Assessment of intra-tumoral karyotypic heterogeneity by interphase cytogenetics in paraffin wax sections

Induction of tetrasomy by human papillomavirus type 16 E7 protein is independent of pRb binding and disruption of differentiation

We have demonstrated previously that high-risk human papillomaviruses (HPVs) induce tetrasomy in low-grade squamous intraepithelial lesions of the cervix. In this study we show that the E6 and E7 genes of high-risk HPV-16, but not those of low-risk HPV-6, are independently able to induce tetrasomy when constitutively expressed in proliferating monolayer cultures of primary human keratinocytes. Of seven HPV-16 E7 mutants analysed (H2P, Delta6-10, Delta21-24, C24G, S31G/S32G, A50S and S71I), five were severely impaired in their ability to induce tetrasomy in monolayer and raft culture. Only mutant C24G induced tetrasomy to levels comparable with wild-type E7 in monolayer and raft culture. This mutant shows strongly reduced binding to the retinoblastoma gene product pRb. The casein kinase II phosphorylation defective mutant S31G/S32G induced tetrasomy to levels comparable with wild-type E7 in raft culture, but not in monolayer culture, and induction of tetrasomy did not correlate with raft morphology. These results indicate that pRb protein binding is not required for HPV-16 E7 associated tetrasomy and that tetrasomy is not directly related to the ability of this protein to disrupt keratinocyte differentiation.

Numerical aberrations of chromosome 1 in cervical intraepithelial neoplasia are strongly associated with infection with high-risk human papillomavirus types

The aims of this study were to assess the relationships between numerical aberrations of chromosome 1 and the presence of high-risk human papillomavirus (HPV). Five normal samples, 11 CIN1, 13 CIN2, 18 CIN3, and nine carcinomas were studied by in situ hybridization (ISH), using a DNA probe for the centromere of chromosome 1 (cen#1) and a DNA probe cocktail for HPV types 16 and 18. A short fragment polymerase chain reaction hybridization line probe assay (SPF-PCR-LiPA) technique was used to detect 25 HPV types. The mean number of cen#1 per nucleus (chromosome index, CI) was measured, and the fractional areas of dysplastic epithelium with HPV16/18 infection and with cen#1 aneusomy were estimated. Disomy was found in all normal epithelium and in 36% of CIN1. Tetrasomy was observed in 64% of CIN1, 15% of CIN2, and 17% of CIN3. Hyper-tetrasomy was observed in 77% of CIN2, 83% of CIN3, and 100% of invasive carcinomas. High-risk HPVs were present in 20%, 75%, and 94% of disomic, tetrasomic, and hyper-tetrasomic lesions, respectively. The mean CI value was significantly higher in the lesions infected with high-risk HPV than in the lesions not infected by high-risk HPV (p < 0.001), due to the significantly higher prevalence of hyper-tetrasomy. The ISH study disclosed that HPV16/18 was exclusively found within dysplastically altered epithelium. The area with aneusomy is mostly enclosed within the area infected with HPV. In 83% of the HPV16/18-positive CIN lesions, the fractional area of HPV-infected epithelium was equal to, or larger than, the fractional area with aneusomy. In conclusion, aneusomy for chromosome 1 is strongly associated with high-grade CIN lesions and infection with high-risk HPV; it is likely that the occurrence of numerical aberrations of chromosome 1 is preceded by infection with high-risk HPV.

Dual colour FISH in paraffin wax embedded bone trephines for identification of numerical and structural chromosomal abnormalities in acute myeloid leukaemia and myelodysplasia

AIMS/BACKGROUND

The advent of new treatments for haematological malignancies has led to the need for a correlation between cytogenetic and morphological abnormalities. This study aimed to achieve this by the application of interphase cytogenetics to marrow trephine sections, a technique not previously reported for formalin fixed, paraffin wax embedded trephine biopsies.

METHODS

Dual colour fluorescence in situ hybridisation (FISH) was used to detect numerical and structural abnormalities in routinely processed paraffin wax embedded trephine biopsies. Three cases with t(8;21) and three with t(15;17) were analysed, together with a case of trisomy 8. Chromosome specific probes were hybridised with sections and disclosed by fluorescein isothiocyanate and rhodamine/Texas red labelled antidigoxigenin and antibiotin amplification; translocations were identified by colocalisation of probes using a double wavelength bypass filter.

RESULTS

A translocation signal was present in 12% and 11.5% of the cells counted in the t(8;21) and t(15;17) cases, respectively, but in none of the normal controls (p < 0.001). In the case of trisomy 8, 9% of the cells counted contained three hybridisation signals for chromosome 8, whereas no cell contained more than two in the normal control (p < 0.001).

CONCLUSIONS

This technique is useful for archived routinely processed material, enabling it to be used as a research tool but also, and perhaps more importantly, in clinical practice.

Loss of sequences on the short arm of chromosome 17 is a late event in squamous carcinoma of the cervix

AIMS

To determine by fluorescence in situ hybridisation (FISH) whether deletion of D17S34, a subtelomeric probe for 17p, occurs in invasive squamous carcinoma of the cervix, and to determine the extent of such loss by analysis of the p53 and HER2/NEU genes.

METHODS

Fourteen invasive squamous cell carcinomas of the cervix were investigated by FISH for D17S34, p53, and HER2/NEU. Dual hybridisation of each probe with the chromosome 17 alpha satellite (D17Z1) probe was performed on paraffin wax embedded sections, and the fluorescence ratios of the paired signals were determined. Broad spectrum human papillomavirus (HPV) typing by ISH and GP5+/6+ polymerase chain reaction was also performed.

RESULTS

Twelve tumours were HPV positive, nine with HPV-16, and one each with types 18, 31, and 39. Loss of D17S34 was identified in four tumours, one of which was HPV negative. In one tumour, D17S34 loss was accompanied by loss of p53 only, suggesting that deletion was limited to the p arm. A second tumour showed simultaneous losses of all probes, indicative of whole chromosome 17 loss during tumour growth. The two remaining specimens showed loss of D17S34 only, diffuse in one, and localised within the tumour in the other. Aberrations of p53 or HER2/NEU were not seen independently of D17S34 loss, and loss did not correlate with HPV presence or type.

CONCLUSIONS

These data show that D17S34 loss is prevalent, marking 28% of the invasive squamous carcinomas in this study. The observed intratumoral heterogeneity indicates that, at least in some cases, this loss occurs after invasion and is therefore a late event in the path of cervical carcinogenesis.

Chromosome 17 aneusomy detected by fluorescence in situ hybridization in vulvar squamous cell carcinomas and synchronous vulvar skin

Vulvar squamous cell carcinoma (SCC) affects a spectrum of women with granulomatous vulvar diseases, human papillomavirus (HPV) infections, and chronic inflammatory vulvar dermatoses. To determine whether there is evidence of chromosomal instability occurring in synchronous skin surrounding vulvar SCCs, we investigated abnormalities in chromosome 17 copy number. Samples of SCC, vulvar intraepithelial neoplasia (VIN), and surrounding vulvar skin were obtained from all vulvar excisions performed for squamous neoplasia at Albany Medical College from 1996 to 1997. Histological categorization, fluorescent in situ hybridization (FISH) for the alpha satellite region of chromosome 17, DNA content by image analysis, and Ki-67 labeling were evaluated. Controls of normal vulvar skin not associated with cancer were used for comparison. One hundred ten specimens were obtained from 33 patients with either SCC or VIN 3 and consisted of 49 neoplastic, 52 nonneoplastic, and 9 histologically normal vulvar skin samples. The majority of SCCs (88%) and a minority (18%) of VIN 3 excisions were associated with lichen sclerosus. Normal vulvar skin controls did not exhibit chromosome 17 polysomy (cells with more than four FISH signals), whereas 56% of normal vulvar skin associated with cancer did. Moreover, the frequency of polysomy significantly increased as the histological classification progressed from normal to inflammatory to neoplastic lesions. The largest mean value and variance for chromosome 17 copy number was identified in SCCs (2.4 +/- 1.0) with intermediate values identified, in decreasing order, for SCC in situ (2.1 +/- 1.0), VIN 2 (2.1 +/- 0.8), lichen sclerosus (2.0 +/- 0.5), lichen simplex chronicus (1.9 +/- 0.4), and normal skin associated with SCC (1.8 +/- 0.4) compared with control vulvar skin (1.5 +/- 0. 05). Concordance of chromosome 17 aneusomy between cancers and synchronous skin lesions was found in 48% of patients. Loss of chromosome 17 was identified 5% of all samples and was significantly associated with women with SCC in situ (HPV-related). Both DNA content and Ki-67 labeling positively and significantly correlated with mean chromosome 17 copy number (r = 0.1, P: = 0.007). A high degree of genetic instability (aneuploidy) occurs in the skin surrounding vulvar carcinomas. As these events could be detected in histologically normal skin and inflammatory lesions (lichen sclerosus), chromosomal abnormalities may be a driving force in the early stages of carcinogenesis. Differences in chromosomal patterns (loss or gain) support the concept of at least two pathways in vulvar carcinogenesis.

Basal keratinocyte tetrasomy in low-grade squamous intra-epithelial lesions of the cervix is restricted to high and intermediate risk HPV infection but is not type-specific

Human papillomavirus (HPV) infection appears to be an early event in cervical carcinogenesis with additional abnormalities being required for biological transformation. We have analysed 179 low-grade cervical squamous intra-epithelial lesions (SILs) and 15 normal cervices for the presence of HPV using both in situ hybridization and polymerase chain reaction (PCR). PCR was performed with GP5+/GP6+ primers followed by hybridization using probes for low (HPV 6, 11, 40, 42, 43, 44), intermediate (HPV 31, 33, 35, 39, 51, 52, 58, 59, 66 and 68) and high-risk HPVs (HPV 16, 18, 45 and 56). Interphase cytogenetic analysis using pericentromeric probes for chromosomes 1, 3, 4, 6, 10, 11, 17, 18 and X was also performed to identify numerical chromosomal abnormalities. Tetrasomy of all nine chromosomes was identified within basal keratinocytes, was restricted to epithelia infected with high risk (17 of 46) or intermediate risk (23 of 83) HPVs but was not HPV type-specific. Tetrasomy was not identified in any of the epithelia infected with low risk HPVs (n = 62). These numbers include multiple infection. These findings indicate that the induction of tetrasomy is a property restricted to high and intermediate-risk HPV types but that it is not type-specific. The factors governing which lesions will develop this abnormality are as yet unclear.

Interphase cytogenetic analysis of cervical intraepithelial neoplasia

The aim of this study was to detect numerical chromosomal aberrations that may be involved in the progression of cervical intraepithelial neoplasia (CIN) toward cervical carcinoma. Therefore, cervical lesions (five CIN 1, seven CIN 2, six CIN 3, six invasive carcinomas, and six normal samples) were studied by in situ hybridization (ISH) on serial 3-microm-thick paraffin tissue sections, using a panel of eight centromeric DNA probes for chromosomes 1, 3, 6, 7, 8, 11, 17, and X. An estimation of the percentage of dysplastic epithelium with abnormal ISH signals per nucleus was made. Chromosome aneusomy could be detected in all persisting and high-grade CIN lesions and invasive carcinomas. In most cases, when one of the chromosomes showed aneusomy then all studied chromosomes showed numerical changes. Interestingly, the abnormal ISH signals were found only in a varying part of the morphologically dysplastic epithelium, the remainder showing no such changes. In aneuploid regions of the CIN 1 lesions the mean chromosome index for all chromosomes was 1.97+/-0.03 with a range of 1.92 to 2.00. The chromosome index ratios of chromosomes 1, 7, and X showed a significant positive correlation with CIN grade (r > or = 0.74; P < or = 0.006). It is concluded that chromosome aneusomy of chromosomes 1, 7, and X may be involved in the progression of CIN lesions.

Interphase karyotypic analysis of chromosomes 11, 17 and X in invasive squamous-cell carcinoma of the cervix: morphological correlation with HPV infection

Human papillomavirus (HPV) infection has been widely implicated in cervical carcinogenesis, but it appears to be an early event, with other genetic abnormalities being required for biological transformation. In this study, interphase cytogenetic analysis of numerical abnormalities of chromosomes 11, 17 and X was performed on paraffin-embedded tissue sections from 25 invasive squamous-cell carcinomas of the cervix and compared with both histopathological features and the morphological distribution of HPV sequences as determined by in situ hybridisation. Numerical differences between chromosomes were identified in 76% of cases, with underrepresentation of chromosomes 11 and/or 17 relative to X in 64% of the total; 22 of 25 cases were HPV-positive, containing either HPV 16, 18 or 31. There was no relationship between the distribution of viral sequences and chromosomal pattern, suggesting that HPV infection precedes karyotypic changes. Our findings suggest that relative reduction in number of chromosomes 11 and 17 is important in the development of invasive cervical neoplasia and are consistent with the putative presence of relevant tumour-suppressor genes on these chromosomes.