ABSTRACT
Here we describe the expression and function of a HIF-1-regulated protein pyruvate dehydrogenase kinase-1 (PDK-1) in head and neck squamous cancer (HNSCC). Using RNAi to downregulate hypoxia-inducible PDK-1, we found that lactate and pyruvate excretion after 16-48 h of hypoxia was suppressed to normoxic levels. This indicates that PDK-1 plays an important role in maintaining glycolysis. Knockdown had no effect on proliferation or survival under hypoxia. The immunohistochemical expression of PDK-1 was assessed in 140 cases of HNSCC. PDK-1 expression was not expressed in normal tissues but was upregulated in HNSCC and found to be predominantly cytoplasmic with occasional strong focal nuclear expression. It was strongly related to poor outcome (P=0.005 split by median). These results indicate that HIF regulation of PDK-1 has a key role in maintaining lactate production in human cancer and that the investigation of PDK-1 inhibitors should be investigated for antitumour effects.
Subject(s)
Carcinoma, Squamous Cell/metabolism , Head and Neck Neoplasms/metabolism , Hypoxia/metabolism , Lactic Acid/biosynthesis , Protein Serine-Threonine Kinases/physiology , Base Sequence , Carcinoma, Squamous Cell/pathology , Cell Line, Tumor , DNA Primers , Gene Silencing , Head and Neck Neoplasms/pathology , Humans , Polymerase Chain Reaction , Prognosis , Pyruvate Dehydrogenase Acetyl-Transferring Kinase , RNA InterferenceABSTRACT
Burkholderia cepacia, a major pathogen amongst individuals with cystic fibrosis (CF), is intrinsically resistant to most clinically available antibiotics. We report the identification of an immunodominant antigen in CF patients infected with B. cepacia, a multidrug-resistance efflux pump called BcrA. The bcrA gene encodes a 46 kDa peptide with 14 potential alpha-helices that belongs to the major facilitator superfamily of drug transporters. A recombinant Escherichia coli strain was constructed containing the bcrA gene, which resulted in a four-fold increase in resistance to tetracycline and an eight-fold increase in resistance to nalidixic acid. These results demonstrate that the bcrA gene is part of a drug efflux system that is potentially a major contributor to the high-level antibiotic resistance observed in B. cepacia and thus a potential target for novel therapeutics.
