The proto-oncogene c-myc and apoptosis

Targeting c-Myc with decoy oligodeoxynucleotide-loaded polycationic nanoparticles inhibits cell growth and induces apoptosis in cancer stem-like cells (NTERA-2)

BACKGROUND

An increase in cancer stem cell (CSC) populations and their resistance to common treatments could be a result of c-Myc dysregulations in certain cancer cells. In the current study, we investigated anticancer effects of c-Myc decoy ODNs loaded-poly (methacrylic acid-co-diallyl dimethyl ammonium chloride) (PMA-DDA)-coated silica nanoparticles as carriers on cancer-like stem cells (NTERA-2).

METHODS AND RESULTS

The physicochemical characteristics of the synthesized nanocomposites (SiO2@PMA-DDA-DEC) were analyzed using FT-IR, DLS, and SEM techniques. UV-Vis spectrophotometer was applied to analyze the release pattern of decoy ODNs from the nanocomposite. Furthermore, uptake, cell viability, apoptosis, and cell cycle assays were used to investigate the anticancer effects of nanocomposites loaded with c-Myc decoy ODNs on NTERA-2 cancer cells. The results of physicochemical analytics demonstrated that SiO2@PMA-DDA-DEC nanocomposites were successfully synthesized. The prepared nanocomposites were taken up by NTERA-2 cells with high efficiency, and could effectively inhibit cell growth and increase apoptosis rate in the treated cells compared to the control group. Moreover, SiO2@PMA-DDA nanocomposites loaded with c-Myc decoy ODNs induced cell cycle arrest at the G0/G1 phase in the treated cells.

CONCLUSIONS

The conclusion drawn from this study is that c-Myc decoy ODN-loaded SiO2@PMA-DDA nanocomposites can effectively inhibit cell growth and induce apoptosis in NTERA-2 cancer cells. Moreover, given that a metal core is incorporated into this synthetic nanocomposite, it could potentially be used in conjunction with irradiation as part of a decoy-radiotherapy combinational therapy in future investigations.

MYC Oncogene: A Druggable Target for Treating Cancers with Natural Products

Various diseases, including cancers, age-associated disorders, and acute liver failure, have been linked to the oncogene, MYC. Animal testing and clinical trials have shown that sustained tumor volume reduction can be achieved when MYC is inactivated, and different combinations of therapeutic agents including MYC inhibitors are currently being developed. In this review, we first provide a summary of the multiple biological functions of the MYC oncoprotein in cancer treatment, highlighting that the equilibrium points of the MYC/MAX, MIZ1/MYC/MAX, and MAD (MNT)/MAX complexes have further potential in cancer treatment that could be used to restrain MYC oncogene expression and its functions in tumorigenesis. We also discuss the multifunctional capacity of MYC in various cellular cancer processes, including its influences on immune response, metabolism, cell cycle, apoptosis, autophagy, pyroptosis, metastasis, angiogenesis, multidrug resistance, and intestinal flora. Moreover, we summarize the MYC therapy patent landscape and emphasize the potential of MYC as a druggable target, using herbal medicine modulators. Finally, we describe pending challenges and future perspectives in biomedical research, involving the development of therapeutic approaches to modulate MYC or its targeted genes. Patients with cancers driven by MYC signaling may benefit from therapies targeting these pathways, which could delay cancerous growth and recover antitumor immune responses.

Matrine, a potential c-Myc inhibitor, suppresses ribosome biogenesis and nucleotide metabolism in myeloid leukemia

Previous studies have shown that matrine, a natural compound extracted from the herb Sophora flavescens, has a good anti-leukemia effect, but its key target and mechanism remains unclear. Here, we found that only c-Myc could respond rapidly to matrine treatment in three myeloid leukemia cell lines, and matrine inhibited both transcription and translation of c-Myc. Ribosome biogenesis and nucleotide metabolism, the key downstream of c-Myc, were significantly suppressed after matrine treatment. Therefore, our results confirmed that matrine is a special c-Myc inhibitor which suppresses ribosome biogenesis and nucleotide metabolism by inhibiting c-Myc in myeloid leukemia. This study provides scientific basis for the development of matrine derivatives to c-Myc-driven cancers.

Genetic Basis of Dilated Cardiomyopathy in Dogs and Its Potential as a Bidirectional Model

Simple Summary

Heart disease is a leading cause of death for both humans and dogs. Inherited heart diseases, including dilated cardiomyopathy (DCM), account for a proportion of these cases. Human and canine patients with DCM suffer from an enlarged heart that can no longer pump efficiently, resulting in heart failure. This causes symptoms or clinical signs like difficulty breathing, irregular heartbeat, and eventually death. The symptoms or clinical signs of this disease vary in age of onset at the beginning of symptoms, sex predisposition, and overall disease progression. Despite the many similarities in DCM in both species, only a few candidate genes so far have been linked to this disease in dogs versus tens of genes identified in human DCM. Additionally, the use of induced pluripotent stem cells, or engineered stem cells, has been widely used in the study of human genetic heart disease but has not yet been fully adapted to study heart disease in dogs. This review describes the current knowledge on the genetics and subtypes of naturally occurring DCM in dogs, and how advances in research might benefit the dog but also the human patient. Additionally, a novel method using canine engineered stem cells to uncover unknown contributions of mistakes in DNA to the progression of DCM will be introduced along with its applications for human DCM disease modeling and treatment.

Abstract

Cardiac disease is a leading cause of death for both humans and dogs. Genetic cardiomyopathies, including dilated cardiomyopathy (DCM), account for a proportion of these cases in both species. Patients may suffer from ventricular enlargement and systolic dysfunction resulting in congestive heart failure and ventricular arrhythmias with high risk for sudden cardiac death. Although canine DCM has similar disease progression and subtypes as in humans, only a few candidate genes have been found to be associated with DCM while the genetic background of human DCM has been more thoroughly studied. Additionally, experimental disease models using induced pluripotent stem cells have been widely adopted in the study of human genetic cardiomyopathy but have not yet been fully adapted for the in-depth study of canine genetic cardiomyopathies. The clinical presentation of DCM is extremely heterogeneous for both species with differences occurring based on sex predisposition, age of onset, and the rate of disease progression. Both genetic predisposition and environmental factors play a role in disease development which are identical in dogs and humans in contrast to other experimental animals. Interestingly, different dog breeds have been shown to develop distinct DCM phenotypes, and this presents a unique opportunity for modeling as there are multiple breed-specific models for DCM with less genetic variance than human DCM. A better understanding of DCM in dogs has the potential for improved selection for breeding and could lead to better overall care and treatment for human and canine DCM patients. At the same time, progress in research made for human DCM can have a positive impact on the care given to dogs affected by DCM. Therefore, this review will analyze the feasibility of canines as a naturally occurring bidirectional disease model for DCM in both species. The histopathology of the myocardium in canine DCM will be evaluated in three different breeds compared to control tissue, and the known genetics that contributes to both canine and human DCM will be summarized. Lastly, the prospect of canine iPSCs as a novel method to uncover the contributions of genetic variants to the pathogenesis of canine DCM will be introduced along with the applications for disease modeling and treatment.

MYC: a multipurpose oncogene with prognostic and therapeutic implications in blood malignancies

MYC oncogene is a transcription factor with a wide array of functions affecting cellular activities such as cell cycle, apoptosis, DNA damage response, and hematopoiesis. Due to the multi-functionality of MYC, its expression is regulated at multiple levels. Deregulation of this oncogene can give rise to a variety of cancers. In this review, MYC regulation and the mechanisms by which MYC adjusts cellular functions and its implication in hematologic malignancies are summarized. Further, we also discuss potential inhibitors of MYC that could be beneficial for treating hematologic malignancies.

Methionine restriction breaks obligatory coupling of cell proliferation and death by an oncogene Src in Drosophila

Oncogenes often promote cell death as well as proliferation. How oncogenes drive these diametrically opposed phenomena remains to be solved. A key question is whether cell death occurs as a response to aberrant proliferation signals or through a proliferation-independent mechanism. Here, we reveal that Src, the first identified oncogene, simultaneously drives cell proliferation and death in an obligatorily coupled manner through parallel MAPK pathways. The two MAPK pathways diverge from a lynchpin protein Slpr. A MAPK p38 drives proliferation whereas another MAPK JNK drives apoptosis independently of proliferation signals. Src-p38-induced proliferation is regulated by methionine-mediated Tor signaling. Reduction of dietary methionine uncouples the obligatory coupling of cell proliferation and death, suppressing tumorigenesis and tumor-induced lethality. Our findings provide an insight into how cells evolved to have a fail-safe mechanism that thwarts tumorigenesis by the oncogene Src. We also exemplify a diet-based approach to circumvent oncogenesis by exploiting the fail-safe mechanism.

Cadmium sulfate induces apoptosis in planarians

With rapid socio-economic development, heavy metal pollution in water has become common and affects both environment and human health. Cadmium (Cd) has been recognized as one of the heavy metals which cause acute or chronic toxic effects if ingested. Although its toxicity is undisputed, the underlying molecular mechanisms in vivo are not fully understood. Planarians, a model organism famous for their regenerative prowess, have long been utilized to study the effects of chemical exposure. In this study, we observed apoptosis with TUNEL assay in planarians induced by cadmium sulfate (CdSO₄) in a dose-dependent manner. The apoptosis-related genes were detected with quantitative RT-PCR. Significant changes in c-Myc, P53, and BcL-2 were indicated, which may play a partial role in the regulation of the process of apoptosis in the planarians. H&E staining showed that Cd had obvious biological toxicity in the planarians. Here, new insights on metal toxicity mechanisms are provided, contributing to understand how CdSO₄ induces the pathological and physiological processes of apoptosis in the living bodies. Meanwhile, planarians are proved to be a freshwater pollution indicator and toxicological research model.

Optimized Approaches for the Induction of Putative Canine Induced Pluripotent Stem Cells from Old Fibroblasts Using Synthetic RNAs

Simple Summary

A non-integrating and self-replicating Venezuelan equine encephalitis RNA replicon system can potentially make a great contribution to the generation of clinically applicable canine induced pluripotent stem cells. Our study shows a new method to utilize the synthetic RNA-based approach for canine somatic cell reprogramming regarding transfection and reprogramming efficiency.

Abstract

Canine induced pluripotent stem cells (ciPSCs) can provide great potential for regenerative veterinary medicine. Several reports have described the generation of canine somatic cell-derived iPSCs; however, none have described the canine somatic cell reprogramming using a non-integrating and self-replicating RNA transfection method. The purpose of this study was to investigate the optimal strategy using this approach and characterize the transition stage of ciPSCs. In this study, fibroblasts obtained from a 13-year-old dog were reprogrammed using a non-integrating Venezuelan equine encephalitis (VEE) RNA virus replicon, which has four reprogramming factors (collectively referred to as T7-VEE-OKS-iG and comprised of hOct4, hKlf4, hSox2, and hGlis1) and co-transfected with the T7-VEE-OKS-iG RNA and B18R mRNA for 4 h. One day after the final transfection, the cells were selected with puromycin (0.5 µg/mL) until day 10. After about 25 days, putative ciPSC colonies were identified showing TRA-1-60 expression and alkaline phosphatase activity. To determine the optimal culture conditions, the basic fibroblast growth factor in the culture medium was replaced with a modified medium supplemented with murine leukemia inhibitory factor (mLIF) and two kinase inhibitors (2i), PD0325901(MEK1/2 inhibitor) and CHIR99021 (GSK3β inhibitor). The derived colonies showed resemblance to naïve iPSCs in their morphology (dome-shaped) and are dependent on mLIF and 2i condition to maintain an undifferentiated phenotype. The expression of endogenous pluripotency markers such as Oct4, Nanog, and Rex1 transcripts were confirmed, suggesting that induced ciPSCs were in the late intermediate stage of reprogramming. In conclusion, the non-integrating and self-replicating VEE RNA replicon system can potentially make a great contribution to the generation of clinically applicable ciPSCs, and the findings of this study suggest a new method to utilize the VEE RNA approach for canine somatic cell reprogramming.

Syntheses and Evaluation of New Bisacridine Derivatives for Dual Binding of G-Quadruplex and i-Motif in Regulating Oncogene c-myc Expression

The c-myc oncogene is an important regulator for cell growth and differentiation, and its aberrant overexpression is closely related to the occurrence and development of various cancers. Thus, the suppression of c-myc transcription and expression has been investigated for cancer treatment. In this study, various new bisacridine derivatives were synthesized and evaluated for their binding with c-myc promoter G-quadruplex and i-motif. We found that a9 could bind to and stabilize both G-quadruplex and i-motif, resulting in the downregulation of c-myc gene transcription. a9 could inhibit cancer cell proliferation and induce SiHa cell apoptosis and cycle arrest. a9 exhibited tumor growth inhibition activity in a SiHa xenograft tumor model, which might be related to its binding with c-myc promoter G-quadruplex and i-motif. Our results suggested that a9 as a dual G-quadruplex/i-motif binder could be effective in both oncogene replication and transcription and become a promising lead compound for further development with improved potency and selectivity.

MYC Participates in Lipopolysaccharide-Induced Sepsis via Promoting Cell Proliferation and Inhibiting Apoptosis

OBJECTIVE

This study aimed to explore the potential mechanism of MYC proto-oncogene, BHLH Transcription Factor (MYC) gene, on sepsis.

MATERIALS AND METHODS

In this experimental study, rat-derived H9C2 cardiomyocyte cells were cultured in vitro, followed by lipopolysaccharide (LPS) treatment with different concentration gradients. The cholecystokinin octapeptide (CCK-8) assay, enzyme-linked immunoassay (ELISA) assay, quantitative reverse transcription polymerase chain reaction (qRT-PCR), cell transfection, Western blot and flow cytometry were used to observe the cellular apoptosis and proliferation of cells in both treated LPS groups and normal control group.

RESULTS

The result of CCK-8 assay showed that silencing MYC inhibited cellular proliferation of sepsis in absence or presence of LPS treatment. ELISA assay showed that the expressions of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were decreased in MYC silenced group, but they were increased after LPS treatment. Moreover, Flow cytometry assay showed that MYC silencing contributed to the apoptosis of sepsis cells. Furthermore, the expression of inflammatory factors showed that MYC silencing elevated the expression of inflammation factors.

CONCLUSION

MYC might take part in the process of LPS induced sepsis through suppressing apoptosis and inducing cell proliferation. Moreover, MYC might reduce inflammation during the progression of LPS induced sepsis.

Role of Anillin in Tumour: From a Prognostic Biomarker to a Novel Target

Anillin (ANLN), an actin-binding protein, reportedly plays a vital role in cell proliferation and migration, particularly in cytokinesis. Although there have been findings pointing to a contribution of ANLN to the development of cancer, the association of ANLN to cancer remains not fully understood. Here, we gather evidence to determine the applicability of ANLN as a prognostic tool for some types of cancer, and the impact that ANLN has on the hallmarks of cancer. We searched academic repositories including PubMed and Google Scholar to find and review studies related to cancer and ANLN. The conclusion is that ANLN could be a potent target for cancer treatment, but the roles ANLN, other than in cytokinesis and its influence on tumour microenvironment remodeling in cancer development, must be further elucidated, and specific ANLN inhibitors should be found.

MicroRNA-141-5p Acts as a Tumor Suppressor via Targeting RAB32 in Chronic Myeloid Leukemia

MicroRNA-141-5p (miR-141-5p), an important member of the miR-200 family, has been reported to be involved in cellular proliferation, migration, invasion, and drug resistance in different kinds of human malignant tumors. However, the role and function of miR-141-5p in chronic myeloid leukemia (CML) are unclear. In this current study, we found that the level of miR-141-5p was significantly decreased in peripheral blood cells from CML patients compared with normal blood cells and human leukemic cell line (K562 cells) compared with normal CD34⁺ cells, but was remarkably elevated in patients after treatment with nilotinib or imatinib. Suppression of miR-141-5p promoted K562 cell proliferation and migration in vitro. As expected, overexpression of miR-141-5p weakened K562 cell proliferation, migration, and promoted cell apoptosis. A xenograft model in nude mice showed that overexpression of miR-141-5p markedly suppressed tumor growth in vivo. Mechanistic studies suggested that RAB32 was the potential target of miR-141-5p, and silencing of RAB32 suppressed the proliferation and migration of K562 cells and promoted cell apoptosis. Taken together, our study demonstrates that miR-141-5p plays an important role in the activation of K562 cells in vitro and may act as a tumor suppressor via targeting RAB32 in the development of CML.

Dual regulation of lin28a by Myc is necessary during zebrafish retina regeneration

Cellular reprogramming leading to induction of Muller glia-derived progenitor cells (MGPCs) with stem cell characteristics is essential for zebrafish retina regeneration. Although several regeneration-specific genes are characterized, the significance of MGPC-associated Mycb induction remains unknown. Here, we show that early expression of Mycb induces expression of genes like ascl1a, a known activator of lin28a in MGPCs. Notably, mycb is simultaneously activated by Ascl1a and repressed by Insm1a in regenerating retina. Here, we unravel a dual role of Mycb in lin28a expression, both as an activator through Ascl1a in MGPCs and a repressor in combination with Hdac1 in neighboring cells. Myc inhibition reduces the number of MGPCs and abolishes normal regeneration. Myc in collaboration with Hdac1 inhibits her4.1, an effector of Delta-Notch signaling. Further, we also show the repressive role of Delta-Notch signaling on lin28a expression in post-injured retina. Our studies reveal mechanistic understanding of Myc pathway during zebrafish retina regeneration, which could pave way for therapeutic intervention during mammalian retina regeneration.

Sirtuin-4 (SIRT4), a therapeutic target with oncogenic and tumor-suppressive activity in cancer

Several members of the sirtuin (SIRT) family, a highly conserved family of NAD⁺-dependent enzymes, have been shown to play a critical role in both promoting and/or suppressing tumorigenesis. In this study, recent progress in the field concerning SIRT4 and cancer was reviewed, and the relationship between SIRT4 and tumors was investigated. Subsequently, we evaluated the role of SIRT4 with oncogenic or tumor-suppressive activity in cancer, which may provide insight in identifying the underlying mechanism of action of SIRT4 in cancer. Finally, we explored the potential of SIRT4 as a therapeutic target in cancer therapy.

Circular RNA PVT1 expression and its roles in acute lymphoblastic leukemia

AIM

The roles of circular RNA PVT1 (circPVT1) are explored in the patients with acute lymphoblastic leukemia (ALL).

METHODS

The circPVT1 level was detected by qRT-PCR and western blot. The apoptotic cells were examined by the annexin V assay in lentiviral shRNA knockdown cells.

RESULTS

circPVT1 was highly expressed in ALL compared with normal bone marrow samples. circPVT1 expression was also significantly higher in ALL cell lines. circPVT1 knockdown inhibited cell proliferation and induced cell apoptosis through suppression of its neighbor gene c-Myc, and antiapoptotic Bcl-2 protein expression.

CONCLUSION

circPVT1 is upregulated in ALL. Silencing circPVT1 results in cell growth arrest and apoptosis of the cells. Our results also suggested a therapeutic potential of targeting circPVT1 in ALL.

Oxidative stress-mediated p53/p21WAF1/CIP1 pathway may be involved in microcystin-LR-induced cytotoxicity in HepG2 cells

A previous study showed that microcystin-LR (MC-LR) exerted cytotoxicity and induced apoptosis in HepG2 cells. In the present study, we investigated whether oxidative stress-mediated p53/p21^WAF1/CIP1 is involved in this process to further elucidate the mechanism of cytotoxicity induced by MC-LR. Morphological evaluation showed that MC-LR induced time- and dose-dependent cytotoxicity in HepG2 cells. Biochemical assays revealed that MC-LR exposure altered the protein levels of HSP70 and HSP90, generally inhibited superoxide dismutase and catalase, reduced glutathione content, and increased the cellular malondialdehyde level of HepG2 cells, suggesting that MC-LR may induce biochemical disturbance and oxidative stress in HepG2 cells. The protein levels of p-p53 and p21 were markedly increased by MC-LR exposure in a concentration-dependent manner, suggesting that p53 and p21 may be involved in the process. Moreover, we also found that the proto-oncogene c-myc was significantly activated in HepG2 cells following MC-LR exposure, indicating that c-myc in HepG2 cells was potentially involved in response to MC-LR-induced apoptosis. These findings may contribute to further understanding the in vitro molecular mechanism of MC-LR hepatotoxicity.

C-Myc functions as a competing endogenous RNA in acute promyelocytic leukemia

Recent reports have described a new post-transcriptional regulation that RNA transcripts can crosstalk with each other by competing for their common microRNAs. These RNA transcripts termed competing endogenous RNAs (ceRNAs) regulate the distribution of miRNAs on their targets. One corollary from ceRNA interaction is that chromosomal translocation in acute promyelocytic leukemia (APL) would perturb ceRNA regulation due to altered expression of 3'UTRs. In our study, we demonstrate that expression of PML/RARα, the APL-associated fusion oncogene is repressed by c-Myc mRNA transcript independent of protein-coding function but dependent upon microRNA. Attenuation of c-Myc transcript results in PML/RARα-degraded cellular phenotypes in APL cells, but these Myc reduction-associated cell phenotypes are sufficient to abrogate in a microRNA dependent manner. We also show that let-7 microRNA family members promote differentiation of All-Trans-Retinoic Acid (ATRA)-induced NB4 cells and their activities are affected by expression levels of both c-Myc and PML/RARα through altering miRNA targets. These results indicate that c-Myc mRNA represses PML/RARα expression via altering the distribution of let-7 miRNAs on their targets. Our findings reveal a previously unrecognized role of c-Myc as a potential ceRNA for PML/RARα in APL.

Differentially expressed proteins in the human esophageal cancer cell line Eca‑109, in the presence and absence of gemcitabine

The present study aimed to screen and study the roles of differentially expressed proteins in the human esophageal cancer cell line Eca‑109, in the presence and absence of gemcitabine (GEM). The 3‑(4,5)‑dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) method was used to assay the vitality of the Eca‑109 cells following treatment with GEM (1‑16 µg/ml). The cell apoptosis was measured by using fluorescence activated cell sorting. The proteins in the treated Eca‑109 cells were extracted, validated, and assayed via two‑dimensional gel electrophoresis combined with matrix‑assisted laser desorption/ionization time of flight mass spectrometry (MALDI‑TOF‑MS). The differentially expressed proteins were then determined by western blotting. Furthermore, alterations in mitochondrial ultrastructure of the treated cells were observed under a transmission electron microscope. GEM significantly inhibited the growth of the Eca‑109 cells in a concentration‑ and time‑dependent manner, and the 50% inhibition concentration (IC50) value was 3.87 µg/ml. The MALDI‑TOF‑MS analysis revealed that there were three differentially expressed proteins following the GEM treatment, compared with the control. The differential proteins were verified to be B cell lymphoma‑2 associated X, apoptosis regulator (Bax)‑α, apoptosis‑associated speck‑like protein containing a CARD (ASC) and myeloid cell leukemia sequence (Mcl)‑1. Western blotting revealed that the expression levels of ASC and Bax‑α proteins in the treated cancer cells were significantly upregulated, whereas the Mcl‑1 protein expression was markedly downregulated compared with the control. Furthermore, the GEM treatment destroyed the mitochondrial ultrastructure of the cancer cells, leaving swelled mitochondria, a fading matrix and destroyed the mitochondrial cristae. GEM significantly inhibits the growth and promotes apoptosis of the Eca‑109 cells, due to the alterations in the expression levels of the differential proteins, including ASC, Mcl‑1 and Bax‑α.

Resveratrol controlled the fate of porcine pancreatic stem cells through the Wnt/β-catenin signaling pathway mediated by Sirt1

Porcine pancreatic stem cells (PSCs) are considered promising transplant materials that may be used to treat diabetes, but some problems, such as insufficient cell number and low differentiation efficiency, should be solved before its clinical application. Resveratrol is a natural polyphenolic compound that can alleviate the complications of diabetes. In this study, we aimed to explore the specific effect of resveratrol on porcine PSCs. We treated porcine PSCs with 10 μM, 25 μM resveratrol to explore the effect of resveratrol on porcine PSCs. We found that 10 μM resveratrol improved the proliferation of porcine PSCs, increased the expression of A-β-catenin (active β-catenin), Pcna, C-Myc, Bcl-2 and sirtuin-1 (Sirt1), and decreased the expression of P53, Caspase3. While 25 μM resveratrol had almost opposite effect compared with 10 μM resveratrol group. The utilization of Dickkopf-related protein 1 (DKK1, Wnt signaling pathway inhibitor) and nicotinamide (Sirt1 inhibitor) suggested that resveratrol regulated cell proliferation by controlling Wnt signaling pathway and this effect was mediated by Sirt1. Our results further revealed that 10 μM resveratrol promoted the formation of β-like cells regulated by Wnt/β-catenin signal pathway. Relatively low-dose resveratrol could improve porcine PSCs fate. It lays theoretical foundation for diabetes treatment with cell transplantation in future.

Stepping out of the shadows: Oncogenic and tumor-promoting protein tyrosine phosphatases

Protein tyrosine phosphorylation is critical for proper function of cells and organisms. Phosphorylation is regulated by the concerted but generically opposing activities of tyrosine kinases (PTKs) and tyrosine phosphatases (PTPs), which ensure its proper regulation, reversibility, and ability to respond to changing physiological situations. Historically, PTKs have been associated mainly with oncogenic and pro-tumorigenic activities, leading to the generalization that protein dephosphorylation is anti-oncogenic and hence that PTPs are tumor-suppressors. In many cases PTPs do suppress tumorigenesis. However, a growing body of evidence indicates that PTPs act as dominant oncogenes and drive cell transformation in a number of contexts, while in others PTPs support transformation that is driven by other oncogenes. This review summarizes the known transforming and tumor-promoting activities of the classical, tyrosine specific PTPs and highlights their potential as drug targets for cancer therapy.

Design, Synthesis, and Evaluation of New Selective NM23-H2 Binders as c-MYC Transcription Inhibitors via Disruption of the NM23-H2/G-Quadruplex Interaction

c-MYC is one of the important human proto-oncogenes, and transcriptional factor NM23-H2 can activate c-MYC transcription by recognizing the G-quadruplex in the promoter of the gene. Small molecules that inhibit c-MYC transcription by disrupting the NM23-H2/G-quadruplex interaction might be a promising strategy for developing selective anticancer agents. In recent studies, we developed a series of isaindigotone derivatives, which can bind to G-quadruplex and NM23-H2, thus down-regulating c-MYC ( J. Med. Chem. 2017 , 60 , 1292 - 1308 ). Herein, a series of novel isaindigotone derivatives were designed, synthesized, and screened for NM23-H2 selective binding ligands. Among them, compound 37 showed a high specific binding affinity to NM23-H2, effectively disrupting the interaction of NM23-H2 with G-quadruplex, and it strongly down-regulated c-MYC transcription. Furthermore, 37 induced cell cycle arrest and apoptosis, and it exhibited good tumor growth inhibition in a mouse xenograft model. This work provides a new strategy to modulate c-MYC transcription for the development of selective anticancer drugs.

Colorectal Cancer Stem Cells Acquire Chemoresistance Through the Upregulation of F-Box/WD Repeat-Containing Protein 7 and the Consequent Degradation of c-Myc

The cancer stem cell (CSC) paradigm suggests that tumors are organized hierarchically. Chugai previously established an LGR5⁺ human colorectal cancer (CRC) stem-cell-enriched cell line (colorectal CSCs) that expresses well-accepted colorectal CSC markers and that can dynamically switch between proliferative and drug-resistant noncycling states. We performed this study to elucidate the molecular mechanisms responsible for evading cell death in colorectal CSCs mediated by anticancer agents. During the cell cycle arrest caused by anticancer agents, we found that c-Myc expression was substantially decreased in colorectal CSCs. The c-Myc expression alterations were mediated by upregulation of F-box/WD repeat-containing protein 7 (FBXW7), as evidenced through FBXW7-small interfering RNA knockdown experiments that resulted in enhanced cell sensitivity to anticancer agents. Upregulation of FBXW7 following drug treatment was not evident in commercially available cancer cell lines. Colorectal CSCs were induced to differentiation by Matrigel and fetal bovine serum. Differentiated CSCs treated with anticancer agents did not show upregulation of FBXW7 and were more sensitive to irinotecan (CPT-11), highlighting the potential CSC-specific nature of our data. The FBXW7 over-expression was further validated in resected liver metastatic sites in CRC patients after chemotherapy. In conclusion, our study revealed that a CSC-specific FBXW7-regulatory mechanism is strongly associated with resistance to chemotherapeutic agents. Inhibition of FBXW7-upregulation in CSCs following chemotherapy may enhance the response to anticancer agents and represents an attractive strategy for the elimination of colorectal CSCs. Stem Cells 2017;35:2027-2036.

New Disubstituted Quindoline Derivatives Inhibiting Burkitt's Lymphoma Cell Proliferation by Impeding c-MYC Transcription

The c-MYC oncogene is overactivated during Burkitt's lymphoma pathogenesis. Targeting c-MYC to inhibit its transcriptional activity has emerged as an effective anticancer strategy. We synthesized four series of disubstituted quindoline derivatives by introducing the second cationic amino side chain and 5-N-methyl group based on a previous study of SYUIQ-5 (1) as c-MYC promoter G-quadruplex ligands. The in vitro evaluations showed that all new compounds exhibited higher stabilities and binding affinities, and most of them had better selectivity (over duplex DNA) for the c-MYC G-quadruplex compared to 1. Moreover, the new ligands prevented NM23-H2, a transcription factor, from effectively binding to the c-MYC G-quadruplex. Further studies showed that the selected ligand, 7a4, down-regulated c-MYC transcription by targeting promoter G-quadruplex and disrupting the NM23-H2/c-MYC interaction in RAJI cells. 7a4 could inhibit Burkitt's lymphoma cell proliferation through cell cycle arrest and apoptosis and suppress tumor growth in a human Burkitt's lymphoma xenograft.

New Approaches To the Understanding of the Molecular Basis of Oral Cancer

Cancers of the oral cavity, salivary glands, larynx, and pharynx, collectively referred to as squamous cell carcinomas of the head and neck (HNSCC), are the sixth most common cancer among men in the developed world. The prognosis of HNSCC patients is still poor, which reflects the fact that although the risk factors for HNSCC are well-recognized, very little is known about the molecular mechanisms responsible for this malignancy. This review describes some of the current efforts and technological advances that have focused on the creation of a complete information infrastructure for genes expressed during squamous cell carcinogenesis. These include: the recently described HNSCC-specific chromosomal alterations (cCAP); the Head and Neck Cancer Genome Anatomy Project (HN-CGAP), whose goal is the systematic identification and cataloguing of known and novel genes expressed during tumor development; and the use of laser-capture microdissection (LCM), which is pivotal for the comprehensive molecular characterization of normal, pre-cancerous, and malignant cells by means of DNA-array technology. The latter provides the means for the analysis of expression patterns of thousands of genes simultaneously. The use of LCM for proteomics and DNA analysis is also included in this review. These revolutionary approaches are likely to have an unprecedented impact on cancer biology, and provide exciting opportunities to unravel the still-unknown mechanisms involved in squamous cell carcinogenesis. They are also expected to provide a molecular blueprint for HNSCC, thus helping to identify suitable markers for the early detection of pre-neoplastic lesions, as well as novel targets for pharmacological intervention in this disease.

Therapeutic aspects of c-MYC signaling in inflammatory and cancerous colonic diseases

Colonic inflammation is required to heal infections, wounds, and maintain tissue homeostasis. As the seventh hallmark of cancer, however, it may affect all phases of tumor development, including tumor initiation, promotion, invasion and metastatic dissemination, and also evasion immune surveillance. Inflammation acts as a cellular stressor and may trigger DNA damage or genetic instability, and, further, chronic inflammation can provoke genetic mutations and epigenetic mechanisms that promote malignant cell transformation. Both sporadical and colitis-associated colorectal carcinogenesis are multi-step, complex processes arising from the uncontrolled proliferation and spreading of malignantly transformed cell clones with the obvious ability to evade the host’s protective immunity. In cells upon DNA damage several proto-oncogenes, including c-MYC are activated in parelell with the inactivation of tumor suppressor genes. The target genes of the c-MYC protein participate in different cellular functions, including cell cycle, survival, protein synthesis, cell adhesion, and micro-RNA expression. The transcriptional program regulated by c-MYC is context dependent, therefore the final cellular response to elevated c-MYC levels may range from increased proliferation to augmented apoptosis. Considering physiological intestinal homeostasis, c-MYC displays a fundamental role in the regulation of cell proliferation and crypt cell number. However, c-MYC gene is frequently deregulated in inflammation, and overexpressed in both sporadic and colitis-associated colon adenocarcinomas. Recent results demonstrated that endogenous c-MYC is essential for efficient induction of p53-dependent apoptosis following DNA damage, but c-MYC function is also involved in and regulated by autophagy-related mechanisms, while its expression is affected by DNA-methylation, or histone acetylation. Molecules directly targeting c-MYC, or agents acting on other genes involved in the c-MYC pathway could be selected for combined regiments. However, due to its context-dependent cellular function, it is clinically essential to consider which cytotoxic drugs are used in combination with c-MYC targeted agents in various tissues. Increasing our knowledge about MYC-dependent pathways might provide direction to novel anti-inflammatory and colorectal cancer therapies.

The Hsp90 inhibitor SNX-7081 is synergistic with fludarabine nucleoside via DNA damage and repair mechanisms in human, p53-negative chronic lymphocytic leukemia

Clinical trials of heat shock protein 90 (Hsp90) inhibitors have been limited by high toxicity. We previously showed that the Hsp90 inhibitor, SNX-7081, synergizes with and restores sensitivity to fludarabine nucleoside (2-FaraA) in human chronic lymphocytic leukemia (CLL) cells with lesions in the p53 pathway (Best OG, et al., Leukemia Lymphoma 53:1367-75, 2012). Here, we used label-free quantitative shotgun proteomics and comprehensive bioinformatic analysis to determine the mechanism of this synergy. We propose that 2-FaraA-induced DNA damage is compounded by SNX-7081-mediated inhibition of DNA repair, resulting in enhanced induction of apoptosis. DNA damage responses are impaired in part due to reductions in checkpoint regulators BRCA1 and cyclin D1, and cell death is triggered following reductions of MYC and nucleolin and an accumulation of apoptosis-inducing NFkB2 p100 subunit. Loss of nucleolin can activate Fas-mediated apoptosis, leading to the increase of pro-apoptotic proteins (BID, fas-associated factor-2) and subsequent apoptosis of p53-negative, 2-FaraA refractory CLL cells. A significant induction of DNA damage, indicated by increases in DNA damage marker γH2AX, was observed following the dual drug treatment of additional cell lines, indicating that a similar mechanism may operate in other p53-mutated human B-lymphoid cancers. These results provide valuable insight into the synergistic mechanism between SNX-7081 and 2-FaraA that may provide an alternative treatment for CLL patients with p53 mutations, for whom therapeutic options are currently limited. Moreover, this drug combination reduces the effective dose of the Hsp90 inhibitor and may therefore alleviate any toxicity encountered.

Involvement of c-Myc in the proliferation of MCF-7 human breast cancer cells induced by bHLH transcription factor DEC2

Differentiated embryonic chondrocyte expressed gene 1 (DEC1; BHLHE40/Stra13/Sharp2) and differentiated embryonic chondrocyte expressed gene 2 (DEC2; BHLHE41/Sharp1) are basic helix-loop-helix (bHLH) transcriptional factors that are involved in the regulation of cell differentiation, circadian rhythms, response to hypoxia and carcinogenesis. Previous studies have demonstrated that the expression of DECs is induced under hypoxic conditions in various normal and cancer cell lines. In the present study, using RT-qPCR and western blot analysis, we demonstrated that hypoxia induced the expression of DEC1 and DEC2 in MCF-7 human breast cancer cells; their expression levels reached a peak at different time points. In particular, we found that the expression pattern of the hypoxia-inducible factor (HIF)-1α protein was similar to DEC1, and that of the HIF-2α protein was identical to that of DEC2. The knockdown of HIF-2α using siRNA suppressed the phosphorylation of Akt, as well as the expression of DEC2 and c-Myc. Hypoxia failed to affect the expression of DEC2 and c-Myc when the PI3K/Akt signaling pathway was blocked. In addition, the overexpression of DEC1 and DEC2 was induced by transfecting the cells with a pcDNA vector. The overexpression of DEC2, but not that of DEC1, increased the proliferation of the MCF-7 cells under both normoxic and hypoxic conditions. Concomitantly, the expression of c-Myc was upregulated by exposure to hypoxia and by the overexpression of DEC2. In conclusion, DEC2 participates in hypoxia-induced cell proliferation by functioning as a target gene of the PI3K/Akt signaling pathway and regulating the expression of c-Myc.

AKT and MET signalling mediates antiapoptotic radioresistance in head neck cancer cell lines

OBJECTIVES

Induction of apoptosis is a major mechanism of radiosensitivity in different types of cancer. In contrast, EGFR/PI3K/AKT signalling and recently the presence of so-called cancer stem cells are discussed as reasons for radioresistance.

MATERIALS AND METHODS

The study investigates mechanisms of apoptosis, key oncogenes of the PI3K/AKT pathway and the presence of cancer cells with stem cell properties during irradiation in two cell lines (PCI-9A, and PCI-15) of head and neck squamous cell carcinoma. WST-1-tests, qRT-PCR, western blots and FACS analysis were performed for analysis.

RESULTS

The two cell lines presented different degrees of cell death upon irradiation. The radiosensitive cell line PCI-9A showed increased apoptosis after irradiation measured by expressed cleaved caspases 3 and 7 while the radioresistant cell line PCI-15 upregulated antiapoptotic Survivin and BCL2A1 mRNA. Besides, increased PI3K/AKT- and ERK1/2-signalling was associated with radioresistance accompanied by loss of PTEN function through phosphorylation on S380. Blockade of pAKT increased radiation-induced cell death, and moreover, led to an upregulation of pMET in the radioresistant cell line. The percentage of ALDH-positive tumour cells was markedly decreased after irradiation in the radiosensitive cell line.

CONCLUSIONS

Functional apoptosis is mandatory for sensitivity to irradiation in head neck cancer cells. Upregulation of the AKT-pathway seems to be one reason for poor radioresponse. Activated MET may also predict radioresistance, possibly through ERK1/2 signalling. Moreover MET may indicate the presence of cancer stem cells facilitating radioresistance as shown by increased ALDH expression.

Regenerative medicine for the heart: perspectives on stem-cell therapy

SIGNIFICANCE

Despite decades of progress in cardiovascular biology and medicine, heart disease remains the leading cause of death, and there is no cure for the failing heart. Since heart failure is mostly caused by loss or dysfunction of cardiomyocytes (CMs), replacing dead or damaged CMs with new CMs might be an ideal way to reverse the disease. However, the adult heart is composed mainly of terminally differentiated CMs that have no significant self-regeneration capacity.

RECENT ADVANCES

Stem cells have tremendous regenerative potential and, thus, current cardiac regenerative research has focused on developing stem cell sources to repair damaged myocardium.

CRITICAL ISSUES

In this review, we examine the potential sources of cells that could be used for heart therapies, including embryonic stem cells and induced pluripotent stem cells, as well as alternative methods for activating the endogenous regenerative mechanisms of the heart via transdifferentiation and cell reprogramming. We also discuss the current state of knowledge of cell purification, delivery, and retention.

FUTURE DIRECTIONS

Efforts are underway to improve the current stem cell strategies and methodologies, which will accelerate the development of innovative stem-cell therapies for heart regeneration.

Apoptosis induced by desmethyl-lasiodiplodin is associated with upregulation of apoptotic genes and downregulation of monocyte chemotactic protein-3

There is growing interest in the discovery of bioactive metabolites from endophytes as an alternative source of therapeutics. Identification of their therapeutic targets is essential in understanding the underlying mechanisms and enhancing the resultant therapeutic effects. As such, bioactive compounds produced by endophytic fungi from plants at the National Park, Pahang, Malaysia, were investigated. Five known compounds were identified using LC-UV-MS-NMR and they include trichodermol, 7-epi-brefeldin A, (3R,4S)-4-hydroxymellein, desmethyl-lasiodiplodin and cytochalasin D. The present study went on to investigate the potential anticancer effects of these compounds and the corresponding molecular mechanisms of the lead compound against human breast adenocarcinoma, MCF-7. For the preliminary screening, the cytotoxicity and apoptotic effects of these compounds against MCF-7 were examined. The compounds were also tested against noncarcinogenic hepatocytes (WRL68). The differential cytotoxicity was then determined using the MTT assay. Desmethyl-lasiodiplodin was found to suppress the growth of MCF-7, yielding an inhibitory concentration (IC50) that was seven-fold lower than that of the normal cells. The cytotoxic effect of desmethyl-lasiodiplodin was accompanied by apoptosis. Subsequent analysis demonstrated increased expression levels of caspase 3, c-myc and p53. Further, desmethyl-lasiodiplodin resulted in inhibition of monocyte chemotactic protein (MCP)-3, a cytokine involved in cell survival and metastasis. Hence, this study proposed that desmethyl-lasiodiplodin inhibited growth and survival of MCF-7 through the induction of apoptosis. This anticancer effect is mediated, in part, by upregulation of apoptotic genes and downregulation of MCP-3. As desmethyl-lasiodiplodin elicited minimal impact against normal hepatocytes, our findings also imply its potential use as a specific apoptotic agent in breast cancer treatment.

Transient Plasmacytosis With Trisomy of Chromosome 8 in a Patient With Multiple Myeloma: A Case Report

A 96-year-old woman with a 5-year history of multiple myeloma was admitted to our hospital because of increasing fatigue and fever. Bone marrow plasma cell analysis showed t(11;14), del(13q), and del(17p13). Her condition deteriorated, and she developed plasmacytosis resembling plasma cell leukemia. Chromosome analysis showed trisomy of chromosome 8 in the circulating plasma cells. The plasmacytosis resolved spontaneously without chemotherapy after about 5 weeks, and the trisomy became undetectable. The findings suggest that trisomy 8 might have contributed to the transient plasmacytosis, and that chromosome 8 carries genes associated with plasma cell proliferation, maturation, and apoptosis.

Optimization of oncogene expression through intra-population competition

Although functional roles have been assigned to many genes, e.g. those involved in cell-cycle regulation, growth signaling, or cancer, considerably less is known about the quantitative relationship between gene expression levels and outcome. We devised an intra-population competition to study oncogene dosage. Cell populations were engineered to express a range of H-Ras oncogene levels. Cells with different levels of H-Ras then "competed" for an increased share of the total cell population. Using flow cytometry to track the population composition over time, we determined the relationship between the different H-Ras oncogene expression levels and the net proliferation rate. Under culture conditions in which wild-type Ras activation was suppressed, we found that increased and maximal net proliferation occurred when the H-Ras G12V oncogene was expressed at a level 1.2-fold that of wild-type Ras. As the H-Ras G12V expression levels increased above this optimal level, proliferation rates decreased. Our findings suggest that the tumor evolution process may optimize gene expression levels for maximal cell proliferation. In principle, engineered intra-population competitions can be used to determine proliferation rates associated with the level of any ectopically expressed gene. The approach also may be used to determine proliferation rates associated with different cell species in a heterogeneous population or to improve the proliferation rate of a cell line. We also envision that the tracking of intra-population competitions could be utilized to investigate the evolution of tumors in the body.

The co-repressor SMRT delays DNA damage-induced caspase activation by repressing pro-apoptotic genes and modulating the dynamics of checkpoint kinase 2 activation

Checkpoint kinase 2 (Chk2) is a major regulator of DNA damage response and can induce alternative cellular responses: cell cycle arrest and DNA repair or programmed cell death. Here, we report the identification of a new role of Chk2 in transcriptional regulation that also contributes to modulating the balance between survival and apoptosis following DNA damage. We found that Chk2 interacts with members of the NCoR/SMRT transcriptional co-regulator complexes and serves as a functional component of the repressor complex, being required for recruitment of SMRT on the promoter of pro-apoptotic genes upon DNA damage. Thus, the co-repressor SMRT exerts a critical protective action against genotoxic stress-induced caspase activation, repressing a functionally important cohort of pro-apoptotic genes. Amongst them, SMRT is responsible for basal repression of Wip1, a phosphatase that de-phosphorylates and inactivates Chk2, thus affecting a feedback loop responsible for licensing the correct timing of Chk2 activation and the proper execution of the DNA repair process.

Cohesin is required for activation of MYC by estradiol

Cohesin is best known as a multi-subunit protein complex that holds together replicated sister chromatids from S phase until G2. Cohesin also has an important role in the regulation of gene expression. We previously demonstrated that the cohesin complex positively regulates expression of the oncogene MYC. Cell proliferation driven by MYC contributes to many cancers, including breast cancer. The MYC oncogene is estrogen-responsive and a transcriptional target of estrogen receptor alpha (ERα). Estrogen-induced cohesin binding sites coincide with ERα binding at the MYC locus, raising the possibility that cohesin and ERα combine actions to regulate MYC transcription. The objective of this study was to investigate a putative role for cohesin in estrogen induction of MYC expression. We found that siRNA-targeted depletion of a cohesin subunit, RAD21, decreased MYC expression in ER-positive (MCF7 and T47D) and ER-negative (MDA-MB-231) breast cancer cell lines. In addition, RAD21 depletion blocked estradiol-mediated activation of MYC in ER-positive cell lines, and decreased ERα binding to estrogen response elements (EREs) upstream of MYC, without affecting total ERα levels. Treatment of MCF7 cells with estradiol caused enrichment of RAD21 binding at upstream enhancers and at the P2 promoter of MYC. Enriched binding at all sites, except the P2 promoter, was dependent on ERα. Since RAD21 depletion did not affect transcription driven by an exogenous reporter construct containing a naked ERE, chromatin-based mechanisms are likely to be involved in cohesin-dependent MYC transcription. This study demonstrates that ERα activation of MYC can be modulated by cohesin. Together, these results demonstrate a novel role for cohesin in estrogen-mediated regulation of MYC and the first evidence that cohesin plays a role in ERα binding.

Enhanced liver tumor promotion but not liver initiation activity in rats subjected to combined administration of omeprazole and β-naphthoflavone

Omeprazole (OPZ) and β-naphthoflavone (BNF) are cytochrome P450 (CYP)1A inducers and have liver tumor promoting effects. In this study, we investigated the co-promoting and co-initiating effects of OPZ and BNF in rats. In Experiment 1, male rats were subjected to partial hepatectomy (PH), and given oral doses of 138 or 276 mg/kg OPZ, 0.125% or 0.25% BNF or 138 mg/kg OPZ+0.125% BNF (n = 9~12) for 6 weeks after N-diethylnitrosamine (DEN) initiation. In Experiment 2, male rats were treated with oral doses of 138 or 276 mg/kg OPZ, 0.03% or 0.06% BNF or 138 mg/kg OPZ+0.03% BNF (n = 11~12) for 9 days starting 1 week before initiating treatment. As an initiating treatment, 2-Amino-3,4-dimethylimidazo[4,5-f]quinolone (MeIQx) was orally administered 12 hr after PH. The rats were fed a basal diet for 15 days, followed by a diet containing 0.015% 2-acetylaminofluorene for the next 10 days with a single oral dose of carbon tetrachloride. In Experiment 1, the number and area of glutathione S-transferase placental form-positive foci in the OPZ+BNF group were significantly higher than the average values of the High OPZ or the High BNF group. The expression of cyclooxygenase-2 (Cox-2) and COX-2 protein in the liver significantly increased in the OPZ+BNF group. In Experiment 2, liver initiation activity was not enhanced by the co-administration of OPZ+BNF. The results of our studies suggest that the co-administration of OPZ and BNF results in synergistic effects in the liver tumor promotion probably owing to increased COX-2 expression, but no modifying effect in the liver initiation activity of MeIQx in rats.

Baicalin induces apoptosis in SW620 human colorectal carcinoma cells in vitro and suppresses tumor growth in vivo

In the United States, colorectal cancer (CRC) is the second most frequent malignancy and the fourth most common cause of cancer death. Baicalin, a flavone derivative isolated and purified from the dry root of Scutellaria, was assessed for its antitumor effects in human SW620 CRC cells. Baicalin (200 μM) inhibited proliferation of SW620 cells. Baicalin (200 μM) increased activities of caspase-3, -8, and -9 in SW620 cells. Furthermore, flow cytometric analysis of baicalin-treated SW620 cells showed an increase in sub-G1 cells, and the dihydroethidium assay showed significant enhancement of intracellular peroxide production in baicalin-treated cells. Addition of N-acetylcysteine prevented most of the baicalin-induced apoptosis, which in turn mediated cytotoxicity in human SW620 cells. In vivo, baicalin (50 mg/kg/day, i.p.) treatment inhibited 55% of tumor growth in xenografted nude mice by 4 weeks, compared to that of the vehicle control (p < 0.05). Baicalin had no noteworthy influence on body weight. Thus, we suggest the development of baicalin as a potential leading antitumor agent in CRC.

In vitro and in vivo anti-tumour activities of echinoside A and ds-echinoside A from Pearsonothuria graeffei

BACKGROUND

Echinoside A (EA) and ds-echinoside A (DSEA) are triterpene glycosides isolated from the sea cucumber Pearsonothuria graeffei. DSEA, the desulfurisation product of EA, has the following structure: β-D-xylopyranosyl-holost-8(9),11(12)-diene-3β,17α-diol. In the present study, we examined the anti-tumour activities-in particular, the structure-activity relationships-of EA and DSEA in vitro and in vivo.

RESULTS

Both EA and DSEA exhibited an inhibitory effect on cell proliferation, along with apoptosis-inducing activity, in HepG2 cells. Moreover, they significantly arrested the cell cycle in the G₀/G₁ phase. A reverse transcriptase-polymerase chain reaction assay revealed that EA and DSEA significantly increased the expression of the cell-cycle-related genes, namely, p16, p21 and c-myc, and decreased that of cyclin D₁. Western blotting analysis demonstrated that they down-regulated the expression of Bcl-2, and enhanced mitochondria cytochrome c release, caspase-3 activation, and poly(adenosine diphosphate ribose) polymerase, cleavage. Nuclear factor kappa B (NF-κB) expression was significantly decreased by DSEA, but was unaffected by EA. EA and DSEA (2.5 mg kg⁻¹) treatment of mice bearing H22 hepatocarcinoma tumours reduced the tumour weight by 49.8% and 55.0%, respectively.

CONCLUSION

EA and DSEA exhibit marked anti-cancer activity in HepG2 cells, by blocking cell-cycle progression and inducing apoptosis through the mitochondrial pathway. DSEA-induced apoptosis was more potent than EA-induced apoptosis. Furthermore, the two triterpene glycosides derived from P. graeffei may induce apoptosis of HepG2 cells in an NF-κB-dependent or NF-κB-independent manner, depending on their structure.

Stable transfection of CHO cells with the c-myc gene results in increased proliferation rates, reduces serum dependency, and induces anchorage independence

Induction of the transcription factor Myc promotes cell proliferation and transformation by activating growth-promoting genes and/or by transcriptionally repressing the expression of growth arrest genes. However, a number of studies have shown that c-Myc is a potent inducer of apoptosis in the absence of serum or growth factors. To further examine the role of Myc in cell growth and proliferation, and the advantages of this positive regulator in cell culture we transfected the CHO-K1 cell line with a human c-myc gene driven by MMLV 5'-LTR promoter. Over-expression of ectopic c-Myc resulted in a significant increase in growth rate and maximum cell number, in both suspension and attached batch culture accompanied by a similar decrease in specific glucose consumption rate. Interestingly, there was no manifestation of the widely reported apoptotic death by c-myc in the absence of serum. Additionally, over-expression of c-Myc appeared to induce morphological transformation and partial anchorage-independence.

Down-regulation of Thanatos-associated protein 11 by BCR-ABL promotes CML cell proliferation through c-Myc expression

Bcr-Abl activates various signaling pathways in chronic myelogenous leukemia (CML) cells. The proliferation of Bcr-Abl transformed cells is promoted by c-Myc through the activation of Akt, JAK2 and NF-κB. However, the mechanism by which c-Myc regulates CML cell proliferation is unclear. In our study, we investigated the role of Thanatos-associated protein 11 (THAP11), which inhibits c-Myc transcription, in CML cell lines and in hematopoietic progenitor cells derived from CML patients. The induction of THAP11 expression by Abl kinase inhibitors in CML cell lines and in CML-derived hematopoietic progenitor cells resulted in the suppression of c-Myc. In addition, over-expression of THAP11 inhibited CML cell proliferation. In colony forming cells derived from CML-aldehyde dehydrogenase (ALDH)(hi) /CD34(+) cells, treatment with Abl kinase inhibitors and siRNA depletion of Bcr-Abl induced THAP11 expression and reduced c-Myc expression, resulting in inhibited colony formation. Moreover, overexpression of THAP11 significantly decreased the colony numbers, and also inhibited the expression of c-myc target genes such as Cyclin D1, ODC and induced the expression of p21(Cip1) . The depletion of THAP11 inhibited JAK2 or STAT5 inactivation-mediated c-Myc reduction in ALDH(hi) /CD34(+) CML cells. Thus, the induced THAP11 might be one of transcriptional regulators of c-Myc expression in CML cell. Therefore, the induction of THAP11 has a potential possibility as a target for the inhibition of CML cell proliferation.

Mediterranean mussel gene expression profile induced by okadaic acid exposure

Seasonal seawater temperature increases define optimal growth conditions for Dinoflagellate species which can reach high concentrations in water column and also in filter-feeding organisms like Mytilus galloprovincialis. Commonly produced by Dinophysis and Prorocentrum spp., okadaic acid (OA) and its analogues are responsible for the Diarrheic Shellfish Poisoning (DSP) syndrome in humans. Closure of shellfishing grounds is therefore recommended by the EU when DSP toxin levels in shellfish exceed 16 μg OA 100 g(-1) flesh. Despite not being responsible for casualties either in humans or mussels, DSP outbreaks are considered natural events causing health and economic issues due to the frequency of their occurrence. Since gene expression studies offer a wide range of different solutions, we used a mussel cDNA microarray to evaluate gene expression changes in the digestive gland of mussels fed for five weeks with OA-contaminated nutrient. Among the differentially expressed genes we observed a general up-regulation of transcripts coding for stress proteins, proteins involved in cellular synthesis, and a few not annotated proteins. Overall, at the first time point analyzed we identified 58 candidate transcripts for OA-induced stress in mussels, half of which have unknown function. In this paper we present the first gene expression analysis performed on Mediterranean mussels exposed to okadaic acid. The characterization of these transcripts could be useful for the identification of an early physiological response to OA exposure.

The impact of C-MYC gene expression on gastric cancer cell

The upregulation or mutation of C-MYC has been observed in gastric, colon, breast, and lung tumors and in Burkitt's lymphoma. However, little is known about the role C-MYC plays in gastric adenocarcinoma. In the present study, we intended to investigate the influence of C-MYC on the growth, proliferation, apoptosis, invasion, and cell cycle of the gastric cancer cell line SGC7901 and the gastric cell line HFE145. C-MYC cDNA was subcloned into a constitutive vector PCDNA3.1 followed by transfection in normal gastric cell line HFE145 by using liposome. Then stable transfectants were selected and appraised. Specific inhibition of C-MYC was achieved using a vector-based siRNA system which was transfected in gastric cancer cell line SGC7901. The apoptosis and cell cycles of these clones were analyzed by using flow cytometric assay. The growth and proliferation were analyzed by cell growth curves and colony-forming assay, respectively. The invasion of these clones was analyzed by using cell migration assay. The C-MYC stable expression clones (HFE-Myc) and C-MYC RNAi cells (SGC-MR) were detected and compared with their control groups, respectively. HFE-Myc grew faster than HFE145 and HFE-PC (HFE145 transfected with PCDNA3.1 vector). SGC-MR1, 2 grew slower than SGC7901 and SGC-MS1, 2 (SGC7901 transfected with scrambled control duplexes). The cell counts of HFE-Myc in the third, fourth, fifth, sixth, and seventh days were significantly more than those of control groups (P < 0.05). Those of SGC-MR1, 2 in the fourth, fifth, sixth, and seventh days were significantly fewer than those of control groups (P < 0.05). Cell cycle analysis showed that proportions of HFE-Myc and SGC-MR cells in G0-G1 and G2-M were different significantly with their control groups, respectively (P < 0.05). The apoptosis rate of HFE-Myc was significantly higher than those of control groups (P < 0.05). Results of colony-forming assay showed that the colony formation rate of HFE-Myc was higher than those of control groups; otherwise, the rate of SGC-MR was lower than those of their control groups (P < 0.05). The results of cell migration assay showed that there were no significant differences between experimental groups and control groups (P > 0.05). In conclusion, C-MYC can promote the growth and proliferation of normal gastric cells, and knockdown of C-MYC can restrain the growth and proliferation of gastric cancer cells. It can induce cell apoptosis and help tumor cell maintain malignant phenotype. But it can have not a detectable influence on the ability of invasion of gastric cancer cells.

Prevalence of c-myc expression in breast lesions associated with microcalcifications detected by routine mammography

CONTEXT AND OBJECTIVE

Genetic abnormalities in cell proliferation-regulating genes have been described in premalignant lesions. The aims here were to evaluate c-myc protein expression in non-palpable breast lesions associated with microcalcifications, detected by screening mammography, and to compare these results with histopathological, clinical and epidemiological variables.

DESIGN AND SETTING

Analytical cross-sectional study, with retrospective data collection, in a university hospital in São Paulo.

METHODS

Seventy-nine female patients who underwent routine mammography between 1998 and 2004 were studied. Lesions classified by the Breast Imaging Reporting and Data System (BI-RADS) as 4 or 5 underwent percutaneous biopsy using a large-core needle. Ninety-eight lesions were studied anatomopathologically. Paraffin blocks properly representing the lesions were selected for immunohistochemical analyses using the streptavidin-biotin-peroxidase technique with monoclonal mouse c-myc antibodies.

RESULTS

Among the 98 lesions, 29 (29.6%) contained malignant neoplasia; 40 (40.8%) had a positive immunohistochemical reaction for c-myc. When the groups were divided between lesions without atypias versus atypical lesions plus malignant lesions, 31.03% of the 58 lesions without atypias were positive for c-myc and 55% of the 40 malignant and atypical lesions (P = 0.018). Comparing the atypical lesions with ductal carcinoma in situ versus the benign lesions without atypias, c-myc was present in 51.61% of the 31 atypical lesions and 31.03% of the benign lesions without atypias (P = 0.057).

CONCLUSION

C-myc protein was more frequently expressed in atypical and malignant lesions than in benign lesions without atypias. C-myc expression correlated with the presence of atypias (P = 0.018).

Differentially expressed genes in eutopic and ectopic endometrium of women with endometriosis

OBJECTIVE

To elucidate the potential mechanisms involved in the physiopathology of endometriosis. We analyzed the differential gene expression profiles of eutopic and ectopic tissues from women with endometriosis.

DESIGN

Prospective laboratory study.

SETTING

University hospital.

PATIENT(S)

Seventeen patients in whom endometriosis was diagnosed and 11 healthy fertile women.

INTERVENTION(S)

Endometrial biopsy specimens from the endometrium of healthy women without endometriosis and from the eutopic and ectopic endometrium tissues of patients with endometriosis were obtained in the early proliferative phase of the menstrual cycle.

MAIN OUTCOME MEASURE(S)

Six paired samples of eutopic and ectopic tissue were analyzed by subtractive hybridization. To evaluate the expression of genes found by rapid subtraction hybridization methods, we measured CTGF, SPARC, MYC, MMP, and IGFBP1 genes by real-time polymerase chain reaction in all samples.

RESULT(S)

This study identified 291 deregulated genes in the endometriotic lesions. Significant expression differences were obtained for SPARC, MYC, and IGFBP1 in the peritoneal lesions and for MMP3 in the ovarian endometriomas. Additionally, significant differences were obtained for SPARC and IGFBP1 between the peritoneal and ovarian lesions. No significant differences were found for the studied genes between the control and the eutopic endometrium.

CONCLUSION(S)

This study identified 291 genes with differential expression in endometriotic lesions. The deregulation of the SPARC, MYC, MMP3, and IGFBPI genes may be responsible for the loss of cellular homeostasis in endometriotic lesions.

Metastases suppressor NM23-H2 interaction with G-quadruplex DNA within c-MYC promoter nuclease hypersensitive element induces c-MYC expression

Regulatory influence of the G-quadruplex or G4 motif present within the nuclease hypersensitive element (NHE) in the promoter of c-MYC has been noted. On the other hand, association of NM23-H2 to the NHE leads to c-MYC activation. Therefore, NM23-H2 interaction with the G4 motif within the c-MYC NHE presents an interesting mechanistic possibility. Herein, using luciferase reporter assay and chromatin immunoprecipitation we show NM23-H2 mediated c-MYC activation involves NM23-H2-G4 motif binding within the c-MYC NHE. G4 motif complex formation with recombinant NM23-H2 was independently confirmed using fluorescence energy transfer, which also indicated that the G4 motif was resolved to an unfolded state within the protein-bound complex. Taken together, this supports transcriptional role of NM23-H2 via a G4 motif.

Apoptotic signaling by c-MYC

c-MYC has a pivotal function in growth control, differentiation and apoptosis, and its abnormal expression is associated with many tumors. Overexpression of c-MYC sensitizes cells to apoptosis by a variety of stimuli. The decision of a cell to undergo apoptosis and how this apoptotic response is regulated by c-MYC depends on the specific cell type and the physiological status of the cell. Multiple cooperating molecular pathways of cell survival and apoptosis determine whether a cell lives or dies, and understanding how c-MYC interfaces with these pathways to influence the survival of cells is important to understand normal and abnormal development, tumor initiation and progression, and response of tumors to different treatment regimens. This article will provide an overview of the function of the tumor suppressor gene product p53 in the c-MYC-mediated apoptotic response and how c-MYC amplifies the intrinsic mitochondrial pathway and triggers and/or amplifies the death receptor pathways. Finally, a model for how deregulated c-MYC prematurely triggers the normal apoptotic response associated with terminal myeloid differentiation while also blocking the differentiation program is presented.

Noncanonical DNA motifs as transactivation targets by wild type and mutant p53

Sequence-specific binding by the human p53 master regulator is critical to its tumor suppressor activity in response to environmental stresses. p53 binds as a tetramer to two decameric half-sites separated by 0–13 nucleotides (nt), originally defined by the consensus RRRCWWGYYY (n = 0–13) RRRCWWGYYY. To better understand the role of sequence, organization, and level of p53 on transactivation at target response elements (REs) by wild type (WT) and mutant p53, we deconstructed the functional p53 canonical consensus sequence using budding yeast and human cell systems. Contrary to early reports on binding in vitro, small increases in distance between decamer half-sites greatly reduces p53 transactivation, as demonstrated for the natural TIGER RE. This was confirmed with human cell extracts using a newly developed, semi–in vitro microsphere binding assay. These results contrast with the synergistic increase in transactivation from a pair of weak, full-site REs in the MDM2 promoter that are separated by an evolutionary conserved 17 bp spacer. Surprisingly, there can be substantial transactivation at noncanonical ½-(a single decamer) and ¾-sites, some of which were originally classified as biologically relevant canonical consensus sequences including PIDD and Apaf-1. p53 family members p63 and p73 yielded similar results. Efficient transactivation from noncanonical elements requires tetrameric p53, and the presence of the carboxy terminal, non-specific DNA binding domain enhanced transactivation from noncanonical sequences. Our findings demonstrate that RE sequence, organization, and level of p53 can strongly impact p53-mediated transactivation, thereby changing the view of what constitutes a functional p53 target. Importantly, inclusion of ½- and ¾-site REs greatly expands the p53 master regulatory network.

Within human cells, the tumor suppressor p53 is the central node of regulation required to elicit multiple biological responses that include cell cycle arrest and death in response to stress or DNA damage, where mutations in p53 are a hallmark of cancer. As a master regulatory gene, p53 controls the action of target genes within its network by directly interacting with a widely accepted consensus DNA binding sequence, composed of two decamer ½-sites that can be separated by up to 13 bases. While mismatches from consensus sequence are frequent, the canonical consensus sequence places a limitation upon the organization and number of target genes within the p53 transcriptional network. Using yeast and human cell systems, our goal was to further understand how the DNA sequence, DNA organization, and level of p53 expression might influence the inclusion of genes within the p53 regulatory network. We found that increases in spacer beyond a few bases greatly reduce responsiveness to p53. Importantly, we established that p53 can function from noncanonical sequences comprising only a decamer ½-site or a ¾-site. These findings further define and expand the universe of potential downstream target genes which may be regulated by p53 and bring further diversity into the p53 regulatory network.