Inherited carcinomas of the kidney

Studies of families with inherited carcinomas have provided powerful tools to identify the genes involved in the pathogenesis of human cancers. In this review, we summarize the clinical, pathological, and genetic characteristics of the inherited carcinomas of the kidney. We emphasize the observation that different genes predispose to histologically different types of renal carcinoma. Hereditary papillary renal carcinoma, a recently described inherited disorder, is discussed in detail along with the predisposing gene, the MET protooncogene. The data support a classification of renal carcinomas based on molecular genetics.

Absence or reduction of Fhit expression in most clear cell renal carcinomas

The FHIT gene at human chromosome region 3p14.2 straddles the common fragile site, FRA3B, and numerous homozygous deletions in cancer cell lines and primary tumors. Also, the 3p14.2 chromosome breakpoint of the familial clear cell kidney carcinoma-associated translocation, t(3;8)(p14.2;q24), disrupts one FHIT allele between exons 3 and 4, fulfilling one criterion for a familial tumor suppressor gene: that one allele is constitutionally inactivated. Because the FHIT gene sustains biallelic intragenic deletions rather than mutations, there has not been evidence that the FHIT gene frequently plays a role in kidney cancer, although replacement of Fhit expression in a Fhit-negative renal carcinoma cell line suppressed tumor growth in nude mice. We have now assessed 41 clear cell renal carcinomas for expression of Fhit by immunohistochemistry. Normal renal tubule epithelial cells express Fhit uniformly and strongly, whereas 51% of the tumors are completely negative, 34% of tumors show a mixture of positive and negative cells, and 14% are uniformly positive, although usually less strongly positive than the normal epithelial cells. Most interestingly, there was a correlation between complete absence of Fhit and the G1 morphological grade and early clinical stage. Morphological grades G2 and G3 exhibited a mixture of positive and negative cells with a tendency for a higher fraction of negative cells in G3. Fhit inactivation is likely to be an early event in G1 tumors and may be associated with progression in G2 and G3 tumors.

Loss of heterozygosity on chromosome 6q27 and p53 mutations in epithelial ovarian cancer

Loss of heterozygosity (LOH) in chromosome region 6q27 and p53 mutations were studied to attempt to clarify the genetic etiology of ovarian cancer, with particular reference to clear cell adenocarcinoma (CCC), which has a poor prognosis. 6q27 LOH in 70 epithelial ovarian cancer patients was examined using four restriction fragment length polymorphism markers located at 6q27; p53 mutations in tumor DNA were detected using polymerase chain reaction single-strand conformation polymorphism and sequencing. 6q27 LOH was confirmed in 26 of 48 informative cases (54.2%). No differences in the incidence of 6q27 LOH were seen by histologic type; 6q27 LOH was observed in 45% (5/11) of CCCs. p53 mutations were detected in 19 of the 48 tumors (39.6%), but in only one (9%) CCC. These results suggest that a putative tumor suppressor gene involved in the onset of epithelial ovarian cancer is located at 6q27. This gene is one of the keys to clarifying the genetic etiology of epithelial ovarian cancer and particularly CCC, given the low incidence of p53 mutations in this tumor type.

Collecting duct carcinomas of the kidney: a comparative loss of heterozygosity study with clear cell renal cell carcinoma

Origin of collecting duct carcinomas (CDC) of the kidney is not entirely known, although it is thought that they originate from the distal collecting duct system, whereas clear cell renal cell carcinoma (cRCC) may originate from the proximal tubular epithelium. In cRCC, the von Hippel Lindau gene (vHL) is damaged in almost 100% of cases; the frequency of vHL deletions in CDC is not known. Loss of heterozygosity (LOH) of CDC and cRCC of vHL (3p), p16 (9p), p53 (17p) and the retinoblastoma (RB) gene (13q) was studied to evaluate possible genetic differences between the two. LOH of the vHL was seen in 77.7% of cRCC and in 55% of CDC. P16 was lost in 33% of cRCC and in 50% of CDC. LOH in p53 was observed in 0/8 cases of cRCC compared to 18.7% in CDC. LOH in 13q was seen in 25% of both CDC and cRCC. The high LOH rate of the vHL gene in CDC has not been observed previously. The findings indicate that CDC and cRCC share certain genetic alterations, including frequent deletion of the vHL gene. CDC is not clearly related to cRCC but may be of heterogeneous origin.

[Von Hippel-Lindau disease and renal cancer: 10 years of genetic progress. GEFVHL (French-Speaking Study Group on von Hippel-Lindau disease)]

Von Hippel-Lindau (VHL) disease is a genetic disease predisposing to the development of various tumours (haemangioblastomas of the neuraxis and retina, tumours of the membranous labyrinth, renal clear cell carcinomas or cysts, phaeochromocytomas, pancreatic cysts or tumours, epididymal cystadenomas), affecting one in 36,000 people. Renal cancer constitutes one of the main causes of death. The VHL gene, situated at 3p25-26, is a tumour suppressor gene which plays a major role in regulation of VEGF transcription and expression. The germ cell mutation can be identified in 70% of patients. Somatic mutations of the VHL gene are also responsible for sporadic clear cell carcinomas. In the urological setting, any patient presenting with "sporadic" bilateral clear cell renal cancer or detected at an early age, or bilateral epididymal cystadenomas, should be investigated for the presence of VHL disease.

Frequent PTEN/MMAC mutations in endometrioid but not serous or mucinous epithelial ovarian tumors

Epithelial ovarian cancer comprises three major histological subtypes (serous, mucinous, and endometrioid), and it is becoming clear that the developmental pathways for these subtypes are fundamentally different. In particular, endometrioid ovarian cancers probably arise by the malignant transformation of ectopic endometrial implants called endometriosis and not the ovarian surface epithelium. The PTEN/MMAC gene on chromosome 10q23 is a tumor suppressor implicated in the pathogenesis of a wide variety of malignancies, but to date, somatic mutations in PTEN have not been identified in studies of predominantly serous ovarian cancers. In endometrial cancers, PTEN mutations are very common in tumors of the endometrioid type but have rarely been found in serous types, and we hypothesized that a similar histological subtype bias might be occurring in ovarian cancer. We have analyzed 81 ovarian tumors, including 34 endometrioid, 29 serous, 10 mucinous, and 8 clear cell tumors, for loss of heterozygosity (LOH) on 10q23 and for mutations in all 9 coding exons of PTEN. LOH was common among the endometrioid (43%) and serous (28%) tumors but was infrequent among the other histological subtypes. Somatic PTEN mutations were detected in seven (21%) of the endometrioid tumors, and in all informative cases, the mutation was accompanied by loss of the wild-type allele. One mucinous tumor without 10q23 LOH was shown to harbor two somatic PTEN mutations. In this tumor, the histological appearance of the mucinous areas was atypical, and the mucinous areas contained foci of endometrioid differentiation. The majority of tumors with PTEN mutations were grade 1 and/or stage 1, suggesting that inactivation of PTEN is an early event in ovarian tumorigenesis. No PTEN mutations were found among the serous or clear cell tumors. The identification of frequent somatic PTEN mutations in endometrioid ovarian tumors indicates that it plays a significant role in the etiology of this subtype. The absence of mutations in other histological subtypes is consistent with the hypothesis that epithelial ovarian cancers arise through distinct developmental pathways.

Clear cell carcinoma of the pancreas: an adenocarcinoma with ductal phenotype

AIMS

Primary clear cell carcinoma of the pancreas resembling metastatic renal carcinoma has only rarely been described. To date it has been poorly characterized as a distinct tumour entity.

METHODS AND RESULTS

We report a case of clear cell carcinoma in a 53-year-old man involving the head of the pancreas and which had a small intraductal papillary component. The clear cell portion comprised about 90% of the tumour mass. It showed predominantly a solid growth pattern with a few scattered tubular structures. Immunocytochemically the tumour cells stained positively for cytokeratins 7, 8, 18 and 19, whereas the reaction for vimentin and neuroendocrine markers was negative. K-ras analysis revealed a point mutation at codon 12 with mutation of GGT to GAT.

CONCLUSION

The intraductal tumour component of this clear cell carcinoma as well as the cytokeratin pattern and the K-ras mutation suggest that this rare type of pancreatic cancer has a ductal phenotype.

Mutations in the BRCA1-associated RING domain (BARD1) gene in primary breast, ovarian and uterine cancers

Germline alterations of BRCA1 result in susceptibility to breast and ovarian cancer. The protein encoded by BRCA1 interacts in vivo with the BRCA1-associated RING domain (BARD1) protein. Accordingly, BARD1 is likely to be a critical factor in BRCA1-mediated tumor suppression and may also serve as a target for tumorigenic lesions in some human cancers. We have now determined the genomic structure of BARD1 and performed a mutational analysis of 58 ovarian tumors, 50 breast tumors and 60 uterine tumors. Seven polymorphisms were detected within the 2.34 kb coding sequence of BARD1 . Somatically acquired missense mutations were observed in one breast carcinoma and one endometrial tumor; in at least one of these cases, tumor formation was accompanied by loss of the wild-type BARD1 allele, following the paradigm for known tumor suppressor genes. In addition, a germline alteration of BARD1 was identified in a clear cell ovarian tumor (Gln564His); again, loss of the wild-type BARD1 allele was observed in the malignant cells of this patient. The Gln564His patient was also diagnosed with two other primary cancers: a synchronous lobular breast carcinoma and a stage IA clear cell endometrioid cancer confined to an endometrial polyp 6 years earlier. These findings suggest an occasional role for BARD1 mutations in the development of sporadic and hereditary tumors.

Oncogene and HSP-70 expression in primary tumor cell cultures of renal cell carcinoma compared to their corresponding cell line

BACKGROUND

Tumor progression in renal cell carcinoma (RCC) can be explained by a multistep model, in which the activation of certain oncogenes such as c-neu and c-fos appear to be early events in tumorigenesis, while the expression of p53 and pan-ras are found in advanced stages.

MATERIAL AND METHODS

The expression of oncogenes and growth factors was examined in 29 primary tumor cell cultures (PTCC) of RCC using immunocytochemistry.

RESULTS

In PTCC high expression of c-neu and c-fos was present in all tumors, whereas mdr, TGF-alpha, EGF, c-myc, pan-ras, p53 and HSP-70 was detected at low expression levels. In 27% (8/29) of PTCC, cell lines (CL) were established. Oncogene expression was increased in CL compared to PTCC.

CONCLUSION

The pattern of oncogene expressions found in CL is similar to findings described in highly malignant tumors in vivo. Therefore, the establishment of CL seems to depend on a selective recruitment of tumor cells with an upregulated oncogene expression.

Nuclear overexpression of p53 protein does not correlate with gene mutation in primary peritoneal carcinoma

Primary peritoneal carcinoma (PPC) is an aggressive malignancy of the female coelomic epithelium. Previously we had analyzed 29 cases of PPC for p53 protein accumulation by immunocytochemistry. P53 was overexpressed in 83% (24 of 29) of PPCs, including 21 tumors with diffuse intense staining of 100% of tumor nuclei and three additional tumors with significant focal staining. Here we report results of a mutational analysis on the entire p53 coding sequence of 22 of these cases (comprising 18 p53-positive and four negative tumors), using single-strand conformation polymorphism (SSCP) and direct sequence analysis. Only 2 of 22 (9%) patients harbored a p53 mutation (which, interestingly, were identical and consisted of a codon 259 Asp --> His exchange), despite diffuse overexpression of high levels of nuclear p53 protein in most cases. This result indicates that (1) the abnormal p53 expression is usually not caused by mutations of the p53 gene in PPC and (2) PPC is part of a growing number of tumors that share evidence of p53 dysfunction in the absence of mutation.

Contribution of BRCA1 mutations to ovarian cancer

BACKGROUND

Inherited mutations in the BRCA1 gene confer a high risk of breast and ovarian cancer in some families. To determine the contribution of BRCA1 mutations to ovarian cancer in the general population, we analyzed DNA samples from a consecutive series of women with ovarian cancer seen at one center.

METHODS

We studied 374 women who received a diagnosis of epithelial ovarian cancer before the age of 70 years and were treated at the Royal Marsden Hospital between July 1993 and September 1995. Genomic DNA was analyzed by multiplex heteroduplex analysis. Variants were further identified by sequencing.

RESULTS

Probable germ-line BRCA1 mutations were identified in 13 of the 374 women (3 percent; 95 percent confidence interval, 2 to 6 percent). Six of the variants have not been described previously. Of the 13 mutations, 12 are predicted to result in a truncated protein product. An additional variant results in an in-frame deletion just outside the putative zinc-finger domain. Nine of the 12 women with truncating mutations had family histories of breast or ovarian cancer or both.

CONCLUSIONS

Assuming that our method has a sensitivity of 70 percent, mutations in BRCA1 occur in approximately 5 percent (95 percent confidence interval, 3 to 8 percent) of women in whom ovarian cancer is diagnosed before the age of 70 years.

A case-matched molecular comparison of extraovarian versus primary ovarian adenocarcinoma

BACKGROUND

Extraovarian müllerian adenocarcinoma (EOM) resembles primary ovarian carcinoma (POC) both histologically and clinically, yet little is known regarding the molecular genetic characteristics of this entity. The objective of this study was to compare the expression of three molecular markers of tumor behavior in EOMs and POCs.

METHODS

Forty-four patients meeting strict criteria for EOM were identified and matched to POC controls for age, stage, tumor histology and grade, cytoreductive surgery, and survival. Immunohistochemistry was used to determine overexpression of p53 and HER-2/neu. DNA content was evaluated by flow cytometry. Direct DNA sequencing of exons 5-8 of the p53 gene was performed in nine EOM tumors. Statistical comparisons were made using chi-square, Kaplan-Meier, and Mantel-Cox log rank methods.

RESULTS

Overexpression of HER-2/neu was demonstrated in 59% (26 of 44) of the EOM group versus 36% overexpression (16 of 44) in the POC controls (P = 0.05). Overexpression of p53 was noted in 48% of the EOM cases, similar to the 59% incidence observed in the control group (P = 0.29). Missense mutations were found in 9 of 9 EOM tumors showing strong p53 nuclear immunostaining. No significant difference in the incidence of aneuploidy was observed when EOM cases were compared with POC controls (65% vs. 63%). High tumor grade was strongly associated with HER-2/neu overexpression in the EOM group (P = 0.002). None of the parameters studied were predictive of prognosis within the EOM and POC groups.

CONCLUSIONS

Although overexpression of p53 protein, p53 gene mutations, and abnormal DNA content were similar between EOMs and POCs, EOMs demonstrated almost twice the rate of HER-2/neu overexpression. This result suggests that distinct genetic events may be responsible for malignant transformation in EOMs versus POCs.

In situ detection of parathyroid hormone-related protein in ovarian clear cell carcinoma

A case of ovarian clear cell carcinoma associated with hypercalcemia is reported. A 67-year-old woman developed the lung metastasis 8 months after primary surgery. The patient manifested symptoms of humoral hypercalcemia of malignancy (HHM) during the last 3 months of her clinical course. Serum and urinary C-terminus parathyroid hormone-related protein (PTHrP) levels were remarkably high. No increase in interleukin (IL) 1beta, tumor necrosis factor (TNF) alpha, vitamin D3 metabolites or intact PTH was detected. Pamidronate disodium treatment was transiently suppressed her serum calcium level. The patient died despite seven courses of chemotherapy. Autopsy showed multiorgan metastases and accelerated osteoclastic bone resorption; skeletal metastasis was not detected. Immunohistochemical analysis clearly showed the localization of PTHrP at both the primary and metastatic sites. The transcripts of PTHrP at pulmonary metastatic sites were revealed by in situ hybridization and the reverse transcription polymerase chain reaction (RT-PCR) method. PTHrP was the causative factor for HHM in this case. It is therefore suggested that hypercalcemia may have occurred after PTHrP production had overcome the homeostatic level during the terminal stage, although PTHrP production continued irrespective of the patient's serum calcium level.

Comparison of DNA gains and losses in primary renal clear cell carcinomas and metastatic sites: importance of 1q and 3p copy number changes in metastatic events

Archival material from primary and metastatic renal clear cell carcinomas of 25 patients was studied by comparative genomic hybridization. Copy number changes of entire chromosomes or chromosomal subregions were detected in 22 primary and 21 metastatic tumors. Copy number changes affected the following chromosomes in at least 20% of the 25 primary tumors (minimal common region given in parentheses): gains were noted for chromosomes 1 (1q21-->q23), 5 (5q31-->q34), 7 (7p), 8 (8q), 16 (16p), 17 (17q12-->qter), 19, and 22 (22q12-->qter); losses were revealed for chromosomes 3 (3p21-->pter), 8 (8p23-->pter), 14(14q21-->qter), and Y. The same chromosomal regions that were involved in primary renal clear cell carcinomas were also found in the respective metastatic tumors but with strikingly different frequencies for a few regions. Metastatic tumors showed a significantly higher frequency of complete or partial gains of the long arm of chromosome 1, in particular at 1q21-->q23 than primary tumors (16 cases versus 6 cases; P < 0.005). These data suggest a correlation of metastatic events in renal clear cell carcinomas with an increase in the copy number of genes located at 1q, in particular at 1q21-->q23. In contrast, the entire or partial loss of the short arm of chromosome 3 was significantly less frequent in metastatic tumors (8 cases versus 15 cases; P < 0.025). The validity of 1q and 3p copy number changes detected by comparative genomic hybridization was confirmed by interphase cytogenetics with region-specific yeast artificial chromosomes to paraffin-embedded tumor tissue sections.

Deletion mapping on chromosome 10q25-q26 in human endometrial cancer

To understand genetic events which play a role in the development and/or progression of human endometrial cancer, we studied allelotypes on all autosomal chromosomes, as well as chromosome X, with 42 microsatellite markers and 56 endometrial cancers. The most frequent loss of heterozygosity (LOH) was observed on the long arm of chromosome 10 (14 of 30, 47%), which was commonly detected in grade 1 cancer. We constructed a detailed deletion map and defined two commonly deleted regions in 10q25-q26; one was the 8 cM region between D10S209 and D10S216, the other was the 12 cM region between D10S217 and D10S590. Replication errors at two or more loci were observed in 24 of 56 tumours (43%), suggesting that disruption of the DNA mismatch repair system also plays an important role in the course of endometrial carcinogenesis.

Allelic deletions of the VHL gene detected in multiple microscopic clear cell renal lesions in von Hippel-Lindau disease patients

Patients with von Hippel-Lindau (VHL) disease develop a spectrum of bilateral clear-cell renal lesions including cysts and renal cell carcinomas (RCCs). VHL gene deletions have been previously reported in VHL-associated macroscopic RCC. Although histological analysis suggests that microscopic cystic lesions in the VHL patients may represent precursors of the RCC, there is at present no direct molecular evidence of their relationship. To investigate the relationship between cystic lesions and RCC, 26 microdissected archival renal lesions from two VHL disease patients were studied for loss of heterozygosity at the VHL gene locus using polymerase chain reaction single-strand conformation polymorphism analysis. The renal lesions included 2 benign cysts, 5 atypical cysts, 5 microscopic RCCs in situ, 5 cysts lined by a single layer of cells, in which RCCs in situ were developing, and 2 microscopic and 7 macroscopic RCCs. Except for a single benign cyst, 25 of 26 renal lesions showed nonrandom allelic loss of the VHL gene. In either of the 2 patients, the same VHL allele was deleted in all of the lesions tested, indicating loss of the wild-type allele and retention of the inherited, mutated VHL allele. The results suggest that all clear-cell lesions in the VHL kidney represent neoplasms and that the loss of the VHL gene occurs early in their development. Atypical and benign cysts most likely represent the initial phenotype in malignant transformation to the RCC.

Losses at 3p common deletion sites in subtypes of kidney tumours: histopathological correlations

Deletions of the short arm of chromosome 3 (3p) have been recognized as characteristic features of clear cell renal cell carcinomas (clear cell RCC). We analysed 55 clear-cell RCCs and 30 non-clear-cell kidney tumours (10 papillary and 7 chromophobic RCCs, 11 oncocytomas and 2 collecting duct carcinomas) in loss of heterozygosity (LOH) studies using microsatellite markers for previously observed regions of common deletions on 3p in kidney tumours (3p25, 3p21.3, 3p14.2 and 3p12-13). Alterations were found in all 55 cases of clear-cell RCCs at two to four of the 3p regions. Extensive losses were not found in non-clear-cell tumours except for collecting duct carcinomas; 1 of 10 papillary RCCs showed interstitial deletion limited to a single 3p21.3 locus. LOH analyses using microsatellite markers for regions of common deletions at 3p may be of value in differential diagnosis of kidney tumours.

Frequent deletion of chromosome 1p sequences in an aggressive histologic subtype of endometrial cancer

The molecular genetic events underlying endometrial tumorigenesis are ill-defined at present. We have identified a region on the short arm of chromosome 1 which is frequently deleted in endometrial cancers. The region of deletion has been localized to bands 1p32-33. Deletion of 1p32-33 is seen more frequently in cancers of the highly aggressive papillary serous type than in cancers of the less-aggressive endometrioid type. These data suggest the presence of a tumor suppressor gene on 1p32-33 which is specifically involved in the development of endometrial cancers with poor outcome.

Establishment of two human renal cell carcinoma cell lines with different chemosensitivity

Two cell lines, SKR1 and NKK1, were established from renal cell carcinomas (RCC) with different histopathologic characteristics: SKR1 from grade 3, solid type, pleomorphic cell type carcinoma in a 66-year-old male and NKK1 from grade 2, alveolar type, clear cell carcinoma in a 49-year-old female. Electron microscopic study showed the presence of microvilli on cell surface and desmosome-like structures between cells in both lines. Doubling time and plating efficiency of SKR1 were 28 h and 37%, respectively, whereas those of NKK1 were 45 h and 22%, respectively. The chromosome number of both cell lines was 100% aneuploid with a mode of 74 chromosomes for SKR1 and 84 for NKK1. Both SKR1 and NKK1 induced tumors at the site of subcutaneous injection of nude mice. The morphologic characteristics of the tumor were similar to those of each original tumor. NKK1 was about 20 times more resistant to doxorubicin and vinblastine as compared to SKR1. Expression of P-glycoprotein was considered to be one of the factors responsible for such multidrug resistant phenotype of NKK1 cells. These two lines with different chemosensitivity may be a useful model for developing new therapeutic strategies for RCC.

Clinicopathologic correlation of DNA flow cytometric content analysis (DFCA), surgical staging, and estrogen/progesterone receptor status in endometrial adenocarcinoma

DNA flow cytometric content analysis (DFCA) and estrogen (ER) and progesterone (PR) receptor levels are reported to be prognostic with regard to the malignant potential of endometrial adenocarcinoma. We retrospectively reviewed the records of 50 patients presenting with endometrial adenocarcinoma between July 1990 and December 1992, to determine the extent of any pathologic features reported at the time of hysterectomy. Patients whose tumors were nondiploid (aneuploid) by flow cytometry generally presented with a higher pathologic stage, higher grade, and more frequent lymph node involvement. In addition, the majority of clear cell and uterine papillary serous (UPS) adenocarcinoma were also nondiploid. Fourteen of 21 ER-positive tumors aneuploid, as were 18 of 37 PR-positive tumors. We also found DNA-A (DNA content aneuploid) patterns frequently associated with tumor characteristics implicated by other authors as related to aggressiveness. Further studies comparing the molecular biology of tumors to their clinicopathologic features and behavior are needed to fully understand the ultimate malignant potential.

Endometrial carcinoma: the prognostic impact of papillary serous carcinoma (UPSC) in relation to nuclear grade, DNA ploidy and p53 expression

In a histopathological review of 266 women with stage I-IV endometrial carcinoma, the prognostic significance of uterine papillary serous carcinoma (UPSC) and clear cell carcinoma (CCC) of the endometrium was compared with that of ordinary adenocarcinoma and adenoacanthoma. UPSC and CCC were diagnosed in 31/266 (12%) and 6/266 (2%) of the patients respectively. The median follow-up time was 79 months (range 3 to 133 months). 49% of the patients with UPSC or CCC died of their cancer compared with 31% in the adenocarcinoma + adenoacanthoma group (RH=2.25; p=0.0022). Strong expression of the mutated p53 gene product was significantly more common in the UPSC + CCC group than in the reference group (64% vs. 19%), (p<0.0001). In a Cox multivariate analysis including histopathological and clinical variables, UPSC and CCC were still significant predictors of survival (p<0.05). When nuclear grade was added to the analysis, UPSC + CCC as well as the degree of differentiation lost most of their prognostic impact. In a final multivariate analysis, DNA ploidy was found to be the strongest predictor of outcome besides age and clinical stage.

p53 protein expression and gene analysis in clear cell adenocarcinoma of the vagina and cervix

OBJECTIVE

p53 is the most commonly mutated gene in human cancers. The objective of this study was to determine if clear cell adenocarcinomas (CCAs) of the vagina and cervix are associated with p53 gene mutations or alterations in p53 tumor-suppressor protein expression.

METHODS

Paraffin-embedded tissue specimens from 21 women (median age 22 years) with clear cell adenocarcinoma of the vagina or cervix were studied. Fifteen women had a prior history of in utero exposure to diethylstilbestrol. p53 protein expression was detected by immunohistochemical (IHC) analysis with monoclonal antibody DO-7 (Dako Corp.) which recognizes both wild-type and mutant p53 proteins. For p53 gene analysis, genomic DNA from malignant tissue was isolated and exons 4-10 were amplified by PCR and subjected to mutation screening by single-stranded conformation polymorphism (SSCP) analysis.

RESULTS

p53 protein was detected by IHC in tumors from 14 of 21 cases (67%). The observed p53 staining patterns were heterogeneous in both the proportion and intensity of tumor cells stained but were clearly overexpressed relative to the surrounding benign stroma. Metastatic tumors from 3 women with metastatic disease were also positive for p53 staining. SSCP analysis did not identify p53 mutations in any of the cases and strongly suggests that the tumors contained only wild-type p53 alleles.

CONCLUSIONS

Recent studies have demonstrated that wild-type p53 may accumulate in response to DNA damage which normally leads to growth arrest or programmed cell death. Our observations are consistent with the hypothesis that p53 overexpression in CCAs of the vagina and cervix is a response to generalized DNA damage, rather than a result of p53 protein half-life prolongation resulting from mutational inactivation of p53. Overexpression of wild-type p53 protein in vaginal and cervical CCA may relate to the more favorable prognosis of this subset of tumors in comparison to other gynecologic tumors containing mutated p53 genes.