High thymidylate synthase expression in colorectal cancer with microsatellite instability: implications for chemotherapeutic strategies.

UNLABELLED: Colon cancers displaying microsatellite instability (MSI) are clinically less aggressive. Based on in vitro studies and recent clinical data, cancers displaying MSI do not respond to 5-fluorouracil (5-FU). The reasons why MSI tumors are clinically less aggressive and do not respond to 5-FU-based therapies have not been fully elucidated. PURPOSE: We investigated biomolecular markers in an attempt to explain the different clinical behavior and chemotherapeutic responses of MSI and non-MSI colon cancers. EXPERIMENTAL DESIGN: One hundred ninety-two sporadic colon cancers were tested for MSI with five mononucleotide markers and methylation of the hMLH1 promoter. Slides were stained for thymidylate synthase (TS), p53, MDM2, p21(WAF1/CIP1), beta-catenin, vascular endothelial growth factor, hMLH1, hMSH2, and hMSH6. Tumors were regarded as having wild-type, functional p53 (Fp53) if reduced expression of p53 and positive MDM2 and p21(WAF1/CIP1) expressions were found. RESULTS: Of the cases, 12.5% were MSI-H (at least two markers mutated). Of MSI-H cases, 83.3% were characterized by a complete loss of at least one of the mismatch repair proteins, in particular loss of hMLH1 by promoter hypermethylation. MSI-H colon cancers showed higher expression of TS compared with MSS (no mutated markers)/MSI-L (one mutated marker) colon cancers (66.6% for MSI-H versus 14.8% MSS/MSI-L; P < 0.0001); 20.8% of MSI-H cases showed high expression of the vascular endothelial growth factor, compared with 45.8% MSS/MSI-L colon cancers (P = 0.0005); 45.8% MSI-H cases had Fp53 compared 11.9% MSS/MSI-L cases (P < 0.0001). CONCLUSIONS: About 12% of colon cancers display MSI mostly due to lack of hMLH1 resulting from promoter hypermethylation. These tumors have high expression of TS and retain fully functional p53 system. Thus, these data suggest why sporadic hMLH1-defective colon cancers often do not respond to 5-FU.

Successful treatment of CCl4-induced acute liver failure with portal vein arterialization in the rat.

BACKGROUND: Optimization of the conditions for regeneration is a major goal in the management of patients with acute liver failure (ALF). Previous observations suggested that hyperoxygenation of the liver may improve its regenerative capacity. Thus, this study aimed to determine whether an additional supply of oxygenated blood achieved by portal vein arterialization (PVA) is protective in rat ALF caused by toxin administration or hepatectomy. METHODS: Sprague-Dawley rats were subjected or not to PVA after CCl(4) intoxication or extended hepatectomy. PVA was performed by interposing a stent between the left renal artery and splenic vein after left nephrectomy and splenectomy. Liver injury was evaluated by the serum ALT level and necrotic cell count. Hepatocyte regeneration was assessed by calculating the mitotic index and bromodeoxyuridine (BrdU) staining. The 10-day survival was assessed in separate experimental groups. RESULTS: The pO(2) in portal blood increased significantly following PVA. In the CCl(4)-induced ALF, serum ALT levels and necrosis were significantly reduced in arterialized than non-arterialized rats. PVA greatly promotes liver regeneration in both models. Finally, PVA significantly improved survival compared to controls (CCl(4): 100 versus 40%; 90% hepatectomy: 90 versus 30%). Interestingly, in the CCl(4)-induced ALF, survival was 100% even when the shunt was closed after 48 h. CONCLUSION: These data indicate that the additional supply of arterial oxygenated blood through PVA promotes a rapid regeneration leading to the resolution of toxic-induced massive liver necrosis and a faster restoration of liver mass after partial hepatectomy in rats. Thus, PVA may represent a novel tool for optimizing hepatocyte regeneration.