Abstract AP20: STROMAL CELL EXPRESSION OF THE RECEPTOR TYROSINE KINASE DDR2 PROMOTES OVARIAN CANCER METASTASIS
Authors: Greenwade Molly , Beck Holly , Grither Whitney , Wilke Daniel , Massad Katina , Guo Lei , Longmore Greg , Fuh Katherine 
Published: June 2021

OBJECTIVES: Understand the role of stromal discoid domain receptor 2 (DDR2) expression in ovarian cancer metastasis

METHODS: 111 high-grade serous ovarian cancer specimens were examined for stromal DDR2 protein expression by immunohistochemistry (IHC) and correlated with survival. The stromal cell contribution of DDR2 for the steps of metastasis were evaluated through mesothelial cell clearance, Matrigel invasion assays, and germline knock-out mice. DDR2 low versus DDR2 high primary stromal cells were cultured from normal omenutum: human peritoneal mesothelial cells (HPMC) and normal omental fibroblasts (NOF). DDR2 knock-out (KO) and wild-type (WT) mice were used to evaluate metastasis. DDR2 positive (ID8Trp53-/-BRCA2-/- and ES2) tumor cells were used. Mesothelial cell clearance area was evaluated by measuring the size of the clearance area, invasion was evaluated by the number of tumor cells per high power field (hpf), and metastatic spread evaluated by number of tumors nodules and tumor weight. Collagen contribution was evaluated with Masson's trichrome stain and second harmonic generation (SHG). In addition, the media of genetically inhibited DDR2 or therapeutic inhibition of DDR2 in the NOFs (siControl vs siDDR2) was removed and then added to tumor cells to evaluate for invasion. Therapeutic inhibition was performed with a small molecule developed in a collaborating lab, WRG-R28.

RESULTS: Patients with high stromal cell DDR2 expression had a median overall survival (OS) of 171 months vs. low stromal cell DDR2 expression (OS) of 28 months (p&lt;0.0001). Mesothelial cell clearance was performed with HPMCsiControl vs siDDR2 and found to have decreased tumor cell clearance with HPMCsiDDR2 when compared to HPMCsiControl. Additionally, tumor cell invasion was decreased by 2-fold in the NOFsiDDR2 compared to NOFsiControl in two discrete NOFs. Furthermore, media from NOFsiControl vs NOFsiDDR2 was removed and co-cultured with DDR2+ tumor cells and found to have 50% less invasion for tumor cells co-cultured with NOFsiDDR2 compared to NOFsiControl. DDR2 KO mice had significantly less tumor weight (0.025g vs 0.05, p&lt;0.05) than DDR2 WT mice. Collagen content was found to be less intense at 45% compared to 80%, p&lt;0.0001 in the DDR2KO vs DDR2WT. SHG analysis showed DDR2 WT tumors to be more perpendicular than DDR2 KO tumors were more parallel to the tumor-stromal border. Therapeutic inhibition with WRG-R28 treatment of the NOFs resulted in 2-fold decrease in invasive tumor cells (150 vs 75 cells/hpf, p&lt;0.01) as well as inhibition of mesothelial cell clearance by the tumor cells treated with WRG-R28 compared to DMSO.

CONCLUSIONS: The stromal contribution of DDR2 promotes tumor cell clearance of mesothelial cells and metastatic spread. This suggests that stromal expression of DDR2 may be a potential target to guide future therapy particularly in the maintenance setting.

Citation Format: Molly Greenwade, Holly Beck, Whitney Grither, Daniel Wilke, Katina Massad, Lei Guo, Greg Longmore, Katherine Fuh. STROMAL CELL EXPRESSION OF THE RECEPTOR TYROSINE KINASE DDR2 PROMOTES OVARIAN CANCER METASTASIS [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr AP20.