Recent studies using glycogen synthase kinase-3B (GSK-3B)-deficient mouse embryonic fibroblasts suggest that GSK-3B positively regulates nuclear factor KB (NFKB)-mediated gene transcription. Because NFKB is suggested to participate in cell proliferation and survival pathways in pancreatic cancer, we investigated the role of GSK-3B in regulating these cellular processes. Herein, we show that pancreatic cancer cells contain a pool of active GSK-3B and that pharmacologic inhibition of GSK-3 kinase activity using small molecule inhibitors or genetic depletion of GSK-3B by RNA interference leads to decreased cancer cell proliferation and survival. Mechanistically, we show that GSK-3B influences NFKBmediated gene transcription at a point distal to the IK kinase complex, as only ectopic expression of the NFKB subunits p65/p50, but not an IK kinase B constitutively active mutant, could rescue the decreased cellular proliferation and survival associated with GSK-3B inhibition. Taken together, our results simultaneously identify a previously unrecognized role for GSK-3B in cancer cell survival and proliferation and suggest GSK-3B as a potential therapeutic target in the treatment of pancreatic cancer. (Cancer Res 2005; 65(6): 2076-81)

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.

Actin reorganization at the immunological synapse is required for the amplification and generation of a functional immune response. Using small interfering RNA, we show here that dynamin 2 (Dyn2), a large GTPase involved in receptor-mediated internalization, did not alter antibody-mediated T cell receptor internalization but considerably affected T cell receptor-stimulated T cell activation by regulating multiple biochemical signaling pathways and the accumulation of F-actin at the immunological synapse. Moreover, Dyn2 interacted directly with the Rho family guanine nucleotide exchange factor Vav1, and this interaction was required for T cell activation. These data identify a functionally important interaction between Dyn2 and Vav1 that regulates actin reorganization and multiple signaling pathways in T lymphocytes.

The discovery of the rules governing the inhibition of the various HDAC isoforms is likely to be key to identifying improved therapeutics that act as epigenetic modulators of gene transcription. Herein we present results on the modification of the CAP region of a set of triazolylphenyl-based HDACIs, and show that the nature of substitution on the phenyl ring plays a role in their selectivity for HDAC1 versus HDAC6, with low to moderate selectivity (2-51-fold) being achieved. In light of the valuable selectivity and potency that were identified for the triazolylphenyl ligand 6b in the inhibition of HDAC6 (IC50 = 1.9 nM), this compound represents a valuable research tool and a candidate for further chemical modifications. Lastly, these new HDACIs were studied for both their anticancer and antimalarial activity, which serve to validate the superior activity of the HDACI 10c.