CpG-Immunomer DNA enhances antisense protein kinase A RIa-Inhibition of Multidrug-Resistant Colon Carcinoma Growth in Nude Mice: Molecular Basis for Combinatorial Therapy
Purpose: CpG DNAs induce cytokines, activate natural killer cells, and elicit vigorousT-cell response leading to antitumor effects. Antisense oligodeoxynucleotides targeted against the RIa subunit of protein kinaseA (antisense PKARIa) induce growth arrest, apoptosis, and differentiation in a variety of cancer cell lines in vitro and in vivo.This study investigated the use of a combinatorial therapy consisting of the RNA-DNA second-generation antisense PKA RIa and the CpG immunomer (CpGDNA linked through 3V-3Vlinkage containing two accessible 5Vends). Experimental Design: HCT-15 multidrug-resistant colon carcinoma growth in nude mice was used as an experimental model. The inhibitory effect on tumor growth and apoptotic activity of antisense RIa and CpGimmunomer, singly and in combination, were measured by tumor growth, levels of RIa subunit, and antiapoptotic and proapoptotic proteins. Effect onhost-immune system was measured by mouse spleen size, interleukin-6 (IL-6) levels in mouse blood, and nuclear factor-nB (NF-nB) transcription activity inmouse spleen cells. Results: In combination, CpG immunomer and antisense PKA RIa induced additive/supraadditive effect on the inhibition of tumor growth. Antisense RIa but not CpG immunomer increased Bax andBak proapoptotic proteinlevels and decreased Bcl-2 and RIa proteinlevels in tumor cells. CpG immunomer but not antisense RIa induced an enlargement of mouse spleen, increased IL-6 levels in mouse blood, and increased NF-nB transcription activity in mouse spleen cells. Conclusions:These results show that type IPKA down-regulation and induction of apoptosis in tumor cells by antisense PKA RIa, and host-immune stimulation by CpG immunomer are responsible at the molecular level for the supra-additive effects of tumor growth inhibition. Thus, antisense PKA RIa and CpG immunomer in combination work cooperatively and as tumor-targeted therapeutics to treat human cancer.
Clinical cancer research
Cancer Therapy (excl Chemotherapy and Radiation Therapy)