A unique cell-surface protein phenotype distinguishes human small-cell from non-small-cell lung cancer.

Abstract

Radioiodination (125I) and two-dimensional polyacrylamide gel electrophoresis were used to determine that small- (oat) cell lung carcinoma (SCC).sbd. a tumor with neuroendocrine features.sbd.possesses a surface protein pattern distinct from the other types of lung cancer cells (squamous, adeno-, and large-cell undifferentiated carcinoma). Twelve distinguishing proteins, 40-70 kilodaltons (kDal), characterized 4 lines of SCC; 3 of these, designated E (60 kDal; pI = 7.3), S (30 kDal; pI = 6.0), and U (57 kDal; pI = 5.6), may be unique SCC gene products and were identified only in [35S]methionine labeling of SCC and not in non-SCC or human fibroblasts. Two lines of adeno-, 1 of squamous and 1 of undifferentiated large-cell lung carcinoma exhibited similar surface protein patterns to one another. Nine distinguishing proteins (40-100 kDal) and at least 5 large proteins (> 100 kDal) were unique to these lines. The surface protein phenotypes for SCC and non-SCC were distinct from those for human lymphoblastoid cells and fibroblasts. However, the neuroendocrine features of SCC were further substantiated because 6 of the 12 distinguishing SCC surface proteins, including E and U, were identified on human neuroblastona cells. The proteins identified should help define differentiation steps for normal and neoplastic bronchial epithelial cells, prove useful in better classifying lung cancers, and be instrumental in tracing formation of neuroendocrine cells.