Cancer: Cancer is a complex disease characterized by deregulation of cell proliferation and apoptotic mechanisms, stromal and microenvironmental changes, angiogenesis and cell metastasis. Cancer research in our lab focuses on understanding how tumor cells acquire the ability to metastasize to distant organs and survive in these foreign environments (Fig 1). This is the major cause of death in cancer patients and there currently no therapeutic agents available to prevent the spread of cancer. Our work has shown that the activation of the Ras/ERK and p130CAS/Crk/Rac pathways by integrin and growthfactor receptors promote cell metastasis by coordinately activating the migration and survival machineries of pancreatic cancer cells. This allows tumor cells to invade tissues and survival in foreign and unfavorable environments. We are also investigating the role of the metastatic genes RhoC and src kinase in mediating cytoskeletal changes that lead to cancer cell migration, metastasis, and angiogenesis. To investigate these signaling pathways in vitro and in vivo, we are currently utilizing quantitative proteomics and transgenic animal models (zebrafish and mice) of pancreatic cancer combined with intravital confocal and spectral 2-photon microscopy (Fig 2). Finally, in collaboration with researchers at the Moores Cancer Center at UCSD (http://cancer.ucsd.edu/summaries/rklemke.asp), we are investigating the role Ras/ERK, src/p130CAS/Crk/Rac, and RhoC signaling in mediating cancer stem cell propagation and metastasis using animal models of pancreatic cancer and surgically resected tissue obtained from pancreatic cancer patients.

Figure 1. Schematic showing tumor cell metastasis. Invasive cancer cells migrate from the primary tumor site into the surrounding tissue towards blood vessels. These cells then penetrate the vessel wall (intravasate), gaining access to the vessel lumen. Cells are then carried to distant organs by normal blood flow, where they lodge in small capillaries of various organs. These cells can then extravasate through the vessel wall into the surrounding tissue, where they form secondary tumors. This process is the major cause of death in cancer patients and there are no therapeutic agents to prevent the spread of cancer.

Figure 2. Front and side views of the spectral confocal and 2-photon microscope in the Klemke laboratory. It is a Nikon C1si-true Spectral Imaging Confocal Laser Scanning Microscope interfaced with a Spectra-Physics Mai Tai Ti:Sapphire tunable laser (700-1040 nm). The microscope can simultaneously acquire 32 channels of fluorescence spectra in a 320 nm wide wavelength range in a single pass and is equipped with the best available oil and water objects. The system is also equipped with perfect focus capabilities and an environmental chamber for long term imaging experiments of live specimens.

Figure 3. Orthotopic mouse model of pancreatic cancer. RFP- expressing pancreatic tumor cells (red) were orthotopically implanted into the pancreas of nude mice and imaged 18 days later. Image shown is the exposed intravital tumor growing in the pancreas in the peritoneal cavity of the animal.

Figure 4. Cell metastasis is a highly dynamic process that occurs in multiple steps. (1). Cancer cells migrate away from the primary tumor in search of blood vessels. (2). Once they locate a blood vessel they penetrate through the vascular wall and gain access to the vessel lumen. This process in referred to as intravasation. (3) Once inside the vessel lumen the tumor cells are carried by blood flow to distant sites in the body where they typically lodge in small capallaries present in various organs including the lungs, liver, brain, and bone. (4) The trapped tumors cells can then penetrate the vessel wall and migrate (extravasate) out of the vasculature into the surrounding tissues, where they grow, forming a secondary tumor and vascular supply. While tumor cell metastasis is the primary cause of patient death, there are currently no therapeutic means available to prevent this process (movie courtesy of Nova). (Click on Image to Play)

Figure 5. Developing tumors secrete angiogenic factors (shown as grey particles) that stimulate the remodeling of existing vessels or the growth of new vessels in a process referred to as angiogenesis. The growing vessels integrate into the tumor mass delivering nutrients and oxygen. The new vascular supply facilitates tumor growth and provides a means for tumor cells to escape (metastasize) and travel to distant sites in the body. An intense research effort is underway to develop therapeutics to block angiogenesis in hopes of irradicating cancer progression. (Click on Image to Play)