Studying lung cancer in the laboratory: 3--Use of cell lines to investigate the biology of lung cancer.

Ectopic production of polypeptide and steroid hormones has been well documented in patients with small cell lung cancer'2 and in small cell lung cancer xenografts.5 The use of defined serum free media has allowed easy evaluation of the production of these substances by small cell lung cancer cell lines.67 In one study of 13 different lines,7 appreciable amounts of 14 different hormones were found, with up to 10 different hormones produced by any one cell line. The exact meaning of hormone production by these tumours in patients is unclear. Some studies have shown a positive correlation between serum concentrations and extent of disease or clinical response,89 while others have found no such effect.25 No attempt has been made to clarify this problem by studying hormone production by tumour cells in vitro. Recently much interest has been shown in the production of three other biological "markers" by small cell lung cancer cell lines. Neurone specific enolase, the neuronal form of the glycolytic enzyme enolase, has been found in neuroendocrine (APUD) tumours and is secreted by small cell lung cancer cell lines.'0°" The BB isoenzyme of creatine kinase (CKBB) has also been detected in large amounts in small cell lung cancer cultures'2 but, like neurone specific enolase, is not found in non-small cell lung cancer cell lines (table). A good correlation between serum concentrations and both disease extent and response to treatment has been demonstrated for both these