Biomedical subjects

Ana M Bajo

Publications and source records attributed to Ana M Bajo.

7 recordsLinked to original sources

PubMed2005

Expression of vasoactive intestinal peptide and functional VIP receptors in human prostate cancer: antagonistic action of a growth-hormone-releasing hormone analog.

Vasoactive intestinal peptide (VIP) functions as a mitogenic agent in the human prostate gland acting by autocrine/paracrine mechanisms. Here we extend knowledge on the VIP system (expression of VIP and VIP receptors, functionality of VIP receptors) at this level by analyzing the differences between human normal prostate and prostate carcinoma specimens. RT-PCR showed the expression of mRNA for VIP in normal and malignant tissues, whereas VIP levels, as measured by enzyme immuno-analysis, were about two times higher in adenocarcinoma samples. Real-time RT-PCR indicated a minor expression of VPAC2 receptors in the prostate gland, as well as the overexpression of VPAC1 and PAC1 receptors in malignant tissue specimens. Radio-labeled binding experiments with [125I]VIP showed an increased number of VIP binding sites (2.5 times for the high- and 1.7 times for the low-affinity sites) during malignant transformation, whereas the affinity values were unaffected. The receptors were functional in control and cancer tissues as shown by the ability of increasing VIP doses to stimulate adenylate cyclase activity. Interestingly, JV-1-53 (a GHRH-related peptide analog) (at 0.1 microM) behaved as a potent VIP antagonist since it inhibited by 60% the maximal VIP effect upon the enzyme activity. The results further explain the mechanisms of the autocrine/paracrine actions of VIP in human prostate and prostatic carcinoma through the observation of differences between healthy tissue and malignant transformation. Moreover, present data support the potential usefulness of VIP and/or synthetic peptide analogs for diagnostic or radiotherapeutic purposes as well as for long-term peptide therapy in this malignancy.

Aged↗

PubMed2003

Targeted doxorubicin-containing luteinizing hormone-releasing hormone analogue AN-152 inhibits the growth of doxorubicin-resistant MX-1 human breast cancers.

PURPOSE: The receptors for luteinizing hormone-releasing hormone receptor (LHRH-R) are found in >50% of human breast cancers. Doxorubicin (DOX) was linked to [D-Lys(6)]LHRH to form a cytotoxic conjugate, AN-152, which can be targeted to tumor cells expressing LHRH-R. We evaluated the effects of AN-152 on the estrogen-independent, DOX-resistant human mammary carcinoma line MX-1, xenografted into nude mice. EXPERIMENTAL DESIGN: Nude mice bearing MX-1 tumors were administered five i.v. injections of AN-152 or DOX at doses equivalent to 3 mg/kg DOX. Tumor growth was followed, and changes in the expression of LHRH-R on tumors were evaluated by radioreceptor assays, reverse transcription-PCR, and Western blotting. The effects of AN-152 on the expression of human epidermal growth factor receptor (HER)-2 were investigated. Because LHRH-R are coupled to various G proteins, which are involved in mitogenic signaling, we determined the outcome of treatment with AN-152 on the levels of mRNA for different G proteins. RESULTS: Treatment with AN-152 significantly (P < 0.05) decreased the final tumor volume to 978.56 +/- 176.85 mm(3), compared with the control tumors, which measured 2837.38 +/- 515.38 mm(3). Tumor doubling time was likewise significantly (P < 0.05) extended by AN-152 to 12.01 +/- 1.99 days from 6.45 +/- 0.36 days for the controls. Therapy with AN-152, but not with DOX, resulted in a significant decrease of LHRH-R levels on MX-1 tumors. The expression of mRNAs for HER-2, HER-3, Galpha(i2), and Galpha(11) and the levels of HER-2 and HER-3 proteins were also significantly reduced by AN-152. CONCLUSIONS: Cytotoxic LHRH analogue AN-152 could be considered for targeted chemotherapy of DOX-resistant breast cancers expressing LHRH-R.

Animals↗

PubMed2003

Growth hormone-releasing hormone (GHRH) antagonists inhibit the proliferation of androgen-dependent and -independent prostate cancers.

The antiproliferative effects of an antagonist of growth hormone-releasing hormone (GHRH) JV-1-38 were evaluated in nude mice bearing s.c. xenografts of LNCaP and MDA-PCa-2b human androgen-sensitive and DU-145 androgen-independent prostate cancers. In the androgen-sensitive models, JV-1-38 greatly potentiated the antitumor effect of androgen deprivation induced by surgical castration, but was ineffective when given alone. Thus, in castrated animals bearing MDA-PCa-2b cancers, the administration of JV-1-38 for 35 days virtually arrested tumor growth (94% inhibition vs. intact control, P < 0.01; and 75% vs. castrated control, P < 0.05). The growth of LNCaP tumors was also powerfully suppressed by JV-1-38 combined with castration (83% inhibition vs. intact control, P < 0.01; and 68% vs. castrated control, P < 0.05). However, in androgen-independent DU-145 cancers, JV-1-38 alone could inhibit tumor growth by 57% (P < 0.05) after 45 days. In animals bearing MDA-PCa-2b and LNCaP tumors, the reduction in serum prostate-specific antigen levels, after therapy with JV-1-38, paralleled the decrease in tumor volume. Inhibition of MDA-PCa-2b and DU-145 cancers was associated with the reduction in the expression of mRNA and protein levels of vascular endothelial growth factor. The mRNA expression for GHRH receptor splice variants was found in all these models of prostate cancer. Our results demonstrate that GHRH antagonists inhibit androgen-independent prostate cancers and, after combination with androgen deprivation, also androgen-sensitive tumors. Thus, the therapy with GHRH antagonist could be considered for the management of both androgen-dependent or -independent prostate cancers.

Animals↗

PubMed2003

Solubilization of adenylyl cyclase from human myometrium in a alphas-coupled form.

Adenylyl cyclase (AC) was extracted from human myometrium with either non-ionic (Lubrol-PX or Triton X-100) or zwitterionic (3-[3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, CHAPS) detergents. The soluble enzyme was stimulated by forskolin, a hydrophobic activator, in the presence of Mg2+ indicating that the catalytic subunit had not been damaged after solubilization. The enzyme was also activated by 5'-guanylyl imidodiphosphate (Gpp(NH)p) showing that the catalytic unit was not separated from stimulatory guanine nucleotide binding protein (Gs) during the extraction. Both activators showed different effects on the stimulatory efficacy and potency of AC activity solobulized with detergents. Gel filtration of Lubrol-PX and CHAPS extracts over a Sepharose CL-2B column partially resolved AC and its complexes. The chromatographic profile for Lubrol-solubilized AC presented a main peak of about 200 kDa whereas CHAPS-solubilized AC showed a dominant peak of about 1100 kDa. The heterodisperse peaks obtained revealed that the catalytic AC subunit was not separated from Gs proteins after gel filtration, and that AC could be associated with other cellular proteins. When Lubrol extract was submitted to anionic-exchange chromatography, the enzyme was purified about 7.5 fold (enzymatic activity of 48.1 pmol/min/mg of protein). The catalytic subunit was co-eluted with both AC-activating proteins Galphas large (52.2 kDa) and Galphas small (48.7 kDa). This is the first demonstration of the stable physical association of AC with both alphas subunits of G proteins in human myometrium.

Adenylyl Cyclases↗

PubMed2002

Effects of long-term treatment with the luteinizing hormone-releasing hormone (LHRH) agonist Decapeptyl and the LHRH antagonist Cetrorelix on the levels of pituitary LHRH receptors and their mRNA expression in rats.

The effects of depot formulations of the luteinizing hormone-releasing hormone (LHRH) agonist Decapeptyl (25 microg/day) for 30 days or LHRH antagonist Cetrorelix pamoate (100 microg/day) for 30 days and daily injections of 100 microg of Decapeptyl for 10 days on the expression of mRNA for pituitary LHRH receptor (LHRH-R) and the levels of LHRH-R protein were evaluated in rats. Serum sex steroid concentrations and the weights of the reproductive organs were greatly reduced in all groups treated with analogs, demonstrating an efficient blockade of the pituitary-gonadal axis. Decapeptyl microcapsules elevated serum LH in female rats, but decreased it in male rats. LHRH-R mRNA expression in female pituitaries was reduced to 41% and 56-65% on days 10 and 30, respectively, whereas LHRH-R protein was 64% of control on day 10 and returned to pretreatment levels on day 30. Decapeptyl microcapsules reduced LHRH-R mRNA expression in male pituitaries to 58% on day 30 but not LHRH-R protein. Daily injections of Decapeptyl caused a desensitization of LH responses in female rats, while raising LHRH-R mRNA expression in female rats by 23% and LHRH-R protein levels by 119%. Cetrorelix pamoate reduced serum LH in female rats and diminished LHRH-R mRNA to 30% and 26% and LHRH-R protein to 57% and 48% on days 10 and 30, respectively. Elevated LHRH-R protein levels of ovariectomized rats were reduced after 10-day treatment with Cetrorelix or 100 microg/day Decapeptyl. Thus, changes in the mRNA expression after treatment with Cetrorelix, but not always Decapeptyl, paralleled those of LHRH-R protein. The inhibitory effect of Cetrorelix on serum LH, pituitary LHRH-R mRNA, and LHRH-R protein was greater than that of Decapeptyl.

Animals↗

PubMed2002

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.

Adult↗

PubMed2002

Effective treatment of experimental ES-2 human ovarian cancers with a cytotoxic analog of luteinizing hormone-releasing hormone AN-207.

The receptors for luteinizing hormone-releasing hormone (LHRH) are found in 80% of human ovarian carcinomas. These receptors can be used for targeted chemotherapy with cytotoxic analogs of LHRH, such as AN-207, consisting of 2-pyrrolinodoxorubicin (AN-201) linked to [D-Lys ]LHRH. We investigated the effects of AN-207 and AN-201 on the growth of LHRH receptor-positive ES-2 human ovarian cancers. The effects of the treatment on mRNA and protein levels of human epidermal growth factor (EGF) receptors (EGFR and HER-2) in ovarian tumors were determined by RT-PCR and immunoblotting. In Experiment 1, nude mice bearing ES-2 ovarian tumors were injected i.v. with 250 nmol/kg doses of AN-207, AN-201, the carrier [D-Lys ]LHRH, an unconjugated mixture of AN-201 and [D-Lys ]LHRH or vehicle. AN-207 caused a significant ( <0.01) 59.5% inhibition in tumor growth while its components were ineffective. In Experiment 2, mice with large ES-2 tumors were treated with AN-207 or AN-201 at 250 nmol/kg. Again, AN-207, but not AN-201, inhibited tumor growth. In Experiment 3, the site of action of AN-207 was investigated. The blockade of LHRH receptors with Cetrorelix partially suppressed the antitumor effect of AN-207. Treatment with AN-207 significantly ( <0.01) decreased the expression of mRNA for EGFR, and HER-2 by 27 and 34%, respectively, as compared to controls and reduced the receptor protein levels of EGFR and HER-2 by 35 and 36%, respectively ( <0.05). The results indicate that cytotoxic LHRH analog AN-207 could be considered for chemotherapy of ovarian cancers expressing LHRH receptors.

Animals↗