B cell translocation gene 2 enhances susceptibility of HeLa cells to doxorubicin-induced oxidative damage

Doxorubicin induces phosphorylation of lamin A/C and loss of nuclear membrane integrity: A novel mechanism of cardiotoxicity

Lamin A/C, essential inner nuclear membrane proteins, have been linked to progeria, a disease of accelerated aging, and many other diseases, which include cardiac disorder. Lamin A/C mutation and its phosphorylation are associated with altering nuclear shape and size. The role of lamin A/C in regulating normal cardiac function was reported earlier. In the present study, we hypothesized that Doxorubicin (Dox) may alter total lamin A/C expression and phosphorylation, thereby taking part in cardiac injury. An in vitro cellular injury model was generated with Dox (0.1-10.0 μM) treatment on cardiomyoblast cells (H9c2) to prove our hypothesis. Increased size and irregular (ameboid) nucleus shape were observed in H9c2 cells after Dox treatment. Similarly, we have observed a significant increase in cell death on increasing the Dox concentration. The expression of lamin A/C and its phosphorylation at serine 22 significantly decreased and increased, respectively in H9c2 cells and rat hearts after Dox exposure. Phosphorylation led to depolymerization of the lamin A/C in the inner nuclear membrane and was evidenced by their presence throughout the nucleoplasm as observed by immunocytochemistry techniques. Thinning and perforation on the walls of the nuclear membrane were observed in Dox-treated H9c2 cells. LMNA-overexpression in H9c2 protected the cells from Dox-induced cell death, reversing all changes described above. Further, improvement of lamin A/C levels was observed in Dox-treated H9c2 cells when treated with Purvalanol A, a CDK1 inhibitor and N-acetylcysteine, an antioxidant. The study provides new insight regarding Dox-induced cardiac injury with the involvement of lamin A/C and alteration of inner nuclear membrane structure.

The molecular mechanisms of peptidyl-prolyl cis/trans isomerase Pin1 and its relevance to kidney disease

Pin1 is a member of the peptidyl-prolyl cis/trans isomerase subfamily and is widely expressed in various cell types and tissues. Alterations in Pin1 expression levels play pivotal roles in both physiological processes and multiple pathological conditions, especially in the onset and progression of kidney diseases. Herein, we present an overview of the role of Pin1 in the regulation of fibrosis, oxidative stress, and autophagy. It plays a significant role in various kidney diseases including Renal I/R injury, chronic kidney disease with secondary hyperparathyroidism, diabetic nephropathy, renal fibrosis, and renal cell carcinoma. The representative therapeutic agent Juglone has emerged as a potential treatment for inhibiting Pin1 activity and mitigating kidney disease. Understanding the role of Pin1 in kidney diseases is expected to provide new insights into innovative therapeutic interventions and strategies. Consequently, this review delves into the molecular mechanisms of Pin1 and its relevance in kidney disease, paving the way for novel therapeutic approaches.

MicroRNA-409-3p/BTG2 signaling axis improves impaired angiogenesis and wound healing in obese mice

Wound healing is facilitated by neoangiogenesis, a complex process that is essential to tissue repair in response to injury. MicroRNAs are small, noncoding RNAs that can regulate the wound healing process including stimulation of impaired angiogenesis that is associated with type-2 diabetes (T2D). Expression of miR-409-3p was significantly increased in the nonhealing skin wounds of patients with T2D compared to the non-wounded normal skin, and in the skin of a murine model with T2D. In response to high glucose, neutralization of miR-409-3p markedly improved EC growth and migration in human umbilical vein endothelial cells (HUVECs), promoted wound closure and angiogenesis as measured by increased CD31 in human skin organoids, while overexpression attenuated EC angiogenic responses. Bulk mRNA-Seq transcriptomic profiling revealed BTG2 as a target of miR-409-3p, where overexpression of miR-409-3p significantly decreased BTG2 mRNA and protein expression. A 3' untranslated region (3'-UTR) luciferase assay of BTG2 revealed decreased luciferase activity with overexpression of miR-409-3p, while inhibition had opposite effects. Mechanistically, in response to high glucose, miR-409-3p deficiency in ECs resulted in increased mTOR phosphorylation, meanwhile BTG-anti-proliferation factor 2 (BTG2) silencing significantly decreased mTOR phosphorylation. Endothelial-specific and tamoxifen-inducible miR-409-3p knockout mice (MiR-409IndECKO ) with hyperglycemia that underwent dorsal skin wounding showed significant improvement of wound closure, increased blood flow, granulation tissue thickness (GTT), and CD31 that correlated with increased BTG2 expression. Taken together, our results show that miR-409-3p is a critical mediator of impaired angiogenesis in diabetic skin wound healing.

Dual LSD1 and HDAC6 Inhibition Induces Doxorubicin Sensitivity in Acute Myeloid Leukemia Cells

Defects in epigenetic pathways are key drivers of oncogenic cell proliferation. We developed a LSD1/HDAC6 multitargeting inhibitor (iDual), a hydroxamic acid analogue of the clinical candidate LSD1 inhibitor GSK2879552. iDual inhibits both targets with IC₅₀ values of 540, 110, and 290 nM, respectively, against LSD1, HDAC6, and HDAC8. We compared its activity to structurally similar control probes that act by HDAC or LSD1 inhibition alone, as well as an inactive null compound. iDual inhibited the growth of leukemia cell lines at a higher level than GSK2879552 with micromolar IC₅₀ values. Dual engagement with LSD1 and HDAC6 was supported by dose dependent increases in substrate levels, biomarkers, and cellular thermal shift assay. Both histone methylation and acetylation of tubulin were increased, while acetylated histone levels were only mildly affected, indicating selectivity for HDAC6. Downstream gene expression (CD11b, CD86, p21) was also elevated in response to iDual treatment. Remarkably, iDual synergized with doxorubicin, triggering significant levels of apoptosis with a sublethal concentration of the drug. While mechanistic studies did not reveal changes in DNA repair or drug efflux pathways, the expression of AGPAT9, ALOX5, BTG1, HIPK2, IFI44L, and LRP1, previously implicated in doxorubicin sensitivity, was significantly elevated.

BTG2 Serves as a Potential Prognostic Marker and Correlates with Immune Infiltration in Lung Adenocarcinoma

Background

B-cell translocation gene 2 (BTG2) has been revealed to be involved in the occurrence and development of multiple cancers. However, the role of BTG2 in lung adenocarcinoma (LUAD) is still ambiguous. Thus, this study aims to investigate the prognostic value of BTG2 and its correlation with immune infiltration in LUAD.

Methods

The expression of BTG2 in LUAD was analyzed using the TIMER and UALCAN databases. The correlations between BTG2 expression and clinicopathological factors were investigated using the UALCAN databases. The Kaplan–Meier plotter, GEPIA, and TCGA databases were employed to assess the prognostic value of BTG2. The STRING database and Cytoscape software were used to construct an interaction network and mine co-expression genes. The TISIDB database was examined for a correlation between BTG2 and driver genes in LUAD. Enrichment analysis of co-expressed genes and BTG2 was performed using the LinkedOmics database. Finally, the correlations between BTG2 and immune infiltrates were investigated using the TIMER, GEO, and TISIDB database.

Results

BTG2 was significantly downregulated in LUAD. The decreased expression of BTG2 in LUAD was significantly correlated with higher cancer stages and shorter duration of overall survival. The expressions of BTG2-related co-expression genes were associated with the prognosis in LUAD. The expression of BTG2 was closely associated with the mutations of TP53 and ROS1. Enrichment analysis revealed that BTG2 was significantly correlated with immune‐associated signaling pathways and function. In addition, the expression of BTG2 was found to be closely related to immune infiltration, multiple gene markers of immune cells, chemokines, and chemokine receptors.

Conclusion

Our findings have effectively demonstrated that BTG2 expression was downregulated in LUAD, indicating poor prognosis. Closely relating to immune cell infiltration, BTG2 may be a promising immune-related biomarker and molecular target for patients with LUAD.

Deletion of B-cell translocation gene 2 (BTG2) alters the responses of glial cells in white matter to chronic cerebral hypoperfusion

BACKGROUND

Subcortical ischemic vascular dementia, one of the major subtypes of vascular dementia, is characterized by lacunar infarcts and white matter lesions caused by chronic cerebral hypoperfusion. In this study, we used a mouse model of bilateral common carotid artery stenosis (BCAS) to investigate the role of B-cell translocation gene 2 (BTG2), an antiproliferation gene, in the white matter glial response to chronic cerebral hypoperfusion.

METHODS

Btg2-/- mice and littermate wild-type control mice underwent BCAS or sham operation. Behavior phenotypes were assessed by open-field test and Morris water maze test. Brain tissues were analyzed for the degree of white matter lesions and glial changes. To further confirm the effects of Btg2 deletion on proliferation of glial cells in vitro, BrdU incorporation was investigated in mixed glial cells derived from wild-type and Btg2-/- mice.

RESULTS

Relative to wild-type mice with or without BCAS, BCAS-treated Btg2-/- mice exhibited elevated spontaneous locomotor activity and poorer spatial learning ability. Although the severities of white matter lesions did not significantly differ between wild-type and Btg2-/- mice after BCAS, the immunoreactivities of GFAP, a marker of astrocytes, and Mac2, a marker of activated microglia and macrophages, in the white matter of the optic tract were higher in BCAS-treated Btg2-/- mice than in BCAS-treated wild-type mice. The expression level of Gfap was also significantly elevated in BCAS-treated Btg2-/- mice. In vitro analysis showed that BrdU incorporation in mixed glial cells in response to inflammatory stimulation associated with cerebral hypoperfusion was higher in Btg2-/- mice than in wild-type mice.

CONCLUSION

BTG2 negatively regulates glial cell proliferation in response to cerebral hypoperfusion, resulting in behavioral changes.

Role of TNF-α-Inducing Protein Secreted by Helicobacter pylori as a Tumor Promoter in Gastric Cancer and Emerging Preventive Strategies

The tumor necrosis factor-α (TNF-α)-inducing protein (tipα) gene family, comprising Helicobacter pylori membrane protein 1 (hp-mp1) and tipα, has been identified as a tumor promoter, contributing to H. pylori carcinogenicity. Tipα is a unique H. pylori protein with no similarity to other pathogenicity factors, CagA, VacA, and urease. American H. pylori strains cause human gastric cancer, whereas African strains cause gastritis. The presence of Tipα in American and Euro-Asian strains suggests its involvement in human gastric cancer development. Tipα secreted from H. pylori stimulates gastric cancer development by inducing TNF-α, an endogenous tumor promoter, through its interaction with nucleolin, a Tipα receptor. This review covers the following topics: tumor-promoting activity of the Tipα family members HP-MP1 and Tipα, the mechanism underlying this activity of Tipα via binding to the cell-surface receptor, nucleolin, the crystal structure of rdel-Tipα and N-terminal truncated rTipα, inhibition of Tipα-associated gastric carcinogenesis by tumor suppressor B-cell translocation gene 2 (BTG2/TIS21), and new strategies to prevent and treat gastric cancer. Thus, Tipα contributes to the carcinogenicity of H. pylori by a mechanism that differs from those of CagA and VacA.

CDK9 Blockade Exploits Context-dependent Transcriptional Changes to Improve Activity and Limit Toxicity of Mithramycin for Ewing Sarcoma

There is a need to develop novel approaches to improve the balance between efficacy and toxicity for transcription factor-targeted therapies. In this study, we exploit context-dependent differences in RNA polymerase II processivity as an approach to improve the activity and limit the toxicity of the EWS-FLI1-targeted small molecule, mithramycin, for Ewing sarcoma. The clinical activity of mithramycin for Ewing sarcoma is limited by off-target liver toxicity that restricts the serum concentration to levels insufficient to inhibit EWS-FLI1. In this study, we perform an siRNA screen of the druggable genome followed by a matrix drug screen to identify mithramycin potentiators and a synergistic "class" effect with cyclin-dependent kinase 9 (CDK9) inhibitors. These CDK9 inhibitors enhanced the mithramycin-mediated suppression of the EWS-FLI1 transcriptional program leading to a shift in the IC₅₀ and striking regressions of Ewing sarcoma xenografts. To determine whether these compounds may also be liver protective, we performed a qPCR screen of all known liver toxicity genes in HepG2 cells to identify mithramycin-driven transcriptional changes that contribute to the liver toxicity. Mithramycin induces expression of the BTG2 gene in HepG2 but not Ewing sarcoma cells, which leads to a liver-specific accumulation of reactive oxygen species (ROS). siRNA silencing of BTG2 rescues the induction of ROS and the cytotoxicity of mithramycin in these cells. Furthermore, CDK9 inhibition blocked the induction of BTG2 to limit cytotoxicity in HepG2, but not Ewing sarcoma cells. These studies provide the basis for a synergistic and less toxic EWS-FLI1-targeted combination therapy for Ewing sarcoma.

Translational downregulation of Twist1 expression by antiproliferative gene, B-cell translocation gene 2, in the triple negative breast cancer cells

Twist1, a key transcription factor regulating epithelial–mesenchymal transition and cancer metastasis, is highly expressed in invasive cancers in contrast to the loss of BTG2^/TIS21 expression. Based on our observation that forced expression of BTG2^/TIS21 downregulated Twist1 protein expression without altering mRNA level, we investigated molecular mechanisms of the BTG2^/TIS21-inhibited Twist1 translation in the triple negative breast cancer (TNBC) cells and in vivo BTG2^/TIS21-knockout (KO) mice and human breast cancer tissues. (1) C-terminal domain of Twist1 and Box B of BTG2^/TIS21 interacted with each other, which abrogated Twist1 activity. (2) BTG2^/TIS21 inhibited translational initiation by depleting eIF4E availability via inhibiting 4EBP1 phosphorylation. (3) Expression of BTG2^/TIS21 maintained p-eIF2α that downregulates initiation of protein translation, confirmed by eIF2α-AA mutant expression and BTG2^/TIS21 knockdown in MEF cells. (4) cDNA microarray analysis revealed significantly higher expression of initiation factors-eIF2A, eIF3A, and eIF4G2-in the BTG2^/TIS21-KO mouse than that in the wild type. (5) BTG2^/TIS21-inhibited translation initiation lead to the collapse of polysome formation and the huge peak of 80s monomer in the BTG2^/TIS21 expresser, but not in the control. (6) mRNAs and protein expressions of elongation factors were also downregulated by BTG2^/TIS21 expression in TNBC cells, but much higher in both TIS21-KO mice and lymph node-positive human breast cancers. (7) BTG2^/TIS21-mediated Twist1 loss was not due to the protein degradation by ubiquitination and autophagy activation. (8) Twist1 protein level was significantly higher in various organs of TIS21-KO mice compared with that in the control, indicating the in vivo role of BTG2^/TIS21 gene in the regulation of Twist1 protein level. Altogether, the present study support our hypothesis that BTG2^/TIS21 is a promising target to combat with metastatic cancers with high level of Twist1 without BTG2^/TIS21 expression.

Identification of Casiopeina II-gly secondary targets through a systems pharmacology approach

Casiopeinas are a group of copper-based compounds designed to be used as less toxic, more efficient chemotherapeutic agents. In this study, we analyzed the in vitro effects of Casiopeina II-gly on the expression of canonical biological pathways. Using microarray data from HeLa cell lines treated with Casiopeina II-gly, we identified biological pathways that are perturbed after treatment. We present a novel approach integrating pathway analysis and network theory: The Pathway Crosstalk Network. We constructed a network with deregulated pathways, featuring links between those pathways that crosstalk with each other. We identified modules grouping deregulated pathways that are functionally related. Through this approach, we were able to identify three features of Casiopeina treatment: (a) Perturbation of signaling pathways, related to induction of apoptosis; (b) perturbation of metabolic pathways, and (c) activation of immune responses. These findings can be useful to drive new experimental exploration on their role in adverse effects and efficacy of Casiopeinas.

Tumor suppressors BTG1 and BTG2: Beyond growth control

Since the identification of B‐cell translocation gene 1 (BTG1) and BTG2 as antiproliferation genes more than two decades ago, their protein products have been implicated in a variety of cellular processes including cell division, DNA repair, transcriptional regulation and messenger RNA stability. In addition to affecting differentiation during development and in the adult, BTG proteins play an important role in maintaining homeostasis under conditions of cellular stress. Genomic profiling of B‐cell leukemia and lymphoma has put BTG1 and BTG2 in the spotlight, since both genes are frequently deleted or mutated in these malignancies, pointing towards a role as tumor suppressors. Moreover, in solid tumors, reduced expression of BTG1 or BTG2 is often correlated with malignant cell behavior and poor treatment outcome. Recent studies have uncovered novel roles for BTG1 and BTG2 in genotoxic and integrated stress responses, as well as during hematopoiesis. This review summarizes what is currently known about the roles of BTG1 and BTG2 in these and other cellular processes. In addition, we will highlight the molecular mechanisms and biological consequences of BTG1 and BTG2 deregulation during cancer progression and elaborate on the potential clinical implications of these findings.

Inhibition of TNFα-interacting protein α (Tipα)-associated gastric carcinogenesis by BTG2/TIS21 via downregulating cytoplasmic nucleolin expression

To understand the regulation of Helicobacter pylori (H. pylori)-associated gastric carcinogenesis, we examined the effect of B-cell translocation gene 2 (BTG2) expression on the biological activity of Tipα, an oncoprotein secreted from H. pylori. BTG2, the human ortholog of mouse TIS21 (BTG2/TIS21), has been reported to be a primary response gene that is transiently expressed in response to various stimulations. Here, we report that BTG2 is constitutively expressed in the mucous epithelium and parietal cells of the gastric gland in the stomach. Expression was increased in the mucous epithelium following H. pylori infection in contrast to its loss in human gastric adenocarcinoma. Indeed, adenoviral transduction of BTG2/TIS21 significantly inhibited Tipα activity in MKN-1 and MGT-40, human and mouse gastric cancer cells, respectively, thereby downregulating tumor necrosis factor-α (TNFα) expression and Erk1/2 phosphorylation by reducing expression of nucleolin, a Tipα receptor. Chromatin immunoprecipitation proved that BTG2/TIS21 inhibited Sp1 expression and its binding to the promoter of the nucleolin gene. In addition, BTG2/TIS21 expression significantly reduced membrane-localized nucleolin expression in cancer cells, and the loss of BTG2/TIS21 expression induced cytoplasmic nucleolin availability in gastric cancer tissues, as evidenced by immunoblotting and immunohistochemistry. Higher expression of BTG2 and lower expression of nucleolin were accompanied with better overall survival of poorly differentiated gastric cancer patients. This is the first report showing that BTG2/TIS21 inhibits nucleolin expression via Sp1 binding, which might be associated with the inhibition of H. pylori-induced carcinogenesis. We suggest that BTG2/TIS21 is a potential inhibitor of nucleolin in the cytoplasm, leading to inhibition of carcinogenesis after H. pylori infection.

Apoptosis during embryonic tissue remodeling is accompanied by cell senescence

This study re-examined the dying process in the interdigital tissue during the formation of free digits in the developing limbs. We demonstrated that the interdigital dying process was associated with cell senescence, as deduced by induction of β-gal activity, mitotic arrest, and transcriptional up-regulation of p21 together with many components of the senescence-associated secretory phenotype. We also found overlapping domains of expression of members of the Btg/Tob gene family of antiproliferative factors in the regressing interdigits. Notably, Btg2 was up-regulated during interdigit remodeling in species with free digits but not in the webbed foot of the duck. We also demonstrate that oxidative stress promoted the expression of Btg2, and that FGF2 and IGF1 which are survival signals for embryonic limb mesenchyme inhibited Btg2 expression. Btg2 overexpression in vivo and in vitro induced all the observed changes during interdigit regression, including oxidative stress, arrest of cell cycle progression, transcriptional regulation of senescence markers, and caspase-mediated apoptosis. Consistent with the central role of p21 on cell senescence, the transcriptional effects induced by overexpression of Btg2 are attenuated by silencing p21. Our findings indicate that cell senescence and apoptosis are complementary processes in the regression of embryonic tissues and share common regulatory signals.

Shifting p53-induced senescence to cell death by TIS21(/BTG2/Pc3) gene through posttranslational modification of p53 protein

Cellular senescence and apoptosis can be regulated by p53 activity, although the underlying mechanism of the switch between the two events remains largely unknown. Cells exposed to cancer chemotherapy can escape to senescence phenotype rather than undergoing apoptosis. By employing adenoviral transduction of p53 or TIS21 genes, we observed shifting of p53 induced-senescence to apoptosis in EJ bladder cancer cells, which express H-RasV12 and mutant p53; transduction of p53 increased H-RasV12 expression along with senescence phenotypes, whereas coexpression with TIS21 (p53+TIS21) induced cell death rather than senescence. The TIS21-mediated switch of senescence to apoptosis was accompanied by nuclear translocation of p53 protein and its modifications on Ser-15 and Ser-46 phosphorylation and acetylations on Lys-120, -320, -373 and -382 residues. Mechanistically, TIS21(/BTG2) regulated posttranslational modification of p53 via enhancing miR34a and Bax expressions as opposed to inhibiting SIRT1 and Bcl2 expression. At the same time, TIS21 increased APAF-1 and p53AIP1 expressions, but inhibited the interaction of p53 with iASPP. In vitro tumorigenicity was significantly reduced in the p53+TIS21 expresser through inhibiting micro-colony proliferation by TIS21. Effect of TIS21 on the regulation of p53 activity was confirmed by knockdown of TIS21 expression by RNA interference. Therefore, we suggest TIS21 expression as an endogenous cell death inducer at the downstream of p53 gene, which might be useful for intractable cancer chemotherapy.

Reduction of selenium-binding protein 1 sensitizes cancer cells to selenite via elevating extracellular glutathione: a novel mechanism of cancer-specific cytotoxicity of selenite

Selenium is an essential trace element and has been extensively studied for preventive effects on cancers. Recent emerging evidence has also shown that selenium at supranutritional dosage has a preferential cytotoxicity in cancer cells and chemotherapeutic drug-resistant cells, but the underlying mechanisms remain largely unknown. This study was to investigate the roles of two distinct representatives of selenium-containing proteins, selenium-binding protein 1 (SBP1) and glutathione peroxidase 1 (GPX1), in selenite-mediated cancer-specific cytotoxicity. We found that there was a significantly inverse correlation between SBP1 and GPX1 protein level in human breast cancers and adjacent matched nontumor tissues (Pearson r=-0.4347, P=0.0338). Ectopic expression of GPX1 enhanced selenite cytotoxicity through down-regulation of SBP1, and SBP1 was likely to be a crucial determinant for selenite-mediated cytotoxicity. Reduction of SBP1 in cancer cells and epirubicin-resistant cells on selenite exposure resulted in a dramatic increase in the generation of hydrogen peroxide and superoxide anion, which in turn caused oxidative stress and triggered apoptosis. Furthermore, knockdown SBP1 by small interfering RNA increased selenite sensitivity by elevating extracellular glutathione (GSH), which spontaneously reacted with selenite and led to the rapid depletion of selenium (IV) in growth medium and the high-affinity uptake of selenite. In conclusion, these findings would improve our understanding of the roles of selenium-containing proteins in selenite-mediated cytotoxicity, and revealed a potent mechanism of the selective cytotoxicity of selenite in cancer cells and drug-resistant cells, in which SBP1 was likely to play an important role in modulating the extracellular microenvironment by regulating the levels of extracellular GSH.

miR-25 modulates NSCLC cell radio-sensitivity through directly inhibiting BTG2 expression

A large proportion of the NSCLC patients were insensitive to radiotherapy, but the exact mechanism is still unclear. This study explored the role of miR-25 in regulating sensitivity of NSCLC cells to ionizing radiation (IR) and its downstream targets. Based on measurement in tumor samples from NSCLC patients, this study found that miR-25 expression is upregulated in both NSCLC and radio-resistant NSCLC patients compared the healthy and radio-sensitive controls. In addition, BTG expression was found negatively correlated with miR-25a expression in the both tissues and cells. By applying luciferase reporter assay, we verified two putative binding sites between miR-25 and BTG2. Therefore, BTG2 is a directly target of miR-25 in NSCLC cancer. By applying loss-and-gain function analysis in NSCLC cell lines, we demonstrated that miR-25-BTG2 axis could directly regulated BTG2 expression and affect radiotherapy sensitivity of NSCLC cells.

Accumulation of cytolytic CD8+ T cells in B16-melanoma and proliferation of mature T cells in TIS21-knockout mice after T cell receptor stimulation

In vivo and in vitro effects of TIS21 gene on the mature T cell activation and antitumor activities were explored by employing MO5 melanoma orthograft and splenocytes isolated from the TIS21-knockout (KO)(2) mice. Proliferation and survival of mature T cells were significantly increased in the KO than the wild type (WT3)e cells, indicating that TIS21 inhibits the rate of mature T cell proliferation and its survival. In MO5 melanoma orthograft model, the KO mice recruited much more CD8(+) T cells into the tumors at around day 14 after tumor cell injection along with reduced tumor volumes compared with the WT. The increased frequency of granzyme B+ CD8+ T cells in splenocytes of the KO mice compared with the WT may account for antitumor-immunity of TIS21 gene in the melanoma orthograft. In contrast, reduced frequencies of CD107a+ CD8+ T cells in the splenocytes of KO mice may affect the loss of CD8+ T cell infiltration in the orthograft at around day 19. These results indicate that TIS21 exhibits antiproliferative and proapoptotic effects in mature T cells, and differentially affects the frequencies of granzyme B+ CD8+ T-cells and CD107a+ CD8+ T-cells, thus transiently regulating in vivo anti-tumor immunity.

Protein methylation and interaction with the antiproliferative gene, BTG2/TIS21/Pc3

The last one and half a decade witnessed an outstanding re-emergence of attention and remarkable progress in the field of protein methylation. In the present article, we describe the early discoveries in research and review the role protein methylation played in the biological function of the antiproliferative gene, BTG2/TIS21/PC3.

B-cell translocation gene 2 mediates crosstalk between PI3K/Akt1 and NFκB pathways which enhances transcription of MnSOD by accelerating IκBα degradation in normal and cancer cells

BACKGROUND

B-cell translocation gene 2 (BTG2) belongs to antiproliferative (ARPO) gene family and the expression of BTG2, human ortholog of rat PC3 and mouse TIS21 gene, has been shown to render cancer cells more sensitive to doxorubicin treatment by upregulating MnSOD expression without regulating any other reactive oxygen species (ROS) scavenging enzymes.

RESULTS

In the present study, by employing exogenous and endogenous BTG2/TIS21/Pc3 expression by transfection and transduction analyses, and by knockdown of gene expression using RNA interference or using gene knockout cells, we observed that BTG2 increased the binding of activated NF-κB (p65/RelA) to the enhancer element of MnSOD gene in the 2nd intron, which was regulated by p-Akt1, and the induction of MnSOD by BTG2 was accompanied with subsequent downregulation of ROS level and cyclin B1 biosynthesis along with the increase of p21WAF1, resulting in the G2/M arrest independent of p53.

CONCLUSIONS

These results show for the first time that BTG2 mediates crosstalk between PI3K-Akt1 and NF-κB pathways, which regulates p53-independent induction of G2/M phase arrest both in normal and cancer cells.

Regulation of Btg2(/TIS21/PC3) expression via reactive oxygen species-protein kinase C-ΝFκΒ pathway under stress conditions

Human B-cell translocation gene 2 (BTG2), an ortholog of mouse TIS21 (12-O-tetradecanoyl phorbol-13-acetate inducible sequence 21) and rat PC3 (Pheochromocytoma Cell 3), is a tumor suppressor gene that belongs to an antiproliferative gene family. Btg2 is involved in a variety of biological processes including cell growth, development, differentiation, senescence, and cell death and its expression is strongly regulated by p53. Recently, we have reported transient induction of Btg2 expression in response to oxidative damage; however, the regulatory mechanism was not explored. In the present study we revealed ΝFκΒ as the upstream mediator involved in Btg2 transcription in response to cell stress challenges such as serum deprivation and oxidative stress i.e. H2O2, TPA or doxorubicin treatments in several cell lines. We observed close interrelation between generation of reactive oxygen species (ROS), enhanced IκBα degradation, nuclear translocation of ΝFκΒ (p65/RelA) and the significant increase of Btg2 expression independent of p53 status. ChIP analysis revealed an enrichment of RelA (p65) bound to the κB response element on Btg2 promoter in response to the cell stress challenges. Employing various inhibitors led to cytoplasmic accumulation of IκBα, decreased p65 nuclear translocation along with significant reduction of Btg2 expression. Generation of ROS was the common event mediating ΝFκΒ activation and Btg2 transcription. Furthermore, PKC activation was also found to be a critical factor mediating ROS-mediated signals to NFκB pathway that culminate on Btg2 regulation, and specifically PKC-δ was responsible for this regulation under oxidative stress. However, serum deprivation-associated ROS generation bypassed PKC activation for induction of Btg2 expression via NFκB activation. The present data imply that oxidative stress upregulates Btg2 expression via ROS-PKC-ΝFκΒ cascade, independent of p53 status that in turn could be involved in mediating various biological phenotypes depending on the cellular context.

Signals regulating necrosis of cardiomyoblast by BTG2(/TIS21/PC3) via activation of GSK3β and opening of mitochondrial permeability transition pore in response to H2O2

To investigate signal transduction pathway of cell death regulated by a tumor suppressor after oxidative stress, cardiomyoblasts were virally transfected with BTG2(/TIS21/PC3) (BTG2) and subsequently treated with H2O2. Heart muscle rarely expresses BTG2 unless oxidative stress occurs, however, ischemia induced BTG2 expression and necrosis, not apoptosis, of cardiomyoblasts. BTG2-expressioning cardiomyblasts showed impaired recoveries of survival kinases, Akt and Erk, thus sustaining GSK-3β activity in 30 min of H2O2 exposure, in contrast to their rapid recoveries in LacZ control. The phenomenon was accompanied by the failure of ATP regeneration and the sustained activation of AMPK in the BTG2 expresser. Furthermore, H2O2 treatment markedly induced BTG2 translocation from nuclei to mitochondria along with cell death by cyclophilin D activation and mPTP opening. Exogenous and endogenous effect of BTG2 was confirmed by chemical inhibitors and BTG2-KO-MEF, respectively. Here, we suggest tumor suppressor, BTG2, as one of the regulators of necrosis in myocardium via inhibiting Akt/Erk, but activating GSK3β and cyclophilin D, which resulted in mPTP opening in response to H2O2.

B-cell translocation gene 2: expression in the rat ovary and potential association with adenine nucleotide translocase 2 in mitochondria

The B-cell translocation gene 2 (Btg2) is an anti-proliferative tumor suppressor gene that behaves as a transcriptional regulator. The present study investigated gonadotropin induction of Btg2 in the rat ovary and the mechanism of Btg2 action as a partner of mitochondrial protein adenine nucleotide translocase 2 (Ant2). Transient induction of Btg2 as well as Btg1 mRNA levels by LH/hCG was observed in ovarian granulosa cells. Btg2 protein levels were also stimulated by LH/hCG. LH-induced gene expression of Btg2 required ERK signal pathway. Studies of deletion mutants in HeLa cells showed that deletion of Btg2 C-terminus (Btg2/ΔC) abolished the interaction with Ant2. In fact, the expression levels of Btg2/ΔC construct were decreased in mitochondrial fraction. Btg2 was also expressed in mitochondria and interacted with Ant2 in preovulatory granulosa cells. Interestingly, a Btg2/ΔC construct inhibited an action of Btg2 wild-type on ATP and H(2)O(2) production. These findings demonstrate the gonadotropin stimulation of Btg2 in the ovary and, the physical interaction of Btg2 with Ant2 in mitochondria.

Whole genome gene expression analysis reveals casiopeína-induced apoptosis pathways

Copper-based chemotherapeutic compounds Casiopeínas, have been presented as able to promote selective programmed cell death in cancer cells, thus being proper candidates for targeted cancer therapy. DNA fragmentation and apoptosis-in a process mediated by reactive oxygen species-for a number of tumor cells, have been argued to be the main mechanisms. However, a detailed functional mechanism (a model) is still to be defined and interrogated for a wide variety of cellular conditions before establishing settings and parameters needed for their wide clinical application. In order to shorten the gap in this respect, we present a model proposal centered in the role played by intrinsic (or mitochondrial) apoptosis triggered by oxidative stress caused by the chemotherapeutic agent. This model has been inferred based on genome wide expression profiling in cervix cancer (HeLa) cells, as well as statistical and computational tests, validated via functional experiments (both in the same HeLa cells and also in a Neuroblastoma model, the CHP-212 cell line) and assessed by means of data mining studies.

Endogenous BTG2 expression stimulates migration of bladder cancer cells and correlates with poor clinical prognosis for bladder cancer patients

BACKGROUND

The B-cell translocation gene 2 (BTG2) is considered to act as a tumour-suppressor gene because of its antiproliferative and antimigratory activities. Higher levels of BTG2 expression in tumour cells have been linked to a better clinical outcome for several cancer entities. Here, we investigated the expression and function of BTG2 in bladder cancer.

METHODS

The expression of BTG2 in bladder cancer cells was silenced by RNA interference. Cell motility was investigated by wound healing and Boyden chamber assays. The protein expression of BTG2 in bladder cancer was studied by immunohistochemistry.

RESULTS

We observed that targeted suppression of BTG2 by RNA interference did not result in growth stimulation but led to a substantial inhibition of bladder cancer cell motility. Tissue microarray analyses of bladder cancer cystectomy specimens revealed that higher BTG2 expression levels within the tumours correlated strongly with a decreased cancer-specific survival for bladder cancer patients.

CONCLUSION

These results indicate that endogenous BTG2 expression contributes to the migratory potential of bladder cancer cells. Moreover, high levels of BTG2 in bladder cancers are linked to decreased cancer-specific survival. These findings question the conception that BTG2 generally acts as a tumour suppressor and typically represents a favourable clinical marker for cancer patients.

TIS21(/BTG2/PC3) accelerates the repair of DNA double strand breaks by enhancing Mre11 methylation and blocking damage signal transfer to the Chk2(T68)-p53(S20) pathway

DNA double strand breaks (DSBs) occur more frequently in TIS21(-/-) mouse embryo fibroblasts than that in wild type MEFs (wt-MEFs). Therefore, the role TIS21 plays in the DNA damage response was investigated. Adenoviral transduction of Huh7 tumor cells with the TIS21 gene accelerated the repair of DSBs induced by etoposide treatment as evaluated by clearance of γH2AX foci and the Comet assay. TIS21 increased methylation of Mre11 and protein arginine methyltransferase 1 (PRMT1) activity, leading to Mre11 activation in vitro and in vivo, as determined by immunoprecipitation and radiolabeling analyses. When downstream DNA damage response mediators were evaluated in various human cancer cells lines, TIS21 was found to strongly inhibit Chk2(T68) and p53(S20) phosphorylation by p-ATM(S1981) but not p53(S15). The loss of Chk2 activation after etoposide treatment reduced apoptosis in the cells by downregulating the expression of E2F1 and Bax. These data suggest that TIS21 regulates DSB repair and apoptosis. Expression of TIS21 promoted the repair of DSBs and reduced apoptosis by blocking the damage signal from p-ATM(S1981) to Chk2(T68)-p53(S20)via the activation of Mre11 and PRMT1.

15-Lipoxygenase-1-enhanced Src-Janus kinase 2-signal transducer and activator of transcription 3 stimulation and monocyte chemoattractant protein-1 expression require redox-sensitive activation of epidermal growth factor receptor in vascular wall remodeling

To understand the mechanisms by which 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE) activates signal transducer and activator of transcription 3 (STAT3), we studied the role of epidermal growth factor receptor (EGFR). 15(S)-HETE stimulated tyrosine phosphorylation of EGFR in a time-dependent manner in vascular smooth muscle cells (VSMCs). Interference with EGFR activation blocked 15(S)-HETE-induced Src and STAT3 tyrosine phosphorylation, monocyte chemoattractant protein-1 (MCP-1) expression and VSMC migration. 15(S)-HETE also induced tyrosine phosphorylation of Janus kinase 2 (Jak2) in VSMCs, and its inhibition substantially reduced STAT3 phosphorylation, MCP-1 expression, and VSMC migration. In addition, Src formed a complex with EGFR and Jak2, and its inhibition completely blocked Jak2 and STAT3 phosphorylation, MCP-1 expression, and VSMC migration. 15(S)-HETE induced the production of H(2)O(2) via an NADPH oxidase-dependent manner and its scavengers, N-acetyl cysteine (NAC) and catalase suppressed 15(S)-HETE-stimulated EGFR, Src, Jak2, and STAT3 phosphorylation and MCP-1 expression. Balloon injury (BI) induced EGFR, Src, Jak2, and STAT3 phosphorylation, and inhibition of these signaling molecules attenuated BI-induced MCP-1 expression and smooth muscle cell migration from the medial to the luminal surface resulting in reduced neointima formation. In addition, inhibition of EGFR blocked BI-induced Src, Jak2, and STAT3 phosphorylation. Similarly, interference with Src activation suppressed BI-induced Jak2 and STAT3 phosphorylation. Furthermore, adenovirus-mediated expression of dnJak2 also blocked BI-induced STAT3 phosphorylation. Consistent with the effects of 15(S)-HETE on the activation of EGFR-Src-Jak2-STAT3 signaling in VSMCs in vitro, adenovirus-mediated expression of 15-lipoxygenase 1 (15-Lox1) enhanced BI-induced EGFR, Src, Jak2, and STAT3 phosphorylation leading to enhanced MCP-1 expression in vivo. Blockade of Src or Jak2 suppressed BI-induced 15-Lox1-enhanced STAT3 phosphorylation, MCP-1 expression, and neointima formation. In addition, whereas dominant negative Src blocked BI-induced 15-Lox1-enhanced Jak2 phosphorylation, dnJak2 had no effect on Src phosphorylation. Together, these observations demonstrate for the first time that the 15-Lox1-15(S)-HETE axis activates EGFR via redox-sensitive manner, which in turn mediates Src-Jak2-STAT3-dependent MCP-1 expression leading to vascular wall remodeling.

Cancer biomarker discovery: the entropic hallmark

Background

It is a commonly accepted belief that cancer cells modify their transcriptional state during the progression of the disease. We propose that the progression of cancer cells towards malignant phenotypes can be efficiently tracked using high-throughput technologies that follow the gradual changes observed in the gene expression profiles by employing Shannon's mathematical theory of communication. Methods based on Information Theory can then quantify the divergence of cancer cells' transcriptional profiles from those of normally appearing cells of the originating tissues. The relevance of the proposed methods can be evaluated using microarray datasets available in the public domain but the method is in principle applicable to other high-throughput methods.

Methodology/Principal Findings

Using melanoma and prostate cancer datasets we illustrate how it is possible to employ Shannon Entropy and the Jensen-Shannon divergence to trace the transcriptional changes progression of the disease. We establish how the variations of these two measures correlate with established biomarkers of cancer progression. The Information Theory measures allow us to identify novel biomarkers for both progressive and relatively more sudden transcriptional changes leading to malignant phenotypes. At the same time, the methodology was able to validate a large number of genes and processes that seem to be implicated in the progression of melanoma and prostate cancer.

Conclusions/Significance

We thus present a quantitative guiding rule, a new unifying hallmark of cancer: the cancer cell's transcriptome changes lead to measurable observed transitions of Normalized Shannon Entropy values (as measured by high-througput technologies). At the same time, tumor cells increment their divergence from the normal tissue profile increasing their disorder via creation of states that we might not directly measure. This unifying hallmark allows, via the the Jensen-Shannon divergence, to identify the arrow of time of the processes from the gene expression profiles, and helps to map the phenotypical and molecular hallmarks of specific cancer subtypes. The deep mathematical basis of the approach allows us to suggest that this principle is, hopefully, of general applicability for other diseases.

Up-regulation of cell cycle arrest protein BTG2 correlates with increased overall survival in breast cancer, as detected by immunohistochemistry using tissue microarray

BACKGROUND

Previous studies have shown that the ADIPOR1, ADORA1, BTG2 and CD46 genes differ significantly between long-term survivors of breast cancer and deceased patients, both in levels of gene expression and DNA copy numbers. The aim of this study was to characterize the expression of the corresponding proteins in breast carcinoma and to determine their correlation with clinical outcome.

METHODS

Protein expression was evaluated using immunohistochemistry in an independent breast cancer cohort of 144 samples represented on tissue microarrays. Fisher's exact test was used to analyze the differences in protein expression between dead and alive patients. We used Cox-regression multivariate analysis to assess whether the new markers predict the survival status of the patients better than the currently used markers.

RESULTS

BTG2 expression was demonstrated in a significantly lower proportion of samples from dead patients compared to alive patients, both in overall expression (P = 0.026) and cell membrane specific expression (P = 0.013), whereas neither ADIPOR1, ADORA1 nor CD46 showed differential expression in the two survival groups. Furthermore, a multivariate analysis showed that a model containing BTG2 expression in combination with HER2 and Ki67 expression along with patient age performed better than a model containing the currently used prognostic markers (tumour size, nodal status, HER2 expression, hormone receptor status, histological grade, and patient age). Interestingly, BTG2 has previously been described as a tumour suppressor gene involved in cell cycle arrest and p53 signalling.

CONCLUSIONS

We conclude that high-level BTG2 protein expression correlates with prolonged survival in patients with breast carcinoma.

E-cadherin transcriptional down-regulation by epigenetic and microRNA-200 family alterations is related to mesenchymal and drug-resistant phenotypes in human breast cancer cells

The conversion of early stage tumors into invasive malignancies with an aggressive phenotype has been associated with the irreversible loss of E-cadherin expression. The loss of E-cadherin expression in human tumors, including breast cancer, has been attributed to promoter CpG island hypermethylation and direct inhibition by transcriptional repressors. Recent evidence demonstrates that up-regulation of E-cadherin by microRNA-200b (miR-200b) and miR-200c through direct targeting of transcriptional repressors of E-cadherin, ZEB1, and ZEB2, inhibits epithelial-to-mesenchymal transition (EMT), a crucial process in the tumor progression. We demonstrate that microRNA miR-200 family-mediated transcriptional up-regulation of E-cadherin in mesenchymal MDA-MB-231 and BT-549 cells is associated directly with translational repression of ZEB1 and indirectly with increased acetylation of histone H3 at the E-cadherin promoter. The increase in histone H3 acetylation may be attributed to the disruption of repressive complexes between ZEB1 and histone deacetylases and to the inhibition of SIRT1, a class III histone deacetylase. These events inhibit EMT and reactivate a less aggressive epithelial phenotype in cancer cells. Additionally, disruption of ZEB1-histone deacetylase repressor complexes and down-regulation of SIRT1 histone deacetylase up-regulate proapoptotic genes in the p53 apoptotic pathway resulting in the increased sensitivity of cancer cells to the chemotherapeutic agent doxorubicin.

Oncogenic human papillomaviruses block expression of the B-cell translocation gene-2 tumor suppressor gene

Human papillomavirus (HPV)-induced carcinogenesis is critically dependent on the activities of the viral E6 and E7 oncogenes. Here, we demonstrate that expression of the putative tumor suppressor gene B-cell translocation gene-2 (BTG2) is reinduced in HPV16- and HPV18-positive cancer cells on silencing of viral oncogene expression, indicating that BTG2 is repressed by oncogenic HPVs. Inhibition of BTG2 expression was mediated by the HPV E6 oncogene and occurred in a p53-dependent manner. Luciferase reporter gene analyses revealed that BTG2 repression takes place at the transcriptional level and is dependent on the integrity of the major p53-response element within the BTG2 promoter. Ectopic expression of BTG2 acted antiproliferative in cervical cancer cells. Tissue specimens commonly exhibited reduced BTG2 protein levels in HPV-positive high-grade lesions (CIN2/3) and cervical carcinomas, when compared with normal cervical epithelium. These findings identify the antiproliferative BTG2 gene as a novel cellular target blocked by the HPV E6 oncoprotein.