Hypoxia induces expression of the urokinase receptor (uPAR) and activates uPAR-dependent cell signaling in cancer cells. This process promotes epithelial-mesenchymal transition (EMT). uPAR overexpression in cancer cells also promotes EMT.In this study, we tested whether uPAR may be targeted to reverse cancer cell EMT. When MDA-MB 468 breast cancer cells were cultured in 1% O 2 , uPAR expression increased, as anticipated. Cell-cell junctions were disrupted, vimentin expression increased, and E-cadherin was lost from cell surfaces, indicating EMT. Transferring these cells back to 21% O 2 decreased uPAR expression and reversed the signs of EMT. In uPAR-overexpressing MDA-MB 468 cells, EMT was reversed by silencing expression of endogenously produced urokinase-type plasminogen activator (uPA), which is necessary for uPAR-dependent cell signaling, or by targeting uPAR-activated cell signaling factors, including phosphatidylinositol 3-kinase, Src family kinases, and extracellular signal-regulated kinase. MDA-MB 231 breast cancer cells express high levels of uPA and uPAR and demonstrate mesenchymal cell morphology under normoxic culture conditions (21% O 2 ). Silencing uPA expression in MDA-MB-231 cells decreased expression of vimentin and Snail, and induced changes in morphology characteristic of epithelial cells. These results demonstrate that uPAR-initiated cell signaling may be targeted to reverse EMT in cancer. Epithelial-mesenchymal transition (EMT)2 is a well recognized process in embryonic development (1). To facilitate migration of neural crest cells out of the neuroectoderm, N-cadherin-based cell adhesions are lost. Endocardial cells adopt a mesenchymal cell phenotype during formation of cardiac septa and valves. EMT also may be involved in metastasis of epithelial cell malignancies (2). In cancer cell EMT, E-cadherin protein and activity are decreased, causing disruption of cell-cell junctions and loss of cell polarity. At the same time, cancer cells that undergo EMT demonstrate increased expression of mesenchymal cell proteins such as vimentin. Loss of E-cadherin, in human malignancies, may reflect mutation of the E-cadherin gene or E-cadherin promoter hypermethylation (3-5). E-cadherin expression also may be repressed at the transcriptional level by Slug, Snail, or Twist (6 -9). Experimental regulation of E-cadherin expression controls cancer progression in mouse model systems (10 -13).Activation of the phosphatidylinositol 3-kinase (PI3K) and Akt promotes EMT in cancer cells (14). Akt phosphorylates and thereby inactivates glycogen synthase kinase-3␤ (GSK-3␤), increasing Snail activity by regulating Snail expression, degradation, and nuclear localization (6,7,15,16). Wnt signaling also regulates GSK-3␤ and thereby supports EMT by downstream effects on Snail and Slug (17). Extracellular signal-regulated kinase (ERK1/2) increases expression of Snail (18). Rac1 and its alternatively spliced variant, Rac1b, control Snail expression and activity, through a pathway that involves reactive oxygen species and NF-B...

Signaling by urokinase-type plasminogen activator receptor (uPAR) can cause epithelial-mesenchymal transition (EMT) in cultured breast cancer cells. In this report, we show that uPAR signaling can also induce cancer stem cell (CSC)-like properties. Ectopic overexpression of uPAR in human MDA-MB-468 breast cancer cells promoted the emergence of a CD24 − /CD44 + phenotype, characteristic of CSCs, while increasing the cell surface abundance of integrin subunits β1/CD29 and α6/CD49f that represent putative mammary gland stem cell biomarkers. uPAR overexpression increased mammosphere formation in vitro and tumor formation in an immunocompromized severe combined immunodeficient (SCID) mouse model of orthotopic breast cancer. Hypoxic conditions that are known to induce EMT in MDA-MB-468 cells also increased cell surface β1/CD29, mimicking the effects of uPAR overexpression. Antagonizing uPAR effector signaling pathways reversed the increase in cell surface integrin expression. Whereas uPAR overexpression did not induce EMT in MCF-7 breast cancer cells, CSC-like properties were nevertheless still induced along with an increase in tumor initiation and growth in the orthotopic setting in SCID mice. Notably, in MCF-7 cell mammospheres, which display a well-defined acinus-like structure with polarized expression of Ecadherin and β1-integrin, cell collapse into the central cavity was decreased by uPAR overexpression, suggesting that uPAR signaling may stabilize epithelial morphology. In summary, our findings show that uPAR signaling can induce CSC-like properties in breast cancer cells, either concomitantly with or separately from EMT. Cancer Res; 70(21); 8948-58. ©2010 AACR.

Cancer cells condition macrophages and other inflammatory cells in the tumor microenvironment so that these cells are more permissive for cancer growth and metastasis. Conditioning of inflammatory cells reflects, at least in part, soluble mediators (such as transforming growth factor β and IL-4) that are released by cancer cells and alter the phenotype of cells of the innate immune system. Signaling pathways in cancer cells that potentiate this activity are incompletely understood. The urokinase receptor (uPAR) is a cell-signaling receptor known to promote cancer cell survival, proliferation, metastasis, and cancer stem cell-like properties. The present findings show that uPAR expression in diverse cancer cells, including breast cancer, pancreatic cancer, and glioblastoma cells, promotes the ability of these cells to condition co-cultured bone marrow-derived macrophages so that the macrophages express significantly increased levels of arginase 1, a biomarker of the alternatively activated M2 macrophage phenotype. Expression of transforming growth factor β was substantially increased in uPAR-expressing cancer cells via a mechanism that requires uPA-initiated cell signaling. uPAR also controlled expression of IL-4 in cancer cells via a mechanism that involves activation of ERK1/2. The ability of uPAR to induce expression of factors that condition macrophages in the tumor microenvironment may constitute an important mechanism by which uPAR promotes cancer progression.

Pain is highly prevalent in patients with pancreas cancer and contributes to the morbidity of the disease. Pain may be due to pancreatic enzyme insufficiency, obstruction, and/or a direct mass effect on nerves in the celiac plexus. Proper supportive care to decrease pain is an important aspect of the overall management of these patients. There are limited data specific to the management of pain caused by pancreatic cancer. Here we review the literature and offer recommendations regarding multiple modalities available to treat pain in these patients. The dissemination and adoption of these best supportive care practices can improve quantity and quality of life for patients with pancreatic cancer. Implications for Practice Pain management is important to improve the quality of life and survival of a patient with cancer. The pathophysiology of pain in pancreas cancer is complex and multifactorial. Despite tumor response to chemotherapy, a sizeable percentage of patients are at risk for ongoing cancer‐related pain and its comorbid consequences. Accordingly, the management of pain in patients with pancreas cancer can be challenging and often requires a multifaceted approach.

Binding of urokinase-type plasminogen activator (uPA)1 to its receptor, uPAR, in estrogen receptor-α (ERα) expressing breast cancer cells, transiently activates ERK downstream of FAK, Src family kinases, and H-Ras. Herein, we show that when uPAR is over-expressed, in two separate ERα-positive breast cancer cell lines, ERK activation occurs autonomously of uPA and is sustained. Autonomous ERK activation by uPAR requires H-Ras and Rac1. A mutated form of uPAR, which does not bind vitronectin (uPAR-W32A), failed to induce autonomous ERK activation. Expression of human uPAR or mouse uPAR but not uPARW32A in MCF-7 cells provided a selection advantage when these cells were deprived of estrogen in cell culture for two weeks. Similarly, MCF-7 cells that express mouse uPAR formed xenografts in SCID mice that survived and increased in volume in the absence of estrogen supplementation, probably reflecting the pro-survival activity of phospho-ERK. Autonomous uPAR signaling to ERK was sensitive to the EGFR tyrosine kinase inhibitors, Erlotinib and Gefitinib. The transition in uPAR signaling from uPA-dependent and transient to autonomous and sustained is reminiscent of the transformation in ErbB2/ HER2 signaling observed when this gene is amplified in breast cancer. uPAR over-expression may provide a pathway for escape of breast cancer cells from ERα-targeting therapeutics.