Genetic variants of immunoglobulin γ and κ chains influence humoral immunity to the cancer-testis antigen XAGE-1b (GAGED2a) in patients with non-small cell lung cancer.

GM (γ marker) allotypes, genetic variants of immunoglobulin γ chains, have been reported to be associated strongly with susceptibility to lung cancer, but the mechanism(s) underlying this association is not known. One mechanism could involve their contribution to humoral immunity to lung tumour-associated antigens. In this study, we aimed to determine whether particular GM and KM (κ marker) allotypes were associated with antibody responsiveness to XAGE-1b, a highly immunogenic lung tumour-associated cancer-testis antigen. Sera from 89 patients with non-small cell lung cancer (NSCLC) were allotyped for eight GM and two KM determinants and characterized for antibodies to a synthetic XAGE-1b protein. The distribution of various GM phenotypes was significantly different between XAGE-1b antibody-positive and -negative patients (P = 0·023), as well as in the subgroup of XAGE-1b antigen-positive advanced NSCLC (P = 0·007). None of the patients with the GM 1,17 21 phenotype was positive for the XAGE-1b antibody. In patients with antigen-positive advanced disease, the prevalence of GM 1,2,17 21 was significantly higher in the antibody-positive group than in those who lacked the XAGE-1b antibody (P = 0·026). This phenotype also interacted with a particular KM phenotype: subjects with GM 1,2,17 21 and KM 3,3 phenotypes were almost four times (odds ratio = 3·8) as likely to be positive for the XAGE-1b antibody as the subjects who lacked these phenotypes. This is the first report presenting evidence for the involvement of immunoglobulin allotypes in immunity to a cancer-testis antigen, which has important implications for XAGE-1b-based immunotherapeutic interventions in lung adenocarcinoma.

Stimulation of calcium mobilization but not proliferation by bombesin and tachykinin neuropeptides in human small cell lung cancer cells.

The tachykinin family of neuropeptides, including substance P and neurokinins A and B, induce a transient increase in intracellular free calcium concentration in human small cell lung carcinoma (SCLC) cells, as measured with a calcium indicator fura-2. The effects are dose dependent and even greater than that of bombesin at equimolar concentrations in these cells. The tachykinins, like bombesin, induce calcium mobilization mainly from intracellular store(s). None of the peptides, however, shows a stimulatory effect on DNA synthesis. In addition, exogenously applied bombesin does not stimulate DNA synthesis at any concentration tested. We also examined the effects of a recently reported bombesin antagonist [D-Arg1, D-Phe5, D-Trp7,9, Leu11]substance P in SCLC cells, and compared them to those in Swiss 3T3 fibroblasts in which the mitogenic effect of bombesin is well characterized. The antagonist at 10(-5) M completely abolishes the Ca2+-mobilizing effect of 10(-7) M bombesin in SCLC cells, and that of 10(-9) M but not 10(-7) M bombesin in Swiss 3T3 cells. The antagonist at this concentration effectively inhibits the mitogenic action of bombesin (10(-9) M) in Swiss 3T3 cells; however, much higher doses (approximately 10(-4) M) are needed to inhibit DNA synthesis in SCLC cells. Moreover, the antagonist inhibits DNA synthesis in bombesin/gastrin-releasing peptide-nonproducing cells with a similar dose dependency as in producing cells. These results indicate that bombesin/gastrin-releasing peptide and other calcium mobilizing peptides do not always act as a growth factor in SCLC cells, and that the bombesin antagonist could inhibit growth of SCLC cells through a mechanism other than bombesin antagonism.

Endothelin-1 activates phospholipase C and mobilizes Ca2+ from extra- and intracellular pools in osteoblastic cells.

The effect of endothelin-1 (ET), a novel vasoactive peptide derived from endothelial cells, on osteoblastic MC3T3-E1 cells was studied. ET specifically binds to a single class of high-affinity receptors in MC3T3-E1 cells and induces phospholipase C activation with the production of two second messengers, inositol trisphosphate and 1,2-diacylglycerol, and a biphasic increase in intracellular free Ca2+ concentration ([Ca2+]i), which consists of an initial transient increase and an ensuing sustained plateau, as measured with a fluorescent indicator, fura-2. The second plateau phase but not the initial transient increase in [Ca2+]i induced by ET is abolished by removal of extracellular Ca2+ but not by either nicardipine, verapamil, or diltiazem. The ET-stimulated production of inositol trisphosphate is not abolished by removal of extracellular Ca2+, indicating that ET-stimulated phospholipase C activation is not a consequence of an increase in Ca2+ influx across the plasma membrane. ET causes stimulation of DNA synthesis and reduction of alkaline phosphatase activity in MC3T3-E1 cells. A protein kinase C activator phorbol 12,13-dibutyrate mimics these effects of ET. The results demonstrate that ET activates the inositol lipid signaling pathway and induces mobilization of Ca2+ from both extra- and intracellular pools and activation of protein kinase C in osteoblastic MC3T3-E1 cells.