Proliferation Of Human Breast Cancer Research Articles

Parameters of dynamic contrast-enhanced MRI as imaging markers for angiogenesis and proliferation in human breast cancer.

BackgroundBreast cancer is the most common malignancy and the leading cause of cancer death in women worldwide; however, early diagnosis has been difficult due to its complex pathological structure. This study evaluated the value of morphological examination in conjunction with dynamic contrast-enhanced MRI (DCE-MRI) for more precise diagnosis of breast cancer, as well as their correlation with angiogenesis and proliferation biomarkers.Material/MethodsDCE-MRI parameters (including Ktrans: volume transfer coefficient reflecting vascular permeability, Kep: flux rate constant, Ve: extracellular volume ratio reflecting vascular permeability, and ADC: apparent diffusion coefficient) were obtained from 124 patients with breast cancer (124 lesions). Microvessel density (MVD) was evaluated by the immunohistochemical analysis of tumor vessels for CD31 and CD105 expression. The proliferation was assessed by analyzing Ki67.ResultsKtrans values were in the order of: malignant lesions > benign lesions > normal glands. Similar results were observed for Kep. The opposite changes were seen with Ve. Ktrans and Kep values were significantly higher in invasive ductal carcinoma (IDC) and ductal carcinoma in situ (DCIS) than in mammary ductal dysplasia (MDD; ANOVA followed by Dunnett’s test). In sharp contrast, ADC values were lower in IDC and DCIS than in MDD, and Ve was not significantly different among the three groups. The data from MIP (maximum intensity projection) showed that benign breast lesions had no or only one blood vessel, whereas malignant lesions had two or more blood vessels. In addition, expression of CD105 and Ki67, the commonly recognized markers for angiogenesis and proliferation, respectively, were closely correlated with MRI parameters as revealed by Pearson analysis.ConclusionsDetermination of Ktrans, Kep and ADC values permits estimation of tumor angiogenesis and proliferation in breast cancer and DCE-MRI parameters can be used as imaging biomarkers to predict patient prognosis and the biologic aggressiveness of the tumor.

Alteration of somatostatin receptor 2 expression in canine mammary gland tumor.

Somatostatin receptor 2 (SSTR2) is a negative regulator of cell proliferation in human breast cancer. Since there is little information about SSTR2 in canine mammary gland tumor (MGT), we clarified its distribution and expression level in normal mammary gland, benign MGT and malignant MGT. SSTR2 expression determined by immunohistochemical staining was observed in the cytoplasm of luminal epithelial cells. The intensity was negatively correlated with malignancy: normal tissues and some of the benign tumors had the highest levels, while the malignant tumors had little or no SSTR2 expression. As for the Western blotting, SSTR2 protein level in benign tumors was significantly lower than the normal mammary gland. On the other hand, SSTR2 protein levels in two of three malignant tumors were higher than the other groups. These results suggest that SSTR2 expression alters according to the malignancy of canine MGT.

Synthesis, crystal structure and anticancer activity of a novel ternary copper(II) complex with Schiff base derived from 2-amino-4-fluorobenzoic acid and salicylaldehyde

The ternary copper(II) complex with 1,10-phenanthroline and Schiff base derived from 2-amino-4-fluorobenzoic acid and salicylaldehyde, was synthesized and characterized by IR and 1H NMR spectroscopy, elemental analysis, and single crystal X-ray diffraction. X-ray crystallography shows that the copper atom adopts square pyramidal geometry and is five coordinated by the nitrogen atom from CN, two nitrogen atoms from 1,10-phenanthroline, the hydroxyl oxygen atom and the carboxylate oxygen atom. Our studies on the anticancer activity of the complex indicate that the complex can inhibit the cellular proliferation in human breast cancer MDA-MB-231 cells. In addition, it has proteasome-inhibitory activity in human breast cancer MDA-MB-231 cells. The inhibition of the tumor proteasomal activity results in the accumulation of ubiquitinated proteins and ubiquitinated form of IκB-α, a natural proteasome substrate, followed by induction of apoptosis. The results suggest that the title complex, as a potent proteasome inhibitor, has potential to be developed into a novel anticancer drug.

156. Is mammaglobin-A tissue expression associated with angiogenesis, lymph-angiogenesis or cell proliferation in human breast cancer?

156. Is mammaglobin-A tissue expression associated with angiogenesis, lymph-angiogenesis or cell proliferation in human breast cancer?

C5a stimulates the proliferation of breast cancer cells via Akt-dependent RGC-32 gene activation

Complement system activation contributes to various immune and inflammatory diseases, as well as cancers.However, the role of complement activation in the proliferation of cancer cells is not clear. In the present study, we investigated the consequences of complement activation on the proliferation of breast cancer cells and its possible mechanisms. We focused our study on the potential roles of the anaphylatoxins C3a and C5a in the proliferation of human breast cancer, as two important immune mediators generated after complement activation. Our study revealed that C5a stimulation, but not C3a, enhanced the proliferation of human breast cancer cells in vitro. Moreover, the expression of response gene to complement 32 (RGC-32) was pronounced in breast cancer cells in response to C5a stimulation. Notably, blockade of the C5a receptor markedly reduced the expression of RGC-32 and the proliferation of breast cancer cells stimulated by C5a. Meanwhile, silencing of RGC-32 expression reduced the proliferation of breast cancer cells induced by C5a treatment. Further investigation revealed that Akt activation was involved in C5a-induced RGC-32 expression and breast cancer cell proliferation. In conclusion, the present study indicates that C5a may promote the proliferation of breast cancer cells through Akt1 activation of the RGC-32 gene.

Amyloid precursor protein (APP) is an androgen‐induced gene associated with cell proliferation in human breast cancer. Immunolocalization of APP in human breast carcinoma. See also Takagi, K., et al.

Cancer ScienceVolume 104, Issue 11 p. November cover-November cover Cover ImageOpen Access Amyloid precursor protein (APP) is an androgen-induced gene associated with cell proliferation in human breast cancer. Immunolocalization of APP in human breast carcinoma. See also Takagi, K., et al. Kiyoshi Takagi, Kiyoshi TakagiSearch for more papers by this authorShigehiro Ito, Shigehiro ItoSearch for more papers by this authorToshiaki Miyazaki, Toshiaki MiyazakiSearch for more papers by this authorYasuhiro Miki, Yasuhiro MikiSearch for more papers by this authorYukiko Shibahara, Yukiko ShibaharaSearch for more papers by this authorTakanori Ishida, Takanori IshidaSearch for more papers by this authorMika Watanabe, Mika WatanabeSearch for more papers by this authorSatoshi Inoue, Satoshi InoueSearch for more papers by this authorHironobu Sasano, Hironobu SasanoSearch for more papers by this authorTakashi Suzuki, Takashi SuzukiSearch for more papers by this author Kiyoshi Takagi, Kiyoshi TakagiSearch for more papers by this authorShigehiro Ito, Shigehiro ItoSearch for more papers by this authorToshiaki Miyazaki, Toshiaki MiyazakiSearch for more papers by this authorYasuhiro Miki, Yasuhiro MikiSearch for more papers by this authorYukiko Shibahara, Yukiko ShibaharaSearch for more papers by this authorTakanori Ishida, Takanori IshidaSearch for more papers by this authorMika Watanabe, Mika WatanabeSearch for more papers by this authorSatoshi Inoue, Satoshi InoueSearch for more papers by this authorHironobu Sasano, Hironobu SasanoSearch for more papers by this authorTakashi Suzuki, Takashi SuzukiSearch for more papers by this author First published: 30 October 2013 https://doi.org/10.1111/cas.12269Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume104, Issue11November 2013Pages November cover-November cover RelatedInformation

LINE-1 ORF-1p functions as a novel HGF/ETS-1 signaling pathway co-activator and promotes the growth of MDA-MB-231 cell

Long interspersed nucleotide element (LINE)-1 ORF-1p is encoded by the human pro-oncogene LINE-1. It is involved in the development and progression of several human carcinomas, such as hepatocellular carcinoma and lung and breast cancers. The hepatocyte growth factor (HGF)/ETS-1 signaling pathway is involved in regulation of cancer cell proliferation, metastasis and invasion. The biological function of the interaction between LINE-1 ORF-1p and the HGF/ETS-1 signaling pathway in regulation of human breast cancer proliferation remains largely unknown. Here, we showed that LINE-1 ORF-1p enhanced ETS-1 transcriptional activity and increased expression of downstream genes of ETS-1. Interaction between ETS-1 and LINE-1 ORF-1p was identified by immunoprecipitation assays. LINE-1 ORF-1p modulated ETS-1 activity through cytoplasm/nucleus translocation and recruitment to the ETS-1 binding element in the MMP1 gene promoter. We also showed that LINE-1 ORF-1p promoted proliferation and anchorage-independent growth of MDA-MB-231 breast cancer cells. By investigating a novel role of the LINE-1 ORF-1p in the HGF/ETS-1 signaling pathway and MDA-MB-231 cells, we demonstrated that LINE-1 ORF-1p may be a novel ETS-1 coactivator and molecular target for therapy of human triple negative breast cancer.

NAF-1 and mitoNEET are central to human breast cancer proliferation by maintaining mitochondrial homeostasis and promoting tumor growth

Mitochondria are emerging as important players in the transformation process of cells, maintaining the biosynthetic and energetic capacities of cancer cells and serving as one of the primary sites of apoptosis and autophagy regulation. Although several avenues of cancer therapy have focused on mitochondria, progress in developing mitochondria-targeting anticancer drugs nonetheless has been slow, owing to the limited number of known mitochondrial target proteins that link metabolism with autophagy or cell death. Recent studies have demonstrated that two members of the newly discovered family of NEET proteins, NAF-1 (CISD2) and mitoNEET (mNT; CISD1), could play such a role in cancer cells. NAF-1 was shown to be a key player in regulating autophagy, and mNT was proposed to mediate iron and reactive oxygen homeostasis in mitochondria. Here we show that the protein levels of NAF-1 and mNT are elevated in human epithelial breast cancer cells, and that suppressing the level of these proteins using shRNA results in significantly reduced cell proliferation and tumor growth, decreased mitochondrial performance, uncontrolled accumulation of iron and reactive oxygen in mitochondria, and activation of autophagy. Our findings highlight NEET proteins as promising mitochondrial targets for cancer therapy.

Abstract 5573: Discovery of potent oridonin derivatives for the treatment of breast cancer.

Abstract Oridonin, a diterpenoid derived from the herbal Rabdosia rubescens, has been reported to have antitumor effects on various types of cancer cells. However, its relatively low aqueous solubility and bioavailability have limited its development into clinical applications. Herein, we chemically modified oridonin and generated a series of novel analogues. We then employed MTT assay to detect their effects on cell growth and a number of new and potent molecules have been identified. Among them, compounds CYD-6-86 and CYD-6-92 significantly inhibited the proliferation of human breast cancer MDA-MB-231 and MCF-7 cells. Furthermore, both compounds induced enhanced apoptosis in a dose- and time-dependent fashion when compared with oridonin. Cell cycle analysis indicated that both CYD-6-86 and CYD-6-92 induced S phase arrest in MDA-MB-231 cells and G0/G1 phase arrest in MCF-7 cells, while oridonin induced G2/M phase arrest in MDA-MB-231 and MCF-7 cells. Consistent with oridonin, Western blot analysis showed that CYD-6-86 and CYD-6-92 inhibited the expression of NF-κB and Bcl-2, and increased expression of Bax and cleaved PARP. Intriguingly, compounds CYD-6-86 and CYD-6-92 have demonstrated to suppress the growth of adriamycin-resistant MCF-7 clone, while at the same dosage oridonin displayed no effect on these cells. Our findings suggest that these new analogues may be superior to the natural product oridonin to overcome the chemo-resistance, and have great potential to be developed as novel therapeutics for the treatment of breast cancer. Citation Format: Yusong Zhang, Chunyong Ding, Zhengduo Yang, Haijun Chen, Lili Chu, Jia Zhou, Qiang Shen. Discovery of potent oridonin derivatives for the treatment of breast cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5573. doi:10.1158/1538-7445.AM2013-5573

Cyclopamine is a novel Hedgehog signaling inhibitor with significant anti-proliferative, anti-invasive and anti-estrogenic potency in human breast cancer cells

Stimulation of Hedgehog (Hh) signaling induces carcinogenesis or promotes cell survival in cancers of multiple organs. In epithelial cancer with aberrant Hedgehog activation, abrogation of Hedgehog signaling by cyclopamine, a naturally occurring Hedgehog-specific small-molecule inhibitor, causes profound inhibition of tumor growth. In the present study, cyclopamine displayed a significant potency in suppressing the proliferation of both estrogen-responsive (MCF-7) and estrogen-independent (MDA-MB-231) human breast cancer cells. Cyclopamine induced a robust G1 cell cycle arrest and elicited notable effects on the expression of cyclin D1 through modulation of the MAPK/ERK signaling pathway. Cyclopamine also inhibited the invasive ability of both breast cancer cell lines by suppressing the expression levels of NF-κB, MMP2 and MMP9 protein. Furthermore, in estrogen-responsive MCF-7 cells, cyclopamine significantly downregulated the production of estrogen receptor-α protein. Our results implicate cyclopamine as a novel, potent inhibitor of human breast cancer proliferation and estrogen responsiveness that could potentially be developed into a promising therapeutic agent for the treatment of breast cancer.

VPA inhibits breast cancer cell migration by specifically targeting HDAC2 and down-regulating Survivin

Cell migration plays major roles in human breast cancer-related death, but the molecular mechanisms remain unclear. Valproic acid (VPA) is a broad-spectrum inhibitor of class I and II histone deacetylases and shows great anticancer activity in a variety of human cancers including breast cancer. In this study, we found that VPA significantly inhibited cell migration but not proliferation of human breast cancer MDA-MB-231 cells. Mechanistic studies found that VPA significantly inhibited the expression of Survivin. Knockdown of Survivin could obviously inhibited cell migration, while over-expression of Survivin markedly rescued the inhibition of VPA on cell migration. Further studies found that knockdown of HDAC2 completely mimicked the effects of VPA on Survivin and cell migration, and over-expression of Survivin could also rescue the effects of HDAC2 knockdown on cell migration. Collectively, these results indicated that HDAC2 may be the specific target of VPA in breast cancer cells, and specific inhibition of HDAC2, especially by small molecular chemicals may lead to less side-effects and provide a better strategy than VPA application for human breast cancer treatment.

High expression of miR-21 in tumor stroma correlates with increased cancer cell proliferation in human breast cancer

Low-risk and high-risk breast cancer patients are stratified primarily according to their lymph node (LN) status and grading. However, some low-risk patients relapse, and some high-risk patients have a favorable clinical outcome, implying a need for better prognostic and predictive tests. Micro RNAs are often aberrantly expressed in cancer and microRNA-21 is upregulated in a variety of cancers, including breast cancer. High miR-21 levels have been associated with poor prognosis. To determine the cellular localization of miR-21 and to compare its expression levels with histopathological features, we performed in situ hybridization and semi-quantitative assessment of the miR-21 signal on 12 LN negative grade I (assumed low risk), and 12 LN positive grade II (high risk) breast cancers. miR-21 was predominantly seen in cancer associated fibroblast-like cells, with no difference in expression levels between grade I and grade II carcinomas. Immunohistochemical scoring of the prognostic proliferation marker Ki-67 and tumor suppressor p53 showed that the miR-21 expression levels significantly correlated with the Ki-67 score (p = 0.043), whereas no correlation between p53 and miR-21 was found. Our results indicate that miR-21 may contribute to improve clinical stratification according to growth rate and facilitate tailored treatment of breast cancer patients.

Estrogen regulates proliferation of ERneg breast cancer cells by stimulating Kv11.1 channel activity

Breast cancer is a major cause of death among women worldwide. Paradoxically, in breast cancer cells displaying estrogen receptor negative (ERneg) phenotype, estrogen (E2) is still the main determinant of cell proliferation. Unfortunately, ERneg cells do not respond to ER-targeted therapies, as they lack canonical α- and/or β-estrogen receptors therefore, novel strategies need to be developed to lessen its morbidity. Recent translational research in cancer biology has revealed that the Kv11.1 potassium ion channel (alias hERG) is robustly expressed in cancers of varying histogenesis, including prostate cancer and breast cancer, but not in adjacent non-neoplastic tissue. It has been shown that blocking Kv11.1 channel activity inhibits proliferation in human breast cancer however; its role in cancer cell proliferation is unknown. In this work we report that in the ERneg human breast cancer cell line SKBr3, E2 stimulates proliferation by modulating Kv11.1 ion channel activity. Our experiments show that the E2-activated G protein coupled receptor, GPR30, mediates stimulation of the protein kinase PKCα which in turn stimulates Kv11.1 channel activity by phosphorylating S890. Understanding E2-regulated metabolism of Kv11.1 in ERneg breast cancer cells will provide a compelling opportunity to identify targets for antiproliferative therapy for this deadly form of breast cancer.

Unregulated miR-96 induces cell proliferation in human breast cancer by downregulating transcriptional factor FOXO3a.

FOXO transcription factors are key tumor suppressors in mammalian cells. Until now, suppression of FOXOs in cancer cells was thought to be mainly due to activation of multiple onco-kinases by a phosphorylation-ubiquitylation-mediated cascade. Therefore, it was speculated that inhibition of FOXO proteins would naturally occur through a multiple step post-translational process. However, whether cancer cells may downregulate FOXO protein via an alternative regulatory mechanism is unclear. In the current study, we report that expression of miR-96 was markedly upregulated in breast cancer cells and breast cancer tissues compared with normal breast epithelial cells (NBEC) and normal breast tissues. Ectopic expression of miR-96 induced the proliferation and anchorage-independent growth of breast cancer cells, while inhibition of miR-96 reduced this effect. Furthermore, upregulation of miR-96 in breast cancer cells resulted in modulation of their entry into the G1/S transitional phase, which was caused by downregulation of cyclin-dependent kinase (CDK) inhibitors, p27Kip1 and p21Cip1, and upregulation of the cell-cycle regulator cyclin D1. Moreover, we demonstrated that miR-96 downregulated FOXO3a expression by directly targeting the FOXO3a 3′-untranslated region. Taken together, our results suggest that miR-96 may play an important role in promoting proliferation of human breast cancer cells and present a novel mechanism of miRNA-mediated direct suppression of FOXO3a expression in cancer cells.

Purification of Lectin from Larvae of the fly,Musca domestica, and in Vitro Anti-Tumor Activity in MCF-7 Cells

A new lectin was purified from larvae of the fly, Musca domestica L. (Diptera: Muscidae) (MLL-2, 38 kDa) using affinity chromatography and HPLC. Anti-tumor activity of MLL-2 was demonstrated by its inhibition of proliferation of human breast cancer (MCF-7) cells in a time-and dose-dependent manner. The results of acridine orange staining indicated that MLL-2 caused apoptosis in MCF-7 cells. DNA fragmentation in MCF-7 cells has been detected by TUNEL. Flow cytometric analysis also demonstrated that MLL-2 caused dose-dependent apoptosis of MCF-7 cells through cell arrest at G2/M phase. The MLL-2 induced a sustained increase in concentration of intracellular free calcium. Western blot revealed that MLL-2 induced apoptosis in MCF-7 cells was associated with typical apoptosis proteins in the mitochondrial pathway. In addition, the caspase-3 activity in MCF-7 cells treated with MLL-2 for 48 hours was significantly increased compared to controls (407.4 ± 3.0 vs. 1749.2 ± 6.0, P <0.01). Since MLL-2 induced apoptosis in MCF-7cells the mitochondrial pathway may be the main pathway of antitumor activity.

Combined Src and ER blockade impairs human breast cancer proliferation in vitro and in vivo

Antiestrogen therapies arrest susceptible estrogen receptor (ER)-positive breast cancers by increasing p27. Since Src phosphorylates p27 to promote p27 proteolysis, Src activation observed in up to 40% of ER-positive cancers may contribute to antiestrogen resistance. In this article, we show that treatment with the Src-inhibitor saracatinib (AZD0530) together with ER-blocking drugs increased breast cancer cell cycle arrest via p27. Saracatinib and fulvestrant together more effectively increased p27, reduced Ki67, and impaired MDA-MB-361 xenograft tumor growth in vivo than either of the drugs alone. In contrast, saracatinib monotherapy rapidly gave rise to drug resistance. Since combined ER and Src inhibition delays development of resistance in vivo, these data support further clinical investigation of saracatinib in combination with fulvestrant for women with ER-positive breast cancer. Proteomic analysis revealed striking bypass activation of the mTOR pathway in saracatinib-resistant tumors. mTORC1 activation also arose following long-term culture of ER-positive breast cancer lines in the presence of saracatinib. These data indicate the utility of proteomic analysis of drug-resistant tumors to identify potential means of drug resistance. The use of mTOR kinase inhibitors with saracatinib may subvert drug resistance and prove to be more effective than saracatinib alone.

1-Benzyl-indole-3-carbinol is a novel indole-3-carbinol derivative with significantly enhanced potency of anti-proliferative and anti-estrogenic properties in human breast cancer cells

Indole-3-carbinol (I3C), a natural autolysis product of a gluccosinolate present in Brassica vegetables such as broccoli and cabbage, has anti-proliferative and anti-estrogenic activities in human breast cancer cells. A new and significantly more potent I3C analogue, 1-benzyl-I3C was synthesized, and in comparison to I3C, this novel derivative displayed an approximate 1000-fold enhanced potency in suppressing the growth of both estrogen responsive (MCF-7) and estrogen-independent (MDA-MB-231) human breast cancer cells (I3C IC 50 of 52 μM, and 1-benzyl-I3C IC 50 of 0.05 μM). At significantly lower concentrations, 1-benzyl-I3C induced a robust G1 cell cycle arrest and elicited the key I3C-specific effects on expression and activity of G1-acting cell cycle genes including the disruption of endogenous interactions of the Sp1 transcription factor with the CDK6 promoter. Furthermore, in estrogen responsive MCF-7 cells, with enhanced potency 1-benzyl-I3C down-regulated production of estrogen receptor-alpha protein, acts with tamoxifen to arrest breast cancer cell growth more effectively than either compound alone, and inhibited the in vivo growth of human breast cancer cell-derived tumor xenografts in athymic mice. Our results implicate 1-benzyl-I3C as a novel, potent inhibitor of human breast cancer proliferation and estrogen responsiveness that could potentially be developed into a promising therapeutic agent for the treatment of indole-sensitive cancers.

Abstract 229: Omega-3 fatty acids strongly induce apoptosis in human breast cancer cells in vitro and in vivo via formation of reactive oxygen species and caspase 8 activation

Abstract [Hypothesis] The present study sought to investigate the in vitro and in vivo anticancer effect of two representative omega-3 fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), with a focus on assessing the role of fatty acid-induced oxidative stress and apoptosis as mechanisms for their anticancer actions. [Methods] We used in vitro cell culture of MCF-7 human breast cancer cells and in vivo athymic nude mice model to study the effect of omega-3 fatty acids on cancer cell proliferation and the mechanism of the cell death. [Results] In vitro studies showed that DHA and EPA each strongly reduced the viability and DNA synthesis of MCF-7 human breast cancer cells in culture, and they also promoted cell death via apoptosis. Mechanistically, accumulation of reactive oxygen species and activation of caspase 8 contributed critically to the induction of apoptotic cell death. Co-presence of antioxidants or a selective inhibition or knockdown of caspase 8 each effectively abrogated the cytotoxic effect of DHA. Using athymic nude mice as an in vivo model, we found that feeding animals with 5% fish oil-containing diet for 6 weeks significantly reduced the growth of MCF-7 human breast cancer cells through inhibition of cancer cell proliferation as well as promotion of cell death. Using 3-nitrotyrosine as a parameter, we confirmed that fish oil diet significantly increased oxidative stress in tumor cells in vivo. Analysis of fatty acid content in plasma and tissues showed that feeding animals a 5% fish oil diet significantly increased DHA and EPA levels in both normal and tumorous mammary tissues by 329 and 300%, respectively. [Conclusion] The results of this investigation clearly showed that omega-3 fatty acids strongly inhibited human breast cancer proliferation both in vitro and in vivo via formation of reactive oxygen species and induction of apoptosis by caspase 8 activation. This study calls for further studies in human subjects to assess the effectiveness of fish oil as a dietary supplement in the treatment of certain types of cancers. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 229.

Ets2 Maintains hTERT Gene Expression and Breast Cancer Cell Proliferation by Interacting with c-Myc

Human telomerase reverse transcriptase (hTERT) underlies cancer cell immortalization, and the expression of hTERT is regulated strictly at the gene transcription. Here, we report that transcription factor Ets2 is required for hTERT gene expression and breast cancer cell proliferation. Silencing Ets2 induces a decrease of hTERT gene expression and increase in human breast cancer cell death. Reconstitution with recombinant hTERT rescues the apoptosis induced by Ets2 depression. In vitro and in vivo analyses show that Ets2 binds to the EtsA and EtsB DNA motifs on the hTERT gene promoter. Mutation of either Ets2 binding site reduces the hTERT promoter transcriptional activity. Moreover, Ets2 forms a complex with c-Myc as demonstrated by co-immunoprecipitation and glutathione S-transferase pulldown assays. Immunological depletion of Ets2, or mutation of the EtsA DNA motif, disables c-Myc binding to the E-box, whereas removal of c-Myc or mutation of the E-box also compromises Ets2 binding to EtsA. Thus, hTERT gene expression is maintained by a mechanism involving Ets2 interactions with the c-Myc transcription factor and the hTERT gene promoter, a protein-DNA complex critical for hTERT gene expression and breast cancer cell proliferation.

A Small-Molecule Enhancer of Signal Transducer and Activator of Transcription 1 Transcriptional Activity Accentuates the Antiproliferative Effects of IFN-γ in Human Cancer Cells

The transcription factor signal transducer and activator of transcription (STAT) 1 can mediate antiproliferative and proapoptotic effects in cancer cells, and a number of mechanisms have been found whereby STAT1 signaling is attenuated in tumors thereby increasing their malignant behavior. Thus, enhancing gene transcription mediated by STAT1 may be an effective approach to cancer therapy. A high-throughput screen was developed to identify molecules that could enhance STAT1-dependent gene expression. Through this approach, it was found that 2-(1,8-naphthyridin-2-yl)phenol (2-NP) caused a 2-fold increase in STAT1-dependent reporter gene expression compared with that seen with maximally effective concentrations of IFN-gamma alone. This effect was specific to STAT1 because 2-NP had no effect on unrelated transcription factors such as nuclear factor (NF) kappaB or the highly homologous transcription factor STAT3. STAT1-dependent gene activation was enhanced by this compound in a variety of human and murine cell lines and was independent of the stimulus used. Furthermore, 2-NP enhanced the expression of the bona fide endogenous STAT1 target gene interferon regulatory factor 1. 2-NP increased the duration of STAT1 tyrosine phosphorylation in response to IFN-gamma, and this may underlie its enhancement of STAT1-dependent transcription. Reflecting the fact that STAT1 can exert tumor-suppressive effects, 2-NP enhanced the ability of IFN-gamma to inhibit the proliferation of human breast cancer and fibrosarcoma cells. Tumor cells lacking STAT1 were unaffected by either IFN-gamma or 2-NP. These findings indicate that enhancement of STAT1 transcriptional activity may have utility in anticancer therapies, and that cell-based screens for modulators of transcription factor function can be a useful approach for drug discovery.