Antitumor and anti-metastatic effects of cyclooxygenase-2 inhibition by celecoxib on human colorectal carcinoma xenografts in nude mouse rectum.

We examined the effects of the preferential cyclooxygenase-2 (COX-2) inhibitor celecoxib on tumorigenesis, angiogenesis, apoptosis, vascular endothelial growth factor (VEGF) protein expression and metastasis in HT-29 human colorectal carcinoma cell xenografts in nude mouse rectum. COX-2 mRNA expression was examined in the xenograft and metastatic sites. The antitumor effect of celecoxib in the xenografts was evaluated by measuring the weight of the peri-ano-rectal tumor. The anti-metastatic effect of celecoxib was assessed by quantification of lymph node and lung metastases by amplification of a cancer-related human DNA by TaqMan PCR. The effects of celecoxib on angiogenesis, apoptosis, prostaglandin E2 (PGE2) production and VEGF protein expression in the xenografts were evaluated by means of microvessel density (MVD) counting, terminal deoxynucleotidyl transferase-mediated nick end labeling assay, quantitative enzyme-linked immunosorbent assay and western blotting, respectively. The rectal xenograft model showed lymph node and lung metastases with enhanced expression of COX-2 mRNA in each organ. Celecoxib inhibited rectal xenograft growth in a dose-dependent manner as follows: 150 ppm, 33.0% (p=0.000220); 750 ppm, 46.4% (p=0.0000292); 1500 ppm, 63.4% (p=0.0000109). Celecoxib inhibited lymph node metastasis in a dose-dependent manner as follows: 150 ppm, 86.7% (p=0.0263); 750 ppm, 90.3% (p=0.00638); 1500 ppm, 96.0% (p=0.000894). Celecoxib also inhibited lung metastasis as follows: 750 ppm, 53.3% (p=0.0107); 1500 ppm, 78.3% (p=0.00022). Celecoxib (1500 ppm) significantly inhibited PGE2 production by 68.4% (p=0.000157) and MVD counting by 48.2% (p=1.3x10-12) and induced apoptosis 2.5-fold (p=3.0x10-14) in the rectal xenograft. Celecoxib suppressed VEGF protein expression in the rectal xenograft. These studies demonstrate that celecoxib reduces the growth and metastatic potential of colorectal carcinoma in mice through COX-2 inhibition, anti-angiogenesis and apoptosis induction. The studies using HT-29 human colorectal carcinoma cell xenografts in nude mouse rectum also provide important information that supports that the COX-2 inhibitor celecoxib has a high potential for use as a clinical agent for inhibition of hematological and lymphatic metastases of colorectal cancer.

Anti-metastatic effect of capecitabine on human colon cancer xenografts in nude mouse rectum.

Capecitabine (N4-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) is a new fluoropyrimidine carbamate, which is converted to 5-fluorouracil (5-FU) by 3 sequential steps of enzyme reactions. We investigated the possibility of using capecitabine to prevent metastasis with a metastasis model of gastrointestinal cancer developed by the intrarectal injection of green fluorescent protein (GFP)-expressing colon cancer HT-29 cells (HT-29-GFP) into nude mice. Lung and lymph node metastasis in the HT-29-GFP rectal xenograft was assessed through both observation of GFP fluorescence and quantification of metastasis by amplification of a cancer-related human DNA by TaqMan PCR. Furthermore, for each organ, we examined mRNA levels of cancer-specific thymidine phosphorylase (dThdPase), which is an essential enzyme for capecitabine activation, by the quantitative RT-PCR method. Capecitabine inhibited the HT-29-GFP xenograft growth by 60.8% and 43.8% in the subcutaneous and rectal xenograft models, respectively. Furthermore, it inhibited both lung and lymph node metastasis by 99.9%. dThdPase expression in the tumor cells of both the rectal xenograft and metastatic lung tumor cells was upregulated by 10.0- and 24.3-fold that in the HT-29-GFP cells in vitro, respectively. These results indicated that capecitabine might effectively inhibit or suppress metastasis via upregulation of dThdPase expression. Capecitabine administration might be highly expected to reduce metastasis and improve survival of patients with gastrointestinal cancers.