Characterization of a rat model with site-specific bone metastasis induced by MDA-MB-231 breast cancer cells and its application to the effects of an antibody against bone sialoprotein

Metastasis into the skeleton is a serious complication of certain neoplastic diseases such as breast, prostate and lung cancer, but the reasons for this osteotropism are poorly understood. Our aim was to establish a physiologically relevant animal model that is characterized by osteolytic lesions confined to the hind leg of nude rats. For this purpose, we injected 1x10(5) MDA-MB-231 human breast cancer cells transfected with GFP into the superficial epigastric artery, which is an anastomosing vessel between the femoral and iliac arteries. As assessed with the aid of X-rays, computed tomography and immunohistochemisty, osteolytic lesions occurred exclusively in the femur, tibia and fibula of the animals. The tumor take rate was 93% in a series of 96 rats and the increase in lesion size was observed up to 110 days after tumor cell inoculation. When applying this animal model to the effects of an antibody against bone sialoprotein (BSP), a significantly reduced osteolytic lesion size was observed after preincubation of cells (2 hr, 600 microg/ml anti-BSP) prior to intra-arterial tumor cell injection resulting in 19 T/C% at day 60 after tumor implantation (p < 0.05). In addition, the osteolytic lesion size was also significantly reduced after s.c. treatment of the animals with the antibody (20 mg/kg anti-BSPx3 within 5 days after tumor implantation), resulting in 30 T/C% at day 60 after tumor cell implantation (p < 0.05). In conclusion, the novel rat model for site-specific osteolytic lesions provides in vivo evidence that preincubation of MDA-MB-231GFP cells and treatment of rats after tumor implantation with an antibody against BSP significantly reduces the size of lytic lesions in bone.     

Decreased levels of osteopontin and bone sialoprotein II are correlated with reduced proliferation, colony formation, and migration of GFP-MDA-MB-231 cells

MDA-MB-231 human breast cancer cells transfected with GFP were used as model to determine the reduction in proliferation, colony formation, and migration in response to agents with anti-metastatic properties. These agents consisted of antisense oligonucleotides (ASOs) directed against osteopontin (OPN), bone sialoprotein II (BSP II), and osteonectin (ON), as well as an antibody directed against BSP II. A bisphosphonate derivative (ibandronate) and an alkylphosphocholine (erucylphospho-NNN-trimethylpropanolamine; ErPC3) were used as positive controls. The ASOs directed against OPN, BSP II and ON suppressed the expression of their respective target proteins by 81%, 74% and 69%, respectively. They were barely but significantly active in inhibiting the proliferation, but intermediately to highly active in inhibiting the colony formation and migration of GFP-MDA-MB-231 breast cancer cells. The antibody against human BSP II was significantly more active than all ASOs used and was equally active or even surpassed the activity of ibandronate and ErPC3 in all three assays. The results obtained suggest a specific anti-metastatic activity of this antibody as well as of the ASOs found effective in decreasing OPN and BSP II expression.     

骨涎蛋白单克隆抗体抑制亲骨转移人乳腺癌细胞血管侵袭机制的探讨

目的:探讨骨涎蛋白(BSP)单克隆抗体对亲骨转移人乳腺癌细胞株MDA-MB-23180血管侵袭能力的影响.方法:MTT法检测BSP抗体对MDA-MB-231BO细胞的增殖作用;鸡胚尿囊绒膜(CAM)实验检测BSP抗体对MDA-MB-231BO细胞血管侵袭能力的影响.结果:BSP抗体对MDA-MB-231BO细胞的生长具有特异抑制作用,其抑制率和剂量呈正相关,BSP抗体浓度为100 μg/mL时,抑制率为35.18%.BSP抗体能特异性抑制MDA-MB-231BO细胞穿透鸡胚血管内皮细胞和基底膜,抑制效应与抗体浓度呈正相关.100μg/mL的BSP抗体可以明显抑制MDA-MB-231BO细胞侵入鸡胚血管.结论:BSP抗体对MDA-MB-231BO细胞的血管侵袭能力具有特异抑制作用,提示BSP抗体可抑制乳腺癌靶向骨转移的进程.     

Downregulation of osteopontin and bone sialoprotein II is related to reduced colony formation and metastasis formation of MDA-MB-231 human breast cancer cells

Osteopontin (OPN), bone sialoprotein (BSPII), and osteonectin (ON) belong to a family of glycoproteins, which have been linked to cancer metastasis and progression. Here, we report on the selection of antisense oligonucleotides (ASOs), which are effective in reducing their protein levels. In human MDA-MB-231 breast cancer cells, the maximum inhibition of protein expression ranged from 84% (OPN) to 75% (BSPII) and 70% (ON). Erucylphospho-NNN-trimethylpropanolamine (ErPC3) was used as positive control and combination partner. Exposure to ErPC3 inhibited colony formation of MDA-MB-231 cells by 11% (10 microM), 45% (14 microM) and 78% (20 microM). The clonogenicity of breast cancer cells was reduced by 15%, 11%, 8% (5 microM), 39%, 19%, 14% (10 microM) and 46%, 39%, 21% (20 microM) in response to ASO-OPN-04, ASO-BSPII-06 and ASO-ON-03, respectively. Combination of ErPC3 with the ASOs caused additive combination effects. Pre-exposure to the ASOs, but not to the NSO, inhibited formation of osteolytic metastasis in three of four (ASO-OPN-04, P<0.03) and two of four (ASO-BSPII-06) nude rats, and reduced metastasis lesions significantly (T/C%=4.3 and 9.1, P=0.05, respectively). We conclude that downregulation of OPN and BSPII reduces colony formation of MDA-MB-231 cells and formation of osteolytic metastasis in nude rats.     

Over-expression of bone sialoprotein enhances bone metastasis of human breast cancer cells in a mouse model

Bone sialoprotein (BSP) is a major non-collagenous protein found almost exclusively in bone and other mineralized tissues including enamel, dentin and cementum. Although a role for BSP in mineralization has been indicated, BSP also appears to function in patho-physiological processes, including the metastasis of breast and prostate cancer cells to bone. The purpose of this study was to determine the role of BSP in the homing of cancer cells and to provide insights into the role of BSP in physiological as well as pathological processes. We established cultures of MDA-231 breast cancer cells stably transfected with DNA constructs of pIRES2-EGFP (green fluorescent protein) expressing human BSP (hBSP) cDNA (231BSP) under a CMV promoter, or with an antisense sequence of hBSP cDNA (231BSPAS), or with an empty vector as a control (231EV). These 3 cell groups were selected for neomycin resistance using G418 and analyzed by flow cytometry for GFP expression. The resultant cultured cells expressed different levels of hBSP as detected by RT-PCR and Western blot. Among the three, 231BSP expressed the highest levels of hBSP while 231BSPAS expressed the lowest. The capacity of the tumor cells to metastasize to bone was determined in nude mice (5 in each group) by intra-cardiac injection of the cells from the 3 different groups. Four weeks after inoculation, radiological examination revealed that all the 5 mice in the 231BSP cell group had developed osteolytic bone metastases. In the 231BSPAS group only 1 mouse demonstrated metastatic bone lesions while 3 out of 5 mice in the control group (231EV) developed metastatic lesions in the bone. These results strongly suggest that BSP over-expression in human tumor cells can enhance bone metastasis of MDA-231 cells whereas repressed expression of BSP, using antisense BSP cDNA, inhibits this effect in a mouse model.     

骨形态发生蛋白9对人乳腺癌MDA-MB-231细胞增殖和凋亡的影响

目的:探讨骨形态发生蛋白9(bone morphogenetic protein9,BMP9)在体内、外对人乳腺癌MDA-MB-231细胞增殖和凋亡的影响。方法:将pAdtrack-CMV/BMP9和pAdtrack-CMV/GFP腺病毒感染MDA-MB-231细胞,RT-PCR法检测MDA-MB-231/GFP和MDA-MB-231/BMP9细胞中BMP9mRNA的表达,MTT法、平板集落形成实验和FCM法检测细胞增殖和凋亡的情况。建立裸鼠MDA-MB-231、MDA-MB-231/GFP和MDA-MB-231/BMP9移植瘤模型,测量移植瘤体积,TUNEL法检测肿瘤细胞的凋亡情况。结果:MDA-MB-231和MDA-MB-231/GFP细胞中无BMP9mRNA的表达,MDA-MB-231/BMP9细胞中有明显BMP9mRNA表达;MDA-MB-231/BMP9细胞增殖抑制率高于MDA-MB-231/GFP细胞(P<0.05),而细胞集落形成率明显低于MDA-MB-231/GFP和MDA-MB-231组(P<0.05),细胞凋亡率则明显高于MDA-MB-231/GFP和MDA-MB-231组(P<0.05)。MDA-MB-231/BMP9组的裸鼠移植瘤体积明显小于MDA-MB-231/GFP和MDA-MB-231组(P<0.001),而移植瘤细胞中的凋亡指数则明显高于MDA-MB-231/GFP和MDA-MB-231组(P<0.001)。结论:BMP9可在体内、外抑制人乳腺癌MDA-MB-231细胞增殖并促进其凋亡。     

Sclerostin blockade promotes bone metastases of Wnt-responsive breast cancer cells

The secreted protein sclerostin is primarily produced by osteocytes and suppresses osteoblast differentiation and function by inhibiting the canonical Wnt signaling pathway. Genetic and pharmacological inhibition of sclerostin has been shown to increase bone formation and an anti-sclerostin antibody has been clinically approved for the treatment of osteoporosis. Canonical Wnt signaling is also involved in the progression of several types of cancers including breast cancer. Here, we studied the effects of sclerostin inhibition on the development of bone metastases of breast cancer using mouse models. TOPFLASH assay and real-time PCR analysis of AXIN2, a target of canonical Wnt signaling, revealed that, among four cell lines tested, MDA-MB-231 human breast cancer cells responded highly to the canonical Wnt ligand Wnt3a, whereas other cell lines exhibited marginal responses. Consistent with these results, treatment with an anti-sclerostin antibody significantly increased the bone metastases of MDA-MB-231 but not those of other breast cancer cells. Immunohistochemical studies demonstrated that an anti-sclerostin antibody induced intracellular accumulation of β-catenin in bone-colonized MDA-MB-231 cells. Suspension culture assays showed that Wnt3a accelerated the tumorsphere formation of MDA-MB-231 cells, whereas monolayer cell proliferation and migration were not affected. Furthermore, the numbers of osteoclasts and their precursor cells in bone metastases of MDA-MB-231 were significantly increased in mice treated with an anti-sclerostin antibody. These results collectively suggest that sclerostin blockade activates canonical Wnt signaling in ligand-responsive breast cancer cells metastasized to bone, thereby increasing bone metastases, likely to have been mediated at least in part by enhancing stem cell-like properties of cancer cells and osteoclastogenesis.     

Bone morphogenetic protein-9 regulates expression of long non-coding RNAs in breast cancer cells北大核心CSCD

Objective: To screen out the long non-coding RNAs (LncRNAs) related to bone morphogenetic protein-9 (BMP-9) expression, and to investigate the role of BMP-9 in the growth, differentiation, migration and apoptosis of breast cancer cells by regulating the expression of LncRNA. Methods: MDA-MB-231 cells were infected with the recombinant adenovirus Ad-BMP-9 carrying whole BMP -9 gene (named as MDA-MB-231/BMP-9 cells) or the empty vehicle adenovirus Ad-GFP carrying green fluorescent protein (GFP) gene (named as MDA-MB-231/GFP cells), respectively. Microarray technology was used to detect the difference in LncRNAs expression between MDAMB- 231/BMP-9 and MDA-MB-231/GFP cells. The changes of LncRNA LINC00443, LINC00638, LINC00486, RHNO1, SERHL, HOXA11-AS, IQCA1, LINC00461, LOC440173, LHFPL, ANKRD36BP2, BVES-AS1, LINC00937 and LINC00608 were validated by real-time fluorescent quantitative PCR. The biological funcation and related pathways of the above LncRNAs were analyzed by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Results: The expression level of BMP-9 mRNA in MDA-MB-231/BMP-9 cells was significantly higher than that in MDA-MB-231/GFP cells (as the control). Compared with the control group, the expression levels of LncRNAs in MDA-MB-231/BMP-9 cells changed significantly. The expression levels of LINC00443, LINC00638 and LINC00486 were up-regulated, while the expression levels of IQCA1, LINC00461, LOC440173, LHFPL and ANKRD36BP2 were down-regulated. The altered LncRNAs participated in the formation of cytoskeleton, cell membrane and so on, or played roles as signal molecules in intercellular signal transduction. Conclusion: The expression profile of LncRNAs in MDA-MB-231 cells with BMP-9 overexpression is significantly changed, indicating that LncRNAs may play key roles in the proliferation and invasion of breast cancer MDA-MB-231 cells regulated by BMP-9. © 2019 by TUMOR.     

Cilengitide inhibits metastatic bone colonization in a nude rat model

Integrins αvβ3 and αvβ5 are considered to play an important role in the pathogenesis of breast cancer bone metastases. This study investigates the effects of the αvβ3/αvβ5 integrin-specific inhibitor cilengitide during early metastatic bone colonization. The impact of cilengitide on the migration, invasion and proliferation of MDA-MB-231 human breast carcinoma cells as well as on bone resorption by osteoclasts was investigated in vitro. For in vivo experiments, nude rats were treated with cilengitide for 30 days starting one day after site-specific tumor cell inoculation in the hind leg, and the course of metastatic changes in bone was followed using flat-panel volumetric computed tomography (VCT) and magnetic resonance imaging (MRI). Vascular changes in bone metastases were investigated using dynamic contrast-enhanced (DCE-) MRI-derived parameters amplitude A and exchange rate coefficient kep. In vitro, cilengitide treatment resulted in a decrease in proliferation, migration and invasion of MDA-MB-231 cells, as well as of osteoclast activity. In vivo, the development of bone metastasis in the hind leg of rats was not prevented by adjuvant cilengitide treatment, but cilengitide reduced the volumes of osteolytic lesions and respective soft tissue tumors of developing bone metastases as assessed with VCT and MRI, respectively. DCE-MRI revealed significant changes in the A and kep parameters including decreased relative blood volume and increased vessel permeability after cilengitide treatment indicating vessel remodeling. In conclusion, during early pathogenic processes of bone colonization, cilengitide treatment exerted effects on tumor cells, osteoclasts and vasculature reducing the skeletal lesion size of experimental skeletal metastases.     

骨唾液酸蛋白对乳腺癌 MDA-MB-231 细胞 PI3K-AKT 信号通路的影响

目的:探讨骨唾液酸蛋白(bone sialoprotein,BSP)对乳腺癌MDA-MB-231细胞PI3K-AKT信号通路的影响。方法:BSP基因沉默的乳腺癌MDA-MB-231细胞(简称231BO-BSP27)经重组人BSP(recombinant human BSP,rhBSP)和PI3K-AKT抑制剂LY294002处理后,Western blotting检测磷酸化AKT水平的变化,实时定量PCR检测caspase-3、cyclin D1 mRNA表达水平,MTT法检测细胞增殖能力。结果:与BSP基因未沉默的对照组231BO-Scrambled细胞相比,BSP基因沉默的231BO-BSP27细胞BSP蛋白表达明显下调(74.32±2.18)%(P<0.01);AKT磷酸化水平明显下降(33.30±2.61)%(P<0.01),而caspase-3和cyclin D1 mRNA表达分别上升和下降(1.000±0.000 vs 1.733±0.039,1.000±0.000 vs 0.370±0.012;均P<0.01);231BO-BSP27细胞增殖能力显著下降(P<0.05)。外源添加rhBSP蛋白分别上调231BO-Scrambled和231BO-BSP27细胞AKT磷酸化水平(17.86±2.27)%和(33.78±1.51)%(均P<0.01),231BO-BSP27细胞caspase-3 mRNA表达降低(1.000±0.039 vs 0.541±0.091,P<0.01)、cyclin D1 mRNA表达升高(1.000±0.000 vs 2.921±0.032,P<0.01),促进231BO-Scrambled和231BO-BSP27细胞的增殖(均P<0.01)。LY294002则能逆转rhBSP对231BO-Scrambled和231BO-BSP27细胞AKT磷酸化激活作用(P<0.05),使231BO-BSP27细胞caspase-3 mRNA表达升高(P<0.01)、cyclin D1 mRNA表达降低(P<0.01),使该两种细胞增殖能力下降(均P<0.01)。结论:BSP通过PI3K-AKT信号通路调控乳腺癌MDA-MB-231细胞caspase-3和cyclin D1的表达,并影响细胞的增殖。     

The heat shock protein 90 inhibitor, 17-allylamino-17-demethoxygeldanamycin, enhances osteoclast formation and potentiates bone metastasis of a human breast cancer cell line

Breast cancer metastasis to the bone occurs frequently, causing numerous complications including severe pain, fracture, hypercalcemia, and paralysis. Despite its prevalence and severity, few effective therapies exist. To address this, we examined whether the heat shock protein 90 (Hsp90) inhibitor, 17-allylamino-17-demethoxygeldanamycin (17-AAG), would be efficacious in inhibiting breast cancer metastasis to bone. Utilizing the human breast cancer subline, MDA-MB-231SA, previously in vivo selected for its enhanced ability to generate osteolytic bone lesions, we determined that 17-AAG potently inhibited its in vitro proliferation and migration. Moreover, 17-AAG significantly reduced MDA-MB-231SA tumor growth in the mammary-fat pad of nude mice. Despite these findings, 17-AAG enhanced the incidence of bone metastasis and osteolytic lesions following intracardiac inoculation in the nude mouse. Consistent with these findings, 17-AAG enhanced osteoclast formation 2- to 4-fold in mouse bone marrow/osteoblast cocultures, receptor activator of nuclear factor kappaB ligand (RANKL)-stimulated bone marrow, and RAW264.7 cell models of in vitro osteoclastogenesis. Moreover, the drug enhanced osteoclastogenesis in human cord blood progenitor cells, demonstrating that its effects were not limited to mouse models. In addition to 17-AAG, other Hsp90 inhibitors, such as radicicol and herbimycin A, also enhanced osteoclastogenesis. A pro-osteolytic action of 17-AAG independent of tumor presence was also determined in vivo, in which 17-AAG-treated tumor-naive mice had reduced trabecular bone volume with an associated increase in osteoclast number. Thus, HSP90 inhibitors can stimulate osteoclast formation, which may underlie the increased incidence of osteolysis and skeletal tumor incidence caused by 17-AAG in vivo. These data suggest an important contraindication to the Hsp90 targeted cancer therapy currently undergoing clinical trial.     

Cadherin-11-mediated interactions with bone marrow stromal/osteoblastic cells support selective colonization of breast cancer cells in bone

Cell adhesion molecules have been implicated in the selective colonization of cancer in distant organs. Breast cancer has a strong predilection for spreading to bone. Cadherin-11, which is one of the classical type-2 cadherin family members and mediates homophilic cell-cell adhesion, is constitutively expressed in stromal and osteoblastic cells in bone marrow. Elevated cadherin-11 expression is also found in aggressive human breast cancers. Here, we investigated the role of the interactions between breast cancer cells and bone marrow stromal/osteoblastic cells via cadherin-11 in the selective spread to bone. The bone-seeking clone of the MDA-MB-231 human breast cancer cells showed greater cadherin-11 expression than the parental and the brain-seeking clone. Cadherin-11 overexpression in MDA-MB-231 cells increased bone metastases with promoted bone resorption, while the natural variant form of cadherin-11 that is unable to establish cell-cell adhesion did not. Of note, introduction of cadherin-11 showed no effects on lung metastases. Fluorescence-activated cell sorter analysis using the fluorescent dye-labeled cancer cells showed that early colonization in bone marrow was increased by cadherin-11. Co-cultures with the MC3T3-E1 osteoblastic cells that constitutively expressed cadherin-11 caused an up-regulation of parathyroid hormone-related protein (PTH-rP) production in MDA-MB-231 cells overexpressing cadherin-11. The conditioned medium of the co-cultures increased osteoclastogenesis, which was blocked by a neutralizing antibody to PTH-rP. In conclusion, our results suggest that cadherin-11 promotes homing and migration to bone and osteoclastogenesis through mediating the homophilic interactions of breast cancer cells with marrow stromal/osteoblastic cells, thereby enhancing bone metastases.     

建立乳腺癌骨转移动物模型方法的比较研究

 目的　对四种乳腺癌骨转移动物模型的构建方法进行比较研究。方法　32只4～6周龄雌性裸鼠随机分为A、B、C、D 4组,每组8只,每只裸鼠以5×105个MDA-MB-231细胞按分组分别注射入左第二乳房脂肪垫、尾静脉、左心室和左胫骨骨髓腔。观察A组裸鼠乳腺原位成瘤情况、全组注射致死情况和全组49 d后骨转移发生情况。结果　A组乳腺原位移植瘤形成率为87.5 %（7／8）。仅C组注射致死裸鼠1只。各组骨转移发生率分别为：0（0／8）、12.5 %（1／8）、71.4 %（5／7）、100 %（8／8）。A组和C组、A组和D组、B组和C组、B组和D组之间骨转移发生率差异均有统计学意义。结论　肿瘤细胞经乳腺原位移植和尾静脉注射移植两种方法不适用于建立乳腺癌骨转移模型;肿瘤细胞经左心室注射移植和骨原位移植方法能稳定地获得骨转移,是乳腺癌骨转移动物模型构建的可行方法。     

沉默环状RNA hsa_circ_0001785表达对乳腺癌MDA-MB-231细胞增殖、迁移及侵袭能力的影响

目的:探究环状RNA（circRNA）hsa_circ_0001785在乳腺癌组织和细胞中的表达变化及其对乳腺癌细胞增殖、迁移和侵袭能力的影响。方法:qRT-PCR实验检测hsa_circ_0001785在乳腺癌组织和乳腺癌细胞（MDA-MB-231和SK-BP-3）中的相对表达水平；CCK-8和克隆形成实验检测沉默或上调表达hsa_circ_0001785对MDA-MB-231细胞活性和克隆形成能力的影响；划痕愈合实验和Transwell侵袭实验检测沉默或上调表达hsa_circ_0001785对MDA-MB-231细胞迁移及侵袭能力的影响。结果:hsa_circ_0001785在乳腺癌组织中的相对表达水平明显高于癌旁组织，hsa_circ_0001785在MDA-MB-231和SK-BP-3细胞中的相对表达水平明显高于人乳腺上皮细胞MCF10A。在MDA-MB-231细胞沉默hsa_circ_0001785，MDA-MB-231细胞的活性和克隆形成能力明显降低，迁移距离显著减少，侵袭能力也明显下降。而在MDA-MB-231细胞中上调表达hsa_circ_0001785，MDA-MB-231细胞的活性和克隆形成能力显著升高，迁移距离明显升高，侵袭能力也明显升高。结论:hsa_circ_0001785在乳腺癌组织和乳腺癌细胞（MDA-MB-231和SK-BP-3）中的表达水平明显升高；沉默hsa_circ_0001785显著抑制乳腺癌MDA-MB-231细胞的增殖、迁移和侵袭能力，而上调表达hsa_circ_0001785明显促进乳腺癌MDA-MB-231细胞的增殖、迁移和侵袭能力。     

小鼠动物模型中骨髓播散肿瘤细胞的检测方法

目的：探究小鼠骨髓中播散肿瘤细胞(disseminated tumor cells,DTCs)的检测方法。方法：采用慢病毒感染的方法构建MDA-MB-231-GFP/Luc乳腺癌细胞系,将MDA-MB-231-GFP/Luc细胞经左心室接种于NOD-SCID小鼠体内,构建骨髓DTCs小鼠模型。采用荧光定量RT-qPCR、流式细胞计数、骨组织连续切片免疫荧光染色三种检测方法对小鼠骨髓DTCs进行定量和组织学定位研究。结果：荧光定量RT-qPCR法和流式细胞计数法的检测下限分别为22个和25个绿色荧光蛋白阳性(GFP⁺)细胞。骨组织连续切片免疫荧光染色法虽然不能定量骨髓DTCs数量,但可观察到GFP⁺DTCs在骨组织中的分布,定位于成骨细胞或骨基质附近。结论：三种检测方法联合使用可满足小鼠骨转移研究动物实验中骨髓DTCs的定量和定位研究的需求,可为乳腺癌骨转移和骨髓中休眠癌细胞研究提供方法学支持。     

Upregulated hPuf-A promotes breast cancer tumorigenesis

hPuf-A is a member of RNA-binding PUF family that regulates mRNA translation. Redistribution of hPuf-A from the nucleolus to the nucleoplasm upon genotoxic stress modulates the poly(ADP-ribosyl)ation activity of PARP-1. Here, we report a novel function of hPuf-A involved in promoting breast cancer progression. Immunohistochemical studies showed higher expression levels of hPuf-A in stage I, II, III, and IV breast cancer specimens in contrast with those of hPuf-A in ductal carcinoma in situ. The presence of hPuf-A is highly associated with colony formation capacities in breast cancer T47D and MDA-MB-231 cells. Xenograft growth of hPuf-A-silenced and hPuf-A overexpressing MDA-MB-231 cells in nude mice was substantially in concert with colony formation capacities. This promoting effect of hPuf-A in tumorigenesis might be correlated with the regulation of its associated mRNAs, such as RbAp48 and DDX3. Collectively, hPuf-A may have diagnostic values in breast cancer progression.     

Nek2 as a novel molecular target for the treatment of breast carcinoma

We investigated the role of Nek2, a member of the serine-threonine kinase family, in the tumorigenic growth of breast carcinoma. Increased expression of Nek2 was observed in all breast carcinoma cell lines examined (BT20, BT474, Hs578T, MCF7, MDA-MB-231, T47D, and ZR-75-1) by immunoblotting. By treatment with Nek2 short interfering RNA (siRNA), expression of Nek2 was clearly decreased in both estrogen receptor (ER)-positive (MCF7) and ER-negative (MDA-MB-231) breast carcinoma cell lines. Cell growth, colony formation in soft agar, and in vitro invasiveness of these cell lines were substantially suppressed by Nek2 siRNA treatment. In a xenograft nude mouse model with subcutaneous implantation of MCF7 or MDA-MB-231, subcutaneous injection of Nek2 siRNA around the tumor nodules resulted in a reduction of tumor size compared with those of control siRNA injection. Taken together, Nek2 appears to play a pivotal role in tumorigenic growth of breast carcinoma cells, and could be a useful therapeutic molecular target for the treatment of breast carcinoma both in ER-positive and ER-negative cases. ( Cancer Sci 2009; 100: 111–116)     

In vitro and in vivo antitumorigenic activity of a mixture of lysine, proline, ascorbic acid, and green tea extract on human breast cancer lines MDA-MB-231 and MCF-7

Current treatments are generally ineffective once breast cancer has metastasized; median survival is reduced to 2–3 yr. Previous research studies demonstrating potent synergistic antitumor activity of lysine, proline, ascorbic acid, and epigallocatechin gallate prompted us to investigate the in vivo inhibitory effect of a nutrient mixture containing lysine, proline, arginine, ascorbic acid, and epigallocatechin gallate (NM) on the growth of human cancer xenografts in female athymic nude mice. Five to six week old female mice were inoculated with 3×10⁶ breast cancer cells MDA-MB-231. After injection, the mice were randomly divided into two groups A and B; group A was fed a regular diet and group B with the regular diet supplemented with 0.5% of the nutrient mixture (NM). Four weeks later, the mice were sacrificed, and their tumors were excised, weighed, and processed for histology. We also tested the effect of NM in vitro on estrogen-receptor positive (ER⁺) MCF-7 and estrogen-receptor negative (ER⁻) MDA-MB-231 breast cancer cell lines by measuring: cell proliferation by MTT assay, expression of MMPs by gelatinase zymography, invasion through Matrigel, and VEGF by ELISA. MCF-7 cells were also treated with estradiol to study enhanced invasion and expression of MMPs and VEGF. Results showed that NM inhibited the growth and reduced the size of tumors in female nude mice by 27%. Furthermore, histological evaluation revealed increased mitotic index, MMP-9 and VEGF secretion, and PAS material (mucin) in the control group tissues. In vitro studies showed NM inhibited MDA-MB-231 cell growth by 34% at 500 μg/mL and MCF-7 cell growth by 18% at 1000 μg/mL. Invasion of MDA-MB-231 through Matrigel was inhibited by 50%, 60%, and 95% by 10, 50, and 100 μg/mL of NM, respectively. The results of this study demonstrated that the nutrient mixture tested significantly suppressed tumor growth of breast cancer cells in female athymic nude mice and significantly inhibited MMP expression, angiogenesis, and invasion in breast cancer cells, in vitro, offering promise for therapeutic use in the treatment of breast cancer.     

Sustained conditional knockdown reveals intracellular bone sialoprotein as essential for breast cancer skeletal metastasis

Increased bone sialoprotein (BSP) serum levels are related to breast cancer skeletal metastasis, but their relevance is unknown. We elucidated novel intracellular BSP functions by a conditional knockdown of BSP. Conditional MDA-MB-231 subclones were equipped with a novel gene expression cassette containing a tet-regulated miRNA providing knockdown of BSP production. These clones were used to assess the effect of BSP on morphology, proliferation, migration, colony formation and gene expression in vitro, and on soft tissue and osteolytic lesions in a xenograft model by three imaging methods. BSP knockdown caused significant anti-proliferative, anti-migratory and anti-clonogenic effects in vitro (p<0.001). In vivo, significant decreases of soft tissue and osteolytic lesions (p<0.03) were recorded after 3 weeks of miRNA treatment, leading to complete remission within 6 weeks. Microarray data revealed that 0.3% of genes were modulated in response to BSP knockdown. Upregulated genes included the endoplasmic reticulum stress genes ATF3 and DDIT3, the tumor suppressor gene EGR1, ID2 (related to breast epithelial differentiation), c-FOS and SERPINB2, whereas the metastasis associated genes CD44 and IL11 were downregulated. Also, activation of apoptotic pathways was demonstrated. These results implicate that intracellular BSP is essential for breast cancer skeletal metastasis and a target for treating these lesions.