Presence and role of Simian Virus 40 (SV40) in malignant pleural mesothelioma

No Implication of Simian virus 40 in pathogenesis of Malignant Pleural Mesothelioma in Slovenia

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 μm 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. Free full text available at www.tumorionline.it

Improved survival after introduction of chemotherapy for malignant pleural mesothelioma in Slovenia: Population-based survey of 444 patients

Background

Malignant pleural mesothelioma is a rare tumour with increasing frequency throughout the world. Due to long latency after exposure to asbestos, restrictions in the production and use of asbestos have not yet alleviated the burden of mesothelioma. During the last decade, several trials confirmed the benefit of systemic treatment with drugs such as doublets with cisplatina and gemcitabine or pemetrexed for carefully selected patients in good performance status. The purpose of this survey was to assess the impact of systemic treatment for the whole national population of patients with mesothelioma.

Patients and methods.

A retrospective study included all patients in Slovenia with histologically confirmed diagnosis of malignant pleural mesothelioma in the period from 1974 till 2008. Data from the Cancer Registry of Slovenia were supplemented by review of clinical records of the Institute of Oncology in Ljubljana where virtually all non-surgical treatment for mesothelioma was performed. We analysed the incidence, treatment, and survival of patients treated in the era of infrequent chemotherapy (1974–2003, the first period) and after it (2004–2008, the second period).

Results

The survey included 444 patients, of whom 325 and 119 were diagnosed in the first and second period, respectively. Joinpoint regression analysis showed that after 1995 the trend in crude incidence rates increased more rapidly; the annual change was 0.03 per 100,000 per year before 1995 and 0.06 per 100,000 per year after. There was clear male predominance (70%) throughout the period covered by the survey. The proportion of patients above 65 years of age increased from 41.8% to 54.6% for the first and second period, respectively (p = 0.02). With a total of 52 (11.7%) operated patients, surgical treatment was rare and used only for selected patients with early disease and without comorbidity, leading to their relatively long median survival of 13.6 months. Chemotherapy was applied to 56 (17.2%) and to 96 (80.7%) patients during the first and second period, respectively. While a variety of older drugs were used in the first period, the most common regimen in the second period (applied to 91 patients) was doublet of low-dose gemcitabine in prolonged infusion and cisplatin. For the whole population of patients regardless the mode of treatment, median survival was 7.4 and 12.6 months (p-value = 0.037) for the first and second period, respectively.

Conclusions

Increasing incidence, male predominance and increased proportion of older patients confirm that the burden of mesothelioma persists in spite of a 15-years old ban in the production of asbestos. Modern chemotherapy, and in particular treatment with low-dose gemcitabine in prolonged infusion and cisplatin significantly prolonged median survival of patients with malignant pleural mesothelioma in Slovenia.

BIRC5 promoter SNPs do not affect nuclear survivin expression and survival of malignant pleural mesothelioma patients

PURPOSE

Malignant pleural mesothelioma is an incurable, asbestos-associated cancer. Its incidence is rapidly increasing and survival remains short. Apoptosis deregulation is an important feature of cancer and survivin, a member of the inhibitor-of-apoptosis-protein family encoded by the BIRC5 gene, has been suggested to have a role in the development and progression of several cancers. Genetic variability, in particular single nucleotide polymorphisms in the BIRC5 promoter, may affect the protein's expression levels. The aim of our study was to elucidate the effects of BIRC5 promoter single nucleotide polymorphisms on survivin expression, patient survival and age at diagnosis in malignant pleural mesothelioma.

METHODS

Archival mesothelioma samples from 101 Slovenian patients were immunohistochemically analysed for survivin expression. DNA was extracted from tumour samples and genotyped for three BIRC5 promoter single nucleotide polymorphisms (-31G > C, -241C > T and -625G > C). Genotypes were associated with nuclear survivin expression. Nuclear survivin expression, genotypes, haplotypes, histological type, gender and asbestos exposure were included in univariate Cox survival analyses.

RESULTS

Survivin expression was detected in both tumour cell nuclei and cytoplasms in all analysed samples. No association between BIRC5 promoter polymorphism genotypes or haplotypes and nuclear survivin expression was found. Polymorphism -241C > T affected patients' age at diagnosis. Survival analysis confirmed that younger age at diagnosis and epitheloid histological type improved survival, but no significant effects of nuclear survivin expression or genotype/haplotype on overall survival were observed.

CONCLUSION

Our findings indicate no relationship between BIRC5 genotypes and survivin expression or overall survival in mesothelioma patients. We observed that BIRC5 -241C > T polymorphism had a significant effect on patient age at diagnosis.