Antibiotic treatment as sole management of Helicobacter pylori-negative gastric MALT lymphoma: a single center experience with prolonged follow-up.

Relatively little is known about the long-term outcome of patients with Helicobacter pylori (HP)-negative gastric lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) with antibiotic therapy as sole management. We have analyzed all patients with HP-negative gastric MALT lymphoma undergoing antibiotic therapy as sole management of their disease. HP negativity was defined as negative histology, breath test and serology, and response to treatment, survival and long-term outcome was assessed together with clinico-pathological characteristics including t(11; 18) (q21; q21) translocation. Out of 97 patients with gastric MALT lymphoma, 24 were HP-negative, and 13 (5 females and 8 males) underwent only antibiotic management for initial therapy. Eight had stage I and five were found to have stage II disease, with three patients suffering from an underlying autoimmune disease. Antibiotic therapy consisted of standard HP eradication regimens consisting of clarithromycin in all patients, along with metronidazole in seven and amoxicillin in six plus a proton-pump inhibitor. After a median follow-up of 95 months (42-, 181+), 12/13 patients are alive. Six patients with stage I disease achieved an objective response (five complete (CR) and one partial remission, 46 %), four had stable disease (lasting 11-27 months), and three progressed. All patients with stable disease received chemotherapy, but only one patient due to clear cut progression. One patient relapsed 23 months after initial CR, and achieved a second CR with antibiotics now lasting 87 months. These results indicate that a relevant percentage of patients with HP-negative gastric MALT lymphoma may benefit from antibiotic therapy and do not require additional oncological therapies. Our data suggest that the remissions seen in these patients might be durable as evidenced by prolonged follow-up in our series.

High-throughput analysis of single hematopoietic stem cell proliferation in microfluidic cell culture arrays.

Heterogeneity in cell populations poses a major obstacle to understanding complex biological processes. Here we present a microfluidic platform containing thousands of nanoliter-scale chambers suitable for live-cell imaging studies of clonal cultures of nonadherent cells with precise control of the conditions, capabilities for in situ immunostaining and recovery of viable cells. We show that this platform mimics conventional cultures in reproducing the responses of various types of primitive mouse hematopoietic cells with retention of their functional properties, as demonstrated by subsequent in vitro and in vivo (transplantation) assays of recovered cells. The automated medium exchange of this system made it possible to define when Steel factor stimulation is first required by adult hematopoietic stem cells in vitro as the point of exit from quiescence. This technology will offer many new avenues to interrogate otherwise inaccessible mechanisms governing mammalian cell growth and fate decisions.

Clofarabine/cyclophosphamide for debulking before stem cell transplantation.

BACKGROUND: Allogeneic haematopoietic stem cell transplantation (HSCT) is the only curative rescue therapy for patients (pts) with chemotherapy-refractory acute leukaemia. Disease control prior to HSCT is essential for long-term disease-free survival after HSCT. PATIENTS AND METHODS: We have retrospectively analysed the outcome of 20 pts aged 21-64 years with refractory leukaemia (acute myeloid leukaemia, n = 16; acute lymphatic leukaemia, n = 4) who received debulking therapy with clofarabine (10 mg/m², days 1-4) and cyclophosphamide (200 mg/m², days 1-4; ClofCy) prior to HSCT. RESULTS: Clofarabine/cyclophosphamide (1-4 cycles) was well tolerated and resulted in a substantial reduction of leukaemic cells in all pts. HSCT was performed in 15 of 20 pts. After HSCT (myeloablative, n = 9; dose-reduced, n = 6), all pts showed engraftment and full donor chimerism (related donors, n = 4 or unrelated donors, n = 11) and all pts achieved complete haematologic remission (CR). The median survival after HSCT is 531 days (range: 48-1462 days), and six pts are still alive after a median of 1245 days. Seven pts died after they had relapsed between days +152 and +1496. One patient died from acute graft-versus-host disease (day +48) and one from systemic fungal infection (day +87). CONCLUSION: Clofarabine/cyclophosphamide is a novel effective treatment approach for pts with chemotherapy-refractory acute leukaemia prior to HSCT. Whether this novel debulking protocol leads to improved long-term outcome in pts with refractory leukaemias remains to be determined in forthcoming clinical studies.

Retrospective comparison of the effectiveness of various treatment modalities of extragastric MALT lymphoma: a single-center analysis.

We have performed a retrospective analysis of all patients with extragastric mucosa-associated lymphoid tissue (MALT) lymphoma treated at our institution to compare the efficacy of first-line therapeutic modalities including surgery, radiation, systemic therapy, and antibiotics. One hundred eighty-five patients with extragastric MALT lymphoma with a median age of 63 (interquartile range (IQR) 50-74) years and a median follow-up time of 49 (IQR 18-103) months were retrospectively analyzed. Time to progression and time to next therapy were used as surrogate endpoints for efficacy. Patients having either surgery (100 %), chemo/immunotherapy (85.5 %), or radiation (80 %) had significantly (p = 0.01) higher response rates than patients treated with antibiotics (33.3 %). Patients who were irradiated had significantly more progressive disease, but also the longest follow-up time. Stage, elevated LDH, anemia, elevated beta-2 microglobulin, plasmacytic differentiation, monoclonal gammopathy, or autoimmune disease did not influence the rate of disease progression nor did complete remission or partial remission from initial therapy influence time to and rate of progression. There was no significant difference in the median time to progression (p = 0.141), but the estimated time to progression (p = 0.023) as well as the estimated time to next therapy (p = 0.021) was significantly different among the various cohorts favoring surgery, chemo/immunotherapy, and radiation. Our results suggest extragastric MALT lymphoma as a potential systemic disease irrespective of initial stage. Radiation, surgery, and chemo/immunotherapy seem to be equally effective in achieving remissions and prolonged progression free survivals, but a curative potential is questionable. Localized MALT lymphomas affecting the thyroid gland or the lungs have excellent long-term progression-free survivals with surgical treatment only.

Fatal skin and pulmonary infection caused by Hormographiella aspergillata in a leukaemic patient: case report and literature overview.

Invasive systemic fungal infections are a major cause of morbidity and mortality in patients after hematopoietic stem cell transplantation. We report the case of a fatal infection with Hormographiella aspergillata in a patient undergoing allogenic peripheral blood stem cell transplantation for acute myeloid leukaemia.

Improved outcome in patients with chronic myelogenous leukemia after allogeneic hematopoietic stem cell transplantation over the past 25 years: a single-center experience.

Although imatinib has become standard first-line therapy in chronic myelogenous leukemia (CML), allogeneic hematopoietic stem cell transplantation (HSCT) is still considered to be an important treatment alternative for patients with drug resistance or advanced disease. We retrospectively analyzed 175 adult CML patients who underwent HSCT at our institution between 1983 and 2007, with the aim to compare outcomes in patient subgroups and to identify prognostic variables. The median follow-up was 65 months. The probability of overall survival (OS) for all patients was 62%, with a significant improvement seen in the imatinib-era (2001-2007) compared to previous time periods (P <.05). Furthermore, a significantly better outcome for patients with chronic phase CML compared to patients with accelerated or blast phase could be observed (P < .05). Cumulative incidence (CI) of treatment-related mortality (TRM) was 9.7% at 100 days and 1 year after HSCT. CI of relapse was 5% at 1 year and 7.5% at 3 years after HSCT. Post-HSCT outcome was not influenced by pretreatment therapy with imatinib, donor type, or a conditioning regimen with total body irradiation (TBI). These data confirm earlier observations and suggest that allogeneic HSCT is still an important treatment option for high-risk patients with CML, and should thus remain an integral component in current and future treatment algorithms.

Prospective isolation and molecular characterization of hematopoietic stem cells with durable self-renewal potential.

Hematopoietic stem cells (HSCs) are generally defined by their dual properties of pluripotency and extensive self-renewal capacity. However, a lack of experimental clarity as to what constitutes extensive self-renewal capacity coupled with an absence of methods to prospectively isolate long-term repopulating cells with defined self-renewal activities has made it difficult to identify the essential components of the self-renewal machinery and investigate their regulation. We now show that cells capable of repopulating irradiated congenic hosts for 4 months and producing clones of cells that can be serially transplanted are selectively and highly enriched in the CD150(+) subset of the EPCR(+)CD48(-)CD45(+) fraction of mouse fetal liver and adult bone marrow cells. In contrast, cells that repopulate primary hosts for the same period but show more limited self-renewal activity are enriched in the CD150(-) subset. Comparative transcriptome analyses of these 2 subsets with each other and with HSCs whose self-renewal activity has been rapidly extinguished in vitro revealed 3 new genes (VWF, Rhob, Pld3) whose elevated expression is a consistent and selective feature of the long-term repopulating cells with durable self-renewal capacity. These findings establish the identity of a phenotypically and molecularly distinct class of pluripotent hematopoietic cells with lifelong self-renewal capacity.

Ubiquitous expression of the monomeric red fluorescent protein mCherry in transgenic mice.

The use of the green fluorescent protein (GFP) to label specific cell types and track gene expression in animal models, such as mice, has evolved to become an essential tool in biological research. Transgenic animals expressing genes of interest linked to GFP, either as a fusion protein or transcribed from an internal ribosomal entry site (IRES) are widely used. Enhanced GFP (eGFP) is the most common form of GFP used for such applications. However, a red fluorescent protein (RFP) would be highly desirable for use in dual-labeling applications with GFP derived fluorescent proteins, and for deep in vivo imaging of tissues. Recently, a new generation of monomeric (m)RFPs, such as monomeric (m)Cherry, has been developed that are potentially useful experimentally. mCherry exhibits brighter fluorescence, matures more rapidly, has a higher tolerance for N-terminal fusion proteins, and is more photostable compared with its predecessor mRFP1. mRFP1 itself was the first true monomer derived from its ancestor DsRed, an obligate tetramer in vivo. Here, we report the successful generation of a transgenic mouse line expressing mCherry as a fluorescent marker, driven by the ubiquitin-C promoter. mCherry is expressed in almost all tissues analyzed including pre- and post-implantation stage embryos, and white blood cells. No expression was detected in erythrocytes and thrombocytes. Importantly, we did not encounter any changes in normal development, general physiology, or reproduction. mCherry is spectrally and genetically distinct from eGFP and, therefore, serves as an excellent red fluorescent marker alone or in combination with eGFP for labelling transgenic animals.

Correction to: Ruxolitinib therapy formyelofibrosis in Austria : Consensus on therapy management.

Correction to:Wien Klin Wochenschr 2018 https://doi.org/10.1007/s00508-018-1365-5 The original version of this article unfortunately contained a mistake. Table Nr. 1 was inconsistent. The corrected version of Table 1 is given below. We apologize for any inconveniences this may have ….

Ruxolitinib therapy for myelofibrosis in Austria : Consensus on therapy management.

The oral Janus associated kinase (JAK1/2) inhibitor ruxolitinib has been available for treatment of patients with intermediate or high-risk myelofibrosis in Europe since 2012. Since its introduction, the expertise of prescribing doctors with respect to ruxolitinib function, efficacy and adverse effects has consistently been augmented, resulting in therapy modalities that are better tailored to individual patients as well as in increased safety of the treatment. The present consensus on ruxolitinib therapy management has been elaborated by Austrian experts in myeloproliferative neoplasms in line with international treatment guidelines. Our recommendations aim to contribute to an improved management of patients with myelofibrosis treated with ruxolitinib.

Reverse transcription-PCR for t(11;18)(q21;q21) staging and monitoring in mucosa-associated lymphoid tissue lymphoma.

PURPOSE: Subclinical dissemination as well as persistence after therapy may be difficult to assess on clinical and histologic examinations in patients with mucosa-associated lymphoid tissue (MALT) lymphoma. We have analyzed the use of reverse transcription-PCR (RT-PCR) for the detection of t(11;18)(q21;q21) in histologically infiltrated and normal biopsies at diagnosis and during follow-up to determine its clinical and prognostic effect. EXPERIMENTAL DESIGN: Twenty-one patients with t(11;18)(q21;q21)+ MALT lymphoma were included in this retrospective study. Presence of t(11;18)(q21;q21) was determined by RT-PCR done on 316 biopsies of various tissues obtained during staging and follow-up. RESULTS: Infiltration with lymphoma was histologically detected in 67 of 316 biopsies, whereas molecular infiltration was established in 104 of 316 biopsies. All histologically positive specimens were also positive in RT-PCR. There was a good concordance (P = 0.0001) between histology and RT-PCR at the time of disease presentation with only one further infiltration site identified by RT-PCR. In 8 of 12 patients with persistent lymphoma, RT-PCR revealed tumor infiltration in histologically unsuspected sites. Eight of nine treated patients with histologic and clinical complete remission (CR) remained RT-PCR positive. CR on RT-PCR was achieved later than histologic CR (between 13-59 months) without any further therapy in five of these eight patients; only one patient with persistent t(11;18)(q21;q21) relapsed histologically. CONCLUSIONS: This study shows the potential of RT-PCR for t(11;18)(q21;q21) done on routine paraffin-embedded specimens to identify disseminated disease in tissues otherwise not diagnostic of MALT lymphoma involvement. T(11;18)(q21;q21) persistence in patients with clinical and histologic CR does not necessarily require therapeutic intervention.

Austrian recommendations for the management of primary myelofibrosis, post-polycythemia vera myelofibrosis and post-essential thrombocythemia myelofibrosis: an expert statement.

The entity "myelofibrosis" represents a subgroup of the Philadelphia chromosome-negative myeloproliferative neoplasms. It comprises primary myelofibrosis, post-polycythemia vera myelofibrosis and post-essential thrombocythemia myelofibrosis. This heterogeneous disease is characterized by clonal myeloproliferation, dysregulated kinase signalling and the abnormal expression of several proinflammatory cytokines. Clinically, patients present with symptoms related to thrombocytosis/leukocytosis, anemia and/or progressive splenomegaly. Mutations in Janus kinase 2, an enzyme that is essential for the normal development of erythrocytes, granulocytes, and platelets, notably the V617F mutation, have been identified in approximately 60% of patients with primary myelofibrosis. Recent molecular advances have not only elucidated critical pathways in the pathogenesis of the disease, but also contributed to a more precise assessment of a patient's individual risk. While allogeneic stem cell transplantation remains the only curative treatment, the natural course of the disease and the patient's survival and quality of life may be improved by new treatments, notably ruxolitinib, the first Janus kinase 1/2 inhibitor approved for the management of myelofibrosis. Additional treatment options are being explored.

Phase II study of oxaliplatin for treatment of patients with mucosa-associated lymphoid tissue lymphoma.

PURPOSE: Various chemotherapeutic regimens have been applied for treatment of mucosa-associated lymphoid tissue (MALT) lymphoma, but no standard regimen has been identified to date. In view of the activity of oxaliplatin (L-OHP) in various types of lymphoma, we performed a phase II study to evaluate the activity of L-OHP for treatment of MALT lymphoma. The primary objective of this study was to determine the objective response rate according to WHO standard criteria. PATIENTS AND METHODS: A total of 16 patients with MALT lymphoma of various sites of origin (four of the ocular adnexa, five of the salivary glands, three of the stomach, two of the lung, and one of the colon and the breast) were administered L-OHP at a dose of 130 mg/m2 infused during 2 hours every 3 weeks. Restaging was performed every two cycles; treatment was continued until complete remission (CR) or for a maximum of six cycles in responders. RESULTS: Sixty-five cycles were administered (median, four; range, two to six); toxicity consisted of transient sensory neuropathy in eight patients and nausea/emesis WHO grade 2 in two patients, whereas hematologic adverse effects (thrombocytopenia and leukocytopenia grade 2) occurred in only one patient each. Fifteen patients responded to chemotherapy, with nine achieving CR (56%), six (37.5%) achieving partial response, and one achieving stable disease; the median time to response was 4 months (range; 2 to 4 months). CONCLUSION: These data suggest L-OHP is a highly active agent for treatment of MALT lymphoma. However, a longer follow-up is needed to judge whether these remissions are durable.

Frequency of chromosomal aberrations involving MALT1 in mucosa-associated lymphoid tissue lymphoma in patients with Sjögren's syndrome.

PURPOSE: Mucosa-associated lymphoid tissue (MALT) lymphoma develops in the context of longstanding antigenic stimulation such as infection with Helicobacter pylori or autoimmune disease, including Sjögren's syndrome (SS). Recently, two chromosomal aberrations involving the MALT1 gene, i.e., t(11;18)(q21;q21) and t(14;18)(q32;q21) have been reported as genetic events specific for MALT lymphoma. In view of the association between SS and the development of MALT lymphoma, we have analyzed the frequency of t(11;18)(q21;q21) and t(14;18)(q32;q21) in patients with MALT lymphomas arising in the background of SS. EXPERIMENTAL DESIGN: A retrospective analysis of patients diagnosed with MALT lymphoma and SS was performed. The t(11;18)(q21;q21) was analyzed using reverse transcriptase-PCR, whereas t(14;18)(q32;q21) was assessed by two-color interphase fluorescence in situ hybridization. RESULTS: Twenty-six patients (20 female and 6 male) with MALT lymphoma and SS could be identified. The lymphoma was located in the parotid (n = 14), orbit (n = 2), and submandibular gland (n = 1), whereas 9 patients had gastric MALT lymphoma. Seven of 26 patients (27%) harbored t(11;18)(q21;q21). Interestingly, only 1 of 17 patients (6%) with extragastrointestinal lymphoma was positive, as opposed to 6 of 9 patients (67%) with gastric MALT lymphoma. Four of 26 patients were positive for t(14;18)(q32;q21): 3 of 17 extragastrointestinal (18%) and 1 of 9 gastric lymphomas (11%). CONCLUSIONS: The overall frequency of MALT1 rearrangement appears to be low in patients with extragastrointestinal MALT lymphoma associated with SS. By contrast, MALT1 rearrangement was demonstrated in 7 of 9 patients (78%) with gastric MALT lymphoma and SS. This finding may explain at least in part why gastric MALT lymphomas in patients with SS are refractory to H. pylori eradication therapy.

Monoclonal immunoglobulin production is a frequent event in patients with mucosa-associated lymphoid tissue lymphoma.

PURPOSE: Mucosa-associated lymphoid tissue (MALT) lymphoma comprises 7% of all newly diagnosed non-Hodgkin's lymphomas and is therefore among the most common lymphoma entities. Monoclonal gammopathy due to production of a monoclonal immunoglobulin by lymphoma cells is a well-known phenomenon associated with various types of B-cell non-Hodgkin's lymphomas. The objective of the present study was to evaluate the incidence and clinical relevance of paraprotein (PP) production in patients with MALT lymphoma. EXPERIMENTAL DESIGN: Fifty two patients were prospectively evaluated with regard to differentiation of the MALT lymphoma cells, t(11;18) translocation, monoclonal immunoglobulin production, Helicobacter pylori (HP) status, stage, treatment, and clinical outcome. RESULTS: Nineteen of 52 MALT lymphoma patients (36%) had PP (8 IgMkappa, 6 IgGkappa, 4 IgMlambda, and 1 IgAkappa). The histologic feature of plasmacytic differentiation correlated significantly with the production of PP (P = 0.001). No correlation was found between PP and clinical stage, HP status, and t(11;18) status. PP was, however, negatively associated with response to eradication of HP in gastric MALT lymphoma, and PP levels declined significantly in patients responding to chemotherapy or radiation. Importantly, both immunofixation and serum electrophoresis have to be performed to detect low PP levels. CONCLUSIONS: In conclusion, PP levels may probably be used as a potential prognostic tool for response to HP eradication, and serial measurements may also allow for noninvasive assessment of response to radiation or chemotherapy in patients with MALT lymphoma.

Effective treatment of primary plasma cell leukemia with thalidomide and dexamethasone - a case report.

Plasma cell leukemia (PCL) is an aggressive disease with poor prognosis and a median survival of only 2-6 months. Currently, no standard therapy is available, but intensive polychemotherapy appears to be more effective than the conventional melphalan plus prednisone. However, the efficacy of thalidomide in PCL has not yet been widely evaluated. Recently, treatment with thalidomide has been reported to yield promising results in refractory multiple myeloma. Here, we report on a patient with primary PCL in whom first-line treatment with thalidomide/dexamethasone resulted in a rapid response and achievement of a very good partial remission.

Clinical features, treatment and outcome of mucosa-associated lymphoid tissue (MALT) lymphoma of the ocular adnexa: single center experience of 60 patients.

BACKGROUND: Orbital marginal zone B-cell lymphoma (OAML) constitutes for the most frequent diagnosis in orbital lymphoma. Relatively little data, however, have been reported in larger cohorts of patients staged in a uniform way and no therapy standard exists to date. MATERIAL AND METHODS: We have retrospectively analyzed 60 patients diagnosed and treated at our institution 1999-2012. Median age at diagnosis was 64 years (IQR 51-75) and follow-up time 43 months (IQR 16-92). All patients had undergone uniform extensive staging and histological diagnosis was made by a reference pathologist according to the WHO classification. RESULTS: The majority of patients presented with stage IE (n = 40/60, 67%), three had IIE/IIIE and the remaining 17 stage IVE. Seven patients with IVE had bilateral orbital disease whereas the others showed involvement of further organs. Treatment data were available in 58 patients. Local treatment with radiotherapy (14/58, 24%) or surgery (3/58, 5%) resulted in response in 82% of patients. A total of 26 patients (45%) received systemic treatment with a response rate of 85%. Nine patients received antibiotics as initial therapy; response rate was 38%. Watchful-waiting was the initial approach in 6/58 patients. In total 28/58 patients (48%) progressed and were given further therapy. Median time-to-progression in this cohort was 20 months (IQR 9-39). There was no difference in time-to-progression after first-line therapy between the different therapy arms (p = 0.14). Elevated beta-2-microglobulin, plasmacytic differentiation, autoimmune disorder and site of lymphoma were not associated with a higher risk for progress. CONCLUSION: Our data underscore the excellent prognosis of OAML irrespective of initial therapy, as there was no significant difference in time-to-progression and response between local or systemic therapy. In the absence of randomized trials, the least toxic individual approach should be chosen for OAML.

Distinct stromal cell factor combinations can separately control hematopoietic stem cell survival, proliferation, and self-renewal.

Hematopoietic stem cells (HSCs) are identified by their ability to sustain prolonged blood cell production in vivo, although recent evidence suggests that durable self-renewal (DSR) is shared by HSC subtypes with distinct self-perpetuating differentiation programs. Net expansions of DSR-HSCs occur in vivo, but molecularly defined conditions that support similar responses in vitro are lacking. We hypothesized that this might require a combination of factors that differentially promote HSC viability, proliferation, and self-renewal. We now demonstrate that HSC survival and maintenance of DSR potential are variably supported by different Steel factor (SF)-containing cocktails with similar HSC-mitogenic activities. In addition, stromal cells produce other factors, including nerve growth factor and collagen 1, that can antagonize the apoptosis of initially quiescent adult HSCs and, in combination with SF and interleukin-11, produce >15-fold net expansions of DSR-HSCs ex vivo within 7 days. These findings point to the molecular basis of HSC control and expansion.

Heterogeneity of neoplastic stem cells: theoretical, functional, and clinical implications.

Accumulating evidence suggests that human cancers develop through a step-wise, but nonlinear process of cellular diversification and evolution. Recent mutational analyses indicate that this process is more complex and diverse than anticipated before whole-genome sequencing methods were readily available. Examples are also emerging now of genetically abnormal clones of cells that have acquired mutations with known oncogenic potential but, nevertheless, may show no manifestations of malignant change for many years. To accommodate these diverse realities, we suggest the term neoplastic refer to clones of cells that have any type of somatic aberrancy associated with an increased propensity to become malignant, and the derivative term neoplastic stem cell be adopted to identify the cells responsible for the long-term maintenance of such clones. Neoplastic clones would thus include those that never evolve further, as well as those that eventually give rise to fully malignant populations, and all stages in between. The term cancer stem cells would then be more appropriately restricted to cells generating subclones that have established malignant properties. More precise molecular understanding of the different stem cell states thus distinguished should contribute to the development of more effective prognostic and therapeutic tools for cancer diagnosis and treatment.

The Lin28b-let-7-Hmga2 axis determines the higher self-renewal potential of fetal haematopoietic stem cells.

Mouse haematopoietic stem cells (HSCs) undergo a postnatal transition in several properties, including a marked reduction in their self-renewal activity. We now show that the developmentally timed change in this key function of HSCs is associated with their decreased expression of Lin28b and an accompanying increase in their let-7 microRNA levels. Lentivirus-mediated overexpression of Lin28 in adult HSCs elevates their self-renewal activity in transplanted irradiated hosts, as does overexpression of Hmga2, a well-established let-7 target that is upregulated in fetal HSCs. Conversely, HSCs from fetal Hmga2(-/-) mice do not exhibit the heightened self-renewal activity that is characteristic of wild-type fetal HSCs. Interestingly, overexpression of Hmga2 in adult HSCs does not mimic the ability of elevated Lin28 to activate a fetal lymphoid differentiation program. Thus, Lin28b may act as a master regulator of developmentally timed changes in HSC programs with Hmga2 serving as its specific downstream modulator of HSC self-renewal potential.