Oncotarget

Research Papers:

HSP90 overexpression potentiates the B-cell receptor and fibroblast growth factor receptor survival signals in chronic lymphocytic leukemia cells

Hasan Mahmud, Mariana Mendez, Bedabrata Mukhopadhyay, Jennifer Holter-Chakrabarty and Asish K. Ghosh _

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Oncotarget. 2020; 11:2037-2046. https://doi.org/10.18632/oncotarget.27409

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Abstract

Hasan Mahmud1, Mariana Mendez2, Bedabrata Mukhopadhyay1, Jennifer Holter-Chakrabarty1 and Asish K. Ghosh1,2

1 Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA

2 Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA

Correspondence to:

Asish K. Ghosh,email: [email protected]

Keywords: CLL; HSP90; BCR; CD79a; PTPN22

Received: August 12, 2019     Accepted: December 16, 2019     Published: June 02, 2020

ABSTRACT

Chronic lymphocytic leukemia (CLL) is still an incurable disease despite aggressive chemotherapies including the B-cell receptor (BCR) targeted-inhibitors. Therefore, we assessed the expression status of key signal mediators of the BCR pathway in CLL cells. Indeed, we detected aberrantly elevated levels of CD79a, B-cell adaptor for PI3K (BCAP) and phospholipase C (PLC)γ2, key mediators of BCR signal, in CLL cells. As HSP90 is also overexpressed in CLL cells, we hypothesized that HSP90 could potentiate the BCR signal via stabilization of multiple key components of the BCR-signalosome. We found that HSP90 formed a multi-molecular complex with CD79a, BCAP, PLCγ2, LYN, SYK, Bruton tyrosine kinase (BTK) and AKT and that, pharmacologic inhibition or partial depletion of HSP90 reduced the expression of these signal mediators in CLL cells. In addition, our findings also demonstrated that HSP90 could stabilize the tyrosine phosphatase, PTPN22 which positively regulates AKT phosphorylation, and the constitutively active fibroblast growth factor receptor 3 (FGFR3) in CLL cells. Finally, HSP90 inhibition induced apoptosis in CLL cells in a dose-dependent manner likely via downregulation of anti-apoptotic proteins MCL-1 and XIAP, but not BCL2, reported to be overexpressed in CLL cells. In total, our findings suggest that HSP90-inhibition may sensitize the leukemic B-cells to BCR-targeted agents, particularly those become resistant to these therapies.


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