Aminopeptidase Expression in Multiple Myeloma Associates with Disease Progression and Sensitivity to Melflufen

Abstract

Multiple myeloma (MM) is characterized by extensive immunoglobulin production leading to an excessive load on protein homeostasis in tumor cells. Aminopeptidases contribute to proteolysis by catalyzing the hydrolysis of amino acids from proteins or peptides and function downstream of the ubiquitin–proteasome pathway. Notably, aminopeptidases can be utilized in the delivery of antibody and peptide-conjugated drugs, such as melflufen, currently in clinical trials. We analyzed the expression of 39 aminopeptidase genes in MM samples from 122 patients treated at Finnish cancer centers and 892 patients from the CoMMpass database. Based on ranked abundance, LAP3, ERAP2, METAP2, TTP2, and DPP7 were highly expressed in MM. ERAP2, XPNPEP1, DPP3, RNPEP, and CTSV were differentially expressed between relapsed/refractory and newly diagnosed MM samples (p < 0.05). Sensitivity to melflufen was detected ex vivo in 11/15 MM patient samples, and high sensitivity was observed, especially in relapsed/refractory samples. Survival analysis revealed that high expression of XPNPEP1, RNPEP, DPP3, and BLMH (p < 0.05) was associated with shorter overall survival. Hydrolysis analysis demonstrated that melflufen is a substrate for aminopeptidases LAP3, LTA4H, RNPEP, and ANPEP. The sensitivity of MM cell lines to melflufen was reduced by aminopeptidase inhibitors. These results indicate critical roles of aminopeptidases in disease progression and the activity of melflufen in MM.

Identification of Dipeptidyl Peptidase (DPP) Family Genes in Clinical Breast Cancer Patients via an Integrated Bioinformatics Approach

“…Many biological processes involve these proteins, including cancer cell defense against oxidative stress. A previous study demonstrated that DPP3 and DPP7 are highly expressed in multiple myelomas [ 13 ]. DPP3 overexpression was positively associated with KEAP1 mutant tumors, and it further promoted lung cancer development [ 14 ].…”

Novel Peptide-drug Conjugate Melflufen Efficiently Eradicates Bortezomib-resistant Multiple Myeloma Cells Including Tumor-initiating Myeloma Progenitor Cells

“…These data confirm inferior survival of MM patients with higher RNPEP gene expression, observed in an independent cohort of patients published elsewhere. 34 Together, these data suggest association of ApB with BTZ-resistance and poor prognosis in MM.…”

“…Moreover, elevated RNPEP gene expression is associated with a shorter progression-free and overall survival of MM patients, thus confirming higher RNPEP expression as a risk factor previously described in other patient cohorts. 34 Likewise, elevated RNPEP gene expression is observed in plasma cell precursors, a B-lymphoid cell compartment, where the tumor-initiating MMPC or “stem” cells are residing. 41 Hence, elevated ApB levels are associated with aggressive myeloma clones conferring tumor initiation and therapy resistance in MM.…”

Spotlight on Melphalan Flufenamide: An Up-and-Coming Therapy for the Treatment of Myeloma

“…It should be emphasized that a detailed study on aminopeptidase gene expression in myeloma revealed that some aminopeptidases were highly expressed in MM. 46 Moreover, the high expression of some of these aminopeptidase genes, ie, X-prolyl aminopeptidase 1 (XPNPEP1), Arginyl aminopeptidase (RNPEP), Dipeptidyl peptidase 3 (DPP3), and Bleomycin hydrolase (BLMH), was significantly associated with shorter overall survival. More importantly, hydrolysis analysis demonstrated that melflufen is a substrate of Leucine aminopeptidase 3 (LAP3), leukotriene A4 hydrolase (LTA4H), arginyl aminopeptidase (RNPEP), other than aminopeptidase N (ANPEP alias CD13), suggesting that CD13 is not the unique melflufen target in MM.…”