Targeting NEDD8-activating enzyme is a new approach to treat canine diffuse large B-cell lymphoma.

Canine diffuse large B-cell lymphoma (DLBCL), the most common hematologic malignancy of dogs, is associated with poor overall survival. The lack of conventional chemotherapies with sustainable efficacy warrants investigation of novel therapies. Pevonedistat (MLN4924) is a potent and selective small molecule NEDD8-activating enzyme inhibitor. In human activated B-cell-like (ABC) diffuse large B-cell lymphoma, pevonedistat induces lymphoma cell apoptosis, DNA damage and G1 cell cycle arrest by inhibiting the nuclear factor-κB (NF-κB) pathway. Genomic and transcriptomic studies showed that the NF-κB pathway is deregulated in canine DLBCL. Our results showed that pevonedistat treatment significantly reduces the viability of canine DLBCL cells by inducing G1 cell cycle arrest and apoptosis. Pevonedistat treatment inhibits NF-κB pathway activation and downregulates NF-κB target genes in canine DLBCL. Moreover, administration of pevonedistat to mice bearing canine DLBCL xenograft tumours resulted in tumour regression. Our in vivo and in vitro studies provide justification for future clinical application of pevonedistat as a potential new anti-cancer therapy that may benefit both canine and human species.

STAT3 Expression and Activity are Up-Regulated in Diffuse Large B Cell Lymphoma of Dogs.

BACKGROUND: The Janus Kinase (JAK) and Signal Transducer and Activator of Transcription (STAT) pathways play important roles in the pathogenesis of diffuse large B cell lymphoma (DLBCL) in humans, and up-regulated STAT3 expression and activity are associated with worse clinical outcome in humans. No studies have evaluated the JAK-STAT signaling pathway in DLBCL of dogs. HYPOTHESIS: STAT3 pathway is deregulated in DLBCL in dogs. We aim to assess the expression, activation, and cellular localization of STAT3 and mitogen-activated protein kinase ERK1/2 in DLBCL of dogs. ANIMALS: Forty-three client-owned dogs diagnosed with DLBCL by histopathology METHODS: Retrospective analysis of DLBCL in dogs, including patient characteristics and treatment, immunohistochemistry, and protein expressions by Western blot. RESULTS: A higher percentage of STAT3 and p-STAT3 immunolabelled cells were observed in DLBCL of dogs when compared to normal canine lymph nodes. In STAT3 immunolabelled cells, STAT3 has higher nuclear expression in lymphoma samples than in normal or reactive lymph nodes. In addition to up-regulated STAT3 expression and activation, mitogen-activated kinase ERK1/2 activation is up-regulated in DLBCL of dogs. CONCLUSION AND CLINICAL IMPORTANCE: Compared with the normal canine lymph node, DLBCL of dogs has up-regulated STAT3 pathway. Our results support future investigation of JAK inhibitors in the treatment of DLBCL in dogs.

JAK1/2 Inhibitors AZD1480 and CYT387 Inhibit Canine B-Cell Lymphoma Growth by Increasing Apoptosis and Disrupting Cell Proliferation.

BACKGROUND: Canine diffuse large B-cell lymphoma (DLBCL) is a common and aggressive hematologic malignancy. The lack of conventional therapies with sustainable efficacy warrants further investigation of novel therapeutics. The Janus kinase (JAK) and signal transducer and activator of transcription (STAT) pathways play important roles in the pathogenesis of hematologic malignancies in humans including DLBCLs. AZD1480 and CYT387 are novel JAK1/2 inhibitors that have been used in clinical trials for treating various hematologic cancers in humans. No studies have characterized the antitumor effects of JAK inhibitors on DLBCL in dogs. HYPOTHESIS/OBJECTIVES: We hypothesize that JAK1/2 inhibitors AZD1480 and CYT387 can effectively inhibit growth of canine DLBCL in vitro. We aim to assess the antitumor activity of AZD1480 and CYT387 in canine DLBCL and to determine the underlying mechanisms of action. METHODS: In vitro study of canine lymphoma cell growth, proliferation, and apoptosis by viability, proliferation and apoptosis assays. RESULTS: A significant decrease in viable canine lymphoma cells was observed after AZD1480 and CYT387 treatments. In addition, AZD1480 and CYT387 treatment resulted in decreased lymphoma cell proliferation and increased early apoptosis. CONCLUSION AND CLINICAL IMPORTANCE: AZD1480 and CYT387 inhibit canine lymphoma cell growth in a dose-dependent manner. Our findings justify further phase I/II clinical investigations of the safety and efficacy of JAK1/2 inhibitors in canine DLBCL and suggest new opportunities for novel anticancer therapies.