The NCI-H209 cell line was derived by A.F. Gazdar and associates in 1979 from the bone marrow of a patient with small cell cancer of the lung. The bone marrow specimen was taken prior to therapy. The line is a classic SCLC cell line which expresses elevated levels of four biochemical markers (neuron specific enolase, brain isoenzyme of creatine kinase, L-DOPA decarboxylase and bombesin-like immunoreactivity. C-myc DNA sequences are not amplified. No gross structural DNA abnormalities were detected. The line produces normal amounts of p53 mRNA relative to normal lung. This is a cell line that grows as large aggregates in suspension. Only the aggregates are viable, but no meaningful viability percentage can be measured. The medium will normally contain large amounts of cell debris. The cells express an aberrant form of RB1 that is not phosphorylated, apparently due to a single point mutation at codon 706 (Cys-Phe).