In-vitro metabolism of celecoxib, a cyclooxygenase-2 inhibitor, by allelic variant forms of human liver microsomal cytochrome P450 2C9: correlation with CYP2C9 genotype and in-vivo pharmacokinetics.

In-vitro studies were conducted to assess the impact of CYP2C9 genotype on the metabolism (methyl hydroxylation) and pharmacokinetics of celecoxib, a novel cyclooxygenase-2 inhibitor and CYP2C9 substrate. When compared to cDNA-expressed wild-type CYP2C9 (CYP2C9*1), the Vmax/Km ratio for celecoxib methyl hydroxylation was reduced by 34% and 90% in the presence of recombinant CYP2C9*2 and CYP2C9*3, respectively. These data indicated that the amino acid substitution at position 359 (Ile to Leu) elicited a more pronounced effect on the metabolism of celecoxib than did a substitution at position 144 (Arg to Cys). The Vmax/Km ratio was also decreased in microsomes of livers genotyped CYP2C9*1/*2 (47% decrease, mean of two livers), or CYP2C9*1/*3 (59% decrease, one liver). In all cases, these changes were largely reflective of a decrease in Vmax, with a minimal change in Km. Based on simulations of the in-vitro data obtained with the recombinant CYP2C9 proteins, it was anticipated that the pharmacokinetics of celecoxib (as a much as a five-fold increase in plasma AUC) would be altered (versus CYP2C9*1/*1 subjects) in subjects genotyped heterozygous or homozygous for the CYP2C9*2 (Cys144) or CYP2C9*3 (Leu359) allele. In a subsequent clinical study, the AUC of celecoxib was increased (versus CYP2C9*1/*1 subjects) approximately 2.2-fold (range, 1.6-3-fold) in two CYP2C9*1/*3 subjects and one CYP2C9*3/*3 subject receiving a single oral dose (200 mg) of the drug. In contrast, there was no significant change in celecoxib AUC in two subjects genotyped CYP2C9*1/*2.

Postoperative management of local colorectal cancer: therapy and surveillance.

Adjuvant therapy is widely recommended for stage III colon cancer and stages II and III rectal cancer. Although fluorouracil-based regimens are standard, newer agents either alone or in combination may improve response rates. Although nearly all patients enter a postoperative surveillance program after surgical resection, the clinical effectiveness of such surveillance, which is not standardized, is questionable. Critical review of the use of different components (laboratory, radiographic, and endoscopic) of these programs finds little support for intensive surveillance.

Colorectal cancer staging and adjuvant chemotherapy.

Colorectal cancer is a significant cause of morbidity and mortality in Western populations. The standard of care for staging patients with colorectal cancer to determine prognosis and identify patients who will receive adjuvant therapy continues to be histopathology of regional lymph nodes. However, the significant variability in survival within each staging category likely reflects the heterogeneity of detecting micrometastatic disease employing this technique. Novel molecular markers of micrometastases currently in development will permit more accurate staging of patients with colorectal cancer. These advances in staging will distinguish patients who will maximally benefit from adjuvant therapy from those who have an especially good prognosis in whom chemotherapy can be avoided. In addition, new adjuvant chemotherapeutic agents, novel combinations of those agents and creative dosing schedules currently being investigated will offer considerable advantages with respect to ease of administration, safety and tolerability, quality of life and efficacy. Ultimately, it is anticipated that advances in molecular diagnostics will define unique biochemical characteristics of patients' tumours, permitting individualization of chemotherapeutic regimens employing novel agents that specifically exploit those characteristics.

Guanylyl cyclase C messenger RNA is a biomarker for recurrent stage II colorectal cancer.

BACKGROUND: Patients with stage II colorectal cancer and no histologic evidence of lymph node invasion develop recurrent disease, presumably because of undetected micrometastases. Guanylyl cyclase C is expressed by intestinal and colorectal cancer cells but not by extraintestinal tissues or tumors. OBJECTIVE: To examine the expression of guanylyl cyclase C messenger RNA (mRNA) in lymph nodes of patients with node-negative colorectal cancer who did and did not have recurrent disease. DESIGN: Case-control study. SETTING: Tertiary care academic medical center. PATIENTS: Paraffin-embedded lymph nodes were obtained from 21 patients with histologically confirmed node-negative colorectal cancer who had undergone resection. Controls included 11 patients without disease recurrence 6 or more years after resection, and case-patients included 10 patients whose disease recurred up to 3 years after resection. MEASUREMENTS: Sections of paraffin-embedded lymph nodes were obtained from each patient and were pooled, and their RNA was analyzed by reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: Guanylyl cyclase C mRNA was expressed in lymph nodes from all patients with recurrent disease but not in those from patients without recurrent disease (P = 0.004). Nested RT-PCR that used primers for carcinoembryonic antigen, a marker for colorectal cancer, identified carcinoembryonic antigen mRNA in lymph nodes from only 1 of 10 patients with recurrent disease and those from 0 of 11 patients without recurrent disease. The odds ratio for death associated with expression of guanylyl cyclase C mRNA in regional lymph nodes was 15.0 (95% CI, 1.1 to 756.7). CONCLUSIONS: Expression of guanylyl cyclase C mRNA in lymph nodes is associated with recurrence of colorectal cancer in patients with stage II disease. Analysis of guanylyl cyclase mRNA expression by RT-PCR may be useful for colorectal cancer staging.

Use of shoulder flexors to achieve isometric elbow extension in C6 tetraplegic patients during weight shift.

The anterior deltoid muscle has been found to be active during elbow extension in normal volunteers and in C6 tetraplegic patients lacking a functional triceps. Using surface electromyography (EMG) on normal volunteers and on patients with spinal cord injury (SCI) at the C6 motor level, we evaluated whether the anterior deltoid and biceps brachii muscles are active during closed chain elbow extension in a simulated weight shift position. Thirteen normal volunteers performed isometric contractions at 5 submaximal levels of force ranging from 4-25 kg. Six SCI patients performed isometric contractions at force levels of 20%, 40%, 60%, 80% and 100% maximum voluntary contraction (MVC). Surface EMG over the right biceps, triceps, and anterior deltoid muscles was recorded for each participant and the root mean square (rms) electromyographic activity level for each muscle was determined at each level of force. Statistical analyses using repeated ANOVA with Tukey HSD post-hoc tests were performed for each level of force. The results indicated increasing rms activity of the triceps and anterior deltoid muscles with increasing force in normal volunteers to a significant degree (P < 0.05). SCI patients showed significant increasing activity of the anterior deltoid with increasing force, but showed minimal triceps rms activity. In both groups, the biceps showed minimal rms activity. SCI patients exhibited significantly greater rms activity of the anterior deltoid at low force compared with normal volunteers. The results suggest that the anterior deltoid aids in isometric elbow extension during a simulated weight shift maneuver.