Drug sensitivity profiling identifies potential therapies for lymphoproliferative disorders with overactive JAK/STAT3 signaling.

Heikki Kuusanmäki,Krister Wennerberg,Olli Dufva,Muntasir M Majumder,Satu Mustjoki,Caroline A Heckman,Hanna Rajala,Elina Parri,Arjan J Van Adrichem,Bhagwan Yadav,Alun Parsons,Wing C Chan

doi:10.18632/oncotarget.22178

Heikki Kuusanmäki, Krister Wennerberg + Show 10 more

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https://doi.org/10.18632/oncotarget.22178

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Abstract

Constitutive JAK/STAT3 signaling contributes to disease progression in many lymphoproliferative disorders. Recent genetic analyses have revealed gain-of-function STAT3 mutations in lymphoid cancers leading to hyperactivation of STAT3, which may represent a potential therapeutic target. Using a functional reporter assay, we screened 306 compounds with selective activity against various target molecules to identify drugs capable of inhibiting the cellular activity of STAT3. Top hits were further validated with additional models including STAT3-mutated natural killer (NK)-cell leukemia/lymphoma cell lines and primary large granular lymphocytic (LGL) leukemia cells to assess their ability to inhibit STAT3 phosphorylation and STAT3 dependent cell viability. We identified JAK, mTOR, Hsp90 and CDK inhibitors as potent inhibitors of both WT and mutant STAT3 activity. The Hsp90 inhibitor luminespib was highly effective at reducing the viability of mutant STAT3 NK cell lines and LGL leukemia patient samples. Luminespib decreased the phosphorylation of mutant STAT3 at Y705, whereas JAK1/JAK2 inhibitor ruxolitinib had reduced efficacy on mutant STAT3 phosphorylation. Additionally, combinations involving Hsp90, JAK and mTOR inhibitors were more effective at reducing cell viability than single agents. Our findings show alternative approaches to inhibit STAT3 activity and suggest Hsp90 as a therapeutic target in lymphoproliferative disorders with constitutively active STAT3.

Highlights

STAT3 is a transcription factor that participates in tumorigenesis by upregulating expression of cancer promoting genes such as anti-apoptotic BCL2-family members (Mcl-1, Bcl-2, Bcl-XL) and cell cycle regulators (c-Myc, Cyclin D1) [1, 2]
Using a STAT3 luciferase reporter assay, we identified four drug classes, Janus kinase (JAK), mammalian target of rapamycin (mTOR), cyclindependent kinase (CDK) and heat shock protein 90 (Hsp90) inhibitors amongst 306 approved and investigational compounds with greatest potency against both mutant and WT STAT3 activity
We extended these results to models of STAT3-driven lymphoproliferative malignancies demonstrating that Hsp90 inhibition effectively reduced both mutant and WT STAT3 phosphorylation and viability of natural killer (NK) cell leukemia/ lymphoma cell lines and large granular lymphocytic (LGL) leukemia patient samples with naturally occurring STAT3 mutations

Summary

Introduction

STAT3 is a transcription factor that participates in tumorigenesis by upregulating expression of cancer promoting genes such as anti-apoptotic BCL2-family members (Mcl-1, Bcl-2, Bcl-XL) and cell cycle regulators (c-Myc, Cyclin D1) [1, 2]. Mechanisms leading to overactive STAT3 signaling include fusion genes with kinase activity, loss of phosphatases, chronic stimulation of cytokine receptors via extrinsic cytokines, and activating mutations in upstream tyrosine kinases [7, 8]. The majority are gain-offunction mutations, such as Y640F and D661V, and occur in the SH2 domain of the STAT3 protein leading to increased tyrosine 705 phosphorylation (Y705), which is needed for protein dimerization and activation [19]. Earlier studies have not systematically examined whether targeted compounds, including JAK inhibitors and STAT3 antagonists, are effective at reducing mutant STAT3 activity. It is not known whether mutant STAT3 confers a distinct drug response profile compared to WT STAT3

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