TP53 copy number expansion is associated with the evolution of increased body size and an enhanced DNA damage response in elephants.
Level 5 - mechanism / opinion, no new human data
Mechanistic comparative genomic and bench cellular research
PubMed 27642012 · doi:10.7554/eLife.11994
What was done
Comparative genomic and functional molecular analyses were performed on the elephant (Proboscidean) genome to evaluate TP53 copy number, determine whether TP53 retrogenes (TP53RTGs) are transcribed and translated, and examine their regulatory role in DNA damage response, apoptosis induction, and TP53 signaling sensitivity under genotoxic stress.
What was found
The elephant genome encodes 20 copies of the tumor suppressor gene TP53. Several TP53 retrogenes are transcribed and likely translated. Although TP53RTGs do not directly function as transcription factors, they regulate TP53 signaling, contributing to hyperactive signaling, heightened sensitivity to genotoxic stress, and increased apoptosis following DNA damage in elephant cells. No other quantitative values were reported in the abstract.
Why it matters
This study provides a molecular explanation for Peto's paradox by showing how TP53 copy number expansion allowed large-bodied mammals to evade increased cancer risk.
Limits
The abstract does not report specific sample sizes, cell line details, or numerical effect sizes for DNA damage sensitivity and apoptotic rates. The findings are based on comparative genomics and bench-level cellular assays without in vivo cancer rate measurements.
Cited by
- supports Elephants rarely get cancer because they have multiple copies of the p53 gene, which acts as a guardian of the genome preventing mutations.