Stimulate Cancer Cell Invasion Research Articles

ADAM17-mediated EGFR ligand shedding directs macrophage-promoted cancer cell invasion.

Macrophages in the tumor microenvironment have a substantial impact on tumor progression. Depending on the signaling environment in the tumor, macrophages can either support or constrain tumor progression. It is therefore of therapeutic interest to identify the tumor-derived factors that control macrophage education. With this aim, we correlated the expression of A Disintegrin and Metalloproteinase (ADAM) proteases, which are key mediators of cell-cell signaling, to the expression of protumorigenic macrophage markers in human cancer cohorts. We identified ADAM17, a sheddase upregulated in many cancer types, as a protein of interest. Depletion of ADAM17 in cancer cell lines reduced the expression of several protumorigenic markers in neighboring macrophages in vitro as well as in mouse models. Moreover, ADAM17-/- educated macrophages demonstrated a reduced ability to induce cancer cell invasion. Using mass spectrometry-based proteomics and ELISA, we identified heparin-binding EGF (HB-EGF) and amphiregulin, shed by ADAM17 in the cancer cells, as the implicated molecular mediators of macrophage education. Additionally, RNA-Seq and ELISA experiments revealed that ADAM17-dependent HB-EGF ligand release induced the expression and secretion of CXCL chemokines in macrophages, which in turn stimulated cancer cell invasion. In conclusion, we provide evidence that ADAM17 mediates a paracrine EGFR-ligand-chemokine feedback loop, whereby cancer cells hijack macrophages to promote tumor progression.

Targeting of the tumor immune microenvironment by metformin.

Stimulating antitumor immunity is an attractive idea for suppressing tumors. CD4 + and CD8 + T cells as well as natural killer cells (NK) are the primary antitumor immune cells in the tumor microenvironment (TME). In contrast to these cells, regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), cancer-associated fibroblasts (CAFs), and tumor-associated macrophages (TAMs) release several molecules to suppress antitumor immunity and stimulate cancer cell invasion and proliferation. Adjuvant treatment with certain nontoxic agents is interesting to boost antitumor immunity. Metformin, which is known as an antidiabetes drug, can modulate both antitumor and protumor immune cells within TME. It has the ability to induce the proliferation of CD8 + T lymphocytes and NK cells. On the other hand, metformin attenuates polarization toward TAMs, CAFs, and Tregs. Metformin also may stimulate the antitumor activity of immune system cells, while it interrupts the positive cross-talk and interactions between immunosuppressive cells and cancer cells. The purpose of this review is to explain the basic mechanisms for the interactions and communications between immunosuppressive, anti-tumoral, and cancer cells within TME. Next, we discuss the modulating effects of metformin on various cells and secretions in TME.

Increased Six1 expression in macrophages promotes hepatocellular carcinoma growth and invasion by regulating MMP-9.

Increased Six1 expression is commonly observed in a variety of cancers and is positively correlated with cancer progression and metastasis. Nevertheless, the mechanism by which Six1 affects the development of hepatocellular carcinoma (HCC) is still unclear. A series of experiments involving cell counting kit‐8, colony formation and Transwell assay was used to determine cell proliferation, migration and invasion respectively. Histological examination and immunofluorescence assay were also performed. The messenger RNA and protein expression of interesting genes were determined by real‐time reverse transcription‐polymerase chain reaction and western blotting respectively. We found that Six1 was up‐regulated in HCC and was associated with worse histological grade and poor survival rate. Increased expression of Six1 was shown to be able to boost cell growth, invasion, migration and epithelial‐mesenchymal transition (EMT), whereas silencing of Six1 suppressed these malignant phenotypes. Mechanistic investigations revealed that, in macrophages, matrix metalloproteinase 9 (MMP‐9) was up‐regulated by Six1. Interestingly, Six1 expression in macrophages was also able to trigger MMP‐9 induction in HCC cells. Moreover, macrophage Six1 expression was able to induce interleukin‐6 (IL‐6) up‐regulation and increase the activity of signal transducer and activator of transcription 3 (STAT3) in HCC cells, which accounted for the elevated levels of MMP‐9 and the higher invasive levels seen in HCC. Increased expression of Six1 in HCC aggravates the malignant behaviour of cancer cells, and we provide novel evidence that macrophage Six1 can stimulate cancer cell invasion by elevating MMP‐9 expression.

The YB-1/EZH2/amphiregulin signaling axis mediates LPA-induced breast cancer cell invasion.

Lysophosphatidic acid (LPA) has been known to induce epithelial-mesenchymal transition (EMT) to stimulate cancer cell invasion, and resveratrol (3,5,4'-trans-trihydroxystilbene; REV) suppresses the invasion and metastasis of various cancers. The current study aimed to identify the underlying mechanism by which LPA aggravates breast cancer cell invasion and the reversal of this phenomenon. Immunoblotting and quantitative RT-PCR analysis revealed that LPA induces amphiregulin (AREG) expression. Silencing of Y-box binding protein 1 (YB-1) or enhancer of zeste homolog 2 (EZH2) expression efficiently inhibited LPA-induced AREG expression. In addition, transfection of the cells with YB-1 siRNA abrogated LPA-induced EZH2 and AREG expression, leading to attenuation of breast cancer cell invasion. Furthermore, we observed that both REV and 5-fluorouracil (5-Fu) significantly reduce LPA-induced YB-1 phosphorylation and subsequent breast cancer invasion. Importantly, combined treatment of REV with 5-Fu showed more significant inhibition of LPA-induced breast cancer invasion compared to single treatment. Therefore, our data demonstrate that the YB-1/EZH2 signaling axis mediates LPA-induced AREG expression and breast cancer cell invasion and its inhibition by REV and 5-Fu, providing potential therapeutic targets and inhibition of breast cancer.

Podoplanin in Inflammation and Cancer.

Podoplanin is a small cell-surface mucin-like glycoprotein that plays a crucial role in the development of the alveoli, heart, and lymphatic vascular system. Emerging evidence indicates that it is also involved in the control of mammary stem-cell activity and biogenesis of platelets in the bone marrow, and exerts an important function in the immune response. Podoplanin expression is upregulated in different cell types, including fibroblasts, macrophages, T helper cells, and epithelial cells, during inflammation and cancer, where it plays important roles. Podoplanin is implicated in chronic inflammatory diseases, such as psoriasis, multiple sclerosis, and rheumatoid arthritis, promotes inflammation-driven and cancer-associated thrombosis, and stimulates cancer cell invasion and metastasis through a variety of strategies. To accomplish its biological functions, podoplanin must interact with other proteins located in the same cell or in neighbor cells. The binding of podoplanin to its ligands leads to modulation of signaling pathways that regulate proliferation, contractility, migration, epithelial–mesenchymal transition, and remodeling of the extracellular matrix. In this review, we describe the diverse roles of podoplanin in inflammation and cancer, depict the protein ligands of podoplanin identified so far, and discuss the mechanistic basis for the involvement of podoplanin in all these processes.

Decellularized human colorectal cancer matrices polarize macrophages towards an anti-inflammatory phenotype promoting cancer cell invasion via CCL18.

Macrophages are frequently identified in solid tumors, playing important roles in cancer progression. Their remarkable plasticity makes them very sensitive to environmental factors, including the extracellular matrix (ECM). In the present work, we investigated the impact of human colorectal tumor matrices on macrophage polarization and on macrophage-mediated cancer cell invasion. Accordingly, we developed an innovative 3D-organotypic model, based on the decellularization of normal and tumor tissues derived from colorectal cancer patients' surgical resections. Extensive characterization of these scaffolds revealed that DNA and other cell constituents were efficiently removed, while native tissue characteristics, namely major ECM components, architecture and mechanical properties, were preserved. Notably, normal and tumor decellularized matrices distinctly promoted macrophage polarization, with macrophages in tumor matrices differentiating towards an anti-inflammatory M2-like phenotype (higher IL-10, TGF-β and CCL18 and lower CCR7 and TNF expression). Matrigel invasion assays revealed that tumor ECM-educated macrophages efficiently stimulated cancer cell invasion through a mechanism involving CCL18. Notably, the high expression of this chemokine at the invasive front of human colorectal tumors correlated with advanced tumor staging. Our approach evidences that normal and tumor decellularized matrices constitute excellent scaffolds when trying to recreate complex microenvironments to understand basic mechanisms of disease or therapeutic resistance.

Abstract A66: Runx3 drives metastatic programs in pancreas cancer

Abstract The extreme proclivity of pancreatic ductal adenocarcinoma (PDA) for metastatic spread is the principal cause of mortality for this disease, even for patients who successfully undergo surgical resection of the primary tumor. We have engaged in a concerted effort to define the fundamental molecular and cellular drivers of PDA through the use of cognate genetically engineered mouse models that recapitulate the spectrum of human PDA. Recently, we incorporated conditional deletion of Smad4 into the KPC mouse model and noted a significant attenuation of metastatic burden in the resultant KPDC mice. Gene expression analysis identified the Runt family transcription factor Runx3 as highly expressed in metastatic KPC tumors, but minimally expressed in PDA from KPDC mice. We showed that aberrant expression of Runx3 strongly enhanced the metastatic potential of PDA through an orchestrated program that stimulated cancer cell invasion and migration and also helped generate a niche for disseminated cells to establish themselves in foreign tissues (such as the liver or lung) and form metastases. Runx3 expression additionally inhibited proliferation by upregulating expression of the cell cycle inhibitor Cdkn1a (p21), initiating a metastatic switch that favored PDA dissemination over local outgrowth. We have also identified influences of Runx3 expression on key developmental and immune-regulatory signaling pathways that are known to be aberrantly regulated in PDA. Because Runx3 has been shown to interact with Smad4 and p53, the genomic context of PDA expressing Runx3 critically modulates its function through de novo or altered protein complex formation. Defining the dichotomous, contextual roles of Runx3 as both a tumor “suppressor” and “promoter” may provide insight into the proximal cause of lethality in patients, thereby informing clinical prioritization of local versus systemic therapies for individual patients with PDA. Citation Format: Martin C. Whittle, Libing Feng, Ashley Dotson, Fiona Pakiam, Sunil R. Hingorani.{Authors}. Runx3 drives metastatic programs in pancreas cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr A66.

The hallmarks of CAFs in cancer invasion

The ability of cancer cells to move out of the primary tumor and disseminate through the circulation to form metastases is one of the main contributors to poor patient outcome. The tumor microenvironment provides a niche that supports cancer cell invasion and proliferation. Carcinoma-associated fibroblasts (CAFs) are a highly enriched cell population in the tumor microenvironment that plays an important role in cancer invasion. However, it remains unclear whether CAFs directly stimulate cancer cell invasion or they remodel the extracellular matrix to make it more permissive for invasion. Here we discuss paracrine communication between cancer cells and CAFs that promotes tumor invasion but also stimulates CAFs to remodel the matrix increasing cancer dissemination.

Tumor-derived microvesicles mediate human breast cancer invasion through differentially glycosylated EMMPRIN.

Tumor cells secrete not only a variety of soluble factors, but also extracellular vesicles that are known to support the establishment of a favorable tumor niche by influencing the surrounding stroma cells. Here we show that tumor-derived microvesicles (T-MV) also directly influence the tumor cells by enhancing their invasion in a both autologous and heterologous manner. Neither the respective vesicle-free supernatant nor MV from benign mammary cells mediate invasion. Uptake of T-MV is essential for the proinvasive effect. We further identify the highly glycosylated form of the extracellular matrix metalloproteinase inducer (EMMPRIN) as a marker for proinvasive MV. EMMPRIN is also present at high levels on MV from metastatic breast cancer patients in vivo. Anti-EMMPRIN strategies, such as MV deglycosylation, gene knockdown, and specific blocking peptides, inhibit MV-induced invasion. Interestingly, the effect of EMMPRIN-bearing MV is not mediated by matrix metalloproteinases but by activation of the p38/MAPK signaling pathway in the tumor cells. In conclusion, T-MV stimulate cancer cell invasion via a direct feedback mechanism dependent on highly glycosylated EMMPRIN.

Abstract 185: Cancer associated fibroblasts stimulates cancer cell invasion through CXCL12-CXCR4 signaling in gastric cancer

Abstract Objectives: Gastric cancer is one of the most threatening malignancies with a high incidence and metastasis rate. Many patients are diagnosed in an advanced stage sometimes with multi-organ metastasis, which leads a poor prognosis of gastric tumors. Chemokine and their receptors have been originally demonstrated as essential mediators of leukocyte directional migration, particularly during infection and inflammation, and have further emerged as crucial players in all stages of tumor development. It has been reported that an important CXCL12-CXCR4 signaling is involved in tumor development and metastasis in several types of cancer including gastric cancer. Cancer associated fibroblasts (CAF) are reported to communicate microenvironment-derived signals through chemokine/chemokine receptor interaction such as CXCL12-CXCR4 signaling. The aim of our study was to evaluate the role of CXCL12-CXCR4 signaling in crosstalk between gastric cancer and CAF. Methods and Results: We evaluated CXCL12 and CXCR4 expression status by immunohistochemistry using a nonbiased database of 89 curatively resected gastric cancers. As a result, CXCL12/ CXCR4 expression are significant correlation with metastasis. Furthermore, we performed Western blotting analysis for CXCL12 and CXCR4 in human gastric cancer cell lines. CXCR4 expression was detectable in all gastric cancer cell lines. We isolated CAF from human gastric cancer tissue resected in our institute. We performed Western blotting analysis for alpha-SMA and CXCL12 in CAF, and confirmed higher expression in CAF than normal fibroblast (NF) isolated from normal gastric mucosa of same patients. Then we established stable AGS gastric cancer cell line expressing GFP. Invasion assay revealed that AGS (gastric cancer cell line) cells with CAF showed more invasive phenotype than that without CAF. We also found the motility of GFP-expressing AGS was elevated during direct co-culture of GFP-expressing AGS cells and CAF compared with NF. Conclusions: These findings revealed that cancer associated fibroblasts were implicated in cancer cell invasion and metastasis through CXCL12-CXCR4 signaling in gastric cancer. The therapeutic blockade of this pathway with CXCR4 antagonist might abrogate gastric cancer cell invasion and metastasis. Citation Format: Daisuke Izumi, Takatsugu Ishimoto, Hietaka Sugihara, Hiroshi Sawayama, Ryuichi Karashima, Satoshi Ida, Yu Imamura, Shiro Iwagami, Yoshifumi Baba, Yasuo Sakamoto, Yuji Miyamoto, Naoya Yoshida, Hideo Baba. Cancer associated fibroblasts stimulates cancer cell invasion through CXCL12-CXCR4 signaling in gastric cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 185. doi:10.1158/1538-7445.AM2014-185

Collagen Signaling Enhances Tumor Progression after Anti-VEGF Therapy in a Murine Model of Pancreatic Ductal Adenocarcinoma

There is growing evidence that antiangiogenic therapy stimulates cancer cell invasion and metastasis. However, the underlying molecular mechanisms responsible for these changes have not been fully defined. Here, we report that anti-VEGF therapy promotes local invasion and metastasis by inducing collagen signaling in cancer cells. We show that chronic VEGF inhibition in a genetically engineered mouse model of pancreatic ductal adenocarcinoma (PDA) induces hypoxia, a less differentiated mesenchymal-like tumor cell phenotype, TGF-β expression, and collagen deposition and signaling. In addition, we show that collagen signaling is critical for protumorigenic activity of TGF-β in vitro. To further model the impact of collagen signaling in tumors, we evaluated PDA in mice lacking Sparc, a protein that reduces collagen binding to cell surface receptors. Importantly, we show that loss of Sparc increases collagen signaling and tumor progression. Together, these findings suggest that collagen actively promotes PDA spread and that enhanced disease progression associated with anti-VEGF therapy can arise from elevated extracellular matrix-mediated signaling.

Macrophages stimulate gastric and colorectal cancer invasion through EGFR Y1086, c-Src, Erk1/2 and Akt phosphorylation and smallGTPase activity

The interactions between cancer cells and their microenvironment are crucial for malignant progression, as they modulate invasion-related activities. Tumor-associated macrophages are generally considered allies in the process of tumor progression in several types of cancer, although their role on gastric and colorectal carcinomas is still poorly understood. In this report, we studied the influence of primary human macrophages on gastric and colorectal cancer cells, considering invasion, motility/migration, proteolysis and activated intracellular signaling pathways. We demonstrated that macrophages stimulate cancer cell invasion, motility and migration, and that these effects depend on matrix metalloproteinase (MMP) activity and on the activation of epidermal growth factor receptor (EGFR) (at the residue Y(1086)), PLC-γ (phospholipase C-gamma) and Gab1 (GRB2-associated binding protein-1), as evidenced by siRNA (small interference RNA) experiments. Epidermal growth factor (EGF)-immunodepletion impaired macrophage-mediated cancer cell invasion and motility, suggesting that EGF is the pro-invasive and pro-motile factor produced by macrophages. Macrophages also induced gastric and colorectal cancer cell phosphorylation of Akt, c-Src and ERK1/2, and led to an increase of RhoA and Cdc42 activity. Interestingly, whereas macrophage-mediated cancer cell c-Src and ERK1/2 phosphorylation occurred downstream EGFR activation, Akt phosphorylation seems to be a parallel event, taking place in an EGFR-independent manner. The involvement of EGF, EGFR-downstream signaling partners and MMPs in macrophage-mediated invasion provides novel insights into the molecular crosstalk established between cancer cells and macrophages, opening new perspectives for the design of new and more efficient therapeutic strategies to counteract cancer cell invasion.

Insights into Ectodomain Shedding and Processing of Protein-tyrosine Pseudokinase 7 (PTK7)

The membrane PTK7 pseudokinase, a component of both the canonical and noncanonical/planar cell polarity Wnt pathways, modulates cell polarity and motility in biological processes as diverse as embryo development and cancer cell invasion. To determine the individual proteolytic events and biological significance of the ectodomain shedding in the PTK7 function, we used highly invasive fibrosarcoma HT1080 cells as a model system. Current evidence suggested a likely link between PTK7 shedding and cell invasion in our HT1080 cell model system. We also demonstrated that in HT1080 cells the cleavage of the PTK7 ectodomain by an ADAM proteinase was coupled with the membrane type-1 matrix metalloproteinase (MT1-MMP) cleavage of the PKP(621)↓LI site in the seventh Ig-like domain of PTK7. Proteolytic cleavages led to the generation of two soluble, N-terminal and two matching C-terminal, cell-associated fragments of PTK7. This proteolysis was a prerequisite for the intramembrane cleavage of the C-terminal fragments of PTK7 by γ-secretase. γ-Secretase cleavage was predominantly followed by the efficient decay of the resulting C-terminal PTK7 fragment via the proteasome. In contrast, in HT1080 cells, which overexpressed the C-terminal PTK7 fragment, the latter readily entered the nucleus. Our data imply that therapeutic inhibition of PTK7 shedding may be used to slow cancer progression.

Human monocytes and proinflammatory cytokines stimulate breast and prostate cancer cell invasion

The objective of this study is to determine how monocyte/macrophages stimulate cancer cell growth and invasion. Co‐cultures with freshly isolated human monocytes or monocytoid cell lines stimulated invasion of several breast and prostate cancer cell lines. The co‐cultures produced high levels of IL‐6 and IL‐8 and increased MCP‐1 and Gro‐α chemokines above cancer cell or monocyte culture supernatants alone. Addition of purified recombinant interleukin‐8 and MCP‐1 proteins stimulated monocyte and cancer cell chemotaxis in Matrigel‐coated Transwell chambers. The co‐cultures also stimulated cancer cell NF‐κB reporter activity and nuclear localization. The co‐culture induced cancer cell invasion was blocked by biochemical inhibitors or dominant negative expression of IκBα or RhoA N19 mutants that inhibited NF‐κB activity. These studies indicate that human breast and prostate cancer cells cross‐communicate with monocytoid cells to stimulate cancer cell invasion in a NF‐κB dependent manner. This model has potential to identify treatments that block monocyte/macrophage‐induced cancer cell invasion and progression. Supported by Prostate S.P.O.RE. P50CA90386 and CDMRP DAMD‐17‐02‐1‐0162.

Bladder Cancer Cell Invasion Is Enhanced by Cross-Talk with Fibroblasts Through Hepatocyte Growth Factor

To examine the effects of fibroblast-derived humoral factors, especially hepatocyte growth factor (HGF), on the invasive potential of bladder cancer cells. Stromal cells in cancer tissue are thought to play an important role in the transformation and invasion of cancer cells. The influence of fibroblast cells (TIG-1 cells) and HGF on the invasive potential of bladder cancer cells (5637, T24, J82, HT1376, and MGHU-1 cells) was evaluated by in vitro cell invasion assay. The expression of HGF and c-Met, which is the receptor of HGF, was examined by reverse transcriptase-polymerase chain reaction. To clarify the relationship between the serum HGF level and invasive bladder cancer, we measured the serum concentrations of HGF in patients with bladder cancer without metastatic disease and normal controls, using an enzyme-linked immunosorbent assay. The in vitro cell invasion assay showed that the number of invading bladder cancer cells was significantly increased by the conditioned medium (CM) of the fibroblast cells. HGF neutralization antibody partially inhibited the enhancement of invasiveness by fibroblast CM. The CM of fibroblasts cultured with bladder cancer CM stimulated cancer cell invasion more strongly (with increased HGF secretion) than did the CM of fibroblasts cultured without bladder cancer CM. The serum HGF levels were significantly greater in patients with muscle-invasive bladder cancer (regardless of tumor size) than in patients with non-muscle-invasive bladder cancer. The present results have suggested that bladder cancer cell invasion is enhanced by cross-talk with fibroblasts through humoral factors, including HGF. Elucidation of this mechanism could lead to novel therapeutic strategies for bladder cancer.

Helicobacter pylori Induces Gastric Epithelial Cell Invasion in a c-Met and Type IV Secretion System-dependent Manner

Helicobacter pylori interacts with gastric epithelial cells, activating signaling pathways important for carcinogenesis. In this study we examined the role of H. pylori on cell invasion and the molecular mechanisms underlying this process. The relevance of H. pylori cag pathogenicity island-encoded type IV secretion system (T4SS), CagA, and VacA for cell invasion was also investigated. We found that H. pylori induces AGS cell invasion in collagen type I and in Matrigel invasion assays. H. pylori-induced cell invasion requires the direct contact between bacteria and cancer cells. H. pylori-mediated cell invasion was dependent on the activation of the c-Met receptor and on increased MMP-2 and MMP-9 activity. The abrogation of the c-Met receptor using the specific NK4 inhibitor or the silencing of c-Met expression with small interference RNA suppressed both cell invasion and MMP activity. Studies with different H. pylori strains revealed that cell invasion, c-Met tyrosine phosphorylation, and increased MMP-2 and MMP-9 activity were all dependent on the presence of a functional bacterial T4SS, but not on VacA cytotoxicity. Our findings demonstrate that H. pylori strains with a functional T4SS stimulate gastric epithelial cell invasion through a c-Met-dependent signaling pathway that comprises an increase in MMP-2 and MMP-9 activity.

Listeria monocytogenes produces a pro-invasive factor that signals via ErbB2/ErbB3 heterodimers.

We have previously demonstrated that conditioned medium from bacteria, some of which were isolated from the colon of cancer patients, stimulate cancer cell invasion in vitro through a 13-mer beta-casein-derived peptide. Since invasion signalling pathways are coordinated by the balance between protein kinases and phosphatases, we investigated the effect of conditioned medium from bacteria on the overall cellular tyrosine phosphorylation. The tyrosine phosphorylation level of HCT-8/E11 human colon cancer cells treated with the pro-invasive conditioned medium of Listeria, prepared on top of collagen type I gels (CM(Coll) Listeria/TSB), were analysed by means of immunoprecipitation and Western blot, with specific anti-phosphotyrosine antibodies. We demonstrated that CM(Coll) Listeria/TSB increases the tyrosine phosphorylation level of ErbB2 and ErbB3, members of the epidermal growth factor receptor (EGFR) family, and the association between ErbB3 and the phosphatidylinositol 3-kinase (PI3K) regulatory subunit (p85alpha). CM(Coll) Listeria/TSB-stimulated ErbB3 tyrosine phosphorylation and cancer cell invasion were independent from EGFR expression and activity but dependent on ErbB2 activity. The interaction between Listeria and collagen type I produces, next to the 13-mer peptide, at least another pro-invasive factor that signals via ErbB2/ErbB3 heterodimers.

ERK1/2 and p38 pathways are required for P2Y receptor-mediated prostate cancer invasion

The G protein-coupled P2Y purinoceptors have wide physiological functions, but their role(s) in tumor progression remain unclear. Here, we report that stimulation of P2Y receptors enhances prostate cancer cell invasion in two human prostate carcinoma cell lines, which is mediated by ERK1/2 and p38 signaling pathways. P2Y agonists stimulated prostate cancer cell invasion, and increased the activities of ERK1/2 and p38 protein kinases. The stimulated cancer cell invasion was inhibited by the presence of MEK1 inhibitor PD98059 or p38 inhibitor SB203580. Expression of dominant-negative mutant of MEK1 (KA-MEK1), or up-regulation of MKP-5 (a dual-specificity phosphatase of p38), both reduced the invasion of cultured prostate cancer cells. These results suggest that P2Y receptors and their down-stream ERK1/2 and p38 protein kinases are important regulators promoting prostate cancer invasion.

Beta-casein-derived peptides, produced by bacteria, stimulate cancer cell invasion and motility.

In colon cancer, enteric bacteria and dietary factors are major determinants of the microenvironment but their effect on cellular invasion is not known. We therefore incubated human HCT-8/E11 colon cancer cells with bacteria or bacterial conditioned medium on top of collagen type I gels. Listeria monocytogenes stimulate cellular invasion through the formation of a soluble motility-promoting factor, identified as a 13mer beta-casein-derived peptide (HKEMPFPKYPVEP). The peptide is formed through the combined action of Mpl, a Listeria thermolysin-like metalloprotease, and a collagen-associated trypsin-like serine protease. The 13mer peptide was also formed by tumour biopsies isolated from colon cancer patients and incubated with a beta-casein source. The pro- invasive 13mer peptide-signalling pathway implicates activation of Cdc42 and inactivation of RhoA, linked to each other through the serine/threonine p21- activated kinase 1. Since both changes are necessary but not sufficient, another pathway might branch upstream of Cdc42 at phosphatidylinositol 3-kinase. Delta opioid receptor (deltaOR) is a candidate receptor for the 13mer peptide since naloxone, an deltaOR antagonist, blocks both deltaOR serine phosphorylation and 13mer peptide-mediated invasion.