DUSP1 inhibition in the treatment of high grade serous ovarian carcinoma (141.5)

Abstract

<b>Objectives:</b> Dual Specificity Phosphatase (DUSP) proteins regulate signaling cascades involved in tumor progression, but there are limited studies of DUSPs in epithelial ovarian carcinoma, especially in high-grade serous ovarian carcinoma (HGSOC). The study objective was to elucidate <i>DUSP1</i>'s contribution to HGSOC progression and examine a <i>DUSP1/6</i> inhibitor (DUSPi) in therapy-resistant HGSOC. <b>Methods:</b> Bioinformatic analyses were conducted using The Cancer Genome Atlas (TCGA) Ovarian Serous Cystadenocarcinoma Firehose Database and PanCancer Atlas. qPCR was completed to determine the mRNA expression of <i>DUSP1</i>. Fifty percent inhibitory concentration of DUSPi was determined using colony formation assays. Reverse-phase protein array (RPPA) examined the effect of DUSPi on cellular signaling. The antitumoral effect of DUSPi was examined using a patient-derived xenograft (PDX) model. Quantitative data were expressed as mean +/- standard error of the mean. RPPA relative protein levels were determined for each and designated as log2 intensities and subsequently median-centered. Analysis of variance with Tukey correction was used for multiple comparisons. The level of significance was set at 0.05. <b>Results:</b> Of 24 DUSP proteins examined in HGSOC, <i>DUSP1</i> mRNA was significantly upregulated (p<0.001, one-way ANOVA). Progression-free survival (PFS) and overall survival (OS) were significantly higher in patients with low <i>DUSP1</i> expression (PFS: 15.41 vs 22.22 months, Log-rank test, p=0.0010, HR: 1.65, 95% CI: 1.213-2.259; OS: 41.52 vs 52.40 months, Log-rank test, p=0.0183, HR: 1.462, 95% CI: 1.064-2.00). Elevated <i>DUSP1</i> protein expression was noted in our tissue microarray of 137 serous ovarian carcinoma primary and recurrent tumors. Olaparib-resistant HGSOC cells had significantly increased <i>DUSP1</i> expression compared to olaparib-sensitive HGSOC cells (unpaired t-test, p<0.0001). The RPPA analysis revealed 34 proteins with significantly (p<0.05) altered expression after treatment with DUSPi. DUSPi led to the significant downregulation of <i>WEE1</i> and <i>ATR</i>. Phosphor-AMPK (AMPK-a2_pS345), part of the mTORC pathway that can serve both tumor-suppressive and oncogenic roles, was elevated and dual phosphorylated ERK (MAPK_pT202_Y204). RPPA findings were confirmed in TCGA data and by immunoblotting. A therapy-resistant PDX model was used to examine DUSPi <i>in vivo</i> activity. DUSPi led to a decrease in total flux (photons/sec), indicating tumor regression, in the mice treated with DUSPi compared to control. At the end of the study, there was no evidence of ascites or tumor burden in mice treated with DUSPi. <b>Conclusions:</b> <i>DUSP1</i> expression is associated with poor progression-free and overall survival. After treatment with a novel <i>DUSP1/6</i> inhibitor (DUSPi), cell viability was significantly reduced. We defined the differential activation of signaling following DUSPi via RPPA. DUSP inhibition significantly resulted in altering the expression of multiple pathway proteins, including increasing AMPK phosphorylation. Finally, we identified a robust <i>in vivo</i> antitumor response with DUSPi in PDX models.