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BackgroundGlioblastoma is one of the deadliest forms of cancer, in part because of its highly invasive nature. The tumor suppressor PTEN is frequently mutated in glioblastoma and is known to contribute to the invasive phenotype. However the downstream events that promote invasion are not fully understood. PTEN loss leads to activation of the atypical protein kinase C, PKCι. We have previously shown that PKCι is required for glioblastoma cell invasion, primarily by enhancing cell motility. Here we have used time-lapse videomicroscopy to more precisely define the role of PKCι in glioblastoma.ResultsGlioblastoma cells in which PKCι was either depleted by shRNA or inhibited pharmacologically were unable to coordinate the formation of a single leading edge lamellipod. Instead, some cells generated multiple small, short-lived protrusions while others generated a diffuse leading edge that formed around the entire circumference of the cell. Confocal microscopy showed that this behavior was associated with altered behavior of the cytoskeletal protein Lgl, which is known to be inactivated by PKCι phosphorylation. Lgl in control cells localized to the lamellipod leading edge and did not associate with its binding partner non-muscle myosin II, consistent with it being in an inactive state. In PKCι-depleted cells, Lgl was concentrated at multiple sites at the periphery of the cell and remained in association with non-muscle myosin II. Videomicroscopy also identified a novel role for PKCι in the cell cycle. Cells in which PKCι was either depleted by shRNA or inhibited pharmacologically entered mitosis normally, but showed marked delays in completing mitosis.ConclusionsPKCι promotes glioblastoma motility by coordinating the formation of a single leading edge lamellipod and has a role in remodeling the cytoskeleton at the lamellipod leading edge, promoting the dissociation of Lgl from non-muscle myosin II. In addition PKCι is required for the transition of glioblastoma cells through mitosis. PKCι therefore has a role in both glioblastoma invasion and proliferation, two key aspects in the malignant nature of this disease.

Oncolytic virus (OV) therapy has emerged as a novel tool in our therapeutic arsenals for fighting cancer. As a live biologic agent, OV has the ability to target and selectively amplify at the tumor sites. We have reported that a vaccinia-based OV (Pexa-Vec) has shown good efficacy in preclinical models and in clinical trials. To give an additional tool to clinicians to allow both treatment of the tumor and improved visualization of tumor margins, we developed new viral-based platforms with 2 specific gene reporters. Methods: We incorporated the human sodium iodide symporter (hNIS) and the human somatostatin receptor 2 (hSSR2) in the vaccinia-based OV and tested viral constructs for their abilities to track and treat tumor development in vivo. Results: Early and high-level expression of hNIS is detrimental to the recombinant virus, leading to the aggregation of hNIS protein and early cell death. Putting hNIS under a late synthetic promoter allowed a higher functional expression of the protein and much stronger 123 I or 99 Tc uptake. In vivo, the hNIS-containing virus infected and amplified in the tumor site, showing a better efficacy than the parental virus. The hNIS expression at the tumor site allowed for the imaging of viral infection and tumor regression. Similarly, hSSR2-containing OV vaccinia infected and lysed cancer cells. Conclusion: When tumor-bearing mice were given hNIS-and hSSR2-containing OV, 99 Tc and 111 In signals coalesced at the tumor, highlighting the power of using these viruses for tumor diagnosis and treatment.