Complex karyotypes in flow cytometrically DNA-diploid squamous cell carcinomas of the head and neck

Chromosomal instability in oral cancer cells

Chromosomal instability is a common feature of human tumors, including oral cancer. Although a tumor karyotype may remain quite stable over time, chromosomal instability can lead to 'variations on a theme' of a clonal cell population, often with each cell within a tumor possessing a different karyotype. Thus, chromosomal instability appears to be an important acquired feature of tumor cells, since propagation of such a diverse cell population may facilitate evasion of standard therapies. There are several sources of chromosomal instability, although the primary causes appear to be defects in chromosomal segregation, telomere stability, cell-cycle checkpoint regulation, and the repair of DNA damage. Our understanding of the biological basis of chromosomal instability in cancer cells is increasing rapidly, and we are finding that the seemingly unrelated origins of this phenomenon may actually be related through the complex network of cellular signaling pathways. Here, we review the general causes of chromosomal instability in human tumors. Specifically, we address the state of our knowledge regarding chromosomal instability in oral cancer, and discuss various mechanisms that enhance the ability of cancer cells within a tumor to express heterogeneous karyotypes. In addition, we discuss the clinical relevance of factors associated with chromosomal instability as they relate to tumor prognosis and therapy.

Characterization of 10 vulvar carcinoma cell lines by karyotyping, comparative genomic hybridization and flow cytometry

OBJECTIVE AND METHODS

Ten vulvar squamous cell carcinoma cell lines established at the University of Michigan (UM-SCV-1A, -1B, -2, -3, -4, -6, -7) and at the University of Turku (UT-SCV-1, -2, -3) were characterized by G-banding karyotyping, comparative genomic hybridization (CGH), and deoxyribonucleic acid (DNA) flow cytometry.

RESULTS

All cell lines had hyperdiploid DNA content as measured by flow cytometry. The DNA index (DI) remained relatively stable through different passages in 9 of 10 cases. DIs of UM-SCV-3 and UT-SCV-2 were near-diploid, as were the corresponding karyotypes. The 10 SCVs showed remarkable genetic similarities with respect to consistent chromosome rearrangements. Loss of 3p, noted in 8/10 SCVs, was narrowed to the smallest common region at 3p11-3p13. Loss of 8pter-p11 was observed in 10/10 cell lines. Loss of 11qter-q23 was present in UM-SCV-1 and -2, and in all four recently karyotyped SCVs. Other consistent losses include Xpter-p11 in 6/10, and 18qter-q11 in 7/10 cell lines. Common gains included gain of 8q in 8/10 and 3q in 6/10. Consistent copy number imbalances were confirmed by CGH; concerning loss of 3p, in 63%, to loss of 8p in 70%, to gain of 3q in 83%, and to gain of 8q in 75% of the cell lines.

CONCLUSIONS

CGH and karyotyping showed concordance in defining copy number imbalances, thus supporting the accuracy of CGH to detect chromosome imbalances in tumors that cannot be karyotyped.

Prognostic factors in carcinoma of the larynx: relevance of DNA ploidy, S-fractions and localization of the tumour

The influence of the cell cycle profile and the site of the primary tumour on the overall survival were examined in 36 patients with squamous cell carcinoma of the larynx. DNA ploidy (p = 0.0091), the overall proliferative activity (p = 0.0001), the overall proliferative activity of diploid tumour cells (p = 0.0017) and primary tumour site (p = 0.0008) were found to be significant single prognostic factors of the overall survival. Multivariate analysis showed that only the overall proliferative activity was prognostically significant (p = 0.013). The results of the study show that the supraglottic site of the tumours correlates significantly with DNA ploidy (p = 0.0334) and the overall proliferative activity of tumour cells (p = 0.0159), whereas the correlation with proliferative activity of diploid tumour cells (p = 0.1416) has not been confirmed by this study. Glottic tumours showed a prognostically significant correlation with the overall proliferative activity (p = 0.0037) and proliferative activity of diploid tumour (p = 0.0054). Such a prognostic correlation was not found for DNA ploidy (p = 0.6542).

Ploidy in human papillomavirus positive and negative vulvar squamous cell carcinomas and adjacent skin lesions

To better characterize the two clinicopathologic types of squamous cell carcinoma, human papillomavirus (HPV) positive and negative, and their adjacent skin changes, we performed cytomorphometric analysis on 12 HPV-positive squamous cell carcinomas and adjacent vulvar intraepithelial neoplasia and 22 HPV-negative squamous cell carcinomas and adjacent squamous cell hyperplasia and lichen sclerosis. Our results were that 83% (10 of 12) HPV-positive carcinomas and 78% (7 of 9) adjacent vulvar intraepithelial neoplasia were aneuploid, compared with 59% (13 of 22) HPV-negative carcinomas, 6% (1 of 16) squamous cell hyperplasias and 0% (0 of 20) lichen scleroses. Seventy-five percent (9 of 12) HPV carcinomas and 78% (7 of 9) vulvar intraepithelial neoplasias showed two aneuploid peaks, but no HPV-negative carcinoma or non-neoplastic epithelial lesion showed multiple aneuploid peaks. Fifty percent of squamous cell hyperplasias (8 of 16) and lichen scleroses (10 of 20) adjacent to HPV-negative carcinomas were hypodiploid. The mean DNA indices were: 1.70 for the dominant tumor cell population of HPV-positive carcinoma, 1.64 for the dominant population of vulvar intraepithelial intraepithelial neoplasia, 1.41 for HPV-negative carcinoma, 0.85 for squamous cell hyperplasia and 0.83 for lichen sclerosis. In conclusion, the higher rate of aneuploidy, higher mean DNA index, and presence of multiploid peaks in HPV-positive carcinomas and adjacent vulvar intraepithelial neoplasias compared with the lower rate of aneuploidy, lower mean DNA index, absence of multiploid peaks of HPV-negative carcinomas and tendency to hypodiploidy in squamous cell hyperplasia and lichen sclerosis support the hypothesis that there are two clinicopathologic types of vulvar carcinoma, with different pathogenetic mechanisms. The similarities in ploidy findings between vulvar HPV-positive carcinomas and vulvar intraepithelial neoplasia and those previously published for cervical carcinoma and cervical intraepithelial neoplasia support the view that these two cancers are analogous and have similar pathogenetic mechanisms. The frequent finding of hypodiploidy in squamous cell hyperplasia and lichen sclerosis next to HPV-negative carcinomas requires further investigation of the molecular pathogenesis of this cancer type.