Recent advances in immuno-oncology and its application to urological cancers.

Recent advances in immuno-oncology have the potential to transform the practice of medical oncology. Antibodies directed against negative regulators of T-cell function (checkpoint inhibitors), engineered cell therapies and innate immune stimulators, such as oncolytic viruses, are effective in a wide range of cancers. Immune'based therapies have had a clinically meaningful impact on the treatment of advanced melanoma, and the lessons regarding use of single agents and combinations in melanoma may be applicable to the treatment of urological cancers. Checkpoint inhibitors, cytokine therapy and therapeutic vaccines are already showing promise in urothelial bladder cancer, renal cell carcinoma and prostate cancer. Critical areas of future immuno-oncology research include the prospective identification of patients who will respond to current immune-based cancer therapies and the identification of new therapeutic agents that promote immune priming in tumours, and increase the rate of durable clinical responses.

Multiple proteins mediate IQGAP1-stimulated cell migration.

Cell migration, a highly complex physiological phenomenon that requires the co-ordinated and tightly regulated function of several proteins, is mediated by a number of signalling pathways. Elucidation of the molecular mechanisms of cell migration impacts our comprehension of numerous cell functions, ranging from development and immune surveillance to angiogenesis and metastasis. The scaffold protein IQGAP1, which binds multiple proteins and regulates their functions, promotes cell motility. Many of the IQGAP1 binding proteins have been implicated in cell migration. In this study, we employed a multifaceted strategy to identify proteins that contribute to IQGAP1-stimulated cell migration. Using specific IQGAP1 point mutant constructs, an interaction with actin was shown to be essential for IQGAP1 to increase cell migration. In contrast, eliminating the binding of Ca(2+)/calmodulin, but not Ca(2+)-free calmodulin, augmented the ability of IQGAP1 to stimulate cell migration. Consistent with these findings, selective inhibition of calmodulin function at the plasma membrane with a specific peptide inhibitor enhanced cell migration mediated by IQGAP1. Interestingly, immunofluorescence staining and confocal microscopy suggest that localization of Cdc42 at the leading edge is not necessary for maximal migration of epithelial cells. Coupled with the observations that Cdc42 and Rac1 contribute to IQGAP1-stimulated cell migration, these data suggest that IQGAP1 serves as a junction to integrate multiple signalling molecules to facilitate cell migration.

IQGAP1 stimulates proliferation and enhances tumorigenesis of human breast epithelial cells.

The scaffold protein IQGAP1 integrates signaling pathways and participates in diverse cellular activities. IQGAP1 is overexpressed in a number of human solid neoplasms, but its functional role in tumorigenesis has not been previously evaluated. Here we report that IQGAP1 contributes to neoplastic transformation of human breast epithelial cells. The amount of IQGAP1 in breast carcinoma is greater than that in normal tissue, with highly metastatic breast epithelial cells expressing the highest levels. Overexpression of IQGAP1 enhances proliferation of MCF-7 breast epithelial cells. Reduction of endogenous IQGAP1 by RNA interference impairs both serum-dependent and anchorage-independent growth of MCF-7 cells. Consistent with these in vitro observations, immortalized MCF-7 cells overexpressing IQGAP1 form invasive tumors in immunocompromised mice, whereas tumors derived from MCF-7 cells with stable knockdown of IQGAP1 are smaller and less invasive. In vitro analysis with selected IQGAP1 mutant constructs and a chemical inhibitor suggests that actin, Cdc42/Rac1, and the mitogen-activated protein kinase pathway contribute to the mechanism by which IQGAP1 increases cell invasion. Collectively, our data reveal that IQGAP1 enhances mammary tumorigenesis, suggesting that it may be a target for therapeutic intervention.

Disruption of cyclin D3 blocks proliferation of normal B-1a cells, but loss of cyclin D3 is compensated by cyclin D2 in cyclin D3-deficient mice.

Peritoneal B-1a cells differ from splenic B-2 cells in the molecular mechanisms that control G(0)-S progression. In contrast to B-2 cells, cyclin D2 is up-regulated in a rapid and transient manner in phorbol ester (PMA)-stimulated B-1a cells, whereas cyclin D3 does not accumulate until late G(1) phase. This nonoverlapping expression of cyclins D2 and D3 suggests distinct functions for these proteins in B-1a cells. To investigate the contribution of cyclin D3 in the proliferation of B-1a cells, we transduced p16(INK4a) peptidyl mimetics (TAT-p16) into B-1a cells before cyclin D3 induction to specifically block cyclin D3-cyclin-dependent kinase 4/6 assembly. TAT-p16 inhibited DNA synthesis in B-1a cells stimulated by PMA, CD40L, or LPS as well as endogenous pRb phosphorylation by cyclin D-cyclin-dependent kinase 4/6. Unexpectedly, however, cyclin D3-deficient B-1a cells proliferated in a manner similar to wild-type B-1a cells following PMA or LPS stimulation. This was due, at least in part, to the compensatory sustained accumulation of cyclin D2 throughout G(0)-S progression. Taken together, experiments in which cyclin D3 was inhibited in real time demonstrate the key role this cyclin plays in normal B-1a cell mitogenesis, whereas experiments with cyclin D3-deficient B-1a cells show that cyclin D2 can compensate for cyclin D3 loss in mutant mice.

Antigen receptor-mediated changes in glucose metabolism in B lymphocytes: role of phosphatidylinositol 3-kinase signaling in the glycolytic control of growth.

The bioenergetic response of B lymphocytes is subject to rapid changes following antigen encounter in order to provide ATP and anabolic precursors necessary to support growth. However, the pathways involved in glucose acquisition and metabolism are unknown. We find that B lymphocytes rapidly increase glucose uptake and glycolysis following B-cell antigen receptor (BCR) crosslinking. Inhibition of glycolysis blocks BCR-mediated growth. Prior to S-phase entry, glucose metabolism shifts from primarily glycolytic to include the pentose phosphate pathway. BCR-induced glucose utilization is dependent upon phosphatidylinositol 3-kinase (PI-3K) activity as evidenced by inhibition of glucose uptake and glycolysis with LY294002 treatment of normal B cells and impaired glucose utilization in B cells deficient in the PI-3K regulatory subunit p85alpha. Activation of Akt is sufficient to increase glucose utilization in B cells. We find that glucose utilization is inhibited by coengagement of the BCR and FcgammaRIIB, suggesting that limiting glucose metabolism may represent an important mechanism underlying FcgammaRIIB-mediated growth arrest. Taken together, these findings demonstrate that both growth-promoting BCR signaling and growth-inhibitory FcgammaRIIB signaling modulate glucose energy metabolism. Manipulation of these pathways may prove to be useful in the treatment of lymphoproliferative disorders, wherein clonal expansion of B lymphocytes plays a role.

Highly efficient molecular delivery into mammalian cells using carbon nanotube spearing.

Introduction of exogenous DNA into mammalian cells represents a powerful approach for manipulating signal transduction. The available techniques, however, are limited by low transduction efficiency and low cell viability after transduction. Here we report a highly efficient molecular delivery technique, named nanotube spearing, based on the penetration of nickel-embedded nanotubes into cell membranes by magnetic field driving. DNA plasmids containing the enhanced green fluorescent protein (EGFP) sequence were immobilized onto the nanotubes, and subsequently speared into targeted cells. We have achieved an unprecedented high transduction efficiency in Bal17 B-lymphoma, ex vivo B cells and primary neurons with high viability after transduction. This technique may provide a powerful tool for highly efficient gene transfer into a variety of cells, especially the hard-to-transfect cells.

Identification and characterization of the Cdc42-binding site of IQGAP1.

IQGAP1 is a multi-domained protein that integrates signaling of the Rho family GTPase Cdc42 with regulation of the cytoskeleton. Using SPOT analysis and in vitro peptide competition assays we have identified a 24 amino acid region of IQGAP1 that is necessary for Cdc42 binding. Both in vitro and in vivo analyses reveal that deletion of this sequence abolishes binding of IQGAP1 to Cdc42. In addition, the ability of IQGAP1 to increase the amount of active Cdc42 in cells is abrogated upon removal of this region. An IQGAP1 mutant lacking the Cdc42 binding site mislocalizes to the cell periphery. These observations specifically define a short sequence of IQGAP1 that is required for its interaction with Cdc42 and demonstrate that Cdc42 binding is necessary for the normal subcellular distribution of IQGAP1.

B cell receptor-induced cAMP-response element-binding protein activation in B lymphocytes requires novel protein kinase Cdelta.

The cAMP-response element-binding protein (CREB) is activated by phosphorylation on Ser-133 and plays a key role in the proliferative and survival responses of mature B cells to B cell receptor (BCR) signaling. The signal link between the BCR and CREB activation depends on a phorbol ester (phorbol 12-myristate 13-acetate)-sensitive protein kinase C (PKC) activity and not protein kinase A or calmodulin kinase; however, the identity and role of the PKC(s) activity has not been elucidated. We found the novel PKCdelta (nPKCdelta) activator bistratene A is sufficient to induce CREB phosphorylation in murine splenic B cells. The pharmacological inhibitor Gö6976, which targets conventional PKCs and PKCmu, has no effect on CREB phosphorylation, whereas the nPKCdelta inhibitor rottlerin blocks CREB phosphorylation following BCR cross-linking. Bryostatin 1 selectively prevents nPKCdelta depletion by phorbol 12-myristate 13-acetate when coapplied, coincident with protection of BCR-induced CREB phosphorylation. Ectopic expression of a kinase-inactive nPKCdelta blocks BCR-induced CREB phosphorylation in A20 B cells. In addition, BCR-induced CREB phosphorylation is significantly diminished in nPKCdelta-deficient splenic B cells in comparison with wild type mice. Consistent with the essential role for Bruton's tyrosine kinase and phospholipase Cgamma2 in mediating PKC activation, Bruton's tyrosine kinase- and phospholipase Cgamma2-deficient B cells display defective CREB phosphorylation by the BCR. We also found that p90 RSK directly phosphorylates CREB on Ser-133 following BCR cross-linking and is positioned downstream of nPKCdelta. Taken together, these results suggest a model in which BCR engagement leads to the phosphorylation of CREB via a signaling pathway that requires nPKCdelta and p90 RSK in mature B cells.

IQGAP1 is a component of Cdc42 signaling to the cytoskeleton.

The Ras-GAP related protein IQGAP1 binds several proteins, including actin, calmodulin, E-cadherin and the Rho family GTPase Cdc42. To gain insight into its in vivo function, IQGAP1 was overexpressed in mammalian cells. Transfection of IQGAP1 significantly increased the levels of active, GTP-bound Cdc42, resulting in the formation of peripheral actin microspikes. By contrast, transfection of an IQGAP1 mutant lacking part of the GAP-related domain (IQGAP1deltaGRD) substantially decreased the amount of GTP-bound Cdc42 in cell lysates. Consistent with these findings, IQGAP1DeltaGRD blocked Cdc42 function in cells that stably overexpress constitutively active Cdc42 and abrogated the effect of bradykinin on Cdc42. In cells transfected with IQGAP1deltaGRD, bradykinin was unable to activate Cdc42, translocate Cdc42 to the membrane fraction, or induce filopodia production. IQGAP1deltaGRD transfection altered cellular morphology, producing small, round cells that closely resemble Cdc42-/- cells. Some insight into the mechanism was provided by in vitro analysis, which revealed that IQGAP1deltaGRD increased the intrinsic GTPase activity of Cdc42, thereby increasing the amount of inactive, GDP-bound Cdc42. These data imply that IQGAP1 has a crucial role in transducing Cdc42 signaling to the cytoskeleton.

IQGAP1 promotes cell motility and invasion.

The dynamic processes of cell migration and invasion are largely coordinated by Rho family GTPases. The scaffolding protein IQGAP1 binds to Cdc42, increasing the amount of active Cdc42 both in vitro and in cells. Here we show that overexpression of IQGAP1 in mammalian cells enhances cell migration in a Cdc42- and Rac1-dependent manner. Importantly, cell motility was significantly decreased both by knock down of endogenous IQGAP1 using small interfering RNA and by transfection of a dominant negative IQGAP1 construct, IQGAP1DeltaGRD. Cell invasion was similarly altered by manipulating intracellular IQGAP1 concentrations. Moreover, invasion mediated by constitutively active Cdc42 was attenuated by IQGAP1DeltaGRD. Thus, IQGAP1 has a fundamental role in cell motility and invasion.