Pan-RAF Inhibition Shows Anti-Leukemic Activity in RAS-Mutant Acute Myeloid Leukemia Cells and Potentiates the Effect of Sorafenib in Cells with FLT3 Mutation.

Joseph D Khoury,Sanam Loghavi,Ying Wang,Sujan Piya,Jing Wang,Gautam Borthakur,Hong Yang,Mehrnoosh Tashakori

doi:10.3390/cancers12123511

Joseph D Khoury, Sanam Loghavi + Show 6 more

Open Access

https://doi.org/10.3390/cancers12123511

Copy DOI

Journal: Cancers	Publication Date: Nov 25, 2020
Citations: 14	License type: CC BY 4.0

Affiliation: The University of Texas MD Anderson Cancer Center

Abstract

Simple SummaryWe demonstrate that the pan-RAF inhibitor LY3009120 induces apoptosis and inhibits proliferation in AML cells harboring RAS or FLT3 mutations through action on the RAS/RAF/MEK/ERK and the AKT/mTOR pathways. Notably, pan-RAF inhibition combined with Ara-C overcomes drug resistance mediated by bone marrow-derived mesenchymal stem cells. Furthermore, the combination of LY3009120 and tyrosine kinase inhibition with sorafenib appears to synergistically increase apoptosis in AML cells carrying FLT3-ITD mutation.RAF molecules play a critical role in cell signaling through their integral impact on the RAS/RAF/MEK/ERK signaling pathway, which is constitutively activated in a sizeable subset of acute myeloid leukemia (AML) patients. We evaluated the impact of pan-RAF inhibition using LY3009120 in AML cells harboring mutations upstream and downstream of RAF. LY3009120 had anti-proliferative and pro-apoptotic effects and suppressed pERK1/2 levels in leukemic cells with RAS and FLT3 mutations. Using reverse protein phase array analysis, we identified reductions in the expression/activation of cell signaling components downstream of RAF (activated p38) and cell cycle regulators (Wee1/cyclin B1, Cdc2/Cdk1, activated Rb, etc.). Notably, LY3009120 potentiated the effect of Ara-C on AML cells and overcame bone marrow mesenchymal stromal cell-mediated chemoresistance, with RAS-mutated cells showing a notable reduction in pAKT (Ser473). Furthermore, the combination of LY3009120 and sorafenib resulted in significantly higher levels of apoptosis in AML cells with heterozygous and hemizygous FLT3 mutations. In conclusion, pan-RAF inhibition in AML using LY3009120 results in anti-leukemic activity, and combination with Ara-C or sorafenib potentiates its effect.

Highlights

The RAS/RAF/MEK/ERK (MAPK) signaling pathway plays a critical role in the transmission of proliferative signals from extracellular stimuli to downstream effectors
We investigated the antileukemic effect of LY3009120 on acute myeloid leukemia (AML) cell lines harboring activating mutations upstream and downstream of RAF resulting in constitutive activation of MAPK signaling
All cell lines showed time- and dose-dependent growth inhibition, cell death, and apoptosis, with the most notable effect being on OCI/AML3 cells treated for 96 h. (Figure 1A–C)

Summary

Introduction

The RAS/RAF/MEK/ERK (MAPK) signaling pathway plays a critical role in the transmission of proliferative signals from extracellular stimuli to downstream effectors. Constitutive activation of the MAPK pathway results from gain-of-function mutations in genes encoding pathway constituents, NRAS, a common finding in up to 11% of patients with acute myeloid leukemia (AML) [3,4,5] In another sizeable subset of AML patients, constitutive ERK activation is due to gain-of-function tyrosine kinase domain mutations in upstream signaling molecules, FLT3 [6]. Direct targeting of oncogenic RAS proteins in myeloid malignancies has not been feasible clinically far; multiple agents targeting upstream and/or downstream components of the pathway have been developed. Most notable among the former are kinases inhibitors that target

Methods

Results

Discussion

Conclusion