Neural Cell Adhesion Molecule Expression and Messenger RNA Splicing Patterns in Lung Cancer Cell Lines Are Correlated with Neuroendocrine Phenotype and Growth Morphology

Diverse histological types of lung cancer express neuroendocrine (NE) markers. We studied the expression and alternative splicing forms of the neural cell adhesion molecule (NCAM) NKH-1, a member of the immunoglobulin superfamily, in §6 lung cancer cell lines representing all histological types. We found a strong correlation between expression of NCAM with both NE phenotype and lack of substrate adhesion in culture. Several cell lines expressed high levels of the leukocyte antigen Leu-7 (HNK-1) but were negative for NCAM antigen and mRNA, indicating that the Leu-7 antigen is distinct from NCAM. All of the NCAM-positive cell lines demonstrate a single 6.2-kilobase mRNA, and analysis of the known 3' alternative splices shows predominant expression of only the membrane form with the small intracytoplasmic domain. We conclude that (a) expression of NCAM is associated with NE phenotype regardless of the histological type of lung cancer; (b) these cell lines share a single form of NCAM; (c) with few exceptions, NCAM expression is associated with cell to cell adhesion and lack of substrate adhesion (growing as floating clusters); and (d) Leu-7 antigen is distinct from NCAM. This form of NCAM may play a functional role in NE differentiation or may be a part of the NE program expressed by these cells.