title: Cyclin D1 overexpression induces epidermal growth factor-independent resistance to apoptosis linked to BCL-2 in human A431 carcinoma.
abstract: Overexpression of EGF receptors and constitutive cyclin D1 expression are frequently associated with human squamous carcinomas. We have now investigated whether these parameters influence susceptibility to okadaic acid induced cell death in EGF-receptor overexpressing mutant p53 A431 human carcinoma. Exposure of these cells to 20 nM okadaic acid induced apoptosis-associated caspase 3 activation, DNA fragmentation, cleavage of Poly ADP-Ribose Polymerase (PARP), p53-independent expression of pro-apoptotic bax, and loss of proliferation-promoting cyclin D1. All these alterations were antagonized by concurrent addition of exogenous EGF. Ectopic overexpression of the cyclin D1 gene in A431 carcinoma conferred resistance to 20 nM okadaic acid irrespective of exogenous EGF, associated with a parallel induction of anti-apoptotic bcl-2. Treatment with a subtoxic concentration of a bispecific bcl-2/bcl xL antisense oligonucleotide cooperated with okadaic acid to down-regulate bcl-2 and sensitize cyclin D1-overexpressing cells to okadaic acid. Although EGF protects EGF-R proficient epithelial cells from diverse apoptotic stimuli through Mcl-1, this is the first report demonstrating that cyclin D1 overexpression provides an EGF independent protection from okadaic acid-induced cell death through induction of bcl-2. We also show that this anti-apoptotic effect of cyclin D1 overexpression, can be partly antagonized with antisense strategies that down-regulate anti-apoptotic bcl-2 family members.
authors.affiliation: IVIC, Tumor Cell Biology Laboratory, CMBC, Apartado 21827, Caracas, 1020 A, Venezuela. mrieber@pasteur.ivic.ve
authors.forename: Manuel
authors.initials: M
authors.lastname: Rieber
authors.forename: Mary Strasberg
authors.initials: MS
authors.lastname: Rieber
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics* / Q000502:physiology; D001483:Base Sequence; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D056741:Cyclin D; D016213:Cyclins / Q000235:genetics*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D019940:Genes, bcl-1; D019254:Genes, bcl-2; D006801:Humans; D019319:Okadaic Acid / Q000494:pharmacology; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D051020:bcl-X Protein / Q000235:genetics
chemical_list: C494826:BAX protein, human; C494811:BCL2L1 protein, human; D056741:Cyclin D; D016213:Cyclins; D020319:Oligodeoxyribonucleotides, Antisense; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019319:Okadaic Acid; D004815:Epidermal Growth Factor; C505407:CASP3 protein, human; D053148:Caspase 3