Abstract 1618: Thromboxane A2 receptor controls migration and metastasis of triple-negative breast cancer cells

Abstract

Abstract Background: Triple negative breast cancers (TNBCs) have poor prognosis and there are no effective targeted therapies available. Thromboxane A2 receptor (TBXA2R) is a G protein coupled receptor whose ligand is a prostanoid produced by cyclooxygenase and thromboxane A2 synthase. There are two isoforms of TBXA2R as results of alternative splicing. TBXA2Rα and β differ in the cytoplasmic tail distal at amino acid residue 328. High expression of TBXA2R has been linked with poor progression free survival of breast cancer cells, but it is unknown how TBXA2R contributes to the progression of breast cancers and which isoform(s) is involved. Methods: TBXA2R expression in breast cancer was determined by RT-PCR, Western blot and immunohistochemistry using isoform specific primer sets or antibodies. Small hairpin RNAs and CRISPR-CAS9 were used to knock down or knock out TBXA2R expression. Tumor cell migration was evaluated by wound healing and Boyden chamber assays. Cell proliferation and survival was evaluated by MTS and trypan blue based cell counting. Xenograft models were used to assess breast tumor growth, progression, and metastasis. Results: While TBXA2Rα is ubiquitously expressed in breast cancer cells, TBXA2Rβ is selectively expressed in triple negative breast cancer. Activation of TBXA2R had no discernible effects on proliferation or survival of MDA-MB-231 cells. However, TBXA2R activation led to rapid activation of RhoA and cytoskeletal reorganizations of TNBC cells. TBXA2R activation also led to rapid activation of protein kinase N1 (PKN1), a kinase frequently amplified in TNBCs. Inhibition or depletion of TBXA2R led to reduced tumor cell migration in vitro and prevented breast cancer metastasis in vivo. Further analyses found that inhibition or depletion of TBXA2R compromised the ability of TNBC cells to extravasate in an animal model. Conclusions: Our data suggest that TBXA2R can contribute to TNBC progression and metastasis by controlling tumor cell cytoskeleton reorganization and motility. Citation Format: Yuanqin Zhang, Xuejing Zhang, Daotai Nie. Thromboxane A2 receptor controls migration and metastasis of triple-negative breast cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1618.