CD99 in malignant hematopoiesis

Uncoupling histone modification crosstalk by engineering lysine demethylase LSD1

Biochemical crosstalk between two or more histone modifications is often observed in epigenetic enzyme regulation, but its functional significance in cells has been difficult to discern. Previous enzymatic studies revealed that Lys14 acetylation of histone H3 can inhibit Lys4 demethylation by lysine-specific demethylase 1 (LSD1). In the present study, we engineered a mutant form of LSD1, Y391K, which renders the nucleosome demethylase activity of LSD1 insensitive to Lys14 acetylation. K562 cells with the Y391K LSD1 CRISPR knockin show decreased expression of a set of genes associated with cellular adhesion and myeloid leukocyte activation. Chromatin profiling revealed that the cis-regulatory regions of these silenced genes display a higher level of H3 Lys14 acetylation, and edited K562 cells show diminished H3 mono-methyl Lys4 near these silenced genes, consistent with a role for enhanced LSD1 demethylase activity. These findings illuminate the functional consequences of disconnecting histone modification crosstalk for a key epigenetic enzyme.

Dissecting cellular heterogeneity and intercellular communication in cholangiocarcinoma: implications for individualized therapeutic strategies

Background: Cholangiocarcinoma is characterized by significant cellular heterogeneity and complex intercellular communication, which contribute to its progression and therapeutic resistance. Therefore, unraveling this complexity is essential for the development of effective treatments. Methods: We employed single-cell RNA sequencing (scRNA-seq) to investigate cellular heterogeneity and intercellular communication in cholangiocarcinoma and adjacent normal tissues from two patients. Distinct cell types were identified, and gene ontology analyses were conducted to determine enriched pathways. Moreover, cell-cell communications were analyzed using CellChat, a computational framework. Additionally, we performed sub-clustering analysis of T cells and fibroblasts. Results: The scRNA-seq analysis revealed distinct cell clusters and diverse cellular compositions of cholangiocarcinoma. CellChat analysis underscored an amplified outgoing signal from fibroblasts within the tumor, suggesting their pivotal role in the tumor microenvironment. Furthermore, T cell sub-clustering analysis revealed an active immune response within the tumor and new tumor-specific T cell clonotypes, suggesting scope for targeted immunotherapies. Moreover, fibroblast sub-clustering analysis indicated distinct functional states and highlighted the role of activated fibroblasts in shaping intercellular communication, particularly via CD99 and FN1 signaling. Conclusion: Our findings reveal the intricate cellular heterogeneity and dynamic intercellular communication in cholangiocarcinoma, providing valuable insights into disease progression and potential therapeutic strategies.

Advances in Acute Myeloid Leukemia Classification, Prognostication and Monitoring by Flow Cytometry

Although final classification of acute myeloid leukemia (AML) integrates morphologic, cytogenetic, and molecular data, flow cytometry remains an essential component of modern AML diagnostics. Here, we review the current role of flow cytometry in the classification, prognostication, and monitoring of AML. We cover immunophenotypic features of key genetically defined AML subtypes and their effects on biological and clinical behaviors, review clinically tractable strategies to differentiate leukemias with ambiguous immunophenotypes more accurately and discuss key principles of standardization for measurable residual disease monitoring. These advances underscore flow cytometry's continued growth as a powerful diagnostic, management, and discovery tool.

Acute Undifferentiated Leukemia With a Balanced t(5;10)(q35;p12) Resulting in Fusion of HNRNPH1 With MLLT10

BACKGROUND/AIM

Acute undifferentiated leukemia (AUL) is leukemia which does not express lineage-specific antigens. Such cases are rare, accounting for 2.7% of all acute leukemia. The reported genetic information of AULs is limited to less than 100 cases with abnormal karyotypes and a few cases carrying chimeric genes or point mutation of a gene. We herein present the genetic findings and clinical features of a case of AUL.

CASE REPORT

Bone marrow cells obtained at diagnosis from a 31-year-old patient with AUL were genetically investigated. G-Banding karyotyping revealed an abnormal karyotype: 45,X,-Y,t(5;10)(q35;p12),del(12)(p13)[12]/46,XY[5]. Array comparative genomic hybridization examination confirmed the del(12)(p13) seen by G-banding but also detected additional losses from 1q, 17q, Xp, and Xq corresponding to the deletion of approximately 150 genes from these five chromosome arms. RNA sequencing detected six HNRNPH1::MLLT10 and four MLLT10::HNRNPH1 chimeric transcripts, later confirmed by reverse-transcription polymerase chain reaction together with Sanger sequencing. Fluorescence in situ hybridization analysis showed the presence of HNRNPH1::MLLT10 and MLLT10::HNRNPH1 chimeric genes.

CONCLUSION

To the best of our knowledge, this is the first AUL in which a balanced t(5;10)(q35;p12) leading to fusion of HNRNPH1 with MLLT10 has been detected. The relative leukemogenic importance of the chimeras and gene losses cannot be reliably assessed, but both mechanisms were probably important in the development of AUL.