Shewanella oneidensis Hfq promotes exponential phase growth, stationary phase culture density, and cell survival.

BACKGROUND: Hfq is an RNA chaperone protein that has been broadly implicated in sRNA function in bacteria. Here we describe the construction and characterization of a null allele of the gene that encodes the RNA chaperone Hfq in Shewanella oneidensis strain MR-1, a dissimilatory metal reducing bacterium. RESULTS: Loss of hfq in S. oneidensis results in a variety of mutant phenotypes, all of which are fully complemented by addition of a plasmid-borne copy of the wild type hfq gene. Aerobic cultures of the hfq∆ mutant grow more slowly through exponential phase than wild type cultures, and hfq∆ cultures reach a terminal cell density in stationary phase that is ~2/3 of that observed in wild type cultures. We have observed a similar growth phenotype when the hfq∆ mutant is cultured under anaerobic conditions with fumarate as the terminal electron acceptor, and we have found that the hfq∆ mutant is defective in Cr(VI) reduction. Finally, the hfq∆ mutant exhibits a striking loss of colony forming units in extended stationary phase and is highly sensitive to oxidative stress induced by H2O2 or methyl viologen (paraquat). CONCLUSIONS: The hfq mutant in S. oneidensis exhibits pleiotropic phenotypes, including a defect in metal reduction. Our results also suggest that hfq mutant phenotypes in S. oneidensis may be at least partially due to increased sensitivity to oxidative stress.

Napabucasin Drug-Drug Interaction Potential, Safety, Tolerability, and Pharmacokinetics Following Oral Dosing in Healthy Adult Volunteers.

Napabucasin is an orally administered reactive oxygen species generator that is bioactivated by the intracellular antioxidant nicotinamide adenine dinucleotide phosphate:quinone oxidoreductase 1. Napabucasin induces cell death in cancer cells, including cancer stem cells. This phase 1 study (NCT03411122) evaluated napabucasin drug-drug interaction potential for 7 cytochrome P450 (CYP) enzymes and the breast cancer resistance protein transporter/organic anion transporter 3. Healthy volunteers who tolerated napabucasin during period 1 received probe drugs during period 2, and in period 3 received napabucasin (240 mg twice daily; days 1-11) plus a phenotyping cocktail containing omeprazole (CYP2C19), caffeine (CYP1A2), flurbiprofen (CYP2C9), bupropion (CYP2B6), dextromethorphan (CYP2D6), midazolam (CYP3A) (all oral; day 6), intravenous midazolam (day 7), repaglinide (CYP2C8; day 8), and rosuvastatin (breast cancer resistance protein/organic anion transporter 3; day 9). Drug-drug interaction potential was evaluated in 17 of 30 enrolled volunteers. Napabucasin coadministration increased the area under the plasma concentration-time curve from time 0 extrapolated to infinity (geometric mean ratio [90% confidence interval]) of caffeine (124% [109.0%-141.4%]), intravenous midazolam (118% [94.4%-147.3%]), repaglinide (127% [104.7%-153.3%]), and rosuvastatin (213% [42.5%-1068.3%]) and decreased the area under the plasma concentration-time curve from time 0 extrapolated to infinity of dextromethorphan (71% [47.1%-108.3%]), bupropion (79% [64.6%-97.0%]), and hydroxybupropion (45% [15.7%-129.6%]). No serious adverse events/deaths were reported. Generally, napabucasin is not expected to induce/inhibit drug clearance to a clinically meaningful degree.

Obesity, cholesterol metabolism, and breast cancer pathogenesis.

Obesity and altered lipid metabolism are risk factors for breast cancer in pre- and post-menopausal women. These pathologic relationships have been attributed in part to the impact of cholesterol on the biophysical properties of cell membranes and to the influence of these changes on signaling events initiated at the membrane. However, more recent studies have indicated that the oxysterol 27-hydroxycholesterol (27HC), and not cholesterol per se, may be the primary biochemical link between lipid metabolism and cancer. The enzyme responsible for production of 27HC from cholesterol, CYP27A1, is expressed primarily in the liver and in macrophages. In addition, significantly elevated expression of this enzyme within breast tumors has also been observed. It is believed that 27HC, acting through the liver X receptor in macrophages and possibly other cells, is involved in maintaining organismal cholesterol homeostasis. It has also been shown recently that 27HC is an estrogen receptor agonist in breast cancer cells and that it stimulates the growth and metastasis of tumors in several models of breast cancer. These findings provide the rationale for the clinical evaluation of pharmaceutical approaches that interfere with cholesterol/27HC synthesis as a means to mitigate the impact of cholesterol on breast cancer pathogenesis. Cancer Res; 74(18); 4976-82. ©2014 AACR.