Effect of a c-Met-specific, ATP-competitive small-molecule inhibitor SU11274 on human ovarian carcinoma cell growth, motility, and invasion.

Increased expression of the receptor tyrosine kinase c-Met has been shown to correlate with enhanced cell proliferation, motility, and invasion. The objectives of this study were to characterize total and activated c-Met expression in both normal and malignant human ovarian epithelial cells and to determine the effects of inhibiting the activation of c-Met on ovarian epithelial cell growth, motility, and invasion. Total c-Met was overexpressed in 82 (68%) of 119 ovarian carcinomas, as shown by immunohistochemistry. Quantitative reverse transcription-polymerase chain reaction and Western blot analyses revealed that ovarian carcinoma cell lines had higher levels of c-Met messenger RNA, total protein, and activated protein expression compared to normal ovarian epithelial cell cultures. Using a specific adenosine triphosphate-competitive small-molecule inhibitor, SU11274, activated c-Met was decreased in normal and ovarian carcinoma cell lines. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays showed that cell growth inhibition directly correlated to the level of activated c-Met detected in each cell line (r =-0.87, P = 0.012). Using modified Boyden chamber assays, ovarian carcinoma cells treated with SU11274 demonstrated significantly decreased cell motility and invasion compared to untreated cells (P = 0.003 and P < 0.001, respectively). These data indicate that c-Met is overexpressed in the majority of malignant ovarian epithelial cells both in vivo and in vitro and that decreasing activated c-Met in vitro can significantly decrease ovarian carcinoma cell growth, motility, and invasion. Developing therapies that specifically inhibit the activation of c-Met may represent a novel therapeutic modality for patients with ovarian carcinomas expressing high levels of c-Met.

Determinants of ovarian cancer risk. II. Inferences regarding pathogenesis.

Entrapment of surface epithelium within the ovarian stroma was proposed as an initial event in the pathogenesis of cystadenocarcinoma of the ovary. Subsequent events, including differentiation, proliferation, and eventual malignant transformation of the entrapped epithelium, may occur as a consequence of stimulation by estrogen or estrogen precursors. These events were more likely when the steroid producing stroma itself had been stimulated by high gonadotropins. Animal experiments suggested that gonadotropin excess and stromal stimulation may result by disturbing normal feedback inhibition between ovary and pituitary or by destroying ovarian follicles. By analogy, in humans, a number of common chemicals and drugs may increase gonadotropins by enhancing estrogen degradation in the liver or by directly stimulating production by the pituitary. Elevated gonadotropins may also result via mechanisms that cause primary ovarian failure including pelvic irradiation, exposure to chemicals or metabolites toxic to follicles, or ovarian infections such as mumps.

Determinants of ovarian cancer risk. I. Reproductive experiences and family history.

Reproductive experiences and family history were assessed in 215 white females with epithelial ovarian cancer and in 215 control women matched by age, race, and residence. Pregnancy exerted a strong protective effect against ovarian cancer, which increased with the number of live-born children. After adjustment for parity, an effect of age at first live birth and breast-feeding was not apparent. Menstrual events did not differ significantly between cases and controls, although cases were more likely to have had an earlier menopause and less likely to have had a surgical menopause. Women with ovarian cancer had more frequently used menopausal hormones in cyclic fashion compared to controls. Regarding family history, women with ovarian cancer more frequently reported consanguinity in their ancestry and a highly frequency of primary relatives with cancer of the colon, lung, ovary, and prostate gland.

Molecular evidence for multifocal papillary serous carcinoma of the peritoneum in patients with germline BRCA1 mutations.

BACKGROUND: Papillary serous carcinoma of the peritoneum (PSCP) diffusely involves peritoneal surfaces, while it spares or only superficially involves the ovaries. PSCP is histologically indistinguishable from serous epithelial ovarian carcinoma, and it may develop years after oophorectomy. The molecular pathogenesis of PSCP remains unresolved, although preliminary data suggest a multifocal origin in some cases. Patients with germline BRCA1 mutations may develop PSCP in addition to breast and ovarian carcinomas. The purpose of this study was to utilize the androgen receptor (AR) gene locus to test the hypothesis that some cases of PSCP have a multifocal origin and to determine if patients with germline BRCA1 mutations develop multifocal PSCP. METHODS: Specimens of normal and tumor tissues from 22 women with PSCP were obtained, and DNA was extracted. The AR gene locus was evaluated for patterns of loss of heterozygosity (LOH) and X-chromosome inactivation. The methylation-sensitive Hpa II restriction enzyme was used to differentiate the active and inactive X chromosomes. Germline BRCA1 mutation status of the patients was determined previously. RESULTS: Genetic analysis of tumor specimens indicated that five (23%) of 22 case subjects had patterns of selective LOH at the AR locus, consistent with multifocal, polyclonal disease origin. Two patients with selective LOH also had alternating X-chromosome inactivation patterns. Patients with germline BRCA1 mutations were more likely to have evidence of multifocal disease (two-sided Fisher's exact test, P = .01). CONCLUSIONS: Our results show that PSCP has a multifocal origin in at least some cases. Furthermore, patients with germline BRCA1 mutations are more likely to develop multifocal PSCP than are patients without BRCA1 mutations.

Detailed deletion mapping of chromosome 6q in borderline epithelial ovarian tumors.

We have used PCR amplification of tandem repeats and Southern blot analysis to study the pattern of allelic loss at chromosome 6q in borderline ovarian tumors and compared that with invasive ovarian carcinomas. DNA from 46 borderline ovarian tissues, 20 invasive ovarian tumor tissues, together with corresponding uninvolved (control) tissues was used. The invasive tumors demonstrated the highest percentage of loss of heterozygosity (13 of 45 informative cases, 29%) at the 6q25-27 locus site. In contrast, the borderline ovarian tumors showed only an 11% frequency of loss of heterozygosity (3 of 26). Our results display a sharp contrast in the pattern of loss of heterozygosity between invasive and borderline ovarian tumors and suggest that allelic loss at chromosome 6q may not be involved in the development of borderline ovarian tumors.

A novel 4-cM minimally deleted region on chromosome 11p15.1 associated with high grade nonmucinous epithelial ovarian carcinomas.

Prior cytogenetic and restriction fragment length polymorphism studies have demonstrated that allelic deletion of chromosome 11p is common in human invasive epithelial ovarian tumors. To construct a highly detailed deletion map of chromosome 11p, we used 13 polymorphic microsatellite CA repeat primers to identify regions harboring potential tumor suppressor genes. Twenty-three of 48 samples (48%) of invasive epithelial ovarian cancer showed LOH involving at least one locus, consistent with prior studies. None of the five mucinous tumors showed allelic deletion at any of the 13 primers, suggesting that loss of heterozygosity at chromosome 11p may not be involved in the pathogenesis of mucinous ovarian cancer. Two separate minimally deleted regions were identified in nonmucinous ovarian cancer. The first is an 11-cM region on chromosome 11pl5.5-15.3 that extends from D11S2071 to D11S988 and includes the HRAS locus. The second is a novel 4-cM region on 11p15.1, defined by marker D11S1310. Deletion of both regions at 11p15.5-15.3 and 11p15.1 is strongly associated with high grade nonmucinous epithelial ovarian cancer.

Evidence for the multifocal origin of bilateral and advanced human serous borderline ovarian tumors.

Borderline ovarian tumors (BOTs), or ovarian tumors of low malignant potential, represent a distinct category of epithelial ovarian neoplasms that have a clinically more favorable outcome than invasive epithelial ovarian cancer. Histologically, BOTs and invasive ovarian carcinomas both show cellular proliferation and pleomorphism, but unlike invasive ovarian carcinomas, BOTs lack stromal invasion. Although serous BOTs are frequently confined to a single ovary at the time of diagnosis, bilateral or extra-ovarian spread occurs in 30-40% of cases. The purpose of this study is to determine whether bilateral or extraovarian serous borderline lesions are metastatic sites from the original tumor, or represent separate primary tumors. DNA specimens from multiple tumor sites and normal tissue controls were obtained in eight women with bilateral or extra-ovarian serous borderline tumors. The pattern of loss of heterozygosity at the androgen receptor locus on the X chromosome was evaluated in the multiple tumor sites. In addition, the pattern of X-chromosome inactivation was determined using HpaII restriction endonuclease digestion, followed by PCR amplification of the androgen receptor locus. Multifocality was determined when alternate patterns of X-chromosome inactivation occurred. In two of the eight patients, the left and right ovarian tumor sites had different androgen receptor alleles inactivated, indicating that the bilateral tumors derived independently. In a third patient, the X inactivation pattern in the left ovarian tumor differed from the two peritoneal implants, suggesting that the implants were separate primary tumors, and not metastatic, from the left ovarian tumor. The remaining five patients had the same pattern of loss of heterozygosity and X inactivation in the tumor sites studied. These results suggest that bilateral and advanced stage serous BOTs may be multifocal in origin. This result is in contrast to invasive epithelial ovarian cancer, which has been shown to be unifocal in origin.

Mutation of K-ras protooncogene in human ovarian epithelial tumors of borderline malignancy.

The mutation of K-ras protooncogene was examined in 44 cases of borderline ovarian epithelial tumors and 18 cases of invasive ovarian carcinomas. In borderline tumors, K-ras mutations are a common feature, having been found in 21 of 44 cases (48%). Twenty of the 21 mutations were identified at codon 12, and one was identified at codon 13. A detailed analysis of the mutation pattern of K-ras revealed a close association with the histological cell types of the tumor. Mutation of K-ras was detected at a higher frequency in mucinous borderline tumor (identified in 12 of 19 cases) compared to serous borderline tumor (identified in 9 of 25 cases). K-ras mutation was also detected in invasive mucinous and serous ovarian carcinomas, hence supporting the notion that borderline ovarian tumors may represent a pathological continuum between benign and frankly invasive diseases.

BRCA1-related papillary serous carcinoma of the peritoneum has a unique molecular pathogenesis.

Papillary serous carcinoma of the peritoneum (PSCP) is believed to develop de novo from the peritoneal lining of the pelvis and abdomen. Although it is histologically indistinguishable from serous ovarian carcinoma, PSCP exhibits minimal or absent ovarian involvement and may even develop in a woman years after prophylactic oophorectomy. We have shown previously that patients with germ-line BRCA1 mutations who develop PSCP are more likely to have disease originating from multiple peritoneal sites compared with patients with wild-type BRCA1. In this study, we tested the hypothesis that BRCA1-related PSCP has a unique molecular pathogenesis. DNA was extracted from normal tissue and multiple tumor sites in patients with PSCP. BRCA1 and p53 gene mutations were screened for using single-strand conformation polymorphism. Loss of heterozygosity was determined at the BRCA1 and p53 loci. Immunohistochemical analyses of p53, epidermal growth factor receptor, erbB-2, erbB-3, erbB-4, and Bcl-2 expression were performed. We detected germ-line BRCA1 mutations in 11 (26%) of 43 PSCP patients. BRCA1 mutation carriers had a higher overall incidence of p53 mutations (89% versus 47%; P = 0.052), were more likely to exhibit multifocal or null p53 mutations (63% versus 7%; P = 0.014), and were less likely to exhibit erbB-2 overexpression (P = 0.013) than wild-type BRCA1 case subjects. We propose that the unique molecular pathogenesis of BRCA1-related PSCP may affect the ability of current methods to reliably prevent or detect this disease prior to metastasis.

Frequent microsatellite instability in epithelial borderline ovarian tumors.

To further define the genetic events that could lead to the development of borderline ovarian tumors (BOTs), we analyzed 13 microsatellite markers on chromosomes 3p and q in 18 BOTs and compared the results to 31 serous invasive epithelia] ovarian cancers (IEOCs). Five of the 18 BOTs showed microsatellite instability (MSI) at one or more loci, compared to only 2 of the 31 IEOCs studied (P < 0.04). In two of these five BOTs, MSI was found in multiple loci. All BOTs with MSI were serous, while none of the mucinous type showed any alteration. Loss of heterozygosity was found in only 1 of the 18 BOTs, but in 12 of the 31 IEOCs (P < 0.01). This first report of a relatively high percentage of MSI in BOTs opens a wide spectrum of new hypotheses for borderline ovarian tumorigenesis as well as several new research avenues.

Evidence for a multifocal origin of papillary serous carcinoma of the peritoneum.

Histopathological evidence suggests that papillary serous carcinoma of the peritoneum (PSCP) may be multifocal in origin. Utilizing a PCR based method to detect tandem repeat polymorphisms in formalin fixed tissue, loss of heterozygosity at eight loci on chromosomes 1, 3, 4, and 17 was studied in six cases of PSCP. Loss of heterozygosity was assessed at between 5 and 11 tumor sites/patient. Allelic losses at 4 loci (1q32-qter, 3p14.3-21.1, 17q12, 17q21.3-23) were noted. Three cases demonstrated a different pattern of allelic loss at various anatomic sites within the same patient. In an additional case, a mutation of the p53 gene, detected by quantitative PCR followed by single-strand conformation polymorphism analysis, was detected in only 2 of 5 tumor sites. The pattern of allelic loss and the mutational pattern of the p53 gene varied at tumor sites within the same patient in 4 of 6 cases of PSCP. These findings are consistent with histopathological evidence that PSCP is multifocal in origin.

A novel 4 cM minimal deletion unit on chromosome 6q25.1-q25.2 associated with high grade invasive epithelial ovarian carcinomas.

Detailed deletion mapping of chromosome 6q has shown that the highest percentage of loss of heterozygosity (LOH) is located at 6q25-q27 and suggested that an ovarian cancer associated tumor suppressor gene may reside in this region. To further define the smallest region of common loss, we used 12 tandem repeat markers spanning a region no more than 18 cM, located between 6q25.1 and 6q26, to examine allelic loss in 54 fresh and paraffin embedded invasive ovarian epithelial tumor tissues. Loss of heterozygosity was observed more frequently at the loci defined by marker D6S473 (14 of 32 informative cases, 44%) and marker D6S448 (17 of 40 informative cases, 43%). Detailed mapping of chromosome 6q25-q26 in these tumor samples identified a 4 cM minimal region of LOH between markers D6S473 and D6S448 (6q25.1-q25.2). Loss of heterozygosity at D6S473 correlated significantly both with serous versus non-serous ovarian tumors (P=0.040) and with high grade versus low grade specimens (P=0.023). The results suggest that a 4 cM deletion unit located at 6q25.1-q25.2 may contain the putative tumor suppressor gene which may play a role in the development and progression of human invasive epithelial ovarian carcinomas (IEOC).

A 400 kb novel deletion unit centromeric to the BRCA1 gene in sporadic epithelial ovarian cancer.

Allelic deletions on chromosome 17q21 in sporadic ovarian cancer are common, suggesting that inactivation of a tumor suppressor gene(s) in that region may be important for the etiology of these tumors. The recently identified BRCA1 gene on 17q21, involved in the development of familial breast/ovarian cancer, could be a candidate. However, inactivating mutations on BRCA1 in sporadic ovarian cancer has been rarely described. Furthermore, the potential relationship of BRCA1 gene to ovarian tumors of borderline malignancy remains also unclear. We constructed a highly detailed deletion map of chromosome 17q21 based on PCR amplification of eight polymorphic tandem repeat markers in a 650 kb area including three BRCA1 intragenic markers. DNA from 52 sporadic ovarian cancers and 26 borderline tumors, together with their corresponding normal control tissues were used. Only one borderline tumor showed loss of heterozygosity at one marker, whereas 65% of invasive ovarian cancers displayed allelic loss in at least one of the markers studied. A common deletion unit, located approximately 60kb centromeric to BRCA1, was revealed. These results suggest that inactivation of the BRCA1 gene may not be responsible for the development of borderline ovarian tumors and that another tumor suppressor gene, located centromeric to the BRCA1 gene, may play a role in sporadic ovarian cancer development.

Genetic imbalance on chromosome 17 in papillary serous carcinoma of the peritoneum.

We extend the evaluation of allelic loss patterns on chromosome 17 to papillary serous carcinoma of the peritoneum (PSCP) which is histologically identical to papillary serous ovarian carcinoma (PSOC). DNA was obtained from 11 archival cases of PSCP, with 1-11 tumor sites per case. Using ten loci spanning chromosome 17, loss of heterozygosity (LOH) was identified in all 11 cases (100%). Furthermore, 75-100% of informative cases exhibited LOH at the loci p53, D17S1322 (intragenic to the tumor suppressor gene BRCA1), D17S1327 and MPO. PSCP cases exhibit a higher rate of LOH at most loci when compared with PSOC. Alternating allelic loss at different tumor sites was identified in three cases supporting a multifocal origin of PSCP. Microsatellite instability (MI) is an uncommon event which was identified in four cases. These data implicate chromosome 17 as a potential location of genetic events important in the pathogenesis of PSCP as well as ovarian cancer.

Detailed deletion mapping of chromosome 9p and p16 gene alterations in human borderline and invasive epithelial ovarian tumors.

We used PCR amplification of tandem repeats to study the pattern of allelic loss in borderline and invasive ovarian epithelial tumors using 12 primer pairs to generate a detailed deletion map of chromosome 9p. In the invasive ovarian carcinomas, there were three regions displaying high frequency of loss of heterozygosity (LOH) ranging from 31-38%. In contrast, LOH was a rare event among the borderline ovarian tumors, with one region revealing a rate of 20% and the remaining regions only 0-8% LOH. Therefore, allelic loss does not seem to be important for the development of borderline ovarian tumors. We also examined p16 gene expression and mutations in ovarian cancer cell lines and invasive and borderline ovarian tumor tissues. Southern blot analysis revealed no losses of the p16 gene in either the invasive or borderline ovarian tumors. However, the ovarian carcinoma cell lines showed a 50% homozygous deletion rate. SSCP analysis detected a mobility shift in only one (borderline) tumor. Since the primary invasive ovarian tumors did not show any deletions or mutations, it appears that p16 does not play a role in the pathogenesis of these tumors.

Identification of a 1300 kilobase deletion unit on chromosome 7q31.3 in invasive epithelial ovarian carcinomas.

We have used polymerase chain reaction (PCR) amplification of tandem repeats to study the pattern of allelic loss on chromosome 7q31 in invasive epithelial ovarian carcinomas and borderline ovarian tumors. Using 13 primer sets spanning loci from 7q31 to 7q32, 16 borderline and 54 invasive ovarian tumor tissue, together with their corresponding normal tissue, were analysed. Invasive epithelial ovarian tumors demonstrated loss of heterozygosity (LOH) at one or more loci on 7q in 32 of 54 cases (59%). The invasive epithelial ovarian tumors demonstrated the highest percentage of LOH at the loci D7S643 (20 of 40 informative cases, 50%) and GATA44F09 (18 of 42 informative cases, 43%). In contrary, only one borderline ovarian tumor showed LOH at one locus (GATA44F09, one of 14 informative cases, 7%). Our results display a sharp contrast in the pattern of LOH between invasive and borderline ovarian tumors suggesting that allelic loss at chromosome 7q31.3 may be involved in the development and progression of invasive epithelial ovarian tumors but not borderline ovarian tumors. Further analysis of the deletion map for the invasive epithelial ovarian tumors showed two regions likely to harbor ovarian tumor suppressor genes including a novel 1300 kilobase common loss region flanked by GATA44F09 and D7S643.

Differential expression of NF1 type I and type II isoforms in sporadic borderline and invasive epithelial ovarian tumors.

The NF1 gene, a putative tumor suppressor gene, contains a GAP related domain (GRD) which accelerates hydrolysis of ras-bound GTP to GDP, thereby converting the ras oncogene from its active to inactive form. Two forms of the NF1 GRD transcript (Type I and Type II) are differentially expressed in neuroectodermal tumor tissue relative to differentiated neural cells, and in gastric cancer cell lines relative to normal stomach mucosa. We measured relative expression of NF1 Type II and Type I isoforms in cultured normal and malignant human ovarian surface epithelial cells(HOSE) and in invasive and borderline ovarian tumor tissue. We demonstrated an 11-fold increase in Type II:Type I ratio in 7 HOSE cultures relative to eight ovarian cancer cell lines. Our findings indicate a significant decrease in Type II isoform expression and increase in Type I expression in ovarian cancer cells and tumor tissue relative to HOSE cells. We also demonstrate an increase in Type II:Type I ratio, and a decrease in cell proliferation rate in three ovarian cancer cell lines on treatment with retinoic acid. We propose that differential expression of the NF1 Type I and Type II isoforms is related to cellular differentiation in ovarian epithelial cancer and strategies based on alteration in NF1 isoform expression may have therapeutic potential in ovarian malignancies.

A one centimorgan deletion unit on chromosome Xq12 is commonly lost in borderline and invasive epithelial ovarian tumors.

We have used polymerase chain reaction (PCR) amplification of tandem repeats to study the pattern of allelic loss on chromosome X11.2-q12 in borderline and invasive epithelial ovarian tumors. Using eight microsatellite markers spanning Xq11.2-q12, 41 borderline and 65 invasive ovarian tumors, together with their corresponding normal tissues, were analysed. The highest percentage of loss of heterozygosity (LOH) was observed at the DXS1194 locus in borderline tumors (four of 16 informative cases, 25%) and at the androgen receptor (AR) locus in invasive epithelial ovarian tumors (18 of 47 informative cases, 38%). X chromosome activation studies performed in cases with LOH at the AR locus showed that the allelic loss at the AR locus is not confined to the inactive allele. A one centimorgan region including the AR locus and flanked by the primers DXS1161 and PGK1P1 was identified as the smallest common loss region in both borderline and invasive epithelial ovarian tumors.

Loss of heterozygosity of chromosome 17 in human borderline and invasive epithelial ovarian tumors.

Polymerase chain reaction (PCR) analysis of microsatellite polymorphisms corresponding to four loci which map to chromosome 17p and 11 loci which map to chromosome 17q was performed to screen for loss of heterozygosity (LOH) in paired normal and tumor tissues from 27 cases of borderline epithelial ovarian tumors (BEOT) and 32 cases of invasive epithelial ovarian cancers (IOC). LOH was observed in six of 27 (22%) of the borderline tumors and in 29 of 32 (90%) of the invasive ovarian cancers (P<0.001). At all 15 loci studied, a lower percentage of allelic loss was detected in borderline tumors (0-14%) vs invasive cancer (8-93%). At eight loci this difference was statistically significant. For IOC, one common loss region was identified on chromosome 17p and four distinct common loss regions were on chromosome 17q, which supports the notion that multiple tumor suppressors may reside on chromosome 17 in IOC. These data suggest that LOH on chromosome 17 is an infrequent event in BEOT compared with IOC and therefore may not be important in the distinct pathogenesis of BEOT.

Occult ovarian tumors in women with BRCA1 or BRCA2 mutations undergoing prophylactic oophorectomy.

PURPOSE: To review the findings at prophylactic oophorectomy of a series of women who presented to a familial breast and ovarian cancer clinic. MATERIALS AND METHODS: Data from medical charts, operative notes, and pathology reports were collected on women who had undergone prophylactic oophorectomies because of the elevated risk of ovarian cancer. Because only a subset of patients underwent BRCA1 and BRCA2 testing, each patient's risk of hereditary predisposition was calculated using the Berry-Parmigiani model and family history data. RESULTS: From June 1989 to December 1998, 50 women seen at our clinic underwent prophylactic oophorectomy, 33 of whom had a calculated risk of carrying a germline BRCA1 or BRCA2 mutation greater than 25%. Among this group, four incidental tumors were found (four of 33, or 12%); one tumor was noted at the time of surgery and three were noted only in the final pathology. Two patients had microscopic, poorly differentiated serous adenocarcinomas in multiple sites on both ovaries. A third patient had a bilateral serous borderline tumor with micropapillary features. The fourth patient had a microscopic serous borderline ovarian tumor. All four patients had germline BRCA1 or BRCA2 mutations, and three had unremarkable transvaginal ultrasonography examinations within 6 months before prophylactic surgery. CONCLUSION: Foci of malignant tumor are not uncommon in prophylactic oophorectomies performed in women at very high risk for ovarian cancer and may not be detected on ultrasonograms. Surgeons should have a high suspicion of finding cancer in these women at the time of prophylactic surgery, and careful pathologic assessment of the specimens should be conducted.