PARP inhibition as a prototype for synthetic lethal screens

Genetic interaction between glyoxylate pathway regulator UCC1 and La-motif-encoding SRO9 regulates stress response and growth rate improvement in Saccharomyces cerevisiae

Nonavailability of glucose as a carbon source results in glyoxylate pathway activation, which metabolizes nonfermentable carbon for energy generation in Saccharomyces cerevisiae. Ucc1p of S. cerevisiae inhibits activation of the glyoxylate pathway by targeting Cit2p, a key glyoxylate enzyme for ubiquitin-mediated proteasomal degradation when glucose is available as a carbon source. Sro9p, a La-motif protein involved in RNA biogenesis, interacts physically with the messenger RNA of UCC1; however, its functional relevance is yet to be discovered. This study presents binary epistatic interaction between UCC1 and SRO9, with functional implication on the growth rate, response to genotoxic stress, resistance to apoptosis, and petite mutation. Cells with ucc1Δsro9Δ, as their genetic background, exhibit alteration in morphology, improvement in growth rate, resistance to apoptosis, and petite mutation. Moreover, the study indicates a cross-link between ubiquitin-proteasome system and RNA biogenesis and metabolism, with applications in industrial fermentation and screening for cancer therapeutics.

Personalizing Chinese medicine by integrating molecular features of diseases and herb ingredient information: application to acute myeloid leukemia

Traditional Chinese Medicine (TCM) has been widely used as a complementary medicine in Acute Myeloid Leukemia (AML) treatment. In this study, we proposed a new classification of Chinese Medicines (CMs) by integrating the latest discoveries in disease molecular mechanisms and traditional medicine theory. We screened out a set of chemical compounds on basis of AML differential expression genes and chemical-protein interactions and then mapped them to Traditional Chinese Medicine Integrated Database. 415 CMs contain those compounds and they were categorized into 8 groups according to the Traditional Chinese Pharmacology. Pathway analysis and synthetic lethality gene pairs were applied to analyze the dissimilarity, generality and intergroup relations of different groups. We defined hub CM pairs and alternative CM groups based on the analysis result and finally proposed a formula to form an effective anti-AML prescription which combined the hub CM pairs with alternative CMs according to patients’ molecular features. Our method of formulating CMs based on patients’ stratification provides novel insights into the new usage of conventional CMs and will promote TCM modernization.

Glucosidase II beta subunit (GluIIβ) plays a role in autophagy and apoptosis regulation in lung carcinoma cells in a p53-dependent manner

PURPOSE

Glucosidase II plays a major role in regulating the post-translational modification of N-linked glycoproteins. Previously, we found that the beta subunit of glucosidase II (GluIIβ) levels are significantly increased in lung carcinoma tissues, indicating a potential role in lung tumorigenesis. Here, we investigated the role of GluIIβ in the regulation of autophagy and apoptosis in lung carcinoma- and immortalized human bronchial epithelial-derived cells.

METHODS

A selective glucosidase II inhibitor, bromoconduritol, was used to inhibit GluII enzyme activity and a siRNA-based technology was used to suppress the expression of the GluIIβ encoding gene PRKCSH in lung carcinoma cells differing in p53 status. Cell viability was assessed using a MTT assay, cell cycle progression was assessed using flow cytometry, autophagy was assessed using Western blotting and apoptosis was assessed using an annexin V-FITC/PI double labeling method.

RESULTS

We found that GluIIβ inhibition resulted in the induction of autophagy in all cell lines tested, but apoptosis in only wild-type p53 cells. We also found that GluIIβ inhibition dose-dependently decreased activation of the EGFR/RTK and PI3K/AKT signaling pathways. Although the apoptosis inducing effect of GluIIβ inhibition appeared to be p53-dependent, we found that a combined treatment with lysosomal inhibitors to block autophagy enhanced the apoptotic effect of GluIIβ inhibition in both wild-type p53 and p53-null cells.

CONCLUSIONS

Our data indicate that GluIIβ inhibition results in autophagy and apoptosis in lung carcinoma-derived cells, supporting the hypothesis that this enzyme may play a role in blocking these two tumor suppressive processes. Since blocking autophagy by lysosomal inhibitors enhanced the apoptosis-inducing effect of bromoconduritol, independent of p53 status, their combined use may hold promise for the treatment of cancer, particularly lung cancer.