Analysis of HPV-positive and -negative vulvar carcinomas for alterations in c-myc, Ha-, Ki-, and N-ras genes

Single base instability is promoted in vulvar lichen sclerosus

Single base substitution mutations in codons 248 and 273 of TP53 and codon 12 Kirsten-ras (KRAS) are commonly found in human carcinomas. To determine whether these mutations also occur in normal and inflamed tissues from which carcinomas arise, we utilized the ultra-sensitive polymerase chain reaction/restriction endonuclease/ligase chain reaction mutation assay. Ninety samples of genital skin, including lichen sclerosus (LS) affected skin, adjacent normal and non-adjacent normal, were assayed. Mutations were detected in 103 of 349 assays and consisted of KRAS G34A, G34T, G35A, and TP53 C742T, G818C, C817T, and G818A mutations. Mutant prevalence varied from 1 to 20 per 10(6) wild-type cells. Mutations occurred significantly more frequently in LS (78/224 (35%)) than adjacent normal (20/88 (23%)) and non-adjacent normal genital skin (5/38 (13%)). KRAS G34A mutation was relatively common to all classes of specimen, whereas TP53 gene C742T and G818C mutations were significantly more frequent in LS than normal genital skin. In matched samples, immunohistochemistry evaluation of p53 protein expression revealed the presence of epidermal p53 clones in LS whose presence and number significantly correlated with the presence of TP53 C742T and G818C mutations. Based on these results, it appears oncogenic point mutations occur in normal genital skin, and are selected for in LS.

p16INK4A expression as biomarker for HPV 16-related vulvar neoplasias

Up-regulation of p16INK4A is associated with high-risk human papillomavirus (HPV) in preinvasive and invasive cervical neoplasia. However, its expression in vulvar carcinomas, which have a diverse pathogenesis, has not been extensively studied. One hundred seventy-seven vulvar intraepithelial neoplasms (VIN), squamous cell carcinomas (SCC), and benign squamous epithelia were analyzed for p16 expression. RNA/RNA in situ hybridization was used to detect HPV 16 E6/E7 transcripts in 112. Ninety-five percent of VIN 3 and basaloid or warty SCCs (76/80) and 4% of keratinizing SCC (2/48) were moderately to strongly immunopositive for p16, which localized to nucleus and cytoplasm; 52/58 analyzed (90%) contained HPV 16 transcripts. The positive predictive value (PPV) of moderate to strong diffuse p16 immunostaining and HPV positivity for the diagnosis of VIN 3 and of basaloid or warty SCC was 97% and 95%, respectively. Conversely, 94% of keratinizing SCC contained heterogeneous staining, and when present, it was strictly cytoplasmic and frequently localized to the cells at the epithelial-stromal interface. Benign squamous epithelia were p16 negative, with the exception of lichen sclerosus, which contained focal and heterogeneously p16 positive in 42%. As in the cervix, intense diffuse p16 expression supports an HPV-related neoplastic process in vulvar neoplasia, irrespective of the level of differentiation. Up-regulation of p16 at the epithelial-stromal interface in HPV negative keratinizing SCCs is consistent with an HPV-independent response to alterations associated with invasion. These disparate patterns of p16 expression underscore 2 different mechanisms for p16 expression in HPV-related and HPV-unrelated vulvar carcinomas.

The c-myc activation in cervical carcinomas and HPV 16 infections

Despite the prominent role for Human Papillomavirus (HPV) infection in the development of genital cancer, other genetic or environmental co-factors have also been involved. Studies of c-myc activation in cervical carcinomas have reported that gene over-expression (mainly gene amplification) are common in cervical squamous cell carcinomas and may correlate with the biologic behavior of the neoplasm. Using PCR based technology, DNAs from 79 normal cervical samples and 225 abnormal cervical tissue scrapes were analyzed for HPV detection and typing and for c-myc gene amplification. Significant differences were found between the different cyto/histology groups (P<0.0001) and also with HPV high-risk infected samples (P<0.0002). In this sense, we showed that the average c-myc copy number increased according to the histological grade of the lesion (OR=6.3, CI=2.1-18.8). Also, the results showed that the infection with HPV 16 was tightly associated with c-myc amplification (OR=10.6, CI=3.1-36). These results could indicate that oncogene amplification take place in pre-invasive stages of cervical disease and could cooperate not only in tumor progression but also in cell transformation. Moreover, the results strongly associate the c-myc gene amplification to the infection with the oncogenic HPV 16, showing that the pattern of virus infection and oncogene activation could be specific for different viral genotypes.

Role of cell-cycle regulatory proteins in gynecological cancer

Human malignant tumors are characterized by abnormal proliferation resulting from alterations in cell-cycle regulatory mechanisms. This review summarizes the current knowledge about these aberrations in malignant tumors of the ovary, endometrium, cervix uteri, and vulva. The data indicate that analysis of single cell cycle stimulating or inhibiting proteins partly produces unexpected, apparently paradoxical results, and cell-cycle regulatory pathways should be regarded as a whole in order to identify the molecular mechanisms leading to abnormal tumor cell proliferation. For the papillomavirus (HPV)- associated cervical and vulvar carcinomas, the manifold effects of the viral oncogenes E6 and E7 on cell-cycle control are described.

c-myc gene amplification detected in preinvasive intraepithelial cervical lesions

The aim of the present work was to evaluate the c-myc gene amplification process in cervical samples and to analyze the relationship between the activation of this proto-oncogene and the cytologic and/or histologic status. Thirty-four normal cervical samples and 105 abnormal cervical tissue scrapes, previously used for PAP or histopathologic diagnosis, were analyzed for c-myc gene amplification. Detection of c-myc gene amplification was performed using a polymerase chain reaction (PCR)-based method known as target arbitrarily primed-PCR (TAP-PCR). For c-myc amplification, significant differences were found between normal samples and samples presenting different grades of lesions (P<0.001). A significant difference between high-grade squamous intraepithelial lesions (HG-SIL) and the other stages of cervical disease was also found (P<0.05). This study demonstrated that c-myc copy number increases according to the histologic grade of the lesion. These results could indicate that oncogene amplification takes place in preinvasive stages of cervical disease and could cooperate not only in tumor progression but also in cell transformation.

Allelic loss in human papillomavirus-positive and -negative vulvar squamous cell carcinomas

Vulvar squamous cell carcinoma (VSCC) is a biologically and morphologically diverse disease, consisting of human papillomavirus (HPV)-positive and -negative tumors that differ in their morphological phenotypes and associated vulvar mucosal disorders. This study analyzed the frequencies of allelic loss (loss of heterozygosity (LOH)) in HPV-positive and -negative VSCCs to identify potential targets for the study of preinvasive diseases, to determine whether HPV status influenced patterns of LOH, and to determine whether these patterns differed from HPV-positive tumors of another genital site, cervical squamous cell carcinomas (CSCC). DNA extracted from microdissected archival sections of two index tumors, one each HPV negative and positive, was analyzed for LOH at 65 chromosomal loci. Loci scoring positive with either sample were included in an analysis of 14 additional cases that were also typed for HPV. Frequencies of LOH at loci were computed in a panel of HPV-positive and -negative VSCCs. Twenty-nine loci demonstrated LOH on the initial screen and were used to screen the remaining 14 tumors. High frequencies of LOH were identified, some of which were similar to a prior karyotypic study (3p, 5q, 8p, 10q, 15q, 18q, and 22q) and others of which had not previously been described in VSCC (1q, 2q, 8q, 10p, 11p, 11q, 17p, and 21q). With the exception of 5q and 10p, there were no significant associations between frequency of LOH and HPV status in VSCC. LOH at 3p and 11q were frequent in both VSCC and CSCC; however, allelic losses at several sites, including 5q, 8q, 17p, 21q, and 22q, were much more common in VSCC. VSCCs exhibit a broad range of allelic losses irrespective of HPV status, with high frequencies of LOH on certain chromosomal arms. This suggests that despite their differences in pathogenesis, both HPV-positive and -negative VSCCs share similarities in type and range of genetic losses during their evolution. Whether the different frequencies of LOH observed between VSCC and CSCC are real or reflect differences in stage and/or tumor size remains to be determined by further comparisons. The role of these altered genetic loci in the genesis of preinvasive vulvar mucosal lesions merits additional study.

Expression of ras, c-myc, and p53 proteins in cervical intraepithelial neoplasia

BACKGROUND

The development of cervical carcinoma is influenced by multiple factors, including the presence of certain high risk types of human papillomavirus. The purpose of the current study was to investigate possible cooperating genetic changes by examining the expression of p53, p62 myc, and p21 ras in cervical biopsy specimens.

METHODS

Three hundred and ninety-five cervical biopsy specimens representing normal through high grade cervical intraepithelial neoplasia (CIN) were screened by immunohistochemistry for expression of p53, p62myc, and p21ras.

RESULTS

Neither the proportion of tissues staining positive for a given protein nor the staining patterns within the epithelial layers differed significantly among normal or CIN biopsy samples. However, grade specific nuclear staining of p21ras was found in the cells of 10 lesions that were classified as CIN I by histology.

CONCLUSIONS

These results established the normal distribution and expression patterns of p53, p62myc, and p21ras within 395 cervical biopsy samples representing normal through CIN III histology. The expression of these proteins (e.g., staining intensity and layer of epithelium staining positive) is similar in normal tissues and those demonstrating all grades of CIN.

Oncogenes in gynecologic oncology

Advances in molecular biology have facilitated the recent investigation of gynecological malignancies. The presence of certain oncogenes within gynecological tumors indicates that transformation may be associated with genetic alteration of normal regulatory processes. This paper reviews several oncogenes that have been implicated in the transformation of gynecological tissues.

Diagnosis of congenital syphilis from placental examination: comparison of histopathology, Steiner stain, and polymerase chain reaction for Treponema pallidum DNA

Congenital syphilis is often a presumptive diagnosis (based on serologies), because confirmation requires identification of Treponema pallidum in fetal/neonatal tissues or in the placenta. Placental histological features associated with congenital syphilis include the triad of enlarged hypercellular villi, proliferative fetal vascular changes, and acute or chronic villitis. The authors blindly evaluated 49 formalin-fixed, paraffin-embedded placentas (38 with positive maternal syphilis serologies; 11 with negative serologies) and compared results of histology, Steiner stain, and polymerase chain reaction (PCR) for T pallidum DNA. Histology was categorized as positive (triad present), suspicious (two thirds of triad present), or negative. Treponemal DNA was detected by amplifying a 189 base pair region of the 47 kd treponemal membrane antigen with 44 cycles of PCR; products were detected by Southern blot. Placentas from the 11 seronegative mothers were all negative by histology, Steiner stain, and PCR. Among the 38 placentas from serologically positive mothers, 4 had positive histology (2 of 4 positive Steiner, 4 of 4 positive PCR); 6 had suggestive histology (0 of 6 positive Steiner; 1 of 6 positive PCR); and, 28 had negative histology (0 of 28 positive Steiner; 1 of 28 positive PCR). PCR identification of treponemal DNA was significantly associated with the triad (P = .0003), proliferative fetal vascular changes (P = .0003), acute villitis (P = .003), chronic villitis (P = .004), and spirochetes on Steiner stain (P = .01). These results (1) confirm a strong association between placental histopathologic features and congenital syphilis; (2) indicate that when such features are present, PCR of placental tissue may confirm the diagnosis of congenital syphilis; and (3) suggest that even when such features are absent, PCR of placental tissue may identify additional cases of histologically unsuspected congenital syphilis.

Presence and persistence of HPV infection and p53 mutation in cancer of the cervix uteri and the vulva

We studied 51 cervical carcinomas, among them 25 squamous-cell carcinomas (SCC) and 26 cervical adenocarcinomas (AdCa), and 40 vulvar SCC for the presence of HPV and mutant p53. HPV was detected by PCR, and p53 alterations by temperature-gradient gel electrophoresis/direct sequencing and immunohistochemistry. HPV, mostly type 16/18, was found in 80.4% of the cervical tumors (92.0% of the SCC and 69.2% of the AdCa), but in only 27.5% of vulvar carcinomas. In contrast, p53 mutations were found in 7.8% and 52.5% of cervical and vulvar tumors respectively. Mutant p53 occurred in pre-invasive vulvar lesions, indicating that this oncogenic factor is involved early in carcinogenesis. Further analysis of recurrent/metastatic lesions of 9 cervical and 14 vulvar tumors also showed remarkable differences: in cervical cancer, HPV was persistent, and p53 mutations absent, whereas in vulvar tumors, HPV was mostly absent or not persistent, and the p53 mutation rate was very high (78.6%). These observations suggest that HPV persistence is an important event for the evolution and maintenance of cervical cancer, whereas for vulvar cancers p53 mutation and not HPV activity is a central oncogenic event.

Molecular biology of cervical cancer and its precursors

Cervical cancer develops from well-defined precursor lesions referred to as either cervical intraepithelial neoplasia or squamous intraepithelial lesions. It is now known that specific types of human papillomaviruses (HPV) are the principal etiologic agents for both cervical cancer and its precursors. The high-oncogenic-risk HPV types associated with invasive cervical cancer produce two oncoproteins, designated E6 and E7, which interact with endogenous cell cycle regulatory proteins, including p53 and Rb. The interaction of virally derived and endogenous cellular proteins converges in deregulation of cell cycle progression and appears to be critical for the development of cervical cancers. However, the development of cervical cancer is a multistep process that cannot be explained simply by infection with specific types of HPV. One additional event that appears to play a role in tumor progression is integration of HPV DNA into the host genome. Integration of HPV DNA frequently disrupts the E2 open reading frames, resulting in overexpression of the E6 and E7 oncoproteins and possibly causing genomic instability. Additional cofactors and mutational events may be important in the pathogenesis of invasive cervical cancers and may include chromosomal rearrangements, loss of constitutional heterozygosity, and proto-oncogene activation.