H2BC21 and large cell carcinoma: H460 (large cell carcinoma), H1299 (adenocarcinoma), CRL5889 (squamous cell carcinoma) NSCLC representing each subtype and HBEC3-KT (human bronchial epithelial cells) were initially transfected with siRNA or the H2B peptide expression construct and subjected to clonogenic cell viability assays post exposure to IR.