Synergistic induction of apoptosis in human leukemia T cells by the Akt inhibitor perifosine and etoposide through activation of intrinsic and Fas-mediated extrinsic cell death pathways

Destabilizing the genome as a therapeutic strategy to enhance response to immune checkpoint blockade: a systematic review of clinical trials evidence from solid and hematological tumors

Background: Genomic instability is increased alterations in the genome during cell division and is common among most cancer cells. Genome instability enhances the risk of initial carcinogenic transformation, generating new clones of tumor cells, and increases tumor heterogeneity. Although genome instability contributes to malignancy, it is also an "Achilles' heel" that constitutes a therapeutically-exploitable weakness-when sufficiently advanced, it can intrinsically reduce tumor cell survival by creating DNA damage and mutation events that overwhelm the capacity of cancer cells to repair those lesions. Furthermore, it can contribute to extrinsic survival-reducing events by generating mutations that encode new immunogenic antigens capable of being recognized by the immune system, particularly when anti-tumor immunity is boosted by immunotherapy drugs. Here, we describe how genome-destabilization can induce immune activation in cancer patients and systematically review the induction of genome instability exploited clinically, in combination with immune checkpoint blockade. Methods: We performed a systematic review of clinical trials that exploited the combination approach to successfully treat cancers patients. We systematically searched PubMed, Cochrane Central Register of Controlled Trials, Clinicaltrials.gov, and publication from the reference list of related articles. The most relevant inclusion criteria were peer-reviewed clinical trials published in English. Results: We identified 1,490 studies, among those 164 were clinical trials. A total of 37 clinical trials satisfied the inclusion criteria and were included in the study. The main outcome measurements were overall survival and progression-free survival. The majority of the clinical trials (30 out of 37) showed a significant improvement in patient outcome. Conclusion: The majority of the included clinical trials reported the efficacy of the concept of targeting DNA repair pathway, in combination with immune checkpoint inhibitors, to create a "ring of synergy" to treat cancer with rational combinations.

Understanding the Roles of the Hedgehog Signaling Pathway during T-Cell Lymphopoiesis and in T-Cell Acute Lymphoblastic Leukemia (T-ALL)

The Hedgehog (HH) signaling network is one of the main regulators of invertebrate and vertebrate embryonic development. Along with other networks, such as NOTCH and WNT, HH signaling specifies both the early patterning and the polarity events as well as the subsequent organ formation via the temporal and spatial regulation of cell proliferation and differentiation. However, aberrant activation of HH signaling has been identified in a broad range of malignant disorders, where it positively influences proliferation, survival, and therapeutic resistance of neoplastic cells. Inhibitors targeting the HH pathway have been tested in preclinical cancer models. The HH pathway is also overactive in other blood malignancies, including T-cell acute lymphoblastic leukemia (T-ALL). This review is intended to summarize our knowledge of the biological roles and pathophysiology of the HH pathway during normal T-cell lymphopoiesis and in T-ALL. In addition, we will discuss potential therapeutic strategies that might expand the clinical usefulness of drugs targeting the HH pathway in T-ALL.

Alkylphospholipids are Signal Transduction Modulators with Potential for Anticancer Therapy

BACKGROUND

Alkylphospholipids (APLs) are synthetically derived from cell membrane components, which they target and thus modify cellular signalling and cause diverse effects. This study reviews the mechanism of action of anticancer, antiprotozoal, antibacterial and antiviral activities of ALPs, as well as their clinical use.

METHODS

A literature search was used as the basis of this review.

RESULTS

ALPs target lipid rafts and alter phospholipase D and C signalling cascades, which in turn will modulate the PI3K/Akt/mTOR and RAS/RAF/MEK/ERK pathways. By feedback coupling, the SAPK/JNK signalling chain is also affected. These changes lead to a G2/M phase cell cycle arrest and subsequently induce programmed cell death. The available knowledge on inhibition of AKT phosphorylation, mTOR phosphorylation and Raf down-regulation renders ALPs as attractive candidates for modern medical treatment, which is based on individualized diagnosis and therapy. Corresponding to their unusual profile of activities, their side effects result from cholinomimetic activity mainly and focus on the gastrointestinal tract. These aspects together with their bone marrow sparing features render APCs well suited for modern combination therapy. Although the clinical success has been limited in cancer diseases so far, the use of miltefosine against leishmaniosis is leading the way to better understanding their optimized use.

CONCLUSION

Recent synthetic programs generate congeners with the increased therapeutic ratio, liposomal formulations, as well as diapeutic (or theranostic) derivatives with optimized properties. It is anticipated that these innovative modifications will pave the way for the further successful development of ALPs.

PI3K/AKT inhibitors aggravate death receptor-mediated hepatocyte apoptosis and liver injury

The PI3K/AKT signaling pathway is one of the most frequently activated signaling networks in human cancers and has become a valuable target in anticancer therapy. However, accumulating reports suggest that adverse effects such as severe liver injury and inflammation may accompany treatment with pan-PI3K and pan-AKT inhibitors. Our prior work has demonstrated that activation of the PI3K/AKT pathway has a protective role in Fas- or TNFα-induced hepatocytic cell death and liver injury. We postulated that PI3K or AKT inhibitors may exacerbate liver damage via the death factor-mediated hepatocyte apoptosis. In this study we found that several drugs targeting PI3K/AKT either clinically used or in clinical trials sensitized hepatocytes to agonistic anti-Fas antibody- or TNFα-induced apoptosis and significantly shortened the survival of mice in in vivo liver damage models. The PI3K or AKT inhibitors promoted Fas aggregation, inhibited the expression of cellular FLICE-inhibitory protein S and L (FLIP_L/S), and enhanced procaspase-8 activation. Conversely, cotreatment with the AKT specific activator SC79 reversed these effects. Taken together, these findings suggest that PI3K or AKT inhibitors may render hepatocytes hypersensitive to Fas- or TNFα-induced apoptosis and liver injury.

Novel Sphingolipid-Based Cancer Therapeutics in the Personalized Medicine Era

Sphingolipids are bioactive lipids that participate in a wide variety of biological mechanisms, including cell death and proliferation. The myriad of pro-death and pro-survival cellular pathways involving sphingolipids provide a plethora of opportunities for dysregulation in cancers. In recent years, modulation of these sphingolipid metabolic pathways has been in the forefront of drug discovery for cancer therapeutics. About two decades ago, researchers first showed that standard of care treatments, e.g., chemotherapeutics and radiation, modulate sphingolipid metabolism to increase endogenous ceramides, which kill cancer cells. Strikingly, resistance to these treatments has also been linked to altered sphingolipid metabolism, favoring lipid species that ultimately lead to cell survival. To this end, many inhibitors of sphingolipid metabolism have been developed to further define not only our understanding of these pathways but also to potentially serve as therapeutic interventions. Therefore, understanding how to better use these new drugs that target sphingolipid metabolism, either alone or in combination with current cancer treatments, holds great potential for cancer control. While sphingolipids in cancer have been reviewed previously (Hannun & Obeid, 2018; Lee & Kolesnick, 2017; Morad & Cabot, 2013; Newton, Lima, Maceyka, & Spiegel, 2015; Ogretmen, 2018; Ryland, Fox, Liu, Loughran, & Kester, 2011) in this chapter, we present a comprehensive review on how standard of care therapeutics affects sphingolipid metabolism, the current landscape of sphingolipid inhibitors, and the clinical utility of sphingolipid-based cancer therapeutics.

The molecular mechanism of anticancer action of novel octahydropyrazino[2,1-a:5,4-a']diisoquinoline derivatives in human gastric cancer cells

Objective The aim of the current study was to examine the anticancer activity and the detailed mechanism of novel diisoquinoline derivatives in human gastric cancer cells (AGS). Methods The viability of AGS cells was measured by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Cell cycle analysis and apoptosis assay were performed by standard flow cytometric method. Confocal microscopy bioimaging was used to demonstrate the expression of pivotal proteins engaged in apoptosis (caspase-8, caspase-3, p53) and cell signaling (AKT, ERK1/2). Results All compounds decreased the number of viable cells in a dose-dependent manner after 24 and 48 h of incubation, although compound 2 was a more cytotoxic agent, with IC₅₀ values of 21 ± 2 and 6 ± 2 μM, compared to 80 ± 2 and 45 ± 2 μM for etoposide. The cytotoxic and antiproliferative effects of novel compounds were associated with the induction of apoptosis. The highest percentage of early and late apoptotic cells was observed after 48 h of incubation with compound 2 (89.9%). The value was higher compared to compound 1 (20.4%) and etoposide (24.1%). The novel diisoquinoline derivatives decreased the expression of AKT and ERK1/2. Their mechanism was associated with p53-mediated apoptosis, accumulation of cells in the G2/M phase of cell cycle and inhibition of topoisomerase II. Conclusion These data strongly support compound 2 as a promising molecule for treatment of gastric cancer.

FOXOs Maintaining the Equilibrium for Better or for Worse

A paradigm shift is emerging within the FOXO field and accumulating evidence indicates that we need to reappreciate the role of FOXOs, at least in cancer development. Here, we discuss the possibility that FOXOs are both tumor suppressors as well as promoters of tumor progression. This is mostly dependent on the biological context. Critical to this dichotomous role is the notion that FOXOs are central in preserving cellular homeostasis in redox control, genomic stability, and protein turnover. From this perspective, a paradoxical role in both suppressing and enhancing tumor progression can be reconciled. As many small molecules targeting the PI3K pathway are developed by big pharmaceutical companies and/or are in clinical trial, we will discuss what the consequences may be for the context-dependent role of FOXOs in tumor development in treatment options based on active PI3K signaling in tumors.

Akt targeting as a strategy to boost chemotherapy efficacy in non-small cell lung cancer through metabolism suppression

Metabolic reprogramming is a hallmark of cancer development, mediated by genetic and epigenetic alterations that may be pharmacologically targeted. Among oncogenes, the kinase Akt is commonly overexpressed in tumors and favors glycolysis, providing a rationale for using Akt inhibitors. Here, we addressed the question of whether and how inhibiting Akt activity could improve therapy of non-small cell lung cancer (NSCLC) that represents more than 80% of all lung cancer cases. First, we demonstrated that Akt inhibitors interacted synergistically with Microtubule-Targeting Agents (MTAs) and specifically in cancer cell lines, including those resistant to chemotherapy agents and anti-EGFR targeted therapies. In vivo, we further revealed that the chronic administration of low-doses of paclitaxel - i.e. metronomic scheduling - and the anti-Akt perifosine was the most efficient and the best tolerated treatment against NSCLC. Regarding drug mechanism of action, perifosine potentiated the pro-apoptotic effects of paclitaxel, independently of cell cycle arrest, and combining paclitaxel/perifosine resulted in a sustained suppression of glycolytic and mitochondrial metabolism. This study points out that targeting cancer cell bioenergetics may represent a novel therapeutic avenue in NSCLC, and provides a strong foundation for future clinical trials of metronomic MTAs combined with Akt inhibitors.

High expression of EGFR predicts poor survival in patients with resected T3 stage gastric adenocarcinoma and promotes cancer cell survival

Epidermal growth factor receptor (EGFR) is an essential regulator and biomarker of several types of cancer. However, the association between its expression and prognosis in patients with resected T3 stage gastric adenocarcinoma (RT3-GA) remains to be determined. In total, 683 patients with resectable T3-GA who underwent surgery were retrospectively included in the present study, and their immunohistochemical data for EGFR expression were collected. The associations between the patients' clinicopathologic characteristics and EGFR immunohistochemistry data were analyzed by multiple statistical methods. Annexin V apoptosis and MTT cell viability assays were performed to explore the effect of EGFR on AGS gastric adenocarcinoma cell survival. EGFR expression levels were categorized into two groups: low (406 cases) and high (277 cases). High EGFR was demonstrated to be significantly associated with distant metastasis (P=0.043) and severely decreased median overall survival time (MOST) and recurrence-free survival time (MRFST). MOST and MRFST in the low EGFR group were 39 and 37 months, respectively; whereas in the high EGFR group these values were only 18 and 13 months (P=3.10×10^-9 and P=6.74×10^-8, respectively). Multivariate analysis confirmed that high EGFR expression levels were associated with poor survival, which was associated with significantly increased recurrence risk and ~2-fold elevation in mortality risk [hazard ratio (HR), 1.73; 95% confidence interval (CI), 1.43-2.10; P=2.37×10^-8 and HR, 1.80; 95% CI, 1.50-2.17; P=3.80×10^-10]. Inhibiting EGFR with AG1478 suppressed its effect on promoting AGS cell survival. These results suggest that high EGFR expression indicates poor survival in patients with RT3-GA, which may be correlated with EGFR promoting GA cell survival.

Suppressive effects of tumor cell-derived 5'-deoxy-5'-methylthioadenosine on human T cells

The immunosuppressive tumor microenvironment represents one of the main obstacles for immunotherapy of cancer. The tumor milieu is among others shaped by tumor metabolites such as 5'-deoxy-5'-methylthioadenosine (MTA). Increased intratumoral MTA levels result from a lack of the MTA-catabolizing enzyme methylthioadenosine phosphorylase (MTAP) in tumor cells and are found in various tumor entities. Here, we demonstrate that MTA suppresses proliferation, activation, differentiation, and effector function of antigen-specific T cells without eliciting cell death. Conversely, if MTA is added to highly activated T cells, MTA exerts cytotoxic effects on T cells. We identified the Akt pathway, a critical signal pathway for T cell activation, as a target of MTA, while, for example, p38 remained unaffected. Next, we provide evidence that MTA exerts its immunosuppressive effects by interfering with protein methylation in T cells. To confirm the relevance of the suppressive effects of exogenously added MTA on human T cells, we used an MTAP-deficient tumor cell-line that was stably transfected with the MTAP-coding sequence. We observed that T cells stimulated with MTAP-transfected tumor cells revealed a higher proliferative capacity compared to T cells stimulated with Mock-transfected cells. In conclusion, our findings reveal a novel immune evasion strategy of human tumor cells that could be of interest for therapeutic targeting.

MicroRNA-103 suppresses tumor cell proliferation by targeting PDCD10 in prostate cancer

BACKGROUND

It is known that microRNAs (miRNAs) are a class of small, non-coding RNAs that act as key regulators in various physiological and pathological processes. However, the regulatory mechanisms involving miRNAs in prostate cancer remain largely unknown. Here, we found that miR-103 is down-regulated in prostate cancer and closely associated with tumor proliferation and migration. Our objective was to explore the role of the miR-103 in prostate cancer.

METHODS

In this study, we measured miR-103 level using real-time polymerase chain reaction in the human prostate cancer cell lines, including PC-3, LNCap, 22Rv1, DU145, and the normal prostate epithelium cell line RWPE-1, a total of 25 pairs of primary prostate cancer tissues and adjacent non-cancerous tissues (NCTs) were measured also. In addition, over-expression of miR-103 in prostate cancer cell lines to determine the role of miR-103 in prostate cancer.

RESULTS

We found that miR-103 is down-regulated in prostate cancer and closely associated with tumor proliferation and migration. In addition, over-expression of miR-103 apparently inhibits prostate cancer cell proliferation and migration in vitro. Gain-of-function in vitro experiments further show that miR-103 mimics significantly inhibited prostate cancer cell proliferation, invasion and increase the cell cycle in G1 phase, while promoted cell apoptosis. Subsequent dual-luciferase reporter assay identified one of the proto-oncogene PDCD10 as direct target of miR-103.

CONCLUSIONS

Therefore, our data collectively demonstrate that miR-103 is a proto-oncogene miRNA that can suppress prostate cancer proliferation and migration by down-regulating the oncogene PDCD10, indicating that miR-103 may represent a new potential diagnostic and therapeutic target for prostate cancer treatment.

Six family of homeobox genes and related mechanisms in tumorigenesis protocols

In recent years, the homeobox gene superfamily has been introduced as a master regulator in downstream target genes related to cell development and proliferation. An indispensable role of this family involved in organogenesis development has been widely demonstrated since expression of Six family led to a distinct increase in development of various organs. These functions of Six family genes are primarily based on structure as well as regulatory role in response to external or internal stimuli. In addition to these roles, mutation or aberrant expression of Six family plays a fundamental role in initiation of carcinogenesis, a multistep process including transformation, proliferation, angiogenesis, migration, and metastasis. This suggests that the Six superfamily members can be considered as novel target molecules to inhibit tumor growth and progression. This review focuses on the structure, function, and mechanisms of the Six family in cancer processes and possible strategies to apply these family members for diagnostic, prognostic, and therapeutic purposes.

Antitumor Lipids--Structure, Functions, and Medical Applications

Cell proliferation and metastasis are considered hallmarks of tumor progression. Therefore, efforts have been made to develop novel anticancer drugs that inhibit both the proliferation and the motility of tumor cells. Synthetic antitumor lipids (ATLs), which are chemically divided into two main classes, comprise (i) alkylphospholipids (APLs) and (ii) alkylphosphocholines (APCs). They represent a new entity of drugs with distinct antiproliferative properties in tumor cells. These compounds do not interfere with the DNA or mitotic spindle apparatus of the cell, instead, they incorporate into cell membranes, where they accumulate and interfere with lipid metabolism and lipid-dependent signaling pathways. Recently, it has been shown that the most commonly studied APLs inhibit proliferation by inducing apoptosis in malignant cells while leaving normal cells unaffected and are potent sensitizers of conventional chemo- and radiotherapy, as well as of electrical field therapy. APLs resist catabolic degradation to a large extent, therefore accumulate in the cell and interfere with lipid-dependent survival signaling pathways, notably PI3K-Akt and Raf-Erk1/2, and de novo phospholipid biosynthesis. They are internalized in the cell membrane via raft domains and cause downstream reactions as inhibition of cell growth and migration, cell cycle arrest, actin stress fibers collapse, and apoptosis. This review summarizes the in vitro, in vivo, and clinical trials of most common ATLs and their mode of action at molecular and biochemical levels.

Assessment of the effect of sphingosine kinase inhibitors on apoptosis,unfolded protein response and autophagy of T-cell acute lymphoblastic leukemia cells; indications for novel therapeutics

Sphingosine 1-phosphate (S1P) is a bioactive lipid that is formed by the phosphorylation of sphingosine and catalysed by sphingosine kinase 1 (SK1) or sphingosine kinase 2 (SK2). Sphingosine kinases play a fundamental role in many signaling pathways associated with cancer, suggesting that proteins belonging to this signaling network represent potential therapeutic targets. Over the last years, many improvements have been made in the treatment of T-cell acute lymphoblastic leukemia (T-ALL); however, novel and less toxic therapies are still needed, especially for relapsing and chemo-resistant patients. Here, we analyzed the therapeutic potential of SKi and ROMe, a sphingosine kinase 1 and 2 inhibitor and SK2-selective inhibitor, respectively. While SKi induced apoptosis, ROMe initiated an autophagic cell death in our in vitro cell models. SKi treatment induced an increase in SK1 protein levels in Molt-4 cells, whereas it activated the endoplasmic reticulum (ER) stress/unfolded protein response (UPR) pathway in Jurkat and CEM-R cells as protective mechanisms in a sub-population of T-ALL cells. Interestingly, we observed a synergistic effect of SKi with the classical chemotherapeutic drug vincristine. In addition, we reported that SKi affected signaling cascades implicated in survival, proliferation and stress response of cells. These findings indicate that SK1 or SK2 represent potential targets for treating T-ALL.

The switch from ER stress-induced apoptosis to autophagy via ROS-mediated JNK/p62 signals: A survival mechanism in methotrexate-resistant choriocarcinoma cells

BACKGROUND

Human choriocarcinoma, a highly curable solid tumour, is exceptionally sensitive to methotrexate-based chemotherapy at the metastatic stage. The present study aimed to investigate the molecular basis for this resistance to methotrexate therapy occurs in some cases, and these patients subsequently die from progressive and advanced disease.

METHODS

The autophagy and apoptotic activity regulated by PERK/ATF4 axis in methotrexate-resistant JEG-3 and parental cells were evaluated with western blotting and chromatin immunoprecipitation (ChIP). The regulatory relationships among the reactive oxygen species (ROS), JNK/p62 axis, PERK/ATF4-mediated apoptosis and autophagy were assessed with western blotting, RT-PCR, fluorescence-activated cell sorting as well as ChIP.

RESULTS

The decreased apoptosis in methotrexate-resistant JEG-3 cells was observed with an up-regulation of protective autophagy, suggesting a switch from apoptosis to autophagy, which was regulated via the PERK/ATF4 pathway under condition of endoplasmic reticulum (ER) stress. Further experiments demonstrated that this cell death switch was regulated by ROS-mediated JNK/p62 pathway and subsequently lead to the resistance of choriocarcinoma cells to methotrexate treatment.

CONCLUSIONS

This study provides evidence to explain a survival mechanism of the switch from ER stress-induced apoptosis to autophagy via ROS-mediated JNK/p62 signals in methotrexate-resistant choriocarcinoma cells and may implicate the chemotherapy of methotrexate resistance in choriocarcinoma.

The flavonoid morin from Moraceae induces apoptosis by modulation of Bcl-2 family members and Fas receptor in HCT 116 cells

It is evident based on literature that flavonoids from fruit can safely modulate cancer cell biology and induce apoptosis. Therefore, we investigated the anticancer activity of morin, a flavonoid which is plentiful in twigs of mulberry focusing on apoptosis, and its mechanisms. Morin upregulated the Fas receptor, and activates caspase-8, -9 and -3 in HCT-116 cells. Morin also activates Bid, and induced the loss of mitochondrial membrane potential (MMP, ∆Ψm) with Bax protein activation and cytochrome c release. In addition, morin induced ROS generation which was not blocked by N-acetylcysteine. Morin also suppressed Bcl-2 and cIAP-1, anti-apoptotic proteins, which may contribute to augmentation of morin-triggered apoptosis. As an upstream signaling pathway, suppressed Akt activity by morin was associated to apoptosis. This study suggests that morin induces caspase-dependent apoptosis through extrinsic pathway by upregulating Fas receptor as well as through the intrinsic pathway by modulating Bcl-2 and IAP family members, and ROS generation, and that Akt is the critical upstream signaling that regulates the apoptotic effect of morin in human colon cancer HCT-116 cells.

mTOR inhibition induces EGFR feedback activation in association with its resistance to human pancreatic cancer

The mammalian target of rapamycin (mTOR) is dysregulated in diverse cancers and contributes to tumor progression and drug resistance. The first generation of mTOR inhibitors have failed to show clinical efficiency in treating pancreatic cancers due in part to the feedback relief of the insulin-like growth factor-1 receptor (IGF-1R)-AKT signaling pathway. The second generation of mTOR inhibitors, such as AZD8055, could inhibit AKT activation upon mTOR complex 2 (mTORC2) inhibition. However, whether this generation of mTOR inhibitors can obtain satisfactory activities in pancreatic cancer therapy remains unclear. In this study, we found AZD8055 did not show great improvement compared with everolimus, AZD8055 induced a temporal inhibition of AKT kinase activities and AKT was then rephosphorylated. Additionally, we found that AZD8055-induced transient AKT inhibition increased the expression and activation of epidermal growth factor receptor (EGFR) by releasing its transcriptional factors Fork-head box O 1/3a (FoxO1/3a), which might contribute to cell resistance to AZD8055. The in vitro and in vivo experiments further indicated the combination of AZD8055 and erlotinib synergistically inhibited the mTORC1/C2 signaling pathway, EGFR/AKT feedback activation, and cell growth, as well as suppressed the progression of pancreatic cancer in a xenograft model. This study provides a rationale and strategy for overcoming AZD8055 resistance by a combined treatment with the EGFR inhibitor erlotinib in pancreatic cancer therapy.

Lipid analogues as potential drugs for the regulation of mitochondrial cell death

The mitochondrion plays an important role in the production of energy as ATP, the regulation of cell viability and apoptosis, and the biosynthesis of major structural and regulatory molecules, such as lipids. During ATP production, reactive oxygen species are generated that alter the intracellular redox state and activate apoptosis. Mitochondrial dysfunction is a well-recognized component of the pathogenesis of diseases such as cancer. Understanding mitochondrial function, and how this is dysregulated in disease, offers the opportunity for the development of drug molecules to specifically target such defects. Altered energy metabolism in cancer, in which ATP production occurs largely by glycolysis, rather than by oxidative phosphorylation, is attributable in part to the up-regulation of cell survival signalling cascades. These pathways also regulate the balance between pro- and anti-apoptotic factors that may determine the rate of cell death and proliferation. A number of anti-cancer drugs have been developed that target these factors and one of the most promising groups of agents in this regard are the lipid-based molecules that act directly or indirectly at the mitochondrion. These molecules have emerged in part from an understanding of the mitochondrial actions of naturally occurring fatty acids. Some of these agents have already entered clinical trials because they specifically target known mitochondrial defects in the cancer cell.

Antioxidants in the prevention of UVB-induced keratynocyte apoptosis

Skin cells can respond to UVB-induced damage by counteracting it through antioxidant activation and DNA repair mechanisms or, when damage is massive by undergoing programmed cell death. Antioxidant factors, and, in particular, food compounds, have attracted much interest because of their potential use in new protective strategies for degenerative skin disorders. Melatonin, creatine and hydroxytyrosol show a variety of pharmacological and clinical benefits including anti-oxidant and anti-inflammatory activities. Here, the potential protective actions of antioxidant compounds against UVB-induced apoptosis were investigated in human keratinocytes. The cells were pre-treated with antioxidants before UVB exposure and their effect evaluated by means of ultrastructural and molecular analyses. After UVB radiation typical morphological apoptotic features and in situ DNA fragmentation after TUNEL reaction, appeared. A significant numerical decrease of apoptotic patterns could be observed when antioxidants were administrated before cell death induction. Moreover, both the intrinsic and extrinsic apoptotic pathways appeared activated after UVB radiation, and their down-regulation has been shown when antioxidants were added to cells before death induction. In conclusion, these compounds are able to prevent apoptotic cell death in human keratinocytes exposed to UVB, suggesting, for these molecules, an important role in preventing skin damage.

MicroRNA-103 promotes colorectal cancer by targeting tumor suppressor DICER and PTEN

MicroRNAs (miRNAs) are a class of small, noncoding RNAs that act as key regulators in various physiological and pathological processes. However, the regulatory mechanisms for miRNAs in colorectal cancer remain largely unknown. Here, we found that miR-103 is up-regulated in colorectal cancer and its overexpression is closely associated with tumor proliferation and migration. In addition, repressing the expression of miR-103 apparently inhibits colorectal cancer cell proliferation and migration in vitro and HCT-116 xenograft tumor growth in vivo. Subsequent software analysis and dual-luciferase reporter assay identified two tumor suppressor genes DICER and PTEN as direct targets of miR-103, and up-regulation of DICER and PTEN obtained similar results to that occurred in the silencing of miR-103. In addition, restoration of DICER and PTEN can inhibit miR-103-induced colorectal cancer cell proliferation and migration. Our data collectively demonstrate that miR-103 is an oncogene miRNA that promotes colorectal cancer proliferation and migration through down-regulation of the tumor suppressor genes DICER and PTEN. Thus, miR-103 may represent a new potential diagnostic and therapeutic target for colorectal cancer treatment.

Licochalcone A induces apoptosis in KB human oral cancer cells via a caspase-dependent FasL signaling pathway

Licochalcone A (Lico-A) is a natural phenol licorice compound with multiple bioactivities, including anti-inflammatory, anti-microbial, anti-fungal and osteogenesis-inducing properties. In the present study, we investigated the Lico-A-induced apoptotic effects and examined the associated apoptosis pathway in KB human oral cancer cells. Lico-A decreased the number of viable KB oral cancer cells. However, Lico-A did not have an effect on primary normal human oral keratinocytes. In addition, the IC₅₀ value of Lico-A was determined to be ~50 μM following dose-dependent stimulation. KB oral cancer cells stimulated with Lico-A for 24 h showed chromatin condensation by DAPI staining, genomic DNA fragmentation by agarose gel electrophoresis and a gradually increased apoptotic cell population by FACS analysis. These data suggest that Lico-A induces apoptosis in KB oral cancer cells. Additionally, Lico-A-induced apoptosis in KB oral cancer cells was mediated by the expression of factor associated suicide ligand (FasL) and activated caspase-8 and −3 and poly(ADP-ribose) polymerase (PARP). Furthermore, in the KB oral cancer cells co-stimulation with a caspase inhibitor (Z-VAD-fmk) and Lico-A significantly abolished the apoptotic phenomena. Our findings demonstrated that Lico-A-induced apoptosis in KB oral cancer cells involves the extrinsic apoptotic signaling pathway, which involves a caspase-dependent FasL-mediated death receptor pathway. Our data suggest that Lico-A be developed as a chemotherapeutic agent for the management of oral cancer.

AKT kinase pathway: a leading target in cancer research

AKT1, a serine/threonine-protein kinase also known as AKT kinase, is involved in the regulation of various signalling downstream pathways including metabolism, cell proliferation, survival, growth, and angiogenesis. The AKT kinases pathway stands among the most important components of cell proliferation mechanism. Several approaches have been implemented to design an efficient drug molecule to target AKT kinases, although the promising results have not been confirmed. In this paper we have documented the detailed molecular insight of AKT kinase protein and proposed a probable doxorubicin based approach in inhibiting miR-21 based cancer cell proliferation. Moreover, the inhibition of miR-21 activation by raising the FOXO3A concentration seems promising in reducing miR-21 mediated cancer activation in cell. Furthermore, the use of next generation sequencing and computational drug design approaches will greatly assist in designing a potent drug molecule against the associated cancer cases.

AEG-1 is a target of perifosine and is over-expressed in gastric dysplasia and cancers

BACKGROUND

Perifosine, an alkylphospholipid, is an Akt inhibitor which inhibits the growth of diverse cancer cells. We have reported its inhibitory effects on the growth of gastric cancer cells recently, but its molecular mechanisms are still largely unknown.

AIMS

The purpose of this study was to investigate the effect and regulatory mechanism of perifosine in gastric cancer.

METHODS

Cell viability was determined by sulforhodamine B assay after transiently transfected with AEG-1 specific siRNAs. qRT-PCR and western blot assay were used to determine the mRNA expression and proteins levels of cell signaling molecules examined. Immunohistochemistry was used to detect the AEG-1 expression in 87 gastric carcinomas, 60 dysplasia, and 47 normal gastric mucosa.

RESULTS

Perifosine decreased AEG-1 gene expression along with inhibition of Akt/GSK3β/C-MYC signaling pathway. Knockdown of AEG-1 using siRNA led to significant down-regulation of cyclin D1 expression at both mRNA level and protein level, and inhibited the growth of gastric cancer cells. AEG-1 expression was elevated in gastric dysplasia and cancer tissues compared to normal gastric mucosa (P < 0.01). AEG-1 over-expression correlated with diffuse type of gastric cancer and advanced tumor stages.

CONCLUSIONS

Perifosine inhibits the growth of gastric cancer cells possibly through inhibition of the Akt/GSK3β/C-MYC signaling pathway-mediated down-regulation of AEG-1 that subsequently down-regulated cyclin D1. AEG-1 may play an important role in the carcinogenesis and progression of gastric cancer and could be a therapeutic target of perifosine.

Perifosine--a new option in treatment of acute myeloid leukemia?

INTRODUCTION

Perifosine is a novel targeted oral Akt inhibitor. In preclinical leukemia models, perifosine has an independent cytotoxic potential but also synergizes well with other rationally selected targeted agents. The evidence from clinical trials supporting the use of perifosine in the therapy of leukemias is limited. The optimal dose and schedule have yet to be defined. However, given its favorable toxicity profile and mechanism of action, the therapeutic potential of perifosine should be evaluated in well-designed clinical trials.

AREAS COVERED

The role of the phosphatidylinositol-3 kinase (PI3K)/Akt zpathway in normal cells, cancer and leukemias is discussed. The mechanism of action of perifosine and the basic information on the development and chemical properties are summarized. The evidence from in vivo and in vitro studies is presented. The efficacy and side effect profile are summarized.

EXPERT OPINION

The safety and tolerability profile of perifosine are satisfactory. The evidence from clinical trials in patients with leukemias is very limited. The preclinical data are encouraging. Perifosine has the potential to play a role in the treatment of leukemias in the future. Its role needs to be confirmed in clinical trials.

Notch1 receptor regulates AKT protein activation loop (Thr308) dephosphorylation through modulation of the PP2A phosphatase in phosphatase and tensin homolog (PTEN)-null T-cell acute lymphoblastic leukemia cells

Notch1 activating mutations occur in more than 50% of T-cell acute lymphoblastic leukemia (T-ALL) cases and increase expression of Notch1 target genes, some of which activate AKT. HES1 transcriptionally silences phosphatase and tensin homolog (PTEN), resulting in AKT activation, which is reversed by Notch1 inhibition with γ-secretase inhibitors (GSIs). Mutational loss of PTEN is frequent in T-ALL and promotes resistance to GSIs due to AKT activation. GSI treatments increased AKT-Thr(308) phosphorylation and signaling in PTEN-deficient, GSI-resistant T-ALL cell lines (Jurkat, CCRF-CEM, and MOLT3), suggesting that Notch1 represses AKT independent of its PTEN transcriptional effects. AKT-Thr(308) phosphorylation and downstream signaling were also increased by knocking down Notch1 in Jurkat (N1KD) cells. This was blocked by treatment with the AKT inhibitor perifosine. The PI3K inhibitor wortmannin and the protein phosphatase type 2A (PP2A) inhibitor okadaic acid both impacted AKT-Thr(308) phosphorylation to a greater extent in nontargeted control than N1KD cells, suggesting decreased dephosphorylation of AKT-Thr(308) by PP2A in the latter. Phosphorylations of AMP-activated protein kinaseα (AMPKα)-Thr(172) and p70S6K-Thr(389), both PP2A substrates, were also increased in both N1KD and GSI-treated cells and responded to okadaic acid treatment. A transcriptional regulatory mechanism was implied because ectopic expression of dominant-negative mastermind-like protein 1 increased and wild-type HES1 decreased phosphorylation of these PP2A targets. This was independent of changes in PP2A subunit levels or in vitro PP2A activity, but was accompanied by decreased association of PP2A with AKT in N1KD cells. These results suggest that Notch1 can regulate PP2A dephosphorylation of critical cellular regulators including AKT, AMPKα, and p70S6K.

Perifosine and sorafenib combination induces mitochondrial cell death and antitumor effects in NOD/SCID mice with Hodgkin lymphoma cell line xenografts

The effects of the Akt inhibitor perifosine and the RAF/MEK/ERK inhibitor sorafenib were investigated using two CD30(+)Hodgkin lymphoma cell lines (L-540 and HDLM-2) and the CD30(-)HD-MyZ histiocytic cell line. The combined perifosine/sorafenib treatment significantly inhibited mitogen-activated protein kinase and Akt phosphorylation in two of the three cell lines. Profiling of the responsive cell lines revealed that perifosine/sorafenib decreased the amplitude of transcriptional signatures that are associated with the cell cycle, DNA replication and cell death. Tribbles homolog 3 (TRIB3) was identified as the main mediator of the in vitro and in vivo antitumor activity of perifosine/sorafenib. Combined treatment compared with single agents significantly suppressed cell growth (40-80%, P<0.001), induced severe mitochondrial dysfunction and necroptotic cell death (up to 70%, P<0.0001) in a synergistic manner. Furthermore, in vivo xenograft studies demonstrated a significant reduction in tumor burden (P<0.0001), an increased survival time (81 vs 45 days, P<0.0001), an increased apoptosis (2- to 2.5-fold, P<0.0001) and necrosis (2- to 8-fold, P<0.0001) in perifosine/sorafenib-treated animals compared with mice receiving single agents. These data provide a rationale for clinical trials using perifosine/sorafenib combination.

MicroRNA-27a inhibitors alone or in combination with perifosine suppress the growth of gastric cancer cells

MicroRNA-27a (miR‑27a) is an oncogene that contributes to drug resistance in various types of cancer. However, the involvement of miR‑27a in gastric cancer has yet to be elucidated. Perifosine is an alkylphospholipid exhibiting antitumor activity as shown in both preclinical studies and clinical trials. The effects of perifosine on gastric cancer have yet to be determined. Therefore, this study was conducted to detect the role of miR‑27a and perifosine in human gastric cancer. miR‑27a was found to be expressed in human gastric cancer tissues and cell lines by quantitative reverse-transcription polymerase chain reaction (qRT‑PCR). The correlation between miR‑27a expression and clinicopathological characteristics of gastric cancer. We also explored the growth inhibitory effect of perifosine on human gastric cancer cells with or without co‑targeting miR‑27a by sulforhodamine B (SRB) assay. The results showed that miR‑27a expression was significantly upregulated in gastric cancer tissues, compared with their non‑tumor adjacent tissues. High expression levels of miR‑27a were associated with poor tumor histological grade (P=0.037). MiR‑27a inhibitors suppressed the growth of MGC‑803 cells. Assay results showed that perifosine exerted its activity selectively on the AGS cell line and the growth inhibitory effect of perifosine was enhanced significantly in combination with miR‑27a inhibitors in MGC‑803 cells. In conclusion, our results demonstrated that miR‑27a may be a therapeutic target and potential prognostic biological marker in gastric cancer. MiR‑27a inhibitors alone or in combination with perifosine may be a novel therapeutic approach against gastric cancer.

Edelfosine and perifosine disrupt hepatic mitochondrial oxidative phosphorylation and induce the permeability transition

Edelfosine and perifosine are alkylphospholipids that have been intensively studied as potential antitumor agents. Apoptotic cell death caused by these two compounds is mediated, at least in part, through mitochondria. Additionally, previous works demonstrated that edelfosine induces changes in mitochondrial membrane permeability that are somehow reduced by using cyclosporin A. Therefore, the objective of the present study was not only to confirm mitochondrial permeability transition but also identify direct effects of both ether lipids on mitochondrial hepatic fractions, namely on mitochondrial oxidative phosphorylation and generation of hydrogen peroxide (H(2)O(2)) through the respiratory chain. Results show that edelfosine and perifosine inhibit mitochondrial respiration and decrease transmembrane electric potential. However, despite these effects, edelfosine and perifosine were still able to induce mitochondrial permeability transition in non-energized mitochondria. Interestingly, edelfosine decreased H(2)O(2) production through the respiratory chain. In conclusion, the present work demonstrates previously unknown alterations of mitochondrial physiology directly induced by edelfosine and perifosine. The study is relevant in the understanding of mitochondrial-target effects of both compounds, as well as to acknowledge possible toxic responses in non-tumor organs.

Anticancer mechanisms and clinical application of alkylphospholipids

Synthetic alkylphospholipids (ALPs), such as edelfosine, miltefosine, perifosine, erucylphosphocholine and erufosine, represent a relatively new class of structurally related antitumor agents that act on cell membranes rather than on DNA. They selectively target proliferating (tumor) cells, inducing growth arrest and apoptosis, and are potent sensitizers of conventional chemo- and radiotherapy. ALPs easily insert in the outer leaflet of the plasma membrane and cross the membrane via an ATP-dependent CDC50a-containing 'flippase' complex (in carcinoma cells), or are internalized by lipid raft-dependent endocytosis (in lymphoma/leukemic cells). ALPs resist catabolic degradation, therefore accumulate in the cell and interfere with lipid-dependent survival signaling pathways, notably PI3K-Akt and Raf-Erk1/2, and de novo phospholipid biosynthesis. At the same time, stress pathways (e.g. stress-activated protein kinase/JNK) are activated to promote apoptosis. In many preclinical and clinical studies, perifosine was the most effective ALP, mainly because it inhibits Akt activity potently and consistently, also in vivo. This property is successfully exploited clinically in highly malignant tumors, such as multiple myeloma and neuroblastoma, in which a tyrosine kinase receptor/Akt pathway is amplified. In such cases, perifosine therapy is most effective in combination with conventional anticancer regimens or with rapamycin-type mTOR inhibitors, and may overcome resistance to these agents. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism.

Perifosine enhances mTORC1-targeted cancer therapy by activation of GSK3β in NSCLC cells

mTORC1 inhibitors, including rapamycin and its analogs, have been actively studied both pre-clinically and clinically. However, the single treatment of mTORC1 inhibitors has been modest in most cancer types. We have previously demonstrated that the activation of PI3K/Akt and MEK/ERK signaling pathways attenuates the anticancer efficacy of mTORC1 inhibitors. In this study, we report that mTORC1 inhibition also phosphorylates and inactivates GSK3β, which is a tumor suppressor in lung cancer. Moreover, we show that perifosine, as an Akt inhibitor, decreases rapamycin-induced phosphorylation of GSK3β and elevated p-GSK3β levels in rapamycin-resistant cell lines. Combination of perifosine with mTORC1 inhibitors showed enhanced anticancer efficacy both in cell cultures and in a xenograft mouse model. In addition, perifosine inhibits the growth of both rapamycin sensitive and resistant A549 cells. However, inhibition of GSK3β by a selective inhibitor- LiCl, or downregulation of GSK3β expression by siRNA, reverses the growth inhibitory effects of perifosine on rapamycin resistant cells, suggesting the important role of GSK3β activation in enhancing mTORC1 inhibitors efficacy by perifosine. Thus, our results provide a potential therapeutic strategy to enhance mTORC1-targeted cancer therapy by using perifosine or targeting GSK3β.

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

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive neoplastic disorder arising from T-cell progenitors. T-ALL accounts for 15% of newly diagnosed ALL cases in children and 25% in adults. Although the prognosis of T-ALL has improved, due to the use of polychemotherapy schemes, the outcome of relapsed/chemoresistant T-ALL cases is still poor. A signaling pathway that is frequently upregulated in T-ALL, is the phosphatidylinositol 3-kinase/Akt/mTOR network. To explore whether Akt could represent a target for therapeutic intervention in T-ALL, we evaluated the effects of the novel allosteric Akt inhibitor, MK-2206, on a panel of human T-ALL cell lines and primary cells from T-ALL patients. MK-2206 decreased T-ALL cell line viability by blocking leukemic cells in the G(0)/G(1) phase of the cell cycle and inducing apoptosis. MK-2206 also induced autophagy, as demonstrated by an increase in the 14-kDa form of LC3A/B. Western blotting analysis documented a concentration-dependent dephosphorylation of Akt and its downstream targets, GSK-3α/β and FOXO3A, in response to MK-2206. MK-2206 was cytotoxic to primary T-ALL cells and induced apoptosis in a T-ALL patient cell subset (CD34(+)/CD4(-)/CD7(-)), which is enriched in leukemia-initiating cells. Taken together, our findings indicate that Akt inhibition may represent a potential therapeutic strategy in T-ALL.

Perifosine induces protective autophagy and upregulation of ATG5 in human chronic myelogenous leukemia cells in vitro

AIM

The efficacy of the Akt inhibitor perifosine against chronic myeloid leukemia (CML) cells and its mechanisms of action are unknown. In this study, the cytotoxic effects of perifosine on CML and acute myeloid leukemia (AML) cell lines were compared to elucidate the mechanisms underlying the differences.

METHODS

Human AML cell lines Kasumi-1 and HL-60, and the CML cell line K562 were used. Cell viability was quantitated using MTT assay. Apoptosis was determined using Annexin V-FITC/propidium iodide and Hoechst staining, which were followed by flow cytometry and fluorescence microscopy analysis, respectively. Caspase pathway activation and the expression of autophagy-related genes were examined using Western blot. Autophagy was studied using electron microscopy, the acridine orange staining method, and GFP-LC3 was examined with fluorescence microscopy.

RESULTS

In contrast to AML cell lines, the CML cell lines K562 and K562/G (an imatinib-insensitive CML cell line) were resistant to perifosine (2.5-20 μmol/L) in respect to inhibiting cell growth and inducing apoptosis. Perifosine (2.5, 5, and 10 μmol/L) inhibited Akt and its phosphorylation in AML cells, but not in CML cells. Treatment with perifosine (20 μmol/L) resulted in autophagy in CML cells as shown by the increased formation of acidic vesicular organelles and the accumulation of LC3-II. Treatment of CML cells with perifosine (5, 10, and 20 μmol/L) dose-dependently upregulated AGT5, but not Beclin 1 at the protein level. Furthermore, inhibition of autophagy by chloroquine (40 nmol/L) significantly suppressed the cell growth and induced apoptosis in CML cells treated with perifosine (20 μmol/L).

CONCLUSION

Our results show that CML cell lines were resistant to the Akt inhibitor perifosine in vitro, which is due to perifosine-induced protective autophagy and upregulation of ATG5.

Emerging treatment options for the treatment of neuroblastoma: potential role of perifosine

Achieving a cure for high-risk neuroblastoma, the most common extracranial solid tumor in children, remains a formidable task despite the recent addition of antibody-mediated anti-GD2 immunotherapy to established multimodality therapy. The PI3K/Akt pathway is a pivotal signaling pathway utilized by a plethora of receptor tyrosine kinases that contribute to the aggressive phenotype of high-risk neuroblastoma. Akt is aberrantly activated in high-risk neuroblastoma and is therefore an attractive therapeutic target. Perifosine is the best-characterized Akt inhibitor in preclinical studies and in clinical trials in adults, although safety in children is not yet confirmed. It is a synthetic third-generation alkylphospholipid with good oral bioavailability and modest side effects. Perifosine targets the lipid-binding PH domain of Akt and inhibits the translocation of Akt to the cell membrane, an essential step for Akt activation. It decreases Akt phosphorylation and increases caspase-dependent apoptosis in neuroblastoma cell lines, inhibits growth of neuroblastoma xenografts, and overcomes RTK/ligand-mediated chemoresistance. It is currently being studied in two Phase I clinical trials in children with recurrent or refractory solid tumors including neuroblastoma. In the single agent trial (ClinicalTrials.gov identifier NCT00776867), maximum tolerated dose has not yet been reached and pharmacokinetic data has been accrued. In the second study (ClinicalTrials.gov identifier NCT01049841), patients are treated with a combination of perifosine and the mTOR-inhibitor temsirolimus based on preclinical data showing synergy of the two agents, and the premise that direct Akt inhibition may overcome Akt activation secondary to mTOR inhibition. Based on results from adult trials, it is unlikely that perifosine alone will produce dramatic therapeutic effects against high-risk neuroblastoma. However, given the recent encouraging early-phase combination therapy results in adults with multiple myeloma and colorectal carcinoma, rational perifosine-containing combination regimens hold promise for neuroblastoma therapy. These will be explored after safety in children is established in Phase I studies.

EphB receptors trigger Akt activation and suppress Fas receptor-induced apoptosis in malignant T lymphocytes

Treatment of hematopoietic malignancies often requires allogeneic bone marrow transplantation, and the subsequent graft-versus-leukemia response is crucial for the elimination of malignant cells. Cytotoxic T lymphocytes and NK cells responsible for the immunoelimination express Fas ligand and strongly rely on the induction of Fas receptor-mediated apoptosis for their action. Although cancer cells are removed successfully by graft-versus-leukemia reactions in myeloid malignancies, their efficiency is low in T cell leukemias. This may be partially because of the ability of malignant T cells to escape apoptosis. Our work shows that Eph family receptor EphB3 is consistently expressed by malignant T lymphocytes, most frequently in combination with EphB6, and that stimulation with their common ligands, ephrin-B1 and ephrin-B2, strongly suppresses Fas-induced apoptosis in these cells. This effect is associated with Akt activation and with the inhibition of the Fas receptor-initiated caspase proteolytic cascade. Akt proved to be crucial for the prosurvival response, because inhibition of Akt, but not of other molecules central to T cell biology, including Src kinases, MEK1 and MEK2, blocked the antiapoptotic effect. Overall, this demonstrates a new role for EphB receptors in the protection of malignant T cells from Fas-induced apoptosis through Akt engagement and prevention of caspase activation. Because Fas-triggered apoptosis is actively involved in the graft-versus-leukemia response and cytotoxic T cells express ephrin-Bs, our observations suggest that EphB receptors are likely to support immunoevasivenes of T cell malignancies and may represent promising targets for therapies, aiming to enhance immunoelimination of cancerous T cells.

Randomized placebo-controlled phase II trial of perifosine plus capecitabine as second- or third-line therapy in patients with metastatic colorectal cancer

PURPOSE

In a multicenter, double-blind phase II trial, we compared the efficacy and safety of perifosine plus capecitabine (P-CAP) with placebo plus capecitabine (CAP) in patients with metastatic colorectal cancer (mCRC) who had progressed after as many as two prior therapies.

PATIENTS AND METHODS

Patients (n = 38) not previously treated with capecitabine received P-CAP (perifosine 50 mg orally once daily, days 1 to 21 and CAP 825 mg/m(2) orally twice daily, days 1 to 14) or CAP (825 mg/m(2) orally twice daily, days 1 to 14) in 21-day cycles until disease progression. The primary end point was time to progression (TTP). Secondary end points included overall survival (OS), overall response rate (ORR), safety, and tolerability.

RESULTS

Twenty patients were randomly assigned to P-CAP and 18 to CAP. Median TTP (27.5 v 10.1 weeks; P < .001) and median OS (17.7 v 7.6 months; P = .0052) were improved in patients receiving P-CAP versus CAP. ORR was 20% v 7% in the P-CAP and CAP groups, respectively, and one patient in the P-CAP group had a complete response. A subset analysis of fluorouracil-refractory patients showed a median TTP of 17.6 v 9.0 weeks (P < .001) and median OS of 15.1 v 6.5 months (P = .0061). Toxicities, including diarrhea, nausea, fatigue, and hand-foot syndrome, were manageable.

CONCLUSION

P-CAP showed promising clinical activity compared with CAP in previously treated patients with mCRC. A phase III trial is underway comparing P-CAP with CAP in patients with refractory mCRC.

Regulation of the expression of death receptors and their ligands by melatonin in haematological cancer cell lines and in leukaemia cells from patients

Incorporation of new therapeutic agents remains as a major challenge for treatment of patients with malignant haematological disorders. Melatonin is an indolamine without relevant side effects. It has been shown previously to exhibit synergism with several chemotherapeutic drugs in Ewing sarcoma cells by potentiating the extrinsic pathway of apoptosis. It also sensitizes human glioma cells against TRAIL by increasing DR5 expression. Here, we report the induction of cell death by melatonin in several human malignant haematological cell lines through the activation of the extrinsic pathway of apoptosis. Such activation was mediated by the increase in the expression of the death receptors Fas, DR4 and DR5 and their ligands Fas L and TRAIL, with a remarkable rise in the expression of Fas and Fas L. The cytotoxic effect and the increase in Fas and Fas L were dependent on Akt activation. Results were corroborated in blasts from bone marrow and peripheral blood of acute myeloid leukaemia patients, where melatonin induced cell death and increased both Fas and Fas L expressions. We conclude that melatonin may be considered as a potential antileukaemic agent and its therapeutic use, either alone or in combination with current chemotherapeutic drugs, should be taken into consideration for further research.

Preclinical testing of the Akt inhibitor triciribine in T-cell acute lymphoblastic leukemia

Over the past 20 years, survival rates of T-cell acute lymphoblastic leukemia (T-ALL) patients have improved, mainly because of advances in polychemotherapy protocols. Despite these improvements, we still need novel and less toxic treatment strategies targeting aberrantly activated signaling networks which increase proliferation, survival, and drug resistance of T-ALL cells. One such network is represented by the phosphatidylinositol 3-kinase (PI3K)/Akt axis. PI3K inhibitors have displayed some promising effects in preclinical models of T-ALL. Here, we have analyzed the therapeutic potential of the Akt inhibitor, triciribine, in T-ALL cell lines. Triciribine caused cell cycle arrest and caspase-dependent apoptosis. Western blots demonstrated a dose-dependent dephosphorylation of Akt1/Akt2, and of mammalian target of rapamycin complex 1 downstream targets in response to triciribine. Triciribine induced autophagy, which could be interpreted as a defensive mechanism, because an autophagy inhibitor (chloroquine) increased triciribine-induced apoptosis. Triciribine synergized with vincristine, a chemotherapeutic drug employed for treating T-ALL patients, and targeted the side population of T-ALL cell lines, which might correspond to leukemia initiating cells. Our findings indicate that Akt inhibition, either alone or in combination with chemotherapeutic drugs, may serve as an efficient treatment towards T-ALL cells requiring upregulation of this signaling pathway for their proliferation and survival.

c-Jun NH2-terminal kinase-dependent upregulation of DR5 mediates cooperative induction of apoptosis by perifosine and TRAIL

BACKGROUND

Perifosine, an alkylphospholipid tested in phase II clinical trials, modulates the extrinsic apoptotic pathway and cooperates with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to augment apoptosis. The current study focuses on revealing the mechanisms by which perifosine enhances TRAIL-induced apoptosis.

RESULTS

The combination of perifosine and TRAIL was more active than each single agent alone in inducing apoptosis of head and neck squamous cell carcinoma cells and inhibiting the growth of xenografts. Interestingly, perifosine primarily increased cell surface levels of DR5 although it elevated the expression of both DR4 and DR5. Blockade of DR5, but not DR4 upregulation, via small interfering RNA (siRNA) inhibited perifosine/TRAIL-induced apoptosis. Perifosine increased phosphorylated c-Jun NH2-terminal kinase (JNK) and c-Jun levels, which were paralleled with DR4 and DR5 induction. However, only DR5 upregulaiton induced by perifosine could be abrogated by both the JNK inhibitor SP600125 and JNK siRNA. The antioxidants, N-acetylcysteine and glutathione, but not vitamin C or tiron, inhibited perifosine-induced elevation of p-c-Jun, DR4 and DR5. Moreover, no increased production of reactive oxygen species was detected in perifosine-treated cells although reduced levels of intracellular GSH were measured.

CONCLUSIONS

DR5 induction plays a critical role in mediating perifosine/TRAIL-induced apoptosis. Perifosine induces DR5 expression through a JNK-dependent mechanism independent of reactive oxygen species.

Activity of the novel dual phosphatidylinositol 3-kinase/mammalian target of rapamycin inhibitor NVP-BEZ235 against T-cell acute lymphoblastic leukemia

Recent findings have highlighted that constitutively active phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling is a common feature of T-cell acute lymphoblastic leukemia (T-ALL), where it upregulates cell proliferation, survival, and drug resistance. These observations lend compelling weight to the application of PI3K/Akt/mTOR inhibitors in the therapy of T-ALL. Here, we have analyzed the therapeutic potential of the novel dual PI3K/mTOR inhibitor NVP-BEZ235, an orally bioavailable imidazoquinoline derivative, which has entered clinical trials for solid tumors, on both T-ALL cell lines and patient samples. NVP-BEZ235 was cytotoxic to a panel of T-ALL cell lines as determined by MTT assays. NVP-BEZ235 treatment resulted in cell cycle arrest and apoptosis. Western blots showed a dose- and time-dependent dephosphorylation of Akt and mTORC1 downstream targets in response to NVP-BEZ235. Remarkably, NVP-BEZ235 targeted the side population of both T-ALL cell lines and patient lymphoblasts, which might correspond to leukemia-initiating cells, and synergized with chemotherapeutic agents (cyclophosphamide, cytarabine, dexamethasone) currently used for treating T-ALL patients. NVP-BEZ235 reduced chemoresistance to vincristine induced in Jurkat cells by coculturing with MS-5 stromal cells, which mimic the bone marrow microenvironment. NVP-BEZ235 was cytotoxic to T-ALL patient lymphoblasts displaying pathway activation, where the drug dephosphorylated eukaryotic initiation factor 4E-binding protein 1, at variance with rapamycin. Taken together, our findings indicate that longitudinal inhibition at two nodes of the PI3K/Akt/mTOR network with NVP-BEZ235, either alone or in combination with chemotherapeutic drugs, may be an efficient treatment of those T-ALLs that have aberrant upregulation of this signaling pathway for their proliferation and survival.

Glycosidated phospholipids: uncoupling of signalling pathways at the plasma membrane

Cell expansion and metastasis are considered hallmarks of tumour progression. Therefore, efforts have been made to develop novel anti-cancer drugs that inhibit both the proliferation and the motility of tumour cells. Synthetic alkylphospholipids, compounds with aliphatic side chains that are ether linked to a glycerol backbone, are structurally derived from platelet-activating factor and represent a new class of drugs with anti-proliferative properties in tumour cells. These compounds do not interfere with the DNA or mitotic spindle apparatus of the cell. Instead, they are incorporated into cell membranes, where they accumulate and interfere with lipid metabolism and lipid-dependent signalling pathways. Recently, it has been shown that the most commonly studied alkylphospholipids inhibit proliferation by inducing apoptosis in malignant cells while leaving normal cells unaffected. This review focuses on a novel group of synthetic alkylphospholipids, the glycosidated phospholipids, which contain carbohydrates or carbohydrate-related molecules at the sn-2 position of the glycerol backbone. Members of this subfamily also exhibit anti-proliferative capacity and modulate the cell adhesion, differentiation, and migration of tumour cells. Among this group, Ino-C2-PAF shows the highest efficacy and low cytotoxicity. Apart from its anti-proliferative effect, Ino-C2-PAF strongly reduces cell motility via its inhibitory effect on the phosphorylation of the cytosolic tyrosine kinases FAK and Src. Signalling pathways under the control of the FAK/Src complex are normally required for both migration and proliferation and play a prominent role in tumour progression. We intend to highlight the potential of glycosidated phospholipids, especially Ino-C2-PAF, as a promising new group of drugs for the treatment of hyperproliferative and migration-based skin diseases.

High immunohistochemical expression of p-AKT predicts inferior survival in patients with diffuse large B-cell lymphoma treated with immunochemotherapy

Chemotherapy and rituximab (R) is current standard therapy in diffuse large B-cell lymphoma (DLBCL), but a substantial proportion of patients still fail to reach sustained remission. In vitro studies have indicated that rituximab resistance could be accompanied by dysregulated apoptotic pathways, such as the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway, which can be constitutively activated in DLBCL. In this retrospective, immunohistochemical study on 106 patients treated with R-CHO(E)P (cyclophosphamide, doxorubicin, vincristine, prednisone, rituximab [+etoposide]), we investigated the prognostic role of proteins involved in different apoptotic pathways; phosphorylated AKT (p-AKT), bcl-2, MCL1, bcl-xL, Bax and Bak. High p-AKT expression (>108 cells/mm2, highest quartile, n=27) predicted worse progression-free (PFS) (P=0.02) and overall (OS) (P=0.01) survival, independent of International Prognostic Index and sex. Also bcl-2+ (cut-off 50%) predicted worse PFS (P=0.005) and OS (P=0.05) but after adjustment for clinical factors only the influence on PFS (P=0.03) remained significant. The prognostic impact of p-AKT overexpression was independent of bcl-2 status. MCL1, bcl-xL, Bax and Bak expression did not add any prognostic information. Our results suggest that high p-AKT expression predicts worse outcome, possibly indicating that inhibition of the activated PI3K/AKT pathway could be of clinical interest in DLBCL patients. In addition, bcl-2 status could have prognostic importance also in the era of immunochemotherapy.