All of the rats were sacrificed by decapitation before the intestinal sacs were removed

of the tumors might also contribute to the lack of detectable mutations. Similarly, either there is little or no MEK162 site classifier-constituting peptides/proteins related to EGFR gene mutation status being shed in the blood in a given case, or the quantity of peptides/ proteins in the serum is affected by certain conditions, such as inflammation, the classification of EGFR gene mutation status PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19704093 based on serum proteomic profiling might be impeded despite the presence of mutations in tumors. EGFR encoded by the wild-type EGFR gene is a transmembrane tyrosine kinase receptor with a molecular weight of 170 kDa. The difference between EGFR encoded by EGFR gene with TKI-sensitive mutations and EGFR encoded by wild-type EGFR gene is that the former harbors activating tyrosine kinase domain. These two EGFRs should have similar molecular weights. Due to the high molecular weight, it is important to note that the MALDI-TOF-MS described in this study is neither suited for directly detecting EGFR encoded by EGFR gene with TKI-sensitive mutations nor EGFR encoded by wild-type EGFR gene because the typical observable mass range is 80010000 Da. Instead, we detected the differential peptide/protein profiles between EGFR encoded by EGFR gene with TKI-sensitive mutations and EGFR encoded by wild-type EGFR gene. The identities of the constituting peptides/proteins are unknown at present; it is possible that they are unknown co-expressed peptides/proteins with low molecular weights involved, or that we detected fragments of EGFR or other high molecular weight proteins, such as proteins from the EGFR signaling pathway. It is well known that tumor cell dissemination and apoptotic processes in tumors and at tumor-tissue boundaries involve changes in the proteolytic activities of a series of different proteases that may lead to the formation of protein fragments, thus providing a strong correlation with tumor tissue, and that as well serve as a basis for tumor differentiation and prognosis. In agreement with this assumption, the proteins that have been identified thus far from blood samples by MALDI-TOF-MS have largely been degradation products of larger proteins. We also analyzed the potential implications of EGFR gene mutation status, as identified by the serum proteomic classifier, for predicting clinical outcomes in patients with NSCLC who received EGFR-TKIs. Our findings of a correlation between EGFR gene mutations identified by the classifier and tumor response to EGFR-TKI treatment and such treatment’s lack of impact on OS were also consistent PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19705070 with previous studies in which EGFR gene mutation status was tested in tumor tissue. In patients treated with EGFR-TKIs in the validation group, 59.6% of the patients whose matched samples were labeled as “mutant” responded to EGFR-TKIs, whereas 8.8% of the patients whose matched samples were labeled as “wild” also responded. Although no difference in OS was observed between patients whose matched samples were labeled as “mutant” and “wild”, patients whose matched samples were labeled as “mutant” had significantly longer PFS after EGFR-TKI treatment, which suggests that these patients might have benefitted from the treatment. It should be noted that our study was not specifically designed to test EGFR-TKI treatment and that many patients received other chemotherapeutic 14 / 17 Classification of EGFR in NSCLC agents, which makes data interpretation difficult. Additional clinical studies with specifically defined treatment