The involvement of HR in the repair of DNA lesions induced by topoisomerase II poisons in higher eukaryotes is also supported by a recent work suggesting that RAD51 plays an important role in the repair of etoposide-induced DNA damage in human small cell lung cancer cells [46], and by work by Adachi and colleagues who recently found that knocking out RAD54 in chicken DT40 cells enhances their sensitivity towards the topoisomerase II poison etoposide [13]. This evidence concerns the gene RAD51 and small cell lung carcinoma.