Antisense protein kinase A RIalpha inhibits 7,12-dimethylbenz(a)anthracene-induction of mammary cancer: blockade at the initial phase of carcinogenesis.
OBJECTIVE
There are two types of cyclic AMP (cAMP)-dependent protein kinase (PKA), type I (PKA-I) and type II (PKA-II), which share a common catalytic (C) subunit but contain distinct regulatory (R) subunits, RI versus RII, respectively. Evidence suggests that increased expression of PKA-I and its regulatory subunit (RIalpha) correlates with tumorigenesis and tumor growth. We investigated the effect of sequence-specific inhibition of RIalpha gene expression at the initial phase of 7,12-dimethylbenz(alphaa)anthracene (DMBA)-induced mammary carcinogenesis.


METHODS
Antisense RIalpha oligodeoxynucleotide (ODN) targeted against PKA RIalpha was administered (0.1 mg/day/rat, i.p.) 1 day before DMBA intubation and during the first 9 days post-DMBA intubation to determine the anticarcinogenic effects.


RESULTS
Antisense RIalpha, in a sequence-specific manner, inhibited the tumor production. At 90 days after DMBA intubation, untreated controls and RIalpha-antisense-treated rats exhibited an average mean number of tumors per rat of 4.2 and 1.8, respectively, and 90% of control and 45% of antisense-treated animals had tumors. The antisense also delayed the first tumor appearance. An increase in RIalpha and PKA-I levels in the mammary gland and liver preceded DMBA-induced tumor production, and antisense down-regulation of RIalpha restored normal levels of PKA-I and PKA-II in these tissues. Antisense RIalpha in the liver induced the phase II enzymes, glutathione S-transferase and quinone oxidoreductase, c-fos protein, and activator protein 1 (AP-1)- and cAMP response element (CRE)-directed transcription. In the mammary glands, antisense RIalpha promoted DNA repair processes. In contrast, the CRE transcription-factor decoy could not mimic these effects of antisense RIalpha.


CONCLUSIONS
The results demonstrate that RIalpha antisense produces dual anticarcinogenic effects: (a) increasing DMBA detoxification in the liver by increasing phase II enzyme activities, increasing CRE-binding-protein phosphorylation and enhancing CRE- and Ap-1-directed transcription; and (b) activating DNA repair processes in the mammary gland by down-regulating PKA-I.
Nesterova
Maria V
MV
Cellular Biochemistry Section, Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland, USA.
Cho-Chung
Yoon S
YS
D015127:9,10-Dimethyl-1,2-benzanthracene / Q000494:pharmacology; D000818:Animals; D002273:Carcinogens / Q000494:pharmacology; D020134:Catalytic Domain; D000242:Cyclic AMP / Q000378:metabolism; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism / Q000502:physiology*; D004260:DNA Repair; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004983:Ethanolamines / Q000494:pharmacology; D005260:Female; D005982:Glutathione Transferase / Q000378:metabolism; D047468:Immunoprecipitation; D008099:Liver / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism; D015674:Mammary Neoplasms, Animal / Q000139:chemically induced* / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism; D009252:NADPH Dehydrogenase / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D010766:Phosphorylation; D011485:Protein Binding; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic
D002273:Carcinogens; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D004983:Ethanolamines; D016376:Oligonucleotides, Antisense; C517835:Prkar1a protein, mouse; C517836:Prkar1a protein, rat; D016760:Proto-Oncogene Proteins c-fos; D018808:Transcription Factor AP-1; D015127:9,10-Dimethyl-1,2-benzanthracene; D000242:Cyclic AMP; D016660:NAD(P)H Dehydrogenase (Quinone); D009252:NADPH Dehydrogenase; D005982:Glutathione Transferase; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; C007369:2-diethylaminoethanol