Chronic lymphocytic leukemia (CLL) cells require complex microenvironmental and immunologic interactions to survive and proliferate. Such interactions might be best recreated in animal models; however, this needs extensive verification. We therefore investigated the composition of the T-cell compartment in the El-TCL1 transgenic mouse, currently the most widely used murine model for CLL. Immunophenotyping and transplant approaches were used to define T-cell subsets at various stages of CLL. Analogous to human CLL, we observed a skewing of T-cell subsets from naive to antigen-experienced memory T cells that was more pronounced in lymph nodes than in blood. Transplantation of CLL into non-transgenic recipients was feasible without immunosuppression in a pure C57BL/6 background and resulted in the prominent skewing of the T cells of the recipient mice. Both in spontaneously developed CLL and in the transplantation setting, a loss in T-cell receptor diversity was observed, with a relevant number of clonal T-cell populations arising. This suggests that antigen-dependent differentiation toward the T memory pool is initiated by murine CLL cells. In summary, we validate the TCL1 transgenic mouse model for analysis of T-cell phenotypes and suggest a CLL-dependent antigen-driven skewing of T cells in these mice.

In chronic lymphocytic leukemia (B-CLL), aberrations along the p53 axis lead to decreased overall survival and therapy resistance. Recent studies identified microRNA34a (miR-34a) as a major downstream target of p53. We monitored the expression of miR-34a during disease development in a murine B-CLL model. miR-34a was upregulated more than 20-fold during the leukemic but not during the preleukemic phase. In the human system, B-CLL cells also had 4.6-fold higher miR-34a expression compared with B cells of healthy controls. In B-CLL cells of patients with p53 aberrations, miR-34a expression was consistently low. The broad distribution of miR-34a levels in p53 wild-type patients prompted us to study the correlation between single nucleotide polymorphism 309 (SNP309) in the intronic promoter of MDM2 and miR-34a expression. B-CLL cells of patients with the SNP309 GG genotype had significantly lower miR-34a expression levels compared with patients with the TT genotype (P ‫؍‬ .002). Low miR-34a levels were able to predict shorter time to treatment (P ‫؍‬ .003) and were associated with an abbreviated lymphocyte doubling time. Introduction microRNAs (miRNAs) are small noncoding RNAs that regulate gene expression by near-perfect base pairing with target mRNAs resulting in either degradation or silencing. 1,2 They play important roles in leukemias 3-5 and solid malignancies 6,7 and offer elegant possibilities for future therapeutic intervention. [8][9][10][11] Recently, the miR-34 family, consisting of miR-34a, b, and c, has been described as a downstream target of the tumor suppressor p53. [12][13][14][15][16][17] Overexpression of miR-34 can evoke p53-like effects, including senescence, apoptosis, or cell cycle arrest depending on the cell type analyzed. [12][13][14][15][16][17] In normal unstressed cells, p53 functions are tightly controlled mainly by the ubiquitin ligase murine double minute zprotein (MDM2). It has been demonstrated that single nucleotide polymorphism 309 (SNP309) resulting in a T to G alteration within the first intron of the intronic MDM2 gene promoter, henceforth termed SNP309, can enhance MDM2 expression and therefore lead to a reduced tumor suppressor function of p53. 18 SNP309 has been shown to affect onset of disease or tumor progression in various cancer types including gastric carcinoma, 19 colorectal cancer, 20 and also chronic lymphocytic leukemia (B-CLL). 21 B-CLL is the most prevalent lymphoma in the western world, and p53 deletion has dramatic effects such as therapy resistance and reduced median overall survival from 111 to 32 months. 22 Two independent recent studies suggest that p53 mutations, which go undetected in routine sample workup, are equivalent to p53 deletions in their frequency and prognostic impact. 23,24 In B-CLL miR-34b and c are not expressed, and several studies have confirmed the dependence of miR-34a expression on p53 status in this disease. [25][26][27] However, the reasons for low miR-34a expression in many B-CLL cases without p53 deletions or mutations and its role ...

Obesity is characterised by lipid accumulation in non-adipose tissues, leading to organ degeneration and a wide range of diseases, including diabetes, heart attack and liver cirrhosis. Free fatty acids (FFA) are believed to be the principal toxic triggers mediating the adverse cellular effects of lipids. Here, we show that various cooking oils used in human nutrition cause cell death in yeast in the presence of a triacylglycerol lipase, mimicking the physiological microenvironment of the small intestine. Combining genetic and cell death assays, we demonstrate that elevated FFA concentrations lead to necrotic cell death, as evidenced by loss of membrane integrity and release of nuclear HMGB1. FFA-mediated necrosis depends on functional mitochondria and leads to the accumulation of reactive oxygen species. We conclude that lipotoxicity is executed via a mitochondrial necrotic pathway, challenging the dogma that the adverse effects of lipid stress are exclusively apoptotic.

The Hedgehog (Hh) pathway regulates cell proliferation and survival and contributes to tumorigenesis. We investigated the expression and function of this pathway in B-cell chronic lymphocytic leukemia (CLL) cells and in healthy B lymphocytes. Profiling of cognate Hh pathway members revealed reduced expression of two key Hh signaling effectors, Smoothened (SMOH) and GLI, in CLL cells, whereas transcription levels of other investigated members resembled normal B-lymphocyte levels. Examining the functional role of SMOH and GLI in cell survival, we found that CLL cells were hardly sensitive toward specific SMOH inhibition, but showed an unspecific decline in cell viability in response to high concentrations of the SMOH antagonist cyclopamine. In contrast, treatment with the novel GLI antagonist GANT61 reduced expression of the target gene Patched and preferentially decreased the viability of malignant cells. Specific RNA interference knockdown experiments in a CLL-derived cell line confirmed the autonomous role of GLI in malignant cell survival. GANT61-induced apoptosis in primary leukemic cells was partly attenuated by protective stromal cells, but not soluble sonic hedgehog ligand. In summary, our data show a downregulation of the classical Hh pathway in CLL and suggest an intrinsic SMOH-independent role of GLI in the ex vivo survival of CLL cells.

Key Points Motility of resting CLL cells requires chemokine-mediated RhoA activation but is independent of Tiam1/Rac signals. Tiam1/Rac signals are indispensible for CLL cell proliferation and chemoresistance.