Current ideas on the pathogenesis of osteoporosis in chronic lymphatic leukemia (literature review)

Background. Chronic lymphocytic leukemia (CLL) is the second most common hematological malignancy without a trend towards a decrease in its incidence. 66 % of patients with CLL experience bone fractures as a result of osteoporosis in all age groups, and the detection frequency is no more than 15 %. Insufficient understanding of the osteoporosis pathogenesis in CLL leads to problems in diagnosis, prevention and therapy. The aim of the study. To analyze modern data on the features of the osteoporosis pathogenesis in chronic lymphocytic leukemia. Results and discussion. Osteoporosis is formed when osteoresorption prevails over osteosynthesis due to intercellular interactions of bone tissue and the immune system, dysregulation of intracellular signaling pathways RANKL/RANK/OPG, Wnt, FoxO, RUNX2, initiated by cytokines, growth factors, prostaglandins, and hormones. The degree of osteoresorption in CLL is associated with the severity of the clinical course, chemotherapy and hormonal deprivation. The osteoporosis pathogenesis in CLL is considered as part of a complex set of events, including, firstly, the interaction between leukemic cells (overexpression of PTHrP, RANKL) and bone cells (synthesis of growth factors), which forms a vicious circle of osteoresorption and tumor growth. Secondly, pro-inflammatory markers in CLL (tumor necrosis factor α, interleukin (IL) 1β, IL-6, IL-8, IL-11, granulocyte-macrophage colony-stimulating factor, macrophage colony-stimulating factor, transforming growth factor β, prostaglandin E2) limit osteoblast-induced osteosynthesis and stimulate the expansion of osteoclasts from monocytic suppressor cells of myeloid origin with or without the participation of the RANKL/RANK system. Thirdly, oxidative stress in CLL and impaired efficiency of antioxidant protection with the participation of fibroblast growth factor 23, transcription factor Nrf-2 with activation of JNK, ERK1/2, NF-κB, and also an increase in the RANKL/OPG ratio lead to inhibition of osteoblastogenesis. Conclusion. Analyzing and systematizing data on the osteoporosis pathogenesis in CLL are instrumental for the development of diagnostic criteria for osteoporosis in chronic lymphocytic leukemia that are much-needed in clinical practice and for the improvement of therapeutic tactics.