BRCA2 mutations in primary breast and ovarian cancers.

The second hereditary breast cancer gene, BRCA2, was recently isolated. Germline mutations of this gene predispose carriers to breast cancer, and, to a lesser extent, ovarian cancer. Loss of heterozygosity (LOH) at the BRCA2 locus has been observed in 30-40% of sporadic breast and ovarian tumours, implying that BRCA2 may act as a tumour suppressor gene in a proportion of sporadic cases. To define the role of BRCA2 in sporadic breast and ovarian cancer, we screened the entire gene for mutations using a combination of techniques in 70 primary breast carcinomas and in 55 primary epithelial ovarian carcinomas. Our analysis revealed alterations in 2/70 breast tumours and none of the ovarian carcinomas. One alteration found in the breast cancers was a 2-basepair (bp) deletion (4710delAG) which was subsequently shown to be a germline mutation, the other was a somatic missense mutation (Asp3095Glu) of unknown significance. Our results suggest that BRCA2 is a very infrequent target for somatic inactivation in breast and ovarian carcinomas, similar to the results obtained for BRCA1.

Clonal origin of epithelial ovarian carcinoma: analysis by loss of heterozygosity, p53 mutation, and X-chromosome inactivation.

BACKGROUND: It has been suggested that multiple sites of epithelial ovarian carcinoma on the peritoneal surface reflect polyclonal disease arising from multiple primary tumors in the peritoneal mesothelium, rather than monoclonal disease spread by metastases from one primary ovarian cancer. PURPOSE: The purpose of this study was to investigate whether ovarian cancer has a monoclonal or polyclonal origin. METHODS: DNA specimens were obtained from peripheral blood lymphocytes (normal DNA) and from multiple tumor deposits of 17 women with epithelial ovarian carcinoma: primary tumors, metastatic deposits, and ascites. The clonal origin of each tumor was determined by performing (a) analysis to detect loss of heterozygosity at five loci on chromosomes 5, 11, 13, and 17; (b) sequencing of exons 5-8 of the p53 gene; and (c) X-chromosome inactivation analysis of the phosphoglycerate kinase (PGK) gene. RESULTS: In 15 of the 17 cases analyzed, there was clear evidence of monoclonal origin. The probability that the genetic events documented in these 15 cases occurred as independent events in each tumor deposit ranged from 2.5 x 10(-1) to 3.7 x 10(-16). In two cases, the pattern of allelic deletion and p53 gene mutation was compatible with either a monoclonal origin or origin from two primary ovarian tumors. CONCLUSIONS: The results did not support the hypothesis that ovarian cancer is a multifocal, polyclonal disease. Instead, the data suggest that sporadic epithelial ovarian carcinoma has either a monoclonal or a dual primary origin. IMPLICATIONS: These findings have important implications for understanding of the natural history of ovarian cancer and for clinical strategies aimed at prevention and early detection. Further studies will be required to determine the clonal origin of familial hereditary ovarian cancer.

Spectrum of mutation and frequency of allelic deletion of the p53 gene in ovarian cancer.

BACKGROUND: The p53 gene encodes a nuclear phosphoprotein present in low levels in normal human cells. The wild-type form of this protein functions to restrain inappropriate cellular proliferation. Approximately one half of human epithelial ovarian cancers have mutations in the p53 gene and overexpress the mutant protein product. Deletion of one allele of the p53 gene also frequently occurs in these cancers. PURPOSE: We sought to define the spectrum of mutations in the p53 gene in epithelial ovarian cancer with respect to both the specific codons involved and the type of mutations observed. We also examined the frequency of allelic deletion of the p53 gene in cancers containing p53 gene mutations. METHODS: Tissue samples from the epithelial ovarian cancers of 62 patients were obtained during initial laparotomy. Histologic examination was done to ensure that the experimental samples used in this study contained more than 75% cancer cells. Total RNA was extracted from these samples and separately from matched control noncancerous regions of the surgical specimen or white blood cells. The purified RNAs were reverse transcribed to generate cDNA copies of exons 4-10 of the p53 gene. Two rounds of polymerase chain reaction (PCR) were conducted to produce enough template for DNA sequence analysis of the regions of interest within the p53 gene. Dideoxy sequencing of at least two independent productions of each amplified DNA template was done to confirm the validity of the mutations found. Allelic deletions were identified by PCR and gel electrophoretic techniques to examine three polymorphisms within the p53 gene in cancer-normal DNA pairs. RESULTS: We identified 45 mutations in exons 5-8 of the p53 gene, where mutations frequently have been found in other cancer types. An additional mutation was identified in exon 4. Overall, 72% of the mutations were transitions, 24% transversions, and 4% microdeletions. Allelic deletion of the other p53 allele was seen in 67% of ovarian cancers in which a p53 mutation was present. Germ-line p53 mutations were not found in any patients whose cancers had p53 mutations. CONCLUSIONS AND IMPLICATIONS: Like p53 mutations in other types of human cancers, those in epithelial ovarian cancers are diverse and occur frequently in exons 5-8. The predominance of transition mutations suggests that p53 mutations in ovarian cancer arise because of spontaneous errors in DNA synthesis and repair rather than the direct interaction of carcinogens with DNA. These molecular data are consistent with data from epidemiologic studies that have failed to demonstrate a convincing relationship between exposure to environmental carcinogens and the development of ovarian cancer.

Maintenance of p53 alterations throughout breast cancer progression.

Overexpression of the nuclear phosphoprotein p53 is one of the most common abnormalities in primary human cancer and appears to be due to point mutation within a highly conserved region of the p53 gene which then encodes for a mutant, more stable protein. In this study different stages of breast cancer progression were examined, from in situ to metastatic disease, to determine at what stage mutational activation occurs and whether it is maintained during tumor progression. Two (13%) of 15 pure intraductal tumors expressed high levels of p53 in all malignant epithelial cells. Sequencing of p53 mRNA from one of these tumors demonstrated a nucleotide substitution altering the amino acid composition of the protein. Six (17%) of 35 specimens which contained both in situ and invasive disease expressed high levels of p53. All malignant epithelial cells in these 6 cases stained positively and in no specimen did one component express different levels of the protein than the other growth phase. Sequence analysis of a tissue with significant amounts of both in situ and invasive disease revealed only a single point mutation, without evidence of wild-type nucleotide at the site of substitution, suggesting that p53 mRNA from each component of the tumor contained the same nucleotide substitution. Eleven (50%) of 22 pairs of primary tumors and their lymph node metastases expressed elevated levels of p53, and in each case, expression levels were identical in the primary and secondary sites. Identical mutations were found in the p53 mRNA from two paired primary and metastatic sites. Therefore, mutation within a highly conserved region of the p53 gene leading to overexpression of the protein product can occur in the earliest recognized phase of breast cancer and this alteration is maintained during progression from intraductal to infiltrating carcinoma. Mutations are also conserved during the process of metastatic spread.

Increased erbB-2 gene copies and expression in multiple stages of breast cancer.

In order to examine the role of the erbB-2 oncogene in human breast cancer, gene amplification and expression were examined in multiple stages of tumor progression. Gene amplification ranging from 2-fold to 32-fold was found in 30 (29%) of 130 cases analyzed. Expression of the receptor-like gene product was determined by a combination of Western immunoblotting and immunohistochemistry. In each case of gene amplification, there was high level overexpression (+ + +) of the protein product. In an additional 29 of 111 cases in which expression was studied (26%), there was moderate level overexpression (+ +) of erbB-2 in the absence of gene amplification. Amplification and overexpression of the erbB-2 gene were found in early clinical stages of breast cancer as well as in more advanced cases. In 23 patients, gene number and level of gene expression were equivalent in the primary tumor site compared with single or multiple metastatic sites in regional lymph nodes. Using a combination of immunohistochemistry and in situ cytohybridization, high (+ + +) and moderate (+ +) level overexpression were homogeneously present in all malignant epithelial cells within histological sections of both primary and metastatic tumor. The intraductal component of carcinoma was identified in sections from 16 invasive primary tumors. erbB-2 gene expression in the intraductal lesions was equivalent to or exceeded expression in the infiltrating components of these tumors. Because erbB-2 alterations are (a) present in all clinical stages, (b) maintained during metastatic spread, (c) homogeneously present throughout tumor sections, and (d) present in the in situ as well as infiltrating component, we conclude that these alterations are selected for early and may be important in the initiation of certain mammary cancer.

A prognostic model of recurrence and death in stage I non-small cell lung cancer utilizing presentation, histopathology, and oncoprotein expression.

In order to construct a multivariate model for predicting early recurrence and cancer death for patients with stage I non-small cell lung cancer, 271 consecutive patients (mean age, 63 +/- 8 years) who were diagnosed, treated, and followed at one institution were studied. All patients were clinical stage I with head and chest/abdominal computed tomograms and radionuclide bone scans without evidence of metastatic disease. Pathological material after resection was reviewed to verify histological staging. Follow-up documented the time and location of any recurrence, was a median 56 months in duration, and was complete in all cases. Data recorded included age, sex, smoking history, presenting symptoms, pathological description, and oncoprotein staining for erbB-2 (HER-2/neu), p53, and KI-67 proliferation protein. Immunohistochemistry of oncogene expression was performed on two separate archived paraffin tumor blocks for each patient, with normal lung as control. All analyses were blinded and included Kaplan-Meier survival estimates with Cox proportional hazards regression modeling. Data, including immunohistochemistry, were complete for all 271 patients. Actual 5-year survival was 63% and actuarial 10-year survival was 58%. Significant univariate predictors (P < 0.05) of early recurrence and cancer-death were: male sex; the presence of symptoms; chest pain; type of cough; hemoptysis; tumor size > 3 cm diameter (T2); poor differentiation; vascular invasion; erbB-2 expression; p53 expression; and a higher KI-67 proliferation index (> 5%). An additive oncogene expression curve demonstrated a 5-year survival of 72% for 136 patients without p53 or erbB-2, 58% for 108 patients who expressed either oncogene, and 38% for 27 who expressed both (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of frequent allelic loss on proximal chromosome 17q in sporadic breast carcinoma using microsatellite length polymorphisms.

Analyses of losses of heterozygosity and linkage studies have implicated a gene(s) on chromosome 17q in the genesis of sporadic and early-onset familial breast carcinomas, respectively. To define the critical region of 17q, we examined DNAs from a series of 20 sporadic breast carcinomas and corresponding blood samples for allelic losses of chromosome 17q using microsatellite length polymorphisms. With these highly informative markers (average heterozygosity, 0.73), we observed frequent deletions of 17q at several loci. We found that D17S250 was deleted in 50% (7 of 14), THRA1 in 79% (11 of 14), D17S579 in 59% (11 of 19), NME1 in 29% (5 of 17), MPO in 36% (4 of 11), and GH in 25% (4 of 16) in the tumor set examined. A common region of deletion was found that was flanked by D17S250 to D15S579. These markers have recently been localized to a 6-cM interval of proximal chromosome 17q in bands 17q11.2-q21 and map within the region of the early-onset familial breast cancer locus, implying that the same gene or genes may be involved in both sporadic and familial breast tumors. Thyroid hormone receptor alpha and retinoic acid receptor alpha are two potential candidate genes in this region.

Cell cycle control of BRCA2.

Identifying the conditions and kinetics of the induction of BRCA2 gene expression may implicate roles for the function of the tumor suppressor gene. In this study, expression of BRCA2 mRNA is shown to be regulated by the cell cycle and associated with proliferation in normal and tumor-derived breast epithelial cells. Cells arrested in G(0) or early G1 contained low levels of BRCA2 mRNA. After release into a proliferating state, cells produced maximum levels of BRCA2 mRNA in late G1 and the S-phase. Similar cell cycle control of BRCA2 was observed in fractions of exponentially growing cells isolated by centrifugal elutriation. Expression of BRCA2 was shown to be independent of bulk DNA synthesis. In addition, the kinetics of BRCA2 mRNA up-regulation appeared to be similar to those of BRCA1, suggesting that the two genes could be commonly controlled. These results imply that these two tumor suppressor genes are utilized during growth and may have a protective role in cellular proliferation.

Mutation analysis of the THRA1 gene in breast cancer: deletion/fusion of the gene to a novel sequence on 17q in the BT474 cell line.

We have previously described a common region of deletion and allele loss on chromosome 17q in sporadic breast cancers that is likely to contain a tumor suppressor gene. The region, mapped to 17q12-q21, was bordered by D17S250 and D17S579 on the centromeric and telomeric sides, respectively. This deletion region overlaps the BRCA1 locus, which predisposes to familial breast and ovarian cancer. The most frequent loss of heterozygosity was observed at the thyroid hormone receptor alpha (THRA1) locus. Southern analysis revealed a rearrangement of THRA1 in the BT474 breast cancer cell line. This rearrangement represented a deletion of exons 8-10 of one THRA1 allele that was also coamplified with ERBB2. Northern blots showed two mutant transcripts in BT474 cells. Analysis of the mutant transcripts revealed fusion of the THRA1 exon 7 by splicing to a novel sequence designated BTR for "BT474 transcribed rearrangement." BTR was found to be highly conserved and mapped to 17q. The deletion in BT474 cells spans the entire BRCA1 region. To search for additional mutations in the THRA1 gene, all nine protein-encoding exons of THRA1 were examined for point mutations via single strand conformation analysis in a series of primary breast tumors, breast cancer cell lines, and lymphoblastoid cell lines derived from the youngest affected members of several German breast cancer families. No point mutations were detected, including the unrearranged THRA1 allele in BT474. We have thus excluded THRA1 as a commonly mutated sporadic breast cancer tumor suppressor gene and as the BRCA1 gene.

A SAGE (serial analysis of gene expression) view of breast tumor progression.

To identify molecular alterations involved in the initiation and progression of breast carcinomas, we analyzed the global gene expression profiles of normal mammary epithelial cells and in situ, invasive, and metastatic breast carcinomas using serial analysis of gene expression (SAGE). We identified sets of genes expressed only or most abundantly in a specific stage of breast tumorigenesis or in a certain subtype of tumors through the pair-wise comparison and by hierarchical clustering analysis of these eight SAGE libraries (two/stage). On the basis of these comparisons, we made the following observations: Normal mammary epithelial cells showed the most distinct and least variable gene expression profiles. Many of the genes highly expressed in normal mammary epithelium and lost in carcinomas encoded secreted proteins, cytokines, and chemokines, implicating abnormal paracrine and autocrine signaling in the initiation of breast tumorigenesis. Very few genes were universally up-regulated in all tumors regardless of their stage and histological grade, indicating a high degree of diversity at the molecular level that likely reflects the clinical heterogeneity characteristic of breast carcinomas. Tumors of different histology type and stage had very distinct gene expression patterns. No genes seemed to be specific for metastatic or for in situ carcinomas. We found that the most dramatic and consistent phenotypic change occurred at the normal-to-in situ carcinoma transition. This observation, combined with the fact that many of the genes involved encode secreted, cell-nonautonomous factors, implies that the normal epithelium-to-in situ carcinoma transition may be the most promising target for cancer prevention and treatment.

Phenol sulfotransferases: hormonal regulation, polymorphism, and age of onset of breast cancer.

In recent years, significant effort has been made to identify genes that influence breast cancer risk. Because the high-penetrance breast cancer susceptibility genes BRCA1 and 2 play a role only in a small fraction of breast cancer cases, understanding the genetic risk of the majority of breast cancers will require the identification and analysis of several lower penetrance genes. The estrogen-signaling pathway plays a crucial role in the pathophysiology of breast cancer; therefore, polymorphism in genes involved in this pathway is likely to influence breast cancer risk. Our detailed analysis of gene expression profiles of estrogen- and 4-OH-tamoxifen-treated ZR75-1 breast cancer cells identified members of the sulfotransferase 1A (SULT1A) phenol sulfotransferase family as downstream targets of tamoxifen. On the basis of the induction of SULT1A by 4-OH-tamoxifen and the known inherited variability in SULT1A enzymatic activity, we hypothesized that polymorphism in sulfotransferase genes might influence the risk of breast cancer. Using an RFLP that distinguishes an arginine to histidine change in exon 7 of the SULT1A1 gene, we characterized SULT1A1 genotypes in relation to breast cancer risk. An analysis of 444 breast cancer patients and 227 controls revealed no effect of SULT1A1 genotype on the risk of breast cancer (P = 0.69); however, it did appear to influence the age of onset among early-onset affected patients (P = 0.04). Moreover, individuals with the higher activity SULT1A1*1 allele were more likely to have other tumors in addition to breast cancer (P = 0.004; odds ratio, 3.02; 95% confidence interval, 1.32, 8.09). The large number of environmental mutagens and carcinogens activated by sulfotransferases and the high frequency of the SULT1A1*1 allele in human populations warrants additional studies to address the role of SULT genes in human cancer.

Overexpression and mutation of p53 in endometrial carcinoma.

Immunohistochemical staining for the p53 protein was performed in 107 snap frozen primary endometrial adenocarcinomas and 15 benign uterine tissues using monoclonal antibody PAb1801. No staining was seen in benign samples, whereas intense nuclear staining of cancer cells consistent with overexpression of the p53 protein was observed in 22 of 107 cancers (21%). p53 overexpression was more frequent in advanced (Stage III/IV) cancers (41%) than in early (Stage I/II) cancers (9%) (P less than 0.001), and also was associated with nonendometrioid histology (P = 0.008), positive peritoneal cytology (P = 0.01), extrauterine metastases (P = 0.003), and negative progesterone receptor status (P = 0.04). To confirm the relationship between p53 overexpression and mutation, p53 mRNA from 8 cancers was reverse transcribed and amplified using the polymerase chain reaction. DNA sequencing revealed point mutations in each of the 5 cancers that overexpressed p53, whereas the wild-type sequence was found in 3 cancers that did not overexpress the protein. Each of the 5 mutations resulted in an amino acid substitution in a highly conserved region of the p53 gene where mutations have been found in other cancers. Further studies are warranted to determine whether the association between p53 overexpression and advanced stage disease is due to accumulation of genetic lesions during tumor progression or whether p53 alterations confer a more virulent phenotype.

Overexpression and mutation of p53 in epithelial ovarian cancer.

We examined p53 expression in 107 epithelial ovarian cancers with immunohistochemical techniques using monoclonal antibody PAb1801. High level expression of nuclear p53 protein was detected in the malignant epithelium in 54 (50%) of these cancers. Expression of p53 protein was undetectable in 13 benign gynecological tissues. p53 mRNA from three cancers that overexpressed the protein were sequenced and point mutations which altered the coding sequence of the highly conserved region of the gene were found in each case. Three cancers with undetectable protein levels also were sequenced and were found to be wild-type through the same region of the gene. As in other cancers, overexpression of the p53 protein in ovarian cancer appears to correlate closely with the presence of mutation in the p53 gene. p53 overexpression did not correlate with stage, histological grade, or the ability to perform optimal cytoreductive surgery. A significant correlation (P = 0.04) was observed between p53 overexpression and aneuploidy in advanced stage (III/IV) disease. There was no significant relationship between overall survival and p53 expression. Since mutation and overexpression of p53 are common in epithelial ovarian cancers, further studies are warranted to clarify the role of p53 in ovarian tumorigenesis.

Expression of p53 in human neuroblastoma- and neuroepithelioma-derived cell lines.

Overexpression of the nuclear phosphoprotein p53 has been detected in many different transformed human cell lines and primary adult tumors. Elevated steady-state levels of p53 appear to be the result of an increase in the stability of the protein and, in adult cancers, high levels of the protein are associated with mutation of the p53 gene. In this study, overexpression of p53 was detected in 4 out of 5 human neuroblastoma-derived cell lines. The protein expressed by each of these four lines had a significantly prolonged half-life relative to the p53 protein in immortalized rodent fibroblasts and normal bovine adrenal medullary cells. However, no mutations were detected in the highly conserved regions of the p53 gene in these four neuroblastoma lines and the protein being expressed was not recognized by the mutant-specific anti-p53 monoclonal antibody, PAb 240. Upon retinoic acid-induced differentiation of the LA-N-5 neuroblastoma cell line, the level of p53 protein declined, as did the level of p53 mRNA, but the half-life of the protein remained unchanged. The high level of protein observed in the undifferentiated cell lines appears to result from expression of a stable wild-type p53 protein and increased transcription. In contrast, p53 protein was undetectable in two neuroepithelioma-derived cell lines; the p53 gene in one of these lines contained a nonsense mutation, while the other transcribed truncated p53 mRNA.

Isolation and initial characterization of the BRCA2 promoter.

The hereditary breast cancer susceptibility gene, BRCA2, is considered to be a tumor suppressor gene that may be involved in the cellular response to DNA damage. The transcript for this gene is cell cycle regulated with mRNA levels reaching a peak just before the onset of DNA synthesis. In order to define the mechanisms by which BRCA2 is transcriptionally regulated, we have begun to study upstream regulatory sequences. In this report, we define a minimal promoter region that has strong activity in human breast epithelial cells. Deletions of this sequence narrowed the strong basal activity to a region extending from -66 to +129 with respect to the BRCA2 transcriptional start site. This sequence demonstrated cell cycle regulated activity with kinetics similar to the endogenous transcript. Examination of the sequence revealed several consensus binding sites for transcription factors including an E-box, E2F and Ets recognition motifs. Electrohoretic mobility shift assays revealed specific protein binding to two sequences upstream of the start site; the palindromic E-box and an Ets/E2F site. Site-directed mutagenesis of either of these sites reduced both the basal activity in log phase cells and the cell cycle regulated activity of the promoter. Mutational inactivation of both sites within the same construct effectively eliminated promoter activity. Antibodies to candidate transcription factors used in super shift experiments revealed specific interactions between the BRCA2 promoter and the basic region/helix - loop - helix containing USF-1 and 2 proteins and Elf-1, an Ets domain protein. Binding of these factors depended upon the presence of intact recognition sequences. The USF factors were shown to bind predominantly as a heterodimeric complex of USF-1 and 2 while Elf-1 bound the promoter when it was not occupied by USF. Co-transfection studies with USF proteins and the varicella zoster IE62 protein provide evidence for the involvement of endogenous and exogenous USF in the activation of the BRCA2 promoter. We propose that interactions between USF-1, USF-2 and Elf-1 play an important role in the transcriptional regulation of the BRCA2 gene.

M6P/IGF2 receptor: a candidate breast tumor suppressor gene.

The mannose 6-phosphate/insulin-like growth factor 2 receptor (M6P/IGF2r) functions in the activation of TGFbeta, a potent growth inhibitor for most cell types, the degradation of the mitogen, IGF2, and the intracellular trafficking of lysosomal enzymes. We have found its expression to be significantly reduced in both rat and human hepatocellular carcinomas (HCCs) and recently reported loss of heterozygosity (LOH) at this locus with mutations in the remaining allele in human liver tumors. Using the polymerase chain reaction, we utilized two polymorphisms in the 3' untranslated region of M6P/IGF2r to screen breast tumors for LOH. Forty of 62 (65%) patients were informative (heterozygous) and 12/40 (30%) breast tumors had LOH; 5/19 (26%) carcinomas in situ (CIS) and 7/21 (33%) invasive carcinomas. To investigate the early molecular genetic events in breast carcinogenesis, we screened the CIS with LOH for mutations. In 2/5 (40%) of these tumors, missense mutations were found in the remaining allele that gave rise to significant amino acid substitutions. These findings provide evidence that M6P/IGF2r allelic loss is an early event in the etiology of breast cancer, that this gene functions as a tumor suppressor gene in the breast.

BRCA1 expression is not directly responsive to estrogen.

Expression of the breast cancer susceptibility gene, BRCA1, is induced by 17-beta estradiol (E2) in estrogen receptor containing breast cancer cell lines. Our previous studies have shown that BRCA1 transcription is also regulated with the cell cycle, reaching maximal levels just before the onset of DNA synthesis. In this study, we have examined whether the estrogen induction of BRCA1 is direct or is a result of the mitogenic activity of the hormone. Four lines of evidence lead us to conclude that E2 induces BRCA1 primarily through an increase in DNA synthesis: (1) The kinetics and magnitude of induction are different from the directly E2 inducible gene, pS2; (2) Induction of BRCA1, but not pS2, is blocked by cycloheximide indicating that de novo protein synthesis is required; (3) Other hormonal and growth factor treatments that induce DNA synthesis have a similar effect, including IGF-1, EGF and DNA synthetic flares induced by tamoxifen and retinoic acid; (4) BRCA1 genomic fragments near the 5' end of the gene containing putative estrogen response elements fail to respond to E2 when transfected into breast cancer cell lines. The most consistent explanation for these findings and other published studies is that BRCA1 transcription is induced as a result of the mitogenic activity of E2 in estrogen receptor positive cells.

Localized adenocarcinoma of the lung: oncogene expression of erbB-2 and p53 in 150 patients.

Historical information and pathological material from 150 consecutive patients with localized adenocarcinoma of the lung was collected to evaluate oncogene expression of erbB-2 and p53, and erbB-2 gene amplification. Pathological material after resection was reviewed to verify histological staging, and patient follow-up was complete in all cases for at least 68 months. Immunohistochemistry of erbB-2 (HER-2/neu) and p53 oncogene expression was performed on two separate paraffin tumor blocks for each patient with normal lung as control. Gene amplification of erbB-2 was measured after DNA extraction from 20-micrometer sections of erbB-2-positive and -negative tumors. All analyses were blinded and included Kaplan-Meier survival estimates with Cox proportional hazards regression modeling. Two adequate blocks of tumor and normal lung were available for 138 (92%) patients. Immunohistochemical identification of expression of p53 was observed in 49 (37%) patients and erbB-2 in 17 (13%) patients. DNA dot blot analyses were performed on 17 erbB-2-positive and 13 randomly selected erbB-2-negative tumors. There was 1 (6%) of 17 erbB-2-positve tumors with 4-fold erbB-2 gene amplification. Actual 5-year survival was 63% and actuarial 10-year survival was 59% for the entire population of 150 patients. Significant univariate predictors (P < 0.05) of cancer death were the presence of symptoms, tumor size >3 cm, poor differentiation, visceral pleural invasion, and p53 expression. Multivariate analysis associated symptoms and p53 expression as independent factors with decreased survival. Thus, this project examined p53 and erbB-2 expression in patients with localized adenocarcinoma and associated p53 status with survival. Multicenter collection of data should allow the development of a model of cancer recurrence in this most common lung cancer.

Relationship between p21 expression and mutation of the p53 tumor suppressor gene in normal and malignant ovarian epithelial cells.

In many cell types, p53-mediated growth inhibition is dependent on induction of p21, which is an inhibitor of cyclin-dependent kinases that are required for cell cycle progression. Failure of mutant p53 proteins to transactivate p21 may lead to uncontrolled proliferation. Because many ovarian cancers have mutations in the p53 gene, we examined p21 levels in normal and malignant ovarian epithelial cells to determine whether p21 expression is dependent on wild-type p53. Normal ovarian epithelial cells and two ovarian cancer cell lines with wild-type p53 expressed readily detectable levels of p21, whereas in p53 null and mutant cell lines, expression of p21 was diminished strikingly. A correlation between the status of the p53 gene and p21 expression also was noted in 23 primary epithelial ovarian cancers. Normal levels of p21 RNA were seen in 4/7 (57%) cancers with wild-type p53, whereas 14/16 (88%) cancers with mutant p53 had reduced p21 expression (P < 0.05). In addition, we found that lambda-irradiation of normal and malignant ovarian epithelial cells with wild-type, but not mutant, p53 resulted in induction of p21. These data are suggestive that induction of p21 is a feature of p53-mediated growth inhibition in normal ovarian epithelial cells. Conversely, mutation of the p53 gene in ovarian cancers usually is associated with decreased p21 expression. The lack of an absolute correlation between p21 expression and the status of the p53 gene in ovarian cancers is consistent with other studies that have suggested that p21 may also be regulated by p53-independent pathways.

Frequency of germline and somatic BRCA1 mutations in ovarian cancer.

Germline mutations in the BRCA1 tumor suppressor gene are thought to be the most common cause of hereditary ovarian cancer. The aim of this study was to explore further the role of BRCA1 alterations in the development of ovarian cancers. We sought to determine whether somatic BRCA1 mutations are ever present in ovarian cancers and whether mutation is always accompanied by loss of the wild-type allele. The entire coding region and intronic splice sites of BRCA1 were sequenced using genomic DNA samples from 103 unselected ovarian cancers. Thirteen clearly deleterious BRCA1 mutations and two variants of uncertain significance were found. Blood DNA was available in all but two cases and demonstrated that 4 of 13 mutations and both variants of uncertain significance were germline alterations, whereas in seven cases the mutation was a somatic change present only in the cancer. Using four microsatellite markers, loss of heterozygosity at the BRCA1 locus was found in all 15 ovarian cancers with BRCA1 sequence alterations, compared with only 58% of ovarian cancers that did not have BRCA1 mutations. BRCA1-associated ovarian cancers were characterized by serous histology and moderate histological grade. These data confirm prior reports suggesting that germline mutations in BRCA1 are present in about 5% of women with ovarian cancer. In addition, somatic mutations in BRCA1 occur in the development of some sporadic cases. The finding that both germline and somatic BRCA1 mutations are accompanied by loss of heterozygosity, suggests that loss of this tumor suppressor gene is a critical event in the development of these cancers.