Bombesin stimulates c-fos and c-jun mRNAs in small cell lung cancer cells

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.

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.

Bombesin-like peptides and associated receptors within the brain: distribution and behavioral implications

As we commemorate the 25th anniversary of the journal Peptides, it is timely to review the functional significance of the bombesin (BB)-like peptides and receptors in the CNS. Over two decades ago we published an article in the journal Peptides demonstrating that BB-like peptides are present in high densities in certain rat brain regions (such as the paraventricular nucleus of the hypothalamus). Subsequently, one of the mammalian forms of BB, gastrin-releasing peptide (GRP) containing cell bodies were found in the suprachiasmatic nucleus of the hypothalamus and nucleus of the solitary tract of the hindbrain. Another related peptide, namely neuromedin (NM)B, was detected in the olfactory bulb and dentate gyrus. BB and GRP bind with high affinity to BB(2) receptors, whereas NMB binds with high affinity to BB(1) receptors. The actions of BB or GRP are blocked by BB(2) receptor antagonists such as (Psi(13,14)-Leu(14))BB whereas PD168368 is a BB(1) receptor antagonist. Exogenous administration of BB into the rat brain causes hypothermia, hyperglycemia, grooming and satiety. BB-like peptides activate the sympathetic nervous system and appear to modulate stress, fear and anxiety responses. GRP and NMB modulate distinct biological processes through discrete brain regions or circuits, and globally these peptidergic systems may serve in an integrative or homeostatic function.

Nonpeptide gastrin releasing peptide receptor antagonists inhibit the proliferation of lung cancer cells

The ability of nonpeptide antagonists to interact with gastrin releasing peptide receptors on lung cancer cells was investigated. PD176252 (3-(1H-Indol-3-yl)-N-[1-(5-methoxy-pyridin-2-yl)-cyclohexylmethyl]-2-methyl-2-[3-(4-nitro-phenyl)-ureido]-propionamide) and PD168368 (3-(1H-Indol-3-yl)-2-methyl-2-[3(4-nitro-phenyl)-ureido]-N-(1-pyridin-2-yl-cyclohexylmethyl)-propionamide) inhibited specific 125I-gastrin releasing peptide binding to NCI-H1299 cells with IC50 values of 20 and 1500 nM, respectively. Similar binding results were obtained using NCI-H157, H345 and N592 human lung cancer cells. PD176252 inhibited the ability of 1 nM bombesin to cause elevation of cytosolic calcium in Fura-2 loaded NCI-H345 or H1299 cells, whereas it had no effect on basal cytosolic calcium. PD176252 antagonized the ability of 10 nM bombesin to cause elevation of c-fos mRNA in NCI-H1299 cells. Also, PD176252 inhibited the ability of 100 nM bombesin to cause tyrosine phosphorylation of focal adhesion kinase in NCI-H1299 cells. Using a [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] assay, PD176252 was more potent than PD168368 at inhibiting NCI-H1299 proliferation. Also, 1 microM PD176252 significantly inhibited lung cancer colony number in vitro. PD176252 in a dose-dependent manner inhibited NCI-H1299 xenograft growth in nude mice in vivo. These results indicate that PD176252 is a gastrin releasing peptide receptor antagonist, which inhibits the proliferation of lung cancer cells.

GRP receptor-mediated immediate early gene expression and transcription factor Elk-1 activation in prostate cancer cells

Bombesin (BN) and its mammalian homologue gastrin-releasing peptide (GRP) have been shown to play an important role in human cancer as autocrine and paracrine growth factors. Prostatic neuroendocrine cells are thought to secrete these regulatory peptides and they may therefore interact with their specific, aberrantly expressed GRP receptor (GRP-R) in prostate cancer. In this study, we investigated the effect of BN on immediate early gene expression in two androgen-independent prostate cancer cell lines DU-145 and PC-3 with functional GRP receptor. We found that BN induced c-fos mRNA expression in both cell lines in a time-dependent manner. In contrast, c-jun mRNA was only modestly induced in DU-145 cells but not at all in PC-3 cells. On the protein level, we detected BN-induced stimulation of the c-fos gene product but not of c-jun protein. Sustained increase of the c-myc gene product was detectable in PC-3 but not in DU-145 cells. Concurrently, we demonstrated BN-dependent activation of the transcription factor Elk-1 and significant increase of cell proliferation in both prostate cancer cell lines. Taken together, these data suggest that BN acts as a mitogen in prostate cancer and this might be associated with the activation of the transcription factor Elk-1 and the immediate early gene c-fos.

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.

Bombesin antagonists inhibit growth of MDA-MB-435 estrogen-independent breast cancers and decrease the expression of the ErbB-2/HER-2 oncoprotein and c-jun and c-fos oncogenes

Previous studies showed that antagonists of bombesin (BN)/gastrin-releasing peptide (GRP) inhibit the growth of various cancers by interfering with the growth-stimulatory effects of BN-like peptides and down-regulating epidermal growth factor receptors on tumors. Because the overexpression of the human epidermal growth factor receptor-2 (ErbB-2/HER-2/neu) oncogene plays a role in the progression of many breast cancers, we investigated whether BN/GRP antagonists can affect HER-2 in mammary tumors. Female nude mice bearing orthotopic xenografts of MDA-MB-435 human estrogen-independent breast cancers were treated daily with BN/GRP antagonists RC-3095 (20 microg) or RC-3940-II (10 microg) for 6 weeks. The expression of BN/GRP receptors on tumors was analyzed by reverse transcription-PCR and immunoblotting. We also evaluated whether the mRNA expression for the c-jun and c-fos oncogenes is affected by the therapy. Both BN/GRP antagonists significantly inhibited growth of MDA-MB-435 cancers; RC-3095 reduced tumor volume by 40% and RC-3940-II by 65%. The GRP receptors (subtype 1) were detected in MDA-MB-435 tumors, showing that they mediate the inhibitory effect of the antagonists. Tumor inhibition was associated with a substantial reduction in the expression of mRNA and protein levels of the ErbB/HER receptor family as well as with a decrease in the expression of c-jun and c-fos oncogenes. BN/GRP antagonists RC-3940-II and RC-3095 could be considered for endocrine therapy of estrogen-independent breast cancers that express members of the ErbB/HER receptor family and the c-jun and c-fos oncogenes.

A bombesin receptor subtype-3 peptide increases nuclear oncogene expression in a MEK-1 dependent manner in human lung cancer cells

A synthetic peptide, (D-Phe(6), beta-Ala(11), Phe(13), Nle(14))bombesin-(6-14) was used to investigate the signal transduction mechanisms of bombesin receptor subtype-3. Using NCI-1299#5 human lung cancer cells stably transfected with bombesin receptor subtype-3, 100 nM (D-Phe(6), beta-Ala(11), Phe(13), Nle(14))bombesin-(6-14) elevated the cytosolic Ca2+ from 150 to 250 nM within 10 s. Addition of (D-Phe(6), beta-Ala(11), Phe(13), Nle(14))bombesin-(6-14) caused phosphorylation of mitogen activated protein kinase in a time- and concentration-dependent manner. The mitogen activated protein kinase phosphorylation caused by (D-Phe(6), beta-Ala(11), Phe(13), Nle(14))bombesin-(6-14) was inhibited by 2'-amino-3'-methyoxyflavone (PD98059), a mitogen activated protein kinase kinase (MEK-1) inhibitor. Using a luciferase reporter gene construct, (D-Phe(6), beta-Ala(11), Phe(13), Nle(14))bombesin-(6-14) caused Elk-1 activation after 10 min and the increase in Elk-1 activation caused by (D-Phe(6), beta-Ala(11), Phe(13), Nle(14))bombesin-(6-14) was inhibited by PD98059 as well as a dominant-negative MEK-1. (D-Phe(6), beta-Ala(11), Phe(13), Nle(14))bombesin-(6-14) caused increased c-fos as well as c-jun mRNAs 1 h after addition to NCI-H1299#5 cells. The 47-fold increase in c-fos mRNA caused by 100 nM (D-Phe(6), beta-Ala(11), Phe(13), Nle(14))bombesin-(6-14) was inhibited by PD98059, a dominant-negative MEK-1 and a substance P antagonist but not (3-phenylpropanoyl-D-Ala(24), Pro(26), Psi(26,27), Phe(27))GRP-(20-27) (BW2258U89), a GRP receptor antagonist. These results indicate that (D-Phe(6), beta-Ala(11), Phe(13), Nle(14))bombesin-(6-14) caused increased nuclear oncogene expression and upstream events include mitogen activated protein kinase phosphorylation and Elk-1 activation.

Bombesin and gastrin releasing peptide increase tyrosine phosphorylation of focal adhesion kinase and paxillin in non-small cell lung cancer cells

The effects of some oncogenes, growth factors and neuropeptides are mediated by tyrosine phosphorylation of focal adhesion kinase (p125(FAK)) and paxillin cytoskeletal proteins. In this study the ability of bombesin/gastrin releasing peptide (BB/GRP) to stimulate tyrosine phosphorylation of p125(FAK) and paxillin in non-small cell lung cancer (NSCLC) H1299 cells was investigated. BB, 100 nM caused increased p125(FAK) and paxillin tyrosine phosphorylation maximally after 1 min. The effect of BB on p125(FAK) and paxillin tyrosine phosphorylation was concentration-dependent, being half maximal at 4-8 nM. Also, 100 nM GRP, GRP(14-27) but not GRP(1-16) increased p125(FAK) and paxillin tyrosine phosphorylation indicating that the C-terminal of GRP is essential. BW2258U89, a GRP receptor antagonist, caused a dose-dependent inhibition of BB-stimulated p125(FAK) and paxillin tyrosine phosphorylation with an IC50 value of 3 microM. Cytochalasin D (0.3 microM), which inhibits actin polymerization, reduced the ability of BB to stimulate tyrosine phosphorylation of p125(FAK) and paxillin. Genistein (50 microM) and H-7 (50 microM), which are kinase inhibitors, reduced the tyrosine phosphorylation of p125(FAK) and paxillin stimulated by BB. Also, treatment of NCI-H1299 cells with FAK antisense resulted in decreased FAK tyrosine kinase activity and proliferation. These results suggest that p125(FAK) is an important enzyme for NSCLC proliferation.

Nonpeptide neuromedin B receptor antagonists inhibit the proliferation of C6 cells

The ability of nonpeptide antagonists to interact with neuromedin B receptors on C6 cells was investigated. 2-[3-(2, 6-Diisopropyl-phenyl)-ureido]3-(1H-indol-3-yl)-2-methyl-N-(1-pyridin- 2-yl-cyclohexylmethyl)-proprionate (PD165929), 3-(1H-indol-3-yl)-2-methyl-2-[3(4-nitro-phenyl)-ureido]-N-(1-pyridin- 2-yl-cyclohexylmethyl)-propionamide (PD168368) and 3-(1H-indol-3-yl)-N-[1-(5-methoxy-pyridin-2-yl)-cyclohexylmethyl]- 2-m ethyl-2-[3-(4-nitro-phenyl)-ureido]-propionamide (PD176252) inhibited (125I-Tyr0)neuromedin B binding with IC50 values of 2000, 40 and 50 nM, respectively. Because neuromedin B is a G-protein coupled serpentine receptor, the effects of neuromedin B antagonists on second messenger production and proliferation were investigated. PD168368 inhibited the ability of 10 nM neuromedin B to cause elevation of cytosolic Ca2+, whereas it had no effect on basal cytosolic Ca2+. PD168368 inhibited the ability of 100 nM neuromedin B to cause elevation of c-fos mRNA. Also, PD168368 in a dose-dependent manner inhibited the ability of 100 nM neuromedin B to cause phosphorylation of focal adhesion kinase. Using a [3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] assay, the order of antagonist potency to inhibit C6 proliferation was PD168368=PD176252>PD165929. Also, 1 microM PD168368 and PD176252 significantly inhibited colony number using a proliferation assay in vitro. PD168368 significantly inhibited C6 xenograft growth in nude mice in vivo. These results indicate that PD168368 is a C6 cell neuromedin B receptor antagonist, which inhibits proliferation.

Inhibition of growth of OV-1063 human epithelial ovarian cancers and c- jun and c- fos oncogene expression by bombesin antagonists

Receptors for bombesin are present on human ovarian cancers and bombesin-like peptides could function as growth factors in this carcinoma. Therefore, we investigated the effects of bombesin/gastrin-releasing peptide (GRP) antagonists RC-3940-II and RC-3095 on the growth of human ovarian carcinoma cell line OV-1063, xenografted into nude mice. Treatment with RC-3940-II at doses of 10 microg and 20 microg per day s.c. decreased tumour volume by 60.9% (P< 0.05) and 73.5% (P< 0.05) respectively, after 25 days, compared to controls. RC-3095 at a dose of 20 microg per day reduced the volume of OV-1063 tumours by 47.7% (P = 0.15). In comparison, luteinizing hormone-releasing hormone (LH-RH) antagonist Cetrorelix at a dose of 100 microg per day caused a 64.2% inhibition (P< 0.05). RT-PCR analysis showed that OV-1063 tumours expressed mRNA for bombesin receptor subtypes BRS-1, BRS-2, and BRS-3. In OV-1063 cells cultured in vitro, GRP(14-27) induced the expression of mRNA for c- jun and c- fos oncogenes in a time-dependent manner. Antagonist RC-3940-II inhibited the stimulatory effect of GRP(14-27) on c- jun and c- fos in vitro. In vivo, the levels of c- jun and c- fos mRNA in OV-1063 tumours were decreased by 43% (P< 0.05) and 45% (P = 0. 05) respectively, after treatment with RC-3940-II at 20 microg per day. Exposure of OV-1063, UCI-107 and ES-2 ovarian carcinoma cells to RC-3940-II at 1 microM concentration for 24 h in vitro, extended the latency period for the development of palpable tumours in nude mice. Our results indicate that antagonists of bombesin/GRP inhibit the growth of OV-1063 ovarian cancers by mechanisms that probably involve the downregulation of c- jun and c- fos proto-oncogenes.

Signaling mechanisms regulating bombesin-mediated AP-1 gene induction in the human gastric cancer SIIA

The hormone bombesin (BBS) and its mammalian equivalent gastrin-releasing peptide (GRP) act through specific GRP receptors (GRP-R) to affect multiple cellular functions in the gastrointestinal tract; the intracellular signaling pathways leading to these effects are not clearly defined. Previously, we demonstrated that the human gastric cancer SIIA possesses GRP-R and that BBS stimulates activator protein-1 (AP-1) gene expression. The purpose of our present study was to determine the signaling pathways leading to AP-1 induction in SIIA cells. A rapid induction of c-jun and jun-B gene expression was noted after BBS treatment; this effect was blocked by specific GRP-R antagonists, indicating that BBS is acting through the GRP-R. The signaling pathways leading to increased AP-1 gene expression were delineated using phorbol 12-myristate 13-acetate (PMA), which stimulates protein kinase C (PKC)-dependent pathways, by forskolin (FSK), which stimulates protein kinase A (PKA)-dependent pathways, and by the use of various protein kinase inhibitors. Treatment with PMA stimulated AP-1 gene expression and DNA binding activity similar to the effects noted with BBS; FSK stimulated jun-B expression but produced only minimal increases of c-jun mRNA and AP-1 binding activity. Pretreatment of SIIA cells with either H-7 or H-8 (primarily PKC inhibitors) inhibited the induction of c-jun and jun-B mRNAs in response to BBS, whereas H-89 (PKA inhibitor) exhibited only minimal effects. Pretreatment with tyrphostin-25, a protein tyrosine kinase (PTK) inhibitor, attenuated the BBS-mediated induction of c-jun and jun-B, but the effect was not as pronounced as with H-7. Collectively, our results demonstrate that BBS acts through its receptor to produce a rapid induction of both c-jun and jun-B mRNA and AP-1 DNA binding activity in the SIIA human gastric cancer. Moreover, this induction of AP-1, in response to BBS, is mediated through both PKC- and PTK-dependent signal transduction pathways with only minimal involvement of PKA.

(Tyr(0),Bpa(4))bombesin is a GRP receptor agonist

(Tyr(0),Bpa(4))bombesin, (YB)BB was synthesized and its biologic activity evaluated using T47D breast cancer cells. ((125)I-Tyr(0), Bpa(4))BB bound with high affinity (K(d) = 5 nM) to T47D cells. Specific ((125)I-Tyr(0),Bpa(4))BB binding was inhibited with high affinity by BB, BW2258U89, GRP, GRP(14-27) and NMB (IC(50) values of 10, 2, 15, 20, and 150 nM)but not GRP(1-16) (IC(50) value of > 1000 nM). ((125)I-Tyr(0),Bpa(4))BB bound to the surface of T47D cells at 4 degrees C but was internalized at 37 degrees C. After binding at 4 degrees C followed by irradiation using ultraviolet light, ((125)I-Tyr(0),Bpa(4))BB labeled a 75 kDa protein using T47D cells. (Tyr(0),Bpa(4))BB, 10 nM, elevated cytosolic calcium using T47D cells within 10 s. Also (Tyr(0),Bpa(4))BB, 10 nM, elevated c-fos mRNA after 45 min. These results indicate that (Tyr(0),Bpa(4))BB is an agonist for GRP receptors.

The metabolism of BW2258U89, a GRP receptor antagonist

BW2258U89 is a gastrin releasing peptide (GRP) receptor antagonist which inhibits the proliferation of the neuroendocrine tumor small cell lung cancer (SCLC). Here the biological activity of BW2258U89 and its metabolite were investigated. Using mass spectroscopy (LC-ESI/MS) techniques, three major peaks for BW2258U89 were observed with mass/charge (m/z) ratios of 1081.6, 541.4 and 361.4. After metabolism by mouse plasma enzymes, the major product had a m/z ratio of 1082.5, 541.9 and 361.8 suggesting that BW2258U89 was deamidated. Deamidated (Da) BW2258U89 was synthesized and it inhibited ((125)I-Tyr(4)) BB binding to NCI-H345 SCLC cells with an IC(50)value of 450 nM; BW2258U89 had an IC(50)value of 17 nM. BW2258U89 (1 microM) antagonized the ability of 50 nM BB to elevate cytosolic Ca(2+)in NCI-H345 cells, whereas 1 microM (Da) BW2258U89 did not. One micromolar BW2258U89 antagonized the increase in NCI-H345 c-fos mRNA caused by 10 nM BB, whereas 1 microM (Da) BW2258U89 had little effect. One microM BW2258U89 inhibited NCI-H345 clonal growth significantly whereas 1 microM (Da) BW2258U89 did not. These data suggest that an amidated C-terminal is important for antagonism of SCLC GRP receptors by BW2258U89.

Inhibition of growth of human malignant glioblastoma in nude mice by antagonists of bombesin/gastrin-releasing peptide

The effects of antagonists of bombesin/gastrin-releasing peptide (GRP) on the growth of human malignant glioblastoma cell line U-87MG xenografted into nude mice were evaluated. Nude mice bearing s.c. implanted U-87MG tumors were treated with bombesin/GRP antagonists RC-3095 and RC-3940-II. RC-3095 and RC-3940-II administered s.c. at a dose of 20 micrograms/day for 4 weeks decreased the volume of U-87MG xenografts by 60 and 74%, respectively, compared with controls. RT-PCR analysis showed that U-87MG xenografts expressed mRNA for bombesin receptor subtype (BRS)-1 (GRP receptor) and BRS-2 (neuromedin-B receptor), but the mRNA for GRP ligand was not detected in U-87MG cells suggesting that GRP may stimulate the growth of U-87MG glioblastomas by a paracrine mechanism. The levels of mRNA for c-fos oncogene were decreased by 30-40% in U-87MG tumors treated with RC-3095 or RC-3940-II. In U-373MG glioblastoma cells, which also express BRS-1, and U-87MG cells, cultured in vitro, GRP(14-27) induced the expression of c-fos mRNA, and some c-jun mRNA, in a time-dependent manner with the maximal effect occurring 2 h after the stimulation and a return to basal levels after 8 h. Antagonist RC-3940-II inhibited the stimulation of c-fos by GRP(14-27). Our results indicate that antagonists of bombesin/GRP inhibit the growth of U-87MG glioblastomas by a mechanism that may involve the downregulation of c-fos oncogene.

Targeted cytotoxic analogue of bombesin/gastrin-releasing peptide inhibits the growth of H-69 human small-cell lung carcinoma in nude mice

Recently, we developed a powerful cytotoxic analogue of bombesin AN-215, in which the bombesin-like carrier peptide Gln-Trp-Ala-Val-Gly-His-Leu-psi(CH2-NH)-Leu-NH2 (RC-3094) is conjugated to a potent derivative of doxorubicin, 2-pyrrolinodoxorubicin (AN-201). Small-cell lung carcinomas (SCLCs) are known to express high levels of bombesin receptors. We evaluated whether these receptors could be used for targeting cytotoxic bombesin analogue to H-69 SCLC cells. H-69 cells were xenografted into male nude mice, which then received an intravenous injection of AN-215, cytotoxic radical AN-201, the carrier peptide RC-3094 alone or unconjugated mixture of RC-3094 and AN-201. The levels of mRNA for bombesin receptor subtypes were evaluated by reverse transcription-polymerase chain reaction. In vitro, both the analogue AN-215 and the radical AN-201 showed strong antiproliferative effects on H-69 cells, AN-215 requiring more time to exert its action at 10(-8) M concentration than AN-201. In vivo, the growth of H-69 SCLC tumours was significantly inhibited by the treatment with 200 nmol kg(-1) of AN-215, while equimolar doses of the cytotoxic radical AN-201 or the mixture of AN-201 and the carrier peptide were toxic and produced only a minor tumour inhibition as compared with control groups. mRNA for bombesin receptor subtypes 2 (BRS-2) and 3 (BRS-3) was detected in H-69 tumours. The mRNA levels for BRS-3, but not for BRS-2, were lower in the AN-215-treated tumours as compared with controls. Our results demonstrate that the cytotoxic bombesin analogue AN-215 could be considered for targeted therapy of tumours, such as SCLC, that express bombesin receptors.

Bombesin activates MAP kinase in non-small cell lung cancer cells

The effects of bombesin (BB) on mitogen activated protein (MAP) kinase were investigated using non-small cell lung cancer (NSCLC) cells. By Western blot, both 42 and 44 kDalton forms of MAP kinase were present in NCI-H1299 and NCI-H838 cells. Addition of BB to NCI-H1299 cells resulted in phosphorylation of the MAP kinase substrate myelin basic protein (MBP). Phosphorylation of MBP was maximal 6 min after the addition of 10 nM BB to NCI-H1299 cells. Addition of gastrin releasing peptide (GRP) or GRP14-27 but not GRP1-16 to NCI-H 1299 cells caused MBP phosphorylation. The effects of BB were inhibited by BW2258U89, a BB receptor antagonist, and PD98059, a MAP kinase kinase inhibitor. Also, PD98059 inhibited the clonal growth of NCI-H1299 cells. These data suggest that MAP kinase may be an important regulatory enzyme in NSCLC.

Bombesin/gastrin-releasing peptide antagonists RC-3095 and RC-3940-II inhibit tumor growth and decrease the levels and mRNA expression of epidermal growth factor receptors in H-69 small cell lung carcinoma

BACKGROUND

Antagonists of bombesin/gastrin-releasing peptide (BN/GRP) have been developed to block the autocrine stimulatory effect of BN/GRP on tumors such as small cell lung carcinoma (SCLC). Although several studies have addressed the intracellular events that follow the formation of the receptor-ligand complex, the mechanism of action of BN/GRP antagonists remains unclear.

METHODS

In this study the authors investigated the effect of synthetic BN/GRP antagonists RC-3095 and RC-3940-II on tumor growth and the expression of epidermal growth factor receptors (EGF-R) in H-69 SCLC. Athymic nude mice xenografted with H-69 SCLC were treated subcutaneously for 5 weeks with RC-3095 and RC-3940-II at the dose of 10 microg/animal/day.

RESULTS

RC-3095 decreased tumor volume by approximately 50% (P < 0.05) and RC-3940-II by 70-60% (P < 0.01). Tumor burden also was significantly decreased in the groups treated with RC-3095 and RC-3940-II. Receptor analyses demonstrated high affinity binding sites for BN/GRP and EGF on the untreated H-69 SCLC tumors. After treatment with RC-3095 and RC-3940-II, the concentration of receptors for BN/GRP was decreased by 29.0% and 36.5%, respectively (both, P < 0.01) compared with controls, and EGF-R levels were reduced by 62.3% and 63.0%, respectively (both, P < 0.01). Reverse transcriptase-polymerase chain reaction and Southern blot analyses revealed that the levels of mRNA for EGF-R in tumors were lowered by 31% (P < 0.05) and 43% (P < 0.01), respectively, after treatment with RC-3095 and RC-3940-II.

CONCLUSIONS

This study indicates that the inhibition of growth of H-69 SCLC by BN/GRP antagonists RC-3095 and RC-3940-II is accompanied by a marked decrease in the levels and mRNA expression of EGF-R.

Growth effects of alpha-interferon but not of bombesin or angiotensin II are mediated by activation of STAT proteins

BACKGROUND

The recently discovered Jak/STAT signal transduction pathway is associated with cytokine or growth factor receptors; whether members of the G protein-coupled receptor superfamily also activate this pathway is not yet clear. As a first member, the angiotensin (AT)1A receptor has been demonstrated to phosphorylate Jak and STAT proteins. Bombesin, a neurotransmitter and growth factor in many cells and tissues, activates its G protein-coupled receptor and in addition phosphorylates proteins that might be members of the Jak/STAT family. This study investigated whether bombesin- or angiotensin-mediated growth effects are associated with STAT protein activation.

METHODS

Functional receptors were characterized using ligand-binding studies, second-messenger activation and determination of ligand-mediated growth effects. STAT protein activation was analysed by electrophoretic mobility shift assay (EMSA) using labelled DNA response elements recognizing all known STAT proteins.

RESULTS

Functional bombesin receptors mediating mitogenic effects were demonstrated on Swiss 3T3 fibroblasts, human melanoma cells (A375-6) and primary human lung fibroblasts; however, bombesin-related STAT protein activation was not observed by EMSA. Interferon-alpha typically activated a STAT1-STAT2-p48 heterotrimer, as well as STAT1-3 hetero- and homodimers in human melanoma cells and significantly inhibited growth of this cell line in vitro. Functional AT1A receptors on primary rat cardiac fibroblasts mediated angiotensin-stimulated growth effects but, in contrast to recently published data, did not activate any known STAT protein.

CONCLUSION

Interferon alpha-stimulated growth inhibition is mediated by activation of the Jak/STAT pathway, whereas bombesin or AT1A receptor-mediated effects on cellular proliferation do not involve phosphorylation of STAT proteins.

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).

Enhanced expression of neuropeptides in human breast cancer cell lines following irradiation

Previously, we have observed that the expression of the neuropeptides bombesin (BN-), the mammalian counterpart being gastrin-releasing peptide (GRP), and substance P (SP) in intact normal tissues, such as salivary and laryngeal glands, increases in response to irradiation. In the present study, the aim was to evaluate whether irradiation can have effects on individual cells that normally synthesize neuropeptides. In addition, since these neuropeptides are potentially mitogenic, we studied tumor cells. Therefore, the estrogen receptor-negative human breast cancer cell line MDA-MB-231 and its subline, with acquired doxorubicin resistance, MDA-MB-231 Dox were examined before irradiation and 4, 10, and 15 days after irradiation with 4 Gy (195 kV, 2 Gy fractions with 4 hours interval). Potential dose related changes were studied by delivering single doses of 2 or 9 Gy with the same technique. Immunohistochemical and radioimmunoassay (RIA) methods were used for detection of the SP and BN/GRP. Before, and at all time points following irradiation, a subpopulation in both cell lines displayed an intense immunostaining of SP and BN/GRP. A partial reorganization of the immunoreactive material was observed 10 days after irradiation. The RIA-analyses displayed signs of a dose-related increase, and a time-dependent transient and significant increase in the content of both peptides. The pattern of changes differed between the two peptides, and was especially pronounced in the doxorubicin resistant cells with regard to SP. Another neuropeptide, calcitonin gene related peptide (CGRP), was not detected in the cells used. The results suggest that irradiation has effects on a population of cultured neuropeptide-synthesizing cells. The occurrence and the specific changes obtained in the levels of neuropeptides, in response to irradiation, might imply an importance in the growth of breast cancer cells and in explaining repair processes following irradiation.

Identification of early growth response gene-1 (Egr-1) as a phorbol myristate acetate-induced gene in lung cancer cells by differential mRNA display

Cellular regulatory genes including transcription factors may play an important role in the induction, maintenance, and progression of lung cancer. These regulatory genes are inducible by various mitogenic stimuli including phorbol myristate acetate (PMA). The differential mRNA display method was used to identify potential early response genes regulated by PMA in non-small cell lung cancer (NSCLC) cell lines. Using this technique, several cDNA fragments were found to be potentially differentially regulated by PMA in the squamous NSCLC cell line NCI-H157. One of these cDNA fragments of approximately 100 bp was determined to be differentially induced by at least 30-fold by PMA by northern blot analysis and to hybridize to a single 3.4 kb mRNA species. This cDNA fragment was cloned, sequenced, and identified to be identical to a portion of the 3'-untranslated region of the human early growth response gene-1 (Egr-1). Using Egr-1 cDNA as a probe, it was demonstrated that PMA induces Egr-1 mRNA expression in at least three other NSCLC cells as well. In addition, PMA caused a transient increase in expression of the Egr-1 transcript reaching a maximum level by 1 h before decreasing in NCI-H157 and three other types of NSCLC cells. Treatment of these NSCLC cells with TGF-beta1 showed a transient increase in Egr-1 mRNA similar to PMA which also reached a maximum level after 1 h. Normal human bronchial epithelial (NHBE) cells also showed a rapid, transient increase in expression of Egr-1 mRNA after treatment with PMA. In contrast, treatment of NHBE cells with TGF-beta1 showed that expression of Egr-1 mRNA increased by 1 h but reached a maximum level only after 6 h. These results indicate that both PMA and TGF-beta1 can induce Egr- mRNA expression in NSCLC cells and NHBE cells; however, while PMA induces Egr-1 mRNA similarly in both cell types, TGF-beta1 induces Egr-1 mRNA expression more rapidly and more transiently in NSCLC cells than in NHBE cells. Our results suggest that Egr-1 may play different roles in response to mitogens in normal and malignant lung cells.

Expression of mRNA for gastrin-releasing peptide receptor by human bronchial epithelial cells. Association with prolonged tobacco exposure and responsiveness to bombesin-like peptides

Bombesin-like peptides (BLPs) are important regulators of lung development and may also act as autocrine growth factors in lung tumors. We have previously demonstrated expression of mRNA for the three BLP receptor subtypes (neuromedin B [NMB]) receptor, gastrin-releasing peptide [GRP] receptor, and bombesin receptor subtype 3 [BRS-3]) in human non-small cell lung carcinoma (NSCLC) cell lines and bronchial biopsies using the reverse transcription-polymerase chain reaction (RT-PCR; DeMichele, et al. Am. J. Respir. Cell Mol. Biol. 1994; 11:66-74). We have also previously found that growth responses to BLPs could be elicited in some, but not all, cultures of human bronchial epithelial (HBE) cells (Siegfried, et al. Anat. Rec. 1993; 236:241-247). In this report, we utilized RT-PCR to demonstrate mRNA expression of BLP receptor subtypes in cultured HBE cells and also assessed the response of these cultures to BLPs in proliferation assays. The pattern of mRNA expression was correlated with proliferative response, and the results were also analyzed in relation to smoking history and pulmonary function of the subjects studied. Our results suggest that expression of mRNA for the GRP receptor is associated with a long smoking history (> 25 pack-years [PY], p = 0.02). This association was related to past tobacco exposure, regardless of whether the subjects were still active smokers at the time of tissue procurement. Responsiveness to GRP and NMB in proliferation assays was also found only in those HBE cultures with expression of mRNA for at least one of the known receptors for BLPs, and there was a significant association between expression of mRNA for the GRP receptor and proliferative response to both GRP and NMB (p = 0.048). HBE cultures from subjects with a greater than 25 PY smoking history were also more likely to respond to BLPs in the proliferation assays than cells from subjects with less than a 25 PY history (10 of 16 versus 1 of 7, p = 0.06). Cultures of HBE cells from four of the five subjects with severe obstructive lung disease gave a positive response to GRP and NMB in proliferation assays, compared to five of fifteen without severe obstructive lung disease, but this difference was not significant (p = 0.13). These results suggest there is an increased likelihood of expression of the GRP receptor mRNA in the respiratory epithelium of some individuals with a history of prolonged tobacco exposure, and that expression of the GRP receptor mRNA is accompanied by responsiveness to the mitogenic effects of BLPs. These effects appear to persist after smoking cessation.

Effects of transforming growth factor-beta 1 and phorbol ester on PAI-1 and PA genes in human lung cells

Transforming growth factor-beta (TGF-beta) mediates the production of extracellular matrix proteins, proteases and protease inhibitors in epithelial cells. Both TGF-beta and phorbol-12-myristate-13-acetate (PMA) exert both positive and negative effects on mitogenesis in these as well as other cell types. Phorbol esters act through stimulation of protein kinase C (PKC) and are among the most potent tumor promoters known. The present study was conducted to determine whether the effect of TGF-beta in human non-small cell lung cancer (NSCLC) and normal human bronchial epithelial (NHBE) cells parallels that of the phorbol esters and whether this effect of TGF-beta involves PKC. TGF-beta 1 and PMA increased expression of TGF-beta 1 mRNA 24 hr after their addition to both NSCLC and NHBE cells. The effects of these agents on expression of the mRNAs for TGF-beta 2 and TGF-beta 3 were more complex; while TGF-beta 2 and TGF-beta 3 mRNAs increased transiently in response to TGF-beta 1 in NHBE cells and TGF-beta 3 mRNA increased transiently in some NSCLC cells, expression of these mRNAs decreased in most of these cells in response to PMA with the exception of the carcinoid NCI-H727 where TGF-beta 2 mRNA increased dramatically, TGF-beta 1 and PMA both caused a persistent increase in expression of the mRNAs for both plasminogen activator inhibitor-1 (PAI-1) and plasminogen activator (PA) up to 24 hr in most NSCLC cells, with the increase in PAI-1 mRNA beginning several hours before that of PA mRNA. In contrast, while TGF-beta 1 also increased expression of PAI-1 mRNA in NHBE cells, the expression of PA mRNA decreased simultaneously. The effect of PMA on PAI-1 and PA mRNAs was opposite of TGF-beta 1 in these cells, with expression of PAI-1 mRNA decreasing and PA mRNA increasing after addition of PMA. These data show that there is parallel regulation of the genes for TGF-beta 1, PAI-1 and PA by TGF-beta 1 and PMA in NSCLC, but differential regulation of the genes for PAI-1 and PA by these agents in NHBE cells. The responses of the mRNAs and proteins of TGF-beta 1, PAI-1 and PA to TGF-beta 1 and PMA were inhibited by the serine/ threonine kinase inhibitor H7 in NSCLC cells. Treatment of NSCLC cells with TGF-beta 1 and PMA resulted in a persistent increase in the expression of fibronectin mRNA and protein. This response was blocked by the addition of H7. Inhibition of these effects by H7 in NSCLC cells suggests that H7 blocks TGF-beta responses by inhibiting a protein serine/threonine kinase(s). Because the effects of TGF-beta and PMA on the different TGF-beta isoforms, PA, PAI and fibronectin in NHBE and NSCLC cells are complex, our data suggest that there are distinct mechanisms for controlling the different TGF-beta isoforms, PA, PAI and extracellular matrix proteins in normal lung and lung cancer cells.

Identification and mapping of a putative bombesin receptor gene on human chromosome 17q21.3+

A mouse bombesin receptor cDNA was used as a probe to screen a human P1 genomic library. Clone HBR1 was isolated and used to localize a putative human bombesin receptor gene (HBRKS) on human chromosome 17q21.3 by fluorescent in situ hybridization (FISH). HBRKS was identified and mapped by polymerase chain reaction (PCR) amplification from a Yeast artificial chromosome (YAC) contig spanning 17q21-q23. In addition, a few candidate genes were found by exon-trapping from HBR1.

Differences in c-fos gene product expression in cancers of the gall-bladder and biliary tract

The c-fos gene encodes a 55 kDa nuclear protein product that complexes to a cellular protein, p39. The pattern of expression of c-fos is particularly complex with increased expression of the protein observed in undifferentiated cultured cells while reduced expression is found during terminal differentiation. The expression of c-fos gene was studied by immunohistochemistry in carcinoma of the gall-bladder (n = 13), biliary tract (n = 5) and ampulla of Vater (n = 9). Non-malignant conditions investigated include chronic cholecystitis (n = 11), gall-bladder dysplasia (n = 3) and adenoma (n = 1), and ampullary carcinoma in situ (n = 3). Strong positive granular cytoplasmic immunostaining for c-fos oncoprotein was present in most gall-bladder adenocarcinomas (n = 11; 85%). The single gall-bladder adenoma and only one of the dysplasia cases were positive. Most of the cases of chronic cholecystitis showed either absent or only focal to patchy and weak to moderate c-fos immunoreactivity in the deeper glands and Rokitansky-Aschoff sinuses but not in the superficial epithelium. None of the biliary tract and ampullary tumors showed immunostaining for c-fos. The difference in c-fos immunoreactivity between gall-bladder carcinoma and chronic cholecystitis was statistically significant (P = 0.0002; chi 2 test with continuity correction). In conclusion, c-fos protein may be important in the development of gall-bladder neoplasia with increased c-fos immunoreactivity in gall-bladder carcinoma but not in chronic cholecystitis, biliary tract and ampullary neoplasms. These findings suggest that gall-bladder carcinoma may arise from a different genetic basis compared to biliary tract and ampullary cancers.

Bombesin-mediated AP-1 activation in a human gastric cancer (SIIA)

BACKGROUND

Bombesin, a gut tetradecapeptide homologous to the mammalian gastrin-releasing peptide (GRP), stimulates the growth of the human gastric cancer line SIIA through specific GRP receptors (GRP-Rs); the cellular mechanisms are not known. The purpose of our study was to (1) confirm functional GRP-R in SIIA and (2) determine whether bombesin alters the expression and binding activity of the AP-1 transcription factors, c-jun and jun-B.

METHODS

SIIA cells were treated with bombesin, and intracellular calcium mobilization was measured by means of fura-2 spectrofluorometry. To assess changes in c-jun and jun-B, RNA and protein were extracted for Northern and Western blots, respectively; nuclear protein was extracted for gel mobility shifts to determine AP-1 binding activity.

RESULTS

SIIA cells mobilized intracellular calcium in response to bombesin, exhibiting a functional cell-surface GRP-R. Bombesin treatment increased expression of both c-jun and jun-B mRNA by 0.5 hours, with maximal expression at 1 hour; concomitant increases in steady-state levels of c-Jun and JunB protein were identified. Moreover, bombesin increased binding of the AP-1 proteins as shown by gel shifts.

CONCLUSIONS

The SIIA human gastric cancer possesses functional GRP-R coupled to the calcium second messenger pathway. Further, bombesin stimulates expression of c-jun and jun-B mRNA and protein and increases binding activity of AP-1 proteins. Delineating the cellular pathways involved in bombesin-mediated gene activation will provide important insights into the mechanisms responsible for normal and neoplastic gut growth.

PACAP stimulates c-fos mRNAs in small cell lung cancer cells

The effects of PACAP on c-fos mRNA using small cell lung cancer (SCLC) cell was investigated. PACAP-27 (100 nM) increased c-fos mRNA 5-fold using NCI-N417 cells. The increase was concentration dependent with 0.1 nM PACAP-27 half maximally increasing c-fos mRNA. Also the increase in c-fos mRNA caused by PACAP was time dependent; being maximal after 1 hour and returning to basal values after 4 hours. PACAP-38 but not PACAP(28-38) increased c-fos mRNA. One uM PACAP(6-38), a PACAP receptor antagonist, inhibited the increase in c-fos mRNA caused by 1 nM PACAP. These data indicate that PACAP stimulates nuclear oncogene expression in SCLC cells.

Regulation of nuclear oncogenes expressed in lung cancer cell lines

Lung cancer is a major cause of mortality in the United States and accounts for the majority of all cancer deaths in both men and women. It is hoped that through broadening our understanding of the mechanisms involved in transformation of bronchial epithelial cells we will be able to improve methods of diagnosis and treatment of this disease, with the ultimate goal of reducing on lung cancer mortality. A knowledge of the molecular mechanisms involved in processes such as cell division and differentiation is paramount to this task, because it is known that aberrant responses to growth factors or cytokines found in the normal cellular milieu can lead to abnormal cell growth and/or transformation. Signals initiated at the cell membrane by tumor promoters, growth factors, or cytokines are transduced from the cell membrane to the nucleus and are, in part, mediated centrally by transcription factors encoded by nuclear protooncogenes. The transcription factors myc, jun, and fos have been characterized in both normal and transformed lung epithelial cells through detailed studies using cell lines. In this manuscript, we review what is known about the expression and regulation of these nuclear protooncogenes in normal and malignant epithelial cells of the lung, and their role in the development of lung cancer.

BW 1023U90: a new GRP receptor antagonist for small-cell lung cancer cells

Gastrin-releasing peptide (GRP) receptor antagonists were synthesized and their ability to interact with small-cell lung cancer (SCLC) cells determined. [125I] BW1023U90, bound with high affinity (Kd = 2 nM) to a single class of sites (Bmax = 55 fmol/mg protein) using SCLC cell line NCI-H345. [125I] BW1023U90 binding was time dependent and reversible even at 37 degrees C as the ligand was minimally internalized. Specific [125I] BW1023U90 binding was inhibited with high affinity by GRP as well as bombesin (BB) but not neuromedin B (NMB). BW1023U90 inhibited the ability of BB to elevate cytosolic Ca2+ and increase the growth of SCLC cells. A BW1023U90 analogue, BW2258U89 (10 micrograms/day, SC) slowed SCLC xenograft format on in nude mice and [125I] BW 1023U90 localized to SCLC tumors 1 h after injection into nude mice. BW2258U89 (4% by weight) was placed in microspheres and slowly released over a 3-week period in nude mice bearing SCLC xenografts. The microspheres containing BW2258U89 strongly inhibited SCLC growth in vivo. A radioimmunoassay was developed for the GRP receptor antagonists and the rabbit antiserum cross-reacted totally with BW2258U89 or BW1023U90. BW2258U89 immunoreactivity (5 nM) was detected in the plasma of nude mice containing the microspheres after 1 week. These data suggest that GRP receptor antagonists bind to receptors on SCLC tumors.

Peptides and growth factors in non-small cell lung cancer

Numerous growth factors and receptors that alter proliferation have been identified in lung cancer. In non-small cell lung cancer (NSCLC) cell lines, high levels of vasoactive intestinal peptide (VIP) mRNA have been detected by Northern analysis, and immunoreactive VIP is present. VIP elevates intracellular cAMP and stimulates the clonal growth of NSCLC cells. Also, transforming growth factor alpha (TGF-alpha) mRNA is present in NSCLC cells and TGF-alpha is present in conditioned media exposed to NSCLC cells. TGF-alpha binds with high affinity to epidermal growth factor (EGF) receptors present on NSCLC cells. EGF stimulates tyrosine kinase activity and growth in NSCLC cells. Synthetic peptide antagonists and monoclonal antibodies have been identified that disrupt autocrine growth pathways and inhibit NSCLC growth. These data suggest that VIP and TGF-alpha are important autocrine growth factors for NSCLC.

GRP receptors are present in non small cell lung cancer cells

Previously, GRP receptors were characterized in small cell lung cancer cells and here non-small cell lung cancer (NSCLC) cells were investigated: (125I-Tyr4) bombesin (BN) or 125I-GRP bound with high affinity to NCI-H720 (lung carcinoid) and NCI-H1299 (large cell carcinoma) cells. Binding was specific, time dependent, and saturable. Specific (125I-Tyr4)BN binding to NCI-H1299 cells was inhibited with high affinity by GRP, BN, GRP14-27, (D-Phe6)BN6-13methyl ester, moderate affinity by NMB, and low affinity by GRP1-16. BN (10 nM) transiently elevated cytosolic calcium in a dose dependent manner. BN caused translocation of protein kinase C from the cytosol to the membrane and the translocation caused by BN was reversed by (D-Phe6)BN6-13methylester. BN stimulated arachidonic acid release and the increase caused by BN was reversed by (D-Phe6)BN6-13methylester. Using a clonogenic assay, BN stimulated the growth of NCI-H720 cells, and the number of colonies was reduced using (D-Phe6)BN6-13methylester. These data suggest that GRP receptors that are present in lung carcinoid and NSCLC cells may regulate proliferation.

Neuromedin B stimulates arachidonic acid release, c-fos gene expression, and the growth of C6 glioma cells

The effects of neuromedin B (NMB) on C6 glioma cells were investigated. NMB bound with high affinity (IC50 = 1 nM) to C6 cells whereas BN and GRP were less potent (IC50 = 40 and 100 nM). NMB (1 nM) elevated cytosolic Ca2+ in individual C6 cells and the increase in cytosolic Ca2+ was reversed by 1 microM [D-Arg1, D-Pro2,D-Trp7.9,Leu11]substance P [APTTL]SP, a broad spectrum antagonist. NMB stimulated [3H]arachidonic acid release from C6 cells and the increase in [3H]arachidonic acid release was reversed [APTTL]SP. NMB increased transiently c-fos gene expression in C6 cells. NMB increased the number of C6 colonies in soft agar and the increase in growth caused by NMB was reversed by [APTTL]SP. These data suggest that NMB receptors may regulate the proliferation of C6 cells.