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

The role of vasoactive intestinal peptide in pulmonary diseases

Vasoactive intestinal peptide (VIP) is an abundant neurotransmitter in the lungs and other organs. Its discovery dates back to 1970. And VIP gains attention again due to the potential application in COVID-19 after a research wave in the 1980s and 1990s. The diverse biological impacts of VIP extend beyond its usage in COVID-19 treatment, encompassing its involvement in various pulmonary and systemic disorders. This review centers on the function of VIP in various lung diseases, such as pulmonary arterial hypertension, chronic obstructive pulmonary disease, asthma, cystic fibrosis, acute lung injury/acute respiratory distress syndrome, pulmonary fibrosis, and lung tumors. This review also outlines two main limitations of VIP as a potential medication and gathers information on extended-release formulations and VIP analogues.

Bombesin, endothelin, neurotensin and pituitary adenylate cyclase activating polypeptide cause tyrosine phosphorylation of receptor tyrosine kinases

Numerous peptides including bombesin (BB), endothelin (ET), neurotensin (NTS) and pituitary adenylate cyclase-activating polypeptide (PACAP) are growth factors for lung cancer cells. The peptides bind to G protein-coupled receptors (GPCRs) resulting in elevated cAMP and/or phosphatidylinositol (PI) turnover. In contrast, growth factors such as epidermal growth factor (EGF) or neuregulin (NRG)-1 bind to receptor tyrosine kinases (RTKs) such as the EGFR or HER3, increasing tyrosine kinase activity, resulting in the phosphorylation of protein substrates such as PI3K or phospholipase (PL)C. Peptide GPCRs can transactivate numerous RTKs, especially members of the EGFR/HER family resulting in increased phosphorylation of ERK, leading to cellular proliferation or increased phosphorylation of AKT, leading to cellular survival. GRCR antagonists and tyrosine kinase inhibitors are useful agents to prevent RTK transactivation and inhibit proliferation of cancer cells.

Peptide receptors as cancer drug targets

Neuropeptides function as neuromodulators in the brain, whereby they are released in a paracrine manner and activate G protein-coupled receptors (GPCRs) in adjacent cells. Because neuropeptides are made in, and secreted from, cancer cells, then bind to cell surface receptors, they function in an autocrine manner. Bombesin (BB)-like peptides synthesized by neuroendocrine tumor small cell lung cancer (SCLC) bind to BB receptors (BBRs), causing phosphatidylinositol turnover and phosphorylation of extracellular signal-regulated kinase (ERK). Phosphorylated ERK enters the nucleus and alters gene expression of SCLC cells, stimulating growth. Vasoactive intestinal peptide (VIP) addition to SCLC cells increases their release rate of BB-like peptides via activation of VIP receptors (VIPR), leading to activation of adenylyl cyclase and subsequent elevation of cAMP. Protein kinase A is then stimulated, leading to phosphorylation of cyclic AMP response element binding protein (CREB), which alters gene expression and stimulates proliferation. The growth of SCLC is inhibited by BBR and VIPR antagonists. This review will focus on how GPCRs for VIP and BB are molecular targets for early detection and treatment of cancer.

Vasoactive intestinal peptide increases apoptosis of hepatocellular carcinoma by inhibiting the cAMP/Bcl-xL pathway

Vasoactive intestinal peptide (VIP) is a modulator of inflammatory responses. VIP receptors are expressed in several tumor types, such as colorectal carcinoma. The study described herein was conducted to confirm the presence of VIP and its receptors (VPAC1 and VPAC2) in surgically resected hepatocellular carcinoma (HCC) tissues and in the HCC cell line Huh7. The mechanism responsible for apoptosis of HCC cells was then examined because VIP treatment (10^-10  M) significantly suppressed proliferation of Huh7 cells. In examining apoptosis-related proteins, we found caspase-3 to be significantly increased and Bcl-xL and cyclic AMP (cAMP) response element-binding protein (CREB) to be significantly decreased in Huh7 cells cultured with VIP. Furthermore, the CREB level and phosphorylation were reduced. These effects were reversed by the addition of VIP receptor antagonist or cAMP antagonist Rp-cAMPS. Pretreatment with cAMP analogue blocked the increased apoptosis, suggesting that VIP induces apoptosis via a PKA-independent signaling mechanism. Our data indicate that VIP prevents the progression of HCC by apoptosis through the cAMP/Bcl-xL pathway.

Neuropeptide G Protein-Coupled Receptors as Oncotargets

Neuropeptide G protein-coupled receptors (GPCRs) are overexpressed on numerous cancer cells. In a number of tumors, such as small cell lung cancer (SCLC), bombesin (BB) like peptides and neurotensin (NTS) function as autocrine growth factors whereby they are secreted from tumor cells, bind to cell surface receptors and stimulate growth. BB-drug conjugates and BB receptor antagonists inhibit the growth of a number of cancers. Vasoactive intestinal peptide (VIP) increases the secretion rate of BB-like peptide and NTS from SCLC leading to increased proliferation. In contrast, somatostatin (SST) inhibits the secretion of autocrine growth factors from neuroendocrine tumors (NETs) and decreases proliferation. SST analogs such as radiolabeled octreotide can be used to localize tumors, is therapeutic for certain cancer patients and has been approved for four different indications in the diagnosis/treatment of NETs. The review will focus on how BB, NTS, VIP, and SST receptors can facilitate the early detection and treatment of cancer.

Vasoactive intestinal peptide/pituitary adenylate cyclase activating polypeptide, and their receptors and cancer

PURPOSE OF REVIEW

To summarize the roles of vasoactive intestinal peptide (VIP)/pituitary adenylate cyclase activating polypeptide (PACAP) and their receptors (VPAC1, VPAC2, PAC1) in human tumors as well as their role in potential novel treatments.

RECENT FINDINGS

Considerable progress has been made in understanding of the effects of VIP/PACAP on growth of various tumors as well as in the signaling cascades involved, especially in the role of transactivation of the epidermal growth factor family. The overexpression of VPAC1/2 and PAC1 on a number of common neoplasms (breast, lung, prostate, central nervous system and neuroblastoma) is receiving increased attention both as a means of tumor imaging the location and extent of these tumors, as well as for targeted directed treatment, by coupling cytotoxic agents to VIP/PACAP analogues.

SUMMARY

VIP/PACAP has prominent growth effects on a number of common neoplasms, which frequently overexpressed the three subtypes of their receptors. The increased understanding of their signaling cascades, effect on tumor growth/differentiation and the use of the overexpression of these receptors for localization/targeted cytotoxic delivery are all suggesting possible novel tumor treatments.

Neuropeptides as lung cancer growth factors

This manuscript is written in honor of the Festschrift for Abba Kastin. I met Abba at a Society for Neuroscience meeting and learned that he was Editor-in-Chief of the Journal Peptides. I submitted manuscripts to the journal on "Neuropeptides as Growth Factors in Cancer" and subsequently was named to the Editorial Advisory Board. Over the past 30 years I have published dozens of manuscripts in Peptides and reviewed hundreds of submitted manuscripts. It was always rewarding to interact with Abba, a consummate professional. When I attended meetings in New Orleans I would sometimes go out to dinner with him at the restaurant "Commanders Palace". When I chaired the Summer Neuropeptide Conference we were honored to have him receive the Fleur Strand Award one year in Israel. I think that his biggest editorial contribution has been the "Handbook of Biologically Active Peptides." I served as a Section Editor on "Cancer/Anticancer Peptides" and again found that it was a pleasure working with him. This review focuses on the mechanisms by which bombesin-like peptides, neurotensin and vasoactive intestinal peptide regulate the growth of lung cancer.

VIP, from gene to behavior and back: summarizing my 25 years of research

Vasoactive intestinal peptide (VIP) is an interesting example of a 28-amino acid neuropeptide that is abundantly expressed in discrete brain regions/neurons and hence may contribute to brain function. This short review summarizes my own point of view and encompasses 25 years of work and over 100 publications targeting the understanding of VIP production and biological activity. The review starts with our original cloning of the VIP gene, it then continues to discoveries of regulation of VIP synthesis and the establishment of the first VIP transgenic mice. The review ends with the identification of novel VIP analogs that helped decipher VIP's important role during development, in regulation of the biological clock(s) and diurnal rhythms, sexual activity, learning and memory as well as social behavior, and cancer. This review cites only articles that I have coauthored and gives my own perspective of this exciting ever-growing field.

Generation of PEGylated VPAC1-selective antagonists that inhibit proliferation of a lung cancer cell line

Vasoactive intestinal peptide (VIP) binds to two receptors, VPAC1 and VPAC2. Non-selective VIP antagonists have been shown to inhibit human cancer cell proliferation and reduce tumor growth in mice. Many human cancers over-express VPAC1 but not VPAC2. We show that VPAC1-selective antagonists can inhibit human cancer cell proliferation and identify five positions in the VPAC1-selective antagonist PG 97-269 that may be responsible for VPAC1 selectivity. Position 16 appears to be particularly critical for selectivity, as demonstrated in the replacement of Arg16 of PG 97-269 with the native VIP amino acid; this single change results in greatly reduced VPAC1 binding and selectivity. Finally, we show that site-specific conjugation with a 22kDa polyethylene glycol (PEG) at the C-terminus of VPAC1-selective antagonists further improves VPAC1-selective binding and has minimal effect on antagonistic activity. Our studies have further solidified VPAC1 as a cancer target and offer the possibility of generating highly potent VPAC1-selective antagonists with minimal number of mutations to reduce the risk of immunogenicity and potentially prolonged duration of action to allow more efficient treatment regimen.

Vasoactive intestinal peptide-camptothecin conjugates inhibit the proliferation of breast cancer cells

The effects of vasoactive intestinal peptide-camptothecin (VIP-CPT) conjugates were investigated on breast cancer cells and cells transfected with VIP receptors (R). (Ala(2,8,9,19,24.25.27), Nle(17), Lys(28))VIP, (A-NL-K)VIP, was synthesized and Lys(28) was coupled to a linker, N-methyl-amino-ethyl-glycine, L2, which formed a carbamate bond with CPT. The resulting (A-NL-K)VIP-L2-CPT was cytotoxic for MCF7 breast cancer cells, which have VPAC(1)-R, with IC(50) values of 380 and 90 nM using the MTT and clonogenic assays, respectively. (A-NL-K)VIP, (A-NL-K)VIP-L2 and (A-NL-K)VIP-L2-CPT inhibited specific binding of (125)I-VIP to 3T3 cells transfected with VPAC(1)-R with IC(50) values of 1.9, 56 and 126 nM, respectively. In contrast, (A-NL-K)VIP, (A-NL-K)VIP-L2 and (A-NL-K)VIP-L2-CPT inhibited specific binding of (125)I-Ro25-1553 to 3T3 cells transfected with VPAC(2)-R with IC(50) values of 3.9, 3162 and 2690 nM, respectively. (A-NL-K)VIP, (A-NL-K)VIP-L2 and (A-NL-K)VIP-L2-CPT caused increased cAMP after addition to MCF7 cells. (125)I-(A-NL-K)VIP-L2-CPT was internalized by MCF7 cells at 37 degrees C but not 4 degrees C. These results indicate that (A-NL-K)VIP-L2-CPT is a VPAC(1)-R agonist which is cytotoxic for breast cancer cells.

Effect of vasoactive intestinal peptide on gastric adenocarcinoma

BACKGROUND AND AIM

Vasoactive intestinal peptide (VIP) is a gastrointestinal hormone in the secretin-VIP family. It has been reported that VIP affects some tumor growth, and there is a VIP autocrine regulation in some cancers. However, the effect of VIP on gastric adenocarcinoma is not clear yet. The aim of the present study was to investigate the effect of VIP on gastric adenocarcinoma, especially autocrine regulation of VIP on gastric adenocarcinoma.

METHODS

VIP mRNA and protein, and its receptor mRNA (VIPR(1) and VIPR(2)) were measured in 15 normal antrum mucosa, 20 gastric adenocarcinoma tissues, and the SGC7901 gastric adenocarcinoma cell line by using reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry, or radioimmunoassay methods. The effect of the VIP protein and its antagonist (D-p-Cl-Phe6, Leu17)-VIP on SGC7901 cell growth was detected by methylthiazolyldiphenyl-tetrazolium bromide (MTT) method. The expressions of c-myc mRNA and ornithine decarboxylase (ODC) mRNA in SGC7901 cells before and after the incubated VIP protein and/or its antagonist were also measured by RT-PCR method.

RESULTS

The VIP mRNA expression in gastric adenocarcinoma tissues was significantly higher than that in normal antrum mucosa (P < 0.01). The VIP-positive immunoreactivity cells existed in 40% of gastric adenocarcinoma tissues, but not in normal tissues (P < 0.01). The VIP-positive immunoreactivity nerve fibers were observed in normal tissues, but not in adenocarcinoma tissues (P < 0.01). The expression rate of VIPR(1) mRNA in adenocarcinoma tissues was significantly lower than that in normal tissues, but that of VIPR(2) mRNA in the two kinds of tissues were similar (P > 0.05). In addition, the expression quantity of VIPR(1) mRNA and VIPR(2) mRNA in adenocarcinoma tissues was significantly lower than that in normal tissues (P < 0.05). SGC7901 cells expressed not only VIP mRNA and the VIP protein, but also VIPR(1) and VIPR(2) mRNA. 10(6) SGC7901 cells secreted 13.15 +/- 8.54 pg VIP on average. VIP did not affect the proliferation of SGC7901 cells, but the antagonist stimulated the proliferation of SGC7901 cells from 10(-5) to 10(-8) mol/L concentration incubated for 24-96 h. VIP downregulated the expressions of c-myc and ODC mRNA, but its antagonist upregulated their expressions.

CONCLUSIONS

The expression of VIP mRNA upregulates, but the expressions of VIPR mRNA downregulates in gastric adenocarcinoma tissues. The gastric adenocarcinoma tissues contain endocrine cells to secrete VIP, which show malignant specialities. The VIP autocrine regulation exists in SGC7901 cells, and potentially inhibits the proliferation of the cells by downregulating the expressions of c-myc and ODC mRNA. It suggests that VIP may play an important role in the regulation of the growth of gastric cancer cells.

VIP provides cellular protection through a specific splice variant of the PACAP receptor: a new neuroprotection target

Vasoactive intestinal peptide (VIP) was known to provide neuroprotection. Three VIP receptors have been cloned: VPAC1, VPAC2 and PAC1. A specific splice variant of PAC1 in the third cytoplasmatic loop, hop2, was implicated in VIP-related neuroprotection. We aimed to clone the hop2 splice variant, examine its affinity to VIP and investigate whether it mediates the VIP-related neuroprotective activity. The PAC1 cDNA was cloned from rat cerebral astrocytes. Using genetic manipulation the hop2 splice variant was obtained, then inserted into an expression vector and transfected into COS-7 cells that were used for binding assays. Results showed that VIP bound the cloned hop2 splice variant. Stearyl-neurotensin(6-11) VIP(7-28) (SNH), an antagonist for VIP, was also found to bind hop2. In addition, VIP protected COS-7 cells expressing hop2 from oxidative stress. Parallel assays demonstrated that VIP increased cAMP accumulation in COS-7 cells expressing hop2. These results support the hypothesis that hop2 mediates the cytoprotective effects attributed to VIP.

Novel extended and branched N-terminal analogs of VIP

The effects of vasoactive intestinal peptide (VIP) are primarily mediated through VPAC1 and VPAC2, receptors that are preferentially coupled to adenylate cyclase activation. As a large majority of the potent VIP antagonists have modifications in the N-terminal domain of the peptide, the effect of multiplication of this domain on VIP was examined with the aim of possibly amplifying peptide-receptor (VPAC1) activation. Several VIP analogs were designed and synthesized, each carrying multiplication of the N-terminal domain that was obtained by either linear tandem extension or by parallel branching. Circular dichorism (CD) analysis revealed that these extended/branched peptides maintained an alpha helical structure in organic environment, similar to VIP. A specific branched VIP analog was found to be slightly more potent towards VPAC1-related cAMP production as compared to VIP. This analog could have potential therapeutic value in several disorders, similar to VIP. Two branched N-terminal VIP sequences demonstrated superior receptor binding and activation as compared to two N-terminals in tandem. The results suggest that correct alignment of the VIP N-terminal region is important for receptor binding and activation. However, increased receptor binding was not directly associated with increased cAMP production suggesting steric dynamic interactions.

Immunocytochemical identification of VPAC1, VPAC2, and PAC1 receptors in normal and neoplastic human tissues with subtype-specific antibodies

Human tumors frequently overexpress receptors for vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP). However, none of the VIP/PACAP receptor proteins has been visualized individually in human tumors. Here, we developed and characterized a panel of antipeptide antibodies to the carboxyl-terminal regions of the VIP/PACAP receptor subtypes vasoactive intestinal peptide receptor (VPAC)1, VPAC2, and pituitary adenylate cyclase-activating peptide receptor (PAC)1. Specificity of the antisera was shown by the following: (1) detection of broad bands migrating at Mr 50,000 to 70,000 in Western blots of membranes from receptor-expressing tumors and receptor-transfected cells; (2) cell surface staining of VIP/PACAP receptor-transfected cells; (3) translocation of VIP/PACAP receptor immunostaining in transfected cells after agonist exposure; and (4) abolition of tissue immunostaining by preadsorbtion of the antibodies with their immunizing peptides. The distribution of VIP/PACAP receptors was investigated in 98 human tumors and their tissues of origin. VPAC1, VPAC2, and PAC1 receptors were clearly located at the plasma membrane of the tumor cells in a variety of human neoplasms. In the gastrointestinal tract, VPAC1 receptor immunoreactivity was abundant in the mucosa and myenteric neurons; VPAC2 receptor immunoreactivity was detected in neuroendocrine cells, blood vessels, and smooth muscle; and PAC1 receptor immunoreactivity was found in myenteric neurons. This is the first localization of all of the VIP/PACAP receptor subtypes in human formalin-fixed, paraffin-embedded tissues. VIP/PACAP receptor visualization with this simple and rapid immunohistochemical method will facilitate identification of tumors with a sufficient receptor overexpression for diagnostic or therapeutic intervention.

Differential regulation of activity-dependent neuroprotective protein in rat astrocytes by VIP and PACAP

Activity-dependent neuroprotective protein (ADNP) was shown to be a vasoactive intestinal peptide (VIP) responsive gene in astrocytes derived from the cerebral cortex of newborn rats. The present study was set out to identify VIP receptors that are associated with increases in ADNP expression in developing astrocytes. Using VIP analogues specific for the VPAC1 and the VPAC2 receptors, it was discovered that VIP induced changes in ADNP expression in astrocytes via the VPAC2 receptor. The constitutive synthesis of ADNP and VPAC2 was shown to be age-dependent and increased as the astrocyte culture developed. Pituitary adenylate cyclase-activating polypeptide (PACAP) also induced changes in ADNP expression. The apparent changes induced by VIP and PACAP on ADNP expression were developmentally dependent, and while stimulating expression in young astrocytes, an inhibition was demonstrated in older cultures. In conclusion, VIP, PACAP and the VPAC2 receptor may all contribute to the regulation of ADNP gene expression in the developing astrocyte.

Clinical endocrinology and metabolism. Potential clinical applications of vasoactive intestinal peptide: a selected update

Neuropeptides are expressed in neurons innervating endocrine cells or in endocrine cells and cancer cells, and are released on site to act as hormones and growth factors. Vasoactive intestinal peptide (VIP) was first discovered in the early 1970s and has since become the area of research for many laboratories. VIP has a neuroendocrine role as it is intimately involved with the synthesis, secretion and action of other neuroendocrine hormones as well as cytokines and chemokines. Major outcomes of VIP downregulation encompass developmental and behavioral dysfunctions, including impaired diurnal rhythms. Overexpression of VIP has been associated with diarrhea and cancer, and overexpression of VIP receptors is associated with cancerous growth. This short review outlines some of the recent progress made in VIP research.

Recombinant uteroglobin prevents the experimental crescentic glomerulonephritis

BACKGROUND

Although uteroglobin is known to have an immunomodulatory property and prevents the deposition of immune-complexes on the glomeruli of mice, the therapeutic potential of uteroglobin is uncertain in glomerulonephritis. To test the hypothesis that uteroglobin can prevent glomerulonephritis, we have studied the effects of recombinant uteroglobin on the development of experimental crescentic glomerulonephritis that is induced by anti-glomerular basement membrane (anti-GBM) antibodies.

METHODS AND RESULTS

Glomerulonephritis was induced by the intravenous injection of rabbit anti-GBM globulin antibodies into mice (C57BL/6), and renal injury was evaluated 7, 14, and 21 days afterward. Recombinant uteroglobin or phosphate-buffered saline (PBS) were given intravenously to mice for 3 days after anti-GBM antibody injection. Proteinuria was significantly reduced in mice treated with recombinant uteroglobin compared with disease-control mice at 7 and 14 days after an anti-GBM antibody injection, although the serum creatinine concentration was similar in both groups. The amount of proteinuria was similar in recombinant uteroglobin-treated and normal control mice. By histologic analysis, mesangial matrix expansion, mesangial proliferation, and cellular crescents representing crescentic glomerulonephritis were markedly attenuated by injection of recombinant uteroglobin. The in vitro proliferative responses of mesangial cells to lipopolysaccharide (LPS) were blunted by the addition of recombinant uteroglobin in a dose-dependent manner. The preventive effects exerted by recombinant uteroglobin treatment were based on the inhibition of antibodies and complement-3 deposition on the glomeruli.

CONCLUSION

This study demonstrates the preventive effects of recombinant uteroglobin in an experimental model of crescentic glomerulonephritis, and suggests the therapeutic implications of uteroglobin for human chronic glomerulonephritis.

Hexanoylation of a VPAC2 receptor-preferring ligand markedly increased its selectivity and potency

We synthesized a VIP analog that combines mutations that decrease the affinity for the VPAC1 receptor but maintain a high affinity for the VPAC2 receptor with an amino-terminal hexanoylation that increases the affinity for the VPAC2 receptor with a limited decrease in the affinity of the VPAC1 receptor. The resulting Hexanoyl[A19,K(27,28)]VIP had the expected properties of a high affinity for the VPAC2 receptor and a low affinity for the VPAC1 receptor and also a low affinity for the PAC1 and secretin receptors. With a 1000-fold preference for the VPAC2 receptor and a IC50 value of binding of 1 nM, this compound is the most potent and the most selective agonist presently described.

Effects of the vasoactive intestinal peptide (VIP) and related peptides on glioblastoma cell growth in vitro

The growth rate of numerous cancer cell lines is regulated in part by actions of neuropeptides of the vasoactive intestinal peptide (VIP) family, which also includes pituitary adenylate cyclase-activating peptide (PACAP), glucagon, and peptide histidine/isoleucine (PHI). The aim of this work was to investigate the effect of these peptides on the growth of the rat glioblastoma cell line C6 in vitro. We also sought to determine which binding sites were correlated with the effects observed. Proliferation studies performed by means of a CyQuant trade mark assay showed that VIP and PACAP strongly stimulated C6 cell proliferation at most of the concentrations tested, whereas PHI increased cell proliferation only when associated with VIP. Two growth hormone-releasing factor (GRF) derivatives and the VIP antagonist hybrid peptide neurotensin-VIP were able to inhibit VIP-induced cell growth stimulation, even at very low concentrations. Binding experiments carried out on intact cultured C6 cells, using 125I-labeled VIP and PACAP as tracers, revealed that the effects of the peptides on cell growth were correlated with the expression on C6 cells of polyvalent high-affinity VIP-PACAP binding sites and of a second subtype corresponding to very high-affinity VIP-selective binding species. The latter subtype, which interacted poorly with PACAP with a 10,000-fold lower affinity than VIP, might mediate the antagonist effects of neurotensin- VIP and of both GRF derivatives on VIP-induced cell growth stimulation.

VIP receptor antagonists inhibit mammary carcinogenesis in C3(1)SV40T antigen mice

The effects of a vasoactive intestinal peptide (VIP) receptor antagonist on mammary carcinogenesis were investigated using the C3(1)SV40T antigen (ag) mice. Ten microg/day VIPhybrid (VIPhyb) administered daily subcutaneously increased significantly the survival of C3(1)SV40Tag mice. At 5.2 months, VIPhyb significantly reduced the mammary tumor burden in C3(1)SV40Tag mice relative to control animals. 125I-VIP bound with high affinity to mouse mammary tumor homogenate. Because (Lys15, Arg16, Leu27)VIP1-7GRF8-27 (VPAC1 selective) but not Ro25-1553 (VPAC2 selective) inhibited specific 125I-VIP binding to mammary tumor membranes with high affinity, VPAC1 receptors predominate. By RT-PCR, VPAC1 receptor mRNA was detected in mammary tumors. By Western blot, a major 60 Kdalton band was detected in mammary tumor extracts using VPAC1 receptor antisera. By immunocytochemistry, VPAC1-R immunostaining was detected in the cytosol and plasma membrane but not the nucleus of fixed mammary tumor tissue. Using laser capture microdissected tumor cells and surface enhanced laser desorption/ionization (SELDI) techniques on mammary tumor cells, the proteomic profile was altered in mice treated with VIPhyb. Because VPAC1 receptor antagonists increase the survival and reduce the tumor burden in C3(1)SV40Tag mice, they may function as chemopreventive agents in mammary cancer.

From vasoactive intestinal peptide (VIP) through activity-dependent neuroprotective protein (ADNP) to NAP: a view of neuroprotection and cell division

Accelerated neuronal death brings about cognitive as well as motor and other dysfunctions. A major neuropeptide, vasoactive intestinal peptide (VIP), has been shown to be neuroprotective. However, VIP-based drug design is hampered by the instability of the peptide and its limited bioavailability. Two independent approaches were thus taken to exploit VIP as a lead drug candidate: (1) Potent neuroprotective lipophilic analogs of VIP were synthesized, e.g. [stearyl-norleucine-17] VIP (SNV); and (2) potent neuroprotective peptide derivatives were identified that mimic the activity of VIP-responsive neuroprotective glial proteins. VIP provides neuronal defense by inducing the synthesis and secretion of neuroprotective proteins from astrocytes; activity-dependent neuroprotective protein (ADNP) was discovered as such glial cell mediator of VIP- and SNV-induced neuroprotection. In subsequent studies, an eight-amino-acid peptide, NAP, was identified as the smallest active element of ADNP exhibiting potent neuroprotective activities. This paper summarizes the biological effects of SNV and NAP and further reports advances in NAP studies toward clinical development. An original finding described here shows that NAP, while protecting neurons, demonstrated no apparent effect on cell division in a multiplicity of cell lines, strengthening the notion that NAP is a specific neuroprotective drug candidate.

VIP and PACAP receptors coupled to adenylyl cyclase in human lung cancer: a study in biopsy specimens

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are important neuropeptides in the control of lung physiology. Both of these commonly bind to specific G protein coupled receptors named VPAC(1)-R and VPAC(2)-R, and PAC(1)-R (with higher affinity for PACAP). VIP and PACAP have been implicated in the control of cell proliferation and tumor growth. This study examined the presence of VIP and PACAP receptors in human lung cancer samples, as well as the functionality of adenylyl cyclase (AC) stimulated by both peptides. Results from RT-PCR and immunoblot experiments showed the expression of VPAC(1)-, VPAC(2)- and PAC(1)-R in lung cancer samples. Immunohistochemical studies showed the expression of VPAC(1) and VPAC(2) receptors. These receptors were positively coupled to AC, but the enzyme activity was impaired as compared to normal lung. There were no changes in Galpha(s) or Galpha(i) levels. Present results contribute to a better knowledge of VIP/PACAP actions in lung cancer and support the interest for the development of VIP/PACAP analogues with therapeutic roles.

VIP as a trophic factor in the CNS and cancer cells

The effects of vasoactive intestinal peptide (VIP) on the proliferation of central nervous system (CNS) and cancer cells were investigated. VIP has important actions during CNS development. During neurogenesis, VIP stimulates the proliferation and differentiation of brain neurons. Addition of VIP to embryonic mouse spinal cord cultures increases neuronal survival and activity dependent neurotrophic factor (ADNF) secretion from astroglial cells. VIP is an integrative regulator of brain growth and development during neurogenesis and embryogenesis. Also, VIP causes increased proliferation of human breast and lung cancer cells in vitro. VIP binds with high affinity to cancer cells, elevates the cAMP and increases gene expression of c-fos, c-jun, c-myc and vascular endothelial cell growth factor. The effects of VIP on cancer cells are reversed by VIPhybrid, a synthetic VPAC(1) receptor antagonist. VIPhyb inhibits the basal growth of lung cancer cells in vitro and tumors in vivo and potentiates the ability of chemotherapeutic drugs to kill cancer cells. Due to the high density of VPAC(1) receptors in cancer cells, VIP has been radiolabeled with 123I, 18F and 99mTc to image tumors. It remains to be determined if radiolabeled VIP analogs will be useful agents for early detection of cancer in patients.

In vitro and in vivo treatment of colon cancer by VIP antagonists

Vasoactive intestinal peptide (VIP) is secreted from many cancer lines and VIP binding was observed in many tumors. We have shown before that VIP antagonists are potent inhibitors of neoplastic growth of neuroblastoma, lung and breast cancer cells in vitro. Here, the cultured colon cancer cell line HCT-15 that exhibited VIP receptor expression was treated with the VIP hybrid antagonist neurotensin(6-11)VIP(7-28). The antineoplastic activity was assessed by thymidine incorporation. Neurotensin(6-11)VIP(7-28) efficiently inhibited cancer growth with a maximal effect at nanomolar concentrations. Once the inhibitory properties of the VIP antagonist on colon cancer cells were established, the in vivo curative effects were analyzed. Sprague-Dawley rats were injected with azoxymethane (AOM) (15 mg/kg/week) for 2 weeks, providing artificial induction of colon tumors. The rats were then allocated into four experimental groups: (1) receiving no treatment; (2) receiving treatment with saline; (3, 4) receiving treatment with 10 or 20 microg of neurotensin(6-11)VIP(7-28), respectively. After 10 weeks of daily injections, rats were sacrificed and tumors assessed for stage, volume, location, differentiation and lymphocytic infiltrate. Embedded mucosa was assessed for dysplastic crypts. Results showed that the antagonist treatment reduced the tumor volume, staging, lymphocyte infiltrate and the number of dysplastic crypts. Thus, neurotensin(6-11)VIP(7-28) could serve as an effective cancer treatment and a preventing agent.

A vasoactive intestinal peptide receptor analog alters the expression of homeobox genes

A lipophilic analog of vasoactive intestinal peptide (VIP), stearyl-Nle(17)-neurotensin(6-11)VIP(7-28) (SNH), that inhibited lung cancer growth, has been previously described. The mechanism of SNH inhibition of cancer growth is still being elucidated. The present study examined the effects of SNH on homeobox genes in the colon cancer cell line HT 29 that expresses VIP receptors. Homeobox genes contain a characteristic DNA sequence, coding for a stretch of 61 amino acid homeodomain that binds specific DNA motifs. While the HOX gene family contains a single homeodomain, the POU gene family contains an additional DNA binding homeodomain. HT 29 cells were incubated with SNH; RNA was extracted and subjected to reverse-transcription-polymerase chain reaction (RT-PCR) with primers that matched the conserved area of the various HOX or POU genes. The PCR products that were altered by SNH treatment were sequenced. Three candidate SNH-responsive genes, the HOX A4, the HOX B5 and the PUO V transcription factor I (Oct-3) were identified. Semi-quantitative RT-PCR with specific primers confirmed the increase in HOX A4 and the decrease in Oct-3 expression levels following SNH treatment. Thus, the HOX A4 and the Oct-3 homeobox genes may partially mediate SNH activity on cancer cells.

Genomic effects of polyamide/DNA interactions on mRNA expression

Here we characterize the biological activity of a hairpin polyamide 1 that inhibits binding of the minor-groove transcription factor LEF-1, constitutively expressed in colon cancers. Genome-wide analysis of mRNA expression in DLD1 colon cancer cells treated with 1 reveals that a limited number of genes are affected; the most significant changes correspond to genes related to cell cycle, signaling, and proteolysis rather than the anticipated WNT signaling pathway. Treated cells display increased doubling time and hypersensitivity to DNA damage that most likely results from downregulation of DNA-damage checkpoint genes, including YWAE (14-3-3epsilon protein) and DDIT3. Promoter analyses on a genomic level revealed numerous potential polyamide binding sites and multiple possible mechanisms for transcriptional antagonism, underscoring the utility of gene expression profiling in understanding the effects of polyamides on transcription at the cellular level.