Wednesday, May 9, 2012

Infectious cancer

I don't think anything like this is known in humans but there ARE infectious cancers, and not just the ones caused by viruses. The best known example is the bizarre facial tumors that are threatening the Tasmanian Devil's.

Genome sequences from the infectious tumour were published in February in the journal Cell (Genome Sequencing and Analysis of the Tasmanian Devil and Its Transmissible Cancer), offering clues about how the cancer has spread to devils across the Australian island of Tasmania.

The Tasmanian devil (Sarcophilus harrisii), the largest marsupial carnivore, is endangered due to a transmissible facial cancer spread by direct transfer of living cancer cells through biting. Here we describe the sequencing, assembly, and annotation of the Tasmanian devil genome and whole-genome sequences for two geographically distant subclones of the cancer. Genomic analysis suggests that the cancer first arose from a female Tasmanian devil and that the clone has subsequently genetically diverged during its spread across Tasmania. The devil cancer genome contains more than 17,000 somatic base substitution mutations and bears the imprint of a distinct mutational process. Genotyping of somatic mutations in 104 geographically and temporally distributed Tasmanian devil tumors reveals the pattern of evolution and spread of this parasitic clonal lineage, with evidence of a selective sweep in one geographical area and persistence of parallel lineages in other populations.

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