Our working hypothesis focuses on the convergence of prosurvival, angiogenesis and motility signals at common pathways in the local tumor microenvironment for therapeutic targeting and monitoring. We continue to examine two pathways we identified: the BAG-3 stress co-chaperone protein and the ovarian cancer growth and survival factor and its partner, progranulin (pgrn) and secretory leukocyte protease inhibitor (SLPI). Our findings of selective and specific behavior of BAG3 and its targeting downstream of caspase activition puts this protein in a new light as a selective regulator of pathways involving HSP70. New findings have identified a functional role for the WW domain of BAG3;these findings put BAG3 in the cell cycle as a regulator and as a subject of cell cycle regulation. While not disruptive to the cell cycle as a full protein, disruption of domain-specific events alters proper cell cycle behavior and leads us to a new direction of translational applicability of BAG3. We are advancing our studies of the inhibitor role of BAG3 related invasion through study of differentially regulated miRNAs, having identified altered regulation of miRNA146, known to be an inhibitor of motility. The altered regulation and its function has been confirmed and mechanism studies are ongoing. We continue to analyze functional effects of BAG3 through two in vivo models: Drosophila and our MMTV-BAG3 transgenic mouse model. Characterization continues in collaboration with Dr. Sandstrom of NIMH, demonstrating both the known muscle and a novel neural target and related behavior for Evil. MMTV-BAG3 mice are viable and able to propagate;a DMBA carcinogenesis experiment in virgin mice demonstrated increased abnormalities of breast duct, including malignancy. Ongoing studies will evaluate breast development, malignancy latency, and metastatic potential are collaborative with Dr. Smith of the MBTL, CCR. Our studies of pgrn and its partner protein, SLPI, have advanced. Increased dissemination in vivo of HEY-A8 cells overexpressing SLPI and its mutants was observed and is independent of loss of protease inhibition function. We have submitted a manuscript detailing that this is associated with upregulation of MMP9 at the RNA level with increased protein production. Secondarily, there is increased cleavage from the membrane pro-form in the protease-null SLPI mutants, yielding net increased MMP9 activity. We confirm that SLPI and MMP9 colocalize in serous ovarian cancers by tissue microarray, but this does not occur with endometrioid ovarian cancers, and that the relationship between SLPI and MMP9 holds in a series of clinical ovarian cancer patients treated previously on our triple drug study 95-C-0055. We have new SLPI mutants expressed in both HEY-A8 and HaCaT cells and are charactering altered function in EMT studies. We plan to take this portfolio of activity, including the collaborative anti-SLPI augmentation of paclitaxel xenograft findings forward for translation to the clinic.
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