Fatty acid binding protein 6 is overexpressed in colorectal cancer.
OBJECTIVE
Fatty acid binding protein 6 (FABP6) is a cancer-related protein that acts as an intracellular transporter of bile acid in the ileal epithelium. Because bile acids are implicated in the carcinogenesis of colorectal cancer, we evaluated FABP6 expression in colorectal cancer.


METHODS
The expression of FABP6 mRNA was evaluated in 78 paired samples of cancer/normal tissue representing colorectal cancer cases, plus 16 adenomas, and 16 metastatic lymph nodes. An immunohistochemical study was conducted with paraffin sections. In vitro transfection was done to determine FABP6's biological roles.


RESULTS
The expression of FABP6 mRNA was significantly higher in cancer (75 of 78, 96.2%) than in normal tissue (P<0.001). The expression of mRNA was increased in cancer compared with adenoma, but was dramatically decreased in node metastases. Tumors with high FABP6 expression were smaller in size (P<0.01), more often in the left colon (P<0.05), and had shallower invasion into the bowel wall (P<0.05) compared with those with low expression. There was no significant difference between high- and low-expression tumors regarding clinicopathologic variables such as histologic type, lymph node, or liver metastasis, Dukes' classification, and prognosis. Immunohistochemical study revealed that FABP6 expression was primarily observed in cancer cells. In vitro transfection revealed that transfectants showed weaker invasiveness (P<0.05), more dominant proliferation (P<0.001), and less apoptosis than mock cells.


CONCLUSIONS
The expression of FABP6 was higher in primary colorectal cancers and adenomas than in normal epithelium, but was dramatically decreased in lymph node metastases, suggesting that FABP6 may play an important role in early carcinogenesis.
Ohmachi
Takahiro
T
Department of Surgery and Molecular Oncology, Medical Institute of Bioregulation, Kyushu University, Beppu, Japan.
Inoue
Hiroshi
H
Mimori
Koshi
K
Tanaka
Fumiaki
F
Sasaki
Atsushi
A
Kanda
Tatsuo
T
Fujii
Hiroshi
H
Yanaga
Katsuhiko
K
Mori
Masaki
M
D000236:Adenoma / Q000235:genetics* / Q000473:pathology; D000368:Aged; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D050556:Fatty Acid-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D005768:Gastrointestinal Hormones; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D008198:Lymph Nodes / Q000473:pathology; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
D050556:Fatty Acid-Binding Proteins; D005768:Gastrointestinal Hormones; D012333:RNA, Messenger; C057275:fatty acid-binding protein 6