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  • Title: Combined blockade of protein kinase A and bcl-2 by antisense strategy induces apoptosis and inhibits tumor growth and angiogenesis.
    Author: Tortora G, Caputo R, Damiano V, Bianco R, Fontanini G, Cuccato S, De Placido S, Bianco AR, Ciardiello F.
    Journal: Clin Cancer Res; 2001 Aug; 7(8):2537-44. PubMed ID: 11489837.
    Abstract:
    Protein kinase A type I (PKAI) plays a key role in neoplastic transformation, conveys mitogenic signals from different sources, and is overexpressed in the majority of human tumors. Inhibition of PKAI by different tools results in cancer-cell growth inhibition in vitro and in vivo. We and others have recently shown that a novel class of mixed-backbone oligonucleotides targeting the PKAI subunit RIalpha exhibits improved pharmacokinetic properties and antitumor activity accompanied by increased apoptosis in several human cancer types in vitro and in vivo. The role of bcl-2 in the control of apoptosis has been widely documented, and the inhibition of bcl-2 expression and function may have important therapeutic implications. In fact, oligonucleotides antisense bcl-2 have shown antitumor activity in animal models and have successfully completed early clinical trials. Recent studies have demonstrated a direct role of PKA in the regulation of the bcl-2-dependent apoptotic pathway. Therefore, we have investigated the combined blockade of PKA and bcl-2 by antisense strategy as a potential therapeutic approach. The novel hybrid DNA/RNA mixed-backbone oligonucleotide antisense RIalpha (AS RIalpha) in combination with the antisense bcl-2 (AS bcl-2), cooperatively inhibited bcl-2 expression and soft agar growth and induced apoptosis in different human cancer cell lines. p.o. administration of AS RIalpha in combination with i.p. AS bcl-2 caused a marked antitumor effect and a significant prolongation of survival in nude mice bearing human colon cancer xenografts. Moreover, histochemical analysis of tumor specimens showed inhibition of RIalpha and Ki67 expression, inhibition of angiogenesis, and parallel induction of apoptosis in vivo. The results of our study imply an interaction between the PKA and bcl-2 signaling pathways and, because both antisenses have now entered Phase II trials, provide the rationale to translate this novel therapeutic strategy in a clinical setting.
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