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An activating Pik3ca mutation coupled with Pten loss is sufficient to initiate ovarian tumorigenesis in mice.

ABSTRACT: Mutations in the gene encoding the p110? subunit of PI3K (PIK3CA) that result in enhanced PI3K activity are frequently observed in human cancers. To better understand the role of mutant PIK3CA in the initiation or progression of tumorigenesis, we generated mice in which a PIK3CA mutation commonly detected in human cancers (the H1047R mutation) could be conditionally knocked into the endogenous Pik3ca locus. Activation of this mutation in the mouse ovary revealed that alone, Pik3caH1047R induced premalignant hyperplasia of the ovarian surface epithelium but no tumors. Concomitantly, we analyzed several human ovarian cancers and found PIK3CA mutations coexistent with KRAS and/or PTEN mutations, raising the possibility that a secondary defect in a co-regulator of PI3K activity may be required for mutant PIK3CA to promote transformation. Consistent with this notion, we found that Pik3caH1047R mutation plus Pten deletion in the mouse ovary led to the development of ovarian serous adenocarcinomas and granulosa cell tumors. Both mutational events were required for early, robust Akt activation. Pharmacological inhibition of PI3K/mTOR in these mice delayed tumor growth and prolonged survival. These results demonstrate that the Pik3caH1047R mutation with loss of Pten is enough to promote ovarian cell transformation and that we have developed a model system for studying possible therapies.

SUBMITTER: Kinross KM

PROVIDER: S-EPMC3266789 | biostudies-literature | 2012 Feb

REPOSITORIES: biostudies-literature

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An activating Pik3ca mutation coupled with Pten loss is sufficient to initiate ovarian tumorigenesis in mice.

Kinross Kathryn M KM Montgomery Karen G KG Kleinschmidt Margarete M Waring Paul P Ivetac Ivan I Tikoo Anjali A Saad Mirette M Hare Lauren L Roh Vincent V Mantamadiotis Theo T Sheppard Karen E KE Ryland Georgina L GL Campbell Ian G IG Gorringe Kylie L KL Christensen James G JG Cullinane Carleen C Hicks Rodney J RJ Pearson Richard B RB Johnstone Ricky W RW McArthur Grant A GA Phillips Wayne A WA

The Journal of clinical investigation 20120103 2

Mutations in the gene encoding the p110α subunit of PI3K (PIK3CA) that result in enhanced PI3K activity are frequently observed in human cancers. To better understand the role of mutant PIK3CA in the initiation or progression of tumorigenesis, we generated mice in which a PIK3CA mutation commonly detected in human cancers (the H1047R mutation) could be conditionally knocked into the endogenous Pik3ca locus. Activation of this mutation in the mouse ovary revealed that alone, Pik3caH1047R induced ...[more]

PMID: 22214849

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Project description:BACKGROUND:The PI3K/AKT pathway is activated through PIK3CA or AKT1 mutations and PTEN loss in breast cancer. We conducted a phase II trial with an allosteric AKT inhibitor MK-2206 in patients with advanced breast cancer who had tumors with PIK3CA/AKT1 mutations and/or PTEN loss/mutation. METHODS:The primary endpoint was objective response rate (ORR). Secondary endpoints were 6-month progression-free survival (6?m PFS), predictive and pharmacodynamic markers, safety, and tolerability. Patients had pre-treatment and on-treatment biopsies as well as collection of peripheral blood mononuclear cells (PBMC) and platelet-rich plasma (PRP). Next-generation sequencing, immunohistochemistry, and reverse phase protein arrays (RPPA) were performed. RESULTS:Twenty-seven patients received MK-2206. Eighteen patients were enrolled into the PIK3CA/AKT1 mutation arm (cohort A): 13 had PIK3CA mutations, four had AKT1 mutations, and one had a PIK3CA mutation as well as PTEN loss. ORR and 6?m PFS were both 5.6% (1/18), with one patient with HR+ breast cancer and a PIK3CA E542K mutation experiencing a partial response (on treatment for 36?weeks). Nine patients were enrolled on the PTEN loss/mutation arm (cohort B). ORR was 0% and 6?m PFS was 11% (1/9), observed in a patient with triple-negative breast cancer and PTEN loss. The study was stopped early due to futility. The most common adverse events were fatigue (48%) and rash (44%). On pre-treatment biopsy, PIK3CA and AKT1 mutation status was concordant with archival tissue testing. However, two patients with PTEN loss based on archival testing had PTEN expression on the pre-treatment biopsy. MK-2206 treatment was associated with a significant decline in pAKT S473 and pAKT T308 and PI3K activation score in PBMC and PRPs, but not in tumor biopsies. By IHC, there was no significant decrease in median pAKT S473 or Ki-67 staining, but a drop was observed in both responders. CONCLUSIONS:MK-2206 monotherapy had limited clinical activity in advanced breast cancer patients selected for PIK3CA/AKT1 or PTEN mutations or PTEN loss. This may, in part, be due to inadequate target inhibition at tolerable doses in heavily pre-treated patients with pathway activation, as well as tumor heterogeneity and evolution in markers such as PTEN conferring challenges in patient selection. TRIAL REGISTRATION:ClinicalTrials.gov, NCT01277757 . Registered 13 January 2011.

Dataset Information

An activating Pik3ca mutation coupled with Pten loss is sufficient to initiate ovarian tumorigenesis in mice.

Publications

An activating Pik3ca mutation coupled with Pten loss is sufficient to initiate ovarian tumorigenesis in mice.

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