High frequency of chromosome 9 deletion in ovarian cancer: evidence for three tumour-suppressor loci

Prediction of Chemoresistance-How Preclinical Data Could Help to Modify Therapeutic Strategy in High-Grade Serous Ovarian Cancer

High-grade serous ovarian cancer (HGSOC) is one of the most lethal tumors generally and the most fatal cancer of the female genital tract. The approved standard therapy consists of surgical cytoreduction and platinum/taxane-based chemotherapy, and of targeted therapy in selected patients. The main therapeutic problem is chemoresistance of recurrent and metastatic HGSOC tumors which results in low survival in the group of FIGO III/IV. Therefore, the prediction and monitoring of chemoresistance seems to be of utmost importance for the improvement of HGSOC management. This type of cancer has genetic heterogeneity with several subtypes being characterized by diverse gene signatures and disturbed peculiar epigenetic regulation. HGSOC develops and metastasizes preferentially in the specific intraperitoneal environment composed mainly of fibroblasts, adipocytes, and immune cells. Different HGSOC subtypes could be sensitive to distinct sets of drugs. Moreover, primary, metastatic, and recurrent tumors are characterized by an individual biology, and thus diverse drug responsibility. Without a precise identification of the tumor and its microenvironment, effective treatment seems to be elusive. This paper reviews tumor-derived genomic, mutational, cellular, and epigenetic biomarkers of HGSOC drug resistance, as well as tumor microenvironment-derived biomarkers of chemoresistance, and discusses their possible use in the novel complex approach to ovarian cancer therapy and monitoring.

Gene networks and expression quantitative trait loci associated with adjuvant chemotherapy response in high-grade serous ovarian cancer

BACKGROUND

A major impediment in the treatment of ovarian cancer is the relapse of chemotherapy-resistant tumors, which occurs in approximately 25% of patients. A better understanding of the biological mechanisms underlying chemotherapy resistance will improve treatment efficacy through genetic testing and novel therapies.

METHODS

Using data from high-grade serous ovarian carcinoma (HGSOC) patients in the Cancer Genome Atlas (TCGA), we classified those who remained progression-free for 12 months following platinum-taxane combination chemotherapy as "chemo-sensitive" (N = 160) and those who had recurrence within 6 months as "chemo-resistant" (N = 110). Univariate and multivariate analysis of expression microarray data were used to identify differentially expressed genes and co-expression gene networks associated with chemotherapy response. Moreover, we integrated genomics data to determine expression quantitative trait loci (eQTL).

RESULTS

Differential expression of the Valosin-containing protein (VCP) gene and five co-expression gene networks were significantly associated with chemotherapy response in HGSOC. VCP and the most significant co-expression network module contribute to protein processing in the endoplasmic reticulum, which has been implicated in chemotherapy response. Both univariate and multivariate analysis findings were successfully replicated in an independent ovarian cancer cohort. Furthermore, we identified 192 cis-eQTLs associated with the expression of network genes and 4 cis-eQTLs associated with BRCA2 expression.

CONCLUSION

This study implicates both known and novel genes as well as biological processes underlying response to platinum-taxane-based chemotherapy among HGSOC patients.

The ABO Blood Group is an Independent Prognostic Factor in Patients with Ovarian Cancer

Previous studies have suggested a relationship between ABO blood group and clinical outcome of various cancers. Nevertheless, little is known about the association between ABO blood group and survival in patients with ovarian carcinoma. This study aimed to investigate the prognostic significance of ABO blood group in patients with ovarian carcinoma. 941 patients who were newly diagnosed with ovarian carcinoma between February 2007 and February 2016 were enrolled in the present study. The relationship between ABO blood type and clinical features in patients with ovarian cancer was analyzed using chi-square tests. Overall survival (OS) stratified by B antigen was evaluated using log-rank test and Kaplan-Meier method. Presence of the B antigen (B/AB) had a worse OS than those in the absence of the B antigen (A/O) in all patients with ovarian cancer, especially in patients with FIGO stage I, IV, and menopause. Presence of the B antigen (B/AB) was significantly correlated with OS than those with non-B antigen (A/O) (hazard ratios 1.342; 95% confidence interval 1.069-1.685; P=0.011). Multivariate analyses revealed that presence of the B antigen (B/AB) was independently associated with OS (hazard ratios 1.532; 95% confidence interval 1.111-2.112; P=0.009). This study indicated that presence of the B antigen (B/AB) was an unfavorable prognostic factor in ovarian carcinoma, especially in patients with FIGO stage I, IV, and menopause.

AB0 Blood Group and Ovarian Cancer Survival

Background: Epithelial ovarian cancer is the most lethal gynecological malignancy because is usually diagnosed at advanced stage. New prognostic factors have been investigated but these biomarkers do not have a strong direct relationship with survival. Several studies investigated the association between AB0 blood group with ovarian cancer but with conflicting results. We investigated the association between AB0 blood group and epithelial ovarian cancer patients consecutively surgically treated at our department from 2004 to 2015.

Methods: Clinical charts of ovarian cancer patients treated and followed from 2004 to 2015 were checked for inclusion and exclusion criteria. Clinical and pathological data were recorded in an electronic separate, anonymous, password-protected database. All relevant data were extrapolated and used for final analysis.

Results: A population of 265 ovarian cancer patients was analyzed in this study. 121 (45.6%) patients presented blood type 0, 112 (42.3%) had blood type A, 23 (8.7%) B and 9 (3.4%) AB. A significantly lower percentage of death (8.7%) in patients with blood type B in comparison with patients presenting different genotypes (group 0: 34.7%, group A: 32.1%, group AB: 22.2%) was found. In invasive serous ovarian cancer patients the analysis showed a 5 fold significant reduction of the risk of death in patients with B genotype. However, postoperative residual tumor resulted the most important prognostic factor for overall survival.

Conclusions: AB0 blood group might be a preoperative prognostic factor in epithelial ovarian cancer patients. According to the literature, postoperative residual disease remain the most important prognostic factor also in our study.

Prognostic Impact of ABO Blood Group on the Survival in Patients with Ovarian Cancer

PURPOSE

The impact of ABO blood group on the survival of patients with ovarian cancer remains uncertain. The aim of this study was to evaluate the prognostic value of the ABO blood group in ovarian cancer patients.

METHODS

256 ovarian cancer patients who received a cytoreductive surgery were retrospectively reviewed. The prognostic impact of the ABO blood group with respect to overall survival (OS) was analyzed.

RESULTS

The median follow-up time was 57 months and the 5-year OS was 70.1%. The 5-year OS were 55.0%, 83.3%, 82.5%, and 70.0% in patients with A, B, AB, and O blood type, respectively (p = 0.003). Patients with blood type A had a poorer 5-year OS than patients with blood type non-A (55.0% vs. 75.0%, p = 0.001), especially in patients with age > 50 years (40.0% vs. 62.5%, p = 0.004). Univariate Cox analyses showed that blood type A was significantly associated with OS than those with non-A types (hazard ratio (HR) 2.210, 95% confidence interval (CI) 1.373-3.557, p = 0.001). Blood type A remained an independent prognostic factor for OS than those with non-A blood types in multivariate analyses (HR 2.235, 95% CI 1.360-3.674, p = 0.002).

CONCLUSION

ABO blood group is associated with survival in patients with ovarian cancer, patients with blood type A had a significantly worse OS than patients with non-A blood types, especially in patients with age > 50 years.

Effect of blood type on survival of Chinese patients with esophageal squamous cell carcinoma

BACKGROUND

The aim of this study was to evaluate the prognostic value of ABO blood group in Chinese patients with esophageal squamous cell carcinoma (ESCC) after esophagectomy.

METHODS

This study was a retrospective review of the records of 548 patients with ESCC who received cytoreductive surgery between October 2002 and March 2007. The prognostic impact of ABO blood group on overall survival (OS) was analyzed.

RESULTS

The median follow-up time was 37 months, and the 5-year OS was 43.3%. The overall 5-year OS was 41.2%, 49.7%, 44.0%, and 29.8% for the A, B, O, and AB groups, respectively (P=0.038). Among patients with negative lymph nodes (LNs), the 5-year OS was 59.0%, 68.2%, 57.9%, and 28.6% for the A, B, O, and AB groups, respectively (P<0.001), but blood type had no value in predicting the OS of patients with positive LNs (P=0.524). In multivariate Cox regression analysis of all patients, ABO blood group was not an independent prognostic factor of OS. However, in patients with negative LNs, blood type was an independent prognostic factor of OS, and the higher risk of death for patients of type AB versus non-AB significant in multivariate analyses (hazard ratio [HR], 2.576; 95% confidence interval [CI], 1.349-4.919; P=0.004).

CONCLUSION

ABO blood group is associated with survival in Chinese patients with ESCC. Patients with blood type AB had a significantly worse OS than patients with non-AB type, especially in patients with negative LNs.

Histotype-specific copy-number alterations in ovarian cancer

Background

Epithelial ovarian cancer is characterized by multiple genomic alterations; most are passenger alterations which do not confer tumor growth. Like many cancers, it is a heterogeneous disease and can be broadly categorized into 4 main histotypes of clear cell, endometrioid, mucinous, and serous. To date, histotype-specific copy number alterations have been difficult to elucidate. The difficulty lies in having sufficient sample size in each histotype for statistical analyses.

Methods

To dissect the heterogeneity of ovarian cancer and identify histotype-specific alterations, we used an in silico hypothesis-driven approach on multiple datasets of epithelial ovarian cancer.

Results

In concordance with previous studies on global copy number alterations landscape, the study showed similar alterations. However, when the landscape was de-convoluted into histotypes, distinct alterations were observed. We report here significant histotype-specific copy number alterations in ovarian cancer and showed that there is genomic diversity amongst the histotypes. 76 cancer genes were found to be significantly altered with several as potential copy number drivers, including ERBB2 in mucinous, and TPM3 in endometrioid histotypes. ERBB2 was found to have preferential alterations, where it was amplified in mucinous (28.6%) but deleted in serous tumors (15.1%). Validation of ERBB2 expression showed significant correlation with microarray data (p=0.007). There also appeared to be reciprocal relationship between KRAS mutation and copy number alterations. In mucinous tumors where KRAS mutation is common, the gene was not significantly altered. However, KRAS was significantly amplified in serous tumors where mutations are rare in high grade tumors.

Conclusions

The study demonstrates that the copy number landscape is specific to the histotypes and identification of these alterations can pave the way for targeted drug therapy specific to the histotypes.

Exploiting p70 S6 kinase as a target for ovarian cancer

INTRODUCTION

The p70 S6 kinase (p70(S6K)) is frequently active in ovarian and a wide range of cancer types, and it has a crucial role in several processes considered hallmarks of cancer. Therefore, blocking p70(S6K) expression or activity may present a promising strategy for anticancer treatment.

AREAS COVERED

The current understanding of the molecular mechanisms that govern p70(S6K) regulation as well as its tumorigenic effects, which are involved in the initiation and progression in ovarian cancer, in particular the emerging new role of p70(S6K) in cell migration, which is a prerequisite of tumor metastasis. The p70(S6K) cellular substrates and/or interacting proteins. The current state of drugs that target this kinase, either alone or in combination with other targeted agents.

EXPERT OPINION

Targeting p70(S6K) through the use of small-molecule inhibitors, microRNAs and natural compounds may represent a beneficial new avenue for cancer therapy and opens new areas of investigation in p70(S6K) biology.

Frequent inactivation of a putative tumor suppressor, angiopoietin-like protein 2, in ovarian cancer

Angiopoietin-like protein 2 (ANGPTL2) is a secreted protein belonging to the angiopoietin family, the members of which are implicated in various biological processes, although its receptor remains unknown. We identified a homozygous loss of ANGPTL2 (9q33.3) in the course of screening a panel of ovarian cancer (OC) cell lines for genomic copy-number aberrations using in-house array-based comparative genomic hybridization. ANGPTL2 mRNA expression was observed in normal ovarian tissue and immortalized normal ovarian epithelial cells, but was reduced in some OC lines without its homozygous deletion (18 of 23 lines) and restored after treatment with 5-aza 2'-deoxycytidine. The methylation status of sequences around the ANGPTL2 CpG-island with clear promoter activity inversely correlated with expression. ANGPTL2 methylation was frequently observed in primary OC tissues as well. In an immunohistochemical analysis of primary OCs, ANGPTL2 expression was frequently reduced (51 of 100 cases), and inversely correlated with methylation status. Patients with OC showing reduced ANGPTL2 immunoreactivity had significantly worse survival in the earlier stages (stages I and II), but better survival in advanced stages (stages III and IV). The restoration of ANGPTL2 expression or treatment with conditioned medium containing ANGPTL2 inhibited the growth of OC cells originally lacking the expression of this gene, whereas the knockdown of endogenous ANGPTL2 accelerated the growth of OC cells with the expression of ANGPTL2. These results suggest that, at least partly, epigenetic silencing by hypermethylation of the ANGPTL2 promoter leads to a loss of ANGPTL2 function, which may be a factor in the carcinogenesis of OC in a stage-dependent manner.

Bladder tumour-derived somatic TSC1 missense mutations cause loss of function via distinct mechanisms

More than 50% of transitional cell carcinomas of the bladder show loss of heterozygosity of a region spanning the TSC1 locus at 9q34 and mutations of TSC1 have been identified in 14.5% of tumours. These comprise nonsense mutations, splicing mutations, small deletions and missense mutations. Missense mutations are only rarely found in the germline in TSC disease. Therefore, we have examined six somatic missense mutations found in bladder cancer to determine whether these result in loss of function. We describe loss of function via distinct mechanisms. Five mutations caused mutually exclusive defects at mRNA and protein levels. Of these, two mutations caused pre-mRNA splicing errors that were predicted to result in premature protein truncation and three resulted in markedly reduced stability of exogenous TSC1 protein. Primary tumours with aberrant TSC1 pre-mRNA splicing were confirmed as negative for TSC1 expression by immunohistochemistry. Expression was also significantly reduced in a tumour with a TSC1 missense mutation resulting in diminished protein half-life. A single TSC1 missense mutation identified in a tumour with retained heterozygosity of the TSC1 region on chromosome 9 caused an apparently TSC2- and mTOR-independent localization defect of the mutant protein. We conclude that although TSC1 missense mutations do not play a major role in causation of TSC disease, they represent a significant proportion of somatic loss of function mutations in bladder cancer.

RRIG1 mediates effects of retinoic acid receptor beta2 on tumor cell growth and gene expression through binding to and inhibition of RhoA

The expression of retinoic acid receptor beta2 (RAR-beta2) is frequently lost in various cancers and their premalignant lesions. However, the restoration of RAR-beta2 expression inhibits tumor cell growth and suppresses cancer development. To understand the molecular mechanisms responsible for this RAR-beta2-mediated antitumor activity, we did restriction fragment differential display-PCR and cloned a novel retinoid receptor-induced gene 1 (RRIG1), which is differentially expressed in RAR-beta2-positive and RAR-beta2-negative tumor cells. RRIG1 cDNA contains 2,851 bp and encodes a protein with 276 amino acids; the gene is localized at chromosome 9q34. Expressed in a broad range of normal tissues, RRIG1 is also lost in various cancer specimens. RRIG1 mediates the effect of RAR-beta2 on cell growth and gene expression (e.g., extracellular signal-regulated kinase 1/2 and cyclooxygenase-2). The RRIG1 protein is expressed in the cell membrane and binds to and inhibits the activity of a small GTPase RhoA. Whereas induction of RRIG1 expression inhibits RhoA activation and f-actin formation and consequently reduces colony formation, invasion, and proliferation of esophageal cancer cells, antisense RRIG1 increases RhoA activity and f-actin formation and thus induces the colony formation, invasion, and proliferation of these cells. Our findings therefore show a novel molecular pathway involving RAR-beta2 regulation of RRIG1 expression and RRIG1-RhoA interaction. An understanding of this pathway may translate into better control of human cancer.

Cytogenetic analysis of carboplatin resistance in early-stage epithelial ovarian carcinoma

Ovarian carcinoma is the leading cause of death among women with gynecological malignancies in western Europe. The high mortality rate is largely due to drug resistance. It is thus essential to increase knowledge and understanding of the underlying mechanisms of chemotherapy resistance, which might be caused by changes in the tumor genome. After surgery, carboplatin is the standard treatment for patients with early-stage ovarian cancer. Using comparative genomic hybridization (CGH), we explored cytogenetic alterations in 63 early-stage epithelial ovarian tumors, comparing the aberration patterns in the carboplatin-resistant and carboplatin-sensitive tumors. Several chromosomal regions were more frequently altered in the resistant tumors; some of these differences were statistically significant. We also found differences in tumor histology. Gains of 1q, 5q14 approximately q23, and 13q21 approximately q32, and losses of 8p and 9q were associated with clinical carboplatin resistance. Also, differences were found between the primary resistant and the secondary resistant tumors. Our findings demonstrate biologic observations of clinical drug resistance and specifically reveal chromosomal regions of interest for platinum resistance.

Molecular cytogenetic analysis of gene rearrangements in childhood acute lymphoblastic leukemia

The aims of this study were to estimate the incidences of BCR/ABL, MLL, TEL/AML1 rearrangements, and p16 deletions in childhood acute lymphoblastic leukemia (ALL), to identify new abnormalities, and to demonstrate the usefulness of interphase fluorescence in situ hybridization (FISH). We performed G-banding analysis and FISH using probes for BCR/ABL, MLL, TEL/AML1 rearrangements, and p16 deletions on 65 childhood ALL patients diagnosed and uniformly treated at a single hospital. Gene rearrangements were identified in 73.8% of the patients using the combination of G-banding and FISH, while the chromosomal abnormalities were identified in 49.2% using G-banding alone. Gene rearrangements were disclosed by FISH in 24 (72.7%) of 33 patients with normal karyotype or no mitotic cell in G-banding. Among the gene rearrangements detected by FISH, the most common gene rearrangement was p16 deletion (20.3%) and the incidences of others were 14.1% for TEL/AML1, 11.3% for MLL, and 1.8% for BCR/ABL translocations. Infrequent or new aberrations such as AML1 amplification, MLL deletion, ABL deletion, and TEL/AML1 fusion with AML1 deletion were also observed. We established the rough incidences of gene rearrangements in childhood ALL, found new abnormalities and demonstrated the diagnostic capability of interphase FISH to identify cryptic chromosome aberrations.

The topoisomerase I- and p53-binding protein topors is differentially expressed in normal and malignant human tissues and may function as a tumor suppressor

Topors was identified recently as a human protein that binds to topoisomerase I and p53. Topors contains a highly conserved RING domain and localizes in promyelocytic leukemia nuclear bodies. Relatively little is known regarding topors expression patterns or function. We now demonstrate that topors mRNA and protein are widely expressed in normal human tissues. By contrast, topors mRNA and protein levels are decreased or undetectable in colon adenocarcinomas relative to normal colon tissue, and expression of the topors protein is not detectable in several colon cancer cell lines. The human TOPORS gene is located on chromosome 9p21, with loss of heterozygosity in this region frequently observed in several different malignancies. While we were unable to detect loss of heterozygosity of the TOPORS gene in 16 sporadic colon cancer cases, increased methylation of a CpG island in the TOPORS promoter was evident in colon adenocarcinoma specimens relative to matched normal tissues. Additional studies indicate that forced expression of topors inhibits cellular proliferation and is associated with an accumulation of cells in the G(0)/G(1) phase of the cell cycle. This effect is independent of the topors RING domain and maps to a C-terminal region of the protein. These results suggest that topors functions as a negative regulator of cell growth, and possibly as a tumor suppressor.

Quantitative PCR identifies a minimal deleted region of 120 kb extending from the Philadelphia chromosome ABL translocation breakpoint in chronic myeloid leukemia with poor outcome

Fluorescence in situ hybridization (FISH) analysis has shown previously that 10-15% of chronic myeloid leukemias (CML) have hemizygous deletions of variable sizes affecting regions that flank the ABL and BCR translocation breakpoints on the derivative chromosome 9, and these patients have a poor outcome. FISH studies using large commercial genomic probes have previously suggested that haploinsufficiency of sequences flanking either ABL or BCR modify the disease process of CML and lead to an unfavorable prognosis. In this present study, real-time quantitative PCR (Q-PCR) analysis was used to identify and map much smaller hemizygous microdeletions in a subset of CML patients that were not deleted using large genomic FISH probes. Microdeletions were identified by Q-PCR in 25 of 71 patients selected based on less favorable outcome (chronic phase duration of less than 96 months and a survival time of less than 84 months). In contrast, no microdeletion was detected in any of 18 CML samples selected from a group with a more favorable outcome. Detailed mapping of the 25 Q-PCR microdeletions showed that the minimal deleted region extended approximately 120 kb from the 5' end of the ABL gene in the centromeric direction on the derivative chromosome 9, and the region 3' to BCR on chromosome 22 was excluded. Of the four ESTs and/or genes that map to the 120 kb region, the putative tumor suppressor PRDM12 is the strongest candidate gene. The potential role for each sequence in modifying the clinical behavior of CML is presented.

Gonadoblastoma in a patient with del(9)(p22) and sex reversal: report of a case and review of the literature

Studies of distinct clinical prototypes have significantly contributed to our understanding of evolutionary abnormalities and their association with neoplasia. We describe a phenotypic female, aged 20 years at report, who was examined as an infant for developmental retardation. The clinical characteristics of the 9p- syndrome were present and the external genitalia were those of a normal female. The karyotype was 46XY,del(9)(p22). The parental karyotypes were normal. No SRY deletion or mutation was detected. Sonography showed the presence of a uterus. Basal luteinizing hormone values were normal; follicle stimulating hormone values were high (40 IU/L). Stimulation with human chorionic gonadotropin did not produce any rise in testosterone. The gonads were removed and histologic analysis disclosed dysgenetic gonads with gonadoblastoma in situ. This case constitutes the fourth case of gonadoblastoma developing in an individual with 9p- syndrome and sex reversal. This and analogous prototypes point to a locus (or loci) on the short arm of chromosome 9, which either constitutes a nonspecific suppressor gene or a gonadoblastoma suppressor gene. An alternative hypothesis would be that a gonad not normally differentiated is more prone to gonadoblastoma development without any specific gene involvement.

Cytogenetic alterations in ovarian clear cell carcinoma detected by comparative genomic hybridisation

Ovarian clear cell carcinoma (OCCC) accounts for a small but significant proportion of all ovarian cancers and is a distinct clinical and pathological entity. It tends to be associated with poorer response rates to chemotherapy and with a worse prognosis. Little is known about possible underlying genetic changes. DNA extracted from paraffin-embedded samples of 18 pure OCCC cases was analysed for genetic imbalances using comparative genomic hybridisation (CGH). All of the 18 cases showed genomic alterations. The mean number of alterations detected by CGH was 6 (range 1-15) indicating a moderate level of genetic instability. Chromosome deletions were more common than amplifications. The most prominent change involved chromosome 9 deletions in 10 cases (55%). This correlates with changes seen in other epithelial ovarian cancers. This deletion was confirmed using microsatellite markers to assess loss of heterozygosity (LOH) at four separate loci on chromosome 9. The most distinct region of loss detected was around the IFNA marker at 9p21 with 41% (11 out of 27 cases) LOH. Other frequent deletions involved 1p (five out of 18; 28%); 11q (four out of 18; 22%) and 16 (five out of 18; 28%). Amplification was most common at chromosome 3 (six out of 18; 33%); 13q (four out of 18; 22%) and 15 (three out of 18; 17%). No high-level amplifications were identified. These features may serve as useful prognostic indicators in the management of OCCC.

A novel polymorphism in the PTC gene allows easy identification of allelic loss in basal cell nevus syndrome lesions

Basal cell nevus syndrome (BCNS; also nevoid basal cell carcinoma syndrome [NBCCS]; Gorlin's syndrome) is an autosomal dominant syndrome characterized by multiple basal cell carcinomas, keratocysts, and developmental skeletal defects. Mutation of the human homologue of Drosophila patched (PTC) gene is considered to be the molecular defect in BCNS. PTC mutations have been observed in sporadic tumors including basal cell and ovarian carcinomas and medulloblastoma. The authors report a novel C/T polymorphism in the PTC gene. Forty-eight normal blood samples were screened for the presence of the polymorphism using direct radioactive and automated sequencing of polymerase chain reaction (PCR) products and restriction enzyme digestion. Results demonstrated 20 homozygous T (43%), 11 homozygous C (23%), and 17 heterozygous C/T (35%). The presence of this polymorphism has permitted us to directly detect allelic loss in BCNS, sporadic keratocysts, and basal cell carcinoma (BCC). Further, four BCNS keratocysts and two BCNS-BCC and three non-BCNS keratocysts showed allelic loss of complementary DNA from lesions when compared with their corresponding blood genomic DNA.

Inverse expression of Cdk4 and p16 in epithelial ovarian tumors

OBJECTIVES

The aim of this study was to elucidate the expression and the correlation of two cell cycle regulators, cdk4 and its inhibitor p16, in a series of benign, borderline, and malignant ovarian tumors and to evaluate whether their alterations correlate with clinicopathologial parameters and patients' prognosis in epithelial ovarian carcinomas.

METHODS

Immunohistochemical analysis using anti-cdk4 and anti-p16 antibodies was carried out for 103 paraffin sections of ovarian tumors, and Western blot analysis and cdk4 activity assay were performed in 26 fresh ovarian tumor samples.

RESULTS

The results of immunohistochemistry showed that 60.61 and 69.70% of benign, 69.57 and 56.52% of borderline, and 74.47 and 40. 43% of malignant tumors expressed cdk4 and p16, respectively, demonstrating increased cdk4 and decreased p16 expression in ovarian carcinomas. A significant inverse relationship between cdk4 and p16 expression was found. The loss of p16 expression was more correlated with G(2) and G(3) tumors in contrast with G(1) tumors. No significant correlation was observed between cdk4 expression and clinicopathological parameters. Neither cdk4 nor p16 expression has significant effects on overall survival by the Kaplan-Meier method. When the combined phenotypes of the two proteins were analyzed, patients with cdk4-positive/p16-negative expression had a reduced overall survival than other phenotypes of cdk4/p16.

CONCLUSIONS

These data suggest that inverse expression of cdk4 and p16 may be involved in the development and progression of epithelial ovarian carcinomas. The combined phenotypes of cdk4 and p16 proteins could provide a useful prognostic indicator for patients with epithelial ovarian carcinoma.

Amplification of 9q34 in childhood adrenocortical tumors: a specific feature unrelated to ethnic origin or living conditions

Adrenocortical tumors (ACT) in children under 15 years of age exhibit some clinical and biological features distinct from ACT in adults. Cell proliferation, hypertrophy and cell death in adrenal cortex during the last months of gestation and the immediate postnatal period seem to be critical for the origin of ACT in children. Studies with large numbers of patients with childhood ACT have indicated a median age at diagnosis of about 4 years. In our institution, the median age was 3 years and 5 months, while the median age for first signs and symptoms was 2 years and 5 months (N = 72). Using the comparative genomic hybridization technique, we have reported a high frequency of 9q34 amplification in adenomas and carcinomas. This finding has been confirmed more recently by investigators in England. The lower socioeconomic status, the distinctive ethnic groups and all the regional differences in Southern Brazil in relation to patients in England indicate that these differences are not important to determine 9q34 amplification. Candidate amplified genes mapped to this locus are currently being investigated and Southern blot results obtained so far have discarded amplification of the abl oncogene. Amplification of 9q34 has not been found to be related to tumor size, staging, or malignant histopathological features, nor does it seem to be responsible for the higher incidence of ACT observed in Southern Brazil, but could be related to an ACT from embryonic origin.

A sequence-ready 840-kb PAC contig spanning the candidate tumor suppressor locus DBC1 on human chromosome 9q32-q33

A putative tumor suppressor locus involved in bladder cancer has been mapped to human chromosome 9q32-q33 and designated DBC1. Our previous microsatellite-based deletion mapping study indicated that DBC1 was localized between D9S1848 and AFMA239XA9. We have constructed an 840-kb sequence-ready contig composed of bacteriophage P1-derived artificial chromosomes (PACs), which encompasses DBC1. Clones were initially identified by screening a PAC library with markers localized to the region by physical mapping, and subsequently PAC end probes were used to complete the contig. This contig contains a minimum tiling path of six PAC clones between D9S1848 and AFMA239XA9. Three expressed sequence tags (ESTs) were mapped to the DBC1 region by screening 24 ESTs mapped to the surrounding area by radiation hybrids. One represented the gene for DBCCR1, a known candidate for DBC1, and the other two were novel. This contig and preliminary expression map form the basis for the identification of the bladder cancer tumor suppressor gene in this region.

CDKN2A gene inactivation in epithelial sporadic ovarian cancer

The tumour suppressor gene CDKN2A, located on chromosome 9p21, encodes the cell cycle regulatory protein p16. Inactivation of the CDKN2A gene could lead to uncontrolled cell growth. In order to determine the role of CDKN2A in the development of sporadic ovarian cancer, loss of heterozygosity at 9p21-22, homozygous deletion, mutation and methylation status of the CDKN2A gene as well as CDKN2A expression were examined in a panel of serous papillary ovarian cancer. The frequency of loss of heterozygosity (LOH) for one or more informative markers at 9p21-22 was 65% (15/23). The most common deleted region was located between interferon (IFN)-alpha and D9S171. Homozygous deletions and mutations of the CDKN2A gene were not found. There was no evidence of methylation in exon 1, but methylation in exon 2 of CDKN2A gene was found in 26% (6/23). Absence of CDKN2A gene expression was shown in 27% (6/22) at mRNA level and 21% (4/19) at protein level. These data suggest that the CDKN2A gene is involved in the tumorigenesis of ovarian cancer, but the mechanisms of CDKN2A gene inactivation in serous papillary ovarian cancer remains unclear.

The patched/hedgehog/smoothened signalling pathway in human breast cancer: no evidence for H133Y SHH, PTCH and SMO mutations

The patched/hedgehog/smoothened signalling pathway has been implicated in the development of sporadic tumours associated with the naevoid basal cell carcinoma (Gorlin) syndrome (NBCCS). Mutations in sporadic basal cell carcinomas (BCCs) of the skin and medulloblastomas have been found in genes encoding all three proteins of the pathway. A substantial proportion of breast carcinomas has recently been suggested to contain missense mutations in the human patched (PTCH) and sonic hedgehog (SHH) homologues. However, an independent study showed that the implicated mutation in SHH (H133Y) was absent in a large number of BCCs, medulloblastomas, breast, ovary and colorectal tumours. We searched for the H133Y SHH mutation in 84 primary breast carcinomas, but did not detect this change in any sample. In addition, a subset of 45 primary breast tumours was analysed for mutations in the PTCH coding region and 48 samples in previously implicated exons of human smoothened, but no mutations were found. Although our results do not exclude the presence of clonal alterations of these genes in a small proportion of breast carcinomas, these data do not support the existence of frequent mutations in genes encoding major protein partners of this signalling pathway. The absence of nucleotide changes in PTCH may point to another linked gene in the chromosome region 9q22-q23, previously suggested to contain a breast cancer susceptibility gene.

Structure and methylation-based silencing of a gene (DBCCR1) within a candidate bladder cancer tumor suppressor region at 9q32-q33

Loss of heterozygosity (LOH) on chromosome 9q is the most frequent genetic alteration in transitional cell carcinoma (TCC) of the bladder, indicating the presence of one or more relevant tumor suppressor genes. We previously mapped one of these putative tumor suppressor loci to 9q32-q33 and localized the candidate region within a single YAC 840 kb in size. This locus has been designated DBC1 (for deleted in bladder cancer gene 1). We have identified a novel gene, DBCCR1, in this candidate region by searching for expressed sequence tags (ESTs) that map to YACs spanning the region. Database searching using the entire DBCCR1 cDNA sequence identified several human ESTs and a few homologous mouse. ESTs. However, the predicted 761-amino-acid sequence had no significant homology to known protein sequences. Mutation analysis of the coding region and Southern blot analysis detected neither somatic mutations nor gross genetic alterations in primary TCCs. Although DBCCR1 was expressed in multiple normal human tissues including urothelium, mRNA expression was absent in 5 of 10 (50%) bladder cancer cell lines. Methylation analysis of the CpG island at the 5' region of the gene and the induction of de novo expression by a demethylating agent indicated that this island might be a frequent target for hypermethylation and that hypermethylation-based silencing of the gene occurs in TCC. These findings make DBCCR1 a good candidate for DBC1.

No evidence exists for methylation inactivation of the p16 tumor suppressor gene in ovarian carcinogenesis

The p16ink4/CDKN2/MTS1 tumor suppressor gene encodes a cyclin-dependent kinase inhibitor which plays an important role in regulation of the G1/S phase cell cycle checkpoint. Loss of heterozygosity (LOH) at the p16 locus, 9p21, has been documented in a wide variety of tumors including ovarian carcinoma. However, inactivating mutations of the remaining allele and homozygous deletions are relatively infrequent events in primary tumors, even in cases where expression of p16 at the mRNA and protein level is clearly absent. These findings initially cast doubt on the role of p16 as a tumor suppressor gene in vivo. Recently, an alternative mechanism of p16 inactivation involving methylation of the CpG island in the 5' region of the gene has been demonstrated in a number of malignancies and cell lines. In this study we have analyzed the methylation status of four CpG dinucleotides in a panel of 23 ovarian tumors using a multiplex PCR approach to correlate our findings with the LOH data in this region. Using the microsatellite markers D9S171 and D9S1679 LOH was demonstrated in 4/22 (18%) informative cases. All 23 tumors showed no evidence of methylation at the p16 locus including the 4 tumors demonstrating LOH at 9p21. These results suggest that methylation inactivation of the p16 gene does not play an important role in ovarian carcinogenesis.

A novel candidate tumour suppressor locus at 9q32-33 in bladder cancer: localization of the candidate region within a single 840 kb YAC

Loss of heterozygosity (LOH) on chromosome 9q is the most frequent genetic alteration in transitional cell carcinoma (TCC) of the bladder, implicating the presence of a tumour suppressor gene or genes on 9q. To define the location of a tumour suppressor locus on 9q in TCC, we screened 156 TCCs of the bladder and upper urinary tract by detailed deletion mapping using 31 microsatellite markers on 9q. Partial deletions of 9q were found in 10 TCCs (6%), and LOH at all informative loci on 9q was found in 77 TCCs (49%). In five low grade superficial bladder tumours, the partial deletion was localized to D9S195 located at 9q32-33, with retention of heterozygosity at all other informative loci including D9S103, D9S258, D9S275 and GSN. We constructed a yeast artificial chromosome (YAC) contig covering the deleted region in these five tumours and placed another four unmapped microsatellite markers on this contig map. Using these markers, we further defined the common deleted region to the interval between D9S1848 and AFMA239XA9. The region is covered by a single YAC (852e11), whose size is estimated to be 840 kb. Our data should expedite further fine mapping and identification of the candidate tumour suppressor gene at 9q32-33.

Rare mutations and no hypermethylation at the CDKN2A locus in epithelial ovarian tumours

The tumour-suppressor gene CDKN2A (p16, MTS1, CDK4I) encodes a cell cycle-regulatory protein and is located on chromosome 9p21, a region deleted in a wide variety of human cancers. To determine the role of the CDKN2A gene in the development of ovarian adenocarcinomas, we examined a large series of benign, low malignant potential (LMP) and invasive ovarian neoplasms for evidence of loss of heterozygosity (LOH), homozygous deletions, point mutations and hypermethylation of the CDKN2A locus. We have previously reported LOH on 9p in 45% of malignant ovarian neoplasms and a smaller percentage of benign and LMP tumours. In the current study, 6 malignant tumours were identified with partial deletions of 9p21. In 5 of these, the CDKN2A gene lays within the minimal deleted region. Homozygous deletions of CDKN2A were observed in only 2/88 invasive ovarian tumours and in 5/11 ovarian cancer cell lines. Of 15 primary ovarian tumours analyzed, one nonsense mutation was identified in a mucinous LMP tumour. No evidence of hypermethylation of the CDKN2A gene was found in 50 primary ovarian adenocarcinomas nor in 3 ovarian cancer cell lines. In conclusion, homozygous deletions, mutations and the de novo methylation of 5' CpG island are not frequent modes of inactivation of the CDKN2A gene in ovarian cancer. The target of 9p LOH in ovarian adenocarcinomas is therefore unknown.

Absence of deletions but frequent loss of expression of p16INK4 in human ovarian tumours

The cyclin-dependent kinase inhibitor p16 gene (P16, MTS1, CDKN2) has been shown to be altered by deletion or point mutation in some human tumours and cancer cell lines, suggesting that it works as a tumour suppressor. We analysed p16 gene mutation and p16 protein expression in 42 primary ovarian carcinomas and in five human ovarian cancer cell lines. Polymerase chain reaction (PCR) amplifications of exons 1 and 2 of the gene showed no deletion or gross rearrangement in the p16 gene. The lack of deletion was further demonstrated by Southern blot analysis. Looking for point mutations, we used single-strand confirmation polymorphism (SSCP) analysis and, in half of the tumours, we sequenced both strands of exons 1 and 2. No mutations were detected. In 11 out of 42 patients (26%), however, we detected no protein expression by Western blot analysis, suggesting that decreased expression of p16 rather than deletion of the gene can occur in a significant percentage of human ovarian cancers. In the same experiment CDK4 protein was found homogeneously expressed in all the tumour specimens and in the five cell lines. The lack of expression of p16 was not due to hypermethylation of the gene assessed by digestion of genomic DNAs with a methylation sensitive enzyme, suggesting that other mechanisms, not yet identified, are involved in the decreased expression of the p16 gene in human ovarian tumours.