Fortier, A. | Search bioRxiv

bioRxiv2019

GLUT1 inhibition blocks growth of RB1-positive Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) is a deadly form of breast cancer due to the development of resistance to chemotherapy affecting over 30% of patients. New therapeutics and companion biomarkers are urgently needed. Recognizing the elevated expression of glucose transporter 1 (GLUT1, encoded by SLC2A1) and associated metabolic dependencies in TNBC, we investigated the vulnerability of TNBC cell lines and patient-derived samples to GLUT1 inhibition. We report that genetic or pharmacological inhibition of GLUT1 with BAY-876 impairs the growth of a subset of TNBC cells displaying high glycolytic and lower oxidative phosphorylation (OXPHOS) rates. Pathway enrichment analysis of gene expression data implicates E2F Targets pathway activity as a surrogate of OXPHOS activity. Furthermore, the protein levels of retinoblastoma tumor suppressor (RB1) are strongly correlated with the degree of sensitivity to GLUT1 inhibition in TNBC, where RB1-negative cells are insensitive to GLUT1 inhibition. Collectively, our results highlight a strong and targetable RB1-GLUT1 metabolic axis in TNBC and warrant clinical evaluation of GLUT1 inhibition in TNBC patients stratified according to RB1 protein expression levels.

cancer biology↗

bioRxiv2018

Two lytic bacteriophages that depend on the Escherichia coli multi-drug efflux gene tolC and differentially affect bacterial growth and selection

Bacterial pathogens are increasingly evolving drug resistance under natural selection from antibiotics in medicine, agriculture, and nature. Meanwhile, bacteria ubiquitously encounter bacteriophages and can rapidly evolve phage resistance. However, the role of phages in interacting with drug-resistant and drug-sensitive bacteria remains unclear. To gain insight into such relationships, we screened for and characterized phages that rely on the multi-drug efflux pump gene tolC. First, we screened a collection of 33 environmental and commercial Escherichia coli phages for their ability to infect cells that lacked tolC. Our screen revealed two phages that had reduced efficiency of plating (EOP) on the tolC knockout compared to wild type. We further characterized these phages with bacterial growth curves, transmission electron microscopy, and analysis of phage-resistant mutants. Phage U136B is a curly-tailed virus in family Siphoviridae with no ability to infect a tolC knockout, suggesting TolC is the U136B receptor. Phage 132 is a contractile-tailed virus in family Myoviridae with reduced EOP on cells lacking ompF and its positive regulators tolC and ompR. U136B and 132 differentially effect bacterial growth and lysis, and U136B-resistant mutants contain mutations of the tolC gene. Together, these results show that the tolC gene involved in drug resistance can modify bacteria-phage interactions in multiple ways, altering bacterial lysis and selection. These new phages offer utility for studying evolution, tradeoffs, and infection mechanisms.\n\nImportanceBacteria face strong selection by antibiotics in medicine and agriculture, resulting in increasing levels of drug resistance among bacterial pathogens. Slowing this process will require an understanding of the environmental contexts in which drug resistance evolutionarily increases or decreases. In this study, we investigate two newly-isolated bacteriophages that rely on a bacterial antibiotic resistance gene. These bacteriophages vary in their interactions with drug-resistant bacteria, with one of the phages selecting for phage-resistant mutants that have mutations in the antibiotic resistance gene. Further study of these new phages will be useful to understanding evolutionary tradeoffs and how phages might be applied in natural settings to reverse the problem of drug resistance.

microbiology↗