Zheng et al. [95] used an artificial approach to analyze the effect of an engineered miRNA (amiR) able to target in a perfect complementary way the 3′UTR of XRCC2, a fundamental homologous recombination factor, and XRCC4, an essential nonhomologous end joining factor, in cancer cells along with a siRNA. The gene discussed is XRCC4; the disease is cancer.