HSP27 Promotes Mantle Cell Lymphoma Growth and Mediates Resistance to Venetoclax

Introduction Drug resistance has been a major challenge for the treatment of patients with relapsed or refractory mantle cell lymphoma. Venetoclax is a highly potent, Bcl2-selective inhibitor that is effective in refractory/relapsed MCL patients both as monotherapy or in combination with ibrutinib, but the development of acquired resistance remains inevitable. The heat shock protein HSP27 (encoded by HSPB1) is normally upregulated under conditions of protein folding alteration, such as heat shock. However, it has been demonstrated that HSP27 can promote the growth and metastasis of cancer cells and enable resistance to many anticancer therapies. Accordingly, HSP27 has been targeted for therapy of cancer progression and treatment resistance. We hypothesize that HSP27 can induce therapeutic resistance, and that targeting of HSP27 may overcome venetoclax resistance in MCL.

Methods Primary cells from patients' with or without therapeutic resistance as well as ibrutinib or venetoclax-sensitive and -resistant MCL cell lines were used in this study. We established a HSPB1- knockout (KO) human MCL JeKo-1 cell line using the CRISPR-Cas9 knockout system. Cell viability and cell proliferation assays were tested in triplicate for 72 h. The annexin V/propidium iodide-binding assay was utilized to evaluate apoptosis following venetoclax treatment. The underlying resistance mechanisms were verified by immunoblotting.

Results HSP27 was highly upregulated in primary cells from patients resistant to BTK inhibitors compared to cells from those sensitive to BTK inhibitors. In addition, HSP27 was significantly increased in the Rec-Ven-R MCL cell line, which has acquired venetoclax resistance, compared to the parental Rec-1 cell line. To further investigate the function of HSP27 in regulating growth and therapeutic resistance, we knocked out the HSPB1 gene in JeKo-1 cells using a CRISPR-Cas9 knockout system. We first evaluated the impact of HSP27 on MCL cell growth. HSP27 knockout in the HSP27-high JeKo-1 cells greatly inhibited their growth and proliferation in vitro. Next, we carried out cell viability assays and found that genetic ablation of HSPB1 enhanced the sensitivity to venetoclax. Furthermore, treatment of HSPB1-knockout JeKo-1 cells with 1 uM venetoclax for 24 h and 48 h induced greater apoptosis than in the parental JeKo-1 cells. Western blot analysis of whole cell lysates showed that knockout of HSPB1 triggered an increase in the pro-apoptotic markers cleaved PARP and cleaved caspase 3 after venetoclax treatment for 6 h. Together, these results suggest that HSP27 potentiates the growth and proliferation of MCL cells and mediates the acquired resistance to venetoclax.

Conclusions Targeting HSP27 may overcome venetoclax resistance in MCL cells, which provide impressive insights for therapeutic development to treat refractory/relapsed MCL patients and improve patient prognosis.

Wang:Genentech: Consultancy, Research Funding; Epizyme: Consultancy, Honoraria; Kite, a Gilead Company: Consultancy, Honoraria, Research Funding; Juno Therapeutics: Consultancy, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; InnoCare: Consultancy, Research Funding; Lilly: Consultancy, Research Funding; Oncternal: Consultancy, Research Funding; Loxo Oncology: Consultancy, Research Funding; Miltenyi Biomedicine GmbH: Consultancy, Honoraria; Leukemia & Lymphoma Society LLC: Consultancy, Honoraria; DTRM Biopharma (Cayman) Limited: Consultancy; Deciphera: Consultancy; CStone: Consultancy; BioInvent: Consultancy, Honoraria, Research Funding; BeiGene: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy; Pepromene Bio: Consultancy; Pharmacyclics: Consultancy, Honoraria, Research Funding; VelosBio: Consultancy, Research Funding; Acerta Pharma: Honoraria, Research Funding; Celgene: Research Funding; Genmab: Research Funding; Molecular Templates: Research Funding; Vincerx: Research Funding; Anticancer Association: Honoraria; Clinical Care Options: Honoraria; Dava Oncology: Honoraria; Eastern Virginia Medical School: Honoraria; TS Oncology: Honoraria; Medscape: Honoraria; Meeting Minds Experts: Honoraria; Moffit Cancer Center: Honoraria; Mumbai Hematology Group: Honoraria; OMI: Honoraria; OncLive: Honoraria; Physicians Education Resources (PER): Honoraria; Practice Point Communications (PPC): Honoraria; First Hospital Zhejiang University: Honoraria; BGICS: Honoraria; CAHON: Honoraria; Hebei Cancer Prevention Federation: Honoraria; Imedex: Honoraria; LLC TS Oncology: Honoraria.