title: Increased killing of SCCVII squamous cell carcinoma cells after the combination of Pc 4 photodynamic therapy and dasatinib is associated with enhanced caspase-3 activity and ceramide synthase 1 upregulation.
abstract: Photodynamic therapy (PDT) is not always effective as an anticancer treatment, therefore, PDT is combined with other anticancer agents for improved efficacy. The combination of dasatinib and PDT with the silicone phthalocyanine photosensitizer Pc 4 was assessed for increased killing of SCCVII mouse squamous cell carcinoma cells, a preclinical model of head and neck squamous cell carcinoma, using apoptotic markers and colony formation as experimental end-points. Because each of these treatments regulates the metabolism of the sphingolipid ceramide, their effects on mRNA levels of ceramide synthase, a ceramide-producing enzyme, and the sphingolipid profile were determined. PDT + dasatinib induced an additive loss of clonogenicity. Unlike PDT alone or PDT + dasatinib, dasatinib induced zVAD-fmk-dependent cell killing. PDT or dasatinib-induced caspase-3 activation was potentiated after the combination. PDT alone induced mitochondrial depolarization, and the effect was inhibited after the combination. Annexin V+ and propidium iodide+ cells remained at control levels after treatments. In contrast to PDT alone, dasatinib induced upregulation of ceramide synthase 1 mRNA, and the effect was enhanced after the combination. Dasatinib induced a modest increase in C20:1- and C22-ceramide but had no effect on total ceramide levels. PDT increased the levels of 12 individual ceramides and total ceramides, and the addition of dasatinib did not affect these increases. PDT alone decreased substantially sphingosine levels and inhibited the activity of acid ceramidase, an enzyme that converts ceramide to sphingosine. The data suggest that PDT-induced increases in ceramide levels do not correlate with ceramide synthase mRNA levels but rather with inhibition of ceramidase. Cell killing was zVAD-fmk-sensitive after dasatinib but not after either PDT or the combination and enhanced cell killing after the combination correlated with potentiated caspase-3 activation and upregulation of ceramide synthase 1 mRNA but not the production of ceramide. The data imply potential significance of the combination for cancer treatment.
authors.affiliation: Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48201, USA.
authors.forename: Duska
authors.initials: D
authors.lastname: Separovic
authors.forename: Paul
authors.initials: P
authors.lastname: Breen
authors.forename: Nithin B
authors.initials: NB
authors.lastname: Boppana
authors.forename: Eric
authors.initials: E
authors.lastname: Van Buren
authors.forename: Nicholas
authors.initials: N
authors.lastname: Joseph
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Kraveka
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Rahmaniyan
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Tatyana I
authors.initials: TI
authors.lastname: Gudz
authors.forename: Alicja
authors.initials: A
authors.lastname: Bielawska
authors.forename: Aiping
authors.initials: A
authors.lastname: Bai
authors.forename: Jacek
authors.initials: J
authors.lastname: Bielawski
authors.forename: Jason S
authors.initials: JS
authors.lastname: Pierce
authors.forename: Mladen
authors.initials: M
authors.lastname: Korbelik
mesh_terms: D000008:Abdominal Neoplasms / Q000188:drug therapy; D055573:Acid Ceramidase / Q000037:antagonists & inhibitors / Q000378:metabolism; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy*; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D002518:Ceramides / Q000096:biosynthesis / Q000378:metabolism; D000069439:Dasatinib; D004789:Enzyme Activation; D006258:Head and Neck Neoplasms / Q000188:drug therapy; D007211:Indoles / Q000627:therapeutic use*; D051379:Mice; D008809:Mice, Inbred C3H; D008928:Mitochondria / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics*; D010778:Photochemotherapy / Q000379:methods*; D011419:Propidium; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011743:Pyrimidines / Q000627:therapeutic use*; D012333:RNA, Messenger / Q000096:biosynthesis; D013110:Sphingosine / Q000378:metabolism; D013844:Thiazoles / Q000627:therapeutic use*
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D017304:Annexin A5; D002518:Ceramides; D007211:Indoles; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D012333:RNA, Messenger; D013844:Thiazoles; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C107448:phthalocyanine Pc 4; D011419:Propidium; D010088:Oxidoreductases; C108138:dihydroceramide desaturase; D011505:Protein-Tyrosine Kinases; D053148:Caspase 3; D053453:Caspase 9; D055573:Acid Ceramidase; D013110:Sphingosine; D000069439:Dasatinib