Herein, we show that the hematopoietic-specific GEF VAV1 is ectopically expressed in primary pancreatic adenocarcinomas due to demethylation of the gene promoter. Interestingly, VAV1-positive tumors had a worse survival rate compared to VAV1-negative tumors. Surprisingly, even in the presence of oncogenic KRAS, VAV1 RNAi abrogates neoplastic cellular proliferation in vitro and in vivo, thus identifying Vav1 as a growth-stimulatory protein in this disease. Vav1 acts synergistically with the EGF receptor to stimulate pancreatic tumor cell proliferation. Mechanistically, the effects of Vav1 require its GEF activity and the activation of Rac1, PAK1, and NF-kappaB and involve cyclin D1 upregulation. Thus, the discovery of prooncogenic pathways regulated by Vav1 makes it an attractive target for therapeutic intervention.

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We have assessed the Immunogold Cell-Labeling System (IGS) for potential use in the clinical laboratory. In this technique, cell suspensions incubated with monoclonal mouse antibodies are reacted with anti-mouse antibodies labeled with colloidal gold. Surface marker cells, bearing dark blue-black granules, are easily distinguished by light microscopy. The percentages of T cells, T cell subsets, B cells, monocytes, or granulocytes identified by IGS corresponds with numbers obtained by flow cytometry analysis or immunofluorescence studies. Results by IGS and flow cytometry were similar for samples from patients with aberrant lymphocyte populations (e.g., leukemias) or from transplant recipients. IGS may thus be a useful diagnostic technique for studying neoplasias or other immunologically mediated disorders. This technique can also be used to characterize the surface phenotype of leukemic cell lines. The sensitivity and accuracy of IGS can be evaluated by measurements of different cell lines mixed in predetermined ratios.