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  • 1
    ISSN: 1573-4919
    Keywords: protein kinase A ; site-directed mutagenesis ; breast cancer ; growth arrest ; cAMP response element
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Expression of the RIα regulatory subunit of protein kinase A type I is increased in human cancer cell lines, in primary tumors, in cells after transformation, and in cells upon stimulation of growth. Ala99 (the pseudophosphorylation site) of human RIα was replaced with Ser (RIα-p) for the structure-function analysis of RIα. MCF-7 hormone- dependent breast cancer cells were transfected with an expression vector for the wild-type RIα or mutant RIα-p. Overexpression of RIα-P resulted in suppression of protein kinase A type II, the isozyme of type I kinase, production of kinase exhibiting reduced cAMP activation, and inhibition of cell growth showing an increase in G0/G1 phase of the cell cycle and apoptosis. The wild-type RIα overexpression had no effect on protein kinase A isozyme distribution or cell growth. Overexpression of protein kinase A type II regulatory subunit, RIIβ, suppressed RIα and protein kinase A type I and inhibited cell growth. These results show that the growth of hormone-dependent breast cancer cells is dependent on the functional protein kinase A type I.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4919
    Keywords: retinoic acid ; RARβ ; protein kinase A ; apoptosis ; caspase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Both cAMP and retinoids play a role in cell differentiation and the control of cell growth. A site-selective cAMP analog, 8-Cl-cAMP and retinoic acid synergistically inhibit growth and induce apoptosis in certain cancer cells. In advanced or recurrent malignant diseases, retinoic acid (RA) is not effective even at doses that are toxic to the host. The objective of our present study was to examine the mechanism(s) of synergistic effects of retinoic acid (9-cis, 13-cis or all-trans RA) and 8-Cl-cAMP on apoptosis in human ovarian cancer NIH: OVCAR-3 and OVCAR-8 cells. RA induced growth inhibition and apoptosis in OVCAR-3 and OVCAR-8 cells. 8-Cl-cAMP acted synergistically with RA in inducing and activating retinoic acid receptor β (RARβ) which correlates with growth inhibition and apoptosis in both cell types. In addition, induction of apoptosis by RA plus 8-Cl-cAMP requires caspase-3 activation followed by cleavage of anti-poly(ADP-ribose) polymerase. Furthermore, mutations in CRE-related motif within the RARβ promoter resulted in loss of both transcriptional activation of RARβ and synergy between RA and 8-Cl-cAMP. RARβ expression appears to be associated with induction of apoptosis. Introduction of the RARβ gene into OVCAR-3 cells resulted in gain of RA sensitivity. Loss of RARβ expression, therefore, may contribute to the tumorigenicity of human ovarian cancer cells. Thus, combined treatment with RA and 8-Cl-cAMP may provide an effective means for inducing RARβ expression leading to apoptosis in ovarian cancer cells.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7217
    Keywords: antisense ; protein kinase A ; apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In recent years, several laboratories have explored the possibility of using antisense oligodeoxynucleotides for specific manipulation of gene expression leading to cancer treatment. The enhanced expression of the RIα subunit of cyclic AMP-dependent protein kinase type I (PKA-I) has been correlated with cancer cell growth. In the present study, the effects of an antisense oligodeoxynucleotide targeted against RIα subunit of PKA-I on growth inhibition and apoptosis in MDA-MB-231 human breast cancer cells were investigated. The growth inhibitory effects of RIα antisense oligodeoxynucleotide correlated with a decrease in the RIα mRNA and protein levels. The growth inhibition was accompanied by changes in the cell cycle phase distribution, cell morpbology, cleavage of poly (ADP-ribose) polymerase (PARP), and appearance of apoptotic nuclei. By comparison, mismatched control oligodeoxynucleotide had no effect. On the basis of these results, it can be suggested that the RIα antisense oligodeoxynucleotide, which efficiently depletes the growth stimulatory RIα and induces apoptosis/differentiation, could be used as a therapeutic agent for breast cancer treatment.
    Type of Medium: Electronic Resource
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