SV40 multiple tissue infection and asbestos exposure in a hyperendemic area for malignant mesothelioma

Our plain-English summary of SV40 multiple tissue infection and asbestos exposure in a hyperendemic area for malignant mesothelioma, by M. Comar, C. Rizzardi, R. de Zotti, et al (Cancer Research, 2007).

The study

• Authors: M. Comar, C. Rizzardi, R. de Zotti, M. Melato, M. Bovenzi, J.S. Butel, C. Campello
• Journal: Cancer Research
• Published: 2007;67(18):8456-9
• Cited by: 28 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

To assess the presence of SV40 in malignant mesothelioma tissue, 19 formalin-fixed paraffin-embedded pleural cancer samples of patients from a hyperendemic area of northeastern Italy were analyzed retrospectively. A total of 48 other tissues from the malignant mesothelioma subjects were investigated. The SV40 load was determined by real-time quantitative PCR. Exposure to asbestos was evaluated through a careful review of the occupational history of patients, supplemented by histology and isolation of asbestos bodies. Three of 19 (15.8%) malignant mesothelioma tissues harbored SV40 genomic signals. Two patients with SV40-positive malignant mesothelioma had viral sequences in another tissue. Overall, 3 of 18 (16.7%) normal liver tissues tested positive for SV40, as did 1 of 8 (12.5%) kidney tissues. SV40 viral loads were higher in malignant mesothelioma than in normal cells (P = 0.045). This survey shows that SV40 sustains infections in multiple tissues in malignant mesothelioma patients from a geographic area affected with asbestos-related mesothelioma.

In plain English

This pilot, retrospective study looked for the virus SV40 in archived tissue from 19 patients with pleural mesothelioma in northeastern Italy, an area the authors call hyperendemic for mesothelioma. Asbestos exposure was established for 17 of the 19 patients using national registry guidelines and other criteria, including compensation. The article does not report which asbestos fiber types these patients were exposed to. The authors also tested 48 other tissues from these patients, plus 30 control cervical samples from women with cervical cancer. SV40 was found in 3 of 19 mesothelioma samples (15.8%), all from asbestos-exposed patients. It was also found in 4 of 32 normal tissues (12.5%), including 3 of 18 liver and 1 of 8 kidney samples. Tissues infiltrated by cancer, breast cancers and cervical samples were all negative. Counting any site, 5 of 19 patients were positive. Positive mesotheliomas had a higher estimated share of infected cells than positive normal tissues (12.6% versus 5%; P = 0.045). The authors noted that only two unexposed patients were included and that the study was not designed to explore causes. They concluded that SV40 involvement in patients from this area warrants further investigation.

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: Pilot retrospective laboratory study of archived tissue samples (exploratory survey), using PCR to detect and measure SV40
• Who was studied: 19 selected patients with pleural mesothelioma (12 males, 7 women) from a hyperendemic area of northeastern Italy (provinces of Trieste and Gorizia). In 5 of the women, mesothelioma followed an earlier breast cancer. Besides the 19 mesothelioma samples, 48 other tissues from these patients were tested (kidney, brain, lung, liver and breast cancer samples). 30 cervical samples from women with human papillomavirus-related cancer served as controls.
• Exposure: Asbestos exposure was established for 17 of 19 patients, using the Italian National Mesothelioma Registry (ReNaM) guidelines and/or other criteria, including compensation for recognized occupational mesothelioma. The article does not report which asbestos fiber types these patients were exposed to. The other exposure studied was infection with the simian virus SV40, detected in tissue.
• Main results:
  • SV40 was detected in 3 of 19 (15.8%) mesothelioma specimens. All 3 were from asbestos-exposed patients (3 of 17, 17.6%).
  • Among other tissues from the mesothelioma patients, 4 of 32 (12.5%) normal tissue samples contained SV40. None of the 12 samples infiltrated by cancer cells were positive.
  • Among normal tissues, SV40 was detected in 3 of 18 (16.7%) liver samples and 1 of 8 (12.5%) kidney samples.
  • Breast cancer specimens from 4 mesothelioma patients and cervical scrapings from 30 cervical cancer patients were all negative for SV40.
  • Counting any site, 5 of 19 (26.3%) mesothelioma patients were SV40 positive. In 2 of the 3 patients with SV40-positive mesothelioma, SV40 was also found in normal liver or kidney tissue.
  • SV40-positive mesotheliomas had a higher mean estimated proportion of infected cells than SV40-positive normal tissues (12.6% versus 5%; P = 0.045), assuming one viral genome copy per cell.
• The authors' conclusion: The authors concluded that mesothelioma patients from this area of Italy warrant further investigation of SV40 involvement. They called for a prospective study of fresh samples from new cases with matched controls. They also wrote that their findings support a plausible cofactor role for the virus in this area.
• Limitations the authors state:
  • Only two patients without asbestos exposure were included in the series.
  • The meaning of the findings is uncertain because the survey was not designed to explore questions about whether SV40 contributes to causing mesothelioma.
  • Few reports of SV40 tissue loads exist, and the methods used are not always comparable.
  • The percentage of infected cells was calculated assuming one viral genome copy per cell. Actively infected cells likely carry multiple copies, which would mean fewer infected cells than calculated.

Topics

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

Medical terms in this study, explained in our Lexicon: SV40, Asbestos Exposure, Malignant Mesothelioma, Occupational History, Histology, Asbestos Bodies, Mesothelioma.

Related studies

• Asbestos and SV40 in malignant pleural mesothelioma from a hyperendemic area of north-eastern Italy — M. Comar, N. Zanotta, et al. (2012)
• Evidence against a role for SV40 infection in human mesotheliomas and high risk of false-positive PCR results owing to presence of SV40 sequences in common laboratory plasmids — F. López-Ríos, P.B. Illei, et al. (2004)
• SV40 enhances the risk of malignant mesothelioma among people exposed to asbestos: a molecular epidemiologic case-control study — A. Cristaudo, R. Foddis, et al. (2005)
• The role of SV40 in malignant mesothelioma and other human malignancies — M.A. Pershouse, S. Heivly, et al. (2006)
• Aberrant methylation profile of human malignant mesotheliomas and its relationship to SV40 infection — M. Suzuki, S. Toyooka, et al. (2005)
• Simian virus 40 sequences in blood specimens from healthy individuals of Casale Monferrato, an industrial town with a history of asbestos pollution — C. Pancaldi, V. Balatti, et al. (2009)

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