Transactivation of HER2 by vasoactive intestinal peptide in experimental prostate cancer. Antagonistic action of an analog of growth-hormone-releasing hormone

Receptors for vasoactive intestinal peptide (VIP) and the human epidermal growth factor family of tyrosine kinase receptors (HER) are potent promoters of cell proliferation, survival, migration, adhesion and differentiation in prostate cancer cell lines. In this study, we analyzed the cross-talk between both classes of receptors through the regulation of HER2 transactivation and expression by VIP. Three growth-hormone-releasing hormone analogs endowed with antagonistic activity for VIP receptors (JV-1-51, -52, and -53) abrogated the autocrine/paracrine stimuli of VIP on androgen-independent PC3 cells in the absence or the presence of 10% fetal bovine serum. Semiquantitative and real-time quantitative RT-PCR together with Western blotting showed increased expression levels of both mRNA and proteins for HER2 and HER3 in PC3 and androgen-dependent LNCaP prostate cancer cells as compared to non-neoplastic RWPE-1 cells. VIP (100 nM) stimulated the expression levels of both HER2 and HER3 in PC3 cells in a time-dependent manner. Whereas these effects were relatively slow, VIP rapidly (0.5 min) increased HER2 tyrosine phosphorylation. This pattern of HER transactivation was blocked by H89, a protein kinase A (PKA) inhibitor, as well as by the specific VIP antagonist JV-1-53, indicating the involvement of VIP receptors and PKA activity in phosphorylated HER2 formation. These findings support the merit of further studies on the potential usefulness of VIP receptor antagonists and both HER2 antibodies and tyrosine kinase inhibitors for prostate cancer therapy.Ministerio de Educación y CienciaComunidad de MadridFundación para la Investigación en Urologí

Lipid mobilizing factor from the hypothalamus

Mouse epididymal fat pads were incubated for 2 hours in 3 per cent albumin Krebs-Ringer phosphate buffer (KRP), free of calcium and glucose, or in Krebs-Ringer bicarbonate (KRB) containing calcium. Addition of defatted acetic acid extracts of pituitary stalk and median eminence (SME) of ovine, porcine, bovine and human orgin significantly increased lipolysis as measured by release of glycerol into the KRP incubation medium and inhibited 1- 14C acetate incorporation into lipids. Extracts of porcine SME were the most potent in enhancing glycerol release and showed a log-dose response relationship between 0.1 mg. to 1.0 mg. extract/ml. of medium. Extracts of cerebral cortex from all the species tested were without effect on lipolysis at these dose levels. After gel filtration of porcine SME extracts on Sephadex G-25, lipolytic activity emerged in an area occupied by peptides with molecular weight of 3000 to 5000. The same area contained ACTH-like activity (200 mU./mg.). A comparison of the in vitro lipolytic activity of this hypothalamic fraction indicated that it was active in doses as small as 20 μg./ml. when incubated in KRP with mouse, rat, and hamster fat pads. Higher doses (40 μg./ml.) were required to elicit a lipolytic response from rabbit and guinea pig tissue. Incubation of the hypothalamic fraction with trypsin and chymotrypsin abolished the lipolytic response while pepsin had no effect. Chemical analyses of this hypothalamic fraction showed it to be free of calcium and norepinephrine and its lipolytic activity could not be accounted for by contamination with TSH, oxytocin, vasopressin, α and β-MSH or hypothalamic releasing factors. Most, but not all, of the lipid mobilizing activity of the porcine fraction may be accounted for by ACTH and/or its analogues with adrenocorticotropic activity

On the Half Life of Thyrotropin-Releasing Hormone in Rats

After the injection of 14C-labeled TRH into normal male rats, radioactivity disappeared rapidly from the circulation. The half life of 14C-TRH was found to be 4.16 min; however, the true half life of TRH may be masked, since TRH is rapidly inactivated in the blood to compounds having similar chemical structures and probably similar half lives. Chromatography of methanol extracts of plasma samples taken at 1, 2, and 6 min revealed that some of the radioactivity had the same Rf value as that of TRH, while other areas corresponded to the free acid of TRH (pyro-glu-his-pro-OH), glu-his-pro, and his-pro-NH2. The mean volume of distribution of TRH in our studies was 18.5% of the body weight. Approximately 25% of the radioactivity was excreted into the urine within 60 min after the intravenous injection of 1 µCi of 14C-TRH. Urinary radioactive metabolites appeared to have the same electrophoretic mobilities as TRH and the free acid of TRH

The Status of the Corticotropin Releasing Factor (CRF)

Early in the history of studies on the release of ACTH by stress there were indications that ACTH might be released by multiple factors. But the neurohumoral theory, as formulated by G. W. Harris, suggested that every hypophysial hormone had its unique hypothalamic controlling agent and a search for the unique ACTH-releasing hormone went on for about 20 years. This review reexamines the case for multiple releasers of ACTH