Soluble RANKL production by leukemic cells in a case of chronic lymphocytic leukemia with bone destruction

Evaluation of Bone Turnover Markers in Patients with Acute and Chronic Leukemia

This study investigated different bone biomarkers (cross-linked carboxy-terminal telopeptide of type 1 collagen (CTX-1), pyridinoline (PYD), osteocalcin (OC), interleukin-6 receptor (IL-6R), calcium (Ca), and magnesium (Mg)) in terms of their metabolism in 4 different leukemia subtypes (ALL, AML, CLL and CML). The design was case control study with 30 controls and 60 cases of leukemia patients. Authors have reported many results regarding decrease as well as increase of specific bone biomarker under investigation with each leukemia subtype when compared to control. In addition, Authors reported correlations between each biomarker level and leukemia subtypes.

Unraveling the Bone Tissue Microenvironment in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is the most frequent leukemia in Western countries. Although characterized by the progressive expansion and accumulation of leukemic B cells in peripheral blood, CLL cells develop in protective niches mainly located within lymph nodes and bone marrow. Multiple interactions between CLL and microenvironmental cells may favor the expansion of a B cell clone, further driving immune cells toward an immunosuppressive phenotype. Here, we summarize the current understanding of bone tissue alterations in CLL patients, further addressing and suggesting how the multiple interactions between CLL cells and osteoblasts/osteoclasts can be involved in these processes. Recent findings proposing the disruption of the endosteal niche by the expansion of a leukemic B cell clone appear to be a novel field of research to be deeply investigated and potentially relevant to provide new therapeutic approaches.

The role of macrophages and osteoclasts in the progression of leukemia

ABSTRACTBone marrow microenvironment provides critical regulatory signals for lineage differentiation and maintenance of HSC quiescence, and these signals also contribute to hematological myeloid malignancies. Macrophages exhibit high phenotypic heterogeneity under both physiological and pathological conditions and are mainly divided into proinflammatory M1 and anti-inflammatory M2 macrophages. Furthermore, osteoclasts are multinucleated giant cells that arise by fusion of monocyte/macrophage-like cells, which are commonly known as bone macrophages. Emerging evidence suggests that macrophages and osteoclasts originating from myeloid progenitors lead to two competing differentiation outcomes, and they appear to play an important role in the onset, progression, and bone metastasis of solid cancers. However, little is known about their role in the development of hematological malignancies. In this review, we focus on macrophages and osteoclasts, their role in leukemia, and the potential for targeting these cells in this disease.

Chronic lymphocytic leukemia cells impair osteoblastogenesis and promote osteoclastogenesis: role of TNFα, IL-6 and IL-11 cytokines

Bone skeletal alterations are no longer considered a rare event in Chronic Lymphocytic Leukemia (CLL), especially at more advanced stages of the disease. This study is aimed at elucidating the mechanisms underlying this phenomenon. Bone marrow stromal cells, induced to differentiate toward osteoblasts in osteogenic medium, appeared unable to complete their maturation upon co-culture with CLL cells, CLL cells-derived conditioned media (CLL-cm) or CLL-sera (CLL-sr). Inhibition of osteoblast differentiation was documented by decreased levels of RUNX2 and osteocalcin mRNA expression, by increased osteopontin and DKK-1 mRNA levels, and by a marked reduction of mineralized matrix deposition. The addition of neutralizing TNFα, IL-11 or anti-IL-6R monoclonal antibodies to these co-cultures resulted into restoration of bone mineralization, indicating the involvement of these cytokines: these findings were further supported by silencing TNFα, IL-11 and IL-6 in leukemic cells. We also demonstrated that the addition of CLL-cm to monocytes, previously stimulated with MCSF and RANKL, significantly amplified the formation of large mature osteoclasts as well as their bone resorption activity. Moreover enhanced osteoclastogenesis, induced by CLL-cm, was significantly reduced by treating cultures with the anti-TNFα moAb Infliximab; an analogous effect was observed by the use of the BTK inhibitor Ibrutinib. CLL cells, co-cultured with mature osteoclasts, were interestingly protected from apoptosis and upregulated Ki-67. These experimental results parallel the direct correlation between TNFα amounts in CLL sera and the degree of compact bone erosion we previously described, further strengthening the indication of a reciprocal influence between leukemic cells expansion and bone structure derangement.

A case of fatal osteolytic hypercalcemia complicated with IgG4-related ophthalmic disease leading to renal failure

A 40-year-old male was hospitalized with renal impairment and severe hypercalcemia. His concentration of serum IgG4 was high, but serum whole PTH, 1-25(OH)₂ vitamin D3 and PTHrP were not elevated. Computed tomography showed swelling of the bilateral lacrimal glands and systemic lymphadenopathy. The histological findings of lacrimal gland biopsy fulfilled the diagnostic criteria of IgG4-related ophthalmic disease (IgG4ROD). Bone scintigraphy showed increased ectopic uptake in the stomach, heart, lungs, and kidneys. He died on day 16 of admission, although the therapies for hypercalcemia were continued. Autopsy results showed an increase of osteoclasts in the bone marrow and metastatic calcification in multiple organs, and excluded from the differential diagnosis other disorders which present lymph-node swelling and hypercalcemia such as cancer, lymphoma, Castleman's disease, and sarcoidosis. He was given a diagnosis of IgG4ROD with osteolytic hypercalcemia.

Functional Activation of Osteoclast Commitment in Chronic Lymphocytic Leukaemia: a Possible Role for RANK/RANKL Pathway

Skeletal erosion has been found to represent an independent prognostic indicator in patients with advanced stages of chronic lymphocytic leukaemia (CLL). Whether this phenomenon also occurs in early CLL phases and its underlying mechanisms have yet to be fully elucidated. In this study, we prospectively enrolled 36 consecutive treatment-naïve patients to analyse skeletal structure and bone marrow distribution using a computational approach to PET/CT images. This evaluation was combined with the analysis of RANK/RANKL loop activation in the leukemic clone, given recent reports on its role in CLL progression. Bone erosion was particularly evident in long bone shafts, progressively increased from Binet stage A to Binet stage C, and was correlated with both local expansion of metabolically active bone marrow documented by FDG uptake and with the number of RANKL + cells present in the circulating blood. In immune-deficient NOD/Shi-scid, γcnull (NSG) mice, administration of CLL cells caused an appreciable compact bone erosion that was prevented by Denosumab. CLL cell proliferation in vitro correlated with RANK expression and was impaired by Denosumab-mediated disruption of the RANK/RANKL loop. This study suggests an interaction between CLL cells and stromal elements able to simultaneously impair bone structure and increase proliferating potential of leukemic clone.