Role of the RANKL/RANK system in the induction of interleukin‐8 (IL‐8) in B chronic lymphocytic leukemia (B‐CLL) cells

Abstract

B chronic lymphocytic leukemia (B-CLL) cells express several members of the tumor necrosis factor (TNF) family, such as CD40L, CD30L, and TRAIL. By using the cDNA microarray technology, B-CLL samples were found to overexpress receptor activator of nuclear factor kB (NF-kB) ligand (RANKL), as compared to normal CD19(+) B cells. These findings were validated at the protein level by Western blot and flow cytometry analyses. Moreover, unlike primary normal B cells, leukemic B-CLL cells showed surface expression of RANK, the cognate transmembrane receptor of RANKL. When added in vitro to B-CLL cultures, either alone or in association with chlorambucil or fludarabine, recombinant RANKL did not significantly modulate cell viability, and it minimally affected the IL-8 expression/release. On the other hand, treatment with RANK-Fc chimera potently upregulated the release of IL-8 in the B-CLL culture supernatants, suggesting involvement of reverse signaling through transmembrane RANKL in IL-8 induction. In turn, exposure of B-CLL cells to recombinant IL-8 significantly decreased spontaneous apoptosis as well as chlorambucil- and fludarabine-mediated cytoxicity in B-CLL cells. Since IL-8 has been implicated in progression of B-CLL disease, our findings suggest that, by upregulating IL-8, the RANKL/RANK system may contribute to the pathogenesis of B-CLL.

Receptor Activator for NF-κB Ligand in Acute Myeloid Leukemia: Expression, Function, and Modulation of NK Cell Immunosurveillance

“…With regard to hematopoietic malignancies, RANKL was reported to be expressed in membrane-bound and soluble form in multiple myeloma and may contribute to disease pathology, for example, by induction of osteolysis (20,42,43). In CLL, RANKL expression has been reported to influence the release of IL-8, which acts as autocrine and paracrine growth and survival factor for the malignant cells (19). In this study, we report for the first time to our knowledge that RANKL is expressed on primary leukemia cells in a high proportion of AML cases.…”

“…Recent studies suggested an involvement of RANKL in disease pathophysiology of chronic lymphoid leukemia (CLL) and multiple myeloma as well as metastatic spread of solid tumors (19)(20)(21)(22)(23)(24)(25)32), but nothing was yet known on the role of the RANK-RANKL molecule system in AML. In this study, we analyzed RANKL expression on primary AML cells by flow cytometry and selected malignant cells among PBMCs of leukemia patients by staining for CD33 and CD34.…”

“…Amplicons of membranebound RANKL (mRANKL) were detected in all 30 investigated samples. Notably, this also comprised samples without detectable surface expression on leukemic cells, which could be due to contamination with RANKL-expressing healthy cells like B and T cells (19,29), but may also indicate that RANKL surface expression is regulated posttranscriptionally. The mRNA splice variant specifically coding for sRANKL was detected in 5 (17%) of the samples (Fig.…”

“…This indicates that presence of mRNA for RANKL does not necessarily result in detectable protein expression, which lends further evidence that RANKL expression may substantially be influenced by posttranscriptional and/or posttranslational mechanisms in individual AML patients. (19,33,34). Therefore, we studied whether AML-expressed RANKL was able to transduce reverse signals that influence the cellular activity of the leukemia cells.…”

“…The TNFR family member receptor activator for NF-kB (RANK; TNFRSF11A) and its ligand (receptor activator for NF-kB ligand; RANKL) are mainly known for their key role in regulating bone metabolism (15,16) but were also found to influence the interaction of dendritic cells (DCs) and T cells as well as the pathophysiology of hematopoietic malignancies and metastasis of solid tumors (17)(18)(19)(20)(21)(22)(23)(24)(25). Notably, available data indicate that RANK is also expressed on NK cells (26), but to date nothing is known regarding the functional relevance of RANK-RANKL interaction for NK cell reactivity.…”