Immunoexpression of the alpha subunit of a guanine nucleotide-binding protein (Go) in pulmonary neuroendocrine cells and neoplasms

The alpha subunit of a GTP-binding protein, Go, was investigated in pulmonary neuroendocrine neoplasms and fetal tissues of the lung by an immunohistochemical method. Positive immunostaining for the alpha subunit of Go (Go alpha) was found predominantly on the cell membrane and found occasionally in the cytoplasm. Typical carcinoids were all positively stained (9/9), and small cell carcinoma showed weaker and less frequent staining (5 positive cases in 10). Atypical carcinoids were variously stained (3/4). The tendency for obvious neuroendocrine differentiation to be immunohistochemically determined in typical carcinoids and not in small cell carcinoma is also true of staining for neuron specific enolase (NSE), chromogranin A (CG-A) and synaptophysin. In the lung, Go alpha-immunostaining was positive not only in nerve tissues but also in the airway epithelium. In the fetal lung, serial sections immunostained for NSE, CG-A and Go alpha confirmed that Go alpha-immunoreactive cells belong to the neuroendocrine cell population. The biological significance of Go alpha is unclear in normal and neoplastic lung tissues, but Go alpha is a useful marker of neuroendocrine cells and neoplasms of the lung.