ABSTRACT
CONTEXT: The incidence of colorectal cancers (CRCs) in young Indian patients is higher than the international average. CRCs in young patients are commonly of mucinous type and show microsatellite instability (MSI). AIMS: To ascertain the MSI status of mucinous CRCs in patients ≤40 years of age by molecular testing and to correlate this with immunohistochemical (IHC) analysis and tumor histology. SUBJECTS AND METHODS: Archived formalin-fixed paraffin embedded tissue blocks of 30 young mucinous CRC patients were retrieved. MSI testing was done using two mononucleotide markers - BAT26 and NR24. IHC analysis was done using MLH1, MSH2, and MSH6. Histological features of all cases were studied. Data were analyzed using the SPSS software and the Pearson's chi-square test and Fisher's exact test. RESULTS: Eight out of 30 cases (26.7%) showed MSI by molecular testing. IHC identified seven of these cases. Histological features showing a statistically significant association with MSI were the presence of a well-differentiated adenocarcinoma component (P = 0.003), peritumoral lymphocytes (P = 0.002) and tumor budding (P = 0.021). CONCLUSION: The detection of defective mismatch repair (MMR) proteins using IHC for MLH1, MSH2, and MSH6 and molecular testing using BAT26 and NR24 appears to be a good protocol to detect CRCs with MSI. Histology could be useful in identifying cases that require screening for presence of MMR protein defects.
Subject(s)
Adenocarcinoma, Mucinous/genetics , Biomarkers, Tumor/genetics , Colorectal Neoplasms/genetics , Genetic Markers/genetics , Microsatellite Repeats/genetics , Adenocarcinoma, Mucinous/diagnosis , Adenocarcinoma, Mucinous/pathology , Adult , Colorectal Neoplasms/diagnosis , Colorectal Neoplasms/pathology , DNA Mismatch Repair , DNA-Binding Proteins/metabolism , Female , Humans , Immunohistochemistry , Male , Microsatellite Instability , MutL Protein Homolog 1/metabolism , MutS Homolog 2 Protein/metabolism , Pathology, Molecular , Young AdultABSTRACT
PURPOSE: This study was undertaken to evaluate the efficiency of the pyrosequencing (PSQ) assay for the rapid detection of resistance to rifampicin (RIF), fluoroquinolones (FQs) and second-line injectables (SLIs) such as capreomycin (CAP) and kanamycin (KAN) in Mycobacterium tuberculosis (Mtb) clinical isolates. METHODOLOGY: Pyrosequencing is a simple and accurate short read DNA sequencing method for genome analysis. DNA extraction from Mtb clinical isolates was performed using Tris-HCl buffer and chloroform. The rpoB (RIF), gyrA (FQs) and rrs (aminoglycosides) genes were amplified, followed by sequencing using the PyroMark Q24 ID system. The PSQ results were compared with the results from the conventional drug susceptibility testing performed in the laboratory. RESULTS: The sensitivity of the PSQ assay for the detection of resistance to RIF, FQ, CAP and KAN was 100â%, 100â%, 40â% and 50â%, respectively. The specificity of the PSQ assay was 100â%. CONCLUSION: The PSQ assay is a rapid and effective method for detecting drug resistance mutations from Mtb clinical isolates in a short period of time.
