Comparative Oncological Studies of Feline Bronchioloalveolar Lung Carcinoma, Its Derived Cell Line and Xenograft

Although certain neoplasms are unique to man, others occur across species. One such neoplasm is bronchioloalveolar lung carcinoma (BAC), a neoplasm of the Type II pneumocyte that affects humans, sheep, and small animals (dogs and cats). Human BAC occurs largely in nonsmokers. Sheep BAC is caused by the jaagsiekte retrovirus and is endemic and contagious. Feline BAC is neither endemic nor contagious and occurs sporadically and spontaneously in older purebred cats. In these respects, feline BAC is more closely similar to human BAC than sheep BAC (jaagsiekte) is. To study feline BAC further, we established the first immortal cell line (SPARKY) and transplantable scid mouse xenograft (Sparky-X) from a malignant pleural effusion of a 12-year-old Persian male with autopsy-confirmed BAC. SPARKY exhibited a Type II pneumocyte phenotype characterized by surfactant and thyroid-transcription factor-1 immunoreactivities and lamellar bodies. SPARKY’s karyotype was aneuploid (66 chromosomes: 38, normal cat) and showed evidence of genomic instability analogous to human lung cancers. p53 showed a homozygous G to T transversion at codon 167, the feline equivalent of human codon 175, one of the many hot spots mutated in the lung cancers of smokers. H -ras and K -ras were not altered. By reverse transcription-PCR, SPARKY lacked expression of retroviral JSRV gag transcripts that were present in the lungs of sheep BAC (jaagsiekte). Unlike human BAC xenografts, SPARKY-X retained its unique lepidic BAC growth pattern even though it was grown in murine s.c. tissues. This property may be related to the ability of SPARKY-X to up-regulate its surfactant genes ( SP-A , SP-B , and SP-D ). These studies of feline BAC may allow insights into the human disease that are not possible by studying human BAC directly.