Tumor-associated down-regulation of 15-lipoxygenase-1 is reversed by celecoxib in colorectal cancer.
OBJECTIVE
To evaluate the role of celecoxib on 15-lipoxygenase-1 (15-LOX-1) expression, protein levels, and rates of apoptosis in colorectal cancer cell lines. Also, to evaluate the expression of 15-LOX-1 in human normal mucosa, adenoma, and carcinoma with correlation to overall survival.


BACKGROUND
The function of 15-LOX-1 is to maintain normal rates of apoptosis (programmed cell death). Decreased apoptosis is one mechanism of cancer growth and dissemination. It is our hypothesis that expression of 15-LOX-1 is reduced in human colorectal cancer (CRC) and the administration of celecoxib can reverse this process and induce apoptosis.


METHODS
Effect of celecoxib in cell culture: The effect of 40 micromol/L celecoxib was compared with untreated controls in tissue culture utilizing HT-29 and DLD-1 CRC cell lines. Expression of 15-LOX-1 protein was measured by immunoblot. Induction of apoptosis was evaluated by annexin V staining. All data are presented as mean +/- SEM, with significance defined as P < 0.05. 15-LOX-1 in human CRC: From February 1998 to January 2002, 126 patients underwent surgical resection of either colorectal adenomas (n = 24) or carcinomas (n = 102), or both (n = 25). Tissue was macrodissected, snap frozen, and stored at -80 degrees C. After tissue processing, RNA was extracted and gene expression of 15-LOX-1 was quantified utilizing ABI prism real-time quantitative RT-PCR. Significance evaluated by the Wilcoxon signed rank test.


RESULTS
Effect of celecoxib in cell culture: After 72 hours of treatment with celecoxib, immunoblot demonstrated a 1.5- to 2-fold increase in 15-LOX-1 protein expression in HT-29 and DLD-1 cells, respectively. Celecoxib produced greater than a 2-fold increase in the rate of apoptosis compared with control cells in both cell lines (P < 0.05). 15-LOX-1 in human CRC: The mean age of the patients was 62 +/- 1 years; 78% were white and 48% were female. The mean size of the polyps and cancers were 3.0 +/- 0.4 and 5.0 +/- 0.1 cm, respectively. Expression of 15-LOX-1 relative to S9 was 30 in normal mucosa and significantly down-regulated to 11 in adenomas and 16 in carcinomas (P < 0.05).


CONCLUSIONS
15-LOX-1 gene expression is significantly reduced in both human colorectal adenomas and carcinomas and associated with decreased survival. Administration of celecoxib restores 15-LOX-1 protein expression and induces apoptosis. Down-regulation of 15-LOX-1 is an early event in the adenoma to carcinoma sequence, and reversal with celecoxib may represent one mechanism for chemoprevention of polyps or treatment of carcinomas.
Heslin
Martin J
MJ
Surgical Oncology Research Laboratory, Section of Surgical Oncology, Department of Surgery, University of Alabama at Birmingham, Birmingham, Alabama, USA. martyh@uab.edu
Hawkins
Ashley
A
Boedefeld
William
W
Arnoletti
J Pablo
JP
Frolov
Andrey
A
Soong
Richie
R
Urist
Marshall M
MM
Bland
Kirby I
KI
D000236:Adenoma / Q000201:enzymology / Q000235:genetics* / Q000401:mortality; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001093:Arachidonate 15-Lipoxygenase / Q000235:genetics* / Q000378:metabolism; D015153:Blotting, Western; D002277:Carcinoma / Q000378:metabolism / Q000401:mortality; D000068579:Celecoxib; D015179:Colorectal Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000401:mortality; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D015536:Down-Regulation / Q000187:drug effects*; D015777:Eicosanoids / Q000032:analysis; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D007150:Immunohistochemistry; D008041:Linoleic Acids / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011720:Pyrazoles / Q000494:pharmacology* / Q000627:therapeutic use; D013449:Sulfonamides / Q000494:pharmacology* / Q000627:therapeutic use; D014407:Tumor Cells, Cultured
D016861:Cyclooxygenase Inhibitors; D015777:Eicosanoids; D008041:Linoleic Acids; D011720:Pyrazoles; D013449:Sulfonamides; C024348:13-hydroxy-9,11-octadecadienoic acid; D001093:Arachidonate 15-Lipoxygenase; D000068579:Celecoxib