Faculty Bibliography

Acute pancreatitis is a rare complication of interferon (IFN) and ribavirin (RBV) therapy. The aim of this study was to determine the incidence, clinical presentation, and outcome of acute pancreatitis in patients with chronic hepatitis C virus (HCV) infection treated with IFN and RBV combination therapy. We conducted a retrospective review of 1706 HCV-infected patients treated with IFN alpha-2b and RBV. The diagnosis of drug-induced acute pancreatitis was made based on the presence of epigastric pain, elevated amylase and lipase levels, and the absence of other identifiable causes of pancreatitis. Acute pancreatitis was diagnosed in 7 of 1706 HCV-infected patients (0.4%; 95% CI, 0.2 to 0.8%) who were treated with IFN alpha-2b and RBV. The mean age of the patients (four males and three females) was 51.4 +/- 4.7 years and the median duration of therapy prior to development of pancreatitis was 12.0 weeks (range, 4.0-21.0 weeks). All patients presented with epigastric pain associated with nausea, vomiting, and/or fever. The median amylase and lipase values at the time of diagnosis of pancreatitis were 330.0 U/L (range, 182.0-1813.0 U/L) and 500.0 U/L (range, 171.0-2778.0 U/L), respectively. IFN and RBV were discontinued in all patients at the time of diagnosis and six of the seven patients were hospitalized; one patient refused hospital admission. Pancreatitis resolved in all seven patients and none of these individuals had recurrent pancreatitis during a median follow-up of 18.0 months (range, 3.0-27.0 months). In conclusion, IFN and RBV combination therapy is a potential cause of drug-induced pancreatitis in patients with chronic HCV. In these individuals, pancreatitis is often severe enough to warrant hospital admission, although symptoms resolve promptly after discontinuation of antiviral therapy

Guanylyl cyclase C is a sensitive and specific biomarker for metastatic colorectal cancer. A variant of the guanylyl cyclase C transcript was identified that possesses a 142-bp deletion at the 3' end of exon 1 reflecting alternative splicing of mRNA, introducing a shift in the open reading frame that prevents translation of a guanylyl cyclase C-related product. This variant was identified in human intestine and colon carcinomas, but not in extraintestinal tissues or tumors. These studies demonstrate that GCC and the splice variant contribute to the pool of GCC transcripts detected by RT-PCR in human tissues. They indicate that primers for RT-PCR that amplify regions downstream from the deletion are required to assess the full complement of GCC transcripts (GCC + GCC(var)) in human tissues and body fluids for staging and postoperative surveillance of patients with colorectal cancer.

In humans, guanylyl cyclase C (GCC) is expressed by mucosal cells lining the intestine, from the duodenum to the rectum, but not by extraintestinal tissues. Expression of GCC persists after mucosal cells undergo neoplastic transformation, and this protein has been identified in all primary and metastatic colorectal tumors examined to date, suggesting that GCC may be a highly specific biomarker for colorectal cancer. The utility of GCC as a diagnostic biomarker and therapeutic target is predicated, in part, on defining the variability of its expression in colorectal cancer cells. Similarly, the utility of this biomarker to define tumor burden in diagnosing, staging, and postoperative surveillance of patients is predicated on quantifying GCC expression in cancer cells in tissues and blood. The present studies examined the heterogeneity of GCC expression in eight human colorectal carcinoma cell lines in vitro representing the full spectrum of cytological differentiation. Quantification of GCC expression by ligand binding and stimulation of cGMP accumulation demonstrated that functional GCC expression is heterogeneous in different colorectal cancer cell lines. Qualitative reverse transcription (RT)-PCR demonstrated that all colorectal cancer cells examined expressed GCC mRNA. However, GCC expression varied 100-fold in different colorectal cancer cell lines, determined by a novel quantitative RT-PCR assay. Functional and molecular expressions of GCC were unrelated to the differentiation state of cancer cells. These studies suggest that GCC is heterogeneously expressed by colorectal cancer cells in vitro and suggest a role for quantitative RT-PCR analysis in the development of diagnostic tests using GCC as a biomarker for metastatic colorectal cancer.