Efficacy of Enzyme and Substrate Reduction Therapy with a Novel Antagonist of Glucosylceramide Synthase for Fabry Disease

Fabry disease, an X-linked glycosphingolipid storage disorder, is caused by the deficient activity of α-galactosidase A (α-Gal A). This results in the lysosomal accumulation in various cell types of its glycolipid substrates, including globotriaosylceramide (GL-3) and lysoglobotriaosylceramide (globotriaosyl lysosphingolipid, lyso-GL-3), leading to kidney, heart, and cerebrovascular disease. To complement and potentially augment the current standard of care, biweekly infusions of recombinant α-Gal A, the merits of substrate reduction therapy (SRT) by selectively inhibiting glucosylceramide synthase (GCS) were examined. Here, we report the development of a novel, orally available GCS inhibitor (Genz-682452) with pharmacological and safety profiles that have potential for treating Fabry disease. Treating Fabry mice with Genz-682452 resulted in reduced tissue levels of GL-3 and lyso-GL-3 and a delayed loss of the thermal nociceptive response. Greatest improvements were realized when the therapeutic intervention was administered to younger mice before they developed overt pathology. Importantly, as the pharmacologic profiles of α-Gal A and Genz-682452 are different, treating animals with both drugs conferred the greatest efficacy. For example, because Genz-682452, but not α-Gal A, can traverse the blood-brain barrier, levels of accumulated glycosphingolipids were reduced in the brain of Genz-682452-treated but not α-Gal A-treated mice. These results suggest that combining substrate reduction and enzyme replacement may confer both complementary and additive therapeutic benefits in Fabry disease.

Cell-cycle reprogramming for PI3K inhibition overrides a relapse-specific C481S BTK mutation revealed by longitudinal functional genomics in mantle cell lymphoma

Despite the unprecedented clinical activity of the Bruton tyrosine kinase (BTK) inhibitor ibrutinib in mantle cell lymphoma (MCL), acquired resistance is common. By longitudinal integrative whole-exome and whole-transcriptome sequencing and targeted sequencing, we identified the first relapse-specific C481S mutation at the ibrutinib binding site of BTK in MCL cells at progression following a durable response. This mutation enhanced BTK and AKT activation and tissue-specific proliferation of resistant MCL cells driven by CDK4 activation. It was absent, however, in patients with primary resistance or progression following transient response to ibrutinib, suggesting alternative mechanisms of resistance. Through synergistic induction of PIK3IP1 and inhibition of PI3K-AKT activation, prolonged early G1 arrest induced by PD 0332991 (palbociclib) inhibition of CDK4 sensitized resistant lymphoma cells to ibrutinib killing when BTK was unmutated, and to PI3K inhibitors independent of C481S mutation. These data identify a genomic basis for acquired ibrutinib resistance in MCL and suggest a strategy to override both primary and acquired ibrutinib resistance.

SIGNIFICANCE

We have discovered the first relapse-specific BTK mutation in patients with MCL with acquired resistance, but not primary resistance, to ibrutinib, and demonstrated a rationale for targeting the proliferative resistant MCL cells by inhibiting CDK4 and the cell cycle in combination with ibrutinib in the presence of BTK(WT) or a PI3K inhibitor independent of BTK mutation. As drug resistance remains a major challenge and CDK4 and PI3K are dysregulated at a high frequency in human cancers, targeting CDK4 in genome-based combination therapy represents a novel approach to lymphoma and cancer therapy. Cancer Discov; 4(9); 1022-35. ©2014 AACR. This article is highlighted in the In This Issue feature, p. 973.

Phase 1 study of radiosensitization using bortezomib in patients with relapsed non-Hodgkin lymphoma receiving radioimmunotherapy with 131I-tositumomab

Radioimmunotherapy (RIT) is effective treatment for indolent non-Hodgkin lymphomas (NHLs), but response durations are usually limited, especially in aggressive NHL. We hypothesized that administration of bortezomib as a radiosensitizer with RIT would be tolerable and improve efficacy in NHL. This phase 1 dose-escalation study evaluated escalating doses of bortezomib combined with 131I-tositumomab in patients with relapsed/refractory NHL. Twenty-five patients were treated. Treatment was well tolerated, with primarily hematologic toxicity. The maximum tolerated dose (MTD) was determined to be 0.9 mg/m2 bortezomib, in combination with a standard dose of 75 cGy 131I-tositumomab. Sixteen patients responded (64%), including 44% complete responses (CRs), with 82% CR in patients with follicular lymphoma (FL). At a median follow-up of 7 months, median progression-free survival was 7 months, and seven of 11 patients with FL remained in remission at a median of 22 months. In conclusion, bortezomib can be safely administered in combination with 131I-tositumomab with promising response rates.

Active idiotypic vaccination versus control immunotherapy for follicular lymphoma

PURPOSE

Idiotypes (Ids), the unique portions of tumor immunoglobulins, can serve as targets for passive and active immunotherapies for lymphoma. We performed a multicenter, randomized trial comparing a specific vaccine (MyVax), comprising Id chemically coupled to keyhole limpet hemocyanin (KLH) plus granulocyte macrophage colony-stimulating factor (GM-CSF) to a control immunotherapy with KLH plus GM-CSF.

PATIENTS AND METHODS

Patients with previously untreated advanced-stage follicular lymphoma (FL) received eight cycles of chemotherapy with cyclophosphamide, vincristine, and prednisone. Those achieving sustained partial or complete remission (n=287 [44%]) were randomly assigned at a ratio of 2:1 to receive one injection per month for 7 months of MyVax or control immunotherapy. Anti-Id antibody responses (humoral immune responses [IRs]) were measured before each immunization. The primary end point was progression-free survival (PFS). Secondary end points included IR and time to subsequent antilymphoma therapy.

RESULTS

At a median follow-up of 58 months, no significant difference was observed in either PFS or time to next therapy between the two arms. In the MyVax group (n=195), anti-Id IRs were observed in 41% of patients, with a median PFS of 40 months, significantly exceeding the median PFS observed in patients without such Id-induced IRs and in those receiving control immunotherapy.

CONCLUSION

This trial failed to demonstrate clinical benefit of specific immunotherapy. The subset of vaccinated patients mounting specific anti-Id responses had superior outcomes. Whether this reflects a therapeutic benefit or is a marker for more favorable underlying prognosis requires further study.

Idelalisib, a selective inhibitor of phosphatidylinositol 3-kinase-δ, as therapy for previously treated indolent non-Hodgkin lymphoma

Idelalisib (GS-1101, CAL-101), an oral inhibitor of phosphatidylinositol 3-kinase-δ, was evaluated in a phase I study in 64 patients with relapsed indolent non-Hodgkin lymphoma (iNHL). Patients had a median (range) age of 64 (32-91) years, 34 (53%) had bulky disease (≥1 lymph nodes ≥5 cm), and 37 (58%) had refractory disease. Patients had received a median (range) of 4 (1-10) prior therapies. Eight dose regimens of idelalisib were evaluated; idelalisib was taken once or twice daily continuously at doses ranging from 50 to 350 mg. After 48 weeks, patients still benefitting (n = 19; 30%) enrolled into an extension study. Adverse events (AEs) occurring in 20% or more patients (total%/grade ≥3%) included diarrhea (36/8), fatigue (36/3), nausea (25/3), rash (25/3), pyrexia (20/3), and chills (20/0). Laboratory abnormalities included neutropenia (44/23), anemia (31/5), thrombocytopenia (25/11), and serum transaminase elevations (48/25). Twelve (19%) patients discontinued therapy due to AEs. Idelalisib induced disease regression in 46/54 (85%) of evaluable patients achieving an overall response rate of 30/64 (47%), with 1 patient having a complete response (1.6%). Median duration of response was 18.4 months, median progression-free survival was 7.6 months. Idelalisib is well tolerated and active in heavily pretreated, relapsed/refractory patients with iNHL. These trials were registered at clinicaltrials.gov as NCT00710528 and NCT01090414.

A multicentre study of primary breast diffuse large B-cell lymphoma in the rituximab era

Primary breast diffuse large B-cell lymphoma (DLBCL) is a rare subtype of non-Hodgkin lymphoma (NHL) with limited data on pathology and outcome. A multicentre retrospective study was undertaken to determine prognostic factors and the incidence of central nervous system (CNS) relapses. Data was retrospectively collected on patients from 8 US academic centres. Only patients with stage I/II disease (involvement of breast and localized lymph nodes) were included. Histologies apart from primary DLBCL were excluded. Between 1992 and 2012, 76 patients met the eligibility criteria. Most patients (86%) received chemotherapy, and 69% received immunochemotherapy with rituximab; 65% received radiation therapy and 9% received prophylactic CNS chemotherapy. After a median follow-up of 4·5 years (range 0·6-20·6 years), the Kaplan-Meier estimated median progression-free survival was 10·4 years (95% confidence interval [CI] 5·8-14·9 years), and the median overall survival was 14·6 years (95% CI 10·2-19 years). Twelve patients (16%) had CNS relapse. A low stage-modified International Prognostic Index (IPI) was associated with longer overall survival. Rituximab use was not associated with a survival advantage. Primary breast DLBCL has a high rate of CNS relapse. The stage-modified IPI score is associated with survival.

Long-term follow-up of R-CHOP with bevacizumab as initial therapy for mantle cell lymphoma: clinical and correlative results

BACKGROUND

Emerging evidence indicates that MCL has increased angiogenesis within the tumor microenvironment. We initiated a phase II trial to determine if the addition of bevacizumab to the standard R-CHOP regimen could enhance antitumor effects in patients with previously untreated MCL.

PATIENTS AND METHODS

Eleven patients with previously untreated MCL received bevacizumab at 15 mg/kg on day 1, and standard CHOP-21 (CHOP given every 21 days per cycle) with rituximab (375 mg/m(2) per cycle) on day 3 of each cycle for a total of 6 cycles. Planned study end points included safety and efficacy assessment, and exploratory analysis of angiogenic profiles. The study was suspended in August of 2010 based on safety findings in DLBCL (diffuse large B-cell lymphoma) of increased cardiovascular events with the regimen.

RESULTS

Beyond the standard R-CHOP safety profile, Grade 3 left ventricular dysfunction developed in 2 patients (18%), Grade 1/2 hypertension, proteinuria, and bleeding each developed in 1 patient (9%). The overall response rate was 82% with 36% complete response (CR)/complete response unconfirmed (CRu). The median progression-free survival (n = 11) was 18 months (95% confidence interval, 3-not reached), and 3-year overall survival rate was 82%. Correlative studies showed increased vascular endothelial growth factor receptor 1 expression in tumor cells at baseline, and elevated levels of plasma vascular endothelial growth factor (VEGF) throughout treatment.

CONCLUSION

The addition of bevacizumab to the standard R-CHOP regimen did not appear to significantly improve efficacy beyond that observed from previous studies using R-CHOP alone. Therapeutic strategies that provide sustained inhibition on VEGF-related and VEGF-independent targets within the tumor microenvironment might further improve antiangiogenic effects and warrant further exploration in MCL.

Lymphoma Occurring During Pregnancy: Antenatal Therapy, Complications, and Maternal Survival in a Multicenter Analysis

Purpose

Lymphoma is the fourth most frequent cancer in pregnancy; however, current clinical practice is based largely on small series and case reports.

Patients and Methods

In a multicenter retrospective analysis, we examined treatment, complications, and outcomes for Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) occurring during pregnancy.

Results

Among 90 patients (NHL, n = 50; HL, n = 40), median age was 30 years (range, 18 to 44 years) and median diagnosis occurred at 24 weeks gestation. Of patients with NHL, 52% had advanced-stage versus 25% of patients with HL (P = .01). Pregnancy was terminated in six patients. Among the other 84 patients, 28 (33%) had therapy deferred to postpartum; these patients were diagnosed at a median 30 weeks gestation. This compared with 56 patients (67%) who received antenatal therapy with median lymphoma diagnosis at 21 weeks (P < .001); 89% of these patients received combination chemotherapy. The most common preterm complication was induction of labor (33%). Gestation went to full term in 56% of patients with delivery occurring at a median of 37 weeks. There were no differences in maternal complications, perinatal events, or median infant birth weight based on deferred versus antenatal therapy. At 41 months, 3-year progression-free survival (PFS) and overall survival (OS) for NHL were 53% and 82%, respectively, and 85% and 97%, respectively, for HL. On univariate analysis for NHL, radiotherapy predicted inferior PFS, and increased lactate dehydrogenase and poor Eastern Cooperative Oncology Group performance status (ECOG PS) portended worse OS. For HL patients, nulliparous status and “B” symptoms predicted inferior PFS.

Conclusion

Standard (non-antimetabolite) combination chemotherapy administered past the first trimester, as early as 13 weeks gestation, was associated with few complications and expected maternal survival with lymphoma occurring during pregnancy.

A phase 2 trial of extended induction epratuzumab and rituximab for previously untreated follicular lymphoma: CALGB 50701

BACKGROUND

Rituximab combined with chemotherapy has improved the survival of previously untreated patients with follicular lymphoma (FL). Nevertheless, many patients neither want nor can tolerate chemotherapy, leading to interest in biological approaches. Epratuzumab is a humanized anti-CD22 monoclonal antibody with efficacy in relapsed FL. Because both rituximab and epratuzumab have single-agent activity in FL, the antibody combination was evaluated as initial treatment of patients with FL.

METHODS

Fifty-nine untreated patients with FL received epratuzumab 360 mg/m2 with rituximab 375 mg/m2 weekly for 4 induction doses. This combination was continued as extended induction in weeks 12, 20, 28, and 36. Response assessed by computed tomography was correlated with clinical risk factors, [18F]fluorodeoxyglucose positron emission tomography findings at week 3, Fcγ polymorphisms, immunohistochemical markers, and statin use.

RESULTS

Therapy was well-tolerated, with toxicities similar to expected with rituximab monotherapy. Fifty-two (88.2%) evaluable patients responded, including 25 complete responses (42.4%) and 27 partial responses (45.8%). At 3 years follow-up, 60% of patients remain in remission. Follicular Lymphoma International Prognostic Index (FLIPI) risk strongly predicted progression-free survival (P = .022).

CONCLUSIONS

The high response rate and prolonged time to progression observed with this antibody combination are comparable to those observed after standard chemoimmunotherapies and further support the development of biologic, nonchemotherapeutic approaches for these patients.

Mechanism-based epigenetic chemosensitization therapy of diffuse large B-cell lymphoma

Although aberrant DNA methylation patterning is a hallmark of cancer, the relevance of targeting DNA methyltransferases (DNMT) remains unclear for most tumors. In diffuse large B-cell lymphoma (DLBCL) we observed that chemoresistance is associated with aberrant DNA methylation programming. Prolonged exposure to low-dose DNMT inhibitors (DNMTI) reprogrammed chemoresistant cells to become doxorubicin sensitive without major toxicity in vivo. Nine genes were recurrently hypermethylated in chemoresistant DLBCL. Of these, SMAD1 was a critical contributor, and reactivation was required for chemosensitization. A phase I clinical study was conducted evaluating azacitidine priming followed by standard chemoimmunotherapy in high-risk patients newly diagnosed with DLBCL. The combination was well tolerated and yielded a high rate of complete remission. Pre- and post-azacitidine treatment biopsies confirmed SMAD1 demethylation and chemosensitization, delineating a personalized strategy for the clinical use of DNMTIs.

SIGNIFICANCE

The problem of chemoresistant DLBCL remains the most urgent challenge in the clinical management of patients with this disease. We describe a mechanism-based approach toward the rational translation of DNMTIs for the treatment of high-risk DLBCL.

Induction of prolonged early G1 arrest by CDK4/CDK6 inhibition reprograms lymphoma cells for durable PI3Kδ inhibition through PIK3IP1

Phosphatidylinositol-3-kinase (PI3K) signaling is constitutive in most human cancers. Selective inhibition of PI3Kδ (p110δ) by GS-1101 has emerged as a promising therapy in chronic lymphocytic leukemia and indolent lymphomas. In aggressive non-Hodgkin lymphomas such as mantle cell lymphoma (MCL), however, efficacy has been observed, but the extent and duration of tumor control is modest. To determine if tumor killing by GS-1101 is cell cycle-dependent, we show in primary MCL cells by whole-transcriptome sequencing that, despite aberrant expression and recurrent mutations in Cyclin D1, mutations are rare in coding regions of CDK4, RB1 and other genes that control G1-S cell cycle progression or PI3K/AKT signaling. PI3Kδ is the predominant PI3K catalytic subunit expressed, and inhibition by GS-1101 transiently inhibits AKT phosphorylation but not proliferation in MCL cells. Induction of prolonged early G1-arrest (pG1) by selective inhibition of CDK4/CDK6 with PD 0332991 amplifies and sustains PI3Kδ inhibition, which leads to robust apoptosis. Accordingly, inhibition of PI3Kδ induces apoptosis of primary MCL tumor cells once they have ceased to cycle ex vivo, and this killing is enhanced by PD 0332991 inhibition of CDK4/CDK6. PIK3IP1, a negative PI3K regulator, appears to mediate pG1 sensitization to PI3K inhibition; it is markedly reduced in MCL tumor cells compared with normal peripheral B cells, profoundly induced in pG1 and required for pG1 sensitization to GS-1101. Thus, the magnitude and duration of PI3K inhibition and tumor killing by GS-1101 is pG1-dependent, suggesting induction of pG1 by CDK4/CDK6 inhibition as a strategy to sensitize proliferating lymphoma cells to PI3K inhibition.

Abstract 3424: Induction of prolonged early G1-arrest by CDK4/CDK6 inhibition reprograms cycling lymphoma cells for enhanced and sustained inhibition of PI3Kδ/AKT

The phosphatidylinositol-3-kinase (PI3K) signaling pathway is constitutively activated at a high frequency in cancer. Interest in evaluating the therapeutic utility of selective PI3K subunit inhibition has led to the development of potent PI3Kδ-specific inhibitors. Selective inhibition of PI3Kδ has now emerged as a promising therapy for chronic lymphocytic leukemia and indolent lymphomas. For aggressive non Hodgkin lymphoma such as mantle cell lymphoma (MCL), however, efficacy has been observed but duration of tumor control has been modest, encouraging development of mechanism-based combination therapy.

We hypothesize that induction of G1-cell cycle arrest may reprogram non-indolent lymphomas to PI3Kδ inhibition, and test this hypothesis in MCL based on the following: 1) aberrant cyclin D1 and CDK4 expression is the primary cause for unrestrained cell cycle progression and proliferation in MCL; 2) by induction of prolonged early G1 arrest (pG1) through selective inhibition of CDK4/CDK6, we have developed a novel strategy that both inhibits proliferation of tumor cells and sensitizes them to cytotoxic killing; and 3) induction of pG1 by CDK4/CDK6 inhibition has demonstrated encouraging clinical activity, with an excellent toxicity profile, in a phase I clinical trial in MCL.

Here we show in primary MCL cells (N=10) by whole transcriptome-sequencing (WTS) that mutations in coding regions are rare in Cyclin D1, CDK4 and other genes that control G1 cell cycle progression or in the PI3K/AKT signaling pathway. PI3Kδ is the predominant PI3K catalytic expressed in MCL cells. Selective inhibition of PI3Kδ transiently reduces AKT phosphorylation but does not inhibit the cell cycle in proliferating MCL cells, implying a potential mechanism for resistance. Induction of pG1 by CDK4/CDK6 inhibition amplifies and sustains PI3Kδ inhibition and induces robust apoptosis.

Validating the G1 cell cycle-dependence of PI3Kδ inhibition, all primary MCL cells tested are responsive to PI3Kδ inhibition when they cease to cycle in ex vivo in stromal co-culture. This loss of viability is further accelerated in pG1 induced by CDK4/CDK6 inhibition, despite the presence of cytokines and growth factors that are known to activate PI3K.

This study presents the first sequential combination of selective inhibition of CDK4/CDK6 with a selective partner, a PI3Kδ specific inhibitor, in primary human cancer cells and the first WTS-validated therapeutic strategy that leads to sensitization of MCL cells by cell cycle control. Our data demonstrate, for the first time, that the magnitude and duration of PI3K inhibition is G1 cell cycle-dependent, and suggest a strategy to sensitize proliferating lymphoma cells to selective PI3Kδ inhibition by induction of early G1-arrest through selective CDK4/CDK6 inhibition.

Citation Format: David Chiron, Peter Martin, Maurizio Di Liberto, Xiangao Huang, Scott A. Ely, Brian J. Lannutti, John P. Leonard, Christopher E. Mason, Selina Chen-Kiang. Induction of prolonged early G1-arrest by CDK4/CDK6 inhibition reprograms cycling lymphoma cells for enhanced and sustained inhibition of PI3Kδ/AKT. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3424. doi:10.1158/1538-7445.AM2013-3424

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Bortezomib in combination with rituximab, dexamethasone, ifosfamide, cisplatin and etoposide chemoimmunotherapy in patients with relapsed and primary refractory diffuse large B-cell lymphoma

Patients with relapsed or refractory diffuse large B-cell lymphoma may experience extended survival with second-line chemotherapy and autologous stem cell transplant (ASCT). Since a major determinant of outcome after ASCT is responsiveness to second-line therapy, the development of more effective second-line treatments is desirable. We investigated the addition of bortezomib to rituximab, dexamethasone, ifosfamide, cisplatin and etoposide (VIPER). Fifteen patients were enrolled, of whom seven were refractory to first-line chemotherapy and only three had maintained first response for 1 year. Nine (60%) patients achieved objective responses, of which three (20%) were IWC-PET (International Workshop Criteria positron emission tomography) complete responses. Median progression-free survival was 3 months, and median overall survival was 10 months. At a median follow-up of 26 months, five patients (33%) remained alive. Treatment was well tolerated with no unexpected toxicity. Although response rates did not meet predefined criteria, activity was at least comparable to other second-line approaches despite a poor-prognosis patient population.

Phase II trial of galiximab (anti-CD80 monoclonal antibody) plus rituximab (CALGB 50402): Follicular Lymphoma International Prognostic Index (FLIPI) score is predictive of upfront immunotherapy responsiveness

BACKGROUND

This phase II CALGB trial evaluated the activity and safety of an extended induction schedule of galiximab (G) plus rituximab (R) in untreated follicular lymphoma (FL).

PATIENTS AND METHODS

Patients with previously untreated FL (grades 1, 2, 3a) received 4 weekly infusions of G + R, followed by an additional dose every 2 months four times. International Workshop Response Criteria were used to evaluate response.

RESULTS

Sixty-one patients were treated and antibody infusions were well tolerated. The overall response rate (ORR) is 72.1% (95% confidence interval 59.2% to 82.9%): 47.6% complete response (CR)/unconfirmed complete response (CRu) and 24.6% partial response. At a median follow-up time of 4.3 years (range, 0.3-5.3 years) median progression-free survival (PFS) is 2.9 years. Notably, Follicular Lymphoma International Prognostic Index (FLIPI) correlated with ORR, CR rate, and PFS, and the low-risk FLIPI group (n = 12) achieved a 92% ORR, 75% CR/CRu rate, and 75% 3-year PFS.

CONCLUSIONS

An extended induction schedule of G + R in previously untreated FL is well tolerated and appears particularly efficacious in those patients with low-risk FLIPI scores. In addition, this trial served as the initial platform for additional CALGB 'doublet' combination regimes of rituximab plus other novel targeted agents.

Metronomic therapy for refractory/relapsed lymphoma: the PEP-C low-dose oral combination chemotherapy regimen

BACKGROUND

Metronomic therapy is the application of continuous, low dose chemotherapy. The doses of chemotherapy are usually not sufficient to destroy neoplastic cells, but impact the milieu, particularly angiogenesis.

OBJECTIVE

To determine if the oral PEP-C regimen, consisting of prednisone 20 mgm, etoposide 50 mgm, procarbazine 50 mgm, and cyclophosphamide 50 mgm given in either a daily, alternate day, or fractionated basis, is effective in a variety of lymphomas.

METHODS

One hundred twenty two patients were studied although the majority had low grade or mantle cell lymphoma. All had received at least two or more prior therapies.

RESULTS

Overall, 75% achieved an objective response (OR) with 38% complete responses (CRs) or CRs unconfirmed, and 37% partial responses. ORs were achieved in mantle cell (85%), follicular (88%), marginal zone (71%), and small lymphocytic (67%) lymphomas. Chemosensitive disease was more responsive. Toxicity was minimal.

CONCLUSION

The PEP-C regimen is an easily administered highly effective treatment for heavily pretreated mantle cell and low grade lymphomas.

Stromal endothelial cells establish a bidirectional crosstalk with chronic lymphocytic leukemia cells through the TNF-related factors BAFF, APRIL, and CD40L

Chronic lymphocytic leukemia (CLL) is a clonal B cell disorder of unknown origin. Accessory signals from the microenvironment are critical for the survival, expansion, and progression of malignant B cells. We found that the CLL stroma included microvascular endothelial cells (MVECs) expressing BAFF and APRIL, two TNF family members related to the T cell-associated B cell-stimulating molecule CD40L. Constitutive release of soluble BAFF and APRIL increased upon engagement of CD40 on MVECs by CD40L aberrantly expressed on CLL cells. In addition to enhancing MVEC expression of CD40, leukemic CD40L induced cleavases that elicited intracellular processing of pro-BAFF and pro-APRIL proteins in MVECs. The resulting soluble BAFF and APRIL proteins delivered survival, activation, Ig gene remodeling, and differentiation signals by stimulating CLL cells through TACI, BAFF-R, and BCMA receptors. BAFF and APRIL further amplified CLL cell survival by upregulating the expression of leukemic CD40L. Inhibition of TACI, BCMA, and BAFF-R expression on CLL cells; abrogation of CD40 expression in MVECs; or suppression of BAFF and APRIL cleavases in MVECs reduced the survival and diversification of malignant B cells. These data indicate that BAFF, APRIL, and CD40L form a CLL-enhancing bidirectional signaling network linking neoplastic B cells with the microvascular stroma.

Loss of GM3 synthase gene, but not sphingosine kinase 1, is protective against murine nephronophthisis-related polycystic kidney disease

Genetic forms of polycystic kidney diseases (PKDs), including nephronophthisis, are characterized by formation of fluid-filled cysts in the kidneys and progression to end-stage renal disease. No therapies are currently available to treat cystic diseases, making it imperative to dissect molecular mechanisms in search of therapeutic targets. Accumulating evidence suggests a pathogenic role for glucosylceramide (GlcCer) in multiple forms of PKD. It is not known, however, whether other structural glycosphingolipids (GSLs) or bioactive signaling sphingolipids (SLs) modulate cystogenesis. Therefore, we set out to address the role of a specific GSL (ganglioside GM3) and signaling SL (sphingosine-1-phosphate, S1P) in PKD progression, using the jck mouse model of nephronopthisis. To define the role of GM3 accumulation in cystogenesis, we crossed jck mice with mice carrying a targeted mutation in the GM3 synthase (St3gal5) gene. GM3-deficient jck mice displayed milder PKD, revealing a pivotal role for ganglioside GM3. Mechanistic changes in regulation of the cell-cycle machinery and Akt-mTOR signaling were consistent with reduced cystogenesis. Dramatic overexpression of sphingosine kinase 1 (Sphk1) mRNA in jck kidneys suggested a pathogenic role for S1P. Surprisingly, genetic loss of Sphk1 exacerbated cystogenesis and was associated with increased levels of GlcCer and GM3. On the other hand, increasing S1P accumulation through pharmacologic inhibition of S1P lyase had no effect on the progression of cystogenesis or kidney GSL levels. Together, these data suggest that genes involved in the SL metabolism may be modifiers of cystogenesis, and suggest GM3 synthase as a new anti-cystic therapeutic target.

Comparing decision making between cancer patients and the general population: thoughts, emotions, or social influence?

This study extends a risk information seeking and processing model to explore the relative effect of cognitive processing strategies, positive and negative emotions, and normative beliefs on individuals' decision making about potential health risks. Most previous research based on this theoretical framework has examined environmental risks. Applying this risk communication model to study health decision making presents an opportunity to explore theoretical boundaries of the model, while also bringing this research to bear on a pressing medical issue: low enrollment in clinical trials. Comparative analysis of data gathered from 2 telephone surveys of a representative national sample (n = 500) and a random sample of cancer patients (n = 411) indicated that emotions played a more substantive role in cancer patients' decisions to enroll in a potential trial, whereas cognitive processing strategies and normative beliefs had greater influences on the decisions of respondents from the national sample.

PI 3-kinase and PKCζ mediate insulin-induced potentiation of NMDA receptor currents in Xenopus oocytes

Insulin modulates N-methyl-d-aspartate (NMDA) receptors in the CNS and potentiates recombinant NMDA receptor currents in Xenopus oocytes. We have previously found that insulin's potentiation of NMDA receptor currents in oocytes occurs in a subunit specific manner and via phosphorylation of specific C-terminal sites by protein tyrosine kinases (PTKs) and C-type protein kinases (PKCs). Insulin-mediated current potentiation of receptors containing the NR2A subunit occurs solely through the activation of PKCs. Activation of phosphoinositide 3-kinase (PI 3-kinase) is known to trigger many insulin-stimulated signaling pathways, and we show here that it lies at a critical step in the insulin-mediated potentiation of NMDA receptor currents. Incubation with the PI 3-kinase inhibitor wortmannin eliminates insulin potentiation of NMDA receptor currents in the oocytes. Atypical isoforms of PKC are known to be activated downstream in the insulin signaling pathway via activation of PI 3-kinase. We demonstrate that the atypical isoform PKC zeta (PKCζ) has a role in insulin-stimulated current potentiation of NR2A-containing NMDA receptors using an isoform-specific pseudosubstrate inhibitor of PKCζ.