AVB-S6-500, a receptor tyrosine kinase AXL inhibitor, improves the therapeutic efficacy of trastuzumab in uterine serous cancers (278)

Joan Tankou,Premal Thaker,Katherine Fuh,Shaina Bruce,Matthew Powell,Michael Toboni,Alyssa Oplt,Danny Wilke,Carolyn Mccourt,Lindsay Kuroki,Hollie Noia,Andrea Hagemann,David Mutch

doi:10.1016/s0090-8258(22)01499-8

Abstract

Objectives: To determine whether inhibition of GAS6/AXL can improve efficacy to the humanized anti-HER2 monoclonal antibody trastuzumab by decreasing uterine serous cancer cell invasion and cell survival in vitro and tumor burden in vivo. Methods: We treated three uterine serous cancer cell lines (ARK1, ARK2, PUC198) that expressed Her2/neu and AXL receptors with AVB500 (Aravive Biologics, Houston, TX) in combination with Trastuzumab. Clonogenic proliferation assays were performed after three days of treatment, and relative cell viability was calculated using GraphPad Prism. Next, using a Matrigel invasion assay, we examined the invasive capacity of the ARK1 and ARK2 cell lines after 24 hours of treatment with vehicle, AVB500 alone, Trastuzumab alone, or combination Trastuzumab and AVB500. We also performed proximity ligation and IF colocalization assays to show that Her2/neu and AXL receptors form a complex that results in the transphosphorylation and activation of the AXL. We performed in vivo studies using nod-SCID mice injected with 1 x 107 ARK1 and ARK2 cells intraperitoneally, followed by treatment with vehicle control, AVB alone, or Trastuzumab alone or in combination with AVB500 for 35 days and 21 days, respectively. Results: In uterine serous (ARK 2 and PUC 198) cells, there was a significant reduction in cell proliferation when treated with combination Trastuzumab and AVB500 compared to the Trastuzumab-alone group (0.155nm vs 0.202nm, p=0.015; 0.290 vs 0.015, p=0.0044) in ARK 2 and PUC 198 cell lines, respectively. We also observed a reduction in the number of invading tumor cells when cells were treated with combination Trastuzumab and AVB500 versus Trastuzumab alone (3.9 vs 17.7 invading tumor cells/hpf, p=0.0001; 3.2 vs 17.8 invading tumor cells/hpf, p=0.0004) in ARK 1 and ARK 2 cell lines, respectively. Furthermore, the proximity ligation and co-localization assays demonstrated the physical closeness of AXL and HER2 receptors in ARK2 cells that could account for the co-regulation of these receptors. Finally, we found that mice treated with Trastuzumab plus AVB -500 developed significantly less tumor burden than mice treated with Trastuzumab alone (0.032 g vs 0.083 g, p= 0.024) in the ARK1 xenograft model and (0.142g vs 0.443 g, p= 0.0015) in the ARK2 xenograft model. Conclusions: The GAS6/AXL inhibitor, AVB-500, potentiated the effect of Trastuzumab to decrease uterine serous cancer cell proliferation and invasion in vitro and tumor burden in vivo. Co-localization of AXL and HER2 receptors was seen in both uterine serous cancer cell lines. Our data suggest that the addition of AVB-S6-500 increased the therapeutic efficacy of Trastuzumab therapy in uterine serous cancers. Additional therapeutic and mechanistic experiments are ongoing.

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