Cytotoxic activity of the novel Akt inhibitor, MK-2206, in T-cell acute lymphoblastic leukemia

PTEN Mediates the Silencing of Unintegrated HIV-1 DNA

The integration of viral DNA into a host genome is an important step in HIV-1 replication. However, due to the high failure rate of integration, the majority of viral DNA exists in an unintegrated state during HIV-1 infection. In contrast to the robust expression from integrated viral DNA, unintegrated HIV-1 DNA is very poorly transcribed in infected cells, but the molecular machinery responsible for the silencing of unintegrated HIV-1 DNA remains poorly characterized. In this study, we sought to characterize new host factors for the inhibition of expression from unintegrated HIV-1 DNA. A genome-wide CRISPR-Cas9 knockout screening revealed the essential role of phosphatase and tensin homolog (PTEN) in the silencing of unintegrated HIV-1 DNA. PTEN's phosphatase activity negatively regulates the PI3K-Akt pathway to inhibit the transcription from unintegrated HIV-1 DNA. The knockout (KO) of PTEN or inhibition of PTEN's phosphatase activity by point mutagenesis activates Akt by phosphorylation and enhances the transcription from unintegrated HIV-1 DNA. Inhibition of the PI3K-Akt pathway by Akt inhibitor in PTEN-KO cells restores the silencing of unintegrated HIV-1 DNA. Transcriptional factors (NF-κB, Sp1, and AP-1) are important for the activation of unintegrated HIV-1 DNA in PTEN-KO cells. Finally, the knockout of PTEN increases the levels of active epigenetic marks (H3ac and H3K4me3) and the recruitment of PolII on unintegrated HIV-1 DNA chromatin. Our experiments reveal that PTEN targets transcription factors (NF-κB, Sp1, and AP-1) by negatively regulating the PI3K-Akt pathway to promote the silencing of unintegrated HIV-1 DNA.

WDR54 exerts oncogenic roles in T-cell acute lymphoblastic leukemia

WDR54 has been recently identified as a novel oncogene in colorectal and bladder cancers. However, the expression and function of WDR54 in T-cell acute lymphoblastic leukemia (T-ALL) were not reported. In this study, we investigated the expression of WDR54 in T-ALL, as well as its function in T-ALL pathogenesis using cell lines and T-ALL xenograft. Bioinformatics analysis indicated high mRNA expression of WDR54 in T-ALL. We further confirmed that the expression of WDR54 was significantly elevated in T-ALL. Depletion of WDR54 dramatically inhibited cell viability and induced apoptosis and cell cycle arrest at S phase in T-ALL cells in vitro. Moreover, knockdown of WDR54 impeded the process of leukemogenesis in a Jurkat xenograft model in vivo. Mechanistically, the expression of PDPK1, phospho-AKT (p-AKT), total AKT, phospho-ERK (p-ERK), Bcl-2 and Bcl-xL were downregulated, while cleaved caspase-3 and cleaved caspase-9 were upregulated in T-ALL cells with WDR54 knockdown. Additionally, RNA-seq analysis indicated that WDR54 might regulate the expression of some oncogenic genes involved in multiple signaling pathways. Taken together, these findings suggest that WDR54 may be involved in the pathogenesis of T-ALL and serve as a potential therapeutic target for the treatment of T-ALL.

The pathogenesis and development of targeted drugs in acute T lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is mainly classified into acute T- and B-lymphoblastic leukaemia according to the source of its lymphocytes, thymus and bone. Among them, the incidence of adult T-cell accounts for about 25% of adult acute lymphoblastic leukaemia, but the degree of malignancy is high and the treatment rate and prognosis are poor. At this stage, there are few targeted drugs and the commonly used broad-spectrum chemotherapeutic drugs have poor efficacy and many adverse drug reactions. Understanding and investigating the pathogenesis of T-acute lymphoblastic leukaemia is very important for further developing new targeting drugs and improving existing drugs. Dysregulated signalling pathways are the main aetiological factors of T-acute lymphoblastic leukaemia. They play crucial roles in promoting tumour initiation, progression, drug design and therapy responses. This is primarily because signalling pathways are indispensable for many cellular biological processes, including tumour growth, migration, invasion, metastasis and others. As a result, small molecule inhibitors targeting the major kinase components of the signalling pathway have received a lot of attention and have been developed and evaluated in preclinical models and clinical trials. Already marketed drugs are also being repurposed in combination therapies to further improve efficacy and overcome tumour cell resistance. In this review, we have aimed to examine the latest and most classical signalling pathways in the aetiology of T-acute lymphoblastic leukaemia and shed light on potential targets for novel therapeutic agents to act on.

T-cell acute lymphoblastic leukemia: promising experimental drugs in clinical development

INTRODUCTION

Despite advances in treatment approaches in acute lymphoblastic leukemia (ALL), the prognosis of adults with newly diagnosed T-ALL remains poor, as well as that of adults and children with relapsed disease. Novel targeted therapies are therefore needed.

AREAS COVERED

This review summarizes promising emerging strategies for the treatment of T-ALL.

EXPERT OPINION

The recent molecular characterization of T-ALL has led to the identification of new therapeutic targets. Small-molecules inhibitors and other targeted therapies have therefore been recently developed and are currently under clinical investigations. Similarly, first studies involving monoclonal antibodies and chimeric antigen receptor (CAR) T cells have shown encouraging results. Improvement of outcome with these novel approaches, eventually combined with current standard chemotherapy, is therefore expected in a near future in T-ALL.

Combined treatment with ruxolitinib and MK-2206 inhibits the JAK2/STAT5 and PI3K/AKT pathways via apoptosis in MDA-MB-231 breast cancer cell line

BACKGROUND

Due to deficiencies in the expression of hormone receptors, such as PR, ER and HER2, it is challenging to treat triple-negative breast cancer, which does not respond to single targeted therapy. Ruxolitinib is a Janus kinase (JAK)1/JAK2 inhibitor. MK-2206 is an allosteric AKT inhibitor. Due to the limited activities of ruxolitinib and MK-2206 for monotherapy, the need for cotreatment with other drugs has emerged. This study is the first to examine the effects of ruxolitinib and MK-2206 cotreatment on apoptosis and JAK2/STAT5 and PI3K/AKT signaling in MDA-MB-231 breast cancer cells. Additionally, this work aimed to decrease the side effects of ruxolitinib and increase its anticancer effects with MK-2206 cotreatment.

METHODS AND RESULTS

Cell viability was reduced in a dose- and time-dependent manner after exposure to ruxolitinib, MK-2206 or both for 48 h, as shown by MTT assay. Ruxolitinib had a synergistic antiproliferative effect, as demonstrated by colony formation and wound healing assays. The effects of ruxolitinib, MK-2206 and their combination on apoptosis, as well as PI3K/AKT and JAK/STAT signaling, were examined by western blot analyses. Cotreatment with ruxolitinib and MK-2206 reduced proliferation with the dual inhibition of JAK2/STAT5 and PI3K/AKT signaling by decreasing PI3K, AKT, JAK2, STAT5, Caspase-9, Caspase-7, PARP, c-Myc, and Bcl-2 and increasing P53 and PTEN protein expression.

CONCLUSIONS

Our results revealed the roles of P53 and PTEN in the regulation of apoptosis and the PI3K/AKT and JAK2/STAT5 signaling pathways. The dual inhibition of JAK2/STAT5 and PI3K/AKT may reduce metastasis by decreasing tumor cell survival.

Targeting Leukemia-Initiating Cells and Leukemic Niches: The Next Therapy Station for T-Cell Acute Lymphoblastic Leukemia?

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive subtype of hematological malignancy characterized by its high heterogeneity and potentially life-threatening clinical features. Despite the advances in risk stratification and therapeutic management of T-ALL, patients often suffer from treatment failure and chemotherapy-induced toxicity, calling for greater efforts to improve therapeutic efficacy and safety in the treatment of T-ALL. During the past decades, increasing evidence has shown the indispensable effects of leukemia-initiating cells (LICs) and leukemic niches on T-ALL initiation and progression. These milestones greatly facilitate precision medicine by interfering with the pathways that are associated with LICs and leukemic niches or by targeting themselves directly. Most of these novel agents, either alone or in combination with conventional chemotherapy, have shown promising preclinical results, facilitating them to be further evaluated under clinical trials. In this review, we summarize the latest discoveries in LICs and leukemic niches in terms of T-ALL, with a particular highlight on the current precision medicine. The challenges and future prospects are also discussed.

Modern treatment approaches to adult acute T-lymphoblastic and myeloid/T-lymphoblastic leukemia: from current standards to precision medicine

PURPOSE OF REVIEW

To review the most recent advancements in the management of adult T-cell acute lymphoblastic leukemia (T-ALL), we summarize insights into molecular diagnostics, immunotherapy, targeted therapy and new techniques of drug sensitivity profiling that may support further therapeutic progress in T-ALL subsets.

RECENT FINDINGS

With current induction/consolidation chemotherapy and/or risk-oriented allogeneic stem cell transplantation programs up to 95% adult T-ALL patients achieve a remission and >50% (up to 80% in adolescents and young adults) are cured. The group of patients who fail upfront therapy, between 25% and 40%, is enriched in high-risk characteristics (unfavorable genetics, persistent minimal residual disease) and represents the ideal setting for the study of molecular mechanisms of disease resistance, and consequently explore novel ways of restoration of drug sensitivity and assess patient/subset-specific patterns of drug vulnerability to targeting agents, immunotherapy and cell therapy.

SUMMARY

The emerging evidence supports the contention that precision medicine may soon allow valuable therapeutic chances to adult patients with high-risk T-ALL. The ongoing challenge is to identify the best way to integrate all these new data into the therapeutic path of newly diagnosed patients, with a view to optimize the individual treatment plan and increase the cure rate.

Identification and development of a subtype-selective allosteric AKT inhibitor suitable for clinical development

The serine/threonine protein kinase AKT plays a pivotal role within the PI3K pathway in regulating cellular proliferation and apoptotic cellular functions, and AKT hyper-activation via gene amplification and/or mutation has been implicated in multiple human malignancies. There are 3 AKT isoenzymes (AKT1-3) which mediate critical, non-redundant functions. We present the discovery and development of ALM301, a novel, allosteric, sub-type selective inhibitor of AKT1/2. ALM301 binds in an allosteric pocket created by the combined movement of the PH domain and the catalytic domain, resulting in a DFG out conformation. ALM301 was shown to be highly selective against a panel of over 450 kinases and potently inhibited cellular proliferation. These effects were particularly pronounced in MCF-7 cells containing a PI3KCA mutation. Subsequent cellular downstream pathway analysis in this sensitive cell line revealed potent inhibition of pAKT signalling up to 48 h post dosing. ALM301 treatment was well tolerated in an MCF-7 xenograft model and led to a dose-dependent reduction in tumour growth. Enhanced efficacy was observed in combination with tamoxifen. In summary, ALM301 is a highly specific AKT 1/2 inhibitor with an excellent pharmacological profile suitable for further clinical development.

Targeting dual oncogenic machineries driven by TAL1 and PI3K-AKT pathways in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is a malignancy of thymic T-cell precursors. Overexpression of oncogenic transcription factor TAL1 is observed in 40-60% of human T-ALL cases, frequently together with activation of the NOTCH1 and PI3K-AKT pathways. In this study, we performed chemical screening to identify small molecules that can inhibit the enhancer activity driven by TAL1 using the GIMAP enhancer reporter system. Among approximately 3,000 compounds, PIK- 75, a known inhibitor of PI3K and CDK, was found to strongly inhibit the enhancer activity. Mechanistic analysis demonstrated that PIK-75 blocks transcriptional activity, which primarily affects TAL1 target genes as well as AKT activity. TAL1-positive, AKT-activated T-ALL cells were very sensitive to PIK-75, as evidenced by growth inhibition and apoptosis induction, while T-ALL cells that exhibited activation of the JAK-STAT pathway were insensitive to this drug. Together, our study demonstrates a strategy targeting two types of core machineries mediated by oncogenic transcription factors and signaling pathways in T-ALL.

miR-199a-3p increases the anti-tumor activity of palbociclib in liver cancer models

Palbociclib is in early-stage clinical testing in advanced hepatocellular carcinoma (HCC). Here, we investigated whether the anti-tumor activity of palbociclib, which prevents the CDK4/6-mediated phosphorylation of RB1 but simultaneously activates AKT signaling, could be improved by its combination with a PI3K/AKT/mTOR inhibitor in liver cancer models. The selective pan-AKT inhibitor, MK-2206, or the microRNA-199a-3p were tested in combination with palbociclib in HCC cell lines and in the TG221 HCC transgenic mouse model. The combination palbociclib/MK-2206 was highly effective, but too toxic to be tolerated by mice. Conversely, the combination miR-199a-3p mimics/palbociclib not only induced a complete or partial regression of tumor lesions, but was also well tolerated. After 3 weeks of treatment, the combination produced a significant reduction in number and size of tumor nodules in comparison with palbociclib or miR-199a-3p mimics used as single agents. Moreover, we also reported the efficacy of this combination against sorafenib-resistant cells in vitro and in vivo. At the molecular level, the combination caused the simultaneous decrease of the phosphorylation of both RB1 and of AKT. Our findings provide pre-clinical evidence for the efficacy of the combination miR-199a-3p/palbociclib as anti-HCC treatment or as a new approach to overcome sorafenib resistance.

PI3K Targeting in Non-solid Cancer

Despite the therapeutic progress, relapse remains a major problem in the treatment of acute lymphoblastic leukemia (ALL). Most leukemia cells that survive chemotherapy are found in the bone marrow (BM), thus resistance to chemotherapy and other treatments may be partially attributed to pro-survival signaling to leukemic cells mediated by leukemia cell-microenvironment interactions. Adhesion of leukemia cells to BM stromal cells may lead to cell adhesion-mediated drug resistance (CAM-DR) mediating intracellular signaling changes that support survival of leukemia cells. In ALL and chronic lymphocytic leukemia (CLL), adhesion-mediated activation of the PI3K/AKT signaling pathway has been shown to be critical in CAM-DR. PI3K targeting inhibitors have been approved for CLL and have been evaluated preclinically in ALL. However, PI3K inhibition has yet to be approved for clinical use in ALL. Here, we review the role of PI3K signaling for normal hematopoietic and leukemia cells and summarize preclinical inhibitors of PI3K in ALL.

Role of Autophagy and Apoptosis in Acute Lymphoblastic Leukemia

Background:

Acute lymphoblastic leukemia (ALL) is a malignant disease characterized by an excessive number of immature lymphocytes, including immature precursors of both B- and T cells. ALL affects children more often than adults. Immature lymphocytes lead to arrested differentiation and proliferation of cells. Its conventional treatments involve medication with dexamethasone, vincristine, and other anticancer drugs. Although the current first-line drugs can achieve effective treatment, they still cannot prevent the recurrence of some patients with ALL. Treatments have high risk of recurrence especially after the first remission. Currently, novel therapies to treat ALL are in need. Autophagy and apoptosis play important roles in regulating cancer development. Autophagy involves degradation of proteins and organelles, and apoptosis leads to cell death. These phenomena are crucial in cancer progression. Past studies reported that many potential anticancer agents regulate intracellular signaling pathways.

Methods:

The authors discuss the recent research findings on the role of autophagy and apoptosis in ALL.

Results:

The autophagy and apoptosis are widely used in the treatment of ALL. Most studies showed that many agents regulate autophagy and apoptosis in ALL cell models, clinical trials, and ALL animal models.

Conclusions:

In summary, activating autophagy and apoptosis pathways are the main strategies for ALL treatments. For ALL, combining new drugs with traditional chemotherapy and glucocorticoids treatments can achieve the greatest therapeutic effect by activating autophagy and apoptosis.

The Complexity of the Tumor Microenvironment and Its Role in Acute Lymphoblastic Leukemia: Implications for Therapies

The microenvironment that surrounds a tumor, in addition to the tumor itself, plays an important role in the onset of resistance to molecularly targeted therapies. Cancer cells and their microenvironment interact closely between them by means of a molecular communication that mutually influences their biological characteristics and behavior. Leukemia cells regulate the recruitment, activation and program of the cells of the surrounding microenvironment, including those of the immune system. Studies on the interactions between the bone marrow (BM) microenvironment and Acute Lymphoblastic Leukemia (ALL) cells have opened a scenario of potential therapeutic targets which include cytokines and their receptors, signal transduction networks, and hypoxia-related proteins. Hypoxia also enhances the formation of new blood vessels, and several studies show how angiogenesis could have a key role in the pathogenesis of ALL. Knowledge of the molecular mechanisms underlying tumor-microenvironment communication and angiogenesis could contribute to the early diagnosis of leukemia and to personalized molecular therapies. This article is part of a Special Issue entitled: Innovative Multi-Disciplinary Approaches for Precision Studies in Leukemia edited by Sandra Marmiroli (University of Modena and Reggio Emilia, Modena, Italy) and Xu Huang (University of Glasgow, Glasgow, United Kingdom).

Combined Application of Pan-AKT Inhibitor MK-2206 and BCL-2 Antagonist Venetoclax in B-Cell Precursor Acute Lymphoblastic Leukemia

Aberrant PI3K/AKT signaling is a hallmark of acute B-lymphoblastic leukemia (B-ALL) resulting in increased tumor cell proliferation and apoptosis deficiency. While previous AKT inhibitors struggled with selectivity, MK-2206 promises meticulous pan-AKT targeting with proven anti-tumor activity. We herein, characterize the effect of MK-2206 on B-ALL cell lines and primary samples and investigate potential synergistic effects with BCL-2 inhibitor venetoclax to overcome limitations in apoptosis induction. MK-2206 incubation reduced AKT phosphorylation and influenced downstream signaling activity. Interestingly, after MK-2206 mono application tumor cell proliferation and metabolic activity were diminished significantly independently of basal AKT phosphorylation. Morphological changes but no induction of apoptosis was detected in the observed cell lines. In contrast, primary samples cultivated in a protective microenvironment showed a decrease in vital cells. Combined MK-2206 and venetoclax incubation resulted in partially synergistic anti-proliferative effects independently of application sequence in SEM and RS4;11 cell lines. Venetoclax-mediated apoptosis was not intensified by addition of MK-2206. Functional assessment of BCL-2 inhibition via Bax translocation assay revealed slightly increased pro-apoptotic signaling after combined MK-2206 and venetoclax incubation. In summary, we demonstrate that the pan-AKT inhibitor MK-2206 potently blocks B-ALL cell proliferation and for the first time characterize the synergistic effect of combined MK-2206 and venetoclax treatment in B-ALL.

T-cell Acute Lymphoblastic Leukemia: A Roadmap to Targeted Therapies

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy characterized by aberrant proliferation of immature thymocytes. Despite an overall survival of 80% in the pediatric setting, 20% of patients with T-ALL ultimately die from relapsed or refractory disease. Therefore, there is an urgent need for novel therapies. Molecular genetic analyses and sequencing studies have led to the identification of recurrent T-ALL genetic drivers. This review summarizes the main genetic drivers and targetable lesions of T-ALL and gives a comprehensive overview of the novel treatments for patients with T-ALL that are currently under clinical investigation or that are emerging from preclinical research.

SIGNIFICANCE

T-ALL is driven by oncogenic transcription factors that act along with secondary acquired mutations. These lesions, together with active signaling pathways, may be targeted by therapeutic agents. Bridging research and clinical practice can accelerate the testing of novel treatments in clinical trials, offering an opportunity for patients with poor outcome.

Neuroblastoma-targeted nanoparticles and novel nanotechnology-based treatment methods

Neuroblastoma is a complicated pediatric tumor, originating from the neural crest, which is the most prevalent in adrenal glands, but may rarely be seen in some other tissues as well. Studies are focused on developing new strategies through novel chemo- and immuno-therapeutic drug targets. Different types of oncogenes such as MYCN, tumor suppressor genes such as p53, and some structural genes such as vascular endothelial growth factor are considered as targets for neuroblastoma therapy. The individual expression patterns in NB cells make them appropriate for this purpose. The combined effect of nano-drug delivery systems and specific drug targets will result in lower systemic side effects, prolonged therapeutic effects, and improvements in the pharmacokinetic properties of the drugs. Some of these novel drug delivery systems with a focus on liposomes as carriers are also discussed. In this review, genes and protein products that are beneficial as drug targets in the treatment of neuroblastoma have been discussed.

Integrin αvβ3-Akt signalling plays a role in radioresistance of melanoma

Melanoma is a deadly type of skin cancer that is particularly difficult to treat owing to its resistance to radiation therapy. Here, we attempted to determine the key proteins responsible for melanoma radioresistance, with the aim of improving disease response to radiation therapy. Two melanoma cell lines, SK-Mel5 and SK-Mel28, with different radiosensitivities were analysed via RNA-Seq (Quant-Seq) and target proteins with higher abundance in the more radioresistant cell line, SK-Mel28, identified. Among these proteins, integrin αvβ3, a well-known molecule in cell adhesion, was selected for analysis. Treatment of SK-Mel28 cells with cilengitide, an integrin αvβ3 inhibitor, as well as γ-irradiation resulted in more significant cell death than γ-irradiation alone. In addition, Akt, a downstream signal transducer of integrin αvβ3, showed high basic activation in SK-Mel28 and was significantly decreased upon co-treatment with cilengitide and γ-irradiation. MK-2206, an Akt inhibitor, exerted similar effects on the SK-Mel28 cell line following γ-irradiation. Our results collectively demonstrate that the integrin αvβ3-Akt signalling pathway contributes to radioresistance in SK-Mel28 cells, which may be manipulated to improve therapeutic options for melanoma.

New biomarkers and therapeutic strategies in acute lymphoblastic leukemias: Recent advances

Acute lymphoblastic leukemia (ALL) represents a heterogeneous group of hematologic malignancies, and it is normally characterized by an aberrant proliferation of immature lymphoid cells. Moreover, dysregulation of multiple signaling pathways that normally regulate cellular transcription, growth, translation, and proliferation is frequently encountered in this malignancy. ALL is the most frequent tumor in childhood, and adult ALL patients still correlate with poor survival. This review focuses on modern therapies in ALL that move beyond standard chemotherapy, with a particular emphasis on immunotherapeutic approaches as new treatment strategies. Bi-specific T-cell Engagers (BiTE) antibodies, the chimeric antigen receptor (CAR)-T cells, or CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats [CRISPR]-associated nuclease 9) represent other new innovative approaches for this disease. Target and tailored therapy could make the difference in previously untreatable cases, i.e., precision and personalized medicine. Clinical trials will help to select the most efficient novel therapies in ALL management and to integrate them with existing treatments to achieve durable cures.

New advances in targeting aberrant signaling pathways in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive disorder characterized by malignant transformation of immature progenitors primed towards T-cell development. Over the past 15 years, advances in the molecular characterization of T-ALL have uncovered oncogenic key drivers and crucial signaling pathways of this disease, opening new chances for the development of novel therapeutic strategies. Currently, T-ALL patients are still treated with aggressive therapies, consisting of high dose multiagent chemotherapy. To minimize and overcome the unfavorable effects of these regimens, it is critical to identify innovative targets and test selective inhibitors of such targets. Major efforts are being made to develop small molecules against deregulated signaling pathways, which sustain T-ALL cell growth, survival, metabolism, and drug-resistance. This review will focus on recent improvements in the understanding of the signaling pathways involved in the pathogenesis of T-ALL and on the challenging opportunities for T-ALL targeted therapies.

Targeting mTOR in Acute Lymphoblastic Leukemia

Acute Lymphoblastic Leukemia (ALL) is an aggressive hematologic disorder and constitutes approximately 25% of cancer diagnoses among children and teenagers. Pediatric patients have a favourable prognosis, with 5-years overall survival rates near 90%, while adult ALL still correlates with poorer survival. However, during the past few decades, the therapeutic outcome of adult ALL was significantly ameliorated, mainly due to intensive pediatric-based protocols of chemotherapy. Mammalian (or mechanistic) target of rapamycin (mTOR) is a conserved serine/threonine kinase belonging to the phosphatidylinositol 3-kinase (PI3K)-related kinase family (PIKK) and resides in two distinct signalling complexes named mTORC1, involved in mRNA translation and protein synthesis and mTORC2 that controls cell survival and migration. Moreover, both complexes are remarkably involved in metabolism regulation. Growing evidence reports that mTOR dysregulation is related to metastatic potential, cell proliferation and angiogenesis and given that PI3K/Akt/mTOR network activation is often associated with poor prognosis and chemoresistance in ALL, there is a constant need to discover novel inhibitors for ALL treatment. Here, the current knowledge of mTOR signalling and the development of anti-mTOR compounds are documented, reporting the most relevant results from both preclinical and clinical studies in ALL that have contributed significantly into their efficacy or failure.

IL-7R-mediated signaling in T-cell acute lymphoblastic leukemia: An update

Interleukin 7 (IL-7) and its receptor (IL-7R, a heterodimer of IL-7Rα and γc) are essential for normal lymphoid development. In their absence, severe combined immunodeficiency occurs. By contrast, excessive IL-7/IL-7R-mediated signaling can drive lymphoid leukemia development, disease acceleration and resistance to chemotherapy. IL-7 and IL-7R activate three main pathways: STAT5, PI3K/Akt/mTOR and MEK/Erk, ultimately leading to the promotion of leukemia cell viability, cell cycle progression and growth. However, the contribution of each of these pathways towards particular functional outcomes is still not completely known and appears to differ between normal and malignant states. For example, IL-7 upregulates Bcl-2 in a PI3K/Akt/mTOR-dependent and STAT5-independent manner in T-ALL cells. This is a ‘symmetric image’ of what apparently happens in normal lymphoid cells, where PI3K/Akt/mTOR does not impact on Bcl-2 and regulates proliferation rather than survival. In this review, we provide an updated summary of the knowledge on IL-7/IL-7R-mediated signaling in the context of cancer, focusing mainly on T-cell acute lymphoblastic leukemia, where this axis has been more extensively studied.

Cross Talk Networks of Mammalian Target of Rapamycin Signaling With the Ubiquitin Proteasome System and Their Clinical Implications in Multiple Myeloma

Multiple myeloma (MM) is the second most common hematological malignancy and results from the clonal amplification of plasma cells. Despite recent advances in treatment, MM remains incurable with a median survival time of only 5-6years, thus necessitating further insights into MM biology and exploitation of novel therapeutic approaches. Both the ubiquitin proteasome system (UPS) and the PI3K/Akt/mTOR signaling pathways have been implicated in the pathogenesis, and treatment of MM and different lines of evidence suggest a close cross talk between these central cell-regulatory signaling networks. In this review, we outline the interplay between the UPS and mTOR pathways and discuss their implications for the pathophysiology and therapy of MM.

The Antitumor Effect of Xihuang Pill on Treg Cells Decreased in Tumor Microenvironment of 4T1 Breast Tumor-Bearing Mice by PI3K/AKT~AP-1 Signaling Pathway

To study the antitumor effect of Xihuang pill (XHP) on the number of Treg cells in the tumor microenvironment of 4T1 breast tumor-bearing mice by PI3K/AKT/AP-1 pathway, a mouse model was established. Flow cytometry (FCM) and immunohistochemistry (IHC) were used to detect the number of Treg cells in the tumor microenvironment; terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was used to detect the apoptosis of Treg cells in tumor microenvironment. Quantitative real-time PCR (RT-qPCR) was used to detect the mRNA expression of PI3K, AKT, and AP-1 in Treg cells in tumor microenvironment; immunofluorescence (IF) and Western Blot (WB) were used to detect the protein expression of PI3K, AKT, and AP-1 in Treg cells in tumor microenvironment. Compared with the naive control group, the tumor weight in XHP groups decreased significantly (P < 0.05); FCM and IHC results showed that the number of Treg cells in the tumor microenvironment decreased with the dose of XHP groups (P < 0.05); TUNEL staining showed that the number of Treg cells in tumor microenvironment increased with the dose of XHP groups (P < 0.05); RT-qPCR results showed that the mRNA expression of PI3K and AKT in Treg cells decreased with the dose of XHP groups, while RNA expression of AP-1 increased with the dose of XHP groups (P < 0.05); IF and WB results showed that the protein expression of PI3K and AKT in Treg cells decreased with the dose of XHP groups and the protein expression of AP-1 increased with the dose of XHP groups (P < 0.05). The results suggested that XHP decreased the number of Treg cells via inhibiting PI3K and AKT expression and upregulating AP-1 expression in Treg cells and then promoting the apoptosis of Treg cells. Thus, XHP could improve the immunosuppressive state of tumor microenvironment and reverse the immune escape to inhibit tumor growth.

Healthy CD4+ T lymphocytes are not affected by targeted therapies against the PI3K/Akt/mTOR pathway in T-cell acute lymphoblastic leukemia

An attractive molecular target for novel anti-cancer therapies is the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway which is commonly deregulated in many types of cancer. Nevertheless, the effects of PI3K/Akt/mTOR inhibitors on T lymphocytes, a key component of immune responses, have been seldom explored. In this study we investigated the effects on human CD4+ T-cells of a panel of PI3K/Akt/mTOR inhibitors: BGT226, Torin-2, MK-2206, and ZSTK474. We also assessed their efficacy against two acute leukemia T cell lines. T lymphocytes were stimulated with phytohemagglutinin. Inhibitor effects on cell cycle and apoptosis were analyzed by flow cytometry, while cytotoxicity was assessed by MTT assays. In addition, the activation status of the pathway as well as induction of autophagy were analyzed by Western blotting. Quiescent healthy T lymphocytes were unaffected by the drugs whereas mitogen-stimulated lymphocytes as well as leukemic cell lines displayed a cell cycle block, caspase-dependent apoptosis, and dephosphorylation of key components of the signaling pathway. Autophagy was also induced in proliferating lymphocytes and in JURKAT and MOLT-4 cell lines. When autophagy was inhibited by 3-methyladenine or Bafilomycin A1, drug cytotoxicity was increased, indicating that autophagy is a protective mechanism. Therefore, our findings suggest that PI3K/Akt/mTOR inhibitors preserve lymphocyte viability. This is a valuable result to be taken into account when selecting drugs for targeted cancer therapy in order to minimize detrimental effects on immune function.

Calcineurin complex isolated from T-cell acute lymphoblastic leukemia (T-ALL) cells identifies new signaling pathways including mTOR/AKT/S6K whose inhibition synergize with calcineurin inhibition to promote T-ALL cell death

Calcineurin (Cn) is a calcium activated protein phosphatase involved in many aspects of normal T cell physiology, however the role of Cn and/or its downstream targets in leukemogenesis are still ill-defined. In order to identify putative downstream targets/effectors involved in the pro-oncogenic activity of Cn in T-cell acute lymphoblastic leukemia (T-ALL) we used tandem affinity chromatography, followed by mass spectrometry to purify novel Cn-interacting partners. We found the Cn-interacting proteins to be part of numerous cellular signaling pathways including eIF2 signaling and mTOR signaling. Coherently, modulation of Cn activity in T-ALL cells determined alterations in the phosphorylation status of key molecules implicated in protein translation such as eIF-2α and ribosomal protein S6. Joint targeting of PI3K-mTOR, eIF-2α and 14-3-3 signaling pathways with Cn unveiled novel synergistic pro-apoptotic drug combinations. Further analysis disclosed that the synergistic interaction between PI3K-mTOR and Cn inhibitors was prevalently due to AKT inhibition. Finally, we showed that the synergistic pro-apoptotic response determined by jointly targeting AKT and Cn pathways was linked to down-modulation of key anti-apoptotic proteins including Mcl-1, Claspin and XIAP. In conclusion, we identify AKT inhibition as a novel promising drug combination to potentiate the pro-apoptotic effects of Cn inhibitors.

Metformin, an Anti-diabetic Drug to Target Leukemia

Metformin, a widely used anti-diabetic molecule, has attracted a strong interest in the last 10 years as a possible new anti-cancer molecule. Metformin acts by interfering with mitochondrial respiration, leading to an activation of the AMPK tumor-suppressive pathway to promote catabolic-energy saving reactions and block anabolic ones that are associated with abnormal cell proliferation. Metformin also acts at the organism level. In type 2 diabetes patients, metformin reduces hyperglycemia and increases insulin sensitivity by enhancing insulin-stimulated glucose uptake in muscles, liver, and adipose tissue and by reducing glucose output by the liver. Lowering insulin and insulin-like growth factor 1 (IGF-1) levels that stimulate cancer growth could be important features of metformin's mode of action. Despite continuous progress in treatments with the use of targeted therapies and now immunotherapies, acute leukemias are still of very poor prognosis for relapse patients, demonstrating an important need for new treatments deriving from the identification of their pathological supportive mechanisms. In the last decade, it has been realized that if cancer cells modify and reprogram their metabolism to feed their intense biochemical needs associated with their runaway proliferation, they develop metabolic addictions that could represent attractive targets for new therapeutic strategies that intend to starve and kill cancer cells. This Mini Review explores the anti-leukemic potential of metformin and its mode of action on leukemia metabolism.

Identification of differential PI3K pathway target dependencies in T-cell acute lymphoblastic leukemia through a large cancer cell panel screen

Selective phosphoinositide 3-kinase (PI3K)/AKT/mTOR inhibitors are currently under evaluation in clinical studies. To identify tumor types that are sensitive to PI3K pathway inhibitors we screened compounds targeting PI3Kα/δ (AZD8835), PI3Kβ/δ (AZD8186), AKT (AZD5363) and mTORC1/2 (AZD2014) against a cancer cell line panel (971 cell lines). There was an enrichment of hematological malignancies that were sensitive to AKT and mTOR inhibition, with the greatest degree of sensitivity observed in T-cell acute lymphoblastic leukemia (T-ALL). We found that all NOTCH mutant T-ALL cell lines were sensitive to AKT and mTORC1/2 inhibitors, with only partial sensitivity to agents that target the PI3K α, β or δ isoforms. Induction of apoptosis only occurred following AKTi treatment in cell lines with PTEN protein loss and high levels of active AKT. In summary, we have demonstrated that T-ALL cell lines show differential sensitivity to inhibition at different nodes in the PI3K/AKT/mTOR pathway and inhibiting AKT or mTOR may have a therapeutic benefit in this disease setting.

Aberrant Signaling Pathways in T-Cell Acute Lymphoblastic Leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive disease caused by the malignant transformation of immature progenitors primed towards T-cell development. Clinically, T-ALL patients present with diffuse infiltration of the bone marrow by immature T-cell blasts high blood cell counts, mediastinal involvement, and diffusion to the central nervous system. In the past decade, the genomic landscape of T-ALL has been the target of intense research. The identification of specific genomic alterations has contributed to identify strong oncogenic drivers and signaling pathways regulating leukemia growth. Notwithstanding, T-ALL patients are still treated with high-dose multiagent chemotherapy, potentially exposing these patients to considerable acute and long-term side effects. This review summarizes recent advances in our understanding of the signaling pathways relevant for the pathogenesis of T-ALL and the opportunities offered for targeted therapy.

Targeting signaling and apoptotic pathways involved in chemotherapeutic drug-resistance of hematopoietic cells

A critical problem in leukemia as well as other cancer therapies is the development of chemotherapeutic drug-resistance. We have developed models of hematopoietic drug resistance that are based on expression of dominant-negative TP53 [TP53 (DN)] or constitutively-active MEK1 [MEK1(CA)] oncogenes in the presence of chemotherapeutic drugs. In human cancer, functional TP53 activity is often lost in human cancers. Also, activation of the Raf/MEK/ERK pathway frequently occurs due to mutations/amplification of upstream components of this and other interacting pathways. FL5.12 is an interleukin-3 (IL−3) dependent hematopoietic cell line that is sensitive to doxorubicin (a.k.a Adriamycin). FL/Doxo is a derivative cell line that was isolated by culturing the parental FL5.12 cells in doxorubicin for prolonged periods of time. FL/Doxo + TP53 (DN) and FL/Doxo + MEK1 (CA) are FL/Doxo derivate cell lines that were infected with retrovirus encoding TP53 (DN) or MEK1 (CA) and are more resistant to doxorubicin than FL/Doxo cells. This panel of cell lines displayed differences in the sensitivity to inhibitors that suppress mTORC1, BCL2/BCLXL, MEK1 or MDM2 activities, as well as, the proteasomal inhibitor MG132. The expression of key genes involved in cell growth and drug-resistance (e.g., MDM2, MDR1, BAX) also varied in these cells. Thus, we can begin to understand some of the key genes that are involved in the resistance of hematopoietic cells to chemotherapeutic drugs and targeted therapeutics.

From the outside, from within: Biological and therapeutic relevance of signal transduction in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological cancer that arises from clonal expansion of transformed T-cell precursors. In this review we summarize the current knowledge on the external stimuli and cell-intrinsic lesions that drive aberrant activation of pivotal, pro-tumoral intracellular signaling pathways in T-cell precursors, driving transformation, leukemia expansion, spread or resistance to therapy. In addition to their pathophysiological relevance, receptors and kinases involved in signal transduction are often attractive candidates for targeted drug development. As such, we discuss also the potential of T-ALL signaling players as targets for therapeutic intervention.

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.

Autophagy, a key mechanism of oncogenesis and resistance in leukemia

Autophagy is a lysosomal pathway involved in degradation of intracellular material. It appears as an adaptation mechanism that is essential for cellular homeostasis in response to various stress conditions. Over the past decade, many studies have linked alteration of autophagy with cancer initiation and progression, autoimmune, inflammatory, metabolic, and degenerative diseases. This review highlights recent findings on the impact of autophagy on leukemic transformation of normal hematopoietic stem cells and summarizes its role on leukemic cell response to chemotherapy.

Platycodin D potentiates proliferation inhibition and apoptosis induction upon AKT inhibition via feedback blockade in non-small cell lung cancer cells

AKT is the frequently overexpressed and constitutively active kinase within NSCLC cells and recognized as a promising target for NSCLC treatment. However, AKT inhibition relieves the feedback inhibition of upstream receptor tyrosine kinases (RTKs) that may weaken the efficiency of AKT inhibitors. Platycodin D (PD), isolated from widely-used traditional Chinese medicine Platycodonis Radix, is now found to remarkably enhance the anti-proliferative effect of AKT inhibitors. In this study, combinatorial activity of AKT inhibitor MK2206 and PD on cell proliferation, apoptosis and related signaling were disclosed. Long-term AKT inhibition induced up-regulation of RTKs, including EGFR and HER-2. Co-treatment of MK2206 with PD could abolish this feedback survival through decrease of EGFR, HER-2, and p-AKT, and profound inhibition of 4E-BP1, leading to an amplified anti-proliferative and apoptotic activity in NSCLC cells. Similarly, feedback activation in response to reduction of AKT expression by small interfering RNA (siRNA) was also blocked by PD and apoptotic effect was further enhanced. Thus, PD potentiated proliferative inhibition and apoptotic induction of both AKT inhibitor and siRNA. These findings also reveal the limitations of suppressing feedback-regulated pathways by monotherapy and establish a mechanistic rationale for a novel combination approach targeting AKT for the treatment of NSCLC.

MK-2206 co-treatment with 5-fluorouracil or doxorubicin enhances chemosensitivity and apoptosis in gastric cancer by attenuation of Akt phosphorylation

The anticancer effect of MK-2206, an Akt inhibitor, has been explored in some types of cancers, but its effect on gastric cancer is unclear. In this study, we aimed to investigate its anticancer effect in gastric cancer cells. Cell viability and colony formation assays showed that MK-2206 effectively inhibited the proliferation of SGC-7901 and MKN45 cells. The 50% inhibitory concentration values after 24, 48, and 72 hours' treatment were 22.92, 13.68, and 8.55 μM in SGC-7901 cells and 19.21, 13.10, and 9.11 μM in MKN45 cells, respectively. Treatment with MK-2206 induced apoptosis in SGC-7901 cells as indicated by flow cytometry assay. The combination indexes of MK-2206 and doxorubicin were 0.59 in SGC-7901 cells and 0.57 in MKN45 cells, whereas for 5-fluorouracil (5-FU) the indexes were 0.17 in SGC-7901 cells and 0.73 in MKN45 cells, indicating that MK-2206 could work synergistically with doxorubicin or 5-FU to inhibit cell growth. Furthermore, a small dose (1 μM) of MK-2206 co-treatment with doxorubicin or 5-FU was sufficient for complete inhibition of chemotherapeutic alteration of phosphorylated Akt expression and significant enhancement of pro-apoptosis effect through the activation of caspase pathway. Therefore, MK-2206 effectively inhibits gastric cancer cell growth by attenuation of Akt phosphorylation and synergistically enhances the antitumor effect of doxorubicin and 5-FU via caspase-dependent apoptosis.

AKT isoforms modulate Th1-like Treg generation and function in human autoimmune disease

Foxp3(+) regulatory T cells (Tregs) exhibit plasticity, which dictates their function. Secretion of the inflammatory cytokine IFNγ, together with the acquisition of a T helper 1 (Th1)-like effector phenotype as observed in cancer, infection, and autoimmune diseases, is associated with loss of Treg suppressor function through an unknown mechanism. Here, we describe the signaling events driving the generation of human Th1-Tregs. Using a genome-wide gene expression approach and pathway analysis, we identify the PI3K/AKT/Foxo1/3 signaling cascade as the major pathway involved in IFNγ secretion by human Tregs. Furthermore, we describe the opposing roles of AKT isoforms in Th1-Treg generation ex vivo Finally, we employ multiple sclerosis as an in vivo model with increased but functionally defective Th1-Tregs. We show that the PI3K/AKT/Foxo1/3 pathway is activated in ex vivo-isolated Tregs from untreated relapsing-remitting MS patients and that blockade of the pathway inhibits IFNγ secretion and restores the immune suppressive function of Tregs. These data define a fundamental pathway regulating the function of human Tregs and suggest a novel treatment paradigm for autoimmune diseases.

Therapeutic targeting of IL-7Rα signaling pathways in ALL treatment

Increased understanding of pediatric acute lymphoblastic leukemia (ALL) pathobiology has led to dramatic improvements in patient survival. However, there is still a need to develop targeted therapies to enable reduced chemotherapy intensity and to treat relapsed patients. The interleukin-7 receptor α (IL-7Rα) signaling pathways are prime therapeutic targets because these pathways harbor genetic aberrations in both T-cell ALL and B-cell precursor ALL. Therapeutic targeting of the IL-7Rα signaling pathways may lead to improved outcomes in a subset of patients.

Triple Akt inhibition as a new therapeutic strategy in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive neoplastic disorder in which chemotherapy resistance and refractory relapses occur, with a poorer prognostic outcome.

Constitutively active PI3K/Akt/mTOR pathway is a common feature of T-ALL upregulating cell proliferation, survival and drug resistance. This pathway is currently under clinical trials with small molecules inhibitors (SMI).

To verify whether a multi-inhibition treatment against Akt protein could enhance the efficacy of individual drug administration and overcome drug resistance as well as to obtain a decrease in single drug concentration, we tested on T-ALL cell lines the effects of combined treatments with three Akt inhibitors with different mode of action, GSK690693, MK-2206 and Perifosine.

In cells with hyperactivated Akt, combined administration of the drugs displayed a significant synergistic and cytotoxic effect and affected PI3K/Akt/mTOR pathway at much lower concentration than single drug use. Highest synergistic effect for full inhibition of Akt was also related to the timing of every drug administration. Furthermore the triple treatment had greater efficacy in inducing cell cycle arrest in G₀/G₁ phase and both apoptosis and autophagy.

Targeting Akt as a key protein of PI3K/Akt/mTOR pathway with multiple drugs might represent a new and promising pharmacological strategy for treatment of T-ALL patients.

Knockout Serum Replacement Promotes Cell Survival by Preventing BIM from Inducing Mitochondrial Cytochrome C Release

Knockout serum replacement (KOSR) is a nutrient supplement commonly used to replace serum for culturing stem cells. We show here that KOSR has pro-survival activity in chronic myelogenous leukemia (CML) cells transformed by the BCR-ABL oncogene. Inhibitors of BCR-ABL tyrosine kinase kill CML cells by stimulating pro-apoptotic BIM and inhibiting anti-apoptotic BCL2, BCLxL and MCL1. We found that KOSR protects CML cells from killing by BCR-ABL inhibitors—imatinib, dasatinib and nilotinib. The protective effect of KOSR is reversible and not due to the selective outgrowth of drug-resistant clones. In KOSR-protected CML cells, imatinib still inhibited the BCR-ABL tyrosine kinase, reduced the phosphorylation of STAT, ERK and AKT, down-regulated BCL2, BCLxL, MCL1 and up-regulated BIM. However, these pro-apoptotic alterations failed to cause cytochrome c release from the mitochondria. With mitochondria isolated from KOSR-cultured CML cells, we showed that addition of recombinant BIM protein also failed to cause cytochrome c release. Besides the kinase inhibitors, KOSR could protect cells from menadione, an inducer of oxidative stress, but it did not protect cells from DNA damaging agents. Switching from serum to KOSR caused a transient increase in reactive oxygen species and AKT phosphorylation in CML cells that were protected by KOSR but not in those that were not protected by this nutrient supplement. Treatment of KOSR-cultured cells with the PH-domain inhibitor MK2206 blocked AKT phosphorylation, abrogated the formation of BIM-resistant mitochondria and stimulated cell death. These results show that KOSR has cell-context dependent pro-survival activity that is linked to AKT activation and the inhibition of BIM-induced cytochrome c release from the mitochondria.

Activity of the novel mTOR inhibitor Torin-2 in B-precursor acute lymphoblastic leukemia and its therapeutic potential to prevent Akt reactivation

The PI3K/Akt/mTOR signaling cascade is a key regulatory pathway controlling cell growth and survival, and its dysregulation is a reported feature of B-precursor acute lymphoblastic leukemia (B-pre ALL).

Torin-2 is a novel, second-generation ATP-competitive inhibitor that is potent and selective for mTOR with a superior pharmacokinetic profile to previous inhibitors. It has been shown that Torin-2 displayed dramatic antiproliferative activity across a panel of cancer cell lines.

To investigate if Torin-2 could represent a new option for the treatment of B-pre ALL, we tested its activity on a panel of B-pre ALL cell lines. In all of them Torin-2 showed a powerful cytotoxic activity, inhibiting the growth of each cell line in a dose-dependent manner, with an IC₅₀ in the nanomolar range. Torin-2 caused both apoptosis and autophagy, induced cell cycle arrest in G₀/G₁ phase and affected both mTORC1 and mTORC2 activities as assessed by their specific substrate dephosphorylation.

Torin-2 alone suppressed feedback activation of PI3K/Akt, whereas the mTORC1 inhibitor RAD001 required the addition of the Akt inhibitor MK-2206 to achieve the same effect. These pharmacological strategies targeting PI3K/Akt/mTOR at different points of the signaling pathway cascade might represent a new promising therapeutic strategy for treatment of B-pre ALL patients.

MK-2206 induces apoptosis of AML cells and enhances the cytotoxicity of cytarabine

Genetic alterations in the PI3K/AKT cascade have been linked to various human cancers including acute myeloid leukemia (AML) and have emerged to be promising targets for treatment. In this study, we explored the molecular mechanism and clinical implication of a specific allosteric AKT inhibitor, MK-2206, in the treatment of AML. Four leukemia cell lines, MV-4-11, MOLM-13, OCI/AML3, and U937, were used. Apoptosis and cell cycle distribution were determined by flow cytometry analysis. Expression of anti-apoptotic protein family and glycogen synthase kinase 3β (GSK3β) signaling was determined by western blotting. Drug combination effects of MK-2206 with cytarabine were evaluated by cell proliferation assay, and the combination index values were calculated by CompuSyn software. MK-2206 had no effect on normal peripheral blood mononuclear cells, but induced G1-phase arrest and apoptosis in leukemia cells. Among anti-apoptotic Bcl-2 family members, only myeloid cell leukemia-1 (Mcl-1) was significantly suppressed. Mcl-1 suppression by MK-2206 was closely associated with decreased GSK3β phosphorylation at Ser9, an event leads to GSK3β activation. Furthermore, the effect of MK-2206 on Mcl-1 downregulation was abolished by GSK3β inhibitor, lithium chloride and proteasome inhibitor, MG-132, suggesting that MK-2206 acted through a GSK3β-mediated, proteasome-dependent protein degradation. In addition, co-administration of MK-2206 with cytarabine could enhance the cytotoxic efficacy of cytarabine in leukemia cell lines. In conclusion, we have demonstrated that MK-2206 is an active agent in AML and its efficacy as in combination with cytarabine is implicated.

Deregulation of the EGFR/PI3K/PTEN/Akt/mTORC1 pathway in breast cancer: possibilities for therapeutic intervention

The EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway plays prominent roles in malignant transformation, prevention of apoptosis, drug resistance and metastasis. The expression of this pathway is frequently altered in breast cancer due to mutations at or aberrant expression of: HER2, ERalpha, BRCA1, BRCA2, EGFR1, PIK3CA, PTEN, TP53, RB as well as other oncogenes and tumor suppressor genes. In some breast cancer cases, mutations at certain components of this pathway (e.g., PIK3CA) are associated with a better prognosis than breast cancers lacking these mutations. The expression of this pathway and upstream HER2 has been associated with breast cancer initiating cells (CICs) and in some cases resistance to treatment. The anti-diabetes drug metformin can suppress the growth of breast CICs and herceptin-resistant HER2+ cells. This review will discuss the importance of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway primarily in breast cancer but will also include relevant examples from other cancer types. The targeting of this pathway will be discussed as well as clinical trials with novel small molecule inhibitors. The targeting of the hormone receptor, HER2 and EGFR1 in breast cancer will be reviewed in association with suppression of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway.

Co-operating STAT5 and AKT signaling pathways in chronic myeloid leukemia and mastocytosis: possible new targets of therapy

Chronic myeloid leukemia and systemic mastocytosis are myeloid neoplasms sharing a number of pathogenetic and clinical features. In both conditions, an aberrantly activated oncoprotein with tyrosine kinase activity, namely BCR-ABL1 in chronic myeloid leukemia, and mutant KIT, mostly KIT D816V, in systemic mastocytosis, is key to disease evolution. The appreciation of the role of such tyrosine kinases in these diseases has led to the development of improved therapies with tyrosine kinase-targeted inhibitors. However, most drugs, including new KIT D816V-blocking agents, have failed to achieve long-lasting remissions in advanced systemic mastocytosis, and there is a similar problem in chronic myeloid leukemia, where imatinib-resistant patients sometimes fail to achieve remission, even with second- or third-line BCR-ABL1 specific tyrosine kinase inhibitors. During disease progression, additional signaling pathways become activated in neoplastic cells, but most converge into major downstream networks. Among these, the AKT and STAT5 pathways appear most critical and may result in drug-resistant chronic myeloid leukemia and systemic mastocytosis. Inhibition of phosphorylation of these targets has proven their crucial role in disease-evolution in both malignancies. Together, these observations suggest that STAT5 and AKT are key drivers of oncogenesis in drug-resistant forms of the diseases, and that targeting STAT5 and AKT might be an interesting approach in these malignancies. The present article provides an overview of our current knowledge about the critical role of AKT and STAT5 in the pathophysiology of chronic myeloid leukemia and systemic mastocytosis and on their potential value as therapeutic targets in these neoplasms.

Untangling knots between autophagic targets and candidate drugs, in cancer therapy

Autophagy is an evolutionarily conserved lysosomal mechanism implicated in a wide variety of pathological processes, such as cancer. Autophagy can be regulated by a limited number of autophagy-related genes (Atgs) such as oncogenic Bcl-2/Bcl-XL , mTORC1, Akt and PI3KCI, and tumour suppressive proteins PI3KCIII, Beclin-1, Bif-1, p53, DAPKs, PTEN and UVRAG, which play their crucial roles in regulating autophagy-related cancer. As autophagy has a dual role in cancer cells, with tumour-promoting and tumour-suppressing properties, it has become an attractive target for a series of emerging small molecule drugs. In this review, we reveal new discoveries of related small molecules or chemical compounds that can regulate autophagic pathways and lead to pro-death or pro-survival autophagy, in different types of cancer. We discuss the knots between autophagic targets and candidate drugs, in the hope of shedding new light on exploiting new anti-tumour small molecule drugs for future cancer therapy.

Mutant PIK3CA controls DUSP1-dependent ERK 1/2 activity to confer response to AKT target therapy

Background:

Alterations in the phosphoinositide 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) signalling pathway are frequent in urothelial bladder cancer (BLCA) and thus provide a potential target for novel therapeutic strategies. We investigated the efficacy of the AKT inhibitor MK-2206 in BLCA and the molecular determinants that predict therapy response.

Methods:

Biochemical and functional effects of the AKT inhibitor MK-2206 were analysed on a panel of 11 BLCA cell lines possessing different genetic alterations. Cell viability (CellTiter-Blue, cell counts), apoptosis (caspase 3/7 activity) and cell cycle progression (EdU incorporation) were analysed to determine effects on cell growth and proliferation. cDNA or siRNA transfections were used to manipulate the expression of specific proteins such as wild-type or mutant PIK3CA, DUSP1 or CREB. For in vivo analysis, the chicken chorioallantoic membrane model was utilised and tumours were characterised by weight and biochemically for the expression of Ki-67 and AKT phosphorylation.

Results:

Treatment with MK-2206 suppressed AKT and S6K1 but not 4E-BP1 phosphorylation in all cell lines. Functionally, only cell lines bearing mutations in the hotspot helical domain of PIK3CA were sensitive to the drug, independent of other genetic alterations in the PI3K or MAPK signalling pathway. Following MK-2206 treatment, the presence of mutant PIK3CA resulted in an increase in DUSP1 expression that induced a decrease in ERK 1/2 phosphorylation. Manipulating the expression of mutant or wild-type PIK3CA or DUSP1 confirmed that this mechanism is responsible for the induction of apoptosis and the inhibition of tumour proliferation in vitro and in vivo, to sensitise cells to AKT target therapy.

Conclusion or interpretation:

PIK3CA mutations confer sensitivity to AKT target therapy in BLCA by regulating DUSP1 expression and subsequent ERK1/2 dephosphorylation and can potentially serve as a stratifying biomarker for treatment.

Computational insights into the inhibitory mechanism of human AKT1 by an orally active inhibitor, MK-2206

The AKT signaling pathway has been identified as an important target for cancer therapy. Among small-molecule inhibitors of AKT that have shown tremendous potential in inhibiting cancer, MK-2206 is a highly potent, selective and orally active allosteric inhibitor. Promising preclinical anticancer results have led to entry of MK-2206 into Phase I/II clinical trials. Despite such importance, the exact binding mechanism and the molecular interactions of MK-2206 with human AKT are not available. The current study investigated the exact binding mode and the molecular interactions of MK-2206 with human AKT isoforms using molecular docking and (un)binding simulation analyses. The study also involved the docking analyses of the structural analogs of MK-2206 to AKT1 and proposed one as better inhibitor. The Dock was used for docking simulations of MK-2206 into the allosteric site of AKT isoforms. The Ligplot+ was used for analyses of polar and hydrophobic interactions between AKT isoforms and the ligands. The MoMa-LigPath web server was used to simulate the ligand (un)binding from the binding site to the surface of the protein. In the docking and (un)binding simulation analyses of MK-2206 with human AKT1, the Trp-80 was the key residue and showed highest decrease in the solvent accessibility, highest number of hydrophobic interactions, and the most consistent involvement in all (un)binding simulation phases. The number of molecular interactions identified and calculated binding energies and dissociation constants from the co-complex structures of these isoforms, clearly explained the varying affinity of MK-2206 towards these isoforms. The (un)binding simulation analyses identified various additional residues which despite being away from the binding site, play important role in initial binding of the ligand. Thus, the docking and (un)binding simulation analyses of MK-2206 with AKT isoforms and its structure analogs will provide a suitable model for studying drug-protein interaction and will help in designing better drugs.

Autophagy in acute leukemias: a double-edged sword with important therapeutic implications

Macroautophagy, usually referred to as autophagy, is a degradative pathway wherein cytoplasmatic components such as aggregated/misfolded proteins and organelles are engulfed within double-membrane vesicles (autophagosomes) and then delivered to lysosomes for degradation. Autophagy plays an important role in the regulation of numerous physiological functions, including hematopoiesis, through elimination of aggregated/misfolded proteins, and damaged/superfluous organelles. The catabolic products of autophagy (amino acids, fatty acids, nucleotides) are released into the cytosol from autophagolysosomes and recycled into bio-energetic pathways. Therefore, autophagy allows cells to survive starvation and other unfavorable conditions, including hypoxia, heat shock, and microbial pathogens. Nevertheless, depending upon the cell context and functional status, autophagy can also serve as a death mechanism. The cohort of proteins that constitute the autophagy machinery function in a complex, multistep biochemical pathway which has been partially identified over the past decade. Dysregulation of autophagy may contribute to the development of several disorders, including acute leukemias. In this kind of hematologic malignancies, autophagy can either act as a chemo-resistance mechanism or have tumor suppressive functions, depending on the context. Therefore, strategies exploiting autophagy, either for activating or inhibiting it, could find a broad application for innovative treatment of acute leukemias and could significantly contribute to improved clinical outcomes. These aspects are discussed here after a brief introduction to the autophagic molecular machinery and its roles in hematopoiesis.

Targeting breast cancer initiating cells: advances in breast cancer research and therapy

Over the past 10 years there have been significant advances in our understanding of breast cancer and the important roles that breast cancer initiating cells (CICs) play in the development and resistance of breast cancer. Breast CICs endowed with self-renewing and tumor-initiating capacities are believed to be responsible for the relapses which often occur after various breast cancer therapies. In this review, we will summarize some of the key developments in breast CICs which will include discussion of some of the key genes implicated: estrogen receptor (ER), HER2, BRCA1, TP53, PIK3CA, RB, P16INK1 and various miRs as well some drugs which are showing promise in targeting CICs. In addition, the concept of combined therapies will be discussed. Basic and clinical research is resulting in novel approaches to improve breast cancer therapy by targeting the breast CICs.