BRAFV600Einduces ABCB1/P-glycoprotein expression and drug resistance in B-cells via AP-1 activation.
A subset of patients with chronic lymphocytic leukemia (CLL) and nearly all patients with classic hairy cell leukemia (HCL) harbor somatic BRAF activating mutations. However, the pathological role of activated BRAF in B-cell leukemia development and progression remains unclear. In addition, although HCL patients respond well to the BRAFV600Einhibitor vemurafenib, relapses are being observed, suggesting the development of drug resistance in patients with this mutation. To investigate the biological role of BRAFV600Ein B-cell leukemia, we generated a CLL-like B-cell line, OSUCLL, with doxycycline-inducible BRAFV600Eexpression. Microarray and real-time PCR analysis showed that ABCB1 mRNA is upregulated in these cells, and P-glycoprotein (P-gp) expression as well as function were confirmed by immunoblot and rhodamine exclusion assays. Additionally, pharmacological inhibition of BRAFV600Eand MEK alleviated the BRAFV600E-induced ABCB1/P-gp expression. ABCB1 reporter assays and gel shift assays demonstrated that AP-1 activity is crucial in this mechanism. This study, uncovers a pathological role for BRAFV600Ein B-cell leukemia, and provides further evidence that combination strategies with inhibitors of BRAFV600Eand MEK can be used to delay disease progression and occurrence of resistance.
Division of Medicinal Chemistry & Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, OH, USA.
Yo-Ting
YT
Tsai
Department of Pathology, College of Medicine, The Ohio State University, Columbus, OH, USA.
Gerard
G
Lozanski
Center for Biostatistics, The Ohio State University, Columbus, OH, USA.
Amy
A
Lehman
Department of Internal Medicine, College of Medicine; The Ohio State University, Columbus, OH, USA.
Ellen J
EJ
Sass
Department of Internal Medicine, College of Medicine; The Ohio State University, Columbus, OH, USA.
Erin
E
Hertlein
Division of Medicinal Chemistry & Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, OH, USA.
Santosh B
SB
Salunke
Division of Medicinal Chemistry & Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, OH, USA.
Ching-Shih
CS
Chen
Department of Internal Medicine, College of Medicine; The Ohio State University, Columbus, OH, USA.
Michael R
MR
Grever
Division of Medicinal Chemistry & Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, OH, USA; Department of Internal Medicine, College of Medicine; The Ohio State University, Columbus, OH, USA.
John C
JC
Byrd
Division of Medicinal Chemistry & Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, OH, USA; Department of Internal Medicine, College of Medicine; The Ohio State University, Columbus, OH, USA. Electronic address: david.lucas@osumc.edu.
David M
DM
Lucas
ABCB1; B-cell; BRAF; Leukemia; Lymphoma; P-glycoprotein; Vemurafenib