Differential expression of osteopontin and bone sialoprotein in bone metastasis of breast and prostate carcinoma

The Potential of Extracellular Matrix- and Integrin Adhesion Complex-Related Molecules for Prostate Cancer Biomarker Discovery

Prostate cancer is among the top five cancer types according to incidence and mortality. One of the main obstacles in prostate cancer management is the inability to foresee its course, which ranges from slow growth throughout years that requires minimum or no intervention to highly aggressive disease that spreads quickly and resists treatment. Therefore, it is not surprising that numerous studies have attempted to find biomarkers of prostate cancer occurrence, risk stratification, therapy response, and patient outcome. However, only a few prostate cancer biomarkers are used in clinics, which shows how difficult it is to find a novel biomarker. Cell adhesion to the extracellular matrix (ECM) through integrins is among the essential processes that govern its fate. Upon activation and ligation, integrins form multi-protein intracellular structures called integrin adhesion complexes (IACs). In this review article, the focus is put on the biomarker potential of the ECM- and IAC-related molecules stemming from both body fluids and prostate cancer tissue. The processes that they are involved in, such as tumor stiffening, bone turnover, and communication via exosomes, and their biomarker potential are also reviewed.

A single-cell landscape of pre- and post-menopausal high-grade serous ovarian cancer ascites

High-grade serous ovarian cancer (HGSOC) is a hormone-related cancer with high mortality and poor prognosis. Based on the transcriptome of 57,444 cells in ascites from 10 patients with HGSOC (including 5 pre-menopausal and 5 post-menopausal patients), we identified 14 cell clusters which were further classified into 6 cell types, including T cells, B cells, NK cells, myeloid cells, epithelial cells, and stromal cells. We discovered an increased proportion of epithelial cells and a decreased proportion of T cells in pre-menopausal ascites compared with post-menopausal ascites. GO analysis revealed the pre-menopausal tumor microenvironments (TME) are closely associated with viral infection, while the post-menopausal TME are mostly related to the IL-17 immune pathway. SPP1/CD44-mediated crosstalk between myeloid cells and B cells, NK cells, and stromal cells mainly present in the pre-menopausal group, while SPP1/PTGER4 -mediated crosstalk between myeloid cells and epithelial cells mostly present in the post-menopausal group.

Is Osteopontin a Good Marker for Bone Metastasis in Canine Mammary Gland Tumor and Prostate Cancer?

Osteopontin (OPN) is a protein synthesized by a large number of cells, and its overexpression has been associated with the development and prognosis of cancer. OPN overexpression has been claimed to be a marker for the development of bone metastasis in human cancers, but no prior research has investigated the association between OPN expression and the metastasis of canine mammary gland tumors (MGTs) and prostate cancer (PC). Therefore, we investigated OPN expression in MGTs and PC samples from 50 canine patients with or without metastasis (bone vs. other sites). Higher OPN expression was detected in primary tumor samples from animals with bone metastasis than in those without bone involvement (p = 0.0321). In MGT samples, a significantly lower survival rate was observed in patients with higher OPN expression (p = 0.0171). In animals with PC, there was a strong trend toward lower survival in animals with positive OPN expression; however, this trend was not statistically significant (p = 0.0779). From these findings, it can be concluded that OPN may be a promising target for future MGTs and PC studies because of its role in enhancing cell invasion and metastasis.

B. abortus Infection Promotes an Imbalance in the Adipocyte–Osteoblast Crosstalk Favoring Bone Resorption

Osteoarticular injury is the most common presentation of active brucellosis in humans. Osteoblasts and adipocytes originate from mesenchymal stem cells (MSC). Since those osteoblasts are bone-forming cells, the predilection of MSC to differentiate into adipocytes or osteoblasts is a potential factor involved in bone loss. In addition, osteoblasts and adipocytes can be converted into each other according to the surrounding microenvironment. Here, we study the incumbency of B. abortus infection in the crosstalk between adipocytes and osteoblasts during differentiation from its precursors. Our results indicate that soluble mediators present in culture supernatants from B. abotus-infected adipocytes inhibit osteoblast mineral matrix deposition in a mechanism dependent on the presence of IL-6 with the concomitant reduction of Runt-related transcription factor 2 (RUNX-2) transcription, but without altering organic matrix deposition and inducing nuclear receptor activator ligand kβ (RANKL) expression. Secondly, B. abortus-infected osteoblasts stimulate adipocyte differentiation with the induction of peroxisome proliferator-activated receptor γ (PPAR-γ) and CCAAT enhancer binding protein β (C/EBP-β). We conclude that adipocyte–osteoblast crosstalk during B. abortus infection could modulate mutual differentiation from its precursor cells, contributing to bone resorption.

Unusual Suspects: Bone and Cartilage ECM Proteins as Carcinoma Facilitators

The extracellular matrix (ECM) is the complex three-dimensional network of fibrous proteins and proteoglycans that constitutes an essential part of every tissue to provide support for normal tissue homeostasis. Tissue specificity of the ECM in its topology and structure supports unique biochemical and mechanical properties of each organ. Cancers, like normal tissues, require the ECM to maintain multiple processes governing tumor development, progression and spread. A large body of experimental and clinical evidence has now accumulated to demonstrate essential roles of numerous ECM components in all cancer types. Latest findings also suggest that multiple tumor types express, and use to their advantage, atypical ECM components that are not found in the cancer tissue of origin. However, the understanding of cancer-specific expression patterns of these ECM proteins and their exact roles in selected tumor types is still sketchy. In this review, we summarize the latest data on the aberrant expression of bone and cartilage ECM proteins in epithelial cancers and their specific functions in the pathogenesis of carcinomas and discuss future directions in exploring the utility of this selective group of ECM components as future drug targets.

Mesenchymal Stromal Cells (MSCs): An Ally of B-Cell Acute Lymphoblastic Leukemia (B-ALL) Cells in Disease Maintenance and Progression within the Bone Marrow Hematopoietic Niche

Simple Summary

B-cell acute lymphoblastic leukemia (B-ALL) is the most common pediatric cancer. Even though the cure rate actually exceeds 85%, the prognosis of relapsed/refractory patients is dismal. Recent literature data indicate that the bone marrow (BM) microenvironment could play a crucial role in the onset, maintenance and progression of the disease. In particular, mesenchymal stromal cells (MSCs), which are key components of the BM niche, actively crosstalk with leukemic cells providing crucial signals for their survival and resistance to therapy. We hereby review the main mechanisms exploited by MSCs to nurture and protect B-ALL cells that could become appealing targets for innovative microenvironment remodeling therapies to be coupled with classical leukemia-directed strategies.

Abstract

Mesenchymal stromal cells (MSCs) are structural components of the bone marrow (BM) niche, where they functionally interact with hematopoietic stem cells and more differentiated progenitors, contributing to hematopoiesis regulation. A growing body of evidence is nowadays pointing to a further crucial contribution of MSCs to malignant hematopoiesis. In the context of B-cell acute lymphoblastic leukemia (B-ALL), MSCs can play a pivotal role in the definition of a leukemia-supportive microenvironment, impacting on disease pathogenesis at different steps including onset, maintenance and progression. B-ALL cells hijack the BM microenvironment, including MSCs residing in the BM niche, which in turn shelter leukemic cells and protect them from chemotherapeutic agents through different mechanisms. Evidence is now arising that altered MSCs can become precious allies to leukemic cells by providing nutrients, cytokines, pro-survivals signals and exchanging organelles, as hereafter reviewed. The study of the mechanisms exploited by MSCs to nurture and protect B-ALL blasts can be instrumental in finding new druggable candidates to target the leukemic BM microenvironment. Some of these microenvironment-targeting strategies are already in preclinical or clinical experimentation, and if coupled with leukemia-directed therapies, could represent a valuable option to improve the prognosis of relapsed/refractory patients, whose management represents an unmet medical need.

The antidiabetic drug metformin acts on the bone microenvironment to promote myeloma cell adhesion to preosteoblasts and increase myeloma tumour burden in vivo

Multiple myeloma is a haematological malignancy that is dependent upon interactions within the bone microenvironment to drive tumour growth and osteolytic bone disease. Metformin is an anti-diabetic drug that has attracted attention due to its direct antitumor effects, including anti-myeloma properties. However, the impact of the bone microenvironment on the response to metformin in myeloma is unknown. We have employed in vitro and in vivo models to dissect out the direct effects of metformin in bone and the subsequent indirect myeloma response. We demonstrate how metformin treatment of preosteoblasts increases myeloma cell attachment. Metformin-treated preosteoblasts increased osteopontin (OPN) expression that upon silencing, reduced subsequent myeloma cell adherence. Proliferation markers were reduced in myeloma cells cocultured with metformin-treated preosteoblasts. In vivo, mice were treated with metformin for 4 weeks prior to inoculation of 5TGM1 myeloma cells. Metformin-pretreated mice had an increase in tumour burden, associated with an increase in osteolytic bone lesions and elevated OPN expression in the bone marrow. Collectively, we show that metformin increases OPN expression in preosteoblasts, increasing myeloma cell adherence. In vivo, this translates to an unexpected indirect pro-tumourigenic effect of metformin, highlighting the importance of the interdependence between myeloma cells and cells of the bone microenvironment.

Embracing Mechanobiology in Next Generation Organ-On-A-Chip Models of Bone Metastasis

Bone metastasis in breast cancer is associated with high mortality. Biomechanical cues presented by the extracellular matrix play a vital role in driving cancer metastasis. The lack of in vitro models that recapitulate the mechanical aspects of the in vivo microenvironment hinders the development of novel targeted therapies. Organ-on-a-chip (OOAC) platforms have recently emerged as a new generation of in vitro models that can mimic cell-cell interactions, enable control over fluid flow and allow the introduction of mechanical cues. Biomaterials used within OOAC platforms can determine the physical microenvironment that cells reside in and affect their behavior, adhesion, and localization. Refining the design of OOAC platforms to recreate microenvironmental regulation of metastasis and probe cell-matrix interactions will advance our understanding of breast cancer metastasis and support the development of next-generation metastasis-on-a-chip platforms. In this mini-review, we discuss the role of mechanobiology on the behavior of breast cancer and bone-residing cells, summarize the current capabilities of OOAC platforms for modeling breast cancer metastasis to bone, and highlight design opportunities offered by the incorporation of mechanobiological cues in these platforms.

Bone Tropism in Cancer Metastases

Bone is a frequent site of metastases in many cancers. Both bone properties and the tumor-intrinsic traits are associated with the metastatic propensity to bone (i.e., the bone tropism). Whereas an increasing body of mechanistic studies expanded our understanding on bone tropism, they also revealed complexity across the bone lesions originated from different cancer types. In this review, we will discuss the physical, chemical, and biological properties of bone microenvironment, identify potential players in every stage of bone metastases, and introduce some of the known mechanisms regulating the bone colonization. Our objectives are to integrate the knowledge established in different biological contexts and highlight the determinants of bone tropism.

Role of the bone microenvironment in bone metastasis of malignant tumors - therapeutic implications

BACKGROUND

Bone is one of the most common sites for solid tumor metastasis. Bone metastasis of a malignant tumor seriously affects the quality of life and the overall survival of patients. Evidence has suggested that bone provides a favorable microenvironment that enables disseminated tumor cells to home, proliferate and colonize, leading to the formation of metastases. In the process of bone metastasis the bone microenvironment may be considered as an orchestra that plays a dissonant melody through blending (e.g. cross-talk between osteoclasts, osteoblasts and/or other cells), adding (e.g. a variety of biological factors) or taking away (e.g. blocking a specific pathway) players.

CONCLUSIONS

Here, we review the normal bone microenvironment, bone microenvironment-related factors that promote bone metastasis, as well as mechanisms underlying bone metastasis. In addition, we elude on directions for clinical bone metastasis management, focusing on potential therapeutic approaches to target bone microenvironment-related factors, including bisphosphonate, denosumab, CXCR4/CXCL12 antagonists and cathepsin K inhibitors.

Canine prostatic cancer cell line (LuMa) with osteoblastic bone metastasis

BACKGROUND

Osteoblastic bone metastasis represents the most common complication in men with prostate cancer (PCa). During progression and bone metastasis, PCa cells acquire properties similar to bone cells in a phenomenon called osteomimicry, which promotes their ability to metastasize, proliferate, and survive in the bone microenvironment. The mechanism of osteomimicry resulting in osteoblastic bone metastasis is unclear.

METHODS

We developed and characterized a novel canine prostatic cancer cell line (LuMa) that will be useful to investigate the relationship between osteoblastic bone metastasis and osteomimicry in PCa. The LuMa cell line was established from a primary prostate carcinoma of a 13-year old mixed breed castrated male dog. Cell proliferation and gene expression of LuMa were measured and compared to three other canine prostatic cancer cell lines (Probasco, Ace-1, and Leo) in vitro. The effect of LuMa cells on calvaria and murine preosteoblastic (MC3T3-E1) cells was measured by quantitative reverse-transcription polymerase chain reaction and alkaline phosphatase assay. LuMa cells were transduced with luciferase for monitoring in vivo tumor growth and metastasis using different inoculation routes (subcutaneous, intratibial [IT], and intracardiac [IC]). Xenograft tumors and metastases were evaluated using radiography and histopathology.

RESULTS

After left ventricular injection, LuMa cells metastasized to bone, brain, and adrenal glands. IT injections induced tumors with intramedullary new bone formation. LuMa cells had the highest messenger RNA levels of osteomimicry genes (RUNX2, RANKL, and Osteopontin [OPN]), CD44, E-cadherin, and MYOF compared to Ace-1, Probasco, and Leo cells. LuMa cells induced growth in calvaria defects and modulated gene expression in MC3T3-E1 cells.

CONCLUSIONS

LuMa is a novel canine PCa cell line with osteomimicry and stemness properties. LuMa cells induced osteoblastic bone formation in vitro and in vivo. LuMa PCa cells will serve as an excellent model for studying the mechanisms of osteomimicry and osteoblastic bone and brain metastasis in prostate cancer.

Adapt and conquer: Metabolic flexibility in cancer growth, invasion and evasion

BACKGROUND

It has been known for close to a century that, on average, tumors have a metabolism that is different from those found in healthy tissues. Typically, tumors show a biosynthetic metabolism that distinguishes itself by engaging in large scale aerobic glycolysis, heightened flux through the pentose phosphate pathway, and increased glutaminolysis among other means. However, it is becoming equally clear that non tumorous tissues at times can engage in similar metabolism, while tumors show a high degree of metabolic flexibility reacting to cues, and stresses in their local environment.

SCOPE OF THE REVIEW

In this review, we want to scrutinize historic and recent research on metabolism, comparing and contrasting oncogenic and physiological metabolic states. This will allow us to better define states of bona fide tumor metabolism. We will further contextualize the stress response and the metabolic evolutionary trajectory seen in tumors, and how these contribute to tumor progression. Lastly, we will analyze the implications of these characteristics with respect to therapy response.

MAJOR CONCLUSIONS

In our review, we argue that there is not one single oncogenic state, but rather a diverse set of oncogenic states. These are grounded on a physiological proliferative/wound healing program but distinguish themselves due to their large scale of proliferation, mutations, and transcriptional changes in key metabolic pathways, and the adaptations to widespread stress signals within tumors. We find evidence for the necessity of metabolic flexibility and stress responses in tumor progression and how these responses in turn shape oncogenic progression. Lastly, we find evidence for the notion that the metabolic adaptability of tumors frequently frustrates therapeutic interventions.

Interactions between cancer cells and bone microenvironment promote bone metastasis in prostate cancer

Bone metastasis is the leading cause of death in prostate cancer patients, for which there is currently no effective treatment. Since the bone microenvironment plays an important role in this process, attentions have been directed to the interactions between cancer cells and the bone microenvironment, including osteoclasts, osteoblasts, and bone stromal cells. Here, we explained the mechanism of interactions between prostate cancer cells and metastasis-associated cells within the bone microenvironment and further discussed the recent advances in targeted therapy of prostate cancer bone metastasis. This review also summarized the effects of bone microenvironment on prostate cancer metastasis and the related mechanisms, and provides insights for future prostate cancer metastasis studies.

The Bone Extracellular Matrix as an Ideal Milieu for Cancer Cell Metastases

Bone is a preferential site for cancer metastases, including multiple myeloma, prostate, and breast cancers.The composition of bone, especially the extracellular matrix (ECM), make it an attractive site for cancer cell colonization and survival. The bone ECM is composed of living cells embedded within a matrix composed of both organic and inorganic components. Among the organic components, type I collagen provides the tensile strength of bone. Inorganic components, including hydroxyapatite crystals, are an integral component of bone and provide bone with its rigidity. Under normal circumstances, two of the main cell types in bone, the osteoblasts and osteoclasts, help to maintain bone homeostasis and remodeling through cellular communication and response to biophysical signals from the ECM. However, under pathological conditions, including osteoporosis and cancer, bone remodeling is dysregulated. Once in the bone matrix, disseminated tumor cells utilize normal products of bone remodeling, such as collagen type I, to fuel cancer cell proliferation and lesion outgrowth. Models to study the complex interactions between the bone matrix and metastatic cancer cells are limited. Advances in understanding the interactions between the bone ECM and bone metastatic cancer cells are necessary in order to both regulate and prevent metastatic cancer cell growth in bone.

Osteopontin as a multifaceted driver of bone metastasis and drug resistance

Metastasis to bone frequently occurs in majority of patients with advanced breast cancer and prostate cancer, leading to devastating skeletal-related events and substantially reducing the survival of patients. Currently, the crosstalk between tumor cells and the bone stromal compartment was widely investigated for bone metastasis and the resistance to many conventional therapeutic methods. Osteopontin (OPN), also known as SPP1 (secreted phosphoprotein 1), a secreted and chemokine-like glyco-phosphoprotein is involved in tumor progression such as cell proliferation, angiogenesis, and metastasis. The expression of OPN in tumor tissue and plasma has been clinically proved to be correlated to poor prognosis and shortened survival in patients with breast cancer and prostate cancer. This review summarizes the multifaceted roles that OPN plays in bone microenvironment and drug resistance, with emphasis on breast and prostate cancers, via binding to αvβ3 integrin and CD44 receptor and inducing signaling cascades. We further discuss the promising therapeutic strategy for OPN targeting, mainly inhibiting OPN at transcriptional or protein level or blocking it binding to receptor or its downstream signaling pathways. The comprehending of the function of OPN in bone microenvironment is crucial for the development of novel biomarker and potential therapeutic target for the diagnosis and treatment of bone metastasis and against the emergence of drug resistance in advanced cancers.

JNK inactivation suppresses osteogenic differentiation, but robustly induces osteopontin expression in osteoblasts through the induction of inhibitor of DNA binding 4 (Id4)

Osteoblasts are versatile cells involved in multiple whole-body processes, including bone formation and immune response. Secretory amounts and patterns of osteoblast-derived proteins such as osteopontin (OPN) and osteocalcin (OCN) modulate osteoblast function. However, the regulatory mechanism of OPN and OCN expression remains unknown. Here, we demonstrate that p54/p46 c-jun N-terminal kinase (JNK) inhibition suppresses matrix mineralization and OCN expression but increases OPN expression in MC3T3-E1 cells and primary osteoblasts treated with differentiation inducers, including ascorbic acid, bone morphogenic protein-2, or fibroblast growth factor 2. Preinhibition of JNK before the onset of differentiation increased the number of osteoblasts that highly express OPN but not OCN (OPN-OBs), indicating that JNK affects OPN secretory phenotype at the early stage of osteogenic differentiation. Additionally, we identified JNK2 isoform as being critically involved in OPN-OB differentiation. Microarray analysis revealed that OPN-OBs express characteristic transcription factors, cell surface markers, and cytokines, including glycoprotein hormone α2 and endothelial cell-specific molecule 1. Moreover, we found that inhibitor of DNA binding 4 is an important regulator of OPN-OB differentiation and that dual-specificity phosphatase 16, a JNK-specific phosphatase, functions as an endogenous regulator of OPN-OB induction. OPN-OB phenotype was also observed following LPS from Porphyromonas gingivalis stimulation during osteogenic differentiation. Collectively, these results suggest that the JNK-Id4 signaling axis is crucial in the control of OPN and OCN expression during osteoblastic differentiation.-Kusuyama, J., Amir, M. S., Albertson, B. G., Bandow, K., Ohnishi, T., Nakamura, T., Noguchi, K., Shima, K., Semba, I., Matsuguchi, T. JNK inactivation suppresses osteogenic differentiation, but robustly induces osteopontin expression in osteoblasts through the induction of inhibitor of DNA binding 4 (Id4).

B. Abortus Modulates Osteoblast Function Through the Induction of Autophagy

Osteoarticular brucellosis is the most common localization of human active disease. Osteoblasts are specialized mesenchymal-derived cells involved in bone formation and are considered as professional mineralizing cells. Autophagy has been involved in osteoblast metabolism. The present study demonstrates that Brucella abortus infection induces the activation of the autophagic pathway in osteoblast cells. Autophagy was revealed by upregulation of LC3II/LC3I ratio and Beclin-1 expression as well as inhibition of p62 expression in infected cells. Induction of autophagy was also corroborated by using the pharmacological inhibitors wortmannin, a PI 3-kinase inhibitor, and leupeptin plus E64 (inhibitors of lysosomal proteases). Autophagy induction create a microenvironment that modifies osteoblast metabolism by the inhibition of the deposition of organic and mineral matrix, the induction of matrix metalloproteinase (MMP)-2, osteopontin, and RANKL secretion leading to bone loss. Accordingly, autophagy is also involved in the down-modulation of the master transcription factor in bone formation osterix during B. abortus infection. Taking together our results indicate that B. abortus induces the activation of autophagy pathway in osteoblast cells and this activation is involved in the modulation of osteoblast function and bone formation.

Macrophage Cytokines Enhance Cell Proliferation of Normal Prostate Epithelial Cells through Activation of ERK and Akt

Macrophage infiltrations (inflammation) are associated with prostate disorders such as prostatitis, prostatic hyperplasia and prostate cancer. All prostate disorders have elevated cell proliferation, and are initiated from normal prostate epithelial cells. To date, the mechanism of how macrophages regulate normal prostate epithelial cell proliferation remains largely unknown. Using a 3D co-culture system, we here show that Raw 264.7 macrophages increased cell proliferation of normal prostate epithelial PZ-HPV-7 cells. In addition, these Raw 264.7 macrophages expressed higher levels of Ym1 and CD206. We further identify macrophage-secreted cytokines including CCL3, IL-1ra, osteopontin, M-CSF1 and GDNF as mediators for potentiating PZ-HPV-7 cell proliferation in 3D. All these cytokines differentially activated ERK and Akt. Blockade of both kinases through their inhibitors hindered macrophage-induced cell proliferation of PZ-HPV-7 cells. Hence, our data provide mechanistic insight of how inflammation may contribute to development of prostatic diseases at a very early stage through augment of cell proliferation of normal prostate epithelial cells.

Unique Metabolic Adaptations Dictate Distal Organ-Specific Metastatic Colonization

Metastases arising from tumors have the proclivity to colonize specific organs, suggesting that they must rewire their biology to meet the demands of the organ colonized, thus altering their primary properties. Each metastatic site presents distinct metabolic challenges to a colonizing cancer cell, ranging from fuel and oxygen availability to oxidative stress. Here, we discuss the organ-specific metabolic adaptations that cancer cells must undergo, which provide the ability to overcome the unique barriers to colonization in foreign tissues and establish the metastatic tissue tropism phenotype.

Osteomimicry: How the Seed Grows in the Soil

Metastasis is defined as a very inefficient process, since less than 0.01% of cancer cells injected into the circulation will engraft in a distant organ, where they must acquire the ability to survive and proliferate inside a "foreign" environment. In bone metastases, the interaction with the host organ is much more favoured if tumour cells gain "osteomimicry", that is the ability to resemble a resident bone cell (i.e. the osteoblast), thus intruding in the physiology of the bone. This is accomplished by the expression of osteoblast markers (e.g. alkaline phosphatase) and the production of bone matrix proteins and paracrine factors which deregulate the physiology of bone, fuelling the so-called "vicious cycle". The main challenge of researchers is therefore to identify the genetic profile determining the osteotropism of tumour cells, which would eventually lead to bone colonisation. This could likely provide the answer to a quite intriguing question, that is why some cancers, such as prostate and breast, have a specific predilection to metastasise to the bone. Therefore, it is important to completely address the molecular mechanisms underlying this aspect of bone oncology, identifying relevant pathways, the targeting of which could make any type of bone metastasis curable or avoidable.

Osteopontin inhibits osteoblast responsiveness through the down-regulation of focal adhesion kinase mediated by the induction of low-molecular weight protein tyrosine phosphatase

Osteopontin (OPN), a major marker of osteogenic differentiation, suppresses osteoblast responses to mechanical stress and cytokines, including HGF and PDGF. These OPN-induced effects are mediated through focal adhesion kinase inactivation by the induction of low–molecular weight protein tyrosine phosphatase.

Osteopontin (OPN) is an osteogenic marker protein. Osteoblast functions are affected by inflammatory cytokines and pathological conditions. OPN is highly expressed in bone lesions such as those in rheumatoid arthritis. However, local regulatory effects of OPN on osteoblasts remain ambiguous. Here we examined how OPN influences osteoblast responses to mechanical stress and growth factors. Expression of NO synthase 1 (Nos1) and Nos2 was increased by low-intensity pulsed ultrasound (LIPUS) in MC3T3-E1 cells and primary osteoblasts. The increase of Nos1/2 expression was abrogated by both exogenous OPN overexpression and recombinant OPN treatment, whereas it was promoted by OPN-specific siRNA and OPN antibody. Moreover, LIPUS-induced phosphorylation of focal adhesion kinase (FAK), a crucial regulator of mechanoresponses, was down-regulated by OPN treatments. OPN also attenuated hepatocyte growth factor–induced vitamin D receptor (Vdr) expression and platelet-derived growth factor–induced cell mobility through the repression of FAK activity. Of note, the expression of low–molecular weight protein tyrosine phosphatase (LMW-PTP), a FAK phosphatase, was increased in both OPN-treated and differentiated osteoblasts. CD44 was a specific OPN receptor for LWW-PTP induction. Consistently, the suppressive influence of OPN on osteoblast responsiveness was abrogated by LMW-PTP knockdown. Taken together, these results reveal novel functions of OPN in osteoblast physiology.

Osteopontin is a useful predictor of bone metastasis and survival in patients with locally advanced nasopharyngeal carcinoma

Bone is the most common metastatic site in nasopharyngeal carcinoma (NPC). Osteopontin (OPN) and bone sialoprotein (BSP) are demonstrated to be involved in multiple steps of distant metastasis and correlate with bone metastasis (BM) in cancers. We aim to explore the impacts of OPN and BSP on the prognosis of the patients with locally advanced NPC. A tissue microarray including 162 locally advanced NPC specimens was generated for immunohistochemical evaluation. All of the patients received curative treatment. Twenty-two patients developed BM during follow-up. The OPN expression level was higher in patients with BM than in those without BM (p = 0.005), whereas no significant difference of the BSP expression level was noted (p = 0.634). Univariate analysis demonstrated that a higher level of OPN expression associated with a poorer 8-year metastasis-free survival (MFS) rate (p < 0.001), 8-year bone metastasis-free survival (BMFS) rate (93.6 vs. 87.5 vs. 64.5% for immunoreactivity score 1, 2 and 3, respectively; p = 0.001) and median overall survival (OS) time (p < 0.001). Multivariate Cox analysis confirmed that high level of OPN expression was independent factor associated with decreased BMFS (p = 0.02), MFS (p < 0.001) and OS (p < 0.001). Our findings indicate that OPN is a prognostic biomarker for BM and survival in patients with locally advanced NPC, and therefore it is useful in identifying the patients with an increased risk of cancer progression and BM to guide tailored therapy.

Prostate cancer and bone: the elective affinities

The onset of metastases dramatically changes the prognosis of prostate cancer patients, determining increased morbidity and a drastic fall in survival expectancy. Bone is a common site of metastases in few types of cancer, and it represents the most frequent metastatic site in prostate cancer. Of note, the prevalence of tumor relapse to the bone appears to be increasing over the years, likely due to a longer overall survival of prostate cancer patients. Bone tropism represents an intriguing challenge for researchers also because the preference of prostate cancer cells for the bone is the result of a sequential series of targetable molecular events. Many factors have been associated with the peculiar ability of prostate cancer cells to migrate in bone marrow and to determine mixed osteoblastic/osteolytic lesions. As anticipated by the success of current targeted therapy aimed to block bone resorption, a better understanding of molecular affinity between prostate cancer and bone microenvironment will permit us to cure bone metastasis and to improve prognosis of prostate cancer patients.

A new murine model of osteoblastic/osteolytic lesions from human androgen-resistant prostate cancer

Background

Up to 80% of patients dying from prostate carcinoma have developed bone metastases that are incurable. Castration is commonly used to treat prostate cancer. Although the disease initially responds to androgen blockade strategies, it often becomes castration-resistant (CRPC for Castration Resistant Prostate Cancer). Most of the murine models of mixed lesions derived from prostate cancer cells are androgen sensitive. Thus, we established a new model of CRPC (androgen receptor (AR) negative) that causes mixed lesions in bone.

Methods

PC3 and its derived new cell clone PC3c cells were directly injected into the tibiae of SCID male mice. Tumor growth was analyzed by radiography and histology. Direct effects of conditioned medium of both cell lines were tested on osteoclasts, osteoblasts and osteocytes.

Results

We found that PC3c cells induced mixed lesions 10 weeks after intratibial injection. Invitro, PC3c conditioned medium was able to stimulate tartrate resistant acid phosphatase (TRAP)-positive osteoclasts. Osteoprotegerin (OPG) and endothelin-1 (ET1) were highly expressed by PC3c while dikkopf-1 (DKK1) expression was decreased. Finally, PC3c highly expressed bone associated markers osteopontin (OPN), Runx2, alkaline phosphatase (ALP), bone sialoprotein (BSP) and produced mineralized matrix invitro in osteogenic conditions.

Conclusions

We have established a new CRPC cell line as a useful system for modeling human metastatic prostate cancer which presents the mixed phenotype of bone metastases that is commonly observed in prostate cancer patients with advanced disease. This model will help to understand androgen-independent mechanisms involved in the progression of prostate cancer in bone and provides a preclinical model for testing the effects of new treatments for bone metastases.

The RUNX family in breast cancer: relationships with estrogen signaling

The three RUNX family members are lineage specific master regulators, which also have important, context-dependent roles in carcinogenesis as either tumor suppressors or oncogenes. Here we review evidence for such roles in breast cancer (BCa). RUNX1, the predominant RUNX family member in breast epithelial cells, has a tumor suppressor role reflected by many somatic mutations found in primary tumor biopsies. The classical tumor suppressor gene RUNX3 does not consist of such a mutation hot spot, but it too seems to inhibit BCa; it is often inactivated in human BCa tumors and its haploinsufficiency in mice leads to spontaneous BCa development. The tumor suppressor activities of RUNX1 and RUNX3 are mediated in part by antagonism of estrogen signaling, a feature recently attributed to RUNX2 as well. Paradoxically, however RUNX2, a master osteoblast regulator, has been implicated in various aspects of metastasis in general and bone metastasis in particular. Reciprocating the anti-estrogenic tumor suppressor activity of RUNX proteins, inhibition of RUNX2 by estrogens may help explain their context-dependent anti-metastatic roles. Such roles are reserved to non-osseous metastasis, because ERα is associated with increased, not decreased skeletal dissemination of BCa cells. Finally, based on diverse expression patterns in BCa subtypes, the successful use of future RUNX-based therapies will most likely require careful patient selection.

Adhesion to osteopontin in the bone marrow niche regulates lymphoblastic leukemia cell dormancy

Malignant cells may evade death from cytotoxic agents if they are in a dormant state. The host microenvironment plays important roles in cancer progression, but how niches might control cancer cell dormancy is little understood. Here we show that osteopontin (OPN), an extracellular matrix molecule secreted by osteoblasts, can function to anchor leukemic blasts in anatomic locations supporting tumor dormancy. We demonstrate that acute lymphoblastic leukemia (ALL) cells specifically adhere to OPN in vitro and secrete OPN when localized to the endosteal niche in vivo. Using intravital microscopy to perform imaging studies of the calvarial bone marrow (BM) of xenografted mice, we show that OPN is highly expressed adjacent to dormant tumor cells within the marrow. Inhibition of the OPN-signaling axis significantly increases the leukemic cell Ki-67 proliferative index and leads to a twofold increase in tumor burden in treated mice. Moreover, using cell-cycle-dependent Ara-C chemotherapy to produce minimal residual disease (MRD) in leukemic mice, we show that OPN neutralization synergizes with Ara-C to reduce detectable BM MRD. Taken together, these data suggest that ALL interacts with extracellular OPN within the malignant BM, and that this interaction induces cell cycle exit in leukemic blasts, protecting them from cytotoxic chemotherapy.

Microcalcifications in breast cancer: Lessons from physiological mineralization

Mammographic mammary microcalcifications are routinely used for the early detection of breast cancer, however the mechanisms by which they form remain unclear. Two species of mammary microcalcifications have been identified; calcium oxalate and hydroxyapatite. Calcium oxalate is mostly associated with benign lesions of the breast, whereas hydroxyapatite is associated with both benign and malignant tumors. The way in which hydroxyapatite forms within mammary tissue remains largely unexplored, however lessons can be learned from the process of physiological mineralization. Normal physiological mineralization by osteoblasts results in hydroxyapatite deposition in bone. This review brings together existing knowledge from the field of physiological mineralization and juxtaposes it with our current understanding of the genesis of mammary microcalcifications. As an increasing number of breast cancers are being detected in their non-palpable stage through mammographic microcalcifications, it is important that future studies investigate the underlying mechanisms of their formation in order to fully understand the significance of this unique early marker of breast cancer.

Proteins involved in regulating bone invasion in skull base meningiomas

Background

Bone invasive skull base meningiomas are a subset of meningiomas that present a unique clinical challenge due to brain and neural structure involvement and limitations in complete surgical resection, resulting in higher recurrence and need for repeat surgery. To date, the pathogenesis of meningioma bone invasion has not been investigated. We investigated immunoexpression of proteins implicated in bone invasion in other tumor types to establish their involvement in meningioma bone invasion.

Methods

Retrospective review of our database identified bone invasive meningiomas operated on at our institution over the past 20 years. Using high-throughput tissue microarray (TMA), we established the expression profile of osteopontin (OPN), matrix metalloproteinase-2 (MMP2), and integrin beta-1 (ITGB1). Differential expression in tumor cell and vasculature was evaluated and comparisons were made between meningioma anatomical locations.

Results

MMP2, OPN, and ITGB1 immunoreactivity was cytoplasmic in tumor and/or endothelial cells. Noninvasive transbasal meningiomas exhibited higher vascular endothelial cell MMP2 immunoexpression compared to invasive meningiomas. We found higher expression levels of OPN and ITGB1 in bone invasive transbasal compared to noninvasive meningiomas. Strong vascular ITGB1 expression extending from the endothelium through the media and into the adventitia was found in a subset of meningiomas.

Conclusions

We have demonstrated that key proteins are differentially expressed in bone invasive meningiomas and that the anatomical location of bone invasion is a key determinant of expression pattern of MMP1, OPN, and ITGB1. This data provides initial insights into the pathophysiology of bone invasion in meningiomas and identifies factors that can be pursued as potential therapeutic targets.

Osteopontin is overexpressed in colorectal carcinoma and is correlated with P53 by immunohistochemistry

Osteopontin (OPN), a secreted phosphorylated glycoprotein, has been found to be involved in carcinogenesis, progression and metastasis of several types of cancers. The aim of the present study was to investigate the immunohistochemical expression of OPN in colorectal carcinoma (CRC) and its relationship with clinicopathological parameters and P53. Expression of OPN, Ki-67 and TP53 was detected in 77 cases of CRC by immunohistochemistry and the correlation of the expression of OPN with clinicopathological features, Ki-67 and P53 staining was investigated. Thirty-eight cases (49.4%) of CRC demonstrated OPN overexpression. Overexpression of OPN was associated with lymph node metastasis (P=0.025) and Dukes' stages (P=0.031), but not with gender, histological differentiation, depth of tumor invasion, TNM stages or Ki-67 index. The correlation between expression of OPN and TP53 was statistically significant (P=0.030). In conclusion, OPN is overexpressed in CRC, and plays a role in tumor progression and metastasis, which is possibly regulated by P53.

Alteration of bone sialoprotein expression in osseous metastasized renal cell carcinomas and the tumor surrounding tissue

Bone sialoprotein (BSP) regulates bone metabolism by directly influencing the activity of osteoblasts and osteoclasts. A significant correlation between the tissue expression of BSP in tumors and the occurrence of bone metastases was found in different cancers. Aim of this study was to identify the BSP expression in renal cell carcinomas (RCC) according to their stage of metastatic disease. Tissue samples of patients with RCC who underwent partial resection or nephrectomy were separated into three groups, each with 10 patients showing either no metastases (group I), only soft tissue metastases (group II) or bone metastases (group III) at date of surgery. Immunohistochemical analysis of BSP expression in tumor tissue and corresponding renal parenchyma was performed and evaluated with an established semiquantitative scoring system. BSP expression was detected both in tumor tissue and renal parenchyma. Concerning the expression in malignant tissue, no significant difference could be found between the three groups whereas the corresponding renal parenchyma showed a staining score of 164, 198 and 224 for group I, II and III (P = 0.07). RCC staged T3 showed only a little higher BSP expression than those staged T1/2 (P < 0.21), while the corresponding parenchyma of T3 tumors showed significantly higher expressions (P = 0.02). This pilot study revealed a correlation between expression of BSP and tumor staging and type of metastases, especially for osseous metastases in RCC. Alternation of BSP expression could be detected particularly in renal parenchyma and linked to the type of metastases.

Cancer to bone: a fatal attraction

When cancer metastasizes to bone, considerable pain and deregulated bone remodelling occurs, greatly diminishing the possibility of cure. Metastasizing tumour cells mobilize and sculpt the bone microenvironment to enhance tumour growth and to promote bone invasion. Understanding the crucial components of the bone microenvironment that influence tumour localization, along with the tumour-derived factors that modulate cellular and protein matrix components of bone to favour tumour expansion and invasion, is central to the pathophysiology of bone metastases. Basic findings of tumour-bone interactions have uncovered numerous therapeutic opportunities that focus on the bone microenvironment to prevent and treat bone metastases.

Cancer to bone: a fatal attraction

When cancer metastasizes to bone, considerable pain and deregulated bone remodelling occurs, greatly diminishing the possibility of cure. Metastasizing tumour cells mobilize and sculpt the bone microenvironment to enhance tumour growth and to promote bone invasion. Understanding the crucial components of the bone microenvironment that influence tumour localization, along with the tumour-derived factors that modulate cellular and protein matrix components of bone to favour tumour expansion and invasion, is central to the pathophysiology of bone metastases. Basic findings of tumour-bone interactions have uncovered numerous therapeutic opportunities that focus on the bone microenvironment to prevent and treat bone metastases.

Integrins and bone metastasis: integrating tumor cell and stromal cell interactions

Integrins on both tumor cells and the supporting host stromal cells in bone (osteoclasts, new blood vessels, inflammatory cells, platelets and bone marrow stromal cells) play key roles in enhancing bone metastasis. Tumor cells localize to specific tissues through integrin-mediated contacts with extracellular matrix and stromal cells. Integrin expression and signaling are perturbed in cancer cells, allowing them to "escape" from cell-cell and cell-matrix tethers, invade, migrate and colonize within new tissues and matrices. Integrin signaling through αvβ3 and VLA-4 on tumor cells can promote tumor metastasis to and proliferation in the bone microenvironment. Osteoclast (OC) mediated bone resorption is a critical component of bone metastasis and can promote tumor growth in bone and αvβ3 integrins are critical to OC function and development. Tumors in the bone microenvironment can recruit new blood vessel formation, platelets, pro-tumor immune cells and bone marrow stromal cells that promote tumor growth and invasion in bone. Integrins and their ligands play critical roles in platelet aggregation (αvβ3 and αIIbβ3), hematopoietic cell mobilization (VLA-4 and osteopontin), neoangiogenesis (αvβ3, αvβ5, α6β4, and β1 integrin) and stromal function (osteopontin and VLA-4). Integrins are involved in the pathogenesis of bone metastasis at many levels and further study to define integrin dysregulation by cancer will yield new therapeutic targets for the prevention and treatment of bone metastasis.

Hedgehog signaling induced by breast cancer cells promotes osteoclastogenesis and osteolysis

Bone integrity is maintained by a dynamic equilibrium between the activities of bone-forming osteoblasts and bone-resorbing osteoclasts. Osteolytic lesions are a painful consequence of metastasis of breast cancer cells to bone in an overwhelming majority of breast cancer patients. Factors secreted by breast cancer cells propel a cascade of events that trigger osteoclastogenesis and elevated bone resorption. In the present study, we show that the Hedgehog (Hh) ligands secreted by breast cancer cells promote osteoclast differentiation and potentiate the activity of mature osteoclasts. Paracrine Hh signaling induced by breast cancer cells mediates a detrimental chain of events by the up-regulation of osteopontin (OPN), which in turn enhances osteoclastic activity by up-regulating cathepsin K and MMP9. Hh signaling is essential for osteoclasts because blocking the Hh pathway using the pharmacological Hh inhibitor, cyclopamine, results in an overall decrease in osteoclastogenesis and resorptive activity. Our studies suggest that inhibiting Hh signaling interferes with the ability of pre-osteoclasts to respond to the stimulatory effects of the breast cancer cells, indicating that Hh signaling is vital to osteoclast activity.

cAMP and fibroblast growth factor 2 regulate bone sialoprotein gene expression in human prostate cancer cells

Bone sialoprotein (BSP) is a noncollagenous protein of the extracellular matrix in mineralized connective tissues that has been implicated in the nucleation of hydroxyapatite. Forskolin (FSK), an activator of adenylate cyclase, increased the intracellular cAMP level, which stimulates the proliferation and differentiation of osteoblasts. Fibroblast growth factor 2 (FGF2) is a potent mitogen in many cell types, including osteoblasts. In human prostate cancer DU145 cells, FSK (1 μM) and FGF2 (10 ng/ml) increased BSP and Runx2 mRNA and protein levels at 3 and 12h, respectively. Transient transfection analyses were performed using chimeric constructs of the human BSP gene promoter linked to a luciferase reporter gene. Treatment of DU145 cells with FSK (1 μM) and FGF2 (10 ng/ml) increased the luciferase activities of constructs between -60LUC to -927LUC and -108LUC to -927LUC, including the human BSP gene promoter. Effects of FSK and FGF2 abrogated in constructs included 2bp mutations in the two cAMP response elements (CRE1 and CRE2). Luciferase activities induced by FSK and FGF2 were blocked by protein kinase A and tyrosine kinase inhibitors. Gel mobility shift analyses showed that FSK and FGF2 increased the binding of CRE1 and CRE2. CRE1-protein complexes were supershifted by phospho-CREB1 and c-Fos antibodies, and disrupted by CREB1, c-Jun, JunD, Fra2, p300, Runx2, Dlx5 and Smad1 antibodies. CRE2-protein complexes were disrupted by CREB1, phospho-CREB1, c-Fos, c-Jun, JunD, Fra2, p300, Runx2, Dlx5 and Smad1 antibodies. These studies demonstrate that FSK and FGF2 stimulate BSP transcription in DU145 human prostate cancer cells by targeting the CRE1 and CRE2 elements in the human BSP gene promoter.

Role of the metastasis-promoting protein osteopontin in the tumour microenvironment

Osteopontin (OPN) is a secreted protein present in bodily fluids and tissues. It is subject to multiple post-translational modifications, including phosphorylation, glycosylation, proteolytic cleavage and crosslinking by transglutamination. Binding of OPN to integrin and CD44 receptors regulates signalling cascades that affect processes such as adhesion, migration, invasion, chemotaxis and cell survival. A variety of cells and tissues express OPN, including bone, vasculature, kidney, inflammatory cells and numerous secretory epithelia. Normal physiological roles include regulation of immune functions, vascular remodelling, wound repair and developmental processes. OPN also is expressed in many cancers, and elevated levels in patients’ tumour tissue and blood are associated with poor prognosis. Tumour growth is regulated by interactions between tumour cells and their tissue microenvironment. Within a tumour mass, OPN can be expressed by both tumour cells and cellular components of the tumour microenvironment, and both tumour and normal cells may have receptors able to bind to OPN. OPN can also be found as a component of the extracellular matrix. The functional roles of OPN in a tumour are thus complex, with OPN secreted by both tumour cells and cells in the tumour microenvironment, both of which can in turn respond to OPN. Much remains to be learned about the cross-talk between normal and tumour cells within a tumour, and the role of multiple forms of OPN in these interactions. Understanding OPN-mediated interactions within a tumour will be important for the development of therapeutic strategies to target OPN.

Predictive significance of bone sialoprotein and osteopontin for bone metastases in resected Chinese non-small-cell lung cancer patients: a large cohort retrospective study

BACKGROUND

Bone is one of the most common sites of metastasis in patients with non-small-cell lung cancer (NSCLC). Over-expression of bone sialoprotein (BSP) and osteopontin (OPN) in tumour samples has shown prognostic significance in bone metastasis (BM) of breast and prostate cancer, respectively. However, their importance in BM of NSCLC has not been verified. Therefore, we planned a large cohort retrospective study to investigate the relationship between the expression of these two biomarkers (BSP and OPN) and BM in surgically resected NSCLC patients.

METHODS

180 completely resected NSCLC patients were included in this study. 40 patients subsequently developed BM. Paraffin-embedded primary tumour tissues of patients were supplied to produce a tissue microarray, and immunohistochemistry method was used for evaluation of the expression of BSP and OPN. Different expressions of these two biomarkers among BM group and non-BM group were estimated by chi(2) test. BM-free survival was analyzed by Kaplan-Meier method. The prognostic impact of clinicopathologic variables and biomarker expression was evaluated by Cox proportional hazards model.

RESULTS

BSP expression was associated with BM (p=0.007), whereas OPN expression did not reach statistical significance (p=0.245). Univariate analysis showed that expression of BSP (p=0.010) and N staging (p<0.005) was associated with BM-free survival. Multivariate analyses showed BSP expression (HR=3.322, p=0.003), N staging (HR=1.879, p=0.001), and T staging (HR=1.618, p=0.024) were independent prognostic factors for BM.

CONCLUSIONS

BSP protein expression in the primary resected NSCLC is strongly associated with BM and could be used to identify high-risk patients. Correlation of OPN protein expression and BM needs further investigation.

Gene expression analysis identifies over-expression of CXCL1, SPARC, SPP1, and SULF1 in gastric cancer

To elucidate gene expression signatures associated with gastric carcinogenesis, we performed a genome-wide expression analysis of 46 Finnish and 20 Japanese gastric tissues. Comparative analysis between Finnish and Japanese datasets identified 58 common genes that were differentially expressed between cancerous and non-neoplastic gastric tissues. Twenty-six of these genes were up-regulated in cancer and 32 down-regulated. Of these genes, 64% were also differentially expressed in another unrelated publicly available dataset. The expression levels of four of the up-regulated genes, CXCL1, SPARC, SPP1 and SULF, were further analyzed in 82 gastric tissues using quantitative real-time RT-PCR. This analysis validated the results from the microarray analysis as the expression of these four genes was significantly higher in the cancerous tissue compared with the normal tissue (fold change 3.4-8.9). Over-expression of CXCL1 also positively correlated with improved survival. To conclude, irrespective of the microarray platform or patient population, a common gastric cancer gene expression signature of 58 genes, including CXCL1, SPARC, SPP1, and SULF, was identified. These genes represent potential biomarkers for gastric cancer.

Prognostic value of serum osteopontin in hepatocellular carcinoma patients treated with transarterial chemoembolization

BACKGROUND/AIMS

Osteopontin (OPN) is overexpressed in hepatocellular carcinoma (HCC) with postoperative recurrence or extrahepatic metastasis. However, its prognostic value in patients treated with transarterial chemoembolization (TACE) is unclear. We investigated the utility of serum OPN levels and changes therein as prognostic markers in HCC patients who have received TACE.

METHODS

Forty-six patients with HCC were enrolled. Serum OPN levels were measured before and 4 weeks after TACE. Serum biochemistry and computed tomography (CT) scans were analyzed. We evaluated baseline serum OPN levels and subsequent changes therein in relation to tumor responses and cumulative survival rates following TACE. A decreasing pattern was defined as a decrease after TACE of more than 10% relative to baseline levels. A "responder" was defined as a patient who exhibited a tumor necrosis rate of higher than 50% on the follow-up CT scan.

RESULTS

Higher initial serum OPN levels were associated with a large tumor, portal vein invasion, and an advanced tumor stage. Patients who had lower initial serum OPN levels and those who exhibited decreasing patterns after TACE tended to have more favorable tumor responses (P=0.043 and 0.055, respectively) and exhibited better cumulative survival rates (P=0.036 and 0.030, respectively). However, the initial serum OPN level and subsequent changes in serum OPN levels were not independent predictors for survival on multivariate analysis.

CONCLUSIONS

Serum OPN levels were significantly higher in patients with advanced HCC. In addition, HCC patients with low pretreatment serum OPN levels and those for whom serum OPN declined following TACE exhibited better tumor responses and survived for longer.

Osteopontin induces beta-catenin signaling through activation of Akt in prostate cancer cells

Secretion of osteopontin (OPN) by cancer cells is a known mediator of tumorigenesis and cancer progression in both experimental and clinical studies. Our work demonstrates that OPN can activate Akt, an important step in cancer progression. Both ILK and PI3K are integral proteins in the OPN/Akt pathway, as inhibition of either kinase leads to a loss of OPN-mediated Akt activation. Subsequent to OPN-induced Akt activation, we observe inactivation of GSK-3beta, a regulator of beta-catenin. Osteopontin stimulation leads to an overall increase in beta-catenin protein levels with a resultant transfer of beta-catenin to the nucleus. Through the nuclear import of beta-catenin, OPN increases both the transcription and protein levels of MMP-7 and CD44, which are known TCF/LEF transcription targets. This work describes an important aspect of cancer progression induced by OPN.

Genomic aberrations in hepatocellular carcinoma related to osteopontin expression detected by array-CGH

PURPOSE

We have demonstrated that overexpression of osteopontin (OPN) could contribute to metastasis in hepatocellular carcinoma (HCC), and that OPN-positive cancer cells are often localized in the periphery of cancer nodules adjacent to stromal cells. This study was to identify the difference of intratumor genomic aberrations between OPN-positive and OPN-negative HCC cells.

METHODS

Immunohistochemical staining for OPN was performed in both archival and fresh HCC tumor tissues. Seven cases of OPN-positive HCC were chosen for laser capture microdissection. The OPN-positive and OPN-negative cancer cells were captured separately from serial frozen sections. Genomic DNA was extracted and quantified. Microarray-based comparative genomic hybridization (array-CGH) was used to achieve high-resolution analysis of whole-genome-wide aberrations.

RESULTS

The OPN expression level in HCC tissues was significantly associated with vascular or bile duct invasion (P = 0.003), Edmondson's grade (P = 0.047), and intrahepatic spreading (P = 0.011). When compared with the OPN-negative cancer cells, much more amplifications of chromosomal regions, including 4q13.1-q13.3, 4q21.23-q22.1, and 13q32.1-q32.3, were found in OPN-positive HCC cells. Some candidate tumor-related genes, such as SMR3B, MUC7, EPHA5, SPP1, and CLDN10 were detected with over 1.5-fold amplification.

CONCLUSIONS

There is a significant intratumor genomic heterogeneity between the OPN-positive and negative HCC cells, and OPN-positive HCC cells play a more important role in the development of HCC malignancy than their OPN-negative counterparts.

High expression of osteopontin and CD44v6 in odontogenic keratocysts

BACKGROUND/PURPOSE

Odontogenic keratocysts (OKCs) are more aggressive and more osteolytic lesions than dentigerous cysts (DCs) and radicular cysts (RCs). Osteopontin (OPN) is related to cancer metastasis and bone destruction. Binding of OPN to its cell membrane receptors integrin alphav and CD44v6 can enhance tumor cell motility, migration, invasion and spread. This study assessed the possible contribution of OPN, integrin alphav and CD44v6 to the local aggressive behavior and osteolytic ability of OKCs.

METHODS

We used an immunohistochemical method to examine the expression of OPN, integrin alphav and CD44v6 in tissue sections of 20 OKCs, eight DCs and 10 RCs.

RESULTS

We found strong cytoplasmic OPN immunostaining in lining epithelial cells of 8 of 20 OKCs but not in any DCs and RCs. Positive OPN staining was also noted in the subepithelial connective tissue of four OKCs with intraepithelial expression of OPN. Diffuse and strong membranous integrin alphav staining was discovered in osteoclasts in all our tissue sections and in nearly all lining epithelial cells of DCs and RCs, but not in OKCs. In addition, diffuse and strong membranous CD44v6 staining was also observed in nearly all lining epithelial cells of OKCs, DCs and RCs.

CONCLUSION

Binding of OPN to osteoclast cell membrane receptor integrin alphav can activate the osteoclasts and increase their osteolytic activity. In addition, binding of OPN to OKC lining epithelial cell membrane receptor CD44v6 can enhance the motility, migration, invasion and spread of lining epithelial cells into the surrounding cancellous bone. Therefore, we suggest that the local aggressive behavior and high osteolytic ability of OKCs in the jawbone can be explained at least partially by high expression of OPN and CD44v6 in lining epithelial cells of OKCs and high expression of integrin alphav in osteoclasts.

Increased levels of active c-Src distinguish invasive from in situ lobular lesions

Introduction

Mounting molecular evidence suggests that invasive lobular carcinoma (ILC) is developing from in situ lesions, atypical lobular hyperplasia (ALH), and lobular carcinoma in situ (LCIS). However, little is known about the mechanisms promoting the progression of lobular breast cancer (LBC) to invasive disease. Here, we investigated whether c-Src kinase, an established inducer of invasive states, contributes to the progression from ALH/LCIS to ILC.

Methods

Immunochemistry for c-Src and other cancer-related molecules was performed on archived tissue specimens from 57 LBC patients. Relative c-Src activity was estimated by comparing fluorescence intensity of ILC with that of adjacent ALH/LCIS and nonneoplastic epithelia after staining with an antibody against active c-Src. Expression of active c-Src was correlated with markers of invasion and malignancy and with relapse among LBC patients.

Results

Levels of activated c-Src were increased in ILC relative to ALH/LCIS (1.63-fold ± 0.24 SD) and nonneoplastic epithelia (1.47 ± 0.18 SD). Increased c-Src levels correlated with the activation of c-Src downstream targets (Fak, Stat-3) and the expression of mesenchymal markers. ILC cells with activated c-Src co-expressed metastatic markers (Opn, Cxcr4) and included cells positive for the cancer stem cell marker Aldh1. A tendency for high c-Src levels (P = 0.072) was observed among the seven LBC patients with relapsed disease.

Conclusions

Our data indicate elevated c-Src activity in ILC relative to noninvasive neoplastic tissue. The associated molecular changes suggest that c-Src promotes LBC invasiveness by inducing an epithelial-mesenchymal transition. Therefore, c-Src antagonists might counteract the acquisition of invasiveness during LBC progression. Inhibition of c-Src may also affect ILC cells thought to have a high metastatic potential and to be capable of initiating/maintaining tumor growth. Together with the possible association between high c-Src levels and disease recurrence, our findings encourage the evaluation of c-Src antagonists for the treatment of LBC.

Influence of ADAM28 on biological characteristics of human dental follicle cells

OBJECTIVES

The aim of this study was to investigate the effects of a disintegrin and metalloproteinase 28 (ADAM28) on the biological characteristics of human dental follicle cells (HDFCs) and possible action mechanism.

METHODS

Eukaryotic expression plasmid containing ADAM28 coding region and ADAM28 antisense oligodeoxynucleotides (AS-ODN) with FITC labelling were constructed and synthesised by gene clone and recombination. Then we respectively transfected them into HDFCs by Lipofectamine 2000 system and detected their effects on proliferation, differentiation and apoptosis of HDFCs by MTT assay, cell cycle detection, ALP activity and Annexin V-FITC/PI analysis. Finally we observed the effects of ADAM28 AS-ODN on HDFCs expressing extracellular matrix (ECM) proteins by immunocytochemical staining.

RESULTS

ADAM28 eukaryotic plasmid was constructed and identified successfully, and could be correctly translated and expressed in HDFCs, furthermore overexpression of ADAM28 promoted the HDFCs proliferation and inhibited specific differentiation of HDFCs, while inhibition of ADAM28 exerted the opposite effects and induced apoptosis. Moreover ADAM28 could significantly inhibit the secretion of OPN and type III collagen of HDFCs.

CONCLUSIONS

ADAM28 might actively participate in the network regulation which associates HDFCs proliferation, differentiation, apoptosis with matrix mineralisation during tooth development by interacting with multiple signal molecules.

Global expression profiling reveals regulation of CTGF/CCN2 during lactogenic differentiation

Mammary epithelial cells go through a series of developmental changes during pregnancy and lactation including proliferation, differentiation, secretion and apoptosis. HC11 mouse mammary epithelial cells, which undergo lactogen-induced differentiation in cell culture, were used to follow the changes in gene expression during this process. The expression profiles of over 20,000 genes were compared in HC11 cells undergoing lactogenic differentiation to non-differentiated cells using DNA microarray analysis. Greater than two fold changes were detected in 998 genes in the differentiated cells versus growth controls. Several genes including CTGF/CCN2 exhibited greater than five-fold increase. Validation of the gene expression pattern for more than twenty genes was performed. The results indicate the involvement of numerous genes and pathways in the differentiation of mouse mammary epithelial cells in culture and they identify genetic pathways associated with specific transcriptional regulation. In addition, the expression of a subset of genes regulated by lactogenic differentiation in HC11 cells, including CTGF/CCN2 and osteopontin, was examined in mouse mammary glands revealing expression during pregnancy and lactation that declined during involution of the glands. To probe the mechanism by which epidermal growth factor (EGF), a known inhibitor of lactogenic differentiation in HC11 cells, blocks lactogenesis, the HC11 cells stimulated with lactogenic hormone in the presence of EGF were profiled. This data revealed EGF regulation of a specific subset of genes including important cell cycle regulators. The studies confirm the value of expression profiling in defining gene transcription associated with differentiation of mammary epithelial cells.