Cytoplasmic and nuclear maspin expression in lung carcinomas: an immunohistochemical study using tissue microarrays

Maspin, a serine protease inhibitor related to the serpin family, can inhibit invasion and metastasis of malignancies although direct evidence of the clinicopathologic significance of cytoplasmic relative to nuclear expression is limited. Here, maspin expression was examined on tissue microarrays containing lung carcinoma (n=155) and adjacent noncancerous tissue (n=20) and also 4 lung carcinoma cell lines (LC-1/Sq, LC-IF, PC-14, and AoI) by immunohistochemistry. Maspin expression was compared with clinicopathologic parameters of the tumors. Maspin expression showed positive nuclear staining in basal cells, LC-IF, and PC-14 cell lines, and also cytoplasmic immunoreactivity in secretory and ciliated cells, LC-1/Sq cell line. Cytoplasmic staining was the lowest in adenocarcinoma (AD) and the highest in squamous cell carcinoma as compared with other types of lung carcinoma (P<0.05), and positively correlated with expression of p53 and caspase-3 (P<0.05). The cytoplasmic one showed stronger immunoreactivity in male carcinoma patients than female ones (P<0.05). The nuclear maspin expression gradually increased through squamous cell carcinoma, AD, large cell carcinoma to small cell carcinoma (P<0.05) and was also positively associated with the levels of vascular epithelial growth factor and extracellular matrix metalloproteinase inducer expression (P<0.05). Kaplan-Meier analysis indicated that the cytoplasmic or nuclear maspin expression was not a good prognostic marker for lung carcinomas overall (P>0.05), but the cytoplasmic pattern pointed to good survival for AD cases (P<0.05). It was concluded that the cytoplasmic and nuclear expression patterns of maspin are involved in the cellular differentiation of normal lung tissue and the histogenesis of different lung carcinomas. The cytoplasmic maspin may play an important role in lung carcinomas by regulating apoptosis and thus is a favorable prognostic marker for AD patients, whereas the nuclear location may be linked to promotion of angiogenesis.