Abstract
BackgroundAlthough asbestos acts as a potent carcinogen in pleural mesothelial and pulmonary epithelial cells, it still remains unclear whether asbestos causes specific and characteristic gene alterations in these different kinds of target cells, because direct comparison in an identical patient is not feasible. We experienced a rare synchronous collision tumor composed of malignant pleural mesothelioma (MPM) and primary pulmonary adenocarcinoma (PAC) in a 77-year-old man with a history of long-term smoking and asbestos exposure, and compared the DNA copy number alteration (CNA) and somatic mutation in these two independent tumors.MethodsFormalin-fixed paraffin-embedded (FFPE) tissues of MPM and PAC lesions from the surgically resected specimen were used. Each of these MPM and PAC lesions exhibited a typical histology and immunophenotype. CNA analysis using SNP array was performed using the Illumina Human Omni Express-12_FFPE (Illumina, San Diego, CA, USA) with DNA extracts from each lesion. Somatic mutation analysis using next-generation sequencing was performed using the TruSeq Amplicon Cancer Panel (Illumina).ResultsThe CNA analysis demonstrated a marked difference in the frequency of gain and loss between MPM and PAC. In PAC, copy number (CN) gain was detected more frequently and widely than CN loss, whereas in MPM there was no such obvious difference. PAC did not harbor CNAs that have been identified in asbestos-associated lung cancer, but did harbor some of the CNAs associated with smoking. MPM exhibited CN loss at 9p21.2-3, which is the most common genetic alteration in mesothelioma.ConclusionIn this particular case, asbestos exposure may not have played a primary role in PAC carcinogenesis, but cigarette smoking may have contributed more to the occurrence of CN gains in PAC. This comparative genetic analysis of two different lesions with same amount of asbestos exposure and cigarette smoke exposure has provided information on differences in the cancer genome related to carcinogenesis.
Highlights
Asbestos acts as a potent carcinogen in pleural mesothelial and pulmonary epithelial cells, it still remains unclear whether asbestos causes specific and characteristic gene alterations in these different kinds of target cells, because direct comparison in an identical patient is not feasible
We encountered a patient with a history of both long-term smoking and asbestos exposure who underwent extrapleural pneumonectomy and was proved to have a synchronous collision tumor consisting of malignant pleural mesothelioma (MPM) and primary pulmonary adenocarcinoma (PAC)
copy number alteration (CNA) occurred widely in almost all chromosome regions and was more frequent than in the MPM lesion. These results suggest that asbestos exposure may not have played a primary role in PAC carcinogenesis in this particular case, and that factors other than asbestos may have been involved
Summary
Asbestos acts as a potent carcinogen in pleural mesothelial and pulmonary epithelial cells, it still remains unclear whether asbestos causes specific and characteristic gene alterations in these different kinds of target cells, because direct comparison in an identical patient is not feasible. We experienced a rare synchronous collision tumor composed of malignant pleural mesothelioma (MPM) and primary pulmonary adenocarcinoma (PAC) in a 77-year-old man with a history of long-term smoking and asbestos exposure, and compared the DNA copy number alteration (CNA) and somatic mutation in these two independent tumors. Asbestos is considered to act as a potent carcinogen both in pleural mesothelial cells and pulmonary epithelial cells, several studies have suggested that there seems to be less analogous abnormality observed between neoplasms derived from each of them [8] It still remains unclear whether asbestos causes specific and characteristic gene alterations in these different kinds of target cells, because simultaneous occurrence of these neoplasms after asbestos exposure in an identical patient is exceedingly rare [9, 10], and direct comparison of the respective gene alterations is not feasible.
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