Targeting PI3Kδ and PI3Kγ signalling disrupts human AML survival and bone marrow stromal cell mediated protection.

Genevra Pillinger,Niamh V Loughran,Manar S Shafat,Kristian M Bowles,Stuart A Rushworth,Amina Abdul-Aziz,Matthew J Lawes,Lyubov Zaitseva,Rachel E Piddock

doi:10.18632/oncotarget.9289

Genevra Pillinger, Niamh V Loughran + Show 7 more

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https://doi.org/10.18632/oncotarget.9289

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Abstract

Phosphoinositide-3-kinase (PI3K) is an enzyme group, known to regulate key survival pathways in acute myeloid leukaemia (AML). It generates phosphatidylinositol-3,4,5-triphosphate, which provides a membrane docking site for protein kinaseB activation. PI3K catalytic p110 subunits are divided into 4 isoforms; α,β,δ and γ. The PI3Kδ isoform is always expressed in AML cells, whereas the frequency of PI3Kγ expression is highly variable. The functions of these individual catalytic enzymes have not been fully resolved in AML, therefore using the PI3K p110δ and p110γ-targeted inhibitor IPI-145 (duvelisib) and specific p110δ and p110γ shRNA, we analysed the role of these two p110 subunits in human AML blast survival. The results show that PI3Kδ and PI3Kγ inhibition with IPI-145 has anti-proliferative activity in primary AML cells by inhibiting the activity of AKT and MAPK. Pre-treatment of AML cells with IPI-145 inhibits both adhesion and migration of AML blasts to bone marrow stromal cells. Using shRNA targeted to the individual isoforms we demonstrated that p110δ-knockdown had a more significant anti-proliferative effect on AML cells, whereas targeting p110γ-knockdown significantly inhibited AML migration. The results demonstrate that targeting both PI3Kδ and PI3Kγ to inhibit AML-BMSC interactions provides a biologic rationale for the pre-clinical evaluation of IPI-145 in AML.

Highlights

Clinically, morphologically and biologically acute myeloid leukaemia (AML) appears to represent a heterogeneous group of diseases, the disease seems to rely on common intra-cellular survival and self-renewal pathways downstream of the driver oncogene [1]
To do this we first assessed the effect of various PI3K inhibitors including LY294002 with a concentration of 25μM [21], CAL101 (Idelalisib - PI3Kδ inhibitor, which has been found to have a physiologically relevant concentration of between 0.3-1μM [22]) and IPI-145 (PI3Kδ and PI3Kγ inhibitor, which has a physiologically relevant concentration of 1μM [23]) on AML cell lines
Together we report that PI3Kδ and PI3Kγ are constitutively expressed in all AML samples tested and that specific inhibition of these isoforms in AML significantly reduces survival and colony formation

Summary

Introduction

Morphologically and biologically acute myeloid leukaemia (AML) appears to represent a heterogeneous group of diseases, the disease seems to rely on common intra-cellular survival and self-renewal pathways downstream of the driver oncogene [1]. Tyrosine kinases (TKs) are an attractive potential target in AML, having been shown to be effective drugable targets in other types of leukaemia [2,3,4]. Cell survival and proliferation pathways dependent on TK activation, including MAPK; phosphoinositide 3-kinase (PI3K)/AKT; mTOR; NF-κB and STATs are deregulated in most, if not all, cases of AML [7,8,9,10]. Many of the downstream effects of PI3K are mediated through AKT, which interacts with further downstream signalling molecules, which in turn regulate cell proliferation, cell migration and cell adhesion [8, 11]. It has been observed that activation of the PI3K/AKT pathway is present in over www.impactjournals.com/oncotarget

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