Telomerase activity, apoptosis and cell cycle progression in ataxia telangiectasia lymphocytes expressing TCL1

Actionable perturbations of damage responses by TCL1/ATM and epigenetic lesions form the basis of T-PLL

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.

Preliminary study on the mechanism of oridonin-induced apoptosis in human squamous cell oesophageal carcinoma cell line EC9706

Objective

To study the apoptosis-inducing effect of the Chinese medicine oridonin in the human oesophageal squamous cell carcinoma cell line EC9706, in vitro.

Methods

The effect of oridonin on cell proliferation was studied using the colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Effects on the cell cycle and apoptosis were studied by flow cytometry; effects on intracellular Ca2+ concentration were studied by measuring the fluorescence intensity of a fluorescent Ca2+ probe by laser scanning confocal microscopy.

Results

The EC9706 cell-proliferation rate decreased with time and oridonin concentration (10–40 µmol/l). The number of cells in G0 and G1 phases increased significantly following exposure to oridonin for 48 and 72 h respectively, and oridonin was shown to be most effective at inducing apoptosis in EC9706 cells at 40 µmol/l. Compared with the control group, all concentrations of oridonin tested (10–40 µmol/l) significantly increased the Ca2+ fluorescence intensity of EC9706 cells.

Conclusions

Oridonin was shown to inhibit proliferation and induce apoptosis in the human oesophageal squamous cell carcinoma cell line EC9706, in vitro. These data provide preliminary experimental evidence for the anticancer effects of oridonin, which is as a traditional Chinese medicine used to treat various cancers, including oesophageal squamous cell carcinoma. Further studies are required to elucidate the mode of action.

Tcl1 interacts with Atm and enhances NF-κB activation in hematologic malignancies

The T-cell leukemia/lymphoma 1 (TCL1) oncogene is a target of chromosomal translocations and inversions at 14q31.2, and its rearrangement in T cells causes T-cell prolymphocytic leukemias. TCL1 dysregulation in B cells is responsible for the development of an aggressive form of chronic lymphocytic leukemia (CLL), the most common human leukemia. We have investigated the mechanisms underlying the oncogenic functions of Tcl1 protein using a mass spectrometry approach and have identified Atm (ataxia-telangiectasia mutated) as a candidate Tcl1-interacting protein. The Tcl1-Atm complex formation was validated by coimmunoprecipitation experiments. Importantly, we show that the association of Atm with Tcl1 leads to enhanced IκBα phosphorylation and ubiquitination and subsequent activation of the NF-κB pathway. Our findings reveal functional cross-talk between Atm and Tcl1 and provide evidence for a novel pathway that could be targeted in leukemias and lymphomas.