Drug Discovery

The inactivation of p53 is widely established as a key feature in most cancers. Restoring the function of clinically significant p53 mutant proteins has become a major therapeutic target for cancer therapy. The OncoREX p53 cancer array has 100 functional p53 variants available for screening of small molecules to discover drugs that may target p53.

There are 3 key applications of the OncoREX p53 cancer array:

1. Direct functional correlation between genotype and phenotype

Understanding the way in which SNPs in proteins manifest in human disease is a fundamental goal in the post-genomic era. The OncoREX p53 cancer array enables functional characterisation of the phenotypic effects of 100 different isoforms.

2. Discovering new compounds that can restore the function of mutant p53

The p53 gene is responsible for more than 50% of all cancers, however very few of the protein products have been functionally characterised. The KREX-based p53 cancer array enables quantitative, in situ, highly multiplexed characterisation of the capability of small molecules in restoring the function of clinically significant pathogenic mutant isoforms of p53.

3. Determine the effect of p53 mutations on binding of autoantibodies and antibodies

Quantify differential interaction of patient serum derived autoantibodies or monoclonal/polyclonal antibodies to a panel of 100 p53 mutant proteins.

Binding of p53 to GADD45 promoter element DNA oligo

Study Design: Sengenics KREX-based p53 cancer array probed with a Cy3-labelled GADD45 duplex oligo.

Results: Quantitative analysis shows mechanistic differences between ‘loss of function’ isoforms of p53.

Interaction of p53 and MDM2

Study Design: Sengenics KREX-based p53 cancer array probed with purified Cy3-labelled MDM2 protein.

Results: MDM2-Cy3 bound all proteins on the OncoREX p53 cancer array, though with greatly reduced binding to the W23A and W23G isoforms. Confirmation of the results in a different assay format revealed that only wild-type p53 associated with MDM2.

On-chip phosphorylation of p53 by casein kinase II (CKII)

Study Design: Sengenics KREX-based p53 cancer array probed were incubated in assay buffer containing ATP in the presence and absence of CKII.

Results: Specific phosphorylation of S392 was detected using residue specific antiphosphoserine primary antibody with detection by secondary antibody-peroxidase conjugate and chemiluminescence. Mutations with “X” denote truncations due to introduction of premature stop codons and therefore lack S392.