Selective sensitization to DNA-damaging agents in a human rhabdomyosarcoma cell line with inducible wild-type p53 overexpression.
Drug-induced cytotoxicity or apoptosis may be influenced by the expression of the p53 tumor suppressor gene and by the specific oncogene expressed, which may dictate the threshold at which a cytotoxic response may by induced. The objective of the study was to elucidate how DNA-damaging agents with different mechanisms of action were sensitized in the context of expression of the Pax3/FKHR fusion protein, a transformation event unique to alveolar rhabdomyosarcomas (ARMSs), and wild-type p53 (wtp53). A wtp53 cDNA was subcloned into the pGRE5-2/EBV vector with dexamethasone-inducible overexpression and transfected into Rh30 ARMS cells that express Pax3/FKHR and a mutant p53 phenotype. Following dexamethasone induction of wtp53 overexpression in a derived clone (Cl.#27), growth was slowed, and cells accumulated in G1. Functional wtp53 activity was demonstrated by selective transactivation of p50-2, a wtp53 chloramphenicol acetyltransferase reporter construct, and by up-regulated expression of endogenous p21Waf1. Data demonstrated p53-dependent sensitization (> or = 4-fold) to bleomycin, actinomycin D, and 5-fluorouracil and considerably less p53-dependence (< or = 2-fold) for doxorubicin, topotecan, etoposide, and cisplatin in Cl.#27 compared to an equivalent clone containing the pGRE5-EBV vector alone (VC#3). Data demonstrate that ARMS cells show a selective sensitization to DNA-damaging agents when wtp53 is overexpressed. The cytotoxic activity of agents that are not potentiated substantially must, therefore, depend upon p53-independent factors that relate to the mechanism of drug action.
Gibson
A A
AA
Department of Molecular Pharmacology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
Harwood
F G
FG
Tillman
D M
DM
Houghton
J A
JA
D000970:Antineoplastic Agents / Q000494:pharmacology*; D004247:DNA / Q000187:drug effects*; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000032:analysis; D006801:Humans; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors; D012208:Rhabdomyosarcoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D014157:Transcription Factors; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000032:analysis / Q000502:physiology*
D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D000072041:PAX3 Transcription Factor; C489409:PAX3 protein, human; D051761:Paired Box Transcription Factors; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; C068686:Pax3 protein, mouse; D004247:DNA