Detection of p53 point mutations in primary human vulvar cancer by PCR and temperature gradient gel electrophoresis

Two different, mutually exclusively distributed, TP53 mutations in ovarian and peritoneal tumor tissues of a serous ovarian cancer patient: indicative for tumor origin?

High-grade serous ovarian cancer (HGSOC) is characterized by a TP53 mutation rate of up to 96.7% and associated with a more aggressive tumor biology. The origin of HGSOC is thought to arise either from fallopian tube secretory cells or the ovarian surface epithelium/inclusion cysts, the former with more evidence. Peritoneal tumor spread is heterogeneous, either excessive in the peritoneum (with miliary appearance) or more confined to the ovaries with only few (bigger and exophytically growing) peritoneal implants. Using RNA sequencing and DNA digital droplet polymerase chain reaction (PCR), we identified two different functional TP53 mutations in one HGSOC patient: one exclusively in the ovarian tumor mass and the other exclusively in ascites tumor cells, peritoneal tumor masses, and a lymph node metastasis. In blood, both mutations could be detected, the one from the peritoneal tumors with much higher frequency, presumably because of the higher tumor load. We conclude that this mutually exclusive distribution of two different TP53 mutations in different tumor tissues indicates the development of two independent carcinomas in the peritoneal cavity, probably one originating from a precancerous lesion in the fallopian tube and the other from the ovaries. In addition, in the patient's ascites CD45 and EpCAM, double-positive cells were found-proliferating but testing negative for the above-mentioned TP53 mutations. This mutually exclusive distribution of two TP53 mutations is probably further evidence that HGSOC can originate either from the fallopian tube or (more seldom) the ovaries, the former more prone for excessive peritoneal tumor spread.

Genetic and epigenetic changes in vulvar squamous cell carcinoma and its precursor lesions: a review of the current literature

Vulvar cancer is a relatively rare gynecologic malignancy with an annual incidence in developed countries of approximately 2 per 100,000 women. Vulvar squamous cell carcinoma (VSCC) has two etiological pathways: a high risk human papillomavirus (HPV)-dependent route, which has usual vulvar intraepithelial neoplasia (uVIN) as a precursor lesion, and an HPV-independent route, which is associated with differentiated VIN (dVIN), lichen sclerosus, and genetic alterations, such as TP53 mutations. Research on the molecular etiology of vulvar cancer has increased in the past years, not only regarding genetic alterations, but also epigenetic changes. In genetic alterations, a mutation irreversibly changes the nucleotide sequence of the DNA, or the number of copies of chromosomes per cell is altered. In epigenetics, the nucleotide sequence remains the same but genes can be 'switched' on or off by, for example, DNA methylation or histone modification. We searched the current literature on genetic and epigenetic alterations in VSCC and its precursor lesions. Many studies have reported a higher incidence of somatic mutations in HPV-negative tumors compared to HPV-positive tumors, with TP53 mutations being the most frequent. Allelic imbalances or loss of heterozygosity are more frequently found in higher stages of dysplasia and in invasive carcinomas, but it is not exclusive to HPV-negative tumors. A limited number of studies are available on epigenetic changes in vulvar lesions, with hypermethylation of CDKN2A being the most frequently investigated change. For most genes, hypermethylation occurs more frequently in vulvar squamous cell carcinomas than in precursor lesions. As most studies have focused on HPV infection and TP53 mutations, we suggest that more research should be performed using whole genome or next generation sequencing to determine the true landscape of genetic and epigenetic alterations in vulvar squamous cell carcinoma.

Clinico-pathological and biological prognostic variables in squamous cell carcinoma of the vulva

Several clinical-pathological parameters have been related to survival of patients with invasive squamous cell carcinoma of the vulva, whereas few studies have investigated the ability of biological variables to predict the clinical outcome of these patients. The present paper reviews the literature data on the prognostic relevance of lymph node-related parameters, primary tumor-related parameters, FIGO stage, blood variables, and tissue biological variables. Regarding these latter, the paper takes into account the analysis of DNA content, cell cycle-regulatory proteins, apoptosis-related proteins, epidermal growth factor receptor [EGFR], and proteins that are involved in tumor invasiveness, metastasis and angiogenesis. At present, the lymph node status and FIGO stage according to the new 2009 classification system are the main predictors for vulvar squamous cell carcinoma, whereas biological variables do not have yet a clinical relevance and their role is still investigational.

Vulvo-vaginal cancers: risks, evaluation, prevention and early detection

Vulvar and vaginal cancers are rare and account for approximately 7% of cancers of the female reproductive tract. Vulvar and vaginal neoplasia share similar risk factors: human papillomavirus infection, previous cervical intraepithelial neoplasia or cervical cancer, current smoking, sexual factors, and immunosuppression. Several treatment options are available for patients with documented histologic high-grade intraepithelial vulvar or vaginal neoplasia, including excision, laser vaporization, and 5-fluorouracil. After treatment, lifetime follow-up with cytology and colposcopy is recommended. With the widespread use of the human papillomavirus vaccine, one half to two thirds of vulvar and vaginal cancers may be prevented. Patient education regarding reduction of risk factors for progression and close surveillance of at-risk individuals may prevent the progression to invasive disease.

Vulval cancer: prevention and screening

The incidence of vulval cancer is rising, both in older women and those under 50 years of age. Vulval cancer has at least two types, one arising in association with lichen sclerosus (LS) and the other with vulval intraepithelial neoplasia (VIN). Recent pathological and aetiological descriptions are included, along with the latest description of VIN terminology. Prevention of and screening for vulval cancer will require greater understanding of why some women with LS and VIN are at greater risk: recent studies of molecular change might contribute to this. The use of vulval cytology and toluidine blue staining is described. Patient or vulval awareness may help but clinical features are non-specific. Prophylactic vaccination against HPV and campaigns against smoking may contribute in the future.

TP53 mutations in vulval lichen sclerosus adjacent to squamous cell carcinoma of the vulva

Non-neoplastic epithelial lesions of the vulva (NNEDV) lichen sclerosus (LS) and squamous hyperplasia (SH) have been implicated in the pathogenesis of squamous cell carcinoma of the vulva (SCC). To date, there have been no recognisable precursor lesions for SCC associated with NNEDV. TP53 is the most frequent genetic change in human cancers and can indicate both aetiology and molecular pathogenesis of tumours. A total of 27 SCC patients underwent immunohistochemistry (IHC) and TP53 mutational analysis using microdissection and direct sequencing. There were 19 patients with areas of adjacent epidermis: 17 had NNEDV (four SCCs had more than one adjacent lesion) and two had normal epidermis. In all, 70.4% of the SCCs, 40% LS and 22.2% SH demonstrated overexpression of p53. In total, 77.8% of SCCs, 46.7% of LS and 22.2% SH demonstrated mutations in TP53, with the majority of lesions having a mutation in codon 136. Eight cases were identified where the same mutation was identified in the SCC and in the adjacent area. These data suggest that TP53 mutations develop in NNEDV and are intrinsic to the clonal evolution that leads to SCC. The type of mutation detected is more likely to occur due to endogenous cellular changes rather than exogenous carcinogen exposure.

Recent advances in the pathology of the vulva

This review addresses recent and important advances in our knowledge of several uncommon or rare disorders of the vulva including Paget's disease, vulva intraepithelial neoplasia, lichen sclerosus and squamous hyperplasia and their relationship to squamous carcinoma. Emphasis is placed on the two biologically different types of squamous carcinoma related and unrelated to human papillomavirus infection. Finally, the relatively recent concept of the sentinel node as applied to vulva carcinoma is discussed.

Immunohistochemical analysis of p53 in vulval intraepithelial neoplasia and vulval squamous cell carcinoma

Human papillomavirus (HPV) is thought to cause some vulval squamous cell carcinomas (VSCC) by degrading p53 product. Evidence on whether HPV-negative VSCC results from p53 mutation is conflicting. We performed immunohistochemistry for p53 product on 52 cases of lone vulval intraepithelial neoplasia (VIN), 21 cases of VIN with concurrent VSCC and 67 cases of VSCC. We had previously performed HPV detection and loss of heterozygosity (LOH) analyses on these samples. Abnormal p53 immunoreactivity (p53-positive) rates in HPV-positive VSCC and HPV-negative VSCC were 22% (12/54) and 31% (4/13), respectively (P<0.74). p53 immunoreactivity was associated with LOH at the p53 locus (P<0.004), but neither technique differentiated between HPV-positive and HPV-negative VSCC. p53 immunoreactivity was associated with overall LOH rates (p53-positive VSCC vs p53-negative VSCC mean fractional regional allelic loss 0.41 vs 0.24, respectively, P<0.027). LOH at 3p25 was more frequent in p53-positive VSCC cf p53-negative VSCC (70 vs 21%, respectively, P<0.007). There was a trend in p53 disruption associated with invasive disease; HPV-positive VSCC demonstrated more disruption than VIN associated with VSCC, which had more disruption than lone VIN III (22 vs 10 vs 0%, respectively, P<0.005). In all, three out of 73 cases of VIN were p53-positive. All three were associated with concurrent or previous VSCC. Meta-analysis of previous studies revealed significantly more p53 disruption in HPV-negative VSCC cf HPV-positive VSCC (58 vs 33%, respectively; P<0.0001). p53 immunoreactivity/mutation in VIN only appeared in association with VSCC. These data suggest that HPV-independent vulval carcinogenesis does not exclusively require disruption of p53, p53 disruption may work synergistically with LOH at specific loci and p53-positive VIN should be checked carefully for the presence of occult invasion.

Overexpression of wild-type p53 in lichen sclerosus adjacent to human papillomavirus-negative vulvar cancer

Human papillomavirus is a risk factor for vulvar cancer, whereas human papillomavirus-negative late onset vulvar carcinoma is associated with the dermatologic condition, lichen sclerosus. Human papillomavirus E6 protein targets TP53 for degradation and by inference it has been assumed that human papillomavirus-negative vulvar cancer is dependent upon the acquisition of p53 somatic mutations and subsequent allelic loss. To investigate this, TP53 expression, loss of heterozygosity, and p53 genomic sequence were examined in 29 cases of human papillomavirus-negative vulvar carcinoma with adjacent lichen sclerosus. We examined 37 cases of lichen sclerosus without vulvar carcinoma, 10 cases of nongenital lichen sclerosus, and 12 cases of normal vulvar epithelium served as controls. TP53 was evident in 72% of vulvar carcinoma, 48% in epithelium adjacent to vulvar carcinoma, but was minimal in normal samples. When lichen sclerosus cases were selected to exclude samples with absolutely no TP53 expression through probable failed antigen retrieval or homozygous p53 loss the number of epithelial cells expressing TP53 increased progressively from nongenital lichen sclerosus to lichen sclerosus without vulvar carcinoma, then to lichen sclerosus with vulvar carcinoma (p<0.0001). These data suggest elevated TP53 is a feature of vulvar lichen sclerosus. Seventy-four percent of vulvar carcinoma had chromosome 17p-linked loss of heterozygosity, whereas 47% of adjacent lichen sclerosus featured loss of heterozygosity, but only 31% of vulvar carcinoma had p53 mutations, a frequency less than reported previously. Seven percent of adjacent lichen sclerosus had mutations, showing for the first time the presence of an identical mutation to the matched vulvar carcinoma. These data, however, implicate p53 mutations as a later event in vulvar carcinoma and in marked contrast to the original expectation, our loss of heterozygosity data are consistent with loss of another locus (not p53) on 17p operating as a tumor suppressor in lichen sclerosus destined to develop vulvar carcinoma.

Alterations of the p16/Rb/cyclin-D1 pathway in vulvar carcinoma, vulvar intraepithelial neoplasia, and lichen sclerosus

Three different alterations in the p16/pRb/cyclin-D1 pathway (p16(INK4a)-promoter hypermethylation and expression of pRb and cyclin-D1) were investigated in a series of 38 cases of vulvar carcinoma (VC), 13 cases of vulvar intraepithelial neoplasia (VIN), and 21 cases of lichen sclerosus (LS). Paraffin blocks from 72 patients were selected for investigation of DNA methylation patterns in the CpG island of p16(INK4a) by methylation-specific polymerase chain reaction. Immunohistochemical studies for pRb and cyclin-D1 were performed using the standard avidin-biotin-peroxidase complex method. Epigenetic silencing of p16(INK4a) was detected in 68% of VC, 69.2% of VIN, and 42.8% of LS cases. Lack of pRb protein was found in 21% of VC, 0% of VIN, and 0% of LS cases. Overexpression of cyclin-D1 was found in 21% of VC, 30.8% of VIN, and 0% of LS cases. We conclude (1) that p16(INK4a) epigenetic inactivation most likely represents an early event, insufficient for malignant transformation, that may occur in clinically benign lesions such as LS; (2) that lack of pRb was only detected in fewer than one quarter of the carcinomas and could be considered a late secondary event; and (3) that cyclin-D1, which was overexpressed in VC and VIN, could contribute to the malignant transformation in association with p16 hypermethylation.

The role of p53 and Ki67 in Paget's disease of the vulva and the breast

OBJECTIVE

Paget's disease of the vulva (PDV) and Paget's disease of the breast (PDB) are uncommon diseases, accounting for approximately 1% of all vulval neoplasms and 0.5-4% of all breast cancers, respectively. In 10-30% of vulval cases an invasive adenocarcinoma is present. In such cases the disease is often aggressive and recurrence rate is high. This is in contrast to PDB where the general consensus is that almost all cases are associated with an in situ or invasive ductal carcinoma. Our aim was to examine the presence of the tumor suppressor protein p53 and the proliferation marker Ki67 in PDV and PDB and correlate any differences in the expression of these two proteins with the presence of an underlying carcinoma.

METHODS

Immunohistochemistry was performed on 52 archival cases of PDV, which included 10 with associated invasive adenocarcinoma of the vulva, and on 37 archival cases of PDB, including 26 with available associated ductal carcinoma in situ (DCIS) or invasive carcinoma of the breast. All cases were formalin-fixed and paraffin wax-embedded. Monoclonal antibodies were used with microwave antigen retrieval. Streptavidin-biotin-horseradish peroxidase and 3,3'-diaminobenzidine detection methods were employed to visualize antibody binding and staining. A section was scored positive for p53 if more than 10% of cell nuclei were stained brown and Ki67 was expressed as a percentage of positive cells to the nearest 5% of cells showing nuclear positivity (Ki67 staining index).

RESULTS

p53 was expressed in 15 of 52 (29%) PDV cases and 5 of 37 (13%) cases of PDB. Four of the ten cases (40%) of PDV associated with invasive disease expressed p53 compared with 11 of 42 (26%) cases without invasive disease. The mean Ki67 staining index for PDV associated with invasion was 19%, and for that without invasion, 16%. In the breast cases, the mean staining index was 11%.

CONCLUSION

Our data suggest that p53 may have a role to play in PDV progression, and may be a late event in some cases, especially those associated with invasive disease. Ki67 has no apparent prognostic role in PDV as there was no significant difference between those cases associated with and those without invasive disease. Neither p53 nor Ki67 appears to have a prognostic role to play in PDB.

Loss in 3p and 4p and gain of 3q are concomitant aberrations in squamous cell carcinoma of the vulva

Neoplasm of the vulva is a rare malignancy accounting for <5% of all female genital-tract cancer. However, in recent years the incidence of vulva intraepithelial neoplasia, known to serve as a precursor to carcinoma, has increased in young women generating considerable interest in its pathogenesis. Genetic changes at the molecular level in precursor or invasive vulvar tumors are not well investigated, and DNA copy number changes have not been reported until now. We used comparative genomic hybridization (CGH) to analyze genetic alterations in 10 primary invasive squamous cell carcinomas of the vulva. Chromosomal aberrations were identified in 8/10 cases. The most frequent chromosomal losses were 4p13-pter (five cases), 3p (four cases), and 5q (two cases), and less frequent losses were detected at 6q, 11q, and 13q (one case each). The most frequent chromosomal gains were 3q (four cases) and 8p (three cases), and less frequent gains were found in 9p, 14, 17, and 20q (one case each). The pattern of chromosomal imbalance in vulvar cancer detected by CGH was revealed to be very similar to that in cervical cancers, despite regional differences in their prevalence. These results suggest that the pathogenic pathways in vulvar and cervical carcinomas may be similar and that the genetic background may be common to these two squamous cell carcinomas.

p53 protein expression in squamous cell carcinoma of the vulva

BACKGROUND

The objective of the study was to evaluate the pathogenetic and prognostic value of p53 protein expression in squamous cell carcinoma of the vulva.

METHODS

The clinical data in charts of 167 patients with International Federation of Gynecology and Obstetrics (FIGO) Stages I-III primary tumors who were treated by surgery were reviewed. Samples from the primary tumor were immunostained for p53 protein. p53 overexpression was defined as immunoreactivity in > 5% of nuclei.

RESULTS

p53 overexpression was observed in 92 tumors (55%). p53 overexpression did not correlate with age at diagnosis, FIGO stage, histologic grade, vessel invasion, tumor thickness, tumor greatest dimension, DNA ploidy, or inguinal lymph node metastasis. In the whole group a significantly reduced 5-year corrected survival was observed in patients with p53 overexpression compared with p53 negative patients (P = 0.04). In the different FIGO stages, disease-related survival was not influenced by p53 overexpression in 37 patients with Stage I disease (P = 0.60) or in 86 patients with Stage II disease (P = 0.96). In 44 patients with Stage III disease, p53 overexpression was significantly associated with poorer prognosis (P = 0.004). Independent prognostic factors for corrected survival in the entire group of 167 patients were: vascular invasion, groin metastasis, tumor greatest dimension, and p53 overexpression. In patients with FIGO Stage III disease p53 overexpression was not an independent prognostic factor.

CONCLUSIONS

p53 protein overexpression appears to be involved in the pathogenesis of vulvar squamous cell carcinoma. p53 protein overexpression was significantly associated with disease-related survival. p53 prognostic impact was observed only in patients with advanced disease.