The Oncogene Metadherin Modulates the Apoptotic Pathway Based on the Tumor Necrosis Factor Superfamily Member TRAIL (Tumor Necrosis Factor-related Apoptosis-inducing Ligand) in Breast Cancer

Metadherin (MTDH), the newly discovered gene, is overexpressed in more than 40% of breast cancers. Recent studies have revealed that MTDH favors an oncogenic course and chemoresistance. With a number of breast cancer cell lines and breast tumor samples, we found that the relative expression of MTDH correlated with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) sensitivity in breast cancer. In this study, we found that knockdown of endogenous MTDH cells sensitized the MDA-MB-231 cells to TRAIL-induced apoptosis both in vitro and in vivo. Conversely, stable overexpression of MTDH in MCF-7 cells enhanced cell survival with TRAIL treatment. Mechanically, MTDH down-regulated caspase-8, decreased caspase-8 recruitment into the TRAIL death-inducing signaling complex, decreased caspase-3 and poly(ADP-ribose) polymerase-2 processing, increased Bcl-2 expression, and stimulated TRAIL-induced Akt phosphorylation, without altering death receptor status. In MDA-MB-231 breast cancer cells, sensitization to TRAIL upon MTDH down-regulation was inhibited by the caspase inhibitor Z-VAD-fmk (benzyloxycarbonyl-VAD-fluoromethyl ketone), suggesting that MTDH depletion stimulates activation of caspases. In MCF-7 breast cancer cells, resistance to TRAIL upon MTDH overexpression was abrogated by depletion of Bcl-2, suggesting that MTDH-induced Bcl-2 expression contributes to TRAIL resistance. We further confirmed that MTDH may control Bcl-2 expression partly by suppressing miR-16. Collectively, our results point to a protective function of MTDH against TRAIL-induced death, whereby it inhibits the intrinsic apoptosis pathway through miR-16-mediated Bcl-2 up-regulation and the extrinsic apoptosis pathway through caspase-8 down-regulation.     

Bone morphogenetic protein-4 induced by NDRG2 expression inhibits MMP-9 activity in breast cancer cells

In the current study, we examined the function of N-myc downstream-regulated gene 2 (NDRG2) expression in breast cancer cells, especially focusing on the role of bone morphogenetic protein-4 (BMP-4) induced by NDRG2. NDRG2 expression in MDA-MB-231 cells inhibited the mRNA expression of several matrix metalloproteinases (MMPs) and the gelatinolytic activity of MMP-9. Interestingly, a specific induction of active BMP-4 was exclusively observed in MDA-MB-231-NDRG2 cells but not in MDA-MB-231-mock cells. Neutralization of BMP-4 in MDA-MB-231-NDRG2 cells resulted in the rescue of MMP-9 mRNA expression and migration capacity. In addition, treatment with recombinant BMP-4 dramatically suppressed MMP-9 mRNA expression, gelatinolytic MMP-9 activity, migration, and invasion capacity both in MDA-MB-231 and PMA-treated MCF-7 cells. Collectively, our data show that BMP-4 induced by NDRG2 expression inhibits the metastatic potential of breast cancer cells, especially via suppression of MMP-9 activity.     

Hypoxia Regulates CD44 and Its Variant Isoforms through HIF-1α in Triple Negative Breast Cancer

Background

The CD44 transmembrane glycoproteins play multifaceted roles in tumor progression and metastasis. CD44 expression has also been associated with stem-like breast cancer cells. Hypoxia commonly occurs in tumors and is a major cause of radiation and chemo-resistance. Hypoxia is known to inhibit differentiation and facilitates invasion and metastasis. Here we have investigated the effect of hypoxia on CD44 and two of its isoforms in MDA-MB-231 and SUM-149 triple negative human breast cancer cells and MDA-MB-231 tumors using imaging and molecular characterization.

Methods and Findings

The roles of hypoxia and hypoxia inducible factor (HIF) in regulating the expression of CD44 and its variant isoforms (CD44v6, CD44v7/8) were investigated in human breast cancer cells, by quantitative real-time polymerase chain reaction (qRT-PCR) to determine mRNA levels, and fluorescence associated cell sorting (FACS) to determine cell surface expression of CD44, under normoxic and hypoxic conditions. In vivo imaging studies with tumor xenografts derived from MDA-MD-231 cells engineered to express tdTomato red fluorescence protein under regulation of hypoxia response elements identified co-localization between hypoxic fluorescent regions and increased concentration of ¹²⁵I-radiolabeled CD44 antibody.

Conclusions

Our data identified HIF-1α as a regulator of CD44 that increased the number of CD44 molecules and the percentage of CD44 positive cells expressing variant exons v6 and v7/8 in breast cancer cells under hypoxic conditions. Data from these cell studies were further supported by in vivo observations that hypoxic tumor regions contained cells with a higher concentration of CD44 expression.     

Oxygen-mediated regulation of gelatinase and tissue inhibitor of metalloproteinases-1 expression by invasive cells.

The relative expression of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) is an important determinant in trophoblast invasion of the uterus and tumor invasion and metastasis. Our previous studies have shown that low oxygen levels increase the in vitro invasiveness of trophoblast and tumor cells. The present study examined whether changes in oxygen levels affect TIMP and MMP expression by cultured trophoblast and breast cancer cells. Reverse zymographic analysis demonstrated reduced TIMP-1 protein secretion by HTR-8/SVneo trophoblast cells as well as MDA-MB-231 and MCF-7 breast carcinoma cells cultured in 1% vs 20% oxygen for 24 h. While gelatin zymography revealed no changes in the levels of MMP-9 secreted by HTR-8/SVneo trophoblasts cultured under various oxygen concentrations for 24 h, human MDA-MB-231 breast carcinoma cells displayed increased MMP-9 secretion and human MCF-7 breast cancer cells exhibited reduced secretion of this enzyme when cultured under similar conditions. In contrast, MMP-2 levels remained unchanged in all cultures incubated under similar conditions. Western blot analysis of MMP-9 protein in cell extracts confirmed the results of zymography. To assess the contribution of enhanced MMP activity to hypoxia-induced invasion, the effect of an MMP inhibitor (llomastat) on the ability of MDA-MB-231 cells to penetrate reconstituted extracellular matrix (Matrigel) was examined. Results showed that MMP inhibition significantly decreased the hypoxic upregulation of invasion by these cells. These findings indicate that the increased cellular invasiveness observed under reduced oxygen conditions may be due in part to a shift in the balance between MMPs and their inhibitors favoring increased MMP activity.     

6]-Gingerol inhibits metastasis of MDA-MB-231 human breast cancer cells

Gingerol (Zingiber officinale Roscoe, Zingiberaceae) is one of the most frequently and heavily consumed dietary condiments throughout the world. The oleoresin from rhizomes of ginger contains [6]-gingerol (1-[4′-hydroxy-3′-methoxyphenyl]-5-hydroxy-3-decanone) and its homologs which are pungent ingredients that have been found to possess many interesting pharmacological and physiological activities, such as anti-inflammatory, antihepatotoxic and cardiotonic effects. However, the effects of [6]-gingerol on metastatic processes in breast cancer cells are not currently well known. Therefore, in this study, we examined the effects of [6]-gingerol on adhesion, invasion, motility, activity and the amount of MMP-2 or -9 in the MDA-MB-231 human breast cancer cell line. We cultured MDA-MB-231 cells in the presence of various concentrations of [6]-gingerol (0, 2.5, 5 and 10 μM). [6]-Gingerol had no effect on cell adhesion up to 5 μM, but resulted in a 16% reduction at 10 μM. Treatment of MDA-MB-231 cells with increasing concentrations of [6]-gingerol led to a concentration-dependent decrease in cell migration and motility. The activities of MMP-2 or MMP-9 in MDA-MB-231 cells were decreased by treatment with [6]-gingerol and occurred in a dose-dependent manner. The amount of MMP-2 protein was decreased in a dose-dependent manner, although there was no change in the MMP-9 protein levels following treatment with [6]-gingerol. MMP-2 and MMP-9 mRNA expression were decreased by [6]-gingerol treatment. In conclusion, we have shown that [6]-gingerol inhibits cell adhesion, invasion, motility and activities of MMP-2 and MMP-9 in MDA-MB-231 human breast cancer cell lines.     

PTHrP Expression in Human MDA-MB-231 Breast Cancer Cells Is Critical for Tumor Growth and Survival and Osteoblast Inhibition

This study examined the effects of parathyroid hormone-related protein (PTHrP) derived from human MDA-MB-231 breast cancer cells on the tumor growth and osteoblast inhibition. Results revealed that knocking down PTHrP expression in the breast cancer cells strikingly inhibited the formation of subcutaneous tumors in nude mice. PTHrP knockdown dramatically decreased the levels of cyclins D1 and A1 proteins and arrested the cell cycle progression at the G1 stage. PTHrP knockdown led to the cleavage of Caspase 8 and induced apoptosis of the tumor cells. Interestingly, knocking down PTHrP increased the levels of Beclin1 and LC3-II and promoted the formation of autophagosomes. Knocking down PTHrP expression significantly reduced the abilities of the breast cancer cells to inhibit osteoblast differentiation and bone formation in vitro and in vivo. Finally, we found that PTHrP activated its own expression through an autocrine mechanism in MDA-MB-231 cells. Collectively, these studies suggest that targeting PTHrP expression in the tumor cells could be a potential therapeutic strategy for breast cancers, especially those with skeletal metastases.     

Gain-of-function mutant p53-R280K mediates survival of breast cancer cells

Missense mutations in TP53 resulting in the expression of p53-R175H, p53-R273H, or p53-R280K are frequently detected in human breast cancer. Currently, the role of mutant p53-R280K in breast cancer is relatively unknown, and therefore, the present study analyzed the function of mutant p53-R280K in breast cancer cell growth. To this end, we used small interfering RNA to study the role of mutant p53-R280K in MDA-MB-231 cells, which endogenously express the mutant protein. We found that curcumin induced apoptosis in MDA-MB-231 cells and downregulated mutant p53-R280K. We also observed that knockdown of mutant p53 by small interfering RNA induced apoptosis in MDA-MB-231 cells. Curcumin-induced apoptosis was further enhanced by the overexpression of wild-type p53, but was decreased by mutant p53-R280K overexpression. Our findings indicate that mutant p53-R280K has an important role in mediating the survival of triple-negative breast cancer MDA-MB-231 cells. Furthermore, this study suggests mutant p53-R280K could be used as a therapeutic target for breast cancer cells harboring this TP53 missense mutation.     

Matrine suppresses breast cancer cell proliferation and invasion via VEGF-Akt-NF-<Emphasis Type="Italic">κ</Emphasis>B signaling

Matrine has shown therapeutic and/or adjuvant therapeutic effects on the treatment of some patients with breast cancer. However, its mechanisms of action are largely unknown. To disclose the mechanisms, we investigated in vitro and ex vivo effects of matrine on the cancer cells. Our results confirmed that matrine significantly suppressed the proliferation of highly-metastatic human breast cancer MDA-MB-231 cell line. Matrine displayed synergistic effects with existing anticancer agents celecoxib (the inhibitor of cyclooxygenase-2), trichostatin A (the histone deacetylase inhibitor) and rosiglitazone against the proliferation and VEGF excretions in MDA-MB-231 cells. Matrine induced the apoptosis and cell cycle arrest by reducing the ratios of Bcl-2/Bax protein and mRNA levels in the cancer cells. Matrine significantly reduced the invasion, MMP-9/MMP-2 activation, Akt phosphorylation, nuclear factor κB p-65 expression and DNA binding activity, and mRNA levels of MMP-9, MMP-2, EGF and VEGFR1 in MDA-MB-231 cells. Collectively, our results suggest that matrine inhibits the cancer cell proliferation and invasion via EGF/VEGF-VEGFR1-Akt-NF-κB signaling pathway.     

二氢杨梅素抑制人乳腺癌细胞侵袭和下调MMP-2/-9蛋白表达研究

藤茶活性成分二氢杨梅素(3, 5, 7, 3′, 4′, 5′-六羟基-2, 3-二氢黄酮醇,DMY)体外对几种癌细胞具有抗增殖作用,但机制尚未完全清楚．本文研究DMY对人高转移型乳腺癌MDA-MB-231细胞侵袭的影响,并探讨可能的机制．用MTT法检测DMY对MDA-MB-231细胞的增殖抑制率;明胶酶谱分析明胶酶活力;基质金属蛋白酶(MMP-2/-9)的基因表达水平和蛋白质表达水平分别利用实时定量PCR和Western blot分析进行检测．Transwell模型检测DMY对肿瘤细胞侵袭的影响．结果显示,DMY以剂量依赖方式抑制MDA-MB-231细胞的增殖,作用48 h的IC50为73.6 mg/L．DMY显著抑制明胶酶活性和MMP-2/-9蛋白表达,并抑制MMP-2/-9 的mRNA表达水平．此外,DMY不依赖细胞毒作用和以剂量依赖方式抑制MDA- MB-231细胞的侵袭．这些结果提示：DMY能显著抑制人乳腺癌MDA-MB-231细胞的侵袭和增殖, 其侵袭抑制的机制可能与其下调MMP-2/-9蛋白表达水平相关．     

Selective Androgen Receptor Modulators (SARMs) Negatively Regulate Triple-Negative Breast Cancer Growth and Epithelial:Mesenchymal Stem Cell Signaling

Introduction

The androgen receptor (AR) is the most highly expressed steroid receptor in breast cancer with 75–95% of estrogen receptor (ER)-positive and 40–70% of ER-negative breast cancers expressing AR. Though historically breast cancers were treated with steroidal androgens, their use fell from favor because of their virilizing side effects and the emergence of tamoxifen. Nonsteroidal, tissue selective androgen receptor modulators (SARMs) may provide a novel targeted approach to exploit the therapeutic benefits of androgen therapy in breast cancer.

Materials and Methods

Since MDA-MB-453 triple-negative breast cancer cells express mutated AR, PTEN, and p53, MDA-MB-231 triple-negative breast cancer cells stably expressing wildtype AR (MDA-MB-231-AR) were used to evaluate the in vitro and in vivo anti-proliferative effects of SARMs. Microarray analysis and epithelial:mesenchymal stem cell (MSC) co-culture signaling studies were performed to understand the mechanisms of action.

Results

Dihydrotestosterone and SARMs, but not bicalutamide, inhibited the proliferation of MDA-MB-231-AR. The SARMs reduced the MDA-MB-231-AR tumor growth and tumor weight by greater than 90%, compared to vehicle-treated tumors. SARM treatment inhibited the intratumoral expression of genes and pathways that promote breast cancer development through its actions on the AR. SARM treatment also inhibited the metastasis-promoting paracrine factors, IL6 and MMP13, and subsequent migration and invasion of epithelial:MSC co-cultures.

Conclusion

1. AR stimulation inhibits paracrine factors that are important for MSC interactions and breast cancer invasion and metastasis. 2. SARMs may provide promise as novel targeted therapies to treat AR-positive triple-negative breast cancer.     

Integrin αvβ6 Promotes Lung Cancer Proliferation and Metastasis through Upregulation of IL-8–Mediated MAPK/ERK Signaling

Lung cancer is notorious for high morbidity and mortality around the world. Interleukin (IL)-8, a proinflammatory chemokine with tumorigenic and proangiogenic effects, promotes lung cancer cells growth and migration and contributes to cell aggressive phenotypes. Integrin αvβ6 is a receptor of transmembrane heterodimeric cell surface adhesion, and its overexpression correlates with poor survival from non–small cell lung cancer. However, the cross talk between αvβ6 and IL-8 in lung cancer has not been characterized so far. Herein, human lung cancer samples were analyzed, and it revealed that the immunohistochemical and mRNA expression of integrin αvβ6 was significantly correlated with the expression of IL-8. Furthermore, in vitro, integrin αvβ6 increased cell proliferation, migration, and invasion by impairing the expressions of MMP-2 and MMP-9 and inhibited cell apoptosis in human lung cancer cells A549 and H460. In addition, integrin αvβ6 upregulated IL-8 expression through activating MAPK/ERK signaling. The in vivo experiment showed that integrin αvβ6 promoted tumor growth in xenograft model mice by accelerating tumor volume and reducing apoptosis. Meanwhile, lung metastasis model experiment suggested that integrin αvβ6 stimulated tumor metastasis with the increase of lung/total weight and tumor nodules. Simultaneously, integrin αvβ6 upregulated IL-8 expression detected by both Western blots and immunohistochemistry, along with the activation of MAPK/ERK signaling. Overall, these data suggested that, in vitro and in vivo, integrin αvβ6 promoted lung cancer proliferation and metastasis, at least in part, through upregulation of IL-8–mediated MAPK/ERK signaling. Thus, the inhibition of integrin αvβ6 and IL-8 may be the key for the treatment of lung cancer.     

Luteolin 8-C-β-fucopyranoside inhibits invasion and suppresses TPA-induced MMP-9 and IL-8 via ERK/AP-1 and ERK/NF-κB signaling in MCF-7 breast cancer cells

Matrix metalloproteinase 9 (MMP-9) and interleukin-8 (IL-8) play major roles in tumor progression and invasion of breast cancer cells. The present study was undertaken to investigate the inhibitory mechanism of cell invasion by luteolin 8-C-β-fucopyranoside (named as LU8C-FP), a C-glycosylflavone, in human breast cancer cells. We investigated whether LU8C-FP would inhibit MMP-9 activation and IL-8 expression in 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated MCF-7 breast cancer cells. LU8C-FP suppressed TPA-induced MMP-9 and IL-8 secretion and mRNA expression via inhibition of the MAPK signaling pathway and down-regulation of nuclear AP-1 and NF-κB. TPA-induced phosphorylation of ERK 1/2 was suppressed by LU8C-FP, whereas JNK and p38 MAPK phosphorylation were unaffected. In addition, LU8C-FP blocked the ERK 1/2 pathways following expression of MMP-9 and IL-8. These results suggest LU8C-FP may function to suppress invasion of breast cancer cells through the ERK/AP-1 and ERK/NF-κB signaling cascades.     

分泌蛋白YKL-40增强肿瘤细胞的上皮间质样转化

目的:分泌糖蛋白YKL-40在多种晚期肿瘤病人的血液中显著升高,提示YKL-40蛋白的血浓度是肿瘤恶变的生物标志物。本课题研究YKL-40重组蛋白和过表达YKL-40肿瘤细胞对肿瘤细胞的上皮间质样转化的作用。方法:构建YKL-40过表达的纤维状乳腺癌细胞系MDA-MB-231和非纤维状结肠癌细胞系HCT-116,观察细胞形态学变化,收集细胞和细胞培养液用于Western Blot(WB)检测YKL-40和上皮间质转化标记蛋白Vimentin和N-cadherin。观察重组蛋白YKL-40对原代MDA-MB-231细胞在无血清条件下的细胞存活影响;另外,用细胞存活试剂盒检测YKL-40过表达HCT-116细胞在无血清的培养液中细胞存活情况。最后,用细胞侵袭试验检测YKL-40过表达MDA-MB-231细胞的侵袭力,并用WB和Zymography来测定细胞分泌MMP9蛋白的表达和酶活性。结果:YKL-40过表达增强MDA-MB-231细胞的形态向上皮间质样转化,并显著提高Vimentin、N-cadherin蛋白的表达,但对HCT-116细胞无法诱导上皮间质样转化。在无血清培养基培养条件下,YKL-40可以增强两种细胞的存活能力,并且YKL-40过表达的MDA-MB-231细胞增强了细胞的侵袭能力,促进了MMP9蛋白表达和蛋白活性。结论:YKL-40可以增加肿瘤细胞的存活力,增强纤维状细胞向上皮间质样转化;并且,YKL-40增加MMP9蛋白表达和活性,增强细胞侵袭力。YKL-40是间质样肿瘤细胞EMT的增强子,此发现为抑制肿瘤恶变提供新靶点。     

Salinomycin Promotes Anoikis and Decreases the CD44+/CD24- Stem-Like Population via Inhibition of STAT3 Activation in MDA-MB-231 Cells

Triple-negative breast cancer (TNBC) is an aggressive tumor subtype with an enriched CD44⁺/CD24^- stem-like population. Salinomycin is an antibiotic that has been shown to target cancer stem cells (CSC); however, the mechanisms of action involved have not been well characterized. The objective of the present study was to investigate the effect of salinomycin on cell death, migration, and invasion, as well as CSC-like properties in MDA-MB-231 breast cancer cells. Salinomycin significantly induced anoikis-sensitivity, accompanied by caspase-3 and caspase-8 activation and PARP cleavage, during anchorage-independent growth. Salinomycin treatment also caused a marked suppression of cell migration and invasion with concomitant downregulation of MMP-9 and MMP-2 mRNA levels. Notably, salinomycin inhibited the formation of mammospheres and effectively reduced the CD44⁺/CD24^- stem-like population during anchorage-independent growth. These observations were associated with the inhibition of STAT3 phosphorylation (Tyr705). Furthermore, interleukin-6 (IL-6)-induced STAT3 activation was strongly suppressed by salinomycin challenge. These findings support the notion that salinomycin may be potentially efficacious for targeting breast cancer stem-like cells through the inhibition of STAT3 activation.     

Suberoylanilide Hydroxamic Acid,an Inhibitor of Histone Deacetylase,Enhances Radiosensitivity and Suppresses Lung Metastasis in Breast Cancer In Vitro and In Vivo

Triple-negative breast cancer (TNBC), defined by the absence of an estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 expression, is associated with an early recurrence of disease and poor outcome. Furthermore, the majority of deaths in breast cancer patients are from metastases instead of from primary tumors. In this study, MCF-7 (an estrogen receptor-positive human breast cancer cell line), MDA-MB-231 (a human TNBC cell line) and 4T1 (a mouse TNBC cell line) were used to investigate the anti-cancer effects of ionizing radiation (IR) combined with suberoylanilide hydroxamic acid (SAHA, an inhibitor of histone deacetylase (HDAC)) and to determine the underlying mechanisms of these effects in vitro and in vivo. We also evaluated the ability of SAHA to inhibit the metastasis of 4T1 cells. We found that IR combined with SAHA showed increased therapeutic efficacy when compared with either treatment alone in MCF-7, MDA-MB-231 and 4T1 cells. Moreover, the combined treatment enhanced DNA damage through the inhibition of DNA repair proteins. The combined treatment was induced primarily through autophagy and ER stress. In an orthotopic breast cancer mouse model, the combination treatment showed a greater inhibition of tumor growth. In addition, SAHA inhibited the migration and invasion abilities of 4T1 cells and inhibited breast cancer cell migration by inhibiting the activity of MMP-9. In an in vivo experimental metastasis mouse model, SAHA significantly inhibited lung metastasis. SAHA not only enhances radiosensitivity but also suppresses lung metastasis in breast cancer. These novel findings suggest that SAHA alone or combined with IR could serve as a potential therapeutic strategy for breast cancer.