Reduction in receptors for bombesin and epidermal growth factor in xenografts of human small-cell lung cancer after treatment with bombesin antagonist RC-3095

Dual Anti-cancer and Anti-Itch Activity of PD176252 Analogues: Design, Synthesis and Biological Evaluation

Background:

Cancer patients treated with targeted anti-cancer drug suffer from itch or pruritus. Itch or pruritus is an unpleasant sensation that brings about a negative impact on quality of life, and serious itch may lead to dose reduction and even discontinuation. Gastrin releasing peptide receptor (GRPR) plays a critical role in itch, inflammation and cancer, and GRPR antagonist has obvious effect on cancer, inflammation and itch. The aim of this paper is to develop a new agent with anti-cancer and anti-itch activity.

Methods:

A series of GRPR antagonist PD176252 analogues (3a-3l) were designed and synthesized. Both anticancer and anti-itch activities were evaluated. Anti-cancer activity was evaluated in three human cancer cell lines in vitro, the anti-itch activity in evaluated with Kunming mice by intrathecal injection of chloroquine phosphate as a modeling medium. And the cytotoxicity on normal cells was evaluated.

Results:

Of the tested compounds, compound 3i showed potently anti-cancer activity to all cancer cell lines tested with IC50 values of 10.5µM (lung), 11.6µM (breast) and 12.8µM (liver) respectively and it also showed significant inhibition of the scratching behavior. Comparing with PD17625, compound 3i and 3g gave better inhibition activities against all cancer cell lines, compound 3b, 3c and 3i showed better anti-itch activity. The compound 3i is safe for normal breast and liver normal cells, but it has high cytotoxicity on normal lung cell.

Conclusion:

The synthesized compounds have dual anti-cancer and anti-itch activity, so the development of drug with dual anti-tumor and anti-itch property is possible.

Illuminating the Onco-GPCRome: Novel G protein-coupled receptor-driven oncocrine networks and targets for cancer immunotherapy

G protein-coupled receptors (GPCRs) are the largest gene family of cell membrane-associated molecules mediating signal transmission, and their involvement in key physiological functions is well-established. The ability of GPCRs to regulate a vast array of fundamental biological processes, such as cardiovascular functions, immune responses, hormone and enzyme release from endocrine and exocrine glands, neurotransmission, and sensory perception (e.g. vision, odor, and taste), is largely due to the diversity of these receptors and the layers of their downstream signaling circuits. Dysregulated expression and aberrant functions of GPCRs have been linked to some of the most prevalent human diseases, which renders GPCRs one of the top targets for pharmaceutical drug development. However, the study of the role of GPCRs in tumor biology has only just begun to make headway. Recent studies have shown that GPCRs can contribute to the many facets of tumorigenesis, including proliferation, survival, angiogenesis, invasion, metastasis, therapy resistance, and immune evasion. Indeed, GPCRs are widely dysregulated in cancer and yet are underexploited in oncology. We present here a comprehensive analysis of GPCR gene expression, copy number variation, and mutational signatures in 33 cancer types. We also highlight the emerging role of GPCRs as part of oncocrine networks promoting tumor growth, dissemination, and immune evasion, and we stress the potential benefits of targeting GPCRs and their signaling circuits in the new era of precision medicine and cancer immunotherapies.

Monomeric and Dimeric 68Ga-Labeled Bombesin Analogues for Positron Emission Tomography (PET) Imaging of Tumors Expressing Gastrin-Releasing Peptide Receptors (GRPrs)

The GRPr, highly expressed in prostate PCa and breast cancer BCa, is a promising target for the development of new PET radiotracers. The chelator HBED-CC ( N, N'-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine- N, N'-diacetic acid) was coupled to the bombesin peptides: HBED-C-BN(2-14) 1, HBED-CC-PEG₂-[d-Tyr⁶,β-Ala¹¹,Thi¹³,Nle¹⁴]-BN(6-14) 2, HBED-CC-Y-[d-Phe⁶,Sta¹³,Leu¹⁴]-BN(6-14) (Y = 4-amino-1-carboxymethylpiperidine) 3, and HBED-CC-{PEG₂-Y-[d-Phe⁶,Sta¹³,Leu¹⁴]-BN(6-14)}₂ 4 (homodimer). Compounds 1-4 presented high binding affinities for GRPr (T47D, 0.56-3.51 nM; PC-3, 2.12-4.68 nM). In PC-3 and T47D cells, agonists [⁶⁸Ga]1 and [⁶⁸Ga]2 were mainly internalized while antagonists [⁶⁸Ga]3 and [⁶⁸Ga]4 were surface bound. Cell-related radioactivity reached a maximum after 45 min, while tracer levels followed GRPr expression (PC-3 > T47D > LNCaP > MDA-MB-231). [⁶⁸Ga]4 showed the highest cell-bound radioactivity (PC-3 and T47D). In vivo, tumor (PC-3) targeting for [⁶⁸Ga]3 and [⁶⁸Ga]4 increased over time, with dynamic μPET showing clearer tumors images at later time points. [⁶⁸Ga]3 and [⁶⁸Ga]4 can be considered suitable PET tracers for imaging PCa and BCa expressing GRPr.

How gastrin-releasing peptide receptor (GRPR) and αvβ3 integrin expression reflect reorganization features of tumors after hyperthermia treatments

The outcome of tumor treatment via hyperthermia in the clinic has been reported to be heterogeneous. Here, we assessed how the presence of gastrin-releasing peptide receptor (GRPR) and αvβ3 integrin together with the morphology of the vascularization reflects the growth behavior of tumors after hyperthermia treatment. MDA-MB-231 tumor bearing mice were treated either with high (46 °C) or low dose (42 °C) water hyperthermia for 60 min. Changes of GRPR and αvβ3 integrin expression were assessed via multiplexed optical imaging. Vascularization was reconstructed and quantified by µCT imaging after contrast agent injection. We found that high dose hyperthermia is capable of increasing the expression of GRPR, αvβ3 integrin, CD31, and Ki67 in tumors. Also the morphology of tumor vasculature changed (increased relative blood volume and small-diameter vessel density, decreased expression of α-SMA). Low dose hyperthermia induced comparatively moderate effects on the investigated protein expression pattern and vascular remodeling. We conclude that under defined circumstances, specific temperature doses affect the reorganization of tumor regrowth, which is triggered by residual "dormant" cells even though tumor volumes are transiently decreasing. Further on, GRPR, αvβ3 integrin expression are versatile tools to surveil potential tumor regrow during therapy, beyond the conventional determination of tumor volumes.

(68)Ga-labeled bombesin analogs for receptor-mediated imaging

Targeted receptor-mediated imaging techniques have become crucial tools in present targeted diagnosis and radiotherapy as they provide accurate and specific diagnosis of disease information. Peptide-based pharmaceuticals are gaining popularity, and there has been vast interest in developing (68)Ga-labeled bombesin (Bn) analogs. The gastrin-releasing peptide (GRP) family and its Bn analog have been implicated in the biology of several human cancers. The three bombesin receptors GRP, NMB, and BRS-3 receptor are most frequently ectopically expressed by common, important malignancies. The low expression of Bn/GRP receptors in normal tissue and relatively high expression in a variety of human tumors can be of biological importance and form a molecular basis for Bn/GRP receptor-mediated imaging. To develop a Bn-like peptide with favorable tumor targeting and pharmacokinetic characteristics for possible clinical use, several modifications in the Bn-like peptides, such as the use of a variety of chelating agents, i.e., acyclic and macrocyclic agents with different spacer groups and with different metal ions (gallium), have been performed in recent years without significant disturbance of the vital binding scaffold. The favorable physical properties of (68)Ga, i.e., short half-life, and the fast localization of small peptides make this an ideal combination to study receptor-mediated imaging in patients.

Bombesin-modified 6-14 C-terminal fragments adsorption on silver surfaces: influence of a surface substrate

Surface-enhanced Raman scattering (SERS) spectroscopy has been applied to investigate the interaction with a silver colloidal surface of following seven 6-14 fragments of bombesin (BN) C-terminus: cyclo[D-Phe(6),His(7),Leu(14)]BN(6-14), [D-Phe(6),Leu-NHEt(13),des-Met(14)]BN(6-14), [D-Phe(6),Leu(13)-(R)-p-chloro-Phe(14)]BN(6-14), [D-Phe(6),beta-Ala(11),Phe(13),Nle(14)]BN(6-14), [D-Tyr(6),beta-Ala(11),Phe(13),Nle(14)]BN(6-14), [D-Tyr(6),beta-Phe(11),Phe(13),Nle(14)OH]BN(6-14), and [D-Cys(6),Asn(7),D-Ala(11),Cys(14)]BN(6-14), potent r-GRP-R receptor antagonists used in chemotherapy and potential effective drugs in cancer treatment. The adsorption active sites and molecular orientations on the colloidal silver surface have been determined on the basis of SERS "surface selection rules" subsequent to a detailed SERS analysis. In addition, the similarities and differences of these spectra with the SERS spectra of the peptides immobilized on a roughened silver electrode surface have been examined. From the data, suggestion has been made about structural properties of these peptides on the colloidal surface.

Growth inhibition of non-small-cell lung carcinoma by BN/GRP antagonist is linked with suppression of K-Ras, COX-2, and pAkt

Bombesin (BN) or gastrin-releasing peptide (GRP) can stimulate the growth of neoplasms such as breast cancer and small-cell lung carcinoma (SCLC). Antagonists of BN/GRP have been shown to inhibit these cancers. We evaluated whether antagonists of BN/GRP can suppress the growth of human non-SCLC (NSCLC) xenografted into nude mice. The effect of the administration of BN/GRP antagonist RC-3940-II on the growth of H460 and A549 NSCLC cell lines orthotopically xenografted into the intrapulmonary interstitium was examined. Protein levels of K-Ras, COX-2, Akt/pAkt, WT p53, Erk1/2, and lung resistance-related protein (LRP) in tumors were analyzed by Western blot analaysis, and receptors for BN/GRP were investigated by radioligand-binding studies. The effect of RC-3940-II on the proliferation of H460 and A549 cells in vitro was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays. High-affinity receptors for BN/GRP were found on tumors. Treatment with RC-3940-II significantly (P < 0.001) inhibited growth of H460 and A549 NSCLC xenografts by 30-50% and led to an improved performance status, compared with controls. In H460 NSCLC, the antitumor effect was associated with a significant (P < 0.001) reduction in protein levels of K-Ras, COX-2, pAkt, and pERK1/2 and with a major augmentation in the expression of WT p53, compared with controls. In A549 NSCLC, pAkt and LRP were significantly down-regulated. Our findings demonstrate the efficacy of BN/GRP antagonist RC-3940-II for the treatment of NSCLC. The suppression of K-Ras, COX-2, pAkt, and LRP, as well as the up-regulation of WT p53 might contribute to the antitumor action of BN/GRP antagonists.

The combination of antagonists of LHRH with antagonists of GHRH improves inhibition of androgen sensitive MDA-PCa-2b and LuCaP-35 prostate cancers

BACKGROUND

Antagonists of growth hormone-releasing hormone (GHRH) could extend the duration of response of androgen sensitive prostate cancers to androgen deprivation.

METHODS

We investigated the effect of new GHRH antagonists MZ-J-7-118 and MZ-J-7-138 and luteinizing hormone-releasing hormone (LHRH) antagonist Cetrorelix or castration on androgen sensitive MDA-PCa-2b and LuCaP-35 prostate cancer models xenografted into nude mice. Animals bearing androgen-independent LuCaP-35V prostatic cancer model were also treated with MZ-J-7-118.

RESULTS

Receptors for LHRH and GHRH were present in MDA-PCA-2b, LuCaP-35, and LuCaP-35V tumors. GHRH antagonists increased the inhibitory effect of surgical castration and LHRH antagonists on androgen sensitive MDA-PCa-2b and LuCaP-35 tumors. The time to relapse of androgen-dependent LuCaP-35 tumors was extended by GHRH antagonists. Growth of androgen-independent LuCaP-35V xenografts was also significantly inhibited by MZ-J-7-118. In MDA-PCa-2b tumors treatment with MZ-J-7-118 caused a significant decrease of VEGF and Cetrorelix or its combination with MZ-J-7-118 reduced EGF. The B(max) of EGF receptors was significantly reduced by Cetrorelix, MZ-J-7-118 and their combination.

CONCLUSIONS

Our findings suggest that the use of a combination of antagonists of GHRH and LHRH could improve the therapy for androgen sensitive prostate cancer. Antagonists of GHRH could be also considered for treatment of androgen-independent prostate cancers.

Fast, hungry and unstable: finding the Achilles' heel of small-cell lung cancer

Over 95% of patients with small-cell lung cancer (SCLC) die within five years of diagnosis. The standard of care and the dismal prognosis for this disease have not changed significantly over the past 25 years. Some of the characteristics of SCLC that have defined it as a particularly virulent form of cancer -- rapid proliferation, excessive metabolic and angiogenic dependence, apoptotic imbalance and genetic instability -- are now being pursued as tumor-specific targets for intervention both in preclinical and early phase clinical studies. Here, we summarize areas of ongoing anti-cancer drug development, including classes of agents that target essential pathways regulating proliferation, angiogenesis, apoptotic resistance, chromosomal and protein stability, and cell-cell and cell-matrix interaction.

Impairments of social behavior and memory after neonatal gastrin-releasing peptide receptor blockade in rats: Implications for an animal model of neurodevelopmental disorders

The gastrin-releasing peptide receptor (GRPR) has been implicated in central nervous system (CNS) diseases, including neurodevelopmental disorders associated with autism. In the present study we examined the effects of GRPR blockade during the neonatal period on behavioral measures relevant to animal models of neurodevelopmental disorders. Male Wistar rats were given an intraperitoneal (i.p.) injection of either saline (SAL) or the GRPR antagonist [D-Tpi(6), Leu(13) psi(CH(2)NH)-Leu(14)] bombesin (6-14) (RC-3095; 1 or 10mg/kg) twice daily for 10days from postnatal days (PN) 1 to 10. Animals treated with RC-3095 showed pronounced deficits in social interaction when tested at PN 30-35 and impaired 24-h retention of memory for both novel object recognition (NOR) and inhibitory avoidance (IA) tasks tested at PN 60-71. Neither short-term memory tested 1.5h posttraining nor open field behavior were affected by neonatal GRPR blockade. The implications of the findings for animal models of neurodevelopmental disorders are discussed.

Targeted chemotherapy with cytotoxic bombesin analogue AN-215 inhibits growth of experimental human prostate cancers

We developed a powerful cytotoxic analogue of bombesin AN-215, in which the bombesin (BN)-like carrier peptide is conjugated to 2-pyrrolino doxorubicin (AN-201). Human prostate cancers express high levels of receptors for BN/gastrin releasing peptide (GRP) that can be used for targeted chemotherapy. The effects of targeted chemotherapy with cytotoxic BN analogue AN-215 were evaluated in nude mice bearing subcutaneous xenografts of DU-145, LuCaP-35, MDA-PCa-2b and intraosseous implants of C4-2 human prostate cancers. Intraosseous growth of C4-2 tumors was monitored by serum PSA. BN/GRP receptors were evaluated by 125I-[Tyr4]BN binding assays and RT-PCR. The effects of AN-215 on apoptosis and cell proliferation were followed by histology, and the expression of Bcl-2 and Bax protein was determined by Western blot analysis. Targeted analog AN-215 significantly inhibited growth of subcutaneously implanted DU-145, LuCaP-35 and MDA-PCa-2b prostate cancers by 81% to 91% compared to controls, while cytotoxic radical AN-201 was less effective and more toxic. Serum PSA levels of mice bearing intraosseous C4-2 prostate tumors were significantly reduced. In LuCaP-35 tumors administration of BN antagonist RC-3095 prior to AN-215 blocked the receptors for BN/GRP and inhibited the effects of AN-215. High affinity receptors for BN/GRP and their m-RNA were detected on membranes of all 4 tumor models. Therapy with AN-215, but not with AN-201, decreased the ratio of Bcl-2/Bax in DU-145 and the expression of antiapoptotic Bcl-2 in LuCaP-35 tumors. The presence of BN/GRP receptors on primary and metastatic prostate cancers makes possible targeted chemotherapy with AN-215 for the treatment of this malignancy.

Targeted chemotherapy with cytotoxic bombesin analogue AN-215 can overcome chemoresistance in experimental renal cell carcinomas

BACKGROUND

Multidrug resistance (MDR) mediated by membrane transporters, such as P-glycoprotein (MDR-1) and MDR-associated protein (MRP), remains a challenge in the therapy of renal cell carcinoma (RCC). Chemotherapy targeted to hormone receptors may provide a new approach to overcome chemoresistance. The cytotoxic analogue of bombesin/gastrin-releasing peptide (GRP), AN-215, consists of a superactive derivative of doxorubicin, AN-201, which is linked to a bombesin analogue carrier: RC-3094.

METHODS

The authors examined the expression of bombesin/GRP receptors in 3 human RCC cell lines (A-498, ACHN. and 786-0) by using reverse-transcriptase-polymerase chain reaction (RT-PCR) analysis and radioligand-binding assays. They also evaluated the effects of AN-215 and its cytotoxic radical AN-201 in the same RCC models in vivo, and they studied the effects of AN-215 and AN-201 on the expression levels of MDR-1 and subtype 1 of MRP (MRP-1) by using real-time PCR.

RESULTS

A N-215 significantly (P < 0.05) inhibited the growth of A-498, ACHN, and 786-0 RCC xenografted into nude mice by 59.2-67.6%, whereas the cytotoxic radical AN-201 alone had no significant antitumor effects. The efficacy of AN-215 was independent of the expression patterns of MDR-1 and MRP-1 in these RCC cell lines. The induction of MDR-1 by AN-215 was similar (Experiment 2) or weaker (Experiment 1) compared with AN-201. Both AN-215 and AN-201 caused only a minor induction of MRP-1.

CONCLUSIONS

The current findings indicated that targeted chemotherapy with cytotoxic bombesin/GRP analogue AN-215 can inhibit the growth of RCC, providing a new treatment modality for patients with advanced RCC.

Antagonists of growth hormone releasing hormone (GHRH) and of bombesin/gastrin releasing peptide (BN/GRP) suppress the expression of VEGF, bFGF, and receptors of the EGF/HER family in PC-3 and DU-145 human androgen-independent prostate cancers

BACKGROUND

Antagonists of growth hormone releasing hormone (GHRH) as well as antagonists of bombesin/gastrin releasing peptide (BN/GRP) inhibit the growth of various malignancies (cancers) including prostate cancer.

METHODS

We investigated the effects of GHRH antagonists MZ-J-7-118 and RC-J-29-18, BN/GRP antagonists RC-3940-II and RC-3940-Et and the combination of MZ-J-7-118 and RC-3940-II on the growth of PC-3 and DU-145 human androgen independent prostate cancers xenografted s.c. into nude mice. To elucidate the mechanisms of action of these analogs, growth factors like IGF-II (insulin-like growth factor-II), vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and epidermal growth factor receptor/human epidermal growth factor receptor (EGF-R/HER) family were measured in tumors as well as IGF-I in serum.

RESULTS

Antagonists of GHRH and BN/GRP alone or in combination significantly inhibited growth of PC-3 and DU-145 tumors, the greatest inhibition of tumor volume being achieved by combination of MZ-J-7-118 (5 microg/day) and RC-3940-II (10 microg/day). BN/GRP and GHRH antagonists and their combination also decreased the expression of VEGF significantly in PC-3 and non-significantly in DU-145, as measured by radioimmunoassay for VEGF protein and RT-PCR for mRNA levels of VEGF. GHRH and BN/GRP antagonists reduced bFGF concentrations and the maximal binding capacity of EGF receptors, and their mRNA levels in PC-3 and DU-145 tumors. mRNA levels for HER-2 and -3 were also diminished in PC-3 tumors by GHRH and BN/GRP antagonists. No changes in HER-4 were found after treatment. Serum IGF-I and tumoral IGF-II levels were not affected by the analogs.

CONCLUSIONS

BN/GRP and GHRH antagonists inhibit growth of PC-3 and DU-145 prostate cancers by suppressing the expression of tumoral growth factors such as VEGF and bFGF as well as the receptors for EGF and related HER-2 and -3. Additive effects on tumor inhibition (TI) in vivo, but not on VEGF, bFGF, or members of the EGF/HER receptor family, can be achieved by the joint administration of both classes of analogs.

Targeting gastrin-releasing peptide receptors for cancer treatment

Growth factor receptors play critical roles in cancer cell proliferation and progression. A number of such receptors have been targeted for cancer treatment by either a monoclonal antibody or a specifically designed small molecule to inhibit the receptor function. Bombesin/gastrin-releasing peptide receptors (BN/GRP-Rs) are expressed in a variety of cancer cells and have limited distribution in normal human tissue. Inhibition of BN/GRP-Rs has been shown to block small cell lung cancer growth in vitro. Early phase clinical trials targeting human GRP-R showed anti-cancer activity. This review will focus on the study of the distribution of BN/GRP-Rs in normal and malignant tissues, and various approaches to targeting BN-GRP-Rs for cancer diagnosis and treatment.

Mouse models for human lung cancer

In recent years several new mouse models for lung cancer have been described. These include models for both non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC). Tumorigenesis in these conditional mouse tumor models can be initiated in adult mice through Cre-recombinase-induced activation of oncogenic mutations in a subset of the cells. They present a marked improvement over mouse models that depend on carcinogen induction of tumors. These models permit us to study the consecutive steps involved in initiation and progression and allow us to address questions like the cell of origin, and the role of cancer stem cells in the maintenance of these tumors. They now need to be validated as suitable preclinical models for intervention studies in which questions with respect to therapy response and resistance can be addressed.

Effective Inhibition of Experimental Human Ovarian Cancers with a Targeted Cytotoxic Bombesin Analogue AN-215

PURPOSE

To determine whether the cytotoxic analogue of bombesin/gastrin-releasing peptide (GRP) AN-215 can inhibit the in vivo growth of four human ovarian cancer cell lines. AN-215 consists of 2-pyrrolinodoxorubicin (AN-201), a superactive derivative of doxorubicin linked to a bombesin antagonist carrier des-D-Tpi-RC-3095. This conjugate binds strongly to receptors for bombesin/GRP and can be targeted to tumors that express these receptors. Bombesin/GRP receptors are found in 77% of human ovarian cancer specimens.

EXPERIMENTAL DESIGN

Nude mice bearing xenografts of ES-2, SKOV-3, OV-1063, and UCI-107 human ovarian carcinomas were treated with AN-215. The antitumor effects and the toxicity were determined. The expression of bombesin receptor subtypes was measured by reverse-transcriptase PCR analysis, and the presence of bombesin/GRP receptors was determined by radioligand binding assays.

RESULTS

AN-215 significantly (P < 0.05) inhibited growth of ES-2, OV-1063, and UCI-107 tumors, prevented the metastatic spread of ES-2 cancers, and prolonged the survival of nude mice bearing i.p. ES-2 xenografts. Cytotoxic radical AN-201, the unconjugated mixture of bombesin antagonist RC-3095 and AN-201 or RC-3095 alone had no significant effects. Blockade of bombesin/GRP receptors abolished the effect of AN-215. The expression of bombesin/GRP receptors was not changed after repeated treatment with AN-215.

CONCLUSIONS

Our findings indicate that targeted chemotherapy with cytotoxic bombesin/GRP analogue AN-215 can inhibit ovarian tumors, which express bombesin/GRP receptors. AN-215 might provide a new treatment modality for women with advanced ovarian carcinoma.

Mitogenic effects of gastrin-releasing peptide in head and neck squamous cancer cells are mediated by activation of the epidermal growth factor receptor

Head and neck squamous cell carcinomas (HNSCC) are characterized by upregulation of the epidermal growth factor receptor (EGFR), where EGFR serves as a potential therapeutic target. We previously reported that a gastrin-releasing peptide/gastrin-releasing peptide receptor (GRP/GRPR) autocrine growth pathway is activated early in HNSCC carcinogenesis. In the present study, we examined the mechanism of EGFR activation by GRP/GRPR in HNSCC proliferation. In HNSCC cells that express elevated levels of both GRPR and EGFR, we found that GRP induced rapid phosphorylation of EGFR as well as p44/42-MAPK activation. Using several EGFR-specific tyrosine kinase inhibitors and cells derived from EGFR knockout mice, we demonstrated that GRP-induced p44/42-MAPK activation was dependent upon EGFR activation. Further investigation demonstrated that cleavage of transforming growth factor-alpha (TGF-alpha) by matrix metalloproteinases mediated GRP-induced MAPK activation. In addition, HNSCC proliferation stimulated by GRP was eliminated upon specific inhibition of EGFR or MEK, and GRP failed to stimulate proliferation in EGFR-deficient cells. These results imply that the mitogenic effects of GRP in HNSCC are mediated by extracellular release of TGF-alpha and require the activation of an EGFR-dependent MEK/MAPK-dependent pathway.

Effective treatment of experimental U-87MG human glioblastoma in nude mice with a targeted cytotoxic bombesin analogue, AN-215

Some brain tumours, such as glioblastomas express high levels of receptors for bombesin/gastrin releasing peptide. We investigated whether bombesin/gastrin releasing peptide receptors found in glioblastoma cell lines can be utilised for targeting of a cytotoxic bombesin analogue, AN-215 consisting of a potent derivative of doxorubicin, 2-pyrrolino-doxorubicin (AN-201) linked to a bombesin-like peptide carrier. This study reports the effect of AN-215 on the growth of U-87MG human glioblastomas xenografted into nude mice. High affinity binding of AN-215 to U-87MG tumours was characterised by an IC(50) value of 4.0+/-0.1 nM, as determined by radioreceptor assays. mRNA analyses revealed the presence of mRNA for BN receptor subtypes 1 and 2. Treatment with AN-215 significantly (P<0.05) extended tumour doubling time from 4.54+/-0.2 days to 8.18+/-1.8 days and inhibited tumour growth as demonstrated by a 69.6% reduction in final tumour volume (P<0.001) and a 64.6% decrease in tumour weight as compared to controls. Cytotoxic radical AN-201 at the same dose was ineffective. The antitumour effect of AN-215 could be blocked by pretreatment with an excess of a bombesin antagonist, indicating that the action of this cytotoxic analogue is receptor-mediated. Our results suggest that patients with inoperable brain tumours such as malignant gliomas may benefit from targeted chemotherapy based on cytotoxic bombesin analogue AN-215.

The inhibition of lung cancer cell growth by intracellular immunization with LC-1 ScFv

A monoclonal antibody, LC-1, recognizing lung cancer associated common antigens was obtained in authors' laboratory. Its single chain Fv fragment (ScFv) named LC-1 ScFv was constructed based on recombinant phage displayed techniques. For expression on cell membrane, LC-1 ScFv was cloned into pDisplay vector, which directed the cloned gene to express as cell membrane bound protein. The resulting plasmid was sequenced and then introduced by the lipofectin method into a lung adenocarcinoma cell line SPC-A-1. G418 resistant cells were obtained by G418 selection. After transfection, LC-1 ScFv expression was observed by Western blot analysis and the expression of cognate antigens was down-regulated as shown in ELISA assay. SPC-A-1-pDisplay-ScFv cells grew in vitro at lower speed than the control intact cells and the cells transfected with vacant vector. Flow cytometry analysis detected a substantial increase in G1 phase and decrease in S phase in population of SPC-A-1-pDisplay-ScFv cells compared to SPC-A-1 and SPC-A-1-pDisplay cells. Semi-quantitative RT-PCR analysis showed that c-myc expression was down-regulated in SPC-A-1-pDisplay-ScFv cells. It seems that the antigens recognized by LC-1 may be in some way involved in a growth stimulating pathway and the antibody blocking of the function of the antigens shut down the pathway and thus down-regulate the expression of c-myc and growth of the cells.

Hypothalamic hormones and cancer

The use of peptide analogs for the therapy of various cancers is reviewed. Inhibition of the pituitary-gonadal axis forms the basis for oncological applications of luteinizing hormone-releasing hormone (LH-RH) agonists and antagonists, but direct effects on tumors may also play a role. Analogs of somatostatin are likewise used for treatment of various tumors. Radiolabeled somatostatin analogs have been successfully applied for the localization of tumors expressing somatostatin receptors. Studies on the role of tumoral LH-RH, growth hormone-releasing hormone (GH-RH), and bombesin/GRP and their receptors in the proliferation of various tumors are summarized, but the complete elucidation of all the mechanisms involved will require much additional work. Human tumors producing hypothalamic hormones are also discussed. Treatment of many cancers remains a major challenge, but new therapeutic modalities are being developed based on antagonists of GH-RH and bombesin, which inhibit growth factors or their receptors. Other approaches consist of the use of cytotoxic analogs of LH-RH, bombesin, and somatostatin, which can be targeted to receptors for these peptides in various cancers and their metastases. These new classes of peptide analogs should lead to a more effective treatment for various cancers.

The case for gastrin-releasing peptide acting as a morphogen when it and its receptor are aberrantly expressed in cancer

Gastrin-releasing peptide (GRP) and its receptor (GRP-R) are frequently expressed by cancers of the gastrointestinal tract, breast, lung, and prostate. Most studies have found that GRP and its amphibian homologue bombesin act to increase tumor cell proliferation, leading to the hypothesis that this peptide hormone is a mitogen important for the growth of various cancers. Yet GRP/GRP-R co-expression in cancer promotes the development of a well-differentiated phenotype; while multiple studies suggest that the presence of these 2 proteins confer a survival advantage. Along with recent reports showing that GRP and its receptor critically regulate aspects of colon and lung organogenesis, we argue that these proteins do not function primarily as mitogens when aberrantly expressed in cancer. Rather, we postulate that GRP/GRP-R are onco-fetal antigens that function as morphogens, with their effect on tumor cell proliferation being a component property of their ability to regulate differentiation. Thus aberrant GRP/GRP-R expression in cancer recapitulates, albeit in a dysfunctional manner, their normal role in development.

Molecular genetic abnormalities in the pathogenesis of human lung cancer

In the past few years our knowledge of the molecular pathogenesis of lung cancer has significantly increased. There are several molecular mechanisms involved in the multistage carcinogenesis through which respiratory epithelial cells become preneoplastic and then invasive cancer. In this review we summarize some of these changes including, genomic alterations such as loss of heterozygosity and microsatellite alterations, autocrine-paracrine loops, alterations in oncogenes and tumor suppressor genes, tumor angiogenesis, aberrant promoter methylation and inherited predisposition to lung cancer. Translation of these findings to the clinic is also discussed.

In vivo inhibition of PC-3 human androgen-independent prostate cancer by a targeted cytotoxic bombesin analogue, AN-215

The effectiveness of chemotherapy targeted to bombesin (BN) receptors was evaluated in nude mice bearing PC-3 human androgen-independent prostate cancers. Cytotoxic BN analogue AN-215, consisting of 2-pyrrolinodoxorubicin (AN-201) linked to BN-like carrier peptide RC-3094, was injected i.v. at 150 nmol/kg on days 1, 11 and 21. After treatment with AN-215, tumor volume was 69% (p < 0.01) smaller than that in controls and tumor doubling time was extended from 8.5 +/- 0.7 days to 20.3 +/- 3.5 days (p < 0.05). Cytotoxic radical AN-201, carrier RC-3094 and their unconjugated mixture administered at the same dosage were ineffective. The mortality rate was 12.5% in the AN-201 group and 16.7% in the group treated with the mixture, but no deaths occurred in mice receiving AN-215. Because the ester bond linking AN-201 to the carrier molecule is hydrolyzed much faster in mouse serum than in human serum, in the second experiment we investigated the tolerance to AN-215 and its effect in nude mice bearing PC-3 tumors after pharmacological inhibition of serum carboxylesterases. Two applications of AN-201 at 200 nmol/kg were lethal, whereas no mortality was observed after 4 injections of AN-215 at the same dose. Administration of 200 nmol/kg AN-215 on days 1, 7, 17 and 26 again produced 69% tumor inhibition. BN receptors on membranes of PC-3 tumors were detected by (125)I-[Tyr(4)]BN binding, and expression of mRNA for BRS-3 and GRP-R subtypes was also found. AN-215 showed a high affinity to PC-3 tumors, displacing the radioligand at an IC(50) of 12.95 +/- 0.35 nM. Because BN receptors are present on primary and metastatic prostate cancer, targeted chemotherapy with AN-215 might benefit patients with advanced prostatic carcinoma who relapsed androgen ablation.

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.

Inhibition of growth of MDA-MB-468 estrogen-independent human breast carcinoma by bombesin/gastrin-releasing peptide antagonists RC-3095 and RC-3940-II

BACKGROUND

The growth of breast carcinoma is promoted by autocrine growth factors such as the bombesin (BN)-like peptides and epidermal growth factor (EGF). The stimulatory action of BN-like peptides can be blocked by the use of BN/gastrin-releasing peptide (GRP) antagonists.

METHODS

The authors investigated the effects of synthetic BN/GRP antagonists RC-3095 and RC-3940-II on tumor growth and the expression of mRNA for EGF receptors and three BN receptor subtypes in MDA-MB-468 human breast carcinoma. Athymic nude mice with xenografts of MDA-MB-468 human breast carcinoma were injected subcutaneously for 6 weeks with RC-3940-II at doses of 20 or 40 microg/day. In another study, the effects of RC-3940-II and RC-3095 were compared.

RESULTS

RC-3940-II caused a significant and dose-dependent growth inhibition of MDA-MB-468 tumors in nude mice; therapy with either dose of RC-3940-II significantly (P<0.01) reduced the mean final tumor volume and weight compared with controls. RC-3940-II induced a persistent regression of > 50% of all tumors. One of 3 tumors treated with 20 microg of RC-3940-II and 3 of 5 tumors treated with 40 microg were found to have regressed completely by the end of the study. When RC-3940-II and RC-3095 were compared at the dose of 20 microg/day, both powerfully suppressed growth of MDA-MB-468 tumors, with RC-3940-II causing a complete regression of 2 tumors and RC-3095 a complete regression of 1 tumor. Receptor analyses of untreated MDA-MB-468 tumors revealed an overexpression of EGF receptors and two classes of binding sites for BN/GRP. mRNAs for receptors of GRP, neuromedin B, and BN receptor subtype-3 were detected by reverse transcriptase-polymerase chain reaction.

CONCLUSIONS

A virtual arrest of growth or regression of MDA-MB-468 human breast carcinoma after therapy with RC-3940-II and RC-3095 indicates that these BN/GRP antagonists could provide a new treatment modality for breast tumors expressing BN and EGF receptors.

Presence of receptors for bombesin/gastrin-releasing peptide and mRNA for three receptor subtypes in human prostate cancers

BACKGROUND

Bombesin-like peptides can function as autocrine or paracrine growth factors and stimulate the growth of some cancer cells, including human prostate cancer. Three bombesin receptor subtypes, termed gastrin-releasing peptide receptor (GRPR), neuromedin B receptor (NMBR), and bombesin receptor subtype 3 (BRS-3), have been identified in rodents and humans.

METHODS

We investigated the presence and characteristics of the functional receptors for bombesin/GRP in human prostate adenocarcinoma specimens by radio-receptor assay and the mRNA expression of the three bombesin receptor subtypes by RT-PCR.

RESULTS

Of the 80 specimens of primary prostate cancer examined by receptor binding assays, 50 ( approximately 63%) showed high-affinity, low-capacity binding sites for bombesin/GRP, and 12 of these 50 receptor-positive specimens also showed a second binding site. Of the 22 prostate cancer specimens analyzed by RT-PCR, 20 (91%) expressed GRPR mRNA, 3 (14%) showed NMBR mRNA, and 2 ( approximately 9%) revealed BRS-3 mRNA. No correlation was observed between receptor expression and patients' age or pathological data.

CONCLUSIONS

The detection of a wide distribution of bombesin/GRP receptors in human prostate carcinomas supports the view that they may be involved in modulation of tumor progression and suggests that approaches based on binding of bombesin receptor antagonists or new targeted cytotoxic bombesin analogs to prostate cancers could be considered for the therapy.

Androgen-independent growth is induced by neuropeptides in human prostate cancer cell lines

BACKGROUND

Androgen-independent growth leads to progressive prostate cancer after androgen-ablation therapy. This may be caused by altered specificity of the androgen receptor (AR), by ligand-independent stimulation of the AR, or by paracrine growth modulation by neuropeptides secreted by neuroendocrine (NE) cells.

METHODS

We established and characterized the androgen-independent FGC-DCC from the androgen-dependent LNCaP fast growing colony (FGC) cell line. The androgen-independent DU-145, FGC-DCC, and PC-3, and the androgen-dependent LNCaP and PC-346C cell lines were used to study growth modulation of gastrin-releasing peptide (GRP), calcitonin (CT), serotonin (5-HT), and vasoactive intestinal peptide (VIP) by (3)H-thymidine incorporation. Specificity of the growth-modulating effects was tested with the anti-GRP monoclonal antibody 2A11 and induction of cAMP by neuropeptides.

RESULTS

Androgen-independent growth stimulation by neuropeptides was shown in DU-145 and PC-346C. 2A11 inhibited GRP-induced (3)H-thymidine incorporation in DU-145 and PC-346C and inhibited proliferation of the FGC-DCC and PC-3 cell lines. With some exceptions, cAMP induction paralleled growth stimulation. Dideoxyadenosine (DDA) inhibited the GRP-induced growth effect in DU-145 and PC-346C, whereas oxadiazoloquinoxaline-1-one (ODQ) had no effect on (3)H-thymidine incorporation. None of the neuropeptides stimulated growth of LNCaP, FGC-DCC, or PC-3.

CONCLUSIONS

GRP-induced growth of DU-145 and PC-346C was specific and cAMP-mediated. Androgen-independent growth of FGC-DCC cells was mainly due to an induction of Bcl-2 expression and possibly through the activation of an autocrine and NE-like pathway, as has been shown also for the PC-3 cell line. Growth induction of non-NE cells by neuropeptides could be a possible role for NE cells in clinical prostate cancer.

Molecular pathogenesis of lung cancer

Lung cancer is the largest cancer killer of men and women in the united states. In addition to the progress made from antismoking primary prevention measures, new tools to help treat patients with lung cancer are emerging from the rapid advances in knowledge of the molecular pathogenesis of lung cancer. These tools include molecular and cellular biology and are starting to provide an insight into how the tumor cell, by altering oncogenes and tumor suppressor genes, achieves growth advantage, uncontrolled proliferation and metastatic behavior via disruption of key cell-cycle regulators and signal transduction cascades. Moreover, new knowledge is being developed in terms of the molecular definition of individual susceptibility to tobacco smoke carcinogens. These tools are being translated into clinical strategies to complement surgery, radiotherapy, and chemotherapy and also to assist in primary and secondary prevention efforts. This review summarizes current knowledge of the molecular pathogenesis of lung cancer. From this we know that respiratory epithelial cells require many genetic alterations to become invasive and metastatic cancer. We can detect cells with a few such changes in current and former smokers, offering the opportunity to intercede with a biomarker-monitored prevention and early detection effort. This will be coupled with new advances in computed tomography-based screening. Finally, because the molecular alterations are known, new mechanism-based therapies are being developed and brought to the clinic, including new drugs, vaccines, and gene therapy, which also must be integrated with standard therapies.

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 analog of luteinizing hormone-releasing hormone AN-207 inhibits growth of OV-1063 human epithelial ovarian cancers in nude mice

OBJECTIVE

The aim of the study was to investigate the effects of the cytotoxic analog of luteinizing hormone-releasing hormone AN-207 on the growth of the OV-1063 human epithelial ovarian cancers, which express luteinizing hormone-releasing hormone receptor. AN-207 consists of doxorubicin derivative 2-pyrrolinodoxorubicin (AN-201) linked with the carrier [D-lysine6 ]luteinizing hormone-releasing hormone.

STUDY DESIGN

Female nude mice bearing xenografts of OV-1063 ovarian cancers were treated with analog AN-207, cytotoxic radical AN-201, or agonist [D-lysine6 ]luteinizing hormone-releasing hormone. The levels and expression of messenger ribonucleic acid of receptors for luteinizing hormone-releasing hormone and epidermal growth factor were evaluated.

RESULTS

The growth of OV-1063 tumor was significantly inhibited by 3 to 5 nmol AN- 207 but not by [D-lysine6 ]luteinizing hormone-releasing hormone. Cytotoxic radical AN-201 was toxic at these doses. After treatment with AN-207 receptors for luteinizing hormone-releasing hormone were not detectable, epidermal growth factor receptor levels declined, and expressions of their respective messenger ribonucleic acids were decreased.

CONCLUSIONS

Targeted cytotoxic luteinizing hormone-releasing hormone analog AN-207 is less toxic than equimolar doses of its radical 2-pyrrolinodoxorubicin and effectively inhibits ovarian tumor growth. Targeted chemotherapy may improve management of ovarian cancer.

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.

Progress in understanding the molecular pathogenesis of human lung cancer

We review the molecular pathogenesis of lung cancer including alterations in dominant oncogenes, recessive oncogenes/tumor suppressor genes, alterations in growth regulatory signaling pathways, abnormalities in other pathways, such as apoptosis, autocrine and paracrine growth stimulatory loops, angiogenesis, and host immune responses, other mechanisms of genetic changes, such as microsatellite and methylation alterations, and the potential for inherited predisposition to lung cancer. These changes are related to multistage carcinogenesis involving preneoplastic lesions, and lung development and differentiation. The translational applications of these findings for developing new ways of early detection, prevention, treatment, and prognosis of lung cancer are discussed.

Inhibition of growth of MDA-MB-231 human breast cancer xenografts in nude mice by bombesin/gastrin-releasing peptide (GRP) antagonists RC-3940-II and RC-3095

Bombesin or gastrin-releasing peptide (GRP) may act as autocrine growth factors and play a role in the initiation and progression of breast cancer. We investigated the effect of bombesin/GRP antagonists RC-3095 and RC-3940-II on the growth of the MDA-MB-231 oestrogen-independent human breast cancer cell line xenografted into female nude mice. Bombesin/GRP antagonists, RC-3095 and RC-3940-II, were administered subcutaneously twice daily at a dose of 10 micrograms for 5 weeks. The growth of MDA-MB-231 tumours was inhibited during the treatment, as shown by a reduction in tumour volume. RC-3940-II and RC-3095 significantly decreased the final tumour volume by 72.4% and 57.7%, respectively, and greatly reduced tumour weights. RC-3940-II also significantly increased tumour doubling time and appeared to be more effective than RC-3095 in inhibiting the growth of MDA-MB-231 breast cancers. Serum gastrin and insulin-like growth factor-I (IGF-I) levels in animals treated with RC-3095 or RC-3940-II showed no significant changes as compared with controls. There was a significant decrease in the number of binding sites for epidermal growth factor (EGF), as well as bombesin, in tumour cells after chronic treatment with RC-3095 or RC-3940-II, which might be related to inhibition of tumour growth. Reverse transcription polymerase chain reaction, followed by Southern blot analysis, also showed a reduction in the expression of mRNA for EGF receptors in the group treated with RC-3940-II. Our findings suggest that bombesin/GRP antagonists such as RC-3095 or RC-3940-II could be considered for endocrine therapy for oestrogen-independent breast cancers, but further investigations are necessary.

Growth inhibition of human ovarian cancers by cytotoxic analogues of luteinizing hormone-releasing hormone

BACKGROUND

Receptors for luteinizing hormone-releasing hormone (LH-RH) are found in nearly 80% of human ovarian cancers. The chemotherapeutic agent doxorubicin can be linked to [D-lysine6]LH-RH to form a cytotoxic analogue (AN-152) that may have greater specificity for tumor cells. This study was conducted to investigate the effects of AN-152 on the growth of LH-RH receptor-positive OV-1063 human epithelial ovarian cancers.

METHODS

Nude mice bearing human ovarian tumors, OV-1063 or UCI-107 (LH-RH receptor negative), were injected intraperitoneally with saline (control) or with equimolar doses of AN-152 or doxorubicin; experiments involving mice with OV-1063 tumors also included groups that were administered [D-lysine6]LH-RH either alone or in combination with doxorubicin. Tumor volume, weight, doubling time, and burden (i.e., tumor weight/body weight) as well as tumor apoptotic and mitotic indices were determined. The levels of receptors for LH-RH and epidermal growth factor (EGF) and their messenger RNAs were measured by use of radioreceptor and reverse transcription-polymerase chain reaction assays, respectively.

RESULTS

The growth of OV-1063 ovarian tumors in nude mice, as based on reduction in tumor volume, was inhibited significantly (all P<.05, two-sided) 4 weeks after treatment with AN-152, even at the lowest dose tested (413 nmol/20 g weight); the toxic effects of an equivalent dose of doxorubicin caused substantial mortality. High-affinity receptors for LH-RH and EGF were found on cell membranes of OV-1063 cancers; however, after in vivo treatment with AN-152, LH-RH receptor-binding sites were not detectable and EGF receptors were reduced in number. The growth of UCI-107 ovarian cancers was not inhibited by AN-152.

CONCLUSIONS

In nude mice bearing LH-RH receptor positive OV-1063 epithelial ovarian cancers, systemic administration of AN-152 is less toxic and inhibits tumor growth better than equimolar doses of doxorubicin.

A single in vivo administration of bombesin antagonist RC-3095 reduces the levels and mRNA expression of epidermal growth factor receptors in MXT mouse mammary cancers

Epidermal growth factor (EGF) and its receptors (EGFR) play important roles in tumorigenesis. In various experimental cancers, treatment with antagonists of bombesin/gastrin-releasing peptide (BN/GRP) produces a reduction in EGFRs, concomitant to inhibition of tumor growth. To investigate the mechanisms involved, we monitored concentrations of BN/GRP antagonist RC-3095 in serum of mice, rats, and hamsters given a single subcutaneous or intravenous injection of this analog. In parallel studies, we measured levels and mRNA expression of EGFRs in estrogen-dependent and independent MXT mouse mammary cancers, following a single subcutaneous administration of RC-3095 to tumor-bearing mice. Peak values of RC-3095 in serum were detected 2 min after intravenous or 15 min after subcutaneous injection. The levels of RC-3095 declined rapidly and became undetectable after 3-5 hr. In the estrogen-dependent MXT tumors, the concentration of EGF receptors was reduced by about 60% 6 hr following injection and returned to original level after 24 hr. Levels of mRNA for EGFR fell parallel with the receptor number and were nearly normal after 24 hr. In the hormone-independent MXT cancers, the number of EGFRs decreased progressively, becoming undetectable 6 hr after injection of RC-3095, and returned to normal values at 24 hr, but EGFR mRNA levels remained lower for 48 hr. Thus, in spite of rapid elimination from serum, BN/GRP antagonist RC-3095 can induce a prolonged decrease in levels and mRNA expression of EGFRs. These findings may explain how single daily injections of BN/GRP antagonists can maintain tumor growth inhibition.