Ectopic chromosome around centrosome in metaphase cells as a marker of high-risk human papillomavirus-associated cervical intraepithelial neoplasias

Human Papillomavirus-Induced Chromosomal Instability and Aneuploidy in Squamous Cell Cancers

Chromosomal instability (CIN) and aneuploidy are hallmarks of cancer. CIN is defined as a continuous rate of chromosome missegregation events over the course of multiple cell divisions. CIN causes aneuploidy, a state of abnormal chromosome content differing from a multiple of the haploid. Human papillomavirus (HPV) is a well-known cause of squamous cancers of the oropharynx, cervix, and anus. The HPV E6 and E7 oncogenes have well-known roles in carcinogenesis, but additional genomic events, such as CIN and aneuploidy, are often required for tumor formation. HPV+ squamous cancers have an increased frequency of specific types of CIN, including polar chromosomes. CIN leads to chromosome gains and losses (aneuploidies) specific to HPV+ cancers, which are distinct from HPV- cancers. HPV-specific CIN and aneuploidy may have implications for prognosis and therapeutic response and may provide insight into novel therapeutic vulnerabilities. Here, we review HPV-specific types of CIN and patterns of aneuploidy in squamous cancers, as well as how this impacts patient prognosis and treatment.

HPV16 E6 induces chromosomal instability due to polar chromosomes caused by E6AP-dependent degradation of the mitotic kinesin CENP-E

Chromosome segregation during mitosis is highly regulated to ensure production of genetically identical progeny. Recurrent mitotic errors cause chromosomal instability (CIN), a hallmark of tumors. The E6 and E7 oncoproteins of high-risk human papillomavirus (HPV), which causes cervical, anal, and head and neck cancers (HNC), cause mitotic defects consistent with CIN in models of anogenital cancers, but this has not been studied in the context of HNC. Here, we show that HPV16 induces a specific type of CIN in patient HNC tumors, patient-derived xenografts, and cell lines, which is due to defects in chromosome congression. These defects are specifically induced by the HPV16 oncogene E6 rather than E7. We show that HPV16 E6 expression causes degradation of the mitotic kinesin CENP-E, whose depletion produces chromosomes that are chronically misaligned near spindle poles (polar chromosomes) and fail to congress. Though the canonical oncogenic role of E6 is the degradation of the tumor suppressor p53, CENP-E degradation and polar chromosomes occur independently of p53. Instead, E6 directs CENP-E degradation in a proteasome-dependent manner via the E6-associated ubiquitin protein ligase E6AP/UBE3A. This study reveals a mechanism by which HPV induces CIN, which may impact HPV-mediated tumor initiation, progression, and therapeutic response.

Assessment of mitotic activity in breast cancer: revisited in the digital pathology era

The assessment of cell proliferation is a key morphological feature for diagnosing various pathological lesions and predicting their clinical behaviour. Visual assessment of mitotic figures in routine histological sections remains the gold-standard method to evaluate the proliferative activity and grading of cancer. Despite the apparent simplicity of such a well-established method, visual assessment of mitotic figures in breast cancer (BC) remains a challenging task with low concordance among pathologists which can lead to under or overestimation of tumour grade and hence affects management. Guideline recommendations for counting mitoses in BC have been published to standardise methodology and improve concordance; however, the results remain less satisfactory. Alternative approaches such as the use of the proliferation marker Ki67 have been recommended but these did not show better performance in terms of concordance or prognostic stratification. The advent of whole slide image technology has brought the issue of mitotic counting in BC into the light again with more challenges to develop objective criteria for identifying and scoring mitotic figures in digitalised images. Using reliable and reproducible morphological criteria can provide the highest degree of concordance among pathologists and could even benefit the further application of artificial intelligence (AI) in breast pathology, and this relies mainly on the explicit description of these figures. In this review, we highlight the morphology of mitotic figures and their mimickers, address the current caveats in counting mitoses in breast pathology and describe how to strictly apply the morphological criteria for accurate and reliable histological grade and AI models.

BetaHPV E6 and E7 colocalize with NuMa in dividing keratinocytes

Human papillomaviruses (HPVs) of genus betapapillomavirus (betaHPV) are implicated in skin carcinogenesis, but their exact role in keratinocyte transformation is poorly understood. We show an interaction of HPV5 and HPV8 oncoproteins E6 and E7 with the nuclear mitotic apparatus protein 1 (NuMA). Binding of E6 or E7 to NuMA induces little aneuploidy, cell cycle alterations, or aberrant centrosomes. Intracellular localization of NuMA is not altered by E6 and E7 expression in 2D cultures. However, the localization profile is predominantly cytoplasmic in 3D organotypic skin models. Both viral proteins colocalize with NuMA in interphase cells, while only E7 colocalizes with NuMA in mitotic cells. Intriguingly, a small subset of cells shows E7 at only one spindle pole, whereas NuMA is present at both poles. This dissimilar distribution of E7 at the spindle poles may alter cell differentiation, which may in turn be relevant for betaHPV-induced skin carcinogenesis.

Potential impact of combined high- and low-risk human papillomavirus infection on the progression of cervical intraepithelial neoplasia 2

AIM

Few studies have examined the effect of combined low-risk human papillomavirus (LR-HPV) and high-risk human papillomavirus (HR-HPV) infection on the progression of cervical intraepithelial neoplasia (CIN)2 to CIN3. This multi-institutional prospective cohort study investigated the risk of progression of CIN2 with various combinations of HR-HPV and LR-HPV infection.

METHODS

Between January 2007 and May 2008, 122 women with CIN2 (aged 20-50 years) from 24 hospitals throughout Japan were enrolled in the study. Ninety-three women were analyzed after a 2-year follow-up with cytology, colposcopy, HR-HPV testing and HPV genotyping. Colposcopy-directed biopsy was performed at entry and the end of this study, or when disease progression was suspected.

RESULTS

Among 93 women with CIN2, 87 (93.5%) had HR-HPV infection. Among these 87 cases, 24 (27.6%) progressed to CIN3 and 49 (56.3%) regressed. None of the six women with CIN2 without HR-HPV infection progressed. The progression rate was significantly lower in women with combined HR-HPV and LR-HPV infection (3/28, 10.7%) than in those with HR-HPV infection only (21/59, 35.6%; P = 0.016). Multivariate analyses showed that CIN2 progression in women with HR-HPV infection was negatively associated with LR-HPV co-infection (hazard ratio = 0.152; 95% confidence interval [CI] = 0.042-0.553). CIN2 regression was positively associated with LR-HPV co-infection (odds ratio = 4.553; 95% CI = 1.378-15.039).

CONCLUSION

The risk of CIN2 progression is low in women with combined infection of HR-HPV and LR-HPV. The finding may be useful for management of women diagnosed with CIN2.

Prospective evaluation of the Amplicor HPV test for predicting progression of cervical intraepithelial neoplasia 2

AIM

The aim of this study was to evaluate the clinical performance of the Amplicor HPV test, which detects 13 high-risk human papillomaviruses (HR-HPV), and to determine the association between consistent HR-HPV infection and progression of cervical intraepithelial neoplasia (CIN) 2 to CIN3.

MATERIAL AND METHODS

This multi-institutional prospective study enrolled 122 women diagnosed with CIN2 by central pathological review. Subjects were tested at study entry and every 6 months over a 24-month period by cytology, Amplicor HPV test and colposcopy. Central pathological review was performed at the end of the study or if CIN progression was suspected.

RESULTS

Ninety-three of the 122 participants completed all tests in the study and were included in the analysis. HR-HPV was detected in 87/93 (93.5%) participants at study entry. Twenty-four of the 87 HR-HPV-positive participants progressed to ≥CIN3, compared with none of the six participants who were HR-HPV-negative at study entry. The positive predictive value, negative predictive value, sensitivity and specificity of the Amplicor HPV test at study entry for predicting ≥CIN3 progression were 27.6%, 100%, 100% and 8.7%, respectively. Sixty-two participants were HR-HPV-positive from study entry through to study completion, 24 of whom progressed to ≥CIN3. None of 31 participants without continuous HR-HPV detection progressed to ≥CIN3. For continuous HR-HPV detection, the positive predictive value, negative predictive value, sensitivity and specificity of the Amplicor HPV test were 38.7%, 100%, 100% and 44.9%, respectively.

CONCLUSIONS

All participants who progressed to ≥CIN3 were continuously HR-HPV-positive. The Amplicor HPV test thus demonstrated a good performance for predicting CIN3 progression.

Human papillomavirus type 16 E6 and E7 cause polyploidy in human keratinocytes and up-regulation of G2-M-phase proteins

Human papillomavirus type 16 proteins E6 and E7 have been shown to cause centrosome amplification and lagging chromosomes during mitosis. These abnormalities during mitosis can result in missegregation of the chromosomes, leading to chromosomal instability. Genomic instability is thought to be an essential part of the conversion of a normal cell to a cancer cell. We now show that E6 and E7 together cause polyploidy in primary human keratinocytes soon after these genes are introduced into the cells. Polyploidy seems to result from a spindle checkpoint failure arising from abrogation of the normal functions of p53 and retinoblastoma family members by E6 and E7, respectively. In addition, E6 and E7 cause deregulation of cellular genes such as Plk1, Aurora-A, cdk1, and Nek2, which are known to control the G(2)-M-phase transition and the ordered progression through mitosis.