Tseng et al.[22] performed a gene-gene interaction analysis which revealed that polymorphisms in the XRCC4 (rs1805377) and LIG4 (rs1805388) genes interacted to modulate the risk of lung cancer (adjusted OR, 8.75) and demonstrated that LIG4 rs1805388 and XRCC4 rs1805377 polymorphisms are linked significantly with high fractional allelic loss (FAL), an indicator of genomic instability. The gene discussed is LIG4; the disease is lung cancer.