Down-regulation of BRMS1 by DNA hypermethylation and its association with metastatic progression in triple-negative breast cancer

Breast cancer metastasis suppressor 1 (BRMS1) is a metastasis suppressor gene in several solid tumors. However, the expression and function of BRMS1 in triple-negative breast cancer (TNBC) have not been reported. In this study, we found that BRMS1 was down-regulation in breast cancer cell lines and primary TNBC, while decreased expression of BRMS1 mRNA was significantly associated with lymph node metastasis. And this down-regulation was found to be in accordance with aberrant methylation of the gene. Hypermethylation of the gene was observed in 53.4% (62/116) of the TNBC primary breast carcinomas, while it was found in only 24.1% (28/116) of the corresponding nonmalignant tissues. In addition, BRMS1 expression was restored in MDA-MB-231 after treatment with the demethylating agent, 5-aza-2-deoxycytidine (5-Aza-dC), and demethylation of the highly metastatic cells MDA-MB-231 induced invasion suppression of the cells. Furthermore, the suppression of BRMS1 by siRNA transfection enhanced cancer cells invasion. Collectively, our results suggest that the aberrant methylation of BRMS1 frequently occurs in the down-regulation of BRMS1 in TNBC and that it may play a role in the metastasis of breast cancer.     

Tiam1基因过表达对结直肠癌细胞增殖和转移能力的影响

目的探讨Tiaml（T lymphoma invasion and metastasis1）基因转染对结直肠癌细胞增殖、转移能力的影响。方法采用裸鼠皮下接种结直肠癌细胞的方法观察Tiaml基因对结直肠癌细胞体内增殖能力的影响,利用外科原位移植技术观察Tiaml对体内增殖、转移能力的影响。结果接种HT29／Tiaml细胞（转染Tiaml基因）的裸鼠皮下肿瘤生长明显加快,肿瘤体积自皮下注射后的第7天起与接种HT29／mock细胞（转染对照）的裸鼠皮下肿瘤比差异有统计学意义,接种HT29／Tiaml细胞的裸鼠皮下肿瘤第20天的平均体积是接种HT29／mock细胞组的2．5倍。进行结直肠癌细胞外科原位移植6周后,接种HT29／Tiaml细胞的裸鼠结肠原位肿瘤重量明显大于接种HT29／mock细胞的裸鼠（t=-14．916,P〈0．01）。采用外科原位移植的方法比较HT29／mock和HT29／Tiaml细胞的体内转移能力。在HT29／Tiaml细胞组,7只裸鼠全都发生了腹腔转移,4只发生了肝转移,其中有1只裸鼠发生了广泛转移,包括脾、肺及淋巴结等转移。在HT29／mock细胞组,7只中只有2只裸鼠发生了腹腔转移,没有一只裸鼠发生远处转移。结论Tiaml基因是结直肠癌增殖、转移的促进基因,Tiaml表达可作为结直肠癌增殖、转移过程中一个有价值的指标。     

Primary tumour expression of the cysteine cathepsin inhibitor Stefin A inhibits distant metastasis in breast cancer

Using the clinically relevant 4T1-derived syngeneic murine model of spontaneous mammary metastasis to bone, we have identified the cysteine cathepsin inhibitor Stefin A as a gene differentially expressed in primary and metastatic mammary tumours. In primary tumours, Stefin A expression correlated inversely with metastatic potential in 4T1-derived lines and was not detected in tumour cells in culture, indicating induction only within the tumour microenvironment. Enforced expression of Stefin A in the highly metastatic 4T1.2 cell line significantly reduced spontaneous bone metastasis following orthotopic injection into the mammary gland. Consistent with the mouse data, Stefin A expression correlated with disease-free survival (absence of distant metastasis) in a cohort of 142 primary tumours from breast cancer patients. This was most significant for patients with invasive ductal carcinoma expressing Stefin A, who were less likely to develop distant metastases (log rank test, p = 0.0075). In a multivariate disease-free survival analysis (Cox proportional hazards model), Stefin A expression remained a significant independent prognostic factor in patients with invasive ductal carcinoma (p = 0.0014), along with grade and progesterone receptor (PR) status. In human lung and bone metastases, we detected irregular Stefin A staining patterns, with expression often localizing to micrometastases (<0.2 mm) in direct contact with the stroma. We propose that Stefin A, as a cysteine cathepsin inhibitor, may be a marker of increased cathepsin activity in metastases. Using immunohistology, the cathepsin inhibitor was detected co-expressed with cathepsin B in lung and bone metastases in both the murine model and human tissues. We conclude that Stefin A expression reduces distant metastasis in breast cancer and propose that this may be due to the inhibition of cysteine cathepsins, such as cathepsin B.     

Functional cloning of ARM-1, an adhesion-regulating molecule upregulated in metastatic tumor cells

Interactions of tumor cells with the endothelium and tissue stroma are considered to be critical steps in metastasis formation and progression of cancer. To identify cellular receptors that mediate the binding of tumor cells to endothelium, a murine T cell lymphoma-derived expression library was screened for adhesion-inducing cDNA clones. We identified a novel cell adhesion-promoting molecule, termed ARM-1 (adhesion regulating molecule-1), which is homologous to a human M _r 110.000 tumor-associated antigen. The ARM-1 cDNA codes for a type I transmembrane protein of 407 amino acids with potential O- and N-glycosylation sites that does not belong to any of the known families of cell adhesion molecules. Overexpression of ARM-1 in 293T human embryonic kidney cells significantly increased adhesion to different endothelial cells. ARM-1 expression in 293T cells did not alter integrin expression or β1-integrin-mediated cell adhesion. Northern blot analysis of human breast cancer cell lines revealed 3- to 5-fold elevated ARM-1 mRNA levels in metastatic as compared to non-metastatic cells. In conclusion, we have identified ARM-1 as a novel cell adhesion-promoting receptor that is upregulated in metastatic cancer cells. This revised version was published online in July 2006 with corrections to the Cover Date.     

Selection of more aggressive variants of the GI101A human breast cancer cell line: A model for analyzing the metastatic phenotype of breast cancer

In vivo models utilizing orthotopic injection of tumor cells into nude mice have proven valuable for the study of metastasis. However, breast cancers are among the more difficult of human tumors to grow in immunodeficient mice, with a relatively low tumor take. Fewer still develop spontaneous metastases. The injection of GI101A breast cancer cells into the mammary fatpad (mfp) produced lung metastases in 25% of tumor-bearing mice. Selecting cells from the lung metastases and recycling in vivo resulted in the isolation of a series of variant cell lines. These cell lines were tested for tumorigenicity and metastasis in nude mice following mfp injection compared with the original cell line, and in vitro expression of factors associated with the metastatic phenotype measured. The in vivo selected cell lines were more aggressive, with higher tumor take, faster local growth rate and increased incidence (≥85%) and extent of lung metastasis. However, the metastasis-selected variants showed no increases in expression of the growth factor receptors EGFR or HER-2, and the pro-angiogenic factors VEGF-A and IL-8. Immunohistochemistry of mfp tumors revealed no differences in microvessel density (counting CD-31 positive structures) and cell proliferation (PCNA-positive cells) comparing the GI101A line with selected variants. No TUNEL-positive cells were detected in the tumors of the metastasis-derived variant, with a small number of cells undergoing apoptosis detected in sections of GI101A tumors. In vitro, the metastasis-derived variants were found to have a more robust expression of phosphorylated PKB/Akt, with or without EGF or serum stimulation, suggesting an association between Akt activation and metastatic ability. This new series of isogenic cell lines may be valuable for identifying molecular mechanisms involved in the metastatic progression of breast cancer. This revised version was published online in July 2006 with corrections to the Cover Date.     

Metastastic variants derived following in vivo tumor progression of an in vitro transformed squamous cell carcinoma line acquire a differential growth advantage requiring tumor-host interaction

The purpose of this study was to develop an experimental model of squamous cell carcinoma that can be used to identify molecular and immunologic changes associated with primary events in malignant transformation, and those associated with metastatic tumor progression in the presence of host homeostatic and immunologic factors. Metastatic variants were derived following in vivo tumor progression of the in vitro transformed squamous cell carcinoma line Pam 212. The parental and metastatic cell lines exhibited similar morphologic features and molecular markers of an epithelial lineage, including an epithelial morphology in culture, cell surface expression of integrin 64, and expression of mRNA of cytokeratins K6 and K14. When the growth and metastatic phenotype of the parental and reisolate cell lines was compared, the reisolate cell lines were found to exhibit a greater rate of growth and incidence of metastasis than the parental cell line when reimplanted in vivo. The difference in the growth rate of the parental cell line and the variants observed in vivo was not detected when growth of these lines was compared in vitro, suggesting that the growth advantage and selection of these variants requires tumor-host interaction. The metastatic variants exhibited a similar growth advantage in normal immunocompetent and SCID Balb/c mice, indicating that the growth advantage in vivo is not due to T or B lymphocyte-dependent immune factor(s). We conclude that metastatic variants derived following in vivo tumor progression of an in vitro transformed squamous cell carcinoma line exhibit a differential growth advantage in vivo that requires the host environment. Comparison of these in vitro transformed and in vivo derived metastatic variant cell lines with phenotypic differences in growth and metastasis should prove useful for dissecting the role of tumor and host factor(s) in malignant transformation and metastatic tumor progression of squamous cell carcinoma.     

The invasive and metastatic properties of hormone-independent but hormone-responsive variants of MCF-7 human breast cancer cells

We have previously isolated a series of MCF-7 human breast cancer cell variants which no longer require estrogen-supplementation for tumor growth in nude mice (Clarkeet al. Proc Natl Acad Sci USA 86: 3649–3653, 1989). We now report that these hormone-independent and hormone-responsive variants (MIII, MCF7/LCC1) can invade locally from solid mammary fat pad tumors, and produce primary extensions on the surface of intraperitoneal structures including liver, pancreas, and diaphragm. Both lymphatic and hematogenous dissemination are observed, resulting in the establishing of pulmonary, bone, and renal metastases. The pattern of metastasis by MIII and MCF7/LCC1 cells closely resembles that frequently observed in breast cancer patients, and provides the first evidence of metastasis from MCF-7 cells growingin vivo without supplementary estrogen. The interexperimental incidence of metastases, and the time from cell inoculation to the appearance of metastatic disease are variable. The increased metastatic potential is not associated with an increase in either the level of laminin attachment, laminin receptor mRNA expression, or secreted type IV collagenolytic activity. We also did not detect a significant decrease in the steady-state mRNA levels of the metastasis inhibitor nm23 gene. However, when growing without estrogenin vitro, MCF7/LCC1 cells produce elevated levels of the estrogen-inducible cathepsin D enzyme.     

Chemokine CCL2/MCP-1 negatively regulates metastasis in a highly bone marrow-metastatic mouse breast cancer model

Bone is the most frequent site of breast cancer metastasis, and once such metastasis occurs, complete remission is extremely difficult to achieve. In an effort to define the mechanisms underlying metastatic spread of breast cancer to bone, we previously developed and characterized the highly bone metastatic 4T1E/M3 mouse breast cancer cells. We found that following injection into mice, 4T1E/M3 cells exhibited greater bone metastasis and greater in vitro anchorage-independent growth and cell migration than their parental cells (4T1E). We also found that expression of intracellular adhesion molecule-1 (ICAM-1) is crucially involved in these metastatic activities of 4T1E/M3 cells. In the present study, our analysis of gene and protein expression revealed that production of chemokine CCL2 (MCP-1) is dramatically reduced in 4T1E/M3 cells, and that restoration of CCL2 expression in 4T1E/M3 cells diminishes their metastasis to bone and lung. Overexpression of CCL2 in 4T1E/M3 cells significantly reduced not only in vitro anchorage-independent cell growth and cell migration, but also mRNA and cell surface expression of ICAM-1. Conversely, knocking down CCL2 in 4T1E parental cells augmented their metastatic spread to spine and lung. The expression of ICAM-1 was also upregulated in 4T1E-derived CCL2 knockdown cells. Taken together, these results suggest that CCL2 expression may negatively regulate breast cancer metastasis to bone marrow and lung in our model and that expression of ICAM-1 plays a crucial role in that process.     

Vascular endothelial growth factor expression promotes the growth of breast cancer brain metastases in nude mice

Patients with breast cancer brain metastases cannot be cured and have a poor prognosis, with a median survival time of six months after diagnosis, despite developments in diagnostic and therapeutic modalities. In large part the progress in understanding the biology of breast cancer brain metastasis has been limited by the lack of suitable cell lines and experimental models. The objective of this study was to develop a reliable experimental model to study the pathogenesis of breast cancer brain metastases, using intra-internal carotid artery injection of breast cancer cells into nude mice. Brain metastasis-selected variant cells were recovered after three cycles of injection into the internal carotid artery of nude mice and harvest of brain metastases, resulting in variants termed MDA-231 BR1, -BR2 and -BR3. The metastasis-selected cells had increased potential for experimental brain metastasis and mice injected with these cells had significantly shorter mean survival than mice injected with the original cell line. Brain metastatic lesions of the selected variants contained significantly more CD31-positive blood vessels than metastases of the non-selected cell line. The variants selected from brain metastases released significantly more VEGF-A and IL-8 into culture supernatants than the original cell line, and more VEGF-A RNA when cultured in normoxic conditions. Mice injected with MDA-231 BR3 into the carotid artery were treated with the VEGF-receptor tyrosine kinase inhibitor PTK787/Z 222584. Oral administration of the inhibitor resulted in a significant decrease in brain tumor burden, reduced CD31-positive vessels in the brain lesions and incidence of PCNA positive tumor cells, and increased apoptosis in the tumor, as measured by TUNEL labeling. We conclude that elevated VEGF expression contributes to the ability of breast cancer cells to form brain metastases. Targeting endothelial cells with a VEGF-receptor specific tyrosine kinase inhibitor reduced angiogenesis and restricted the growth of the brain metastases.     

Trp53 deletion stimulates the formation of metastatic pancreatic tumors

The presence of distant metastases is a common finding on diagnosis of pancreatic cancer; however, the mechanisms underlying the dissemination of this tumor type remain poorly understood. Loss of the p53 tumor suppressor protein has been associated with tumor progression and metastasis in several tumor types including pancreatic ductal adenocarcinoma. Here, we describe the generation of a progressive and metastatic pancreatic cancer mouse model after the somatic and sporadic delivery of avian retroviruses encoding the mouse polyoma virus middle T antigen to elastase-tv-a transgenic mice with a pancreas-specific deletion of the Trp53 tumor suppressor locus. In this model, the tumors metastasize most frequently to the liver, consistent with human pancreatic carcinomas. Analysis of metastatic lesions demonstrated that concomitant loss of the Ink4a/Arf locus was not required for metastasis; however, pancreas-specific deletion of a single Ink4a/Arf allele cooperated with Trp53 deletion in a haploinsufficient manner to accelerate tumor development. Thus, our findings illustrate the potential role of p53 loss of function in pancreatic tumor progression, demonstrate the feasibility of modeling pancreatic cancer metastasis after somatic and sporadic oncogene activation, and indicate that our model may provide a useful experimental system for investigation of the molecular mechanisms underlying pancreatic cancer progression and metastasis.     

Multiple forms of BRMS1 are differentially expressed in the MCF10 isogenic breast cancer progression model

Clinical studies evaluating the mRNA expression level of the BRMS1 metastasis suppressor in the progression of breast cancer have not been consistent. The purpose of this study was to characterize endogenous BRMS1 mRNA and protein in a model of the progression of breast cancer. BRMS1 protein expression was evaluated in the genetically related MCF10 cell lines representing ‘normal’ breast epithelial cells (MCF10A), pre-malignant breast disease (MCF10AT), comedo ductal carcinoma in situ (MCF10DCIS.com), and metastatic carcinoma (MCF10CAa.1 and MCF10CAd.1α) with two antibodies that recognize distinct epitopes in the BRMS1 protein. Nuclear expression of the characteristic ~35 kDa BRMS1 protein was detected in all cell lines. Because BRMS1 was expressed in the metastatic MCF10 variants, the BRMS1 exons were sequenced to scan for possible genetic mutations. BRMS1 was wild-type with the exception of a synonymous T/C transition in exon 7. However, alternatively spliced variants were detected by RT-PCR. Two variants, BRMS1.v2 and BRMS1.v4 were only detected in the MCF10A and AT cell lines, while BRMS1 and BRMS1.v3 were detected in all lines. These results demonstrate that expression of the characteristic ~35 kDa BRMS1 protein is not sufficient to prevent metastasis. The differential expression of alternative splice variants suggests caution should be taken when evaluating BRMS1 mRNA in clinical samples.     

The Measure of DAMPs and a role for S100A8 in recruiting suppressor cells in breast cancer lung metastasis

To determine whether there was a relationship between damage associated molecular pattern molecule (DAMP) expression and recruitment of suppressor cells to sites of metastasis we measured relative expression of DAMPs, regulatory T cells (Tregs), and myeloid derived suppressor cells (MDSC) in mice at various stages of breast cancer progression using the 4T1 model. Although S100A8 was expressed at relatively low levels in the tumor cells, expression was 100-fold higher in the lung and liver which are common sites of metastasis for this tumor. Despite the relatively high level of S100A8 expression in the lungs of naïve mice, the level of expression increased further and was significantly elevated after only 7 days of tumor growth. The same pattern was observed for MDSC, and both S100A8 and MDSC expression peaked in the lungs of mice following 21 days of tumor growth. Characterization of MDSC from the lungs revealed expression of RAGE, and the cells were capable of migrating in a dose-dependent manner toward S100A8. In addition, the MDSC expressed low levels of MHC Class I, MHC Class II, CD80, and secreted TGF-β. Taken together, these data suggest that expression of S100A8 in the lungs may facilitate recruitment of MDSC, which may in turn aid in establishing a metastatic niche capable of suppressing a localized immune response.     

c-Src expression is predictive of poor prognosis in breast cancer patients with bone metastasis, but not in patients with visceral metastasis

c-Src expression is critical for breast cancer progression and it is particularly important for bone metastasis. In this study, we aimed to evaluate the effect of c-Src on prognosis in metastatic breast cancer patients, and to conduct subgroup analysis to explore the role of c-Src in bone metastasis and visceral metastasis respectively. We analyzed a total of 102 paraffin-embedded primary tumor tissue sections from metastatic breast cancer patients using immunohistochemical staining for c-Src, including 61 patients with bone metastases. Clinical data were collected retrospectively. We utilized survival analysis and the Cox proportional hazards model to explore the prognostic value of c-Src expression in metastatic breast cancer. The c-Src expression rate was 54.9% in the 102 metastatic breast cancer patients. Patients who exhibited c-Src expression demonstrated poor progression-free survival (PFS) (p = 0.044) and disease-specific survival (DSS) (p = 0.017). Subgroup analysis demonstrated that c-Src positive patients exhibited significantly worse bone metastasis-free survival (p = 0.027) and DSS (p = 0.024), whereas in patients with non-bone metastasis no significant difference was observed in PFS (p = 0.819) and DSS (p = 0.381). Multivariate analysis demonstrated that c-Src expression was an independent predictor of DSS for patients with bone metastasis. Our findings demonstrate that c-Src expression is a potential independent predictor of poor prognosis in breast cancer patients with bone metastasis.     

Ubiquitous Brms1 expression is critical for mammary carcinoma metastasis suppression via promotion of apoptosis

Morbidity and mortality of breast cancer patients are drastically increased when primary tumor cells are able to spread to distant sites and proliferate to become secondary lesions. Effective treatment of metastatic disease has been limited; therefore, an increased molecular understanding to identify biomarkers and therapeutic targets is needed. Breast cancer metastasis suppressor 1 (BRMS1) suppresses development of pulmonary metastases when expressed in a variety of cancer types, including metastatic mammary carcinoma. Little is known of Brms1 function throughout the initiation and progression of mammary carcinoma. The goal of this study was to investigate mechanisms of Brms1-mediated metastasis suppression in transgenic mice that express Brms1 using polyoma middle T oncogene-induced models. Brms1 expression did not significantly alter growth of the primary tumors. When expressed ubiquitously using a β-actin promoter, Brms1 suppressed pulmonary metastasis and promoted apoptosis of tumor cells located in the lungs but not in the mammary glands. Surprisingly, selective expression of Brms1 in the mammary gland using the MMTV promoter did not significantly block metastasis nor did it promote apoptosis in the mammary glands or lung, despite MMTV-induced expression within the lungs. These results strongly suggest that cell type-specific over-expression of Brms1 is important for Brms1-mediated metastasis suppression.     

NDRG1基因与乳腺癌转移的关系及其转染对乳腺癌细胞株增殖及侵袭力的影响

目的探讨NDRG1基因与乳腺癌转移的关系及其转染对乳腺癌细胞株增殖及侵袭力的影响。方法免疫组织化学SP法、即时荧光定量逆转录聚合酶链反应(real time RT-PCR)检测10例新鲜乳腺浸润性导管癌和27例石蜡包埋乳腺癌组织中NDRG1蛋白和mRNA的表达。脂质体介导NDRG1基因瞬时转染高侵袭高转移性人乳腺癌细胞株MDA-MB-231;用5-溴-2-脱氧尿苷(BrdU)掺入法、流式细胞术观察NDRG1基因转染后对细胞增殖和细胞周期的影响;细胞体外侵袭实验和迁移实验观察转染后细胞侵袭和迁移能力的变化。结果NDRG1蛋白和mRNA表达分别为:无转移的乳腺癌组织阳性率为100%(14/14)和0·82±0·14,而有转移的乳腺癌组织中为69·2%(9/13)和0·17±0·11,均明显降低;对两株细胞的检测中,高侵袭高转移的MDA-MB-231细胞株中NDRG1mRNA的表达水平(0·14±0·02)明显低于低侵袭低转移的MCF7细胞株(1·51±0·11)。NDRG1基因瞬时转染MDA-MB-231细胞后,与未转染组和pEGFP-N3组相比,pEGFP-NDRG1-N3转染组中,细胞BrdU掺入率降低,细胞周期G0/G1期比例增高,S期比例明显减低;同时细胞体外侵袭能力下降,而体外迁移能力则差异无统计学意义。结论NDRG1基因的表达与乳腺癌的转移呈负相关关系,提示该基因可望成为早期预测乳腺癌转移的分子生物学标记物之一;NDRG1基因通过脂质体转染高侵袭高转移性人乳腺癌MDA-MB-231细胞株,可抑制肿瘤细胞增殖、降低其侵袭能力,提示其可作为一个候选的肿瘤转移抑制基因,并有望成为乳腺癌基因治疗的新的候选基因。     

Decline in the expression of the serine proteinase inhibitor maspin is associated with tumour progression in ductal carcinomas of the breast

Maspin is an inhibitor of serine proteinases with tumour suppressor activity. Its expression appears to be reduced in advanced stages of breast cancer. A large series of archival breast tissue specimens has been examined, including normal glands (n=7), fibrocystic change (n=22), ductal carcinoma in situ (DCIS, n=12), infiltrating carcinomas (n=128) and their lymph node metastases (n=65), using a specific monoclonal antibody. Myoepithelium invariably showed strong maspin expression. In epithelial cells, the strongest expression was found in normal breast and fibrocystic change. A significant stepwise decrease in maspin expression (p<0.0001) occurred in the sequence DCIS - invasive cancer - lymph node metastasis. However, a subset of infiltrating carcinomas showed strong maspin expression, significantly associated with a lower rate of lymph node metastasis at the time of diagnosis (p<0.01). This was independent of tumour size and grade. The in vivo observations presented here are in keeping with data obtained in prior in vitro experiments. Maspin emerges as an indicator of tumour progression and metastatic potential, and might be exploited to predict breast cancer prognosis. According to in vitro data, its tumour suppressor activity is likely to involve both the modulation of cell motility/invasiveness and the inhibition of angiogenesis.     

Genome-wide in vivo RNAi screen identifies ITIH5 as a metastasis suppressor in pancreatic cancer

The overwhelming majority of pancreatic ductal adenocarcinoma (PDAC) is not diagnosed until the cancer has metastasized, leading to an abysmal average life expectancy (3–6 months post-diagnosis). Earlier detection and more effective treatments have been hampered by inadequate understanding of the underlying molecular mechanisms controlling metastasis. We hypothesized that metastasis suppressors are involved in controlling metastasis in pancreatic cancer. Using an unbiased genome-wide shRNA screen, an shRNA library was transduced into the non-metastatic PDAC line S2-028 followed by intrasplenic injection. Resulting liver metastases were individually isolated from these mice. One liver metastatic nodule contained shRNA for ITIH5 (Inter-alpha-trypsin inhibitor heavy chain 5), suggesting that ITIH5 may act as a metastasis suppressor. Consistent with this notion, metastatic PDAC cell lines had significantly lower protein expression of ITIH5 compared to immortalized pancreatic ductal epithelial cells and non-/poorly-metastatic PDAC cell lines. By manipulating expression of ITIH5 in different PDAC cell lines (over-expression in metastatic, knockdown in non-metastatic) functional and selective regulation of metastasis was observed for ITIH5. Orthotopic tumor growth of PDAC cells was not blocked following orthotopic injection. In vitro ITIH5 over-expression inhibited motility and invasion. Immunohistochemical analysis of a human PDAC tissue microarray revealed that ITIH5 expression inversely correlated with both survival and invasion/metastasis. ITIH5 is, therefore, functionally validated as a PDAC metastasis suppressor and shows promise as a prognostic biomarker.     

Spontaneous formation of tumorigenic hybrids between breast cancer and multipotent stromal cells is a source of tumor heterogeneity

Breast cancer progression involves cancer cell heterogeneity, with generation of invasive/metastatic breast cancer cells within populations of nonmetastatic cells of the primary tumor. Sequential genetic mutations, epithelial-to-mesenchymal transition, interaction with local stroma, and formation of hybrids between cancer cells and normal bone marrow-derived cells have been advocated as tumor progression mechanisms. We report herein the spontaneous in vitro formation of heterotypic hybrids between human bone marrow-derived multipotent stromal cells (MSCs) and two different breast carcinoma cell lines, MDA-MB-231 (MDA) and MA11. Hybrids showed predominantly mesenchymal morphological characteristics, mixed gene expression profiles, and increased DNA ploidy. Both MA11 and MDA hybrids were tumorigenic in immunodeficient mice, and some MDA hybrids had an increased metastatic capacity. Both in culture and as xenografts, hybrids underwent DNA ploidy reduction and morphological reversal to breast carcinoma-like morphological characteristics, while maintaining a mixed breast cancer-mesenchymal expression profile. Analysis of coding single-nucleotide polymorphisms by RNA sequencing revealed genetic contributions from both parental partners to hybrid tumors and metastasis. Because MSCs migrate and localize to breast carcinoma, our findings indicate that formation of MSC-breast cancer cell hybrids is a potential mechanism of the generation of invasive/metastatic breast cancer cells. Our findings reconcile the fusion theory of cancer progression with the common observation that breast cancer metastases are generally aneuploid, but not tetraploid, and are histopathologically similar to the primary neoplasm.