BCL-2 functions as an activator of the AKT signaling pathway in pancreatic cancer

Glutamate rescues heat stress-induced apoptosis of Sertoli cells by enhancing the activity of antioxidant enzymes and activating the Trx1-Akt pathway in vitro

Heat stress reduces the number of Sertoli cells, which is closely related to an imbalanced redox status. Glutamate functions to maintain the equilibrium of redox homeostasis. However, the role of glutamate in heat treated Sertoli cells remains unclear. Herein, Sertoli cells from 3-week-old piglets were treated at 44 °C for 30 min (heat stress). Glutamate levels increased significantly following heat stress treatment, followed by a gradual decrease during recovery, while glutathione (GSH) showed a gradual increase. The addition of exogenous glutamate (700 μM) to Sertoli cells before heat stress significantly reduced the heat stress-induced apoptosis rate, mediated by enhanced levels of antioxidant substances (superoxide dismutase (SOD), total antioxidant capacity (TAC), and GSH) and reduced levels of oxidative substances (reactive oxygen species (ROS) and malondialdehyde (MDA)). Glutamate addition to Sertoli cells before heat stress upregulated the levels of glutamate-cysteine ligase, modifier subunit (Gclm), glutathione synthetase (Gss), thioredoxin (Trx1) and B-cell leukemia/lymphoma 2 (Bcl-2), and the ratio of phosphorylated Akt (protein kinase B)/total Akt. However, it decreased the levels of Bcl2-associated X protein (Bax) and cleaved-caspase 3. Addition of the inhibitor of glutaminase (Gls1), Bptes (Bis-2-(5-phenylacetamido-1,3,4-thiadiazol-2-yl)ethyl sulfide, 30 μM)to Sertoli cells before heat stress reversed these effects. These results inferred that glutamate rescued heat stress-induced apoptosis in Sertoli cells by enhancing activity of antioxidant enzymes and activating the Trx1-Akt pathway. Thus, glutamate supplementation might represent a novel strategy to alleviate the negative effect of heat stress.

Epigallocatechin-3-Gallate Prevents the Acquisition of a Cancer Stem Cell Phenotype in Ovarian Cancer Tumorspheres through the Inhibition of Src/JAK/STAT3 Signaling

Three-dimensional tumorsphere cultures recapitulate the expression of several cancer stem cell (CSC) biomarkers and represent an effective in vitro platform to screen the anti-CSC properties of drugs. Whereas ovarian carcinoma is among the leading causes of death for women, ovarian CSC (OvCSC), a highly malignant subpopulation of ovarian cancer cells, is thought to be responsible for therapy resistance, metastasis, and tumor relapse. Epigallocatechin-3-gallate (EGCG), a diet-derived active polyphenol found in green tea leaves, can suppress ovarian cancer cell proliferation and induce apoptosis. However, its capacity to prevent the acquisition of cancer stemness traits in ovarian malignancies remains unclear. Here, we exploited the in vitro three-dimensional tumorsphere culture model to explore the capacity of EGCG to alter CSC biomarkers expression, signal transducing events and cell chemotaxis. Total RNA and protein lysates were isolated from human ES-2 ovarian cancer cell tumorspheres for gene assessment by RT-qPCR and protein expression by immunoblot. Real-time cell chemotaxis was assessed with xCELLigence. Compared with their parental adherent cells, tumorspheres expressed increased levels of the CSC markers NANOG, SOX2, PROM1, and Fibronectin. EGCG treatment reduced dose-dependently tumorspheres size and inhibited the transcriptional regulation of those genes. Src and JAK/STAT3 signaling pathways appeared to be relevant for CSC phenotype and chemotactic response. In conclusion, these data highlight and support the chemopreventive benefits of the diet-derived EGCG and its capacity to target intracellular transducing events that regulate the acquisition of an invasive CSC phenotype.

Targeted Therapy of B7 Family Checkpoints as an Innovative Approach to Overcome Cancer Therapy Resistance: A Review from Chemotherapy to Immunotherapy

It is estimated that there were 18.1 million cancer cases worldwide in 2018, with about 9 million deaths. Proper diagnosis of cancer is essential for its effective treatment because each type of cancer requires a specific treatment procedure. Cancer therapy includes one or more approaches such as surgery, radiotherapy, chemotherapy, and immunotherapy. In recent years, immunotherapy has received much attention and immune checkpoint molecules have been used to treat several cancers. These molecules are involved in regulating the activity of T lymphocytes. Accumulated evidence shows that targeting immune checkpoint regulators like PD-1/PD-L1 and CTLA-4 are significantly useful in treating cancers. According to studies, these molecules also have pivotal roles in the chemoresistance of cancer cells. Considering these findings, the combination of immunotherapy and chemotherapy can help to treat cancer with a more efficient approach. Among immune checkpoint molecules, the B7 family checkpoints have been studied in various cancer types such as breast cancer, myeloma, and lymphoma. In these cancers, they cause the cells to become resistant to the chemotherapeutic agents. Discovering the exact signaling pathways and selective targeting of these checkpoint molecules may provide a promising avenue to overcome cancer development and therapy resistance. Highlights: (1) The development of resistance to cancer chemotherapy or immunotherapy is the main obstacle to improving the outcome of these anti-cancer therapies. (2) Recent investigations have described the involvement of immune checkpoint molecules in the development of cancer therapy resistance. (3) In the present study, the molecular participation of the B7 immune checkpoint family in anticancer therapies has been highlighted. (4) Targeting these immune checkpoint molecules may be considered an efficient approach to overcoming this obstacle.

Combined Inhibition of Bcl2 and Bcr-Abl1 Exercises Anti-Leukemia Activity but Does Not Eradicate the Primitive Leukemic Cells

Background: The management of Philadelphia Chromosome-positive (Ph+) hematological malignancies is strictly correlated to the use of BCR-ABL1 tyrosine kinase inhibitors (TKIs). However, these drugs do not induce leukemic stem cells death and their persistence may generate a disease relapse. Published reports indicated that Venetoclax, a selective BCL2 inhibitor, could be effective in Ph+ diseases, as BCL2 anti-apoptotic activity is modulated by BCR-ABL1 kinase. We, therefore, investigated if BCL2 inhibition, alone or combined with Nilotinib, a BCR-ABL1 inhibitor, affects the primitive and committed Ph+ cells survival. Methods: We used Ph+ cells isolated from leukemic patients at diagnosis. To estimate the therapeutic efficacy of BCL2 and BCR-ABL1 inhibition we employed long-term culture, proliferation and apoptosis assay. Immunoblot was used to evaluate the ability of treatment to interfere with the down-stream targets of BCR-ABL1. Results: Blocking BCL2, we observed reduced proliferation and clonogenic potential of CML CD34-positive cells and this cytotoxicity was improved by combination with BCR-ABL1 inhibitor. However, BCL2 inhibition, alone or in combination regiment with BCR-ABL1 inhibitor, did not reduce the self-renewal of primitive leukemic cells, while strongly induced cell death on primary Ph+ Acute Lymphoblastic Leukemia (ALL). Conclusion: Our results suggest that primitive CML leukemic cells are not dependent on BCL2 for their persistence and support that committed CML and Ph + ALL cells are dependent by BCL2 and BCR-ABL1 cooperation for their survival. The antileukemic activity of BCL2 and BCR-ABL1 dual targeting may be a useful therapeutic strategy for Ph+ ALL patients.

NLGN3 Upregulates Expression of ADAM10 to Promote the Cleavage of NLGN3 via Activating the LYN Pathway in Human Gliomas

The neuron derived synaptic adhesion molecular neuroligin-3 (NLGN3) plays an important role in glioma growth. While the role of autocrine NLGN3 in glioma has not been well-studied. The expression of NLGN3 in glioma was detected using immunohistochemistry. We further explored its function and regulatory mechanism in U251 and U87 cells with high expression of NLGN3. Knockdown of endogenous NLGN3 significantly reduced the proliferation, migration, and invasion of glioma cells and down-regulated the activity of the PI3K-AKT, ERK1/2, and LYN signaling pathways. In comparison, overexpression of NLGN3 yielded opposite results. Our results further demonstrate that LYN functions as a feedback mechanism to promote NLGN3 cleavage. This feedback regulation was achieved by upregulating the ADAM10 sheddase responsible for NLGN3 cleavage. Inhibition of ADAM10 suppressed the proliferation, migration, and invasion of glioma cells; oppositely, the expression of ADAM10 was correlated with a higher likelihood of lower grade glioma (LGG) in the brain. Our study demonstrates that glioma-derived NLGN3 promotes glioma progression by upregulating activity of LYN and ADAM10, which in turn promote NLGN3 cleavage to form a positive feedback loop. This pathway may open a potential therapeutic window for the treatment of human glioma.

Crosstalk between miRNAs and signaling pathways involved in pancreatic cancer and pancreatic ductal adenocarcinoma

Pancreatic cancer (PC) is the seventh leading cause of cancer-related deaths worldwide with 5-year survival rates below 8%. Most patients with PC and pancreatic ductal adenocarcinoma (PDAC) die after relapse and cancer progression as well as resistance to treatment. Pancreatic tumors contain a high desmoplastic stroma that forms a rigid mass and has a potential role in tumor growth and metastasis. PC initiates from intraepithelial neoplasia lesions leading to invasive cancer through various pathways. These lesions harbor particular changes in signaling pathways involved in the tumorigenesis process. These events affect both the epithelial cells, including the tumor and the surrounding stroma, and eventually lead to the formation of complex signaling networks. Genetic studies of PC have revealed common molecular features such as the presence of mutations in KRAS gene in more than 90% of patients, as well as the inactivation or deletion mutations of some tumor suppressor genes including TP53, CDKN2A, and SMAD4. In recent years, studies have also identified different roles of microRNAs in PC pathogenesis as well as their importance in PC diagnosis and treatment, and their involvement in various signaling pathways. In this study, we discussed the most common pathways involved in PC and PDAC as well as their role in tumorigenesis and progression. Furthermore, the miRNAs participating in the regulation of these signaling pathways in PC progression are summarized in this study. Therefore, understanding more about pathways involved in PC can help with the development of new and effective therapies in the future.

TMPRSS13 promotes cell survival, invasion, and resistance to drug-induced apoptosis in colorectal cancer

Cancer progression is often accompanied by increased levels of extracellular proteases capable of remodeling the extracellular matrix and promoting pro-cancerous signaling pathways by activating growth factors and receptors. The type II transmembrane serine protease (TTSP) family encompasses several proteases that play critical roles in cancer progression; however, the expression or function of the TTSP TMPRSS13 in carcinogenesis has not been examined. In the present study, we found TMPRSS13 to be differentially expressed at both the transcript and protein levels in human colorectal cancer (CRC). Immunohistochemical analyses revealed consistent high expression of TMPRSS13 protein on the cancer cell surface in CRC patient samples; in contrast, the majority of normal colon samples displayed no detectable expression. On a functional level, TMPRSS13 silencing in CRC cell lines increased apoptosis and impaired invasive potential. Importantly, transgenic overexpression of TMPRSS13 in CRC cell lines increased tolerance to apoptosis-inducing agents, including paclitaxel and HA14-1. Conversely, TMPRSS13 silencing rendered CRC cells more sensitive to these agents. Together, our findings suggest that TMPRSS13 plays an important role in CRC cell survival and in promoting resistance to drug-induced apoptosis; we also identify TMPRSS13 as a potential new target for monotherapy or combination therapy with established chemotherapeutics to improve treatment outcomes in CRC patients.

Noncanonical Cell Fate Regulation by Bcl-2 Proteins

Bcl-2 proteins are widely known as key controllers of mitochondrial outer membrane permeabilization, arguably the most important step of intrinsic apoptosis. Accumulating evidence indicate that most, if not all, members of the Bcl-2 protein family also mediate a number of apoptosis-unrelated functions. Intriguingly, many of these functions ultimately impinge on cell fate decisions via apoptosis-dependent or -independent mechanisms, delineating a complex network through which Bcl-2 family members regulate cell survival and death. Here, we critically discuss the mechanisms through which Bcl-2 proteins influence cell fate as they regulate autophagy, cellular senescence, inflammation, bioenergetic metabolism, Ca²⁺ fluxes, and redox homeostasis.

Integrated Therapeutic Targeting of the Prostate Tumor Microenvironment

Prostate cancer is a common and deadly cancer among men. The heterogeneity that characterizes prostate tumors contributes to clinical challenges in the diagnosis, prognosis, and treatment of this malignancy. While localized prostate cancer can be treated with surgery or radiotherapy, metastatic disease to the lymph nodes and the bone requires aggressive treatment with androgen deprivation treatment (ADT). Unfortunately, this often eventually progresses to metastatic castration-resistant prostate cancer (mCRPC). Advanced prostate cancer treatment today involves 1st- and 2nd-line taxane chemotherapy and 2nd-generation antiandrogens. The process of epithelial mesenchymal transition (EMT), during which epithelial cells lose their adhesions and their polarity, is a critical contributor to prostate cancer metastasis. In this article, we aim to integrate the current understanding of mechanisms dictating the dynamics of phenotypic EMT, with apoptosis outcomes in prostate tumors in response to antiandrogen and taxane chemotherapy for the treatment of advanced disease. Novel insights into the signaling mechanisms that target the functional interface between apoptosis and EMT will be considered in the context of potential clinical markers of tumor prognosis, as well as for effective therapeutic targeting of α- and β- adrenergic signaling (by novel and existing chemotherapeutic agents and antiandrogens). Interfering with EMT and apoptosis simultaneously toward eradicating the tumor mass is of major significance in combating the lethal disease and increasing patient survival.

Disruption of Immune Homeostasis in Human Dendritic Cells via Regulation of Autophagy and Apoptosis by Porphyromonas gingivalis

As fundamental processes of immune homeostasis, autophagy, and apoptosis must be maintained to mitigate risk of chronic inflammation and autoimmune diseases. Periodontitis is a chronic inflammatory disease characterized by oral microbial dysbiosis, and dysregulation of dendritic cell (DC) and T cell responses. The aim of this study was to elucidate the underlying mechanisms by which the oral microbe Porphyromonas gingivalis (P. gingivalis) manipulates dendritic cell signaling to perturb both autophagy and apoptosis. Using a combination of Western blotting, flow cytometry, qRT-PCR and immunofluorescence analysis, we show a pivotal role for the minor (Mfa1) fimbriae of P. gingivalis in nuclear/cytoplasmic shuttling of Akt and FOXO1 in human monocyte-derived DCs. Mfa1-induced Akt nuclear localization and activation ultimately induced mTOR. Activation of the Akt/mTOR axis downregulated intracellular LC3II, also known as Atg8, required for autophagosome formation and maturation. Use of allosteric panAkt inhibitor MK2206 and mTOR inhibitor rapamycin confirmed the role of Akt/mTOR signaling in autophagy inhibition by P. gingivalis in DCs. Interestingly, this pathway was also linked to induction of the anti-apoptotic protein Bcl2, decreased caspase-3 cleavage and decreased expression of pro-apoptotic proteins Bax and Bim, thus promoting longevity of host DCs. Addition of ABT-199 peptide to disrupt the interaction of antiapoptotic Bcl2 and its proapoptotic partners BAK/BAX restored apoptotic death to P. gingivalis-infected DC cells. In summary, we have identified the underlying mechanism by which P. gingivalis promotes its own survival and that of its host DCs.

Vicenin-2 acts as a radiosensitizer of the non-small cell lung cancer by lowering Akt expression

Non-small cell lung cancer (NSCLC) has a very high rate of incidence and is resistant to chemo- and radiotherapy. Vicenin-2 (VCN-2) is a flavonoid obtained from Ocimum sanctum L. and it has been reported to have radioprotective, anticancer, and radiosensitizing properties. We have conducted this study to check the effect of VCN-2 on the cell viability and the effect on PTEN (Phosphatase and tensin homolog), PI3KCA (Phosphatidylinositol 4, 5-biphosphate 3-kinase catalytic subunit alpha isoform/PI3K 110α subunit), and Akt1 when VCN-2 was used alone and in combination with radiation in the NSCLC cell line NCI-H23 (H23). We have also checked the effect of VCN-2 on various pro- and anti-apoptotic genes and the ultra-morphological changes that occurred in the cells when VCN-2 is used alone and in combination with radiation. VCN-2 was able to lower cancer cell survival and phosphorylated Akt while promoting the expression of pro-apoptotic genes and down-regulating anti-apoptotic genes. We also observed the apoptosis-associated ultra-morphological changes in the VCN-2-treated cells. Our study have demonstrated that VCN-2 can be a potential chemotherapeutic and radiosensitizing agent in NSCLC. © 2018 BioFactors, 45(2):200-210, 2019.

Mitosis inhibitors in anticancer therapy: When blocking the exit becomes a solution

Current microtubule-targeting agents (MTAs) remain amongst the most important antimitotic drugs used against a broad range of malignancies. By perturbing spindle assembly, MTAs activate the spindle assembly checkpoint (SAC), which induces mitotic arrest and subsequent apoptosis. However, besides toxic side effects and resistance, mitotic slippage and failure in triggering apoptosis in various cancer cells are limiting factors of MTAs efficacy. Alternative strategies to target mitosis without affecting microtubules have, thus, led to the identification of small molecules, such as those that target spindle Kinesins, Aurora and Polo-like kinases. Unfortunately, these so-called second-generation of antimitotics, encompassing mitotic blockers and mitotic drivers, have failed in clinical trials. Our recent understanding regarding the mechanisms of cell death during a mitotic arrest pointed out apoptosis as the main variable, providing an opportunity to control the cell fates and influence the effectiveness of antimitotics. Here, we provide an overview on the second-generation of antimitotics, and discuss possible strategies that exploit SAC activity, mitotic slippage/exit and apoptosis induction, in order to improve the efficacy of anticancer strategies that target mitosis.

Recent Advances in Comprehending the Signaling Pathways Involved in the Progression of Breast Cancer

This review describes recent advances in the comprehension of signaling pathways involved in breast cancer progression. Calcium sensing receptor (CaSR), caveolae signaling, signaling referred to hypoxia-inducing factors and disturbances in the apoptotic machinery are related to more general biological mechanisms and are considered first. The others refer to signaling pathways of more specific biological mechanisms, namely the heparin/heparin-sulfate interactome, over-expression of miRNA-378a-5p, restriction of luminal and basal epithelial cells, fatty-acid synthesis, molecular pathways related to epithelial to mesenchimal transition (EMT), HER-2/neu gene amplification and protein expression, and the expression of other members of the epithelial growth factor receptor family. This progress in basic research is fundamental to foster the ongoing efforts that use the new genotyping technologies, and aim at defining new prognostic and predictive biomarkers for a better personalized management of breast cancer disease.

MicroRNA-34 dysregulation in gastric cancer and gastric cancer stem cell

Gastric cancer is a major cause of cancer mortality worldwide, with a low survival rate for patients with advanced forms of the disease. Over the recent decades, the investigation of the pathophysiological mechanisms of tumourigenesis has opened promising avenues to understand some of the complexities of cancer treatment. However, tumour regeneration and metastasis impose great difficulty for gastric cancer cure. In recent years, cancer stem cells - a small subset of tumour cells in many cancers - have become a major focus of cancer research. Cancer stem cells are capable of self-renewal and are known to be responsible for tumour initiation, metastasis, therapy resistance and cancer recurrence. Recent studies have revealed the key role of microRNAs - small noncoding RNAs regulating gene expression - in these processes. MicroRNAs play crucial roles in the regulation of a wide range of biological processes in a post-transcriptional manner, though their expression is dysregulated in most malignancies, including gastric cancer. In this article, we review the consequences of aberrant expression of microRNA-34 in cancer and cancer stem cells, with a specific focus on the miR-34 dysregulation in gastric cancer and gastric cancer stem cells. We address the critical effects of the aberrant expression of miR-34 and its target genes in maintaining cancer stem cell properties. Information collection and discussion about the advancements in gastric cancer stem cells and microRNAs can be useful for providing novel insights into patient treatment.

Role of Notch signaling pathway in pancreatic cancer

Pancreatic cancer (PC) is one of the highly aggressive malignancies in the United States. It has been shown that multiple signaling pathways are involved in the pathogenesis of PC, such as JNK, PI3K/AKT, Rho GTPase, Hedgehog (Hh) and Skp2. In recent years, accumulated evidence has demonstrated that Notch signaling pathway plays critical roles in the development and progression of PC. Therefore, in this review we discuss the recent literature regarding the function and regulation of Notch in the pathogenesis of PC. Moreover, we describe that Notch signaling pathway could be down-regulated by its inhibitors or natural compounds, which could be a novel approach for the treatment of PC patients.

Phospho-Akt overexpression is prognostic and can be used to tailor the synergistic interaction of Akt inhibitors with gemcitabine in pancreatic cancer

Background

There is increasing evidence of a constitutive activation of Akt in pancreatic ductal adenocarcinoma (PDAC), associated with poor prognosis and chemoresistance. Therefore, we evaluated the expression of phospho-Akt in PDAC tissues and cells, and investigated molecular mechanisms influencing the therapeutic potential of Akt inhibition in combination with gemcitabine.

Methods

Phospho-Akt expression was evaluated by immunohistochemistry in tissue microarrays (TMAs) with specimens tissue from radically-resected patients (n = 100). Data were analyzed by Fisher and log-rank test. In vitro studies were performed in 14 PDAC cells, including seven primary cultures, characterized for their Akt1 mRNA and phospho-Akt/Akt levels by quantitative-RT-PCR and immunocytochemistry. Growth inhibitory effects of Akt inhibitors and gemcitabine were evaluated by SRB assay, whereas modulation of Akt and phospho-Akt was investigated by Western blotting and ELISA. Cell cycle perturbation, apoptosis-induction, and anti-migratory behaviors were studied by flow cytometry, AnnexinV, membrane potential, and migration assay, while pharmacological interaction with gemcitabine was determined with combination index (CI) method.

Results

Immunohistochemistry of TMAs revealed a correlation between phospho-Akt expression and worse outcome, particularly in patients with the highest phospho-Akt levels, who had significantly shorter overall and progression-free-survival. Similar expression levels were detected in LPC028 primary cells, while LPC006 were characterized by low phospho-Akt. Remarkably, Akt inhibitors reduced cancer cell growth in monolayers and spheroids and synergistically enhanced the antiproliferative activity of gemcitabine in LPC028, while this combination was antagonistic in LPC006 cells. The synergistic effect was paralleled by a reduced expression of ribonucleotide reductase, potentially facilitating gemcitabine cytotoxicity. Inhibition of Akt decreased cell migration and invasion, which was additionally reduced by the combination with gemcitabine. This combination significantly increased apoptosis, associated with induction of caspase-3/6/8/9, PARP and BAD, and inhibition of Bcl-2 and NF-kB in LPC028, but not in LPC006 cells. However, targeting the key glucose transporter Glut1 resulted in similar apoptosis induction in LPC006 cells.

Conclusions

These data support the analysis of phospho-Akt expression as both a prognostic and a predictive biomarker, for the rational development of new combination therapies targeting the Akt pathway in PDAC. Finally, inhibition of Glut1 might overcome resistance to these therapies and warrants further studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-016-0371-1) contains supplementary material, which is available to authorized users.

Novel Approaches to Apoptosis-Inducing Therapies

Induction of apoptotic programmed cell death is one of the underlying principles of most current cancer therapies. In this review, we discuss the limitations and drawbacks of this approach and identify three distinct, but overlapping strategies to avoid these difficulties and further enhance the efficacy of apoptosis-inducing therapies. We postulate that the application of multi-targeted small molecule inhibitor cocktails will reduce the risk of the cancer cell populations developing resistance towards therapy. Following from these considerations regarding population genetics and ecology, we advocate the reconsideration of therapeutic end points to maximise the benefits, in terms of quantity and quality of life, for the patients. Finally, combining both previous points, we also suggest an altered focus on the cellular and molecular targets of therapy, i.e. targeting the (cancer cells') interaction with the tumour microenvironment.

Broad targeting of resistance to apoptosis in cancer

Apoptosis or programmed cell death is natural way of removing aged cells from the body. Most of the anti-cancer therapies trigger apoptosis induction and related cell death networks to eliminate malignant cells. However, in cancer, de-regulated apoptotic signaling, particularly the activation of an anti-apoptotic systems, allows cancer cells to escape this program leading to uncontrolled proliferation resulting in tumor survival, therapeutic resistance and recurrence of cancer. This resistance is a complicated phenomenon that emanates from the interactions of various molecules and signaling pathways. In this comprehensive review we discuss the various factors contributing to apoptosis resistance in cancers. The key resistance targets that are discussed include (1) Bcl-2 and Mcl-1 proteins; (2) autophagy processes; (3) necrosis and necroptosis; (4) heat shock protein signaling; (5) the proteasome pathway; (6) epigenetic mechanisms; and (7) aberrant nuclear export signaling. The shortcomings of current therapeutic modalities are highlighted and a broad spectrum strategy using approaches including (a) gossypol; (b) epigallocatechin-3-gallate; (c) UMI-77 (d) triptolide and (e) selinexor that can be used to overcome cell death resistance is presented. This review provides a roadmap for the design of successful anti-cancer strategies that overcome resistance to apoptosis for better therapeutic outcome in patients with cancer.

Current and future intratumoral targeted treatment for pancreatic cancer

Pancreatic cancer is an insidious type of cancer with its symptoms manifested upon extensive disease. The overall 5-year survival rates between 0.4 and 4%. Surgical resection is an option for only 10% of the patients with pancreatic cancer. Local recurrence and hepatic metastases occur within 2 years after surgery. There are currently several molecular pathways investigated and novel targeted treatments are on the market. However; the nature of pancreatic cancer with its ability to spread locally in the primary site and lymph nodes indicates that further experimentation with local interventional therapies could be a future treatment proposal as palliative care or adjunct to gene therapy and chemotherapy/radiotherapy. In the current review, we will summarize the molecular pathways and present the interventional treatment options for pancreatic cancer.

Small molecule inhibitors of bcl-2 family proteins for pancreatic cancer therapy

Pancreatic cancer (PC) has a complex etiology and displays a wide range of cellular escape pathways that allow it to resist different treatment modalities. Crucial signaling molecules that function downstream of the survival pathways, particularly at points where several of these pathways crosstalk, provide valuable targets for the development of novel anti-cancer drugs. Bcl-2 family member proteins are anti-apoptotic molecules that are known to be overexpressed in most cancers including PC. The anti-apoptotic machinery has been linked to the observed resistance developed to chemotherapy and radiation and therefore is important from the targeted drug development point of view. Over the past ten years, our group has extensively studied a series of small molecule inhibitors of Bcl-2 against PC and provide solid preclinical platform for testing such novel drugs in the clinic. This review examines the efficacy, potency, and function of several small molecule inhibitor drugs targeted to the Bcl-2 family of proteins and their preclinical progress against PC. This article further focuses on compounds that have been studied the most and also discusses the anti-cancer potential of newer class of Bcl-2 drugs.

Effect of miR-451 on the biological behavior of the esophageal carcinoma cell line EC9706

BACKGROUND

MicroRNAs play important roles in coordinating a variety of cellular processes. Abnormal expression of miRNAs has been linked to several cancers. However, the functional role of miR-451 in esophageal squamous cell carcinoma remains unclear.

AIMS

The present study explored the effects of miR-451 on the biological behavior of the esophageal carcinoma cell line EC9706.

METHODS

Synthetic miR-451 mimics were transfected into EC9706 cells using Lipofectamine™ 2000. The expression of miR-451 was analyzed by RT-PCR and the expressions of Bcl-2, AKT and phosphorylated AKT were analyzed by Western blotting. The MTT assay, soft agar colony formation assay, transwell assay and FACS were used to assess the effect of miR-451 on EC9706 cell proliferation, invasion, metastasis and apoptosis. Tumor growth was assessed by subcutaneous inoculation of cells into BALB/c nude mice.

RESULTS

In comparison to the controls, a significant increase in the expression of miR-451 was associated with significantly decreased expressions of Bcl-2, AKT and p-AKT, and a significant increase in the apoptosis rate. The number of cell clones was significantly decreased by miR-451 expression, which also caused the inhibition of cell proliferation. The average number of cells penetrating the matrigel was significantly lower than the controls. Injection of miR-451 inhibited tumor growth in a xenograft model.

CONCLUSIONS

Upregulated expression of miR-451 induced apoptosis and suppressed cell proliferation, invasion and metastasis in the esophageal carcinoma cell line EC9706. In addition, injection of miR-451 inhibited tumor growth in a xenograft model of esophageal cancer.

Lentivirus-mediated bcl-2 gene therapy improves function and structure of chemotherapy-damaged ovaries in wistar rats

OBJECTIVE

This study aimed to explore the roles and mechanisms of lentivirus-mediated bcl-2 gene therapy in repairing the function and structure of chemotherapy-damaged ovaries in rats.

METHOD OF STUDY

The lentivirus vector carrying the bcl-2 gene (pGC-FU -EGFP-bcl-2) was constructed and condensed at a high titer. Wistar rats were divided into seven groups based on the treatment they were given: no treatment [the normal control (NC) group]; intraperitoneal injection of cyclophosphamide (the CTX group); bilateral ovarian injection of pGC-FU-EGFP-bcl-2 (the bcl-2 group) or empty vector pGC-FU-EGFP (the enhanced green fluorescent protein (EGFP) group); bilateral ovarian injection of normal saline (the NS + CTX group), pGC-FU-EGFP (the EGFP + CTX group), or pGC-FU-EGFP-bcl-2 (the bcl-2 + CTX group) followed by intraperitoneal injection of CTX. At 15, 30, 45, and 60 days after injection, the rats were killed, serum levels of estradiol (E₂) and follicle-stimulating hormone (FSH) were detected by radioimmunoassay; ovarian structure and follicles were observed under a microscope, the apoptosis of granulosa cells was detected by terminal deoxynucleotidyide transferase-mediated biotin-dUTP biotin nick-end labeling, and the expression of Bcl-2 in the ovaries was detected by Western blotting.

RESULTS

After the injection of pGC-FU-EGFP-bcl-2, the serum level of E₂ was elevated, whereas that of FSH was dropped, follicles were increased, the CTX-induced apoptosis of granulosa cells was inhibited, and the expression of Bcl-2 was up-regulated.

CONCLUSION

The lentivirus-mediated bcl-2 gene therapy can improve ovarian function and structure damaged by chemotherapy and, therefore, might be a potential method to treat CTX-induced pre-mature ovarian failure.

Molecular pathogenesis of pancreatic cancer and clinical perspectives

Pancreatic cancer remains stubbornly resistant to many key cytotoxic chemotherapeutic agents and novel targeted therapies. The molecular heterogeneity of this cancer may account for therapy failures to date, although our growing arsenal of novel targeted agents could translate into patient survival. The main objectives of this review are to elucidate histological subtypes of pancreatic neoplasms that exhibit the characteristic of a gradual process of differentiation from benign entities to malignant ones. In addition, important genes, molecular abnormalities, and significant pathways of pancreatic cancer are analyzed and a potential clinical interpretation is presented (p16/cdkn2a, k-ras mutations, smad-4/tgf-/stat3, stk-11, braf, brca-2, neurotensin, mucs proteins, palb2, mitochondrial mutations, DNA mismatch repair genes, methylation, microrna expression, epithelial-to-mesenchymal transition, egfr mutations, the pi3k-akt-mtor pathway, the vegf pathway, heat shock proteins, cxcr4, the cox pathway, the src pathway, the hedgehog pathway, pancreatic stellate cells, a progression model, and molecular events in uncommon pancreatic tumors). Finally, future therapeutic directions are elucidated.

Combinatorial therapies improve the therapeutic efficacy of nanoliposomal ceramide for pancreatic cancer

Poor prognosis cancers, such as pancreatic cancer, represent inherent challenges for ceramide-based nanotherapeutics due to metabolic pathways, which neutralize ceramide to less toxic or pro-oncogenic metabolites. We have recently developed a novel 80 nanometer diameter liposomal formulation that incorporates 30 molar percent C6-ceramide, a bioactive lipid that is pro-apoptotic to many cancer cells, but not to normal cells. In this manuscript, we evaluated the efficacy of combining nanoliposomal C6-ceramide (Lip-C6) with either gemcitabine or an inhibitor of glucosylceramide synthase. We first assessed the biological effect of Lip-C6 in PANC-1 cells, a gemcitabine-resistant human pancreatic cancer cell line, and found that low doses alone did not induce cell toxicity. However, cytotoxicity was achieved by combining Lip-C6 with either non-toxic sub-therapeutic concentrations of gemcitabine or with the glucosylceramide synthase inhibitor D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP). Furthermore, these combinations with Lip-C6 cooperatively inhibited PANC-1 tumor growth in vivo. Mechanistically, Lip-C6 inhibited pro-survival Akt and Erk signaling, whereas the nucleoside analog gemcitabine did not. Furthermore, by including PDMP within the nanoliposomes, which halted ceramide neutralization as evidenced by LC-MS3, the cytotoxic effects of Lip-C6 were enhanced. Collectively, we have demonstrated that nanoliposomal ceramide can be an effective anti-pancreatic cancer therapeutic in combination with gemcitabine or an inhibitor of ceramide neutralization.

Molecular biology of pancreatic cancer

In spite of continuous research efforts directed at early detection and treatment of pancreatic cancer, the outlook for patients affected by the disease remains dismal. With most cases still being diagnosed at advanced stages, no improvement in survival prognosis is achieved with current diagnostic imaging approaches. In the absence of a dominant precancerous condition, several risk factors have been identified including family history, chronic pancreatitis, smoking, diabetes mellitus, as well as certain genetic disorders such as hereditary pancreatitis, cystic fibrosis, familial atypical multiple mole melanoma, and Peutz–Jeghers and Lynch syndromes. Most pancreatic carcinomas, however, remain sporadic. Current progress in experimental molecular techniques has enabled detailed understanding of the molecular processes of pancreatic cancer development. According to the latest information, malignant pancreatic transformation involves multiple oncogenes and tumor-suppressor genes that are involved in a variety of signaling pathways. The most characteristic aberrations (somatic point mutations and allelic losses) affect oncogenes and tumor-suppressor genes within RAS, AKT and Wnt signaling, and have a key role in transcription and proliferation, as well as systems that regulate the cell cycle (SMAD/DPC, CDKN2A/p16) and apoptosis (TP53). Understanding of the underlying molecular mechanisms should promote development of new methodology for early diagnosis and facilitate improvement in current approaches for pancreatic cancer treatment.

Bcl-2 upregulation induced by miR-21 via a direct interaction is associated with apoptosis and chemoresistance in MIA PaCa-2 pancreatic cancer cells

BACKGROUND AND AIMS

Bcl-2 was previously shown to be associated with apoptosis and chemoresistance and carry multiple regulating pathways. However, the roles and mechanisms of miRNA (miR)-21 in regulation of Bcl-2 in pancreatic cancer remain to be elucidated. The aim of this study was to explore the regulation of Bcl-2 expression by miR-21 and its impact on apoptosis, chemoresistance and growth of pancreatic cancer cells using a pancreatic cancer cell line, MIA PaCa-2.

METHODS

miR-21 mimics and inhibitor were transfected to MIA PaCa-2 pancreatic cancer cells, respectively. Alteration in Bcl-2/Bax expression was subsequently evaluated. Then, luciferase activity was observed after miR-21 mimics and pRL-TK plasmids containing wild-type and mutant 3'UTRs of Bcl-2 mRNA were co-transfected. Finally, apoptosis, chemosensitivity to gemcitabine and cell proliferation were evaluated.

RESULTS

Upregulation of Bcl-2 expression was detected in cells transfected with miR-21 mimics, accompanied by downregulated Bax expression, less apoptosis, lower caspase-3 activity, decreased chemosensitivity to gemcitabine and increased proliferation compared with the control cells. Cells transfected with miR-21 inhibitor revealed an opposite trend. There was a significant increase in luciferase activity in the cells transfected with the wild-type pRL-TK plasmid, in contrast to those transfected with the mutant one, indicating that miR-21 promotes Bcl-2 expression by binding directly to the 3'UTR of Bcl-2 mRNA.

CONCLUSIONS

Upregulation of Bcl-2 directly induced by miR-21 is associated with apoptosis, chemoresistance and proliferation of MIA PaCa-2 pancreatic cancer cells.

DJ-1 cleavage by matrix metalloproteinase 3 mediates oxidative stress-induced dopaminergic cell death

Oxidative stress is commonly implicated in aging and neurodegenerative conditions such as Parkinson's disease (PD). Mutations in DJ-1 are associated with autosomal recessive early-onset PD. We investigated whether DJ-1 can be degraded in oxidative-stressed dopaminergic neuronal cells, leading to loss of its protective role against oxidative stress. We have shown previously and herein that the active form of matrix metalloproteinase-3 (MMP3) was accumulated in dopamine-producing CATH.a cells in the presence of MPP(+). We show that catalytically active MMP3 cleaved DJ-1, and impaired its antioxidant function. In CATH.a cells, both monomeric and dimeric forms of DJ-1 were diminished in the presence of MPP(+), and this was reversed by MMP3 knockdown or inhibition. While DJ-1 expression was decreased in the substantia nigra of mice administered with MPTP, its degradation was largely attenuated in MMP3 knockout mice. The AKT-signaling pathway, thought to mediate the effect of DJ-1 on cell survival, was also altered. MPP(+) caused decrease in both phospho-Thr308 and phospho-Ser473 forms of AKT, and this was restored by NNGH. Our data suggest that DJ-1 is fragmented by the intracellular MMP3 in response to cell stress, abolishing the protective role of DJ-1 against oxidative damage, and this contributes to the pathogenesis of PD.

Targeting Bcl-2-mediated cell death as a novel therapy in pancreatic cancer

BACKGROUND

Bcl-2 is an essential regulator of programmed cell death (PCD). Overexpression of Bcl-2 is common in pancreatic cancer; the high levels have been shown to correlate with resistance to PCD. This resistance is mediated by binding of Bcl-2 via its BH-3 domain to diverse proteins, including the Bax/Bak family members, various protein kinases, and beclin 1, which are involved in regulation of autophagy (type II PCD). Small molecule inhibitors of BH-3-mediated binding of Bcl-2 have been recently developed, although no investigation has been conducted in pancreatic cancer, a malignancy characterized by extreme resistance to PCD.

METHODS

The effect of the Bcl-2 binding inhibitor A-779024 on PCD was assessed by fluorescence activated cell sorting; the effect on Bcl-2 and other PCD-related proteins was analyzed by immunoblotting. Induction of autophagy was determined by fluorescence microscopy using a stably transfected GFP-LC3 construct to visualize autophagosome formation. Co-localization of Bcl-2 with binding partners regulating PCD was examined by immunoprecipitation and confocal immunofluorescent microscopy.

RESULTS

A-779024 induced PCD in a dose- and time-dependent fashion. No change was seen in the protein levels of Bcl-2, Bax, Bcl-XL, or Mcl-1. Contrary to prediction, A-779024 was ineffective at inducing autophagy in these cells. Co-localization studies demonstrated that Bcl-2 was not bound to beclin 1 and, therefore, treatment with A-779024 could not induce release of beclin 1 and initiation of autophagy.

CONCLUSIONS

Disruption of Bcl-2 activity using the small molecule inhibitor A-779024 induces apoptotic but not autophagic PCD. This approach may be a novel therapy, either alone or in combination with other treatments such as chemotherapy or autophagy modulating agents in pancreatic cancer.

The role of oxysterol binding protein-related protein 5 in pancreatic cancer

The expression of oxysterol binding protein-related protein (ORP) 5 is related to invasion and a poor prognosis in pancreatic cancer patients. ORP5 induced the expression of sterol response element binding protein (SREBP) 2 and activated the downstream gene of sterol response element. ChIP using SREBP2 antibody revealed that histone deacetylase 5 (HDAC5) was one of the downstream genes of SREBP2. The effect of HMG-CoA reductase inhibitors (statins) were analyzed according to the expression level of ORP5. The invasion rate and growth was suppressed in cells that strongly expressed ORP5 in a time- and dose-dependent manner, but had less effect in cells weakly expressing ORP5, suggesting that when the potential of invasion and growth relies on the cholesterol synthesis pathway, it becomes sensitive to HMG-CoA reductase inhibitor. Furthermore, HDAC inhibitor, tricostatin A, induced the expression of phosphatase and tensin homolog as well when ORP5 was suppressed or the cells were treated with statin. Treatment with both statin and tricostatin A showed a synergistic antitumor effect in cells that highly expressed ORP5. Therefore, in some pancreatic cancers, continuous ORP5 expression enhances the cholesterol synthesis pathway and this signal transduction regulates phosphatase and tensin homolog through HDAC5 expression. This is the first report to detail how the signal transduction of cholesterol synthesis is related to cancer invasion and why statins can suppress invasion and growth.

CTEN/tensin 4 expression induces sensitivity to paclitaxel in prostate cancer

BACKGROUND

Recently, we established paclitaxel-resistant prostate cancer cell lines (PC-3-TxR and DU145-TxR). To determine the mechanisms of paclitaxel resistance in PC-3-TxR cells, we compared the gene expression profiles between PC-3 and PC-3-TxR cells. Our results indicated that expression of the C-terminal tensin like protein (CTEN, tensin 4) gene was down-regulated by 10-fold in PC-3-TxR cells. We investigated the possibility that CTEN overexpression restores paclitaxel sensitivity.

METHODS

We investigated how knockdown and overexpression of CTEN in androgen-independent cell lines affect paclitaxel sensitivity by colony formation assay and growth inhibition assay. To determine the mechanisms by which CTEN affects paclitaxel sensitivity, we investigated the relationships between CTEN and F-actin or epidermal growth factor receptor (EGFR) in PC-3 cells. We also examined the association between expression of CTEN and grade of prostate cancer by immunohistochemistry using tissue microarray analysis.

RESULTS

Down-regulation of CTEN, which is located in the cytoskeleton, played an important role in paclitaxel resistance in PC-3-TxR cells. Knockdown of CTEN expression in PC-3 cells induced paclitaxel resistance. Overexpression of CTEN in PC-3-TxR and DU145-TxR cells restored paclitaxel sensitivity. CTEN expression was inversely correlated with F-actin and EGFR expression. Then knockdown of actin and EGFR in PC-3-TxR cells recovered paclitaxel sensitivity, indicating that CTEN down-regulation mediates paclitaxel resistance through elevation of EGFR and actin expression. Moreover, CTEN expression was inversely correlated with Gleason score.

CONCLUSIONS

These results strongly suggested that CTEN plays an important role in paclitaxel sensitivity and that CTEN expression level may be a prognostic predictive factor for PCa patients.

TW-37, a small-molecule inhibitor of Bcl-2, inhibits cell growth and induces apoptosis in pancreatic cancer: involvement of Notch-1 signaling pathway

Overexpression of Bcl-2 family proteins has been found in a variety of aggressive human carcinomas, including pancreatic cancer, suggesting that specific agents targeting Bcl-2 family proteins would be valuable for pancreatic cancer therapy. We have previously reported that TW-37, a small-molecule inhibitor of Bcl-2 family proteins, inhibited cell growth and induced apoptosis in pancreatic cancer. However, the precise role and the molecular mechanism of action of TW-37 have not been fully elucidated. In our current study, we found that TW-37 induces cell growth inhibition and S-phase cell cycle arrest, with regulation of several important cell cycle-related genes like p27, p57, E2F-1, cdc25A, CDK4, cyclin A, cyclin D1, and cyclin E. The cell growth inhibition was accompanied by increased apoptosis with concomitant attenuation of Notch-1, Jagged-1, and its downstream genes such as Hes-1 in vitro and in vivo. We also found that down-regulation of Notch-1 by small interfering RNA or gamma-secretase inhibitors before TW-37 treatment resulted in enhanced cell growth inhibition and apoptosis. Our data suggest that the observed antitumor activity of TW-37 is mediated through a novel pathway involving inactivation of Notch-1 and Jagged-1.

Oncogenic transformation of human ovarian surface epithelial cells with defined cellular oncogenes

Ovarian surface epithelium (OSE) is considered to give rise to epithelial ovarian carcinomas (EOCs). To elucidate early processes contributing to the development of EOCs from the OSE, two batches of primary human OSE cells were transduced with non-viral human genes (mutant Cdk4, cyclinD1 and hTERT) so as to efficiently establish normal diploid OSE cells without chromosomal instability. Then defined genetic alterations frequently observed in EOCs were transduced into the OSE cells. A combination of p53 inactivation and oncogenic Kras transduction did not confer tumor-forming ability in immunodeficient mice, though additional transduction of Akt or combined transduction of c-myc with bcl-2 did result in tumor formation. In the latter case, tumors demonstrated phenotypes reminiscent of human EOCs, including cytokeratin expression, a highly aggressive phenotype, metastatic behavior and formation of ascites. These results indicate that inactivation of p53 and activation of the Ras pathway play critical roles in ovarian carcinogenesis in co-operation with the Akt or c-myc pathways. This first in vitro model system faithfully recapitulating the development of EOCs using normal human OSE cells should greatly facilitate further studies of EOCs.

TW-37, a small-molecule inhibitor of Bcl-2, inhibits cell growth and invasion in pancreatic cancer

Bcl-2 family of proteins plays critical roles in human cancers, including pancreatic cancer, suggesting that the discovery of specific agents targeting Bcl-2 family proteins would be extremely valuable for pancreatic cancer therapy. We have previously reported the synthesis and characterization of TW-37, which seems to be a negative regulator of Bcl-2. In this investigation, we tested our hypothesis whether TW-37 could be an effective inhibitor of cell growth, invasion and angiogenesis in pancreatic cancer cells. Using multiple cellular and molecular approaches such as MTT assay, apoptosis enzyme-linked immunosorbent assay, real-time reverse transcription-polymerase chain reaction, Western blotting, electrophoretic mobility shift assay for measuring DNA binding activity of NF-kappaB, migration, invasion and angiogenesis assays, we found that TW-37, in nanomolar concentrations, inhibited cell growth in a dose- and time-dependent manner. This was accompanied by increased apoptosis and concomitant attenuation of NF-kappaB, and downregulation of NF-kappaB downstream genes such as MMP-9 and VEGF, resulting in the inhibition of pancreatic cancer cell migration, invasion and angiogenesis in vitro and caused antitumor activity in vivo. From these results, we conclude that TW-37 is a potent inhibitor of progression of pancreatic cancer cells, which could be due to attenuation of Bcl-2 cellular signaling processes. Our findings provide evidence showing that TW-37 could act as a small-molecule Bcl-2 inhibitor on well-characterized pancreatic cancer cells in culture as well as when grown as tumor in a xenograft model. We also suggest that TW-37 could be further developed as a potential therapeutic agent for the treatment of pancreatic cancer.