Preventing ovarian cancer cell metastasis through inhibition of discoidin domain receptor 2 (DDR2) in the tumor microenvironment: a metabolomic analysis

Abstract

Objectives: Discoidin domain receptor 2 (DDR2) is a tyrosine kinase activated by fibrillar collagen type 1. DDR2 expression in both cancer cells and stromal cells is critical for metastases in breast cancer. In ovarian cancer, DDR2 stabilizes Snail, a critical factor in the epithelial to mesenchymal transition, which facilitates cancer cell invasion and metastases. Snail has also been shown to reprogram glucose metabolism in breast cancer cells, thereby allowing cancer cell survival under metabolic stress. This study aimed to investigate how stromal DDR2 expression in normal omental and ovarian cancer associated fibroblasts (NOF and CAF) regulates tumor cell invasion by analyzing changes in stromal cell metabolomics. Methods: Matrigel invasion assays were performed using immortalized normal omental fibroblasts (NOF206) and ES2 ovarian cancer cells. NOF206s were transfected with two different siRNAs to produce transient siDDR2 knockdown. Lysates and conditioned media were collected of siControl (DDR2-expressing), Dharmacon siDDR2 and Sigma siDDR2 (DDR2 non-expressing) cells. Mass spectrometry was performed and metabolites were identified. Quantitative RT-PCR was performed to evaluate changes in the expression of mesenchymal markers based on DDR2 expression. Results: DDR2 expressing tumor cells invaded less when co-cultured with DDR2-non expressing NOFs compared to DDR2 expressing NOFs (51 vs 155 cells per hpf, p Conclusions: Genetic inactivation of DDR2 results in marked changes in the metabolism of normal omental fibroblasts resulting in decreased tumor cell invasion. These findings suggest a novel role of DDR2 in metabolism and stromal cell energy generation. The significance of these findings requires further study on the complex relationship between ovarian cancer and the stromal environment.