Abstract P2-06-05: TP-0903, an AXL kinase inhibitor, reduces inflammatory breast cancer aggressiveness and macrophage polarization through additional mechanisms that may include JAK2 and Aurora B
Authors: Cheng Y , Funakoshi Y , Wang X , Warner SL , Bearss DJ , Ueno NT 
Published: May 2019

Background: Inflammatory breast cancer (IBC) is the most lethal and aggressive type of breast cancer; it accounts for 2-4% of breast cancer cases but causes 8-10% of breast cancer deaths. Novel targeted therapy to improve the outcomes of patients with IBC is urgently needed. The receptor tyrosine kinase AXL is a driver for metastasis and drug resistance in various cancers, including breast cancer. Our previous work showed that AXL signaling contributes to the aggressiveness of IBC. In addition, emerging evidence indicates that the tumor microenvironment components, particularly tumor-associated macrophages, are critical drivers of the IBC clinical phenotype and promote IBC metastasis. AXL signaling has been shown to modulate the tumor microenvironment. In the present study, we investigated the impact of TP-0903, a small-molecule AXL kinase inhibitor, with additional activity against Aurora B and Janus kinase 2 (JAK2), on IBC cells and macrophage polarization.

Methods: The effects of TP-0903 on IBC cell proliferation, migration/invasion, and mammosphere formation were analyzed. The effects of TP-0903 on the polarization of human monocytic cells THP-1 were tested in vitro. In addition, the signaling pathways involved in TP-0903-regulated M2 macrophage polarization were investigated using Western blotting.

Results: The half-maximal inhibitory concentration (IC50) of TP-0903 in an array of IBC cells (including SUM149, SUM190, BCX010, FC-IBC-02, MDA-IBC-3, and KPL4) ranged from 66 nM to 346 nM, suggesting a strong cell growth inhibitory effect. TP-0903 treatment decreased the migration, invasion, and mammosphere formation of IBC cells. In addition, TP-0903 inhibited both AXL signaling and Aurora B activation, which induced a G2/M cell cycle arrest in IBC cells. Based on the importance of AXL and JAK2 in the regulation of the tumor microenvironment, we showed that TP-0903 decreased expression of CD163/CD206 and the CCL17/CCL18 cytokine, and markers of M2 macrophages, suggesting that TP-0903 treatment inhibits the polarization of THP-1 cells to M2 macrophages in vitro. We also found that TP-0903 treatment decreased the phosphorylation of STAT6, a critical molecule in M2 polarization, and that knockdown of STAT6 expression decreased M2 macrophage polarization, indicating that TP-0903 may regulate macrophage polarization via STAT6 signaling.

Conclusion: Our results demonstrated the dual functions of TP-0903 targeting of both IBC cells and macrophages, possibly via the targeting of multiple kinases, including AXL and Aurora B. Examinations of the impact of TP-0903 on the cross-talk between IBC cells and macrophages in vitro and in vivo and the related mechanisms are ongoing and will be presented at the meeting.

Citation Format: Cheng Y, Funakoshi Y, Wang X, Warner SL, Bearss DJ, Ueno NT. TP-0903, an AXL kinase inhibitor, reduces inflammatory breast cancer aggressiveness and macrophage polarization through additional mechanisms that may include JAK2 and Aurora B [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-06-05.