PTEN loss as a context-dependent determinant of patient outcomes in obese and non-obese endometrioid endometrial cancer patients.

Abstract

5521 Background: Aberrations in the PI3K pathway, the central relay pathway of insulin signals, occur in the majority of endometrioid endometrial cancers. We explored the prognostic utility of PIK3CA, PIK3R1, and PTEN mutations, as well as PTEN protein loss, in the context of patient weight. Methods: Patients (pts) treated for endometrial cancer at a single institution between 2000 and 2009 were identified. Tumor DNA was extracted and exome sequencing performed using a 454 platform with confirmation of hot spot mutations by Sequenom. PTEN protein expression was determined by immunohistochemistry and reverse phase protein array (RPPA). RPPA for 135 relevant proteins was performed using a GeneTAC arrayer to create spot arrays. Slides were scanned, analyzed, and quantitated using Microvigene software. Results: One hundred eighty seven endometrioid endometrial cancer specimens were included. Median age was 61 yrs and median body mass index (BMI) was 33.5 kg/m2. The majority of pts had early stage (I/II) disease (74%) and grade 2 tumors (66%). There were no statistically significant associations between progression free survival (PFS) and PIK3CA, PIK3R1, PTEN mutation or loss. However, when stratified by BMI, PTEN loss was associated with a significantly improved PFS (p< 0.006) in obese (BMI > 30 kg/m2) pts. In contrast, PTEN loss was associated with a worse PFS (p<0.06) in non-obese (BMI < 30 kg/m2) pts. Further, PTEN loss in obese and non-obese pts resulted in distinct protein changes by RPPA, with canonical PI3K pathway activation observed only in the non-obese PTEN loss cohort. PTEN loss in obese pts was associated with decreased expression of CATENIN and phosphorylated FOXO3A. Conclusions: These data suggest the impact of PTEN loss on tumor biology and clinical outcomes must be interpreted in the context of BMI and provide potential explanation for prior discrepant findings on effect of PTEN status on prognosis in endometrial cancer. These data describe a clinically important interaction between metabolic state and tumor genetics that could potentially unveil the biologic underpinning of obesity-related cancers and may be relevant to ongoing clinical trials with PI3K pathway inhibitors.