Bcl-2 overexpression and hypoxia synergistically act to modulate vascular endothelial growth factor expression and in vivo angiogenesis in a breast carcinoma line

Does the Expression of Vascular Endothelial Growth Factor (VEGF) and Bcl-2 Have a Prognostic Significance in Advanced Non-Small Cell Lung Cancer?

Lung cancer is the most common cause of mortality from malignant tumors worldwide. The five-year survival rate for people with advanced stages varies considerably, from 35.4% to 6.9%. The angiogenic potential of bcl2 is not well known, nor is the way in which tumor cells with excessive bcl2 expression affect VEGF production. Hypothetically, given that tumor growth, progression and metastasis are dependent on angiogenesis, the antiapoptotic effect is expected to form a link between these two molecules. The aim of this study was to evaluate the relationship between bcl-2 and VEGF expression, clinicopathological features and survival in 216 patients with advanced NSCLC. Archival tumor tissues were examined by immunohistochemistry for the expression of bcl-2 and VEGF. Immunoreactivity for bcl-2 was observed in 41.4% of NSCLCs, 51% of squamous and 34.8% of adenocarcinomas-expressed Bcl-2. There was an inverse correlation of mononuclear stromal reaction and bcl-2 expression in adenocarcinoma (p < 0.0005). A total of 71.8% NSCLCs were VEGF positive, 56% of squamous and 82.2% of adenocarcinomas. High level of VEGF expression was significantly associated with histology type (p = 0.043), low histology grade (p = 0.014), clinical stage IV (p = 0.018), smoking history (p = 0.008) and EGFR mutations (p = 0.026). There was an inverse correlation in the expression of Bcl-2 and VEGF in NSCLC patients (p = 0.039, r = -0.163). Two-year survival of patients with unresectable NSCLC was 39.3%, and 50% of patients were alive at 17 months. Our results demonstrated no difference in survival for patients in advanced NSCLC grouped by bcl-2 and VEGF status. Additionally, we observed an inverse correlation in the expression of Bcl-2 and VEGF in NSCLC and mononuclear reaction and bcl-2 expression in adenocarcinomas.

Postoperative radiotherapy for thymus salivary gland carcinoma: A case report

BACKGROUND

Salivary gland cancer is a rare disease in which cancer cells form in the tissues of the salivary glands. It mostly occurs in the glands that have secretion functions, such as the parotid gland, sublingual gland and submandibular gland. This is very rare when it occurs in other nonsecreting glands. Here, we report one case of salivary gland carcinoma occurring in the thymus and discuss related diagnoses and treatment progress.

CASE SUMMARY

One 33-year-old middle-aged man presented with a thymus mass without any clinical symptoms when he underwent regular physical examination. Later, the patient was admitted to the hospital for further examination. Computed tomography (CT) showed that there was a mass of 3 cm × 2.8 cm × 1.5 cm in the thymus area. The patient had no symptom of discomfort or tumor- related medical history before. After completing the preoperative examinations, it was confirmed that the patient had indications for surgery. The surgeon performed a transthoracoscope "thymectomy + pleural mucostomy" for him. During the operation, the tumor tissue was quickly frozen, and the symptomatic section showed a malignant tumor. The final pathological result suggested thymus salivary gland carcinoma- mucoepidermoid carcinoma (MEC). In the second month after surgery, we performed local area radiotherapy for the patient, with a total radiation dose of 50.4 Gy/28Fx. After 12 mo of surgery, the patient underwent positron emission tomography-CT examination, which indicated that there was no sign of tumor recurrence or metastasis. After 16 mo of operation, CT scan re-examination showed that there was no sign of tumor recurrence or metastasis. As of the time of publication, the patient was followed up for one and a half years. He had no sign of tumor recurrence and continued to survive.

CONCLUSION

The incidence of MEC in the thymus is low, and its diagnosis needs to be combined with clinical features and imaging methods. Histopathological analysis plays a key role in the diagnosis of the disease. Patients with early-stage disease have a good prognosis and long survival period. In contrast, patients with advanced-stage disease have a poor prognosis and short survival period. Combining radiotherapy and chemotherapy in inoperable patients may prolong survival.

BCL-2 isoform β promotes angiogenesis by TRiC-mediated upregulation of VEGF-A in lymphoma

Bcl-2 (B-cell lymphoma 2), the first identified anti-apoptosis factor, encodes two transcripts, the long isoform α and the short isoform β. The current understanding of the Bcl-2 function mainly focuses on Bcl-2α, while little is known about the function of Bcl-2β, which lacks the transmembrane domain and contains 10 unique amino acids at the C-terminus instead. Here, we analyzed the expressions of BCL-2 two isoforms in diffused large B-cell lymphoma (DLBCL) and found a significant positive correlation between them. Then, with the CRISPR/Cas9-based transcriptional activator (CRISPRa), we generated mouse B-cell lymphomas with Bcl-2 upregulation from the endogenous locus, in which both Bcl-2α and Bcl-2β levels were increased. Bcl-2β itself promoted angiogenesis both in vitro and in vivo through increased vascular endothelial growth factor A (VEGF-A). Inhibiting VEGF receptors with Axitinib reduced angiogenesis induced by Bcl-2β overexpression. Co-immunoprecipitation and mass spectrometry analysis revealed that Bcl-2β interacted with the T-complex protein ring complex (TRiC). Disruption of TRiC significantly impaired the angiogenesis-promoting activity of Bcl-2β, indicated by reduced VEGF-A protein level and HUVEC tube formation. Thus, our study suggests that Bcl-2 isoform β plays a role in promoting tumor angiogenesis through the Bcl-2β-TRiC-VEGF-A axis.

Sinking Our Teeth in Getting Dental Stem Cells to Clinics for Bone Regeneration

Dental stem cells have been isolated from the medical waste of various dental tissues. They have been characterized by numerous markers, which are evaluated herein and differentiated into multiple cell types. They can also be used to generate cell lines and iPSCs for long-term in vitro research. Methods for utilizing these stem cells including cellular systems such as organoids or cell sheets, cell-free systems such as exosomes, and scaffold-based approaches with and without drug release concepts are reported in this review and presented with new pictures for clarification. These in vitro applications can be deployed in disease modeling and subsequent pharmaceutical research and also pave the way for tissue regeneration. The main focus herein is on the potential of dental stem cells for hard tissue regeneration, especially bone, by evaluating their potential for osteogenesis and angiogenesis, and the regulation of these two processes by growth factors and environmental stimulators. Current in vitro and in vivo publications show numerous benefits of using dental stem cells for research purposes and hard tissue regeneration. However, only a few clinical trials currently exist. The goal of this review is to pinpoint this imbalance and encourage scientists to pick up this research and proceed one step further to translation.

Bcl-xL: A Focus on Melanoma Pathobiology

Apoptosis is the main mechanism by which multicellular organisms eliminate damaged or unwanted cells. To regulate this process, a balance between pro-survival and pro-apoptotic proteins is necessary in order to avoid impaired apoptosis, which is the cause of several pathologies, including cancer. Among the anti-apoptotic proteins, Bcl-xL exhibits a high conformational flexibility, whose regulation is strictly controlled by alternative splicing and post-transcriptional regulation mediated by transcription factors or microRNAs. It shows relevant functions in different forms of cancer, including melanoma. In melanoma, Bcl-xL contributes to both canonical roles, such as pro-survival, protection from apoptosis and induction of drug resistance, and non-canonical functions, including promotion of cell migration and invasion, and angiogenesis. Growing evidence indicates that Bcl-xL inhibition can be helpful for cancer patients, but at present, effective and safe therapies targeting Bcl-xL are lacking due to toxicity to platelets. In this review, we summarized findings describing the mechanisms of Bcl-xL regulation, and the role that Bcl-xL plays in melanoma pathobiology and response to therapy. From these findings, it emerged that even if Bcl-xL plays a crucial role in melanoma pathobiology, we need further studies aimed at evaluating the involvement of Bcl-xL and other members of the Bcl-2 family in the progression of melanoma and at identifying new non-toxic Bcl-xL inhibitors.

Tumor microenvironment promotes breast cancer chemoresistance

Breast cancer is presently the most predominant tumor type and the second leading cause of tumor-related deaths among women. Although advancements in diagnosis and therapeutics have momentously improved, chemoresistance remains an important challenge. Tumors oppose chemotherapeutic agents through a variety of mechanisms, with studies revealing that the tumor microenvironment (TME) is central to this process. The components of TME including stromal cells, immune cells, and non-stromal factors on exposure to chemotherapy promote the acquisition of resistant phenotype. Consequently, limited targeting of tumor cells leads to tumor recurrence after chemotherapy. Here, in this article, we summarize how TME alters chemotherapy responses in breast cancer. Furthermore, the role of different stromal cells viz., CAFs, TAMs, MSCs, endothelial cells, and cancer stem cells (CSC) in breast cancer chemoresistance is discussed in greater detail.

Bcl-2 Overexpression and Hypoxia Synergistically Enhance Angiogenic Properties of Dental Pulp Stem Cells

Post-implantation cell survival and angio-/vasculogenesis are critical for the success of cell-based regenerative strategies. The current study aimed to overexpress B-cell lymphoma 2 (Bcl-2) gene in dental pulp stem cells (DPSCs) and examine the anti-apoptotic and angio-/vasculogenic effects both in-vitro and in-vivo. DPSCs were transduced with Bcl-2-green fluorescent protein (GFP) lentiviral particles and examined for cell proliferation and apoptosis. The cells were cultured under normoxic or hypoxic (0.5 mM CoCl₂) conditions and examined for the expression of angiogenic factors and effects on endothelial cell proliferation, migration and vessel morphogenesis. Cells with or without hypoxic preconditioning were used in in-vivo Matrigel plug assay to study the post-implantation cell survival and angio-/vasculogenesis. Bcl-2-overexpressing-DPSCs showed significantly lower apoptosis than that of null-GFP-DPSCs under serum-free conditions. Under hypoxia, Bcl-2-overexpressing-DPSCs expressed significantly higher levels of vascular endothelial growth factor compared to that under normoxia and null-GFP-DPSCs. Consequently, Bcl-2-overexpressing-DPSCs significantly enhanced endothelial cell proliferation, migration and vascular tube formation on Matrigel. Immunohistological assessment of in-vivo transplanted Matrigel plugs showed significantly higher cell survival and vasculature in hypoxic preconditioned Bcl-2-overexpressing-DPSC group compared to null-GFP-DPSC group. In conclusion, Bcl-2 overexpression and hypoxic-preconditioning could be synergistically used to enhance post-implantation cell survival and angio-/vasculogenic properties of DPSCs.

Rapeseed flower pollen bio-green synthesized silver nanoparticles: a promising antioxidant, anticancer and antiangiogenic compound

Based on recent researches, bio synthesized silver nanoparticles (Ag-NPs) seem to have the potential in declining angiogenesis and oxidative stress. In the current study, rapeseed flower pollen (RFP) water extract was triggered to synthesize RFP-silver nanoparticles (RFP/Ag-NPs). Moreover, antioxidant, antiangiogenesis and cytotoxicity of the RFP/Ag-NPs against MDA-MB-231, MCF7 and carcinoma cell lines and normal human skin fibroblast HDF were compared. Results indicated that RFP/Ag-NPs have a peak at 430 nm, spherical shape and an average size of 24 nm. According to the results of FTIR, rapeseed pollen capped Ag-NPs. RFP/Ag-NPs have cytotoxicity on MDA-MB-231 and MCF7 cells and decrease cancerous cell viability (IC₅₀ = 3 µg/ml and 2 µg/ml, respectively) in a dose- and time-dependent manner. The morphological data showed that the RFP/Ag-NPs increase the percentage of apoptotic cells compared to the control group and normal cells (human skin fibroblast cells). The apoptotic morphological change was also confirmed with a flow cytometric analysis. RFP/ Ag-NPs' antioxidant activity was evaluated by measuring their ability to scavenge ABTS and DPPH free radicals. The IC₅₀ values were determined at 800 and 830 μg/ml for ABTS and DPPH tests, respectively. According to the results, green-synthesized RFP/Ag-NPs as a safe efficient apoptosis inducer and strong antioxidant compound have the potential to suppress breast cancer carcinogenesis by VEGF down-regulatiion and thus sensitizing them against apoptosis. However, further researches are required to clarify RFP/Ag-NPs' cell specificity and therapeutic doses in in vivo conditions.

Synthesis and biological evaluation of N-biphenyl-nicotinic based moiety compounds: A new class of antimitotic agents for the treatment of Hodgkin Lymphoma

We previously demonstrated that some N-biphenylanilides caused cell-cycle arrest at G2/M transition in breast cancer cells. Among them we choose three derivatives, namely PTA34, PTA73 and RS35 for experimentation in solid tumor cell lines, classical Hodgkin Lymphoma (cHL) cell lines and bona fide normal cell lines. Almost all tumor cells were sensitive to compounds in the nanomolar range whereas, they were not cytotoxic to normal ones. Interestingly the compounds caused a strong G2/M phase arrest in cHL cell lines, thus, here we investigated whether they affected the integrity of microtubules in such cells. We found that they induced a long prometaphase arrest, followed by induction of apoptosis which involved mitochondria. PTA73 and RS35 induced the mitotic arrest through the fragmentation of microtubules which prevented the kinethocore-mitotic spindle interaction and the exit from mitosis. PTA34 is instead a tubulin-targeting agent because it inhibited the tubulin polymerization as vinblastine. As such, PTA34 maintained the Cyclin B1-CDK1 regulatory complex activated during the G2/M arrest while inducing the inactivation of Bcl-2 through phosphorylation in Ser70, the degradation of Mcl-1 and a strong activation of BIML and BIMS proapoptotic isoforms. In addition PTA34 exerted an antiangiogenic effect by suppressing microvascular formation.

Bcl-2 expression in circulating tumor cells (CTCs) of patients with small cell lung cancer (SCLC) receiving front-line treatment

INTRODUCTION

To investigate the presence of Bcl-2⁺CTCs in chemotherapy-naïve SCLC patients and their clinical relevance during front-line treatment.

METHODS

Peripheral blood was obtained from 66 consecutive-patients before chemotherapy administration, after one-cycle and at relapse. CTCs were detected by CellSearch and immunofluorescence using anti-Bcl-2, anti-M30, anti-cytokeratins(CK), anti-CD45 and anti-vimentin(Vim) antibodies.

RESULTS

Before treatment, CTCs were detected in 62.1% and 72.7% of patients using the CellSearch and immunofluorescence (Bcl-2⁺/CD45^-), respectively. One-treatment cycle significantly decreased both CTCs' detection rate(p < 0.001) and their absolute number (p < 0.001). On relapse, both the number of positive-patients and the absolute number of CTC subpopulations were significantly increased, compared to post-1st cycle (CellSearch: p = 0.002 and immunofluorescence: p < 0.001). Immunofluorescence revealed an important CTC heterogeneity (Bcl2⁺/Vim⁺, Bcl2⁺/Vim^-, Bcl2⁺/CK⁺, Bcl2⁺/CK^- and Bcl2⁺/M30^- CTCs). Moreover, 50.0% of patients without detectable CTCs by CellSearch had detectable Bcl-2⁺/CD45^- cells. Multivariate analysis revealed a significant association between Bcl-2⁺/CD45^-cells at baseline and PFS (HR = 4.5;p = 0.005) and OS (HR: 4.3; p = 0.001). Bcl-2⁺/CD45^-cells after one-treatment cycle were significantly associated with shorter OS (HR: 13.9; p = 0.007).

CONCLUSIONS

These results demonstrate an important phenotypic CTCs heterogeneity based on the co-expression of Bcl-2, CK, Vim and M30 in SCLC patients. The changes of Bcl-2⁺/CD45^- CTCs during treatment seem to be a dynamic biomarker associated with treatment efficacy and patients' clinical outcome.

microRNA-181a inhibits ocular neovascularization by interfering with vascular endothelial growth factor expression

AIM

Excess angiogenesis or neovascularization plays a key role in the pathophysiology of several ocular diseases such as retinopathy of prematurity, diabetic retinopathy, and exudative age-related macular degeneration. microRNA-181a (miR-181a) was found highly expressed in retina and choroidal tissues. This study intends to investigate the role of miR-181a in the regulation of ocular neovascularization in different pathophysiological conditions.

METHOD

We performed the RNA sequence to identify the microRNAs components of anti-angiogenic lymphocyte-derived microparticles (LMPs). The effect of miR-181a on human retinal endothelial cells proliferation was assessed in vitro. The impact of miR-181a on angiogenesis was confirmed using in vitro angiogenesis assay, ex vivo choroidal explant, and in vivo retinal neovascularization. The expression of major angiogenic factors was assessed by real-time qPCR.

RESULTS

RNA sequence revealed that miR-181a is selectively enriched in LMPs. Importantly, the inhibition of miR-181a significantly abrogated the effect of LMPs on endothelial viability, but overexpression of miR-181a reduced endothelial cell viability in a dose-dependent manner. miR-181a strongly inhibited in vitro angiogenesis and ex vivo choroidal neovascularization. The strong anti-angiogenic effect of miR-181a was also displayed on the retinal neovascularization of the in vivo mouse model of oxygen-induced retinopathy. In keeping with its effect, several angiogenesis-related genes were dysregulated in the miR-181a overexpressed endothelial cells.

CONCLUSION

These data may open unexpected avenues for the development of miR-181a as a novel therapeutic strategy that would be particularly useful and relevant for the treatment of neovascular diseases.

Oncosuppressors and Oncogenes: Role in Haemangioma Genesis and Potential for Therapeutic Targeting

Genetic lesions in proto-oncogenes result in the perturbation of angiogenesis, the formation of neovessels from a pre-existing microvasculature. Similarly, the subversion of tumor suppressor genes promotes tumor vascularization. Excessive neovessel formation is associated with various neoplasms such as infantile hemangiomas (IH). Hemangiomas are the most common tumors in pediatric patients and at present have no definitive treatment. The pathogenesis of IH is not well understood; however, both vasculogenesis and angiogenesis are associated with hemangioma genesis. A number of factors that modulate angiogenesis and vasculogenesis have been shown to be dysregulated in IH. Several of the oncogenes and tumor suppressors linked to the promotion of angiogenesis are also altered in infantile hemangioma. In this review, the roles of oncogenes and tumor suppressor genes during neovascularization and hemangioma genesis are explored. In addition, the potential for targeting these genes in IH therapy is discussed.

Antitumor activity of a novel anti-vascular endothelial growth factor receptor-1 monoclonal antibody that does not interfere with ligand binding

Vascular endothelial growth factor receptor-1 (VEGFR-1) is a tyrosine kinase transmembrane receptor that has also a soluble isoform containing most of the extracellular ligand binding domain (sVEGFR-1). VEGF-A binds to both VEGFR-2 and VEGFR-1, whereas placenta growth factor (PlGF) interacts exclusively with VEGFR-1. In this study we generated an anti-VEGFR-1 mAb (D16F7) by immunizing BALB/C mice with a peptide that we had previously reported to inhibit angiogenesis and endothelial cell migration induced by PlGF. D16F7 did not affect binding of VEGF-A or PlGF to VEGFR-1, thus allowing sVEGFR-1 to act as decoy receptor for these growth factors, but it hampered receptor homodimerization and activation. D16F7 inhibited both the chemotactic response of human endothelial, myelomonocytic and melanoma cells to VEGFR-1 ligands and vasculogenic mimicry by tumor cells. Moreover, D16F7 exerted in vivo antiangiogenic effects in a matrigel plug assay. Importantly, D16F7 inhibited tumor growth and was well tolerated by B6D2F1 mice injected with syngeneic B16F10 melanoma cells. The antitumor effect was associated with melanoma cell apoptosis, vascular abnormalities and decrease of both monocyte/macrophage infiltration and myeloid progenitor mobilization. For all the above, D16F7 may be exploited in the therapy of metastatic melanoma and other tumors or pathological conditions involving VEGFR-1 activation.

Functional Relationship and Gene Ontology Classification of Breast Cancer Biomarkers

Breast cancer is a complex disease that still imposes a significant healthcare burden on women worldwide. The etiology of breast cancer is not known but significant advances have been made in the area of early detection and treatment. The advent of advanced molecular biology techniques, mapping of the human genome and availability of high throughput genomic and proteomic strategies opens up new opportunities and will potentially lead to the discovery of novel biomarkers for early detection and prognostication of breast cancer. Currently, many biomarkers, particularly the hormonal and epidermal growth factor receptors, are being utilized for breast cancer prognosis. Unfortunately, none of the biomarkers in use have sufficient diagnostic, prognostic and/or predictive power across all categories and stages of breast cancer. It is recognized that more useful information can be generated if tumors are interrogated with multiple markers. But choosing the right combination of biomarkers is challenging, because 1) multiple pathways are involved, 2) up to 62 genes and their protein products are potentially involved in breast cancer-related mechanisms and 3) the more markers evaluated, the more the time and cost involved. This review summarizes the current literature on selected biomarkers for breast cancer, discusses the functional relationships, and groups the selected genes based on a Gene Ontology™ classification.

BCL-XL overexpression promotes tumor progression-associated properties

By using human melanoma and glioblastoma cell lines and their derivative BCL-X_L overexpressing clones, we investigated the role of BCL-X_L in aggressive features of these two tumor histotypes. We found that in both models, BCL-X_L overexpression increased in vitro cell migration and invasion and facilitated tumor cells to form de novo vasculogenic structures. Furthermore, BCL-X_L overexpressing cells exhibited higher tumors sphere formation capacity and expressed higher levels of some stem cell markers, supporting the concept that BCL-X_L plays essential roles in the maintenance of cancer stem cell phenotype. BCL-X_L expression reduction by siRNA, the exposure to a BCL-X_L-specific inhibitor and the use of a panel of human melanoma cell lines corroborated the evidence that BCL-X_L regulates tumor progression-associated properties. Finally, the vascular markers and the vasculogenic mimicry were up-regulated in the BCL-X_L overexpressing xenografts derived from both tumor histotypes. In conclusion, our work brings further support to the understanding of the malignant actions of BCL-X_L and, in particular, to the concept that BCL-X_L promotes stemness and contributes to the aggressiveness of both melanoma and glioblastoma.

Survivin expression, HPV positivity and microvessel density in oropharyngeal carcinomas and relationship with survival time

INTRODUCTION

Among head and neck cancers, those of the oral cavity and oropharynx are the second most prevalent following the larynx. This study aimed to research immunohistochemical expression of survivin, HPV positivity and microvessel density in tumors and their relationships with prognosis.

MATERIAL AND METHODS

Pathological materials and demographic properties of 46 patients were retrospectively evaluated. Survivin, HPV and CD34 (for microvessel density evaluation) antibodies were applied tumoral tissues. Survival times, clinical stage and differentiation were evaluated.

RESULTS

In univariate analysis, we observed that survivin, microvessel density and stage were significantly associated with survival time (p < 0.05). In multivariate analysis, only survivin and microvessel density were associated with survival time (p < 0.05). But we did not find significant correlation between neither tumor differentiation nor HPV positivity and survival (p > 0.05).

CONCLUSIONS

Survivin levels and microvessel density were found to be effective prognostic factors and were related to survival in oral cavity and oropharyngeal cancers. Treatments targeting survivin expression and angiogenesis might be employed against these tumor groups.

Antisense Oligonucleotides Targeting Y-Box Binding Protein-1 Inhibit Tumor Angiogenesis by Downregulating Bcl-xL-VEGFR2/-Tie Axes

Y-box binding protein-1 (YB-1), involved in cancer progression and chemoradiation resistance, is overexpressed in not only cancer cells but also tumor blood vessels. In this study, we investigated the potential value of amido-bridged nucleic acid (AmNA)-modified antisense oligonucleotides (ASOs) targeting YB-1 (YB-1 ASO^A) as an antiangiogenic cancer therapy. YB-1 ASO^A was superior to natural DNA-based ASO or locked nucleic acid (LNA)-modified YB-1 ASO in both knockdown efficiency and safety, the latter assessed by liver function. YB-1 ASO^A administered i.v. significantly inhibited YB-1 expression in CD31-positive angiogenic endothelial cells, but not in cancer cells, in the tumors. With regard to the mechanism of its antiangiogenic effects, YB-1 ASO^A downregulated both Bcl-xL/VEGFR2 and Bcl-xL/Tie signal axes, which are key regulators of angiogenesis, and induced apoptosis in vascular endothelial cells. In the xenograft tumor model that had low sensitivity to anti-VEGF antibody, YB-1 ASO^A significantly suppressed tumor growth; not only VEGFR2 but also Tie2 expression was decreased in tumor vessels. In conclusion, YB-1/Bcl-xL/VEGFR2 and YB-1/Bcl-xL/Tie signal axes play pivotal roles in tumor angiogenesis, and YB-1 ASO^A may be feasible as an antiangiogenic therapy for solid tumors.

Non-canonical roles of Bcl-2 and Bcl-xL proteins: relevance of BH4 domain

Bcl-2 protein family is constituted by multidomain members originally identified as modulators of programmed cell death and whose expression is frequently misbalanced in cancer cells. The lead member Bcl-2 and its homologue Bcl-xL proteins are characterized by the presence of all four conserved BH domain and exert their antiapoptotic role mainly through the involvement of BH1, BH2 and BH3 homology domains, that mediate the interaction with the proapoptotic members of the same Bcl-2 family. The N-terminal BH4 domain of Bcl-2 and Bcl-xL is responsible for the interaction with other proteins that do not belong to Bcl-2 protein family. Beyond a classical role in inhibiting apoptosis, BH4 domain has been characterized as a crucial regulator of other important cellular functions attributed to Bcl-2 and Bcl-xL, including proliferation, autophagy, differentiation, DNA repair, cell migration, tumor progression and angiogenesis. During the last two decades a strong effort has been made to dissect the molecular pathways involved the capability of BH4 domain to regulate the canonical antiapoptotic and the non-canonical activities of Bcl-2 and Bcl-xL, creating the basis for the development of novel anticancer agents targeting this domain. Indeed, recent evidences obtained on in vitro and in vivo model of different cancer histotypes are confirming the promising therapeutic potential of BH4 domain inhibitors supporting their future employment as a novel anticancer strategy.

N'-((2-(6-bromo-2-oxo-2H-chromen-3-yl)-1H-indol-3-yl)methylene)benzohydrazide as a probable Bcl-2/Bcl-xL inhibitor with apoptotic and anti-metastatic potential

A wide number of marketed drugs and drug candidates in cancer clinical development contain halogen substituents. The aim of the present study was to synthesize a series of halogen incorporated indole-coumarin hybrid schiff bases - N'-((2-(2-oxo-2H-chromen-3-yl)-1H-indol-3-yl)methylene)benzohydrazides and to investigate their apoptotic and anti-migratory potential in human breast adenocarcinoma cells as well as to examine their Bcl-2 and Bcl-xL protein binding ability via in silico docking. Hybrid 5g with a bromine atom in position-7 of coumarin ring displayed significant dose dependent cytotoxic activity with high selectivity to MCF-7 cells in MTT assay. Cell cycle progression analysis of 5g treated cells using flow cytometer exhibited a cell cycle arrest in the S phase and accumulation of cells in the subG1 phase. The apoptotic mode of cell death induced by 5g was further confirmed by Annexin-V staining assay. The wound healing assay revealed a profound impairment in the migration of MCF-7 cells presumably due to down-regulation of Bcl-2 and Bcl-xL proteins induced by 5g as observed in immunoblotting analysis. SAR studies of these hybrid molecules based on cell viability and docking were also probed. The most active pharmacophore 5g was found to bind favourably to Bcl-2 and Bcl-xL in docking simulation analysis suggesting it to be a probable small molecule Bcl-2/Bcl-xL inhibitor and a potential lead for breast cancer chemotherapy with apoptotic and anti-metastatic properties.

The Development of an Angiogenic Protein "Signature" in Ovarian Cancer Ascites as a Tool for Biologic and Prognostic Profiling

Advanced ovarian cancer (AOC) is one of the leading lethal gynecological cancers in developed countries. Based on the important role of angiogenesis in ovarian cancer oncogenesis and expansion, we hypothesized that the development of an "angiogenic signature" might be helpful in prediction of prognosis and efficacy of anti-angiogenic therapies in this disease. Sixty-nine samples of ascitic fluid- 35 from platinum sensitive and 34 from platinum resistant patients managed with cytoreductive surgery and 1st-line carboplatin-based chemotherapy- were analyzed using the Proteome ProfilerTM Human Angiogenesis Array Kit, screening for the presence of 55 soluble angiogenesis-related factors. A protein profile based on the expression of a subset of 25 factors could accurately separate resistant from sensitive patients with a success rate of approximately 90%. The protein profile corresponding to the "sensitive" subset was associated with significantly longer PFS (8 [95% Confidence Interval {CI}: 8-9] vs. 20 months [95% CI: 15-28]; Hazard ratio {HR}: 8.3, p<0.001) and OS (20.5 months [95% CI: 13.5-30] vs. 74 months [95% CI: 36-not reached]; HR: 5.6 [95% CI: 2.8-11.2]; p<0.001). This prognostic performance was superior to that of stage, histology and residual disease after cytoreductive surgery and the levels of vascular endothelial growth factor (VEGF) in ascites. In conclusion, we developed an "angiogenic signature" for patients with AOC, which can be used, after appropriate validation, as a prognostic marker and a tool for selection for anti-angiogenic therapies.

Hypoxia induced epithelial-mesenchymal transition and vasculogenic mimicry formation by promoting Bcl-2/Twist1 cooperation

Hypoxia plays a pivotal role in tumor progression. The functions of hypoxia and subsequent Bcl-2/Twist1 activation in epithelial-mesenchymal transition (EMT) and vasculogenic mimicry (VM) formation are currently unclear. This study aimed to investigate the role of Bcl-2/Twist1 cooperation in hypoxia-induced EMT and VM formation. In in vitro experiments, we found that hypoxia resulted in co-overexpression of Bcl-2 and Twist1, facilitated Twist1 nuclear translocation and promoted EMT and VM formation. Co-overexpression of Bcl-2 and Twist1 under normoxia could also induce EMT and promote VM formation. Furthermore, blocking Bcl-2 or Twist1 attenuated the effects of hypoxia on EMT progress and VM formation in hepatocellular carcinoma cells. In in vivo experiments, the mechanism by which hypoxia promoted Bcl-2 and Twist1 co-overexpression and induced EMT process and VM formation was demonstrated using murine xenograft models. These results above suggest that hypoxia could activate the cooperation of Bcl-2 and Twist1, Bcl-2 plays an important role in assisting Twist1 nuclear translocation which could change the expression of a wide range of genes and lead to the induction of EMT and VM formation.

BH3-mimetic small molecule inhibits the growth and recurrence of adenoid cystic carcinoma

OBJECTIVES

To evaluate the anti-tumor effect of BM-1197, a new potent and highly specific small molecule inhibitor of Bcl-2/Bcl-xL, in preclinical models of human adenoid cystic carcinoma (ACC).

METHODS

Low passage primary human adenoid cystic carcinoma cells (UM-HACC-2A,-2B,-5,-6) and patient-derived xenograft (PDX) models (UM-PDX-HACC) were developed from surgical specimens obtained from 4 patients. The effect of BM-1197 on cell viability and cell cycle were evaluated in vitro using this panel of low passage ACC cells. The effect of BM-1197 on tumor growth, recurrence and tumor cell apoptosis in vivo was evaluated with the PDX model of ACC (UM-PDX-HACC-5).

RESULTS

Exposure of low passage primary human ACC cells to BM-1197 mediated an IC50 of 0.92-2.82 μM. This correlated with an increase in the fraction of apoptotic cells (p<0.0001) and an increase in caspase-3 activity (p<0.0001), but no noticeable differences in cell cycle (p>0.05). In vivo, BM-1197 inhibited tumor growth (p=0.0256) and induced tumor cell apoptosis (p=0.0165) without causing significant systemic toxicities, as determined by mouse weight over time. Surprisingly, weekly BM-1197 decreased the incidence of tumor recurrence (p=0.0297), as determined by Kaplan-Meier analysis.

CONCLUSION

These data demonstrated that single agent BM-1197 induces apoptosis and inhibits tumor growth in preclinical models of adenoid cystic carcinoma. Notably, single agent BM-1197 inhibited tumor recurrence, which is considered a major clinical challenge in the clinical management of adenoid cystic carcinoma. Collectively, these results suggest that patients with adenoid cystic carcinoma might benefit from therapy with a BH3-mimetic small molecule.

Disruptive environmental chemicals and cellular mechanisms that confer resistance to cell death

Cell death is a process of dying within biological cells that are ceasing to function. This process is essential in regulating organism development, tissue homeostasis, and to eliminate cells in the body that are irreparably damaged. In general, dysfunction in normal cellular death is tightly linked to cancer progression. Specifically, the up-regulation of pro-survival factors, including oncogenic factors and antiapoptotic signaling pathways, and the down-regulation of pro-apoptotic factors, including tumor suppressive factors, confers resistance to cell death in tumor cells, which supports the emergence of a fully immortalized cellular phenotype. This review considers the potential relevance of ubiquitous environmental chemical exposures that have been shown to disrupt key pathways and mechanisms associated with this sort of dysfunction. Specifically, bisphenol A, chlorothalonil, dibutyl phthalate, dichlorvos, lindane, linuron, methoxychlor and oxyfluorfen are discussed as prototypical chemical disruptors; as their effects relate to resistance to cell death, as constituents within environmental mixtures and as potential contributors to environmental carcinogenesis.

Molecular inhibition of prostaglandin E2 with GW627368X: Therapeutic potential and preclinical safety assessment in mouse sarcoma model

Prostaglandin E2, the major COX-2 product, acts via 4 functionally distinct prostanoid receptors, EP(1-4). PGE-2, through its receptors, feeds back to positively increase COX-2 expression augmenting its own synthesis thereby driving angiogenesis, while suppressing apoptosis and innate immunity. In addition to the well characterized PGE2/EP4/cAMP/PKA/CREB, EP4 activation increases GSK3 phosphorylation via PI3K and Akt consequently reducing β-catenin phosphorylation. EP4 induces angiogenesis by enhancing VEGF production via ERK activation. These effects of EP4 are asserted either directly or via EGFR transactivation depending on the type of cancer. In view of the safety concerns regarding long term use of COX-2 inhibitors and to find more effective alternatives, we evaluated the potential of EP4 prostanoid receptor as a target for treating cancer progression using a highly selective EP4 antagonist, 4-(4,9-diethoxy-1,3-dihydro-1-oxo-2H-benz[f]isoindol-2-yl)-N-(phenylsulfonyl)-benzeneacetamide. Oral administration of GW627368X showed significant tumor regression characterized by tumor reduction and induction of apoptosis. Reduction in prostaglandin E2 synthesis also led to reduced level of VEGF in plasma. Regulation of multiple pathways downstream of EP4 was evident by down regulation of COX-2, p-Akt, p-MAPK and p-EGFR. Considering wide distribution of the EP4 prostanoid receptor in major organs and the array of physiological processes it contributes to, the safety profile of the drug was analyzed. No major organ toxicity, immunosupression, behavioral change or change in blood parameters attributable to the drug was observed. The results assert the significance of EP4 prostanoid receptor as a therapeutic target as well as the safety of EP4 blockade by GW627368X.

Inhibitory effects of B-cell lymphoma 2 on the vasculogenic mimicry of hypoxic human glioma cells

The aim of this study was to investigate the mechanisms and effects of B-cell lymphoma 2 (Bcl-2) on the vasculogenic mimicry (VM) of human glioma cells. U87 cells were cultured under hypoxic conditions and then divided into four groups: Control, 3-(5-hydroxymethyl-2-furyl)-1-benzylindazole (YC-1), ABT-737 and YC-1 + ABT-737. These groups were treated with the corresponding simulators. The expression of hypoxia-inducible factor-1α (HIF-1α), matrix metalloproteinase (MMP)-2, MMP-14 and Bcl-2 in each group was determined using a reverse transcription-quantitative polymerase chain reaction and western blot analysis. Compared with that in the control group, the mRNA and protein expression of MMP-2, MMP-14 and Bcl-2 in the YC-1 and ABT-737 groups was significantly reduced. The expression of HIF-1α, however, was only significantly reduced in the YC-1 group (P<0.05). Compared with those in the YC-1 + ABT-737 group, the expression levels of the four proteins in the YC-1 and ABT-737 groups were not significantly different, with the exception of the expression of HIF-1α in the ABT-737 group, which was significantly enhanced (P<0.05). The mRNA expression levels of HIF-1α, MMP-2 and MMP-14 in the YC-1 group were significantly different from those in the ABT-737 group (P<0.01); however, no significant difference was observed in the expression of Bcl-2. In conclusion, Bcl-2 may be an important factor in the VM formation of human malignant glioma U87 cells under hypoxic conditions. Certain functions of Bcl-2 may be attributed to the HIF-1α-MMP-2-MMP-14-VM channel, whereas other functions may be independent of the channel.

Interrogation of gossypol therapy in glioblastoma implementing cell line and patient-derived tumour models

BACKGROUND

Glioblastoma (GBM), being a highly vascularised and locally invasive tumour, is an attractive target for anti-angiogenic and anti-invasive therapies. The GBM/endothelial cell response to gossypol/temozolomide (TMZ) treatment was investigated with a particular aim to assess treatment effects on cancer hallmarks.

METHODS

Cell viability, endothelial tube formation and GBM tumour cell invasion were variously assessed following combined treatment in vitro. The U87MG-luc2 subcutaneous xenograft model was used to investigate therapeutic response in vivo. Viable tumour response to treatment was interrogated using immunohistochemistry. Combined treatment protocols were also tested in primary GBM patient-derived cultures.

RESULTS

An endothelial/GBM cell viability inhibitory effect, as well as an anti-angiogenic and anti-invasive response, to combined treatment have been demonstrated in vitro. A significantly greater anti-proliferative (P=0.020, P=0.030), anti-angiogenic (P=0.040, P<0.0001) and pro-apoptotic (P=0.0083, P=0.0149) response was observed when combined treatment was compared with single gossypol/TMZ treatment response, respectively. GBM cell line and patient-specific response to gossypol/TMZ treatment was observed.

CONCLUSIONS

Our results indicate that response to a combined gossypol/TMZ treatment is related to inhibition of tumour-associated angiogenesis, invasion and proliferation and warrants further investigation as a novel targeted GBM treatment strategy.

Removal of the BH4 domain from Bcl-2 protein triggers an autophagic process that impairs tumor growth

Here, we show that forced expression of a B-cell lymphoma 2 (bcl-2) protein lacking residues 1 to 36 at the N-terminal, including the entire Bcl-2 homology 4 (BH4) domain, determines reduction of in vitro and in vivo human melanoma growth. Noteworthy, melanoma cells in vivo exhibit markedly increased autophagy, as response to expression of bcl-2 protein deleted of its BH4 domain. This observation led to the identification of a novel gain of function for bcl-2 protein lacking the BH4 domain. In particular, upon different autophagic stimuli in vitro, overexpression of bcl-2 protein deleted of BH4 domain induces autophagosome accumulation, conversion of microtubule-associated protein 1 light chain 3B-II, reduced expression of p62/SQSTM1 protein, and thereby enhanced autophagic flux. The relevance of Beclin-1 is evidenced by the fact that 1) the autophagy-promoting and growth-inhibiting properties are partially rescued by Beclin-1 knockdown in cells expressing bcl-2 protein lacking the BH4 domain, 2) Beclin-1 only interacts with wild-type but not with deleted bcl-2, and 3) BH4 domain removal from bcl-2 protein does not influence in vitro and in vivo growth of tumor cells expressing low levels of endogenous Beclin-1. These results provide new insight into molecular mechanism of bcl-2 functions and represent a rationale for the development of agents interfering with the BH4 domain of bcl-2 protein.

BH4 domain of bcl-2 protein is required for its proangiogenic function under hypoxic condition

Beyond its classical role as apoptosis inhibitor, bcl-2 protein promotes tumor angiogenesis and the removal of N-terminal bcl-2 homology (BH4) domain abrogates bcl-2-induced hypoxia-inducible factor 1 (HIF-1)-mediated vascular endothelial growth factor (VEGF) expression in hypoxic cancer cells. Using M14 human melanoma cell line and its derivative clones stably overexpressing bcl-2 wild-type or deleted of its BH4 domain, we found that conditioned media (CM) from cells expressing BH4-deleted bcl-2 protein showed a reduced capability to increase in vitro human endothelial cells proliferation and differentiation, and in vivo neovascularization compared with CM from cells overexpressing wild-type bcl-2. Moreover, xenografts derived from cells expressing bcl-2 lacking BH4 domain showed a reduction of metastatic potential compared with tumors derived from wild-type bcl-2 transfectants injection. Stably expressing the Flag-tagged N-terminal sequence of bcl-2 protein, encompassing BH4 domain, we found that this domain is sufficient to enhance the proangiogenic HIF-1/VEGF axis under hypoxic condition. Indeed, lacking of BH4 domain abolishes the interaction between bcl-2 and HIF-1α proteins and the capability of exogenous bcl-2 protein to localize in the nucleus. Moreover, when endoplasmic reticulum-targeted bcl-2 protein is overexpressed in cells, this protein lost the capability to synergize with hypoxia to induce the proangiogenic HIF-1/VEGF axis as shown by wild-type bcl-2 protein. These results demonstrate that BH4 domain of bcl-2 is required for the ability of this protein to increase tumor angiogenesis and progression and indicate that bcl-2 nuclear localization may be required for bcl-2-mediated induction of HIF-1/VEGF axis.

Hemostatic gelatin sponge is a superior matrix to matrigel for establishment of LNCaP human prostate cancer in nude mice

BACKGROUND

Matrigels, solubilized basement membrane preparations, are often used to support tumor development in animal models. However, tumors formed by a mixture of tumor cells and Matrigel may vary significantly. The purpose of this study was to compare tumor development and growth of LNCaP human prostate cancer cells mixed with Matrigel or in gelatin sponges.

METHODS

LNCaP cells were mixed with Matrigel or absorbed into VETSPON, a gelatin sponge, and inoculated into the subcutis of nude mice. Tumor incidence and growth rate were determined. Gene expression and cell growth and survival in tumor lesions were evaluated by immunohistochemistry (IHC), immunoblotting, and RT-PCR.

RESULTS

All mice (12/12) inoculated with LNCaP cells in VETSPON produced tumors, compared to 70% (19/27) of mice injected with the cells with Matrigel. Tumor volume also varied less with VETSPON implants. No significant differences were observed in gene expression, cell growth, apoptosis, and microvessel density in tumors established from the two types of implants. However, in samples collected on days 1 and 4, more cells in Matrigel implants than those in VETSPON implants were stained positive for cleaved-caspase 3 and -PARP1. Expression of VEGF-A, HIF-1α, and Bcl-2 was elevated in the early VETSPON implants.

CONCLUSION

These data indicate that VETSPON promotes tumor cell survival at the early stage of implantation and suggest that the gelatin sponge is superior to Matrigel in supporting development and progression of human prostate cancer in nude mice. This model should be useful for preclinical studies in nude mice using LNCaP cells.

Implication of tumor microenvironment in chemoresistance: tumor-associated stromal cells protect tumor cells from cell death

Tumor development principally occurs following the accumulation of genetic and epigenetic alterations in tumor cells. These changes pave the way for the transformation of chemosensitive cells to chemoresistant ones by influencing the uptake, metabolism, or export of drugs at the cellular level. Numerous reports have revealed the complexity of tumors and their microenvironment with tumor cells located within a heterogeneous population of stromal cells. These stromal cells (fibroblasts, endothelial or mesothelial cells, adipocytes or adipose tissue-derived stromal cells, immune cells and bone marrow-derived stem cells) could be involved in the chemoresistance that is acquired by tumor cells via several mechanisms: (i) cell-cell and cell-matrix interactions influencing the cancer cell sensitivity to apoptosis; (ii) local release of soluble factors promoting survival and tumor growth (crosstalk between stromal and tumor cells); (iii) direct cell-cell interactions with tumor cells (crosstalk or oncologic trogocytosis); (iv) generation of specific niches within the tumor microenvironment that facilitate the acquisition of drug resistance; or (v) conversion of the cancer cells to cancer-initiating cells or cancer stem cells. This review will focus on the implication of each member of the heterogeneous population of stromal cells in conferring resistance to cytotoxins and physiological mediators of cell death.

Hypoxia-induced vasculogenic mimicry formation via VE-cadherin regulation by Bcl-2

Vasculogenic mimicry (VM) refers to the unique ability of highly aggressive tumor cells to mimic the pattern of embryonic vasculogenic networks. Hypoxia plays a pivotal role in the formation of VM. Hypoxia-induced Bcl-2 overexpression is observed in many types of tumors including melanoma, in which it is associated with tumorigenicity and angiogenesis. VE-cadherin, the major endothelial adhesion molecule controlling cellular junctions and blood vessel formation, is also overexpressed in melanoma. Despite these connections, whether hypoxia induces VM formation via VE-cadherin regulation by Bcl-2 is not confirmed. We used human melanoma cells to upregulate or knockdown the expression of Bcl-2 to investigate the possible molecular mechanism of VM formation under hypoxia. Bcl-2 overexpression increased VE-cadherin expression and VM formation under normoxia, whereas Bcl-2 siRNA significantly decreased VE-cadherin expression and VM formation under hypoxia. We then demonstrated that Bcl-2 regulated VE-cadherin transcription activity by Western blot, three-dimensional cultures, reporter gene assay, and clinical analysis. Therefore, Bcl-2-dependent VE-cadherin overexpression may be an important mechanism by which hypoxia induces VM.

Coexpression of Bcl-2 with epithelial-mesenchymal transition regulators is a prognostic indicator in hepatocellular carcinoma

The anti-apoptosis factor Bcl-2 is known to contribute to tumorigenesis and metastasis. Epithelial-mesenchymal transition (EMT) may also participate in tumor invasion and metastasis. This study investigated the relationship between coexpression profiles of Bcl-2 and EMT regulators in hepatocellular carcinoma (HCC) tumor samples and clinical outcome. The nuclear (Nu) and cytoplasmic (Cyt) expression of Bcl-2 and the EMT regulators Twist-1, Twist-2, and Snail were determined by immunohistochemical staining in tumor tissue isolated from 97 HCC patients. The clinical prognostic values of both individual protein expression and various expression combinations were investigated using univariate and multivariate survival analysis. Results showed that patients with nuclear expression of Bcl-2 had worse clinical outcomes than patients exhibiting cytoplasmic expression. Overall survival was significantly shorter in HCC patients individually expressing Bcl-2-Nu, Twist-1-Nu, Twist-1-Cyt, and Snail (all P<0.05). Patients coexpressing Bcl-2-Nu with Twist-1-Nu, Twist-1-Cyt, Twist-2, or Snail had even worse prognoses than those expressing no biomarker or any one biomarker alone (all P<0.05). Multivariate analysis showed that HCC patients coexpressing Bcl-2-Nu with Twist-1-Cyt had the worst prognosis. This study provides clinical evidence that nuclear expression of Bcl-2 combined with cytoplasmic expression of Twist-1 is a predictor of very poor prognosis in HCC. Coexpression profiles of Bcl-2 and EMT regulators might aid in the selection of the most efficacious therapy for patients with HCC.

A novel classification of lung cancer into molecular subtypes

The remarkably heterogeneous nature of lung cancer has become more apparent over the last decade. In general, advanced lung cancer is an aggressive malignancy with a poor prognosis. The discovery of multiple molecular mechanisms underlying the development, progression, and prognosis of lung cancer, however, has created new opportunities for targeted therapy and improved outcome. In this paper, we define "molecular subtypes" of lung cancer based on specific actionable genetic aberrations. Each subtype is associated with molecular tests that define the subtype and drugs that may potentially treat it. We hope this paper will be a useful guide to clinicians and researchers alike by assisting in therapy decision making and acting as a platform for further study. In this new era of cancer treatment, the 'one-size-fits-all' paradigm is being forcibly pushed aside-allowing for more effective, personalized oncologic care to emerge.

Modulation of YY1 and p53 expression by transforming growth factor-β3 in prostate cell lines

Transforming growth factor-β (TGF-β) is the prototype of a family of secreted polypeptide growth factors. These cytokines play very important roles during development, as well as in normal physiological and disease processes, by regulating a wide array of cellular processes, such as cell growth, differentiation, migration, apoptosis, and extracellular matrix production. TGF-β utilizes a multitude of intracellular signalling pathways in addition to Smads with actions that are dependent on circumstances, including dose, target cell type, and context. The aims of this research were (i) to verify the effects of dose-dependent TGF-β3 treatment on YY1 and p53 expression, in BPH-1 cell line, human benign prostate hyperplasia, and two prostate cancer cell lines, LNCaP, which is androgen-sensitive, and DU-145, which is androgen-non responsive, (ii) establish a correlation between p53 and YY1 and (iii) determine the expression of a number of important intracellular signalling pathways in TGF-β3-treated prostate cell lines. The expression of YY1, p53, PI3K, AKT, pAKT, PTEN, Bcl-2, Bax, and iNOS was evaluated through Western blot analysis on BPH-1, LNCaP, and DU-145 cultures treated with 10 and 50 ng/ml of TGF-β3 for 24 h. The production of nitric oxide (NO) was determined by Griess reagent and cell viability through MTT assay. The results of this research demonstrated profound differences in the responses of the BPH-1, LNCaP, and DU-145 cell lines to TGF-β3 stimulation. We believe that the findings could be important because of the clinical relevance that they may assume and the therapeutic implications for TGF-β treatment of prostate cancer.

Involvement of BH4 domain of bcl-2 in the regulation of HIF-1-mediated VEGF expression in hypoxic tumor cells

In addition to act as an antiapoptotic protein, B-cell lymphoma (bcl)-2 can also promote tumor angiogenesis. In this context, we have previously demonstrated that under hypoxia bcl-2 promotes hypoxia-inducible factor-1 (HIF-1)-mediated vascular endothelial growth factor (VEGF) expression in melanoma and breast carcinoma. Here, we report on the role of the BH4 domain in bcl-2 functions, by showing that removal of or mutations at the BH4 domain abrogate the ability of bcl-2 to induce VEGF protein expression and transcriptional activity under hypoxia in human melanoma cells. We have also extended this observation to other human tumor histotypes, such as colon, ovarian and lung carcinomas. The involvement of BH4 on HIF-1α protein expression, stability, ubiquitination and HIF-1 transcriptional activity was also demonstrated in melanoma experimental model. Moreover, we validated the role of the BH4 domain of bcl-2 in the regulation of HIF-1/VEGF axis, demonstrating that BH4 peptide is sufficient to increase HIF-1α protein half-life impairing HIF-1α protein ubiquitination, and to enhance VEGF secretion in melanoma cells exposed to hypoxia. Finally, we found that the mechanism by which bcl-2 regulates HIF-1-mediated VEGF expression does not require BH1 and BH2 domains, and it is independent of antiapoptotic and prosurvival function of bcl-2.

Bcl-2 regulates HIF-1alpha protein stabilization in hypoxic melanoma cells via the molecular chaperone HSP90

BACKGROUND

Hypoxia-Inducible Factor 1 (HIF-1) is a transcription factor that is a critical mediator of the cellular response to hypoxia. Enhanced levels of HIF-1alpha, the oxygen-regulated subunit of HIF-1, is often associated with increased tumour angiogenesis, metastasis, therapeutic resistance and poor prognosis. It is in this context that we previously demonstrated that under hypoxia, bcl-2 protein promotes HIF-1/Vascular Endothelial Growth Factor (VEGF)-mediated tumour angiogenesis.

METHODOLOGY/PRINCIPAL FINDINGS

By using human melanoma cell lines and their stable or transient derivative bcl-2 overexpressing cells, the current study identified HIF-1alpha protein stabilization as a key regulator for the induction of HIF-1 by bcl-2 under hypoxia. We also demonstrated that bcl-2-induced accumulation of HIF-1alpha protein during hypoxia was not due to an increased gene transcription or protein synthesis. In fact, it was related to a modulation of HIF-1alpha protein expression at a post-translational level, indeed its degradation rate was faster in the control lines than in bcl-2 transfectants. The bcl-2-induced HIF-1alpha stabilization in response to low oxygen tension conditions was achieved through the impairment of ubiquitin-dependent HIF-1alpha degradation involving the molecular chaperone HSP90, but it was not dependent on the prolyl hydroxylation of HIF-1alpha protein. We also showed that bcl-2, HIF-1alpha and HSP90 proteins form a tri-complex that may contribute to enhancing the stability of the HIF-1alpha protein in bcl-2 overexpressing clones under hypoxic conditions. Finally, by using genetic and pharmacological approaches we proved that HSP90 is involved in bcl-2-dependent stabilization of HIF-1alpha protein during hypoxia, and in particular the isoform HSP90beta is the main player in this phenomenon.

CONCLUSIONS/SIGNIFICANCE

We identified the stabilization of HIF-1alpha protein as a mechanism through which bcl-2 induces the activation of HIF-1 in hypoxic tumour cells involving the beta isoform of molecular chaperone HSP90.

Hypoxia-induced Bcl-2 expression in endothelial cells via p38 MAPK pathway

Angiogenesis and apoptosis are reciprocal processes in endothelial cells. Bcl-2, an anti-apoptotic protein, has been found to have angiogenic activities. The purpose of this study was to determine the role of Bcl-2 in hypoxia-induced angiogenesis in endothelial cells and to investigate the underlying mechanisms. Human aortic endothelial cells (HAECs) were exposed to hypoxia followed by reoxygenation. Myocardial ischemia and reperfusion mouse model was used and Bcl-2 expression was assessed. Bcl-2 expression increased in a time-dependent manner in response to hypoxia from 2 to 72h. Peak expression occurred at 12h (3- to 4-fold, p<0.05). p38 inhibitor (SB203580) blocked hypoxia-induced Bcl-2 expression, whereas PKC, ERK1/2 and PI3K inhibitors did not. Knockdown of Bcl-2 resulted in decreased HAECs' proliferation and migration. Over-expression of Bcl-2 increased HAECs' tubule formation, whereas knockdown of Bcl-2 inhibited this process. In this model of myocardial ischemia and reperfusion, Bcl-2 expression was increased and was associated with increased p38 MAPK activation. Our results showed that hypoxia induces Bcl-2 expression in HAECs via p38 MAPK pathway.

Regulated cell death pathways: new twists in modulation of BCL2 family function

A number of cell death pathways have been recognized. Though apoptosis and autophagy have been well characterized, programmed necrosis has recently received attention and may provide clinical alternatives to suppress resistant tumors. Necrosis is primarily characterized by large-scale permeabilization, swelling, and rupture of cell membranes and the release of pro-inflammatory cytokines. Traditionally, necrosis in cancer cells has been indicative of poor prognoses, as chronic inflammation was found to encourage tumor growth. Yet, many antitumor effects associated with necrosis have been discovered in certain settings, such as the formation of an effective antitumor immune response. In this way, finding ways to attenuate the pro-tumor effects of necrosis while engaging the antitumor pathways via drugs, radiation, and sensitization may prove valuable as a clinical focus for the future. We hypothesize that the use of Bcl-2 inhibitors may enhance necrotic death characterized by inflammation and antitumor immunity. In this article, we briefly review apoptosis and autophagy and reason how necrosis may be a suitable alternative therapeutic endpoint. We then highlight novel inhibitors of Bcl-2 that may provide clinical application of our hypothesis in the future.

Bcl-2 mediated modulation of vascularization in prostate cancer xenografts

PURPOSE

We previously demonstrated that Bcl-2 overexpression enhances the radiation resistance of PC-3 human prostate cancer cells and xenografts by inhibiting apoptosis, increasing proliferation, and promoting angiogenesis. To further elucidate the relationship between Bcl-2 expression and the angiogenic potential of PC-3-Bcl-2 cells, tumorigenicity, angiogenesis, and lymphangiogenesis were evaluated and compared in a Bcl-2 overexpressing clone in vitro and in vivo.

EXPERIMENTAL DESIGN

Human prostate cancer cells over expressing Bcl-2 were studied in vitro and in vivo to determine the angiogenic and lymphangiogenic properties of these cells.

RESULTS

Increased Bcl-2 expression enhanced the tumorigenicity of prostate cancer xenografts. It also enhanced the expression and secretion of key angiogenic and lymphangiogenic factors that stimulated the synthesis of CD31-positive blood vessels and LYVE-1 positive lymphatics. Specifically, the increased angiogenic and lymphangiogenic potential correlated with increased serum levels of basic fibroblast growth factor (bFGF), interleukin 8 (CXCL8), and matrix metalloproteinase (MMP 9). In vitro analysis demonstrated that Bcl-2 expressing tumor cells secreted bFGF and vascular endothelial growth factor (VEGF) into culture supernatants. Microarray analysis of Bcl-2 expressing PC-3 cells demonstrated increased transcription of genes involved in metabolism, such as interleukins, growth factors, tumor necrosis factors (TNF) family members, and peptidases.

CONCLUSIONS

Together, these results demonstrate that Bcl-2 can regulate tumoral angiogenesis and lymphangiogenesis and suggest that therapy targeted at Bcl-2 expression, angiogenesis, and lymphangiogenesis may synergistically modulate tumor growth and confirm that Bcl-2 is a pivotal target for cancer therapy.

Involvement of nuclear factor-kappa B in bcl-xL-induced interleukin 8 expression in glioblastoma

We recently reported that bcl-xL regulates interleukin 8 (CXCL8) protein expression and promoter activity in glioblastoma cells. In this paper we demonstrate that CXCL8 induction by bcl-xL is mediated through a nuclear factor-kappa B (NF-kB)-dependent mechanism. Mutational studies on the CXCL8 promoter showed that NF-kB binding site was required for bcl-xL-induced promoter activity and an enhanced nuclear expression of NF-kB subunits p65 and p50 was observed after bcl-xL over-expression. Electrophoretic mobility shift assay showed an increased DNA-binding activity of NF-kB in bcl-xL over-expressing cells and the use of specific antibodies confirmed the involvement of p65 and p50 in NF-kB activity on CXCL8 promoter sequence. NF-kB activity regulation by bcl-xL involved IkBalpha and IKK complex signaling pathway. In fact, bcl-xL over-expression induced a decrease of cytoplasmic expression of the IkBalpha protein, paralleled by an increase in the phosphorylation of the same IkBalpha and IKKalpha/beta. Moreover, the down-regulation of the ectopic or endogenous bcl-xL expression through RNA interference confirmed the ability of bcl-xL to modulate NF-kB pathway, and the transient expression of a degradation-resistant form of the cytoplasmic NF-kB inhibitor IkBalpha in bcl-xL transfectants confirmed the involvement of that inhibitor in bcl-xL-induced CXCL8 expression and promoter activity. In conclusion, our results demonstrate the role of NF-kB as the mediator of bcl-xL-induced CXCL8 up-regulation in glioblastoma cells.

Expanding circle of inhibition: small-molecule inhibitors of Bcl-2 as anticancer cell and antiangiogenic agents

The specific targeting of diseases, particularly cancer, is a primary aim in drug development, as specificity reduces unwelcome effects on healthy tissue and increases drug efficacy at the target site. Drug specificity can be increased by improving the delivery system or by selecting drugs with affinity for a molecular ligand specific to the disease state. The role of the prosurvival Bcl-2 protein in maintaining the normal balance between apoptosis and cellular survival has been recognized for more than a decade. Bcl-2 is vital during development, much less so in adults. It has also been noted that some cancers evade apoptosis and obtain a survival advantage through aberrant expression of Bcl-2. The new and remarkably diverse class of drugs, small-molecule inhibitors of Bcl-2 (molecular weight approximately 400 to 800 Daltons), is examined herein. We present the activities of these compounds along with clinical observations, where available. The effects of Bcl-2 inhibition on attenuation of tumor cell growth are discussed, as are studies revealing the potential for Bcl-2 inhibitors as antiangiogenic agents. Despite an enormous body of work published for the Bcl-2 family of proteins, we are still learning exactly how this group of molecules interacts and indeed what they do. The small-molecule inhibitors of Bcl-2, in addition to their therapeutic potential, are proving to be an important investigative tool for understanding the function of Bcl-2.