ABSTRACT
Retinoic acid receptor responder 1 (RARRES1) is a retinoid regulated gene. Its expression is frequently down-regulated through DNA hypermethylation in several types of malignant tissues. This study investigated the clinical significance of RARRES1 protein and its association with RARRES3 protein expression in 161 (26 adenoma, 13 distal normal mucosa and 122 primary colorectal adenocarcinoma) paraffin-embedded colorectal tissues by immunohistochemistry. RARRES1 protein was detected at the highest levels in terminally differentiated cells of normal mucosal tissues and all 26 adenoma tissues. Among 122 colorectal adenocarcinomas, the poorly differentiated adenocarcinomas and Dukes' stage D tumours showed a significant decrease in RARRES1 expression (P < 0.001 and P < 0.01, respectively). RARRES1 expression was significantly (P < 0.001) correlated with RARRES3 expression, which was positively associated with tumour differentiation (P < 0.001). Difference in expression of RARRES1 among 119 patients had no apparent effect on patient survival. Our results suggest the role of RARRES1 in colorectal epithelial differentiation, and the down-regulation of RARRES1 is related to stage D progression.
Subject(s)
Adenocarcinoma/pathology , Cell Transformation, Neoplastic/metabolism , Colorectal Neoplasms/pathology , Membrane Proteins/metabolism , Adenocarcinoma/metabolism , Aged , Cell Transformation, Neoplastic/pathology , Colorectal Neoplasms/metabolism , Female , Humans , Immunohistochemistry , Male , Middle Aged , Neoplasm Staging/methods , Receptors, Retinoic Acid/metabolism , Survival AnalysisABSTRACT
Retinoids mediate a wide spectrum of antitumor activities through induction of growth arrest, differentiation or apoptosis. To determine whether the effects of retinoids are mediated by specific gene activation or repression, one-day treatments of SC-M1 CL23 gastric cancer cells with vehicle alone or all-TRANS retinoic acid (tRA) (10 microM) were compared using differential display analysis. A 432-bp cDNA fragment from the tRA-treated cells was differentially amplified and its sequence analysis indicated homology with the calcium-binding protein S100P. Levels of S100P mRNA were increased 3.5-fold in SC-M1 CL23 gastric cancer cells treated with 10 microM tRA for 1 day, and the regulation was time- and concentration-dependent. Treatment with tRA (10 microM) also increased S100P mRNA levels in tRA-sensitive HtTA cells but not in inherent RA-resistant TMC-1 cells. However, the tRA-mediated increase in S100P expression was maintained in SC-M1/R cells that were established long-term in tRA-containing medium and had acquired partial RA resistance to tRA-induced growth suppression. In conclusion, tRA increases S100P expression, and the regulation remains intact in cells which develop acquired RA resistance.
Subject(s)
Gene Expression/physiology , Receptors, Retinoic Acid/genetics , S100 Proteins/metabolism , Tretinoin/metabolism , Base Sequence , Blotting, Northern , Cell Line, Tumor , DNA Primers , Fluorometry , Gene Expression Profiling , Humans , Molecular Sequence Data , Reverse Transcriptase Polymerase Chain Reaction , S100 Proteins/genetics , Sequence Analysis, DNAABSTRACT
BACKGROUND: The retinoid-inducible gene I (RIG1), belonging to the family of type II tumor suppressor genes, was isolated from human gastric cancer cells treated with all-trans retinoic acid. The activity of the RIG1 gene was investigated in this study. MATERIALS AND METHODS: HtTA cervical and TSGH9201 gastric cancer cells were transiently transfected with expression vectors that synthesized RIG1-myc or RIG1-EGFP fusion protein. Cell growth was analyzed by measuring the incorporation of bromodeoxyuridine. Apoptosis was evaluated by the formation of in situ DNA breakage. The activities of mitogen-activated kinase signal pathways were analyzed using signal pathway trans-reporting systems. RESULTS: Expression of the RIG1-myc fusion protein resulted in decreased cell growth. Both RIG1-EGFP and RIG1-myc fusion proteins induced cellular apoptosis that was characterized by the presence of apoptotic bodies and in situ DNA breakage. The transactivation activities of Elk1, c-Jun and CHOP proteins were suppressed by 80, 50 and 88%, respectively, in HtTA cells expressing the RIG1-myc fusion protein for two days. Similarly, the transactivation activities of the CHOP protein was suppressed in TSGH9201 and HtTA cells transiently expressing RIG1-myc and RIG1-EGFP, respectively. CONCLUSION: The RIG1 fusion proteins exhibited growth suppressive and apoptosis-inducing activity. The protein negatively-regulated signal pathways of extracellular signal-regulated kinase, c-Jun N-terminal kinase and p38 mitogen-activated kinase.
