A dominant-negative effect drives selection of TP53 missense mutations in myeloid malignancies

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• TP53 is the most frequently mutated gene in human cancers.
• Missense mutations dominate the TP53 mutational spectrum, with gain-of-function (GOF) activities proposed but not fully understood.
• The selective pressures driving TP53 mutations remain enigmatic.

Purpose of the Study:

• To investigate the functional consequences of common TP53 missense mutations.
• To determine whether TP53 missense mutations exhibit loss-of-function, dominant-negative effect (DNE), or gain-of-function (GOF) activities.
• To elucidate the selective pressures favoring TP53 missense mutations in cancer, particularly myeloid malignancies.

Main Methods:

• CRISPR-Cas9 gene editing to create isogenic human leukemia cell lines with specific TP53 missense mutations.
• Functional assays, DNA-binding studies, and transcriptional analyses to assess p53 protein activity.
• Mutational scanning of p53 variants and analysis of mouse models and clinical data from acute myeloid leukemia patients.

Main Results:

• Functional, DNA-binding, and transcriptional analyses revealed loss of function and dominant-negative effect (DNE) for TP53 missense mutations, with no evidence of GOF.
• Missense variants in the DNA-binding domain of p53 were shown to exert a DNE.
• In mice, DNE of p53 missense variants conferred a selective advantage to hematopoietic cells under DNA damage conditions.
• Analysis of acute myeloid leukemia patient data showed no evidence of GOF for TP53 missense mutations.

Conclusions:

• Dominant-negative effect (DNE) is the primary mechanism driving the selection of TP53 missense mutations in myeloid malignancies.
• The findings clarify the functional impact of TP53 mutations, shifting focus from GOF to DNE as the key selective pressure.
• This study provides critical insights into the molecular basis of cancer development driven by TP53 alterations.