Description:
<jats:p> Biological effects of substance P (SP) are mediated by the neurokinin-1 (NK<jats:sub>1</jats:sub>) receptor that exists as a full-length and as a carboxy-terminally truncated isoform in humans. Although NK<jats:sub>1</jats:sub> receptor mRNA and binding sites have been detected in certain malignancies, little is known about the cellular and subcellular localization of NK<jats:sub>1</jats:sub> receptor protein in human neoplastic tissues. We developed and characterized a novel anti-peptide antibody to the carboxy-terminal region of the human full-length NK<jats:sub>1</jats:sub> receptor. Specificity of the anti-serum was demonstrated by (1) detection of a broad band migrating at molecular mass 70,000-90,000 Da in Western blots of membranes from NK<jats:sub>1</jats:sub>-expressing tissues; (2) cell-surface staining of NK<jats:sub>1</jats:sub>-transfected cells; (3) translocation of NK<jats:sub>1</jats:sub> receptor immunostaining after SP exposure; and (4) abolition of tissue immunostaining by preadsorption of the antibody with its immunizing peptide. Distribution of NK<jats:sub>1</jats:sub> receptors was investigated in 72 formalin-fixed, paraffin-embedded human tumors showing that NK<jats:sub>1</jats:sub> receptors were frequently expressed in glioblastomas and breast and pancreatic carcinomas. Immunoreactive NK<jats:sub>1</jats:sub> receptors were clearly confined to the plasma membrane and uniformly present on nearly all tumor cells. Development of this novel NK<jats:sub>1</jats:sub> receptor antibody allows the efficient localization of NK<jats:sub>1</jats:sub> receptor protein in human formalin-fixed, paraffin-embedded tissues. NK<jats:sub>1</jats:sub> receptor visualization with this simple and rapid immunohistochemical method will facilitate identification of tumors with a sufficient receptor overexpression for diagnostic or therapeutic intervention using SP analogs. </jats:p>