The proteasome inhibitor bortezomib may increase osteoblast-related markers in multiple myeloma (MM) patients; however, its potential osteoblastic stimulatory effect is not known. In this study, we show that bortezomib significantly induced a stimulatory effect on osteoblast markers in human mesenchymal cells without affecting the number of osteoblast progenitors in bone marrow cultures or the viability of mature osteoblasts. Consistently we found that bortezomib significantly increased the transcription factor Runx2/Cbfa1 activity in human osteoblast progenitors and osteoblasts without affecting nuclear and cytoplasmatic active ␤-catenin levels. IntroductionMultiple myeloma (MM) is a plasma cell malignancy characterized by the high capacity to induce osteolytic bone lesions. 1 Hystomorphometric studies showed that osteoblast formation and function are profoundly impaired in MM patients and critical in the bone lesion development. [1][2][3] Several mechanisms are involved in MMinduced osteoblast suppression 1,4,7 including the production of Wnt inhibitors as DKK-1 or sFRP-2 5,6 or the impairment of osteoblast formation and differentiation through the block of the critical osteoblast transcription factor Runx2/Cbfa1. 7 In turn, osteoblastic cells also regulate myeloma cell growth 8,9 and the increase of bone formation in mice results in a reduction of tumoral burden. 10 Recent data suggest that ubiquitin-proteasome pathway, which is the major cellular degradative system and therapeutic target in myeloma cells, 11 also regulates osteoblast differentiation. [12][13][14] The ubiquitin-proteasome pathway can modulate the BMP-2 expression, 12 which can induce osteoblast differentiation through the Wnt signaling 13 and regulates the proteolytic degradation of the osteoblast transcription factor Runx2/ Cbfa1. 14 Recently, Garrett et al 12 demonstrated that proteasome inhibitors as PS1 and epoximicin stimulate bone formation in neonatal murine calvarial bones and in vivo in mice. 12 A strong correlation between the capacity of these compounds to inhibit proteasomal activity in osteoblasts and their bone-forming activity was also demonstrated. 12 Preliminary observations obtained in MM patients treated with the proteasome inhibitor bortezomib show an increase of serum bone-specific alkaline phosphatase and other osteoblast related markers suggesting a potential osteoblast stimulatory effect of this drug. [15][16][17][18] Currently it is not known whether the proteasome inhibitor bortezomib may have a direct effect on osteoblast differentiation and formation in vitro in human cultures and in vivo in MM patients. Patients, materials, and methods DrugsBortezomib was purchased from Janssen-Cilag (Milan, Italy). For in vitro studies, the drug was reconstituted in DMSO at a stock concentration of 50 mM, and this stock was diluted in medium just before use, so that the concentration of DMSO never exceeded 0.1%. The proteasome inhibitors MG-132 and MG-262 were purchased from BIOMOL International (Plymouth Meeting, PA; DBA srl, M...

Several papers authored by international experts have proposed recommendations on the management of BCR-ABL1+ chronic myeloid leukemia (CML). Following these recommendations, survival of CML patients has become very close to normal. The next, ambitious, step is to bring as many patients as possible into a condition of treatment-free remission (TFR). The Gruppo Italiano Malattie EMatologiche dell’Adulto (GIMEMA; Italian Group for Hematologic Diseases of the Adult) CML Working Party (WP) has developed a project aimed at selecting the treatment policies that may increase the probability of TFR, taking into account 4 variables: the need for TFR, the tyrosine kinase inhibitors (TKIs), the characteristics of leukemia, and the patient. A Delphi-like method was used to reach a consensus among the representatives of 50 centers of the CML WP. A consensus was reached on the assessment of disease risk (EUTOS Long Term Survival [ELTS] score), on the definition of the most appropriate age boundaries for the choice of first-line treatment, on the choice of the TKI for first-line treatment, and on the definition of the responses that do not require a change of the TKI (BCR-ABL1 ≤10% at 3 months, ≤1% at 6 months, ≤0.1% at 12 months, ≤0.01% at 24 months), and of the responses that require a change of the TKI, when the goal is TFR (BCR-ABL1 >10% at 3 and 6 months, >1% at 12 months, and >0.1% at 24 months). These suggestions may help optimize the treatment strategy for TFR.

Careful evaluation of marrow plasmacytosis, urinary paraprotein, background immunoglobulins, ESR, and paraprotein isotype might help identify at presentation patients with benign monoclonal gammopathies requiring stricter monitoring.

Chronic myeloid leukemia (CML) patients in sustained “deep molecular response” may stop TKI treatment without disease recurrence; however, half of them lose molecular response shortly after TKI withdrawing. Well-defined eligibility criteria to predict a safe discontinuation up-front are still missing. Relapse is probably due to residual quiescent TKI-resistant leukemic stem cells (LSCs) supposedly transcriptionally low/silent and not easily detectable by BCR-ABL1 qRT-PCR. Bone marrow Ph+ CML CD34+/CD38− LSCs were found to specifically co-express CD26 (dipeptidylpeptidase-IV). We explored feasibility of detecting and quantifying CD26+ LSCs by flow cytometry in peripheral blood (PB). Over 400 CML patients (at diagnosis and during/after therapy) entered this cross-sectional study in which CD26 expression was evaluated by a standardized multiparametric flow cytometry analysis on PB CD45+/CD34+/CD38− stem cell population. All 120 CP-CML patients at diagnosis showed measurable PB CD26+ LSCs (median 19.20/μL, range 0.27–698.6). PB CD26+ LSCs were also detectable in 169/236 (71.6%) CP-CML patients in first-line TKI treatment (median 0.014 cells/μL; range 0.0012–0.66) and in 74/112 (66%), additional patients studied on treatment-free remission (TFR) (median 0.015/μL; range 0.006–0.76). Notably, no correlation between BCR-ABL/ABLIS ratio and number of residual LSCs was found both in patients on or off TKIs. This is the first evidence that “circulating” CML LSCs persist in the majority of CML patients in molecular response while on TKI treatment and even after TKI discontinuation. Prospective studies evaluating the dynamics of PB CD26+ LSCs during TKI treatment and the role of a “stem cell response” threshold to achieve and maintain TFR are ongoing.

Background After discontinuing ruxolitinib, the outcome of patients with myelofibrosis reportedly has been poor. The authors investigated whether disease characteristics before the receipt of ruxolitinib may predict drug discontinuation in patients with myelofibrosis and whether reasons for drug discontinuation, disease phase at discontinuation, and salvage therapies may influence the outcome. Methods A centralized electronic clinical database was created in 20 European hematology centers, including clinical and laboratory data for 524 patients who received ruxolitinib for myelofibrosis. Results At 3 years, 40.8% of patients had stopped ruxolitinib. Baseline predictors of drug discontinuation were: intermediate‐2–risk/high‐risk category (Dynamic International Prognostic Score System), a platelet count <100 ×109 per liter, transfusion dependency, and unfavorable karyotype. At last contact, 268 patients (51.1%) had discontinued therapy, and the median drug exposure was 17.5 months. Fifty patients (18.7%) died while taking ruxolitinib. The reasons for discontinuation in the remaining 218 patients were the lack (22.9%) or loss (11.9%) of a spleen response, ruxolitinib‐related adverse events (27.5%), progression to blast phase (23.4%), ruxolitinib‐unrelated adverse events (9.2%), and allogeneic transplantation during response (5.1%). The median survival after ruxolitinib was 13.2 months and was significantly better in the 167 patients who discontinued ruxolitinib in chronic phase (27.5 vs 3.9 months for those who discontinued in blast phase; P < .001). No survival differences were observed among patients who discontinued ruxolitinib in chronic phase because of lack of response, loss of response, or ruxolitinib‐related adverse events. The use of investigational agents and/or ruxolitinib rechallenge were associated with improved outcome. Conclusions The survival of patients with myelofibrosis after discontinuation of ruxolitinib is poor, particularly for those who discontinue in blast phase. Salvage therapies can improve outcome, emphasizing the need for novel therapies.