Blockade of epidermal growth factor receptors chemosensitizes breast cancer cells through up-regulation of Bnip3L

BNIP3 and Nix: Atypical regulators of cell fate

Since their discovery nearly 25 years ago, the BCL-2 family members BNIP3 and BNIP3L (aka Nix) have been labelled 'atypical'. Originally, this was because BNIP3 and Nix have divergent BH3 domains compared to other BCL-2 proteins. In addition, this atypical BH3 domain is dispensable for inducing cell death, which is also unusual for a 'death gene'. Instead, BNIP3 and Nix utilize a transmembrane domain, which allows for dimerization and insertion into and through organelle membranes to elicit cell death. Much has been learned regarding the biological function of these two atypical death genes, including their role in metabolic stress, where BNIP3 is responsive to hypoxia, while Nix responds variably to hypoxia and is also down-stream of PKC signaling and lipotoxic stress. Interestingly, both BNIP3 and Nix respond to signals related to cell atrophy. In addition, our current view of regulated cell death has expanded to include forms of necrosis such as necroptosis, pyroptosis, ferroptosis, and permeability transition-mediated cell death where BNIP3 and Nix have been shown to play context- and cell-type specific roles. Perhaps the most intriguing discoveries in recent years are the results demonstrating roles for BNIP3 and Nix outside of the purview of death genes, such as regulation of proliferation, differentiation/maturation, mitochondrial dynamics, macro- and selective-autophagy. We provide a historical and unbiased overview of these 'death genes', including new information related to alternative splicing and post-translational modification. In addition, we propose to redefine these two atypical members of the BCL-2 family as versatile regulators of cell fate.

BNIP3L/NIX-mediated mitophagy: molecular mechanisms and implications for human disease

Mitophagy is a highly conserved cellular process that maintains the mitochondrial quantity by eliminating dysfunctional or superfluous mitochondria through autophagy machinery. The mitochondrial outer membrane protein BNIP3L/Nix serves as a mitophagy receptor by recognizing autophagosomes. BNIP3L is initially known to clear the mitochondria during the development of reticulocytes. Recent studies indicated it also engages in a variety of physiological and pathological processes. In this review, we provide an overview of how BNIP3L induces mitophagy and discuss the biological functions of BNIP3L and its regulation at the molecular level. We further discuss current evidence indicating the involvement of BNIP3L-mediated mitophagy in human disease, particularly in cancer and neurological disorders.

Prognostic Autophagy-Related Genes of Gastric Cancer Patients on Chemotherapy

Background: Chemotherapy resistance based on fluorouracil and cisplatin is one of the most encountered postoperative clinical problems in patients diagnosed with gastric cancer (GC), resulting in poor prognosis. Aim of the Study: This study aimed to combine autophagy-related genes (ARGs) to investigate the susceptibility patients with GC to postoperative chemotherapy. Methods: Based on The Cancer Genome Atlas (TCGA) database, gene expression data for GC patients undergoing chemotherapy were integrated and analyzed. Prognostic genes were screened based on univariate and multivariate analysis regression analysis. Subjects were divided into high-risk and low-risk groups according to the median risk score. Kaplan-Meier method was used to evaluate OS and DFS. The accuracy of the prediction was determined by the subject operating characteristic curve analysis. In addition, stratified analyses based on different clinical variables was performed to assess the correlation between risk scores and clinical variables. Quantitative real-time (qRT) PCR was used to verify the expression of CXCR4 in GC tissues and cell lines. Results: A total of nine ARGs related to the prognosis of chemotherapy patients were screened out. Compared with normal gastric mucosa cell, CXCR4 showed elevated expression in GC and was significantly associated with survival. Based on GEO and TCGA databases, the model accurately predicted DFS and OS after chemotherapy. Conclusion: This study established prognostic markers based on nine genes, predicting that ARGs are related to chemotherapy susceptibility of GC patients, which can provide better individualized treatment regimens for clinical practice.

Mitochondrial dynamics and mitophagy in lung disorders

Mitochondria are biosynthetic, bioenergetic, and signaling organelles which are critical for physiological adaptations and cellular stress responses to the environment. Various endogenous and environmental stress affects critical processes in mitochondrial homeostasis such as oxidative phosphorylation, biogenesis, mitochondrial redox system which leads to the formation of reactive oxygen species (ROS) and free radicals. The state of function of the mitochondrion is particularly dependent on the dynamic balance between mitochondrial biogenesis, fusion and fission, and degradation of damaged mitochondria by mitophagy. Increasing evidence has suggested a prominent role of mitochondrial dysfunction in the onset and progression of various lung pathologies, ranging from acute to chronic disorders. In this comprehensive review, we discuss the emerging findings of multifaceted regulations of mitochondrial dynamics and mitophagy in normal lung homeostasis as well as the prominence of mitochondrial dysfunction as a determining factor in different lung disorders such as lung cancer, COPD, IPF, ALI/ARDS, BPD, and asthma. The review will contribute to the existing understanding of critical molecular machinery regulating mitochondrial dynamic state during these pathological states. Furthermore, we have also highlighted various molecular checkpoints involved in mitochondrial dynamics, which may serve as hopeful therapeutic targets for the development of potential therapies for these lung disorders.

Pyrazole Substituted 9-Anilinoacridines as HER2 Inhibitors Targeting Breast Cancer - An In-Silico Approach

BACKGROUND

Breast cancer is one of the malignant tumours which mainly affect the female population. Total 20% of the cases of breast cancer are due to overexpression of Human epidermal growth factor receptor-2 (HER2), which is the dominant tyrosine kinase receptor. In general, 9-anilinoacridine derivatives play an important role as antitumor agents due to their DNA-intercalating properties.

OBJECTIVE

Some novel 9-anilinoacridines substituted with pyrazole moiety(1a-z) were designed, and their HER2enzyme (PDB id-3PP0) inhibition activity was evaluated by molecular docking studies using the Glide module of Schrodinger suite 2019-4.

METHODS

Glide module of the Schrodinger suite was used to perform docking studies, qikprop module was used for in-silico ADMET screening, and the Prime-MM-GBSA module was used for free binding energy calculations. Using GLIDE scoring functions, we can determine the binding affinity of ligands (1a-z) towards HER2.

RESULTS

The inhibitory activity of ligands against HER2 was mainly due to the strong hydrophobic and hydrogen bonding interactions. Almost all the compounds 1a-z have a good binding affinity with Glide scores in the range of -4.9 to -9.75 compared to the standard drugs CK0403(-4.105) and Tamoxifen (-3.78). From the results of in-silico ADMET properties, most of the compounds fall within the recommended values. MM-GBSA binding calculations of the most potent inhibitors are more favourable.

CONCLUSION

The results of in-silico studies provide strong evidence for the consideration of valuable ligands in pyrazole substituted 9-anilinoacridines as potential HER2 inhibitors, and the compounds, 1v,s,r,d, a,o with significant Glide scores may produce significant anti-breast cancer activity for further development.

Degradation of engulfed mitochondria is rate-limiting in Optineurin-mediated mitophagy in neurons

Mitophagy, the selective removal of damaged mitochondria, is thought to be critical to maintain neuronal homeostasis. Mutations of proteins in the pathway cause neurodegenerative diseases, suggesting defective mitochondrial turnover contributes to neurodegeneration. In primary rat hippocampal neurons, we developed a mitophagy induction paradigm where mild oxidative stress induced low levels of mitochondrial damage. Mitophagy-associated proteins were sequentially recruited to depolarized mitochondria followed by sequestration into autophagosomes. The localization of these mitophagy events had a robust somal bias. In basal and induced conditions, engulfed mitochondria remained in non-acidified organelles for hours to days, illustrating efficient autophagosome sequestration but delayed lysosomal fusion or acidification. Furthermore, expression of an ALS-linked mutation in the pathway disrupted mitochondrial network integrity and this effect was exacerbated by oxidative stress. Thus, age-related decline in neuronal health or expression of disease-associated mutations in the pathway may exacerbate the slow kinetics of neuronal mitophagy, leading to neurodegeneration.

Quality Control in Neurons: Mitophagy and Other Selective Autophagy Mechanisms

The cargo-specific removal of organelles via selective autophagy is important to maintain neuronal homeostasis. Genetic studies indicate that deficits in these pathways are implicated in neurodegenerative diseases, including Parkinson's and amyotrophic lateral sclerosis. Here, we review our current understanding of the pathways that regulate mitochondrial quality control, and compare these mechanisms to those regulating turnover of the endoplasmic reticulum and the clearance of protein aggregates. Research suggests that there are multiple mechanisms regulating the degradation of specific cargos, such as dysfunctional organelles and protein aggregates. These mechanisms are critical for neuronal health, as neurons are uniquely vulnerable to impairment in organelle quality control pathways due to their morphology, size, polarity, and postmitotic nature. We highlight the consequences of dysregulation of selective autophagy in neurons and discuss current challenges in correlating noncongruent findings from in vitro and in vivo systems.

Mitophagy in Cancer: A Tale of Adaptation

：In the past years, we have learnt that tumors co-evolve with their microenvironment, and that the active interaction between cancer cells and stromal cells plays a pivotal role in cancer initiation, progression and treatment response. Among the players involved, the pathways regulating mitochondrial functions have been shown to be crucial for both cancer and stromal cells. This is perhaps not surprising, considering that mitochondria in both cancerous and non-cancerous cells are decisive for vital metabolic and bioenergetic functions and to elicit cell death. The central part played by mitochondria also implies the existence of stringent mitochondrial quality control mechanisms, where a specialized autophagy pathway (mitophagy) ensures the selective removal of damaged or dysfunctional mitochondria. Although the molecular underpinnings of mitophagy regulation in mammalian cells remain incomplete, it is becoming clear that mitophagy pathways are intricately linked to the metabolic rewiring of cancer cells to support the high bioenergetic demand of the tumor. In this review, after a brief introduction of the main mitophagy regulators operating in mammalian cells, we discuss emerging cell autonomous roles of mitochondria quality control in cancer onset and progression. We also discuss the relevance of mitophagy in the cellular crosstalk with the tumor microenvironment and in anti-cancer therapy responses.

Chasing the FOXO3: Insights into Its New Mitochondrial Lair in Colorectal Cancer Landscape

Colorectal cancer (CRC) poses a formidable challenge in terms of molecular heterogeneity, as it involves a variety of cancer-related pathways and molecular changes unique to an individual’s tumor. On the other hand, recent advances in DNA sequencing technologies provide an unprecedented capacity to comprehensively identify the genetic alterations resulting in tumorigenesis, raising the hope that new therapeutic approaches based on molecularly targeted drugs may prevent the occurrence of chemoresistance. Regulation of the transcription factor FOXO3a in response to extracellular cues plays a fundamental role in cellular homeostasis, being part of the molecular machinery that drives cells towards survival or death. Indeed, FOXO3a is controlled by a range of external stimuli, which not only influence its transcriptional activity, but also affect its subcellular localization. These regulation mechanisms are mediated by cancer-related signaling pathways that eventually drive changes in FOXO3a post-translational modifications (e.g., phosphorylation). Recent results showed that FOXO3a is imported into the mitochondria in tumor cells and tissues subjected to metabolic stress and cancer therapeutics, where it induces expression of the mitochondrial genome to support mitochondrial metabolism and cell survival. The current review discusses the potential clinical relevance of multidrug therapies that drive cancer cell fate by regulating critical pathways converging on FOXO3a.

In-silico Design, ADMET Screening, MM-GBSA Binding Free Energy of Some Novel Isoxazole Substituted 9-Anilinoacridines as HER2 Inhibitors Targeting Breast Cancer

BACKGROUND

Human Epidermal development factor Receptor-2 (HER2) is a membrane tyrosine kinase which is overexpressed and gene amplified in human breast cancers. HER2 amplification and overexpression have been linked to important tumor cell proliferation and survival pathways for 20% of instances of breast cancer. 9-aminoacridines are significant DNA-intercalating agents because of their antiproliferative properties.

OBJECTIVE

Some novel isoxazole substituted 9-anilinoacridines(1a-z) were designed by in-silico technique for their HER2 inhibitory activity. Docking investigations of compounds 1a-z are performed against HER2 (PDB id-3PP0) by using Schrodinger suit 2016-2.

METHODS

Molecular docking study for the designed molecules 1a-z are performed by Glide module, in-silico ADMET screening by QikProp module and binding free energy by Prime-MMGBSA module of Schrodinger suit. The binding affinity of designed molecules 1a-z towards HER2 was chosen based on GLIDE score.

RESULTS

Many compounds showed good hydrophobic communications and hydrogen bonding associations to hinder HER2. The compounds 1a-z, aside from 1z have significant Glide scores in the scope of - 4.91 to - 10.59 when compared with the standard Ethacridine (- 4.23) and Tamoxifen (- 3.78). The in-silico ADMET properties are inside the suggested about drug likeness. MM-GBSA binding of the most intense inhibitor is positive.

CONCLUSION

The outcomes reveal that this study provides evidence for the consideration of isoxazole substituted 9-aminoacridine derivatives as potential HER2 inhibitors. The compounds, 1s,x,v,a,j,r with significant Glide scores may produce significant anti breast cancer activity and further in vitro and in vivo investigations may prove their therapeutic potential.

Critical role of FOXO3a in carcinogenesis

FOXO3a is a member of the FOXO subfamily of forkhead transcription factors that mediate a variety of cellular processes including apoptosis, proliferation, cell cycle progression, DNA damage and tumorigenesis. It also responds to several cellular stresses such as UV irradiation and oxidative stress. The function of FOXO3a is regulated by a complex network of processes, including post-transcriptional suppression by microRNAs (miRNAs), post-translational modifications (PTMs) and protein–protein interactions. FOXO3a is widely implicated in a variety of diseases, particularly in malignancy of breast, liver, colon, prostate, bladder, and nasopharyngeal cancers. Emerging evidences indicate that FOXO3a acts as a tumor suppressor in cancer. FOXO3a is frequently inactivated in cancer cell lines by mutation of the FOXO3a gene or cytoplasmic sequestration of FOXO3a protein. And its inactivation is associated with the initiation and progression of cancer. In experimental studies, overexpression of FOXO3a inhibits the proliferation, tumorigenic potential, and invasiveness of cancer cells, while silencing of FOXO3a results in marked attenuation in protection against tumorigenesis. The role of FOXO3a in both normal physiology as well as in cancer development have presented a great challenge to formulating an effective therapeutic strategy for cancer. In this review, we summarize the recent findings and overview of the current understanding of the influence of FOXO3a in cancer development and progression.

Pentoxifylline Added to Steroid Window Treatment Phase Modified Apoptotic Gene Expression in Pediatric Patients With Acute Lymphoblastic Leukemia

Pentoxifylline is a xanthine that possesses antitumor properties and that can induce higher apoptosis in the leukemic cells of pediatric patients with acute lymphoblastic leukemia (ALL) during treatment with prednisone. We conducted a phase 1 pilot, controlled, randomized trial to evaluate the gene expression modified by pentoxifylline during the steroid window of induction to remission phase in patients newly diagnosed with ALL. Experimental and control treatments induced broad changes in the gene expression profile. Patients who received just prednisone upregulated 377 and downregulated 344 genes, in contrast with patients treated with the experimental treatment (combination of prednisone and pentoxifylline), who demonstrated upregulation of 1319 and downregulation of 1594 genes. The most important genes modified in this pathway are those with proapoptotic activity, the majority of these overexpressed. Thus, the addition of pentoxifylline to the treatment with prednisone during steroid window in patients with ALL modified the gene expression profile and changed different signal pathways of the leukemic cell. The combination of both drugs represents a therapeutic alternative for potentiating antileukemic therapy.

Early clinical development of epidermal growth factor receptor targeted therapy in breast cancer

INTRODUCTION

Epidermal growth factor receptor (EGFR) targeted treatment has been evaluated but has not shown a clear clinical benefit for breast cancer. This review article aims to consider the knowledge of the biological background of EGFR pathways in dissecting clinical studies of EGFR targeted treatment in breast cancer. Areas covered: This review focuses on the role of the EGFR pathway and the investigational drugs that target EGFR for breast cancer. Expert opinion: Recent studies have indicated that EGFR targeted therapy for breast cancer has some promising effects for patients with triple-negative breast cancer, basal-like breast cancer, and inflammatory breast cancer. However, predictive and prognostic biomarkers for EGFR targeted therapy have not been identified. The overexpression or amplification of EGFR itself may not be the true factor of induction of the canonical pathway as an oncogenic driver of breast cancer. Instead, downstream, non-canonical pathways related to EGFR may contribute to some aspects of the biological behavior of breast cancer; therefore, the blockade of the receptor could result in sufficient suppression of downstream pathways to inhibit the aggressive behavior of breast cancer. Mechanistic studies to investigate the dynamic interaction between the EGFR pathway and non-canonical pathways are warranted.

FOXO3a and the MAPK p38 are activated by cetuximab to induce cell death and inhibit cell proliferation and their expression predicts cetuximab efficacy in colorectal cancer

BACKGROUND

Cetuximab, a monoclonal antibody against EGFR used for the treatment of colorectal cancer (CRC), is ineffective in many patients. The aim of this study was to identify the signalling pathways activated by cetuximab in CRC cells and define new biomarker of response.

METHODS

We used in vitro, in vivo models and clinical CRC samples to assess the role of p38 and FOXO3a in cetuximab mechanism of action.

RESULTS

We show that cetuximab activates the MAPK p38. Specifically, p38 inhibition reduced cetuximab efficacy on cell growth and cell death. At the molecular level, cetuximab activates the transcription factor FOXO3a and promotes its nuclear translocation via p38-mediated phosphorylation, leading to the upregulation of its target genes p27 and BIM and the subsequent induction of apoptosis and inhibition of cell proliferation. Finally, we found that high FOXO3a and p38 expression levels are associated with better response rate and improved outcome in cetuximab-treated patients with CRC harbouring WT KRAS.

CONCLUSIONS

We identify FOXO3a as a key mediator of cetuximab mechanism of action in CRC cells and define p38 as its activator in this context. Moreover, high FOXO3a and p38 expression could predict the response to cetuximab in patients with CRC harbouring WT KRAS.

Exploring relationship between FOXQ1 gene and colorectal cancer using microarray technology

AIM: To compare the difference in gene expression profiles in human colorectal cancer cell line DLD1 before and after FOXQ1 knockdown using the microarray technology.

METHODS: RNA was extracted from DLD1 cells and then hybridized with the probes on Whole Human Genome Oligo Microarray (4 × 44 K, Agilent Technologies) and miRCURY LNA Array (v.18.0, Agilent Technologies). Multiple target genes were then analyzed with Genespring and Genepix software. Quantitative real-time PCR was applied for the validation of microarray results.

RESULTS: After FOXQ1 knockdown, of 41093 tested genes, 255 were up-regulated and 176 down-regulated. This result was partially validated by qRT-PCR. After FOXQ1 knockdown, of 2075 tested microRNAs, 31 were up-regulated and 12 down-regulated.

CONCLUSION: The whole genome microarray provides clues and evidence for the function of FOXQ1 in the development and progression of colorectal cancer.

N0436 (Alliance): A Phase II Trial of Irinotecan With Cetuximab in Patients With Metastatic Breast Cancer Previously Exposed to Anthracycline and/or Taxane-Containing Therapy

BACKGROUND

Irinotecan has a 20% to 25% response rate (RR) in patients with previously treated metastatic breast cancer (MBC). Epidermal growth factor receptor (EGFR) is overexpressed in some MBC, especially in triple-negative breast cancer (TNBC). Cetuximab is a monoclonal antibody against EGFR with additive preclinical activity with irinotecan.

PATIENTS AND METHODS

We report a 1-stage phase II study on MBC, measurable disease, and previous anthracycline and/or taxane therapy. Patients received cetuximab 400 mg/m(2) on day 1 cycle 1 then 250 mg/m(2) weekly thereafter and irinotecan 80 mg/m(2) on days 1 and 8 of each 21-day cycle. The primary end point was overall RR (ORR) according to Response Evaluation Criteria in Solid Tumors criteria (version 1.1).

RESULTS

Of 19 eligible patients enrolled from February to September 2006, 14 patients (74%) had visceral disease, seven patients (37%) were hormone receptor-positive, two patients (11%) HER2-positive, and 11 patients (58%) were triple-negative. Patients received a median of 2 cycles (range, 1-37). Confirmed ORR was 11% (95% confidence interval [CI], 1%-33%), with 1 partial response and 1 complete response. One patient had stable disease for 8 months. RR for TNBC versus non-TNBC was 18% versus 0% (P = .49). Median time to progression was 1.4 months (95% CI, 1.0-2.2) and median overall survival was 9.4 months (95% CI, 2.8-16.1). Twelve patients had disease progression within 2 cycles during therapy. Because of a low RR and rapid disease progression, the study leadership decided to close the trial early.

CONCLUSION

The tolerability of the combination of cetuximab and irinotecan is acceptable but demonstrated low overall activity. Potentially promising results were noted in patients with TNBC and further studies of these patients might be considered.

The roles of Cdk5-mediated subcellular localization of FOXO1 in neuronal death

Deficiency of cyclin-dependent kinase 5 (Cdk5) has been linked to the death of postmitotic cortical neurons during brain development. We now report that, in mouse cortical neurons, Cdk5 is capable of phosphorylating the transcription factor FOXO1 at Ser249 in vitro and in vivo. Cellular stresses resulting from extracellular stimulation by H2O2 or β-amyloid promote hyperactivation of Cdk5, FOXO1 nuclear export and inhibition of its downstream transcriptional activity. In contrast, a loss of Cdk5 leads to FOXO1 translocation into the nucleus: a shift due to decreased AKT activity but independent of S249 phosphorylation. Nuclear FOXO1 upregulates transcription of the proapoptotic gene, BIM, leading to neuronal death, which can be rescued when endogenous FOXO1 was replaced by the cytoplasmically localized form of FOXO1, FOXO1-S249D. Cytoplasmic, but not nuclear, Cdk5 attenuates neuronal death by inhibiting FOXO1 transcriptional activity and BIM expression. Together, our findings suggest that Cdk5 plays a novel and unexpected role in the degeneration of postmitotic neurons through modulation of the cellular location of FOXO1, which constitutes an alternative pathway through which Cdk5 deficiency leads to neuronal death.

Evaluating the evidence for targeting FOXO3a in breast cancer: a systematic review

Background

Tumour cells show greater dependency on glycolysis so providing a sufficient and rapid energy supply for fast growth. In many breast cancers, estrogen, progesterone and epidermal growth factor receptor-positive cells proliferate in response to growth factors and growth factor antagonists are a mainstay of treatment. However, triple negative breast cancer (TNBC) cells lack receptor expression, are frequently more aggressive and are resistant to growth factor inhibition. Downstream of growth factor receptors, signal transduction proceeds via phosphatidylinositol 3-kinase (PI3k), Akt and FOXO3a inhibition, the latter being partly responsible for coordinated increases in glycolysis and apoptosis resistance. FOXO3a may be an attractive therapeutic target for TNBC. Therefore we have undertaken a systematic review of FOXO3a as a target for breast cancer therapeutics.

Methods

Articles from NCBI were retrieved systematically when reporting primary data about FOXO3a expression in breast cancer cells after cytotoxic drug treatment.

Results

Increased FOXO3a expression is common following cytotoxic drug treatment and is associated with apoptosis and cell cycle arrest. There is some evidence that metabolic enzyme expression is also altered and that this effect is also elicited in TNBC cells. FOXO3a expression serves as a positive prognostic marker, especially in estrogen (ER) receptor positive cells.

Discussion

FOXO3a is upregulated by a number of receptor-dependent and -independent anti-cancer drugs and associates with apoptosis. The identification of microRNA that regulate FOXO3a directly suggest that it offers a tangible therapeutic target that merits wider evaluation.

Combination of novel HER2-targeting antibody 1E11 with trastuzumab shows synergistic antitumor activity in HER2-positive gastric cancer

The synergistic interaction of two antibodies targeting the same protein could be developed as an effective anti-cancer therapy. Human epidermal growth factor receptor 2 (HER2) is overexpressed in 20-25% of breast and gastric cancer patients, and HER2-targeted antibody therapy using trastuzumab is effective in many of these patients. Nonetheless, improving therapeutic efficacy and patient survival is important, particularly in patients with HER2-positive gastric cancer. Here, we describe the development of 1E11, a HER2-targeted humanized monoclonal antibody showing increased efficacy in a highly synergistic manner in combination with trastuzumab in the HER2-overexpressing gastric cancer cell lines NCI-N87 and OE-19. The two antibodies bind to sub-domain IV of the receptor, but have non-overlapping epitopes, allowing them to simultaneously bind HER2. Treatment with 1E11 alone induced apoptosis in HER2-positive cancer cells, and this effect was enhanced by combination treatment with trastuzumab. Combination treatment with 1E11 and trastuzumab reduced the levels of total HER2 protein and those of aberrant HER2 signaling molecules including phosphorylated HER3 and EGFR. The synergistic antitumor activity of 1E11 in combination with trastuzumab indicates that it could be a novel potent therapeutic antibody for the treatment of HER2-overexpressing gastric cancers.

Ixabepilone alone or with cetuximab as first-line treatment for advanced/metastatic triple-negative breast cancer

BACKGROUND

Despite high initial sensitivity to chemotherapy, TNBC is associated with a poor prognosis, highlighting the need for novel therapeutic strategies. The aim of this multicenter, randomized, open-label phase II trial was to assess the efficacy of ixabepilone as monotherapy, and the combination of ixabepilone with cetuximab, as first-line treatment in patients with triple-negative locally advanced nonresectable and/or metastatic breast cancer.

PATIENTS AND METHODS

Women were randomly assigned to receive either ixabepilone (40 mg/m(2)) every 21 days (n = 40), or ixabepilone (40 mg/m(2)) every 21 days with cetuximab (400 mg/m(2) loading dose, followed by 250 mg/m(2)) once weekly (n = 39). The primary end point of the trial was to estimate the response rates of ixabepilone monotherapy and ixabepilone with cetuximab combination therapy.

RESULTS

Of 79 randomized patients, 77 were treated. Based on an intent-to-treat analysis, an objective response rate of 30% (95% confidence interval [CI], 16.6-46.5) was observed in the monotherapy arm, and 35.9% (95% CI, 21.2-52.8) in the combination arm. Median progression-free survival was 4.1 months in both treatment groups. Safety findings were consistent with the known individual toxicity profiles of ixabepilone and cetuximab. Skin and subcutaneous tissue disorders were more common with combination therapy, as were discontinuations because of adverse events.

CONCLUSION

Ixabepilone monotherapy and the ixabepilone and cetuximab combination demonstrated similar levels of clinical activity in first-line treatment of advanced TNBC, with a predictable safety profile. Further investigation of novel therapies for TNBC is required to improve patient outcomes.

SIRT3 deacetylates FOXO3 to protect mitochondria against oxidative damage

Progressive accumulation of defective mitochondria is a common feature of aged cells. SIRT3 is a NAD(+)-dependent protein deacetylase that regulates mitochondrial function and metabolism in response to caloric restriction and stress. FOXO3 is a direct target of SIRT3 and functions as a forkhead transcription factor to govern diverse cellular responses to stress. Here we show that hydrogen peroxide induces SIRT3 to deacetylate FOXO3 at K271 and K290, followed by the upregulation of a set of genes that are essential for mitochondrial homeostasis (mitochondrial biogenesis, fission/fusion, and mitophagy). Consequently, SIRT3-mediated deacetylation of FOXO3 modulates mitochondrial mass, ATP production, and clearance of defective mitochondria. Thus, mitochondrial quantity and quality are ensured to maintain mitochondrial reserve capacity in response to oxidative damage. Maladaptation to oxidative stress is a major risk factor underlying aging and many aging-related diseases. Hence, our finding that SIRT3 deacetylates FOXO3 to protect mitochondria against oxidative stress provides a possible direction for aging-delaying therapies and disease intervention.

Autophagic flux and oxidative capacity of skeletal muscles during acute starvation

Autophagy is an important proteolytic pathway in skeletal muscles. The roles of muscle fiber type composition and oxidative capacity remain unknown in relation to autophagy. The diaphragm (DIA) is a fast-twitch muscle fiber with high oxidative capacity, the tibialis anterior (TA) muscle is a fast-twitch muscle fiber with low oxidative capacity, and the soleus muscle (SOL) is a slow-twitch muscle with high oxidative capacity. We hypothesized that oxidative capacity is a major determinant of autophagy in skeletal muscles. Following acute (24 h) starvation of adult C57/Bl6 mice, each muscle was assessed for autophagy and compared with controls. Autophagy was measured by monitoring autophagic flux following leupeptin (20 mg/kg) or colchicine (0.4 mg/kg/day) injection. Oxidative capacity was measured by monitoring citrate synthase activity. In control mice, autophagic flux values were significantly greater in the TA than in the DIA and SOL. In acutely starved mice, autophagic flux increased, most markedly in the TA, and several key autophagy-related genes were significantly induced. In both control and starved mice, there was a negative linear correlation of autophagic flux with citrate synthase activity. Starvation significantly induced AMPK phosphorylation and inhibited AKT and RPS6KB1 phosphorylation, again most markedly in the TA. Starvation induced Foxo1, Foxo3, and Foxo4 expression and attenuated the phosphorylation of their gene products. We conclude that both basal and starvation-induced autophagic flux are greater in skeletal muscles with low oxidative capacity as compared with those with high oxidative capacity and that this difference is mediated through selective activation of the AMPK pathway and inhibition of the AKT-MTOR pathways.

FOXO3 expression during colorectal cancer progression: biomarker potential reflects a tumour suppressor role

BACKGROUND

In previous studies, the Forkhead/winged-helix-box-class-O3 (FOXO3) transcription factor has displayed both tumour suppressive and metastasis-promoting properties.To clarify its role in human colorectal cancer (CRC) progression, we examined in vivo FOXO3 expression at key points of the metastatic cascade.

METHODS

Formalin-fixed paraffin-embedded resection specimens from normal colon, adenomas, primary CRC specimens of different pathological stage and CRC specimens with matched liver metastases were used to generate three separate custom-designed tissue microarray (TMA) representations of metastatic progression. Triplicate cores, immunostained for FOXO3 were scored semiquantitatively by two investigators.

RESULTS

The FOXO3 expression is significantly reduced in CRC specimens compared with normal tissue, and progressive FOXO3 downregulation is associated with advancing pathological stage. In addition, recurrent stage I/II primary tumours show a significantly lower FOXO3 expression compared with stage-matched non-recurrent tumours. When stratified according to high and low FOXO3 expression, mean disease-free survival in the low-expressing group was 28 months (95% CI 15.8-50.6) compared with 64 months (95% CI 52.9-75.4) in the high-expressing group.

CONCLUSION

We have demonstrated an association between low FOXO3 expression and CRC progression in vivo using purpose-designed TMAs. Forkhead/winged-helix-box-class-O3 may represent a novel biomarker of nodal and distant disease spread with clinical utility in CRC.

Regulation of Apoptosis by HER2 in Breast Cancer

HER2 is a trans-membrane receptor tyrosine kinase that activates multiple growth-promoting signaling pathways including PI3K-AKT and Ras-MAPK. Dysregulation of HER2 is a frequent occurrence in breast cancer that is associated with poor patient outcomes. A primary function of HER2 is suppressing apoptosis to enhance cell survival giving rise to uncontrolled proliferation and tumor growth. There has been much investigation into the mechanisms by which apoptosis is suppressed by HER2 in hopes of finding clinical targets for HER2-positive breast cancers as these cancers often become resistant to therapies that directly target HER2. Several apoptotic mechanisms have been shown to be deregulated in HER2-overexpressing cells with examples in both the intrinsic and extrinsic apoptotic pathways. HER2-mediated activation of PI3K-AKT signaling is required for many of the mechanisms HER2 uses to suppress apoptosis. HER2 overexpression is correlated with increases in anti-apoptotic Bcl-2 proteins including Bcl-2, Bcl-xL, and Mcl-1. HER2 also suppresses p53-mediated apoptosis by upregulation of MDM2 by activation of AKT. In addition, survivin expression is often increased with HER2 overexpression leading to inhibition of caspase activation. There is also recent evidence to suggest HER2 can directly influence apoptosis by translocation to the mitochondria to inhibit cytochrome c release. HER2 can also suppress cellular reaction to death ligands, especially TRAIL-induced apoptosis. Elucidation of the mechanisms of apoptotic suppression by HER2 suggest that clinical treatment will likely need to target multiple components of these pathways as there is redundancy in HER2-mediated cell survival. Several therapies have attempted to target Bcl-2 proteins that have promising pre-clinical results. Next-generation HER2 targeting therapies include irreversible pan-ERBB inhibitors and antibody-drug conjugates, such as T-DM1 that has very promising clinical results thus far. Further investigation should include elucidating mechanisms of resistance to HER2-targeted therapies and targeting of multiple components of HER2-mediated cell survival.

Computational identification and modeling of crosstalk between phosphorylation, O-β-glycosylation and methylation of FoxO3 and implications for cancer therapeutics

FoxO3 is a member of the forkhead class of transcription factors and plays a major role in the regulation of diverse cellular processes, including cell cycle arrest, DNA repair, and protection from stress stimuli by detoxification of reactive oxygen species. In addition, FoxO3 is a tumor suppressor and has been considered as a novel target for cancer therapeutics. Phosphorylation of FoxO3 via the AKT, IKK, and ERK pathways leads to deregulation, cytoplasmic retention, degradation of FoxO3 and favors tumor progression. Identification of the amino acid residues that are the target of different posttranslational modifications (PTMs) provides a foundation for understanding the molecular mechanisms of FoxO3 modifications and associated outcomes. In addition to phosphorylation, serine and threonine residues of several proteins are regulated by a unique type of PTM known as O-β-glycosylation, which serves as a functional switch. We sought to investigate the crosstalk of different PTMs on the FoxO3 which leads to the onset/progression of various cancers and that could also potentially be targeted as a therapeutic point of intervention. A computational workflow and set of selection parameters have been defined for the identification of target sites and crosstalk between different PTMs. We identified phosphorylation, O-β-GlcNAc modification, and Yin Yang sites on Ser/Thr residues, and propose a potential novel mechanism of crosstalk between these PTMs. Furthermore, methylation potential of human FoxO3 at arginine and lysine residues and crosstalk between methylation and phosphorylation have also been described. Our findings may facilitate the study of therapeutic strategies targeting posttranslational events.

Mechanisms of Trastuzumab resistance in ErbB2-driven breast cancer and newer opportunities to overcome therapy resistance

The Human Epidermal Growth Factor Receptor 2 (Her2, ErbB2 or Neu) is overexpressed in about 20 – 25% of breast cancers and is causally linked to oncogenesis, providing opportunities for targeted therapy. Trastuzumab (Herceptin^™, Genentech Inc, San Francisco, CA), a humanized monoclonal antibody against ErbB2, is a successful example of this concept and has vastly improved the response to treatment and overall survival in a majority of ErbB2+ breast cancer patients. However, lack of response in some patients as well as relapse during the course of therapy in others, continue to challenge researchers and clinicians alike towards a better understanding of the fundamental mechanisms of Trastuzumab action and resistance to treatment. The exact in vivo mechanism of action of Trastuzumab remains enigmatic, given its direct effects on the ErbB2 signaling pathway as well as indirect contributions from the immune system, by virtue of the ability of Trastuzumab to elicit Antibody-Dependent Cellular Cytotoxicity. Consequently, multiple mechanisms of resistance have been proposed. We present here a comprehensive review of our current understanding of the mechanisms, both of Trastuzumab action and clinical resistance to Trastuzumab-based therapies. We also review newer strategies (based on ErbB2 receptor biology) that are being explored to overcome resistance to Trastuzumab therapy.

Deciphering the role of forkhead transcription factors in cancer therapy

Forkhead O transcription factors (FOXO) are critical for the regulation of cell cycle arrest, cell death, and DNA damage repair. Inactivation of FOXO proteins may be associated with tumorigenesis, including breast cancer, prostate cancer, glioblastoma, rhabdomyosarcoma, and leukemia. Accumulated evidence shows that activation of oncogenic pathways such as phosphoinositide-3-kinase/AKT/IKK or RAS/mitogen-activated protein kinase suppresses FOXO transcriptional activity through the phosphorylation of FOXOs at different sites that ultimately leads to nuclear exclusion and degradation of FOXOs. In addition, posttranslational modifications of FOXOs such as acetylation, methylation and ubiquitination also contribute to modulating FOXO3a functions. Several anti-cancer drugs like paclitaxel, imatinib, and doxorubicin activate FOXO3a by counteracting those oncogenic pathways which restrain FOXOs functions. In this review, we will illustrate the regulation of FOXOs and reveal potential therapeutics that target FOXOs for cancer treatment.

Knockdown of FLOT1 impairs cell proliferation and tumorigenicity in breast cancer through upregulation of FOXO3a

PURPOSE

Lipid rafts, specialized domains in cell membranes, function as physical platforms for various molecules to coordinate a variety of signal transduction processes. Flotinllin-1 (FLOT1), a marker of lipid rafts, is involved in the progression of cancer, but the precise mechanism remains unclear. The aim of the present study was to examine the role of FLOT1 on the tumorigenesis of breast cancer cells and its clinical significance in progression of the disease.

EXPERIMENTAL DESIGN

FLOT1 expression was analyzed in 212 paraffin-embedded, archived clinical breast cancer samples by using immunohistochemistry (IHC). The effect of FLOT1 on cell proliferation and tumorigenesis was examined in vitro and in vivo. Western blotting and luciferase reporter analyses were carried out to identify the effects of downregulating FLOT1 on expression of cell cycle regulators and transcriptional activity of FOXO3a.

RESULTS

IHC analysis revealed high expression of FLOT1 in 129 of the 212 (60.8%) paraffin-embedded archived breast cancer specimens. The overall expression level of FLOT1 significantly correlated with clinical staging and poor patient survival of breast cancer. Strikingly, we found that silencing FLOT1 inhibited proliferation and tumorigenicity of breast cancer cells both in vitro and in vivo, which was further shown to be mechanistically associated with suppression of Akt activity, enhanced transcriptional activity of FOXO3a, upregulation of cyclin-dependent kinase inhibitor p21(Cip1) and p27(Kip1), and downregulation of the CDK regulator cyclin D1.

CONCLUSIONS

FLOT1 plays an important role in promoting proliferation and tumorigenesis of human breast cancer and may represent a novel prognostic biomarker and therapeutic target for the disease.

Novel insights into FOXOlogy: FOXOs and their putative role in thyroid carcinogenesis

FOXO transcription factors regulate genes directly involved in the control of cell cycle arrest, apoptosis, DNA damage repair and antioxidative defense mechanisms. Genetic FOXO alterations and inactivation of FOXOs through oncogenic signaling cascades have been identified in several human cancers and contribute to uncoordinated cellular proliferation. To date, little is known about FOXOs in the thyroid context. In this article we will first provide an introduction into the topic of forkhead transcription factors by explaining the principles of FOXO function and regulation. We will then address specific aspects of FOXO3 function in the thyroid and possible consequences of FOXO3 deregulation in thyroid malignancy. Finally, we discuss the potential role of the PI3K/Akt/FOXO3 axis for a targeted drug therapy of advanced thyroid carcinoma.

Unregulated miR-96 induces cell proliferation in human breast cancer by downregulating transcriptional factor FOXO3a

FOXO transcription factors are key tumor suppressors in mammalian cells. Until now, suppression of FOXOs in cancer cells was thought to be mainly due to activation of multiple onco-kinases by a phosphorylation-ubiquitylation-mediated cascade. Therefore, it was speculated that inhibition of FOXO proteins would naturally occur through a multiple step post-translational process. However, whether cancer cells may downregulate FOXO protein via an alternative regulatory mechanism is unclear. In the current study, we report that expression of miR-96 was markedly upregulated in breast cancer cells and breast cancer tissues compared with normal breast epithelial cells (NBEC) and normal breast tissues. Ectopic expression of miR-96 induced the proliferation and anchorage-independent growth of breast cancer cells, while inhibition of miR-96 reduced this effect. Furthermore, upregulation of miR-96 in breast cancer cells resulted in modulation of their entry into the G1/S transitional phase, which was caused by downregulation of cyclin-dependent kinase (CDK) inhibitors, p27(Kip1) and p21(Cip1), and upregulation of the cell-cycle regulator cyclin D1. Moreover, we demonstrated that miR-96 downregulated FOXO3a expression by directly targeting the FOXO3a 3'-untranslated region. Taken together, our results suggest that miR-96 may play an important role in promoting proliferation of human breast cancer cells and present a novel mechanism of miRNA-mediated direct suppression of FOXO3a expression in cancer cells.

BH3-only proteins: the death-puppeteer's wires

Most cell death in vertebrates proceeds through the intrinsic pathway of apoptosis and results from unregulated increase of mitochondrial membrane permeability. Bcl2-associated X protein (Bax) and Bcl2-antagonist/killer protein (Bak), the effector proapoptotic members of the Bcl-2 family, are, in their active state, the principal accomplices for this permeabilization process. How exactly Bax and Bak are activated has been a matter of major investigation in the last decade, and suitable tools offered by quantitative cytometric methodologies have significantly contributed to the understanding of the function of Bcl-2 family members. Here, we review the most relevant findings in this field and highlight one common trait that has emerged from the diverse new theories: a crucial role in the control of Bax/Bak activation has to be attributed to the BH3-only subset of the Bcl-2 family. BH3-only proteins exert their proapoptotic activity by hierarchical and tightly tuned interactions with other Bcl-2 family members and operate as sensors of intracellular/extracellular death signals and vectors of information to the core apoptotic machinery. Given their essential role in apoptosis, BH3-only molecules are proposed as molecular targets for the cure of diseases associated with abnormal cell death, as in the case with neurodegenerative conditions. As well, they are explored as possible tools for cancer therapy, according to the concept that molecules mimicking the BH3 domain of these proteins could selectively and efficiently cooperate in the cell killing by chemotherapeutic drugs. A few BH3 mimetics are currently being tested in clinical trials of hematologic and solid tumors. Nevertheless, the knowledge about the cellular and molecular mechanisms that regulate responsiveness to BH3 therapy has to be further expanded and will benefit from recent advances in cytometric quantitative technologies.

Synthesis and preliminary biological evaluation of high-drug-load paclitaxel-antibody conjugates for tumor-targeted chemotherapy

The goal of this study was to design paclitaxel (PTX)-monoclonal antibody (mAb) prodrug conjugates (PTXMAbs) with the ability to deliver therapeutically significant doses of the drug to the tumor while avoiding the previously observed solubility limitations of conjugates with PTX:mAb molar ratios of >3. New PTX conjugates were synthesized using the discrete poly(ethylene glycol) (dPEG) as linkers. These compounds, PTX-L-Lys[(dPEG12)(3)-dPEG4]-dPEG6-NHS (9a and 9b, for L = GL or SX, respectively), were then conjugated to the antiepidermal growth factor receptor mAb, C225 at increasing PTX:C225 ratios, producing completely soluble conjugates. Unlike the earlier PTXMAbs, buffered solutions of these conjugates remained homogeneous for extended periods of time. Fluorescence-activated cell sorting (FACS) analysis indicated preserved immunogenicity of the conjugates at all four substitution ratios, while cytotoxicity studies in MDA-MB-468 breast cancer cells indicated preservation of drug cytotoxicity. These conjugates may have potential in the development of high-drug-load tumor-targeting taxanes.

New drugs for breast cancer

Recently there have been significant advances in rational drug design for the treatment of breast cancer, especially in the area of targeted drug therapy. These include drugs which target the HER2 receptor and angiogenesis and the novel class of drug the PARP inhibitors. Some of these agents, for example, trastuzumab used in the treatment of HER2 positive breast cancer are already established as the standard of care. However, the duration of adjuvant trastuzumab, whether to continue it beyond progression in metastatic disease and the mechanism for developing trastuzumab resistance, remain to be determined. There is also much still to be learnt regarding other targeted therapies; the efficacy of different agents, the optimal duration of use and combination of therapies. Many of these agents are already in clinical trials, the results of which are likely to change clinical practice.

BNIP3 subfamily BH3-only proteins: mitochondrial stress sensors in normal and pathological functions

The BNIP3 subfamily of BH3-only proteins consists of BNIP3 and BNIP3-like (BNIP3L) proteins. These proteins form stable homodimerization complexes that localize to the outer membrane of the mitochondria after cellular stress. This promotes either apoptotic or non-apoptotic cell death such as autophagic cell death. Although the mammalian cells contain both members of this subfamily, the genome of Caenorhabditis elegans codes for a single BNIP3 ortholog, ceBNIP3, which shares homology in the transmembrane (TM) domain and in a conserved region close to the BH3 domain of mammalian BNIP3 protein. The cell death activities of BNIP3 and BNIP3L are determined by either the BH3 domain or the C-terminal TM domain. The TM domain of BNIP3 is unique, as it is capable of autonomous stable dimerization and contributes to mitochondrial localization of BNIP3. In knockout mouse models, BNIP3L was shown to be essential for normal erythrocyte differentiation and hematopoietic homeostasis, whereas BNIP3 plays a role in cellular responses to ischemia/reperfusion injury in the heart. Both BNIP3 and BNIP3L play a role in cellular responses to stress. Under hypoxia, both BNIP3 and BNIP3L expression levels are elevated and contribute to hypoxia-induced cell death. In addition, these proteins play critical roles in disease states. In heart disease, both BNIP3 and BNIP3L play a critical role in cardiomyocyte cell death following ischemic and non-ischemic injuries. In cancer, expression of BNIP3 and BNIP3L is downregulated by promoter hypermethylation or by homozygous deletion of the gene locus in certain cancers, whereas their expression was increased in other cancers. In addition, BNIP3 expression has been correlated with poor prognosis in some cancers. The results reviewed here suggest that BNIP3 and BNIP3L may be novel therapeutic targets for intervention because of their pathological roles in regulating cell death in disease states.

A new fork for clinical application: targeting forkhead transcription factors in cancer

Forkhead O transcription factors (FOXO) play a pivotal role in the regulation of a myriad of cellular functions including cell cycle arrest, cell death, and protection from stress stimuli. Activation of cell survival pathways such as phosphoinositide-3-kinase/AKT/IKK or RAS/mitogen-activated protein kinase are known to phosphorylate FOXOs at different sites which cause FOXOs nuclear exclusion and degradation, resulting in the suppression of FOXO's transcriptional activity. Perturbation of FOXO's function leads to deregulated cell proliferation and accumulation of DNA damage, resulting in diseases such as cancer. Emerging evidence shows that active FOXO proteins are crucial for keeping cells in check; and inactivation of FOXO proteins is associated with tumorigenesis, including breast cancer, prostate cancer, glioblastoma, rhabdomyosarcoma, and leukemia. Moreover, clinically used drugs like paclitaxel, imatinib, and doxorubicin have been shown to achieve their therapeutic effects through activation of FOXO3a and FOXO3a targets. In this review, we will focus the novel functions of FOXOs revealed in recent studies and further highlight FOXOs as new therapeutic targets in a broad spectrum of cancers.

PAR bZIP-bik is a novel transcriptional pathway that mediates oxidative stress-induced apoptosis in fibroblasts

PAR bZIP (cells knockout for PAR bZIP transcription factors) proteins, thyrotroph embryonic factor (TEF), albumin D-site-binding protein (DBP), and hepatic leukemia factor (HLF), are a family of transcription factors that have been shown to contribute to the expression of genes involved in detoxification and drug metabolism. Recently, we showed that PAR bZIP proteins were able to regulate the BH3-only gene bcl-gS in tumor cells. Here, we have extended the role of these transcription factors in the control of apoptosis executors by analyzing the expression of BH3-only genes in PAR bZIP triple knockout mouse fibroblasts. We found that bik was the only BH3-only gene downregulated in knockout cells. Consistently, transfection of TEF or DBP induces the expression of endogenous bik, regardless of the presence of active p53. Moreover, both promoter-reporter and chromatin immunoprecipitation assays indicate that PAR bZIP proteins activate the bik promoter directly. Treatment with different stress stimuli reveals a higher survival of knockout fibroblasts compared with that of wild-type cells, especially after incubation with H(2)O(2), which suggest that PAR bZIP proteins participate in oxidative stress-induced apoptosis. Furthermore, the apoptotic cell death promoted by treatment with H(2)O(2) can be impaired by reducing the expression of Bik in wild-type fibroblasts or enhanced by the overexpression of Bik in knockout cells. These findings reveal a novel transcriptional pathway relevant in transducing the apoptotic response to oxidative stress.

FOXO3a mediates the cytotoxic effects of cisplatin in colon cancer cells

Cisplatin is a conventional chemotherapeutic agent that binds covalently to purine DNA bases and mediates cellular apoptosis. A better understanding of the downstream cellular targets of cisplatin will provide information on its mechanism of action and help to understand the mechanism of drug resistance. In this study, we have investigated the effects of cisplatin in a panel of colon carcinoma cell lines and the involvement of the phosphoinositide-3-kinase/forkhead/winged helix box class O (FOXO) pathway in cisplatin action and resistance. Cisplatin-sensitive and cisplatin-resistant cell lines have been characterized in cell viability, flow cytometry, and clonogenic assays. The main components of the phosphoinositide-3-kinase/protein kinase B pathway, particularly FOXO3a, have been analyzed in sensitive and resistant cells on cisplatin treatment. Interestingly, in sensitive cells, cisplatin induces FOXO3a dephosphorylation and nuclear translocation, and expression of its target genes, whereas in resistant cells the effect of cisplatin on FOXO3a is incomplete. Consistent with this, protein kinase B/FOXO signaling axis modulators triciribine and psammaplysene A sensitize the resistant HT29 cells to cisplatin treatment. Critically, knockdown of FOXO3a expression using small interfering RNA rescues sensitive SW620 cells from cisplatin-induced short- and long-term cell death. Together, our findings suggest that FOXO3a is a relevant mediator of the cytotoxic effects of cisplatin in colon cancer cells.

Regulation of pro-apoptotic BH3-only proteins and its contribution to cancer progression and chemoresistance

The BH3-only members of the Bcl-2 protein family function as damage sensors in the cell and initiate the apoptotic cascade. Apoptosis is the primary mechanism by which the body gets rid of genetically defective cells and is critical for preventing the accumulation of cells with tumorigenic potential. BH3-only proteins have evolved to respond to distinct forms of cellular stress or DNA damage by inactivating the protective function of the prosurvival members of the Bcl-2 family. Therefore, a downregulated expression or activity of these proteins may favour tumor development. Moreover, the pro-apoptotic proteins are required for the success of most cancer treatments, including chemotherapy. Resistance to chemotherapy, a common feature of cancer, often reflects an inability of tumor cells to undergo apoptosis. Deciphering the regulation and activity of the BH3-only proteins may provide the basis for novel therapeutic strategies aimed at promoting tumor cell death or enhancing susceptibility to chemotherapeutic agents. This review summarizes the current knowledge of BH3-only proteins and their contribution to tumorigenesis and chemoresistance.

The transcription factor FOXO3a is a crucial cellular target of gefitinib (Iressa) in breast cancer cells

Gefitinib is a specific inhibitor of the epidermal growth factor receptor (EGFR) that causes growth delay in cancer cell lines and human tumor xenografts expressing high levels of EGFR. An understanding of the downstream cellular targets of gefitinib will allow the discovery of biomarkers for predicting outcomes and monitoring anti-EGFR therapies and provide information for key targets for therapeutic intervention. In this study, we investigated the role of FOXO3a in gefitinib action and resistance. Using two gefitinib-sensitive (i.e., BT474 and SKBR3) as well as three other resistant breast carcinoma cell lines (i.e., MCF-7, MDA-MB-231, and MDA-MB-453), we showed that gefitinib targets the transcription factor FOXO3a to mediate cell cycle arrest and cell death in sensitive breast cancer cells. In the sensitive cells, gefitinib treatment causes cell cycle arrest predominantly at the G(0)-G(1) phase and apoptosis, which is associated with FOXO3a dephosphorylation at Akt sites and nuclear translocation, whereas in the resistant cells, FOXO3a stays phosphorylated and remains in the cytoplasm. The nuclear accumulation of FOXO3a in response to gefitinib was confirmed in tumor tissue sections from breast cancer patients presurgically treated with gefitinib as monotherapy. We also showed that knockdown of FOXO3a expression using small interfering RNA (siRNA) can rescue sensitive BT474 cells from gefitinib-induced cell-proliferative arrest, whereas reintroduction of active FOXO3a in resistant MDA-MB-231 cells can at least partially restore cell-proliferative arrest and sensitivity to gefitinib. These results suggest that the FOXO3a dephosphorylation and nuclear localization have a direct role in mediating the gefitinib-induced proliferative arrest and in determining sensitivity to gefitinib.

"Sly as a FOXO": new paths with Forkhead signaling in the brain

The Forkhead transcription factor FOXO3a has emerged as a versatile target for diseases that impact upon neuronal survival, vascular integrity, immune function, and cellular metabolism. Enthusiasm is high to fill a critical treatment void through FOXO3a signaling for several neurodegenerative disorders that include aging, neuromuscular disease, systemic lupus erythematosus, stroke, and diabetic complications. Here we discuss the influence of FOXO3a upon cell survival and longevity, the intricate signal transduction pathways of FOXO3a, insights into present disease models, and the potential clinical translation of FOXO3a signaling into novel therapeutic strategies.

FoxO3 controls autophagy in skeletal muscle in vivo

Autophagy allows cell survival during starvation through the bulk degradation of proteins and organelles by lysosomal enzymes. However, the mechanisms responsible for the induction and regulation of the autophagy program are poorly understood. Here we show that the FoxO3 transcription factor, which plays a critical role in muscle atrophy, is necessary and sufficient for the induction of autophagy in skeletal muscle in vivo. Akt/PKB activation blocks FoxO3 activation and autophagy, and this effect is not prevented by rapamycin. FoxO3 controls the transcription of autophagy-related genes, including LC3 and Bnip3, and Bnip3 appears to mediate the effect of FoxO3 on autophagy. This effect is not prevented by proteasome inhibitors. Thus, FoxO3 controls the two major systems of protein breakdown in skeletal muscle, the ubiquitin-proteasomal and autophagic/lysosomal pathways, independently. These findings point to FoxO3 and Bnip3 as potential therapeutic targets in muscle wasting disorders and other degenerative and neoplastic diseases in which autophagy is involved.

The emerging roles of forkhead box (Fox) proteins in cancer

Forkhead box (Fox) proteins are a superfamily of evolutionarily conserved transcriptional regulators, which control a wide spectrum of biological processes. As a consequence, a loss or gain of Fox function can alter cell fate and promote tumorigenesis as well as cancer progression. Here we discuss the evidence that the deregulation of Fox family transcription factors has a crucial role in the development and progression of cancer, and evaluate the emerging role of Fox proteins as direct and indirect targets for therapeutic intervention, as well as biomarkers for predicting and monitoring treatment responses.