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Research Articles: Therapeutics, Targets, and Development

STAT3 inhibition in prostate and pancreatic cancer lines by STAT3 binding sequence oligonucleotides: differential activity between 5' and 3' ends

Departments of ¹ Surgery, and ² Biochemistry and Molecular Biology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey and ³ Veterans Administration-New Jersey Health Care System, East Orange, New Jersey

Requests for reprints: Beverly Barton, Department of Surgery, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, 185 South Orange Avenue, Newark, NJ 07103. Phone: 973-972-0662; Fax: 1-973-972-3892. E-mail: bartonbe{at}umdnj.edu

Abstract

Signal transducers and activators of transcription (STAT) were originally discovered as components of signal transduction pathways. Persistent aberrant activation of STAT3 is a feature of many malignancies including prostate cancer and pancreatic cancer. One consequence of persistently activated STAT3 in malignant cells is that they depend on it for survival; thus, STAT3 is an excellent molecular target for therapy. Previously, we reported that single-stranded oligonucleotides containing consensus STAT3 binding sequences (13410 and 13411) were more effective for inducing apoptosis in prostate cancer cells than antisense STAT3 oligonucleotides. Control oligonucleotides (scrambled sequences) had no effect. Here, we report that authentic STAT3 binding sequences, identified from published literature, were more effective for inducing apoptosis in prostate cancer cells and pancreatic cancer cells than was oligonucleotide 13410. Moreover, the authentic STAT3 binding sequences showed differing efficacies in the malignant cell lines depending on whether the canonical STAT3 binding sequence was truncated at the 5' or the 3' end. Finally, expression of one STAT3-regulated gene was decreased following treatment, suggesting that STAT3 may regulate the same set of genes in the two types of cancer. We conclude that truncating the 5' end left intact enough of the canonical STAT3 binding site for effective hybridization to the genome, whereas truncation of the 3' end, which is outside the canonical binding site, may have affected binding of required cofactors essential for STAT3 activity, thereby reducing the capacity of this modified oligonucleotide to induce apoptosis. Additional experiments to answer this hypothesis are under way. [Mol Cancer Ther 2008;7(6):1543–50]

Grant support: NIH grant CA 121782, Department of Veterans Affairs Research & Development Merit Award (B.E. Barton), and NIH grant AI142529 (V.N. Pandey).

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Note: Current address for S. Tripathi: Enzon Pharmaceuticals, 20 Kingsbridge Road, Piscataway, NJ.

Received 2/11/08; revised 3/26/08; accepted 4/ 2/08.