Marc A Vooijs

Natural resistance‐associated macrophage protein 2 (NRAMP 2; also known as DMT1 and encoded by SLC11A2 ) is mainly known for its iron transport activity. Recently, the DMT1 isoform lacking the iron‐response element (nonIRE) was associated with aberrant NOTCH pathway activity. In this report, we investigated the function of DMT1 nonIRE in normal and malignant hematopoiesis. Knockdown of Dmt1 nonIRE in mice showed that it has non‐canonical functions in hematopoietic stem cell differentiation: its knockdown suppressed development along the myeloid and lymphoid lineages, while promoting the production of platelets. These phenotypic effects on the hematopoietic system induced by Dmt1 nonIRE knockdown were linked to suppression of Notch/Myc pathway activity. Conversely, our data indicate a non‐canonical function for DMT1 nonIRE overexpression in boosting NOTCH pathway activity in T‐cell leukemia homeobox protein 1 ( TLX1 )‐defective leukemia. This work sets the stage for future investigation using a multiple‐hit T‐cell acute lymphoblastic leukemia (T‐ALL) model to further investigate the function of DMT1 nonIRE in T‐ALL disease development and progression.

Background Treatment resistance and tumor relapse are the primary causes of mortality in glioblastoma (GBM), with intratumoral heterogeneity playing a significant role. Patient-derived cancer organoids have emerged as a promising model capable of recapitulating tumor heterogeneity. Our objective was to develop patient-derived GBM organoids (PGO) to investigate treatment response and resistance. Methods GBM samples were used to generate PGOs and analyzed using whole-exome sequencing (WES) and single-cell karyotype sequencing. PGOs were subjected to temozolomide (TMZ) to assess viability. Bulk RNA sequencing was performed before and after TMZ. Results WES analysis on individual PGOs cultured for 3 time points (1–3 months) showed a high inter-organoid correlation and retention of genetic variants (range 92.3%–97.7%). Most variants were retained in the PGO compared to the tumor (range 58%–90%) and exhibited similar copy number variations. Single-cell karyotype sequencing demonstrated preservation of genetic heterogeneity. Single-cell multiplex immunofluorescence showed maintenance of cellular states. TMZ treatment of PGOs showed a differential response, which largely corresponded with MGMT promoter methylation. Differentially expressed genes before and after TMZ revealed an upregulation of the JNK kinase pathway. Notably, the combination treatment of a JNK kinase inhibitor and TMZ demonstrated a synergistic effect. Conclusions Overall, these findings demonstrate the robustness of PGOs in retaining the genetic and phenotypic heterogeneity in culture and the application of measuring clinically relevant drug responses. These data show that PGOs have the potential to be further developed into avatars for personalized adaptive treatment selection and actionable drug target discovery and as a platform to study GBM biology.