Overcoming MITF-conferred drug resistance through dual AURKA/MAPK targeting in human melanoma cells.

G Pathria,V Borgdorff,G Superti-Furga,B Garg,K Garg,S N Wagner,C Wagner

doi:10.1038/cddis.2015.369

Abstract

MITF (microphthalmia-associated transcription factor) is a frequently amplified lineage-specific oncogene in human melanoma, whose role in intrinsic drug resistance has not been systematically investigated. Utilizing chemical inhibitors for major signaling pathways/cellular processes, we witness MITF as an elicitor of intrinsic drug resistance. To search kinase(s) targets able to bypass MITF-conferred drug resistance, we employed a multi-kinase inhibitor-directed chemical proteomics-based differential affinity screen in human melanocytes carrying ectopic MITF overexpression. A subsequent methodical interrogation informed mitotic Ser/Thr kinase Aurora Kinase A (AURKA) as a crucial regulator of melanoma cell proliferation and migration, independent of the underlying molecular alterations, including TP53 functional status and MITF levels. Crucially, assessing the efficacy of investigational AURKA inhibitor MLN8237, we pre-emptively witness the procurement of a molecular program consistent with acquired drug resistance. This involved induction of multiple MAPK (mitogen-activated protein kinase) signaling pathway components and their downstream proliferation effectors (Cyclin D1 and c-JUN) and apoptotic regulators (MITF and Bcl-2). A concomitant AURKA/BRAF and AURKA/MEK targeting overcame MAPK signaling activation-associated resistance signature in BRAF- and NRAS-mutated melanomas, respectively, and elicited heightened anti-proliferative activity and apoptotic cell death. These findings reveal a previously unreported MAPK signaling-mediated mechanism of immediate resistance to AURKA inhibitors. These findings could bear significant implications for the application and the success of anti-AURKA approaches that have already entered phase-II clinical trials for human melanoma.

Highlights

Signaling activity, while offering avenues for combinatorial therapeutics, re-allude to the inalienability of this signaling hub from melanoma cell biology.[4,5,6,7,8,10] a significant proportion of melanomas harboring mut-BRAF allele remain intrinsically resistant to BRAF inhibitors
We systematically investigated the role of Microphthalmia-associated transcription factor (MITF) in intrinsic drug resistance, followed by development of therapeutic strategies that thwart/bypass the liaison between BRAF(V600E) and MITF
With MITF’s qualification as a lineage-specific oncogene[14] in human melanoma, and its tight regulation downstream of mitogen-activated protein kinase (MAPK) signaling[18,21] (Supplementary Figure S1C), the heightened sensitivity of HMEL-B/M to MAPK signaling inhibitors is not unfounded. These data corroborate similar findings demonstrating increased responsiveness of MITFHigh melanoma cells to MAPK signaling inhibitors.[22]. These results may argue for MAPK inhibition as a sufficient means to overcome MITF-associated features, in light of a recent report demonstrating BRAF-i-mediated MITF induction,[17] and the highly pervasive acquired resistance to targeted BRAF inhibition,[5,6,7,8,9] identification of new targets able to simultaneously overcome/ bypass MITF and BRAF(V600E) activities is essential

Summary

Introduction

Signaling activity, while offering avenues for combinatorial therapeutics, re-allude to the inalienability of this signaling hub from melanoma cell biology.[4,5,6,7,8,10] a significant proportion of melanomas harboring mut-BRAF allele remain intrinsically resistant to BRAF inhibitors. Microphthalmia-associated transcription factor (MITF) is a basic helix–loop–helix transcription factor that has critical role in melanocytic development and melanomagenesis.[13,14] MITF has been described as a lineage-specific oncogene in melanoma, which in collaboration with constitutively active mutated BRAF capably transforms melanocytes.[14] MITF carries a diverse functionality and has been shown to influence a wide range of cellular phenotypes, including proliferation, apoptosis, migration and differentiation.[15] This functional diversity has inturn been ascribed to different MITF expression levels.[15] some investigative studies in melanoma cells have suggested a role for MITF in both intrinsic and acquired resistance to general as well as targeted therapeutics, including MAPK signaling inhibitors,[9,14,16,17] a systematic interrogation of this MITF functionality has largely gone unexplored. We systematically investigated the role of MITF in intrinsic drug resistance, followed by development of therapeutic strategies that thwart/bypass the liaison between BRAF(V600E) and MITF

Methods

Results

Conclusion