title: Differential expression of IGF-1 mRNA isoforms in colorectal carcinoma             and normal colon tissue.
abstract: The insulin-like growth factor (IGF)-1 gene consists of 6 exons resulting in the expression of 6 variant forms of mRNA (IA, IB, IC, IIA, IIB and IIC) due to an alternative splicing. The mechanisms of IGF-1 gene splicing and the role of local expression manifested by IGF-1 mRNA variants in colorectal carcinoma (CRC) have not been extensively investigated. Therefore, the aim of our study was to analyse the expression of IGF-1 mRNA isoforms [A, B, C, P1 (class I) and P2 (class II)], as well as the protein expression in CRC and control samples isolated from 28 patients. The expression of Ki-67 was also analysed and clinical data were obtained. For this purpose, we used quantitative real-time PCR (qPCR) and immunocytochemistry. The expression of mRNAs coding for all splicing isoforms of IGF-1 was observed in every tissue sample studied, with a significantly lower expression noted in the CRC as compared to the control samples. The cytoplasmic expression of IGF-1 protein was found in 50% of the CRC and in ~40% of the non-tumor tissues; however, no significant quantitative inter-group differences were observed. The expression of the IGF-1 gene in the 2 groups of tissues was controlled by the P1 and P2 promoters in a similar manner. No significant differences were detected in the expression of the IGF-1 A and B isoforms; however, their expression was significantly higher compared to that of isoform C. No significant differences were observed between the expression of Ki-67 mRNA in the CRC and control tissue even though the expression of the Ki-67 protein was higher in the CRC compared to the control samples. Ki-67 protein expression was associated with the macroscopic and microscopic aspects of CRC. A significant positive correlation was found between the local production of total mRNA and isoform A and the expression of Ki-67 mRNA, although only in the non-tumor tissues. In CRC samples, the local expression of the total IGF-1 mRNA and all splicing isoforms of IGF-1 mRNA decreased as compared to the normal colon tissues, although however, with conservation of both gene promoter activities and with the continued principal splicing IGF-1 mRNA isoforms.
authors.affiliation: Department of Histology and Embryology, Poznan University of Medical Sciences, Poznań, Poland. akasprza@ump.edu.pl
authors.forename: Aldona
authors.initials: A
authors.lastname: Kasprzak
authors.forename: Witold
authors.initials: W
authors.lastname: Szaflarski
authors.forename: Jacek
authors.initials: J
authors.lastname: Szmeja
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Andrzejewska
authors.forename: Wiesława
authors.initials: W
authors.lastname: Przybyszewska
authors.forename: Elżbieta
authors.initials: E
authors.lastname: Kaczmarek
authors.forename: Maria
authors.initials: M
authors.lastname: Koczorowska
authors.forename: Tomasz
authors.initials: T
authors.lastname: Kościński
authors.forename: Maciej
authors.initials: M
authors.lastname: Zabel
authors.forename: Michał
authors.initials: M
authors.lastname: Drews
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000328:Adult; D000368:Aged; D017398:Alternative Splicing; D014408:Biomarkers, Tumor / Q000235:genetics; D016022:Case-Control Studies; D003106:Colon / Q000378:metabolism*; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism; D019394:Ki-67 Antigen; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D011379:Prognosis; D011401:Promoter Regions, Genetic / Q000235:genetics; D059368:RNA Isoforms / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen; D059368:RNA Isoforms; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I