Discovery of gene expression-based pharmacodynamic biomarker for a p53 context-specific anti-tumor drug Wee1 inhibitor.
BACKGROUND
Wee1 is a tyrosine kinase regulating S-G2 cell cycle transition through the inactivating phosphorylation of CDC2. The inhibition of Wee1 kinase by a selective small molecule inhibitor significantly enhances the anti-tumor efficacy of DNA damaging agents, specifically in p53 negative tumors by abrogating S-G2 checkpoints, while normal cells with wild-type p53 are not severely damaged due to the intact function of the G1 checkpoint mediated by p53. Since the measurement of mRNA expression requires a very small amount of biopsy tissue and is highly quantitative, the development of a pharmacodynamic (PD) biomarker leveraging mRNA expression is eagerly anticipated in order to estimate target engagement of anti-cancer agents.


RESULTS
In order to find the Wee1 inhibition signature, mRNA expression profiling was first performed in both p53 positive and negative cancer cell lines treated with gemcitabine and a Wee1 inhibitor, MK-1775. We next carried out mRNA expression profiling of skin samples derived from xenograft models treated with the Wee1 inhibitor to identify a Wee1 inhibitor-regulatory gene set. Then, the genes that were commonly modulated in both cancer cell lines and rat skin samples were extracted as a Wee1 inhibition signature that could potentially be used as a PD biomarker independent of p53 status. The expression of the Wee1 inhibition signature was found to be regulated in a dose-dependent manner by the Wee1 inhibitor, and was significantly correlated with the inhibition level of a direct substrate, phosphorylated-CDC2. Individual genes in this Wee1 inhibition signature are known to regulate S-G2 cell cycle progression or checkpoints, which is consistent with the mode-of-action of the Wee1 inhibitor.


CONCLUSIONS
We report here the identification of an mRNA gene signature that was specifically changed by gemcitabine and Wee1 inhibitor combination treatment by molecular profiling. Given the common regulation of expression in both xenograft tumors and animal skin samples, the data suggest that the Wee1 inhibition gene signature might be utilized as a quantitative PD biomarker in both tumors and surrogate tissues, such as skin and hair follicles, in human clinical trials.
Mizuarai
Shinji
S
Department of Oncology, Tsukuba Research Institute, Merck Research Laboratories, Banyu Pharmaceutical Co, Ltd, Tsukuba, Ibaraki 300-2611, Japan. shinji_mizuarai@merck.com
Yamanaka
Kazunori
K
Itadani
Hiraku
H
Arai
Tsuyoshi
T
Nishibata
Toshihide
T
Hirai
Hiroshi
H
Kotani
Hidehito
H
D000704:Analysis of Variance; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D014408:Biomarkers, Tumor / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D045744:Cell Line, Tumor; D019926:Cyclin B / Q000378:metabolism; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D020869:Gene Expression Profiling; D006801:Humans; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051381:Rats; D011923:Rats, Nude; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012867:Skin / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays; D000093542:Gemcitabine
D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D018797:Cell Cycle Proteins; D019926:Cyclin B; D009687:Nuclear Proteins; D016159:Tumor Suppressor Protein p53; D003841:Deoxycytidine; D011505:Protein-Tyrosine Kinases; C499349:WEE1 protein, human; D000093542:Gemcitabine