title: Contribution of growth and cell cycle checkpoints to radiation survival in Drosophila.
abstract: Cell cycle checkpoints contribute to survival after exposure to ionizing radiation (IR) by arresting the cell cycle and permitting repair. As such, yeast and mammalian cells lacking checkpoints are more sensitive to killing by IR. We reported previously that Drosophila larvae mutant for grp (encoding a homolog of Chk1) survive IR as well as wild type despite being deficient in cell cycle checkpoints. This discrepancy could be due to differences either among species or between unicellular and multicellular systems. Here, we provide evidence that Grapes is needed for survival of Drosophila S2 cells after exposure to similar doses of IR, suggesting that multicellular organisms may utilize checkpoint-independent mechanisms to survive irradiation. The dispensability of checkpoints in multicellular organisms could be due to replacement of damaged cells by regeneration through increased nutritional uptake and compensatory proliferation. In support of this idea, we find that inhibition of nutritional uptake (by starvation or onset of pupariation) or inhibition of growth factor signaling and downstream targets (by mutations in cdk4, chico, or dmyc) reduced the radiation survival of larvae. Further, some of these treatments are more detrimental for grp mutants, suggesting that the need for compensatory proliferation is greater for checkpoint mutants. The difference in survival of grp and wild-type larvae allowed us to screen for small molecules that act as genotype-specific radiation sensitizers in a multicellular context. A pilot screen of a small molecule library from the National Cancer Institute yielded known and approved radio-sensitizing anticancer drugs. Since radiation is a common treatment option for human cancers, we propose that Drosophila may be used as an in vivo screening tool for genotype-specific drugs that enhance the effect of radiation therapy.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder 80309-0347, USA.
authors.forename: Burnley
authors.initials: B
authors.lastname: Jaklevic
authors.forename: Lyle
authors.initials: L
authors.lastname: Uyetake
authors.forename: Willy
authors.initials: W
authors.lastname: Lemstra
authors.forename: Julia
authors.initials: J
authors.lastname: Chang
authors.forename: William
authors.initials: W
authors.lastname: Leary
authors.forename: Anthony
authors.initials: A
authors.lastname: Edwards
authors.forename: Smruti
authors.initials: S
authors.lastname: Vidwans
authors.forename: Ody
authors.initials: O
authors.lastname: Sibon
authors.forename: Tin
authors.initials: T
authors.lastname: Tin Su
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D002166:Camptothecin / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects*; D002478:Cells, Cultured / Q000187:drug effects / Q000528:radiation effects; D000071877:Checkpoint Kinase 1; D002945:Cisplatin / Q000494:pharmacology; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000196:embryology / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D007814:Larva / Q000187:drug effects / Q000528:radiation effects*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D011836:Radiation Tolerance; D011839:Radiation, Ionizing; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D013217:Starvation
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D036341:Intercellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D011838:Radiation-Sensitizing Agents; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C444435:Mei-41 protein, Drosophila; D017346:Protein Serine-Threonine Kinases; C000605877:grp protein, Drosophila; D002945:Cisplatin; D002166:Camptothecin