CCI-007, a novel small molecule with cytotoxic activity against infant leukemia with MLL rearrangements

Klaartje Somers,Murray D Norris,Alan Kwek,Molly Clifton,Toshihiko Imamura,Wendi Hoang,Chelsea Mayoh,Mawar Karsa,Victoria W Wen,Andrei V Gudkov,Angelika Bongers,Sarah Cruikshank,Bing Liu,Sukey Pan,Ursula R Kees,Daria A Chudakova,Michelle J Henderson,Michelle Haber,Olga B Chernova,Marissa J Scandlyn ,Shiloh Middlemiss

doi:10.18632/oncotarget.10022

Abstract

There is an urgent need for the development of less toxic, more selective and targeted therapies for infants with leukemia characterized by translocation of the mixed lineage leukemia (MLL) gene. In this study, we performed a cell-based small molecule library screen on an infant MLL-rearranged (MLL-r) cell line, PER-485, in order to identify selective inhibitors for MLL-r leukemia. After screening initial hits for a cytotoxic effect against a panel of 30 cell lines including MLL-r and MLL wild-type (MLL-wt) leukemia, solid tumours and control cells, small molecule CCI-007 was identified as a compound that selectively and significantly decreased the viability of a subset of MLL-r and related leukemia cell lines with CALM-AF10 and SET-NUP214 translocation. CCI-007 induced a rapid caspase-dependent apoptosis with mitochondrial depolarization within twenty-four hours of treatment. CCI-007 altered the characteristic MLL-r gene expression signature in sensitive cells with downregulation of the expression of HOXA9, MEIS1, CMYC and BCL2, important drivers in MLL-r leukemia, within a few hours of treatment. MLL-r leukemia cells that were resistant to the compound were characterised by significantly higher baseline gene expression levels of MEIS1 and BCL2 in comparison to CCI-007 sensitive MLL-r leukemia cells.In conclusion, we have identified CCI-007 as a novel small molecule that displays rapid toxicity towards a subset of MLL-r, CALM-AF10 and SET-NUP214 leukemia cell lines. Our findings suggest an important new avenue in the development of targeted therapies for these deadly diseases and indicate that different therapeutic strategies might be needed for different subtypes of MLL-r leukemia.

Highlights

Leukemia characterised by rearrangement of the mixed lineage leukemia (MLL) gene is a highly aggressive cancer that occurs in over 70% of infant acute lymphoblastic leukemia (ALL) and 35-50% of infant acute myeloid leukemia (AML) [1, 2]
The library was screened against an infant MLL-AF4 leukemia cell line (PER-485) in parallel with a human neuroblastoma cell line (BE(2)-C) as representative of a MLL wild-type (MLL-wt) pediatric tumour, using Alamar Blue viability assays at a single dose of 10 μM for each compound
The aim of this parallel screen was to exclude non-MLL-r-selective hits with cytotoxic activity in both cell lines, thereby selecting for compounds more likely to affect the viability of only the MLL-r leukemia cells. 418 compounds were shown to decrease the viability of PER-485 cells while BE(2)-C cell viability was unaffected

Summary

Introduction

Leukemia characterised by rearrangement of the mixed lineage leukemia (MLL) gene is a highly aggressive cancer that occurs in over 70% of infant acute lymphoblastic leukemia (ALL) and 35-50% of infant acute myeloid leukemia (AML) [1, 2]. Despite the development of infant-specific treatment protocols and incorporation of risk-directed therapy according to prognostic features, the cure rates for infant leukemia have stagnated over recent years [3, 5,6,7]. The occurrence of a MLL gene rearrangement is considered a prognostic factor for high-risk disease, warranting intensified chemotherapy, which often results in problems with toxicity and infection in these highrisk patients [3, 4, 7, 8]. It is clear that there is an urgent need for more selective and targeted therapies for MLL-rearranged (MLL-r) leukemia, to decrease the side effects of therapy, boost overall survival and improve treatment outcome for these patients

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