P53 And K-Ras Gene In Colonic Lavage And P53 Autoantibodies In Serum In Patients With Colonic Adenomas.

Tropomyosins (TMs) are microfilamental proteins present in all eukaryotic cells with organ specific isoforms and distinct functions.We demonstrated that non-muscle human TM isoform 5 (hTM5) is the predominant colon epithelial hTM and UC patients show significant autoantibody response against hTM5 (Gastroenterology 1998;Il4:9I2).In an attempt to identify colon epithelial hTM isoform, we used a common TM probe, REN 29, to screen a cDNA library prepared from poly (A)+ RNAs from T-84 cells.We obtained a novel clone called TC-22 whose nucleotide sequence of coding region is identical to that of hTM5 except the last exon 9 (aa222-247).Using the peptide specific to TC-22, we prepared a murine monoclonal antibody (mAb) termed TC-22-4.TC-22-4 mAb was utilized to examine 25 colonic mucosal specimens (surgical and biopsy) for the expression of TC-22 isoform by western blot analysis (WB).Of the 25 specimens, 5 were from primary colon cancer (PCC), and 4 from normal segments of PCc.Recto-sigmoid biopsy was taken from 9 UC, 2 Crohn s disease (CD) and 5 normal spastic colon.Mucosal extract was enriched for TMs and examined by WB using lOug proteins for each sample.Positive control included LCI mAb that detects hTM5.TC-22-4 reacted with TC-22TM isoform at Mr 30K in 4 of 5 PCC, and I of 4 normal area of PeC.None of 5 normal and 2 CD colon mucosa reacted.However, 2 of 9 UC (I with primary sclerosing cholangitis, I with 14 year history of UC with an adenomatous polyp) reacted at Mr 30K with TC-22-4.Each of the UC specimens from this area showed active colitis without severe dysplasia.All 25 specimens reacted with LCl.Conclusion: TC-22, a novel hTM isoform, is strongly associated with colon carcinoma.Further studies are needed to examine if the expression of TC-22 may be a clinically useful biomarker for cancer surveillance in Uc.