Knockdown of Rad51 expression induces radiosensitivity of gastrointestinal stromal tumor cells

Purpose: Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm of the gastrointestinal tract. Resistance to ionizing radiation (IR) is the a potential cause contributing to the failure of radiotherapy in GIST patients. Rad51 is a key factor for homologous recombination repair. Although Rad51 expression is associated with DNA double-strand damage induced by ionizing radiation, the correlation of Rad51 expression with radiosensitivity in gastrointestinal stromal tumor cells is unclear and remains to be elucidated. Herein, we investigated the effect of Rad51 on the radiosensitivity of gastrointestinal stromal tumor cells.

Methodology: Immunohistochemistry was conducted to evaluate the expression of Rad51 in GIST tissues. Rad51 expression was determined after exposure to radiation (0,4,8,16 Gy) . After suppression of Rad51 expression, using a plasmid vector mediated short hairpin RNA (shRNA) expression system, CCK-8, colony formation assay, and flow cytometry were applied to assess cell proliferation, apoptosis and radiosensitivity. Western blot and immunofluorescence were applied to assess γ-H2AX and Rad51 protein expression levels and focal site formation, and comet assay was used to verify DNA double-strand damage.

Results: Rad51 was detected to be high expression in GIST tumor tissues compared with normal tissues from individuals (P <0.05). Moreover, Rad51 was elevated with radiation in a dose-dependent manner. Inhibition of Rad51 expression induces radiosensitivity of GIST cells by arresting cells in the G2/M phase. In addition, the suppression of Rad51 expression enhanced radiation-induced apoptosis of the cells by promoting DNA damage and delaying DNA repair, and inhibited proliferation potentials of GIST882 cells.

Conclusions: Our study supports that the suppression of Rad51 expression is an effective strategy for radiosensitization in gastrointestinal stromal tumor and opens up new scenarios of use of radiotherapy, especially if combined with molecularly targeted therapy,can improve patients’ prognosis.

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