Differential expression of the LAMB3 and LAMC2 genes between small cell and non-small cell lung carcinomas

To identify genes differentially expressed between small cell lung carcinom a (SCLC) cells and non-SCLC cells, mRNA differential display was applied to 3 SCLC cell lines and 6 non-SCLC cell lines. The LAMBS gene was identified as being expressed only in non-SCLC cells and not in SCLC cells. The LAMB3 gene encodes the laminin beta 3 chain, which is a unique component of lami nin-5. Laminin-5 is a heterotrimer protein consisting of the alpha 3, beta 3, and gamma 2 chains, and another unique component of laminin-5 is the gam ma 2 chain encoded by the LAMC2 gene. RT-PCR analysis of the LAMBS and LAMC 2 genes in 45 lung cancer cell lines revealed that both the LAMB3 and LAMC2 genes were co-expressed in 21 of 32 non-SCLC cell lines (66%) but only in one of 13 SCLC cell lines (8%). Coexpression of the LAMB3 and LAMC2 genes w as also observed in all 4 cases of primary non-SCLC cells examined but not in the corresponding non-cancerous lung cells. Since alpha 6 beta 4 integri n, the specific laminin-5 binding receptor, is known to be expressed only i n non-SCLC cells and not in SCLC cells, it was indicated that laminin-5 is a critical microenvironmental factor for the growth of non-SCLC cells but n ot of SCLC cells, The differences in the expression of integrins and lamini ns would be critical factors to distinguish SCLC and non-SCLC cells, and su ch differences might be associated with the unique biological properties of SCLC cells, including metastatic potential and drug sensitivity. (C) 2000 Academic Press.