No evidence for a role of Merkel cell polyomavirus in small cell lung cancer among Iranian subjects

Association of polyomavirus infection with lung cancer: A systematic review and meta-analysis

AIM

The objective of this study was to investigate the pooled prevalence and possible association between polyomavirus infection and lung cancer.

METHODS

A systematic publication search was conducted by identifying relevant cross-sectional and case-control studies from major online databases. Heterogeneity, OR, and corresponding 95 % CI were applied to all studies through meta-analysis and forest plot. Random effects models were used to calculate the overall pooled prevalence. Visual inspection of a funnel plot plotting the log-transformed OR and its associated standard error of the log (OR) was combined with the Begg and Egger test to examine the presence and influence of publication bias. Analyzes were performed using Stata software v.14.1.

RESULTS

23 articles (33 datasets) were included in the meta-analysis, of which 14 datasets were case/control and the rest were cross-sectional studies. The pooled polyomavirus infection rate in lung cancer patients was 0.06 % (0.02-0.11 %). In subgroup analysis, the pooled prevalence of JCV, MCPyV, KI, SV40, BKV, WU, MU, and STL was 21 %, 7 %, 6 %, 2 %, 0 %, 0 %, 0 %, and 0 % respectively. An association has been found between polyomavirus infection and lung cancer [summary OR 6.33 (95 % CI (1.76-22.77); I2=67.45 %)]. The subgroup analysis, based on the virus type, showed a strong association between MCPyV and lung cancer [summary OR 13.61 (95 % CI 2.41-76.59; I2=40.0 %)]. despite the high prevalence of JCV DNA in lung cancer tissue, analysis of case-control studies showed that JCV is not associated with lung cancer and does not increase the risk of lung cancer.

CONCLUSION

This study showed a significant association between polyomaviruses infection with lung cancer. The results also revealed a pooled prevalence of 6 % for polyomaviruses in lung tumor patients. Altogether, the findings of the present work suggest that Merkel cell polyomavirus infection is a potential risk factor for lung cancer.

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).

Possible Oncogenic Viruses Associated with Lung Cancer

Lung cancer is the most common cause of cancer death worldwide. Tobacco smoking is the most predominant etiology for lung cancer. However, only a small percentage of heavy smokers develop lung cancer, which suggests that other cofactors are required for lung carcinogenesis. Viruses have been central to modern cancer research and provide profound insights into cancer causes. Nevertheless, the role of virus in lung cancer is still unclear. In this article, we reviewed the possible oncogenic viruses associated with lung cancer.

Merkel cell polyomavirus and non-Merkel cell carcinomas: guilty or circumstantial evidence?

Merkel cell polyomavirus (MCPyV) is the major causative factor of the rare but aggressive cancer, Merkel cell carcinoma (MCC). Two characteristics of MCPyV-positive MCCs are integration of the viral genome and expression of a truncated version of one of its oncogenic proteins, namely large T antigen. The strong association of MCPyV with MCC development has incited researchers to further investigate a possible role of this virus in other cancers. However, many of the examples displaying the presence of the virus in the various non-MCC cancers are not able to clearly demonstrate a direct connection between cellular transformation and the presence of the virus. The prevalence of the virus is significantly lower in non-MCC cancers compared to MCCs, with a lower level of viral load and sparse viral protein expression. Moreover, the state of the viral genome, and whether a truncated large T antigen is expressed, has rarely been investigated. Nonetheless, considering the strong oncogenic potential of MCPyV proteins in MCC, the plausible contribution of MCPyV to transformation and cancer growth in non-MCC tumors cannot be ruled out. Furthermore, the absence of MCPyV in cancers does not exclude a hit-and-run mechanism, or the oncoproteins of MCPyV may potentiate the neoplastic process mediated by co-infecting oncoviruses such as high-risk human papillomaviruses and Epstein-Barr virus. The current review is focusing on the available data describing the presence of MCPyV in non-MCC tumors, with an aim to provide a comprehensive overview of the corresponding literature and to discuss the potential contribution of MCPyV to non-MCC cancer in light of this.