Mammalian target of rapamycin inhibition induces cell cycle arrest in diffuse large B cell lymphoma (DLBCL) cells and sensitises DLBCL cells to rituximab

A novel telomere-related genes model for predicting prognosis and treatment responsiveness in diffuse large B-cell lymphoma

Diffuse large B cell lymphoma (DLBCL) is a highly heterogeneous disease with diverse clinical and molecular features. Telomere maintenance is widely present in tumors, but there is a lack of relevant reports on the role of telomere-related genes (TRGs) in DLBCL. In this study, we used consensus clustering based on TRGs expression to identify two molecular clusters with distinct prognoses and immune cell infiltration. We developed a TRGs scoring model using univariate Cox regression and LASSO regression in the GSE10846 training cohort. DLBCL patients in the high-risk group had a worse prognosis than those in the low-risk group, as revealed by Kaplan-Meier curves. The scoring model was validated in the GSE10846 testing cohort and GSE87371 cohort, respectively. The high-risk group was characterized by elevated infiltration of activated DCs, CD56 dim natural killer cells, myeloid-derived suppressor cells, monocytes, and plasmacytoid DCs, along with reduced infiltration of activated CD4 T cells, Type 2 T helper cells, γδ T cells, NK cells, and neutrophils. Overexpression of immune checkpoints, such as PDCD1, CD274, and LAG3, was observed in the high-risk group. Furthermore, high-risk DLBCL patients exhibited increased sensitivity to bortezomib, rapamycin, AZD6244, and BMS.536924, while low-risk DLBCL patients showed sensitivity to cisplatin and ABT.263. Using RT-qPCR, we found that three protective model genes, namely TCEAL7, EPHA4, and ELOVL4, were down-regulated in DLBCL tissues compared with control tissues. In conclusion, our novel TRGs-based model has great predictive value for the prognosis of DLBCL patients and provides a promising direction for treatment optimization.

The Role of mTOR in B Cell Lymphoid Malignancies: Biologic and Therapeutic Aspects

Non-Hodgkin lymphoma's (NHL) incidence is rising over time, and B cell lymphomas comprise the majority of lymphomas. The phosphoinositide 3-kinase (PI3K)/v-akt murine thymoma viral oncogene homologue 1 (Akt)/mammalian target of the rapamycin (mTOR) signaling pathway plays a critical role in a variety of cellular processes, such as cell proliferation and survival. Its role in lymphomagenesis is confirmed in many different types of B cell lymphomas. This review is mainly focused on the PI3K/v-akt/mTOR pathway-related oncogenic mechanisms in B cell NHLs with an emphasis on common B cell lymphoma types [diffuse large B cell lymphoma (DLBCL) and mantle cell lymphoma (MCL)]. Furthermore, it summarizes the literature regarding the clinical applications of the mTOR inhibitors temsirolimus and everolimus in B cell NHLs, which have been tested in a range of clinical trials enrolling patients with B cell malignancies, either as monotherapy or in combination with other agents or regimens.

Potential Pathogenic Impact of Cow’s Milk Consumption and Bovine Milk-Derived Exosomal MicroRNAs in Diffuse Large B-Cell Lymphoma

Epidemiological evidence supports an association between cow’s milk consumption and the risk of diffuse large B-cell lymphoma (DLBCL), the most common non-Hodgkin lymphoma worldwide. This narrative review intends to elucidate the potential impact of milk-related agents, predominantly milk-derived exosomes (MDEs) and their microRNAs (miRs) in lymphomagenesis. Upregulation of PI3K-AKT-mTORC1 signaling is a common feature of DLBCL. Increased expression of B cell lymphoma 6 (BCL6) and suppression of B lymphocyte-induced maturation protein 1 (BLIMP1)/PR domain-containing protein 1 (PRDM1) are crucial pathological deviations in DLBCL. Translational evidence indicates that during the breastfeeding period, human MDE miRs support B cell proliferation via epigenetic upregulation of BCL6 (via miR-148a-3p-mediated suppression of DNA methyltransferase 1 (DNMT1) and miR-155-5p/miR-29b-5p-mediated suppression of activation-induced cytidine deaminase (AICDA) and suppression of BLIMP1 (via MDE let-7-5p/miR-125b-5p-targeting of PRDM1). After weaning with the physiological termination of MDE miR signaling, the infant’s BCL6 expression and B cell proliferation declines, whereas BLIMP1-mediated B cell maturation for adequate own antibody production rises. Because human and bovine MDE miRs share identical nucleotide sequences, the consumption of pasteurized cow’s milk in adults with the continued transfer of bioactive bovine MDE miRs may de-differentiate B cells back to the neonatal “proliferation-dominated” B cell phenotype maintaining an increased BLC6/BLIMP1 ratio. Persistent milk-induced epigenetic dysregulation of BCL6 and BLIMP1 expression may thus represent a novel driving mechanism in B cell lymphomagenesis. Bovine MDEs and their miR cargo have to be considered potential pathogens that should be removed from the human food chain.

Immune-based therapies in diffuse large B-cell lymphoma

INTRODUCTION

Diffuse large B-cell lymphoma (DLBCL) is an aggressive and clinically heterogeneous malignancy originating from B-cells with up to 40% of patients experiencing primary refractory disease or relapse after first-line treatment. However, the past 5 years have seen a flurry of new drug approvals for DLBCL anchored upon new immune therapies, including chimeric antigen receptor (CAR) T-cells and antibody-based therapies.

AREAS COVERED

This article summarizes recent advances in the treatment of DLBCL, including in the first line and relapsed and refractory setting (second-line and beyond). A literature search was conducted for publications relevant to the immunotherapeutic approach to DLBCL from 2000 through March 2023 within PubMed and articles were reviewed. The search terms were immunotherapy, monoclonal antibodies, chimeric antigen receptor modified T-cell (CAR-T), and classification of DLBCL. Relevant clinical trials and pre-clinical studies exploring the strengths and weaknesses of current immune therapies against DLBCL were chosen. We additionally explored how intrinsic differences amongst DLBCL subtype biology and endogenous host immune recruitment contribute to variable therapeutic efficacy.

EXPERT OPINION

Future treatments will minimize chemotherapy exposure and be chosen by underlying tumor biology, paving the way for the promise of chemotherapeutic free regimens and improved outcomes for poor-risk subgroups.

TBL1X: At the crossroads of transcriptional and posttranscriptional regulation

Over the past 2 decades, the adaptor protein transducin β-like 1 (TBL1X) and its homolog TBL1XR1 have been shown to be upregulated in solid tumors and hematologic malignancies, and their overexpression is associated with poor clinical outcomes. Moreover, dysregulation of the TBL1 family of proteins has been implicated as a key component of oncogenic prosurvival signaling, cancer progression, and metastasis. Herein, we discuss how TBL1X and TBL1XR1 are required for the regulation of major transcriptional programs through the silencing mediator for tetanoid and thyroid hormone receptor (SMRT)/nuclear receptor corepressor (NCOR)/ B cell lymphoma 6 (BCL6) complex, Wnt/β catenin, and NF-κB signaling. We outline the utilization of tegavivint (Iterion Therapeutics), a first-in-class small molecule targeting the N-terminus domain of TBL1, as a novel therapeutic strategy in preclinical models of cancer and clinically. Although most published work has focused on the transcriptional role of TBL1X, we recently showed that in diffuse large B-cell lymphoma (DLBCL), the most common lymphoma subtype, genetic knockdown of TBL1X and treatment with tegavivint resulted in decreased expression of critical (onco)-proteins in a posttranscriptional/β-catenin-independent manner by promoting their proteasomal degradation through a Skp1/Cul1/F-box (SCF)/TBL1X supercomplex and potentially through the regulation of protein synthesis. However, given that TBL1X controls multiple oncogenic signaling pathways in cancer, treatment with tegavivint may ultimately result in drug resistance, providing the rationale for combination strategies. Although many questions related to TBL1X function remain to be answered in lymphoma and other diseases, these data provide a growing body of evidence that TBL1X is a promising therapeutic target in oncology.

Phase II Study of Single-Agent and Combination Everolimus and Panobinostat in Relapsed or Refractory Diffuse Large B-Cell Lymphoma

Novel therapeutics are needed for patients with relapsed or refractory diffuse large B-cell lymphoma (R/R DLBCL). Everolimus is an mTOR pathway inhibitor with synergistic anti-tumor activity when combined with histone deacetylase inhibitors, such as panobinostat, in preclinical lymphoma models. In this Phase II study, we evaluated overall response rate to single and combination everolimus and panobinostat in R/R DLBCL. Fifteen patients were enrolled to single-agent and 18 to combination. One patient responded to everolimus, while none responded to panobinostat. Though 25% of patients responded to combination therapy, responses were not durable with significant toxicity. We demonstrated minimal single-agent activity and prohibitive toxicity with combination therapy.

A phase I trial of inotuzumab ozogamicin in combination with temsirolimus in patients with relapsed or refractory CD22-positive B-cell non-Hodgkin lymphomas

This phase I trial evaluated the safety, tolerability, and preliminary activity of inotuzumab ozogamicin in combination with temsirolimus in patients with relapsed/refractory CD22 positive B-cell non-Hodgkin lymphomas. Nineteen patients received at least one dose of both study drugs. Dose-limiting toxicities consisted of thrombocytopenia, hypertriglyceridemia, oral mucositis, clinical deterioration, and the inability to receive at least three doses of temsirolimus during cycle 1. The most common grade ≥3 treatment-related adverse events were thrombocytopenia (n = 8), neutropenia (n = 5), and two patients each hyperphosphatemia, lymphopenia, and hypertriglyceridemia. The recommended phase II dose was inotuzumab ozogamicin 0.8 mg/m² on day 1 in combination with temsirolimus 10 mg on days 8, 15, and 22 every 28 days. Among 18 patients evaluable, seven (39%) with follicular lymphoma had a partial remission. This drug combination is not possible within a therapeutically useful range of doses due to toxicities. Antitumor activity was observed in heavily pretreated patients (ClinicalTrials.gov, Identifier NCT01535989).

Optimization and Pharmacokinetic Evaluation of Synergistic Fenbendazole and Rapamycin Co-Encapsulated in Methoxy Poly(Ethylene Glycol)-b-Poly(Caprolactone) Polymeric Micelles

Purpose

We aimed to develop a nanocarrier formulation incorporating fenbendazole (FEN) and rapamycin (RAPA) with strong efficacy against A549 cancer cells. As FEN and RAPA are poorly soluble in water, it is difficult to apply them clinically in vivo. Therefore, we attempted to resolve this problem by encapsulating these drugs in polymeric micelles.

Methods

We evaluated drug synergy using the combination index (CI) values of various molar ratios of FEN and RAPA. We formed and tested micelles composed of different polymers. Moreover, we conducted cytotoxicity, stability, release, pharmacokinetic, and biodistribution studies to investigate the antitumor effects of FEN/RAPA-loaded mPEG-b-PCL micelles.

Results

We selected mPEG-b-PCL-containing FEN and RAPA at a molar ratio of 1:2 because these particles were consistent in size and had high encapsulation efficiency (EE, %) and drug loading (DL, %) capacity. The in vitro cytotoxicity was assessed for various FEN, RAPA, and combined FEN/RAPA formulations. After long-term exposures, both the solutions and the micelles had similar efficacy against A549 cancer cells. The in vivo pharmacokinetic study revealed that FEN/RAPA-loaded mPEG-b-PCL micelles had a relatively higher area under the plasma concentration–time curve from 0 to 2 h (AUC_{0–2 h}) and 0 to 8 h (AUC_{0–8 h}) and plasma concentration at time zero (C_o) than that of the FEN/RAPA solution. The in vivo biodistribution assay revealed that the IV injection of FEN/RAPA-loaded mPEG-b-PCL micelles resulted in lower pulmonary FEN concentration than the IV injection of the FEN/RAPA solution.

Conclusion

When FEN and RAPA had a 1:2 molar ratio, they showed synergism. Additionally, using data from in vitro cytotoxicity, synergism between a 1:2 molar ratio of FEN and RAPA was observed in the micelle formulation. The FEN/RAPA-loaded mPEG-b-PCL micelle had enhanced bioavailability than the FEN/RAPA solution.

Targeted inhibition of mRNA translation initiation factors as a novel therapeutic strategy for mature B-cell neoplasms

Cancer development is frequently associated with dysregulation of mRNA translation to enhance both increased global protein synthesis and translation of specific mRNAs encoding oncoproteins. Thus, targeted inhibition of mRNA translation is viewed as a promising new approach for cancer therapy. In this article we review current progress in investigating dysregulation of mRNA translation initiation in mature B-cell neoplasms, focusing on chronic lymphocytic leukemia, follicular lymphoma and diffuse large B-cell lymphoma. We discuss mechanisms and regulation of mRNA translation, potential pathways by which genetic alterations and the tumor microenvironment alters mRNA translation in malignant B cells, preclinical evaluation of drugs targeted against specific eukaryotic initiation factors and current progress towards clinical development. Overall, inhibition of mRNA translation initiation factors is an exciting and promising area for development of novel targeted anti-tumor drugs.

Integrating transcriptome-wide association study and copy number variation study identifies candidate genes and pathways for diffuse non-Hodgkin's lymphoma

BACKGROUND

The genetic basis of diffuse non-Hodgkin's lymphoma (DNHL) is largely unknown now. We conducted a large-scale transcriptome-wide association study (TWAS) of DNHL to identify novel candidates for DNHL.

METHODS

The GWAS summary data of DNHL was obtained from the UKBiobank, involving 685 cases and 451,579 controls. TWAS of DNHL was performed using tissue-specific gene expression weights generated from the Genotype-Tissue Expression (GTEx) data. The DNHLTWAS results were further validated by a previous published copy number alterations (CNA) study of DNHL. Gene ontology (GO) and pathway enrichment analysis of identified candidate genes were conducted by the DAVID 6.8.

RESULTS

We identified 214 genes with TWAS P value < 0.05 for DNHL, such as MRPL19 (P_TWAS = 0.0010), CRCP (P_TWAS = 0.0010) and SEMA3C (P_TWAS = 0.0010). After further comparing the 214 genes with copy number variations of DNHL patients, we found 1 overlapped gene, BCL10 (P_TWAS = 0.0100). We also detected 6 common GO terms shared between gene set enrichment analysis results of TWAS and CNAs, such as cytosol (P_TWAS = 0.0003, PCNAs = 4.99 × 10^-7) and membrane (P_TWAS = 0.0048, P_CNAs = 0.0046). The pathway enrichment analysis of TWAS and CNAs detected 3 common pathways, including HIF-1 signaling pathway (P_TWAS = 0.0195, P_CNAs = 1.96 × 10^-5), mTOR signaling pathway (P_TWAS = 0.0242, P_CNAs = 6.75 × 10^-5) and adipocytokine signaling pathway (P_TWAS = 0.0392, P_CNAs = 0.0103).

CONCLUSIONS

Our study identified multiple DNHL associated genes and pathways, providing novel useful information for the pathogenetic studies of DNHL.

VicTORia: a randomised phase II study to compare vinorelbine in combination with the mTOR inhibitor everolimus versus vinorelbine monotherapy for second-line chemotherapy in advanced HER2-negative breast cancer

PURPOSE

Improving the outcome of patients with HER2-negative metastatic breast cancer experiencing tumour progression following first-line chemotherapy remains an urgent medical need. The purpose of the VicTORia trial was to show superiority of everolimus in combination with vinorelbine versus vinorelbine monotherapy as second-line chemotherapy for patients with advanced HER2 negative breast cancer.

METHODS

In this randomised phase II trial, 133 patients were recruited in 32 centres in Germany. Patients were randomised 1:1 to second-line chemotherapy either with vinorelbine plus everolimus (arm1) or vinorelbine alone (arm2). Primary endpoint was progression-free survival (PFS). Secondary endpoints were PFS rate at 6 months, overall survival (OS), overall response rate (ORR) and safety. Baseline PI3 K mutational status was determined in plasma samples.

RESULTS

Median progression-free survival was not different between arms (arm1 vs. arm2: 4.01 months, 95% CI 2.40-6.09 vs. 4.08, 95% CI 2.80-5.33). PFS rate at 6 months (arm1 vs. arm2: 39.4%, 95% CI 27.6-50.9% vs. 36.6%, 95% CI 24.6-48.6%), median OS (arm1 vs. arm2: 16.3 months, 95% CI 11.4-19.0 vs. 13.8 months, 95% CI 10.2-19.1) and ORR were not different between arms. Most frequent grade 3/4 adverse events were neutropenia (50% vs. 40%), gastrointestinal toxicities (19.1% vs. 6.1%), and infections (19.1% vs. 7.7%). PI3 K mutational status was neither associated with PFS nor with OS.

CONCLUSION

Although well tolerated, the efficacy of everolimus and vinorelbine combination therapy was not superior to vinorelbine monotherapy. There was no correlation between PI3 K mutational status and efficacy. EudracCT No 2011-001024-38, ClinicalTrials.gov No NCT01520103.

Turning to Computer-aided Drug Design in the Treatment of Diffuse Large B-cell Lymphoma: Has it been Helpful?

INTRODUCTION

Amidst the numerous effective therapeutic options available for the treatment of Diffuse Large B-cell Lymphoma (DLBCL), about 30-40% of patients treated with first-line chemoimmunotherapy still experience a relapse or refractory DLBCL. This has necessitated a continuous search for new therapeutic agents to augment the existing therapeutic arsenal.

METHODS

The dawn of Computer-Aided Drug Design (CADD) in the drug discovery process has accounted for persistency in the application of computational approaches either alone or in combinatorial strategies with experimental methods towards the identification of potential hit compounds with high therapeutic efficacy in abrogating DLBCL.

RESULTS

This review showcases the interventions of structure-based and ligand-based computational approaches which have led to the identification of numerous small molecule inhibitors against implicated targets in DLBCL therapy, even though many of these potential inhibitors are piled-up awaiting further experimental validation and exploration.

CONCLUSION

We conclude that a successful and a conscious amalgamation of CADD and experimental approaches could pave the way for the discovery of the next generation potential leads in DLBCL therapy with improved activities and minimal toxicities.

Phase IB Study of Induction Chemotherapy With XELOX, Followed by Radiation Therapy, Carboplatin, and Everolimus in Patients With Locally Advanced Esophageal Cancer

PURPOSE

Preclinical studies have shown synergy between everolimus, an mTOR inhibitor, radiation, and platinum agents. We conducted a phase IB trial to determine the recommended phase II dose of everolimus with carboplatin and radiation.

MATERIALS AND METHODS

Patients with stage II/III esophageal cancer were enrolled. Following 2 cycles of Capecitabine/Oxaliplatin (XELOX), patients with no disease progression, received 50.4 Gy in 28 fractions and concurrent weekly carboplatin (area under the curve=2), with escalating doses of everolimus. A standard 3+3 dose escalation design was used.

RESULTS

Nineteen patients were enrolled. Two patients were screen failures and 4 were removed due to poor tolerance to XELOX (n=2) or disease progression (n=2). All treated patients had adenocarcinoma. Median age was 58 (44 to 71 y) and 85% were male patients. One patient at dose level 1 was replaced due to ongoing anxiety. One of 6 patients had a dose-limiting toxicity of bowel ischemia that was fatal. At dose level 2, two of 6 patients had a dose-limiting toxicity (fever with neutropenia and nausea). The recommended phase II dose of everolimus was 2.5 mg QOD. Grade ≥3 toxicities included lymphopenia (11%), nausea (10%), low white blood cell (8.0%) vomiting (5.5%), decreased neutrophils (4.0%). All patients achieved an R0 resection with a pathologic response rate of 40% and a pathologic complete response (ypCR) rate of 23%. The 2-year progression-free survival and overall survival were 50% and 49.6%, respectively.

CONCLUSIONS

The recommended phase II dose of everolimus with concurrent weekly carboplatin and radiation is 2.5 mg QOD.

Metabolic Reprogramming of Non-Hodgkin's B-Cell Lymphomas and Potential Therapeutic Strategies

Metabolism is a wide and general term that refers to any intracellular pathways the cell utilizes in order to satisfy its energetic demand and to support cell viability and/or division. Along with phenotypic changes, all mammalian cells including immune cells modulate their metabolic program in order to reach their effector functions. Exacerbated metabolism and metabolic flexibility are also hallmarks of tumor initiation and of tumor cell progression in a complex tumor microenvironment. Metabolic reprogramming is mainly directed by the serine/threonine kinase mTOR (mammalian target of rapamycin). mTOR exists in two structurally and functionally distinct complexes, mTORC1 and mTORC2 that coordinate environmental signals and metabolic/anabolic pathways to provide macromolecules and energy needed for survival and growth. Activation of mTORC1 is required during development, differentiation and activation of immune cells. Aberrant and persistent activation of mTORC1 is often observed in malignant B cells such as Non-Hodgkin's (NH) B-cell lymphomas. Here, we review recent insights on cell metabolism and on basic mechanisms of mTORC1 regulation and metabolic functions. We highlight the distinct mechanisms driving mTORC1 activation in the three most-common types of NH B-cell lymphomas (Diffuse Large B Cell Lymphomas, Follicular Lymphomas, and Mantle Cell Lymphomas), for which the first generation of mTORC1 inhibitors (rapalogs) have been extensively evaluated in preclinical and clinical settings. Finally, we discuss the reasons for limited clinical success of this therapy and focus on potential therapeutic strategies targeting metabolic pathways, upstream and downstream of mTORC1, that can be combined to rapalogs in order to improve patient's outcome.

Everolimus

Everolimus (RAD001) is an oral protein kinase inhibitor of the mTOR (mammalian target of rapamycin) serine/threonine kinase signal transduction pathway. The mTOR pathway regulates cell growth, proliferation and survival, and is frequently deregulated in cancer.The EMA has approved Everolimus as Afinitor^® for the treatment of hormone receptor-positive, HER2/neu-negative advanced breast cancer, in combination with exemestane, in postmenopausal women without symptomatic visceral disease after recurrence or progression following a nonsteroidal aromatase inhibitor, for the treatment of unresectable or metastatic, well- or moderately differentiated neuroendocrine tumors of pancreatic origin in adults with progressive disease, and for the treatment of unresectable or metastatic, well-differentiated (Grade 1 or Grade 2) nonfunctional neuroendocrine tumors of gastrointestinal or lung origin in adults with progressive disease, and for the treatment of patients with advanced renal cell carcinoma, whose disease has progressed on or after treatment with VEGF-targeted therapy And as Votubia^® for the treatment of adult patients with renal angiomyolipoma associated with tuberous sclerosis complex (TSC), who are at risk of complications (based on factors such as tumor size or presence of aneurysm, or presence of multiple or bilateral tumors) but who do not require immediate surgery, and for the treatment of patients with subependymal giant cell astrocytoma (SEGA) associated with TSC who require therapeutic intervention but are not amenable to surgery, and as an add-on treatment in patients from 2 years of age with seizures related to TSC that have not responded to other treatments ( https://www.novartis.com/news/media-releases/novartis-drug-votubiar-receives-eu-approval-treat-refractory-partial-onset ). The FDA has approved Everolimus as Afinitor^® for the treatment of postmenopausal women with advanced hormone receptor-positive, HER2-negative breast cancer in combination with exemestane, after the failure of treatment with letrozole or anastrozole, for the treatment of adult patients with progressive neuroendocrine tumors of pancreatic origin (PNET) with unresectable, locally advanced or metastatic disease, for the treatment of adult patients with advanced RCC after failure of treatment with sunitinib or sorafenib, for the treatment of adult patients with renal angiomyolipoma and tuberous sclerosis complex (TSC), not requiring immediate surgery. for the treatment of adult and pediatric patients, 3 years of age or older, with SEGA associated with TSC who require therapeutic intervention but are not candidates for curative surgical resection. Everolimus shows promising clinical activity in additional indications. Multiple Phase II and Phase III trials of everolimus alone or in combination and will help to further elucidate the role of mTOR in oncology. For a review on everolimus as immunosuppressant, please consult other sources.

Pharmacokinetically-targeted dosed everolimus maintenance therapy in lymphoma patients

BACKGROUND

Everolimus, an mTOR inhibitor, is active in refractory lymphomas. However, toxicity with flat dosing limits its usage. Speculatively, pharmacokinetically-targeted dosing could improve tolerability. Therefore, we studied serum-trough dosing with rituximab as maintenance after high-dose cyclophosphamide (HDC) consolidation in lymphoma patients.

PATIENTS/METHODS

After HDC, everolimus was dosed to serum trough levels (goal 3-15 ng/mL), with quarterly rituximab infusions for 1 year while maintaining < grade II non-hematologic and < grade III hematologic toxicities. Adult patients in first PR/CR with: mantle cell, transformed, double-hit, or high risk chronic lymphocytic leukemia or in second PR for any relapsed B cell lymphoma were eligible. Prophylaxis was given for encapsulated organisms, HSV and PCP. Serum IgG levels were maintained > 500 mg/dL.

RESULTS

49 patients, median age: 59.0 years enrolled; MCL (26), CLL (10), transformed lymphoma (7), and other histologies (6). During the life of the study, the most frequent everolimus dosing has been 2.5 mg daily or 2.5 mg every other day; at these doses, serum levels are within the therapeutic range and non-hematologic toxicity is rare. At a median follow-up of 27.1 months, three patients remain on active therapy. Two patients withdrew secondary to potentially-attributable adverse events including a bacterial pneumonia and a viral pneumonia; this low rate of discontinuation compares well to other long-term everolimus trials. While a 58 and 76% EFS at 30 months for the entire cohort and MCL cohort, respectively, compares similarly to previously published HDC/rituximab data, longer follow-up is required.

CONCLUSIONS

Pharmacokinetically-targeted dosing appears to increase everolimus tolerability. This finding may be applicable to other patient populations.

Post-autologous transplant maintenance therapies in lymphoma: current state and future directions

Disease relapse following high-dose chemotherapy and autologous stem cell transplant (ASCT) remains the principal cause of mortality in patients with relapsed or refractory lymphomas. In an effort to prevent post-ASCT relapse, a number of studies have evaluated the role of maintenance therapy with varying success. In diffuse large B-cell lymphoma, studies evaluating maintenance rituximab (MR) following ASCT failed to demonstrate improved outcomes. In follicular lymphoma, MR was associated with an improvement in PFS; however, no overall survival (OS) benefit was noted. Emerging data evaluating MR in mantle cell lymphoma (MCL) have demonstrated improvements in PFS, although a consistent improvement in OS has yet to be demonstrated. Given the aggressive and incurable nature of MCL, it is prudent for practitioners to weigh the risks and benefits of MR in the post-ASCT setting. Similarly, post-ASCT maintenance therapy with brentuximab vedotin in Hodgkin lymphoma, has led to improved PFS and may be considered in those with a high risk of relapse. Ongoing clinical studies evaluating a multitude of novel maintenance therapies are crucial to the efforts of further defining and optimizing the role of post-transplant maintenance therapy in lymphoma.

m-TOR inhibitors and their potential role in haematological malignancies

It is widely demonstrated that the PI3K-AKT-mTOR signalling is critical in normal myeloid and lymphoid development and function. Thus, it is not strange that this pathway is often deregulated in haematological tumours, providing a strong preclinical rationale for the use of drugs targeting the PI3K-AKT-mTOR axis in haematological malignancies. The main focus of this review is to examine the mammalian target of rapamycin (mTOR, also termed mechanistic target of rapamycin [MTOR]) signalling pathways and to provide a brief overview of rapalogs and second-generation mTOR inhibitors used to target its aberrant activation in cancer treatment. We will also discuss the results obtained with the use of these agents in patients with acute leukaemia, Hodgkin lymphoma, non-Hodgkin lymphomas, multiple myeloma and Waldenström macroglobulinaemia. Ongoing clinical trials in haematological malignancies that are investigating first- and second-generation mTOR inhibitors as single agents and as components of combination regimens are also presented.

Inhibition of 4EBP phosphorylation mediates the cytotoxic effect of mechanistic target of rapamycin kinase inhibitors in aggressive B-cell lymphomas

Mechanistic target of rapamycin (mTOR) complex 1 is a central integrator of nutrient and growth factor inputs that controls cell growth in eukaryotes. The second generation of mTOR kinase inhibitors (TORKi), directly targeting the mTOR catalytic site, are more effective than rapamycin and its analogs in cancer treatment, particularly in inducing apoptosis. However, the mechanism underlying the cytotoxic effect of TORKi remains elusive. Herein, we demonstrate that TORKi-induced apoptosis is predominantly dependent on the loss of mTOR complex 1-mediated 4EBP activation. Knocking out RICTOR, a key component of mTOR complex 2, or inhibiting p70S6K has little effect on TORKi-induced apoptosis. Conversely, increasing the eIF4E:4EBP ratio by either overexpressing eIF4E or knocking out 4EBP1/2 protects lymphoma cells from TORKi-induced cytotoxicity. Furthermore, downregulation of MCL1 expression plays an important role in TORKi-induced apoptosis, whereas BCL-2 overexpression confers resistance to TORKi treatment. We further show that the therapeutic effect of TORKi in aggressive B-cell lymphomas can be predicted by BH3 profiling, and improved by combining it with pro-apoptotic drugs, especially BCL-2 inhibitors, both in vitro and in vivo Taken together, the study herein provides mechanistic insight into TORKi cytotoxicity and identified a potential way to optimize its efficacy in the clinical treatment of aggressive B-cell lymphoma.

Targeting mTOR for the treatment of B cell malignancies

Mechanistic target of rapamycin (mTOR) is a serine/threonine kinase that functions as a key regulator of cell growth, division and survival. Many haematologic malignancies exhibit elevated or aberrant mTOR activation, supporting the launch of numerous clinical trials aimed at evaluating the potential of single agent mTOR-targeted therapies. While promising early clinical data using allosteric mTOR inhibitors (rapamycin and its derivatives, rapalogs) have suggested activity in a subset of haematologic malignancies, these agents have shown limited efficacy in most contexts. Whether the efficacy of these partial mTOR inhibitors might be enhanced by more complete target inhibition is being actively addressed with second generation ATP-competitive mTOR kinase inhibitors (TOR-KIs), which have only recently entered clinical trials. However, emerging preclinical data suggest that despite their biochemical advantage over rapalogs, TOR-KIs may retain a primarily cytostatic response. Rather, combinations of mTOR inhibition with other targeted therapies have demonstrated promising efficacy in several preclinical models. This review investigates the current status of rapalogs and TOR-KIs in B cell malignancies, with an emphasis on emerging preclinical evidence of synergistic combinations involving mTOR inhibition.

c-Myc Alteration Determines the Therapeutic Response to FGFR Inhibitors

Purpose: Lately, emerging evidence has suggested that oncogenic kinases are associated with specific downstream effectors to govern tumor growth, suggesting potential translational values in kinase-targeted cancer therapy. Tyrosine kinase FGFR, which is aberrant in various cancer types, is one of the most investigated kinases in molecularly targeted cancer therapy. Herein, we investigated whether there exists key downstream effector(s) that converges FGFR signaling and determines the therapeutic response of FGFR-targeted therapy.Experimental Design: A range of assays was used to assess the role of c-Myc in FGFR aberrant cancers and its translational relevance in FGFR-targeted therapy, including assessment of drug sensitivity using cell viability assay, signaling transduction profiling using immunoblotting, and in vivo antitumor efficacy using cancer cell line-based xenografts and patient-derived xenografts models.Results: We discovered that c-Myc functioned as the key downstream effector that preceded FGFR-MEK/ERK signaling in FGFR aberrant cancer. Disruption of c-Myc overrode the cell proliferation driven by constitutively active FGFR. FGFR inhibition in FGFR-addicted cancer facilitated c-Myc degradation via phosphorylating c-Myc at threonine 58. Ectopic expression of undegradable c-Myc mutant conferred resistance to FGFR inhibition both in vitro and in vivo c-Myc level alteration stringently determined the response to FGFR inhibitors, as demonstrated in FGFR-responsive cancer subset, as well as cancers bearing acquired or de novo resistance to FGFR inhibition.Conclusions: This study reveals a stringent association between FGFR and the downstream effector c-Myc in FGFR-dependent cancers, and suggests the potential therapeutic value of c-Myc in FGFR-targeted cancer therapy. Clin Cancer Res; 23(4); 974-84. ©2016 AACR.

Targeting translation: eIF4E as an emerging anticancer drug target

The translation initiation factor eIF4E mediates a rate-limiting process that drives selective translation of many oncongenic proteins such as cyclin D1, survivin and VEGF, thereby contributing to tumour growth, metastasis and therapy resistance. As an essential regulatory hub in cancer signalling network, many oncogenic signalling pathways appear to converge on eIF4E. Therefore, targeting eIF4E-mediated cap-dependent translation is considered a promising anticancer strategy. This paper reviews the strategies that can be used to target eIF4E, highlighting agents that target eIF4E activity at each distinct level.

The role of next-generation sequencing in understanding the genomic basis of diffuse large B cell lymphoma and advancing targeted therapies

Next Generation Sequencing (NGS) has redefined the genetic landscape of Diffuse Large B-Cell Lymphoma (DLBCL) by identifying recurrent somatic mutations. Importantly, in some cases these mutations impact potentially actionable targets, thus affording novel personalized therapy opportunities. At the forefront of today's precision therapy era, how to best incorporate NGS into daily clinical practice is of primordial concern, in order to tailor patient's treatment regimens according to their individual mutational profiles. With the advent of cell-free DNA sequencing, which provides a sensitive and less invasive means of monitoring DLBCL patients, the clinical feasibility of NGS has been greatly improved. This article reviews the current landscape of DLBCL mutations, as well as the targeted therapies developed to counter their effects, and discusses how best to utilize NGS data for treatment decision-making.

Blimp-1/PRDM1 regulates the transcription of human CS1 (SLAMF7) gene in NK and B cells

CS1 (CRACC/CD319/SLAMF7) is a member of SLAM (Signaling Lymphocyte Activation Molecule) family receptors and is expressed on NK cells, a subset of CD8(+) T lymphocytes, activated monocytes, mature dendritic cells and activated B cells. In NK cells, CS1 signaling induces cytolytic function of NK cells against targets whereas in B cells CS1 induces proliferation and autocrine cytokine production. CS1 is upregulated in multiple myeloma cells and contributes to clonogenic growth and tumorigenicity. However, the mechanism of CS1 upregulation is unknown. In this study, we analyzed the transcriptional regulation of human CS1 gene in NK and B cells. The promoter region of CS1 contains a Blimp-1/PRDM1 binding site and relative luciferase activities of successive deletion mutants of CS1 promoter were different between Blimp-1/PRDM1-positive and Blimp-1/PRDM1-negative cells. Proximal region of CS1 promoter contains a CAAT box and atypical TATA-box that might result in common transcription initiation at -29 nucleotides upstream of the ATG translation start codon. Electrophoretic Mobility Shift Assay (EMSA) and Chromatin Immunoprecipitation (ChIP) assays revealed Blimp-1/PRDM1 binds to the CS1 promoter region. Mutating the Blimp-1/PRDM1 site at -750 to -746 decreased the transcriptional activity of CS1 promoter implicating a trans-activating function of Blimp-1/PRDM1 in human CS1 gene regulation. The finding that Blimp-1/PRDM1 enhances transcription of CS1 gene in multiple myeloma cells may help in developing novel strategies for therapeutic intervention in multiple myeloma.

Synergistic induction of apoptosis by combination of BTK and dual mTORC1/2 inhibitors in diffuse large B cell lymphoma

Diffuse large B cell lymphoma is generally treated by chemotherapy and there is an unmet medical need for novel targeted therapies or combination therapies. Using in vitro screening, we have identified the combination of ibrutinib, an inhibitor of the tyrosine kinase BTK, and AZD2014, an mTOR catalytic inhibitor, as being highly synergistic in killing ABC-subtype DLBCL cell lines. Simultaneous inhibition of BTK and mTOR causes apoptosis both in vitro and in vivo and results in tumor regression in a xenograft model. We identify two parallel mechanisms that underlie apoptosis in this setting: cooperative inhibition of cap-dependent translation, and the inhibition of an NF-κB/IL10/STAT3 autocrine loop. Combined disruption of these pathways is required for apoptosis. These data represent a rational basis for the dual inhibition of BTK and mTOR as a potential treatment for ABC-subtype DLBCL.

Emerging drugs for diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most frequent non-Hodgkin lymphoma in western countries. Despite the addition of rituximab to chemotherapy, the prognosis is still poor and almost one-third of patients fail or relapse after first-line treatment. Gene expression profiling has identified three main signatures related to subgroups with different biological characteristics and responses to treatment. Novel agents targeting the oncogenic drivers of these subsets are currently under investigation with the aim of providing a tailored approach and avoiding unnecessary toxicity. Herein, we review the emerging therapies for DLBCL with a focus on preclinical and early clinical trials as well as future directions.

Everolimus in diffuse large B-cell lymphomas

ABSTRACT 

Satisfactory treatment of relapsed/refractory diffuse large B-cell lymphoma (DLBCL) is not currently available and novel therapies are needed. mTOR is an intracellular kinase that is part of an aberrantly activated pathway in DLBCL. Preclinical studies in DLBCL cell lines demonstrated that everolimus, an oral selective mTOR inhibitor, induces cell cycle arrest and is synergistic with rituximab. Phase I studies indicated 10 mg daily to be the best dosing of everolimus in DLBCL. A large Phase II study in relapsed/refractory DLBCL confirmed the substantial activity (overall response rate: 30%) and good tolerability of everolimus in DLBCL, with thrombocytopenia being the main toxicity. The combination of everolimus and rituximab showed encouraging results (objective response rate: 38%; complete response: 13%), without increasing toxicity. Combination studies of everolimus with novel agents or with immunochemotherapy are underway.

mTOR regulates brain morphogenesis by mediating GSK3 signaling

Balanced control of neural progenitor maintenance and neuron production is crucial in establishing functional neural circuits during brain development, and abnormalities in this process are implicated in many neurological diseases. However, the regulatory mechanisms of neural progenitor homeostasis remain poorly understood. Here, we show that mammalian target of rapamycin (mTOR) is required for maintaining neural progenitor pools and plays a key role in mediating glycogen synthase kinase 3 (GSK3) signaling during brain development. First, we generated and characterized conditional mutant mice exhibiting deletion of mTOR in neural progenitors and neurons in the developing brain using Nestin-cre and Nex-cre lines, respectively. The elimination of mTOR resulted in abnormal cell cycle progression of neural progenitors in the developing brain and thereby disruption of progenitor self-renewal. Accordingly, production of intermediate progenitors and postmitotic neurons were markedly suppressed. Next, we discovered that GSK3, a master regulator of neural progenitors, interacts with mTOR and controls its activity in cortical progenitors. Finally, we found that inactivation of mTOR activity suppresses the abnormal proliferation of neural progenitors induced by GSK3 deletion. Our findings reveal that the interaction between mTOR and GSK3 signaling plays an essential role in dynamic homeostasis of neural progenitors during brain development.

Postulated mechanisms of resistance of B-cell non-Hodgkin lymphoma to rituximab treatment regimens: strategies to overcome resistance

Antibody-mediated immunotherapy has gained significant momentum since 1997 when the US Food and Drug Administration approved the first monoclonal antibody (mAb) for the treatment of B-cell non-Hodgkin lymphoma (B-NHL), namely, rituximab (chimeric anti-CD20 mAb). Subsequently, more than 20 approved mAbs have been in use clinically for the treatment of various cancers and several non-cancer-related diseases. Further, the combination treatment of mAbs with chemotherapy, immunotherapy, proteaosome inhibitors, and other inhibitors has resulted in synergistic anti-tumor activity with significant objective clinical responses. Despite their successful clinical use, the underlying mechanisms of rituximab's in vivo activities remain elusive. Further, it is not clear why a subset of patients is initially unresponsive and many responding patients become refractory and resistant to further treatments; hence, the underlying mechanisms of resistance are not known, Attempts have been made to develop model systems to investigate resistance to mAb therapy with the hope to apply the findings in both the generation of new therapeutics and in their use as new prognostic biomarkers. This review focuses on the development of resistance to rituximab treatments and discusses possible underlying mechanisms of action, postulated mechanisms of resistance in model systems, and suggested means to overcome resistance. Several prior reviews on the subject of rituximab resistance have been published and the present review both complements as well as adds new topics of relevance.

Targeting PI3-kinase (PI3K), AKT and mTOR axis in lymphoma

Targeted therapy represents a transformation in oncology, a field that has relied primarily on non-selective cytotoxic therapies. Phosphatidylinositol 3-kinase (PI3K) is a family of ubiquitous signalling molecules involved in a wide variety of cellular processes and likewise, in a broad selection of human cancers. The discovery that the p110-δ form of PI3K is differentially expressed in normal and malignant lymphocytes has led to the development of specific inhibitors that are currently in clinical trials for lymphoma. Downstream effectors of PI3K, including v-akt murine thymoma viral oncogene homolog 1 (AKT; also termed AKT1) and mechanistic target of rapamycin (serine/threonine kinase) (mTOR) are similarly important in lymphoma, and agents targeting these components of the PI3K-AKT-mTOR axis are also underway, although at earlier stages of development. In this review we examine the role of PI3K-AKT-mTOR in normal and malignant lymphocytes, as well as the preclinical and clinical status of a number of inhibitors of this pathway.

Calcineurin inhibitor--free graft-versus-host disease prophylaxis with post-transplantation cyclophosphamide and brief-course sirolimus following reduced-intensity peripheral blood stem cell transplantation

Calcineurin inhibitors (CNIs) form the foundation of current graft-versus-host disease (GVHD) prophylaxis regimens. We hypothesized that a CNI-free regimen consisting of post-transplantation cyclophosphamide (PTCy) and brief-course sirolimus would reduce chronic GVHD and nonrelapse mortality (NRM) after reduced-intensity conditioning allogeneic peripheral blood stem cell transplantation (PBSCT). Twenty-six patients (median age, 61 years) underwent unmanipulated PBSCT from an 8/8 locus-matched donor (matched related donor, n = 17; natched unrelated donor, n = 9). GVHD prophylaxis consisted of PTCy and brief-course sirolimus. Donor engraftment occurred in all patients. The cumulative incidence (CI) of grade II-IV acute GVHD, grade III-IV acute GVHD, and chronic GVHD was 46%, 15%, and 31% respectively. One-year NRM was 4%. The median time to immunosuppression discontinuation was day +138. With a median follow-up of 20 months, the estimated 2-year overall survival was 71%, estimated disease-free survival was 64%, and estimated relapse incidence was 32%. In patients with a lymphoid malignancy (eg, chronic lymphoblastic leukemia, non-Hodgkin lymphoma, Hodgkin disease), 2-year disease-free survival was 100%, and there were no relapses. Good immune reconstitution was evidenced by low cytomegalovirus reactivation rate of 21% (4 of 19 at-risk patients). GVHD prophylaxis with PTCy and sirolimus achieves consistent donor engraftment, low rates of chronic GVHD and NRM, and excellent outcomes in recipients of HLA-identical related and unrelated donor allogeneic PBSCT.

Everolimus

Everolimus (RAD001, Afinitor®) is an oral protein kinase inhibitor of the mammalian target of rapamycin (mTOR) serine/threonine kinase signal transduction pathway. The mTOR pathway regulates cell growth, proliferation, and survival and is frequently deregulated in cancer. Everolimus has been approved by the FDA and the EMA for the treatment of advanced renal cell carcinoma (RCC), subependymal giant cell astrocytoma (SEGA) associated with tuberous sclerosis (TSC), pancreatic neuroendocrine tumors (PNET), in combination with exemestane in advanced hormone-receptor (HR)-positive, HER2-negative breast cancer. Everolimus shows promising clinical activity in additional indications. Multiple phase 2 and phase 3 trials of everolimus alone or in combination are ongoing and will help to further elucidate the role of mTOR in oncology. For a review on everolimus as immunosuppressant, please consult other sources.

Expression and significance of leptin receptor, p-STAT3 and p-AKT in diffuse large B-cell lymphoma

We investigated the expression and clinical significance of leptin receptor (OBR), p-STAT3 and p-AKT in patients with diffuse large B-cell lymphoma (DLBCL) by immunohistochemical analysis. Immunohistochemistry revealed high expression of OBR, p-STAT3 and p-AKT in 45.0% (36/80), 28.8% (23/80) and 18.8% (15/80) cases of DLBCL, respectively, and minimal staining in 100% (20/20) cases of RLH (P<0.05). Compared with GCB group, the non-GCB group had higher p-STAT3 expression rate (21/57 vs. 2/23, P<0.01). The expression of OBR was positively related with that of p-STAT3 and p-AKT in DLBCL patients (P<0.05). Our data suggest that OBR stimulates the JAK/STAT and PI3K/AKT signaling pathway and induces the phosphorylation of STAT3 and AKT. This may be involved in carcinogenesis and prognosis of DLBCL. The specific inhibitions could interfere in the combination of leptin with OBR and obstruct the JAK/STAT and PI3K/AKT signaling pathways, which could lead to new research and treatment strategies for DLBCL treatment.

A phase I study of everolimus and CHOP in newly diagnosed peripheral T-cell lymphomas

BACKGROUND

We performed a phase I study to determine the dose and safety of everolimus as a combination chemotherapy in peripheral T-cell lymphoma (PTCL).

METHODS

Four dose levels (2.5 to 10 mg) of everolimus from days 1 to 14 with CHOP (750 mg/m(2) cyclophosphamide, 50 mg/m(2) doxorubicin, and 1.4 mg/m(2) (maximum 2 mg) vincristine on day 1, and 100 mg/day prednisone on days 1 to 5) every 21 days were planned.

RESULTS

Fifteen patients newly diagnosed with stage III/IV PTCL were enrolled. One of 6 patients at dose level 2 (5 mg everolimus) had grade 3 hepatotoxicity and 3 of 6 patients at level 3 (7.5 mg everolimus) had grade 4 hematologic toxicities (two grade 4 thrombocytopenia and one grade 4 neutropenia with fever lasting more than 3 days). The recommended dose of everolimus for combination was 5 mg. There were no differences in steady state trough concentrations of everolimus between cycles 1 and 2 for all three dose levels. All evaluable patients achieved response (8 complete and 6 partial).

CONCLUSIONS

Everolimus (5 mg) can be safely combined with CHOP leading to a feasible and effective regimen for PTCL. The subsequent phase II is now in progress.

Inhibition of pan-class I phosphatidyl-inositol-3-kinase by NVP-BKM120 effectively blocks proliferation and induces cell death in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most frequent aggressive lymphoma, with a great demand for novel treatments for relapsing and refractory disease. Constitutive activation of the phosphatidyl-inositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway is often detected in this lymphoma. Inhibition of this signaling cascade with the pan-class I PI3K inhibitor NVP-BKM120 decreased cell proliferation and increased apoptotic cell death. DLBCL proliferation was further decreased if NVP-BKM120-induced autophagy was blocked. Treatment with NVP-BKM120 was associated with an increase of the pro-apoptotic BH3-only proteins Puma and Bim and down-regulation of the anti-apoptotic Bcl-xL and Mcl-1. Translation of Bcl-xL and Mcl-1 is facilitated by cap-dependent mRNA translation, a process that was partially inhibited by NVP-BKM120. Overall, we demonstrated here the potential of NVP-BKM120 for the treatment of DLBCL.

Trilayer micelles for combination delivery of rapamycin and siRNA targeting Y-box binding protein-1 (siYB-1)

A three layer (trilayer) polymeric micelle system based on the self-association of the triblock polymer poly(ethylene glycol)-b-poly{N-[N-(2-aminoethyl)-2-aminoethyl] aspartamide}-b-poly(ε-caprolactone) (PEG-b-PAsp(DET)-b-PCL) has been synthesized and investigated for combination delivery of rapamycin (RAP) and siRNA targeting Y-box binding protein-1 (siYB-1). The trilayer micelle is composed of (a) a hydrophilic poly(ethylene glycol) (PEG) block constituting the outer layer to improve pharmacokinetics, (b) an intermediate compartment composed of the cationic poly{2-[(2-aminoethyl)amino] ethyl aspartamide} (PAsp(DET)) segment for interacting with siYB-1, and (c) an inner hydrophobic poly(ε-caprolactone) (PCL) compartment for encapsulation of RAP. A major advantage of this system is biocompatibility since PEG and PCL are both approved by the FDA, and PAsp(DET) is a non-toxic pH responsive cationic poly(amino acid)-based polymer. In this study, it has been shown that PCL can encapsulate RAP with high loading efficiencies, and PAsp(DET) can successfully interact with siRNA for efficient transfection/knockdown with negligible cytotoxicity. The enhanced therapeutic efficacy of RAP/siYB-1 micelles was demonstrated in cell cultures and in a PC3 xenograft nude mouse model of human prostate cancer. Herein, we demonstrate that trilayer micelles are a promising approach to improve the simultaneous delivery of combination siRNA/drug therapies.

Discovery of the novel mTOR inhibitor and its antitumor activities in vitro and in vivo

The phosphoinositide 3-kinase (PI3-K)/Akt and mTOR signaling pathway plays a critical role in cell survival and proliferation and is often aberrantly activated in many types of cancer. The mTOR kinase protein, one of the key molecules in this pathway, has been shown to be an important target for cancer therapy. In the present study, a ligand docking method was used to screen for novel scaffold mTOR inhibitors. Sixty thousand compounds in the Natural Product Database were screened against the mTOR homologous structure, and 13 commercially available compounds listed in the top-ranked 100 compounds were selected for further examination. Compound [(E)-3-(4-(benzo[d][1,3]dioxol-5-yl)-2-oxobut-3-en-1-yl)- 3-hydroxyindolin-2-one; designated herein as 3HOI-BA-01] was then selected for further study of its antitumor activity. An in vitro study has shown that 3HOI-BA-01 inhibited mTOR kinase activity in a dose-dependent manner by directly binding with mTOR. In a panel of non-small cell lung cancer cells, the compound also attenuated mTOR downstream signaling, including the phosphorylation of p70S6K, S6, and Akt, resulting in G1 cell-cycle arrest and growth inhibition. Results of an in vivo study have shown that intraperitoneal injection of 3HOI-BA-01 in A549 lung tumor-bearing mice effectively suppressed cancer growth without affecting the body weight of the mice. The expression of downstream signaling molecules in the mTOR pathway in tumor tissues was also reduced after 3HOI-BA-01 treatment. Taken together, we identified 3HOI-BA-01 as a novel and effective mTOR inhibitor.

Activation of the PI3K/AKT/mTOR pathway in diffuse large B cell lymphoma: clinical significance and inhibitory effect of rituximab

Diffuse large B cell lymphoma (DLBCL) represents the most common subtype of non-Hodgkin lymphoma and accounts for approximately 30% of newly diagnosed lymphoid neoplasms in Western countries, and 40-50% in China. A better understanding of the biology of DLBCL is needed for the development of potential therapeutic agents that target specific intracellular pathways. In this study, expression of the important components of the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway and their clinical significance were investigated in 73 DLBCL cases. The effect of rituximab alone or combined with the PI3K/AKT/mTOR pathway inhibitor rapamycin was further evaluated in the DLBCL cell lines. A total of 73 patients were identified, including 45 men and 28 women aged 18 to 78 years (median age 50 years). Of these patients, p-AKT was positive in 40 cases (54.8%), p-p70S6K in 34 cases (46.6%), and p-4E-BP1 in 33 cases (45.2%). Activation of the PI3K/AKT/mTOR pathway was related to poor disease outcome in DLBCL patients treated with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) but not in those treated with rituximab-CHOP. Rituximab combined with rapamycin synergically downregulated the PI3K/AKT/mTOR signaling pathway. Western blot analysis revealed a baseline activation status of the PI3K/AKT/mTOR pathway in DLBCL cell lines, with high levels of p-AKT, p-mTOR, in addition to downstream molecules p-p70S6K and p-4E-BP1. The results indicate that the PI3K/AKT/mTOR pathway is a potentially important signaling route and an unfavorable prognostic factor for DLBCL. Patients with PI3K/AKT/mTOR activation experience a more rapidly deteriorating clinical course with poor treatment response and decreased survival time. Addition of rituximab could downregulate PI3K/AKT/mTOR activation, reversing its negative effect on chemotherapy-treated patients. In addition, our results indicate that the combination of rituximab and inhibition of the activated PI3K/AKT/mTOR pathway could be a promising target for DLBCL therapeutic intervention in the future.

Activity of the mTOR inhibitor RAD001, the dual mTOR and PI3-kinase inhibitor BEZ235 and the PI3-kinase inhibitor BKM120 in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most deadly cancers worldwide with only few therapeutic options for patients with advanced disease. There is growing evidence indicating that activation of the PI3K/Akt/mTOR pathway plays an important role in HCC and therefore represents a promising target for novel therapeutic approaches. The aim of this study was to evaluate and compare the antitumour activity of the mTOR inhibitor RAD001, the dual mTOR and PI3-kinase inhibitor BEZ235 and the PI3-kinase inhibitor BKM120 in vitro and in vivo.

EXPERIMENTAL DESIGN

The antitumour effects of RAD001, BEZ235 and BKM120 were analysed in seven hepatoma cell lines as mono and combination therapy with Doxorubicin, Cisplatin, Irinotecan or 5-Flourouracil in vitro and in xenografts. Cell-cycle progression, apoptosis, and autophagy were analysed. Furthermore, effects on mitochondrial respiration and glycolysis were assessed.

RESULTS

Treatment with RAD001, BEZ235 and BKM120 markedly reduced tumour cell viability. Combination of PI3K inhibitors with chemotherapy was most effective. RAD001, BEZ235 and BKM120 reduced tumour growth mainly by inhibiting cell-cycle progression rather than by inducing apoptosis. Interestingly, the antitumour effects were strongly associated with a reduction of mitochondrial respiration. BKM120, which exhibited the strongest antiproliferative effect, most strongly impaired oxidative phosphorylation compared with the other drugs.

CONCLUSIONS

In this study, BKM120 showed the strongest antitumour activity. Our findings suggest impairment of mitochondrial function as a relevant mechanism of BKM120. Moreover, combination of PI3K and mTOR inhibitors with cytotoxic agents could be promising option for non-cirrhotic HCC patients.