PIK3CA mutations are mutually exclusive with PTEN loss in diffuse large B-cell lymphoma

Research progress on the mechanism of common inflammatory pathways in the pathogenesis and development of lymphoma

In recent years, the incidence and mortality rates of lymphoma have gradually increased worldwide. Tumorigenesis and drug resistance are closely related to intracellular inflammatory pathways in lymphoma. Therefore, understanding the biological role of inflammatory pathways and their abnormal activation in relation to the development of lymphoma and their selective modulation may open new avenues for targeted therapy of lymphoma. The biological functions of inflammatory pathways are extensive, and they are central hubs for regulating inflammatory responses, immune responses, and the tumour immune microenvironment. However, limited studies have investigated the role of inflammatory pathways in lymphoma development. This review summarizes the relationship between abnormal activation of common inflammatory pathways and lymphoma development to identify precise and efficient targeted therapeutic options for patients with advanced, drug-resistant lymphoma.

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.

Genomic determinants in advanced endometrial cancer patients with sustained response to hormonal therapy- case series and review of literature

The incidence of endometrial cancer is increasing, however treatment options for advanced disease are limited. Hormonal therapy has demonstrated positive outcomes for Stage IV EC. Next generation sequencing (NGS) has increased our understanding of molecular mechanisms driving EC. In this case series, we selected six patients at our institution with Stage IV, hormone receptor positive, endometrial cancer currently being treated with hormonal therapy. All patients achieved SD for at least ≥ 1.5 years. We studied NGS data on all six patients to assess for any common genomic marker which could predict the SD of at least 1.5 years achieved in this group. Institutional Review Board (IRB) approval was obtained from Staten Island University Hospital and Northwell Health, New York. PTEN, PIK3CA, PIK3R1, and ARID1A mutations were found in 83%, 67% 50%, and 67% of patients respectively. TP53 and FGFR2 were both found in 50% of patients. All patients were positive for estrogen and/or progesterone receptor (ER+ and/or PR+). We did not find any one common mutation that could have predicted the observed response (or SD of ≥1.5 years) to hormone therapy. However, our data reflects the prevalence of various mutations reported in literature: (1) Hormone Receptor status is a positive prognostic indicator (2) PTEN/PIK3CA mutations can occur concurrently in EC (3) ARID1A coexists with PTEN (4) FGFR and PTEN pathways may be interlinked. We suggest NGS be employed frequently in patients with endometrial cancer to identify targetable mutations. Additional larger studies are needed to characterize the interplay between mutations.

Case Report: SMARCA4 (BRG1)-deficient undifferentiated carcinoma of gallbladder with genetic analysis

SMARCA4 (BRG1)-deficient undifferentiated carcinoma is a rare and highly aggressive malignancy. It has been reported to occur in a multiple range of organs. However, to the best of our knowledge, SMARCA4 (BRG1)-deficient undifferentiated carcinoma of gallbladder has not yet been reported. Here, we describe a case of SMARCA4 (BRG1)-deficient undifferentiated carcinoma of gallbladder. Through comprehensive genetic analysis, we hypothesized that in addition to SMARCA4 (BRG1) deficiency, other genetic changes might also be involved in the tumorigenesis of undifferentiated gallbladder cancer in this patient, particularly somatic mutations in the CTNNB1, KRAS, PIK3CA, TP53, CREBBP, and FANCI genes. To the best of our knowledge, this is the first report of SMARCA4 (BRG1)-deficient undifferentiated carcinoma of gallbladder with genetic analysis.

The Metabolism and Immune Environment in Diffuse Large B-Cell Lymphoma

Cells utilize different metabolic processes to maintain their growth and differentiation. Tumor cells have made some metabolic changes to protect themselves from malnutrition. These metabolic alterations affect the tumor microenvironment and macroenvironment. Developing drugs targeting these metabolic alterations could be a good direction. In this review, we briefly introduce metabolic changes/regulations of the tumor macroenvironment and microenvironment and summarize potential drugs targeting the metabolism in diffuse large B-cell lymphoma.

Novel agents in relapsed/refractory diffuse large B-cell lymphoma

Patients with relapsed or refractory (R/R) diffuse large B-cell lymphoma (DLBCL), ineligible for or relapsing after autologous stem-cell transplant or chimeric antigen-receptor T-cell therapies have poor outcomes. Several novel agents, polatuzumab vedotin, tafasitamab, loncastuximab tesirine, and selinexor, have been approved and offer new opportunities for this difficult to treat population. Studies are evaluating combination of these agents with chemotherapy and other emerging therapies. Additionally, advances in our understanding of DLBCL biology, genetics, and immune microenvironment have allowed for the identification of new therapeutic targets like Ikaros and Aiolos, IRAK4, MALT1, and CD47 with several agents in ongoing clinical trials. In this chapter we review updated data supporting the use of the approved agents and discuss other emerging novel therapies for patients with R/R DLBCL.

Design and Optimization of Thienopyrimidine Derivatives as Potent and Selective PI3Kδ Inhibitors for the Treatment of B-Cell Malignancies

Phosphoinositide 3-kinase δ (PI3Kδ) plays a critical role in B lymphocyte (B-cell) development and activation and has been a validated target for the treatment of B-cell malignancies. Herein, we report a series of thienopyrimidine derivatives as novel potent and selective PI3Kδ inhibitors based on a scaffold hopping design strategy. Among them, compound 6 exhibited nanomolar PI3Kδ potency and a favorable selectivity profile compared to other class I PI3K isoforms. In cellular assays, compound 6 showed antiproliferative activity against a panel of B-cell lymphoma cell lines in a low micromolar range, caused cell cycle arrest, and induced apoptosis in Pfeiffer and SU-DHL-6 cells. Further, compound 6 inhibited the activation of mouse B-cells. With support from in vivo pharmacokinetic studies, compound 6 demonstrated significant anticancer efficacy in a Pfeiffer xenograft mouse model. Overall, compound 6 is a promising PI3Kδ inhibitor worthy of further preclinical investigation for the treatment of B-cell malignancies.

The utility of cerebrospinal fluid-derived cell-free DNA in molecular diagnostics for the PIK3CA-related megalencephaly-capillary malformation (MCAP) syndrome: a case report

The megalencephaly-capillary malformation (MCAP) syndrome is an overgrowth disorder caused by mosaic gain-of-function variants in PIK3CA It is characterized by megalencephaly or hemimegalencephaly, vascular malformations, somatic overgrowth, among other features. Epilepsy is commonly associated with MCAP, and a subset of individuals have cortical malformations requiring resective epilepsy surgery. Like other mosaic disorders, establishing a molecular diagnosis is largely achieved by screening lesional tissues (such as brain or skin), with a low diagnostic yield from peripheral tissues (such as blood). Therefore, in individuals with MCAP in whom lesional tissues are scarce or unavailable or those ineligible for epilepsy surgery, establishing a molecular diagnosis can be challenging. Here we report on the utility of cerebrospinal fluid (CSF)-derived cfDNA for the molecular diagnosis of an individual with MCAP syndrome harboring a mosaic PIK3CA variant (c.3139C > T, p.His1047Tyr). The proband presented with asymmetric megalencephaly without significant dysgyria. He did not have refractory epilepsy and was therefore not a candidate for epilepsy surgery. However, he developed diffuse large B-cell lymphoma (DLBCL) in late childhood, with four CSF samples obtained via lumbar puncture for cancer staging during which one sample was collected for cfDNA extraction and sequencing. PIK3CA variant allele fractions in CSF cell-free DNA (cfDNA), skin fibroblasts, and peripheral blood were 3.08%, 37.31%, and 2.04%, respectively. This report illustrates the utility of CSF-derived cfDNA in MCAP syndrome. Minimally invasive-based molecular diagnostic approaches utilizing cfDNA not only facilitate accurate genetic diagnosis but also have important therapeutic implications for individuals with refractory epilepsy as repurposed PI3K-AKT-MTOR pathway-inhibitors become more widely available.

Smoothened (SMO) regulates insulin-like growth factor 1 receptor (IGF1R) levels and protein kinase B (AKT) localization and signaling

The oncoprotein Smoothened (SMO), a Frizzled-class-G-protein-coupled receptor, is the central transducer of hedgehog (Hh) signaling. While canonical SMO signaling is best understood in the context of cilia, evidence suggests that SMO has other functions in cancer biology that are unrelated to canonical Hh signaling. Herein, we provided evidence that elevated levels of human SMO show a strong correlation with elevated levels of insulin-like growth factor 1 receptor (IGF1R) and reduced survival in diffuse large B-cell lymphoma (DLBCL). As an integral component of raft microdomains, SMO plays a fundamental role in maintaining the levels of IGF1R in lymphoma and breast cancer cells as well IGF1R-associated activation of protein kinase B (AKT). Silencing of SMO increases lysosomal degradation and favors a localization of IGF1R to late endosomal compartments instead of early endosomal compartments from which much of the receptor would normally recycle. In addition, loss of SMO interferes with the lipid raft localization and retention of the remaining IGF1R and AKT, thereby disrupting the primary signaling context for IGF1R/AKT. This activity of SMO is independent of its canonical signaling and represents a novel and clinically relevant contribution to signaling by the highly oncogenic IGF1R/AKT signaling axis.

Comprehensive characterization of PTEN mutational profile in a series of 34,129 colorectal cancers

Loss of expression or activity of the tumor suppressor PTEN acts similarly to an activating mutation in the oncogene PIK3CA in elevating intracellular levels of phosphatidylinositol (3,4,5)-trisphosphate (PIP3), inducing signaling by AKT and other pro-tumorigenic signaling proteins. Here, we analyze sequence data for 34,129 colorectal cancer (CRC) patients, capturing 3,434 PTEN mutations. We identify specific patterns of PTEN mutation associated with microsatellite stability/instability (MSS/MSI), tumor mutational burden (TMB), patient age, and tumor location. Within groups separated by MSS/MSI status, this identifies distinct profiles of nucleotide hotspots, and suggests differing profiles of protein-damaging effects of mutations. Moreover, discrete categories of PTEN mutations display non-identical patterns of co-occurrence with mutations in other genes important in CRC pathogenesis, including KRAS, APC, TP53, and PIK3CA. These data provide context for clinical targeting of proteins upstream and downstream of PTEN in distinct CRC cohorts.

PIK3CA Mutations in Diffuse Gliomas: An Update on Molecular Stratification, Prognosis, Recurrence, and Aggressiveness

Introduction:

PIK3CA is one of the most mutated oncogenes in solid tumors. In breast cancer (ER-positive, HER2-negative), these events represent a predictive biomarker of response to alpelisib. In glioblastomas (GBM), PIK3CA mutations were described as early constitutive events. Here, we investigated PIK3CA mutational profile across glioma molecular subgroups and its relevance during glioma recurrence. Furthermore, PIK3CA mutations’ effect in PI3K pathway, prognosis, and response to therapy was also explored.

Material and Methods:

Exons 10 and 21 of PIK3CA mutations were evaluated in 394 gliomas and 19 glioma recurrences from Instituto Português de Oncologia Lisboa Francisco Gentil (IPOLFG) and compared with The Cancer Genome Atlas (TCGA) data. TIMER2.0 and NetMHCpan4.1 were used to assess the immune-microenvironment contribution.

Results:

PIK3CA mutations were identified among all glioma subgroups, although with no impact on their stratification or prognosis. In both cohorts (IPOLFG and TCGA), PIK3CA mutation frequencies in IDH-mutant and IDH-wild-type GBM were similar (IPOLFG: 9% and 3%; TCGA: 8% and 2%). These mutations were not mutually exclusive with PTEN deletion and EGFR amplification. Despite their reduced frequency, we discovered PIK3CA mutations were maintained during glioma recurrence regardless of administered therapies. The immune microenvironment might not contribute to this phenotype as PIK3CA mutations did not influence immune cell infiltration.

Conclusions:

Despite the absence of a predominant effect in glioma stratification, PIK3CA mutations were maintained during glioma recurrence, possibly contributing to glioma cell survival, representing promising therapeutic targets in recurrent glioma. Nevertheless, understanding the potential synergistic effects between PIK3CA mutations, PTEN deletion, and EGFR amplification is pivotal to targeted therapies’ efficiency.

miRNA-425-5p enhances diffuse large B cell lymphoma growth by targeting PTEN

BACKGROUND

At present, cancer is one of the greatest threats to mankind, and is associated with the highest rates of morbidity and comorbidity. Recently, the advancements in molecular biology have led to an in-depth understanding of the underlying pathophysiology, which may further impact the lead time in the context of early discovery and effective therapy of cancer. Therefore, the present study proposes a better understanding of the role of micro(miR)-425-5p in diffuse large B-cell lymphoma (DLBC).

METHODS

qRT-PCR was carried out to detect the relevant proteins, miRNA and mRNA RNA gene expression in DLBC cells. The effect of miR-425-5p on DLBC growth was examined by CCK-8 and colony formation assays. The binding relationship between genes was verified by dual-luciferase reporter gene assay.

RESULTS

We demonstrated how the over-expression of miR-425-5p can lead to increased progression of DLBC by increasing the cellular proliferation rate and colony-forming ability. Additionally, we also found that the expression of miR-425-5p could be significantly inhibited on the basis of phosphatase and tensin homolog (PTEN) signaling pathways.

CONCLUSIONS

The present study concludes that miR-425-5p is responsible for the oncogenic progression and relapse of DLBC tumorigenesis via PTEN/PI3K signaling, which can thus be effectively used to achieve better therapeutic outcomes.

Targeting the PI3K/AKT/mTOR Signaling Pathway in Primary Central Nervous System Lymphoma: Current Status and Future Prospects

Primary Central Nervous System Lymphoma (PCNSL) is a rare invasive extranodal non- Hodgkin lymphoma, a vast majority of which is Diffuse Large B-Cell Lymphoma (DLBCL). Although high-dose methotrexate-based immunochemotherapy achieves a high remission rate, the risk of relapse and related death remains a crucial obstruction to long-term survival. Novel agents for the treatment of lymphatic malignancies have significantly broadened the horizons of therapeutic options for PCNSL. The PI3K/AKT/mTOR signaling pathway is one of the most important pathways for Bcell malignancy growth and survival. Novel therapies that target key components of this pathway have shown antitumor effects in many B-cell malignancies, including DLBCL. This review will discuss the aberrant status of the PI3K/AKT/mTOR signaling pathways in PCNSL and the application prospects of inhibitors in hopes of providing alternative clinical therapeutic strategies and improving prognosis.

Large-Scale Proteomic Analysis of Follicular Lymphoma Reveals Extensive Remodeling of Cell Adhesion Pathway and Identifies Hub Proteins Related to the Lymphomagenesis

Simple Summary

Follicular lymphoma represents the major subtype of indolent B-cell non-Hodgkin lymphomas, ranging from about 20 to 30% of all B-NHLs cases in western countries. Yet, the global proteome profile of follicular lymphoma remains largely undocumented; thus, we aimed to employ for the first time a comprehensive proteomic analysis to outline its molecular landscape. A total of 15 lymphoma fine-needle aspiration biopsy samples and 14 controls were evaluated by label-free quantitative proteomics. Among the 7673 proteins identified in our dataset, 1186 proteins were differentially expressed between lymphoma and control samples. Importantly, dysregulated proteins were enriched in biological processes such as B-cell receptor signaling pathway, cellular adhesion molecules pathway, or membrane trafficking. Additionally, we identified several novel hub proteins related to lymphomagenesis. To summarize, we have determined the molecular characteristics of follicular lymphoma and discovered proteins which may hold potential for biomarkers or therapeutic targets.

Abstract

Follicular lymphoma (FL) represents the major subtype of indolent B-cell non-Hodgkin lymphomas (B-NHLs) and results from the malignant transformation of mature B-cells in lymphoid organs. Although gene expression and genomic studies have identified multiple disease driving gene aberrations, only a few proteomic studies focused on the protein level. The present work aimed to examine the proteomic profiles of follicular lymphoma vs. normal B-cells obtained by fine-needle aspiration biopsy (FNAB) to gain deep insight into the most perturbed pathway of FL. The cells of interest were purified by magnetic-activated cell sorting (MACS). High-throughput proteomic profiling was performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and allowed to identify of 6724 proteins in at least 75% of each group of samples. The ‘Total Protein Approach’ (TPA) was applied to the absolute quantification of proteins in this study. We identified 1186 differentially abundant proteins (DAPs) between FL and control samples, causing an extensive remodeling of several molecular pathways, including the B-cell receptor signaling pathway, cellular adhesion molecules, and PPAR pathway. Additionally, the construction of protein–protein interactions networks (PPINs) and identification of hub proteins allowed us to indicate the key player proteins for FL pathology. Finally, ICAM1, CD9, and CD79B protein expression was validated in an independent cohort by flow cytometry (FCM), and the results were consistent with the mass spectrometry (MS) data.

PTEN Loss and Cyclin A2 Upregulation Define a PI3K/AKT Pathway Activation in Helicobacter pylori-induced MALT and DLBCL Gastric Lymphoma With Features of MALT

Helicobacter pylori infection is strongly associated with primary gastric diseases, such as extranodal mucosa-associated lymphoid tissue (MALT) lymphoma, diffuse large B-cell lymphoma (DLBCL) with histologic evidence of MALT origin, and gastric carcinoma. The cytotoxin-associated gene A (CagA) protein behaves as a bacterial oncoprotein, promoting tumorigenesis via dysregulation of the phosphatidylinositol 3-kinase/AKT pathway (PI3K/AKT). We investigated the molecular mechanisms of PI3K/AKT pathway dysregulation in H. pylori-induced MALT and DLBCL gastric lymphoma. Immunohistochemical assays for CagA, phospho(p)-S473-AKT, PTEN, SHIP, and cyclin A2 proteins were performed on samples from 23 patients with H. pylori-positive MALT lymphoma and 16 patients with H. pylori-positive gastric DLBCL. We showed that CagA localization is correlated with the activation of the AKT pathway in both MALT and DLBCL lymphoma cells. Interestingly, we found a close association between the loss of PTEN, the overexpression of cyclin A2, and the phosphorylation of AKT in gastric MALT and DLBCL tumor cells.

The role of PI3K inhibitors in the treatment of malignant lymphomas

Deregulated phosphatidylinositide 3-kinase (PI3K) signaling plays a crucial role in the biology of different lymphoma entities leading to the proliferation and survival of the malignant cells. Due to novel treatment options and modern supportive care, the outcome of patients with lymphomas has significantly improved in the past years. However, patients with relapsed or refractory disease still have a limited prognosis. PI3K inhibitors represent a modern and effective therapeutic option for patients with different types of lymphoma. However, the efficacy of PI3K inhibitors varies among lymphoma entities. Additionally, severe toxicity including infectious and autoimmune complications leading to therapy-related deaths has been observed. Next-generation PI3K inhibitors show promising efficacy and manageable toxicity profiles. Future research might identify effective combinatorial therapy approaches for PI3K inhibitors to further improve response rates. This review discusses the most recent developments in the field of PI3K inhibition in different subtypes of lymphoma.

Effect of AKT1 (p. E17K) Hotspot Mutation on Malignant Tumorigenesis and Prognosis

The substitution of the seventeenth amino acid glutamate by lysine in the homologous structural domain of the Akt1 gene pleckstrin is a somatic cellular mutation found in breast, colorectal, and ovarian cancers, named p. Glu17Lys or E17K. In recent years, a growing number of studies have suggested that this mutation may play a unique role in the development of tumors. In this review article, we describe how AKT1(E17K) mutations stimulate downstream signals that cause cells to emerge transformed; we explore the differential regulation and function of E17K in different physiological and pathological settings; and we also describe the phenomenon that E17K impedes tumor growth by interfering with growth-promoting and chemotherapy-resistant AKT1^lowQCC generation, an intriguing finding that mutants may prolong tumor patient survival by activating feedback mechanisms and disrupting transcription. This review is intended to provide a better understanding of the role of AKT1(E17K) in cancer and to inform the development of AKT1(E17K)-based antitumor strategies.

Can Next-Generation PI3K Inhibitors Unlock the Full Potential of the Class in Patients With B-Cell Lymphoma?

Although outcomes after first-line therapy for patients with indolent or aggressive non-Hodgkin lymphoma (NHL) are continually improving, relapse is still common. Current treatment options for patients with relapsed or refractory disease have limited efficacy, and various targeted therapies are under investigation to help improve outcomes in this patient population. The phosphatidylinositol 3-kinase (PI3K) pathway was identified as being involved in hematologic malignancies, leading to significant research for potential therapeutic agents. This has led to 3 PI3K inhibitors (idelalisib, copanlisib, and duvelisib) being approved for the treatment of patients with relapsed or refractory follicular lymphoma who have received at least 2 prior systemic therapies, with reported response rates of 40% to 59%. With potential class-specific and PI3K isoform-related toxicities that may limit clinical utility, the safety of the approved PI3K inhibitors has been carefully evaluated to weigh the risk/benefit ratio of therapy. Currently, there are no approved PI3K inhibitors for patients with aggressive NHL. A number of newer PI3K inhibitors are in clinical development for the treatment of relapsed or refractory NHL, aiming to improve treatment benefit for patients. We discuss a number of attributes that are important to increase the therapeutic potential of newer PI3K inhibitors. More promising results may come from combination trials with these newer PI3K inhibitors, developed to limit toxicities (including long-term adverse events), and other antitumor agents.

Advances in targeted therapy for malignant lymphoma

The incidence of lymphoma has gradually increased over previous decades, and it ranks among the ten most prevalent cancers worldwide. With the development of targeted therapeutic strategies, though a subset of lymphoma patients has become curable, the treatment of refractory and relapsed diseases remains challenging. Many efforts have been made to explore new targets and to develop corresponding therapies. In addition to novel antibodies targeting surface antigens and small molecular inhibitors targeting oncogenic signaling pathways and tumor suppressors, immune checkpoint inhibitors and chimeric antigen receptor T-cells have been rapidly developed to target the tumor microenvironment. Although these targeted agents have shown great success in treating lymphoma patients, adverse events should be noted. The selection of the most suitable candidates, optimal dosage, and effective combinations warrant further investigation. In this review, we systematically outlined the advances in targeted therapy for malignant lymphoma, providing a clinical rationale for mechanism-based lymphoma treatment in the era of precision medicine.

Is There a Role for Dual PI3K/mTOR Inhibitors for Patients Affected with Lymphoma?

The activation of the PI3K/AKT/mTOR pathway is a main driver of cell growth, proliferation, survival, and chemoresistance of cancer cells, and, for this reason, represents an attractive target for developing targeted anti-cancer drugs. There are plenty of preclinical data sustaining the anti-tumor activity of dual PI3K/mTOR inhibitors as single agents and in combination in lymphomas. Clinical responses, including complete remissions (especially in follicular lymphoma patients), are also observed in the very few clinical studies performed in patients that are affected by relapsed/refractory lymphomas or chronic lymphocytic leukemia. In this review, we summarize the literature on dual PI3K/mTOR inhibitors focusing on the lymphoma setting, presenting both the three compounds still in clinical development and those with a clinical program stopped or put on hold.

Evaluation of the PIK3 pathway in peripheral T-cell lymphoma and NK/T-cell lymphoma

Peripheral T‐cell lymphomas (PTCL) and natural killer (NK)/T‐cell lymphomas (NKTCL) are a heterogeneous group of aggressive malignancies with dismal outcomes and limited treatment options. While the phosphatidylinositol 3‐kinase (PIK3) pathway has been shown to be highly activated in many B‐cell lymphomas, its therapeutic relevance in PTCL and NKTCL remains unclear. The aim of this study is to investigate the expression of PIK3 and phosphatase and tensin homolog (PTEN) in these subtypes of lymphoma and to identify potential therapeutic targets for clinical testing. Therefore, the expression of PIK3α, PIK3β, PIK3γ, PIK3δ and PTEN was analyzed in 88 cases of PTCL and NKTCL samples by immunohistochemistry. All PTCL and NKTCL samples demonstrated high expression of PIK3 isoforms. In particular, high PIK3α expression was significantly associated with poor survival, even after adjustment for age, International Prognostic Index (IPI) score and anthracycline‐based chemotherapy in first line. Notably, copanlisib, a pan‐class I inhibitor with predominant activities towards PIK3α and PIK3δ isoforms, effectively inhibited phosphorylation of AKT, 4E‐BP‐1 and STAT3, causing G₀/G₁ cell cycle arrest and resulting in suppression of tumour cell growth in vitro and in vivo. This study provides evidence that targeting the PIK3 pathway, particularly simultaneous inhibition of PIK3α and δ, could be a promising approach for the treatment of PTCL and NKTCL.

Unraveling the Heterogeneous Mutational Signature of Spontaneously Developing Tumors in MLH1-/- Mice

Mismatch repair deficient (MMR-D) tumors exemplify the prototypic hypermutator phenotype. Owing to the high mutation rates, plenty of neo-antigens are present on the tumor cells' surface, ideally shared among different cancer types. The MLH1 knock out mouse represents a preclinical model that resembles features of the human MMR-D counterpart. While these mice develop neoplasias in a sequential twin-peaked manner (lymphomas > gastrointestinal tumors (GIT)) we aimed at identification of underlying molecular mechanisms. Using whole-genome sequencing, we focused on (I) shared and (II) mutually exclusive mutations and describe the process of ongoing mutational events in tumor-derived cell cultures. The landscape of MLH1^-/- tumors is heterogeneous with only a few shared mutations being detectable among different tumor entities (ARID1A and IDH2). With respect to coding microsatellite analysis of MMR-D-related target genes, partial overlap was detectable, yet recognizing shared antigens. The present study is the first reporting results of a comparison between spontaneously developing tumors in MMR-D driven tumorigenesis. Additionally to identifying ARID1A as potential causative mutation hotspot, this comprehensive characterization of the mutational landscape may be a good starting point to refine therapeutic concepts.

Silencing the PIK3CA Gene Enhances the Sensitivity of Childhood Leukemia Cells to Chemotherapy Drugs by Suppressing the Phosphorylation of Akt

PURPOSE

This study aimed to investigate the effects of PIK3CA on the sensitivity of acute B lymphocytic leukemia cells (Nalm-6 cells) to chemotherapy drugs.

MATERIALS AND METHODS

Children's normal B lymphocytes and Nalm-6 cells were cultured. Nalm-6 cells were transfected with PIK3CA siRNA (siPIK3CA group) or its negative control (PIK3CA-Control group). Normal Nalm-6 cells were named Mock group. Nalm-6 cells transfected by PIK3CA siRNA were treated with Akt inhibitor (siPIK3CA+Akti-1/2 group). mRNA and protein expression was detected by qRT-PCR and Western blot. Proliferation and sensitivity to chemotherapeutic drugs was detected by MTT assay. Cell cycle and apoptosis was explored by low cytometry. Transwell assay was performed to test invasion.

RESULTS

PIK3CA mRNA (p=0.008) and protein (p=0.006) expression was higher in Nalm-6 cells than that in normal B lymphocytes. Compared with the Mock group and PIK3CA-Control group, Nalm-6 cells of the siPIK3CA group had lower OD495 values (all p<0.05) and invasion cell numbers (p=0.03 and p=0.025), as well as a higher proportion of G0/G1 phase cells (p=0.020 and p=0.022), percentage of apoptosis (p=0.016 and p=0.022), and inhibition rate (all p<0.05). pAkt expression in the siPIK3CA group (p=0.026 and p=0.031) and siPIK3CA+Akti-1/2 group (p=0.019 and p=0.023) was lower than that in the Mock group.

CONCLUSION

PIK3CA silencing inhibited Nalm-6 cell proliferation and invasion, and promoted their apoptosis and sensitivity to chemotherapeutic drugs, potentially through regulation of the PI3K/AKT signaling pathway.

Sleeping Beauty Screen Identifies RREB1 and Other Genetic Drivers in Human B-cell Lymphoma

Follicular lymphoma and diffuse large B-cell lymphoma (DLBCL) are the most common non-Hodgkin lymphomas distinguishable by unique mutations, chromosomal rearrangements, and gene expression patterns. Here, it is demonstrated that early B-cell progenitors express 2',3'-cyclic-nucleotide 3' phosphodiesterase (CNP) and that when targeted with Sleeping Beauty (SB) mutagenesis, Trp53R270H mutation or Pten loss gave rise to highly penetrant lymphoid diseases, predominantly follicular lymphoma and DLBCL. In efforts to identify the genetic drivers and signaling pathways that are functionally important in lymphomagenesis, SB transposon insertions were analyzed from splenomegaly specimens of SB-mutagenized mice (n = 23) and SB-mutagenized mice on a Trp53R270H background (n = 7) and identified 48 and 12 sites with statistically recurrent transposon insertion events, respectively. Comparison with human data sets revealed novel and known driver genes for B-cell development, disease, and signaling pathways: PI3K-AKT-mTOR, MAPK, NFκB, and B-cell receptor (BCR). Finally, functional data indicate that modulating Ras-responsive element-binding protein 1 (RREB1) expression in human DLBCL cell lines in vitro alters KRAS expression, signaling, and proliferation; thus, suggesting that this proto-oncogene is a common mechanism of RAS/MAPK hyperactivation in human DLBCL. IMPLICATIONS: A forward genetic screen identified new genetic drivers of human B-cell lymphoma and uncovered a RAS/MAPK-activating mechanism not previously appreciated in human lymphoid disease. Overall, these data support targeting the RAS/MAPK pathway as a viable therapeutic target in a subset of human patients with DLBCL.

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.

Targeting the B cell receptor pathway in non-Hodgkin lymphoma

INTRODUCTION

Dysregulated B cell receptor (BCR) signaling has been identified as a potent contributor to tumor survival in B cell non-Hodgkin lymphomas (NHLs). This pathway's emergence as a rational therapeutic target in NHL led to development of BCR-directed agents, including inhibitors of Bruton's tyrosine kinase (BTK), spleen tyrosine kinase (SYK), and phosphatidylinositol 3 kinase (PI3K). Several drugs have become valuable assets in the anti-lymphoma armamentarium.

AREAS COVERED

We provide an overview of the BCR pathway, its dysregulation in B cell NHL, and the drugs developed to target BCR signaling in lymphoma. Mechanisms, pharmacokinetics, pharmacodynamics, efficacy, and toxicity of currently available BTK, SYK, and PI3K inhibitors are described.

EXPERT OPINION

While the excellent response rates and favorable toxicity profile of the BTK inhibitor ibrutinib in certain NHL subtypes have propelled it to consideration as frontline therapy in selected populations, additional data and clinical studies are needed before other agents targeting BCR signaling influence clinical practice similarly. PI3K inhibitors remain an option for some relapsed indolent lymphomas and chronic lymphocytic leukemia, but their widespread use may be limited by adverse effects. Future research should include efforts to overcome resistance to BTK inhibitors, combination therapy using BCR-targeted agents, and exploration of novel agents.

Regulation of Hematopoietic Cell Development and Function Through Phosphoinositides

One of the most paramount receptor-induced signal transduction mechanisms in hematopoietic cells is production of the lipid second messenger phosphatidylinositol(3,4,5)trisphosphate (PIP₃) by class I phosphoinositide 3 kinases (PI3K). Defective PIP₃ signaling impairs almost every aspect of hematopoiesis, including T cell development and function. Limiting PIP₃ signaling is particularly important, because excessive PIP₃ function in lymphocytes can transform them and cause blood cancers. Here, we review the key functions of PIP₃ and related phosphoinositides in hematopoietic cells, with a special focus on those mechanisms dampening PIP₃ production, turnover, or function. Recent studies have shown that beyond “canonical” turnover by the PIP₃ phosphatases and tumor suppressors phosphatase and tensin homolog (PTEN) and SH2 domain-containing inositol-5-phosphatase-1 (SHIP-1/2), PIP₃ function in hematopoietic cells can also be dampened through antagonism with the soluble PIP₃ analogs inositol(1,3,4,5)tetrakisphosphate (IP₄) and inositol-heptakisphosphate (IP₇). Other evidence suggests that IP₄ can promote PIP₃ function in thymocytes. Moreover, IP₄ or the kinases producing it limit store-operated Ca²⁺ entry through Orai channels in B cells, T cells, and neutrophils to control cell survival and function. We discuss current models for how soluble inositol phosphates can have such diverse functions and can govern as distinct processes as hematopoietic stem cell homeostasis, neutrophil macrophage and NK cell function, and development and function of B cells and T cells. Finally, we will review the pathological consequences of dysregulated IP₄ activity in immune cells and highlight contributions of impaired inositol phosphate functions in disorders such as Kawasaki disease, common variable immunodeficiency, or blood cancer.

Phase I/II evaluation of RV1001, a novel PI3Kδ inhibitor, in spontaneous canine lymphoma

Background

RV1001 is a novel, potent, and selective PI3Kδ inhibitor. The purpose of this study was to evaluate the safety and efficacy of RV1001 in canine Non-Hodgkin lymphoma (NHL).

Methods and results

Inhibition of endogenous pAKT by RV1001 in primary canine NHL cells was determined by Western blotting. A phase I study of RV1001 was performed in 21 dogs with naïve and drug resistant T and B-cell NHL to assess safety, pharmacokinetic profile, and response to therapy. The objective response rate was 62% (complete response (CR) n = 3; partial response (PR) n = 10), and responses were observed in both naïve and chemotherapy-resistant B and T cell NHL. This study provided the recommended starting dose for a phase II, non-pivotal, exploratory, open label multi-centered clinical trial in 35 dogs with naïve and drug resistant T and B-cell NHL, to further define the efficacy and safety profile of RV1001. The objective response rate in the phase II study was 77% (CR n = 1; PR n = 26). Clinical toxicities were primarily hepatobiliary and gastrointestinal, and were responsive to dose modifications and/or temporary drug discontinuation. Hepatotoxicity was the primary dose limiting toxicity.

Conclusions

RV1001 exhibits good oral bioavailability, an acceptable safety profile, and biologic activity with associated inhibition of pAKT in dogs with B and T cell NHL. Data from these studies can be leveraged to help inform the design of future studies involving isoform-selective PI3K inhibitors in humans.

Voxtalisib (XL765) in patients with relapsed or refractory non-Hodgkin lymphoma or chronic lymphocytic leukaemia: an open-label, phase 2 trial

BACKGROUND

Patients with relapsed or refractory lymphoma or chronic lymphocytic leukaemia have a poor prognosis. Therapies targeting more than one isoform of PI3K, as well as mTOR, might increase antitumour activity. We aimed to investigate the efficacy and safety of voxtalisib (also known as XL765 or SAR245409), a pan-PI3K/mTOR inhibitor, in patients with relapsed or refractory lymphoma, or chronic lymphocytic leukaemia/small lymphocytic lymphoma.

METHODS

We did a non-randomised, open-label, phase 2 trial at 30 oncology clinics in the USA, Belgium, Germany, France, the Netherlands, and Australia. Patients aged 18 years or older with Eastern Cooperative Oncology Group (EGOG) performance status score of 2 or lower and relapsed or refractory mantle cell lymphoma, follicular lymphoma, diffuse large B-cell lymphoma, or chronic lymphocytic leukaemia/small lymphocytic lymphoma were enrolled and treated with voxtalisib 50 mg orally twice daily in 28-day continuous dosing cycles until progression or unacceptable toxicity. The primary endpoint was the proportion of patients in each disease-specific cohort who achieved an overall response, defined as a complete response or partial response. All patients who received more than 4 weeks of treatment and who completed a baseline and at least one post-baseline tumour assessment were analysed for efficacy and all patients were analysed for safety. This study is registered with ClinicalTrials.gov, number NCT01403636, and has been completed.

FINDINGS

Between Oct 19, 2011, and July 24, 2013, 167 patients were enrolled (42 with mantle cell lymphoma, 47 with follicular lymphoma, 42 with diffuse large B-cell lymphoma, and 36 with chronic lymphocytic leukaemia/small lymphocytic lymphoma. The median number of previous anticancer regimens was three (IQR 2-4) for patients with lymphoma and four (2-5) for patients with chronic lymphocytic leukaemia/small lymphocytic lymphoma. Of 164 patients evaluable for efficacy, 30 (18·3%) achieved an overall response (partial, n=22; complete, n=8); 19 (41·3%) of 46 with follicular lymphoma, five (11·9%) of 42 with mantle cell lymphoma, two (4·9%) of 41 with diffuse large B-cell lymphoma, and four (11·4%) of 35 with chronic lymphocytic leukaemia/small lymphocytic lymphoma. The safety profile was consistent with that of previous studies of voxtalisib. The most frequently reported adverse events were diarrhoea (in 59 [35%] of 167 patients), fatigue (in 53 [32%]), nausea (in 45 [27%]), pyrexia (in 44 [26%,]), cough (in 40 [24%]), and decreased appetite (in 35 [21%]). The most frequently reported grade 3 or worse adverse events were anaemia (in 20 [12%] of 167 patients), pneumonia (in 14 [8%]), and thrombocytopenia (in 13 [8%]). Serious adverse events occurred in 97 (58·1%) of 167 patients.

INTERPRETATION

Voxtalisib 50 mg given orally twice daily had an acceptable safety profile, with promising efficacy in patients with follicular lymphoma but limited efficacy in patients with mantle cell lymphoma, diffuse large B-cell lymphoma, or chronic lymphocytic leukaemia/small lymphocytic lymphoma.

FUNDING

Sanofi.

Critically dysregulated signaling pathways and clinical utility of the pathway biomarkers in lymphoid malignancies

Accumulating evidence confirmed that many dysregulated signaling pathways and aberrant genetic alterations contribute to the oncogenesis and heterogeneity of lymphoid malignancies. Therapeutically targeting dysregulating signaling pathways and their hidden oncogenic biomarkers are becoming available, but did not show desired therapeutic effect in current clinical practice. It is meaningful to further understand the underlying mechanisms of the dysregulated signaling pathways and to address the potential utility of pathway-related biomarkers. To precisely identify the dysregulation of signaling pathways and the “driver” oncogenic biomarkers, as well as to develop reliable and reproducible risk-stratification based on biomarkers will be challenging. Nevertheless, pathway-based targeted therapy will raise the hope to improve the outcomes of the patients with lymphoid malignancies, especially with aggressive types, and the efficient utility of pathway-related biomarkers in diagnosis, prognosis, prediction of lymphoid malignancies may also be able to power precision medicine.

Pan-phosphatidylinositol 3-kinase inhibition with buparlisib in patients with relapsed or refractory non-Hodgkin lymphoma

Activation of the phosphatidylinositol 3-kinase/mechanistic target of rapamycin pathway plays a role in the pathogenesis of non-Hodgkin lymphoma. This multicenter, open-label phase 2 study evaluated buparlisib (BKM120), a pan-class I phosphatidylinositol 3-kinase inhibitor, in patients with relapsed or refractory non-Hodgkin lymphoma. Three separate cohorts of patients (with diffuse large B-cell lymphoma, mantle cell lymphoma, or follicular lymphoma) received buparlisib 100 mg once daily until progression, intolerance, or withdrawal of consent. The primary endpoint was overall response rate based on a 6-month best overall response by cohort; secondary endpoints included progression-free survival, duration of response, overall survival, safety, and tolerability. Overall, 72 patients (26 with diffuse large B-cell lymphoma, 22 with mantle cell lymphoma, and 24 with follicular lymphoma) were treated. The overall response rates were 11.5%, 22.7%, and 25.0% in patients with diffuse large B-cell lymphoma, mantle cell lymphoma, and follicular lymphoma, respectively; two patients (one each with diffuse large B-cell lymphoma and mantle cell lymphoma) achieved a complete response. The most frequently reported (>20%) adverse events of any grade in the population in which safety was studied were hyperglycemia, fatigue, and nausea (36.1% each), depression (29.2%), diarrhea (27.8%), and anxiety (25.0%). The most common grade 3/4 adverse events included hyperglycemia (11.1%) and neutropenia (5.6%). Buparlisib showed activity in relapsed or refractory non-Hodgkin lymphoma, with disease stabilization and sustained tumor burden reduction in some patients, and acceptable toxicity. Development of mechanism-based combination regimens with buparlisib is warranted. (This study was funded by Novartis Pharmaceuticals Corporation and registered with ClinicalTrials.gov number, NCT01693614).

PQR309 Is a Novel Dual PI3K/mTOR Inhibitor with Preclinical Antitumor Activity in Lymphomas as a Single Agent and in Combination Therapy

Purpose: Activation of the PI3K/mTOR signaling pathway is recurrent in different lymphoma types, and pharmacologic inhibition of the PI3K/mTOR pathway has shown activity in lymphoma patients. Here, we extensively characterized the in vitro and in vivo activity and the mechanism of action of PQR309 (bimiralisib), a novel oral selective dual PI3K/mTOR inhibitor under clinical evaluation, in preclinical lymphoma models.Experimental Design: This study included preclinical in vitro activity screening on a large panel of cell lines, both as single agent and in combination, validation experiments on in vivo models and primary cells, proteomics and gene-expression profiling, and comparison with other signaling inhibitors.Results: PQR309 had in vitro antilymphoma activity as single agent and in combination with venetoclax, panobinostat, ibrutinib, lenalidomide, ARV-825, marizomib, and rituximab. Sensitivity to PQR309 was associated with specific baseline gene-expression features, such as high expression of transcripts coding for the BCR pathway. Combining proteomics and RNA profiling, we identified the different contribution of PQR309-induced protein phosphorylation and gene expression changes to the drug mechanism of action. Gene-expression signatures induced by PQR309 and by other signaling inhibitors largely overlapped. PQR309 showed activity in cells with primary or secondary resistance to idelalisib.Conclusions: On the basis of these results, PQR309 appeared as a novel and promising compound that is worth developing in the lymphoma setting. Clin Cancer Res; 24(1); 120-9. ©2017 AACR.

PI3Kδ-selective and PI3Kα/δ-combinatorial inhibitors in clinical development for B-cell non-Hodgkin lymphoma

INTRODUCTION

The efficacy of the prototypical phosphatidylinositol-3-kinase (PI3K) inhibitor idelalisib for the treatment of chronic lymphocytic leukemia (CLL) and indolent non-Hodgkin lymphoma (iNHL) has led to development of multiple compounds targeting this pathway. Areas Covered: We review the hypothesized therapeutic mechanisms of PI3K inhibitors, including abrogation of B cell receptor signaling, blockade of microenvironmental pro-survival signals, and enhancement of anti-tumor immunity. We examine toxicities of idelalisib, including bacterial infections (possibly secondary to drug-induced neutropenia), opportunistic infections (possibly attributable to on-target inhibition of T cell function), and organ toxicities such as transaminitis and enterocolitis (possibly autoimmune, secondary to on-target inhibition of p110δ in regulatory T cells). We evaluate PI3K inhibitors that have entered trials for the treatment of lymphoma, focusing on agents with selectivity for PI3Kα and PI3Kδ. Expert Opinion: PI3K inhibitors, particularly those that target p110δ, have robust efficacy in the treatment of CLL and iNHL. However, idelalisib has infectious and autoimmune toxicities that limit its use. Outside of trials, idelalisib should be restricted to CLL patients with progression on ibrutinib or iNHL patients with progression on two prior therapies. Whether newer PI3K inhibitors will demonstrate differentiated toxicity profiles in comparable patient populations while retaining efficacy remains to be seen.

PIK3CA amplification and PTEN loss in diffused large B-cell lymphoma

Although it has been known that PIK3CA was amplified and PTEN was deficient on protein level in DLBCL, the clinicopathological significance of PIK3CA and PTEN genetic change on DNA level hasn't been established. Here, in our present study, to understand the clinical significance of genetic status of PIK3CA and PTEN in DLBCL, fluorescent in-situ hybridization (FISH) was employed to evaluate the genetic change of PIK3CA and PTEN in clinical sample tissues consist of 205 cases. Incidentally, to understand the clinicopathological significance of genetic change of PIK3CA and PTEN, Cross-table analysis was used to analyze the association between genetic change of PIK3CA and PTEN versus clinicopathological variables available to us, including age, gender, size, location, international prognosis index, performance state, B-symptom, clinical stage, Extra nodal site, concentration of lactate dehydrogenase, therapeutic effects, treatment and overall prognosis. It was found that PIK3CA was amplified and PTEN was deficient on DNA level, the percentage of amplification and loss was 12.7% (26/205) and 12.2% (25/205), respectively. Additionally, no significant association was observed between genetic change of PIK3CA and PTEN versus clinicopathological variables available. Nor was the significant correlation found between loss of PTEN versus PIK3CA amplification. Our results suggest that PTEN deficiency and amplification of PIK3CA on DNA level was an event in the pathogenesis of DLBCL.

AKT Hyperactivation and the Potential of AKT-Targeted Therapy in Diffuse Large B-Cell Lymphoma

AKT signaling is important for proliferation and survival of tumor cells. The clinical significance of AKT activation in diffuse large B-cell lymphoma (DLBCL) is not well analyzed. Here, we assessed expression of phosphorylated AKT (p-AKT) in 522 DLBCL patients. We found that high levels of p-AKT nuclear expression, observed in 24.3% of the study cohort, were associated with significantly worse progression-free survival and Myc and Bcl-2 overexpression. However, multivariate analysis indicated that AKT hyperactivation was not an independent factor. miRNA profiling analysis demonstrated that 63 miRNAs directly or indirectly related to the phosphatidylinositol 3-kinase/AKT/mechanistic target of rapamycin pathway were differentially expressed between DLBCLs with high and low p-AKT nuclear expression. We further targeted AKT signaling using a highly selective AKT inhibitor MK-2206 in 26 representative DLBCL cell lines and delineated signaling alterations using a reverse-phase protein array. MK-2206 treatment inhibited lymphoma cell viability, and MK-2206 sensitivity correlated with AKT activation status in DLBCL cells. On MK-2206 treatment, p-AKT levels and downstream targets of AKT signaling were significantly decreased, likely because of the decreased feedback repression; Rictor and phosphatidylinositol 3-kinase expression and other compensatory pathways were also induced. This study demonstrates the clinical and therapeutic implications of AKT hyperactivation in DLBCL and suggests that AKT inhibitors need to be combined with other targeted agents for DLBCL to achieve optimal clinical efficacy.

PIK3CA expression in diffuse large B cell lymphoma tissue and the effect of its knockdown in vitro

PIK3CA has been extensively investigated from its molecular mechanism perspective and epidemiological association with its mutations in different types of cancers. However, little has been reported regarding the clinicopathological significance of PIK3CA expression in diffuse large B cell lymphoma (DLBCL). In the present study, we investigated the clinicopathological significance of PIK3CA in DLBCL by performing immunohistochemical evaluation of PIK3CA in tissue microarrays consisting of 199 cases of DLBCL. Kaplan-Meier survival analysis was performed to analyze the association between PIK3CA expression and overall prognosis. To further investigate the role of PIK3CA mediated in the proliferation, cell cycle and apoptosis of DLBCL cells, Cell Counting Kit-8 (CCK-8) and flow cytometry assays were carried out in DLBCL cell lines after successful, stable knockdown of PIK3CA using lentiviral short hairpin RNA inference. Our results indicated that although PIK3CA was shown to be extensively expressed in DLBCL, no significant association was observed between PIK3CA expression and clinical outcome or between PIK3CA expression and other clinicopathological parameters, except between performance state (PS) and phosphorylated AKT (p-AKT) expression. In vitro studies revealed that in DLBCL cell lines OCI-LY8 and OCI-LY1, knockdown of PIK3CA could significantly reduce proliferation and promote apoptosis in a G1-phase arrested manner. Additionally, p27 was shown to be markedly upregulated, whereas p-AKT and cyclin D1 were found to be pronouncedly downregulated after stable knockdown of PIK3CA. Together, our results support the oncogenic property of PIK3CA in DLBCL.

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.

Oncogenic Signaling Pathways and Pathway-Based Therapeutic Biomarkers in Lymphoid Malignancies

Lymphoma is characterized by heterogeneous biology, pathologic features, and clinical outcome. This has been proven by accumulating pathologic and molecular evidence attributed to underlying aberrant alterations at genetic, epigenetic, transcriptional, protein, microenvironmental levels, and dysregulated oncogenic signaling pathways. In the era of precision medicine, targeting oncogenic pathways to design drugs and to optimize treatment regimens for the lymphoma patients is feasible and clinically significant. As such, further understanding of the biology and the mechanisms behind lymphoma development and identification of oncogenic pathway activation and pathway-based biomarkers to better design precise therapies are challenging but hopeful. Furthermore, pathway-based targeted therapies in combination with traditional chemotherapy, single specific targeted antibody therapy, and immunotherapy might raise the hope for the patients with lymphoma, especially for relapsed and refractory lymphoma patients.

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.

The PTEN tumor suppressor gene and its role in lymphoma pathogenesis

The phosphatase and tensin homolog gene PTEN is one of the most frequently mutated tumor suppressor genes in human cancer. Loss of PTEN function occurs in a variety of human cancers via its mutation, deletion, transcriptional silencing, or protein instability. PTEN deficiency in cancer has been associated with advanced disease, chemotherapy resistance, and poor survival. Impaired PTEN function, which antagonizes phosphoinositide 3-kinase (PI3K) signaling, causes the accumulation of phosphatidylinositol (3,4,5)-triphosphate and thereby the suppression of downstream components of the PI3K pathway, including the protein kinase B and mammalian target of rapamycin kinases. In addition to having lipid phosphorylation activity, PTEN has critical roles in the regulation of genomic instability, DNA repair, stem cell self-renewal, cellular senescence, and cell migration. Although PTEN deficiency in solid tumors has been studied extensively, rare studies have investigated PTEN alteration in lymphoid malignancies. However, genomic or epigenomic aberrations of PTEN and dysregulated signaling are likely critical in lymphoma pathogenesis and progression. This review provides updated summary on the role of PTEN deficiency in human cancers, specifically in lymphoid malignancies; the molecular mechanisms of PTEN regulation; and the distinct functions of nuclear PTEN. Therapeutic strategies for rescuing PTEN deficiency in human cancers are proposed.

Phase I safety and pharmacokinetic dose-escalation study of pilaralisib polymorph E, a phosphoinositide 3-kinase inhibitor in tablet formulation, in patients with solid tumors or lymphoma

PURPOSE

Pilaralisib (SAR245408), a pan-class I PI3K inhibitor, has been investigated in Phase I/II trials in several solid tumors and lymphomas in capsule and tablet formulations of polymorph A (capsule-A and tablet-A). This Phase I study was conducted to determine the recommended Phase II dose (RP2D) of a more thermodynamically stable form of pilaralisib (polymorph E), in tablet formulation (tablet-E), in patients with advanced solid tumors or relapsed/refractory lymphoma.

METHODS

A modified '3 + 3' dose-escalation design was employed. Patients received pilaralisib once daily (QD; starting dose 400 mg) for two 28-day cycles. Primary endpoints were safety and pharmacokinetics (PK). Exploratory endpoints were pharmacodynamics and efficacy.

RESULTS

Eighteen patients were enrolled: Six patients received pilaralisib 400 mg QD and 12 patients received pilaralisib 600 mg QD. Two patients in the 600 mg QD cohort had dose-limiting toxicities (DLTs) (one patient with Grade 3 maculopapular rash and one patient with Grade 3 generalized rash and Grade 4 lipase increased). The most frequently occurring treatment-related, treatment-emergent adverse events were decreased appetite (22 %), dry skin (22 %), nausea (22 %) and vomiting (22 %). In PK analyses, individual exposures observed with 600 mg tablet-E were within the range of data at steady state from previous studies of 400 mg tablet-A and 600 mg capsule-A. Five patients (28 %) had stable disease as best response.

CONCLUSIONS

With pilaralisib tablet-E, the RP2D was 600 mg QD, drug exposure was similar to the 400 mg tablet-A and 600 mg capsule-A formulations, and safety was consistent with the known safety profile of pilaralisib.

Dual inhibition of histone deacetylases and phosphoinositide 3-kinases: effects on Burkitt lymphoma cell growth and migration

Burkitt lymphoma is a highly aggressive non-Hodgkin lymphoma that is characterized by MYC deregulation. Recently, the PI3K pathway has emerged as a cooperative prosurvival mechanism in Burkitt lymphoma. Despite the highly successful results of treatment that use high-dose chemotherapy regimens in pediatric Burkitt lymphoma patients, the survival rate of pediatric patients with progressive or recurrent disease is low. PI3Ks are also known to regulate cell migration, and abnormal cell migration may contribute to cancer progression and dissemination in Burkitt lymphoma. Little is known about Burkitt lymphoma cell migration, but the cooperation between MYC and PI3K in Burkitt lymphoma pathogenesis suggests that a drug combination could be used to target the different steps involved in Burkitt lymphoma cell dissemination and disease progression. The aim of this study was to investigate the effects of the histone deacetylase inhibitor suberoylanilide hydroxamic acid combined with the PI3K inhibitor LY294002 on Burkitt lymphoma cell growth and migration. The combination enhanced the cell growth inhibition and cell-cycle arrest induced by the PI3K inhibitor or histone deacetylase inhibitor individually. Moreover, histone deacetylase inhibitor/PI3K inhibitor cotreatment suppressed Burkitt lymphoma cell migration and decreased cell polarization, Akt and ERK1/2 phosphorylation, and leads to RhoB induction. In summary, the histone deacetylase inhibitor/PI3Ki combination inhibits cell proliferation and migration via alterations in PI3K signaling and histone deacetylase activity, which is involved in the acetylation of α-tubulin and the regulation of RhoB expression.

Phase I Trial of the Pan-PI3K Inhibitor Pilaralisib (SAR245408/XL147) in Patients with Chronic Lymphocytic Leukemia (CLL) or Relapsed/Refractory Lymphoma

PURPOSE

This phase I expansion-cohort study evaluated the safety, pharmacokinetics, pharmacodynamics, and preliminary efficacy of the pan-PI3K inhibitor pilaralisib (SAR245408/XL147) in patients with chronic lymphocytic leukemia (CLL) or relapsed or refractory lymphoma.

PATIENTS AND METHODS

Patients were treated with the maximum tolerated dose of pilaralisib previously determined in patients with solid tumors (600 mg capsules once daily). Adverse events (AE) and response were evaluated. Plasma pharmacokinetics and pharmacodynamic effects on cytokines and chemokines were also assessed.

RESULTS

Twenty-five patients were included in the study: 10 with CLL and 15 with lymphoma. The most frequent AEs of any grade were diarrhea (92.0%), pyrexia (52.0%), and fatigue (44.0%). The most frequent grade ≥3 AEs were neutropenia (32.0%), diarrhea (20.0%), and anemia (16.0%). Pilaralisib exposure on cycle 1 day 28 was similar to exposure in patients with solid tumors. In patients with CLL, pilaralisib significantly reduced plasma levels of several cytokines and chemokines involved in B-cell trafficking. Five patients (50.0%) with CLL and 3 patients (20.0%) with lymphoma had a partial response. Six patients (60.0%) with CLL had nodal shrinkage ≥50%. Overall, 14 patients (56.0%; 7 patients with CLL and 7 patients with lymphoma) had progression-free survival ≥6 months.

CONCLUSIONS

Pilaralisib demonstrated an acceptable safety profile in patients with CLL and lymphoma, generally consistent with findings in patients with solid tumors. Single-agent pilaralisib showed preliminary clinical activity in patients with CLL and lymphoma, supporting further development.

Efficacy, safety, pharmacokinetics and pharmacodynamics of SAR245409 (voxtalisib, XL765), an orally administered phosphoinositide 3-kinase/mammalian target of rapamycin inhibitor: a phase 1 expansion cohort in patients with relapsed or refractory lymphoma

The maximum tolerated dose of SAR245409 (voxtalisib), a pan-class I phosphoinositide 3-kinase (PI3K) and mammalian target of rapamycin (mTOR) inhibitor, was determined in a phase 1 dose-escalation study in advanced solid tumors. We report safety, pharmacokinetics (PK), pharmacodynamics and preliminary efficacy of SAR245409 capsules 50 mg twice daily in an expansion cohort of 16 patients with relapsed/refractory lymphoma. The most common treatment-related adverse events (AEs) were nausea (31.3%) and diarrhea (25.0%). The most common grade 3/4 treatment-related AE was increased alanine aminotransferase (12.5%). PK results were consistent with solid tumors, confirming a relatively short steady-state half-life (mean 4.61 h). Among 12 evaluable patients, one complete response and two partial responses were achieved in patients with and without PI3K/mTOR pathway alterations. In a patient with mantle cell lymphoma achieving PR, SAR245409 was associated with significant inhibition of PI3K/mTOR and extracellular signal-related kinase (ERK) pathways. Preliminary efficacy warrants further evaluation of SAR245409 in lymphoma.

Status of PI3K/Akt/mTOR pathway inhibitors in lymphoma

The phosphatidylinositol-3-kinase (PI3K) pathway is well known to regulate a wide variety of essential cellular functions, including glucose metabolism, translational regulation of protein synthesis, cell proliferation, apoptosis, and survival. Aberrations in the PI3K pathway are among the most frequently observed in cancer, and include amplifications, rearrangements, mutations, and loss of regulators. As a net result of these anomalies, the PI3K pathway is activated in many malignancies, including in Hodgkin and non-Hodgkin lymphomas, and yields a competitive growth and survival advantage, increased metastatic ability, and resistance to conventional therapy. Numerous inhibitors targeting various nodes in the PI3K pathway are undergoing clinical development, and their current status in lymphoma will be the focus of this review.

Current clinical regulation of PI3K/PTEN/Akt/mTOR signalling in treatment of human cancer

PURPOSE

PTEN is an essential tumour suppressor gene which encodes a phosphatase protein that antagonises the PI3K/Akt/mTOR antiapoptotic pathway. Impairment of this tumour suppressor pathway potentially becomes a causal factor for development of malignancies. This review aims to assess current understanding of mechanisms of dysfunction involving the PI3K/PTEN/Akt/mTOR pathway linked to tumorigenesis and evaluate the evidence for targeted therapy directed at this signalling axis.

METHODS

Relevant articles in scientific databases were identified using a combination of search terms, including "malignancies", "targeted therapy", "PTEN", and "combination therapy". These databases included Medline, Embase, Cochrane Review, Pubmed, and Scopus.

RESULTS

PI3K/PTEN expression is frequently deregulated in a majority of malignancies through genetic, epigenetic, and post-transcriptional modifications. This contributes to the upregulation of the PI3K/Akt/mTOR pathway which has been the focus of intense clinical studies. Targeted agents aimed at this pathway offer a novel treatment approach in a variety of haematologic malignancies and solid tumours. Compared to single-agent use, greater response rates were obtained in combination regimens, supporting further investigation of suitable drug combinations in a broad spectrum of malignancies.

CONCLUSION

Activation of the PI3K/PTEN/Akt/mTOR pathway is implicated both in the pathogenesis of malignancies and development of resistance to anticancer therapies. Therefore, PI3K/Akt/mTOR inhibitors are a promising therapeutic option, in association with systemic cytotoxic and biological therapies, to enable sustained clinical outcomes in cancer treatment. Therapeutic strategies could be tailored according to appropriate biomarkers and patient-specific mutation profiles to maximise benefit of combination therapies.

Constitutive AKT activation in follicular lymphoma

BACKGROUND

The phosphoinositide 3- kinase (PI3K) pathway is involved in the growth of various human cancers, including lymphoid malignancies. However its role in the pathogenesis of follicular lymphoma (FL) has not been yet described.

METHODS

To clarify this point, biopsy tissue samples from 38 human FL cases were investigated for PIK3CA somatic mutations in exon 9 and 20 using direct sequencing. The same samples were analyzed using western blotting and immunohistochemistry to detect expression of AKT, phosphorylated AKT (pAKT), and PTEN proteins. Two cases of benign lymphadenitis were used as controls.

RESULTS

AKT expression was present in all FL and lymphadenitis cases. 14/38 (37%) FL and 2/2 lymphadenitis cases expressed pAKT. 9/38 (24%) FL samples showed high level of pAKT, whereas 5/38 (13%) FL cases and 2/2 benign lymphadenitis samples expressed low level of pAKT. PTEN expression was observed in 30/38 (79%) FL and 2/2 benign lymphadenitis cases, whereas 8/38 (21%) FL cases showed loss of PTEN expression. 3 cases with positive pAKT did not express PTEN. PIK3CA mutations were not detected in any sample.

CONCLUSIONS

These data suggest that the PI3K/AKT signaling pathway could be activated in a subset of FL cases, due to either AKT phosphorylation or PTEN downregulation, in the absence of PIK3CA mutations.

PI3K/mTOR inhibition markedly potentiates HDAC inhibitor activity in NHL cells through BIM- and MCL-1-dependent mechanisms in vitro and in vivo

PURPOSE

The aim of this study is to explore the efficacy and define mechanisms of action of coadministration of the PI3K/mTOR inhibitor BEZ235 and pan-HDAC inhibitor panobinostat in diffuse large B-cell lymphoma (DLBCL) cells.

EXPERIMENTAL DESIGN

Various DLBCL cells were exposed to panobinostat and BEZ235 alone or together after which apoptosis and signaling/survival pathway perturbations were monitored by flow cytometry and Western blot analysis. Genetic strategies defined the functional significance of such changes, and xenograft mouse models were used to assess tumor growth and animal survival.

RESULTS

Panobinostat and BEZ235 interacted synergistically in ABC-, GC-, and double-hit DLBCL cells and MCL cells but not in normal CD34(+) cells. Synergism was associated with pronounced AKT dephosphorylation, GSK3 dephosphorylation/activation, Mcl-1 downregulation, Bim upregulation, increased Bcl-2/Bcl-xL binding, diminished Bax/Bak binding to Bcl-2/Bcl-xL/Mcl-1, increased γH2A.X phosphorylation and histone H3/H4 acetylation, and abrogation of p21(CIP1) induction. BEZ235/panobinostat lethality was not susceptible to stromal/microenvironmental forms of resistance. Genetic strategies confirmed significant functional roles for AKT inactivation, Mcl-1 downregulation, Bim upregulation, and Bax/Bak in synergism. Finally, coadministration of BEZ235 with panobinostat in immunocompromised mice bearing SU-DHL4-derived tumors significantly reduced tumor growth in association with similar signaling changes observed in vitro, and combined treatment increased animal survival compared with single agents.

CONCLUSIONS

BEZ235/panobinostat exhibits potent anti-DLBCL activity, including in poor-prognosis ABC- and double-hit subtypes, but not in normal CD34(+) cells. Synergism is most likely multifactorial, involving AKT inactivation/GSK3 activation, Bim upregulation, Mcl-1 downregulation, enhanced DNA damage, and is operative in vivo. Combined PI3K/mTOR and HDAC inhibition warrants further attention in DLBCL.