Isaac P. Witz

A Possible Role for CXCR4 and Its Ligand, the CXC Chemokine Stromal Cell-Derived Factor-1, in the Development of Bone Marrow Metastases in Neuroblastoma

The homing of hemopoietic stem cells to the bone marrow is mediated by specific interactions occurring between CXCR4, which is expressed on hemopoietic stem cells, and its ligand, stromal cell-derived factor-1 (SDF-1), a CXC chemokine secreted by bone marrow stromal cells. In the present study we evaluated the possibility that neuroblastoma cells use a mechanism similar to that used by hemopoietic stem cells to home to the bone marrow and adhere to bone marrow stromal cells. Our study suggests that CXCR4 expression may be a general characteristic of neuroblastoma cells. SH-SY5Y neuroblastoma cells express not only CXCR4, but also its ligand, SDF-1. CXCR4 expression on SH-SY5Y neuroblastoma cells is tightly regulated by tumor cell-derived SDF-1, as demonstrated by the ability of neutralizing Abs against human SDF-1α to up-regulate CXCR4 expression on the tumor cells. The reduction in CXCR4 expression following short term exposure to recombinant human SDF-1α can be recovered as a result of de novo receptor synthesis. Recombinant human SDF-1α induces the migration of CXCR4-expressing SH-SY5Y neuroblastoma cells in CXCR4- and heterotrimeric G protein-dependent manners. Furthermore, SH-SY5Y cells interact at multiple levels with bone marrow components, as evidenced by the fact that bone marrow-derived constituents promote SH-SY5Y cell migration, adhesion to bone marrow stromal cells, and proliferation. These results suggest that SH-SY5Y neuroblastoma cells are equipped with adequate machinery to support their homing to the bone marrow. Therefore, the ability of neuroblastoma tumors to preferentially form metastases in the bone marrow may be influenced by a set of complex CXCR4-SDF-1 interactions.

CXCL10 Promotes Invasion-Related Properties in Human Colorectal Carcinoma Cells

CXCL10 was recently shown to exert antimalignancy functions by influencing the tumor microenvironment. Here, we have taken a different approach, investigating the effects of CXCL10 directly on tumor-promoting functions in colorectal carcinoma (CRC) cells. CXCL10 expression was detected in preferred metastatic sites of CRC (liver, lungs, and lymph nodes), and its CXCR3 receptor was expressed by eight CRC cell lines (detected: reverse transcription-PCR and/or flow cytometry). Detailed analysis was done on two cell lines derived from primary CRC tumors (SW480, KM12C) and their metastatic descendents (SW620 and KM12SM). The three known variants of CXCR3 (CXCR3-A, CXCR3-B, and CXCR3-alt) were detected in all four cell lines. CXCR3 expression was also observed on colorectal tumor cells in biopsies of CRC patients (immunohistochemistry). CXCL10 and CXCR3 expression were potently induced in CRC cells by Interferon gamma and all four CRC cell lines responded to CXCL10 by extracellular signal-regulated kinase 1/2 dephosphorylation. The chemokine did not affect tumor cell growth or angiogenesis-related functions in the tumor cells, such as CXCL8 and vascular endothelial growth factor secretion. Importantly, CXCL10 significantly up-regulated invasion-related properties in CRC cells: It promoted matrix metalloproteinase 9 expression and induced CRC cell migration. Of note, CXCL10-induced migration was detected only in the two metastatic cells and not in their primary counterparts. Also, CXCL10 promoted the adhesion of metastatic cells to laminin. These results suggest that CXCL10 can be exploited by CRC cells toward their progression, thus possibly antagonizing the antimalignancy effects of the chemokine on the tumor microenvironment. Therefore, care should be taken when considering CXCL10 as a therapeutic antitumor modality for CRC treatment.

The selectin–selectin ligand axis in tumor progression

This review will document that the selectin–selectin ligand axis is actively involved in tumor progression and drives this process. The involvement of selectins and their ligands in tumor progression takes place at three levels which will be reviewed: Interaction of tumor cells with platelets and leukocytes resulting in the formation of circulating emboli; interaction of tumor cells with endothelial cells leading to extravasation of the tumor cells; and utilization of reciprocal pro malignancy signals delivered by the selectins or by their ligands to interacting cells that express the corresponding co-receptor. We propose that the selectin–selectin ligand mediated interactions between cells in the tumor microenvironment constitute an axis of evil, that it be included in the list of pro malignancy factors, and that molecules associated with this axis serve as targets for cancer therapy.

Tumor–Microenvironment Interactions: Dangerous Liaisons

The interaction between microenvironmental components and tumor cells is bidirectional. Tumor cells and their products are capable of regulating and altering gene expression in nontumor cells residing in or infiltrating into the microenvironment and exert selective pressures on such cells, thereby shaping their phenotype. Conversely, microenvironmental components regulate gene expression in tumor cells thereby directing the tumor into one or several possible molecular evolution pathways, some of which may lead to metastasis. This review summarizes six instances in which the tumor liaises with different components of its microenvironment. These liaisons result, in most cases, in enhanced tumor progression. In these cases (responses of tumor and nontumor cells to microenvironmental stress, the interaction of the tumor with fibroblasts, endothelial cells and macrophages, the formation of the metastatic niche, and the interaction of the tumor with immunoglobulins) the tumor, directly or indirectly, alters the phenotype of its interaction partners thereby enlisting them to promote its progression. Does the tumor need all these pathways to form metastasis? Is there a hierarchy of interactions with respect to impact on tumor progression? These questions remain open. They may be answered by approaches employed in the analysis of hypercomplex systems.

The Tumor Microenvironment: The Making of a Paradigm

AbstractWhat has been will be again, what has been done will be done again; there is nothing new under the sun(Ecclesiastes 1:9) Stephen Paget was the conceptual father of the role played by the Tumor Microenvironment (TME) in tumor progression. The focus of this essay is the developmental phase of the post Paget TME research. Attempts will be made to highlight some of the pioneering work of scientists from the late sixties through the eighties of last century who laid the foundations for the contemporary scientific achievements of TME research but whose ground breaking studies are rarely cited. This review should serve as a small tribute to their great work.

Tumor-Bound Immunoglobulins:in SituExpressions Of Humoral Immunity

Publisher Summary An accurate and precise evaluation of tumor-host relations is an essential prerequisite for a rational approach to cancer therapy, in particular immunotherapy, and to a correct assessment of prognosis. The host–tumor relationship is assessed mainly by the capacity of immune components, such as lymphocytes, macrophages, or antibodies, to react in vitro against tumor cells. It is noted that the expression of immunity is not equal in all sites of the body. It is significant to evaluate in situ tumor immunity concerning the immune-histology of the malignant area in relation to prognosis or treatment. This chapter summarizes the available data on the presence, properties, and functions of humoral immune components, mainly immunoglobulins, at the site of malignant tumors. It focuses on the studies that deal with nonlymphoid malignancies. Common methods used to detect tumor-associated immunoglobulins (TAIg) include (1) the treatment of tumor fragments with low pH buffers or with salt solutions of high molarity, (2) direct membrane immunofluorescence of tumor cells, (3) radioimmunofixation, and (4) mixed hemadsorption. The chapter considers several TAIg such as Ig class and IgG subclass.

Yin-yang activities and vicious cycles in the tumor microenvironment.

A solid tumor is an ecosystem composed of tumor cells, resident and infiltrating nontumor cells, and molecules present in proximity to these cells. This ecosystem can be collectively described as the tumor microenvironment. Both the tumor cells as well as the neighboring nontumor cells take part in

The relationship between in vitro fertilization and naturally occurring antibodies: evidence for increased production of antiphospholipid autoantibodies*

OBJECTIVE Assessment of possible effects of ovarian stimulation during in vitro fertilization (IVF) treatment cycles on circulating levels of antiphospholipid and antinuclear autoantibodies. DESIGN The study was performed prospectively. Sera were obtained at three time points along IVF treatment cycle. Levels of autoantibodies directed against nuclear components, mitochondrial antigens, and phospholipids were determined using enzyme-linked immunosorbent assay. PATIENTS Thirty-five patients, who underwent at least one previous IVF attempt, and 36 age- and sex-matched controls were analyzed. All participants were randomly selected. RESULTS The mean levels of antiphospholipid (but not antinuclear) autoantibodies in sera from IVF-treated patients were found to be significantly higher than the corresponding values of the control group (for immunoglobulin [Ig]M isotype: anticardiolipin, antiphosphatidyl L-serine; for IgG isotype: anticardiolipin, antiphosphatidyl L-serine, and antiphosphatidylcholine; P less than 0.0001, assessed by Mann-Whitney test). The autoantibody levels remained more or less constant at different time points along the treatment cycle. No correlation with age and number of previous IVF cycles was demonstrated. CONCLUSIONS Serum levels of antiphospholipid (but not antinuclear) autoantibodies increase after IVF treatment. Based on these preliminary data, it is not yet possible to estimate if the observed changes in autoantibody levels might have any future clinical influence on infertile patients undergoing IVF treatment.

The focal adhesion kinase (P125FAK) is constitutively active in human malignant melanoma.

Malignant melanoma cells show high aggressiveness and metastatic potential. Tumor cells as they become more metastatic, gradually lose their dependence on both adhesion and serum. Thus, in the process of tumor progression cells undergo series of changes that allow them to adapt to different tissue milieu. This implies that during this process, points on the integrin pathway may become constitutively activated. In the present study we investigated the possible role of FAK, being one of the key members of the integrin-signaling pathway, in the multistep progression towards a malignant phenotype in human melanoma. In our study we show that in melanoma cells there is neither an increase in the amount of FAK nor in its phosphorylation capacity, but rather in its levels of constitutive activation. Indeed, in all melanoma cells tested and not in nevus and neuroblastoma cells, we observed various degrees of constitutive activation of FAK. Our results also suggest that FAK constitutive activation is regulated at least in part by the cytoskeleton, implying that steps along the integrin signaling pathway involving FAK could be among the oncogenic mechanisms that operate in melanoma and may account for the highly aggressive, anchorage independent phenotype of this tumor.

Progression of mouse mammary tumors: MCP-1-TNFα cross-regulatory pathway and clonal expression of promalignancy and antimalignancy factors

The progression of breast cancer is affected by multiple cellular and microenvironmental components. The monocyte chemoattractant MCP‐1, IL‐6 and matrix metalloproteinases (MMP) were suggested to promote, each on its own, breast cancer progression. We recently demonstrated that the high‐tumorigenicity phenotype of the DA3 and CSML murine mammary adenocarcinoma cells is correlated with a high expression of MCP‐1, IL‐6 and MMP. This raised the possibility that common intrinsic tumor‐derived factors regulate the concordant expression of these 3 components. The aim of the present study was to gain insight into the mode by which the secretion of MCP‐1, IL‐6 and MMP from murine mammary adenocarcinoma cells is regulated. This was investigated in cellular clones established from a highly malignant variant of the DA3 tumor (DA3‐high). We also determined the secretion of the antimalignancy chemokine IP‐10 from these cells. The results indicate that the secretion levels of IL‐6, MMP and IP‐10 varied between the clones. In contrast, all the clones secreted uniformly high levels of MCP‐1, suggesting that MCP‐1 constitutes an important feature of the malignancy phenotype of mammary carcinoma. In most of the clones, elevated levels of 1 of the 3 promalignancy factors did not correlate with a high expression of the other 2 factors and vice versa. These findings indicate that the 3 promalignancy factors are not coregulated by a common intrinsic tumor‐derived factor. Rather, these results suggest that the individual capacities of the different clones to secrete these factors are summed up in the high‐malignancy DA3 parental tumor population, which secretes relatively high levels of MCP‐1, IL‐6 and MMP as compared to DA3 cells expressing a low‐malignancy phenotype. In contrast to the lack of coordinated intrinsic regulation of MCP‐1, IL‐6 and MMP, it was found that recombinant TNFα, a product of tumor‐associated macrophages contributing to breast cancer progression, upregulated the secretion of MCP‐1, IL‐6 and MMP from all the clones. These results suggest a key role for this microenvironmental, monocyte‐derived cytokine in the coordinated regulation of these 3 molecules. Furthermore, additional results demonstrated that monocytic cell‐derived TNFα upregulated MCP‐1 secretion from the tumor cells and that MCP‐1 in turn promoted the secretion of TNFα from monocytic cells. This may result in a positive feedback loop, whereby the tumor cells and the monocytic cells at tumor site promote each others ability to express and secrete promalignancy factors. We next attempted to assess the contribution of the promalignancy factors MCP‐1, IL‐6 and MMP and of the antimalignancy factor IP‐10 to mammary adenocarcinoma progression. To this end, a preliminary formula was developed in which the net balance between secretion levels of the promalignancy factors and that of the antimalignancy IP‐10 chemokine from different clones was related to their in vivo tumorigenicity profile. This formula suggests that a balance between the secretion levels of these factors plays an important role in determining the malignancy phenotype of mammary carcinomas. In all, our findings demonstrate that the mammary tumor cell population is composed of a heterogeneous assortment of clones whose individual characteristics are averaged in the whole population. The malignancy potential of such tumors is thus determined, inter alia, by a combinatorial effect of several promalignancy and antimalignancy factors secreted from each of the clones comprising these tumors. Our results also suggest that the expression of such factors is determined by several nonmutually exclusive regulatory mechanisms.