Targeting of HSP70/HSF1 Axis Abrogates In Vitro Ibrutinib-Resistance in Chronic Lymphocytic Leukemia.

Federica Frezzato,Sabrina Manni,Livio Trentin,Elisa Pagnin,Silvia Imbergamo,Valentina Trimarco,Andrea Visentin,Alessia Tonini,Anna Maria Brunati,Nayla Mouawad,Edoardo Ruggeri,Leonardo Martinello,Francesco Piazza,Samuela Carraro,Serena Pizzo,Monica Facco,Stefano Pravato,Filippo Severin

doi:10.3390/cancers13215453

Federica Frezzato, Sabrina Manni + Show 16 more

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https://doi.org/10.3390/cancers13215453

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Abstract

Simple SummaryThe use of ibrutinib has changed the management and clinical history of patients with multiple-treated chronic lymphocytic leukemia (CLL). Nevertheless, an increasing number of patients develop resistance to treatment, with mechanisms still to be fully clarified. Since HSP70 plays a pivotal role in mediating the survival and the progression of CLL, we herein addressed the role of HSP70 and its regulator HSF1 in the development of ibrutinib-mediated resistance. We found an increase in both proteins when the treatment was failing, and thus the disease was progressing. This suggests the involvement of HSP70 in mechanisms of drug resistance. Moreover, we demonstrated that the use, at different levels, of HSP70/HSF1 axis inhibitors could represent a novel rational therapeutic approach to overcome ibrutinib resistance in those patients who relapsed after this type of treatment.The Btk inhibitor ibrutinib has significantly changed the management of chronic lymphocytic leukemia (CLL) patients. Despite its clinical efficacy, relapses occur, and outcomes after ibrutinib failure are poor. Although BTK and PLCγ2 mutations have been found to be associated with ibrutinib resistance in a fair percentage of CLL patients, no information on resistance mechanisms is available in patients lacking these mutations. The heat shock protein of 70 kDa (HSP70) and its transcription factor heat shock factor 1 (HSF1) play a role in mediating the survival and progression of CLL, as well as taking part in drug resistance in various cancers. We demonstrated that resveratrol and related phenols were able to induce apoptosis in vitro in leukemic cells from CLL untreated patients by acting on the HSP70/HSF1 axis. The same was achieved in cells recovered from 13 CLL patients failing in vivo ibrutinib treatment. HSP70 and HSF1 levels decreased following in vitro treatment, correlating to apoptosis induction. We suggest an involvement of HSP70/HSF1 axis in controlling resistance to ibrutinib in CLL cells, since their inhibition is effective in inducing in vitro apoptosis in cells from ibrutinib refractory patients. The targeting of HSP70/HSF1 axis could represent a novel rational therapeutic strategy for CLL, also for relapsing patients.

Highlights

Chronic lymphocytic leukemia (CLL) is a neoplastic disorder of the elders, characterized by the accumulation of clonal B lymphocytes, due to uncontrolled growth and resistance to apoptosis
Since most heat shock factor 1 (HSF1)-phosphorylating molecules belong to two RAS-signaling pathways (PI3K/AKT/mTOR and RAF/MEK/ERK), taking advantage of a previous RPPA analysis [9], we correlated heat shock protein of 70 kDa (HSP70) expression to different proteins related to these pathways
We focused on two proteins, HSP70 and its transcription factor HSF1, since they are implicated in various stages of carcinogenesis, such as the promotion of cell proliferation, resistance to apoptosis, neo-angiogenesis, metastasis and, above all, resistance to radio- and chemo-therapy [14,35]

Summary

Introduction

Chronic lymphocytic leukemia (CLL) is a neoplastic disorder of the elders, characterized by the accumulation of clonal B lymphocytes, due to uncontrolled growth and resistance to apoptosis. Therapeutic armamentarium of CLL changed recently from the introduction of novel active agents [1]. The introduction of Bruton’s tyrosine kinase (Btk) inhibitor ibrutinib has significantly changed the management of patients with CLL, achieving extremely high efficacy even in high-risk and chemo-refractory patients. Mutations affecting Btk residue C481, which is bound covalently by ibrutinib, or phospholipase Cγ2 (PLCγ2), an immediate downstream target of Btk, or activation of non-classical NF-κB signalling were identified in patients who progressed or were intrinsic resistant to ibrutinib [8]. These mutations are not univocal, indicating that additional mechanisms remain to be clarified

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