BTK Inhibitors Induce ABC-DLBCL Cell Apoptosis By Inhibiting CYLD Phosphorylation

BTK inhibitors induce ABC-DLBCL cell apoptosis by inhibiting CYLD phosphorylation

Xin Xu¹, Zhigang Zhu¹, Feng Liu¹ , Weijie Zhong¹,Huabao Xiong², Tiefeng Feng³, and Qingshan Li³

¹Geriatrics Department, GuangZhou First People's Hospital, GuangDong, 510180, People's Republic of China.

²Precision Immunology Institute, Mount Sinai School of Medicine, New York, NY 10029, U.S.A.

³Hemotology Department, GuangZhou First People's Hospital, GuangDong, 510180, People's Republic of China.

Activated B cell-like diffuse large B cell lymphoma (ABC-DLBCL) is a common aggressive diffuse large B cell lymphoma (DLBCL). Even though CD20 antibody (Rituximab) combination therapy improved the total prognosis of DLBCL, there are still many relapsed and refractory ABC-DLBCL cases. The new treatment options are urgently needed.

Pathogenesis of ABC-DLBCL is different from germinal center B cell-like diffuse large B cell lymphoma (GCB-DLBCL), which is related to activation of B cell antigen receptor(BCR) signaling. The Bruton tyrosine kinase(BTK) plays a central role in BCR signaling. Inhibition of BTK function will affect BCR signaling activity, which is involved in maintaining the malignant phenotype in B-cell lymphoma. Now in clinic, BTK inhibitors like Ibrutinib or Acalabrutinib are used extensively in chronic lymphocytic leukemia/small lymphocytic lymphoma(CLL/SLL), mantle cell lymphoma(MCL) as first line therapy or second line therapy. But in DLBCL its role is unclear now.Some DLBCL clinic trials got the better PFS and OS in BTK inhibitor combination therapy group(combined with Rituximab or RCHOP) but some got the negative results. Whether BTK inhibitors can definitely improve ABC-DLBCL survival and the mechanism how BTK inhibitors inducing cell death are needed further investigations.

CYLD (cylindromatosis) is a tumor suppressor, its activity is inhibited by phosphorylation, which is related to apoptosis regulation pathway NF-kB in many kinds of tumors.In this study, we found that CYLD to be constitutively phosphorylated in ABC-DLBCL cell line models (HBL-1 and OCI-Ly10) as well as primary samples from patients with non-GCB DLBCL. We subsequently examined the effect of BTK inhibitors Ibrutinib (PCI-32765) and Acalabrutinib (ACP-196) on CYLD phosphorylation.

We found that BTK inhibitors Ibrutinib and Acalabrutinib both induced ABC-DLBCL apoptosis by down-regulating CYLD phosphorylation in vivo and in vitro, even in the Rituximab resistant ABC-DLBCL cell line.Combination of BTK inhibitors and Rituximab would enhance this effect. Knockdown of CYLD in ABC-DLBCL cells reduced the level of cell death induced by BTK inhibitors, which showed that this cell death induced by BTK inhibitors was CYLD dependent.

Through this study, we conclude that BTK inhibitors induce CYLD inactivation by regulating CYLD phosphorylation is clinical beneficial in ABC-DLBCL therapy, especially the relapsed or refractory ABC-DLBCL cases after Rituximab therapy.