The basement membrane is considered to act as a barrier which hinders
cancer cells from invading the surrounding stroma. In order to assess changes in essential components during
neoplasia in the lung, we immunohistochemically studied distribution patterns of laminins alpha 3 and alpha 5 in 40
adenocarcinomas and 8
squamous cell carcinomas. The a 5 chain was generally preserved at the periphery, frequently disrupted in foci with alveolar collapse and absent in foci of fibroblastic proliferation within
adenocarcinomas. Fragmentation and absence of
laminin alpha 3 chain were more prominent than for alpha 5 chain.
Laminin alpha 3 chain was partially fragmented or absent in peripheral areas of
adenocarcinomas, being significantly different from alpha 5 chain. Non-small cell
lung cancers with reduced alpha 5 chain showed a tendency for greater
lymph node metastasis. In cultured normal air way epithelial cells, both
laminin alpha 3 and alpha 5 chains were found to be expressed by northern analysis. Eleven of the twelve cultured
lung cancer cell lines did not express alpha 3 chain and expression of alpha 5 chain was reduced in three. Quantitative RT-PCR analysis also demonstrated expression of
laminin alpha 3 chain in
adenocarcinoma tissues to be significantly lower than in normal lung tissues. These results suggest that expression of
laminin alpha chains is often reduced in
lung cancer cells and this might contribute to basement membrane fragmentation and subsequent proliferation of stromal elements, as well as play some role in the process of
cancer cell invasion.