Mechanisms of metastasis: epithelial-to-mesenchymal transition and contribution of tumor microenvironment

Ob/ob serum promotes a mesenchymal cell phenotype in B16BL6 melanoma cells

In 2009, malignant melanoma was responsible for approximately 9,000 deaths in the US. These deaths are often associated with aggressive metastasis to secondary sites such as the lungs. Epidemiological and animal studies suggest that obesity is a risk factor for melanoma. Others have shown that B16BL6 melanoma cells metastasize more aggressively in obese ob/ob than in lean mice. However, the mechanism by which obesity promotes B16BL6 melanoma metastasis in ob/ob mice has not been identified. In the present study, we used serum obtained from control and ob/ob leptin-deficient obese mice to determine if obese serum increases the aggressive phenotype of melanoma cells. Results showed that ob/ob serum has higher levels of resistin, insulin, tPAI1, IL-6, TNF-α, and MCP-1 compared to control serum. We showed that ob/ob serum increases the invasive ability of B16BL6 melanomas. To further determine the mechanism by which ob/ob serum increases the invasive ability of melanomas, we determined the effect of ob/ob and control serum on genes associated with the epithelial-to-mesenchymal transition (EMT). Cancer cells with a mesenchymal phenotype have a higher metastatic ability. Snai1 and Twist are genes that are strongly associated with EMT and metastasis of melanomas. Our results showed that ob/ob serum increases the expression of Snai1 and Twist. Moreover, ob/ob serum increased matrix metalloproteast 9 (MMP9) activity and decreased the expression of E-cadherin and the metastasis suppressor gene Kiss1. In summary, results suggest that obesity may increase the metastatic ability of melanoma by promoting a mesenchymal cell phenotype.

Progression of BRAF-induced thyroid cancer is associated with epithelial-mesenchymal transition requiring concomitant MAP kinase and TGFβ signaling

Mice with thyroid-specific expression of oncogenic BRAF (Tg-Braf) develop papillary thyroid cancers (PTCs) that are locally invasive and have well-defined foci of poorly differentiated thyroid carcinoma (PDTC). To investigate the PTC-PDTC progression, we performed a microarray analysis using RNA from paired samples of PDTC and PTC collected from the same animals by laser capture microdissection. Analysis of eight paired samples revealed a profound deregulation of genes involved in cell adhesion and intracellular junctions, with changes consistent with an epithelial-mesenchymal transition (EMT). This was confirmed by immunohistochemistry, as vimentin expression was increased and E-cadherin lost in PDTC compared with adjacent PTC. Moreover, PDTC stained positively for phospho-Smad2, suggesting a role for transforming growth factor (TGF)β in mediating this process. Accordingly, TGFβ-induced EMT in primary cultures of thyroid cells from Tg-Braf mice, whereas wild-type thyroid cells retained their epithelial features. TGFβ-induced Smad2 phosphorylation, transcriptional activity and induction of EMT required mitogen-activated protein kinase (MAPK) pathway activation in Tg-Braf thyrocytes. Hence, tumor initiation by oncogenic BRAF renders thyroid cells susceptible to TGFβ-induced EMT, through a MAPK-dependent process.

Microenvironment induced spheroid to sheeting transition of immortalized human keratinocytes (HaCaT) cultured in microbubbles formed in polydimethylsiloxane

The in vivo cellular microenvironment is regulated by a complex interplay of soluble factors and signaling molecules secreted by cells and it plays a critical role in the growth and development of normal and diseased tissues. In vitro systems that can recapitulate the microenvironment at the cellular level are needed to investigate the influence of autocrine signaling and extracellular matrix effects on tissue homeostasis, regeneration, disease development and progression. In this study, we report the use of microbubble technology as a means to culture cells in a controlled microenvironment in which cells can influence their function through autocrine signaling. Microbubbles (MB) are small spherical cavities about 100-300 μm in diameter formed in hydrophobic polydimethylsiloxane (PDMS) with ∼60-100 μm circular openings and aspect ratio ∼3.0. We demonstrate that the unique architecture of the microbubble compartment is advantaged for cell culture using HaCaT cells, an immortalized keratinocyte cell line. We observe that HaCaT cells, seeded in microbubbles (15-20 cells/MB) and cultured under standard conditions, adopt a compact 3D spheroidal morphology. Within 2-3 days, the cells transition to a sheeting morphology. Through experimentation and simulation we show that this transition in morphology is due to the unique architecture of the microbubble compartment which enables cells to condition their local microenvironment. The small media volume per cell and the development of shallow concentration gradients allow factors secreted by the cells to rise to bioactive levels. The kinetics of the morphology transition depends on the number of cells seeded per microbubble; higher cell seeding induces a more rapid transition. HaCaT cells seeded onto PDMS cured in 96-well plates also form compact spheroids but they do not undergo a transition to a sheeting morphology even after several weeks of culture. The importance of soluble factor accumulation in driving this morphology transition in microbubbles is supported by the observation that spheroids do not form when cells - seeded into microbubbles or onto PDMS cured in 96-well plates - are cultured in media conditioned by HaCaT cells grown in standard tissue culture plate. We observed that the addition of TGF-β1 to the growth media induced cells to proliferate in a sheeting morphology from the onset both on PDMS cured in 96-well plates and in microbubbles. TGF-β1 is a morphogen known to regulate epithelial-to-mesenchymal transition (EMT). Studies of the role of Ca(2+) concentration and changes in E-cadherin expression additionally support an EMT-like HaCaT morphology transition. These findings taken together validate the microbubble compartment as a unique cell culture platform that can potentially transform investigative studies in cell biology and in particular the tumor microenvironment. Targeting the tumor microenvironment is an emerging area of anti-cancer therapy.

Estrogen receptor silencing induces epithelial to mesenchymal transition in human breast cancer cells

We propose the hypothesis that loss of estrogen receptor function which leads to endocrine resistance in breast cancer, also results in trans-differentiation from an epithelial to a mesenchymal phenotype that is responsible for increased aggressiveness and metastatic propensity. siRNA mediated silencing of the estrogen receptor in MCF7 breast cancer cells resulted in estrogen/tamoxifen resistant cells (pII) with altered morphology, increased motility with rearrangement and switch from a keratin/actin to a vimentin based cytoskeleton, and ability to invade simulated components of the extracellular matrix. Phenotypic profiling using an Affymetrix Human Genome U133 plus 2.0 GeneChip indicated geometric fold changes ≥ 3 in approximately 2500 identifiable unique sequences, with about 1270 of these being up-regulated in pII cells. Changes were associated with genes whose products are involved in cell motility, loss of cellular adhesion and interaction with the extracellular matrix. Selective analysis of the data also showed a shift from luminal to basal cell markers and increased expression of a wide spectrum of genes normally associated with mesenchymal characteristics, with consequent loss of epithelial specific markers. Over-expression of several peptide growth factors and their receptors are indicative of an increased contribution to the higher proliferative rates of pII cells as well as aiding their potential for metastatic activity. Signalling molecules that have been identified as key transcriptional drivers of epithelial to mesenchymal transition were also found to be elevated in pII cells. These data support our hypothesis that induced loss of estrogen receptor in previously estrogen/antiestrogen sensitive cells is a trigger for the concomitant loss of endocrine dependence and onset of a series of possibly parallel events that changes the cell from an epithelial to a mesenchymal type. Inhibition of this transition through targeting of specific mediators may offer a useful supplementary strategy to circumvent the effects of loss of endocrine sensitivity.

Proteasome inhibition causes epithelial-mesenchymal transition upon TM4SF5 expression

Transmembrane 4 L six family member 5 (TM4SF5) is highly expressed in hepatocarcinoma and causes epithelial-mesenchymal transition (EMT) of hepatocytes. We found that TM4SF5-expressing cells showed lower mRNA levels but maintained normal protein levels in certain gene cases, indicating that TM4SF5 mediates stabilization of proteins. In this study, we explored whether regulation of proteasome activity and TM4SF5 expression led to EMT. We observed that TM4SF5 expression caused inhibition of proteasome activity and proteasome subunit expression, causing morphological changes and loss of cell-cell contacts. shRNA against TM4SF5 recovered proteasome expression, with leading to blockade of proteasome inactivation and EMT. Altogether, TM4SF5 expression appeared to cause loss of cell-cell adhesions via proteasome suppression and thereby proteasome inhibition, leading to repression of cell-cell adhesion molecules, such as E-cadherin.

Tenascin C induces epithelial-mesenchymal transition-like change accompanied by SRC activation and focal adhesion kinase phosphorylation in human breast cancer cells

Tenascin C (TNC) is an extracellular matrix glycoprotein up-regulated in solid tumors. Higher TNC expression is shown in invading fronts of breast cancer, which correlates with poorer patient outcome. We examined whether TNC induces epithelial-mesenchymal transition (EMT) in breast cancer. Immunohistochemical analysis of invasive ductal carcinomas showed that TNC deposition was frequent in stroma with scattered cancer cells in peripheral margins of tumors. The addition of TNC to the medium of the MCF-7 breast cancer cells caused EMT-like change and delocalization of E-cadherin and β-catenin from cell-cell contact. Although amounts of E-cadherin and β-catenin were not changed after EMT in total lysates, they were increased in the Triton X-100-soluble fractions, indicating movement from the membrane into the cytosol. In wound healing assay, cells were scattered from wound edges and showed faster migration after TNC treatment. The EMT phenotype was correlated with SRC activation through phosphorylation at Y418 and phosphorylation of focal adhesion kinase (FAK) at Y861 and Y925 of SRC substrate sites. These phosphorylated proteins colocalized with αv integrin-positive adhesion plaques. A neutralizing antibody against αv or a SRC kinase inhibitor blocked EMT. TNC could induce EMT-like change showing loss of intercellular adhesion and enhanced migration in breast cancer cells, associated with FAK phosphorylation by SRC; this may be responsible for the observed promotion of TNC in breast cancer invasion.

Increase in preoperative serum reactive oxygen metabolite levels indicates nodal extension in patients with clinical stage I lung adenocarcinoma

PURPOSE

Reactive oxygen species contribute to various features of malignant tumors, including carcinogenesis, aberrant growth, metastasis, and angiogenesis. Investigation of serum oxidative stress levels may predict the tumor's condition, including malignant and metastatic potential.

METHODS

We recruited 46 patients (27 men, 19 women; median age 70 years) with clinical stage I lung adenocarcinoma who had undergone pulmonary resection with mediastinal lymph node dissection. Preoperative serum reactive oxygen metabolite (ROM) levels were measured as an indicator of oxidative stress.

RESULTS

The serum ROM level was significantly correlated with the increase in tumor size (P = 0.018) and pathological nodal extension (P = 0.005). Multivariate analysis revealed that pathological nodal extension was significantly correlated with the increase in serum ROM level (P = 0.027). The prognostic cutoff value was determined according to receiver operating characteristic curve analysis for patients with and those without nodal extension; the cutoff value was determined to be 318 Carratelli units (U.CARR).

CONCLUSION

The findings of our study revealed that patients with clinical stage I lung adenocarcinoma and a serum ROM level above 318 U.CARR were likely to develop nodal extension. The finding of a significant correlation between serum ROM level and nodal extension may help in the development of new treatment strategies.

Androgen regulation of epithelial-mesenchymal transition in prostate tumorigenesis

Prostate cancer patient mortality is ascribed to the spread of cancerous cells to areas outside the prostate gland and the inability of current treatment strategies to effectively block progression to metastasis. Understanding the cellular mechanisms contributing to the dissemination of malignant cells and metastasis is critically significant to the generation of effective therapeutic modalities for improved patient survival while combating therapeutic resistance. In recent years, the phenomenon of epithelial-mesenchymal transitions (EMTs) has received considerable attention due to accumulating evidence indicating a role for this developmentally conserved process in tumorigenesis. Cancer cells at the invasive edges of tumors undergo EMT under the influence of contextual signals that they receive from the microenvironment, such as TGF-β. Also derived from developmental studies is the fact that EMT induction is reversible; thus, upon removal of EMT-inducing signals, cells occasionally revert to the epithelial state of their cellular ancestors via the process of mesenchymal-epithelial transition. This article discusses the current evidence supporting a central role for EMT and its reverse process, mesenchymal-epithelial transition, in the metastatic progression of prostate cancer to advanced disease and the involvement of androgen signaling in its regulation towards the development of castration-resistant prostate cancer.

Proline-rich tyrosine kinase 2 (Pyk2) promotes cell motility of hepatocellular carcinoma through induction of epithelial to mesenchymal transition

AIMS

Proline-rich tyrosine kinase 2 (Pyk2), a non-receptor tyrosine kinase of the focal adhesion kinase (FAK) family, is up-regulated in more than 60% of the tumors of hepatocellular carcinoma (HCC) patients. Forced overexpression of Pyk2 can promote the proliferation and invasion of HCC cells. In this study, we aimed to explore the underlying molecular mechanism of Pyk2-mediated cell migration of HCC cells.

METHODOLOGY/PRINCIPAL FINDINGS

We demonstrated that Pyk2 transformed the epithelial HCC cell line Hep3B into a mesenchymal phenotype via the induction of epithelial to mesenchymal transition (EMT), signified by the up-regulation of membrane ruffle formation, activation of Rac/Rho GTPases, down-regulation of epithelial genes E-cadherin and cytokeratin as well as promotion of cell motility in presence of lysophosphatidic acid (LPA). Suppression of Pyk2 by overexpression of dominant negative PRNK domain in the metastatic HCC cell line MHCC97L transformed its fibroblastoid phenotype to an epithelial phenotype with up-regulation of epithelial genes, down-regulation of mesenchymal genes N-cadherin and STAT5b, and reduction of LPA-induced membrane ruffle formation and cell motility. Moreover, overexpression of Pyk2 in Hep3B cells promoted the phosphorylation and localization of mesenchymal gene Hic-5 onto cell membrane while suppression of Pyk2 in MHCC97L cells attenuated its phosphorylation and localization.

CONCLUSION

These data provided new evidence of the underlying mechanism of Pyk2 in controlling cell motility of HCC cells through regulation of genes associated with EMT.

Ginsenoside Rg3 inhibits CXCR4 expression and related migrations in a breast cancer cell line

BACKGROUND

Ginsenoside Rg3 is an extract from the natural product ginseng. Previous studies have linked Rg3 with anti-metastasis of cancer in vivo and in vitro. CXC receptor 4 (CXCR4) is a vital molecule in migration and homing of cancer to the docking regions.

METHODS

In this study, the effects of Rg3 on CXCR4 expression were investigated in a breast cancer cell line. Immunohistochemistry, chemotaxis and wound healing mobility assays were performed in cultured MDA-MB-231 cells.

RESULTS

At a dosage without obvious cytotoxicity, Rg3 treatment elicits a weak CXCR4 stain color, decreases the number of migrated cells in CXCL12-elicited chemotaxis and reduces the width of the scar in wound healing.

CONCLUSION

This work suggests that Rg3 is a new CXCR4 inhibitor from a natural product.

Phytochemicals: cancer chemoprevention and suppression of tumor onset and metastasis

Carcinogenesis is a multi-step process which could be prevented by phytochemicals. Phytochemicals from dietary plants and other plant sources such as herbs are becoming increasingly important sources of anticancer drugs or compounds for cancer chemoprevention or adjuvant chemotherapy. Phytochemicals can prevent cancer initiation, promotion, and progression by exerting anti-inflammatory and anti-oxidative stress effects which are mediated by integrated Nrf2, NF-kappaB, and AP-1 signaling pathways. In addition, phytochemicals from herbal medicinal plants and/or some dietary plants developed in recent years have been shown to induce apoptosis in cancer cells and inhibition of tumor growth in vivo. In advanced tumors, a series of changes involving critical signaling molecules that would drive tumor cells undergoing epithelial-mesenchymal transition and becoming invasive. In this review, we will discuss the potential molecular targets and signaling pathways that mediate tumor onset and metastasis. In addition, we will shed light on some of the phytochemicals that are capable of targeting these signaling pathways which would make them potentially applicable to cancer chemoprevention, treatment and control of cancer progression.

Tissue transglutaminase promotes drug resistance and invasion by inducing mesenchymal transition in mammary epithelial cells

Recent observations that aberrant expression of tissue transglutaminase (TG2) promotes growth, survival, and metastasis of multiple tumor types is of great significance and could yield novel therapeutic targets for improved patient outcomes. To accomplish this, a clear understanding of how TG2 contributes to these phenotypes is essential. Using mammary epithelial cell lines (MCF10A, MCF12A, MCF7 and MCF7/RT) as a model system, we determined the impact of TG2 expression on cell growth, cell survival, invasion, and differentiation. Our results show that TG2 expression promotes drug resistance and invasive functions by inducing epithelial-mesenchymal transition (EMT). Thus, TG2 expression supported anchorage-independent growth of mammary epithelial cells in soft-agar, disrupted the apical-basal polarity, and resulted in disorganized acini structures when grown in 3D-culture. At molecular level, TG2 expression resulted in loss of E-cadherin and increased the expression of various transcriptional repressors (Snail1, Zeb1, Zeb2 and Twist1). Tumor growth factor-beta (TGF-β) failed to induce EMT in cells lacking TG2 expression, suggesting that TG2 is a downstream effector of TGF-β-induced EMT. Moreover, TG2 expression induced stem cell-like phenotype in mammary epithelial cells as revealed by enrichment of CD44(+)/CD24(-/low) cell populations. Overall, our studies show that aberrant expression of TG2 is sufficient for inducing EMT in epithelial cells and establish a strong link between TG2 expression and progression of metastatic breast disease.

Survivin enhances motility of melanoma cells by supporting Akt activation and {alpha}5 integrin upregulation

Survivin expression in melanoma is inversely correlated with patient survival. Transgenic mice harboring melanocyte-specific overexpression of survivin exhibit increased susceptibility to UV-induced melanoma and metastatic progression. To understand the mechanistic basis for metastatic progression, we investigated the effects of survivin on the motility of human melanocytes and melanoma cells. We found that survivin overexpression enhanced migration on fibronectin and invasion through Matrigel, whereas survivin knockdown under subapoptotic conditions blocked migration and invasion. In melanocytes, survivin overexpression activated the Akt and mitogen-activated protein kinase pathways. Akt phosphorylation was required for survivin-enhanced migration and invasion, whereas Erk phosphorylation was required only for enhanced invasion. In both melanocytes and melanoma cells, survivin overexpression was associated with upregulation of α5 integrin (fibronectin receptor component), the antibody-mediated blockade or RNA interference-mediated knockdown of which blocked survivin-enhanced migration. Knockdown of α5 integrin did not affect Akt activation, but inhibition of Akt phosphorylation prevented α5 integrin upregulation elicited by survivin overexpression. Together, our results showed that survivin enhanced the migration and invasion of melanocytic cells and suggested that survivin may promote melanoma metastasis by supporting Akt-dependent upregulation of α5 integrin.

The role of fibroblast Tiam1 in tumor cell invasion and metastasis

The co-evolution of tumors and their microenvironment involves bidirectional communication between tumor cells and tumor-associated stroma. Various cell types are present in tumor-associated stroma, of which fibroblasts are the most abundant. The Rac exchange factor Tiam1 is implicated in multiple signaling pathways in epithelial tumor cells and lack of Tiam1 in tumor cells retards tumor growth in Tiam1 knock-out mouse models. Conversely, tumors arising in Tiam1 knock-out mice have increased invasiveness. We have investigated the role of Tiam1 in tumor-associated fibroblasts as a modulator of tumor cell invasion and metastasis, using retroviral delivery of short hairpin RNA to suppress Tiam1 levels in three different experimental models. In spheroid co-culture of mammary epithelial cells and fibroblasts, Tiam1 silencing in fibroblasts led to increased epithelial cell outgrowth into matrix. In tissue-engineered human skin, Tiam1 silencing in dermal fibroblasts led to increased invasiveness of epidermal keratinocytes with premalignant features. In a model of human breast cancer in mice, co-implantation of mammary fibroblasts inhibited tumor invasion and metastasis, which was reversed by Tiam1 silencing in co-injected fibroblasts. These results suggest that stromal Tiam1 may play a role in modulating the effects of the tumor microenvironment on malignant cell invasion and metastasis. This suggests a set of pathways for further investigation, with implications for future therapeutic targets.

Hypoxia response pathway in border cell migration

Cell invasion and metastasis mark the most lethal phase of cancer, but little is known about the key molecular events that initiate this crucial turning point. Low oxygen, or hypoxia, is thought to be one trigger for metastasis. Hypoxic conditions within the tumor mass are thought to activate signaling pathways that stimulate invasiveness of cancer cells spreading the disease. However, the molecular basis of this process is not well understood. A recent study used Drosophila ovarian border cell migration to model the type of cell migration that occurs in tumors in response to oxygen deprivation through the activation of the hypoxia response pathway (Doronkin et al. Oncogene. 2009). This model organism approach revealed a highly sophisticated mechanism of control of cell migration that is regulated by multiple genetic inputs tied to the hypoxic response. Genetic manipulations with the components of the HIF-1 (hypoxia-inducible factor 1) pathway were able to either inhibit or block the migration of border cells or cause unprecedented acceleration of their migration. The HIF-1-mediated transcriptional cascade appears to be the major regulator of border cell locomotion. Based on the similarity of the fly and human HIF-1 pathways, this model organism study might lead to improvements in understanding hypoxia-induced metastasizing of human cancers. This article discusses new findings in the context of their relevance to cancer metastasis and speculates on the potential regulatory mechanisms and future research directions.

Breast carcinoma cells re-express E-cadherin during mesenchymal to epithelial reverting transition

BACKGROUND

Epithelial to mesenchymal transition (EMT), implicated as a mechanism for tumor dissemination, is marked by loss of E-cadherin, disruption of cell adhesion, and induction of cell motility and invasion. In most intraductal breast carcinomas E-cadherin is regulated epigenetically via methylation of the promoter. E-cadherin expression is therefore dynamic and open to modulation by the microenvironment. In addition, it has been observed that metastatic foci commonly appear more differentiated than the primary tumor, suggesting that cancer cells may further undergo a mesenchymal to epithelial reverting transition (MErT) in the secondary organ environment following the EMT that allows for escape.

RESULTS

We first examined E-cadherin expression in primary breast tumors and their corresponding metastases to liver, lung and brain and discovered that 62% (10/16) of cases showed increased E-cadherin expression in the metastases compared to the primaries. These observations led to the question of whether the positive metastatic foci arose from expansion of E-cadherin-positive cells or from MErT of originally E-cadherin-negative disseminated cells. Thus, we aimed to determine whether it was possible for the mesenchymal-like MDA-MB-231 breast cancer cells to undergo an MErT through the re-expression of E-cadherin, either through exogenous introduction or induction by the microenvironment. Ectopic expression of full-length E-cadherin in MDA-MB-231 cells resulted in a morphological and functional reversion of the epithelial phenotype, with even just the cytosolic domain of E-cadherin yielding a partial phenotype. Introduction of MDA-MB-231 cells or primary explants into a secondary organ environment simulated by a hepatocyte coculture system induced E-cadherin re-expression through passive loss of methylation of the promoter. Furthermore, detection of E-cadherin-positive metastatic foci following the spontaneous metastasis of MDA-MB-231 cells injected into the mammary fat pad of mice suggests that this re-expression is functional.

CONCLUSIONS

Our clinical observations and experimental data indicate that the secondary organ microenvironment can induce the re-expression of E-cadherin and consequently MErT. This phenotypic change is reflected in altered cell behavior and thus may be a critical step in cell survival at metastatic sites.

Demonstration of Cancer Cell Migration Using a Novel Microfluidic Device

Migration of cancer cells from the primary organ site via the bloodstream to distant sites is critical to the development of malignant metastasis and is in part determined by soluble host factors in the serum. Conventional Boyden chamber assays to evaluate cell motility require high volumes of reagents and are impractical for high-throughput analysis. We have designed and evaluated a poly-dimethylsiloxane (PDMS) microfluidic device in order to systematically study cancer cell migration. Photolithography and soft lithography processes were used to fabricate the PDMS devices from a negative photoresist (SU-8) mold. The device provides two separate identical chambers that are interconnected by an array of identical narrow channels, 10 μm high, 25 μm wide, and 1000 μm long. One chamber is seeded with cancer cells whose migration characteristics are to be evaluated, while the other chamber contains media with chemoattractants toward which the cancer cells migrate. In this microfluidic chamber model, the migration of cancer cells within and across the microfluidic channels over a prescribed time was quantified using time-lapse photographs. The microfluidic chamber is a cost-effective platform that uses small volumes of reagents, can maintain stable chemokine gradients, allow real-time quantitative study of cancer cell migration, and provide information about cellular dynamics and biomechanical analysis. This work demonstrated the utility of the microfluidic device as a platform to study cancer cell migration as well as the potential applications in the identification of specific chemokine agents and development of drugs targeting cell migration.

Stromal CXCR4 and CXCL12 expression is associated with distant recurrence and poor prognosis in rectal cancer after chemoradiotherapy

BACKGROUND

Distant recurrence remains the major cause of mortality in rectal cancer patients with preoperative chemoradiotherapy (CRT). Recently, cancer stroma has been implicated in influencing proliferation, invasion, and metastasis of cancer cells. It has been reported that expression of CXCR4 and its ligand CXCL12 are associated with migration, invasion, and proliferation of colorectal cancer.

MATERIALS AND METHODS

A total of 53 patients with rectal cancer underwent preoperative CRT. Total RNAs of residual rectal cancer stromal cells after CRT were obtained from formalin-fixed paraffin-embedded (FFPE) specimens using microdissection. The expression levels of CXCR4 and CXCL12 genes were measured using real-time reverse transcription polymerase chain reaction (RT-PCR). Immunohistochemical staining of these markers after CRT was also investigated.

RESULTS

Of the 53 patients, 16 (30.1%) and 14 (26.4%) showed detectable CXCR4 and CXCL12 levels, respectively. We found a significant positive correlation between expression levels of CXCR4 and CXCL12. Patients who developed distant recurrence had twofold higher expression levels of both CXCR4 and CXCL12 compared with those without recurrence after CRT (P < 0.01). Elevated expression levels were also associated with poor probability of recurrence-free survival in both genes (P < 0.01). Additionally, positive CXCL12 expression, but not CXCR4, was significantly correlated with poorer overall survival (P < 0.01). CXCR4 and CXCL12 expression determined using immunohistochemistry was observed in not only cancer but also stromal cells.

CONCLUSION

Our results suggest that evaluation of the expression of both genes may be useful for predicting distant recurrence and poor prognosis in rectal cancer patients treated with preoperative CRT followed by surgery.

The EphB6 receptor cooperates with c-Cbl to regulate the behavior of breast cancer cells

Cancer invasiveness plays a major role in the mortality of patients with solid tumors, and deregulated cell adhesion and migration are suspected to drive invasive behavior. Since Eph receptor tyrosine kinases control both cell attachment and migration, they may act to define the level of cancer invasiveness. EphB6 is an unusual Eph receptor, lacking catalytic capacity due to alterations in its kinase domain. Interestingly, increased metastatic activity is associated with reduced EphB6 receptor expression in several tumor types, including breast cancer. This emphasizes the potential of EphB6 to act as a suppressor of cancer aggressiveness; however, the mechanism of its action is not well understood. We show that restoration of EphB6 expression in invasive breast cancer cells supports actin-dependent spreading and attachment and blocks invasiveness. EphB6 stimulation induces its tyrosine phosphorylation, which is crucial for its function and is mediated by the EphB4 receptor. This is accompanied by EphB6-c-Cbl interaction and phosphorylation of c-Cbl partner, the Abl kinase. Cbl silencing suppresses Abl phosphorylation, cell adhesion, and morphologic changes and blocks the ability of EphB6 to inhibit invasiveness, confirming its importance for EphB6 activity. Despite its crucial role in EphB6 responses, EphB4 also acts in an EphB6-independent manner to enhance invasive activity, suggesting that cancer invasiveness may be defined by the balance in the EphB6-EphB4 system. Overall, our observations suggest a new role for EphB6 in suppressing cancer invasiveness through c-Cbl-dependent signaling, morphologic changes, and cell attachment and indicate that EphB6 may represent a useful prognostic marker and a promising target for therapeutic approaches.

Molecular interactions in cancer cell metastasis

Metastasis, the process by which cancer cells leave the primary tumour, disseminate and form secondary tumours at anatomically distant sites, is a serious clinical problem as it is disseminated disease, which is often impossible to eradicate successfully, that causes the death of most cancer patients. Metastasis results from a complex molecular cascade comprising many steps, all of which are interconnected through a series of adhesive interactions and invasive processes as well as responses to chemotactic stimuli. In spite of its clinical significance, it remains incompletely understood. This review provides an overview of some of the molecular interactions that are critical to metastasis. It summarises the principle molecular players in the major steps of the metastatic cascade. These are: (1) tumour angiogenesis, (2) disaggregation of tumour cells from the primary tumour mass, mediated by cadherins and catenins, (3) invasion of, and migration through, the basement membrane (BM) and extracellular matrix (ECM) surrounding the tumour epithelium, and subsequent invasion of the BM of the endothelium of local blood vessels. This is mediated through integrins and proteases, including urokinase form of plasminogen activator (uPA), matrix metalloproteinases (MMPs) and cathepsins, (4) intravasation of the tumour cells into the blood vessels prior to hematogeneous dissemination to distant sites, (5) adhesion of the circulating tumour cells to the endothelial cell lining at the capillary bed of the target organ site. This occurs through adhesive interactions between cancer cells and endothelial cells involving selectins, integrins and members of the immunoglobulin superfamily (IgSF), (6) invasion of the tumour cells through the endothelial cell layer and surrounding BM (extravasation) and target organ tissue and (7) the development of secondary tumour foci at the target organ site.

Linking optics and mechanics in an in vivo model of airway fibrosis and epithelial injury

Chronic mucosal and submucosal injury can lead to persistent inflammation and tissue remodeling. We hypothesized that microstructural and mechanical properties of the airway wall could be derived from multiphoton images. New Zealand White rabbits were intubated, and the tracheal epithelium gently denuded every other day for five days (three injuries). Three days following the last injury, the tracheas were excised for multiphoton imaging, mechanical compression testing, and histological analysis. Multiphoton imaging and histology confirm epithelial denudation, mucosal ulceration, subepithelial thickening, collagen deposition, immune cell infiltration, and a disrupted elastin network. Elastase removes the elastin network and relaxes the collagen network. Purified collagenase removes epithelium with subtle subepithelial changes. Young's modulus [(E) measured in kiloPascal] was significantly elevated for the scrape injured (9.0+/-3.2) trachea, and both collagenase (2.6+/-0.4) and elastase (0.8+/-0.3) treatment significantly reduced E relative to control (4.1+/-0.7). E correlates strongly with second harmonic generation (SHG) signal depth decay for enzyme-treated and control tracheas (R(2)=0.77), but not with scrape-injured tracheas. We conclude that E of subepithelial connective tissue increases on repeated epithelial wounding, due in part to changes in elastin and collagen microstructure and concentration. SHG depth decay is sensitive to changes in extracellular matrix content and correlates with bulk Young's modulus.

Targeting the EGF receptor for ovarian cancer therapy

Ovarian carcinoma is the leading cause of death from gynecologic malignancy in the US. Factors such as the molecular heterogeneity of ovarian tumors and frequent diagnosis at advanced stages hamper effective disease treatment. There is growing emphasis on the identification and development of targeted therapies to disrupt molecular pathways in cancer. The epidermal growth factor (EGF) receptor is one such protein target with potential utility in the management of ovarian cancer. This paper will discuss contributions of EGF receptor activation to ovarian cancer pathogenesis and the status of EGF receptor inhibitors and EGF receptor targeted therapies in ovarian cancer treatment.

Complete reversal of epithelial to mesenchymal transition requires inhibition of both ZEB expression and the Rho pathway

Background

Epithelial to Mesenchymal Transition (EMT) induced by Transforming Growth Factor-β (TGF-β) is an important cellular event in organogenesis, cancer, and organ fibrosis. The process to reverse EMT is not well established. Our purpose is to define signaling pathways and transcription factors that maintain the TGF-β-induced mesenchymal state.

Results

Inhibitors of five kinases implicated in EMT, TGF-β Type I receptor kinase (TβRI), p38 mitogen-activated protein kinase (p38 MAPK), MAP kinase kinase/extracellular signal-regulated kinase activator kinase (MEK1), c-Jun NH-terminal kinase (JNK), and Rho kinase (ROCK), were evaluated for reversal of the mesenchymal state induced in renal tubular epithelial cells. Single agents did not fully reverse EMT as determined by cellular morphology and gene expression. However, exposure to the TβRI inhibitor SB431542, combined with the ROCK inhibitor Y27632, eliminated detectable actin stress fibers and mesenchymal gene expression while restoring epithelial E-cadherin and Kidney-specific cadherin (Ksp-cadherin) expression. A second combination, the TβRI inhibitor SB431542 together with the p38 MAPK inhibitor SB203580, was partially effective in reversing EMT. Furthermore, JNK inhibitor SP600125 inhibits the effectiveness of the TβRI inhibitor SB431542 to reverse EMT. To explore the molecular basis underlying EMT reversal, we also targeted the transcriptional repressors ZEB1 and ZEB2/SIP1. Decreasing ZEB1 and ZEB2 expression in mouse mammary gland cells with shRNAs was sufficient to up-regulate expression of epithelial proteins such as E-cadherin and to re-establish epithelial features. However, complete restoration of cortical F-actin required incubation with the ROCK inhibitor Y27632 in combination with ZEB1/2 knockdown.

Conclusions

We demonstrate that reversal of EMT requires re-establishing both epithelial transcription and structural components by sustained and independent signaling through TβRI and ROCK. These findings indicate that combination small molecule therapy targeting multiple kinases may be necessary to reverse disease conditions.

Fate tracing reveals the pericyte and not epithelial origin of myofibroblasts in kidney fibrosis

Understanding the origin of myofibroblasts in kidney is of great interest because these cells are responsible for scar formation in fibrotic kidney disease. Recent studies suggest epithelial cells are an important source of myofibroblasts through a process described as the epithelial-to-mesenchymal transition; however, confirmatory studies in vivo are lacking. To quantitatively assess the contribution of renal epithelial cells to myofibroblasts, we used Cre/Lox techniques to genetically label and fate map renal epithelia in models of kidney fibrosis. Genetically labeled primary proximal epithelial cells cultured in vitro from these mice readily induce markers of myofibroblasts after transforming growth factor beta(1) treatment. However, using either red fluorescent protein or beta-galactosidase as fate markers, we found no evidence that epithelial cells migrate outside of the tubular basement membrane and differentiate into interstitial myofibroblasts in vivo. Thus, although renal epithelial cells can acquire mesenchymal markers in vitro, they do not directly contribute to interstitial myofibroblast cells in vivo. Lineage analysis shows that during nephrogenesis, FoxD1-positive((+)) mesenchymal cells give rise to adult CD73(+), platelet derived growth factor receptor beta(+), smooth muscle actin-negative interstitial pericytes, and these FoxD1-derivative interstitial cells expand and differentiate into smooth muscle actin(+) myofibroblasts during fibrosis, accounting for a large majority of myofibroblasts. These data indicate that therapeutic strategies directly targeting pericyte differentiation in vivo may productively impact fibrotic kidney disease.

Association of the actin-binding protein transgelin with lymph node metastasis in human colorectal cancer

Metastatic dissemination of primary tumors is responsible for 90% of colorectal cancer (CRC) deaths. The presence of positive lymph nodes, which separates stage I/II from stage III CRC, is a particularly key factor in patient management. Here, we describe results of a quantitative proteomic survey to identify molecular correlates of node status. Laser capture microdissection and two-dimensional difference gel electrophoresis were used to establish expression profiles for 980 discrete protein features in 24 human CRC specimens. Protein abundances were determined with a median technical coefficient of variation of 10%, which provided an ability to detect small differences between cancer subtypes. Transgelin, a 23-kDa actin-binding protein, emerged as a top-ranked candidate biomarker of node status. The area under the receiver operating characteristic curve for transgelin in predicting node status was 0.868 (P = .002). Significantly increased frequency of moderate- and high-level transgelin expression in node-positive CRC was also seen using semiquantitative immunohistochemistry to analyze 94 independent CRC specimens on tissue microarrays (P = .036). Follow-up studies in CRC cell lines demonstrated roles for transgelin in promoting invasion, survival, and resistance to anoikis. Transgelin localizes to the nucleus of CRC cells, and its sequence and properties suggest that it may participate in regulation of the transcriptional program associated with the epithelial-to-mesenchymal transition.

Cancer stem cells, hypoxia and metastasis

The successful growth of a metastasis, by definition, requires the presence of at least 1 cancer stem cell. Metastasis is a complex process, and an important contributor to this process is the influence of the tissue microenvironment, both cell-cell and cell-matrix interactions and the pathophysiologic conditions in tumors, such as hypoxia. A number of studies have suggested that normal stem cells may reside in "niches," where cell-cell and cell-matrix interactions can provide critical signals to support and maintain the undifferentiated phenotype of the stem cells. In this article, the evidence that these niches may be hypoxic is described, and the potential role that hypoxia may play in maintaining the stem cell phenotype in cancers is discussed. Recent work has suggested that there may be a linkage between the stem cell phenotype and that induced by the process of epithelial-mesenchymal transition (EMT). EMT plays an important role in cell movement and organ formation during embryogenesis, and it is currently hypothesized to be a major mechanism by which epithelial cancers may generate cells that can form metastases. Recent evidence suggests that the expression of certain genes involved in EMT is influenced by low oxygen levels, again suggesting a linkage between stem cells and hypoxia. Whether this supposition is correct remains an open question that will only be answered by further experimentation, but the potential role of hypoxia is critical because of its widespread existence in tumors and its known role in resistance to both radiation and drug treatment.

Molecular plasticity of E-cadherin and sialyl lewis x expression, in two comparative models of mammary tumorigenesis

Background

The process of metastasis involves a series of steps and interactions between the tumor embolus and the microenvironment. Key alterations in adhesion molecules are known to dictate progression from the invasive to malignant phenotype followed by colonization at a distant site. The invasive phenotype results from the loss of expression of the E-cadherin adhesion molecule, whereas the malignant phenotype is associated with an increased expression of the carbohydrate ligand-binding epitopes, (e.g. Sialyl Lewis ^x/a) that bind endothelial E-selectin of the lymphatics and vasculature.

Methodology

Our study analyzed the expression of two adhesion molecules, E-cadherin and Sialyl Lewis x (sLe^x), in both a canine mammary carcinoma and human inflammatory breast cancer (IBC) model, using double labelled immunofluorescence staining.

Results

Our results demonstrate that canine mammary carcinoma and human IBC exhibit an inversely correlated cellular expression of E-cadherin and sLe^x within the same tumor embolus.

Conclusions

Our results in these two comparative models (canine and human) suggest the existence of a biologically coordinated mechanism of E-cadherin and sLe^x expression (i.e. molecular plasticity) essential for tumor establishment and metastatic progression.

The basics of epithelial-mesenchymal transition

The origins of the mesenchymal cells participating in tissue repair and pathological processes, notably tissue fibrosis, tumor invasiveness, and metastasis, are poorly understood. However, emerging evidence suggests that epithelial-mesenchymal transitions (EMTs) represent one important source of these cells. As we discuss here, processes similar to the EMTs associated with embryo implantation, embryogenesis, and organ development are appropriated and subverted by chronically inflamed tissues and neoplasias. The identification of the signaling pathways that lead to activation of EMT programs during these disease processes is providing new insights into the plasticity of cellular phenotypes and possible therapeutic interventions.

The basics of epithelial-mesenchymal transition

The origins of the mesenchymal cells participating in tissue repair and pathological processes, notably tissue fibrosis, tumor invasiveness, and metastasis, are poorly understood. However, emerging evidence suggests that epithelial-mesenchymal transitions (EMTs) represent one important source of these cells. As we discuss here, processes similar to the EMTs associated with embryo implantation, embryogenesis, and organ development are appropriated and subverted by chronically inflamed tissues and neoplasias. The identification of the signaling pathways that lead to activation of EMT programs during these disease processes is providing new insights into the plasticity of cellular phenotypes and possible therapeutic interventions.

Fibroblast growth factor receptor 2-positive fibroblasts provide a suitable microenvironment for tumor development and progression in esophageal carcinoma

PURPOSE

Tumor fibroblasts (TF) have been suggested to play an essential role in the complex process of tumor-stroma interactions and tumorigenesis. The aim of the present study was to investigate the specific role of TF in the esophageal cancer microenvironment.

EXPERIMENTAL DESIGN

An Affymetrix expression microarray was used to compare gene expression profiles between six pairs of TFs and normal fibroblasts from esophageal squamous cell carcinoma (ESCC). Differentially expressed genes were identified, and a subset was evaluated by quantitative real-time PCR and immunohistochemistry.

RESULTS

About 43% (126 of 292) of known deregulated genes in TFs were associated with cell proliferation, extracellular matrix remodeling, and immune response. Up-regulation of fibroblast growth factor receptor 2 (FGFR2), which showed the most significant change, was detected in all six tested TFs compared with their paired normal fibroblasts. A further study found that FGFR2-positive fibroblasts were only observed inside the tumor tissues and not in tumor-surrounding stromal tissues, suggesting that FGFR2 could be used as a TF-specific marker in ESCC. Moreover, the conditioned medium from TFs was found to be able to promote ESCC tumor cell growth, migration, and invasion in vitro.

CONCLUSIONS

Our study provides new candidate genes for the esophageal cancer microenvironment. Based on our results, we hypothesize that FGFR2(+)-TFs might provide cancer cells with a suitable microenvironment via secretion of proteins that could promote cancer development and progression through stimulation of cancer cell proliferation, induction of angiogenesis, inhibition of cell adhesion, enhancement of cell mobility, and promotion of the epithelial-mesenchymal transition.

The basics of epithelial-mesenchymal transition

The origins of the mesenchymal cells participating in tissue repair and pathological processes, notably tissue fibrosis, tumor invasiveness, and metastasis, are poorly understood. However, emerging evidence suggests that epithelial-mesenchymal transitions (EMTs) represent one important source of these cells. As we discuss here, processes similar to the EMTs associated with embryo implantation, embryogenesis, and organ development are appropriated and subverted by chronically inflamed tissues and neoplasias. The identification of the signaling pathways that lead to activation of EMT programs during these disease processes is providing new insights into the plasticity of cellular phenotypes and possible therapeutic interventions.

Ral overactivation in malignant peripheral nerve sheath tumors

Ras leads an important signaling pathway that is deregulated in neurofibromatosis type 1 and malignant peripheral nerve sheath tumor (MPNST). In this study, we show that overactivation of Ras and many of its downstream effectors occurred in only a fraction of MPNST cell lines. RalA, however, was overactivated in all MPNST cells and tumor samples compared to nontransformed Schwann cells. Silencing Ral or inhibiting it with a dominant-negative Ral (Ral S28N) caused a significant reduction in proliferation, invasiveness, and in vivo tumorigenicity of MPNST cells. Silencing Ral also reduced the expression of epithelial mesenchymal transition markers. Expression of the NF1-GTPase-related domain (NF1-GRD) diminished the levels of Ral activation, implicating a role for neurofibromin in regulating RalA activation. NF1-GRD treatment caused a significant decrease in proliferation, invasiveness, and cell cycle progression, but cell death increased. We propose Ral overactivation as a novel cell signaling abnormality in MPNST that leads to important biological outcomes with translational ramifications.

Identification of differentially expressed subnetworks based on multivariate ANOVA

Background

Since high-throughput protein-protein interaction (PPI) data has recently become available for humans, there has been a growing interest in combining PPI data with other genome-wide data. In particular, the identification of phenotype-related PPI subnetworks using gene expression data has been of great concern. Successful integration for the identification of significant subnetworks requires the use of a search algorithm with a proper scoring method. Here we propose a multivariate analysis of variance (MANOVA)-based scoring method with a greedy search for identifying differentially expressed PPI subnetworks.

Results

Given the MANOVA-based scoring method, we performed a greedy search to identify the subnetworks with the maximum scores in the PPI network. Our approach was successfully applied to human microarray datasets. Each identified subnetwork was annotated with the Gene Ontology (GO) term, resulting in the phenotype-related functional pathway or complex. We also compared these results with those of other scoring methods such as t statistic- and mutual information-based scoring methods. The MANOVA-based method produced subnetworks with a larger number of proteins than the other methods. Furthermore, the subnetworks identified by the MANOVA-based method tended to consist of highly correlated proteins.

Conclusion

This article proposes a MANOVA-based scoring method to combine PPI data with expression data using a greedy search. This method is recommended for the highly sensitive detection of large subnetworks.

Staged stromal extracellular 3D matrices differentially regulate breast cancer cell responses through PI3K and beta1-integrins

Background

Interactions between cancer cells and stroma are critical for growth and invasiveness of epithelial tumors. The biochemical mechanisms behind tumor-stromal interactions leading to increased invasiveness and metastasis are mostly unknown. The goal of this study was to analyze the direct effects of staged stroma-derived extracellular matrices on breast cancer cell behavior.

Methods

Early and late three-dimensional matrices were produced by NIH-3T3 and tumor-associated murine fibroblasts, respectively. After removing fibroblasts, extracted matrices were re-cultured with breast epithelial cells of assorted characteristics: MCF-10A (non-tumorigenic), MCF-7 (tumorigenic, non-invasive), and MDA-MB-231 (tumorigenic, invasive). Effects prompted by staged matrices on epithelial cell's growth, morphology and invasion were determined. Also, matrix-induced velocity, directionality and relative track orientation of invasive cells were assessed in the presence or absence of inhibitors of phosphoinositide-3 kinase (PI3K) and/or beta-1 integrin.

Results

We observed that assorted breast epithelial cells reacted differently to two-dimensional vs. staged, control (early) and tumor-associated (late), three-dimensional matrices. MCF-10A had a proliferative advantage on two-dimensional substrates while MCF-7 and MDA-MB-231 showed no difference. MCF-10A and MCF-7 formed morphologically distinguishable aggregates within three-dimensional matrices, while MDA-MB-231 exhibited increased spindle-shape morphologies and directional movements within three-dimensional matrices. Furthermore, MDA-MB-231 acquired a pattern of parallel oriented organization within tumor-associated, but not control matrices. Moreover, tumor-associated matrices induced PI3K and beta1-integrin dependent Akt/PKB activity in MDA-MB-231 cells. Interestingly, beta1-integrin (but not PI3K) regulated tumor-associated matrix-induced mesenchymal invasion which, when inhibited, resulted in a change of invasive strategy rather than impeding invasion altogether.

Conclusion

We propose that both cells and matrices are important to promote effective breast cancer cell invasion through three-dimensional matrices and that beta1-integrin inhibition is not necessarily sufficient to block tumor-matrix induced breast cancer cell invasion. Additionally, we believe that characterizing stroma staging (e.g., early vs. late or tumor-associated) might be beneficial for predicting matrix-induced cancer cell responses in order to facilitate the selection of therapies.

Expression of Na,K-ATPase-beta(1) subunit increases uptake and sensitizes carcinoma cells to oxaliplatin

Purpose

The ovarian carcinoma subline A2780/C10B (C10B) is an oxaliplatin resistant clone derived from the human ovarian carcinoma cell line A2780. The C10B cells are characterized by mesenchymal phenotype, decreased platinum uptake and increased glutathione levels (Hector et al. in Cancer Lett 245:195–204, 2007; Varma et al. in Oncol Rep 14:925–932, 2005). Na,K-ATPase-β subunit (Na,K-β₁) functions as a cell–cell adhesion molecule in epithelial cells and is reduced in a variety of carcinoma cells that show mesenchymal phenotype. The purpose of this study is to evaluate the relationship between Na,K-β expression and sensitivity to oxaliplatin.

Methods

Cell lines used include A2780, C10B, C10B transfected with Na,K-β₁ (C10B-Na,K-β) and a canine kidney carcinoma cell line MSV-MDCK also transfected with Na,K-β₁ (MSV-MDCK-β subunit). Cytotoxicity studies were performed by sulforhodamine-blue assay. The Na,K-α₁ and Na,K-β₁ subunit localization and expression were by immunofluorescence microscopy and Western blot analysis. Platinum accumulation measurements were by atomic absorption spectrophotometry.

Results

C10B cells express highly reduced levels of Na,K-β₁ subunit. Exogenous expression of Na,K-β₁ increased platinum accumulation and sensitized C10B cells to oxaliplatin. The pharmacological inhibitor of Na,K-ATPase ouabain did not alter the oxaliplatin accumulation indicating that Na,K-β₁ sensitizes cells in a Na,K-ATPase enzyme activity independent manner. These findings were also confirmed in MSV-MDCK-β subunit cells.

Conclusions

This study for the first time reveals that reduced expression of the Na,K-β₁ protein is associated with oxaliplatin resistance in cancer cells and demonstrates a novel role for this protein in sensitizing the cells to oxaliplatin. This study suggests a potentially important role for Na,K-β₁ in both prognosis and therapy of oxaliplatin resistant malignancies.

Epithelial-mesenchymal transition markers in pancreatic ductal adenocarcinoma

OBJECTIVES

Expression of transcription factors that mediate epithelial-mesenchymal transition (EMT), such as Twist and Slug, is correlated with poor prognosis in many tumor types. Selected EMT markers were studied in a series of pancreatic ductal adenocarcinomas (PDAs) and benign pancreatic tissues to determine whether expression levels correlated with diagnosis, histologic grade, or patient outcome.

METHODS

Immunohistochemical stains for Twist, Slug, and N-cadherin were performed using a tissue microarray containing 68 PDAs and 38 samples of normal pancreas or chronic pancreatitis tissues.

RESULTS

Twist and Slug were identified in both the nucleus and cytoplasm of benign pancreatic ductal epithelium, chronic pancreatitis, and PDA. Compared with normal ductal epithelium, nuclear levels of Twist are decreased in PDA. None of the other EMT markers showed significant differences in staining indices among the diagnostic groups. There were no correlations between EMT marker expression and histologic grade. Epithelial-mesenchymal transition marker expression was not associated with N-cadherin expression, patient outcome, or duration of survival.

CONCLUSIONS

Decreased expression of nuclear Twist is observed in malignant pancreatic epithelium. However, use of Twist as a diagnostic marker is precluded because decreased expression is also seen in chronic pancreatitis. None of the markers studied were predictive of patient outcome.

Gene silencing for epidermal growth factor receptor variant III induces cell-specific cytotoxicity

Epidermal growth factor receptor variant III (EGFRvIII) is a constitutively active mutant form of EGFR that is expressed in 40% to 50% of gliomas and several other malignancies. Here, we describe the therapeutic effects of silencing EGFRvIII on glioma cell lines in vitro and in vivo. A small interfering RNA molecule against EGFRvIII was introduced into EGFRvIII-expressing glioma cells (U87Delta) by electroporation resulting in complete inhibition of expression of EGFRvIII as early as 48 h post-treatment. During EGFRvIII silencing, a decrease in the proliferation and invasiveness of U87Delta cells was accompanied by an increase in apoptosis (P < 0.05). Notably, EGFRvIII silencing inhibited the signal transduction machinery downstream of EGFRvIII as evidenced by decreases in the activated levels of Ras and extracellular signal-regulated kinase. A lentivirus capable of expressing anti-EGFRvIII short hairpin RNA was also able to achieve progressive silencing of EGFRvIII in U87Delta cells in addition to inhibiting cell proliferation, invasiveness, and colony formation in a significant manner (P < 0.05). Silencing EGFRvIII in U87Delta cultures with this virus reduced the expression of factors involved in epithelial-mesenchymal transition including N-cadherin, beta-catenin, Snail, Slug, and paxillin but not E-cadherin. The anti-EGFRvIII lentivirus also affected the cell cycle progression of U87Delta cells with a decrease in G(1) and increase in S and G(2) fractions. In an in vivo model, tumor growth was completely inhibited in severe combined immunodeficient mice (n = 10) injected s.c. with U87Delta cells treated with the anti-EGFRvIII lentivirus (P = 0.005). We conclude that gene specific silencing of EGFRvIII is a promising strategy for treating cancers that contain this mutated receptor.

Allergic pulmonary inflammation promotes the recruitment of circulating tumor cells to the lung

Allergen-induced respiratory inflammation facilitates and/or elicits the extravasation of proinflammatory leukocytes by well-understood mechanisms that mediate the movement of multiple cell types. The nonspecific character of these pathways led us to hypothesize that circulating cancer cells use similar mechanisms, promoting secondary tumor formation at distal sites. To test this hypothesis, the frequency of metastasis to the lung as a function of allergic pulmonary inflammation was assessed following the i.v. injection of B16-F10 melanoma cells in mice. These studies showed that allergen-induced pulmonary inflammation resulted in a >3-fold increase in lung metastases. This increase was dependent on CD4(+) T-cell activities; however, it occurred independent of the induced eosinophilia associated with allergen provocation. Interventional strategies showed that existing therapeutic modalities for asthma, such as inhaled corticosteroids, were sufficient to block the enhanced pulmonary recruitment of cancer cells from circulation. Additional mechanistic studies further suggested that the ability of circulating cancer cells to extravasate to surrounding lung tissues was linked to the activation of the vascular endothelium via one or more Galpha(i)-coupled receptors. Interestingly, a survey of a clinical breast cancer surgical database showed that the incidence of asthma was higher among patients with lung metastases. Thus, our data show that allergic respiratory inflammation may represent a risk factor for the development of lung metastases and suggest that amelioration of the pulmonary inflammation associated with asthma will have a direct and immediate benefit to the 7% to 8% of breast cancer patients with this lung disease.

Identification of secreted proteins that mediate cell-cell interactions in an in vitro model of the lung cancer microenvironment

Non-small cell lung cancer (NSCLC) cells with somatic mutations in K-ras recruit to the tumor a variety of cell types (hereafter collectively termed "stromal cells") that can promote or inhibit tumorigenesis by mechanisms that have not been fully elucidated. Here, we postulated that stromal cells in the tumor microenvironment alter the tumor cell secretome, including those proteins required for tumor growth and dissemination, and we developed an in vitro model to test this hypothesis. Coculturing a murine K-ras mutant lung adenocarcinoma cell line (LKR-13) with a murine lung stromal cell (macrophage, endothelial cell, or fibroblast) enhanced stromal cell migration, induced endothelial tube formation, increased LKR-13 cell proliferation, and regulated the secretion of proteins involved in angiogenesis, inflammation, cell proliferation, and epithelial-to-mesenchymal transition. Among these proteins, CXCL1 has been reported to promote NSCLC development, whereas interleukin-18 (IL-18) has an undefined role. Genetic and pharmacologic strategies to inhibit CXCL1 and IL-18 revealed that stromal cell migration, LKR-13 cell proliferation, and LKR-13 cell tumorigenicity required one or both of these proteins. We conclude that stromal cells enhanced LKR-13 cell tumorigenicity partly through their effects on the secretome of LKR-13 cells. Strategies to inhibit tumor/stromal cell interactions may be useful as therapeutic approaches in NSCLC patients.

Epilysin (MMP-28)--structure, expression and potential functions

Epilysin (MMP-28) is the newest member of the matrix metalloproteinase (MMP) family of extracellular proteases. Together the MMPs can degrade almost all components of the extracellular matrix (ECM). MMPs also regulate cell behaviour by releasing growth factors and biologically active peptides from the ECM by modulating cell surface receptors and adhesion molecules and by regulating the activity of mediators of the inflammatory pathways. Epilysin differs from most other MMPs as it is expressed in a number of normal tissues, suggestive of functions in tissue homeostasis. The epilysin homologue in Xenopus laevis (XMMP-28) is expressed in neural tissues, where it cleaves the neural cell adhesion molecule. Enhanced expression of epilysin has been observed in basal keratinocytes during wound healing and in different forms of cancer. There are, however, also reports on the downregulation of epilysin in malignant cells. The roles of epilysin in cancer seem to vary based on tumor type and stage of the disease. Importantly, epilysin can induce stable epithelial to mesenchymal transition (EMT) when overexpressed in epithelial lung carcinoma cells. Transforming growth factor beta (TGF-beta) is a crucial mediator of this process, which was characterized by the loss of E-cadherin and increased cell migration and invasion. Current results suggest a plausible interaction between epilysin and TGF-beta also under physiological circumstances, where epilysin activity may not induce EMT but, instead, trigger less permanent changes in TGF-beta signalling and cell motility.

The role of endothelial-to-mesenchymal transition in cancer progression

Recent evidence has demonstrated that endothelial-to-mesenchymal transition (EndMT) may have a significant role in a number of diseases. Although EndMT has been previously studied as a critical process in heart development, it is now clear that EndMT can also occur postnatally in various pathologic settings, including cancer and cardiac fibrosis. During EndMT, resident endothelial cells delaminate from an organised cell layer and acquire a mesenchymal phenotype characterised by loss of cell–cell junctions, loss of endothelial markers, gain of mesenchymal markers, and acquisition of invasive and migratory properties. Endothelial-to-mesenchymal transition -derived cells are believed to function as fibroblasts in damaged tissue, and may therefore have an important role in tissue remodelling and fibrosis. In tumours, EndMT is an important source of cancer-associated fibroblasts (CAFs), which are known to facilitate tumour progression in several ways. These new findings suggest that targeting EndMT may be a novel therapeutic strategy, which is broadly applicable not only to cancer but also to various other disease states.

Cancer as an overhealing wound: an old hypothesis revisited

What is the relationship between the wound-healing process and the development of cancer? Malignant tumours often develop at sites of chronic injury, and tissue injury has an important role in the pathogenesis of malignant disease, with chronic inflammation being the most important risk factor. The development and functional characterization of genetically modified mice that lack or overexpress genes that are involved in repair, combined with gene-expression analysis in wounds and tumours, have highlighted remarkable similarities between wound repair and cancer. However, a few crucial differences were also observed, which could account for the altered metabolism, impaired differentiation capacity and invasive growth of malignant tumours.

CRBP-I in the renal tubulointerstitial compartment of healthy rats and rats with renal fibrosis

BACKGROUND

Cellular retinol-binding protein I (CRBP-I), a member of the intracellular lipid-binding protein (iLBP) superfamily, is a specific marker of quiescent stellate cells in the healthy human liver. In the diseased fibrotic/cirrhotic liver, portal and septal myofibroblasts acquire CRBP-I expression, while activated hepatic stellate cells maintain their CRBP-I expression. Here, we investigate the distribution of CRBP-I in the renal cortex of healthy rats and rats with renal fibrosis.

METHODS

Kidneys of healthy and adriamycin-treated rats were studied by immunohistochemistry, using antibodies against CRBP-I, desmin, vimentin and alpha-smooth muscle actin (alpha-SMA). Double stainings were done with immunofluorescence. Western blotting was performed to semi-quantify the expression levels of vimentin, desmin, alpha-SMA and CRBP-I.

RESULTS

In the normal rat kidney, the convoluted proximal tubular epithelial cells express CRBP-I; no expression is found in the interstitium, nor in the glomeruli. In the adriamycin-induced fibrotic rat kidney, CRBP-I expression diminishes in the convoluted proximal tubular epithelial cells, whereas peritubular myofibroblasts in the interstitium acquire CRBP-I expression.

CONCLUSIONS

In the tubulointerstitial compartment of the adriamycin-induced fibrotic rat kidney, CRBP-I is expressed in a different pattern than in the healthy rat kidney. As the convoluted proximal tubular epithelial cells dedifferentiate during fibrosis, CRBP-I expression decreases. Furthermore, de novo expression of CRBP-I is found in activated myofibroblast-like cells in the interstitium of adriamycin-treated rats. CRBP-I is therefore a useful marker to identify a subpopulation of activated/ myodifferentiated fibroblasts in the rat kidney.

Cancer cell iron metabolism and the development of potent iron chelators as anti-tumour agents

Cancer contributes to 50% of deaths worldwide and new anti-tumour therapeutics with novel mechanisms of actions are essential to develop. Metabolic inhibitors represent an important class of anti-tumour agents and for many years, agents targeting the nutrient folate were developed for the treatment of cancer. This is because of the critical need of this factor for DNA synthesis. Similarly to folate, Fe is an essential cellular nutrient that is critical for DNA synthesis. However, in contrast to folate, there has been limited effort applied to specifically design and develop Fe chelators for the treatment of cancer. Recently, investigations have led to the generation of novel di-2-pyridylketone thiosemicarbazone (DpT) and 2-benzoylpyridine thiosemicarbazone (BpT) group of ligands that demonstrate marked and selective anti-tumour activity in vitro and also in vivo against a wide spectrum of tumours. Indeed, administration of these compounds to mice did not induce whole body Fe-depletion or disturbances in haematological or biochemical indices due to the very low doses required. The mechanism of action of these ligands includes alterations in expression of molecules involved in cell cycle control and metastasis suppression, as well as the generation of redox-active Fe complexes. This review examines the alterations in Fe metabolism in tumour cells and the systematic development of novel aroylhydrazone and thiosemicarbazone Fe chelators for cancer treatment.

Phenotypic plasticity of neoplastic ovarian epithelium: unique cadherin profiles in tumor progression

The mesodermally derived normal ovarian surface epithelium (OSE) displays both epithelial and mesenchymal characteristics and exhibits remarkable phenotypic plasticity during post-ovulatory repair. The majority of epithelial ovarian carcinomas (EOC) are derived from the OSE and represent the most lethal of all gynecological malignancies, as most patients (approximately 70%) present at diagnosis with disseminated intra-abdominal metastasis. The predominant pattern of EOC metastasis involves pelvic dissemination rather than lymphatic or hematologic spread, distinguishing EOC from other solid tumors. Acquisition of the metastatic phenotype involves a complex series of interrelated cellular events leading to dissociation (shedding) and dispersal of malignant cells. A key event in this process is disruption of cell-cell contacts via modulation of intercellular junctional components. In contrast to most carcinomas that downregulate E-cadherin expression during tumor progression, a unique feature of primary well-differentiated ovarian cancers is a gain of epithelial features, characterized by an increase in expression of E-cadherin. Subsequent reacquisition of mesenchymal features is observed in more advanced tumors with concomitant loss of E-cadherin expression and/or function during progression to metastasis. The functional consequences of this remarkable phenotypic plasticity are not fully understood, but may play a role in modulation of cell survival in suspension (ascites), chemoresistance, and intraperitoneal anchoring of metastatic lesions.

Role of cancer microenvironment in metastasis: focus on colon cancer

One person on three will receive a diagnostic of cancer during his life. About one third of them will die of the disease. In most cases, death will result from the formation of distal secondary sites called metastases. Several events that lead to cancer are under genetic control. In particular, cancer initiation is tightly associated with specific mutations that affect proto-oncogenes and tumour suppressor genes. These mutations lead to unrestrained growth of the primary neoplasm and a propensity to detach and to progress through the subsequent steps of metastatic dissemination. This process depends tightly on the surrounding microenvironment. In fact, several studies support the point that tumour development relies on a continuous cross-talk between cancer cells and their cellular and extracellular microenvironments. This signaling cross-talk is mediated by transmembrane receptors expressed on cancer cells and stromal cells. The aim of this manuscript is to review how the cancer microenvironment influences the journey of a metastatic cell taking liver invasion by colorectal cancer cells as a model.

Recent advances in metastasis research

Advances in the early prediction, detection, and treatment of metastatic disease has improved the outlook in cancer patients in recent decades, however, metastasis remains the major cause of death in affected individuals. Metastasis occurs in a series of discreet biological steps in which a single, frequently clinically occult micrometastatic cell travels from the primary tumor to a distant location, where it lodges, grows, and ultimately results in the patient's death. Recent work has provided many new insights in the mechanisms and biology behind metastatic spread. This short review surveys some of the most important recent developments that have helped increase our understanding of the three broad phases of metastasis - the genesis of the metastatic cell through the loss of local constraints in the primary tumor microenvironment, dissemination of the cell to a distant organ while avoiding immune surveillance, and finally lodging and growth of the overt metastasis. These studies are providing mounting evidence that the interactions between tumor and normal cells and tissues are critical for disease progression - a paradigm that will provide a fertile area for future research.