Chemokines in neuroectodermal development and their potential implication in cancer stem cell-driven metastasis

Expression of Slug is regulated by c-Myb and is required for invasion and bone marrow homing of cancer cells of different origin

In metastatic cancer cells, the process of invasion is regulated by several transcription factors that induce changes required for migration and resistance to apoptosis. Slug (SNAI2, Snail2) is involved in epithelial mesenchymal transition in physiological and in pathological contexts. We show here that in embryonic kidney, colon carcinoma, chronic myeloid leukemia-blast crisis, and in neuroblastoma cells, expression of Slug is transcriptionally regulated by c-Myb via Myb binding sites in the 5'-flanking region and in the first intron of the slug gene. In embryonic kidney and neuroblastoma cells, c-Myb induced vimentin, fibronectin, and N-cadherin expression and membrane ruffling via actin polymerization consistent with the acquisition of a mesenchymal-like phenotype. Furthermore, down-regulation of endogenous c-Myb levels in colon carcinoma cells led to increased expression of E-cadherin and reduced levels of vimentin. Some of these changes are predominantly Slug-dependent as Slug silencing via RNA interference (RNAi) reverts the cells to a quasi-parental condition. Changes in gene expression and morphology induced by c-Myb-activated Slug correlated with increased ability to migrate (embryonic kidney) and to invade through a Matrigel membrane (embryonic kidney, colon carcinoma, neuroblastoma). c-Myb-dependent Slug expression was also essential for the homing of chronic myeloid leukemia K562 cells to the bone marrow. In summary, we show here that the proto-oncogene c-Myb controls Slug transcription in tumor cells of different origin. Such a regulatory pathway contributes to the acquisition of invasive properties that are important for the metastatic process.

Role of Chemokines and Chemokine Receptors in Prostate Cancer Development and Progression

Prostate cancer (PC) is the second leading cause of cancer deaths in men in America and Western Europe. Epidemiological studies suggest that prostate cancer incidences increased in last few years in Asian. The causes or consequences of increasing trend of prostate cancer incidence are not completely known. Emerging evidences suggest that among the many risk factors, inflammation is the major risk factor for developing prostate cancer and its progression to metastasis. It is proposed that exposure to environmental factors such as infectious agents, dietary agents and saturated lipids leads to injury of the prostate due to chronic inflammation and regenerative risk factor lesions referred to as proliferative inflammatory atrophy (PIA). These phenomena predominantly control by a number of proinflammatory macro molecules such as chemokines, and their receptors. Some recent studies suggest that many of these pro-inflammatory chemokines and their receptors are the products of protooncogenes in many cancers including that of the prostate. This review will focus on the current biology of chemokines and chemokine receptors in prostate cancer. An understanding of this axis may enable researchers to develop targeted strategies for prostate cancer.

A basal-cell-like compartment in head and neck squamous cell carcinomas represents the invasive front of the tumor and is expressing MMP-9

Head and neck squamous cell carcinomas (HNSCCs) are the most frequent malignancies of the upper aerodigestive tract. The cancer stem cell (CSC) hypothesis concludes that CSCs constitute the dangerous tumor cell population due to their ability of self-renewal and being associated with relapse of tumor disease, invasiveness and resistance to chemo(radio)therapy. The aim of this study was to look for CSC candidates and expression of MMP-9 that previously was implicated in HNSCC invasiveness. Immunohistochemical, immunofluorescence and Western blot analysis were performed on HNSCC tumor specimens using antibodies specific for MMP-9, CD44, ALDH1 and CK14. Gelatinolytic activity was assessed by zymography. Pearson correlation analysis was used for statistical comparison. Immunohistochemical analysis found CD44 and MMP-9 to co-localize in tumor cells at the invasive front. Western blot analysis demonstrated a significant correlation (p=0.0047) between CD44 and MMP-9 in the tested tissues. In addition gelatinolytic activity of HNSCC tissues was found to significantly correlate (p=0.0010) with MMP-9 expression. The CD44(+) invasive front of the tumor was also positive for ALDH1 and CK14, all of them being typically expressed by cells in the basal cell layer of normal stratified squamous epithelia that also harbors the epithelial stem cells. The observations point to a role of a MMP-9 positive basal-cell-like cell layer in the process of HNSCC invasiveness. This compartment likely contains CSCs since it is expressing the putative CSC markers CD44, ALDH1 and CK14. This cell layer therefore should be considered a major therapeutic target in the treatment of head and neck cancer.

Chemokine signaling in cancer: one hump or two?

Chemokines and their receptors play essential roles in the development and function of multiple tissues. Chemokine expression, particularly CXCL12 and its receptor CXCR4, has prognostic significance in several cancers apparently due to chemokine mediated growth and metastatic spread. These observations provide the rationale for pursuing CXCR4 inhibition for cancer chemotherapy. However, the multiple homeostatic functions of CXCR4 may preclude global inhibition as a therapeutic strategy. Here I review CXCR4 signaling and how it might differ in normal and transformed cells with special emphasis on the role that altered CXCR4 counter-regulation might play in tumor biology. I propose that CXCR4 mediates unique signals in cancer cells as a consequence of abnormal counter-regulation and that this results in novel biological responses. The importance of testing this hypothesis lies in the possibility that targeting abnormal CXCR4 signaling might provide an anti-tumor effect without disturbing normal CXCR4 functions.

Chemokine receptor CXCR4 as a therapeutic target for neuroectodermal tumors

Chemokines (chemotactic cytokines) are a family of proteins associated with the trafficking and activation of leukocytes and other cell types in immune surveillance and inflammatory response. Besides their roles in the immune system, they play pleiotropic roles in tumor initiation, promotion, and progression. Chemokines can be classified into four subfamilies of chemokines, CXC, CC, C, or CX3C, based on their number and spacing of conserved cysteine residues near the N-terminus. This CXC subfamily can be further subclassified into two groups, depending on the presence or absence of a tripeptide motif glutamic acid-leucine-arginine (ELR) in the N-terminal domain. ELR(-)CXCL12, which binds to CXCR4 has been frequently implicated in various cancers. Over the past several years, studies have increasingly shown that the CXCR4/CXCL12 axis plays critical roles in tumor progression, such as invasion, angiogenesis, survival, homing to metastatic sites. This review focuses on involvement of CXCR4/CXCL12 interaction in neuroectodermal cancers and their therapeutic potentials. As an attractive therapeutic target of CXCR4/CXCL12 axis for cancer chemotherapy, development history and application of CXCR4 antagonists are described.

Chemokines and the microenvironment in neuroectodermal tumor-host interaction

Chemokines and chemokine receptors play an important role in immune homeostasis and surveillance. Altered or defective expression of chemokines and/or chemokine receptors could lead to a disease state including autoimmune disorder or cancer. Tumors from glioblastoma, melanoma, and neuroblastoma secrete high levels of chemokines that can promote tumor growth and progression or induce stromal cells present in the tumor microenvironment to produce cytokines or chemokines which, in turn, can regulate angiogenesis, tumor growth, and metastasis. On the other hand, chemokines secreted by tumor or stromal cells can also attract leukocytes such as dendritic cells, macrophages, neutrophils, and lymphocytes which may downmodulate tumor growth. New therapies that are aimed at limiting tumor growth and progression by attracting immune effector cells to the tumor site with chemokines may hold the key to the successful treatment of cancer, although this approach may be hampered by possible tumor growth-stimulating effects of chemokines.

Chemokines in neuroectodermal cancers: the crucial growth signal from the soil

Although chemokines and their receptors were initially identified as regulators of cell trafficking during inflammation and immune response, they have emerged as crucial players in all stages of tumor development, primary growth, migration, angiogenesis, and establishment as metastases in distant target organs. Neuroectodermal tumors regroup neoplasms originating from the embryonic neural crest cells, which display clinical and biological similarities. These tumors are highly malignant and rapidly progressing diseases that disseminate to similar target organs such as bone marrow, bone, liver and lungs. There is increasing evidence that interaction of several chemokine receptors with corresponding chemokine ligands are implicated in the growth and invasive characteristics of these tumors. In this review we summarize the current knowledge on the role of CXCL12 chemokine and its CXCR4 and CXCR7 receptors in the progression and survival of neuroectodermal tumors, with particular emphasis on neuroblastoma, the most typical and enigmatic neuroectodermal childhood tumor.