Expression of α subunit of guanine nucleotide-binding protein Go in Merkel cell carcinoma

The α subunit of guanine nucleotide-binding protein G_o(G_oα), which was initially isolated from bovine brain, interacts with muscarinic cholinergic receptors and regulates neuronal calcium channels. G_oα is known to be localized in neural tissues, some endocrine cells, and neuroendocrine tumors. We have immunohistochemically investigated the expression of G_oα in 4 cases of Merkel cell carcinoma using the method of microwave treatment. In all cases of Merkel cell carcinoma, G_oα was consistently detected on the plasma membrane and cytoplasm of the tumor cells. Nerve fibers in the skin were also positive for G_oα, but other epidermal or dermal components such as keratinocytes, melanocytes, fibroblasts, or lymphoid cells were negative. Tumor cells of squamous cell carcinoma, cutaneous lymphoma, sweat gland carcinoma, and malignant melanoma were negative for G_o4aL. The present study indicates that G_oα may be a useful immunohistochemical marker of Merkel cell carcinoma.