Laura Muñoz-Moreno

Inhibitory effects of antagonists of growth hormone‐releasing hormone on growth and invasiveness of PC3 human prostate cancer

New approaches are needed to the therapy of advanced prostate cancer. This study determined the effect of growth hormone‐releasing hormone (GHRH) antagonists, JMR‐132 and JV‐1‐38 on growth of PC3 tumors as well as on angiogenesis and metastasis through the evaluation of various factors that contribute largely to the progression of prostate cancer. Human PC3 androgen‐independent prostate cancer cells were injected subcutaneously into nude mice. The treatment with JMR‐132 (10 μg/day) or JV‐1‐38 (20 μg/day) lasted 41 days. We also evaluated the effects of JMR‐132 and JV‐1‐38 on proliferation, cell adhesion and migration in PC‐3 cells in vitro. Several techniques (Western blot, reverse transcription polymerase chain reaction, immunohistochemistry, ELISA and zymography) were used to evaluate the expression levels of GHRH receptors and its splice variants, GHRH, vascular endothelial growth factor (VEGF), hypoxia inducible factor (HIF)‐1α, metalloproteinases (MMPs) −2 and −9, β‐catenin and E‐cadherin. GHRH antagonists suppressed the proliferation of PC‐3 cells in vitro and significantly inhibited growth of PC3 tumors. After treatment with these analogues, we found an increase in expression of GHRH receptor accompanied by a decrease of GHRH levels, a reduction in both VEGF and HIF‐1α expression and in active forms of MMP‐2 and MMP‐9, a significant increase in levels of membrane‐associated β‐catenin and a significant decline in E‐cadherin. These results support that the blockade of GHRH receptors can modulate elements involved in angiogenesis and metastasis. Consequently, GHRH antagonists could be considered as suitable candidates for therapeutic trials in the management of androgen‐independent prostate cancer.

Regulation of HER expression and transactivation in human prostate cancer cells by a targeted cytotoxic bombesin analog (AN-215) and a bombesin antagonist (RC-3095)

Bombesin (BN) and gastrin‐releasing peptide (GRP) have been shown to stimulate the growth of human prostate cancer in vivo and in vitro by mechanisms initiated by binding of the peptide to BN/GRP receptor (GRPR). GRPR is overexpressed in a variety of human cancers, including human prostatic carcinoma. This led us to evaluate the effectiveness of blocking GRPR and of chemotherapy targeted to GRPR in androgen‐dependent (LNCaP) and androgen‐independent (PC‐3) prostate cancer cells, which exhibit different features of disease progression. Thus, we used a cytotoxic BN/GRP analog, AN‐215, consisting of 2‐pyrrolinodoxorubicin (AN‐201) linked to BN‐like carrier peptide, and a BN/GRP receptor antagonist, RC‐3095. Semiquantitative RT‐PCR and Western blotting revealed that mRNA and protein levels for GRPR increased in prostate cancer cells as compared with nonneoplastic RWPE‐1 cells. Immunofluorocytochemistry and Western blot assays revealed that AN‐215 was the most effective analog decreasing both the expression of epidermal growth factor receptor family members and the activation of epidermal growth factor receptor and HER‐2, which are associated to a poor prognosis. Furthermore, analogs targeted to BN/GRP receptors, AN‐215 and RC‐3095, blocked the effect of BN on cell growth in RWPE‐1, LNCaP and PC‐3 cells. These findings shed light on the mechanisms of action of these analogs and support the view that the use of AN‐215 and RC‐3095 for blocking BN/GRP receptors for targeted therapy may be of benefit for treatment of advanced prostate cancer.

Growth hormone-releasing hormone antagonists abolish the transactivation of human epidermal growth factor receptors in advanced prostate cancer models

SummaryGrowth hormone-releasing hormone (GHRH) and its receptors have been implicated in a variety of cellular phenotypes related with tumorigenesis process. Human epidermal growth factor receptor family members (HER) such as EGFR and HER2 are involved in mitogenic signaling pathways implicated in the progression of prostate cancer. We analyzed the cross-talk between GHRH and EGF receptors in prostate cancer. The effects of GHRH in HER signaling were evaluated on human androgen-independent PC3 prostate cancer cells in vitro and GHRH antagonist in vitro and in nude mice xenografts of PC3 prostate cancer. Time-course studies indicated that GHRH had a stimulatory activity on both the expression of EGFR and HER2. GHRH analogues, JMR-132 and JV-1–38, endowed with antagonistic activity for GHRH receptors, abrogated the response to GHRH in PC3 cells. GHRH stimulated a rapid ligand-independent activation of EGFR and HER2 involving at least cAMP/PKA and Src family signaling pathways. GHRH also stimulated a slow ligand-dependent activation of EGFR and HER2 involving an extracellular pathway with an important role for ADAM. Preliminary results also revealed an increase of mRNA for GHRH and GHRH receptor induced by EGF. The inhibition of tumor growth, in vivo, was associated with a substantial reduction in the expression of mRNA and protein levels of EGFR and HER2 in the tumors. GHRH antagonist JV-1–38, significantly decreased the phosphorylated Src levels. The cross-talk between HER and GHRH-R may be impeded by combining drugs acting upon GHRH receptors and HER family members in human advanced prostate cancer.

Antitumoral effects of vasoactive intestinal peptide in human renal cell carcinoma xenografts in athymic nude mice

We studied antitumor effect of VIP in human renal cell carcinoma (RCC) (A498 cells xenografted in immunosuppressed mice). VIP-treated cells gave resulted in p53 upregulation and decreased nuclear β-catenin translocation and NFκB expression, MMP-2 and MMP-9 activities, VEGF levels and CD-34 expression. VIP led to a more differentiated tubular organization in tumours and less metastatic areas. Thus, VIP inhibits growth of A498-cell tumours acting on the major issues involved in RCC progression such as cell proliferation, microenvironment remodelling, tumour invasion, angiogenesis and metastatic ability. These antitumoral effects of VIP offer new therapeutical possibilities in RCC treatment.

Novel enantiopure cyclopentadienyl Ti(IV) oximato compounds as potential anticancer agents

The synthesis and characterization of new enantiopure cyclopentadienyl titanium oximato compounds (S,R)-[(η(5)-C5H5)Ti{к(2)NO,(R)NH·HCl}Cl2] (R=Ph (phenyl) 1a·HCl, Bn (benzyl) 1b·HCl, 2-pic (2-picolyl) 1c·HCl), (S,R)-[(η(5)-C5H5)TiCl2{к(2)NO,(Ph)NH}] (1a) and (S,R)-[(η(5)-C5H5)2TiCl{к(2)NO,(R)NH}] (R=Ph 2a, Bn 2b, 2-pic 2c), along with studies on their behavior in D2O at different pD values are reported. The structure of previously described ammonium-oxime (2S,5R)-{NOH,(Bn)NH·HCl} (b·HCl) and novel titanium derivative 1a have been determined by single crystal X-ray crystallography. The effect of the compounds on cytotoxicity, cell adhesion and migration of the androgen-independent prostate cancer PC-3 cells has been assessed. Compounds 2b and 2c are more cytotoxic than additive doses of titanocene dichloride and free oxime proligand, probing the synergistic effect of these novel compounds. The cytotoxicity of 2b and 2c has been further evaluated against human renal Caki-1, colon DLD-1 and triple negative breast MDA-MB-231 cancer cell lines. The activity found for 2c on PC-3 and Caki-1 is higher than that of highly active Titanocene Y (bis-[(p-methoxybenzyl)cyclopentadienyl]titanium(IV) dichloride), while showing selectivity against renal cancer when compared to a non-tumorigenic human renal (HEK-293T) cell line. Compounds 2b and especially 2c are apoptotic in Caki-1 cancer cell lines. Cell adhesion and wound-healing assays confirmed that derivatives 1c·HCl, 2b and 2c affect the adhesion and migration patterns of the PC-3 cell line. Interactions of the novel compounds with plasmid (pBR322) DNA have also been studied, showing that the oximato Ti(IV) derivatives have a weak or no interaction with DNA at physiological pH.

Signalling pathways involved in antitumoral effects of VIP in human renal cell carcinoma A498 cells: VIP induction of p53 expression

Vasoactive intestinal peptide (VIP) decreases cell proliferation through PI3K signalling and prevents tumour progression in clear renal cell carcinoma (RCC). Here we analyzed the signalling pathways that mediate such VIP effects by using human RCC A498 cells. The effects of treatment with 1 μM VIP and/or specific protein kinase inhibitors such as H89, Wortmannin and PD98059 were studied by cell adhesion assay, ELISA of VEGF165 and ROS production assays. Semiquantitative RT-PCR and western blot were performed to study p53 expression. VIP increased cell adhesion and ROS production, and decreased VEGF165 secretion through PI3K signalling. Moreover, VIP increased nuclear expression of tumour suppressor p53. VIP effects could be blocked by cell incubation with a specific p53 inhibitor, cyclin pifithrin-α hydrobromide (CPFT-αH). In conclusion, this study provides a p53-dependent mechanism by which VIP regulates cell proliferation in RCC development. It supports a potential usefulness of VIP in new therapies of RCC.

Growth hormone-releasing hormone (GHRH) promotes metastatic phenotypes through EGFR/HER2 transactivation in prostate cancer cells

The involvement of growth hormone-releasing hormone (GHRH) in several relevant processes that contribute to prostate cancer progression was analyzed. Firstly, we evaluated GHRH effects on cell proliferation and adhesion in human cancer prostate cell lines, LNCaP and PC3, by using specific assays (BrdU incorporation and collagen adhesion). The expression levels of the main marker molecules of these processes were measured by RT-PCR, Western blotting and zymography assays. GHRH increased both cell proliferation and proliferating cell nuclear antigen (PCNA) levels in LNCaP cells and in PC3 cells; however, such a rise was faster in the PC3 cells that represent the most aggressive stage of prostate cancer. Furthermore, GHRH significantly reduced cell adhesion and E-cadherin levels in LNCaP and PC3 cells and up-regulated the total and nuclear expression of β-catenin in PC3 cells. In addition, we assessed cell cycle, cell migration and VEGF secretion in PC3 cells. GHRH augmented the number of cells in G2/M-phase but diminished that corresponding to G1-phase. Cell-cycle specific markers were evaluated since GHRH effects may be related to their differential expression; we observed a decrease of p53, p21, and Bax/Bcl2 ratio. Furthermore, GHRH increased the expression of CD44, c-myc and cyclin D1, MMP-2 and MMP-9 activity, and VEGF secretion. We also observed that EGFR and/or HER2 transactivation is involved in cell adhesion, cell migration and VEGF secretion produced by GHRH. Consequently, present results define GHRH as a proliferative, anti-apoptotic and migratory agent in prostate cancer.

Growth hormone-releasing hormone induced transactivation of epidermal growth factor receptor in human triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) is a subset of breast cancers which is negative for expression of estrogen and progesterone receptors and human epidermal growth factor receptor-2 (HER2). Chemotherapy is currently the only form of treatment for women with TNBC. Growth hormone-releasing hormone (GHRH) and epidermal growth factor (EGF) are autocrine/paracrine growth factors in breast cancer and a substantial proportion of TNBC expresses receptors for GHRH and EGF. The aim of this study was to evaluate the interrelationship between both these signaling pathways in MDA-MB-468 human TNBC cells. We evaluated by Western blot assays the effect of GHRH on transactivation of EGF receptor (EGFR) as well as the elements implicated. We assessed the effect of GHRH on migration capability of MDA-MB-468 cells as well as the involvement of EGFR in this process by means of wound-healing assays. Our findings demonstrate that in MDA-MB-468 cells the stimulatory activity of GHRH on tyrosine phosphorylation of EGFR is exerted by two different molecular mechanisms: i) through GHRH receptors, GHRH stimulates a ligand-independent activation of EGFR involving at least cAMP/PKA and Src family signaling pathways; ii) GHRH also stimulates a ligand-dependent activation of EGFR implicating an extracellular pathway with an important role for metalloproteinases. The cross-talk between EGFR and GHRHR may be impeded by combining drugs acting upon GHRH receptors and EGFR family members. This combination of GHRH receptors antagonists with inhibitors of EGFR signalling could enhance the efficacy of both types of agents as well as reduce their doses increasing therapeutic benefits in management of human breast cancer.

Anti-proliferative and pro-apoptotic effects of GHRH antagonists in prostate cancer

Growth hormone-releasing hormone (GHRH) and its receptors have been implicated in the progression of various tumors. In vitro and in vivo studies have demonstrated that GHRH antagonists inhibit the growth of several cancers. GHRH antagonists, JMR-132 and JV-1-38 inhibit the growth of androgen-independent prostate tumors. Here we investigated the involvement of GHRH antagonists in proliferative and apoptotic processes. We used non-tumoral RWPE-1 and tumoral LNCaP and PC3 human prostatic epithelial cells, as well as an experimental model of human tumor PC3 cells. We evaluated the effects of JMR-132 and JV-1-38 antagonists on cell viability and proliferation in the three cell lines by means of MTT and BrdU assays, respectively, as well as on cell cycle and apoptotic process in PC3 cells. The expression levels of PCNA, p53, p21, CD44, Cyclin D1, c-myc, Bax and Bcl2 were determined in both in vivo and in vitro models by means of Western-blot and RT-PCR. GHRH antagonists suppressed cell proliferation and decreased the levels of the proliferation marker, PCNA, in the three cell lines and in PC3 tumor. GHRH antagonists led to an increase of cells in S-phase and a decrease in G1 and G2/M phases, and induced S-phase arrest and increase of apoptotic cells. The effects of GHRH-antagonists on cell cycle could be due to the changes observed in the expression of p21, p53, Bax, Bcl2, CD44, Cyclin D1, c-myc and caspase 3. Present results confirm and extend the role of GHRH antagonists as anti-proliferative and pro-apoptotic molecules in prostate cancer.

Polyphenolic carbosilane dendrimers as anticancer agents against prostate cancer

Carbosilane dendrimers containing vanillin on the surface have been prepared with the purpose of combining the unique antioxidant and anticancer properties of polyphenols and dendrimers. These new compounds exhibit antioxidant potency as free-radical scavengers, as determined by DPPH and ABTS. Remarkably, all synthesized dendrimers exhibit improved antioxidant efficacy compared to vanillin. Anticancer activity has been studied against HeLa cervical and PC3 human prostate cancer cell lines. Proliferation, cell cycle, adhesion and migration in human prostate tumor cells have been studied. Data revealed a general trend indicating that polyphenolic dendrimers are more cytotoxic than their monopolyphenolic counterparts in both cancer cell lines.