Stromelysin-3 expression is an early event in human oral tumorigenesis

Stromelysin-3 (ST3/MMP11) is associated with human tumour progression. To determine the clinical significance of ST3 in oral tumorigenesis, its expression was analysed in different stages of tobacco-associated oral cancer. Immunohistochemical analysis of ST3 expression in 79 oral precancerous lesions, 177 SCCs and 35 histologically normal oral tissues was carried out and corroborated by immunoblotting and RT-PCR. ST3/MMP11 protein expression was observed in 45/79 (57%) precancerous lesions [28/48 (58%) with hyperplasia and 17/31 (55%) with dysplasia] and in 123/177 (70%) oral SCCs. In precancerous lesions, ST3 expression was higher compared to normal oral tissues (p = 0.000) and associated with MVD (p = 0.05), a marker for angiogenesis. ST3 was also expressed in cells cultured from precancerous and cancerous lesions that had undergone epithelial-to-mesenchymal transition. In oral cancer patients, ST3 positivity was associated with lymph node involvement (p = 0.025) and increased intratumoral MVD (p = 0.009). Ninety-eight oral SCC patients were followed up for a period of 94 months (median 22.5 months). Kaplan-Meier survival analysis showed that ST3 expression was not a significant prognostic indicator. ST3 expression in oral hyperplastic and dysplastic lesions suggests its association with progression of phenotypic alterations acquired early during the malignant transformation pathway of oral epithelium and implicates it not only in angiogenesis and invasion but also in tumorigenesis. Thus, ST3 may serve as a potential target for developing molecular therapeutics for early intervention in oral tumorigenesis.     

Identification of HLA-A3-restricted CD8+ T cell epitopes derived from mammaglobin-A,a tumor-associated antigen of human breast cancer

Mammaglobin-A is highly overexpressed in breast cancer cell lines and primary breast tumors. This pattern of expression is restricted to mammary epithelium and metastatic breast tumors. Thus, mammaglobin-A-specific T cell immune responses may provide an important approach for the design of breast cancer-specific immunotherapy. The purpose of our study was to define the T cell-mediated immune response to mammaglobin-A. We determined that the frequency of mammaglobin-A-reactive CD8+ and CD4+ T cells in breast cancer patients is significantly higher than that observed in healthy female controls using limiting dilution analyses (p = 0.026 and p = 0.02, respectively). We identified 8 mammaglobin-A-derived 9-mer peptides with the highest binding affinity for the HLA-A3 molecule (Mam-A3.1-8) using a computer-assisted analysis of the mammaglobin-A protein sequence. Subsequently, we determined that CD8+ T cells from breast cancer patients reacted to peptides Mam-A3.1 (23-31, PLLENVISK), Mam-A3.3 (2-10, KLLMVLMLA), Mam-A3.4 (55-63, TTNAIDELK) and Mam-A3.8 (58-66, AIDELKECF) using an IFN-gamma enzyme-linked immunospot assay. A CD8+ T cell line generated in vitro against HLA-A*0301-transfected TAP-deficient T2 cells loaded with these peptides showed significant cytotoxic activity against the Mam-A3.1 peptide. This CD8+ T cell line showed a significant HLA-A3-restricted cytotoxic activity against mammaglobin-A-positive but not mammaglobin-A-negative breast cancer cells. In summary, our study identified four HLA-A3-restricted mammaglobin-A-derived epitopes naturally expressed by breast cancer cells, indicating the immunotherapeutic potential of this novel antigen for the treatment and prevention of breast cancer.     

Stromelysin-1/matrix metalloproteinase-3 (MMP-3) expression accounts for invasive properties of human astrocytoma cell lines

Tumor invasiveness is an intrinsic feature of most glial tumors that accounts for their malignant and locally destructive nature. We evaluated the subcutaneous (sc) tumorigenicity and in vivo invasiveness of 9 astrocytoma cell lines together with their respective metalloprotease activity in order to establish their biologic behavior and malignant potential. Invasiveness was assessed with an in vivo invasion assay using tracheal xenotransplants subcutaneously implanted into Scid mice. This assay permitted us to evaluate the penetration of tumor cells into the transplanted deepithelialized tracheas previously inoculated with either normal primary glial cells or with astrocytoma-derived cell lines. Although only 2 cell lines were tumorigenic after sc inoculation, 5 out of 9 tumor cell lines were tumorigenic in the tracheal graft system. The astrocytoma cell lines showed varying levels of penetration into the tracheal wall. The tumor lines GOS3, M059K, CCFSTTG1 and A172, as well as primary normal astrocytes, were nontumorigenic and noninvasive in this experimental model. LN405, SW1088 and SW1783 cells that were not tumorigenic as sc xenotransplants, on the other hand, grew well in the tracheal graft system showing low levels of in vivo invasiveness. U87MG and U118MG cells were tumorigenic as sc xenotransplants and showed high levels of invasiveness. In parallel to these in vivo studies, the constitutive levels of secreted gelatinases and stromelysins (MMP-3 and MMP-11) were investigated using conditioned media submitted to gelatin or casein-substrate zymography and Western blot analysis. Neither the gelatinases (MMP-2 and MMP-9) nor MMP-11 showed a direct correlation with the levels of in vivo tumor cell invasiveness. Conversely, secretion of MMP-3 correlated closely with tumorigenicity and invasiveness. In vitro tumor cell invasiveness was significantly reduced after incubation with the metalloproteinase inhibitor GM6001. This positive correlation between MMP-3 and the depth of tracheal wall penetration led us to conclude that the invasive properties of brain tumor cells may be due to the direct or indirect proteolytic effects of MMP-3 on extracellular matrix (ECM) macromolecules and that this enzyme might be a potential target for future therapies.     

Protein production by osteoblasts: modulation by breast cancer cell-derived factors

Breast cancer cells (BCC) frequently metastasize to bone where they may cause tumor-induced osteolysis (TIO). While the important eroding role of the osteoclasts in TIO is well admitted, the possibility that BCC and/or osteoblasts activated by tumoral factors could also directly degrade bone matrix in this pathology has been much less investigated. We show here that the net collagen amount produced in vitro by normal human osteoblasts and osteoblast-like cells was significantly reduced by culture medium conditioned by several BCC lines, including three newly isolated ones. There was no evidence for a decrease in collagen synthesis, as assessed by the production of the carboxyterminal propeptide of type I collagen. In contrast, the effect of BCC-derived medium on collagen amount was attenuated by inhibitors of matrix metalloproteinases (MMPs) as well as by tranexamic acid, an inhibitor of the plasminogen conversion to plasmin, while it was abolished in presence of the two kinds of proteinase inhibitors. This osteoblastic protein degradation activity appeared to be attributable to factors secreted by the osteoblasts as well as by BCC. These factors had molecular weights lower as well as higher than 10kD. Our data suggest that besides the eroding action of osteoclasts, BCC- and osteoblast-derived MMPs and serine proteinases might play a direct role in bone collagen degradation in TIO.     

Expression of Ets-related transcription factors and matrix metalloproteinase genes in human breast cancer cells

The expression levels of ets and MMP genes was examined in two breast cancer cell lines of differing invasive potential. The more invasive MDA-MB-231 cell line had higher levels of Ets-1, Ets-2, PEA3, ERM, Tel, Net, MMP-13 and -14 mRNA than MCF-7 cells. MMP-1, -3 and -16 mRNAs were expressed equally. TPA stimulated MMP-1, -9 and TIMP-1 mRNA expression in both cell lines. MMP-2 and MMP-7 mRNAs were not detected in either cell line. The Ets-1 protein was only detected in MDA-MB-231 cells and its level increased following TPA stimulation. TPA induced MMP-9 activity in MCF-7 cells and increased its activity in MDA-MB-231 cells, however, MMP-2 activity was not detected.     

Induction of matrix metalloproteinases MMP-1 and MMP-2 by co-culture of breast cancer cells and bone marrow fibroblasts

Two invasive breast cancer cell lines (MDA-MB-231 and BT-549) were found to be more adherent and have greater migratory capacity on bone marrow fibroblasts than three non-invasive cell lines (MCF-7, T47D and BT-483). Antibodies to the adhesion molecules CD44, E-cadherin, ICAM-1, and integrin chains 2, 3, 4, 5, 6, v, 1, 3 and 7 failed to inhibit breast cancer cell migration through bone marrow fibroblasts. Inhibitors of matrix metalloproteases, 1, 10-phenanthroline, Ro-9790, TIMP-1 and TIMP-2 were able to attenuate the migration of MDA-MB-231 cells through bone marrow fibroblast monolayers suggesting a role for these enzymes in the migration of breast cancer cells through bone marrow adherent layers. Co-culture of MDA-MB-231 cells and bone marrow fibroblasts resulted in augmentation of the levels of the matrix metalloproteases MMP-1 and MMP-2 in culture supernatants. Soluble factors produced by bone marrow fibroblasts were responsible for the increase in MMP-1 levels. However, maximal MMP-2 production was dependent on direct contract between the breast cancer cells and the bone marrow fibroblasts. Modulation of MMP production by cell–cell contact or soluble factors suggests a mechanism by which breast cancer cells can enhance their ability to invade the bone marrow microenvironment.     

Proteolysis in human breast and colorectal cancer.

Proteolysis occurs when proteinase activity exceeds inhibitor activity. Proteolysis is normally tightly regulated and is involved in cancer invasion and metastasis. The aim of this study was to compare proteolysis in breast and colorectal cancer. Proteinase and inhibitor expression were analysed in paired tumour and normal tissue samples from 43 breast and 24 colorectal cancer patients using substrate zymography, Western blotting and quenched fluorescence substrate hydrolysis. The expression of the latent forms of matrix metalloproteinase-2 (MMP-2), MMP-3 and MMP-9, urokinase plasminogen activator (uPA), tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2 expression were observed in both tumour and normal tissue samples from breast and colorectal tissue; however, expression was greater in the tumour tissue. Expression of active MMP-2 and MMP-9 and the total MMP activity were greater in tumour compared to normal samples in both tissues (P < 0.05). The expression of all proteinases and total MMP activity was greater in colorectal tissue than breast tissue samples. Breast and colorectal cancer demonstrated different proteinase profiles, however proteolysis in both tissues was greater in tumour tissue than normal tissue.     

Upregulation of matrix metalloproteinases (MMPs) in breast cancer xenografts: a major induction of stromal MMP-13

In human breast cancer (HBC), as with many carcinoma systems, most matrix metalloproteinases (MMPs) are largely expressed by the stromal cells, whereas the tumour cells are relatively silent in MMP expression. To determine the tissue source of the most relevant MMPs, we xenografted HBC cell lines and HBC tissues into the mammary fat pad (MFP) or bone of immunocompromised mice and measured the expression of human and mouse MMP-2, -9, -11, -13, membrane-type-1 MMP (MT1-MMP), MT2-MMP and MT3-MMP by species-specific real-time quantitative RT-PCR. Our data confirm a stromal origin for most tumour-associated MMPs and indicate marked and consistent upregulation of stromal (mouse) MMP-13 and MT1-MMP in all xenografts studied, irrespective of implantation in the MFP or bone environments. In addition, we show increased expression of both human MMP-13 and human MT1-MMP by the MDA-MB-231 tumour cells grown in the MFP compared to in vitro production. MMP protein and activity data confirm the upregulation of MMP mRNA production and indicate an increase in the activated MMP-2 species as a result of tumour implantation. These data directly demonstrate tumour induction of MMP production by stromal cells in both the MFP and bone environments. These xenografts are a valuable means for examining in vivo production of MMPs and suggest that MMP-13 and MT1-MMP will be relevant targets for inhibiting breast cancer progression.     

Relationship between galectin-3 expression and TRAIL sensitivity in breast cancer

Evaluation of: Mazurek N, Byrd JC, Sun Y, Ueno S, Bresalier RS. A galectin-3 sequence polymorphism confers TRAIL sensitivity to human breast cancer cells. Cancer DOI: 10.1002/cncr.26078 (2011) (Epub ahead of print).

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) binds to death receptors expressed on cancer cells and induces apoptosis. Triple-negative breast cancer cell lines are more sensitive to TRAIL or TRAIL-death receptor agonistic monoclonal antibody-induced apoptosis compared with HER-2/neu-overexpressing or luminal cell lines. The paper under evaluation sought to determine whether the His64/Pro64 polymorphism of galectin-3, which is associated with breast cancer incidence, affects sensitivity to TRAIL. None of five breast cancer cell lines homozygous for Pro64 galectin-3 were sensitive to TRAIL, but two out of two homozygous His64 cell lines and one out of two heterozygous His64 cell lines were sensitive. Transfection of galectin-3 null BT549 breast cancer cells with His64 galectin-3 rendered them sensitive to TRAIL, while Pro64 galectin-3-transfected cells remained resistant to TRAIL. This article highlights that galectin-3 receptor expression and genotype may be useful markers in predicting TRAIL or agonistic antibody sensitivity of breast cancer patients.     

低氧环境下罗勒多糖对乳腺癌细胞TIMPs mRNA表达的影响

目的： 〖HT5"SS〗探讨低氧对人乳腺癌细胞株MDA231金属蛋白酶组织抑制剂（TIMPs）mRNA表达的影响,以及罗勒多糖(basil polysaccharide,BP)对TIMPs的作用。〖HT5W〗方法：〖HT5"SS〗 分别置MDA231细胞株于常氧（21% O2、5% CO2）、低氧（1% O2、5% CO2和94% N2）环境中和罗勒多糖（200 μg/ml）培养6 h,RTPCR技术检测不同处理组细胞TIMP1、2、3 mRNA水平。〖HT5W〗结果： 〖HT5"SS〗MDA231细胞株表达TIMP1、2 mRNA,未检测到TIMP3 mRNA;低氧环境下MDA231细胞株TIMP1、2 mRNA水平显著上升(P<0.05);罗勒多糖处理后TIMPs mRNA的含量,无论常氧组还是低氧组都有显著改变：常氧环境下罗勒多糖可明显下调MDA231细胞株中TIMP1、2 mRNA的表达(P<0.05),而低氧环境下则显著上调其表达(P<0.05)。〖HT5W〗结论：〖HT5"SS〗 罗勒多糖在常氧及低氧环境下对MDA231细胞TIMP1、2基因表达的影响效应截然相反,提示抗肿瘤药物及生物疗法的体外机制研究设计应充分考虑氧环境的影响。     

Osteolytic bone metastasis in breast cancer

Summary Metastasis of breast cancer cells to bone consists of multiple sequential steps. To accomplish the process of metastasis to bone, breast cancer cells are required to intrinsically possess or acquire the capacities that are necessary for them to proliferate, invade, migrate, survive, and ultimately arrest in bone. These capacities are essential for any cancer cells to develop distant metastases in organs such as lungs and liver as well as bone. Once breast cancer cells arrest in bone, bone is a storehouse of a variety of cytokines and growth factors and thus provides an extremely fertile environment for the cells to grow. However, breast cancer cells are unable to progress in bone unless they destroy bone with the assistance of bone-resorbing osteoclasts. Thus, the capacity of breast cancer cells to collaborate with osteoclasts is likely to be specific and is likely critical for them to cause osteolytic bone metastases. Evidence to support the concept that there is an intimate relationship between breast cancer cells and osteoclasts is described using anin vivo bone metastasis model in which human breast cancer cells are inoculated into the left ventricle of nude mice. The roles of cell adhesion molecules including cadherins and laminin and matrix metalloproteinases in the development of osteolytic bone metastases by breast cancer are also discussed.     

Expression of SART3 antigen and induction of CTLs by SART3-derived peptides in breast cancer patients

We recently reported the SART3 tumour-rejection antigen as possessing tumour epitopes capable of inducing HLA-class I-restricted cytotoxic T lymphocytes (CTLs). This study investigated expression of the SART3 antigen in breast cancer to explore an appropriate molecule for use in specific immunotherapy of breast cancer patients. The SART3 antigen was detected in all of the breast cancer cell lines tested, 30 of 40 (75%) breast cancer tissue samples, and 0 of 3 non-tumourous breast tissue samples. SART3 derived peptides at positions 109-118 and 315-323 induced HLA-A24 restricted CTLs that reacted to breast cancer cells from the peripheral blood mononuclear cells (PBMCs) of breast cancer patients. Therefore, the SART3 antigen and its peptides could be an appropriate molecule for use in specific immunotherapy of the majority of HLA-A24-positive breast cancer patients.     

Caveolin-1在浸润性乳腺癌间质中的表达及临床病理意义

目的:探讨窖蛋白-1(Caveolin-1)在乳腺癌间质中的表达及其与乳腺癌发生、发展及转移的关系。方法:运用免疫组织化学SP法研究Caveolin-1在正常乳腺癌间质和正常乳腺间质中的表达。结果:80例乳腺癌组织中间质Caveolin-1的表达阳性率分别为55%,而在36例正常乳腺组织中间质Caveolin-1的表达阳性率为75%,两者比较有显著差异(P=0.042);间质Caveolin-1的表达阳性率在乳腺癌高、中分化组明显高于低分化组,转移阳性组明显高于转移阴性组,其差异均有统计学意义(P=0.025);复发组间质Caveolin-1的表达阳性率也明显低于未复发组,其差异有统计学意义(P=0.012)。K-M生存曲线显示间质Caveolin-1的表达阴性患者的无瘤生存率也明显低于间质Caveolin-1的表达阳性患者(P=0.008)。多因素COX逐步回归分析结果显示间质Caveolin-1是无瘤生存率(P=0.031)的独立因素。结论:间质Cave-olin-1可能在乳腺癌的发生、发展及转移过程中起着关键性作用。     

Caveolin-1在浸润性乳腺癌间质中的表达及临床病理意义

目的：探讨窖蛋白-1（Caveolin-1）在乳腺癌间质中的表达及其与乳腺癌发生、发展及转移的关系。方法：运用免疫组织化学SP法研究Caveolin-1在正常乳腺癌间质和正常乳腺间质中的表达。结果：80例乳腺癌组织中间质Caveolin-1的表达阳性率分别为55%,而在36例正常乳腺组织中间质Caveolin-1的表达阳性率为75%,两者比较有显著差异（P=0.042）;间质Caveolin-1的表达阳性率在乳腺癌高、中分化组明显高于低分化组,转移阳性组明显高于转移阴性组,其差异均有统计学意义（P=0.025）;复发组间质Caveolin-1的表达阳性率也明显低于未复发组,其差异有统计学意义（P=0.012）。K-M生存曲线显示间质Caveolin-1的表达阴性患者的无瘤生存率也明显低于间质Caveolin-1的表达阳性患者（P=0.008）。多因素COX逐步回归分析结果显示间质Caveolin-1是无瘤生存率（P=0.031）的独立因素。结论：间质Cave-olin-1可能在乳腺癌的发生、发展及转移过程中起着关键性作用。     

Role of RANKL-induced osteoclast formation and MMP-dependent matrix degradation in bone destruction by breast cancer metastasis

Bone metastasis of breast cancer induces severe osteolysis with increased bone resorption. Osteoclast differentiation regulated by the receptor activator of NF-kappaB ligand (RANKL) in osteoblasts and matrix degradation induced by matrix metalloproteinases (MMPs) are thought to be involved in the process of bone resorption. When nude mice were inoculated with human breast cancer cells, MDA-MB-231(MDA-231), numerous osteoclasts resorbed bone and the degradation of the bone matrix markedly progressed in the femur and tibia with metastasis of the MDA-231 tumour. The expression of RANKL, MMP-13 and membrane-type 1-MMP mRNA was markedly elevated in bone with metastasis. When MDA-231 cells were cocultured with mouse calvaria, MDA-231 markedly induced bone resorption measured by calcium release from the calvaria, and the expression of RANKL, MMP-2 and MMP-13 was elevated in the calvaria after the coculture. The separation of MDA-231 from the calvaria using filter insert showed decreased bone resorption, suggesting that cell-to-cell interaction is essential for cancer-induced bone resorption. Adding MDA-231 cells to bone marrow cultures markedly induced osteoclast formation, and the expression of RANKL in osteoblasts was enhanced by contact with the cell surface of MDA-231 cells. These results indicate that RANKL-induced osteoclast formation and MMP-dependent matrix degradation are associated with osteolysis because of bone metastasis of breast cancer.     

Emmprin in epithelioid sarcoma: expression in tumor cell membrane and stimulation of MMP-2 production in tumor-associated fibroblasts

Emmprin is a transmembrane glycoprotein on tumor cells that stimulates peritumoral fibroblasts to produce matrix metalloproteinases (MMPs). Emmprin and the induced MMPs play a crucial role in tumor progression, invasion and metastasis of human carcinomas (epithelial malignancies). However, only a few reports have addressed its role in soft tissue sarcomas. This study investigated the expression and role of emmprin in epithelioid sarcoma (ES). Immunoblot studies of 2 ES cell lines showed that they express emmprin, and co-culture of these ES cells with dermal fibroblasts resulted in upregulation of gelatinase A (MMP-2) in fibroblasts, as shown by zymography, immunoblotting and enzyme immunoassay. This stimulation was inhibited by an activity-blocking peptide against emmprin and by antiemmprin antibody. In addition, in vivo, immunohistochemical analysis of 5 ES patient cases demonstrated diffuse emmprin expression in ES cells and MMP-2 expression in both ES cells and peritumoral fibroblasts. The histopathological findings that peritumoral fibroblasts that were not in direct contact with emmprin-expressing ES cells exhibit upregulated MMP-2 prompted us to look for a soluble form of emmprin. Soluble full-length emmprin released from ES cells was detected in conditioned medium and shown to stimulate MMP-2 production by fibroblasts. In conclusion, emmprin is expressed in ES in both membrane and soluble forms and stimulates MMP-2 production via interactions with fibroblasts, which could play a role in ES cell stromal invasion and vascular involvement.     

Polymorphisms of matrix metalloproteinases 1, 2, 3 and 9 and susceptibility to lung,breast and colorectal cancer in over 30,000 subjects

A variety of susceptibility genes have been associated with cancer but definitive conclusions have been difficult to draw partly hampered by the small number of subjects in each study. We undertook a comprehensive genetic meta‐analysis of all matrix metalloproteinase (MMP) genes investigated using an allelic‐association case–control model in the 3 major cancers of lung, breast and colorectal cancer. Electronic databases were searched until and including July 2008 for any MMP genetic association study in lung, breast and colorectal cancer. Odds ratio (OR) and 95% confidence intervals (CI) were determined for each gene disease association using fixed and random effect models. Twenty‐five studies addressing 5 polymorphisms in 4 genes were analyzed among 30,651 individuals (15,328 cases and 15,253 controls). The MMP‐1 nt‐1607 polymorphism was significantly associated with colorectal cancer in both the dominant (OR, 1.66; 95% CI, 1.14–2.42; p = 0.008) and recessive (OR, 1.59; 95% CI, 1.15–2.20; p = 0.005) models. MMP‐2^1306C→T (OR, 0.53; 95% CI, 0.40–0.72; p < 0.0001) and 735^C→T (OR, 0.65; 95% CI, 0.53–0.79; p < 0.0001) were significantly associated with protection against lung cancer. No association was found with the MMP 1, 2, 3 or 9 polymorphisms with breast cancer, MMP‐1, 3 or 9 with lung cancer or MMP‐2, 3 or 9 with colorectal cancer. There may be a genetic influence in the development of colorectal and lung cancer. Subjects with the MMP‐1 nt‐1607 polymorphism have an increased association with colorectal cancer. Those homozygous for either the MMP‐2/1306T or 735T allele may be at reduced risk of lung cancer, although the evidence base is small. © 2009 UICC     

Low dentin matrix protein 1 expression correlates with skeletal metastases development in breast cancer patients and enhances cell migratory capacity in vitro

Small integrin-binding ligand N-linked glycoproteins (SIBLINGs) constitute a family of extracellular matrix proteins involved in bone homeostasis. Their pattern of expression has been primarily reported in bone and tooth and, more recently, in several cancer types. Dentin matrix protein 1 (DMP1), a SIBLING family member, expression was investigated by immunohistochemistry in a retrospective series of 148 primary human breast cancers. Correlations between DMP1 expression levels in the tumors and clinicopathologic features, bone metastases development and relapse of the disease were examined. DMP1 was expressed by 63.5% of the breast tumors analyzed. Significant inverse associations were found between DMP1 expression levels and the size and grade of the tumors (both, P < 0.0001). High DMP1 expression levels in the primary breast lesions were associated with a lower risk of subsequent development of skeletal metastases (P = 0.009). Patients with tumors expressing high levels of DMP1 had a significantly higher disease-free survival rate than those with low DMP1-expressing tumors (P = 0.0062). When DMP1 expression was examined in breast cancer cell lines, we found that non invasive MCF-7 and T47-D cells expressed higher levels than highly invasive MDA-MB-231 and Hs578T cells. Moreover, the specific inhibition of DMP1 expression in MCF-7 cells using siRNAs promoted significantly their migratory capability. Our data implicate for the first time DMP1 expression in breast cancer progression and bone metastases development.     

Ets‐1 controls breast cancer cell balance between invasion and growth

Ets‐1 overexpression in human breast cancers is associated with invasiveness and poor prognosis. By overexpressing Ets‐1 or a dominant negative mutant in MMT breast cancer cells, we previously highlighted the key role of Ets‐1 in coordinating multiple invasive features of these cells. Interestingly, we also noticed that Ets‐1 decreased the density of breast cancer cells cultured in three‐dimensional extracellular matrix gels. The 3D context was instrumental to this phenomenon, as such downregulation was not observed in cells grown on two‐dimensional plastic or matrix‐coated dishes. Ets‐1 overexpression was deleterious to anchorage‐independent growth of MMT cells in soft agar, a standard model for in vitro tumorigenicity. The relevance of this mechanism was confirmed in vivo, during primary tumor growth and in a metastatic assay of lung colonization. In these models, Ets‐1 was associated with epithelial‐to‐mesenchymal transition features and modulated the ratio of Ki67‐positive cells, while hardly affecting in vivo apoptotic cell death. Finally, siRNA‐mediated knockdown of Ets‐1 in human breast cancer cell lines also decreased colony growth, both in anchorage‐independent assays and 3D extracellular matrix cultures. These in vitro and in vivo observations shed light on an unsuspected facet of Ets‐1 in breast tumorigenesis. They show that while promoting malignancy through the acquisition of invasive features, Ets‐1 also attenuates breast tumor cell growth and could therefore repress the growth of primary tumors and metastases. This work also demonstrates that 3D models may reveal mechanisms of tumor biology that are cryptic in standard 2D models.