Background In Dayao County, Chuxiong Yi Autonomous Prefecture, Yunnan Province, China, 5% of the surface is scattered with blue asbestos, where has a high incidence of malignant pleural mesothelioma (MPM). Simian virus 40 (SV40) is a small circular double-stranded DNA polyomavirus that can cause malignant transformation of normal cells of various human and animal tissue types and promote tumor growth. Early epidemiological surveys show that the incidence of malignant mesothelioma in crocidolite contaminated areas of Dayao County is dozens of times higher than that of the general population.
Objective To investigate whether the oncogenic SV40 is associated with the occurrence of MPM in the crocidolite contaminated area of Dayao County, Yunnan Province.
Methods Tumor tissues from 51 patients with MPM (40 of whom had a history of asbestos exposure) and pleural tissues from 12 non-MPM patients (including diseases such as pulmonary maculopathy and pulmonary tuberculosis) were collected from January 2014 to December 2019 at the Department of Thoracic Surgery of the Fourth Affiliated Hospital of Dali University (the First People's Hospital of Chuxiong Yi Autonomous Prefecture) and People's Hospital of Dayao County. Meanwhile, human normal pleural mesothelial cell line Met5A (SV40-transformed mesothelial cells) and MPM cell lines NCI-H28 (epithelial-like type), NCI-H2052 (sarcoma-like type) and NCI-H2452 (biphasic mixed type) were cultured in vitro. After extraction of genomic DNA from each group of cells and tissues, the gene fragments of SV40 large T antigen (TAg) were amplified by polymerase chain reaction (PCR) with three sets of low contamination risk primers (SVINT, SVfor2 and SVTA1). In addition, the presence of SV40 TAg in MPM tumor tissue and MPM cell lines was detected by Western blotting and immunohistochemical staining with 2 SV40-related antibodies (Pab l01 and PAb416).
Results PCR, Western blotting and immunohistochemical staining results showed that Met5A cell line had positive SV40 and contained the SV40 TAg gene and protein. In contrast, various MPM cell lines NCI-H28, NCI-H2052 and NCI-H2452 were negative for SV40. PCR reactions were negative for all three sets of low contamination risk primers in 12 non-MPM tissues and 51 MPM tissues. SV40 TAg was not detected in 12 non-MPM tissues and 51 MPM tissues by immunohistochemical staining.
Conclusion The occurrence of MPM in crocidolite contaminated areas in Yunnan Province may not be closely related to SV40 virus infection, while crocidolite exposure may be the main cause of MPM.
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