Nutlin-3a selects for cells harbouring TP53 mutations

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• TP53 mutations are prevalent in human cancers, necessitating reliable methods for studying mutagenesis.
• The human TP53 knock-in immortalisation assay (HIMA) is used to study TP53 mutagenesis but requires lengthy TP53 sequencing.
• Wild-type TP53 (TP53-WT) cultures require extensive maintenance during the HIMA.

Purpose of the Study:

• To enhance the selectivity of the HIMA for identifying TP53 mutations.
• To evaluate Nutlin-3a, an MDM2 inhibitor, as a tool to discriminate between TP53-WT and TP53-mutated cells.
• To improve the efficiency of TP53 mutation screening in cell culture models.

Main Methods:

• Human TP53 knock-in (Hupki) mouse embryo fibroblast (HUF) cell lines with wild-type or mutated TP53 were treated with Nutlin-3a.
• The effect of Nutlin-3a on cell growth and p53 activation was assessed in established immortalized HUF lines.
• Nutlin-3a sensitivity/resistance was evaluated in emerging immortal clones during the HIMA, followed by TP53 sequencing.

Main Results:

• Nutlin-3a activated the p53 pathway and inhibited growth in TP53-WT HUFs, while TP53-mutated HUFs showed resistance.
• In the HIMA, Nutlin-3a-resistant clones consistently harbored diverse TP53 mutations.
• Nutlin-3a-sensitive clones were predominantly TP53-WT, with only one exception.

Conclusions:

• Incorporating a Nutlin-3a counter-screen significantly improves the specificity and efficiency of the HIMA.
• This approach allows for the selection of TP53-mutated clones before sequencing, reducing effort.
• TP53-WT clones can be efficiently discarded, streamlining cancer mutation studies.