Abstract P6-15-18: PELP1-KDM1 Axis: A Novel Therapeutic Target for Blocking Local Estrogen Synthesis
Authors: Cortez V , Mann M , Challa R , Tekmal SR , Suzuki T , Miyata N , Vadlamudi RK. 
Published: April 2011

Background: Local estrogen production via deregulated expression of aromatase (Cyp19), the key enzyme in the biosynthesis of estrogen, contributes to tumor progression in post-menopausal women. Aromatase inhibitors (AI) are effective in enhancing patient survival although long term use is limited by systemic side effects and therapy resistance. Therefore, identifying novel pathways that contributes to in situ E2 in breast tumors and therapeutic agents to block these pathways are urgently needed. Recent studies from our lab demonstrated PELP1 proto-oncogene cooperates with HER2/neu and modulates epigenetic changes at aromatase promoter by interacting with lysine specific demethylase (KDM1) leading to local E2 synthesis. In this study, we examined the therapeutic efficacy of targeting the PELP-KDM1 axis in blocking local E2 production.

Methods: Three breast cancer model cells which exhibit local E2 were used: (a) MCF7 cells overexpressing HER2/neu onogene (MCF7-HER2), (b) MCF7 cells overexpressing proto-oncogene PELP1 (MCF7-PELP1), (c) MCF7 cells with acquired Letrozole resistance (MCF7-Ca-LTLT); parental MCF7 cells were used as controls. Therapeutic potential of KDM1 targeting drugs, (1) Pargyline, a monoamine oxidase inhibitor, (2) NCL-1, a KDM1-selective inhibitor to block PELP1-KDM1 axis were tested using proliferation, aromatase reporter, ChIP and RTqPCR assays. Efficacy of the KDM1 targeting drugs alone or in combination with Letrozole, and Dasatinib was also measured. Pre-clinical, post-memopausal nude mice based models were used to validate the drug effect in vivo.

Results: Depletion of PELP1 or KDM1 using siRNA substantially reduced proliferation of all three model cells and affected epigenetic modifications at the aromatase promoter. Reporter gene and ChIP assays showed growth factors and HER2/neu enhance PELP1 and KDM1 recruitment to the aromatase promoter. KDM1 inhibitors {pargyline (3mM) and NCL1 (10uM)} substantially inhibited growth of all three model cells. In postmenopausal xenograft based model, treatment with pargyline significantly inhibited the growth of local E2 producing tumor cells. IHC and ChIP analysis revealed alterations in histone methyl modifications in treated ER positive tumors. Combinatorial therapy of AI (Letrozole), Src kinaseinhibitor (Dasatinib) with Pargyline or NCL1 showed most promising therapeutic effect compared to single agent therapy to inhibit growth of therapy resistant cells.

Conclusions: Drugs targeting the PELP1-KDM1 are effective in reversing the methyl modifications at aromatase promoter that are affected by proto-oncogenes PELP1, HER2 and blocking growth of local E2 producing cells. Our results suggest targeting of PELP1-KDM1 axis in combination with current endocrine therapies will have a better therapeutic effect and may inhibit or delay development of AI resistance. This study is funded by Komen grant KG090447 and NIH grant CA095681.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-15-18.