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Background Mutational analysis of the KRAS gene has recently been established as a complementary in vitro diagnostic tool for the identification of patients with colorectal cancer who will not benefit from anti-epidermal growth factor receptor (EGFR) therapies. Assessment of the mutation status of KRAS might also be of potential relevance in other EGFR-overexpressing tumors, such as those occurring in breast cancer. Although KRAS is mutated in only a minor fraction of breast tumors (5%), about 60% of the basal-like subtype express EGFR and, therefore could be targeted by EGFR inhibitors. We aimed to study the mutation frequency of KRAS in that subtype of breast tumors to provide a molecular basis for the evaluation of anti-EGFR therapies. Methods Total, genomic DNA was obtained from a group of 35 formalin-fixed paraffin-embedded, triple-negative breast tumor samples. Among these, 77.1% (27/35) were defined as basal-like by immunostaining specific for the established surrogate markers cytokeratin (CK) 5/6 and/or EGFR. KRAS mutational status was determined in the purified DNA samples by Real Time (RT)-PCR using primers specific for the detection of wild-type KRAS or the following seven oncogenic somatic mutations: Gly12Ala, Gly12Asp, Gly12Arg, Gly12Cys, Gly12Ser, Gly12Val and Gly13Asp. Results We found no evidence of KRAS oncogenic mutations in all analyzed tumors. Conclusions This study indicates that KRAS mutations are very infrequent in triple-negative breast tumors and that EGFR inhibitors may be of potential benefit in the treatment of basal-like breast tumors, which overexpress EGFR in about 60% of all cases.

14 páginas, 4 figuras.-- PMID: 19257890 [PubMed].-- PMCID: PMC2656544.-- Información adicional (Suppl. files S1-S6) disponible en: http://www.biomedcentral.com/1471-2407/9/74/additional/, Additional files: 1. Wound healing assay 231-control cells.-- 2. Wound healing assay 231-E-cadherin cells.-- 3. Wound healing assay 231-P-cadherin cells.-- 4. Complete list of genes modulated by E-cadherin and/or P-cadherin (at least 2 fold with respect to control cells) in 231 cells.-- 5. Potential signaling networks mediated by E-cadherin-regulated genes at the biological process level.-- 6. Potential signaling networks mediated by P-cadherin-regulated genes at the biological process level., [Background]: Alterations in the cadherin-catenin adhesion complexes are involved in tumor initiation, progression and metastasis. However, the functional implication of distinct cadherin types in breast cancer biology is still poorly understood., [Methods]: To compare the functional role of E-cadherin and P-cadherin in invasive breast cancer, we stably transfected these molecules into the MDA-MB-231 cell line, and investigated their effects on motility, invasion and gene expression regulation., [Results]: Expression of either E- and P-cadherin significantly increased cell aggregation and induced a switch from fibroblastic to epithelial morphology. Although expression of these cadherins did not completely reverse the mesenchymal phenotype of MDA-MB-231 cells, both E- and P-cadherin decreased fibroblast-like migration and invasion through extracellular matrix in a similar way. Moreover, microarray gene expression analysis of MDA-MB-231 cells after expression of E- and P-cadherins revealed that these molecules can activate signaling pathways leading to significant changes in gene expression. Although the expression patterns induced by E- and P-cadherin showed more similarities than differences, 40 genes were differentially modified by the expression of either cadherin type., [Conclusion]: E- and P-cadherin have similar functional consequences on the phenotype and invasive behavior of MDA-MB-231 cells. Moreover, we demonstrate for the first time that these cadherins can induce both common and specific gene expression programs on invasive breast cancer cells. Importantly, these identified genes are potential targets for future studies on the functional consequences of altered cadherin expression in human breast cancer., This work has been supported by grants from the Fundación Mutua Madrileña (2006) and SAF2007-63075 to GMB; SAF 2007-63051 to AC; PI051890 and SAF2004-08258-C02-01 to JP. David Sarrió currently is a recipient of a Marie Curie Intra-European Fellowship of the European Commission (PIEF-GA-2008-221083). Gema Moreno-Bueno is a junior investigator of the "Ramón y Cajal Program" of the Spanish Ministry of Education and Science (2004).