Jan Sällström

Uneven distribution of HPV 16 E6 prototype and variant (L83V) oncoprotein in cervical neoplastic lesions

A previous Swedish study revealed that both prototype and variant HPV16 E6 oncoprotein, occur in about equal numbers in high-grade cervical intraepithelial neoplasia (HCIN), whereas variant HPV16 predominates in invasive cervical squamous carcinoma. Most of the malignant HPV16 variants contain a common mutation, L83V, in the E6 oncoprotein. In the present investigation, 28 HPV16 positive, invasive cervical adenocarcinomas were collected from a total number of 131 adenocarcinomas. These HPV16-positive cases were evaluated with analysis of the E6 gene, using a recently described PCR-SSCP method for identification of the specific mutation (L83V) in the E6 gene. The results obtained were correlated to findings in 103 preinvasive, HCIN, and 31 invasive cervical squamous carcinomas also infected with HPV16. The HPV16 E6 variant L83V was present in 40% of the HCIN lesions, in 54% of the invasive adenocarcinomas, in comparison to 81% of the invasive squamous carcinomas. The difference between HCIN and squamous carcinomas was statistically significant, P< 0.001, whereas the difference between HCIN and invasive adenocarcinomas was not statistically significant, P = 0.604. Prototype HPV16 and its E6 variant L83V are both prevalent in preinvasive and invasive cervical lesions in Swedish women. However, the obvious predominance of HPV16 variant in squamous carcinomas was not seen in adenocarcinomas. A single amino-acid shift in the HPV16 E6 gene appears to result in a different transforming potential in squamous and glandular cervical lesions.

The significance of p53 codon 72 polymorphism for the development of cervical adenocarcinomas

Infection with the human papillomavirus is an important co-factor in the development of cervical carcinomas. Accordingly, HPV DNA is recognised in most of these tumours. Polymorphism of the p53 gene, codon 72, is also considered a risk factor in the development of cervical carcinoma. However, this finding is contradicted by several observers. In the present investigation, 111 cases of adenocarcinoma of the cervix collected through the Swedish Cancer Registry and 188 controls (females with normal cytology at organised gynaecological screening) were analysed with regard to p53, codon 72, polymorphism using a PCR- and SSCP-based technique. In the controls, 9% showed pro/pro, 44% pro/arg and 47% arg/arg, whereas in the invasive adenocarcinomas, the corresponding figures were 0%, 29% and 71%, respectively. The difference was statistically significant (P = 0.001). HPV DNA was identified in 86 tumours (HPV 18 in 48, HPV 16 in 31 and HPV of unknown type in 7 cases) and 25 tumours were HPV negative. The p53, codon 72, genotypes observed in HPV-positive and HPV-negative cervical adenocarcinomas were not statistically different (P = 0.690). The results indicate that women homozygotic for arg/arg in codon 72 of the p53 gene are at an increased risk for the development of cervical adenocarcinomas. However, this genetic disposition seems to be unrelated to the HPV infection.

A complex nine base pair deletion in RET exon 11 common in sporadic medullary thyroid carcinoma

Genetic alteration of the RET proto-oncogene is associated with multiple endocrine neoplasia type 2A and 2B (MEN 2A and MEN 2B), familial medullary thyroid carcinoma (FMTC) and Hirschprungs disease. Oncogenically activated RET has also been demonstrated in sporadic medullary thyroid tumors, which in some cases show somatic missense mutations. We have recently described a complex 9 bp deletion in RET exon 11 in a single case of sporadic MTC. In order to determine the prevalence of this mutation among sporadic MTC tumors, we have now analysed 15 cases and five normal controls by PCR-based nonradioactive single-strand conformational polymorphism analysis (PCR-SSCP) and fragment size analysis of exon 11. DNA was extracted from microdissected tumor tissue or normal cells and subjected to nested PCR prior to analysis. A markedly divergent SSCP pattern and a PCR fragment 9 bp shorter than normal were demonstrated in 14 of the 15 MTC tumors. Sequencing revealed the deletion of nine bases encompassing a key cysteine at codon 634, often altered in MEN 2A. Four lymphocyte controls and normal thyroid tissue from one patient failed to show the deletion. Several factors in the DNA sequence environment immediately surrounding the deletions, including an extended inverted repeat, several direct repeats and a so-called symmetric element suggest that the deletional events may be non-random.

Rapid test for identification of a human papillomavirus 16 E6 L83V variant.

A variant of human papillomavirus (HPV) 16 has been shown recently to be more prevalent in invasive cervical carcinoma than in preinvasive lesions. This HPV 16 variant possesses a common mutation (T to G) in nucleotide 350 (codon 83) of the E6 gene, resulting in an amino acid shift, L83V, in the E6 protein. This mutation was believed to signify preinvasive cervical lesions with a high probability of progression to invasive carcinoma. The purpose of the present investigation is to describe a rapid method for the detection of this variant HPV 16, E6 (L83V). Paraffin blocks of 18 gynecologic biopsy specimens were collected, all displaying the morphology of cervical intraepithelial neoplasia (CIN I-III) and a positive HPV 16 test. Sections from these blocks were used for DNA extraction. A DNA sequence of the E6 gene containing 176 bases (including codon 83) was amplified by polymerase chain reaction (PCR) and analyzed by non-radioactive single-strand conformational polymorphism (SSCP) analysis. A divergent SSCP pattern was observed in 7 of the HPV 16 positive biopsy specimens. A DNA sequence analysis of the PCR products revealed the conversion of Leu to Val in codon 83 of the E6 gene, correlating to the divergent band pattern. This PCR-SSCP method can be used to test for HPV 16 in women who are at serious risk of developing invasive cervical carcinoma.

Polymerase Chain Reaction (PCR) In Situ Hybridization: Detection of Human Papillomavirus (HPV) DNA in SiHa Cell Monolayers

In situ hybridization (ISH) with labelled cDNA probes has become a valuable tool for the detection of human papillomavirus (HPV) as it allows direct correlation of virus infection and morphological diagnosis: This method, however, is limited to detect 10-50 DNA copies per cell which was demonstrated on HeLa cells. In the following study, we present a more sensitive in situ method, PCR in situ hybridization (PISH), able to detect a single HPV-DNA copy per cell. We developed a model with SiHa cells containing 1-2 HPV 16 copies per cell. SiHa cells stain negative with in situ hybridization. After amplifying the HPV-DNA in situ using PCR prior to the hybridization step, we were able to get positive results using either enzymatic detection methods or immunogold silver staining (IGSS).

Genotyping of Human Papillomavirus (HPV) by Single-Strand Conformational Polymorphism (SSCP)

Nowadays, the polymerase chain reaction (PCR) is the most sensitive and widely used method for the detection of human papillomavirus (HPV) using ethidium bromide gel electrophoresis together with hybridization assays for typing. In this study, we demonstrate single-strand conformational. polymorphism (SSCP) as simultaneous detection and typing method for PCR-amplified products. SSCP as first described by Orita et al.l,2 employs denaturation of double strand DNA into single strand DNA and separation of the products by polyacrylamide gel electrophoresis (PAGE). This method makes possible the detection of HPV-DNA conformational. changes resulting in indivual. band patterns of the most common HPV-types.