GAS6-AXL inhibition by AVB-500 overcomes resistance to paclitaxel in endometrial cancer by decreasing tumor cell glycolysis (276)

Abstract

<b>Objectives:</b> Chemotherapy is often ineffective in advanced-stage and aggressive histologic subtypes of endometrial cancer. Overexpression of the receptor tyrosine kinase AXL has been found to be associated with therapeutic resistance, metastasis, and poor prognosis. The mechanism of how inhibition of AXL improves response to chemotherapy is still largely unknown. We aimed to determine whether treatment with AVB-500, a selective inhibitor of <i>GAS6</i>-AXL, improves endometrial cancer cell sensitivity to chemotherapy, particularly through metabolic changes. <b>Methods:</b> Immunohistochemistry (IHC) was performed on a tissue microarray containing specimens from patients with primary and metastatic uterine serous carcinoma. Blind scoring was performed by two reviewers. Kaplan-Meier methods were used to generate time-to-event curves. Cell viability was performed with high-grade endometrial, chemo-resistant cell lines, ARK1 and PUC198. Cells were treated with paclitaxel and with AVB-500+paclitaxel. Intraperitoneal (IP) ARK1 or PUC198 tumors were treated with vehicle, AVB-500, paclitaxel, or AVB-500+paclitaxel. A Seahorse Analyzer was used for glycolytic rate assays. Isotope tracing was used for <i>in vivo</i> metabolite abundance quantification. <b>Results:</b> We found that both <i>GAS6</i> and AXL expression were higher by IHC in tumors with a poor response to chemotherapy compared to tumors with a good response to chemotherapy (<i>GAS6</i>: 40.9% vs 30.4%, p=0.012; AXL: 60.7% vs 42.7%, p=0.013). Median PFS and OS were longer in patients with low <i>GAS6</i> expressing tumors compared to high <i>GAS6</i> expressing tumors (PFS: 33.6 mo vs 10.6 mo, p=0.003; OS: 39.5 mo vs 27.7 mo, p=0.003). We showed that chemotherapy-resistant endometrial cancer cell lines, ARK1 and PUC198, had improved sensitivity and synergy with paclitaxel when treated in combination with AVB-500. ARK1 and PUC198 <i>in vivo</i> IP models had significantly fewer tumors (ARK1: 2.8 vs 7.9, p=0.028; PUC198: p=0.029) and decreased tumor weight (ARK1: p<0.001; PUC198: p=0.006) when treated with AVB-500+paclitaxel versus paclitaxel alone. Treatment with AVB-500 + paclitaxel decreased AKT signaling, which resulted in a decrease in basal glycolysis. Finally, treatment with AVB-500 + paclitaxel decreased multiple glycolytic metabolites, including fructose-1,6-bisphosphate (p=0.002), 3-phosphoglyceric acid (p=0.014), phosphoenolpyruvate (p=0.013), and lactate (p=0.024) versus treatment with paclitaxel alone. <b>Conclusions:</b> Our study provides a strong preclinical rationale for combining AVB-500 with paclitaxel in aggressive endometrial cancer models. Additionally, the continued identification of viable biomarkers is critical to the success of targeted therapies, such as AVB-500. Given AXL's role in glucose homeostasis, one or more glycolytic intermediates may prove to be a useful biomarker to help predict sensitivity in patients, thus tailoring who would benefit from this treatment combination.