Procalcitonin elevation in febrile recipients during pre-transplant conditioning with anti-thymocyte globulin.

Infection is a major contributor to non-relapse mortality in allogeneic hematopoietic stem cell transplantation (allo-HSCT). Detecting infectious diseases in febrile patients during pretransplant conditioning is crucial for subsequent transplant success. Procalcitonin (PCT) is an auxiliary diagnostic marker of severe bacterial infections and has been proposed as a useful predictor of infection in patients undergoing allo-HSCT. Pre-transplant use of anti-thymocyte globulin (ATG) can cause side effects, such as fever and hypotension, which must be distinguished from infectious diseases. Although ATG administration may increase PCT levels, data on PCT levels in febrile patients after ATG administration are limited. Furthermore, no studies have compared PCT levels during allo-HSCT conditioning using ATG or non-ATG regimens. To investigate whether ATG increases PCT levels during febrile episodes in pre-transplant conditioning and whether PCT could be used to discriminate infections during this period, we analyzed 17 ATG and 59 non-ATG patients with fever and who underwent PCT level measurements during pre-transplant conditioning. Our findings revealed that ATG administration was the only significant factor that increased PCT positivity during fever (p = 0.01). In contrast, infectious diseases did not affect PCT positivity in the ATG group (p = 0.24). Furthermore, bloodstream infection was a significant risk factor for PCT positivity in patients who received non-ATG regimens (p < 0.01). Incorporating PCT levels into the diagnostic workup for infectious diseases requires careful consideration, particularly for patients receiving ATG regimens.

Successful Management of Total Plasma Exchange for Hemolytic Cold Agglutinin Disease.

Therapeutic plasma exchange (TPE) is a strategy for treating cold agglutinin disease (CAD) in order to manage hemolytic complications. However, there are no reports of hemolysis during TPE. A 41-year-old man with secondary CAD was unable to undergo initial TPE because of red blood cell agglutination and hemolysis in his extracorporeal circulation. To avoid low temperatures, the patient and extracorporeal circulation were kept warm by covering and heating them, and finally, he was able to successfully receive TPE three times. Although our approach still has room for improvement, our management protocol appears to be an effective treatment modality for such cases.

Outcomes of allogeneic stem cell transplantation for patients with hematologic diseases ≥60 years old.

Hematologic diseases frequently affect people >60 years old, and allogeneic stem cell transplantation (allo-SCT) is a potentially curative treatment for these patients. Although several multicenter studies proposed the risk assessment of allo-SCT for the elderly, they receive different treatments and management at each facility. Therefore, accumulating data from institutions that exhibit relatively the same treatment policy and patient care is important. This retrospective study aimed to clarify the prognostic factors of allo-SCT for the elderly in our institution. Of the 104 patients, 51.0% were 60-64 years old, and 49.0% were ≥65 years old. The 3-year overall survival (OS) was 40.9% and 35.7% for patients 60-64 and ≥65 years old, respectively, which is not significant. While the disease status prior to allo-SCT demonstrated strong effects on the 3-year OS for patients that are 60-64 years old (in remission, 76.9%; non-remission, 15.7%, p<0.001), this effect was smaller for patients ≥65 years old (in remission, 43.1%; non-remission, 30.1%, p=0.048). Multivariate analysis revealed that the performance status (PS), not the disease status prior to allo-SCT, was the prognostic risk factor of OS for patients aged ≥65 years. Our data suggest that PS is a useful predictor of better OS following allo-SCT, especially for patients ≥65 years old.

[Acute myeloid leukemia with type I CBFB::MYH11 fusion gene not detected by screening test for leukemia-related chimeric genes].

A 27-year-old woman with pancytopenia was admitted to our hospital. Bone marrow aspiration revealed 52.2% myeloperoxidase-positive myeloblasts, leading to a diagnosis of acute myeloid leukemia. While a screening test for chimeric genes related to leukemia initially yielded negative results, including for the CBFB::MYH11 fusion gene, G-banded karyotyping uncovered the presence of inv (16)(p13.1q22). Further investigation by fluorescence in situ hybridization (FISH) confirmed the split signals for CBFB. A second screening test for leukemia-related chimeric genes with different PCR primers revealed the elusive CBFB::MYH11 fusion gene. Subsequently, the type I CBFB::MYH11 fusion gene was identified through exhaustive exploration using RNA sequencing for fusion gene discovery. This exceptional case highlights the existence of a distinctive subtype of CBFB::MYH11 that may yield false-negative results in conventional chimeric fusion screening, thus emphasizing the indispensable utility of PCR primer modification, FISH, and RNA sequencing in the investigative process.

Panuveitis induced by donor-derived CD8+ T cells after allogeneic hematopoietic stem cell transplantation for adult T-cell leukemia.

Purpose: This article presents a case of panuveitis that occurred after unrelated allogeneic hematopoietic stem cell transplantation (allo-HSCT) in a patient with lymphoma-type human T-cell leukemia virus type-1 (HTLV-1)-associated adult T-cell leukemia (ATL). Observations: A 45-year-old man developed unilateral panuveitis 18 months after undergoing allo-HSCT. He underwent vitrectomy, and depositions of grey-white granules localized on the retinal artery were observed in the eye. Cytological examination of the vitreous aspirates showed that the atypical lymphoid cells stained positive for CD3 and CD8, but negative for CD4, B-cell markers, and cytomegalovirus antigen. Interphase fluorescence in situ hybridization using X- and Y-chromosome probes revealed complete donor chimerism in CD8+ T cells in the vitreous aspirates. Conclusions and importance: Donor-derived CD8+ T lymphocytes can induce panuveitis like HTLV-1-assiciated uveitis after allo-HSCT in patients with ATL. Pathological diagnosis of vitreous infiltration by vitrectomy is helpful in patients with ATL. Donor-derived CD8+ T lymphocytes-induced panuveitis is recurrent but susceptible to regional corticosteroid treatment.

Prognostic value of pre-transplantation total metabolic tumor volume on 18fluoro-2-deoxy-D-glucose positron emission tomography-computed tomography in relapsed and refractory aggressive lymphoma.

Relapsed and refractory aggressive lymphoma have a poor prognosis. High-dose chemotherapy followed by autologous hematopoietic stem cell transplantation (auto-HSCT) is effective in chemosensitive patients. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is among the few options for non-chemosensitive patients. 18Fluoro-2-deoxy-D-glucose positron emission tomography-computed tomography (18FDG-PET/CT) is the standard tool for evaluating response to chemotherapy and residual tumor volume. However, accurate assessment of residual tumor volume is not currently being achieved in clinical practice, and its value in prognostic and therapeutic stratification remains unclear. To answer this question, we investigated the efficacy of quantitative indicators, including total metabolic tumor volume (TMTV), in predicting prognosis after auto-HSCT and allo-HSCT. We retrospectively analyzed 39 patients who received auto-HSCT and 28 who received allo-HSCT. In the auto-HSCT group, patients with a higher TMTV had a poor prognosis due to greater risk of relapse. In the allo-HSCT group, patients with a higher TMTV had a lower progression-free survival rate and a significantly higher relapse rate. Neither Deauville score nor other clinical parameters were associated with prognosis in either group. Therefore, pre-transplant TMTV on PET is effective for prognostic prediction and therapeutic decision-making for relapsed or refractory aggressive lymphoma.

Risk factors for late cytomegalovirus infection after completing letermovir prophylaxis.

Prophylactic use of letermovir (LMV) markedly reduces the incidence of early clinically significant cytomegalovirus (csCMV) infection within the first 100 days after allogeneic hematopoietic cell transplantation (allo-HCT), which improves transplant outcomes. However, some patients eventually develop late-csCMV infection (beyond day 100) after completing LMV prophylaxis. To assess the incidence of late-csCMV infection as well as its risk factors and impacts on transplant outcome, a total of 81 allo-HCT recipients who had not developed early csCMV infection during LMV prophylaxis were retrospectively analyzed. Among them, 23 (28.4%) patients developed late-csCMV infection (until day 180) at a median time of 131 days after transplantation and 30 days after LMV discontinuation, respectively. Late-csCMV infection was correlated with apparent delayed immune reconstitution: patients transplanted from HLA-mismatched donors (hazard ratio [HR] = 13.0, p = 0.011) or CMV-IgG-negative donors (HR = 2.39, p = 0.043) had a significantly higher risk. In this study, transplant outcomes did not differ between patients with and without late-csCMV infection. This suggests a need to clarify the efficacy of extended administration of LMV for preventing late-csCMV infection in a larger number of allo-HCT recipients, especially those with "high-risk" donors.

C11orf21, a novel RUNX1 target gene, is down-regulated by RUNX1-ETO.

The fusion protein RUNX1-ETO is an oncogenic transcription factor generated by t(8;21) chromosome translocation, which is found in FAB-M2-type acute myeloid leukemia (AML). RUNX1-ETO is known to dysregulate the normal RUNX1 transcriptional network, which should involve essential factors for the onset of AML with t(8;21). In this study, we screened for possible transcriptional targets of RUNX1 by reanalysis of public data in silico, and identified C11orf21 as a novel RUNX1 target gene because its expression was down-regulated in the presence of RUNX1-ETO. The expression level of C11orf21 was low in AML patient samples with t(8;21) and in Kasumi-1 cells, which carry RUNX1-ETO. Knockdown of RUNX1-ETO in Kasumi-1 cells restored C11orf21 expression, whereas overexpression of RUNX1 up-regulated C11orf21 expression. In addition, knockdown of RUNX1 in other human leukemia cells without RUNX-ETO, such as K562, led to a decrease in C11orf21 expression. Of note, the C11orf21 promoter sequence contains a consensus sequence for RUNX1 binding and it was activated by exogenously expressed RUNX1 based on our luciferase reporter assay. This luciferase signal was trans-dominantly suppressed by RUNX1-ETO and site-directed mutagenesis of the consensus site abrogated the reporter activity. This study demonstrated that C11orf21 is a novel transcriptional target of RUNX1 and RUNX1-ETO suppressed C11orf21 transcription in t(8;21) AML. Thus, through this in silico approach, we identified a novel transcriptional target of RUNX1, and the depletion of C11orf21, the target gene, may be associated with the onset of t(8;21) AML.

Incidence of refractory cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation.

Post-transplant cytomegalovirus (CMV) disease can be almost completely avoided by current infection control procedures. However, CMV reactivation occurs in more than half of patients, and some patients can develop clinically resistant CMV infections. Whether resistance is due to the host's immune status or a viral resistance mutation is challenging to confirm. Therefore, a prospective observational analysis of refractory CMV infection was conducted in 199 consecutive patients who received allogeneic hematopoietic stem cell transplantation at a single institution. Among them, 143 (72%) patients received anti-CMV drugs due to CMV reactivation, and only 17 (8.5%) exhibited refractory CMV infection. These patients had clinically refractory infection. However, viral genome analysis revealed that only one patient exhibited a mutation associated with the anti-CMV drug resistance. Clinical resistance was mainly correlated with host immune factors, and the incidence of resistance caused by gene mutations was low at the early stage after a transplantation.

Platelet decrease and efficacy of platelet-rich plasma return following peripheral blood stem cell apheresis.

BACKGROUND: Peripheral blood stem cell (PBSC) transplantation is a key treatment option for hematological diseases and is widely performed in clinical practice. Platelet loss is one of the major complications of PBSC apheresis, and platelet-rich plasma (PRP) return is considered in case of platelet decrease following apheresis; however, little is known about the frequency and severity of platelet loss and the efficacy of PRP return postapheresis. METHODS: We assessed changes in platelet counts following PBSC-related apheresis in 270 allogeneic (allo)- and 105 autologous (auto)-PBSC settings. We also evaluated the efficacy of PRP transfusion on platelet recovery postapheresis. RESULTS: In both allo- and auto-PBSC settings, the preapheresis platelet count (range, 84-385 and 33-558 × 109 /L, respectively) decreased postapheresis (range, 57-292 and 20-429 × 109 /L, respectively), whereas severe platelet decrease (<50 × 109 /L) was only observed in auto-PBSC patients (n = 9). We confirmed that platelet count before apheresis was a risk factor for severe platelet decrease (<50 × 109 /L) following auto-PBSC apheresis (odds ratio 0.749, P < .049). PRP return postapheresis facilitated platelet recovery in more than 80% of cases in both allo and auto settings. CONCLUSION: Lower platelet count preapheresis is a useful predictor of severe platelet decrease following auto-PBSC apheresis and PRP return is an effective process to facilitate platelet recovery postapheresis.

Tyrosine kinase inhibitors induce alternative spliced BCR-ABLIns35bp variant via inhibition of RNA polymerase II on genomic BCR-ABL.

To elucidate dynamic changes in native BCR-ABL and alternatively spliced tyrosine kinase inhibitor (TKI)-resistant but function-dead BCR-ABLIns35bp variant, following commencement or discontinuation of TKI therapy, each transcript was serially quantified in patients with chronic myeloid leukemia (CML) by deep sequencing. Because both transcripts were amplified together using conventional PCR system for measuring International Scale (IS), deep sequencing method was used for quantifying such BCR-ABL variants. At the initial diagnosis, 7 of 9 patients presented a small fraction of cells possessing BCR-ABLIns35bp , accounting for 0.8% of the total IS BCR-ABL, corresponding to actual BCR-ABLIns35bp value of 1.1539% IS. TKI rapidly decreased native BCR-ABL but not BCR-ABLIns35bp , leading to the initial increase in the proportion of BCR-ABLIns35bp . Thereafter, both native BCR-ABL and BCR-ABLIns35bp gradually decreased in the course of TKI treatment, whereas small populations positive for TKI-resistant BCR-ABLIns35bp continued fluctuating at low levels, possibly underestimating the molecular response (MR). Following TKI discontinuation, sequencing analysis of 54 patients revealed a rapid relapse, apparently derived from native BCR-ABL+ clones. However, IS fluctuating at low levels around MR4.0 marked a predominant persistence of cells expressing function-dead BCR-ABLIns35bp , suggesting that TKI resumption was unnecessary. We clarified the possible mechanism underlying mis-splicing BCR-ABLIns35bp , occurring at the particular pseudo-splice site within intron8, which can be augmented by TKI treatment through inhibition of RNA polymerase II phosphorylation. No mutations were found in spliceosomal genes. Therefore, monitoring IS functional BCR-ABL extracting BCR-ABLIns35bp would lead us to a correct evaluation of MR status, thus determining the adequate therapeutic intervention.

Aromatase is a novel neosubstrate of cereblon responsible for immunomodulatory drug-induced thrombocytopenia.

Immunomodulatory drugs (IMiDs) are key agents for the treatment of multiple myeloma and myelodysplastic syndrome with chromosome 5q deletion. IMiDs exert their pleiotropic effects through the recruitment of neosubstrates to cereblon, a substrate receptor of the E3 ubiquitin ligase complex; therefore, identification of cell-specific neosubstrates is important to understand the effects of IMiDs. In clinical practice, IMiDs induce thrombocytopenia, which frequently results in the discontinuation of IMiD treatment. In the current study, we sought to identify the molecular mechanism underlying thrombocytopenia induced by IMiD treatment. We found that IMiDs strongly impaired proplatelet formation, a critical step in functional platelet production, through the inhibition of autocrine estradiol signaling in human megakaryocytes. Furthermore, we identified aromatase, an indispensable enzyme for estradiol biosynthesis, as a novel neosubstrate of cereblon. IMiDs promoted the recruitment of aromatase to cereblon, resulting in the degradation of aromatase in a proteasome-dependent manner. Finally, aromatase was significantly degraded in the bone marrow of patients with multiple myeloma who developed thrombocytopenia with IMiD treatment. These data suggest that aromatase is a neosubstrate of cereblon that is responsible for IMiD-induced thrombocytopenia.

Hippo kinase loss contributes to del(20q) hematologic malignancies through chronic innate immune activation.

Heterozygous deletions within chromosome 20q, or del(20q), are frequent cytogenetic abnormalities detected in hematologic malignancies. To date, identification of genes in the del(20q) common deleted region that contribute to disease development have remained elusive. Through assessment of patient gene expression, we have identified STK4 (encoding Hippo kinase MST1) as a 20q gene that is downregulated below haploinsufficient amounts in myelodysplastic syndrome (MDS) and myeloproliferative neoplasm (MPN). Hematopoietic-specific gene inactivation in mice revealed Hippo kinase loss to induce splenomegaly, thrombocytopenia, megakaryocytic dysplasia, and a propensity for chronic granulocytosis; phenotypes that closely resemble those observed in patients harboring del(20q). In a JAK2-V617F model, heterozygous Hippo kinase inactivation led to accelerated development of lethal myelofibrosis, recapitulating adverse MPN disease progression and revealing a novel genetic interaction between these 2 molecular events. Quantitative serum protein profiling showed that myelofibrotic transformation in mice was associated with cooperative effects of JAK2-V617F and Hippo kinase inactivation on innate immune-associated proinflammatory cytokine production, including IL-1ß and IL-6. Mechanistically, MST1 interacted with IRAK1, and shRNA-mediated knockdown was sufficient to increase IRAK1-dependent innate immune activation of NF-κB in human myeloid cells. Consistent with this, treatment with a small molecule IRAK1/4 inhibitor rescued the aberrantly elevated IL-1ß production in the JAK2-V617F MPN model. This study identified Hippo kinase MST1 (STK4) as having a central role in the biology of del(20q)-associated hematologic malignancies and revealed a novel molecular basis of adverse MPN progression that may be therapeutically exploitable via IRAK1 inhibition.

Anti-GPRC5D/CD3 Bispecific T-Cell-Redirecting Antibody for the Treatment of Multiple Myeloma.

Although treatment advances over recent decades have significantly improved survival of patients with multiple myeloma, there is still an unmet medical need for more effective treatments. In this study, we identified G-protein-coupled receptor family C group 5 member D (GPRC5D) expression on the surface of malignant cells involved in multiple myeloma, but except for plasma cells and B cells, not at appreciable levels on normal hematopoietic cells and bone marrow progenitors, including hematopoietic stem cells. In addition, we constructed IgG-based anti-GPRC5D/CD3 bispecific T-cell-redirecting antibodies (GPRC5D TRAB), which suppressed the tumor growth of GPRC5D-positive myeloma cells through the activation of T cells in vitro and in vivo in xenograft models. Collectively, these findings suggest that GPRC5D is an antigen specific to multiple myeloma and a potential target of TRAB therapy.

Comparative Quantification of Chemotherapy-Induced Nausea and Emesis between the Common Terminology Criteria for Adverse Events and the Multinational Association of Supportive Care in Cancer Antiemesis Tool.

Chemotherapy-induced nausea and vomiting (CINV) are generally evaluated according to the Common Terminology Criteria for Adverse Events (CTCAE). The Multinational Association for Supportive Care in Cancer (MASCC) developed the MASCC Antiemesis Tool (MAT) to facilitate recognition for CINV between patients and oncology specialists. In the present study, MAT and CTCAE were comparatively assessed in Japanese patients with hematological malignancies. A total of 61 patients were eligible for this study. The CTCAE data were collected from an electronic medical record system. The patients were asked to complete the Japanese version of MAT in the hospital, on the first and fourth days after the start of chemotherapy. The percentages of patients in whom nausea was completely controlled, with severity scores of zero, ranged from 70.5 to 82.0% for CTCAE and from 59.0 to 75.4% for MAT, during the first five days after the chemotherapy. The percentages of patients who had no vomiting ranged from 93.4 to 96.7% for CTCAE and from 90.2 to 98.4% for MAT. During the observation periods, the day-to-day response profiles of patients who received antiemetic treatment were comparable between CTCAE and MAT cohorts, and these two assessment tools showed good, positive correlations for nausea severity scores. The present study shows that the MAT is a useful tool for assessing the severity of CINV in patients with hematological malignancy, is comparable to CTCAE, and facilitates the identification of poor cancer care conditions by medical staff.

Human Herpes Virus-6-Associated Encephalitis/Myelitis Mimicking Calcineurin Inhibitor-Induced Pain Syndrome in Allogeneic Stem Cell Transplantation Recipients.

Human herpes virus-6 (HHV6)-associated myelitis and calcineurin inhibitor-induced pain syndrome (CIPS) are serious complications of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Because these 2 complications cause similar sensory nerve-related symptoms, such as paresthesia, pruritus, and severe pain occurring around the engraftment, it can be difficult to differentially diagnose the 2 conditions. We retrospectively analyzed 435 recipients to distinguish clinical symptoms of these 2 complications. Twenty-four patients (5.5%) developed HHV6-associated encephalitis/myelitis; of these, 11 (2.5%) presented only with myelitis-related symptoms (HHV6-associated myelitis), which was confirmed by the detection of HHV6 DNA, and 8 (1.8%) had CIPS, with undetected HHV6 DNA. All patients with HHV6-associated myelitis or CIPS exhibited similar sensory nerve-related symptoms. Diagnostic images did not provide definite evidence specific for each disease. Symptoms of all patients with CIPS improved after switching to another immunosuppressant. Overall survival rate at 2 years for patients with HHV6-associated encephalitis/myelitis was significantly lower than that of CIPS (13.1% versus 29.2%; P = .049) or that of patients without HHV6-associated encephalitis/myelitis or CIPS (42.4%; P = .036), whereas there was no significant difference among the latter 2 groups (P = .889). The development of HHV6-associated encephalitis/myelitis but not CIPS was significantly associated with poor prognosis. Thus, transplant physicians should be aware that sensory nerve-related symptoms indicate early manifestations that might be correlated with reactivation of HHV6 or CIPS. Therefore, identification of HHV6 DNA is crucial for making a differential diagnosis and immediately starting appropriate treatments for each complication.

Gastrointestinal Graft-versus-Host Disease Is a Risk Factor for Postengraftment Bloodstream Infection in Allogeneic Hematopoietic Stem Cell Transplant Recipients.

Bloodstream infection (BSI) is a well-known cause of morbidity and mortality in allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients. Here, we conducted a retrospective study to assess the morbidity, etiology, risk factors, and outcomes of BSI in the postengraftment period (PE-BSI) after allo-HSCT. Forty-three of 316 patients (13.6%) developed 57 PE-BSI episodes, in which 62 pathogens were isolated: Gram-positive bacteria, gram-negative bacteria, and fungi, respectively, accounted for 54.8%, 35.5%, and 9.7% of the isolates. Multivariate analysis revealed methylprednisolone use for graft-versus-host disease (GVHD) prophylaxis (odds ratio [OR], 6.49; 95% confidence interval [CI], 1.49 to 28.2; P = .013) and acute gastrointestinal GVHD (GI-GVHD) (OR, 8.82; 95% CI, 3.99 to 19.5; P < .0001) as risk factors for developing PE-BSI. This finding suggested that GI-GVHD increases the risk of bacterial translocation and subsequent septicemia. Moreover, among patients with GI-GVHD, insufficient response to corticosteroids, presumably related to an intestinal dysbiosis, significantly correlated with this complication. Patients with PE-BSI presented worse outcome compared with those without (3-year overall survival, 47.0% versus 18.6%; P < .001). Close microbiologic monitoring for BSIs and minimizing intestinal dysbiosis may be crucial to break the vicious cycle between GI-GVHD and bacteremia and to improve transplant outcomes especially in patients who require additional immunosuppressants.

Expansion of NKG2C-expressing Natural Killer Cells after Umbilical Cord Blood Transplantation in a Patient with Peripheral T-cell Lymphoma with Cytotoxic Molecules.

A 64-year-old woman presented with generalized lymphadenopathy and systemic manifestations. The examination of a biopsy specimen revealed peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) expressing cytotoxic molecules. Umbilical cord blood transplantation was successful during a partial remission state after the administration of salvage chemotherapy. The donor-derived large granular lymphocytes started to increase as a result of cytomegalovirus reactivation. The fraction of natural killer (NK) cells expressing the NKG2C molecule accounted for one-third of the total lymphocytes for almost two years. We implicitly indicate the association between the persistence of donor-derived NKG2C+ NK cell-expansion and maintaining a complete remission in similar cases of aggressive PTCL-NOS.

Mobilization of human immature hematopoietic progenitors through combinatory use of bortezomib and immunomodulatory drugs.

Combination use of the proteasome inhibitor bortezomib and the immunomodulatory drugs lenalidomide or thalidomide has provided superior outcomes in multiple myeloma over their single use; however, these combinations can produce significant toxicities. Unexpectedly, we found a small but significant increase in the population of immature granulocytes and erythrocytes/megakaryocytes in peripheral blood in 16 of 22 patients (73%) treated with dexamethasone in combination with bortezomib and immunomodulatory drugs (triplet), but not in any of 25 patients treated with either bortezomib or immunomodulatory drugs with dexamethasone (doublet). These immature cells gradually increased to a peak level (mean 2.6% per white blood cells) with triplet therapy, and disappeared immediately after therapy cessation. The numbers of circulating CD34+ cells and colony-forming cells derived from peripheral blood mononuclear cells increased after triplet therapy compared with those in patients treated by either bortezomib or immunomodulatory drugs plus dexamethasone. Furthermore, triplet regimen downregulated the expression of CXCR4, a chemokine receptor essential for bone marrow retention, on CD34+ cells, suggesting an unexpected effect on normal hematopoietic stem/progenitor cells through the reduced interaction with the bone marrow microenvironment. Our observations suggest that combination use should be carefully evaluated to exert synergistic anti-myeloma effects while avoiding unexpected adverse events.