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

Abstract

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 Ͻ 0.02-0.006) reduced the expression of the TC22 transcript and significantly (p Ͻ 0.05 to Ͻ0.0002) reduced the expression of TC22 protein in a dose-dependent and reversible manner. Rosiglitazone, a specific peroxisome proliferator-activated receptor-␥ (PPAR␥) agonist, similarly and significantly (p Ͻ 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␥ 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.

Loss of caveolin-1 in prostate cancer stroma correlates with reduced relapse-free survival and is functionally relevant to tumour progression

“…We then employed the 84‐gene Cancer Pathway Finder PCR Array to analyse the expression profile of WPMY‐1 cells in which Cav‐1 had been stably silenced. This array includes genes involved in biological processes relevant to tumourigenesis and cancer progression, such as cell cycle, adhesion, angiogenesis, invasion, and metastasis (Figure D).…”

Systematic review: molecular chemoprevention of colorectal malignancy by mesalazine

“…5‐ASA upregulates PPAR‐γ expression and interferes with PPAR‐γ active centre, which may explain some anti‐neoplastic effects of this drug 69,70 . Interestingly, 5‐ASA, sulfasalazine and rosiglitazone (a specific PPAR‐γ agonist) significantly reduced the cellular expression of TC22, a novel human tropomyosin (hTM) isoform, which is expressed in all tested colorectal carcinomas, but not in normal colon epithelial cells 71 . This implies TC22 being modulated by PPAR‐γ and suggests a novel anti‐neoplastic molecular effect of mesalazine.…”

“…69,70 Interestingly, 5-ASA, sulfasalazine and rosiglitazone (a specific PPAR-c agonist) significantly reduced the cellular expression of TC22, a novel human tropomyosin (hTM) isoform, which is expressed in all tested colorectal carcinomas, but not in normal colon epithelial cells. 71 This implies TC22 being modulated by PPAR-c and suggests a novel anti-neoplastic molecular effect of mesalazine. New anti-inflammatory and anti-neoplastic compounds will probably use PPAR-c as molecular target.…”

Diatom-Based Nanomedicine for Colorectal Cancer Treatment: New Approaches for Old Challenges

“…Small interfering ribonucleic acid (RNA) has recently reinforced the therapeutic strategies against cancer angiogenesis, allowing for the sequence-specific post-transcriptional downregulation of genes involved in the angiogenesis cascade [ 76 ]. Small interfering RNA targeting a novel tropomyosin isoform TC-22 associated with metastatic CRC reduced protein levels and angiogenesis by 45 to 50% [ 77 ]. However, although siRNAs can target overexpressed proteins with higher efficiency than antibodies, they may modify cell functionalities and cause non-specific toxicity [ 78 ].…”