Autologous Hematopoetic Stem Cell Transplantation for Refractory Crohn Disease: A Randomized Clinical Trial

IMPORTANCE

Case reports and series suggest hematopoietic stem cell transplantation (HSCT) may benefit some patients with Crohn disease.

OBJECTIVE

To evaluate the effect of autologous HSCT on refractory Crohn disease.

DESIGN, SETTING, AND PARTICIPANTS

Parallel-group randomized clinical trial conducted in 11 European transplant units from July 2007 to September 2011, with follow-up through March 2013. Patients were aged 18 to 50 years with impaired quality of life from refractory Crohn disease not amenable to surgery despite treatment with 3 or more immunosuppressive or biologic agents and corticosteroids.

INTERVENTIONS

All patients underwent stem cell mobilization before 1:1 randomization to immunoablation and HSCT (n = 23) or control treatment (HSCT deferred for 1 year [n = 22]). All were given standard Crohn disease treatment as needed.

MAIN OUTCOMES AND MEASURES

Sustained disease remission at 1 year, a composite primary end point comprising clinical remission (Crohn Disease Activity Index (CDAI) <150 [range, 0-600]), no use of corticosteroids or immunosuppressive or biologic drugs for at least the last 3 months, and no endoscopic or radiological evidence of active (erosive) disease anywhere in the gastrointestinal (GI) tract. Secondary outcomes were individual components of the primary composite outcome and other measures of disease activity, laboratory results, quality of life and functional status, and GI tract imaging.

RESULTS

Twenty-three patients underwent HSCT and 22 received standard Crohn disease treatment (controls). Sustained disease remission was achieved in 2 patients undergoing HSCT (8.7%) vs 1 control patient (4.5%) (absolute difference, 4.2% [95% CI, -14.2% to 22.6%]; P = .60). Fourteen patients undergoing HSCT (61%) vs 5 control patients (23%) had discontinued immunosuppressive or biologic agents or corticosteroids for at least 3 months (difference, 38.1% [95% CI, 9.3% to 59.3%]; P = .01). Ten vs 2 patients had a CDAI less than 150 (remission) at the final evaluation, 8 (34.8%) vs 2 (9.1%) for 3 or more months (difference, 25.7% [95% CI, 1.1% to 47.1%]; P = .052). Eight (34.8%) vs 2 (9.1%) patients were adjudicated free of active disease on endoscopy and radiology at final assessment (difference, 25.7% [95% CI, 1.1% to 47.1%]; P = .054). There were 76 serious adverse events in patients undergoing HSCT vs 38 in controls. One patient undergoing HSCT died.

CONCLUSIONS AND RELEVANCE

Among adult patients with refractory Crohn disease not amenable to surgery who had impaired quality of life, HSCT, compared with conventional therapy, did not result in a statistically significant improvement in sustained disease remission at 1 year and was associated with significant toxicity. These findings do not support the widespread use of HSCT for patients with refractory Crohn disease.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00297193.

New insights into hematopoietic stem cell transplantation for chronic lymphocytic leukemia: a 2015 perspective

A considerable body of evidence demonstrates that allogeneic hematopoietic stem cell transplantation (HSCT) offers the only potentially curative treatment option for patients with chronic lymphocytic leukemia (CLL). However, this approach is suitable for only a minority of CLL patients, owing to its significant treatment-related mortality and morbidity. Until recently, internationally accepted guidelines suggested that HSCT should be considered in physically fit CLL patients who carry poor-risk features, such as TP53 abnormalities, or who had a short response to previous immunochemotherapy. However, several new agents and alternative treatment strategies are available that demonstrate impressive and durable responses, even in CLL patients who previously might have been candidates for transplant. The decision about which patients merit HSCT therefore remains important, and HSCT must now be considered in light of other less toxic therapies. Until data on the long-term efficacy of novel treatment approaches mature, the choice of HSCT vs alternative strategies must be assessed on a patient-by-patient basis, and treatment in the setting of randomized clinical trials should be pursued whenever possible.

Targeting dysfunctional myeloid cells delays disease development and improves immune function in a CLL mouse model (TUM6P.1009)

Previous in vitro studies have shown that myeloid cells play a key role in apoptosis-resistance in chronic lymphocytic leukemia (CLL). However, their composition and function have not been thoroughly investigated in vivo. Using the Eµ-TCL1 mouse model of CLL, we observed severe skewing of myeloid cell populations along with CLL development. Monocytes and M2-like macrophages infiltrated the peritoneal cavity of leukemic mice. Monocytes expressing high levels of inflammatory factors like IL-10, TNFα and CXCL9 accumulated also in the spleen, the main site of disease, and were severely skewed towards Ly6Clow phenotype. Along with that, the percentage of MHC-IIhi dendritic cells (DCs) and macrophages significantly dropped in the spleen, suggesting monocyte differentiation arrest. Myeloid cell depletion using liposomal clodronate resulted in a significant control of CLL development, repair of innate immune cell phenotypes and partial resolution of systemic inflammation. Also, CLL-induced loss of naive T cells was resolved. CLL-associated monocytes and DCs aberrantly express high PD-L1 levels suggesting their contribution in T cell defects. Importantly, PD-L1 blockade very effectively prevented CLL development and was accompanied with a re-activation of immune effector cells. This included restoration of mature macrophages and MHC-IIhi DCs. Our preclinical data suggests that targeting myeloid cell survival and immunosuppression can serve as a novel strategy for CLL immunotherapy.

Practices in prescribing protein substitutes for PKU in Europe: No uniformity of approach

BACKGROUND

There appears little consensus concerning protein requirements in phenylketonuria (PKU).

METHODS

A questionnaire completed by 63 European and Turkish IMD centres from 18 countries collected data on prescribed total protein intake (natural/intact protein and phenylalanine-free protein substitute [PS]) by age, administration frequency and method, monitoring, and type of protein substitute. Data were analysed by European region using descriptive statistics.

RESULTS

The amount of total protein (from PS and natural/intact protein) varied according to the European region. Higher median amounts of total protein were prescribed in infants and children in Northern Europe (n=24 centres) (infants <1 year, >2-3g/kg/day; 1-3 years of age, >2-3 g/kg/day; 4-10 years of age, >1.5-2.5 g/kg/day) and Southern Europe (n=10 centres) (infants <1 year, 2.5 g/kg/day, 1-3 years of age, 2 g/kg/day; 4-10 years of age, 1.5-2 g/kg/day), than by Eastern Europe (n=4 centres) (infants <1 year, 2.5 g/kg/day, 1-3 years of age, >2-2.5 g/kg/day; 4-10 years of age, >1.5-2 g/kg/day) and with Western Europe (n=25 centres) giving the least (infants <1 year, >2-2.5 g/kg/day, 1-3 years of age, 1.5-2 g/kg/day; 4-10 years of age, 1-1.5 g/kg/day). Total protein prescription was similar in patients aged >10 years (1-1.5 g/kg/day) and maternal patients (1-1.5 g/kg/day).

CONCLUSIONS

The amounts of total protein prescribed varied between European countries and appeared to be influenced by geographical region. In PKU, all gave higher than the recommended 2007 WHO/FAO/UNU safe levels of protein intake for the general population.

Managing high-risk CLL during transition to a new treatment era: stem cell transplantation or novel agents?

Allogeneic hematopoietic stem cell transplantation (HSCT) has been considered as the treatment of choice for patients with high-risk chronic lymphocytic leukemia (HR-CLL; ie, refractory to purine analogs, short response [<24 months] to chemoimmunotherapy, and/or presence of del[17p]/TP53 mutations). Currently, treatment algorithms for HR-CLL are being challenged by the introduction of novel classes of drugs. Among them, BCR signal inhibitors (BCRi) and B-cell lymphoma 2 antagonists (BCL2a) appear particularly promising. As a result of the growing body of favorable outcome data reported for BCRi/BCL2a, uncertainty is emerging on how to advise patients with HR-CLL about indication for and timing of HSCT. This article provides an overview of currently available evidence and theoretical considerations to guide this difficult decision process. Until the risks and benefits of different treatment strategies are settled, all patients with HR-CLL should be considered for treatment with BCRi/BCL2a. For patients who respond to these agents, there are 2 treatment possibilities: (1) performing an HSCT or (2) continuing treatment with the novel drug. Individual disease-specific and transplant-related risk factors, along with patient's preferences, should be taken into account when recommending one of these treatments over the other.

Transplantation in chronic lymphocytic leukemia: does it still matter in the era of novel targeted therapies?

Allogeneic stem cell transplantation (HSCT) offers the only potentially curative approach in chronic lymphocytic leukemia (CLL). However, this applies only to a minority of patients, and is associated with significant treatment-related mortality and morbidity. HSCT must therefore always be considered in view of other, potentially less toxic therapies. Several new agents demonstrate impressive and durable responses in high-risk patients who might be candidates for HSCT. Therefore the choice of HSCT versus a novel agent is one that must be gauged on a patient-by-patient basis; this will change as data mature on the use of these novel agents in CLL.

The reliability of immunohistochemical analysis of the tumor microenvironment in follicular lymphoma: a validation study from the Lunenburg Lymphoma Biomarker Consortium

The cellular microenvironment in follicular lymphoma is of biological and clinical importance. Studies on the clinical significance of non-malignant cell populations have generated conflicting results, which may partly be influenced by poor reproducibility in immunohistochemical marker quantification. In this study, the reproducibility of manual scoring and automated microscopy based on a tissue microarray of 25 follicular lymphomas as compared to flow cytometry is evaluated. The agreement between manual scoring and flow cytometry was moderate for CD3, low for CD4, and moderate to high for CD8, with some laboratories scoring closer to the flow cytometry results. Agreement in manual quantification across the 7 laboratories was low to moderate for CD3, CD4, CD8 and FOXP3 frequencies, moderate for CD21, low for MIB1 and CD68, and high for CD10. Manual scoring of the architectural distribution resulted in moderate agreement for CD3, CD4 and CD8, and low agreement for FOXP3 and CD68. Comparing manual scoring to automated microscopy demonstrated that manual scoring increased the variability in the low and high frequency interval with some laboratories showing a better agreement with automated scores. Manual scoring reliably identified rare architectural patterns of T-cell infiltrates. Automated microscopy analyses for T-cell markers by two different instruments were highly reproducible and provided acceptable agreement with flow cytometry. These validation results provide explanations for the heterogeneous findings on the prognostic value of the microenvironment in follicular lymphoma. We recommend a more objective measurement, such as computer-assisted scoring, in future studies of the prognostic impact of microenvironment in follicular lymphoma patients.

A niche-like culture system allowing the maintenance of primary human acute myeloid leukemia-initiating cells: a new tool to decipher their chemoresistance and self-renewal mechanisms

Acute myeloid leukemia-initiating cells (LICs) are responsible for the emergence of leukemia and relapse after chemotherapy. Despite their identification more than 15 years ago, our understanding of the mechanisms responsible for their self-renewal activity and their chemoresistance remains poor. The slow progress in this area is partly due to the difficulty of studying these cells ex vivo. Indeed, current studies are reliant on xenotransplantation assays in immunodeficient mice. In this paper, we report that by modeling key elements of the bone marrow niche using different stromal feeder layers and hypoxic culture conditions, we can maintain LICs over at least 3 weeks and support their self-renewal properties demonstrated through primary and secondary successful xenograft. We provide a proof of principle that this niche-like culture system can be used to study LIC chemoresistance following in vitro cytarabine treatment similarly to the xenograft chemotherapy model. We found that although LICs are believed to be more chemoresistant than non-LICs, functionally defined LICs are not enriched after cytarabine treatment, and heterogeneity in their resistance to treatment can be seen between patients and even within the same patient. We present a culture system that can be used as an in vitro surrogate for xenotransplantation and that has the potential to dramatically increase the throughput of the investigation of LICs. This would further provide the means by which to identify and target the functionality of the different signaling pathways involved in the maintenance and resistance of LICs to improve acute myeloid leukemia treatments.

Psychosocial factors associated with impact of cancer in longterm haematological cancer survivors

To assess the impact of cancer (IOC) on subsequent quality of life (QOL), 718 long-term haematological cancer survivors completed validated psychosocial, functional and QOL scales, including IOC. Fifteen percent reported significant psychological distress, 18% high levels of fatigue and 10% moderate to severe functional impairment. These groups of participants also showed poorer QOL. There were no significant differences in psychological distress (P = 0·76), fatigue (P = 0·23) or functional impairment (P = 0·74) across different cancer subtypes. Two separate hierarchical regression analyses examined the combined association of disease-type, psychosocial and other factors on negative and positive IOC scores respectively. Higher negative IOC scores were significantly associated (P ≤ 0·001) with medical comorbidity, psychological distress, lower social support, high fatigue levels and functional impairment. Paediatric patients (diagnosed at <17 years) had significantly higher negative IOC scores than adult patients (P = 0·001); greater years since diagnosis was significantly (P < 0·001) associated with less negative IOC. Higher positive IOC was associated with acute leukaemia (P = 0·01); lower positive IOC with paediatric patients (P < 0·001), white ethnicity (P < 0·001), higher education (P = 0·003), no partner (P = 0·01) and lower social support (P = 0·01). Screening for medical comorbidity, psychological distress and fatigue identifies those needing most support and should allow earlier interventions to address negative and positive IOC to improve the well-being of cancer survivors.

Dietary management of urea cycle disorders: European practice

BACKGROUND

There is no published data comparing dietary management of urea cycle disorders (UCD) in different countries.

METHODS

Cross-sectional data from 41 European Inherited Metabolic Disorder (IMD) centres (17 UK, 6 France, 5 Germany, 4 Belgium, 4 Portugal, 2 Netherlands, 1 Denmark, 1 Italy, 1 Sweden) was collected by questionnaire describing management of patients with UCD on prescribed protein restricted diets.

RESULTS

Data for 464 patients: N-acetylglutamate synthase (NAGS) deficiency, n=10; carbamoyl phosphate synthetase (CPS1) deficiency, n=29; ornithine transcarbamoylase (OTC) deficiency, n=214; citrullinaemia, n=108; argininosuccinic aciduria (ASA), n=80; arginase deficiency, n=23 was reported. The majority of patients (70%; n=327) were aged 0-16y and 30% (n=137) >16y. Prescribed median protein intake/kg body weight decreased with age with little variation between disorders. The UK tended to give more total protein than other European countries particularly in infancy. Supplements of essential amino acids (EAA) were prescribed for 38% [n=174] of the patients overall, but were given more commonly in arginase deficiency (74%), CPS (48%) and citrullinaemia (46%). Patients in Germany (64%), Portugal (67%) and Sweden (100%) were the most frequent users of EAA. Only 18% [n=84] of patients were prescribed tube feeds, most commonly for CPS (41%); and 21% [n=97] were prescribed oral energy supplements.

CONCLUSIONS

Dietary treatment for UCD varies significantly between different conditions, and between and within European IMD centres. Further studies examining the outcome of treatment compared with the type of dietary therapy and nutritional support received are required.

Antigen presenting cell-mediated expansion of human umbilical cord blood yields log-scale expansion of natural killer cells with anti-myeloma activity

Natural killer (NK) cells are important mediators of anti-tumor immunity and are active against several hematologic malignancies, including multiple myeloma (MM). Umbilical cord blood (CB) is a promising source of allogeneic NK cells but large scale ex vivo expansion is required for generation of clinically relevant CB-derived NK (CB-NK) cell doses. Here we describe a novel strategy for expanding NK cells from cryopreserved CB units using artificial antigen presenting feeder cells (aAPC) in a gas permeable culture system. After 14 days, mean fold expansion of CB-NK cells was 1848-fold from fresh and 2389-fold from cryopreserved CB with >95% purity for NK cells (CD56⁺/CD3⁻) and less than 1% CD3⁺ cells. Though surface expression of some cytotoxicity receptors was decreased, aAPC-expanded CB-NK cells exhibited a phenotype similar to CB-NK cells expanded with IL-2 alone with respect to various inhibitory receptors, NKG2C and CD94 and maintained strong expression of transcription factors Eomesodermin and T-bet. Furthermore, CB-NK cells formed functional immune synapses with and demonstrated cytotoxicity against various MM targets. Finally, aAPC-expanded CB-NK cells showed significant in vivo activity against MM in a xenogenic mouse model. Our findings introduce a clinically applicable strategy for the generation of highly functional CB-NK cells which can be used to eradicate MM.

HIF-2α protects human hematopoietic stem/progenitors and acute myeloid leukemic cells from apoptosis induced by endoplasmic reticulum stress

Hematopoietic stem and progenitor cells (HSPCs) are exposed to low levels of oxygen in the bone marrow niche, and hypoxia-inducible factors (HIFs) are the main regulators of cellular responses to oxygen variation. Recent studies using conditional knockout mouse models have unveiled a major role for HIF-1α in the maintenance of murine HSCs; however, the role of HIF-2α is still unclear. Here, we show that knockdown of HIF-2α, and to a much lesser extent HIF-1α, impedes the long-term repopulating ability of human CD34(+) umbilical cord blood cells. HIF-2α-deficient HSPCs display increased production of reactive oxygen species (ROS), which subsequently stimulates endoplasmic reticulum (ER) stress and triggers apoptosis by activation of the unfolded-protein-response (UPR) pathway. HIF-2α deregulation also significantly decreased engraftment ability of human acute myeloid leukemia (AML) cells. Overall, our data demonstrate a key role for HIF-2α in the maintenance of human HSPCs and in the survival of primary AML cells.

Bendamustine for non-Hodgkin lymphoma. Interview by Louise Rishton

Professor John Gribben is Chair of the International Workshop on non-Hodgkin Lymphoma and the Gordon Hamilton Fairley Chair of Medical Oncology at St. Bartholomew's Hospital, Bart's Cancer Institute, London, UK, a Cancer Research UK Centre of Excellence. His doctoral studies were performed at University College London, UK as the recipient of a Wellcome Trust Fellowship Award and he continued post-doctoral training with Professor Lee Nadler at the Dana-Farber Cancer Institute (Harvard Medical School, MA, USA). In 1992, Gribben was appointed to the Faculty at Harvard Medical School, where he remained as Associate Professor of Medicine and an Attending Physician at the Dana-Farber Cancer Institute and Brigham and Women's Hospital (MA, USA), until returning to London in 2005. Gribben is a founding member of the CLL Research Consortium, Associate Editor of Blood and was elected a Fellow of the Academy of Medical Science. His primary research interests include the immunotherapy of cancer (including stem cell transplantation), the identification of B-cell-tumor antigens and the detection and treatment of minimal residual disease in leukemia and lymphoma.

Mobilized peripheral blood stem cells compared with bone marrow from HLA-identical siblings for reduced-intensity conditioning transplantation in acute myeloid leukemia in complete remission: a retrospective analysis from the Acute Leukemia Working Party of EBMT

Reduced-intensity conditioning (RIC)-alloSCT is increasingly used for acute myelogenous leukemia. Limited data are available for the comparison of peripheral blood stem cells with bone marrow for RIC-alloSCT. We used the European Group for Blood and Marrow Transplantation (EBMT) ALWP data to compare the outcome of mobilized peripheral blood stem cells (PBSC) (n = 1430) vs. bone marrow (BM) (n = 107) for acute myelogenous leukemia (AML) patients with complete remission that underwent RIC-alloSCT from compatible sibling donors. The leukemia features, the disease status, and the time from diagnosis were similar between the two groups. Engraftment was achieved in 99% and 93% in the PBSC and BM groups, respectively (P < 0.0001). The day of engraftment was significantly earlier for the PBSC vs. the BM group, 15 (1-59) and 19 (5-69), respectively (P < 0.001). Acute GVHD, severe GVHD (grade III-IV) and chronic GVHD did not differ between the groups. leukemia-free survival (LFS), relapse, and non-relapsed mortality (NRM) were 51 ± 2%, 32 ± 1%, and 17 ± 1% vs. 50 ± 6%, 38 ± 6%, and 12 ± 3% for the PBSC and BM groups, respectively. Our results indicate faster engraftment, but no difference in GVHD, LFS, relapse, and NRM when comparing PBSC to BM grafts from sibling donors following RIC conditioning. This is the first study comparing PBSC to BM grafts in the RIC setting, analyzing a homogeneous population of patients with AML in remission. Whether PBSC should be preferred for advanced phases of the disease, where the outcome is dominated by relapse incidences, needs further investigation.

EBNA3B-deficient EBV promotes B cell lymphomagenesis in humanized mice and is found in human tumors

Epstein-Barr virus (EBV) persistently infects more than 90% of the human population and is etiologically linked to several B cell malignancies, including Burkitt lymphoma (BL), Hodgkin lymphoma (HL), and diffuse large B cell lymphoma (DLBCL). Despite its growth transforming properties, most immune-competent individuals control EBV infection throughout their lives. EBV encodes various oncogenes, and of the 6 latency-associated EBV-encoded nuclear antigens, only EBNA3B is completely dispensable for B cell transformation in vitro. Here, we report that infection with EBV lacking EBNA3B leads to aggressive, immune-evading monomorphic DLBCL-like tumors in NOD/SCID/γc-/- mice with reconstituted human immune system components. Infection with EBNA3B-knockout EBV (EBNA3BKO) induced expansion of EBV-specific T cells that failed to infiltrate the tumors. EBNA3BKO-infected B cells expanded more rapidly and secreted less T cell-chemoattractant CXCL10, reducing T cell recruitment in vitro and T cell-mediated killing in vivo. B cell lines from 2 EBV-positive human lymphomas encoding truncated EBNA3B exhibited gene expression profiles and phenotypic characteristics similar to those of tumor-derived lines from the humanized mice, including reduced CXCL10 secretion. Screening EBV-positive DLBCL, HL, and BL human samples identified additional EBNA3B mutations. Thus, EBNA3B is a virus-encoded tumor suppressor whose inactivation promotes immune evasion and virus-driven lymphomagenesis.

ERIC recommendations on TP53 mutation analysis in chronic lymphocytic leukemia

Recent evidence suggests that - in addition to 17p deletion - TP53 mutation is an independent prognostic factor in chronic lymphocytic leukemia (CLL). Data from retrospective analyses and prospective clinical trials show that ∼5% of untreated CLL patients with treatment indication have a TP53 mutation in the absence of 17p deletion. These patients have a poor response and reduced progression-free survival and overall survival with standard treatment approaches. These data suggest that TP53 mutation testing warrants integration into current diagnostic work up of patients with CLL. There are a number of assays to detect TP53 mutations, which have respective advantages and shortcomings. Direct Sanger sequencing of exons 4-9 can be recommended as a suitable test to identify TP53 mutations for centers with limited experience with alternative screening methods. Recommendations are provided on standard operating procedures, quality control, reporting and interpretation. Patients with treatment indications should be investigated for TP53 mutations in addition to the work-up recommended by the International workshop on CLL guidelines. Patients with TP53 mutation may be considered for allogeneic stem cell transplantation in first remission. Alemtuzumab-based regimens can yield a substantial proportion of complete responses, although of short duration. Ideally, patients should be treated within clinical trials exploring new therapeutic agents.

Management options, survivorship, and emerging treatment strategies for follicular and Hodgkin lymphomas

Our understanding of the biology underlying lymphoma is continually increasing and leading to improved treatment strategies for affected patients. However, clinical approaches differ between disease subtypes based on the likelihood of achieving durable remissions. For example, follicular lymphoma (FL) is a common and indolent form of non-Hodgkin lymphoma, in which most patients relapse after treatment and periods of remission become progressively shorter after each course of treatment. Thus, the main focus of research efforts in FL is to develop improved treatment strategies that provide prolonged periods of disease remission. In contrast, Hodgkin lymphoma (HL), although rare, is considered to be highly curable with current treatments and the clinical need is for effective-management strategies, potentially avoiding chemotherapy, that reduce long-term toxicity and improve quality of life for patients. This report summarizes the latest advances in our understanding of FL and HL, and demonstrates the different approaches required when developing novel treatment strategies for the two diseases.

Targeting the microenvironment

The microenvironment in which cancer arises plays a critical role in tumorigenesis. Although previously regarded as an innocent bystander, evidence has accumulated over the past 10 years that the microenvironment contributes to tumor growth and progression by providing nutrients and survival signals, and protecting the tumor from normal immune responses and anticancer drugs. Exactly how normal stromal cells, whose function should be to suppress malignant growth, become co-opted into facilitating tumor development is only just beginning to be understood, but a complex story is emerging wherein tumor and stromal cells appear to co-evolve. A better understanding of tumor-stromal interactions and the molecular alterations that result in stromal dysfunction may help to identify patients who will benefit from either more aggressive or risk-adapted therapy regimens, and/or novel compounds that disrupt the tumor microenvironment and re-establishing normal control mechanisms.

Abstract 4489: The activity of novel, potent, selective PI3K/mTOR pathway inhibitors in B-cell malignancies

Background: Activation of the PI3K pathway is implicated in a number of tumour types, including haematological malignancies. Agents that target this pathway at different levels (e.g. RTK, PI3K, mTOR etc) have shown promising activity in preclinical models and in early phase trials. We have therefore investigated the activity of novel, potent, pan- and isoform-selective PI3K pathway inhibitors in lymphoma and myeloma models. Methods: Compounds studied included those with selectivity for mTOR (INK128, mTOR IC50 1.6 nM), PI3Kδ/γ (INK713, INK1048, IC50s &lt;10 nM for δ/γ isoforms, &gt;50 nM for others) and PI3Kδ/γ/β (INK1138, IC50s &lt;10 nM for each isoform). IC87114 (δ- selective), GDC-0941 (α/δ selective), rapamycin and doxorubicin were included as comparators. Agents were studied in a panel of lymphoma and myeloma cell lines, in normal PBMCs and in primary tumours cultured with stromal cells. Effects on cell viability and proliferation were assessed using the Guava Viacount assay, on apoptosis induction by annexin V labelling, and on cell cycle distribution by flow cytometry. PI3K pathway activity and inhibition was determined by Western blotting as well as mass spectrometry. Results: In cell lines, inhibition of mTOR by INK128 resulted in potent inhibition of cell proliferation, in many at concentrations as low as 10 nM. Selective PI3K inhibitors were less potent anti-proliferative agents, although activity was seen in cells with activation of the PI3K pathway as determined by western blot analysis. For all compounds tested, the major impact was on cell proliferation rather than cell viability. PI3K inhibitors showed little effect on cell viability at concentrations &lt; 1µM. The effect of these compounds in primary mantle cell lymphoma, follicular lymphoma, chronic lymphocytic leukaemia and myeloma samples was variable, both between and within tumour types, possibly due to differences in basal PI3K pathway activity. Effects in normal PBMCs were markedly different to those seen in tumour cells, with a concentration-dependent increase in cell number with either mTOR or PI3K inhibition. Conclusion: Selective PI3K pathway inhibition, particularly at the level of mTOR, results in cytostatic, and at higher concentrations cytotoxic, responses in haematological malignancies. The variable activity of these compounds between cell lines and primary samples suggests it will be important to characterise the activity of the PI3K pathway in individual tumours to identify patients likely to benefit from such agents.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4489.