Sourcing Antibiotic-Resistant Escherichia coli in Aquatic Ecosystems: A Combined Laboratory and Field Module.

The emergence of antibiotic-resistant bacteria represents a growing threat in aquatic ecosystems. In this combined field and laboratory activity, students will determine whether Escherichia coli, an indicator bacteria species commonly found in aquatic ecosystems, shows signs of resistance to common antibiotics. In addition, students will use molecular biology techniques to identify whether Escherichia coli cells sourced from different hosts (i.e., phylogroups) show different patterns of antibiotic resistance. This activity will help students to gain experience in environmental microbiology, environmental science, molecular biology, and public health. This module is also designed to provide instructors with flexibility to pick and choose activities that best meet the needs of their class or research program.

Synthesis and evaluation of etoposide and podophyllotoxin analogs against topoisomerase IIα and HCT-116 cells.

Etoposide is a widely-used anticancer agent that targets human type II topoisomerases. Evidence suggests that metabolism of etoposide in myeloid progenitor cells is associated with translocations involved in leukemia development. Previous studies suggest halogenation at the C-2' position of etoposide reduces metabolism. Halogens were introduced into the C-2' position by electrophilic aromatic halogenation onto etoposide (ETOP, 1), podophyllotoxin (PPT, 2), and 4-dimethylepipodophyllotoxin (DMEP, 3), and to bridge the gap of knowledge regarding the activity of these metabolically stable analogs. Five halogenated analogs (6-10) were synthesized. Analogs 8-10 displayed variable ability to inhibit DNA relaxation. Analog 9 was the only analog to show concentration-dependent enhancement of Top2-mediated DNA cleavage. Dose response assay results indicated that 8 and 10 were most effective at decreasing the viability of HCT-116 and A549 cancer cell lines in culture. Flow cytometry with 8 and 10 in HCT-116 cells provide evidence of sub-G1 cell populations indicative of apoptosis. Taken together, these results indicate C-2' halogenation of etoposide and its precursors, although metabolically stable, decreases overall activity relative to etoposide.

Enoxacin and Epigallocatechin Gallate (EGCG) Act Synergistically to Inhibit the Growth of Cervical Cancer Cells in Culture.

Cervical cancer is a major cause of death in females worldwide. While survival rates have historically improved, there remains a continuous need to identify novel molecules that are effective against this disease. Here, we show that enoxacin, a drug most commonly used to treat a broad array of bacterial infections, is able to inhibit growth of the cervical cancer cells. Furthermore, our data show that epigallocatechin gallate (EGCG), a plant bioactive compound abundant in green tea, and known for its antioxidant effects, similarly functions as an antiproliferative agent. Most importantly, we provide evidence that EGCG functions synergistically against cancer cell proliferation in combined treatment with enoxacin. These data collectively suggest that enoxacin and EGCG may be useful treatment options for cases of cervical cancer.

The cardiac glycoside convallatoxin inhibits the growth of colorectal cancer cells in a p53-independent manner.

Cardiac glycosides are plant-derived molecules that have shown antiproliferative properties against cancer cells, though the mechanism of action is not completely understood. We show that one cardiac glycoside, convallatoxin, presents antiproliferative effects against colorectal cancer cells in culture and that the resulting cell death is independent of the p53 tumor suppressor. Our data suggest that convallatoxin may be useful in the treatment of cancers that harbor inactivating mutations in the p53 signaling pathway.

ISG20L1 is a p53 family target gene that modulates genotoxic stress-induced autophagy.

BACKGROUND: Autophagy is characterized by the sequestration of cytoplasm and organelles into multimembrane vesicles and subsequent degradation by the cell's lysosomal system. It is linked to many physiological functions in human cells including stress response, protein degradation, organelle turnover, caspase-independent cell death and tumor suppression. Malignant transformation is frequently associated with deregulation of autophagy and several tumor suppressors can modulate autophagic processes. The tumor suppressor p53 can induce autophagy after metabolic or genotoxic stress through transcriptionally-dependent and -independent mechanisms. In this study we expand on the former mechanism by functionally characterizing a p53 family target gene, ISG20L1 under conditions of genotoxic stress. RESULTS: We identified a p53 target gene, ISG20L1, and show that transcription of the gene can be regulated by all three p53 family members (p53, p63, and p73). We generated an antibody to ISG20L1 and found that it localizes to the nucleolar and perinucleolar regions of the nucleus and its protein levels increase in a p53- and p73-dependent manner after various forms of genotoxic stress. When ectopically expressed in epithelial cancer-derived cell lines, ISG20L1 expression decreased clonogenic survival without a concomitant elevation in apoptosis and this effect was partially rescued in cells that were ATG5 deficient. Knockdown of ISG20L1 did not alter 5-FU induced apoptosis as assessed by PARP and caspase-3 cleavage, sub-G1 content, and DNA laddering. Thus, we investigated the role of ISG20L1 in autophagy, a process commonly associated with type II cell death, and found that ISG20L1 knockdown decreased levels of autophagic vacuoles and LC3-II after genotoxic stress as assessed by electron microscopy, biochemical, and immunohistochemical measurements of LC3-II. CONCLUSIONS: Our identification of ISG20L1 as a p53 family target and discovery that modulation of this target can regulate autophagic processes further strengthens the connection between p53 signaling and autophagy. Given the keen interest in targeting autophagy as an anticancer therapeutic approach in tumor cells that are defective in apoptosis, investigation of genes and signaling pathways involved in cell death associated with autophagy is critical.

DeltaNp63 antagonizes p53 to regulate mesoderm induction in Xenopus laevis.

p63, a homolog of the tumor suppressor p53, is critical for the development and maintenance of complex epithelia. The developmentally regulated p63 isoform, DeltaNp63, can act as a transcriptional repressor, but the link between the transcriptional functions of p63 and its biological roles is unclear. Based on our initial finding that the mesoderm-inducing factor activin A is suppressed by DeltaNp63 in human keratinocytes, we investigated the role of DeltaNp63 in regulating mesoderm induction during early Xenopus laevis development. We find that down-regulation of DeltaNp63 by morpholino injection in the early Xenopus embryo potentiates mesoderm formation whereas ectopic expression of DeltaNp63 inhibits mesoderm formation. Furthermore, we show that mesodermal induction after down-regulation of DeltaNp63 is dependent on p53. We propose that a key function for p63 in defining a squamous epithelial phenotype is to actively suppress mesodermal cell fates during early development. Collectively, we show that there is a distinct requirement for different p53 family members during the development of both mesodermal and ectodermal tissues. These findings have implications for the role of p63 and p53 in both development and tumorigenesis of human epithelia.

Delta Np63 alpha expression is regulated by the phosphoinositide 3-kinase pathway.

p63 is a homologue of p53 that functions to maintain progenitor cell populations in stratified epithelia. Delta Np63 alpha is overexpressed in epithelial cancers and has been shown to have oncogenic properties. We have previously reported that inhibition of epidermal growth factor receptor signaling results in a decrease in Delta Np63 alpha expression. Here, we demonstrate Delta Np63 alpha is a target of the phosphoinositide-3-kinase (PI3K) pathway downstream of the epidermal growth factor receptor. Treatment of keratinocytes with epidermal growth factor results in an increase in Delta Np63 alpha expression at the mRNA level, which is abrogated by inhibition of PI3K but not mitogen-activated protein kinase signaling. Small interfering RNA-mediated knockdown of the p110 beta catalytic subunit of PI3K results in a decrease in Delta Np63 alpha protein levels in keratinocytes. The results presented herein suggest that regulation of Delta Np63 alpha expression by the PI3K pathway plays a critical role in the survival and proliferative capacity of squamous epithelia.