Pharmacologic inhibition of STAT5 in acute myeloid leukemia

Bettina Wingelhofer,Dávid Bajusz,Abbarna A Cumaraswamy,Patricia Freund,Florian Grebien,Angelika Berger-Becvar,Frank Ruge,Stefan Kubicek,Jisung Park,Siawash Ahmar,György M Keserű ,Gary Tin,Peter Valent,Elizabeth Heyes ,Barbara Maurer,Charles-Hugues Lardeau,Anna Orlova,Elvin D De Araujo,Patrick T Gunning,Irina Sadovnik,Richard Moriggl

doi:10.1038/s41375-017-0005-9

Abstract

The transcription factor STAT5 is an essential downstream mediator of many tyrosine kinases (TKs), particularly in hematopoietic cancers. STAT5 is activated by FLT3-ITD, which is a constitutively active TK driving the pathogenesis of acute myeloid leukemia (AML). Since STAT5 is a critical mediator of diverse malignant properties of AML cells, direct targeting of STAT5 is of significant clinical value. Here, we describe the development and preclinical evaluation of a novel, potent STAT5 SH2 domain inhibitor, AC-4–130, which can efficiently block pathological levels of STAT5 activity in AML. AC-4–130 directly binds to STAT5 and disrupts STAT5 activation, dimerization, nuclear translocation, and STAT5-dependent gene transcription. Notably, AC-4–130 substantially impaired the proliferation and clonogenic growth of human AML cell lines and primary FLT3-ITD+ AML patient cells in vitro and in vivo. Furthermore, AC-4–130 synergistically increased the cytotoxicity of the JAK1/2 inhibitor Ruxolitinib and the p300/pCAF inhibitor Garcinol. Overall, the synergistic effects of AC-4–130 with TK inhibitors (TKIs) as well as emerging treatment strategies provide new therapeutic opportunities for leukemia and potentially other cancers.

Highlights

STAT5 is a key member of the JAK/STAT core cancer pathway, activated by a plethora of cytokines and growth factors to regulate a wide spectrum of physiologic processes in hematopoietic cells [1, 2]
To verify if AC-4–130 binds to the SH2 domain, a thermal shift assay with full-length STAT5B was performed using a fluorescently labeled EPO receptor peptide which interacts with the SH2 domain
The presence of AC-4–130 effectively displaced the peptide from the STAT5B protein, indicating binding of AC-4–130 to the STAT5 SH2 domain

Summary

Introduction

STAT5 is a key member of the JAK/STAT core cancer pathway, activated by a plethora of cytokines and growth factors to regulate a wide spectrum of physiologic processes in hematopoietic cells [1, 2]. Persistent STAT5 activity (pY-STAT5) is found in many hematopoietic cancers driven by hyper-activated upstream TKs, where it is essential for leukemia cell maintenance and survival [3,4,5,6]. Acute myeloid leukemia (AML) is one of the most common blood cancers in adults, with the majority of patients being over 60 years old. FLT3-ITD mutations lead to constitutive, ligandindependent activation of the kinase [13], and persistent activation of downstream signaling pathways involving PI3K-AKT, RAS-MAPK, and STAT5

Methods

Results

Conclusion