p63 and p73 do not contribute to p53-mediated lymphoma suppressor activity in vivo

Area of Science:

• Molecular Biology
• Oncology
• Genetics

Background:

• The tumor suppressor gene p53 is vital in human cancer.
• The roles of p53 homologues, p63 and p73, in tumor suppression are debated.
• While p63 and p73 can respond to DNA damage, mice lacking these genes do not develop spontaneous tumors.

Purpose of the Study:

• To investigate if radiation exposure uncovers tumor suppressor functions of p63 or p73, alone or with p53.
• To determine the contribution of p63 and p73 to radiation-induced lymphoma development.

Main Methods:

• Utilized mice heterozygous for p63, p73, or double heterozygous for p53/p63 and p53/p73.
• Exposed mice to gamma radiation to induce lymphoma.
• Analyzed tumor latency, spectrum, frequency, and genetic alterations (deletions, loss of heterozygosity) near p63 and p73 loci.
• Assessed p63 and p73 gene expression in radiation-induced tumors.

Main Results:

• No significant differences in tumor development were observed in p63 or p73 heterozygous mice, or double heterozygotes, compared to controls after radiation.
• Deletions near the p63 locus were found in some radiation-induced tumors, often encompassing the knockout allele.
• No deletions or loss of heterozygosity (LOH) involving the p73 gene were detected, and p73 expression remained intact.
• p63 and p73 expression was maintained in radiation-induced tumors.

Conclusions:

• p53 homologues (p63 and p73) do not contribute to the tumor suppressor activity of p53 in the context of radiation-induced lymphoma.
• The findings clarify the distinct roles of p53 family members in cancer suppression, particularly after DNA damage.
• Radiation exposure does not reveal latent tumor suppressor functions for p63 or p73 in lymphoma development.