Transmissible cancers, the genomes that do not melt down

Area of Science:

• Evolutionary Biology
• Genomics
• Cancer Biology

Background:

• Asexual reproduction typically leads to genomic decay due to deleterious mutations.
• Transmissible cancers (clonal cell lineages) are exceptions, surviving for millennia despite high mutation loads.
• Known lineages include canine venereal tumor disease, devil facial tumor diseases (DFT1, DFT2), and bivalve transmissible neoplasia.

Purpose of the Study:

• To explain how transmissible cancers overcome fitness decline from accumulated mutations.
• To propose that high mutation loads may confer indirect fitness advantages.
• To suggest using these host-pathogen systems to address evolutionary biology questions.

Main Methods:

• Analysis of evolutionary theory regarding asexual reproduction and mutation accumulation.
• Review of existing studies on transmissible cancer lineages (dogs, Tasmanian devils, bivalves).
• Comparative genomics of transmissible cancer cell lines.

Main Results:

• Transmissible cancers survive for extended periods despite high mutation burdens.
• High mutation loads might offer indirect fitness benefits, counteracting expected genomic decay.
• Mechanistic insights into transmissible cancer genome evolution have been revealed.

Conclusions:

• Transmissible cancers provide a unique model to study the evolution of longevity and immune evasion.
• Understanding these clonal pathogens is crucial for investigating their long-term survival and host adaptation.
• Further research can leverage these systems to answer fundamental questions in evolutionary biology.