Expression of retinoid-responsive genes occurs in colorectal carcinoma-derived cells irrespective of the presence of resistance to all-trans retinoic acid
✍ Scribed by Waliszewski, Przemyslaw; Waliszewska, Miroslawa K.; Gupta, Manjuela; Milsom, Jeffrey W.; Hurst, Robert E.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 299 KB
- Volume
- 66
- Category
- Article
- ISSN
- 0022-4790
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✦ Synopsis
Background and Objectives: Retinoids are metabolized in human intestinal epithelial cells to all-trans retinoic acid; however, it is unknown whether these cells express retinoid receptors, and whether sensitivity or resistance to the hormone is associated with a particular pattern of expression of retinoid-responsive genes. Methods: Northern blot analysis and reverse transcriptase polymerase chain reaction (RT-PCR) were used to identify mRNAs for retinoid receptors. Both Relative RT-PCR and transfection of retinoid-inducible plasmid were applied to test functionality of the pathway in a model system for colorectal carcinoma progression (primary SW480, all-trans retinoic acid-sensitive cells vs. metastatic SW620, -insensitive cells). Results: Three colorectal carcinoma-derived cell lines were inhibited by the hormone. Retinoic acid receptor type ␣ (hRAR␣) and retinoid X receptor type ␣ (hRXR␣) mRNAs were detected in normal enterocytes, colonocytes, and in all colorectal carcinoma-derived cells studied. Primary carcinomas and metastatic lesions expressed high amounts of hRAR␣ receptor protein, showing no simple correlation between the amounts of mRNA and receptor protein. No pattern of expression of the retinoidresponsive genes was associated with sensitivity or resistance to the retinoid. Expression of the genes occurred irrespective of resistance to the hormone or inactivity of the pathway.
Abbreviations: atRA, all-trans retinoic acid; CAT, chloramphenicol acetyltransferase; CRBP I , cellular retinol binding protein type I; CRABP I, II, cellular retinoic acid binding protein types I and II; EGF-R, epidermal growth factor receptor; hRAR, retinoic acid receptor; hRXR, retinoid X receptor; MK, angiogenic cytokine; RARE, retinoic acid responsive element; TG, transglutaminase; DEPC, diethylpyrocarbonate; DTT, dithiothreitol; dNTP; deoxynucleotidetriphosphate; PMSF, phenylmethylsulfonyl fluoride. These results were presented in part at the 86th Annual Meeting of the