Biological and clinical implication of neuron-specific enolase and creatine kinase BB in small cell lung cancer.

The specificity of neuron-specific enolase (NSE) and creatine kinase BB (CK-BB) for small cell lung cancer (SCLC) was determined by biological and immunohistochemical procedures in lung cancer tissues and cultured cell lines. Average values of extractable NSE and CK-BB of SCLC tissues were significantly higher than those of non-SCLC and normal lung tissues. A large amount of NSE and CK-BB was demonstrated in SCLC cell lines. Immunohistochemical examination showed positive staining for NSE and CK-BB in most cases of SCLC and in a few cases of non-SCLC. From these data NSE and CK-BB should be considered to be highly specific for SCLC. In a clinical study serum values exceeding 10 ng/ml for NSE and 1.5 ng/ml for CK-BB were set as positive for the enzymes. Positive rates in SCLC were 71.4% for NSE and 65.3% for CK-BB, which were significantly higher than those in non-SCLC. All positive cases were in an advanced stage. Consecutive daily NSE determinations during induction chemotherapy showed transient elevation immediately after the initiation of drug administration (tumor lysis syndrome), followed by a decline to normal range in responders. This phenomenon seems to indicate tumor sensitivity to cytotoxic drugs. NSE positive non-SCLC was as sensitive to cytotoxic drugs as SCLC. These findings indicate that lung cancer with elevated serum NSE and CK-BB levels at diagnosis should be strongly suspected of being SCLC in the advanced stage.