K-ras alterations in Danish ovarian tumour patients. From the Danish "Malova" Ovarian Cancer study

KRAS K104 modification affects the KRASG12D-GEF interaction and mediates cell growth and motility

Mutant RAS genes play an important role in regulating tumors through lysine residue 104 to impair GEF-induced nucleotide exchange, but the regulatory role of KRAS K104 modification on the KRAS^G12D mutant remains unclear. Therefore, we simulated the acetylation site on the KRAS^G12D three-dimensional protein structure, including KRAS^G12D, KRAS^G12D/K104A and KRAS^G12D/K104Q, and determined their trajectories and binding free energy with GEF. KRAS^G12D/K104Q induced structural changes in the α2- and α3-helices, promoted KRAS instability and hampered GEF binding (ΔΔG = 6.14 kJ/mol). We found decreased binding to the Raf1 RBD by KRAS^G12D/K104Q and reduced cell growth, invasion and migration. Based on whole-genome cDNA microarray analysis, KRAS^G12D/K104Q decreased expression of NPIPA2, DUSP1 and IL6 in lung and ovarian cancer cells. This study reports computational and experimental analyses of Lys104 of KRAS^G12D and GEF, and the findings provide a target for exploration for future treatment.

Somatic mutations in breast and serous ovarian cancer young patients: a systematic review and meta-analysis

OBJECTIVE

our aim was to evaluate whether somatic mutations in five genes were associated with an early age at presentation of breast cancer (BC) or serous ovarian cancer (SOC).

METHODS

COSMIC database was searched for the five most frequent somatic mutations in BC and SOC. A systematic review of PubMed was performed. Young age for BC and SOC patients was set at ≤ 35 and ≤ 40 years, respectively. Age groups were also classified in < 30 years and every 10 years thereafter.

RESULTS

twenty six (1,980 patients, 111 younger) and 16 studies (598, 41 younger), were analyzed for BC and SOC, respectively. In BC, PIK3CA wild type tumor was associated with early onset, not confirmed in binary regression with estrogen receptor (ER) status. In HER2-negative tumors, there was increased frequency of PIK3CA somatic mutation in older age groups; in ER-positive tumors, there was a trend towards an increased frequency of PIK3CA somatic mutation in older age groups. TP53 somatic mutation was described in 20% of tumors from both younger and older patients; PTEN, CDH1 and GATA3 somatic mutation was investigated only in 16 patients and PTEN mutation was detected in one of them. In SOC, TP53 somatic mutation was rather common, detected in more than 50% of tumors, however, more frequently in older patients.

CONCLUSION

frequency of somatic mutations in specific genes was not associated with early-onset breast cancer. Although very common in patients with serous ovarian cancer diagnosed at all ages, TP53 mutation was more frequently detected in older women.

The molecular background of mucinous carcinoma beyond MUC2

The increasing interest of the oncology community in tumour classification and prediction of outcome to targeted therapies has put emphasis on an improved identification of tumour types. Colorectal mucinous adenocarcinoma (MC) is a subtype that is characterized by the presence of abundant extracellular mucin that comprises at least 50% of the tumour volume and is found in 10–15% of colorectal cancer patients. MC development is poorly understood, however, the distinct clinical and pathological presentation of MC suggests a deviant development and molecular background. In this review we identify common molecular and genetic alterations in colorectal MC. MC is characterized by a high rate of MUC2 expression. Mutation rates in the therapeutically important RAS/RAF/MAPK and PI3K/AKT pathways are significantly higher in MC compared with non‐mucinous adenocarcinoma. Furthermore, mucinous adenocarcinoma shows higher rates of microsatellite instability and is more frequently of the CpG island methylator phenotype. Although the majority of MCs arise from the large intestine, this subtype also develops in other organs, such as the stomach, pancreas, biliary tract, ovary, breast and lung. We compared findings from colorectal MC with tumour characteristics of MCs from other organs. In these organs, MCs show different mutation rates in the RAS/RAF/MAPK and PI3K/AKT pathways as well, but a common mucinous pathway cannot be identified. Identification of conditions and molecular aberrations that are associated with MC generates insight into the aetiology of this subtype and improves understanding of resistance to therapies.

Morphological and molecular basis of ovarian serous carcinoma

Serous carcinoma is the most common type of epithelial ovarian cancer. In this review, we provide a comprehensive picture of ovarian serous cancers from multiple aspects: the first part of this review summarizes the morphological, histological, and immunological signatures of ovarian serous carcinoma; subsequently, we review the history of the evolvement of different grading systems used in ovarian serous cancer; in the end, we focus on characterizing the genetics that underlie the 2-tiered pathways through which ovarian serous cancers are believed to arise: the low-grade and the high-grade pathways.

Low-dose mithramycin exerts its anticancer effect via the p53 signaling pathway and synergizes with nutlin-3 in gynecologic cancers

MDM2 is a direct negative regulator of p53. The p53-independent mdm2-P1 and p53-dependent mdm2-P2 promoters have been recently shown to harbor Sp1 binding sites. Mithramycin, an inhibitor of Sp1 DNA binding, has been used clinically to treat hypercalcemia and some types of neoplastic disorders. In this study, we investigated the mechanisms behind the anticancer effect of mithramycin. In gynecologic cancer cells expressing wild-type p53, mithramycin stabilized p53 and increased the expression of the p53 downstream target genes PUMA and p21, arrested the cell cycle, and induced apoptosis. This activation of the p53 signaling pathway was a specific effect of MTH at concentrations <50 nm. Mithramycin temporally decreased transcription of both the mdm2-P1 and -P2 promoters. This was followed by a subsequent increase of mdm2-P2 promoter activity by activated p53. Up-regulated MDM2 was in its active form, and consequently attenuated p53 activity. Although mithramycin activated p53 and suppressed the growth of human gynecologic cancer cell xenografts in mice, this was accompanied with a secondary up-regulation of MDM2. Combined treatment with mithramycin and nutlin-3, a drug that inhibits MDM2-p53 interaction, overcame a secondary up-regulation of MDM2 and synergistically inhibited cancer cell growth by inducing apoptosis through activation of the p53 signaling pathway. These observations provide a better understanding of the mechanisms of mithramycin activity, and suggest a potential role for combining mithramycin and nutlin-3 as a chemotherapeutic treatment for gynecologic cancers.

Tagging single-nucleotide polymorphisms in candidate oncogenes and susceptibility to ovarian cancer

Low-moderate risk alleles that are relatively common in the population may explain a significant proportion of the excess familial risk of ovarian cancer (OC) not attributed to highly penetrant genes. In this study, we evaluated the risks of OC associated with common germline variants in five oncogenes (BRAF, ERBB2, KRAS, NMI and PIK3CA) known to be involved in OC development. Thirty-four tagging SNPs in these genes were genotyped in approximately 1800 invasive OC cases and 3000 controls from population-based studies in Denmark, the United Kingdom and the United States. We found no evidence of disease association for SNPs in BRAF, KRAS, ERBB2 and PIK3CA when OC was considered as a single disease phenotype; but after stratification by histological subtype, we found borderline evidence of association for SNPs in KRAS and BRAF with mucinous OC and in ERBB2 and PIK3CA with endometrioid OC. For NMI, we identified a SNP (rs11683487) that was associated with a decreased risk of OC (unadjusted P(dominant)=0.004). We then genotyped rs11683487 in another 1097 cases and 1792 controls from an additional three case-control studies from the United States. The combined odds ratio was 0.89 (95% confidence interval (CI): 0.80-0.99) and remained statistically significant (P(dominant)=0.032). We also identified two haplotypes in ERBB2 associated with an increased OC risk (P(global)=0.034) and a haplotype in BRAF that had a protective effect (P(global)=0.005). In conclusion, these data provide borderline evidence of association for common allelic variation in the NMI with risk of epithelial OC.

Preoperative serum tetranectin, CA125 and menopausal status used as single markers in screening and in a risk assessment index (RAI) in discriminating between benign and malignant ovarian tumors

OBJECTIVES

To improve the poor survival in ovarian cancer (OC) patients, the research has been focused on new OC markers. One aim is to find markers to identify the cancers in early preclinical stages by screening. Another aim is to find new diagnostic markers, which may select patients at high risk for OC for quick referral to highly specialized centers in gynecologic oncology. These aims were addressed in the present study by evaluating serum tetranectin (TN) and serum CA125 on a large number of pre- and postmenopausal women with ovarian tumors and controls.

METHODS

The potential ability of the markers to discriminate between the four groups (208 benign ovarian tumor, 153 borderline ovarian tumor (BOT), 445 OC and 1333 age matched controls) in OC screening was examined. We also constructed a risk assessment index (RAI) for discrimination between tumor groups based on these variables and menopausal status.

RESULTS

Highly significant differences in both TN and CA125 levels were found between all the four groups as well as between the different FIGO stages of OC patients. A very high probability of having OC or a benign tumor, respectively, was predicted by the RAI.

CONCLUSIONS

In the case-control part of the study, we found that TN and CA125 deserve to be validated on pre-clinical samples by inclusion in future marker panels. The RAI is also a potential new candidate for a diagnostic tool for selecting patients at high risk for having OC; hence it deserves further evaluation in a prospective clinical study.

Pathogenesis of ovarian cancer: lessons from morphology and molecular biology and their clinical implications

The accepted view of ovarian carcinogenesis is that carcinoma begins in the ovary, undergoes progressive "dedifferentiation" from a well to a poorly differentiated tumor, and then spreads to the pelvic and abdominal cavities before metastasizing to distant sites. It has therefore been reasoned that survival for this highly lethal disease could be improved by developing screening methods that detect disease when it is confined to the ovary. To date, however, no prospective randomized trial of any ovarian cancer screening test(s) has demonstrated a decrease in mortality. We believe that one of the main reasons for this is that the dogma underlying ovarian carcinogenesis is flawed. Based on studies performed in our laboratory during the last decade, we have proposed a model of ovarian carcinogenesis that takes into account the diverse nature of ovarian cancer and correlates the clinical, pathological, and molecular features of the disease. In this model, ovarian tumors are divided into 2 groups designated type I and type II. Type I tumors are slow growing, generally confined to the ovary at diagnosis, and develop from well-established precursor lesions that are termed "borderline" tumors. Type I tumors include low-grade micropapillary serous carcinoma, mucinous, endometrioid, and clear cell carcinomas. They are genetically stable and are characterized by mutations in a number of different genes including KRAS, BRAF, PTEN, and beta-catenin. Type II tumors are rapidly growing highly aggressive neoplasms for which well-defined precursor lesions have not been described. Type II tumors include high-grade serous carcinoma, malignant mixed mesodermal tumors (carcinosarcomas), and undifferentiated carcinomas. This group of tumors has a high level of genetic instability and is characterized by mutation of TP53. The model helps to explain why current screening techniques, aimed at detecting stage I disease, have not been effective. Tumors that remain confined to the ovary for a long period belong to the type I group, but they account for only 25% of the malignant tumors. Most of what is considered ovarian cancer belongs to the type II category, and these are only rarely confined to the ovary. Although the reasons for this are not entirely clear, possible explanations include rapid spread from the ovary early in carcinogenesis and development of carcinoma in extra ovarian sites, notably, the peritoneum and fallopian tube, with secondary involvement of the ovary. The latter tumors are advanced stage at their inception. Therefore, a more realistic end point for the early detection of ovarian cancer is volume and not stage of disease. The model does not replace the histopathologic classification but, by drawing attention to the molecular genetic events that play a role in tumor progression, sheds light on new approaches to early detection and treatment.

Early detection and treatment of ovarian cancer: shifting from early stage to minimal volume of disease based on a new model of carcinogenesis

The goal of ovarian cancer screening is to detect disease when confined to the ovary (stage I) and thereby prolong survival. We believe this is an elusive goal because most ovarian cancer, at its earliest recognizable stage, is probably not confined to the ovary. We propose a new model of ovarian carcinogenesis based on clinical, pathological, and molecular genetic studies that may enable more targeted screening and therapeutic intervention to be developed. The model divides ovarian cancer into 2 groups designated type I and type II. Type I tumors are slow growing, generally confined to the ovary at diagnosis and develop from well-established precursor lesions so-called borderline tumors. Type I tumors include low-grade micropapillary serous carcinoma, mucinous, endometrioid, and clear cell carcinomas. They are genetically stable and are characterized by mutations in a number of different genes including KRAS, BRAF, PTEN, and beta-catenin. Type II tumors are rapidly growing, highly aggressive neoplasms that lack well-defined precursor lesions; most are advanced stage at, or soon after, their inception. These include high-grade serous carcinoma, malignant mixed mesodermal tumors (carcinosarcomas), and undifferentiated carcinomas. The type II tumors are characterized by mutation of TP53 and a high level of genetic instability. Screening tests that focus on stage I disease may detect low-grade type I neoplasms but miss the more aggressive type II tumors, which account for most ovarian cancers. A more rational approach to early detection of ovarian cancer should focus on low volume rather than low stage of disease.

An inhibitory effect on cell proliferation by blockage of the MAPK/estrogen receptor/MDM2 signal pathway in gynecologic cancer

OBJECTIVE

We previously demonstrated that that the Ras/ER/MDM2 pathway was critical for NIH3T3 cell transformation. In this study, we examined the effect of blocking this pathway on cell growth in gynecologic cancer cells.

METHODS

(1) The levels of MDM2, ER, p53 and p21 in endometrial or ovarian cancer cell lines were investigated and compared with that in normal cells by Western blots. (2) The effects of MEK-inhibitor and/or anti-estrogen, and siRNA of MDM2 on cell growth, tumorigenicity in nude mice were examined.

RESULTS

The MDM2 level was enhanced in cancer cells compared with normal cells. Treatment with MEK inhibitor(U0126) resulted in a reduced MDM2 level, enhanced p53 and p21 levels and inhibited cell growth by the induction of premature senescence. The effect of MEK inhibitor on cell growth was affected by ER levels and functions. Treatment with low-dose MEK inhibitor in combination with anti-estrogen (ICI182,780) had a more inhibitory effect on cell growth compared to treatment with MEK inhibitor or anti-estrogen alone in cancer cells. Down-regulation of the MDM2 level by siRNA resulted in the inhibition of growth in cancer cells.

CONCLUSION

The blockage of the MAPK/ER/MDM2 pathway suppress cell proliferation and it is supposed as a new molecular target therapy in estrogen-dependent gynecologic cancers, such as endometrial or ovarian cancer.

Histologic types of epithelial ovarian cancer: have they different risk factors?

OBJECTIVES

The histologic types of epithelial ovarian cancer differ in clinical behavior, descriptive epidemiology, and genetic origins. The goals of the current study were to characterize further the relation of histologic-specific ovarian cancer risks to reproductive and lifestyle attributes.

METHODS

The authors conducted a pooled analysis of 10 case-control studies of ovarian cancer in US White women, involving 1834 patients with invasive epithelial ovarian cancer (1067 serous, 254 mucinous, 373 endometrioid, and 140 clear cell) and 7484 control women.

RESULTS

Risks of all four histological types were inversely associated with parity and oral contraceptive use, but the histologic types showed different associations with nonreproductive factors. Unique associations include an inverse relation of serous cancer risk to body mass index, a positive relation of mucinous cancer risk to cigarette smoking, and a weakly positive relation of endometrioid cancer risk to body mass index. Risk of all histologic types was unassociated with age at menarche, age at menopause, a history of infertility, noncontraceptive estrogen use, and alcohol consumption.

CONCLUSIONS

The most important modifiers of ovarian cancer risk (parity and oral contraceptive use) showed similar associations across the histologies. Nevertheless, the unique associations seen for other modifiers support the conjecture that the histologic types of epithelial ovarian cancer have different etiologies, which should be addressed in future investigations of the molecular basis of ovarian cancers and their responses to therapies.

Role of K-ras and Pten in the development of mouse models of endometriosis and endometrioid ovarian cancer

Epithelial ovarian tumors present a complex clinical, diagnostic and therapeutic challenge because of the difficulty of early detection, lack of known precursor lesions and high mortality rates. Endometrioid ovarian carcinomas are frequently associated with endometriosis, but the mechanism for this association remains unknown. Here we present the first genetic models of peritoneal endometriosis and endometrioid ovarian adenocarcinoma in mice, both based on the activation of an oncogenic K-ras allele. In addition, we find that expression of oncogenic K-ras or conditional Pten deletion within the ovarian surface epithelium gives rise to preneoplastic ovarian lesions with an endometrioid glandular morphology. Furthermore, the combination of the two mutations in the ovary leads to the induction of invasive and widely metastatic endometrioid ovarian adenocarcinomas with complete penetrance and a disease latency of only 7 weeks. The ovarian cancer model described in this study recapitulates the specific tumor histomorphology and metastatic potential of the human disease.

Expression status and mutational analysis of the ras and B-raf genes in ovarian granulosa cell and epithelial tumors

OBJECTIVES

The molecular pathogenesis of granulosa cell tumors of the ovary (GCT) is not understood. Activating mutations in the K-, N-, and H-ras protooncogenes have been identified in a wide range of human cancers, including ovarian epithelial tumors. Furthermore, an apparent association has recently been reported between the presence of ras and B-raf mutations in the same cancer types. Activation of the ras/raf pathway would be predicted to be tumorigenic in granulosa cells.

METHODS

Gene expression patterns of the three ras and B-raf genes were determined in a panel of GCT and ovarian epithelial tumors, and in normal premenopausal ovaries. Expression was determined by RT-PCR using gene-specific primers combined with Southern blot analysis of the PCR products using gene-specific (32)P-labeled probes. Direct sequence analysis was used to screen for known activating mutations.

RESULTS

Widespread expression of the four genes was observed in all tumor types examined. Compared to the normal ovaries, none of the genes was expressed at significantly higher levels in any of the tumor types examined. A heterozygous point mutation in codon 12 of the K-ras gene was found in five of the 10 mucinous tumors. No B-raf mutations were detected in the mucinous tumors. No mutations were detected in any of the genes in the cohort of GCT.

CONCLUSION

These results suggest that neither overexpression nor activating mutations of the ras or B-raf genes are associated with the development of GCT.

Loss of heterozygosity on the X chromosome is an independent prognostic factor in ovarian carcinoma

BACKGROUND

Ovarian carcinoma (OC) is the fifth most frequent female cancer type and the fourth most frequent cause of death from cancer among women in Denmark. At the time they are diagnosed with OC, approximately 70% of patients have advanced disease. It is believed that loss of tumor suppressor gene activity plays an important role in the origin and progression of OC and other malignancies. Loss of heterozygosity (LOH) may be detected in individuals heterozygous for an allele and is associated with loss of function of tumor suppressor genes.

METHODS

The polymorphic marker regions (TP53, CACNLB1, D18S58, DXS538, and DXS454) were amplified by polymerase chain reaction followed by separation using gel electrophoresis before LOH was identified. In total, 160 women with primary epithelial OC were included in the study.

RESULTS

Univariate analyses showed significant differences in survival between patients who had advanced OC with LOH or with retention using the microsatellite markers DXS454 (P = 0.04) and DXS538 (P = 0.01). Multivariate Cox regression analysis that included all patients showed that DXS454 (relative hazard [RH] = 3.5; P = 0.002; 95% confidence interval [95% CI], 1.6-7.8), radicality of primary surgery (RH = 5.5; P < 0.0001; 95% CI, 2.7-11.1), and serum tetranectin level (RH = 0.8; P = 0.009; 95% CI, 0.7-0.9) were independent prognostic factors for survival. Multivariate Cox regression analysis restricted to patients with International Federation of Obstetrics and Gynecology Stage III-IV disease showed that DXS454 (RH = 3.4; P = 0.007; 95% CI, 1.4-8.1), radicality of primary surgery (RH = 5.4; P < 0.0001; 95% CI, 2.2-12.9), and serum tetranectin level (RH = 0.8; P = 0.042; 95% CI, 0.7-1.0) were independent prognostic factors.

CONCLUSIONS

LOH at DXS454 (Xq21-q23) appeared to be correlated with reduced survival in patients with OC.