The role of Bcl-2 and its pro-survival relatives in tumourigenesis and cancer therapy

TMBIM-mediated Ca2+ homeostasis and cell death

Ca²⁺ is a ubiquitous intracellular messenger that regulates numerous physiological activities in humans, animals, plants, and bacteria. Cytosolic Ca²⁺ is kept at a low level, but subcellular organelles such as the endoplasmic reticulum (ER) and Golgi apparatus maintain high-concentration Ca²⁺ stores. Under resting conditions, store Ca²⁺ homeostasis is dynamically regulated to equilibrate between active Ca²⁺ uptake and passive Ca²⁺ leak processes. The evolutionarily conserved Transmembrane BAX Inhibitor-1 Motif-containing (TMBIM) proteins mediate Ca²⁺ homeostasis and cell death. This review focuses on recent advances in functional and structural analysis of TMBIM proteins in regulation of the two related functions. The roles of TMBIM proteins in pathogen infection and cancer are also discussed with prospects for treatment. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.

Mitochondrial Changes in Cancer

Mitochondrial structural and functional integrity defines the health of a cell by regulating cellular metabolism. Thus, mitochondria play an important role in both cell proliferation and cell death. Cancer cells are metabolically altered compared to normal cells for their ability to survive better and proliferate faster. Resistance to apoptosis is an important characteristic of cancer cells and given the contribution of mitochondria to apoptosis, it is imperative that mitochondria could behave differently in a tumor situation. The other feature associated with cancer cells is the Warburg effect, which engages a shift in metabolism. Although the Warburg effect often occurs in conjunction with dysfunctional mitochondria, the relationship between mitochondria, the Warburg effect, and cancer cell metabolism is not clearly decoded. Other than these changes, several mitochondrial gene mutations occur in cancer cells, mitochondrial biogenesis is affected and mitochondria see structural and functional variations. In cancer pharmacology, targeting mitochondria and mitochondria associated signaling pathways to reduce tumor proliferation is a growing field of interest. This chapter summarizes various changes in mitochondria in relevance to cancer, behavior of mitochondria during tumorigenesis, and the progress on using mitochondria as a therapeutic target for cancer.

How to unleash mitochondrial apoptotic blockades to kill cancers?

Apoptosis, especially the intrinsic mitochondrial cell death pathway, is regulated by the BCL-2 family of proteins. Defects in apoptotic machinery are one of the main mechanisms that cells employ to evade cell death and become cancerous. Targeting the apoptotic defects, either by direct inhibition of BCL-2 family proteins or through modulation of regulatory pathways, can restore cell sensitivity to cell death. This review will focus on the aspects of BCL-2 family proteins, their interactions with kinase pathways, and how novel targeted agents can help overcome the apoptotic blockades. Furthermore, functional assays, such as BH3 profiling, may help in predicting responses to chemotherapies and aid in the selection of combination therapies by determining the mitochondrial threshold for initiating cell death.

The protein level and transcription activity of activating transcription factor 1 is regulated by prolyl isomerase Pin1 in nasopharyngeal carcinoma progression

The function of activating transcription factor 1 (ATF1) and the mechanism about why ATF1 was over-phosphorylated in nasopharyngeal carcinoma (NPC) progression is completely undiscovered. In this study, a series of experiments both in vitro and in vivo were used to characterize a promotive function of ATF1 in NPC tumorigenesis and identify prolyl isomerase Pin1 as a novel regulator of ATF1 at post-transcription. First, we found that overexpression of ATF1 promoted colony formation in NPC. However, the high protein level of ATF1 in NPC was not resulted from high mRNA level. Then, a direct interaction between Pin1 and ATF1 at Thr184 was demonstrated using mammalian two-hybrid assay and coimmunoprecipitation. Cycloheximide (CHX) treatment indicated Pin1 stabilized the expression of ATF1 at post-transcription level. We confirmed that Pin1 upregulated ATF1 transcriptional activity of Bcl-2 using luciferase reporter assay, quantitative RT-PCR and western blot. Furthermore, the newly identified phosphorylation of ATF1 at Thr184 was suggested to have an important role in ATF1 function of transcription and tumor promotion. Finally, high expression of Pin1 in NPC tissue was found to be positively correlated with ATF1. The ATF1 promoted NPC tumorigenesis was regulated by Pin1 both in vitro and in vivo. All these findings clearly state that Pin1 is a novel regulator of ATF1 at Thr184 and thereby enhances ATF1 transcription activity and tumorigenesis promotive function in NPC.

N-(3-oxo-acyl) homoserine lactone inhibits tumor growth independent of Bcl-2 proteins

Pseudomonas aeruginosa produces N-(3-oxododecanoyl)-homoserine lactone (C12) as a quorum-sensing molecule for bacterial communication. C12 has also been reported to induce apoptosis in various types of tumor cells. However, the detailed molecular mechanism of C12-triggerred tumor cell apoptosis is still unclear. In addition, it is completely unknown whether C12 possesses any potential therapeutic effects in vivo. Our data indicate that, unlike most apoptotic inducers, C12 evokes a novel form of apoptosis in tumor cells through inducing mitochondrial membrane permeabilization independent of both pro- and anti-apoptotic Bcl-2 proteins. Importantly, C12 inhibits tumor growth in animals regardless of either pro- or anti-apoptotic Bcl-2 proteins. Furthermore, opposite to conventional chemotherapeutics, C12 requires paraoxonase 2 (PON2) to exert its cytotoxicity on tumor cells in vitro and its inhibitory effects on tumor growth in vivo. Overall, our results demonstrate that C12 inhibits tumor growth independent of both pro- and anti-apoptotic Bcl-2 proteins, and through inducing unique apoptotic signaling mediated by PON2 in tumor cells.

Fulvestrant reverses doxorubicin resistance in multidrug-resistant breast cell lines independent of estrogen receptor expression

Drug resistance, a major obstacle to successful cancer chemotherapy, frequently occurs in recurrent or metastatic breast cancer and results in poor clinical response. Fulvestrant is a new type of selective estrogen receptor (ER) downregulator and a promising endocrine therapy for breast cancer. In this study, we evaluated the combination treatment of fulvestrant and doxorubicin in ER-negative multidrug-resistant (MDR) breast cancer cell lines Bads-200 and Bats-72. Fulvestrant potentiated doxorubicin-induced cytotoxicity, apoptosis and G2/M arrest with upregulation of cyclin B1. It functioned as a substrate for P-glycoprotein (P-gp) without affecting its expression. Furthermore, fulvestrant not only restored the intracellular accumulation of doxorubicin but also relocalized it to the nuclei in Bats-72 and Bads-200 cells, which may be another potential mechanism of reversal of P-gp mediated doxorubicin resistance. These results indicated that the combination of fulvestrant and doxorubicin-based chemotherapy may be feasible and effective for patients with advanced breast cancer.

MicroRNA-455-3p Inhibits Tumor Cell Proliferation and Induces Apoptosis in HCT116 Human Colon Cancer Cells

BACKGROUND MicroRNAs have been reported to play significant roles in pathogenesis of colorectal cancer (CRC). In the present study, we aimed to investigate the functional role of microRNA-455-3p (miR-455-3p) in CRC, as well as its underlying mechanisms. MATERIAL AND METHODS Human colon cancer cell line HCT116 cells were transfected with miR-455-3p mimics, inhibitors, or controls. After transfection, the effects of miR-455-3p mimics or inhibitors on cell proliferation were analyzed by 3-(4, 5-dimethyl-2- thiazolyl)-2, 5-diphenyl -2-H-tetrazolium bromide (MTT) assay and BrdU assay, and the effects of miR-455-3p mimics or inhibitors on cell apoptosis were determined. In addition, the underlying mechanisms of cell proliferation and apoptosis were explored by assessing the protein levels of cell cycle regulators and apoptosis-related protein. RESULTS The results showed that overexpression of miR-455-3p significantly inhibited the cell proliferation (P<0.05 or <0.01) in HCT116 cells compared with the control group, but significantly increased the apoptosis (P<0.01). On the contrary, suppression of miR-455-3p significantly increased the cell proliferation but decreased the apoptosis. Moreover, we found that overexpression of miR-455-3p significantly elevated the protein levels of p27 kinase inhibition protein (KIP) 1, Bax, pro-caspase-3, and active caspase-3, and markedly downregulated the levels of B-cell lymphoma-2 (Bcl-2). Contrary results were found by suppression of miR-455-3p. However, there were no significant differences in p21 expression. CONCLUSIONS MiRNA-455-3p functions as an anti-oncogene in HCT116 cells by inhibiting cell proliferation and inducing of apoptosis.

PPARα induces cell apoptosis by destructing Bcl2

PPARα belongs to the peroxisome-proliferator-activated receptors (PPARs) family, which plays a critical role in inhibiting cell proliferation and tumorigenesis, while the molecular mechanism is still unclear. Here we report that PPARα serves as an E3 ubiquitin ligase to govern Bcl2 protein stability. PPARα physically bound to Bcl2 protein. In this process, PPARα/C102 was critical for PPARα binding to BH3 domain of Bcl2, subsequently, PPARα transferred K48-linked polyubiquitin to lysine-22 site of Bcl2 resulting in its ubiquitination and proteasome-dependent degradation. Importantly, overexpression of PPARα enhanced cancer cell chemotherapy sensitivity. In contrast, silenced PPARα decreased this event. These findings revealed a novel mechanism of PPARα governed endogenous Bcl2 protein stability leading to reduced cancer cell chemoresistance, which provides a potential drug target for cancer treatment.

Computationally designed high specificity inhibitors delineate the roles of BCL2 family proteins in cancer

Many cancers overexpress one or more of the six human pro-survival BCL2 family proteins to evade apoptosis. To determine which BCL2 protein or proteins block apoptosis in different cancers, we computationally designed three-helix bundle protein inhibitors specific for each BCL2 pro-survival protein. Following in vitro optimization, each inhibitor binds its target with high picomolar to low nanomolar affinity and at least 300-fold specificity. Expression of the designed inhibitors in human cancer cell lines revealed unique dependencies on BCL2 proteins for survival which could not be inferred from other BCL2 profiling methods. Our results show that designed inhibitors can be generated for each member of a closely-knit protein family to probe the importance of specific protein-protein interactions in complex biological processes.

Microfluidic profiling of apoptosis-related genes after treatment with BH3-mimetic agents in astrocyte and glioblastoma cell lines

Glioblastoma (GB) is the most frequent and biologically the most aggressive primary brain tumor in adults. Standard treatment for newly diagnosed GB consists of surgical resection, radiotherapy and chemotherapy. Resistance to therapy is a major obstacle, even with optimal treatment with a survival median of only 12-15 months. The heterogeneity and treatment response of GB makes this tumor type a challenging area of research. The aim of our study was to study the response of normal human astrocyte (HA) and human GB (T98G) cell lines to apoptosis inhibitors in vitro. ABT-737 is an inhibitor of anti-apoptotic proteins Bcl-2, Bcl-xL, Bcl-w, while MIM-1 is an Mcl-1 protein inhibitor. The viability of the cells was assayed biochemically using the cytotoxic methyl thiazolyl tetrazolium (MTT) assay. Changes in the expression of apoptosis-associated genes (n=93) in two human brain cell lines after treatment with the apoptosis inhibitors ABT-737 and MIM-1 (individually), between the apoptosis inhibitor treated group and the control group, were determined using a commercially pre-designed microfluidic array. Significant changes in apoptotic gene expression with more than a 2.0-fold difference in their expression levels were obtained in both cell lines; the most altered genes were in the HA cell line after MIM-1 treatment (n=42). These results contribute to the importance of apoptosis in normal and cancerous brain tissues and provide information on the effect of apoptosis inhibitors on cell viability and gene expression. Despite extensive investigations, a cure for GB is currently not available. The identification of an apoptotic gene panel and determining the sensitivity of normal and GB brain cells to individual apoptosis inhibitors could help to improve clinical practice and increase our understanding of brain tumor cell metabolism and apoptosis inhibitors in GB cells and astrocytes. Recognizing expression changes in pro-apoptotic and anti-apoptotic genes could contribute to the development of new treatments.

ABT-263 induces apoptosis and synergizes with chemotherapy by targeting stemness pathways in esophageal cancer

Activation of cancer stem cell signaling is central to acquired resistance to therapy in esophageal cancer (EC). ABT-263, a potent Bcl-2 family inhibitor, is active against many tumor types. However, effect of ABT-263 on EC cells and their resistant counterparts are unknown. Here we report that ABT-263 inhibited cell proliferation and induced apoptosis in human EC cells and their chemo-resistant counterparts. The combination of ABT-263 with 5-FU had synergistic lethal effects and amplified apoptosis that does not depend fully on its inhibition of BCL-2 family proteins in EC cells. To further explore the novel mechanisms of ABT-263, proteomic array (RPPAs) were performed and gene set enriched analysis demonstrated that ABT-263 suppresses the expression of many oncogenes including genes that govern stemness pathways. Immunoblotting and immunofluorescence further confirmed reduction in protein expression and transcription in Wnt/β-catenin and YAP/SOX9 axes. Furthermore, ABT263 strongly suppresses cancer stem cell properties in EC cells and the combination of ABT-263 and 5-FU significantly reduced tumor growth in vivo and suppresses the expression of stemness genes. Thus, our findings demonstrated a novel mechanism of ABT-263 antitumor effect in EC and indicating that combination of ABT-263 with cytotoxic drugs is worthy of pursuit in patients with EC.

Propranolol sensitizes thyroid cancer cells to cytotoxic effect of vemurafenib

Treatment options for advanced metastatic or progressive thyroid cancers are limited. Although targeted therapy specifically inhibiting intracellular kinase signaling pathways has markedly changed the therapeutic landscape, side-effects and resistance of single agent targeted therapy often leads to termination of the treatment. The objective of the present study was to identify the antitumor property of the non-selective β-adrenergic receptor antagonist propranolol for thyroid cancers. Human thyroid cancer cell lines 8505C, K1, BCPAP and BHP27 were used in the present study. Broad β-blocker propranolol and β2-specific antagonist ICI118551, but not β1-specific antagonist atenolol, inhibited the growth of 8505C and K1 cells. Propranolol treatment inhibited growth and induced apoptosis of 8505C cells in vitro and in vivo, which are closely associated with decreased expressions of cyclin D1 and anti-apoptotic Bcl-2. Expression of hexokinase 2 (HK2) and glucose transporter 1 (GLUT1) also decreased following propranolol intervention. 18F-FDG PET/CT imaging of the 8505C xenografts validated shrinkage of the tumors in the propranolol-treated group when compared to the phosphate‑buffered saline treated group. Finally, we found that propranolol can amplify the cytotoxicity of vemurafenib and sensitize thyroid cancer cells to cytotoxic effect of vemurafenib. Our present results suggest that propranolol has potential activity against thyroid cancers and investigation of the combination with targeted molecular therapy for progressive thyroid cancers could be beneficial.

Inhibition of DACH1 activity by short hairpin RNA represses cell proliferation and tumor invasion in pancreatic cancer

Cancer of the pancreas is one of the most lethal diseases worldwide. Better understanding of the molecular mechanisms involved in tumorigenesis is of great consequence to elevate the survival rate. Human Dachshund homologue 1 (DACH1) plays a controversial role in human malignancy progression with its expression being altered in a variety of cancers. Nevertheless, its functional roles and molecular mechanisms in pancreatic cancer remain unknown. The expression of DACH1 in pancreatic cancer cell lines and the ductal epithelial cells were evaluated both at mRNA and protein levels. Three pairs of siRNA targeting the DACH1 gene were designed and synthesized, double-stranded short hairpin RNA (shRNA) were annealed and inserted into pGenesil-1 vector, which was confirmed by enzymatic digestion and sequencing analyses. The successfully constructed recombinant plasmids were transfected into Capan-1 cells and our data indicated that knockdown of DACH1 gene expression showed strong correlation with repressing tumorigenesis. The proliferation of Capan-1 cells was significantly repressed as evaluated by CCK-8 and colony formation assays. Flow cymetry revealed that cell apoptosis was promoted in interference plasmid group compared with control groups (P<0.05), whereas cell cycle had no significant differences among the groups (P>0.05). Transwell assay validated the abilities of migration and invasion as being significantly reduced in pshRNA-DACH1 group. Furthermore, our study suggested that DACH1 expression regulates the pancreatic cancer cell apoptosis through interacting with Bcl-2 signaling axis, whereas it controls cell migration and invasion via epithelial-mesenchymal transition (EMT) process.

BH3 mimetic ABT-737 sensitizes colorectal cancer cells to ixazomib through MCL-1 downregulation and autophagy inhibition

The proteasome inhibitor MLN9708 is an orally administered drug that is hydrolyzed into its active form, MLN2238 (ixazomib). Compared with Bortezomib, MLN2238 has a shorter proteasome dissociation half-life and a lower incidence and severity of peripheral neuropathy, which makes it an attractive candidate for colorectal cancer treatment. In the present study, we observed that MLN2238 induced autophagy, as evidenced by conversion of the autophagosomal marker LC3 from LC3I to LC3II, in colorectal cancer cell lines. Mcl-1, an anti-apoptotic Bcl-2 family protein, was markedly elevated after treating a colorectal cancer cell line with MLN2238. We proved that inhibiting Mcl-1 expression enhances MLN2238 induced apoptosis and negatively regulates autophagy. Co-administration of BH3 mimetic ABT-737 with MLN2238 synergistically kills colorectal cancer cells through MCL-1 neutralization and autophagy inhibition. Furthermore, the synergistic killing effect of the combination therapy is correlated with P53 status in colorectal cancer. These data highlight that the combination of ABT-737 with MLN9708 is a promising therapeutic strategy for human colorectal cancer.

Amelioration of Benzo[a]pyrene-induced oxidative stress and pulmonary toxicity by Naringenin in Wistar rats: A plausible role of COX-2 and NF-κB

Naringenin is a naturally occurring flavanones and has been found to exhibit free radical scavenging, enzyme inhibition, antioxidants, anti-inflammatory, and anticancer activities. Present study was designed to evaluate the protective role of naringenin against benzo[a]pyrene (B[a]P)-induced oxidative stress and pulmonary toxicity. Rats were treated with naringenin at a dose of 100 mg/kg body weight (b. wt.), by oral gavage. B[a]P in a single dose of 50 mg/kg b. wt. was given intraperitoneally. Total protein, total cell counts, lactate dehydrogenase, lipid peroxidation, reduced glutathione, antioxidant enzymes activities, lung histology and expression of nuclear factor kappa B (NF-κB), and cyclo-oxygenase-2 (COX-2) was assessed to evaluate protective effects of naringenin. Histopathological and immunohistochemical studies were also carried out to observe lung toxicity and inflammation. B[a]P administration enhanced the levels of lung injury markers and reduced antioxidant enzymes activities. Naringenin treatment attenuated the levels of oxidative stress by restoring antioxidant enzymes, further improved lung histological damage and significant decrease in inflammatory responses. Naringenin also effectively decreased the expression of NF-κB, and COX-2 induced by B[a]P. These findings suggest that naringenin supplementation is beneficial in maintaining the integrity of alveoli and the epithelium that may be used as a protective agent in B[a]P-induced oxidative stress and lung damage. However, further studies are warranted to elucidate the potential mechanism of action of naringenin.

MicroRNA-340 Inhibits Tumor Cell Proliferation and Induces Apoptosis in Endometrial Carcinoma Cell Line RL 95-2

BACKGROUND The purpose of our study was to investigate the functional role of microRNA-340 (miR-340) in endometrial carcinoma (EC). MATERIAL AND METHODS Human EC cell line RL 95-2 was transfected with miR-340 mimics, inhibitors, or controls. After 48 h of transfection, the cell viability was determined by 3-(4, 5-dimethyl-2- thiazolyl)-2, 5-diphenyl -2-H-tetrazolium bromide (MTT) assay. The BrdU assay and apoptosis assay were performed to determine the effects of miR-340 mimics or inhibitors on cell proliferation and apoptosis, respectively. The underlying mechanisms involved in cell proliferation and apoptosis were explored by measuring the protein levels of cell cycle regulators (p27 kinase inhibition protein (KIP) 1 and p21) and apoptosis-related factors (B-cell lymphoma-2 (Bcl-2), Bax, pro-Caspase 3, and active-Caspase-3). RESULTS Overexpression of miR-340 significantly inhibited the cell viability (P<0.05) and cell proliferation (P<0.01) of RL 95-2 cells compared with the control group, but increased the apoptosis (P<0.01). However, suppression of miR-340 had opposite results. Moreover, the protein levels of p27 KIP1, Bax, pro-Caspase 3, and active-Caspase-3 were significantly increased by overexpression of miR-340 but were statistically decreased by suppression of miR-340. Contrary results were found in the protein levels of Bcl-2. However, no significant differences were found in p21 expression. CONCLUSIONS MiRNA-340 acts as an anti-oncogene in EC cell line RL 95-2 by inhibition of tumor cell proliferation and induction of apoptosis.

BRAF-Directed Therapy in Metastatic Colorectal Cancer

Activating BRAF (V-raf murine sarcoma viral oncogene homolog B) mutations occur in approximately 5% to 10% of patients with metastatic colorectal cancer, mostly V600E mutation, and it is associated with distinct clinical and pathological features. To date, there are no approved treatments to target this mutation. BRAF inhibitor monotherapy has limited efficacy, in contrast to metastatic melanoma. Combination strategies that block not only BRAF mutated kinase but other alternative pathways are ongoing and have demonstrated improved activity. This review aims to provide data about new strategies to target to BRAF gene mutation in metastatic colorectal cancer.

Ewing's Sarcoma: An Analysis of miRNA Expression Profiles and Target Genes in Paraffin-Embedded Primary Tumor Tissue

The molecular mechanism responsible for Ewing’s Sarcoma (ES) remains largely unknown. MicroRNAs (miRNAs), a class of small non-coding RNAs able to regulate gene expression, are deregulated in tumors and may serve as a tool for diagnosis and prediction. However, the status of miRNAs in ES has not yet been thoroughly investigated. This study compared global miRNAs expression in paraffin-embedded tumor tissue samples from 20 ES patients, affected by primary untreated tumors, with miRNAs expressed in normal human mesenchymal stromal cells (MSCs) by microarray analysis. A miRTarBase database was used to identify the predicted target genes for differentially expressed miRNAs. The miRNAs microarray analysis revealed distinct patterns of miRNAs expression between ES samples and normal MSCs. 58 of the 954 analyzed miRNAs were significantly differentially expressed in ES samples compared to MSCs. Moreover, the qRT-PCR analysis carried out on three selected miRNAs showed that miR-181b, miR-1915 and miR-1275 were significantly aberrantly regulated, confirming the microarray results. Bio-database analysis identified BCL-2 as a bona fide target gene of the miR-21, miR-181a, miR-181b, miR-29a, miR-29b, miR-497, miR-195, miR-let-7a, miR-34a and miR-1915. Using paraffin-embedded tissues from ES patients, this study has identified several potential target miRNAs and one gene that might be considered a novel critical biomarker for ES pathogenesis.

The Stability and Expression Level of Bok Are Governed by Binding to Inositol 1,4,5-Trisphosphate Receptors

Bok is a member of the Bcl-2 protein family that governs the intrinsic apoptosis pathway, although the role that Bok plays in this pathway is unclear. We have shown previously in cultured cell lines that Bok interacts strongly with inositol 1,4,5-trisphosphate receptors (IP3Rs), suggesting that it may contribute to the structural integrity or stability of IP3R tetramers. Here we report that Bok is similarly IP3R-assocated in mouse tissues, that essentially all cellular Bok is IP3R bound, that it is the helical nature of the Bok BH4 domain, rather than specific amino acids, that mediates binding to IP3Rs, that Bok is dramatically stabilized by binding to IP3Rs, that unbound Bok is ubiquitinated and degraded by the proteasome, and that binding to IP3Rs limits the pro-apoptotic effect of overexpressed Bok. Agents that stimulate IP3R activity, apoptosis, phosphorylation, and endoplasmic reticulum stress did not trigger the dissociation of mature Bok from IP3Rs or Bok degradation, indicating that the role of proteasome-mediated Bok degradation is to destroy newly synthesized Bok that is not IP3R associated. The existence of this unexpected proteolytic mechanism that is geared toward restricting Bok to that which is bound to IP3Rs, implies that unbound Bok is deleterious to cell viability and helps explain the current uncertainty regarding the cellular role of Bok.

FoxA and LIPG endothelial lipase control the uptake of extracellular lipids for breast cancer growth

The mechanisms that allow breast cancer (BCa) cells to metabolically sustain rapid growth are poorly understood. Here we report that BCa cells are dependent on a mechanism to supply precursors for intracellular lipid production derived from extracellular sources and that the endothelial lipase (LIPG) fulfils this function. LIPG expression allows the import of lipid precursors, thereby contributing to BCa proliferation. LIPG stands out as an essential component of the lipid metabolic adaptations that BCa cells, and not normal tissue, must undergo to support high proliferation rates. LIPG is ubiquitously and highly expressed under the control of FoxA1 or FoxA2 in all BCa subtypes. The downregulation of either LIPG or FoxA in transformed cells results in decreased proliferation and impaired synthesis of intracellular lipids.

Deregulation of lipid metabolism in cancer cells is critical to the maintenance of certain malignant features. Here, the authors show that the proliferation of breast cancer cells depends upon the extracellular activity of the endothelial lipase enzyme LIPG whose expression is regulated by the FoxA family of transcription factors.

Prognostic and therapeutic impact of RPN2-mediated tumor malignancy in non-small-cell lung cancer

RNA interference (RNAi) is a powerful gene-silencing platform for cancer treatment. Previously, we demonstrated that ribophorin II (RPN2), which is part of the N-oligosaccharyl transferase complex, regulates docetaxel sensitivity and tumor lethal phenotypes in breast cancer. However, the molecular functions and clinical relevance of RPN2 in non-small-cell lung cancer (NSCLC) remain unknown. Here, we examined RPN2 expression in tumor specimens from recurrent NSCLC patients after resection (n = 32 and = 177) and assessed the correlation between RPN2 expression and various clinical features. We also investigated whether RPN2 affects cancer malignancy in vitro and tumor growth and drug resistance in vivo. Our data show that RPN2 expression confers early and distant recurrence as well as poor survival in NSCLC patients. Furthermore, RPN2 silencing suppressed cell proliferation and invasiveness, and increased the sensitivity to chemotherapeutic drugs in vitro. Remarkably, we found that intrinsic apoptosis signaling is the mechanism of cell death involved with RPN2 knockdown. Strikingly, RPN2 silencing repressed tumorigenicity and sensitized the tumors to cisplatin treatment, which led to the longer survival of NSCLC-bearing mice. In conclusion, these data suggest that RPN2 is involved in the regulation of lethal cancer phenotypes and represents a promising new target for RNAi-based medicine against NSCLC.

Proapoptotic Role of Potassium Ions in Liver Cells

Potassium channels are transmembrane proteins that selectively promote the infiltration of potassium ions. The significance of these channels for tumor biology has become obvious. However, the effects of potassium ions on the tumor or normal cells have seldom been studied. To address this problem, we studied the biological effects of L02 and HepG2 cells with ectogenous potassium ions. Cell proliferation, cell cycle, and apoptosis rate were analyzed. Our results indicated that potassium ions inhibited proliferation of L02 and HepG2 cells and promoted their apoptosis. Potassium ions induced apoptosis through regulating Bcl-2 family members and depolarized the mitochondrial membrane, especially for HepG2 cell. These biological effects were associated with channel protein HERG. By facilitating expression of channel protein HERG, potassium ions may prevent it from being shunted to procancerous pathways by inducing apoptosis. These results demonstrated that potassium ions may be a key regulator of liver cell function. Thus, our findings suggest that potassium ions could inhibit tumorigenesis through inducing apoptosis of hepatoma cells by upregulating potassium ions transport channel proteins HERG and VDAC1.

Cancer stem cells and immunoresistance: clinical implications and solutions

Tumor cells can be contained, but not eliminated, by traditional cancer therapies. A cell minor subpopulation is able to evade attack from therapies and may have cancer stem cell (CSC) characteristics, including self-renewal, multiple differentiation and tumor initiation (tumor initiating cells, or TICs). Thus, CSCs/TICs, aided by the microenvironment, produce more differentiated, metastatic cancer cells which the immune system detects and interacts with. There are three phases to this process: elimination, equilibrium and escape. In the elimination phase the immune system recognizes and destroys most of the tumor cells. Then the latency phase begins, consisting of equilibrium between immunological elimination and tumor cell growth. Finally, a minor attack-resistant subpopulation escapes and forms a clinically detectable tumor mass. Herein we review current knowledge of immunological characterization of CSCs/TICs. Due to the correlation between CTCs/TICs and drug resistance and metastasis, we also comment on the crucial role of key molecules involved in controlling CSCs/TICs properties; such molecules are essential to detect and destroy CSCs/TICs. Monoclonal antibodies, antibody constructs and vaccines have been designed to act against CSCs/TICs, with demonstrated efficacy in human cancer xenografts and some antitumor activity in human clinical studies. Therefore, therapeutic strategies that selectively target CSCs/TICs warrant further investigation. Better understanding of the interaction between CSCs and tumor immunology may help to identify strategies to eradicate the minor subpopulation that escapes conventional therapy attack, thus providing a solution to the problem of drug resistance and metastasis.

Deubiquitylating enzyme USP9x regulates radiosensitivity in glioblastoma cells by Mcl-1-dependent and -independent mechanisms

Glioblastoma is a very aggressive form of brain tumor with limited therapeutic options. Usually, glioblastoma is treated with ionizing radiation (IR) and chemotherapy after surgical removal. However, radiotherapy is frequently unsuccessful, among others owing to resistance mechanisms the tumor cells have developed. Antiapoptotic B-cell leukemia (Bcl)-2 family members can contribute to radioresistance by interfering with apoptosis induction in response to IR. Bcl-2 and the closely related Bcl-xL and Mcl-1 are often overexpressed in glioblastoma cells. In contrast to Bcl-2 and Bcl-xL, Mcl-1 is a short-lived protein whose stability is closely regulated by ubiquitylation-dependent proteasomal degradation. Although ubiquitin ligases facilitate degradation, the deubiquitylating enzyme ubiquitin-specific protease 9x (USP9x) interferes with degradation by removing polyubiquitin chains from Mcl-1, thereby stabilizing this protein. Thus, an inability to downregulate Mcl-1 by enhanced USP9x activity might contribute to radioresistance. Here we analyzed the impact of USP9x on Mcl-1 levels and radiosensitivity in glioblastoma cells. Correlating Mcl-1 and USP9x expressions were significantly higher in human glioblastoma than in astrocytoma. Downregulation of Mcl-1 correlated with apoptosis induction in established glioblastoma cell lines. Although Mcl-1 knockdown by siRNA increased apoptosis induction after irradiation in all glioblastoma cell lines, USP9x knockdown significantly improved radiation-induced apoptosis in one of four cell lines and slightly increased apoptosis in another cell line. In the latter two cell lines, USP9x knockdown also increased radiation-induced clonogenic death. The massive downregulation of Mcl-1 and apoptosis induction in A172 cells transfected with USP9x siRNA shows that the deubiquitinase regulates cell survival by regulating Mcl-1 levels. In contrast, USP9x regulated radiosensitivity in Ln229 cells without affecting Mcl-1 levels. We conclude that USP9x can control survival and radiosensitivity in glioblastoma cells by Mcl-1-dependent and Mcl-1-independent mechanisms.

Evaluation of the anticancer properties of the predicted hBaxBH3-mimetic compound 2-hydroxy-3,5-dinitrobenzamide in a mammary carcinogenesis-induced rat model

Designing small molecular prototypes having potential to disrupt binding interfaces of pro-apoptotic–anti-apoptotic/BH3-only proteins is a promising strategy in cancer chemotherapy.

Mechanism of neem limonoids-induced cell death in cancer: Role of oxidative phosphorylation

We have previously reported that neem limonoids (neem) induce multiple cancer cell death pathways. Here we dissect the underlying mechanisms of neem-induced apoptotic cell death in cancer. We observed that neem-induced caspase activation does not require Bax/Bak channel-mediated mitochondrial outer membrane permeabilization, permeability transition pore, and mitochondrial fragmentation. Neem enhanced mitochondrial DNA and mitochondrial biomass. While oxidative phosphorylation (OXPHOS) Complex-I activity was decreased, the activities of other OXPHOS complexes including Complex-II and -IV were unaltered. Increased reactive oxygen species (ROS) levels were associated with an increase in mitochondrial biomass and apoptosis upon neem exposure. Complex-I deficiency due to the loss of Ndufa1-encoded MWFE protein inhibited neem-induced caspase activation and apoptosis, but cell death induction was enhanced. Complex II-deficiency due to the loss of succinate dehydrogenase complex subunit C (SDHC) robustly decreased caspase activation, apoptosis, and cell death. Additionally, the ablation of Complexes-I, -III, -IV, and -V together did not inhibit caspase activation. Together, we demonstrate that neem limonoids target OXPHOS system to induce cancer cell death, which does not require upregulation or activation of proapoptotic Bcl-2 family proteins.

Sequence and partial functional analysis of canine Bcl-2 family proteins

Dogs present with spontaneous neoplasms biologically similar to human cancers. Apoptotic pathways are deregulated during cancer genesis and progression and are important for therapy. We have assessed the degree of conservation of a set of canine Bcl-2 family members with the human and murine orthologs. To this end, seven complete canine open reading frames were cloned in this family, four of which are novel for the dog, their sequences were analyzed, and their functional interactions were studied in yeasts. We found a high degree of overall and domain sequence homology between canine and human proteins. It was slightly higher than between murine and human proteins. Functional interactions between canine pro-apoptotic Bax and Bak and anti-apoptotic Bcl-xL, Bcl-w, and Mcl-1 were recapitulated in yeasts. Our data provide support for the notion that systems based on canine-derived proteins might faithfully reproduce Bcl-2 family member interactions known from other species and establish the yeast as a useful tool for functional studies with canine proteins.

Antimitotic drugs in the treatment of cancer

Cancer is a complex disease since it is adaptive in such a way that it can promote proliferation and invasion by means of an overactive cell cycle and in turn cellular division which is targeted by antimitotic drugs that are highly validated chemotherapy agents. However, antimitotic drug cytotoxicity to non-tumorigenic cells and multiple cancer resistance developed in response to drugs such as taxanes and vinca alkaloids are obstacles faced in both the clinical and basic research field to date. In this review, the classes of antimitotic compounds, their mechanisms of action and cancer cell resistance to chemotherapy and other limitations of current antimitotic compounds are highlighted, as well as the potential of novel 17-β estradiol analogs as cancer treatment.

Pan-Bcl-2 inhibitor Obatoclax is a potent late stage autophagy inhibitor in colorectal cancer cells independent of canonical autophagy signaling

BACKGROUND

Colorectal cancer is the third most common malignancy in humans and novel therapeutic approaches are urgently needed. Autophagy is an evolutionarily highly conserved cellular process by which cells collect unnecessary organelles or misfolded proteins and subsequently degrade them in vesicular structures in order to refuel cells with energy. Dysregulation of the complex autophagy signaling network has been shown to contribute to the onset and progression of cancer in various models. The Bcl-2 family of proteins comprises central regulators of apoptosis signaling and has been linked to processes involved in autophagy. The antiapoptotic members of the Bcl-2 family of proteins have been identified as promising anticancer drug targets and small molecules inhibiting those proteins are in clinical trials.

METHODS

Flow cytometry and colorimetric assays were used to assess cell growth and cell death. Long term 3D cell culture was used to assess autophagy in a tissue mimicking environment in vitro. RNA interference was applied to modulate autophagy signaling. Immunoblotting and q-RT PCR were used to investigate autophagy signaling. Immunohistochemistry and fluorescence microscopy were used to detect autophagosome formation and autophagy flux.

RESULTS

This study demonstrates that autophagy inhibition by obatoclax induces cell death in colorectal cancer (CRC) cells in an autophagy prone environment. Here, we demonstrate that pan-Bcl-2 inhibition by obatoclax causes a striking, late stage inhibition of autophagy in CRC cells. In contrast, ABT-737, a Mcl-1 sparing Bcl-2 inhibitor, failed to interfere with autophagy signaling. Accumulation of p62 as well as Light Chain 3 (LC3) was observed in cells treated with obatoclax. Autophagy inhibition caused by obatoclax is further augmented in stressful conditions such as starvation. Furthermore, our data demonstrate that inhibition of autophagy caused by obatoclax is independent of the essential pro-autophagy proteins Beclin-1, Atg7 and Atg12.

CONCLUSIONS

The objective of this study was to dissect the contribution of Bcl-2 proteins to autophagy in CRC cells and to explore the potential of Bcl-2 inhibitors for autophagy modulation. Collectively, our data argue for a Beclin-1 independent autophagy inhibition by obatoclax. Based on this study, we recommend the concept of autophagy inhibition as therapeutic strategy for CRC.

Lack of association between the BIM deletion polymorphism and the risk of lung cancer with and without EGFR mutations

INTRODUCTION

The BIM deletion polymorphism in intron 2 was found in a significant percent of the Asian population. Patients with epidermal growth factor receptor (EGFR) mutant lung cancers harboring this BIM polymorphism have shorter progression free survival and overall response rates to EGFR tyrosine kinase inhibitors. However, the association between the BIM deletion polymorphism and lung cancer risk is unknown.

METHODS

The BIM deletion polymorphism was screened by polymerase chain reaction in 765 lung cancer cases and 942 healthy individuals.

RESULTS

Carriers possessing one allele of the BIM polymorphism were observed in 13.0% of control cases and 12.8% of lung cancer cases, similar to incidence rates reported earlier in healthy individuals. Homozygote for the BIM polymorphism was observed in four of 942 healthy controls and three of 765 lung cancer cases. The frequency of the BIM deletion polymorphism in lung cancer patients was not related to age, sex, smoking history, or family history of lung cancer. The BIM deletion polymorphism was found in 30 of 212 patients with EGFR wild type lung cancers and 16 of 120 patients with EGFR mutant lung cancers. The frequency of the BIM polymorphism is similar between cancers with wild type EGFR and mutated EGFR (p = 0.78).

CONCLUSION

The BIM deletion polymorphism was not associated with lung cancer susceptibility. Furthermore, the BIM polymorphism is not associated with EGFR mutant lung cancer.

Influence of MiR-451 on Drug Resistances of Paclitaxel-Resistant Breast Cancer Cell Line

BACKGROUND

This study aimed to investigate the potential influence of microRNA-451 (miR-451) in drug resistances of the Paclitaxel-resistant breast cancer cell line by transfecting miR-451 mimics and miR-451 inhibitors to MCE-7, MCF-7/EPI, and MCF-7/DOC.

MATERIAL AND METHODS

Real-time quantitative PCR (qRT-PCR) was performed for detecting whether transfected miR-451 mimics and miR-451 inhibitors could regulate the expression of miR-451 effectively. The apoptosis of the 3 cell lines was measured by applying Annexin V-APC/PI staining. Western blot was used for the detection of the protein expression of Bcl-2 and Caspase 3 after the transfection of miR-451 mimics /inhibitors. Bioinformatics analysis demonstrated that Bcl-2 protein is a potential target gene for miR-451.

RESULTS

In comparison to the control group, after transfection with miR-451 mimics, there was a significant increase in miR-451 expression in MCF-7, MCF-7/EPI, and MCF-7/DOC. Cells in the three cell lines had increased apoptosis, Bcl-2 protein expression decreased significantly, and Caspase protein expression increased obviously. After the transfection with miR-451 inhibitors, miR-451 expression was significantly decreased and apoptosis in the 3 cell lines had no significant decrease compared with the control group.

CONCLUSIONS

Increased miR-451 expression may negatively regulate Bcl-2 mRNA and protein expression, followed by affecting the protein expression of caspase 3, and accelerate the apoptosis in breast cancer, indicating that miR-451 might influence the drug resistances of the Paclitaxel-resistant breast cancer cell line.

Ursolic Acid Induces Apoptosis of Prostate Cancer Cells via the PI3K/Akt/mTOR Pathway

Ursolic acid (UA), a pentacyclic triterpenoid, is known to exert antitumor activity in breast, lung, liver and colon cancers. Nonetheless, the underlying mechanism of ursolic acid in prostate cancer cells still remains unclear. In the present study, we report the chemotherapeutic effects of ursolic acid as assessed using in vitro and in vivo models. Treatment of human prostate cancer cells (LNCaP and PC-3) with UA inhibited the proliferation and induced apoptosis in both cell lines as characterized by the increased Annexin V-binding. The induction of apoptosis by UA was associated with a decrease in the levels of Bcl-2, Bcl-xl, survivin, and activated caspase-3. Treatment with UA also inhibited the expression of phosphatidylinositol-3-kinase (PI3K), phosphorylation of Akt and mTOR signaling proteins. Further, administration of UA significantly inhibited the growth of LNCaP prostate tumor xenografts in athymic nude mice, which was associated with inhibition of cell proliferation, induction of apoptosis of tumor cells and decreased expression of PI3K downstream factors, such as p-Akt and p-mTOR in tumor xenograft tissues. Our study demonstrates that UA not only inhibits cell growth but also induces apoptosis through modulation of the PI3K/Akt/mTOR pathway in human prostate cancer cells. We suggest that UA may be a new chemotherapeutic candidate against prostate cancer.

Design, synthesis and preliminary bioactivity studies of imidazolidine-2,4-dione derivatives as Bcl-2 inhibitors

Anti-apoptotic B-cell lymphoma-2 (Bcl-2) proteins are promising targets for cancer therapy. In the present study, a series of imidazolidine-2,4-dione derivatives were designed and synthesized to test their inhibitory activities against anti-apoptotic Bcl-2 proteins. Among them, compound 8k had better growth inhibitory effects on K562 and PC-3 cell lines compared to lead compound WL-276.

Phospholipase D signaling pathways and phosphatidic acid as therapeutic targets in cancer

Phospholipase D is a ubiquitous class of enzymes that generates phosphatidic acid as an intracellular signaling species. The phospholipase D superfamily plays a central role in a variety of functions in prokaryotes, viruses, yeast, fungi, plants, and eukaryotic species. In mammalian cells, the pathways modulating catalytic activity involve a variety of cellular signaling components, including G protein-coupled receptors, receptor tyrosine kinases, polyphosphatidylinositol lipids, Ras/Rho/ADP-ribosylation factor GTPases, and conventional isoforms of protein kinase C, among others. Recent findings have shown that phosphatidic acid generated by phospholipase D plays roles in numerous essential cellular functions, such as vesicular trafficking, exocytosis, autophagy, regulation of cellular metabolism, and tumorigenesis. Many of these cellular events are modulated by the actions of phosphatidic acid, and identification of two targets (mammalian target of rapamycin and Akt kinase) has especially highlighted a role for phospholipase D in the regulation of cellular metabolism. Phospholipase D is a regulator of intercellular signaling and metabolic pathways, particularly in cells that are under stress conditions. This review provides a comprehensive overview of the regulation of phospholipase D activity and its modulation of cellular signaling pathways and functions.

Apoptosis-related gene expression in tumor tissue samples obtained from patients diagnosed with glioblastoma multiforme

Tumors of the brain are very diverse in their biological behavior and are therefore considered a major issue in modern medicine. The heterogeneity of gliomas, their clinical presentation and their responses to treatment makes this type of tumor a challenging area of research. Glioblastoma multiforme (GBM) is the most common, and biologically the most aggressive, primary brain tumor in adults. The standard treatment for patients with newly diagnosed GBM consists of surgical resection, radiotherapy and chemotherapy. However, resistance to chemotherapy is a major obstacle to successful treatment. The aim of this study was to examine the changes occurring in the expression levels of apoptosis-associated genes in tumor tissue biopsy samples from 7 patients diagnosed with GBM and compare our results with a human astrocyte cell line (used as a reference) cultured under basic conditions. For molecular analysis, we used a commercial pre-designed microfluidic array to quantify the expression of 93 apoptosis-associated human genes. Significant changes in the expression levels of genes were observed in the tumor tissue samples obtained from patients with GBM. We determined significant changes in gene expression (n=32) in all apoptotic signaling pathways (BCl-2, TNF, Caspases, NF-κB, IAP and CARD), while the most pronounced deregulation (>5-fold) were observed in 46.9% events. The results of this study underline the importance of apoptosis in heterogenous tumor tissue. The identification of the apoptotic gene panel in tissue biopsies from patients with GBM may help improve the effectiveness of treatments for GBM in clinical practice and may broaden our understanding of brain tumor cell metabolism. Recognizing the changes in the expression of pro-apoptotic and anti-apoptotic genes may aid in the development of novel treatment strategies founded on a molecular basis.

Lupeol Induces Apoptosis and Cell Cycle Arrest of Human Osteosarcoma Cells Through PI3K/AKT/mTOR Pathway

Lupeol, a dietary triterpene present in many fruits and medicinal plants, has been reported to possess many pharmacological properties including anticancer effect in vitro and in vivo However, the activity of lupeol against osteosarcoma remains unclear. The present study is conducted to investigate the anticancer activity and the underlying mechanisms of lupeol on human osteosarcoma cells (MNNG/HOS and MG-63) in vitro and in vivo MNNG/HOS and MG-63 cells were treated by lupeol and subjected to methyl thiazolyl tetrazolium analysis, Hoechst staining, annexin V/propidium iodide double staining, cell cycle analysis, and Western blot analysis. In addition, MNNG/HOS xenograft tumors were established in female nude BALB/c mice, and lupeol was intravenously administered to evaluate the anticancer capacity in vivo Our results showed that lupeol induced apoptosis as well as cell cycle arrest in G0/G1 phase of MNNG/HOS and MG-63 cells in a dose-dependent manner in vitro Furthermore, the protein expression levels of phospho-phosphatidylinositol 3-kinase (p-PI3K), phospho-protein kinase B (p-AKT), p-p70S6K, and cyclin D1 were significantly downregulated, whereas the expression levels of p21 and p27 were upregulated. These protein interactions may play a pivotal role in the regulation of apoptosis and cell cycle arrest. More importantly, our in vivo studies showed that administration of lupeol decreased tumor growth in a dose-dependent manner and has no significant effect on the function of liver and kidney. Taken together, our findings indicated that lupeol can induce apoptosis as well as cell cycle arrest of human osteosarcoma cells through phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin pathway and might offer a promising new approach in the effective treatment of osteosarcoma.

Immunobiology and signaling pathways of cancer stem cells: implication for cancer therapy

Cancer stem cells (CSCs) need to survive cancer treatments with a specific end goal to provide new, more differentiated, metastatic-prone cancerous cells. This happens through diverse signals delivered within the tumor microenvironment where ample evidence indicates that altered developmental signaling pathways play an essential role in maintaining CSCs and accordingly the survival and the progression of the tumor itself. This review summarizes findings on the immunobiological properties of CSCs as compared with cancerous non-stem cells involving the expression of immunological molecules, cytokines and tumor antigens as well as the roles of the Notch, Wnt and Hedgehog pathways in the brain, breast and colon CSCs. We concluded that if CSCs are the main driving force behind tumor support and growth then understanding the molecular mechanisms and the immunological properties directing these cells for immune tolerance is of great clinical significance. Such knowledge will contribute to designing better targeted therapies that could prevent tumor recurrence and accordingly significantly improve cancer treatments and patient survival.

Aptamer-Dendrimer Bioconjugates for Targeted Delivery of miR-34a Expressing Plasmid and Antitumor Effects in Non-Small Cell Lung Cancer Cells

Metastasis and drug resistance are major barriers for the treatment of non-small cell lung cancer (NSCLC). To explore new therapeutic options, we successfully encapsulated MicroRNA-34a (miR-34a), a potent endogenous tumor suppressor in NSCLC into S6 aptamer-conjugated dendrimer to form lung cancer-targeted gene delivery nanoparticles (PAM-Ap/pMiR-34a NPs). PAM-Ap/pMiR-34a NPs had a diameter of 100-200 nm and Zeta potential of ~30 mV at applied N/P ratio. The aptamer conjugation significantly improved cellular uptake as well as gene transfection efficiency of PAM-Ap/pMiR-34a NPs in cultured NSCLC cells. We showed that PAM-Ap/pMiR-34a NPs enhanced the regulation of targeted genes, BCL-2 and p53 in vitro. In addition, we revealed PAM-Ap/pMiR-34a NPs significantly inhibited cell growth, migration, invasion and induced apoptosis of lung cancer cells compared with non-targeted NPs. The method provided a novel therapeutic strategy for the experimental treatment of NSCLC.

Doxorubicin Changes Bax /Bcl-xL Ratio, Caspase-8 and 9 in Breast Cancer Cells

PURPOSE

Doxorubicin is administrated as a single agent in first-line therapy of breast cancer to induce apoptosis in tumor cells. Bax, Bcl-xL, Caspase-8 and 9 proteins are involved in induction of apoptosis. The present study describes Bax, Bcl-xL gene expression and Caspase-8 and 9 protein levels in MCF-7 cells incubated with doxorubicin at different doses an incubation times.

METHODS

The cytotoxic effects of doxorubicin were studied using MTT assay. MCF-7 cells were treated with three concentrations of doxorubicin (0.1, 0.5, 1 μM) and incubated for 24, 48 and 72 hours then expression levels of Bax and Bcl-xL genes were elucidated by Real-time RT-PCR technique and protein levels of caspase-8 and caspase-9 proteins were measured using ELISA method. Morphological modifications of the cells were also monitored via light microscopic images.

RESULTS

Doxorubicin decreased the anti-apoptotic Bcl-xL and increased pro-apoptotic Bax mRNA levels. Doxorubicin induced a significant increase in Bax /Bcl-xL ratio in all doses and incubation times (p<0.05). Highest (more than 10 fold) increase in Bax /Bcl-xL ratio was revealed after 48 h incubation of the cells with in all doses of doxorubicin. Doxorubicin also increased caspase-9 level in a time and dose-dependent manner, while caspase-8 level didn't follow time and dose dependency pattern.

CONCLUSION

Our results confirm that doxorubicin induces mitochondrial-dependent apoptosis by down-regulation of Bcl-xL and up- regulation of Bax and caspase-9 expressions.

The Bcl-2 family: structures, interactions and targets for drug discovery

Two phylogenetically and structurally distinct groups of proteins regulate stress induced intrinsic apoptosis, the programmed disassembly of cells. Together they form the B cell lymphoma-2 (Bcl-2) family. Bcl-2 proteins appeared early in metazoan evolution and are identified by the presence of up to four short conserved sequence blocks known as Bcl-2 homology (BH) motifs, or domains. The simple BH3-only proteins bear only a BH3-motif and are intrinsically disordered proteins and antagonize or activate the other group, the multi-motif Bcl-2 proteins that have up to four BH motifs, BH1-BH4. Multi-motif Bcl-2 proteins are either pro-survival or pro-apoptotic in action and have remarkably similar α-helical bundle structures that provide a binding groove formed from the BH1, BH2, and BH3-motifs for their BH3-bearing antagonists. In mammals a network of interactions between Bcl-2 members regulates mitochondrial outer membrane permeability (MOMP) and efflux of cytochrome c and other death inducing factors from mitochondria to initiate the apoptotic caspase cascade, but the molecular events leading to MOMP are uncertain. Dysregulation of the Bcl-2 family occurs in many diseases and pathogenic viruses have assimilated pro-survival Bcl-2 proteins to evade immune responses. Their role in disease has made the Bcl-2 family the focus of drug design attempts and clinical trials are showing promise for 'BH3-mimics', drugs that mimic the ability of BH3-only proteins to neutralize selected pro-survival proteins to induce cell death in tumor cells. This review focuses on the structural biology of Bcl-2 family proteins, their interactions and attempts to harness them as targets for drug design.

Association of the functional BCL-2 rs2279115 genetic variant and small cell lung cancer

As a well-known oncogene, B cell lymphoma-2 (BCL-2) can promote cancer cell survival through preventing their apoptosis. Several functional BCL-2 single nucleotide polymorphisms (SNPs), such as rs2279115, rs1801018, and rs1564483, have been identified and might contribute to cancer susceptibility. However, the involvement of these SNPs in small cell lung cancer (SCLC) was still unclear. As a result, we investigated associations between these three genetic variants and SCLC risk in a case-control design. Genotypes were determined in two independent case-control sets consisted of 520 SCLC patients and 1040 controls from two medical centers. Odds ratios (ORs) and 95 % confidence intervals (CIs) were calculated utilizing unconditional logistic regression. We found that only BCL-2 rs2279115 genetic variant significantly contributed to decreased SCLC risk in Chinese Han populations, with the rs2279115 A allele as the protective allele. Stratified analyses of association between BCL2 rs2279115 SNP and SCLC risk indicated that the functional polymorphism was only significantly associated with decreased risk of the limited stage SCLC but not the extensive stage disease. Our results indicate that the BCL-2 rs2279115 genetic variant was associated with SCLC risk in Chinese populations and support the hypothesis that SNPs in regulatory regions of oncogenes might contribute to cancer susceptibility.

Emodin induces apoptosis of human breast cancer cells by modulating the expression of apoptosis-related genes

The aim of this study was to investigate the effects of emodin on the proliferation of human breast cancer cells Bcap-37 and ZR-75-30. Cell viability following emodin treatment was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The effects of emodin on apoptosis were determined by flow cytometry using Annexin V-fluorescein isothiocyanate and propidium iodide staining. Quantitative polymerase chain reaction and western blot analysis were used to determine changes in the expression of apoptotic genes and protein, respectively. The effect of emodin on the invasiveness of breast cancer cells was evaluated by Matrigel invasion assay. Treatment of breast cancer cells Bcap-37 and ZR-75-30 with emodin was observed to inhibit the growth and induced apoptosis in a time- and dose-dependent manner. Emodin reduced the level of Bcl-2 and increased levels of cleaved caspase-3, PARP, p53 and Bax. These findings indicate that emodin induces growth inhibition and apoptosis in human breast cancer cells. Emodin may be a potential therapeutic agent for the treatment of breast cancer.

The virus-induced protein APOBEC3G inhibits anoikis by activation of Akt kinase in pancreatic cancer cells

Pancreatic cancer is one of the more common cancers with a poor prognosis. Some varieties of cancer are related to virus infection. As a virus-induced protein, APOBEC3G (A3G) presents extensive anti-virus ability, but the role of A3G in pancreatic cancer was previously unknown. The expression of A3G in pancreatic cancer was examined using TaqMan real-time qPCR, immunohistochemical and immunofluorescent staining. Subsequently, the role of A3G in pancreatic cancer was evaluated in vivo using the tumor xenograft model. Anoikis was detected by colony formation assay and flow cytometry in vitro. The Akt kinase activity and target protein PTEN were examined by co-immunoprecipitation and immunoblot. The virus-induced protein A3G was significantly up-regulated in pancreatic cancer, and the up-regulation of A3G promoted xenograft tumor formation. A3G inactivated PTEN by binding to the C2 tensin-type and PDZ domains, thereby inducing anoikis resistance through Akt activation. Our results demonstrate that the up-regulation of A3G in pancreatic cancer cells induces anoikis resistance, and they provide novel insight into the mechanism by which A3G affects the malignant behavior of pancreatic cancer cells.