Michaela Máchalová

Autocrine signaling by Wnt-5a deregulates chemotaxis of leukemic cells and predicts clinical outcome in chronic lymphocytic leukemia.

Purpose: ROR1, a receptor in the noncanonical Wnt/planar cell polarity (PCP) pathway, is upregulated in malignant B cells of chronic lymphocytic leukemia (CLL) patients. It has been shown that the Wnt/PCP pathway drives pathogenesis of CLL, but which factors activate the ROR1 and PCP pathway in CLL cells remains unclear. Experimental Design: B lymphocytes from the peripheral blood of CLL patients were negatively separated using RosetteSep (StemCell) and gradient density centrifugation. Relative expression of WNT5A, WNT5B, and ROR1 was assessed by quantitative real-time PCR. Protein levels, protein interaction, and downstream signaling were analyzed by immunoprecipitation and Western blotting. Migration capacity of primary CLL cells was analyzed by the Transwell migration assay. Results: By analyzing the expression in 137 previously untreated CLL patients, we demonstrate that WNT5A and WNT5B genes show dramatically (five orders of magnitude) varying expression in CLL cells. High WNT5A and WNT5B expression strongly associates with unmutated IGHV and shortened time to first treatment. In addition, WNT5A levels associate, independent of IGHV status, with the clinically worst CLL subgroups characterized by dysfunctional p53 and mutated SF3B1. We provide functional evidence that WNT5A-positive primary CLL cells have increased motility and attenuated chemotaxis toward CXCL12 and CCL19 that can be overcome by inhibitors of Wnt/PCP signaling. Conclusions: These observations identify Wnt-5a as the crucial regulator of ROR1 activity in CLL and suggest that the autocrine Wnt-5a signaling pathway allows CLL cells to overcome natural microenvironmental regulation. Clin Cancer Res; 22(2); 459–69. ©2015 AACR.

Decreased WNT3 expression in chronic lymphocytic leukaemia is a hallmark of disease progression and identifies patients with worse prognosis in the subgroup with mutated IGHV

The canonical Wnt pathway, dependent on β‐catenin‐controlled transcription, is the most explored Wnt pathway, known to drive the malignant transformation of multiple cell types. Several reports have suggested that this pathway also participates in chronic lymphocytic leukaemia (CLL) pathogenesis. To get a better insight into the role of the Wnt/β‐catenin pathway in CLL we analysed in detail the expression of the most overexpressed Wnt ligand, encoded by the WNT3 gene, in a well‐defined cohort of 137 CLL patients. Our analysis demonstrated that (i) untreated patients with more aggressive disease (with a notable exception of patients with 11q deletion) express less WNT3, (ii) WNT3 declines with disease progression in a significant proportion of patients and (iii) low WNT3 was identified as a strong independent marker indicating shorter treatment‐free survival in CLL patients with IGHV mutation. Interestingly, CLL‐related lymphoid cell lines, but not stromal cells, failed to respond to the ligand‐induced activation of the Wnt/β‐catenin pathway. This opens the possibility that CLL cells use Wnt‐3 to communicate with the cells in the microenvironment. We thus propose that the Wnt/β‐catenin pathway plays a more complex role in CLL pathogenesis than previously anticipated.