No implication of Simian virus 40 in pathogenesis of malignant pleural mesothelioma in Slovenia

Our plain-English summary of No implication of Simian virus 40 in pathogenesis of malignant pleural mesothelioma in Slovenia, by J. Hmeljak, I. Kern, A. Cör (Tumori, 2010).

The study

• Authors: J. Hmeljak, I. Kern, A. Cör
• Journal: Tumori
• Published: 2010;96(5):667-73
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background And Aim: Malignant mesothelioma is predominantly caused by asbestos exposure, although the association of Simian virus 40 in its pathogenesis is currently still under debate. Simian virus 40, a DNA rhesus monkey virus with oncogenic properties, accidentally contaminated early batches of polio vaccine in the 1960s. In the 1990s, viral sequences and proteins were discovered in several human tumors, which triggered research to find a link between Simian virus 40 and human cancers, especially malignant mesothelioma. The aim of our study was to establish an effective laboratory procedure for Simian virus 40 detection and to investigate the presence of Simian virus 40 DNA and small t antigen in mesothelioma samples from Slovenian patients.

Methods And Study Design: Paraffin-embedded malignant pleural mesothelioma specimens from 103 Slovenian patients were collected and used for total DNA isolation and real-time polymerase chain reaction for Simian virus 40 small t and large T DNA analysis. Special attention was devoted to primer design, good laboratory practice and polymerase chain reaction contamination prevention. Polymerase chain reaction products were sequenced and BLAST aligned. One 5 microm thick paraffin section from each patient's tissue block was stained with hematoxylin and eosin for histological typing and one for immunohistochemical detection of Simian virus 40 small t antigen using a monoclonal antibody against Simian virus 40 (Pab280). SV40-expressing Wi-38 cells were used as positive control in both PCR and immunohistochemistry.

Results: In real-time polymerase chain reaction analyses, only 4 samples gave products with primer pairs amplifying small t antigen and were inconsistent and poorly reproducible. BLAST alignment showed no homology with any deposited SV40 sequences. No immunopositive staining for SV40 small t antigen was found in any of the samples.

Conclusions: We found no evidence of SV40 presence in tissue samples from 103 Slovenian patients with malignant pleural mesothelioma. Asbestos exposure remains the main risk factor for malignant pleural mesothelioma in Slovenia.

In plain English

This laboratory study looked for Simian virus 40 (SV40) in malignant pleural mesothelioma tumors from Slovenia. SV40 is a monkey virus that accidentally contaminated early batches of polio vaccine. The authors tested 184 archived, paraffin-embedded tumor samples from 103 patients, collected for diagnosis between 1996 and 2006 at a clinic in Golnik. Patient records documented asbestos exposure in 44 patients (43%), and 38 patients (37%) had no known asbestos exposure. The authors used real-time PCR to look for viral DNA and tissue staining to look for a viral protein called small t antigen. No tumor section stained positive. Of the 180 samples with usable DNA, 175 (97%) showed no viral DNA. The other 5 gave signals that were absent from other samples from the same patients and did not match any known SV40 sequence, so the authors judged them likely false positives. The authors concluded that they found no evidence of SV40 in these patients and that asbestos exposure remains the main risk factor for this cancer in Slovenia. They noted that entirely negative results call for careful interpretation.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory study of archived tumor tissue, testing for SV40 DNA by real-time PCR and for SV40 small t antigen by immunohistochemistry
• Who was studied: 184 formalin-fixed, paraffin-embedded malignant pleural mesothelioma samples from 103 patients (69 male, 34 female, aged 32-88), taken from the pathology archives of the University Clinic of Respiratory and Allergic Diseases in Golnik, Slovenia, and collected for diagnosis between 1996 and 2006
• Exposure: The exposure studied was SV40 virus. Patient records documented asbestos exposure in 44 of 103 patients (43%), and 38 patients (37%) had no known asbestos exposure history. No asbestos fiber types are named.
• Main results:
  • No positive immunostaining for SV40 small t antigen was seen in any of the mesothelioma tissue sections.
  • 4 of the 184 DNA samples (2%) contained poor-quality DNA that could not be amplified; the other 180 (98%) were usable.
  • Of the amplifiable DNA samples, 175 (97%) were SV40 negative with every SV40 primer set.
  • 5 samples (3%) gave products with the small t primers but not with the large T primers. Other samples from the same 5 patients, taken from different paraffin blocks, were consistently negative.
  • The authors judged these 5 results most likely false positives due to contamination or nonspecific amplification. On sequencing, the products did not match any deposited SV40 sequence, whereas control products did, so all tumor samples were considered SV40 negative.
• The authors' conclusion: The authors concluded that they found no evidence of SV40 in tissue from these 103 Slovenian patients with malignant pleural mesothelioma, and that asbestos exposure remains the main risk factor for malignant pleural mesothelioma in Slovenia.
• Limitations the authors state:
  • The authors said the consistently negative results called for careful interpretation.
  • The authors noted that studies with entirely negative findings can be challenged on technical sensitivity. For example, formalin fixation and long-term storage damage DNA and rule out RNA-based testing. They stated that most of their DNA samples were pure and consistently amplifiable.
  • No official record exists of whether contaminated polio vaccine was used in Slovenia, so the authors' conclusion about past vaccine use is indirect.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Malignant Mesothelioma, Asbestos Exposure, Mesothelioma, Paraffin Block, Monoclonal Antibody, SV40, Immunohistochemistry.

Related studies

• Simian virus (SV) 40 like sequences in cell lines and tumour biopsies from Australian malignant mesotheliomas — B.R. McLaren, T. Haenel, et al. (2000)
• Human T cell responses to endogenously presented HLA-A*0201 restricted peptides of Simian virus 40 large T antigen — M.P. Velders, M.F. Macedo, et al. (2001)
• SV40 large T-antigen and human pleural mesothelioma. Screening by polymerase chain reaction and tyramine-amplified immunohistochemistry — K. Dhaene, A. Verhulst, et al. (1999)
• Presence and expression of the simian virus-40 genome in human giant cell tumors of bone — G. Gamberi, M.S. Benassi, et al. (2000)
• Simian virus 40 large T antigen (SV40LTAg) primer specific DNA amplification in human pleural mesothelioma tissue — C. Pepper, B. Jasani, et al. (1996)
• Human mesotheliomas contain the simian virus-40 regulatory region and large tumor antigen DNA sequences — H.I. Pass, J.S. Donington, et al. (1998)

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