PT  - JOURNAL ARTICLE
AU  - Hillary Stires
AU  - Ayodeji O. Olukoya
AU  - Shihong Ma
AU  - Sonali Persaud
AU  - Yanira Guerra
AU  - M. Idalia Cruz
AU  - Carlos Benitez
AU  - Aaron Rozeboom
AU  - Hannah Ceuleers
AU  - Deborah L. Berry
AU  - Britta M. Jacobsen
AU  - Ganesh V. Raj
AU  - Rebecca B. Riggins
TI  - Riluzole suppresses growth and enhances response to endocrine therapy in ER+ breast cancer
AID  - 10.1101/2020.07.30.227561
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.07.30.227561
4099  - http://biorxiv.org/content/early/2020/07/30/2020.07.30.227561.short
4100  - http://biorxiv.org/content/early/2020/07/30/2020.07.30.227561.full
AB  - Background Resistance to endocrine therapy in estrogen receptor-positive (ER+) breast cancer remains a significant clinical problem. Riluzole is FDA-approved for the treatment of amyotrophic lateral sclerosis. A benzothiazole-based glutamate release inhibitor with several context-dependent mechanism(s) of action, Riluzole has shown anti-tumor activity in multiple malignancies, including melanoma, glioblastoma, and breast cancer. In several (but not all) of these studies, Riluzole-mediated growth inhibition is attributed to increased expression of metabotropic glutamate receptors (mGluRs, GRMs). We recently reported that acquisition of Tamoxifen resistance in a cellular model of invasive lobular breast cancer is accompanied by the upregulation of GRM mRNA expression and growth inhibition by Riluzole.Methods In the current study, we tested the ability of Riluzole to reduce cell growth, alone and in combination with endocrine therapy, in a diverse set of ER+ invasive ductal and lobular breast cancer-derived cell lines, primary breast tumor explant cultures, and the estrogen-independent, ESR1-mutated invasive lobular breast cancer patient-derived xenograft model HCI-013EI.Results Single-agent Riluzole suppressed the growth of ER+ invasive ductal and lobular breast cancer cell lines in vitro, inducing a histologic subtype-associated cell cycle arrest (G0-G1 for ductal, G2-M for lobular). In an invasive lobular, endocrine resistant model, Riluzole induced apoptosis and reduced phosphorylation of multiple pro-survival signaling molecules, including Akt/mTOR, CREB, and Src/Fak family kinases. Riluzole in combination with either Fulvestrant or 4-hydroxytamoxifen additively or synergistically suppressed ER+ breast cancer cell growth in vitro. The combination of Riluzole plus Fulvestrant significantly reduced proliferation in primary breast tumor explant cultures, and inhibited HCI-013EI xenograft growth in vivo significantly earlier than Fulvestrant alone.Conclusions These findings suggest Riluzole combined with endocrine therapy may offer therapeutic benefit in diverse ER+ breast cancers, including lobular breast cancer.Competing Interest StatementThe authors have declared no competing interest.ER+estrogen receptor-positiveSERMselective estrogen receptor modulatorSERDselective estrogen receptor downregulatorILCinvasive lobular breast cancerIDCinvasive ductal breast cancer mGluR,mGluR, GRMmetabotropic glutamate receptorALSamyotrophic lateral sclerosisIMEMimproved minimal essential mediaFBSfetal bovine serumCCScharcoal-cleared serumSTRshort tandem repeatDMSOdimethylsulfoxideSEMstandard error of the meanSDstandard deviationPIpropidium iodideFITCfluorescein isothiocyanateBCAbicinchoninic acidPDEpatient-derived explantPCNAproliferating cell nuclear antigenIACUCinstitutional animal care and use committeePDXpatient-derived xenograftE2estradiolSQsubcutaneousPOper os, by mouthmIHCmultiplex immunohistochemistryMWTmicrowave treatmentAR6antigen retrieval buffer 6DAPI4’,6-diamidino-2-phenylindoleZIPzero interaction potencyANOVAanalysis of varianceMM134MDA-MB-134VI cell line2Dtwo-dimensionalNSGNOD scid gammaSCIDsevere combined immunodeficiencyYAP1Yes-associated protein 1TCGAThe Cancer Genome AtlasIRESinternal ribosome entry site