Proteasome inhibition is a highly effective treatment for multiple myeloma (MM). However, virtually all patients develop proteasome inhibitor resistance, which is associated with a poor prognosis. Hyperactive small ubiquitin-like modifier (SUMO) signaling is involved in both cancer pathogenesis and cancer progression. A state of increased SUMOylation has been associated with aggressive cancer biology. We found that relapsed/refractory MM is characterized by a SUMO-high state, and high expression of the SUMO E1-activating enzyme (SAE1/UBA2) is associated with poor overall survival. Consistently, continuous treatment of MM cell lines with carfilzomib (CFZ) enhanced SUMO pathway activity. Treatment of MM cell lines with the SUMO E1-activating enzyme inhibitor subasumstat (TAK-981) showed synergy with CFZ in both CFZ-sensitive and CFZ-resistant MM cell lines, irrespective of the TP53 state. Combination therapy was effective in primary MM cells and in 2 murine MM xenograft models. Mechanistically, combination treatment with subasumstat and CFZ enhanced genotoxic and proteotoxic stress, and induced apoptosis was associated with activity of the prolyl isomerase PIN1. In summary, our findings reveal activated SUMOylation as a therapeutic target in MM and point to combined SUMO/proteasome inhibition as a novel and potent strategy for the treatment of proteasome inhibitor–resistant MM.

FAT atypical cadherin 1 (FAT1), a transmembrane protein, is frequently mutated in various cancer types and has been described as context-dependent tumor suppressor or oncogene. The FAT1 gene is mutated in 12–16% of T-cell acute leukemia (T-ALL) and aberrantly expressed in about 54% of T-ALL cases contrasted with absent expression in normal T-cells. Here, we characterized FAT1 expression and profiled the methylation status from T-ALL patients. In our T-ALL cohort, 53% of patient samples were FAT1 positive (FAT1pos) compared to only 16% FAT1 positivity in early T-ALL patient samples. Aberrant expression of FAT1 was strongly associated with FAT1 promotor hypomethylation, yet a subset, mainly consisting of TLX1-driven T-ALL patient samples showed methylation-independent high FAT1 expression. Genes correlating with FAT1 expression revealed enrichment in WNT signaling genes representing the most enriched single pathway. FAT1 knockdown or knockout led to impaired proliferation and downregulation of WNT pathway target genes (CCND1, MYC, LEF1), while FAT1 overexpressing conveyed a proliferative advantage. To conclude, we characterized a subtype pattern of FAT1 gene expression in adult T-ALL patients correlating with promotor methylation status. FAT1 dependent proliferation and WNT signaling discloses an impact on deeper understanding of T-ALL leukemogenesis as a fundament for prospective therapeutic strategies.

The IL-6–gp130–STAT3 signaling axis is a major regulator of inflammation. Activating mutations in the gene encoding gp130 and germline gain-of-function mutations in STAT3 (STAT3 ^GOF ) are associated with multi-organ autoimmunity, severe morbidity, and adverse prognosis. To dissect crucial cellular subsets and disease biology involved in activated gp130 signaling, the gp130-JAK-STAT3 axis was constitutively activated using a transgene, L-gp130 , specifically targeted to T cells. Activating gp130 signaling in T cells in vivo resulted in fatal, early onset, multi-organ autoimmunity in mice that resembled human STAT3 ^GOF disease. Female mice had more rapid disease progression than male mice. On a cellular level, gp130 signaling induced the activation and effector cell differentiation of T cells, promoted the expansion of T helper type 17 (T _H 17) cells, and impaired the activity of regulatory T cells. Transcriptomic profiling of CD4 ⁺ and CD8 ⁺ T cells from these mice revealed commonly dysregulated genes and a gene signature that, when applied to human transcriptomic data, improved the segregation of patients with transcriptionally diverse STAT3 ^GOF mutations from healthy controls. The findings demonstrate that increased gp130-STAT3 signaling leads to T _H 17-driven autoimmunity that phenotypically resembles human STAT3 ^GOF disease.

Acute myeloid leukemia (AML) is a heterogeneous disease characterized by genomic aberrations in oncogenes, cytogenetic abnormalities, and an aberrant epigenetic landscape. Nearly 50% of AML cases will relapse with current treatment. A major source of therapy resistance is the interaction of mesenchymal stroma with leukemic cells resulting in therapeutic protection. We aimed to determine pro-survival/anti-apoptotic protein networks involved in the stroma protection of leukemic cells. Proteomic profiling of cultured primary AML (n = 14) with Hs5 stroma cell line uncovered an up-regulation of energy-favorable metabolic proteins. Next, we modulated stroma-induced drug resistance with an epigenetic drug library, resulting in reduced apoptosis with histone deacetylase inhibitor (HDACi) treatment versus other epigenetic modifying compounds. Quantitative phosphoproteomic probing of this effect further revealed a metabolic-enriched phosphoproteome including significant up-regulation of acetyl-coenzyme A synthetase (ACSS2, S30) in leukemia-stroma HDACi treated cocultures compared with untreated monocultures. Validating these findings, we show ACSS2 substrate, acetate, promotes leukemic proliferation, ACSS2 knockout in leukemia cells inhibits leukemic proliferation and ACSS2 knockout in the stroma impairs leukemic metabolic fitness. Finally, we identify ACSS1/ACSS2-high expression AML subtype correlating with poor overall survival. Collectively, this study uncovers the leukemia-stroma phosphoproteome emphasizing a role for ACSS2 in mediating AML growth and drug resistance.

Objectives: To determine the incidence of delayed methotrexate elimination (DME) and acute kidney injury (AKI) and their associations with clinical outcomes in patients receiving high-dose methotrexate (HDMTX) for cancer treatment. Methods: The HDMTX European Registry collected medical records data from 12 institutions in 5 European countries to investigate the clinical practice patterns of healthcare providers utilizing HDMTX for cancer treatment. Cancer types included were acute lymphoblastic leukemia (ALL), primary central nervous system lymphoma (PCNSL), non-Hodgkin lymphoma (NHL), osteosarcoma, and other CNS cancers. Primary endpoints were the incidence of DME and AKI; secondary endpoints were clinical outcomes, including hospital length of stay (LOS), delay in the subsequent course of treatment, methotrexate dose reduction, and omission of next course of treatment. Associations between the primary and secondary endpoints were analyzed with Chi-square and Wilcoxon rank-sum tests. Results: Among the 2501 total HDMTX courses analyzed, DME occurred in 302 courses (12.1%), and AKI in 384 courses (15.4%). DME incidence was highest in courses for PCNSL (18.2%) and NHL (17.2%); AKI incidence was highest in ALL courses (21.0%). Incidence of DME and AKI varied by age and methotrexate infusion duration among the different cancer types. Occurrence of DME was associated with longer delays prior to the next course of treatment, longer hospital LOS, and more frequent methotrexate dose reductions and dose omissions. Conclusions: While HDMTX is a very effective and safe treatment, administration of efficacious doses of methotrexate can lead to AKI and DME, and no single or combination of patient or treatment factors was found to reliably predict their occurrence. Thus, diligent monitoring of methotrexate levels is imperative for early detection and prompt management of nephrotoxicity in all settings where HDMTX treatment is administered.

Article Simplified preanalytical laboratory procedures for therapeutic drug monitoring (TDM) in patients treated with high-dose methotrexate (HD-MTX) and glucarpidase was published on July 15, 2024 in the journal Clinical Chemistry and Laboratory Medicine (CCLM) (volume 0, issue 0).