Abstract 4143: Identification of molecular targets for conservative management of early stage, low-grade endometrial cancer through compartment-specific transcriptome profiling

Understanding tumor microenvironment is critical to improving conservative management (non-surgical) strategies for early stage, low grade endometrial cancer (EC). This remains an unmet clinical need for women who wish to maintain fertility and those who cannot undergo surgery due to medical co-morbidities. Current regimens rely on progestin treatment, but resistance and early relapse require improved therapeutic strategies. We sought to evaluate alterations in gene expression in the epithelial and stromal compartment of EC compared to normal endometrium to identify targets for combination therapies. RNA was extracted from microdissected epithelial and stromal compartments of formalin fixed paraffin embedded early stage, low grade EC and normal endometrium (NE). Comprehensive transcriptome profiling was performed with Affymetrix Clariom D assay and pathway analysis was performed. Immunohistochemistry (IHC) was used for validation. Functional studies of differentially expressed genes were performed in EC cell lines, ECC-1 and Hec1A. Focusing on differentially expressed genes in the epithelial compartment of EC vs NE, multiple activated signaling pathways were identified, including eIF2 signaling, eIF4 and p70S6K signaling, PI3K/AKT/mTOR, and hormone signaling. Top gene expression changes with significantly lower expression in EC included RBPMS (RNA-binding protein with multiple splicing), SORD (sorbitol dehydrogenase), DDX17 (DEAD-box helicase 17), and TPT1 (translationally-controlled tumor protein) gene expression, while MTDH (metadherin) was significantly increased in EC. Differential expression of proteins coded by these genes was confirmed by IHC. Additionally, RBPMS silencing enhanced AKT and S6 protein phosphorylation in Hec1A cells and forced expression of RBPMS in ECC-1 cells attenuated Erk1/2 MAP kinase activation. Expression of RBPMS inhibited cell proliferation and knockdown of RBPMS increased proliferation. Treatment of EC cells with everolimus (mTOR inhibitor) resulted in differential inhibition of proliferation based on RBPMS expression. Communication between tumor and stroma is also being evaluated. While estrogen-regulated changes were prominent in early stage low-grade EC, the discovery of alterations in other signaling pathways suggest additional targets for conservative management of the disease. The identification of signaling nodes shared between hormone-regulated pathways and mTOR signaling provides further justification for the ongoin