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Molecular Pharmacology Fast Forward
First published on April 15, 2009; DOI: 10.1124/mol.109.056028

0026-895X/09/7601-183-191$20.00
Mol Pharmacol 76:183-191, 2009

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Mesalamine Suppresses the Expression of TC22, a Novel Tropomyosin Isoform Associated with Colonic Neoplasia

Koushik K. Das, Manisha Bajpai, Yingxin Kong, Jianying Liu, Xin Geng, and Kiron M. Das

Crohn's and Colitis Center of New Jersey, Division of Gastroenterology and Hepatology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick, New Jersey

Although a protective role for mesalamine against colon cancer in ulcerative colitis has been shown epidemiologically, its molecular mechanism is unknown. We cloned and sequenced a novel human tropomyosin (hTM) isoform, TC22, which is an alternatively spliced variant of normal epithelial hTM isoform 5 (hTM5), identical apart from 25 C-terminal amino acids. TC22 is expressed in 100% of colorectal carcinoma but is not expressed in normal colon epithelial cells. To explore a molecular mechanism of chemoprevention, we examined the effect of mesalamine on TC22 expression using LS180 colon cancer cells. Expression of hTM5 and TC22 was investigated at the protein and gene levels by fluorescence-activated cell sorting and real-time reverse transcription-polymerase chain reaction. Small interference RNA (siRNA) against the TC22 variant were transfected into LS180 colon cancer cells, reducing protein and transcript levels by 45 to 50%. Mesalamine or sulfasalazine (2 mM), but not sulfapyridine, significantly (p < 0.02-0.006) reduced the expression of the TC22 transcript and significantly (p < 0.05 to <0.0002) reduced the expression of TC22 protein in a dose-dependent and reversible manner. Rosiglitazone, a specific peroxisome proliferator-activated receptor-{gamma} (PPAR{gamma}) agonist, similarly and significantly (p < 0.002) reduced TC22 protein expression. A polymerase chain reaction array of 84 cancer-related genes performed on TC22 siRNA-transfected cells demonstrated a significant (more than two times) change in targets involved in apoptosis, adhesion, angiogenesis, and tissue remodeling. We conclude that mesalamine, sulfasalazine, and rosiglitazone significantly reduced the cellular expression of TC22, implicating PPAR{gamma} in this modulation. Similar suppression of TC22 by siRNA produced gene level changes on several critical carcinogenic pathways. These findings suggest a novel antineoplastic molecular effect of mesalamine.

Received for publication March 9, 2009.

Accepted for publication April 7, 2009.

Address correspondence to: Dr. Kiron M. Das, UMDNJ-Robert Wood Johnson Medical School, 1 Robert Wood Johnson Place, New Brunswick, NJ 08903. E-mail: daskm{at}umdnj.edu






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