Exploring the association between loss of deubiquitinating enzyme CYLD and drug response in multiple myeloma

Multiple myeloma (MM) is a malignancy of antibody-secreting plasma cells in the bone marrow (BM). MM is the second most common hematological malignancy, accounting for about 14% of blood cancers. Despite the improvements in the treatment of MM, the disease remains incurable, and essentially all patients end up relapsing. Deletion of chromosome 16q, the location of tumor suppressor CYLD, occurs in 35% of MM patients. CYLD is a deubiquitinase, most recognized for its function as a negative regulator of the nuclear factor kappa B (NF-κB) pathway. The loss of CYLD is associated with disease progression and worse survival in MM, but its significance in drug response is unknown. As the loss of CYLD is common in MM, determining its effect on drug response is essential. Analysis of data gained from MM patient samples were used to study the effect of CYLD copy number status on drug response. The treatments were selected based on previous research performed by our group. The effect of homozygous deletion was most significant in inducing resistance to BMS-754807, an inhibitor of insulin-like growth factor 1 receptor. To investigate the role of loss of CYLD on drug response in vitro, cell lines with CYLD knockout (KO) were created using the clustered regularly interspaced short palindromic repeats (CRISPR) – CRISPR associated protein 9 (Cas9) technology. An established CYLD-KO cell line was treated with carfilzomib, bortezomib, dexamethasone and BMS-754807 to assess the effect of CYLD-KO. The CYLD-KO slightly increased the sensitivity to BMS-754807, but essentially no differences were detected in response to the drugs. The effect of CYLD-KO was additionally explored to NF-κB - and Wnt-pathway activation by Western blot analysis, but due to technical difficulties, the results were inconclusive. The loss of CYLD is a common genetic aberration in MM, giving a survival benefit for the malignant cells. Based on the results from patient data analysis, the loss of CYLD could promote drug resistance to BMS-754807, and the effect should be further studied with more cell lines with CYLD-KO. As the population ages, and as the median age of newly diagnosed patients is 70, the need for efficient MM therapies increases. Studying the mechanisms behind drug resistance and sensitivity is essential in the aim of improving the efficacy of MM therapy and, in the end, the overall survival of the patients