Abstract 280: Synthetic lethality of KDM1A and mTOR inhibitors: A novel combination therapy for endometrial cancer
Authors: Pitta-Venkata Prabhakar , Palacios Bridgitte , Chen Yihong , Viswanadhapalli Suryavathi , Pratap Uday P. , Luo Yiliao , Li Mengxing , Altwegg Kristin , Li Xiaonan , Suzuki Takayoshi , Tekmal Rajeshwar Rao , Kost Edward , Sareddy Gangadhara Reddy 
Published: August 2019

Background: Endometrial cancer (EC) is the sixth most common cancer in women. Annually 63,230 new cases are diagnosed with 11,350 deaths estimated in the USA. Currently, advanced EC therapies remain palliative and new therapeutic strategies are urgently needed. Common risk factors include exposure to high levels of estrogen, obesity, and alterations in genetic and epigenetic factors. The lysine-specific demethylase-1A (KDM1A/LSD1) regulates gene expression programs by changing the epigenetic histone marks at the gene promoters. Emerging studies provided the evidence that KDM1A is overexpressed in EC. In studies examining the synthetic lethality of KDM1A inhibition on chemotherapy drug sensitivity, we made an unexpected discovery that KDM1A inhibition potentiate activity of mTOR inhibitors. In this study, we tested the hypothesis that inhibition of KDM1A could sensitize EC to mTOR inhibitor therapy.

Methods: To study the significance of KDM1A inhibition on chemotherapy drug sensitivity, we performed MTT assays to screen 119 FDA approved drugs using KDM1A knockdown HEC1A and RL95 EC cell lines. Effect of KDM1A knockdown or KDM1A inhibitor (NCD-38) therapy on EC cells was examined using MTT cell viability assays and clonogenic survival assays. The effect on cell migration was examined using scratch wound healing assay. Mechanistic studies were conducted using RNA-seq, western blot, qRT-PCR, and IHC analysis. The in vivo efficacy of NCD-38 and sirolimus on EC progression was studied using mouse xenograft models.

Results: Studies using 119 FDA approved drugs identified that mTOR inhibitors sirolimus and temsirolimus has potent synthetic lethality on KDM1A knockdown cells compared to control cells. Cell viability and survival assays demonstrated that KDM1A knockdown or inhibition in combination with sirolimus synergistically reduced cell viability and the survival of EC cells. Further, combination of KDM1A inhibitor and sirolimus reduced the migration of EC cells. Western blot analysis demonstrated that knockdown or inhibition of KDM1A attenuated the activation of mTOR signaling cascade in EC cells. RNA-seq and gene set enrichment analysis identified the down regulation of E2F pathway and DNA replication pathways in KDM1A and mTOR inhibitor treated cells compared to control cells. Further, combination of NCD-38 and sirolimus significantly reduced the in vivo tumor progression in xenograft models. IHC analysis of tumors revealed the downregulation of proliferation marker Ki67 and phosphorylation of mTOR signaling molecules in combination treated tumors compared to vehicle treated tumors.

Conclusions: The results from these studies provide compelling evidence that KDM1A inhibition sensitizes EC cells to mTOR inhibitors, and the use of KDM1A inhibitor in conjunction with mTOR inhibitors may be an attractive therapy for advanced EC patients.

Citation Format: Prabhakar Pitta-Venkata, Bridgitte Palacios, Yihong Chen, Suryavathi Viswanadhapalli, Uday P. Pratap, Yiliao Luo, Mengxing Li, Kristin Altwegg, Xiaonan Li, Takayoshi Suzuki, Rajeshwar Rao Tekmal, Edward Kost, Gangadhara Reddy Sareddy. Synthetic lethality of KDM1A and mTOR inhibitors: A novel combination therapy for endometrial cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 280.