gant-61 and Leukemia--Lymphocytic--Chronic--B-Cell

Targeted sequencing of 103 leukemia-associated genes in leukemia cells from 841 treatment-naive patients with chronic lymphocytic leukemia (CLL) identified 89 (11%) patients as having CLL cells with mutations in genes encoding proteins that putatively are involved in hedgehog (Hh) signaling. Consistent with this finding, there was a significant association between the presence of these mutations and the expression of GLI1 (χ

Topics: Adult; Aged; Aged, 80 and over; Disease Progression; Female; Gene Expression Regulation, Leukemic; Hedgehog Proteins; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Male; Middle Aged; Pyridines; Pyrimidines; Signal Transduction; Zinc Finger Protein GLI1

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.

Topics: Animals; Apoptosis; B-Lymphocytes; Cell Line, Tumor; Cell Survival; Gene Expression Regulation, Neoplastic; Genetic Predisposition to Disease; Hedgehog Proteins; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Oncogene Proteins; Pyridines; Pyrimidines; Receptors, G-Protein-Coupled; RNA, Messenger; Smoothened Receptor; Trans-Activators; Veratrum Alkaloids; Zinc Finger Protein GLI1