A novel genotyping method for rapid identification of the Le gene to select patients for diagnosis with CA19-9.

BACKGROUND: The antigenic determinant of CA19-9 is synthesized by the α1,3/4fucosyltransferase encoded by the Le gene in the Lewis blood group system. Accordingly, a diagnosis with CA19-9 is not appropriate forLe-negative patients who possess the Le gene-mutated le alleles homozygously. METHODS: A Le gene-specific PCR was undertaken to determine c59T>G by using a set of tag-sense and biotin-labeled anti-sense primers and a peptide nucleic acid-le-clamp which bound to G59 in the le alleles. Following mixing with streptavidin-coatedbluelatex beads, the PCR products were developed on a strip on which the complementary tag oligonucleotide to theLe gene-specific amplicon was immobilized. RESULTS: When the PCR products were developed on the strip, a clear line was rapidly observed in Le-positive but not in Le-negative individuals. In contrast, a significant number of cancer patients with Lewis-negative phenotype were found to possess CA19-9, while they were specifically genotyped asLe/-. No contradictory results were observed in cancer patients (n = 315) with respect to their Lewis genotypes and CA19-9 levels. CONCLUSIONS: c59T>G occurred commonly in the le alleles could be specifically and rapidly identified by the present method. This method appeared to be relevant forselecting cancer patientsto bediagnosed with CA19-9.

New observations on the utility of CA19-9 as a biomarker in Lewis negative patients with pancreatic cancer.

BACKGROUND: Carbohydrate antigen 19-9 (CA19-9) is the best-validated biomarker for pancreatic cancer. The National Comprehensive Cancer Network (NCCN) guideline asserts that "CA19-9 will be undetectable in Lewis antigen-negative individuals". However, reports of CA19-9 secretion and its significance in Lewis (-) patients with pancreatic cancer have been inconsistent. This study was to examine serum CA19-9 levels in patients with pancreatic cancer according to Lewis status. METHODS: Patients with pancreatic cancer (1482 cases) were retrieved from a prospectively maintained database. Patients with benign pancreatic disease (210 cases) and normal subjects (315 cases) were used as controls. Lewis genotypes were examined by fucosyltransferase 3 (FUT3) sequencing. RESULTS: In patients with pancreatic cancer, 8.4% of subjects were Lewis (-), but only 41.9% of Lewis (-) subjects had CA19-9 values ≤ 2 U/mL. CA19-9 was even elevated (>37 U/mL) in 27.4% of Lewis (-) patients. The area under the receiver operating characteristic (ROC) curve for CA19-9 as a diagnostic biomarker was 0.842 in Lewis (-) patients with pancreatic cancer, which is closing to that of CA19-9 applied in all of patients with pancreatic cancer (0.898). Lewis (-) status was an independent prognostic factor for shorter survival in a multivariable analysis (hazard ratio (HR), 1.30, 95% confidence interval (CI), 1.03-1.64; P = 0.028). CONCLUSIONS: Not all Lewis (-) patients with pancreatic cancer are non-secretors of CA19-9. Contrary to general understanding, CA19-9 can retain its utility as a biomarker in these patients in spite of Lewis (-) genotype.