Isolation and sequencing of a novel tropomyosin isoform preferentially associated with colon cancer.
OBJECTIVE
Nonmuscle human tropomyosin (hTM) isoforms have distinct functions and may play important roles in various disease processes.


METHODS
In an attempt to identify colon epithelial tropomyosin isoform, a complementary DNA library prepared from a human colon cancer cell line T84 was screened by an oligonucleotide probe complementary to messages of all known hTM isoforms. A novel clone called TC22 was obtained. The amino acid sequence of TC22 isoform is identical to isoform 5 (hTM5) apart from the C terminal domain, amino acids 222-247 coding the exon 9.


RESULTS
Northern blot analysis showed that TC22 message is expressed in transformed epithelial cell lines and tumor tissues but not in normal epithelial cells. We developed a monoclonal antibody specific to TC22 isoform (TC22-4). By Western blot and immunoperoxidase assays, we analyzed 105 colonic specimens (fresh frozen and formalin fixed) from 96 patients with colon polyps (hyperplastic) or adenomas with or without dysplasia and cancer. Twenty-one of 22 (95%) of colon cancer specimens showed the presence of TC22, compared with only 1 of the 17 normal colon specimens and none of the 13 hyperplastic polyps (P < 0.0001). As assayed by immunoperoxidase staining, TC22 expression progressively increased in benign adenomatous polyps (35%) and polyps with mild and severe dysplasia (57% and 100%, respectively).


CONCLUSIONS
We cloned and sequenced a novel hTM isoform, TC22, which is strongly associated with colonic neoplasia and carcinoma. TC22 may provide a useful biomarker for surveillance of colon cancer.
Lin
Jenny L-C
JL
Department of Biological Sciences, University of Iowa, Iowa City, Iowa, USA.
Geng
Xin
X
Bhattacharya
Sangeeta Das
SD
Yu
Jae-Ran
JR
Reiter
Rebecca S
RS
Sastri
Bhagyalakshmi
B
Glazier
Kenneth D
KD
Mirza
Zafar K
ZK
Wang
Kenneth K
KK
Amenta
Peter S
PS
Das
Kiron M
KM
Lin
Jim J-C
JJ
D000236:Adenoma / Q000235:genetics* / Q000378:metabolism; D018256:Adenomatous Polyps / Q000378:metabolism; D000595:Amino Acid Sequence / Q000235:genetics; D001483:Base Sequence / Q000235:genetics; D002460:Cell Line; D003001:Cloning, Molecular; D003106:Colon / Q000378:metabolism; D003110:Colonic Neoplasms / Q000235:genetics* / Q000378:metabolism; D003111:Colonic Polyps / Q000378:metabolism / Q000473:pathology; D018076:DNA, Complementary / Q000235:genetics; D004274:DNA, Recombinant; D014644:Genetic Variation; D006801:Humans; D007124:Immunoenzyme Techniques; D007413:Intestinal Mucosa / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D012016:Reference Values; D014335:Tropomyosin / Q000235:genetics* / Q000378:metabolism
D018076:DNA, Complementary; D004274:DNA, Recombinant; D009363:Neoplasm Proteins; D014335:Tropomyosin