Stimulation and regulation of tumor cell motility in invasion and metastasis

Capsaicinoids: Multiple effects on angiogenesis, invasion and metastasis in human cancers

Cancer progression is a complex multistep process comprising of angiogenesis of the primary tumor, its invasion into the surrounding stroma and its migration to distant organs to produce metastases. Nutritional compounds of the "capsaicinoid" family regulate angiogenesis, invasion and metastasis of tumors. Capsaicinoids display robust anti-angiogenic activity in both cell culture and mice models. However, conflicting reports exist about the effect of capsaicinoids on invasion of metastasis of cancers. While some published reports have described an anti-invasive and anti-metastatic role for capsaicinoids, others have argued that capsaicinoids stimulate invasion and metastasis of cancers. The present review article summarizes these findings involving the bioactivity of capsaicin in angiogenesis, invasion and metastasis of cancer. A survey of literature indicate that they are several articles summarizing the growth-inhibitory activity of capsaicinoids but few describe its effects on angiogenesis, invasion and metastasis in detail. Our review article fills this gap of knowledge. The discovery of a second generation of natural and synthetic capsaicin analogs (with anti-tumor activity) will pave the way to improved strategies for the treatment of several human cancers.

Uveal Melanoma Metastasis Models

Metastatic disease is the leading cause of death among patients with uveal melanoma. Treatment options for patients with clinically disseminated disease are usually unsuccessful. In vitro and in vivo models are important tools to investigate the pathogenesis of metastatic uveal melanomas and develop treatments for the metastases. In vitro experimental approaches focusing on cell invasion/migration which mimic the steps of the complex metastatic process may also be used for the identification of potential anti-invasion/migration drugs that may inhibit the spreading of tumor cells or the development of metastases. The effects of these drugs must subsequently be confirmed in reliable in vivo models before entering the clinical trial phase. Several models of intraocular melanoma with metastases in rodents and rabbits are currently being used. Most experimental models of uveal melanoma metastases require injection or implantation of melanoma cells into orthotopic locations, including into the liver, spleen, tail vein, or the left ventricle of the heart, in order to mimic the metastatic process.

Molecular signatures of metastasis in head and neck cancer

BACKGROUND

Metastases are the primary cause of cancer treatment failure and death, yet metastatic mechanisms remain incompletely understood.

METHODS

We studied the molecular basis of head and neck cancer metastasis by transcriptionally profiling 70 samples from 27 patients-matching normal adjacent tissue, primary tumor, and cervical lymph node metastases.

RESULTS

We identified tumor-associated expression signatures common to both primary tumors and metastases. Use of matching metastases revealed an additional 46 dysregulated genes associated solely with head and neck cancer metastasis. However, despite being metastasis-specific in our sample set, these 46 genes are concordant with genes previously discovered in primary tumors that metastasized.

CONCLUSIONS

Although our data and related studies show that most of the metastatic potential appears to be inherent to the primary tumor, they are also consistent with the notion that a limited number of additional clonal changes are necessary to yield the final metastatic cell(s), albeit in a variable temporal order.

EGF receptor signalling is essential for electric-field-directed migration of breast cancer cells

The mechanisms by which cancer cells migrate to metastasise are not fully understood. Breast cancers are accompanied by electrical depolarisation of tumour epithelial cells. The electrical changes can be detected on the skin and are used to differentiate malignant from benign breast tumours. Could the electrical signals play a role in metastasis by promoting tumour cell migration? We report that electric fields stimulate and direct migration of human breast cancer cells. Importantly, these effects were more significant in highly metastatic tumour cells than in low metastatic tumour cells. Electric-field-enhanced directional migration correlates well with the expression level of EGF receptor (EGFR/ErbB1). To confirm this, we transfected low metastatic clone MTC cells with human ErbB1, which significantly increased the electrotactic response. Inhibition of ErbB1 completely abolished the directional response of MTLn3 cells to an electric field. Transfection of MTLn3 cells and MDA-MB-435 cells with expression vectors for ErbB family members ErbB1, ErbB2 and ErbB3 also significantly enhanced EF-induced migration. These results suggest that electric signals might play a role in metastasis of breast cancers by enhancing cell migration through the ErbB-signalling pathway.

Screening for motility-associated genes in malignant astrocytoma cell lines

The most characteristic feature of a malignant astrocytoma is its early and extensive infiltration into adjacent parenchymal structures. We focused on detecting the possible expression changes as the determining factors for malignant astrocytoma's motile ability. We confirmed that four of 39 genes showed different expression on DD-PCR by RT-PCR and Northern blot analysis. These findings suggest that the genes identified may be important for determining high motility in astrocytoma cell lines. These findings may help us understand the molecular invasion mechanism in astrocytomas.

Expression of Autocrine Motility Factor Correlates with the Angiogenic Phenotype of and Poor Prognosis for Human Gastric Cancer

Autocrine motility factor (AMF) is a cytokine known to regulate tumor cell motility. Recent studies have extended its role to many other aspects of cancer biology. In the present study, we examined the level of AMF expression and its relationship with vascular endothelial growth factor (VEGF) expression and the angiogenic phenotype in human gastric cancer and their effect on survival. The AMF and VEGF expression level and tumor microvessel density (MVD) status in archived tissue specimens from 86 resected gastric cancer cases were determined. AMF expression was significantly higher in both primary tumors and lymph node metastases than in adjacent normal gastric mucosa and normal gastric mucosa from individuals without gastric cancer. In univariate survival analyses, strong AMF expression was associated with inferior survival (P = 0.028). In a Cox proportional hazards model, strong AMF expression (P = 0.019) was independently prognostic of poor survival. Strong AMF expression in the lymph node metastases was associated with poor survival (P = 0.011). Furthermore, AMF expression in the primary tumors was directly correlated with VEGF expression and MVD status. We found the first clinical evidence that AMF expression is directly correlated with VEGF expression and MVD status and predicts clinical outcome in patients with gastric cancer, supporting the hypothesis that the AMF/AMF receptor pathway plays an important role in multiple aspects of cancer biology.

Cellular mechanisms of direct-current electric field effects: galvanotaxis and metastatic disease

Endogenous direct-current electric fields (dcEFs) occur in vivo in the form of epithelial transcellular potentials or neuronal field potentials, and a variety of cells respond to dcEFs in vitro by directional movement. This is termed galvanotaxis. The passive influx of Ca2+ on the anodal side should increase the local intracellular Ca2+ concentration, whereas passive efflux and/or intracellular redistribution decrease the local intracellular Ca2+ concentration on the cathodal side. These changes could give rise to `push-pull' effects, causing net movement of cells towards the cathode. However, such effects would be complicated in cells that possess voltage-gated Ca2+ channels and/or intracellular Ca2+ stores. Moreover, voltage-gated Na+ channels, protein kinases, growth factors, surface charge and electrophoresis of proteins have been found to be involved in galvanotaxis. Galvanotactic mechanisms might operate in both the short term (seconds to minutes) and the long term (minutes to hours), and recent work has shown that they might be involved in metastatic disease. The galvanotactic responses of strongly metastatic prostate and breast cancer cells are much more prominent, and the cells move in the opposite direction compared with corresponding weakly metastatic cells. This could have important implications for the metastatic process and has clinical implications. Galvanotaxis could thus play a significant role in both cellular physiology and pathophysiology.

Motility is rate-limiting for invasion of bladder carcinoma cell lines

Induced migration of tumor cells is generally considered to be one critical step in cancer progression to the invasive and metastatic stage. The implicit caveat of studies that show this is that other, unknown, signaling pathways and biophysical events are actually the operative rate-limiting steps, and not motility per se. Thus, to examine the hypothesis that motility is a single, but overall rate-limiting function required for invasion, disparate motility processes need be blocked with concordant effects on tumor invasion. Recently, we and others have described two signaling pathways that are critical to growth factor-induced motility but not mitogenesis. The key molecular switches are phospholipase C-gamma (PLCgamma) and calpain for cytoskeletal reorganization and rear detachment, respectively. We examined this hypothesis in a highly invasive tumor, bladder carcinoma. Three different human tumor cell lines, 253J-B-V, UMUC and T-24, were tested for invasiveness in vitro by transmigration of a Matrigel barrier. Inhibiting PLCgamma with the pharmacologic agent U73122 or the molecular dominant-negative PLCz construct reduced both invasiveness and motility. The same was noted when calpain was blocked using calpain inhibitor I (ALLN). These results demonstrate that one interventional target for limiting invasion is not necessarily an individual motility pathway but rather cell migration per se.

Increase in hepatocyte growth factor receptor tyrosine kinase activity in renal carcinoma cells is associated with increased motility partly through phosphoinositide 3-kinase activation

Dysregulated cell motility is one of the major characteristics of invasion and metastatic potentials of malignant tumor cells. Here, we examined the hepatocyte growth factor (HGF)-induced cell motility of two human renal carcinoma cell lines, ACHN and VMRC-RCW. Scattering and migration was induced in ACHN in an HGF-dependent manner, whereas they were maintained in VMRC-RCW even in the absence of HGF. In VMRC-RCW, HGF receptor (HGFR) tyrosine kinase was constitutively active, and sequence analysis showed N375S, A1209G and V1290L mutations. However, transfection experiments using porcine aortic endothelial (PAE) cells demonstrated that no single mutation or combination of two or three mutations caused HGF-independent constitutive activation. Conversely, the expressed amount of receptor protein had a pivotal role in the basal kinase activity. With respect to downstream signaling molecules of HGFR in ACHN or VMRC-RCW, the Ras-MAPK pathway was downregulated, whereas phosphoinositide 3-kinase (PI3-kinase) was not further activated by HGF-treatment in VMRC-RCW cells. The PI3-kinase inhibitors, wortmannin and LY294002 strongly inhibited spontaneous migration of VMRC-RCW. One transfected PAE cell line with massive overexpression of HGFR demonstrated scattered morphology and increased PI3-kinase activity in association with increased motility, which was partially inhibited by LY294002. Taken together, our results indicate that the overexpression of HGFR causes increase in cellular motility and PI3-kinase shows the important contribution on the increased motility of renal carcinoma cells.

Genes that regulate metastasis and angiogenesis

Genetic instability and an accumulation of genetic and epigenetic changes during tumor progression lead to an increasingly aggressive and treatment-resistant phenotype, and ultimately metastasis. In recent years it has become well established that angiogenesis, the process by which new vasculature is formed from pre-existing vessels, is an essential component to primary tumor growth and distant metastasis. A greater understanding of the complex multitude of factors involved in tumor angiogenesis and metastasis is fundamental to the development of potential therapeutics to treat malignant disease. As highlighted throughout this review, angiogenesis and metastasis share many common cellular and molecular features. We will briefly discuss the pertinent genes involved in the regulation of angiogenesis and metastasis.

Autocrine and paracrine motility factors and their involvement in invasiveness in a human oral carcinoma cell line

Invasive potentials of malignant cancer cells are regulated by cell motility factors. To examine the regulation of motility and invasiveness in oral squamous carcinoma, we investigated autocrine- and/or paracrine-acting cell motility factors, using a newly established human cell line (IF cells) from oral squamous cell carcinoma, which has highly invasive and metastatic characteristics. Conditioned medium derived from IF cells stimulated cell scattering and migration of GB-d1 gallbladder carcinoma cells, indicating that IF cells secreted cell motility factors. Using antibodies, IF-derived cell motility factors proved to be transforming growth factor (TGF)-alpha and TGF-beta1. Antibodies against TGF-alpha and TGF-beta1 inhibited autonomous migration of the IF cells. On the other hand, in vitro invasion of IF cells was strongly enhanced by hepatocyte growth factor (HGF) but only slightly by TGF-alpha and TGF-beta1. The conditioned medium from fibroblasts enhanced in vitro invasion of IF cells, an event abrogated by anti-HGF antibody, but not by antibodies against TGF-alpha and TGF-beta1. Importantly, IF cells secreted a factor inducing HGF production in fibroblasts and the factor was identified as interleukin-1, which means that a mutual interaction exists between tumour cells and fibroblasts, as mediated by the HGF/HGF-inducer loop. These results indicate that IF cells utilize TGF-alpha and TGF-beta1 as autocrine-acting motility factors and HGF as a paracrine-acting motility factor, and that invasiveness of IF cells is particularly stimulated by HGF derived from stromal fibroblasts. Utilization of multiple cell motility/invasion factors that act in distinct pathways may confer highly invasive and metastatic potentials in IF oral squamous carcinoma cells.

Stromal fibroblasts influence oral squamous-cell carcinoma cell interactions with tenascin-C

In this study we identified tenascin-C (TN-C) and one of its integrin receptors, alpha(v)beta6, in oral squamous-cell carcinoma (SCC) specimens. Neither TN-C nor alpha(v)beta6 are expressed in normal oral mucosa. We also studied 2 human oral squamous-cell carcinoma cell lines: the highly invasive HSC-3 cells, and the poorly invasive SCC-25 cells. We determined that adhesion of these cells to TN-C involves both alpha2 and alpha(v) integrins. Migration on TN-C by oral SCC cells required fibroblast-conditioned medium and did not occur in its absence. This migration was blocked by anti-alpha2 and anti-alpha(v) antibodies and was partially inhibited by antibodies to hepatocyte growth factor, epidermal growth factor and transforming growth factor-beta1. When seeded on TN-C, the poorly invasive SCC-25 cells formed alpha(v)beta6-positive focal contacts; the HSC-3 cells did not. HSC-3, SCC-25 and PTF cells secrete TN-C into the culture medium, as determined by Western blot. However, when HSC-3 cells were inoculated into the floor of the mouth of nude mice, only murine TN-C could be identified in the reactive stroma adjacent to the resulting tumor nests, demonstrating that in vivo, HSC-3 cells do not secrete TN-C. Our results demonstrate that alpha(v)beta6 and tenascin-C are neo-expressed in oral squamous-cell carcinoma, and that the tumor stromal environment is influential in oral SCC behavior.