In some hypoxic tumor cells, the expression of homologous recombination repair (HRR) pathway-related genes, such as RAD51 and BCRA1, will be downregulated (26, 27), while the expression of non-homologous end-joining (NHEJ) pathway-related genes, such as ATM and DNA-PKcs, will be upregulated (28, 29). This evidence concerns the gene RAD51 and neoplasm.