Search

Neuroendocrine differentiation of tumor tissue has been recognized as an important prerequisite for new targeted therapies. To evaluate the suitability of colorectal cancer (CRC) tissue for these treatment approaches and to find a possible link to pretherapeutic conditions of other targeted strategies, we compared neuroendocrine differentiation and KRAS/NRAS/BRAF/PIK3CA/TP53 mutational status in primary and metastatic CRC. Immunohistochemical expression analysis of neuroendocrine markers chromogranin A and synaptophysin was performed on archival CRC tissue, comprising 116 primary tumors, 258 lymph node metastases and 72 distant metastases from 115 patients. All CRC samples but 30 distant metastases were subjected to mutation analysis of KRAS, NRAS, BRAF, PIK3CA, and TP53. Neuroendocrine marker expression was found significantly less frequently in lymph node metastases compared to primary tumors and distant metastases (20%, 31%, 28%, respectively, P = 0.044). KRAS mutation rates increased significantly from primary tumors to lymph node metastases and distant metastases within the neuroendocrine negative CRC group (44%, 53%, 64%, respectively, P = 0.042). Neuroendocrine differentiation was significantly less concordant than KRAS/NRAS/BRAF/PIK3CA/TP53 mutational status in primary tumor/lymph node metastases pairs (65% versus 88%-99%; P < 0.0001) and primary tumor/distant metastases pairs (64% versus 83%-100%; P = 0.027 and P < 0.0001, respectively). According to these data, therapeutic targeting of neuroendocrine tumor cells can be considered only for a subset of CRC patients and biopsies from the metastatic site should be used to guide therapy. A possible importance of lacking neuroendocrine differentiation for progression of KRAS mutant CRC should be further investigated.

Aims: To evaluate a reverse-hybridisation assay (strip assay) designed for the sensitive detection of 10 mutations in codons 12 and 13 of the KRAS gene. The strip assay relies on mutant-enriched PCR followed by reverse-hybridisation of biotinylated amplification products to oligonucleotide probes immobilised as an array of parallel lines on nitrocellulose test strips., Methods: The strip assay was used to analyse genomic DNA isolated from 120 formalin-fixed paraffin-embedded (FFPE) ovarian tissue samples. The samples were analysed in parallel using a biochip-based protocol (biochip assay) covering the same mutation spectrum, and results were compared with respect to sensitivity, specificity and operational input., Results: The strip assay identified 19 (16%) of 120 FFPE samples to carry a KRAS mutation; results were in agreement with those obtained by biochip hybridisation. Both assays had an analytical sensitivity of 1% when performed on FFPE-extracted DNA with approximately the same operational input needed for post-PCR processing. In contrast to the biochip assay, strip assay hybridisation may be automated to a large extent., Conclusions: The strip assay is an accurate and sensitive tool for the low to medium throughput detection of KRAS mutation in genomic DNA isolated from FFPE tissue.

This study is aimed at evaluating the potential of a biochip assay to sensitively detect KRAS mutation in DNA from non-small cell lung cancer (NSCLC) tissue samples. The assay covers 10 mutations in codons 12 and 13 of the KRAS gene, and is based on mutant-enriched PCR followed by reverse-hybridization of biotinylated amplification products to an array of sequence-specific probes immobilized on the tip of a rectangular plastic stick (biochip). Biochip hybridization identified 17 (21%) samples to carry a KRAS mutation of which 16 (33%) were adenocarcinomas and 1 (3%) was a squamous cell carcinoma. All mutations were confirmed by DNA sequencing. Using 10 ng of starting DNA, the biochip assay demonstrated a detection limit of 1% mutant sequence in a background of wild-type DNA. Our results suggest that the biochip assay is a sensitive alternative to protocols currently in use for KRAS mutation testing on limited quantity samples.