title: Suppression of c-Myc and RRM2 expression in pancreatic cancer cells by the sphingosine kinase-2 inhibitor ABC294640.
abstract: Pancreatic cancer remains extremely difficult to treat, with the average lifespan following diagnosis being only 3-6 months, resulting in a death to incidence ratio of 0.94. A major reason for this high mortality rate is resistance to the main chemotherapeutic agent used to treat this disease, gemcitabine. Alterations in nucleoside and gemcitabine metabolism, specifically over-expression of ribonucleotide reductase, have been implicated as a major mechanism of resistance to this drug. Here, we show that inhibition of sphingosine kinase-2 by the specific inhibitor ABC294640 is synergistically cytotoxic with gemcitabine toward three human pancreatic cancer cell lines. Treatment with ABC294640 results in decreased expression of both RRM2 and MYC in all three cell lines. Additionally, expression of c-Myc protein and phosphorylation of Rb at S780 both decrease in a dose-dependent manner in response to ABC294640, while acetylation of H3-K9 and p21 levels increase. Pretreatment with the protein phosphatase 1 inhibitor okadaic acid or the ceramide synthase inhibitor fumonisin B1 fails to prevent the effects of ABC294640 on Rb phosphorylation. These data indicate a role for sphingosine kinase-2 in E2F and c-Myc mediated transcription through alteration of histone acetylation and p21 expression. These effects of ABC294640 suggest that it may be an effective agent for pancreatic cancer, particularly in combination with gemcitabine.
authors: Medical University of South Carolina, Department of Drug Discovery and Pharmaceutical Sciences, Charleston, South Carolina, USA.
authors: Clayton S
authors: CS
authors: Lewis
authors: Medical University of South Carolina, Department of Microbiology and Immunology, Charleston, South Carolina, USA.
authors: Christina
authors: C
authors: Voelkel-Johnson
authors: Apogee Biotechnology Corporation, Hummelstown, Pennsylvania, USA.
authors: Charles D
authors: CD
authors: Smith
mesh_terms: D000107:Acetylation / Q000187:drug effects; D000218:Adamantane / Q000031:analogs & derivatives* / Q000494:pharmacology; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000494:pharmacology; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006657:Histones / Q000378:metabolism; D006801:Humans; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology*; D016160:Retinoblastoma Protein / Q000378:metabolism; D012262:Ribonucleoside Diphosphate Reductase / Q000235:genetics / Q000378:metabolism*; D000093542:Gemcitabine; D000099157:Sphingosine Kinase
chemical_list: D000218:Adamantane; D000964:Antimetabolites, Antineoplastic; D003841:Deoxycytidine; D006657:Histones; D017853:Phosphotransferases (Alcohol Group Acceptor); D016271:Proto-Oncogene Proteins c-myc; D011725:Pyridines; D016160:Retinoblastoma Protein; D012262:Ribonucleoside Diphosphate Reductase; D000093542:Gemcitabine; C548780:3-(4-chlorophenyl)-adamantane-1-carboxylic acid (pyridin-4-ylmethyl)amide; C093713:ribonucleotide reductase M2; C000594250:sphingosine kinase 2, human; D000099157:Sphingosine Kinase
keywords: c-Myc; gemcitabine; pancreatic cancer; ribonucleotide reductase; sphingosine kinase-2