Hmga2 promotes the development of myelofibrosis in Jak2V617F knockin mice by enhancing TGF-ß1 and Cxcl12 pathways.

Myelofibrosis (MF) is a devastating blood disorder. The JAK2V617F mutation has been detected in ∼50% cases of MF. Elevated expression of high-mobility group AT hook 2 (HMGA2) has also been frequently observed in patients with MF. Interestingly, upregulation of HMGA2 expression has been found in association with the JAK2V617F mutation in significant cases of MF. However, the contribution of HMGA2 in the pathogenesis of MF remains elusive. To determine the effects of concurrent expression of HMGA2 and JAK2V617F mutation in hematopoiesis, we transduced bone marrow cells from Jak2V617F knockin mice with lentivirus expressing Hmga2 and performed bone marrow transplantation. Expression of Hmga2 enhanced megakaryopoiesis, increased extramedullary hematopoiesis, and accelerated the development of MF in mice expressing Jak2V617F Mechanistically, the data show that expression of Hmga2 enhances the activation of transforming growth factor-ß1 (TGF-ß1) and Cxcl12 pathways in mice expressing Jak2V617F In addition, expression of Hmga2 causes upregulation of Fzd2, Ifi27l2a, and TGF-ß receptor 2. Forced expression of Cxcl12, Fzd2, or Ifi27l2a increases megakaryocytic differentiation and proliferation in the bone marrow of Jak2V617F mice, whereas TGF-ß1 or Cxcl12 stimulation induces collagen deposition in the bone marrow mesenchymal stromal cells. Together, these findings demonstrate that expression of Hmga2 cooperates with Jak2V617F in the pathogenesis of MF.

Loss of Ezh2 cooperates with Jak2V617F in the development of myelofibrosis in a mouse model of myeloproliferative neoplasm.

An activating JAK2V617F mutation has been found in ∼50% patients with myelofibrosis (MF). Inactivating mutations in histone methyltransferase enhancer of zeste homolog 2 (EZH2) also have been observed in patients with MF. Interestingly, inactivating EZH2 mutations are often associated with JAK2V617F mutation in MF, although their contributions in the pathogenesis of MF remain elusive. To determine the effects of concomitant loss of EZH2 and JAK2V617F mutation in hematopoiesis, we generated Ezh2-deficient Jak2V617F-expressing mice. Whereas expression of Jak2V617F alone induced a polycythemia vera-like disease, concomitant loss of Ezh2 significantly reduced the red blood cell and hematocrit parameters but increased the platelet counts in Jak2V617F knock-in mice. Flow cytometric analysis showed impairment of erythroid differentiation and expansion of megakaryocytic precursors in Ezh2-deficient Jak2V617F mice. Moreover, loss of Ezh2 enhanced the repopulation capacity of Jak2V617F-expressing hematopoietic stem cells. Histopathologic analysis revealed extensive fibrosis in the bone marrow (BM) and spleen of Ezh2-deleted Jak2V617F mice. Transplantation of BM from Ezh2-deleted Jak2V617F mice into wild-type animals resulted in even faster progression to MF. Gene expression profiling and chromatin immunoprecipitation sequence analysis revealed that S100a8, S100a9, Ifi27l2a, and Hmga2 were transcriptionally derepressed, and the H3K27me3 levels in these gene promoters were significantly reduced on Ezh2 deletion in hematopoietic progenitors of Jak2V617F mice. Furthermore, overexpression of S100a8, S100a9, Ifi27l2a, or Hmga2 significantly increased megakaryocytic colonies in the BM of Jak2V617F mice, indicating a role for these Ezh2 target genes in altered megakaryopoiesis involved in MF. Overall, our results suggest that loss of Ezh2 cooperates with Jak2V617F in the development of MF in Jak2V617F-expressing mice.

Crizotinib induces apoptosis and gene expression changes in ALK+ anaplastic large cell lymphoma cell lines; brentuximab synergizes and doxorubicin antagonizes.

BACKGROUND: Anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL) shows 60-70% event free survival with standard treatments. Targeted therapies are being tested for increased benefit and/or reduced toxicity, but interactions with standard agents are not well known. METHODS: We exposed four ALCL cell lines to two targeted agents, crizotinib and brentuximab vedotin, and to two standard agents, doxorubicin and vinblastine. For each agent and combination, we measured apoptosis and expression of approximately 300 previously annotated genes of interest using targeted RNA-sequencing. An aurora kinase inhibitor, alisertib, was similarly tested for gene expression effects. RESULTS: Only crizotinib, alone or in combination, showed significant effects (adjusted P < 0.05) on expression and apoptosis. One hundred and nine of 277 gene expressions showed crizotinib-associated differential expression, mostly downregulation, 62 associated with apoptosis, and 28 associated with both crizotinib and apoptosis. Doxorubicin was antagonistic with crizotinib on gene expression and apoptosis. Brentuximab was synergistic with crizotinib in apoptosis, and not antagonistic in gene expression. Vinblastine also appeared synergistic with crizotinib but did not achieve statistical significance. Alisertib did not show significant expression changes. CONCLUSIONS: Our data suggest that crizotinib induces apoptosis through orderly changes in cell signaling associated with ALK inhibition. Expression effects of crizotinib and associated apoptosis are antagonized by doxorubicin, but apoptosis is synergized by brentuximab vedotin and possibly vinblastine. These findings suggest that concurrent use of crizotinib and doxorubicin may be counterproductive, while the pairing of crizotinib with brentuximab (or vinblastine) may increase efficacy. Alisertib did not induce expression changes at cytotoxic dosage.

Variant histology, IgD and CD30 expression in low-risk pediatric nodular lymphocyte predominant Hodgkin lymphoma: A report from the Children's Oncology Group.

BACKGROUND: Histologic prognostic factors have been described for nodular lymphocyte predominant Hodgkin lymphoma (NLPHL). This study examines histologic and immunophenotypic variants in a clinical trial for pediatric NLPHL. PROCEDURE: One hundred sixty-eight cases of localized NLPHL were examined for histologic variants, CD30 and immunoglobulin D (IgD) expression, and outcome. Histologic types were scored categorically as 0 = 0, 1 ≤ 25%, and 2 > 25% of the sample. RESULTS: Fifty-eight (35.1%) cases showed only typical nodular with or without serpiginous histology (types A and B). The remainder showed mixtures of histologies. The numbers of patients with score 2 are 85 (50.6%) type A, 21 (12.5%) type B, 46 (27.4%) with extranodular large B cells (type C), 3 with T-cell-rich nodular pattern (type D), 55 (32.7%) with diffuse T-cell-rich (type E) pattern, and 2 (1.2%) with diffuse B-cell pattern (type F). Higher level of types C (P = 0.048) and D (P = 0.033) resulted in lower event-free survival (EFS). Cytoplasmic IgD was found in 65 of 130 tested (50%), did not significantly associate with EFS but positively correlated with types C and E histology (P < 0.0001) and negatively correlated with types A (P = 0.0003) and B (P = 0.006). Seventeen (10%) expressed CD30, with no adverse effect. CONCLUSIONS: Variant histology is common in pediatric NLPHL, especially types C and E, which are associated with IgD expression. Type C variant histology and possibly type D are associated with decreased EFS, but neither IgD nor CD30 are adverse features. Variant histology may warrant increased surveillance, but did not affect overall survival.

Childhood Hodgkin International Prognostic Score (CHIPS) Predicts event-free survival in Hodgkin Lymphoma: A Report from the Children's Oncology Group.

BACKGROUND: Early response to initial chemotherapy in Hodgkin lymphoma (HL) measured by computed tomography (CT) and/or positron emission tomography (PET) after two to three cycles of chemotherapy may inform therapeutic decisions. Risk stratification at diagnosis could, however, allow earlier and potentially more efficacious treatment modifications. PATIENTS AND METHODS: We developed a predictive model for event-free survival (EFS) in pediatric/adolescent HL using clinical data known at diagnosis from 1103 intermediate-risk HL patients treated on Children's Oncology Group protocol AHOD0031 with doxorubicin, bleomycin, vincristine, etoposide, prednisone, cyclophosphamide (ABVE-PC) chemotherapy and radiation. Independent predictors of EFS were identified and used to develop and validate a prognostic score (Childhood Hodgkin International Prognostic Score [CHIPS]). A training cohort was randomly selected to include approximately half of the overall cohort, with the remainder forming the validation cohort. RESULTS: Stage 4 disease, large mediastinal mass, albumin (<3.5), and fever were independent predictors of EFS that were each assigned one point in the CHIPS.  Four-year EFS was 93.1% for patients with CHIPS = 0, 88.5% for patients with CHIPS = 1, 77.6% for patients with CHIPS = 2, and 69.2% for patients with CHIPS = 3. CONCLUSIONS: CHIPS was highly predictive of EFS, identifying a subset (with CHIPS 2 or 3) that comprises 27% of intermediate-risk patients who have a 4-year EFS of <80% and who may benefit from early therapeutic augmentation.  Furthermore, CHIPS identified higher risk patients who were not identified by early PET or CT response. CHIPS is a robust and inexpensive approach to predicting risk in patients with intermediate-risk HL that may improve ability to tailor therapy to risk factors known at diagnosis.

Critical role of Jak2 in the maintenance and function of adult hematopoietic stem cells.

Jak2, a member of the Janus kinase family of nonreceptor protein tyrosine kinases, is activated in response to a variety of cytokines, and functions in survival and proliferation of cells. An activating JAK2V617F mutation has been found in most patients with myeloproliferative neoplasms, and patients treated with Jak2 inhibitors show significant hematopoietic toxicities. However, the role of Jak2 in adult hematopoietic stem cells (HSCs) has not been clearly elucidated. Using a conditional Jak2 knockout allele, we have found that Jak2 deletion results in rapid loss of HSCs/progenitors leading to bone marrow failure and early lethality in adult mice. Jak2 deficiency causes marked impairment in HSC function, and the mutant HSCs are severely defective in reconstituting hematopoiesis in recipient animals. Jak2 deficiency also causes significant apoptosis and loss of quiescence in HSC-enriched LSK (Lin(-)Sca-1(+)c-Kit(+)) cells. Jak2-deficient LSK cells exhibit elevated reactive oxygen species levels and enhanced p38 MAPK activation. Mutant LSK cells also show defective Stat5, Erk, and Akt activation in response to thrombopoietin and stem cell factor. Gene expression analysis reveals significant downregulation of genes related to HSC quiescence and self-renewal in Jak2-deficient LSK cells. These data suggest that Jak2 plays a critical role in the maintenance and function of adult HSCs.

A highly curable lymphoma occurs preferentially in the proximal tibia of young patients.

The presentation of two 19-year-old male subjects with stage I non-Hodgkin lymphoma in the proximal tibia prompted an extensive review of institutional and national databases to assess whether there is any statistical evidence that these reflected a previously overlooked syndromic pattern of presentation. The institutional records of a single institution were reviewed for presentation of non-Hodgkin lymphoma in the bone. The records of two additional institutions were reviewed for all reports of non-Hodgkin lymphoma in the tibia. Analysis was performed on data from Surveillance, Epidemiology, and End Results (SEER) dichotomized to bone presentation in the lower extremity versus other bones. Institutional databases included 20 patients with tibial presentation of lymphoma with a median age of 22.5 years (versus 42 for all bone lymphomas; P<0.001). Eighteen out of twenty patients had diffuse large B-cell lymphoma, and all patients aged ≤40 achieved remission and apparent cure. Distinctive and unusual features were a tendency for bilateral involvement of the tibia and sclerotic changes on X-ray. SEER data included 808 cases of bone lymphoma; the fraction of cases presenting in the lower extremity versus other bone sites is higher at ages ≤40 years (38% versus 19%; P<0.0001). Presentation in the lower extremity, as compared with other bone sites, confers 97% overall survival in patients aged ≤40 (versus 82%; P=0.01). This survival effect was independent of stage. In contrast, no significant difference in overall survival was identified for lower extremity versus non-lower extremity site for age >40. These data show a previously undescribed syndromic pattern of disease presentation: bone lymphoma in young patients is likely to present in the lower extremity-specifically the proximal tibia-has atypical sclerotic features on X-ray, is often bilateral, and has an excellent prognosis compared with bone lymphomas at other sites matched for stage and age.

Critical requirement for Stat5 in a mouse model of polycythemia vera.

The JAK2V617F mutation has been identified in most cases of Ph-negative myeloproliferative neoplasms (MPNs) including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Expression of JAK2V617F results in constitutive activation of multiple signaling molecules/pathways. However, the key signaling downstream of JAK2V617F required for transformation and induction of MPNs remains elusive. Using a mouse genetic strategy, we show here that Stat5 is absolutely required for the pathogenesis of PV induced by Jak2V617F. Whereas expression of Jak2V617F in mice resulted in all the features of human PV, including an increase in red blood cells, hemoglobin, hematocrit, white blood cells, platelets, and splenomegaly, deletion of Stat5 in the Jak2V617F knockin mice normalized all the blood parameters and the spleen size. Furthermore, deletion of Stat5 completely abrogated erythropoietin (Epo)-independent erythroid colony formation evoked by Jak2V617F, a hallmark feature of PV. Re-expression of Stat5 in Stat5-deficient Jak2V617F knockin mice completely rescued the defects in transformation of hematopoietic progenitors and the PV phenotype. Together, these results indicate a critical function for Stat5 in the pathogenesis of PV. These findings also provide strong support for the development of Stat5 inhibitors as targeted therapies for the treatment of PV and other JAK2V617F-positive MPNs.

Tyrosine 201 is required for constitutive activation of JAK2V617F and efficient induction of myeloproliferative disease in mice.

The JAK2V617F mutation has been detected in most cases of Ph-negative myeloproliferative neoplasms (MPNs). The JAK2V617F protein is a constitutively activated tyrosine kinase that leads to transformation of hematopoietic progenitors. Previous studies have shown that several tyrosine residues within JAK2 are phosphorylated on growth factor or cytokine stimulation. However, the role of these tyrosine residues in signaling and transformation mediated by JAK2V617F remains unclear. In this study, we sought to determine the role of tyrosine 201, which is a potential binding site for Src homology 2 domain-containing proteins, in JAK2V617F-induced hematopoietic transformation by introducing a tyrosine-to-phenylalanine point mutation (Y201F) at this site. We observed that the Y201F mutation significantly inhibited cytokine-independent cell growth and induced apoptosis in Ba/F3-EpoR cells expressing JAK2V617F. The Y201F mutation also resulted in significant inhibition of JAK2V617F-mediated transformation of hematopoietic cells. Biochemical analyzes revealed that the Y201F mutation almost completely inhibited constitutive phosphorylation/activation of JAK2V617F. We also show that the Y201 site of JAK2V617F promotes interaction with Stat5 and Shp2, and constitutive activation of downstream signaling pathways. Furthermore, using a BM transduction/transplantation approach, we found that tyrosine 201 plays an important role in the induction of MPNs mediated by JAK2V617F.

Efficacy of vorinostat in a murine model of polycythemia vera.

The discovery of the JAK2V617F mutation in most patients with Ph-negative myeloproliferative neoplasms has led to the development of JAK2 kinase inhibitors. However, JAK2 inhibitor therapy has shown limited efficacy and dose-limiting hematopoietic toxicities in clinical trials. In the present study, we describe the effects of vorinostat, a small-molecule inhibitor of histone deacetylase, against cells expressing JAK2V617F and in an animal model of polycythemia vera (PV). We found that vorinostat markedly inhibited proliferation and induced apoptosis in cells expressing JAK2V617F. In addition, vorinostat significantly inhibited JAK2V617F-expressing mouse and human PV hematopoietic progenitors. Biochemical analyses revealed significant inhibition of phosphorylation of JAK2, Stat5, Stat3, Akt, and Erk1/2 in vorinostat-treated, JAK2V617F-expressing human erythroleukemia (HEL) cells. Expression of JAK2V617F and several other genes, including GATA1, KLF1, FOG1, SCL, C/EPBα, PU.1, and NF-E2, was significantly down-regulated, whereas the expression of SOCS1 and SOCS3 was up-regulated by vorinostat treatment. More importantly, we observed that vorinostat treatment normalized the peripheral blood counts and markedly reduced splenomegaly in Jak2V617F knock-in mice compared with placebo treatment. Vorinostat treatment also decreased the mutant allele burden in mice. Our results suggest that vorinostat may have therapeutic potential for the treatment of PV and other JAK2V617F-associated myeloproliferative neoplasms.

Treating diabetes in underserved populations using an interprofessional care team.

Community Health Centers that provide diabetic care for underserved patients have unique challenges. This study describes how interprofessional care improves outcomes and results in cost savings. Interprofessional diabetes education and structured team building are discussed. The team consisted of a physician, nurse practitioner, clinical pharmacist, and a number of pre-medicinal, nursing, and pharmacy students. The outcomes were measured at one year intervals for a total of three years. During the two year period with the interprofessional care team, the diabetic patients in this study achieved a 10% improvement in HgA1c, and 9% improvement in systolic blood pressure, a 5% improvement in diastolic blood pressure, and a 62.6% reduction in triglycerides. These findings suggest that this interprofessional care model in a free clinic significantly improved the HgA1c, triglycerides, and blood pressure.

Effectiveness of high-dose methotrexate in T-cell lymphoblastic leukemia and advanced-stage lymphoblastic lymphoma: a randomized study by the Children's Oncology Group (POG 9404).

The Pediatric Oncology Group (POG) phase 3 trial 9404 was designed to determine the effectiveness of high-dose methotrexate (HDM) when added to multi-agent chemotherapy based on the Dana-Farber backbone. Children with T-cell acute lymphoblastic leukemia (T-ALL) or advanced lymphoblastic lymphoma (T-NHL) were randomized at diagnosis to receive/not receive HDM (5 g/m² as a 24-hour infusion) at weeks 4, 7, 10, and 13. Between 1996 and 2000, 436 patients were enrolled in the methotrexate randomization. Five-year and 10-year event-free survival (EFS) was 80.2% ± 2.8% and 78.1% ± 4.3% for HDM (n = 219) versus 73.6% ± 3.1% and 72.6% ± 5.0% for no HDM (n = 217; P = .17). For T-ALL, 5-year and 10-year EFS was significantly better with HDM (n = 148, 5 years: 79.5% ± 3.4%, 10 years: 77.3% ± 5.3%) versus no HDM (n = 151, 5 years: 67.5% ± 3.9%, 10 years: 66.0% ± 6.6%; P = .047). The difference in EFS between HDM and no HDM was not significant for T-NHL patients (n = 71, 5 years: 81.7% ± 4.9%, 10 years: 79.9% ± 7.5% vs n = 66, 5 years: 87.8% ± 4.2%, 10 years: 87.8% ± 6.4%; P = .38). The frequency of mucositis was significantly higher in patients treated with HDM (P = .003). The results support adding HDM to the treatment of children with T-ALL, but not with NHL, despite the increased risk of mucositis.

Opioid and benzodiazepine utilization patterns in metropolitan and rural Texas.

INTRODUCTION: Although many drugs are implicated in the crisis, opioids and concomitant sedatives are associated with increased overdose risk in both rural and urban communities. Individuals in rural areas are up to 5-fold more likely to experience adverse outcomes related to opioids. The primary objective of this study was to evaluate concomitant use of opioid and benzodiazepine prescriptions in Texas, compare metropolitan and rural differences, and use these data to inform clinicians and to help develop harm reduction strategies. METHODS: Prescribing data were extracted from the Texas Prescription Drug Monitoring Program (PDMP) public use data file, the statewide monitoring program administered by the Texas State Board of Pharmacy. An overlapping drug combination prescription day was defined as any day in which a patient had at least one of the overlapping drug types-eg, opioid + benzodiazepine, opioid + benzodiazepine + carisoprodol. RESULTS: In Texas, 47.4 percent of the counties with the highest number of overlapping days (per patient) bordered other states. Providers who practice in rural areas prescribe opioid and benzodiazepine medications with 8.2 more overlapping days per quarter. DISCUSSION: Taking both opioid and benzodiazepine prescriptions is associated with increased overdose risk. Opioid prescription data provide a distinct view into the opioid epidemic that allows all states and counties to view the trends of opioid utilization. There are only a few studies using PDMP data to compare urban and rural trends. CONCLUSIONS: Rural patients had more benzodiazepine and opioid days overlap than urban patients. The prevalence is higher among older adults and providers who practice in rural areas (average 8.2 more days per quarter). Our findings in Texas indicate a trend downward in overlap for both rural and urban areas over the last year of measurement. However, rural areas are still significantly higher.

Bacillus Calmette-Guérin vaccination as defense against SARS-CoV-2 (BADAS): a randomized controlled trial to protect healthcare workers in the USA by enhanced trained immune responses.

BACKGROUND: A large epidemic, such as that observed with SARS-CoV-2, seriously challenges available hospital capacity, and this would be augmented by infection of healthcare workers (HCW). Bacillus Calmette-Guérin (BCG) is a vaccine against tuberculosis, with protective non-specific effects against other respiratory tract infections in vitro and in vivo. Preliminary analyses suggest that regions of the world with existing BCG vaccination programs have lower incidence and mortality from COVID-19. We hypothesize that BCG vaccination can reduce SARS-CoV-2 infection and disease severity. METHODS: This will be a placebo-controlled adaptive multi-center randomized controlled trial. A total of 1800 individuals considered to be at high risk, including those with comorbidities (hypertension, diabetes, obesity, reactive airway disease, smokers), racial and ethnic minorities, elderly, teachers, police, restaurant wait-staff, delivery personnel, health care workers who are defined as personnel working in a healthcare setting, at a hospital, medical center or clinic (veterinary, dental, ophthalmology), and first responders (paramedics, firefighters, or law enforcement), will be randomly assigned to two treatment groups. The treatment groups will receive intradermal administration of BCG vaccine or placebo (saline) with groups at a 1:1 ratio. Individuals will be tracked for evidence of SARS-CoV-2 infection and severity as well as obtaining whole blood to track immunological markers, and a sub-study will include cognitive function and brain imaging. The majority of individuals will be followed for 6 months, with an option to extend for another 6 months, and the cognitive sub-study duration is 2 years. We will plot Kaplan-Meier curves that will be plotted comparing groups and hazard ratios and p-values reported using Cox proportional hazard models. DISCUSSION: It is expected this trial will allow evaluation of the effects of BCG vaccination at a population level in high-risk healthcare individuals through a mitigated clinical course of SARS-CoV-2 infection and inform policy making during the ongoing epidemic. TRIAL REGISTRATION: ClinicalTrials.gov NCT04348370. Registered on April 16, 2020.

Conditional expression of heterozygous or homozygous Jak2V617F from its endogenous promoter induces a polycythemia vera-like disease.

A somatic point mutation (V617F) in the JAK2 tyrosine kinase was found in a majority of patients with polycythemia vera (PV), essential thrombocythemia, and primary myelofibrosis. However, contribution of the JAK2V617F mutation in these 3 clinically distinct myeloproliferative neoplasms (MPNs) remained unclear. To investigate the role of JAK2V617F in the pathogenesis of these MPNs, we generated an inducible Jak2V617F knock-in mouse, in which the expression of Jak2V617F is under control of the endogenous Jak2 promoter. Expression of heterozygous mouse Jak2V617F evoked all major features of human polycythemia vera (PV), which included marked increase in hemoglobin and hematocrit, increased red blood cells, leukocytosis, thrombocytosis, splenomegaly, reduced serum erythropoietin (Epo) levels and Epo-independent erythroid colonies. Homozygous Jak2V617F expression also resulted in a PV-like disease associated with significantly greater reticulocytosis, leukocytosis, neutrophilia and thrombocytosis, marked expansion of erythroid progenitors and Epo-independent erythroid colonies, larger spleen size, and accelerated bone marrow fibrosis compared with heterozygous Jak2V617F expression. Biochemical analyses revealed Jak2V617F gene dosage-dependent activation of Stat5, Akt, and Erk signaling pathways. Our conditional Jak2V617F knock-in mice provide an excellent model that can be used to further understand the molecular pathogenesis of MPNs and to identify additional genetic events that cooperate with Jak2V617F in different MPNs.

Erythroid lineage-restricted expression of Jak2V617F is sufficient to induce a myeloproliferative disease in mice.

The JAK2V617F mutation has been found in most cases of Ph-negative myeloproliferative neoplasms. Recent studies have shown that expression of Jak2V617F in the hematopoietic compartment causes marked expansion of erythroid progenitors and their transformation to cytokine-independence. To determine if erythroid progenitors are the target cells for induction and propagation of Jak2V617F-evoked myeloproliferative neoplasm, we used a conditional Jak2V617F knock-in mouse and an erythroid-lineage specific EpoRCre line. Erythroid-specific expression of heterozygous or homozygous Jak2V617F resulted in a polycythemia-like phenotype characterized by increase in hematocrit and hemoglobin, increased red blood cells, erythropoietin-independent erythroid colonies and splenomegaly. Transplantation of Jak2V617F-expressing erythroid progenitors from the diseased mice into secondary recipients could not propagate the disease. Our results suggest that erythroid lineage-restricted expression of Jak2V617F is sufficient to induce a polycythemia-like disease in a gene-dose dependent manner. Jak2V617F mutation, however, does not confer leukemia stem cell-like properties to erythroid progenitors.

ALK+ anaplastic large cell lymphoma exhibits phosphatidylinositol-3 kinase/Akt activity with retained but inactivated PTEN--a report from the Children's Oncology Group.

BACKGROUND: ALK+ anaplastic large cell lymphoma (ALCL) is usually a disease of young patients. We investigated phosphatidylinositol-3 kinase (PI3K)/Akt pathway-associated factors in pediatric cases and cell lines. PROCEDURE: Patient materials consisted of tissue slides of ALK+/CD30+ ALCL from 33 patients treated on Pediatric Oncology Group protocols (9219, n = 8 and 9315, n = 25). Slides were examined by immunohistochemistry for phospho(p)-Akt and PTEN, the primary feedback regulator of the pathway, as well as for p27kip1 and stathmin-1. ALCL cell lines SUDHL-1 and Karpas-299 were examined for ALK, pALK, pAkt, p27/Kip1, PTEN, pPTEN, CD30, pSTAT3, and pSTAT5; ALK inhibition was performed using compound PF-2341066 and PTEN genes were sequenced. RESULTS: A majority of patients expressed pAkt, PTEN, and stathmin, with p27kip1 levels less than controls. Cell lines showed expression of ALK, pALK, pSTAT3, pSTAT5, CD30, pAkt, PTEN, and pPTEN, with p27 slightly less than positive controls, and germline PTEN DNA. There was evidence of phosphorylated PTEN (pPTEN) associated with inhibited function. Pharmacologic inhibition of activated ALK diminished pSTAT3, pSTAT5, and CD30 expression but not pAkt or pPTEN in cultured cell lines. CONCLUSION: We conclude that the PI3K/Akt pathway is activated in many, though not all, pediatric ALK+ ALCL. Our data suggest that activation of this pathway involves post-translational regulation of PTEN. Pharmacologic inhibition of activated ALK does not reduce modest levels of activated Akt as it does with the more abundant levels of activated STAT3 or STAT5. Future therapy of ALCL might, in selected patients, best combine agents inhibiting PI3K/Akt with those targeting ALK.