Pooled microbiological findings and efficacy outcomes by pathogen in adults with community-acquired bacterial pneumonia from the Lefamulin Evaluation Against Pneumonia (LEAP) 1 and LEAP 2 phase 3 trials of lefamulin versus moxifloxacin.

OBJECTIVES: Lefamulin, a pleuromutilin antibiotic approved for community-acquired bacterial pneumonia (CABP), was evaluated for microbiological efficacy in a prespecified pooled analysis of LEAP 1 and 2 phase 3 clinical trial data in patients with CABP. METHODS: In LEAP 1, adults (PORT risk class III‒V) received intravenous (IV) lefamulin 150 mg every 12 h (q12h) for 5‒7 days or moxifloxacin 400 mg every 24 h (q24h) for 7 days, with optional IV-to-oral switch. In LEAP 2, adults (PORT II‒IV) received oral lefamulin 600 mg q12h for 5 days or moxifloxacin 400 mg q24h for 7 days. Primary outcomes were early clinical response (ECR) at 96 ± 24 h after treatment start and investigator assessment of clinical response (IACR) 5‒10 days after the last dose. Secondary outcomes included ECR and IACR in patients with a baseline CABP pathogen (detected via culture, urinary antigen testing, serology and/or real-time PCR). RESULTS: Baseline CABP pathogens were detected in 709/1289 patients (55.0%; microbiological intention-to-treat population). The most frequently identified pathogens were Streptococcus pneumoniae (61.9% of patients) and Haemophilus influenzae (29.9%); 25.1% had atypical pathogens and 33.1% had polymicrobial infections. Pathogens were identified most frequently by PCR from sputum, followed by culture from respiratory specimens. In patients with baseline CABP pathogens, ECR rates were 89.3% (lefamulin) and 93.0% (moxifloxacin); IACR success rates were 83.2% and 86.7%, respectively. Results were consistent across CABP pathogens, including drug-resistant isolates and polymicrobial infections. CONCLUSION: Lefamulin is a valuable IV and oral monotherapy option for empirical and directed CABP treatment in adults.

Withaferin A inhibits breast cancer invasion and metastasis at sub-cytotoxic doses by inducing vimentin disassembly and serine 56 phosphorylation.

Withaferin A (WFA) is purified from the plant Withania somnifera and inhibits the vimentin cytoskeleton. Vimentin overexpression in cancer correlates with metastatic disease, induction of epithelial to mesenchymal transition and reduced patient survival. As vimentin functions in cell motility, we wanted to test the hypothesis that WFA inhibits cancer metastasis by disrupting vimentin function. These data showed that WFA had weak cytotoxic and apoptotic activity at concentrations less than or equal to 500 nM, but retained potent anti-invasive activity at these low doses. Imaging of breast cancer cell lines revealed that WFA induces perinuclear vimentin accumulation followed by rapid vimentin depolymerization. A concomitant induction of vimentin ser56 phosphorylation was observed, which is consistent with vimentin disassembly. Structure activity relationships were established using a set of chemically modified WFA analogs and showed that the predicted vimentin-binding region of WFA is necessary to induce vimentin ser56 phosphorylation and for its anti-invasive activity. Pharmacokinetic studies in mice revealed that WFA reaches peak concentrations up to 2 µM in plasma with a half-life of 1.36 hr following a single 4 mg/kg dose. In a breast cancer metastasis mouse model, WFA showed dose-dependent inhibition of metastatic lung nodules and induced vimentin ser56 phosphorylation, with minimal toxicity to lung tissue. Based upon these studies, we conclude that WFA is a potent breast cancer anti-metastatic agent and the anti-metastatic activity of WFA is, at least in part, mediated through its effects on vimentin and vimentin ser56 phosphorylation.

Silencing of TMS1/ASC promotes resistance to anoikis in breast epithelial cells.

Ductal carcinoma in situ (DCIS) is characterized by ductal epithelial cells that have filled the luminal space of the breast duct and survive despite loss of extracellular matrix contact. In normal epithelial cells, the loss of such contact triggers a form of apoptosis known as detachment-induced apoptosis or "anoikis." TMS1/ASC is a bipartite adaptor molecule that participates in inflammatory and apoptotic signaling pathways. Epigenetic silencing of TMS1 has been observed in a significant proportion of human breast and other cancers, but the mechanism by which TMS1 silencing contributes to carcinogenesis is unknown. Here, we examined the role of TMS1 in anoikis. We found that TMS1 expression is induced in response to loss of substratum interactions in breast epithelial cells. siRNA-mediated knockdown of TMS1 leads to anoikis resistance, due in part to the persistent activation of extracellular signal-regulated kinase and an impaired ability to up-regulate the BH3-only protein Bim. We further show that the detachment-induced cleavage of procaspase-8, a newly described mediator of cellular adhesion, is significantly inhibited in the absence of TMS1. These data show a novel upstream role for TMS1 in the promotion of anoikis, and suggest that silencing of TMS1 may contribute to the pathogenesis of breast cancer by allowing epithelial cells to bypass cell death in the early stages of breast cancer development. This conclusion is supported by in vivo data showing that TMS1 is selectively down-regulated in the aberrant epithelial cells filling the lumen of the breast duct in a subset of primary DCIS lesions.

Cyclic adenosine 5'-monophosphate-dependent sphingosine-1-phosphate biosynthesis induces human CYP17 gene transcription by activating cleavage of sterol regulatory element binding protein 1.

In the human adrenal cortex, ACTH activates steroid hormone biosynthesis by acutely increasing cholesterol delivery to the mitochondrion and chronically increasing the transcription of steroidogenic genes (including CYP17) via a cAMP-dependent pathway. In the present study, we characterized the role of sphingolipids in ACTH-dependent steroidogenesis. H295R human adrenocortical cells were treated with ACTH or dibutyryl cAMP (Bt2cAMP) and the content of several sphingolipid species quantified by mass spectrometry. Both ACTH and Bt2cAMP decreased cellular amounts of several sphingolipids, including sphingomyelin, ceramides, and sphingosine and stimulating the activity of sphingosine kinase and increasing the release of sphingosine-1-phosphate (S1P) into the media. S1P increased CYP17 mRNA expression by promoting the cleavage and nuclear localization of sterol regulatory element binding protein (SREBP) 1. Chromatin immunoprecipitation assays revealed that Bt2cAMP and S1P increased acetylation of histone H3 and promoted binding of SREBP1 to the -520/-331 region of the CYP17 promoter. In summary, our studies demonstrate a role for sphingolipid metabolism and SREBP1 in ACTH-dependent CYP17 regulation and steroidogenesis.