cell cycle arrest in the G2/M phase following exposure to 6 Gy irradiation. Furthermore, it was revealed that si-HSPB1 significantly downregulated cyclin B1 and cyclin G1 expression. Additionally, si-HSPB1 promoted apoptosis and depolarized the MMP of cells exposed to 6 Gy irradiation. The expression levels of B-cell lymphoma-2 (Bcl-2), mitochondrial cytochrome c (cyto c) and pro-caspase-8 were downregulated, whereas those of Bcl-2 associated X protein (Bax), cytosolic cyto c and cleaved-caspase-8 were upregulated. Collectively, silencing of HSPB1 increased the radiosensitivity of NSCLC cells by reducing cell viability, depolarizing the MMP, arresting the cell cycle in the G2/M phase and promoting cell apoptosis. Therefore, HSPB1 may be a novel target for increasing radiosensitivity in the treatment of NSCLC.