Explore the vast range of titles available.

T-cell prolymphocytic leukemia (T-PLL) is a rare and poor-prognostic mature T-cell malignancy. Here we integrated large-scale profiling data of alterations in gene expression, allelic copy number (CN), and nucleotide sequences in 111 well-characterized patients. Besides prominent signatures of T-cell activation and prevalent clonal variants, we also identify novel hot-spots for CN variability, fusion molecules, alternative transcripts, and progression-associated dynamics. The overall lesional spectrum of T-PLL is mainly annotated to axes of DNA damage responses, T-cell receptor/cytokine signaling, and histone modulation. We formulate a multi-dimensional model of T-PLL pathogenesis centered around a unique combination of TCL1 overexpression with damaging ATM aberrations as initiating core lesions. The effects imposed by TCL1 cooperate with compromised ATM toward a leukemogenic phenotype of impaired DNA damage processing. Dysfunctional ATM appears inefficient in alleviating elevated redox burdens and telomere attrition and in evoking a p53-dependent apoptotic response to genotoxic insults. As non-genotoxic strategies, synergistic combinations of p53 reactivators and deacetylase inhibitors reinstate such cell death execution. T-cell prolymphocytic leukemia (T-PLL) is a rare malignancy with a poor prognosis. Here, the authors investigate the genomic landscape, gene expression profiles and functional mechanisms in 111 patients, highlighting TCL1 overexpression and ATM aberrations as core lesions which co-operate to impair DNA damage processing.

The tissue microenvironment in chronic lymphocytic leukemia (CLL) has an increasingly recognized role in disease progression, but the molecular mechanisms of cross talk between CLL cells and their microenvironment remain incompletely defined. Bone marrow stromal cells (BMSC) protect CLL cells from apoptosis in a contact-dependent fashion, and have been used for the identification of key pathways such as the CXCR4–CXCL12 axis. To further dissect the molecular impact of BMSC on survival and the molecular activation signature of CLL cells, we co-cultured CLL cells with different BMSC. Gene expression profiling of CLL cells revealed that the lymphoid proto-oncogene TCL1 was among the top genes upregulated in CLL cells by BMSC. TCL1 mRNA and protein upregulation by BMSC was paralleled by decreases of TCL1-interacting FOS/JUN, and confirmed by qRT-PCR, immunoblotting, immunoprecipitations, and flow cytometry. Stroma mediated increases in TCL1 were also associated with decreased levels of TCL1-regulatory micro-RNAs (miR-29b, miR-181b, miR-34b). These findings demonstrate that the microenvironment has a proactive role in the regulation of the known signaling enhancer and pro-survival molecule TCL1 in CLL. This provides a further rationale for therapeutically targeting the cross talk between CLL and BMSC.

Dysregulated T-cell leukemia/lymphoma-1A (TCL1A), a modulator in B-cell receptor (BCR) signaling, is causally implicated in chronic lymphocytic leukemia (CLL). However, the mechanisms of the perturbed TCL1A regulation are largely unknown. To characterize TCL1A-upstream networks, we functionally screened for TCL1A-repressive micro-RNAs (miRs) and their transcriptional regulators. We identified the novel miR-484 to target TCL1A’s 3′-UTR and to be downregulated in CLL. In chromatin immunoprecipitations and reporter assays, the oncogenic transcription factor of myeloid cells, EVI1, bound and activated the miR-484 promoter. Most common in CLL was a pan-EVI1 transcript variant. EVI1 protein expression revealed distinct normal-tissue and leukemia-associated patterns of EVI1/TCL1A co-regulation. EVI1 levels were particularly low in TCL1A-high CLL or such cellular subsets. Global gene expression profiles from a 337-patient set linked EVI1 networks to BCR signaling and cell survival via TCL1A, BTK and other molecules of relevance in CLL. Enforced EVI1, as did miR-484, repressed TCL1A. Furthermore, it reduced phospho-kinase levels, impaired cell survival, mitigated BCR-induced Ca-flux and diminished the in vitro ibrutinib response. Moreover, TCL1A and EVI1 showed a strongly interactive hazard prediction in prospectively treated patients. Overall, we present regressive EVI1 as a novel regulatory signature in CLL. Through enhanced TCL1A and other EVI1-targeted hallmarks of CLL, this contributes to an aggressive cellular and clinical phenotype.

Treatment resistance becomes a challenge at some point in the course of most patients with chronic lymphocytic leukemia (CLL). This applies to fludarabine-based regimens, and is also an increasing concern in the era of more targeted therapies. As cells with low-replicative activity rely on repair that triggers checkpoint-independent noncanonical pathways, we reasoned that targeting the nucleotide excision repair (NER) reaction addresses a vulnerability of CLL and might even synergize with fludarabine, which blocks the NER gap-filling step. We interrogated here especially the replication-independent transcription-coupled-NER ((TC)-NER) in prospective trial patients, primary CLL cultures, cell lines and mice. We screen selected (TC)-NER-targeting compounds as experimental (illudins) or clinically approved (trabectedin) drugs. They inflict transcription-stalling DNA lesions requiring TC-NER either for their removal (illudins) or for generation of lethal strand breaks (trabectedin). Genetically defined systems of NER deficiency confirmed their specificity. They selectively and efficiently induced cell death in CLL, irrespective of high-risk cytogenetics, IGHV status or clinical treatment history, including resistance. The substances induced ATM/p53-independent apoptosis and showed marked synergisms with fludarabine. Trabectedin additionally perturbed stromal-cell protection and showed encouraging antileukemic profiles even in aggressive and transforming murine CLL. This proof-of-principle study established (TC)-NER as a mechanism to be further exploited to resensitize CLL cells.

Nonnatural thiazole-containing oligopeptides (TCOs) bind to the DNA minor groove and inhibit the reaction catalyzed by human topoisomerase I (TopoI). The effect is directly proportional to the number of thiazole monomers in TCO. Several TCOs with three or four thiazole monomers act 3–10 times more efficiently than distamycin A, a natural antibiotic containing pyrrole rings. Additional groups at the N and C termini only slightly affect TopoI inhibition by TCO. The inhibitory effect of TCOs is higher than that of homo-or heterooligopeptides containing imidazole or pyrrole monomers, and the most potent are oligopeptide-oligonucleotide conjugates. The plausible causes of the different effects of distamycin and the nonnatural peptides on DNA relaxation catalyzed by TopoI are discussed.