A vasoactive intestinal peptide antagonist inhibits non-small cell lung cancer growth

The increased proliferation of cultured neuroblastoma cells treated with vasoactive intestinal peptide is enhanced by simultaneous inhibition of neutral endopeptidase

Vasoactive intestinal peptide (VIP) stimulates the neuroblastoma cell line (NMB) to proliferate. Neuropeptide activity can be inhibited by neutral endopeptidases that function intracellularly and in the extracellular milieu. NMB cells express neutral endopeptidase (NEP) activity that can be specifically inhibited by phosphoramidon (PA). Our data now show that phosphoramidon treatment increases the efficacy of VIP-stimulated neuroblastoma proliferation. These results suggest that membrane endopeptidases modulate VIP-associated cell proliferation and enhancement of endopeptidase activity may serve as a target for cancer therapy.

AH6809 antagonizes non-small cell lung cancer prostaglandin receptors

The effects of prostaglandin (PG)E2 on lung cancer cells were investigated. 3H-PGE2 bound with high affinity to membranes derived from small cell lung cancer (SCLC) and non-SCLC (NSCLC) cell lines. Using NSCLC NCI-H1299 membranes, specific 3H-PGE2 binding to NCI-H1299 membranes was inhibited with moderate affinity by PGE2, PGE1, PGF2alpha and 6-isopropoxy-9-xanthone-2-carboxylic acid (AH6809) but not PGD2, LTB4 or 5-HETE. By RT-PCR, EP2 receptor PCR products were detected in extracts derived from lung cancer cells. PGE2 caused cAMP elevation in a concentration-dependent manner using NCI-H1299 cells and the increase in cAMP caused by PGE2 was antagonized by AH6809. PGE2 had no effect on cytosolic Ca2+ but PGE2 caused increased c-fos mRNA in NCI-H1299 cells. AH6809 inhibited the proliferation of NCI-H1299 cells using MTT and clonogenic assays. These results indicate that functional PG receptors are present on NSCLC cells which are antagonized by AH6809.

Inhibition of PC-3 human prostate cancers by analogs of growth hormone-releasing hormone (GH-RH) endowed with vasoactive intestinal peptide (VIP) antagonistic activity

Vasoactive intestinal peptide (VIP) stimulates the proliferation and invasiveness of malignant prostatic cells. Receptors for VIP and the closely related growth hormone-releasing hormone (GH-RH) show considerable homology and are found in prostatic and other carcinomas. Among various analogs of GH-RH synthesized, JV-1-52 is a non-selective VIP/GH-RH antagonist, whereas JV-1-53 is a VIP antagonist devoid of GH-RH antagonistic effect. In our study, nude mice bearing PC-3 human androgen-independent prostate carcinomas were treated with JV-1-52 or JV-1-53 (20 microg/day, s.c.) for 28 days. Both antagonists produced a similar reduction in tumor volume (62-67%, p < 0.01) and tumor weight (59-62%; p < 0.05) vs. controls and extended tumor doubling-time from 9.1 to about 16 days (p < 0.05). To investigate the mechanisms involved, in another study we compared the effects of JV-1-53 with those of somatostatin analog RC-160. VIP antagonist JV-1-53 reduced tumor weight by 67% (p < 0.01) and suppressed the expression of mRNA for c-fos and c-jun oncogenes by about 34% (p < 0.05), without affecting serum levels of insulin-like growth factor-I (IGF-I). In contrast, RC-160 (50 microg/day) reduced serum IGF-I by 19% (p < 0.05), but did not significantly decrease tumor weight. mRNA for VIP and high affinity receptors for VIP were detected on PC-3 tumors. Our results suggest that VIP/GH-RH antagonists can inhibit the growth of androgen-independent prostate cancer by abrogating the autocrine/paracrine mitogenic stimuli of VIP. The ability of GH-RH antagonists to block tumoral VIP receptors, in addition to GH-RH receptors, could be potentially beneficial for prostate cancer therapy.

Vasoactive intestinal peptide (VIP) enhances the cell motility of androgen receptor-transfected DU-145 prostate cancer cells (DU-145/AR)

We established a clonal DU-145 prostate cancer cell line (DU-145/AR) stably transfected with androgen receptor (AR) cDNA and investigated the expression of type 1 vasoactive intestinal peptide (VIP) receptor (VIP1R) and type 2 VIP receptor (VIP2R) mRNA in these cells by reverse transcriptase-polymerase chain reaction analysis and the effect of VIP on the invasion and the haptotactic migration of these cells. DU-145/AR cells constitutively expressed both VIP1R and VIP2R mRNA, but the parent DU-145 cells did not. VIP increased the invasive capacity of DU-145/AR cells. VIP also enhanced the haptotactic migration of these cells to fibronectin. However, the growth of these tumor cells was not affected by VIP at any concentrations used in this study. These results indicate that VIP may play a role in the regulation of the invasion of prostate cancer.

(N-stearyl, norleucine17)VIPhybrid is a broad spectrum vasoactive intestinal peptide receptor antagonist

The effects of a (N-stearyl, Norleucine17) vasoactive intestinal peptide hybrid ((SN)VIPhybrid) on cells stably transfected with VPAC,, VPAC2, or PAC1 receptors were investigated. (SN)VIPhybrid inhibited specific 125I-VIP binding to membranes derived from CHO cells transfected with VPAC, or VPAC2 receptors with high affinity (IC50 = 30 and 50 nM). (SN)VIPhyb inhibited specific 125I-PACAP-27 binding to membranes derived from NIH/3T3 cells transfected with PAC1 receptors with high affinity (IC50 = 65 nM). PACAP-27 caused cAMP elevation in NIH/3T3 cells transfected with PAC1 receptors and the increase cAMP caused by pituitary adenylated cyclase (PACAP) was inhibited by (SN)VIPhyb. Also, the increase in cAMP caused by VIP using CHO cells transfected with VPAC1 or VPAC2 receptors was antagonized by (SN)VIPhyb. These results indicate that (SN)VIPhyb is an antagonist for VPAC1, VPAC2, and PAC1 receptors.

A vasoactive intestinal peptide antagonist inhibits the growth of glioblastoma cells

The effects of a vasoactive intestinal peptide (VIP) receptor antagonist (VIPhyb) on human glioblastoma cells were characterized. Pituitary adenylate cyclase activating polypeptide (125I-PACAP-27) bound with high affinity to U87, U118, and U373 cells. Specific 125I-PACAP-27 binding to U87 cells was inhibited, with high affinity, by PACAP but not VIP or VIPhyb (IC50 = 10, 1500, and 500 nM, respectively). By reverse transcriptase-polymerase chain reaction (RT-PCR), a major 305 bp band was observed indicative of PAC1 receptors. PACAP-27 caused cAMP elevation and the increase in cAMP caused by PACAP-27, was inhibited by the VIPhyb. Also, PACAP-27 caused cytosolic Ca2+ elevation in Fura-2AM loaded U87 cells and the VIPhyb inhibited this increase. Using the MTT growth assay, the VIPhyb was shown to inhibit glioblastoma growth in a concentration-dependent manner. Using a clonogenic assay in vitro, 10 microM VIPhyb significantly inhibited proliferation of U87, U118, and U373 cells. In vivo, 0.4 microg/kg VIPhyb inhibited U87 xenograft proliferation in nude mice. These results suggest that the VIPhyb antagonizes PAC1 receptors on glioblastoma cells and inhibits their proliferation.

A lipophilic vasoactive intestinal peptide analog enhances the antiproliferative effect of chemotherapeutic agents on cancer cell lines

BACKGROUND

Vasoactive intestinal peptide (VIP) is one of several small neuropeptides that affect cancer growth. A lipophilic VIP analog, stearyl-Nle(17)-neuroten-sin(6-11)VIP(7-28) (SNH) that inhibited lung carcinoma growth has been described previously. The experiments performed were clonogenic assays in vitro and tumor xenografts in nude mice in vivo. These studies were now extended to colon carcinoma and to combination therapy with chemotherapeutic agents.

METHODS

Assays were performed with cell lines, and tumor proliferation was assessed using the (3-[4,5-dimethylthiazol-2-yl-5]-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H tetrazolium) (MTS) colorimetric assay for mitochondrial function of living cells.

RESULTS

The lipophilic analog (SNH) enhanced the antiproliferative activity of diverse chemotherapeutic agents: doxorubicine (antibiotic); vinorelbine (vinca alkaloid, antimicrotubule formation); paclitaxel (antimicrotubule agent); gemcitabine (antimetabolite); irinotecan (topoisomerase I inhibitor); and cisplatin (platinum compound acting as an alkylating agent). In all cases, the antiproliferative effect of SNH and the chemotheraputic agent was at least additive and for some combinations and concentrations even synergistic. For example, 2 microM of the antagonist that produced a 15-20% growth inhibition in the nonsmall cell lung carcinoma cell line reduced the IC(50) by 2-4-fold for most of the chemotherapeutic agents tested. Higher analog concentrations were even more efficacious. Similar results were obtained with colon carcinoma cell lines.

CONCLUSIONS

Chemotherapeutic treatment of advanced solid tumors, such as nonsmall cell lung carcinoma, colon carcinoma, or prostate carcinoma, achieves a response rate of between 10% and 30% with significant toxicity. Combination therapy with the lipophilic VIP analog SNH and the preferred chemotherapeutic agent may greatly enhance the response rate, and by permitting a dose reduction, should significantly reduce side effects.

GI side-effects of a possible therapeutic GRF analogue in monkeys are likely due to VIP receptor agonist activity

Growth hormone (GH) is used or is being evaluated for efficacy in treatment of short stature, aspects of aging, cardiac disorders, Crohn's disease, and short bowel syndrome. Therefore, we synthesized several stable growth hormone-releasing factor (GRF) analogues that could be therapeutically useful. One potent analog, [D-Ala(2),Aib(8, 18,)Ala(9, 15, 16, 22, 24-26,)Gab(27)]hGRF(1-27)NH(2) (GRF-6), with prolonged infusion caused severe diarrhea in monkeys; however, it had no side-effects in rats. Because GRF has similarity to VIP/PACAP and VIPomas cause diarrhea, this study investigated the ability of this and other GRF analogues to interact with the VIP/PACAP receptors. Rat VPAC(1)-R (rVPAC(1)-R), human VPAC(1)-R (hVPAC(1)-R), rVPAC(2)-R and hVPAC(2)-R stably transfected CHO and PANC 1 cells were made and T47D breast cancer cells containing native human VPAC(1)-R and AR4-2J cells containing PAC(1)-R were used. hGRF(1-29)NH(2) had low affinity for both rVPAC(1)-R and rVPAC(2)-R while VIP had a high affinity for both receptors. GRF-6 had a low affinity for both rVPAC(1)-R and rVPAC(2)-R and very low affinity for the rPAC(1)-R. VIP had a high affinity, whereas hGRF(1-29)NH(2) had a low affinity for both hVPAC(1)-R and hVPAC(2)-R. In contrast GRF-6, while having a low affinity for hVPAC(2)-R, had relatively higher affinity for the hVPAC(1)-R. In guinea pig pancreatic acini, all GRF analogues were full agonists at the VPAC(1)-R causing enzyme secretion. These results demonstrate that in contrast to native hGRF(1-29)NH(2,) GRF-6 has a relatively high affinity for the human VPAC(1)-R but not for the human VPAC(2)-R, rat VPAC(1)-R, rat VPAC(2)-R or rat PAC(1)-R. These results suggest that the substituted GRF analog, GRF-6, likely causes the diarrheal side-effects in monkeys by interacting with the VPAC(1)-R. Furthermore, they demonstrate significant species differences can exist for possible therapeutic peptide agonists of the VIP/PACAP/GRF receptor family and that it is essential that receptor affinity assessments be performed in human cells or from a closely related species.

VIP receptor antagonists and chemotherapeutic drugs inhibit the growth of breast cancer cells

The effects of vasoactive intestinal peptide (VIP) antagonists on breast cancer cells were investigated. (N-stearyl, norleucine17)VIP hybrid ((SN)VIPhyb) inhibited specific 125I-VIP binding to MCF7, SKBR3, T47D ZR75-1 and MDA-MB231 cells with high affinity (IC50 values of 0.03-0.06 microM). (SN)VIPhyb, 1 microM, inhibited the ability of 10 nM VIP to cause elevation of cAMP and to increase c-fos mRNA. Micromolar concentrations of (SN)VIPhyb inhibited the proliferation of MDA-MB231 or MCF7 cells using a MTT and clonogenic assay. Using a MTT assay, (SN)VIPhyb enhanced the ability of taxol and doxorubicin to inhibit breast cancer growth. Using nude mice bearing MDA-MB231 xenografts, VIPhyb potentiated the ability of taxol to inhibit proliferation. The results indicate that VIP receptor antagonists increase the ability of chemotherapeutic drugs to kill breast cancer cells.

Inverse, protean, and ligand-selective agonism: matters of receptor conformation

Concepts regarding the mechanisms by which drugs activate receptors to produce physiological response have progressed beyond considering the receptor as a simple on-off switch. Current evidence suggests that the idea that agonists produce only varying degrees of receptor activation is obsolete and must be reconciled with data to show that agonist efficacy has texture as well as magnitude. Thus, agonists can block system constitutive response (inverse agonists), behave as positive and inverse agonists on the same receptor (protean agonists), and differ in the stimulus pattern they produce in physiological systems (ligand-selective agonists). The molecular mechanism for this seemingly diverse array of activities is the same, namely, the selective microaffinity of ligands for different conformational states of the receptor. This paper reviews evidence for the existence of the various types of agonism and the potential therapeutic utility of different agonist types.-Kenakin, T. Inverse, protean, and ligand-selective agonism: matters of receptor conformation.

In vitro evaluation of VIP/PACAP receptors in healthy and diseased human tissues. Clinical implications

The evaluation of peptide receptors in man is relevant to identifying the physiological target tissues of a given peptide and to selecting diseases with a sufficient receptor overexpression for diagnostic or therapeutic intervention. VIP/PACAP receptors have been evaluated in normal and diseased human non-neuronal tissues by using in vitro receptor autoradiography with 125I-VIP or 125I-PACAP in tissue sections. As assessed by subtype-selective VIP analogs, VIP receptors of the VPAC1 subtype are found in a wide variety of tissues including liver, breast, kidney, prostate, ureter, bladder, pancreatic ducts, gastrointestinal mucosa, lung, thyroid, adipose, and lymphoid tissues. VPAC2 receptors are predominantly found in vessels and smooth muscles, whereas PAC1 receptors are present in the adrenal medulla. VIP/PACAP receptors are expressed in the majority of the most frequently occurring human tumors, including breast, prostate, pancreas, lung, colon, stomach, liver, and bladder carcinomas, as well as lymphomas and meningiomas, predominantly as VPAC1 receptors, as do their tissues of origin. Although leiomyomas predominantly express VPAC2 receptors, glial tumors, pituitary adenomas, neuroblastomas, paragangliomas, pheochromocytomas, and endometrial carcinomas preferentially express PAC1 receptors. The very wide distribution of VIP/PACAP receptors in the normal human body is indicative of the key role of these peptides in human physiology and pathophysiology. Moreover, the receptor expression in tumors is the molecular basis for clinical applications of VIP/PACAP such as in vivo scintigraphy and radiotherapy of tumors as well as VIP/PACAP analog treatment for tumor growth inhibition.

VPAC1 receptors and lung cancer

VIP/PACAP are autocrine growth factors for lung cancer. VIP and/or PACAP mRNA is present in most lung cancer cell lines examined. Although mRNA for VPAC2-R is not common, VPAC1-R and PAC1-R mRNA is present in many lung cancer cell lines. 125I-VIP binds with high affinity to lung cancer cells and specific 125I-VIP binding is inhibited with high affinity by (Lys15, Arg16, Leu27)VIP1-7 GRF8-27, the VPAC1-R specific agonist, but not by Ro25-1553(18), the VPAC2-R specific agonist. VIP elevates cAMP and increases c-fos gene expression. The increase in cAMP and c-fos mRNA caused by VIP is inhibited by SN(VH). (SH)VH inhibited the proliferation of NCIH1299 cells in the MTT assay, which is based on cytotoxicity. In a recent cell line screen, (SN)VH inhibited the growth of 51 of 56 cancer cell lines including leukemia, lung cancer, colon cancer, CNS cancer, melanoma, ovarian cancer, renal cancer, breast cancer, and prostate cancer (T. Moody, unpublished). It remains to be determined if (SN)VH will be useful for treatment of a wide variety of cancers.

Prostaglandin E2 and vasoactive intestinal peptide increase vascular endothelial cell growth factor mRNAs in lung cancer cells

The effects of prostaglandin E2 (PGE2) and vasoactive intestinal peptide (VIP) on vascular endothelial cell growth factor (VEGF) mRNAs were investigated using lung cancer cells. By RT-PCR, VEGF(121), VEGF(165), and VEGF(189), but not VEGF(206) isoforms were detected in all lung cancer cell lines and biopsy specimens examined. By Northern blot, VEGF mRNA was detected in all small cell lung cancer (SCLC) and non-SCLC (NSCLC) cell lines examined. PGE2, VIP and forskolin caused increased VEGF expression in a time- and concentration-dependent manner using NSCLC cell line NCI-H157. Approximately 1 microM PGE2, 0.1 microM VIP and 50 microM forskolin caused cAMP elevation, 64-, 33- and 128-fold, respectively, using NCI-H157 cells after 5 min. The increase in cAMP caused by PGE(2) and VIP was reversed by somatostatin (SST). Also 1 microM PGE2, 0.1 microM VIP and 50 microM forskolin increased the VEGF mRNA 2.0-, 1.5- and 2.3-fold, respectively, after 4 h. The increase in VEGF mRNA caused by PGE2, VIP and forskolin was inhibited by H-89, a protein kinase A inhibitor. A VIP receptor antagonist, VIPhybrid, inhibited the increase in cAMP and VEGF mRNA caused by VIP. By ELISA, VEGF was detected in the conditioned media exposed to the lung cancer cell lines. These results suggest that VEGF synthesis in and secretion from lung cancer cells can be regulated by agents, which cause adenylyl cyclase activation.

Retinoic acid down-regulates VPAC(1) receptors and TGF-beta 3 but up-regulates TGF-beta 2 in lung cancer cells

The effects of retinoic acid (RA) on lung cancer cells were investigated. Both all-trans (t-RA) and 13-cis RA (c-RA) decreased specific (125)I-VIP binding to NCI-H1299 cells in a time- and concentration-dependent manner. After 20 hr, 30 microM t-RA decreased specific (125)I-VIP binding by 60%. By Scatchard analysis, the density of VIP binding sites but not the affinity was reduced by 42%. NCI-H1299 VPAC(1) receptor mRNA was reduced by 48%. VIP caused a 3-fold elevation in the NCI-H1299 cAMP, and the increase in cAMP caused by VIP was reduced by 38% if the NCI-H1299 cells were treated with t-RA. Using the MTT assay, 3 microM t-RA and 3 microM c-RA inhibited NCI-H1299 proliferation by 60 and 23% respectively. Also, transforming growth factor (TGF)-beta2 increased after treatment of NCI-H1299 cells with t-RA whereas TGF-beta 1 mRNA was unaffected and TGF-beta 3 mRNA was decreased. These results suggest that RA may inhibit lung cancer growth by down-regulating VPAC(1) receptor and TGF-beta 3 mRNA but up-regulating TGF-beta 2 mRNA.

Human renal cell carcinoma expresses distinct binding sites for growth hormone-releasing hormone

Antagonists of growth hormone-releasing hormone (GHRH) inhibit the proliferation of various human cancers in vitro and in vivo by mechanisms that include apparent direct effects through specific binding sites expressed on tumors and that differ from pituitary human GHRH (hGHRH) receptors. In this study, GHRH antagonist JV-1-38 (20 microgram/day per animal s.c.) inhibited the growth of orthotopic CAKI-1 human renal cell carcinoma (RCC) by 83% and inhibited the development of metastases to lung and lymph nodes. Using ligand competition assays with (125)I-labeled GHRH antagonist JV-1-42, we demonstrated the presence of specific high-affinity (K(d) = 0.25 +/- 0.03 nM) binding sites for GHRH with a maximal binding capacity (B(max)) of 70.2 +/- 4.1 fmol/mg of membrane protein in CAKI-1 tumors. These receptors bind GHRH antagonists preferentially and display a lower affinity for hGHRH. The binding of (125)I-JV-1-42 is not inhibited by vasoactive intestinal peptide (VIP)-related peptides sharing structural homology with hGHRH. The receptors for GHRH antagonists on CAKI-1 tumors are distinct from binding sites detected with (125)I-VIP (K(d) = 0.89 +/- 0.14 nM; B(max) = 183.5 +/- 2.6 fmol/mg of protein) and also have different characteristics from GHRH receptors on rat pituitary as documented by the insignificant binding of [His(1),(125)I-Tyr(10), Nle(27)]hGHRH(1-32)NH(2). Reverse transcription-PCR revealed the expression of splice variants of hGHRH receptor in CAKI-1 RCC. Biodistribution studies demonstrate an in vivo uptake of (125)I-JV-1-42 by the RCC tumor tissue. The presence of specific receptor proteins that bind GHRH antagonists in CAKI-1 RCC supports the view that distinct binding sites that mediate the inhibitory effect of GHRH antagonists are present on various human cancers.

Thymosinalpha1 is chemopreventive for lung adenoma formation in A/J mice

The effects of thymosin (THN) alpha1 were investigated using the urethane injection carcinogenesis A/J mouse model. Lung adenomas were observed 2.5, 3, and 4 months after urethane injection (400 mg/kg i.p.) into female A/J mice. Daily administration of THNalpha1 (0.4 mg/kg, s.c.) reduced lung adenoma multiplicity significantly, by approximately 45, 40, and 17%, respectively, 2.5, 3, and 4 months after urethane injection. Animals treated with THNalpha1 had a significantly greater white cell density than control A/J mice. Endogenous THNalpha1-like peptides were detected in the mouse lung. By radioimmunoassay and by Western blot, prothymosin alpha was detected in the mouse lung. By immunocytochemistry, THNalpha1-like peptides were detected in all lung compartments including the bronchus, adenoma, bronchioles, and alveoli. These results indicate that exogenous THNalpha1 prevents lung carcinogenesis in A/J mice.

VIP and the potent analog, stearyl-Nle(17)-VIP, induce proliferation of keratinocytes

Vasoactive intestinal polypeptide (VIP) exhibits effects on cell proliferation. Here, VIP, as well as the related peptide, pituitary adenylate cyclase activating peptide (PACAP), promoted human keratinocyte division. Stearyl-Nle(17)-VIP (SNV) was identified as a superior mitogen for the keratinocytic cell line, HaCaT, both in potency (fM-nM concentrations) and efficacy. Reverse transcription-polymerase chain reaction detected in keratinocytes only PACAP mRNA and the relevant type 1 (VPAC(1)R) and type 2 (VPAC(2)R) receptors, while VIP and the third receptor (PAC(1)) transcripts were absent. Upon serum deprivation of HaCaT, the VPAC(1)R mRNA was apparently increased, while the VPAC(2)R transcript remained constant. Incubation of HaCaT with VIP or SNV increased nitric oxide and cGMP formation. In contrast to VIP, SNV did not augment cAMP. Thus, the paracrine VIP, and autocrine PACAP, related pathways leading to keratinocyte proliferation may involve VPAC(1)R/VPAC(2)R and nitric oxide/cGMP production.

Type 1 vasoactive intestinal peptide receptor expression in PC3/AR cells is evidence of prostate epithelial differentiation

BACKGROUND

Type 1 vasoactive intestinal peptide receptor (VIP1R) is expressed in many secretory epithelial cells. We investigated VIP1R expression as a marker of prostate secretory epithelial differentiation in normal and malignant prostate tissues and in PC-3 human prostate cancer cells either lacking or expressing a functional androgen receptor.

METHODS

VIP1R mRNA in rat prostate was assessed by in situ hybridization. VIP1R mRNA in human prostate tissue was identified by Northern blot hybridization. VIP1R mRNA expression in human prostate cancer cell lines in the presence or absence of androgen was determined by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). Human prostate cell lines were treated with VIP, and changes in intracellular cAMP were measured by radioimmunoassay.

RESULTS

VIP1R mRNA was expressed only in epithelial cells in normal rat prostate. VIP1R mRNA was present in both normal and malignant human prostate. Well-differentiated LNCaP cells expressed functional VIP receptors, while poorly differentiated PC-3 cells did not. PC-3 cells stably expressing the androgen receptor (PC3/AR) did express functional VIP receptors, but VIP1R mRNA levels were not androgen-regulated.

CONCLUSIONS

VIP1R expression indicates epithelial differentiation in normal and malignant prostate. PC3/AR cells and LNCaP cells, both of which express VIP1R and prostate-specific antigen (PSA), are the only prostate cancer cell lines known to express these two markers of prostate epithelial differentiation.

PACAP(6-38) is a PACAP receptor antagonist for breast cancer cells

The effects of pituitary adenylate cyclase activating polypeptide (PACAP) analogs were investigated using breast cancer cells. 125I-PACAP-27 bound with high affinity (Kd = 5 nM) to T47D cells (Bmax = 29,000 per cell). Specific 125I-PACAP-27 binding was inhibited half maximally by PACAP-27, PACAP-38, PACAP(6-38) and PACAP(28-38) with IC50) values of 8, 17, 750 and >3000 nM, respectively. By RT-PCR, PACAP receptor mRNA was present in MCF-7 and T47D cell lines. Polyclonal antibodies to a PACAP receptor fragment (A-8-C) were elicited. The antibodies were affinity purified, recognized a 60-kDa protein by western blot, and stained malignant cells in breast cancer biopsy specimens by immunohistochemistry. PACAP-27 elevated the cAMP in T47D cells and the increase in cAMP caused by PACAP was inhibited by PACAP(6-38). PACAP-27 stimulated c-fos mRNA in T47D cells and the increase in c-fos gene expression caused by PACAP was reversed by PACAP(6-38). PACAP(6-38) inhibited colony formation using a soft agar assay and inhibited breast cancer xenograft growth in nude mice. These data suggest that PACAP(6-38) functions as a breast cancer PACAP receptor antagonist.

MCF-7 breast cancer cells express normal forms of all vasopressin receptors plus an abnormal V2R

We have previously provided evidence that an autocrine loop involving vasopressin is present in perhaps all breast cancers. This study now shows MCF-7 breast cancer cells express mRNAs for all currently recognized vasopressin receptor subtypes (V1a, V1b, and V2). Cloning and DNA sequencing over the entire open reading frame of each mRNA revealed that normal sequences representing each receptor were present. However, in addition, an abnormal mRNA for the V2 receptor, expected to give rise to a truncated 'diabetic' protein, was also expressed. Western analysis revealed that all three normal mRNAs gave rise to proteins of sizes compatible with them being functional receptors. The abnormal V2 receptor mRNA also gave rise to proteins.

Multiple actions of a hybrid PACAP antagonist: neuronal cell killing and inhibition of sperm motility

Pituitary stimulating adenylate cyclase (PACAP) is a major regulatory peptide with two active molecular forms: PACAP-27 and PACAP-38. Both molecular forms promote neuronal survival and protect against neurotoxicity. Based on our previous hybrid peptide strategy in designing vasoactive intestinal peptide (VIP) antagonists, novel PACAP analogues were synthesized (neurotensin6-11 PACAP7-27 and neurotensin6-11 PACAP7-38). In addition to the hybrid modification, the methionine in position 17 was replaced by norleucine (Nle). Treatment of rat cerebral cortical cultures for five days with the putative PACAP antagonists (1 nM) resulted in a 35-45% reduction in neuronal cell counts as compared to controls. Neuronal cell death was already obtained at picomolar concentrations for the neurotensin6-11 PACAP7-27 antagonist with 70% death at 10(-8) M. Co-administration of the PACAP hybrid analogue with picomolar amounts of PACAP-27 or Nle17-PACAP-27 attenuated the reduction in neuronal cell counts. While the protective effects of both analogues exhibited a peak at 1 pM concentrations, the Nle-containing agonist displayed a broader range of active concentrations (10(-12)M-10(-9) M). The putative PACAP antagonist also inhibited sperm motility (golden hamster) in a dose-dependent manner as assessed in vitro. Complete inhibition was observed at 10 microM, suggesting a role for PACAP in sperm motility and sexual function. Thus, previous findings of a large number of PACAP and PACAP receptors in the nervous system and the reproductive system are now correlated with a function in neuronal survival and sperm motility. The structure-activity studies suggest that the methionine in position 17 and the first six amino acids are important in the determination of PACAP activity, knowledge that may facilitate PACAP-based drug design.

VIP and breast cancer

VIP1 receptors are present in breast cancer cells. VIP elevates the cAMP and stimulates nuclear oncogene expression in MCF-7 cells. VIPhybrid is a VIP receptor antagonist that inhibits breast cancer proliferation. A VIP analog has been developed for imaging breast tumors. Therefore VIP1 receptors may be utilized for the early detection and treatment of breast cancer.

Vasoactive intestinal peptide inhibits human small-cell lung cancer proliferation in vitro and in vivo

Small-cell lung carcinoma (SCLC) is an aggressive, rapidly growing and metastasizing, and highly fatal neoplasm. We report that vasoactive intestinal peptide inhibits the proliferation of SCLC cells in culture and dramatically suppresses the growth of SCLC tumor-cell implants in athymic nude mice. In both cases, the inhibition was mediated apparently by a cAMP-dependent mechanism, because the inhibition was enhanced by the adenylate cyclase activator forskolin and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine in proportion to increases in intracellular cAMP levels, and the inhibition was abolished by selective inhibition of cAMP-dependent protein kinase. If confirmed in clinical trials, this antiproliferative action of vasoactive intestinal peptide may offer a new and promising means of suppressing SCLC in human subjects, without the toxic side effects of chemotherapeutic agents.

Tachykinins mediate changes in ion transport in porcine jejunum through release of prostaglandins and neurotransmitters

In the present study, we investigated the mediators involved in substance P (SP) and neurokinin A (NKA) induced ion transport. Stripped preparations of porcine jejunal tissue were mounted in Ussing-chambers and short-circuited. The cyclo-oxygenase inhibitor, piroxicam (10 microM) and the neuronal conduction blocker, tetrodotoxin (TTX) (0.1 microM) both significantly decreased the SP (0.1 microM) (66% and 36%, respectively) and NKA (1 microM) (64% and 31%, respectively) induced increase in short-circuit current (SCC). Pretreatment with both piroxicam and TTX totally abolished the SP and NKA response. SP (0.1 microM) caused a significant release of prostaglandin E2 (PGE2), whereas the release of PGE2 induced by NKA was not significant. Experiments were performed to clarify if vasoactive intestinal polypeptide (VIP) was mediating SP or NKA responses. VIP caused a TTX-insensitive and a concentration-dependent increase in SCC. Two VIP antagonists did not change the response to VIP (10 nM and 0.1 microM). Thus, these antagonists could not be used to further elucidate the role of VIP. We were unable to measure a significant release of VIP after SP or NKA treatment. These results indicate, that SP and NKA regulate ion transport in porcine jejunum, entirely through the release of prostaglandins and enteric neurotransmitters.

Lipoxygenase inhibitors prevent lung carcinogenesis and inhibit non-small cell lung cancer growth

The effects of lipoxygenase inhibitors were investigated using human lung cancer cell lines and A/J mice. By RT-PCR, 5-, 12-, and 15-lipoxygenase mRNA was detected in NSCLC cells. NDGA inhibited 5-LO activity in adenocarcinoma cell line NCI-H1264. Using an MTT assay, NDGA, MK591 and AA861 inhibited the growth of NSCLC cell lines tested with IC50 values of 3, 2, and 7 microM, respectively. Using a clonogenic assay, 10 microM NDGA significantly reduced NSCLC colony number. NDGA significantly slowed NSCLC xenograft growth in nude mice. When the tumors were excised and analyzed, nude mice treated with NDGA had significantly more apoptotic figures than did untreated tumors. A/J mice treated with urethane developed adenomas after 4 months and NDGA administration significantly reduced lung adenoma number. These data indicate that lipoxygenase inhibitors inhibit lung cancer growth and prevent lung carcinogenesis.

PACAP(6-38) inhibits the growth of prostate cancer cells

The effects of pituitary adenylyl cyclase activating polypeptide (PACAP) analogs on prostate cancer cell lines was investigated. 125I-PACAP-27 bound with high affinity to PC-3 cells (Kd = 10 nM) to a single class of sites (Bmax = 30000/cell). By RT-PCR, a major 305 bp band was observed using cDNA derived from PC-3, LNCaP or DU-145 cells. Specific 125I-PACAP binding was inhibited with high affinity by PACAP-27, PACAP-38 and PACAP(6-38) (IC50 values of 15, 10 and 300 nM, respectively) but not by PACAP(28-38). PACAP elevated cAMP and the increase caused by PACAP-27 was reversed by PACAP(6-38). PACAP transiently increased c-fos gene expression and the increase in c-fos mRNA was reversed by PACAP(6-38). PACAP-27 stimulated colony formation in PC-3 cells, whereas PACAP(6-38) reduced colony number and size. In nude mice bearing PC-3 xenografts, PACAP(6-38) significantly slowed tumor growth. These data suggest that biologically active type 1 PACAP receptors are present on human prostate cancer cells and that prostate cancer cell growth is inhibited by PACAP(6-38).

Differential expression and function of PACAP and VIP receptors in four human colonic adenocarcinoma cell lines

Human colonic adenocarcinoma cell lines have conserved several features of the native tissue. Among these is the expression of cell surface receptors for hormones and neurotransmitters that may be involved in the regulation of proliferation and differentiation processes in these cancer cells. Here, we confirm that high-affinity binding sites for the Vasoactive Intestinal Polypeptide (VIP) and for the VIP analogue Pituitary Adenylate-Cyclase Activating Polypeptide (PACAP), were expressed in 4 human colonic adenocarcinoma cell lines, HT29, SW403, DLD-1 and Caco-2, that spontaneously displayed variable phenotypic properties in culture. We demonstrated that after long-term treatments, VIP and PACAP significantly reduced cell proliferation in the 4 cell lines and modulated intracellular cAMP and cGMP levels. Furthermore, conspicuous differences were observed from one cell type to another concerning expression of the receptor subsets or the effects of the neuropeptides on cell growth and on cyclic nucleotides production.

(Arg15, Arg21) VIP: evaluation of biological activity and localization to breast cancer tumors

VIP analogs, which contain a single lysine amino acid, were synthesized and evaluated using breast cancer cells. (Arg15, Arg20) VIP, (Argl5, Arg21) VIP, and (Arg20, Arg21) VIP inhibited 125I-VIP binding to T47D cells with high affinity (IC50 values of 1.2, 1.0, and 0.8 nM, respectively). The VIP analogs elevated cAMP in T47D cells with ED50 values ranging from 0.1-1 nM. Because (Arg15, Arg21) VIP was the most potent at elevating cAMP, it was characterized further. (Arg15, Arg21) VIP transiently increased c-fos gene expression in breast cancer cells. N-Succinimidyl-4-18F (fluoromethly) benzoate was prepared in one chemical step from N-succinimidyl-4-(4-nitrobenzenesulfonyl)oxomethyl)benzoate by adding 18F in acetone at room temperature. This prosthetic group was then reacted with (Arg15, Arg21) VIP ((RR) VIP). (18F-RR) VIP bound with high affinity to T47D cells and was rapidly internalized. (18F-RR) VIP was injected intravenously into nude mice bearing breast cancer xenografts and after 4 h, the density of (18F-RR) VIP was elevated in the tumors relative to normal organs. These data suggest that VIP receptors may be used to localize breast cancer tumors.

Human adrenocortical NCI-H295 cells express VIP receptors. Steroidogenic effect of vasoactive intestinal peptide (VIP)

VIP receptors are frequently overexpressed by various endocrine tumors. In this study the expression of VIP receptors in the human adrenocortical carcinoma cell line NCI-H295 and their involvement in the regulation of steroidogenesis was investigated. NCI-H295 cells express VIP1 and VIP2 receptors as demonstrated by RT-PCR, whereas they do not express VIP itself. The receptors are functionally coupled to steroidogenesis since VIP (10(-9) M to 10(-6) M) exerted a dose-dependent stimulatory effect on the release of aldosterone, cortisol, and DHEA. VIP increased ACTH-stimulated releases of aldosterone and cortisol. The proliferation rate of NCI-H295 cells was not affected by VIP. These data show that NCI-H295 cells express both forms of the VIP receptor and that VIP is involved in an ACTH-independent regulation of steroidogenesis in the adrenal tumor cells.

Identification of VIP/PACAP receptors on rat astrocytes using antisense oligodeoxynucleotides

Vasoactive intestinal peptide (VIP) has been shown to be a potent promoter of neuronal survival. Pituitary adenylate cyclase-activating peptide (PACAP), a homologous peptide, shares activity and receptor molecules with VIP. The neuroprotective effects of VIP have been shown to be mediated via astroglial-derived molecules. Utilizing a battery of antisense oligodeoxynucleotides directed against the multiple cloned VIP-preferring (VIP receptors 1 and 2) or PACAP-preferring receptors (six splice variants derived from the same gene transcript), the authors have demonstrated the existence of a specific PACAP receptor splice variant (PACAP4 or hop2) on astrocytes as well as a VIP type2 receptor. The identification of the receptors was achieved by incubation of the cells in the presence of the specific antisense oligodeoxynucleotide followed by radiolabeled VIP binding and displacement. Polymerase chain reaction (PCR) coupled to direct sequencing identified the expression of the PACAP4-hop2 receptor splice variant in astrocytes. Neuronal survival assays were conducted in mixed neuronal-glial cultures derived from newborn rat cerebral cortex. When these cultures were exposed to the battery of the antisense oligodeoxynucleotides, in serum-free media, only the PACAP-specific ones (e.g., hop2-specific) had an effect in decreasing neuronal cell counts. Thus, the VIP neuronal survival effect is mediated, at least in part, via a specific PACAP receptor (containing a unique insertion of 27 amino acids--the hop2 cassette). These data indicate that a hop2-like PACAP/VIP receptor is the receptor that mediates neurotropism.

Activation of 5-HT1P receptors on submucosal afferents subsequently triggers VIP neurons and chloride secretion in the guinea-pig colon

The role of vasoactive intestinal peptide (VIP) was investigated when mucosal stroking and 5-hydroxytryptamine (5-HT) were used to activate neural reflexes that stimulate chloride secretion in the guinea pig colon. Muscle-stripped segments of colon containing intact submucosal ganglia without myenteric ganglia were set up in modified flux chambers in order to record short-circuit current (Isc). Mucosal stroking with a brush for 1 s or a pulse of 5-HT (injection of 15 microliters of 100 microM 5-HT into 1.5 ml of mucosal solution) caused an increase in Isc that was reduced by the VIP antagonist, neurotensin6-11-VIP7-28, in a concentration-dependent manner. The Isc responses to mucosal stroking and a 5-HT pulse were reduced by 53% and 58%, respectively, by 2 microM neurotensin6-11-VIP7-28. The residual Isc response in the presence of neurotensin6-11-VIP7-28 was abolished by atropine. Blockade of 5-HT1P receptors on submucosal afferent neurons decreased Isc responses to stroking or a 5-HT pulse. The residual Isc response after 5-HT1P receptors were blocked was reduced by only 11-14% by neurotensin6-11-VIP7-28. In the presence of blockade of both 5-HT1P and VIP receptors, atropine abolished the Isc response to both stimuli. The observations suggest that the neural circuitry activated by stroking includes at least two independent pathways. One pathway contains VIP neurons which receive inputs directly or indirectly from 5-HT1P receptor-containing afferents. A second pathway involves muscarinic cholinergic transmission that is independent of 5-HT1P and VIP receptor activation.

Identity of neurotrophic molecules released from astroglia by vasoactive intestinal peptide

Subnanomolar concentrations of VIP elicit a survival-producing action in CNS cultures composed of both astroglia and neurons. This neurotrophic action is mediated by a complex array of substances released by VIP from astrocytes. Included in this glial protein mixture is a cytokine (interleukin-1 alpha), a serine protease inhibitor (protease nexin I), and an extracellular stress protein (activity-dependent neurotrophic factor). In dissociated spinal cord cultures, all of these substances exhibit neuroprotection from neuronal cell death produced by electrical blockade with tetrodotoxin. All these substances produce neuronal cell death when test cultures are treated with neutralizing antisera to any one of them. They are all apparently necessary for the survival of a subpopulation of neurons that are dependent on spontaneous, excitatory neurotransmission. Our view is that these substances are components of a glia-derived environment that regulates, together with target-derived growth factors, the survival fate of developing neurons. In addition, it is our belief that some of these glia-derived substances will be found to have active roles in the injury response to the CNS or in the regulation of VIP-mediated growth in other tissues. Drugs based on these substances may provide therapeutic agents for the treatment of neurodegeneration and tumor growth.

In vitro properties of a high affinity selective antagonist of the VIP1 receptor

A selective high affinity VIP1 receptor antagonist [Acetyl-His1, D-Phe2, Lys15, Arg16, Leu17] VIP(3-7)/GRF(8-27) or PG 97-269 was synthesized, by analogy with recently obtained selective VIP1 receptor agonists. The properties of the new peptide were evaluated on Chinese hamster ovary (CHO) cell membranes expressing either the rat VIP1-, rat VIP2- or the human VIP2-recombinant receptors and on LoVo cell membranes expressing exclusively the human VIP1 receptor. The IC50 values of 125I-VIP binding inhibition by PG 97-269 were 10, 2000, 2 and 3000 nM on the rat VIP1-, rat VIP2-, human VIP1- and human VIP2 receptors, respectively. PG 97-269 had a negligible affinity for the PACAP I receptor type. It did not stimulate adenylate cyclase activity, but inhibited competitively effect of VIP on the VIP1 receptor mediated stimulation of adenylate cyclase activity. The Ki values were respectively of 15 +/- 5 nM and 2 +/- 1 nM for the rat and human VIP1 receptors. Thus the described molecule in the first reported VIP antagonist with an affinity in the nM range and with a high selectivity for the VIP1 receptor subclass. It may be useful for evaluation of the physiological role of VIP in rat and human tissues.

Adrenomedullin expression in human tumor cell lines. Its potential role as an autocrine growth factor

Although adrenomedullin (AM) previously has been identified in human tumors, its role has remained elusive. Analysis by reverse transcriptase-polymerase chain reaction (RT-PCR) revealed AM mRNA in 18 of 20 human normal tissues representing major organs, and 55 of 58 (95%) malignant cell lines. Western blot and high performance liquid chromatography analysis showed immunoreactive AM species of 18, 14, and 6 kDa that are consistent with the precursor, intermediate product, and active peptide, respectively. Immunohistochemistry and in situ RT-PCR performed on paraffin-embedded tumor cell lines of various tissue origins exhibited AM cytoplasmic staining. Neutralizing monoclonal antibody to AM inhibits tumor cell growth in a concentration-dependent manner, an effect that was reversed with the addition of exogenous AM. Responding tumor cells were shown to have approximately 50,000 AM receptors per cell by Scatchard analysis with 125I-AM and expressed AM receptor mRNA by RT-PCR. Our data showed 36 of 48 (75%) tumor cell lines expressed AM receptor mRNA by RT-PCR assessment, all of them also expressed AM. In the presence of AM, cAMP levels were shown to increase in tumor cells. Our collective data demonstrate that AM and AM receptor are expressed in numerous human cancer cell lines of diverse origin and constitute a potential autocrine growth mechanism that could drive neoplastic proliferation.

Regulation of VIP gene expression in general. Human lung cancer cells in particular

Vasoactive intestinal peptide (VIP) is a neuropeptide of multiple functions affecting development and aging. In cancer, for example, VIP was found to function as an autocrine growth factor in nonsmall cell lung cancer (NSCLC) promotion. Furthermore, a VIP hybrid antagonist (neurotensin(6-11)-VIP(7-28)) was found to inhibit NSCLC growth. In the present study, the expression of VIP mRNA was studied using human lung cancer cells. RNA prepared from 19 cell lines was fractionated by 1% agarose gel electrophoresis followed by blotting onto nitrocellulose membranes and hybridization to a VIP-specific RNA probe. VIP mRNA was detected in about 50% of the cell lines tested with a greater abundance in NSCLC. Cultures of the NSCLC NCI-H727 cell line were treated with forskolin, an activator of cyclic AMP (cAMP), and separately with the tumor promoter phorbol 12-myristate 13-acetate (PMA). Northern blot hybridization analysis showed an increase in VIP mRNA levels after 4 h treatment with 50 microM forskolin. Incubation with PMA also showed a significant increase in the levels of VIP transcripts. Cultures were then incubated with PMA in the presence of actinomycin D, a transcription blocker. Results indicated that PMA treatment may induce both VIP mRNA synthesis as well as VIP mRNA stabilization, and suggested a 4-5 h half-life for the VIP mRNA in the absence of PMA. Thus, lung cancer tumor proliferation may be regulated, in part, at the level of VIP gene expression.

Monoclonal antibody alpha IR-3 inhibits non-small cell lung cancer growth in vitro and in vivo

The ability of monoclonal antibody (mAb) alpha IR-3 to interact with non-small cell lung cancer (NSCLC) cells was investigated. MAb alpha IR-3 inhibited specific binding of 125I-IGF-I and 125I-alpha IR-3 to a panel of 8 NSCLC cell lines with high affinity (IC50 = 200 and 50 ng/ml, respectively). 125I-alpha IR-3 bound with high affinity (Kd = 40 ng/ml) to a single class of sites (Bmax = 8,000/cell) using NCI-H838 cells. 125I-alpha IR-3 was internalized when exposed to NCI-H838 or H1299 cells at 37 degrees C but not 4 degrees C. alpha IR-3 immunoprecipitated major 90 and 130 kD proteins. IGF-I stimulated and alpha IR-3 inhibited the clonal growth of NCI-H1299 cells. alpha IR-3 slowed the growth of NCI-H157 and H838 xenografts in nude mice. In a biodistribution study 125I-alpha IR-3 was preferentially localized to the tumor as opposed to other organs. These data suggest that IGF-I may be a regulatory agent in NSCLC.

A VIP hybrid antagonist: from developmental neurobiology to clinical applications

1. The 28 amino acid vasoactive intestinal peptide, VIP, was originally isolated from the intestine, following a bioassay measuring vasodilating properties. Immunocytochemistry, receptor binding assays and in situ hybridizations have demonstrated VIP abundance in the nervous system, suggesting multiple bioactivities. 2. A pharmacological approach was chosen to dissect VIP activities and a prototype VIP antagonist (Met-Hybrid) consisting of a carboxyl fragment of VIP7-28 and a six amino acid fragment of neurotensin, neurotensin6-11-VIP7-28 was synthesized. 3. This hybrid peptide was designed to maintain the binding capacity of one parent molecule (VIP), while loosing the agonistic properties, representing a classical competitive receptor antagonist. Furthermore, the new molecule exhibited increased specificity to central nervous system VIP receptors. 4. The Met-Hybrid was originally discovered as a potent inhibitor of VIP function in vivo. In the adult rodent, acute administration of the antagonist resulted in blockade of VIP-mediated potentiation of sexual behavior and chronic intracerebroventricular application impaired VIP-associated learning abilities. During ontogeny, chronic injections of the molecule resulted in neuronal damage, disruption of the diurnal rhythmicity of motor behavior, and retardation in the acquisition of neonatal reflexes in the rat. 5. During gestation, severe microcephaly was induced by acute administration of the Met-Hybrid to pregnant mice. The hybrid antagonist inhibited VIP-stimulated mitosis in whole embryo cultures and in a variety of cancer cell lines in vitro and in vivo, suggesting therapeutical potential.

Pituitary adenylate cyclase activating peptide receptors regulate the growth of non-small cell lung cancer cells

We have identified pituitary adenylate cyclase activating peptide (PACAP) receptors on small cell lung cancer cell line NCI-N417 in a previous study. In this study, the role of PACAP in the growth and signal transduction of non-small cell lung cancer cells was investigated. Northern blot analysis with a full-length human PACAP receptor cDNA probe revealed a major 7.5-kb hybridizing transcript when total RNA extracted from NCI-H838 cells was used. PACAP bound with high affinity (Kd = 1 nM) to a single class of sites (Bmax = 14,000/cell) when NCI-H838 cells were used. Specific 125I-labeled PACAP binding was inhibited with high affinity by PACAP-27 and PACAP-38, with moderate affinity by PACAP(6-38), and with low affinity by vasoactive intestinal polypeptide, PACAP(28-38), and PACAP(16-38). PACAP-27 elevated cAMP in a dose-dependent manner, and the increase in cAMP caused by PACAP was reversed by PACAP(6-38). PACAP-27, but not vasoactive intestinal polypeptide, elevated cytosolic Ca2+ in individual NCI-H838 cells. PACAP-27 stimulated arachidonic acid release, and the increase caused by PACAP was reversed by PACAP(6-38). PACAP-27 stimulated colony formation in NCI-H838 cells, whereas the PACAP antagonist PACAP(6-38) reduced colony formation in the absence or presence of exogenous PACAP-27. In nude mice bearing NCI-H838 xenografts, PACAP(6-38) slowed tumor growth significantly. These data suggest that biologically active type 1 PACAP receptors are present on human non-small cell lung cancer cells, which exhibit dual signal transduction pathways and regulate cell proliferation.

Characterization of the rat vasoactive intestinal polypeptide receptor gene 5' region

The broad spectrum of vasoactive intestinal polypeptide (VIP) cellular functions are mediated by high-affinity binding sites. To determine regulation of the VIP receptor gene expression, we have isolated and characterized two genomic clones that contain the first three exons and the 5' flanking region of the VIP receptor gene. Using RNase protection assays, receptor gene expression was detected in adult rat lung, liver and intestine, but not in fetal lung, indicating that VIP receptor is expressed in diverse tissues, and its expression is differentially regulated during lung development. The transcription start site of the gene was mapped to a cytosine residue, 76 bp upstream from the ATG initiation codon. Transfection into rat lung cell lines shows that although 126 bp of the VIP receptor 5' DNA sequences are capable of activating VIP receptor gene basal transcription 30-fold over a promoterless control, 488 bp of the 5' sequences further induce this activation to 97-fold over control. However, inclusion of up to 859 bp 5' sequences results in a decrease in basal promoter activity (31-fold over control), indicating that while sequences between -126 and -488 bp contain potential enhancer sequences, sequences between -488 and -859 bp may include a transcriptional repressor sequence. Deletion analysis shows that transcription factor Sp1 plays an important role in activating basal promoter of the VIP receptor gene. DNase I footprinting and gel-mobility-shift assays show that Sp1 binds to its consensus binding sites in the VIP receptor promoter, suggesting that interaction of Sp1 with VIP receptor promoter transactivates this gene.

CD10/NEP in non-small cell lung carcinomas. Relationship to cellular proliferation

The cell surface metalloproteinase CD10/neutral endopeptidase 24.11 (NEP) hydrolyzes a variety of peptide substrates and reduces cellular responses to specific peptide hormones. Because CD10/NEP modulates peptide-mediated proliferation of small cell carcinomas of the lung (SCLC) and normal fetal bronchial epithelium, we evaluated the enzyme's expression in non-small cell lung carcinomas (NSCLC). Bronchoalveolar and large cell carcinoma cell lines had low levels of CD10/NEP expression whereas squamous, adenosquamous, and adenocarcinoma cell lines had higher and more variable levels of the cell surface enzyme. Regional variations in CD10/NEP immunostaining in primary NSCLC specimens prompted us to correlate CD10/NEP expression with cell growth. In primary carcinomas of the lung, clonal NSCLC cell lines and SV40-transformed fetal airway epithelium, subsets of cells expressed primarily CD10/NEP or the proliferating cell nuclear antigen (PCNA). Cultured airway epithelial cells had the lowest levels of CD10/NEP expression when the highest percentage of cells were actively dividing; in addition, these cells grew more rapidly when cell surface CD10/NEP was inhibited. NSCLC cell lines had receptors for a variety of mitogenic peptides known to be CD10/NEP substrates, underscoring the functional significance of growth-related variability in CD10/NEP expression.

Severe microcephaly induced by blockade of vasoactive intestinal peptide function in the primitive neuroepithelium of the mouse

Vasoactive intestinal peptide (VIP) has potent growth-related actions that influence cell mitosis, neuronal survival, and neurodifferentiation in cell culture. VIP can also produce dramatic growth in postimplantation mouse embryos in vitro, characterized by large increases in cell number. The goal of the present study was to assess the role of VIP on early nervous system development in vivo. Pregnant mice were treated with a specific antagonist to VIP. Prenatal administration of the antagonist early in development (E9-E11) produced severe microcephaly characterized by decreased embryonic brain weight with reduced DNA and protein content. The retardation of growth was disproportionally manifested in the brain compared with the body and was prevented by co-treatment with VIP. Identical treatment with the antagonist later in gestation had no detectable effect on embryonic growth. VIP receptors, which were restricted to the central nervous system during this stage of embryonic development, were increased in the neuroepithelium of antagonist-treated embryos while the number of cells in S-phase was significantly decreased. Thus, VIP regulates brain growth in vivo and inhibition of its action provides new insight into a molecular mechanism for microcephaly.

Inhibition of human neuroblastoma growth by a specific VIP antagonist

The 28-amino-acid neuropeptide, vasoactive intestinal peptide (VIP), is a potent mitogen during embryonic development and plays a vital role in brain growth. VIP is also mitogenic for tumor cells, including the human neuroblastoma (NMB). Northern blot analysis has revealed VIP mRNA transcripts in NMB. We now report VIP-like immunoreactivity within these neuroblastoma cells that increased during logarithmic growth and decreased after attaining confluency. About 10(6) seeded cells secreted 5-40 pg of VIP-like immunoreactivity into the medium. These results suggest an autocrine role for VIP in the regulation of neuroblastoma growth. A VIP hybrid antagonist (neurotensin6-11 VIP7-28) that has been shown to inhibit lung cancer proliferation was now tested for inhibition of neuroblastoma growth. Receptor binding studies indicated that the hybrid antagonist displaced [125I]-VIP binding in the neuroblastoma cells (EC50 = 5 x 10(-6)M). Furthermore, as measured by thymidine incorporation and by cell counts, the potent VIP hybrid antagonist inhibited neuroblastoma multiplication in a dose-dependent manner. In conclusion, VIP may be an important regulator of growth of nerve cell progenitors and of tumors derived from neuronal origin and intervening with VIP function may lead to improved treatment of cancer.

Learning and sexual deficiencies in transgenic mice carrying a chimeric vasoactive intestinal peptide gene

The molecular mechanisms responsible for behavior are largely unknown. A state of the art model, paving the path from genes to behavior, is offered by transgenic animals. Candidate molecules are classic neuropeptides, such as vasoactive intestinal peptide (VIP). Transgenic mice harboring a chimeric VIP gene driven by the polyoma promoter were produced. Behavioral studies revealed learning impairment and prolonged retardation in memory acquisition in the genetically altered animals. Furthermore, reduced performance was observed when the male transgenic mice were tested for sexual activity in the presence of receptive females. Surprisingly, radioimmunoassays showed an approx 20% decrease in the VIP content of the transgenic mice brains. To directly assess genetically reduced VIP content as a cause for learning impairment, transgenic mice carrying diphtheria toxin-encoding sequences driven by the rat VIP promoter were created. These animals had reduced brain VIP and exhibited deficiencies in learning abilities, strongly supporting an important neurobiological function for VIP in vivo.