Antitumor activity and pharmacokinetics of a mixed-backbone antisense oligonucleotide targeted to the RIα subunit of protein kinase A after oral administration

Abstract

Overexpression of the RI␣ subunit of cAMP-dependent protein kinase (PKA) has been demonstrated in various human cancers. PKA has been suggested as a potential target for cancer therapy. The goal of the present study was to evaluate an anti-PKA antisense oligonucleotide (mixed-backbone oligonucleotide) as a therapeutic approach to human cancer treatment. The identified oligonucleotide inhibited the growth of cell lines of human colon cancer (LS174T, DLD-1), leukemia (HL-60), breast cancer (MCF-7, MDA-MB-468), and lung cancer (A549) in a time-, concentration-, and sequence-dependent manner. In a dose-dependent manner, the oligonucleotide displayed in vivo antitumor activity in severe combined immunodeficient and nude mice bearing xenografts of human cancers of the colon (LS174T), breast (MDA-MB-468), and lung (A549). The routes of drug administration were intraperitoneal and oral. Synergistic effects were found when the antisense oligonucleotide was used in combination with the cancer chemotherapeutic agent cisplatin. The pharmacokinetics of the oligonucleotide after oral administration of 35 S-labeled oligonucleotide into tumor-bearing mice indicated an accumulation and retention of the oligonucleotide in tumor tissue. This study further provides a basis for clinical studies of the antisense oligonucleotide targeted to the RI␣ subunit of PKA (GEM 231) as a cancer therapeutic agent used alone or in combination with conventional chemotherapy.antisense therapy ͉ oral drug delivery ͉ breast cancer ͉ colon cancer ͉ lung cancer c AMP-dependent protein kinase (PKA) is involved in various cellular functions, including cell proliferation, gene induction, metabolism, secretion, and ion-channel regulation. PKA is composed of two catalytic (C) and two regulatory (R) subunits and has type-I and type-II isozymes, with different R subunits, termed RI and RII, interacting with an identical C subunit (1). Thus far, four isoforms of R subunits, RI␣, RI␤, RII␣, and RII␤, have been identified. Increased expression of the RI␣ subunit of PKA correlates with cell proliferation and neoplastic growth (2). Overexpression of the RI␣ subunit of PKA occurs in various human tumor tissues and cell lines including cancers of breast (3-5), ovary (6, 7), lung (8), and colon (9-11). Furthermore, overexpression of the RI␣ subunit of PKA correlates with malignancy and poor prognosis in cancer patients (5-7). In addition, the RI␣ subunit interacts with the cytochrome c oxidase subunit vb (12), which is involved in controlling multiple drug resistance (13,14), and is associated with tumor sensitivity to cancer chemotherapeutic agents such as cisplatin (15). PKA also phosphorylates the epidermal growth factor receptor and decreases its tyrosine kinase activity and signal transduction both in vitro and in vivo (16). Therefore, the RI␣ subunit of PKA is a potential target for human cancer therapy. In the last decade, there have been increasing efforts to develop PKA-specific inhibitors as cancer therapeutic agents (2, 17).Selective down-regulation of the...

Simultaneous blockade of different EGF-like growth factors results in efficient growth inhibition of human colon carcinoma xenografts

“…In this regard, we found that EGF-related, laterally modi®ed MBOs were very ecient in inhibiting in vivo tumor growth, and did not show any signi®cant toxic eects in nude mice. Laterally modi®ed MBOs have shown bioavailability following oral or rectal administration (Agrawal et al, 1998b;Wang et al, 1999). Preliminary results suggest that oral administration of AR, CR and TGFa MBOs is also able to inhibit GEO tumor growth in nude mice (N Normanno, unpublished observations).…”

The future of antisense therapy: combination with anticancer treatments

“…An improvement of these effects is observed with the MBO GEM 231. This oligo elicits a better in vivo pharmacokinetic and toxicological profile than PS ASOs, and displays antitumor activity in different human tumor xenografts when given orally to mice (Wang et al, 1999).…”

Antisense Protein Kinase A RIα Inhibits 7,12-Dimethylbenz( a )anthracene-Induction of Mammary Cancer

“…It was demonstrated that treating different tumor cell lines with antisense ODNs targeted against the RI␣ subunit of PKA caused inhibition of cell proliferation in vitro (21,22) and tumor growth in vivo (15,23,24). A single administration of RI␣ antisense to nude mice bearing LS-174T human colon carcinomas resulted in an almost complete suppression of tumor growth for 7 days (15).…”