Inhibition of cytoplasmic EZH2 induces antitumor activity through stabilization of the DLC1 tumor suppressor protein.

mRNA expression of the DLC1 tumor suppressor gene is downregulated in many lung cancers and their derived cell lines, with DLC1 protein levels being low or absent. Although the role of increased EZH2 methyltransferase in cancer is usually attributed to its histone methylation, we unexpectedly observed that post-translational destabilization of DLC1 protein is common and attributable to its methylation by cytoplasmic EZH2, leading to CUL-4A ubiquitin-dependent proteasomal degradation of DLC1. Furthermore, siRNA knockdown of KRAS in several lines increases DLC1 protein, associated with a drastic reduction in cytoplasmic EZH2. Pharmacologic inhibition of EZH2, CUL-4A, or the proteasome can increase the steady-state level of DLC1 protein, whose tumor suppressor activity is further increased by AKT and/or SRC kinase inhibitors, which reverse the direct phosphorylation of DLC1 by these kinases. These rational drug combinations induce potent tumor growth inhibition, with markers of apoptosis and senescence, that is highly dependent on DLC1 protein.

GPCRs get fatty: the role of G protein-coupled receptor signaling in the development and progression of nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD), characterized by the abnormal deposition of lipids within the liver not due to alcohol consumption, is a growing epidemic affecting over 30% of the United States population. Both simple fatty liver and its more severe counterpart, nonalcoholic steatohepatitis, represent one of the most common forms of liver disease. Recently, several G protein-coupled receptors have emerged as targets for therapeutic intervention for these disorders. These include those with known hepatic function as well as those involved in global metabolic regulation. In this review, we highlight these emerging therapeutic targets, focusing on several common themes including their activation by microbial metabolites, stimulatory effect on insulin and incretin secretion, and contribution to glucose tolerance. The overlap in ligands, localization, and downstream effects of activation indicate the interdependent nature of these receptors and highlight the importance of this signaling family in the development and prevention of NAFLD.

SRC and ERK cooperatively phosphorylate DLC1 and attenuate its Rho-GAP and tumor suppressor functions.

SRC and ERK kinases control many cell biological processes that promote tumorigenesis by altering the activity of oncogenic and tumor suppressor proteins. We identify here a physiological interaction between DLC1, a focal adhesion protein and tumor suppressor, with SRC and ERK. The tumor suppressor function of DLC1 is attenuated by phosphorylation of tyrosines Y451 and Y701 by SRC, which down-regulates DLC1's tensin-binding and Rho-GAP activities. ERK1/2 phosphorylate DLC1 on serine S129, which increases both the binding of SRC to DLC1 and SRC-dependent phosphorylation of DLC1. SRC inhibitors exhibit potent antitumor activity in a DLC1-positive transgenic cancer model and a DLC1-positive tumor xenograft model, due to reactivation of the tumor suppressor activities of DLC1. Combined treatment of DLC1-positive tumors with SRC plus AKT inhibitors has even greater antitumor activity. Together, these findings indicate cooperation between the SRC, ERK1/2, and AKT kinases to reduce DLC1 Rho-GAP and tumor suppressor activities in cancer cells, which can be reactivated by the kinase inhibitors.

Efficacy of a nitric oxide dressing in decreasing bacterial counts on human skin.

OBJECTIVE: Inhibiting the proliferation of skin bacteria, using nitric oxide (NO), is a potential strategy to prevent infections. This study evaluated the efficacy of using a new NO releasing film dressing to decrease resident human bacterial skin flora compared with the measured microbial activity underneath control sterile Tegaderm transparent dressings. METHODS: A within-subjects design using a sample of convenience compared the bacterial counts under the skin of experimental dressings to those under control dressings. NO releasing film dressings (three) and control dressings (three) were applied without antiseptic preparation to the intact skin on the backs of 67 healthy volunteers. Subsequent skin cultures were obtained from underneath dressing pairs (one experimental and one control) on days three, five, and seven after application. Baseline microflora bacterial counts from uncovered skin was obtained on day three of the study. Comparisons of bacterial counts were analysed. RESULTS: On days three, five and seven, the experimental NO releasing film dressings demonstrated a statistically significant reduction in bacterial count compared with the control dressings. CONCLUSION: The NO releasing film dressings resulted in significantly lower bacterial colony counts as compared to the control dressings at all time points. Incorporating a NO compound into a dressing has an antibacterial effect lasting a minimum of seven days.