Altered bone metabolism has been reported in patients with chronic myeloid leukemia treated with the tyrosine kinase inhibitor imatinib. Several studies have shown that imatinib inhibits the differentiation and activity of osteoclasts in vitro, whereas the effects of imatinib on osteoblast differentiation are less clear. In this study osteoblast differentiation was induced in human mesenchymal stem cells (hMSCs) by treatment with bone morphogenetic protein 2 in vitro. Imatinib inhibited proliferation of hMSCs in a dose-dependent manner. Even though imatinib promoted early osteoblast differentiation assessed by alkaline phosphate activity, mineralization measured by Alizarin Red staining (ARS) was reduced by imatinib. Moreover, the inhibitory effect of imatinib on mineralization was most prominent at low concentrations of imatinib. When we measured the relative mRNA expression levels of Runx2, we found that Runx2 expression was higher in imatinib-treated (5 μM) cultures at early time points during differentiation. On the other hand, the expression of Osterix late during differentiation was lower in imatinib-treated (5 μM) cultures, corresponding to the ARS results. Thus, the effect of imatinib on osteoblast differentiation is not only dependent on the drug concentration, but indeed also on the maturation stage of the cells. This finding might partly explain why previous studies on the effects of imatinib osteoblast differentiation have shown different results.

Imatinib is currently the standard treatment for chronic myeloid leukemia(CML). Previous studies have shown that imatinib affects bone metabolism in CML patients. However, these effects are not well-studied prospectively. The authors studied bone-mineral density (BMD) and bone metabolism in 17 CML patients and matched controls in 2007 and now repeated the analyses prospectively in 2011. All CML patients were in complete cytogenetic remission during this 4-year period and treated with 400 mg imatinib q.d. (n 5 15) or 600 mg imatinib q.d. (n 5 2). Mean treatment duration was 102 months (range 69–129) in 2011. The authors found that serum levels of parathyroid hormone increased significantly in the patients between 2007 and 2011, and seven out of 17 patients had secondary hyperparathyroidism in 2011. However, the mean areal and volumetric BMDs were stable in the CML patients over the 4-year-observation period. Moreover, the CML patients had significantly higher volumetric BMD in the cortical compartment when compared with controls in 2011 and 2007. Thus, despite a high incidence of secondary hyperparathyroidism,there were no signs of osteoporosis or osteomalacia in imatinib-treated CML patients as suggested earlier.

Previous studies have suggested that adherence to imatinib therapy can be an obstacle among patients with chronic myeloid leukemia (CML). We studied adherence to imatinib therapy among CML patients treated at the Sahlgrenska University Hospital. We identified all CML patients that were alive at the 1st of January 2010 (n = 70). Nineteen patients were excluded due to a history of allogenic hematopoietic stem cell transplantation, and nine were excluded due to treatment with other tyrosine kinase inhibitors. Thirty-eight out of 42 patients (90%) treated with imatinib accepted inclusion in the study. The patients were interviewed in a structured way, and adherence was evaluated in a standardized way using the nine-item Morisky Medication Adherence Scale that ranges from 1 to 13. A Morisky score ≤10 indicates nonadherence and ≥11 indicates adherence. In addition, predefined follow-up questions were asked to identify factors known to influence adherence to therapy. In contrast to previous studies, our patients showed good adherence to imatinib therapy with a mean Morisky score of 12.3 out of 13 (range, 9–13). The interviews revealed factors known to predict adherence to therapy, namely being well informed and having frequent contact with a single hematologist. Furthermore, the patients had easy access to the treating clinic and felt that they took part in decisions concerning their disease and treatment. We show that adherence to imatinib can be very good in CML patients, and we suggest that simple measures such as increased patient information and continuity of care will increase adherence in patients with CML.

In chronic myeloid leukemia (CML) treatment response is determined by measurements of BCR-AB1L transcripts in peripheral blood by quantitative real-time PCR (qRT-PCR) and a 2-5 fold increase is considered a warning sign. The BCR-ABL1 gene is mainly expressed in myeloid cells whereas quantification of BCR-ABL1 is performed on the nucleated cell fraction of peripheral blood. Hence, leukocyte composition of the nucleated cell fraction may affect the result of BCR-ABL1 quantification. The aim of this study was to investigate if changes in leukocyte composition of peripheral blood had any effect on BCR-ABL1 transcript levels in CML patients. Six CML patients in complete cytogenetic remission (CCgR) performed a maximal physical exercise test. Blood samples were collected before exercise, at maximal exhaustion and after exercise. A biphasic increase in leukocyte count was observed and the relative proportion of granulocytes in peripheral blood changed significantly after exercise compared with baseline (p < 0.001). The BCR-ABL1 transcript level increased significantly following exercise, in nucleated cell fraction of peripheral blood (p < 0.05) but not in isolated granulocytes. In the nucleated cell fraction, the mean BCR-ABL1 transcript level was 3.3-fold (range 0.7-6.8) higher 180 min after exercise compared with baseline (p < 0.01). In conclusion, physical exercise induced significant increases in BCR-ABL1 transcript levels concomitant with changes in leukocyte content of peripheral blood. We therefore suggest that variations in leukocyte composition of peripheral blood, causing pre-analytic variations that affect BCR-ABL1 quantification, have to be accounted for. Consequently, small variations in BCR-ABL1 transcript levels should be interpreted cautiously in CML patients in CCgR.

The TLR9 agonist CpG-oligodeoxynucleotide (CpG-ODN) with a phosphorothioate backbone (PTO-CpG-ODN) is evaluated in clinical trials as a vaccine adjuvant or as treatment of cancers. Bone morphogenetic proteins (BMPs) regulate growth and differentiation of several cell types, and also induce apoptosis of cancer cells. Cross-talk between BMP- and TLR-signaling has been reported, and we aimed to investigate whether CpG-ODN influenced BMP- induced osteoblast differentiation or BMP- induced apoptosis of malignant plasma cells. We found that PTO-CpG-ODN inhibited BMP-2-induced osteoblast differentiation from human mesenchymal stem cells. Further, PTO-CpG-ODN counteracted BMP-2- and BMP-6-induced apoptosis of the human myeloma cell lines IH-1 and INA-6, respectively. In contrast, PTO-CpG-ODN did not antagonize the antiproliferative effect of BMP- 2 on hMSCs or IH-1 cells. Inhibition of Smad-signaling and p38 MAPK-signaling indicated that apoptosis of IH-1 cells is dependent on Smad-signaling downstream of BMP, whereas the antiproliferative effect of BMP- 2 on IH-1 cells also involves p38 MAPK-signaling. Together, the data suggested a specific inhibition by PTO-CpG-ODN on BMP-Smad-signaling. Supporting this we found that PTO-CpG-ODN inhibited BMP- induced phosphorylation of receptor-Smads in human mesenchymal stem cells and myeloma cell lines. This effect appeared to be independent of TLR9 because GpC-ODN and other ODNs with the ability to form multimeric structures inhibited Smad-signaling as efficiently as PTO-CpG-ODNs, and because knockdown of TLR9 by small interfering RNA in INA-6 cells did not blunt the effect of PTO-CpG-ODN. In conclusion, our results demonstrate that PTO-CpGODN inhibits BMP- signaling, and thus might provoke unwanted TLR9-independent side effects in patients. The Journal of Immunology, 2010, 185: 3131-3139.