New instance of ‘contagious cancer’ in animals

Why in News?

Recently, researchers at the University of Vermont discovered a rare contagious cancer spreading among brown bullhead catfish in Lake Memphremagog (spanning Vermont, USA, and Quebec, Canada).

• It marks only the 4^th major instance of transmissible cancer documented in wild animals and the first-ever recorded in a freshwater species.

Known Contagious Cancers in Animals

Key Mechanisms

• Cellular Parasitism
  • Unlike standard cancers which arise independently inside an individual host due to somatic mutations transmissible cancers act as infectious cellular parasites.
  • The original tumor cell lineage outlives its initial host by spreading physically to new individuals.
• Immune Evasion Strategies
  • Normally, an individual's immune system recognizes foreign tissue via Major Histocompatibility Complex (MHC) surface proteins and destroys it.
  • Transmissible cancer cells survive by downregulating MHC molecules or colonizing host populations with low genetic diversity, masking themselves from the host’s immune surveillance.
• Susceptible to Humans
  • Human immune systems feature high Major Histocompatibility Complex (MHC) diversity, ensuring foreign human cells are quickly rejected as "non-self."
  • Isolated human cancer cells are extremely fragile when exposed to open air or body fluids and die rapidly outside their original host tissue environment.

Strategic Significance

• Studying how transmissible cancer lineages downregulate immune markers helps oncologists design therapies targeting immune evasion mechanisms in human solid tumors.
• Highlights environmental factors (like aquatic pollutants or water temperature shifts) that may increase host susceptibility to emerging transmissible diseases in wild aquatic ecosystems.

Reference

The Hindu | New instance of ‘contagious cancer’ in animals