Presence of Jaagsiekte sheep retrovirus in tissue sections from human bronchioloalveolar carcinoma depends on patients' geographical origin

Bronchioloalveolar carcinoma (BAC) is a rare form of lung cancer that has been histopathologically classified as an adenocarcinoma with a pure bronchioloalveolar growth pattern (in situ alveolar adenocarcinoma) [1]. The ovine pulmonary adenocarcinoma (OPA) has been classified as a mixed adenocarcinoma showing bronchioloalveolar growth patterns; it presents several features resembling the human BAC and is caused by the oncogenic Jaagsiekte sheep retrovirus (JSRV) [1]. The JSRV has been demonstrated to act as a potent carcinogen in the experimental setting and to possess a tropism for sheep lung, whose genome seems to contain several copies of endogenous (i.e., transmitted horizontally) JSRV-related sequences [2]. Recent findings indicate that insertional mutagenesis of JSRV-related sequences might be involved into the development of OPA [3]. Contrasting results for the causative presence of JSRV in subsets of human BACs from different populations using genomic and expression approaches have been reported [1-2, 4-7]. Because of the lack of confirmatory studies, we here tried to further assess the role of the genomic integration of JSRV-related DNA sequences into the BAC pathogenesis.