t(11;16)(q23;p13)/KMT2A-CREBBP in hematologic malignancies: presumptive evidence of myelodysplasia or therapy-related neoplasm?

Fusion partners of KMT2A affect disease phenotype and influence the current World Health Organization classification of hematologic neoplasms. The t(11;16)(q23;p13)/KMT2A-CREBBP is considered presumptive evidence of a myelodysplastic syndrome (MDS) and a MDS-related cytogenetic abnormality in the classification of acute myeloid leukemia (AML). Here, we report 18 cases of hematologic neoplasms with t(11;16). There were 8 males and 10 females with a median age of 51.9 years at time of detection of t(11;16). Of 17 patients with enough clinical information and pathological materials for review, 16 had a history of cytotoxic therapies for various malignancies including 12/15 patients who received topoisomerase II inhibitors, and 15 were classified as having therapy-related neoplasms. The median interval from the diagnosis of primary malignancy to the detection of t(11;16) was 23.2 months. Dysplasia, usually mild, was observed in 7/17 patients. Blasts demonstrated monocytic differentiation in 8/8 patients who developed AML at the time or following detection of t(11;16). t(11;16) was observed as the sole chromosomal abnormality in 10/18 patients. KMT2A rearrangement was confirmed in 11/11 patients. The median survival from the detection of t(11;16) was 15.4 months. In summary, t(11;16)(q23;p13) is rare and overwhelmingly associated with prior exposure of cytotoxic therapy. Instead of being considered presumptive evidence of myelodysplasia, we suggest that the detection of t(11;16) should automatically prompt a search for a history of malignancy and cytotoxic therapy so that proper risk stratification and clinical management are made accordingly. The dismal outcome of patients with t(11;16) is in keeping with that of therapy-related neoplasms.

Bone Marrow Collection: Comparison of Unassisted vs Assisted Bedside Collections by a Laboratory Technologist.

OBJECTIVES: Bone marrow collections are often difficult, and creating quality smears and touch preparations at the bedside can prove challenging. The objective of this study is to compare the quality of bone marrow specimens between unassisted and assisted bone marrow collections by a bone marrow technologist. METHODS: Data for this study were collected from 422 hematopathology reports over 14 months. We recorded the bone marrow quality of the different parts (aspirate smears, touch imprints, core biopsy, and clot/particle sections) as adequate, suboptimal, or inadequate. Student t test statistical analysis was performed between the corresponding parts in the two groups. RESULTS: Our results demonstrate that the quality of assisted bone marrow specimens is significantly better compared with unassisted specimens, particularly for the aspirate smears (P < .0001) and touch imprints (P < .0001). Notably, the quality of aspirate smears was improved, which is important for cytologic evaluation. CONCLUSIONS: We conclude that assistance by a bone marrow technologist resulted in a significant improvement in the quality of bone marrow collection.

The Japanese mutant Aß (ΔE22-Aß(1-39)) forms fibrils instantaneously, with low-thioflavin T fluorescence: seeding of wild-type Aß(1-40) into atypical fibrils by ΔE22-Aß(1-39).

The ΔE693 (Japanese) mutation of the ß-amyloid precursor protein leads to production of ΔE22-Aß peptides such as ΔE22-Aß(1-39). Despite reports that these peptides do not form fibrils, here we show that, on the contrary, the peptide forms fibrils essentially instantaneously. The fibrils are typical amyloid fibrils in all respects except that they cause only low levels of thioflavin T (ThT) fluorescence, which, however, develops with no lag phase. The fibrils bind ThT, but with a lower affinity and a smaller number of binding sites than wild-type (WT) Aß(1-40). Fluorescence depolarization confirms extremely rapid aggregation of ΔE22-Aß(1-39). Size exclusion chromatography (SEC) indicates very low concentrations of soluble monomer and oligomer, but only in the presence of some organic solvent, e.g., 2% (v/v) DMSO. The critical concentration is approximately 1 order of magnitude lower for ΔE22-Aß(1-39) than for WT Aß(1-40). Several lines of evidence point to an altered structure for ΔE22-Aß(1-39) compared to that of WT Aß(1-40) fibrils. In addition to differences in ThT binding and fluorescence, PITHIRDS-CT solid-state nuclear magnetic resonance (NMR) measurements of ΔE22-Aß(1-39) are not compatible with the parallel in-register ß-sheet generally observed for WT Aß(1-40) fibrils. X-ray fibril diffraction showed different D spacings: 4.7 and 10.4 Å for WT Aß(1-40) and 4.7 and 9.6 Å for ΔE22-Aß(1-39). Equimolar mixtures of ΔE22-Aß(1-39) and WT Aß(1-40) also produced fibrils extremely rapidly, and by the criteria of ThT fluorescence and electron microscopic appearance, they were the same as fibrils made from pure ΔE22-Aß(1-39). X-ray diffraction of fibrils formed from 1:1 molar mixtures of ΔE22-Aß(1-39) and WT Aß(1-40) showed the same D spacings as fibrils of the pure mutant peptide, not the wild-type peptide. These findings are consistent with extremely rapid nucleation by ΔE22-Aß(1-39), followed by fibril extension by WT Aß(1-40), and "conversion" of the wild-type peptide to a structure similar to that of the mutant peptide, in a manner reminiscent of the prion conversion phenomenon.

RNA cytosine methylation and methyltransferases mediate chromatin organization and 5-azacytidine response and resistance in leukaemia.

The roles of RNA 5-methylcytosine (RNA:m5C) and RNA:m5C methyltransferases (RCMTs) in lineage-associated chromatin organization and drug response/resistance are unclear. Here we demonstrate that the RCMTs, namely NSUN3 and DNMT2, directly bind hnRNPK, a conserved RNA-binding protein. hnRNPK interacts with the lineage-determining transcription factors (TFs), GATA1 and SPI1/PU.1, and with CDK9/P-TEFb to recruit RNA-polymerase-II at nascent RNA, leading to formation of 5-Azacitidine (5-AZA)-sensitive chromatin structure. In contrast, NSUN1 binds BRD4 and RNA-polymerase-II to form an active chromatin structure that is insensitive to 5-AZA, but hypersensitive to the BRD4 inhibitor JQ1 and to the downregulation of NSUN1 by siRNAs. Both 5-AZA-resistant leukaemia cell lines and clinically 5-AZA-resistant myelodysplastic syndrome and acute myeloid leukaemia specimens have a significant increase in RNA:m5C and NSUN1-/BRD4-associated active chromatin. This study reveals novel RNA:m5C/RCMT-mediated chromatin structures that modulate 5-AZA response/resistance in leukaemia cells, and hence provides a new insight into treatment of leukaemia.

Author Correction: RNA cytosine methylation and methyltransferases mediate chromatin organization and 5-azacytidine response and resistance in leukaemia.

In the originally published version of this Article, the GAPDH loading control blot in Fig. 1a was inadvertently replaced with a duplicate of the DNMT2 blot in the same panel during assembly of the figure. This has now been corrected in both the PDF and HTML versions of the Article.