Down-regulation of RI alpha subunit of cAMP-dependent protein kinase induces growth inhibition of human mammary epithelial cells transformed by c-Ha-ras and c-erbB-2 proto-oncogenes.
MCF-10A is a spontaneously immortalized, non-transformed human mammary epithelial cell line. We have recently obtained MCF-10A clones (MCF-10A HE cells) that are transformed following over-expression of both a human point-mutated c-Ha-ras and the c-erbB-2 proto-oncogenes. Two isoforms of the cAMP-dependent protein kinase (cAK) have been described in mammalian cells. Enhanced levels of type-I cAK (cAKI) are generally found in tumor cells. To determine whether inhibition of cAKI expression may interfere with ras and erbB-2 oncogene-induced transformation of human mammary epithelial cells, we have tested the effects of 2 agents that specifically down-regulate cAKI, such as 8-chloro-cAMP and an anti-sense oligodeoxynucleotide targeted against the RI alpha regulatory subunit of cAKI on MCF-10A HE cells. Treatment of MCF-10A HE cells with 8-chloro-cAMP induces a dose-dependent growth inhibition under both monolayer and soft-agar growth conditions, that is correlated with an accumulation of MCF-10A HE cells in G0/G1 phases of the cell cycle and a reduction of the number of cells in S phase. In contrast, 8-chloro-cAMP has no effect on MCF-10A cell growth. Furthermore, 8-chloro-cAMP treatment of MCF-10A HE cells induces a 4- to 6-fold reduction in p185erbB-2 expression and brings p21ras expression to levels comparable to those found in MCF-10A cells. Treatment of MCF-10A HE cells with an RI alpha anti-sense oligodeoxynucleotide determines a comparable inhibition of both anchorage-dependent and anchorage-independent cell growth. Our results suggest that cAKI may act as a mediator of ras and erbB-2 oncogene action in human breast cells and that interference with cAKI action provides a potential tool for inhibiting the growth-promoting effects of these oncogenes.
Ciardiello
F
F
Cattedra di Oncologia Medica, II Facoltà di Medicina e Chirurgia, Università degli Studi di Napoli, Italy.
Pepe
S
S
Bianco
C
C
Baldassarre
G
G
Ruggiero
A
A
Bianco
C
C
Selvam
M P
MP
Bianco
A R
AR
Tortora
G
G
D016375:Antisense Elements (Genetics); D001483:Base Sequence; D015153:Blotting, Western; D001940:Breast / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D000242:Cyclic AMP / Q000502:physiology; D004848:Epithelium / Q000473:pathology; D005434:Flow Cytometry; D011905:Genes, ras; D006131:Growth Inhibitors; D006801:Humans; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011494:Protein Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D011519:Proto-Oncogenes; D018719:Erb-b2 Receptor Tyrosine Kinases
D016375:Antisense Elements (Genetics); D000242:Cyclic AMP; D006131:Growth Inhibitors; D009838:Oligodeoxyribonucleotides; D011494:Protein Kinases; D011518:Proto-Oncogene Proteins; D016283:Proto-Oncogene Proteins p21(ras); D018719:Erb-b2 Receptor Tyrosine Kinases; C501009:HRAS protein, human