Simian virus 40 may be associated with developing malignant pleural mesothelioma

Our plain-English summary of Simian virus 40 may be associated with developing malignant pleural mesothelioma, by T.D. Thanh, N.V. Tho, N.S. Lam, et al (Oncology Letters, 2016).

The study

• Authors: T.D. Thanh, N.V. Tho, N.S. Lam, N.H. Dung, C. Tabata, Y. Nakano
• Journal: Oncology Letters
• Published: 2016;11(3):2051-2056
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant pleural mesothelioma (MPM) is associated with a history of heavy, long-term exposure to asbestos. However, MPM may also be associated with simian virus 40 (SV40), a polyomavirus. The association between SV40 and MPM remains unclear. The present study was conducted in order to investigate the proportion of SV40 presence in the histological specimens of Vietnamese patients with MPM. Histological specimens were obtained from 45 patients (19 men and 26 women) with MPM at the Pham Ngoc Thach Hospital in Ho Chi Minh City, Vietnam. The specimens were processed and examined in order to detect the presence of the SV40 large T antigen (SV40 Tag) expression using immunohistochemistry. Of the 45 patients, 23 (51%) were epithelioid, 7 (16%) were biphasic, 6 (13%) were sarcomatoid, 4 (9%) were desmoplastic, 4 (9%) were well-differentiated papillary and 1 (2%) was the anaplastic subtype. In total, 9/45 patients (20%) demonstrated SV40 Tag expression. The proportion of patients that demonstrated SV40 Tag expression was not significantly different between the epithelioid subtype and the other subtypes (22 vs. 18%; P=1.000) or between the patients with stage IV disease and other stages (20 vs. 20%; P=1.000). The median survival time was not significantly different between the patients with or without SV40 Tag expression (196 vs. 236 days, P=0.8949). In summary, a 5th of the Vietnamese patients with MPM were associated with infection with SV40. SV40 may be a potential cause of MPM in Vietnam and this potential association requires additional studies.

In plain English

This retrospective study examined tumor samples from 45 patients (19 men and 26 women) diagnosed with malignant pleural mesothelioma between January 2008 and June 2012 at Pham Ngoc Thach Hospital in Ho Chi Minh City, Vietnam. The authors stained the samples for the large T antigen of simian virus 40 (SV40), a protein made by the virus. They also interviewed patients or close relatives about asbestos exposure. Nine of the 45 patients (20%) showed the SV40 protein. Twenty patients (44%) had a history of asbestos exposure. Asbestos bodies were found in 10 of the 22 patients who had samples available, and only 1 of those 22 had both the SV40 protein and asbestos bodies. Survival did not differ significantly between patients with and without the SV40 protein (median 196 vs. 236 days). The authors concluded that SV40 may be another potential cause of mesothelioma in Vietnam and that this needs larger studies with more reliable detection methods. They noted several limitations: the small sample, possible false or missed results from the staining method, and no published data on SV40 levels in Vietnam's general population.

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: retrospective study of archived tissue specimens and medical records, with interviews of patients or close relatives
• Who was studied: 45 patients (19 men, 26 women; mean age 59, range 25 to 88) diagnosed with malignant pleural mesothelioma at Pham Ngoc Thach Hospital, Ho Chi Minh City, Vietnam, between January 2008 and June 2012; 89% were in stage IV
• Exposure: Simian virus 40 (SV40) large T antigen detected in tumor tissue by immunohistochemistry. Asbestos exposure was assessed by interview, defined as ever living in a fiber cement-roofed house or working in asbestos-associated industries, and by counting asbestos bodies in lung tissue or bronchoalveolar lavage fluid. No fiber types were specified.
• Main results:
  • 9 of 45 patients (20%) showed SV40 large T antigen in their tumor specimens
  • 44% of the patients (20 of 45) had a history of asbestos exposure
  • Asbestos bodies were found in 10 of the 22 patients with specimens available (45%)
  • Only 1 of the 22 patients with specimens available (5%) showed both SV40 large T antigen and asbestos bodies
  • SV40 expression was found in 5% of males and 31% of females; this difference was not statistically significant (P=0.0578)
  • SV40 expression did not differ significantly between patients with asbestos bodies (1 of 10) and without them (3 of 12) (P=0.5940)
  • Median survival for all 45 patients was 236 days (95% CI 125 to 366)
  • Median survival did not differ significantly between patients with and without SV40 large T antigen (196 vs. 236 days; P=0.8949)
  • After adjusting for disease stage, chemotherapy did not have a significant effect on survival (adjusted hazard ratio 0.75; 95% CI 0.36 to 1.52; P=0.4317)
• The authors' conclusion: The authors concluded that a fifth of these Vietnamese patients were infected with SV40, that SV40 may be another potential cause of malignant pleural mesothelioma in Vietnam, and that this needs investigation with larger samples and more reliable SV40 detection methods.
• Limitations the authors state:
  • Not all patients had specimens for asbestos body examination, so asbestos exposure may be underestimated
  • SV40 was detected only by immunohistochemistry, which may be less sensitive than molecular methods
  • Immunohistochemistry may give false results because of the staining procedure and interpretation
  • The small sample size gave insufficient power to detect significant differences between groups
  • There are no published data on general SV40 levels in the Vietnamese population
  • Interviews about asbestos exposure history may be affected by recall bias

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, SV40, Immunohistochemistry, Epithelioid, Biphasic Mesothelioma, Sarcomatoid, Desmoplastic Mesothelioma, Well-Differentiated.

Related studies

• Simian virus-40 large-T antigen binds p53 in human mesotheliomas — M. Carbone, P. Rizzo, et al. (1997)
• Human mesothelial cells are unusually susceptible to simian virus 40-mediated transformation and asbestos cocarcinogenicity — M. Bocchetta, I. Di Resta, et al. (2000)
• The retinoblastoma gene family pRb/p105, p107, pRb2/p130 and simian virus-40 large T-antigen in human mesotheliomas — A. De Luca, A. Baldi, et al. (1997)
• Simian virus 40, poliovaccines and human tumors: a review of recent developments — M. Carbone, P. Rizzo, et al. (1997)
• Simian virus 40 large T antigen (SV40LTAg) primer specific DNA amplification in human pleural mesothelioma tissue — C. Pepper, B. Jasani, et al. (1996)
• Progressive aberrant methylation of the RASSF1A gene in simian virus 40 infected human mesothelial cells — S. Toyooka, M. Carbone, et al. (2002)

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