Parkin, a gene implicated in autosomal recessive juvenile parkinsonism, is a candidate tumor suppressor gene on chromosome 6q25-q27

In an effort to identify tumor suppressor gene(s) associated with the frequent loss of heterozygosity observed on chromosome 6q25-q27, we constructed a contig derived from the sequences of bacterial artificial chromosomeP1 bacteriophage artificial chromosome clones defined by the genetic interval D6S1581-D6S1579-D6S305-D6S1599-D6S1008. Sequence analysis of this contig found it to contain eight known genes, including the complete genomic structure of the Parkin gene. Loss of heterozygosity (LOH) analysis of 40 malignant breast and ovarian tumors identified a common minimal region of loss, including the markers D6S305 (50%) and D6S1599 (32%). Both loci exhibited the highest frequencies of LOH in this study and are each located within the Parkin genomic structure. Whereas mutation analysis revealed no missense substitutions, expression of the Parkin gene appeared to be down-regulated or absent in the tumor biopsies and tumor cell lines examined. In addition, the identification of two truncating deletions in 3 of 20 ovarian tumor samples, as well as homozygous deletion of exon 2 in the lung adenocarcinoma cell lines Calu-3 and H-1573, supports the hypothesis that hemizygous or homozygous deletions are responsible for the abnormal expression of Parkin in these samples. These data suggest that the LOH observed at chromosome 6q25-q26 may contribute to the initiation andor progression of cancer by inactivating or reducing the expression of the Parkin gene. Because Parkin maps to FRA6E, one of the most active common fragile sites in the human genome, it represents another example of a large tumor suppressor gene, like FHIT and WWOX, located at a common fragile site.

Cell cycle genes in ovarian cancer: steps toward earlier diagnosis and novel therapies

Human malignant tumors are characterized by abnormal proliferation resulting from alterations in cell cycle-regulatory mechanisms. The regulatory pathways controlling cell cycle phases include several oncogenes and tumor suppressor genes that display a range of abnormalities with potential usefulness as markers of evolution or treatment response in ovarian cancer. This review summarizes the current knowledge about these aberrations in malignant tumors of the ovary. We sought to divide cell cycle-regulatory genes into four subgroups on the basis of their predominant role in a specific phase or during the transition between two phases of the cell cycle.

Ezh2 reduces the ability of HDAC1-dependent pRb2/p130 transcriptional repression of cyclin A

The polycomb group (PcG) proteins are known to be involved in maintaining the silenced state of several developmentally regulated genes. Enhancer of zeste homolog 2 (Ezh2), a member of this large protein family, has also been shown to be deregulated in different tumor types and its role, both as a potential primary effector and as a mediator of tumorigenesis, has become a subject of increased interest. We observed that Ezh2 binds to pRb2/p130, a member of the retinoblastoma family; as such, we were led to consider the possible ability of Ezh2 to modulate cell cycle progression. Both Ezh2 and pRb2/p130 repress gene expression by recruiting histone deacetylase (HDAC1), which decreases DNA accessibility for activating transcription factors. Additionally, we observed that Ezh2 interacts with the C-terminal region of pRb2/p130, essential for interaction with HDAC1. We show that Ezh2 is able to reverse pRb2/p130-HDAC1-mediated repression of the cyclin A promoter. This indicates a functional role of this complex in regulating cyclin A expression, known to be crucial in mediating cell cycle advancement. We also detected a significant decrease in the retention of HDAC1 activity associated with pRb2/p130 when Ezh2 was overexpressed. Finally, electromobility shift assays (EMSA) demonstrated that overexpression of Ezh2 caused the abrogation of the pRb2/p130-HDAC1 complex on the cyclin A promoter. These data, taken together, suggest that Ezh2 competes with HDAC1 in binding to pRb2/p130, disrupting their occupancy on the cyclin A promoter. In this study, we propose a new mechanism for the functional inactivation of pRb2/p130 that ultimately contributes to cell cycle progression and malignant transformation.

Importance of Ezh2 polycomb protein in tumorigenesis process interfering with the pathway of growth suppressive key elements

An understanding of the mechanisms that uncover the dynamic changes in the distribution of the chromatin modifying enzymes and regulatory proteins on their target loci could provide further insight into the phenomenon of malignant transformation. Based on the current available data, it seems more and more clear that an abnormal expression of Ezh2, a member of the Polycomb group (PcG) protein, may be involved in the tumorigenesis process, in addition, different studies identify Ezh2 as a potential marker that distinguish aggressive prostate and breast cancer from indolent one. Recent investigation show that ectopic expression of Ezh2 provides proliferative advantage to primary cells through interaction with the pathways of key elements that control cell growth arrest and differentiation, like members of the retinoblastoma (Rb) family. Here, we outline how these pathways converge and we review the recent advances on the molecular mechanisms that promote cell cycle progression through deregulation of Ezh2 protein level, providing novel links between cancer progression and chromatin remodeling machineries.

Frequent loss of pRb2/p130 in human ovarian carcinoma

PURPOSE

RB2/p130, a member of the retinoblastoma gene family, maps to human chromosome 16q12.2, a region in which deletions have been found in several human neoplasms including breast, prostatic, and ovarian carcinoma. We sought to evaluate pRb2/p130 protein expression and function in ovarian carcinoma.

EXPERIMENTAL DESIGN

pRb2/p130 expression was detected by immunohistochemical and Western blot analyses in 45 primary ovarian carcinoma samples.

RESULTS

Immunohistochemical analysis revealed loss or decrease of pRb2/p130 expression in 18 cases (40%). pRb2/p130 expression was mostly nuclear and inversely correlated to the tumor grade (P < 0.05). Western blot analysis correlated with immunohistochemical expression. Reverse transcription-PCR followed by Southern blot analysis was performed on a representative set of 20 ovarian carcinomas. RB2/p130 mRNA levels were consistent with protein expression. We found a significant increase in the percentage of G(1)-phase-arrested cells in CAOV3 and A2780 ovarian carcinoma cell lines after transduction with an adenovirus carrying the RB2/p130 gene (Ad-CMV-RB2/p130).

CONCLUSIONS

These data indicate that loss or decrease of pRb2/p130 expression is a frequent event in ovarian carcinoma and is regulated mostly at the transcriptional level. Moreover, pRb2/p130 overexpression is able to arrest cell growth in ovarian carcinoma cells, suggesting the putative role of pRb2/p130 as a tumor suppressor in this malignancy.

Quercetin abrogates taxol-mediated signaling by inhibiting multiple kinases

Cell cycle block in G(2)/M initiates apoptosis, but the mechanism of this signaling cascade are largely unknown. The microtubule-perturbing agent Taxol has multiple effects on this signaling pathway and is a potent inducer of apoptosis. The specific pathways activated by low, clinically relevant concentrations of the drug are still largely unknown and are dependent on cell type and drug concentration. In this work, we have investigated why HeLa cells respond to Taxol by undergoing complete apoptosis, whereas MCF-7 cells remain in an intermediate phase with reduced death. Three phases were distinguished in these apoptotic pathways. The initial phase characterized by cellular detachment is followed by a second phase which includes the onset of apoptotic morphology, and p38 and Bcl-2 phosphorylation. These two phases are common to both cell lines. HeLa cells then proceed to the third and final execution phase, which culminates in death, whereas MCF-7 cells do not progress. Interestingly, the isoflavonoid Quercetin, a known general kinase inhibitor and an antioxidant, was able to prevent the onset of Taxol-induced cellular detachment and to protect from cell death. Moreover, it blocked Taxol-induced phosphorylation of p38 and Bcl-2, and prevented a Taxol-induced change in relative mobility of the apoptosis signal-regulating kinase 1 (Ask1). Our data elucidate the signaling pathways activated by Taxol at low clinically relevant concentrations.

Hydrocortisone has a protective effect on CyclosporinA-induced cardiotoxicity

CyclosporinA (CsA) is an immunosuppressive drug which induces severe adverse effects such as cardiotoxicity and nephrotoxicity. In several therapeutic protocols CsA is used in association with corticosteroids to obtain better therapeutic results. Recently, our studies showed that CsA increases blood pressure while inhibit Nitric Oxide (NO) production in vivo. In this study we evaluated in rat cardiomyocytes the effects of CsA, used alone or in association with Hydrocortisone (HY), on intracellular calcium concentration, NO production and lipid peroxidation (MDA level). Our results demonstrated that CsA increased intracellular calcium and such effect was dose-dependent. HY used alone, slightly decreased intracellular calcium, while dramatically reduced CsA-induced calcium fluxes. CsA (3.2 microM) increased lipid peroxidation and this effect was blunted by HY. Both CsA and HY inhibited NO production in rat cardiomyocytes acting on this pathway synergically. Our results demonstrated that in rat cardiomyocytes, CsA toxicity is due to a calcium overload, which in turn induce lipid peroxidation and determines oxidative stress-induced cell injury. Treatment with HY effectively inhibits CsA-induced toxicity, decreasing lipid peroxidation as well as calcium intracellular concentration. Our findings seem to suggest that glucocorticoids may be effective in reducing CsA-induced cardiotoxicity at concentrations which are consistent with current therapeutic doses.

pRb2/p130 and VEGF expression in endometrial carcinoma in relation to angiogenesis and histopathologic tumor grade

PURPOSE

Endometrial cancer is the most common gynecologic malignancy. Established prognostic factors are histologic grade, depth of myometrial invasion, and extrauterine spread including retroperitoneal lymph node metastases. Tumorigenesis is a multistep process involving different genetic changes resulting in uncontrolled cellular proliferation, inhibition of apoptosis, and enhanced vascular proliferation among other events. Angiogenesis, the formation of new blood vessels from a preexisting vascular network, is necessary for invasive tumor growth and metastasis and constitutes an important point in the control of cancer progression. The pathogenesis of the angiogenetic phenotype may involve the inactivation of different tumor suppressor genes.

EXPERIMENTAL DESIGN

We investigated the relationship between the expression levels of VEGF and the retinoblastoma family member pRb2/p130 in endometrial carcinoma in relation to histopathologic tumor grade in a cohort of 50 patients.

RESULTS

We found that VEGF and pRB2/p130 expression were inversely correlated. Additionally, high grade tumors presented a significantly lower number of cells expressing pRb2/p130 when compared to low grade tumors. A significant positive correlation was found, by means of the Spearman coefficient, between VEGF expression and binary grading (0.450, p-value < 0.005) which is an architectural grading system that uses low-magnification assessment of amount of solid growth, pattern of invasion, and presence of necrosis to divide endometrioid carcinomas into low- and high-grade tumors. Additionally, we also found a negative correlation between pRb2/p130 expression levels and binary grading (-0.595, p-value < 0.005). Interestingly, we also found that VEGF and pRb2/p130 expression levels were not related to staging (p-value > 0.005).

CONCLUSIONS

These results open up a new perspective including novel markers that, combined together, may be useful in patient screening for endometrial cancer aggressiveness.

Conservative treatment of early endometrial cancer

Endometrial cancer is the most common cancer of the female genital tract in Europe and in the United States. Endometrial cancer has increased 21% in incidence since 2008, and the death rate has increased more than 100% over the past two decades. Approximately 15% of patients with endometrial cancer are pre-menopausal. The aim of this review is to discuss the conservative management of endometrial cancer. A number of studies largely support the conservative treatment of endometrial carcinoma (EC) in women desiring future fertility. We focus on the role of progestin hormonal therapy, including the risks associated with non-standard care, appropriate candidate selection, expected outcomes, various progestin agents and recommended follow-up.

New players in ovarian cancer

Ovarian cancer is the leading cause of gynecologic cancer mortality worldwide. The aim of this review is to highlight the most recent studies regarding ovarian cancer pathogenesis and the new therapeutic approaches against this insidious disease. We focus on the relevance of some cell cycle genes, transcription factors, and microRNAs in the carcinogenesis of ovarian cancer as well as on a new hypothesis for therapy using histone deacetylase inhibitors. We also report recent studies regarding some mechanisms of chemoresistance, a major obstacle in the treatment of ovarian cancer. Together these studies can improve our knowledge of ovarian cancer tumorigenesis and diagnosis providing new tools to hopefully defeat this deadly disease.

New insights in endometrial carcinogenesis

Endometrial carcinoma is the most common cancer of the female genital tract in Europe and in the United States. Despite advances in defining the biology of endometrial carcinomas, there has been poor progress in determining markers that distinguish preinvasive endometrial proliferations. The aim of this review is to highlight the most recent studies regarding the molecular markers involved in endometrial adenocarcinoma pathogenesis and carcinogenesis. We focus on studies that describe markers with potential to progress from endometrial hyperplasia to invasive disease.

Epithelial ovarian cancer: the role of cell cycle genes in the different histotypes

Cancer is frequently considered to be a disease of the cell cycle; alterations in different families of cell cycle regulators cooperate in tumor development. Molecular analysis of human tumors has shown that cell cycle regulators are frequently mutated in human neoplasms, which underscores how important the maintenance of cell cycle commitment is in the prevention of human cancer. The regulatory pathways controlling cell cycle phases include several oncogenes and tumor suppressor genes which display a range of abnormalities with potential usefulness as markers of evolution or treatment response in epithelial ovarian cancer. This review summarizes the current knowledge about these aberrations in malignant tumors of the ovary. We sought to focus our attention on the genes involved in the development of tumors arising from the ovarian epithelium, which are the most common types of ovarian malignancies.

pRb2/p130 decreases sensitivity to apoptosis induced by camptothecin and doxorubicin but not by taxol

PURPOSE

In addition to their original function as cell cycle regulators, retinoblastoma (Rb) family members were recently reported to modulate the sensitivity of cancer cells to chemotherapeutic agents. The purpose of this study is to investigate the possible role of pRb2/p130 in the sensitivity of ovarian cancer to camptothecin, doxorubicin, and taxol.

EXPERIMENTAL DESIGN

pRb2/p130 was overexpressed in the CAOV-3 ovarian cancer cell line, and the effect of pRb2/p130 overexpression on sensitivity to apoptosis trigged by IC(50) doses of different drugs was evaluated by various methods, including 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, flow cytometry, and Western blot analyses.

RESULTS

The results reported in this study support the conclusion that overexpression of pRb2/p130 in the CAOV-3 ovarian cancer cell line lacking wild-type p53 is able to inhibit apoptosis triggered by camptothecin and doxorubicin through the c-Jun NH(2)-terminal kinase signaling transduction pathway. Conversely, taxol-induced cell death is not influenced by the pRb2/p130 protein level.

CONCLUSIONS

A careful analysis of pRb2/p130 expression in tumor specimens could help to identify the best clinical protocol to be used for each patient, improving efficacy and tolerance and therefore offering additional progress in the treatment of advanced ovarian cancer.

p27kip1 overexpression promotes paclitaxel-induced apoptosis in pRb-defective SaOs-2 cells

p27kip1 is a cyclin-dependent kinase (CDK) inhibitor, which controls several cellular processes in strict collaboration with pRb. We evaluated the role of p27kip1 in paclitaxel-induced apoptosis in the pRb-defective SaOs-2 cells. Following 48 h of exposure of SaOs-2 cells to 100 nM paclitaxel, we observed an increase in p27kip1 expression caused by the decrease of the ubiquitin-proteasome activity. Such increase was not observed in SaOs-2 cells treated with the caspase inhibitors Z-VAD-FMK, suggesting that p27kip1 enhancement at 48 h is strictly related to apoptosis. Finally, we demonstrated that SaOs-2 cells transiently overexpressing the p27kip1 protein are more susceptible to paclitaxel-induced apoptosis than SaOs-2 cells transiently transfected with the empty vector. Indeed, after 48 h of paclitaxel treatment, 41.8% of SaOs-2 cells transiently transfected with a pcDNA3-p27kip1 construct were Annexin V-positive compared to 30.6% of SaOs-2 cells transfected with the empty vector (P < 0.05). In conclusion, we demonstrated that transfection of the pRb-defective SaOs-2 cells with the p27kip1 gene via plasmid increases their susceptibility to paclitaxel-induced apoptosis. The promoting effect of p27kip1 overexpression on apoptosis makes p27kip1 and proteasomal inhibitors interesting tools for therapy in patients with pRb-defective cancers.

MPA increases idarubicin-induced apoptosis in chronic lymphatic leukaemia cells via caspase-3

The caspase family of protease is speculated to have a crucial role in apoptosis. The effect of treatment with Idarubicin (IDA) and Medroxyprogesterone acetate (MPA), used alone or in combination, on the activation of Caspase-3 in canine Chronic Lymphatic Leukaemia (CLL) cells was investigated, in order to clarify the mechanism of chemo- and hormone-therapy mediated apoptosis. Caspase activity was determined by a quantitative fluorimetric assay. Apoptosis was monitored by propidium iodide (PI) and nucleosomes assay. Treatment of CLL cells for 24 h with MPA 5 microM did not significantly activate caspase-3 but its activity was increased almost 5-fold more with IDA 1 microM (P < 0.05) than control. Treatment of CLL cells with IDA 1 microM in equimolecular association with MPA was able to increase the activation of caspase-3 induced by IDA of the 61.2% (P < 0.05) in comparison with IDA alone. The activation of caspase-3 was confirmed evaluating apoptosis by PI and nucleosomes assay. Furthermore, both caspase-3 activation and apoptosis triggered by IDA alone or in combination with MPA were significantly inhibited by specific caspase-3 inhibitor AC-DEVD-CMK. These findings provide an explanation for IDA and MPA induced-apoptosis mechanism.

Multidisciplinary International Conference on Gynecologic Cancer, Bologna, Italy, June 8-12, 2005

The first "Multidisciplinary International Conference on Gynecologic Cancer" which was held in Bologna on June 8-12, 2005, addressed some of the most crucial topics in gynecologic oncology, presented the latest achievements and, at the same time, designed the guidelines for future developments in the field. The scientific program was intended not only to share and compare views and ideas among gynecologists but also with oncologists and researchers in basic science. The scientific committee strongly believed in the "multidisciplinary approach" towards medicine and particularly towards patients.

Molecular pathology of ovarian cancer

Ovarian cancer is the leading cause of death among women with gynecologic malignancies. Epithelial tumors typically constitute 80-90% of ovarian malignancies and are classified primarily as serous, mucinous, endometrioid or clear cell. Current data indicate that each of these histologic subtypes is associated with distinct morphologic and molecular genetic alterations. We describe such genetic alterations with specific reference to histologic subtypes.