Radiation Studies on B Cell Differentiation Marker CD24/SCLC Cluster-4 Antigen Expressing and Non-expressing Lung Cancer Cell Lines and Mouse Fibroblasts

A correlation between CD24 expression and higher intrinsic radiation sensitivity has been described in B-lineage acute lymphoblastic leukaemia (B-ALL). We recently identified the SCLC surface antigen Cluster-4 (CL-4) to be identical to the B cell differentiation marker CD24, except for one amino acid residue. The CD24/CL-4 antigen is highly expressed on SCLC, but rarely on NSCLC cells. In order to investigate the influence of the expression of CD24/CL-4 on the radiation sensitivity in a non-leukaemic cell system, sublines of the human SCLC H249 cell line transfected with mutated ras oncogene, and differing in their CD24/CL-4 expression, were studied. In addition, we stably transfected the NSCLC A125 cell line and the mouse fibroblast NIH3T3 cell line with the CL-4 cDNA. The differential expression of CD24/CL-4 on the cells had no influence on morphology, proliferation and cloning efficiency. Radiation studies were done with cells in exponential growth phase. In the highly resistant NSCLC A125 cells no dif...