Prevalence of Merkel Cell Polyomavirus in Normal and Lesional Skin: A Systematic Review and Meta-Analysis

Merkel Cell Carcinoma and Immunosuppression, UV Radiation, and Merkel Cell Polyomavirus

Importance

Merkel cell carcinoma (MCC) is a rare but aggressive skin cancer. Quantifying the contribution of major potentially modifiable risk factors to the burden of MCC may inform prevention efforts.

Objective

To estimate the population attributable fraction of MCC cases in the US that were attributable to major immunosuppressing conditions (eg, HIV, solid organ transplant, chronic lymphocytic leukemia [CLL]), ambient UV radiation [UVR] exposure, and Merkel cell polyomavirus [MCPyV]).

Design, Setting, and Participants

This epidemiological assessment combined data from population-based registries and case series and included cases of MCC that were diagnosed from January 2001 to December 2019 diagnosed in people with HIV, solid organ transplant recipients, and patients with CLL who were identified through population-based cancer registries and linkages with HIV and transplant registries. UVR-based on cloud-adjusted daily ambient UVR irradiance was merged with cancer registry data on the county of residence at diagnosis. Studies reporting the prevalence of MCPyV in MCC specimens collected in the US were combined via a meta-analysis.

Exposures

HIV, solid organ transplant, CLL, UVR, and MCPyV.

Main Outcomes and Measures

Population attributable fraction of MCC cases attributable to major risk factors.

Results

A total of 38 020 MCCs were diagnosed in the US among xx patients (14 325 [38%] female individuals; 1586 [4%] Hispanic, 561 [1%] non-Hispanic Black, and 35 171 [93%] non-Hispanic White individuals). Compared with the general US population, MCC incidence was elevated among people with HIV (standardized incidence ratio [SIR], 2.78), organ transplant recipients (SIR, 13.1), and patients with CLL (SIR, 5.75). Due to the rarity of these conditions, only 0.2% (95% CI, 0.1%-0.3%) of MCC cases were attributable to HIV, 1.5% (95% CI, 1.4%-1.7%) to solid organ transplant, and 0.8% (95% CI, 0.5%-1.3%) to CLL. Compared with individuals of racial and ethnic minority groups, MCC incidence was elevated among non-Hispanic White individuals at lower and higher ambient UVR exposure levels (incidence rate ratios: 4.05 and 4.91, respectively, for MCC on the head and neck). Overall, 65.1% (95% CI, 63.6%-66.7%) of MCCs were attributable to UVR. Based on a meta-analysis of 19 case series, 63.8% (95% CI, 54.5%-70.9%) of MCCs were attributable to MCPyV. Studies were identified from a MEDLINE search performed on October 12, 2023.

Conclusions and Relevance

The results of this study suggest that most MCC cases in the US were attributable to ambient UVR exposure or MCPyV, with a small fraction due to immunosuppressive conditions. Efforts to lower MCC incidence could focus on limiting UVR exposure.

Merkel Cell Polyomavirus Antibody in Tumor and Plasma Specimens in Patients with Merkel Cell Carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) is associated with Merkel cell polyomavirus (MCPyV) infection. MCPyV antibodies (MCPyV-Ab) in plasma correlate with survival, while MCPyV-Ab within the tumor has never been investigated. This study evaluated plasma MCPyV-Ab and tumor MCPyV-Ab titers to evaluate their role in outcomes and prognostication.

METHODS

A single-institution, prospective database was retrospectively reviewed for patients diagnosed with MCC from 2014 to 2021. MCPyV-Ab plasma and tumor titers, as well as patient and treatment factors, were collected. Two-year overall survival (OS) and disease-free survival (DFS) were examined based on MCPyV-Ab presence in tumor.

RESULTS

Forty patients were identified, with a median follow-up of 27.6 months. Patients were stratified into four groups based on the presence of MCPyV-Ab in plasma (P+, P-) and tumor (T+, T-). Most patients (60.0%) were P-/T-. Of the remaining patients, 22.5% were P+/T+, 12.5% were P-/T+, and 5.0% were P+/T-. Two-year DFS of the P-/T- group was 16.6 months, which was not different from the other groups (p = 0.79). Two-year OS of P-/T- was 18.3 months, and 2-year OS of P-/T+ was 28.1 months, which was similar between groups (p = 0.80).

CONCLUSIONS

Most patients P+ for MCPyV had antibody-positive tumors (T+), and P- patients were also T-; however, there was a subset of patients where plasma and tumor antibody findings were incongruent. Patients with MCPyV-Ab in either plasma or tumor had a trend toward improved 2-year DFS and OS, but was limited by a small cohort. This study offers an exploratory investigation into the relationship between plasma and tumor antibodies to MCPyV on which to base future work.

Merkel Cell Carcinoma Metastases to Caruncle With Orbital Extension: Report and Literature Review

Merkel cell carcinoma (MCC) is an uncommon and aggressive skin cancer of neuroendocrine origin. The tumor usually presents with a locoregional spread and most frequently metastasizes to the skin, liver, bone, lung, and brain. Despite the orbit being a relatively common site of metastases, it has rarely been reported in patients with MCC. The authors present a case of biopsy-proven orbital metastatic MCC in an 86-year-old male who presented with a rapidly enlarging right caruncle/subconjunctival mass with orbital extension and a history of forearm MCC excision 3 years prior. There are only 3 reported cases of distant metastatic MCC to the orbit, all presenting as a mass originating from extraocular muscles; and no cases of caruncle involvement.

Merkel Cell Carcinoma: Integrating Epidemiology, Immunology, and Therapeutic Updates

Merkel cell carcinoma (MCC) is a rare skin cancer characterized by neuroendocrine differentiation. Its carcinogenesis is based either on the integration of the Merkel cell polyomavirus or on ultraviolet (UV) mutagenesis, both of which lead to high immunogenicity either through the expression of viral proteins or neoantigens. Despite this immunogenicity resulting from viral or UV-associated carcinogenesis, it exhibits highly aggressive behavior. However, owing to the rarity of MCC and the lack of epidemiologic registries with detailed clinical data, there is some uncertainty regarding the spontaneous course of the disease. Historically, advanced MCC patients were treated with conventional cytotoxic chemotherapy yielding a median response duration of only 3 months. Starting in 2017, four programmed cell death protein 1 (PD-1)/programmed cell death-ligand 1 (PD-L1) immune checkpoint inhibitors-avelumab, pembrolizumab, nivolumab (utilized in both neoadjuvant and adjuvant settings), and retifanlimab-have demonstrated efficacy in treating patients with disseminated MCC on the basis of prospective clinical trials. However, generating clinical evidence for rare cancers, such as MCC, is challenging owing to difficulties in conducting large-scale trials, resulting in small sample sizes and therefore lacking statistical power. Thus, to comprehensively understand the available clinical evidence on various immunotherapy approaches for MCC, we also delve into the epidemiology and immune biology of this cancer. Nevertheless, while randomized studies directly comparing immune checkpoint inhibitors and chemotherapy in MCC are lacking, immunotherapy shows response rates comparable to those previously reported with chemotherapy but with more enduring responses. Notably, adjuvant nivolumab has proven superiority to the standard-of-care therapy (observation) in the adjuvant setting.

Therapeutic Approaches for Non-Melanoma Skin Cancer: Standard of Care and Emerging Modalities

Skin cancer encompasses a range of cutaneous malignancies, with non-melanoma skin cancers (NMSCs) being the most common neoplasm worldwide. Skin exposure is the leading risk factor for initiating NMSC. Ultraviolet (UV) light induces various genomic aberrations in both tumor-promoting and tumor-suppressing genes in epidermal cells. In conjunction with interactions with a changed stromal microenvironment and local immune suppression, these aberrations contribute to the occurrence and expansion of cancerous lesions. Surgical excision is still the most common treatment for these lesions; however, locally advanced or metastatic disease significantly increases the chances of morbidity or death. In recent years, numerous pharmacological targets were found through extensive research on the pathogenic mechanisms of NMSCs, leading to the development of novel treatments including Hedgehog pathway inhibitors for advanced and metastatic basal cell carcinoma (BCC) and PD-1/PD-L1 inhibitors for locally advanced cutaneous squamous cell carcinoma (cSCC) and Merkel cell carcinoma (MCC). Despite the efficacy of these new drugs, drug resistance and tolerability issues often arise with long-term treatment. Ongoing studies aim to identify alternative strategies with reduced adverse effects and increased tolerability. This review summarizes the current and emerging therapies used to treat NMSC.

Moderne Diagnostik und Therapie des Merkelzellkarzinoms

Das Merkelzellkarzinom (MCC) ist ein seltener, aggressiver Hauttumor mit epithelialer und neuroendokriner Differenzierung, dessen Inzidenz in den letzten Jahrzehnten deutlich zugenommen hat. Risikofaktoren sind fortgeschrittenes Lebensalter, heller Hauttyp, UV‐Exposition und Immunsuppression. Pathogenetisch wird ein durch das Merkelzell‐Polyomavirus (MCPyV) hervorgerufener Typ von einem UV‐induzierten Typ mit hoher Tumormutationslast unterschieden.

Klinisch präsentiert sich das MCC als meist schmerzloser, schnell wachsender, rötlich‐violetter Tumor mit glänzender Oberfläche, der bevorzugt im Kopf‐Hals‐Bereich und an den distalen Extremitäten lokalisiert ist. Eine sichere Diagnose kann nur anhand histologischer und immunhistochemischer Merkmale gestellt werden. Bei Erstdiagnose weisen 20%–26% der Patienten lokoregionäre Metastasen und 8%–14% Fernmetastasen auf, weshalb eine Ausbreitungsdiagnostik unabdingbar ist. Bei fehlenden klinischen Hinweisen auf Metastasen wird eine Sentinel‐Lymphknotenbiopsie empfohlen.

Wesentliche Säulen der Therapie sind die Operation, die adjuvante oder palliative Strahlentherapie und in fortgeschrittenen inoperablen Stadien die medikamentöse Tumortherapie. Die Einführung von Immuncheckpoint‐Inhibitoren führte zu einem Paradigmenwechsel, da sich hiermit ein wesentlich langfristigeres Ansprechen und bessere Überlebensraten als mit Chemotherapie erreichen lassen. Zur Therapie des metastasierten MCC ist in Deutschland der PD‐L1‐Inhibitor Avelumab zugelassen, aber auch die PD‐1‐Antikörper Pembrolizumab und Nivolumab werden mit Erfolg eingesetzt. Adjuvante und neoadjuvante Therapiekonzepte, Immunkombinationstherapien und zielgerichtete Therapien als Monotherapie oder in Kombination mit Immuncheckpoint‐Inhibitoren befinden sich in klinischer Prüfung.

Modern diagnostics and treatment of Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer with epithelial and neuroendocrine differentiation, the incidence of which has increased substantially during the last decades. Risk factors include advanced age, fair skin type, UV exposure, and immunosuppression. Pathogenetically, a type caused by the Merkel cell polyomavirus is distinguished from a UV-induced type with a high tumor mutational burden. Clinically, MCC presents as a mostly painless, rapidly growing, reddish-violet tumor with a shiny surface, which is preferentially localized in the head-neck region and at the distal extremities. A reliable diagnosis can only be made based on histological and immunohistochemical features. At initial diagnosis, 20-26% of patients show locoregional metastases and 8-14% distant metastases, making staging examinations indispensable. If there is no clinical evidence of metastases, a sentinel lymph node biopsy is recommended. Essential columns of therapy are surgery, adjuvant or palliative radiotherapy and, in advanced inoperable stages, medicamentous tumor therapy. The introduction of immune checkpoint inhibitors has led to a paradigm shift, as they provide a considerably longer duration of response and better survival rates than chemotherapy. The PD-L1 inhibitor avelumab is approved for treatment of metastatic MCC in Germany, but the PD-1 antibodies pembrolizumab and nivolumab are also used with success. Adjuvant and neoadjuvant treatment concepts, immune combination therapies and targeted therapies as monotherapy or in combination with immune checkpoint inhibitors are in the clinical trial phase.

Current and preclinical treatment options for Merkel cell carcinoma

INTRODUCTION

Merkel cell carcinoma (MCC) is a rare, highly aggressive form of skin cancer with neuroendocrine features. The origin of this cancer is still unclear, but research in the last 15 years has demonstrated that MCC arises via two distinct etiologic pathways, i.e. virus and UV-induced. Considering the high mortality rate and the limited therapeutic options available, this review aims to highlight the significance of MCC research and the need for advancement in MCC treatment.

AREAS COVERED

With the advent of the immune checkpoint inhibitor therapies, we now have treatment options providing a survival benefit for patients with advanced MCC. However, the issue of primary and acquired resistance to these therapies remains a significant concern. Therefore, ongoing efforts seeking additional therapeutic targets and approaches for MCC therapy are a necessity. Through a comprehensive literature search, we provide an overview on recent preclinical and clinical studies with respect to MCC therapy.

EXPERT OPINION

Currently, the only evidence-based therapy for MCC is immune checkpoint blockade with anti-PD-1/PD-L1 for advanced patients. Neoadjuvant, adjuvant and combined immune checkpoint blockade are promising treatment options.

Cancers attributable to infectious agents in Italy

OBJECTIVES

To provide an evidence-based, comprehensive assessment of the current burden of infection-related cancers in Italy.

METHODS

We calculated the proportion of cancers attributable to infectious agents (Helicobacter pylori [Hp]; hepatitis B virus [HBV] and hepatitis C virus [HCV]; human papillomavirus [HPV]; human herpesvirus-8 [HHV8]; Epstein-Barr virus [EBV]; and human immunodeficiency virus [HIV]) to estimate the burden of infection-related cancer incidence (2020) and mortality (2017). Data on the prevalence of infections were derived from cross-sectional surveys of the Italian population, and relative risks from meta-analyses and large-scale studies. Attributable fractions were calculated based on the counterfactual scenario of a lack of infection.

RESULTS

We estimated that 7.6% of total cancer deaths in 2017 were attributable to infections, with a higher proportion in men (8.1%) than in women (6.9%). The corresponding figures for incident cases were 6.5%, 6.9% and 6.1%. Hp was the first cause of infection-related cancer deaths (3.3% of the total), followed by HCV (1.8%), HIV (1.1%), HBV (0.9%), HPV, EBV and HHV8 (each ≤0.7%). Regarding incidence, 2.4% of the new cancer cases were due to Hp, 1.3% due to HCV, 1.2% due to HIV, 1.0% due to HPV, 0.6% due to HBV and <0.5% due to EBV and HHV8.

CONCLUSIONS

Our estimate of 7.6% of cancer deaths and 6.9% of incident cases that were attributable to infections in Italy is higher than those estimated in other developed countries. Hp is the major cause of infection-related cancer in Italy. Prevention, screening and treatment policies are needed to control these cancers, which are largely avoidable.

Merkel Cell Polyomavirus: Infection, Genome, Transcripts and Its Role in Development of Merkel Cell Carcinoma

The best characterized polyomavirus family member, i.e., simian virus 40 (SV40), can cause different tumors in hamsters and can transform murine and human cells in vitro. Hence, the SV40 contamination of millions of polio vaccine doses administered from 1955-1963 raised fears that this may cause increased tumor incidence in the vaccinated population. This is, however, not the case. Indeed, up to now, the only polyomavirus family member known to be the most important cause of a specific human tumor entity is Merkel cell polyomavirus (MCPyV) in Merkel cell carcinoma (MCC). MCC is a highly deadly form of skin cancer for which the cellular origin is still uncertain, and which appears as two clinically very similar but molecularly highly different variants. While approximately 80% of cases are found to be associated with MCPyV the remaining MCCs carry a high mutational load. Here, we present an overview of the multitude of molecular functions described for the MCPyV encoded oncoproteins and non-coding RNAs, present the available MCC mouse models and discuss the increasing evidence that both, virus-negative and -positive MCC constitute epithelial tumors.

Map of thrombogenesis in viral infections and viral-driven tumours

Viruses are pathogenic agents responsible for approximately 10% of all human cancers and significantly contribute to the global cancer burden. Until now, eight viruses have been associated with the development of a broad range of malignancies, including solid and haematological tumours. Besides triggering and promoting oncogenesis, viral infections often go hand-in-hand with haemostatic changes, representing a potential risk factor for venous thromboembolism (VTE). Conversely, VTE is a cardiovascular condition that is particularly common among oncological patients, with a detrimental impact on patient prognosis. Despite an association between viral infections and coagulopathies, it is unclear whether viral-driven tumours have a different incidence and prognosis pattern of thromboembolism compared to non-viral-induced tumours. Thus, this review aims to analyse the existing evidence concerning the association of viruses and viral tumours with the occurrence of VTE. Except for hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infection, which are associated with a high risk of VTE, little evidence exists concerning the thrombogenic potential associated with oncoviruses. As for tumours that can be induced by oncoviruses, four levels of VTE risk are observed, with hepatocellular carcinoma (HCC) and gastric carcinoma (GC) associated with the highest risk and nasopharyngeal carcinoma (NPC) associated with the lowest risk. Unfortunately, the incidence of cancer-related VTE according to tumour aetiology is unknown. Given the negative impact of VTE in oncological patients, research is required to better understand the mechanisms underlying blood hypercoagulability in viral-driven tumours to improve VTE management and prognosis assessment in patients diagnosed with these tumours.

Epidemiology of Merkel Cell Polyomavirus Infection and Merkel Cell Carcinoma

Merkel cell polyomavirus (MCPyV) is a ubiquitous virus replicating in human dermal fibroblasts. MCPyV DNA can be detected on healthy skin in 67−90% of various body sites, and intact virions are regularly shed from the skin. Infection occurs early in life, and seropositivity increases from 37 to 42% in 1- to 6-year-olds to 92% in adults. Merkel cell carcinoma (MCC) is a rare but very aggressive neuroendocrine tumor of the skin. It develops mainly on sun-exposed areas as a fast-growing, reddish nodule. Two MCC entities exist: about 80% of MCC are MCPyV-associated. Tumorigenesis is driven by viral integration into the host genome and MCPyV oncogene expression. In MCPyV-negative MCC, UV radiation causes extensive DNA damage leading to the deregulation of the cell cycle. In recent decades, MCC incidence rates have increased worldwide, e.g., in the United States, from 0.15 in 1986 to 0.7/100,000 in 2016. Risk factors for the development of MCC include male sex, older age (>75 years), fair skin, intense UV exposure, and immunosuppression. Projections suggest that due to aging populations, an increase in immunosuppressed patients, and enhanced UV exposure, MCC incidence rates will continue to rise. Early diagnosis and prompt treatment are crucial to reducing high MCC morbidity and mortality.

Prevalence of 13 polyomaviruses in actinic keratosis and matched healthy skin samples of immunocompetent individuals

BACKGROUND

Actinic keratosis (AK) is a precursor of cutaneous squamous cell carcinoma (cSCC). UV radiation is the major risk factor for AK, but certain human papillomaviruses (HPVs) of the beta genus are also involved in its development. Differently, the role of polyomaviruses (PyVs) in skin carcinogenesis is still debated. Fiftheen PyVs have been isolated from human tissues so far, including Merkel cell polyomavirus (MCPyV), the aetiological agent of Merkel cell carcinoma.

METHODS

The presence of 13 PyVs was assessed in skin samples from AK patients (n = 342). Matched fresh-frozen scrapings from healthy skin (HS) and AK lesions from 242 patients, and formalin-fixed paraffin-embedded AK biopsies from a different cohort of 100 patients were analyzed by multiplex PyVs genotyping assay.

RESULTS

The most frequent lesion site was the scalp in men (27.3%), and the cheek area in women (29.0%). Differences between men and women were significant for the scalp, the cheek area and the lips. Almost all the scrapings were PyV-positive (HS: 89.7%, AK: 94.6%; p = 0.04). The three most frequent PyVs were MCPyV, HPyV6 and JCPyV (HS: 87.2%, 58.7%, 6.6%, respectively; AK: 88.8%, 51.2%, 9.9%, respectively). HPyV9, TSPyV, BKPyV, HPyV7, LIPyV and SV40 were detected in < 2% of the scrapings. In most cases, matched HS and AK scrapings were both positive (MCPyV: 78.1%, HPyV6: 41.7%), or both negative for the individual genotypes (for the remaining PyVs). PyV prevalence in AK biopsies was 22.0%. Only MCPyV (21.0%) and HPyV6 (3.0%) were detected in these samples.

CONCLUSIONS

PyV prevalence in HS and AK scrapings was high, but detection of PyVs exclusively in AK scrapings was rare. PyV positivity rate in AK biopsies was modest. Further research is need to reach firm conclusions regarding the role of these viruses in AK development.

Merkel Cell Polyomavirus (MCPyV) and Cancers: Emergency Bell or False Alarm?

Merkel cell polyomavirus (MCPyV), the sole member of Polyomavirus associated with oncogenesis in humans, is the major causative factor of Merkel cell carcinoma (MCC), a rare, neuroendocrine neoplasia of the skin. Many aspects of MCPyV biology and oncogenic mechanisms remain poorly understood. However, it has been established that oncogenic transformation is the outcome of the integration of the viral genome into the host DNA. The high prevalence of MCPyV in the population, along with the detection of the virus in various human tissue samples and the strong association of MCPyV with the emergence of MCC, have prompted researchers to further investigate the role of MCPyV in malignancies other than MCC. MCPyV DNA has been detected in several different non-MCC tumour tissues but with significantly lower prevalence, viral load and protein expression. Moreover, the two hallmarks of MCPyV MCC have rarely been investigated and the studies have produced generally inconsistent results. Therefore, the outcomes of the studies are inadequate and unable to clearly demonstrate a direct correlation between cellular transformation and MCPyV. This review aims to present a comprehensive recapitulation of the available literature regarding the association of MCPyV with oncogenesis (MCC and non-MCC tumours).

Seroprevalence of Four Polyomaviruses Linked to Dermatological Diseases: New Findings and a Comprehensive Analysis

Our aim was to study the seroprevalence of human polyomaviruses (HPyV) linked to skin diseases. A total of 552 serum samples were analysed by the enzyme-linked immunosorbent assay to detect IgG antibodies against Merkel cell polyomavirus (MCPyV), HPyV6, HPyV7 and Trichodysplasia spinulosa-associated polyomavirus (TSPyV) using recombinant major capsid proteins of these viruses. The individuals (age 0.8−85 years, median 33) were sorted into seven age groups: <6, 6−10, 10−14, 14−21, 21−40, 40−60 and >60 years. The adulthood seroprevalence was 69.3%, 87.7%, 83.8% and 85% for MCPyV, HPyV6, HPyV7 and TSPyV, respectively. For all four polyomaviruses, there was increasing seropositivity with age until reaching the adulthood level. There was a significant increase in seroreactivity for those age groups in which the rate of already-infected individuals also showed significant differences. The adulthood seropositvity was relatively stable with ageing, except for TSPyV, for which elevated seropositivity was observed for the elderly (>60 years) age group. Since seroepidemiological data have been published with wide ranges for all the viruses studied, we performed a comprehensive analysis comparing the published age-specific seropositivities to our data. Although the cohorts, methods and even the antigens were variable among the studies, there were similar results for all studied polyomaviruses. For MCPyV, geographically distinct genotypes might exist, which might also result in the differences in the seroprevalence data. Additional studies with comparable study groups and methods are required to clarify whether there are geographical differences.