Expression of the retinoblastoma-related gene Rb2/p130 is downregulated in atypical endometrial hyperplasia and adenocarcinoma

The Epigenetic Regulatory Protein CBX2 Promotes mTORC1 Signalling and Inhibits DREAM Complex Activity to Drive Breast Cancer Cell Growth

Chromobox 2 (CBX2) is a chromatin-binding component of polycomb repressive complex 1, which causes gene silencing. CBX2 expression is elevated in triple-negative breast cancer (TNBC), for which there are few therapeutic options. Here, we aimed to investigate the functional role of CBX2 in TNBC. CBX2 knockdown in TNBC models reduced cell numbers, which was rescued by ectopic expression of wild-type CBX2 but not a chromatin binding-deficient mutant. Blocking CBX2 chromatin interactions using the inhibitor SW2_152F also reduced cell growth, suggesting CBX2 chromatin binding is crucial for TNBC progression. RNA sequencing and gene set enrichment analysis of CBX2-depleted cells identified downregulation of oncogenic signalling pathways, including mTORC1 and E2F signalling. Subsequent analysis identified that CBX2 represses the expression of mTORC1 inhibitors and the tumour suppressor RBL2. RBL2 repression, in turn, inhibits DREAM complex activity. The DREAM complex inhibits E2F signalling, causing cell senescence; therefore, inhibition of the DREAM complex via CBX2 may be a key oncogenic driver. We observed similar effects in oestrogen receptor-positive breast cancer, and analysis of patient datasets suggested CBX2 inhibits RBL2 activity in other cancer types. Therapeutic inhibition of CBX2 could therefore repress mTORC1 activation and promote DREAM complex-mediated senescence in TNBC and could have similar effects in other cancer types.

Role of Retinoblastoma Protein Family (Rb/p105 and Rb2/p130) Expression in the Histopathological Classification of Borderline Ovarian Tumors

Borderline ovarian tumors (BOT) are uncommon but not rare epithelial ovarian neoplasms, intermediate between benign and malignant categories. Emerging knowledge supports the notion that subtypes of borderline ovarian tumors comprise distinct biologic, pathogenetic, and molecular entities, precluding a single unifying concept for BOT. The identification of valuable markers for the diagnosis and classification of these tumors is in need. Among the molecular candidates, the Retinoblastoma (Rb) family members Rb/p105 and Rb2/p130 seem to play a pivotal role in ovarian cancer. In particular, Rb/p105, when in the unphosphorylated form, acts as a growth suppressor controlling cell cycle and tumor progression; whereas, the phosphorylated form activates gene transcription and cellular proliferation. While Rb/p105 is ubiquitously confined to the nuclei of cycling and quiescent cells, Rb2/p130 activity is also regulated by intracellular localization. According to this, Rb family members could represent a novel marker in diagnosis and classification risk for patients with BOT. In this study, we evaluated the expression and subcellular localization of proteins of the retinoblastoma (Rb) gene family in 65 ovarian borderline tumors. Statistically significant differences were found in nuclear and cytoplasmic expressions of Rb/p105 and Rb2/p130 according to different examined histotypes. In detail, the nuclear expression of Rb/p105 and Rb2/p130 was more frequently detected in serous (84.6%) than sero-mucinous (42.1%) and mucinous (50%) types. Conversely, the cytoplasmic expression of Rb2/p130 was not detected in serous tumors and frequently observed in mucinous subtypes (80%). Our findings suggest that Rb proteins do not play a key role in the tumor progression of serous borderline tumors since any cases showed cytoplasmic localization. By contrast, the observed higher cytoplasmic expression of Rb2/p130 in intestinal mucinous BOTs is indicative of Rb protein family involvement in the cancerogenesis pathway of mucinous ovarian tumors. Also, mucinous BOTs of intestinal-type, exhibiting low nuclear and high cytoplasmic levels of Rb2/p130 might potentially be considered a high-risk category of malignant evolution. Further studies on larger series are needed to clarify how BOTs could be stratified in different prognostic groups according to their Rb proteins immunohistochemical profile.

Pineoblastoma segregates into molecular sub-groups with distinct clinico-pathologic features: a Rare Brain Tumor Consortium registry study

Pineoblastomas (PBs) are rare, aggressive pediatric brain tumors of the pineal gland with modest overall survival despite intensive therapy. We sought to define the clinical and molecular spectra of PB to inform new treatment approaches for this orphan cancer. Tumor, blood, and clinical data from 91 patients with PB or supratentorial primitive neuroectodermal tumor (sPNETs/CNS-PNETs), and 2 pineal parenchymal tumors of intermediate differentiation (PPTIDs) were collected from 29 centres in the Rare Brain Tumor Consortium. We used global DNA methylation profiling to define a core group of PB from 72/93 cases, which were delineated into five molecular sub-groups. Copy number, whole exome and targeted sequencing, and miRNA expression analyses were used to evaluate the clinico-pathologic significance of each sub-group. Tumors designated as group 1 and 2 almost exclusively exhibited deleterious homozygous loss-of-function alterations in miRNA biogenesis genes (DICER1, DROSHA, and DGCR8) in 62 and 100% of group 1 and 2 tumors, respectively. Recurrent alterations of the oncogenic MYC-miR-17/92-RB1 pathway were observed in the RB and MYC sub-group, respectively, characterized by RB1 loss with gain of miR-17/92, and recurrent gain or amplification of MYC. PB sub-groups exhibited distinct clinical features: group 1-3 arose in older children (median ages 5.2-14.0 years) and had intermediate to excellent survival (5-year OS of 68.0-100%), while Group RB and MYC PB patients were much younger (median age 1.3-1.4 years) with dismal survival (5-year OS 37.5% and 28.6%, respectively). We identified age < 3 years at diagnosis, metastatic disease, omission of upfront radiation, and chr 16q loss as significant negative prognostic factors across all PBs. Our findings demonstrate that PB exhibits substantial molecular heterogeneity with sub-group-associated clinical phenotypes and survival. In addition to revealing novel biology and therapeutics, molecular sub-grouping of PB can be exploited to reduce treatment intensity for patients with favorable biology tumors.

RNA sequencing reveals significant miRNAs in Atypical endometrial hyperplasia

PURPOSE

In this paper, we aimed to investigate the miRNAs that played a regulatory role in the development of atypical endometrial hyperplasia (AEH).

METHODS

RNA sequencing was performed for endometrial tissues from 3 AEH patients and 3 endometrial normal hyperplasia patients. RNA sequencing data were processed and differentially expressed (DE) miRNAs were identified between AEH and controls. The target genes for DE miRNAs were identified and mapped to the protein-protein interaction (PPI) network. The miRNA related functions were predicted and miRNA-disease gene network was constructed.

RESULTS

Total 18 DE miRNAs were overlapped in three sample groups, among which hsa-miR-577, hsa-miR-182-5p and hsa-miR-183-5p were top three miRNAs that targeting largest number of genes. Function analysis showed that the 18 overlapped miRNAs mainly related with cancer and signaling transduction related pathways. PPI network showed that total 12 genes were among top 20 genes based on three network topological features including BCL2, UMPS, MAPK13, PRKCB, CREB1, IGF1, SP1, SMAD3, IGF1R, NOTCH2, WNT5A, TK2. Top 10 miRNAs in miRNA-disease gene network were identified such as hsa-miR-577 (degree = 17), hsa-miR-182-5p (degree = 16) and hsa-miR-3609 (degree = 13).

CONCLUSION

hsa-miR-577 and hsa-miR-182-5p may play regulatory role in AEH through AMPK signal pathway and Wnt signaling pathway.

MiR-17-5p enhances pancreatic cancer proliferation by altering cell cycle profiles via disruption of RBL2/E2F4-repressing complexes

The members of the miR-17-92 cluster are upregulated in various cancers and function as a cluster of oncogenic miRNA. Our study characterized a new function of miR-17-5p, a member of the miR-17-92 cluster, in regulating cell proliferation in pancreatic cancer. Our results indicate that miR-17-5p was up-regulated in pancreatic adenocarcinoma and directly targeted the retinoblastoma-like protein 2 (RBL2), a tumor suppressor belonging to the Rb family. High levels of miR-17-5p and low levels of RBL2 were associated with poor prognosis. RBL2 interacted with the transcription factor E2F4 and bound to the promoter regions of the E2F target genes. Disruption of the RBL2/E2F4 complex by miR-17-5p overexpression shifted the activity of E2F from gene repressing to gene activating, which induced cell cycle entry and proliferation. These results suggest that miR-17-5p promoted proliferation in pancreatic ductal adenocarcinoma cells (PDAC), and altered cell cycle profiles in vivo and in vitro, by disrupting the RBL2/E2F4-associated gene repressing complexes via direct targeting of RBL2. The new regulatory network, involving miR-17-5p and RBL2, emerges as a new target of PDAC treatment.

Melanoma antigen-A11 regulates substrate-specificity of Skp2-mediated protein degradation

Melanoma antigen-A11 (MAGE-A11) is a proto-oncogene involved in androgen receptor signaling and androgen-dependent cell growth. In this report we provide evidence that MAGE-A11 interacts with Skp2 (S phase kinase-associated protein), the substrate recognition protein of the Skp1-Cullin1-F-box E3 ubiquitin ligase, and with Skp2 binding protein, cyclin A. A similar cyclin A binding motif in MAGE-A11 and Skp2 was consistent with a competitive relationship between MAGE-A11 and Skp2 in binding cyclin A. Skp2 inhibited MAGE-A11 interaction with cyclin A. Differential effects of MAGE-A11 on Skp2-mediated protein degradation were also revealed. MAGE-A11 increased Skp2-mediated degradation of cyclin A and retinoblastoma-related protein p130. In contrast, MAGE-A11 decreased Skp2-mediated degradation of E2F1 and Skp2 self-ubiquitination. Stabilization of E2F1 by MAGE-A11 was associated with sequestration and inactivation of Skp2 through the formation of an E2F1-MAGE-A11-Skp2 complex. We conclude that direct interactions of MAGE-A11 with Skp2 and cyclin A regulate the substrate-specificity of Skp2-mediated protein degradation.

Promoter Methylation Status Modulate the Expression of Tumor Suppressor (RbL2/p130) Gene in Breast Cancer

Background

Aberrant expression of tumor suppressor genes may correspond to the abnormal cell development and tumorigenesis. Rbl2/p130, a member of retinoblastoma family of proteins, has growth suppressive properties. Numerous studies reported de-regulation of Rbl2/p130 in various types of cancer as a consequence of a number of genetic alterations. However, role of epigenetic mechanisms like DNA methylation in Rbl2/p130 expression remains elusive.

Methods

In the current study, 76 breast cancer tumors along with normal tissues (n = 76), blood (n = 76) of respective individuals and control blood (n = 50) were analyzed. Rbl2/p130 expression was analyzed by quantitative real time PCR (syber green method). Promoter methylation status was studied through methylation specific PCR of bisulfite converted genomic DNA. Data was analyzed using various statistical tests.

Results

We report significantly reduced Rbl2/p130 expression (P = 0.001) in tumors tissues as compared to control samples. Similarly, Rbl2/p130 expression varies with age and disease stages (P = 0.022), which suggest its involvement in tumor progression. Aberrant promoter methylation (Δmeth) was found in almost all the diseased samples and that was significantly different (P<0.001) with control samples. Similarly, methylation status varies significantly with tumor progression stages (P = 0.022). Hyper-methylation was observed at -1, +3, +15 and +75 of Rbl2/p130 promoter flanking around the TSS. Statistical analysis revealed that Rbl2/p130 expression negatively correlates to its promoter methylation (r = -0.412) in tumor tissues. Our results reflect an epigenetic regulation of Rbl2/p130 expression in breast cancer. This highlights the importance of Rbl2/p130 promoter methylation in breast cancer pathogenesis.

pRb2/p130 localizes to the cytoplasm in diffuse gastric cancer

pRb2/p130 is a key tumor suppressor, whose oncosuppressive activity has mainly been attributed to its ability to negatively regulate cell cycle by interacting with the E2F4 and E2F5 transcription factors. Indeed, pRb2/p130 has been found altered in various cancer types in which it functions as a valuable prognostic marker. Here, we analyzed pRb2/p130 expression in gastric cancer tissue samples of diffuse histotype, in comparison with their normal counterparts. We found a cytoplasmic localization of pRb2/p130 in cancer tissue samples, whereas, in normal counterparts, we observed the expected nuclear localization. pRb2/p130 cytoplasmic delocalization can lead to cell cycle deregulation, but considering the emerging involvement of pRb2/p130 in other key cellular processes, it could contribute to gastric tumorigenesis also through other mechanisms. Our data support the necessity of further investigations to verify the possibility of using pRb2/p130 as a biomarker or potential therapeutic target for diffuse gastric cancer.

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.

A retrospective analysis of the clinicopathologic characteristics of uterine cellular leiomyomas in China

OBJECTIVE

To investigate the clinicopathologic features of uterine cellular leiomyomas (CLs) by comparing them with those of uterine leiomyosarcomas (LMSs).

METHODS

A case-control study comparing 78 cases of CL with 10 cases of LMS was conducted. The patients' records were reviewed to abstract information on tumors features and treatment, immunohistochemical findings, and disease prognosis.

RESULTS

The mean age at diagnosis was 45.3 ± 8.41 years in the CL group. The main clinical CL manifestations were menstrual abnormalities (56.4%), abdominal pain or distension (14.1%), and pelvic pressure (8.9%). Abdominal pain or distension was significantly more common in the LMS than in the CL group (P<0.05). Generally, CL tumors were smaller in diameter than LMS tumors (P<0.05). Moreover, lower levels of Ki-67 and PCNA expression were measured in CL than in LMS tumors (P<0.05). There were no cases of malignant transformation or metastasis in 41 patients with CL who adhered to long-tern follow-up.

CONCLUSION

No symptoms were found to be specifically associated with CL, and management of CL does not need to differ from that of ordinary leiomyoma. In contrast to malignant disease, CL has a favorable long-term prognosis. However, given its "borderline" pathologic nature, patients with CL require clinical surveillance.

Expression of the retinoblastoma-related gene Rb2/p130 in the pathogenesis of serous carcinoma of the ovary

OBJECTIVE

The purpose of this study was to evaluate the immunohistochemical Rb2/p130 expression in a series of benign, borderline, and malignant ovarian tumors.

STUDY DESIGN

Seventy-six operative specimens were analyzed. Frequencies and percents were calculated for variables by each of the 5 disease stage groups in increasing severity and again for the disease stage groups collapsed into benign (serous cystadenoma or endosalpingosis), low-grade [serous borderline tumors (SBT) or low-grade serous carcinoma (LGSC)] and high-grade serous carcinoma.

RESULTS

There was no loss of expression in benign serous cystadenomas (0/18). Ten percent of SBT's (2/20), 47% of LGSC's (9/19), and 16% of HGSC's (3/16) had loss of expression. There was a significant difference in the expression during the progression from cystadenoma to SBT to LGSC.

CONCLUSIONS

Loss of Rb2/p130 expression is a rare event in benign cystadenoma. The progression to LGSC is associated with a decrease in gene expression.

pRb2/p130 protein expression and RBL2 mutation analysis in Burkitt lymphoma from Uganda

Background

The members of the retinoblastoma protein family, pRb, p107 and pRb2 (p130), are central players in controlling the cell cycle. Whereas disturbed function of pRb is commonly seen in human cancers, it is still an open question whether pRb2 is involved in tumorigenic processes. However, altered subcellular localization of pRb2 and mutations in the pRb2-encoding gene RBL2 have been described for some tumours, including Burkitt lymphomas (BL).

Methods

We retrieved 51 biopsy specimens of endemic BL cases from Uganda. The expression of pRb2 was determined by immunohistochemistry. Exons 19-22 of the RBL2 gene, the region known to contain a nuclear localization signal, were screened for mutations by PCR amplification and direct DNA sequencing.

Results

Nearly all of our cases (84.0%) were positive for pRb2 protein expression although this protein is a marker for growth arrest and Burkitt lymphoma is characterized by a high proliferation rate. Of the positive cases, 73.8% were scored as expressing the protein at a high level. Subcellular pRb2 localization was predominantly nuclear and no cases with expression restricted to the cytoplasm were observed. We did not detect any RBL2 mutations in the part of the gene that encodes the C-terminal end of the protein.

Conclusion

The majority of endemic BL cases from Uganda express pRb2, but somatic RBL2 mutations affecting the protein's nuclear localization signal appear to be rare.

Endometrioid uterine cancer: histopathological risk factors of local and distant recurrence

OBJECTIVES

To determine the relationship between histopathological prognostic factors and sites of initial recurrence in endometrioid uterine cancer.

METHODS

A total of 355 patients (Stage I, n=227; II, n=38; III, n=90) underwent primary radical surgery including complete systematic pelvic lymph node (PLN) and para-aortic lymph node (PALN) adenectomy followed by adjuvant chemotherapy who were at risk for recurrence. Relapse-free survival (RFS) and disease-related survival (DRS) were analyzed using the log-rank testing. Multivariate Cox regression analysis and logistic regression analysis were used to determine and estimate independent prognostic factors.

RESULTS

Lymph-vascular space invasion (LVSI), architectural grade (AG), myometrial invasion, and PLN metastasis (PLNM) were identified as independent prognostic factors for RFS. AG (p=0.0043) related with local recurrence. Among patients who received adjuvant chemotherapy, patients with G3 tumor had higher ratio of recurrence (16/45) compared with G1/2 tumor (11/102) (p=0.0004). Meanwhile, PLNM related with distant recurrence (p=0.0008). There was a statistically significant difference in RFS according to the number of positive PLN sites (group 0: n=313, 1: n=16, > or =2: n=26), five-year RFS in each group was 91.9%, 81.3%, and 41.2%, respectively.

CONCLUSIONS

Sites of initial recurrence were related with AG and PLNM in patients with endometrioid uterine cancer. Current chemotherapy alone may not be an effective adjuvant therapy to prevent recurrence in patients with G3 tumor and > or =2 positive PLN sites. Prospective clinical trial needs to be conducted to establish the strategy of adjuvant therapy with these patients.

pRb2/p130: a gene target for diagnosis and treatment of cancer

This application claims: i) a method for detecting cancer cells based on analysis of gene mutations and/or promoter methylation of the pRb2/p130 gene; ii) a method for diagnosing cancer based on analysis of gene mutations and/or promoter methylation of the pRb2/p130 gene; iii) a method for detection of cells that are predisposed to tumorigenesis based on analysis of gene mutations and/or promoter methylation of the pRb2/p130 gene; iv) a method for treating cancer and/or inhibiting tumorigenesis based on demethylation of the pRb2/p130 gene promoter; and v) a method for treating cancer and/or inhibiting tumorigenesis based on inhibition of other proteins that interact with or regulate pRb2/p130. This application is founded on the recognition that: i) pRb2/p130 is a frequent target of genetic or epigenetic alteration in various human cancers; ii) the resulting loss of regulation of cell cycle progression contributes to the phenotypic characteristics of these neoplasms; iii) pRb2/p130 represents a valuable biomarker for detection/diagnosis of some cancers; and iv) pRb2/p130 may be a useful gene target for development of new cancer therapeutics.

Immunohistochemical markers in endometrial hyperplasia: is there a panel with promise? A review

OBJECTIVE

Despite advances in defining the biology of endometrial carcinomas, there has been little progress in determining markers that distinguish preinvasive endometrial proliferations. The goal of this literature review was to identify studies on endometrial hyperplasia (EH) that describe markers with potential to predict response to progestin therapy or potential for progression to invasive disease.

METHODS

Articles published between January 2000 and October 2006 were identified using the key words endometrial hyperplasia and progesterone receptor or estrogen receptor or biologic marker or immunohistochemistry/immunohistochemical. Articles that reported immunohistochemical studies on specimens of human EH +/-endometrioid endometrial carcinoma with a normal comparison group were included. Only those who reported hyperplasia with atypia separately from nonatypical hyperplasia and with a sample size greater than 10 specimens for the sum of complex and atypical samples were included.

RESULTS

A total of 289 abstracts were reviewed and 150 articles potentially met inclusion criteria. Of these, 123 described immunohistochemical studies on human EH specimens. Only 46 met all criteria for analysis of 61 different markers.

CONCLUSIONS

PTEN seems to have the greatest potential for diagnostic utility in EH, perhaps in combination with Bcl-2 and Bax. However, more uniform and rigorous studies are required to confirm these and additional markers' utility diagnostically in a diagnostic panel. As a major clinical priority is to determine which lesions can be treated medically and which require surgical intervention, focusing future studies on markers that distinguish response to hormone therapy or are involved in hormone regulation, will be important future considerations.

Ten-year results of a prospective study on the prognostic role of ploidy in endometrial carcinoma

BACKGROUND

To improve the outcome of endometrial cancer patients, a more accurate prognostic assessment is mandatory. The aims of the study were to evaluate the role of flow cytometric DNA ploidy as an independent prognostic factor in patients with endometrial cancer and to verify if ploidy was able to distinguish patients with different prognosis into homogeneous subgroups for grade of differentiation and stage.

METHODS

In a prospective study, DNA ploidy was evaluated from fresh tumor samples in 174 endometrial cancer patients who underwent surgery as the first treatment. Ploidy, as well as classical parameters, were analyzed in relation to the length of disease-free survival and disease-specific survival.

RESULTS

DNA aneuploidy was found in 49 patients (28.2%). Patients with DNA-aneuploid tumors had a significantly reduced disease-free interval and disease-specific survival (P < .0001). The 10-year survival probability was 53.2% for DNA-aneuploid patients and 91.0% for patients with DNA-diploid tumors. By multivariate analysis DNA-aneuploid type was the strongest independent predictor of poor outcome, followed by age and stage. Patients with DNA-aneuploid tumor had a significantly higher risk ratio for recurrence (5.03) and death due to disease (6.50) than patients with DNA-diploid tumors. Stratification by DNA-ploidy within each group by grade of differentiation allowed identification of patients with significantly different outcome. In grade 2 tumors, 10-year survival was 45.0% in aneuploid cases and 91.9% in diploid cases (P < .0001). Patients with advanced-stage (>I) diploid tumor did significantly better than patients with stage I aneuploid tumor (P = .04).

CONCLUSIONS

The presence of DNA-aneuploid type in endometrial cancer identifies high-risk cases among the patients considered 'low risk' according to stage and grade of differentiation.

Regulation of cellular senescence by Rb2/p130

Growth regulatory functions of Rb2/p130, which aim at a sustained arrest such as in quiescent or differentiated cells, qualify the protein also to act as a central regulator of growth arrest in cellular senescence. In this respect, Rb2/p130 functions are connected to signaling pathways induced by p53, which is a master regulator in cellular senescence. Here, we summarize the pathways, which specify pRb2/p130 to control this arrest program and distinguish its functions from those of pRb/p105.

RB family members as predictive and prognostic factors in human cancer

The retinoblastoma family members--pRb, pRb2/p130 and p107--are tumor suppressor genes involved in controlling four major cellular processes: growth arrest, apoptosis, differentiation and angiogenesis. Molecular genetic studies have identified abnormalities of these tumor suppressor genes in a large proportion of human cancers. These genetic alterations have emerged as significant factors in the pathogenesis and progression of many types of tumors and are therefore likely to provide relevant information to assess risk in cancer patients. There is a pressing clinical need to identify prognostic and predictive factors for patients with cancer, because there is an undeniable importance in being able to determine which patients will have a favorable outcome without further therapy (prognostic factor) and which will need some additional treatment (predictive factor). This review examines the predictive and/or prognostic role of each retinoblastoma family member in human cancer.

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.

Effect of exogenous E2F-1 on the expression of common chromosome fragile site genes, FHIT and WWOX

The expression of two tumor suppressor genes, fragile histidine triad (FHIT) and WW domain containing oxidoreductase (WWOX), encompassing common chromosome fragile regions, FRA3B at 3p14.2 and FRA16D at 16q23, is altered in many epithelial tumors. Since DNA sequence search shows that the FHIT gene has the E2F-1 recognition site in 5'] region, which regulates cell cycle, we tested the effect of E2F-1 overexpression in tumor cells. Ectopic E2F-1 expression led to an increase of Fhit and Wwox expression in allele remaining tumor cells and resulted in induction of apoptosis. Reporter assay showed that the E2F-1 site in FHIT 5' region was involved in the down-stream transcription after exogenous E2F-1 introduction. Chromatin immunoprecipitation detected exogenous E2F-1 binding to the recognition site in FHIT 5' region. The data suggest that E2F-1 overexpression plays a role in suppression of tumor, at least in part trough transcriptional regulation of FHIT and relevant activation of WWOX.

Alteration of the fragile histidine triad gene early in carcinogenesis: an update

An association between common chromosome fragile sites and frequent chromosomal deletions in cancer has been observed and led to the hypothesis that genes at fragile sites may play a role in tumor development. In 1996, the human fragile histidine triad gene, FHIT, was identified by positional cloning at 3p14.2, a chromosomal region spanning the carcinogen-sensitive, common fragile site FRA3B. FHIT gene is lost and inactivated in a large fraction of tumors and early in carcinogenesis. A group of ancestral cancerous cells that carry FHIT alterations, expanding in succeeding cell generations, exhibits a hallmark in carcinogenesis scenario.

Alterations of pRb1-cyclin D1-cdk4/6-p16(INK4A) pathway in endometrial carcinogenesis

The retinoblastoma protein pathway (pRb1-cyclin D1-cdk4/6-p16(INK4A)) participates in the regulation of the cellular processes at the transition of G1/S phases of the cell-cycle. Derailments of this pathway, caused either by lack of pRb1 or p16(INK4A) expression or overexpression of cyclin D1 and/or cdk4/6, are implicated in the deregulation of the cell-cycle machinery, resulting in uncontrolled cell proliferation, tumor heterogeneity, invasion and metastasis. Several studies conducted so far have assessed the deregulation of the pRb1-pathway components in various human tumors and cell-lines, provided these pathway alterations play an obligatory role in tumorigenesis. This review briefly summarizes the current information on the pRb1-cyclin D1-cdk4/6-p16(INK4A) alterations in sporadic uterine cancer, placing emphasis on the influence on the dualistic model of endometrial carcinogenesis.

Role of cell-cycle regulatory proteins in gynecological cancer

Human malignant tumors are characterized by abnormal proliferation resulting from alterations in cell-cycle regulatory mechanisms. This review summarizes the current knowledge about these aberrations in malignant tumors of the ovary, endometrium, cervix uteri, and vulva. The data indicate that analysis of single cell cycle stimulating or inhibiting proteins partly produces unexpected, apparently paradoxical results, and cell-cycle regulatory pathways should be regarded as a whole in order to identify the molecular mechanisms leading to abnormal tumor cell proliferation. For the papillomavirus (HPV)- associated cervical and vulvar carcinomas, the manifold effects of the viral oncogenes E6 and E7 on cell-cycle control are described.

Clinicopathological significance of pRb2/p130 expression in squamous cell carcinoma of the esophagus

PURPOSE

The aim of the current study was to find out the significance of the immunohistochemical expression of pRb2/p130, which is a member of the retinoblastoma gene family, in squamous cell carcinoma of the esophagus.

METHODS

We analyzed immunohistochemically the expression of pRb2/p130 of 107 squamous cell carcinomas (SCCs) of the esophagus and the correlation of pRb2/p130 expression with clinicopathological features was investigated.

RESULTS

Expression of pRb2/p130 was observed in 42 SCCs (39.3%). There was a significant correlation of pRb2/p130 expression with the histological type of well-differentiated SCC (P< 0.0001). The survival rate of patients with esophageal SCCs expressing pRb2/p130 was significantly better than that of patients with tumors without pRb2/p130 expression (P= 0.016). A multivariate analysis demonstrated that pRb2/p130 expression (P= 0.026), venous invasion (P= 0.028), and TNM stage (P= 0.044) were independent prognostic indicators in patients with esophageal SCCs.

CONCLUSIONS

Differentiation of esophageal SCC might be partially mediated by the pRb2/p130 gene, and pRb2/p130 expression can additionally be an indicator of the better prognosis of patients with esophageal SCCs.

Tumor suppressor genes in normal and malignant hematopoiesis

Over the last decade, a growing number of tumor suppressor genes have been discovered to play a role in tumorigenesis. Mutations of p53 have been found in hematological malignant diseases, but the frequency of these alterations is much lower than in solid tumors. These mutations occur especially as hematopoietic abnormalities become more malignant such as going from the chronic phase to the blast crisis of chronic myeloid leukemia. A broad spectrum of tumor suppressor gene alterations do occur in hematological malignancies, especially structural alterations of p15(INK4A), p15(INK4B) and p14(ARF) in acute lymphoblastic leukemia as well as methylation of these genes in several myeloproliferative disorders. Tumor suppressor genes are altered via different mechanisms, including deletions and point mutations, which may result in an inactive or dominant negative protein. Methylation of the promoter of the tumor suppressor gene can blunt its expression. Chimeric proteins formed by chromosomal translocations (i.e. AML1-ETO, PML-RARalpha, PLZF-RARalpha) can produce a dominant negative transcription factor that can decrease expression of tumor suppressor genes. This review provides an overview of the current knowledge about the involvement of tumor suppressor genes in hematopoietic malignancies including those involved in cell cycle control, apoptosis and transcriptional control.

Expression of cell-cycle-associated proteins pRB2/p130 and p27kip in vulvar squamous cell carcinomas

Squamous cell vulvar carcinoma accounts for 4% of all gynecologic malignancies. The cause of vulvar cancer is still unclear. Identification of new biologic factors involved in vulvar carcinogenesis may be useful in clarifying the natural history of this malignancy. We investigated the immunohistochemical expression of the retinoblastoma-related proteins pRB2/p130 and CKI p27kip1 in a series of 51 invasive squamous cell carcinomas of the vulva (ISCCs) and in synchronous normal vulvar skin, non-neoplastic epithelial disorders (NNED) and vulvar intraepithelial neoplasia (VIN). Normal vulvar skin staining showed positivity for both pRB2/p130 and p27kip1. Loss of pRB2/p130 occurred in 29 (57%) of 51 specimens of ISCCs, and in 1 of 7 specimens with VIN (14%; P = .04). We also observed a significant decrease of pRB2/p130 expression from NNED to neoplastic tissues (VIN and ISCCs) (P = .004). Loss of p27kip1 expression was found in 16 of 51 specimens (31%) of invasive carcinomas, in 1 (14%) of 7 specimens of VIN, and in 2 of 18 specimens of NNED (11%). pRB2/p130 and p27(kip1) did not correlate significantly with any of the clinicopathologic parameters examined. Our data indicate that loss of pRB2/p130 and p27kip1 are frequent events in invasive vulvar carcinomas compared with synchronous premalignant lesions, non-neoplastic epithelial disorders, and normal vulvar skin. The significant progressive decrease of pRB2/p130 expression from non-neoplastic epithelial alterations through intraepithelial neoplasia to invasive vulvar carcinomas suggests a role for this tumor suppressor gene in vulvar carcinogenesis.