title: Cell Killing Mechanisms and Impact on Gene Expression by Gemcitabine and 212Pb-Trastuzumab Treatment in a Disseminated i.p. Tumor Model.
abstract: In pre-clinical studies, combination therapy with gemcitabine and targeted radioimmunotherapy (RIT) using 212Pb-trastuzumab showed tremendous therapeutic potential in the LS-174T tumor xenograft model of disseminated intraperitoneal disease. To better understand the underlying molecular basis for the observed cell killing efficacy, gene expression profiling was performed after a 24 h exposure to 212Pb-trastuzumab upon gemcitabine (Gem) pre-treatment in this model. DNA damage response genes in tumors were quantified using a real time quantitative PCR array (qRT-PCR array) covering 84 genes. The combination of Gem with α-radiation resulted in the differential expression of apoptotic genes (BRCA1, CIDEA, GADD45α, GADD45γ, IP6K3, PCBP4, RAD21, and p73), cell cycle regulatory genes (BRCA1, CHK1, CHK2, FANCG, GADD45α, GTSE1, PCBP4, MAP2K6, NBN, PCBP4, and SESN1), and damaged DNA binding and repair genes (BRCA1, BTG2, DMC1, ERCC1, EXO1, FANCG, FEN1, MSH2, MSH3, NBN, NTHL1, OGG1, PRKDC, RAD18, RAD21, RAD51B, SEMA4G, p73, UNG, XPC, and XRCC2). Of these genes, the expression of CHK1, GTSE1, EXO1, FANCG, RAD18, UNG and XRCC2 were specific to Gem/212Pb-trastuzumab administration. In addition, the present study demonstrates that increased stressful growth arrest conditions induced by Gem/212Pb-trastuzumab could suppress cell proliferation possibly by up-regulating genes involved in apoptosis such as p73, by down-regulating genes involved in cell cycle check point such as CHK1, and in damaged DNA repair such as RAD51 paralogs. These events may be mediated by genes such as BRCA1/MSH2, a member of BARC (BRCA-associated genome surveillance complex). The data suggest that up-regulation of genes involved in apoptosis, perturbation of checkpoint genes, and a failure to correctly perform HR-mediated DSB repair and mismatch-mediated SSB repair may correlate with the previously observed inability to maintain the G2/M arrest, leading to cell death.
authors.affiliation: Radioimmune & Inorganic Chemistry Section, Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda MD, United States of America.
authors.forename: Kwon Joong
authors.initials: KJ
authors.lastname: Yong
authors.affiliation: Radioimmune & Inorganic Chemistry Section, Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda MD, United States of America.
authors.forename: Diane E
authors.initials: DE
authors.lastname: Milenic
authors.affiliation: Radioimmune & Inorganic Chemistry Section, Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda MD, United States of America.
authors.forename: Kwamena E
authors.initials: KE
authors.lastname: Baidoo
authors.affiliation: Radioimmune & Inorganic Chemistry Section, Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda MD, United States of America.
authors.forename: Martin W
authors.initials: MW
authors.lastname: Brechbiel
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000473:pathology*; D004249:DNA Damage / Q000235:genetics; D004260:DNA Repair / Q000235:genetics; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D064593:Heterografts; D006801:Humans; D007856:Lead Radioisotopes / Q000008:administration & dosage*; D051379:Mice; D000068878:Trastuzumab / Q000494:pharmacology* / Q000627:therapeutic use; D000093542:Gemcitabine
chemical_list: D000970:Antineoplastic Agents; D007856:Lead Radioisotopes; D003841:Deoxycytidine; D000068878:Trastuzumab; D000093542:Gemcitabine