The mechanisms regulating tumor invasion and metastasis remain largely unknown and these processes are common and life-threatening complications of cancer. Clinical and basic research have demonstrated that the cytokine HGF and its receptor c-Met play an important role in regulating intracellular signaling pathways leading to tumor invasion of most human cancers. Preliminary results have indicated that HGF activates Ras, PI 3-kinase and the MAPK pathway in the prostate cancer cell-line DU145, leading to cell scattering, preceeded by endocytosis of E-cadherin and other adherins junction (AJ) proteins This is followed by increases in invasion that are paralleled by the polarized exocytosis of cathepsin B-positive lysosomes along microtubules. The regulation of membrane trafficking plays a role in cancer progression, yet very little is known about the pertinent mechanisms. We hypothesize that HGF activates the Ras signaling pathway to stimulate both macropinocytic internalization of AJ proteins and to induce kinesindependent lysosome exocytosis, leading to the polarized secretion of cathepsin B and increases in invasion and metastasis.
In Aim #1, biochemical and microscopic approaches will be employed to determine if macropinocytosis plays an important role in AJ uptake. Microscopic and molecular genetic approaches will also be used to determine the nature of the intracellular compartment AJ proteins accumulate in. Finally, we will determine the order Ras, Racl, and PI 3-kinase interact to mediate HGF-induced AJ protein internalization.
In Aim #2, the mechanisms involved in HGF-induced lysosome exocytosis will be explored. This will involve using microscopic and biochemical approaches to determine if HGF induces lysosome movement along microtubules. The role of small G proteins (RhoG, RhoA, etc) and molecular motors (kinesin, myosin V) in lysosome movement will be determined. Finally, molecular genetic approaches will also be used to determine if blocking lysosome redistribution by inactivating select target proteins will prevent or reduce invasion.
In Aim #3, animal models will be used to determine if inactivating the proteins shown to regulate HGF-induced anterogradelysosome transport will prevent or reduce invasion and metastasis. Completion of this project will increase our knowledge concerning the role of vesicle trafficking in tumor invasion and will identify potential therapeutic targets to slow or prevent cancer spread.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Tumor Progression and Metastasis Study Section (TPM)
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Ault, Grace S
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Louisiana State University Hsc Shreveport
Schools of Medicine
United States
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Steffan, Joshua J; Dykes, Samantha S; Coleman, David T et al. (2014) Supporting a role for the GTPase Rab7 in prostate cancer progression. PLoS One 9:e87882
Steffan, Joshua J; Coleman, David T; Cardelli, James A (2011) The HGF-met signaling axis: emerging themes and targets of inhibition. Curr Protein Pept Sci 12:12-22
Steffan, Joshua J; Williams, Brittany C; Welbourne, Tomas et al. (2010) HGF-induced invasion by prostate tumor cells requires anterograde lysosome trafficking and activity of Na+-H+ exchangers. J Cell Sci 123:1151-9
Duhon, Damian; Bigelow, Rebecca L H; Coleman, David T et al. (2010) The polyphenol epigallocatechin-3-gallate affects lipid rafts to block activation of the c-Met receptor in prostate cancer cells. Mol Carcinog 49:739-49
Steffan, Joshua J; Cardelli, James A (2010) Thiazolidinediones induce Rab7-RILP-MAPK-dependent juxtanuclear lysosome aggregation and reduce tumor cell invasion. Traffic 11:274-86
Milligan, Shawn A; Burke, Patrick; Coleman, David T et al. (2009) The green tea polyphenol EGCG potentiates the antiproliferative activity of c-Met and epidermal growth factor receptor inhibitors in non-small cell lung cancer cells. Clin Cancer Res 15:4885-94
Steffan, Joshua J; Snider, Jared L; Skalli, Omar et al. (2009) Na+/H+ exchangers and RhoA regulate acidic extracellular pH-induced lysosome trafficking in prostate cancer cells. Traffic 10:737-53
Coleman, David T; Bigelow, Rebecca; Cardelli, James A (2009) Inhibition of fatty acid synthase by luteolin post-transcriptionally down-regulates c-Met expression independent of proteosomal/lysosomal degradation. Mol Cancer Ther 8:214-24
Rupper, Adam; Cardelli, James (2008) Large-scale purification of latex bead phagosomes from mouse macrophage cell lines and subsequent preparation for high-throughput quantitative proteomics. Methods Mol Biol 445:339-51
Snider, Jared L; Allison, Cody; Bellaire, Bryan H et al. (2008) The beta1 integrin activates JNK independent of CagA, and JNK activation is required for Helicobacter pylori CagA+-induced motility of gastric cancer cells. J Biol Chem 283:13952-63

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