title: siRNA-mediated down-regulation of ceramide synthase 1 leads to apoptotic resistance in human head and neck squamous carcinoma cells after photodynamic therapy.
abstract: BACKGROUND
  The effectiveness of photodynamic therapy (PDT) for cancer treatment correlates with apoptosis. We previously observed that the knockdown of ceramide synthase 6, an enzyme from the de novo sphingolipid biosynthesis pathway, is associated with marked reduction in C18-dihydroceramide and makes cells resistant to apoptosis post-PDT. Down-regulation of ceramide synthase 1 (CERS1) can also render cells resistant to anticancer drugs.
  
  
  OBJECTIVE
  To explore the impact of CERS1 knockdown on apoptosis and the sphingolipid profile, post-PDT, with the silicone phthalocyanine Pc 4, in a human head and neck squamous carcinoma cell line.
  
  
  METHODS
  Besides siRNA transfection and PDT treatment, the following methods were used: immunoblotting for protein expression, mass spectrometry for sphingolipid analysis, spectroflurometry and flow cytometry for apoptosis detection, and trypan blue assay for cell viability evaluation.
  
  
  RESULTS
  CERS1 knockdown led to inhibition of PDT-induced caspase 3-like (DEVDase) activation, of apoptosis and cell death. CERS1 knockdown was associated with global and selective decreases in ceramides and dihydroceramides, in particular C18-, C18:1- and C20-ceramide post-PDT.
  
  
  CONCLUSIONS
  Our novel findings are consistent with the notion that CERS1 regulates apoptotic resistance to PDT, partly via C18- and C20-ceramide, and that CERS1 is a molecular target for controlling resistance to PDT.
authors: Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI, USA.|Karmanos Cancer Institute, Wayne State University, Detroit, MI, USA.
authors: Duska
authors: D
authors: Separovic
authors: Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI, USA.
authors: Paul
authors: P
authors: Breen
authors: Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI, USA.
authors: Nicholas
authors: N
authors: Joseph
authors: Department of Biochemistry and Molecular Biology, Medical University of South Carolina Charleston, SC, U.S.A.
authors: Jacek
authors: J
authors: Bielawski
authors: Department of Biochemistry and Molecular Biology, Medical University of South Carolina Charleston, SC, U.S.A.
authors: Jason S
authors: JS
authors: Pierce
authors: Karmanos Cancer Institute, Wayne State University, Detroit, MI, USA.
authors: Eric
authors: E
authors: VAN Buren
authors: Ralph H. Johnson Veterans Affairs Medical Center, Medical University of South Carolina Charleston, SC, U.S.A.|Department of Neuroscience, Medical University of South Carolina Charleston, SC, U.S.A.
authors: Tatyana I
authors: TI
authors: Gudz
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics / Q000628:therapy*; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002851:Chromatography, High Pressure Liquid; D015536:Down-Regulation; D055785:Gene Knockdown Techniques; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics / Q000628:therapy*; D006801:Humans; D015151:Immunoblotting; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008565:Membrane Proteins / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism; D010778:Photochemotherapy / Q000379:methods*; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000235:genetics; D013107:Sphingolipids / Q000032:analysis / Q000378:metabolism; D051049:Sphingosine N-Acyltransferase / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D014343:Trypan Blue / Q000032:analysis
chemical_list: D008565:Membrane Proteins; D034741:RNA, Small Interfering; D013107:Sphingolipids; C493790:CERS1 protein, human; D051049:Sphingosine N-Acyltransferase; D010447:Peptide Hydrolases; D053148:Caspase 3; C108711:DEVDase; D014343:Trypan Blue