The role of osteopontin in tumor progression and metastasis in breast cancer

Higher prevalence of secretory CSE1L/CAS in sera of patients with metastatic cancer

Metastatic markers are highly useful diagnostic and prognostic indicators of cancer metastasis. Herein, we report that secretory CSE1L/CAS, a cellular apoptosis susceptibility protein, is a new marker for metastatic cancer. CAS was colocalized with matrix metalloproteinase-2 in vesicles surrounding the outside of MCF-7 cell membranes, and the COOH-terminal domain of CAS was associated with matrix metalloproteinase-2-containing vesicles. Immunohistochemical staining for CAS was positive in the stroma and gland lumens of human metastatic cancer tissues. CAS was also detected in conditioned medium from B16-F10 melanoma cells and more frequently in the sera of patients with metastatic cancer than in sera from patients with primary cancer. Specifically, the prevalence of serum CAS in serum samples from 146 patients was 58.2% (32 of 55), 32.0% (8 of 25), and 12.1% (8 of 66) for patients with metastatic, invasive, and primary cancers, respectively. Our results suggest that CAS is a secretory protein associated with cancer metastasis, which may have clinical utility in metastatic cancer screening and diagnosis.

High-density gene expression analysis of tumor-associated macrophages from mouse mammary tumors

Clinical and experimental evidence indicates that tumor-associated macrophages (TAMs) promote malignant progression. In breast cancer, TAMs enhance tumor angiogenesis, tumor cell invasion, matrix remodeling, and immune suppression against the tumor. In this study, we examined late-stage mammary tumors from a transgenic mouse model of breast cancer. We used flow cytometry under conditions that minimized gene expression changes to isolate a rigorously defined TAM population previously shown to be associated with invasive carcinoma cells. The gene expression signature of this population was compared with a similar population derived from spleens of non-tumor-bearing mice using high-density oligonucleotide arrays. Using stringent selection criteria, transcript abundance of 460 genes was shown to be differentially regulated between the two populations. Bioinformatic analyses of known functions of these genes indicated that formerly ascribed TAM functions, including suppression of immune activation and matrix remodeling, as well as multiple mediators of tumor angiogenesis, were elevated in TAMs. Further bioinformatic analyses confirmed that a pure and valid TAM gene expression signature in mouse tumors could be used to assess expression of TAMs in human breast cancer. The data derived from these more physiologically relevant autochthonous tumors compared with previous studies in tumor xenografts suggest tactics by which TAMs may regulate tumor angiogenesis and thus provide a basis for exploring other transcriptional mediators of TAM trophic functions within the tumor microenvironment.

Breast cancer screening and biomarkers

Annual screening mammograms have been shown to be cost-effective and are credited for the decline in mortality of breast cancer. New technologies including breast magnetic resonance imaging (MRI) may further improve early breast cancer detection in asymptomatic women. Serum tumor markers such as CA 15-3, carcinoembyonic antigen (CEA), and CA 27-29 are ordered in the clinic mainly for disease surveillance, and not useful for detection of localized cancer. This review will discuss blood-based markers and breast-based markers, such as nipple/ductal fluid, with an emphasis on biomarkers for early detection of breast cancer. In the future, it is likely that a combination approach to simultaneously measure multiple markers would be most successful in detecting early breast cancer. Ideally, such a biomarker panel should be able to detect breast cancer in asymptomatic patients, even in the setting of normal mammogram and physical examination results.

Osteopontin: a new role for a familiar actor

Our understanding of the events that occur in cancer progression has been enhanced by the use of cell lines in vitro. Changes in gene expression, induction of signalling, and cell motility can all be investigated in this setting. However, other aspects of progression can be revealed only in vivo, especially the interactions of tumour cells with host cells and organ systems. In one such in vivo model, described by McAllister and colleagues, it proved possible to establish a novel function of an already well-characterised protein, osteopontin, adding to its attractiveness as a target in cancer therapy.

Hypoxia skews dendritic cells to a T helper type 2-stimulating phenotype and promotes tumour cell migration by dendritic cell-derived osteopontin

It is well recognized that tissue microenvironments are involved in regulating the development and function of dendritic cells (DC). Oxygen supply, which varies in different tissues, has been accepted as an important microenvironmental factor in regulating the biological functions of several immune cells and as being involved in tumour progression and metastasis. However, little is known about the effect of hypoxia on the biological functions of DC and the effect of these hypoxia-conditioned DC on tumour metastasis. In this study, we analysed the transcriptional profiles of human monocyte-derived immature DC (imDC) and mature DC (mDC) cultured under normoxia and hypoxia by microarray, and found a body of potential targets regulating the functions of DC during hypoxia. In addition, the phagocytic ability of hypoxic imDC markedly decreased compared with that of normoxic imDC. Importantly, hypoxic DC poorly induced the proliferation of allogeneic T cells, but polarized allogeneic CD4(+) naive T cells into a T helper type 2 (Th2) response. Moreover, hypoxic DC secreted large amounts of osteopontin, which were responsible for the enhanced migration of tumour cells. Therefore, our study provides new insights into the biological functions of DC under hypoxic conditions and one of mechanisms underlying tumour immune escape during hypoxia.

Lower osteopontin plasma levels are associated with superior outcomes in advanced non-small-cell lung cancer patients receiving platinum-based chemotherapy: SWOG Study S0003

PURPOSE

S0003 was a phase III trial of carboplatin/paclitaxel with or without the hypoxic cytotoxin tirapazamine in patients with advanced or metastatic non-small-cell lung cancer (NSCLC). We investigated the relationship between clinical outcomes and plasma levels of the hypoxia-associated protein osteopontin (OPN) in patients on this protocol.

PATIENTS AND METHODS

Baseline plasma was obtained from 172 patients. In 56 patients, sequential plasma was obtained after one or two cycles. Concentrations of OPN, as well as plasminogen activator inhibitor-1 (PAI-1) and vascular endothelial growth factor (VEGF), were measured using enzyme-linked immunosorbent assay. Tumor expression of OPN was assessed by immunohistochemistry in 61 matched archival specimens.

RESULTS

Patients with lower OPN levels (below the median) had a significantly superior overall survival compared with patients with higher levels, regardless of treatment arm (hazard ratio [HR] = 0.60, P = .002). A similar correlation was observed for progression-free survival (HR = 0.69, P = .02). When examined as a continuous variable, OPN maintained its significant association with both progression-free (HR = 1.05, P = .01) and overall survival (HR = 1.09, P < .0001). Patients with lower plasma OPN levels were significantly more likely to have tumor response (P = .03). No differences were observed between treatment arms. Tumor OPN levels did not correlate with patient outcomes or with plasma levels. No associations were observed between patient outcomes and VEGF or PAI-1 levels; however, plasma concentrations of these markers were significantly interrelated (P < .0001) and significantly decreased after treatment (P = .0002 and P = .03, respectively).

CONCLUSION

Pretreatment plasma levels of OPN are significantly associated with patient response, progression-free survival, and overall survival in chemotherapy-treated patients with advanced NSCLC.

A rationale for the targeted treatment of oligometastases with radiotherapy

An oligometastatic state has been proposed wherein patients with metastases limited in number and location may benefit from local therapy directed at all known sites of metastases. We describe here the clinical and biological basis for the oligometastatic state. We present evidence for a potentially curative approach to patients with oligometastases using stereotactic body radiotherapy (SBRT) and we review the literature for SBRT directed at specific metastatic sites in the lungs, liver and multiple organs.

Small integrin-binding ligand N-linked glycoproteins (SIBLINGs): multifunctional proteins in cancer

Numerous components and pathways are involved in the complex interplay between cancer cells and their environment. The family of glycophosphoproteins comprising osteopontin, bone sialoprotein, dentin matrix protein 1, dentin sialophosphoprotein and matrix extracellular phosphoglycoprotein - small integrin-binding ligand N-linked glycoproteins (SIBLINGs) - are emerging as important players in many stages of cancer progression. From their detection in various human cancers to the demonstration of their key functional roles during malignant transformation, invasion and metastasis, the SIBLINGs are proteins with potential as diagnostic and prognostic tools, as well as new therapeutic targets.

Breast tumor microenvironment: proteomics highlights the treatments targeting secretome

Tumor secreted substances (secretome), including extracellular matrix (ECM) components, act as mediators of tumor-host communication in the breast tumor microenvironment. Proteomic analysis has emphasized the value of the secretome as a source of prospective markers and drug targets for the treatment of breast cancers. Utilizing bioinformatics, our recent studies revealed global changes in protein expression after the activation of ECM-mediated signaling in breast cancer cells. A newly designed technique integrating a capillary ultrafiltration (CUF) probe with mass spectrometry was demonstrated to dynamically sample and identify in vivo and pure secretome from the tumor microenvironment. Such in vivo profiling of breast cancer secretomes may facilitate the development of novel drugs specifically targeting secretome.

Integrated pipeline for mass spectrometry-based discovery and confirmation of biomarkers demonstrated in a mouse model of breast cancer

Despite their potential to impact diagnosis and treatment of cancer, few protein biomarkers are in clinical use. Biomarker discovery is plagued with difficulties ranging from technological (inability to globally interrogate proteomes) to biological (genetic and environmental differences among patients and their tumors). We urgently need paradigms for biomarker discovery. To minimize biological variation and facilitate testing of proteomic approaches, we employed a mouse model of breast cancer. Specifically, we performed LC-MS/MS of tumor and normal mammary tissue from a conditional HER2/Neu-driven mouse model of breast cancer, identifying 6758 peptides representing >700 proteins. We developed a novel statistical approach (SASPECT) for prioritizing proteins differentially represented in LC-MS/MS datasets and identified proteins over- or under-represented in tumors. Using a combination of antibody-based approaches and multiple reaction monitoring-mass spectrometry (MRM-MS), we confirmed the overproduction of multiple proteins at the tissue level, identified fibulin-2 as a plasma biomarker, and extensively characterized osteopontin as a plasma biomarker capable of early disease detection in the mouse. Our results show that a staged pipeline employing shotgun-based comparative proteomics for biomarker discovery and multiple reaction monitoring for confirmation of biomarker candidates is capable of finding novel tissue and plasma biomarkers in a mouse model of breast cancer. Furthermore, the approach can be extended to find biomarkers relevant to human disease.

Physiological stress induces the metastasis marker AGR2 in breast cancer cells

As an approach to understanding the factors that activate expression of tumor progression genes, the role of physiological stress in the activation of a panel of tumor cell markers was investigated. These studies identify the developmental gene product, anterior gradient 2 (AGR2) as a cancer cell marker specifically up-regulated in response to depletion of serum and oxygen. AGR2 has been identified as a tumor marker in primary and secondary cancer lesions, and as a marker for detection of circulating tumor cells (CTCs). Elevated levels of AGR2 are known to increase the metastatic potential of cancer cells, but conditions leading to increased expression of AGR2 are not well understood. The present results identify novel physiological parameters likely to contribute to AGR2 induction in situ.