Enhanced expression of metallothionein in human non-small-cell lung carcinomas following chemotherapy

Metallothioneins (MTs) are induced by various stimuli and probably confer drug resistance in tumor cells in vitro. To investigate whether MT expression in lung cancer is induced by chemotherapy, ninety-seven surgical specimens from patients who had or not received chemotherapy containing cisplatin, were stained immunohistochemically for MT. In untreated tumors, 23% (15/64) of all tumors and 27% (15/56) of non-small-cell carcinoma (NSCLC) stained positive, while all eight small-cell carcinoma (SCLC) were negative. In treated tumors, 52% (17/33) of all tumors, 80% (12/15) of NSCLC and 28% (5/18) of SCLC stained positive. The proportion of positively-stained tumors was significantly higher in treated NSCLC compared with untreated NSCLC (P = 0.0005) and treated SCLC (P < 0.005). Our results indicate that MT expression increases following chemotherapy and that such expression may confer during resistance in lung cancer, especially NSCLC.