Ctivation of the EGFR downstream signaling pathways, which are important for cancer cell proliferation, invasion, metastasis, and neo-vascularization [5]. One important member of this pathway is KRAS, and the evidence of anti-EGFR therapies improving the clinical benefits 
of wild-type (WT) KRAS in mCRC patients is well known and established [6,7]. The KRAS gene encodes the KRAS BI-78D3 protein that contains 188 amino acid residues with a molecular mass of 21.6kD 18325633 [8]. KRAS is a membrane-associated GTPase thatComputational Analysis of KRAS Mutationsis an early player in many signal transduction pathways. KRAS acts as a molecular on/off switch to recruit and activate the 12926553 proteins necessary for the propagation of the growth factor and other receptor signals, such as c-Raf and PI 3-kinase. When activated, KRAS is involved in the dephosphorylation of GTP to GDP, after which KRAS is turned off. However, the issue of whether patients harboring KRAS mutations can benefit from the addition of cetuximab or panitumumab to standard chemotherapy is under debate. Currently, health authorities in the United States and Europe have indicated that patients with KRAS-mutated tumors should not receive cetuximab or panitumumab. Consequently, only KRAS WT patients are treated with anti-EGFR therapies. KRAS mutations are reported in approximately 40 ?0 of all colorectal cancer specimens [9,10]. These mutations principally occur in codons 12 and 13 and less frequently in codons 61, 63, and 146. Population-based studies have suggested that these mutations might be associated with some tumor phenotypes [11,12]. Interestingly, recent study [13] indicated that the frequency of KRAS mutation was highest in caecal cancers among all subsites. The same group also proposed that luminal contents, including gut microbial communities and their metabolites, might trigger initiating molecular events or, alternatively, influence the tumour microenvironment and promote neoplastic progression [14]. When all these mutations are taken together, approximately 80 of patients have mutations in codon 12 whereas 18 have mutations in codon 13 [15]. Mutations in codons 61 and 146 have also been found to be oncogenic in KRAS, although these mutations occur at much lower prevalence (,5 of total KRAS mutations) than codon 12 and 13 mutations [16]. Mutations in codons 12 and 13 leads to alterations in encoded amino acids adjacent to the GDP/GTP binding pocket, reducing or abolishing the GTPase activity of KRAS after guanine nucleotide activating protein (GAP) binding and locking the protein in an active, GTPbound state [17]. Both codons 12 and 13 in KRAS WT encode the glycine residues. The incorporation of other amino acids, most commonly aspartate and valine at 
codon 12 and aspartate at codon 13 [18], brings about the projection of larger amino acid side chains into the GDP/GTP binding pocket of the protein, interfering with the steric Anlotinib site hindrance in GTP hydrolysis [19]. As a consequence, the EGFR signaling pathway is out of control with constitutive activation of the KRAS protein because of these conformational and structural changes. With regard to anti-EGFR therapy, KRAS mutations conferring resistance to traditional anti-EGFR drugs have been reported [20,21]. Many studies demonstrate that a small number of patients with KRAS-mutated tumors (10 ) have responded to anti-EGFR therapy [22,23] and approximately 15 have long-term disease stabilization [24]. In these patients, codon 13 mutations w.Ctivation of the EGFR downstream signaling pathways, which are important for cancer cell proliferation, invasion, metastasis, and neo-vascularization [5]. One important member of this pathway is KRAS, and the evidence of anti-EGFR therapies improving the clinical benefits of wild-type (WT) KRAS in mCRC patients is well known and established [6,7]. The KRAS gene encodes the KRAS protein that contains 188 amino acid residues with a molecular mass of 21.6kD 18325633 [8]. KRAS is a membrane-associated GTPase thatComputational Analysis of KRAS Mutationsis an early player in many signal transduction pathways. KRAS acts as a molecular on/off switch to recruit and activate the 12926553 proteins necessary for the propagation of the growth factor and other receptor signals, such as c-Raf and PI 3-kinase. When activated, KRAS is involved in the dephosphorylation of GTP to GDP, after which KRAS is turned off. However, the issue of whether patients harboring KRAS mutations can benefit from the addition of cetuximab or panitumumab to standard chemotherapy is under debate. Currently, health authorities in the United States and Europe have indicated that patients with KRAS-mutated tumors should not receive cetuximab or panitumumab. Consequently, only KRAS WT patients are treated with anti-EGFR therapies. KRAS mutations are reported in approximately 40 ?0 of all colorectal cancer specimens [9,10]. These mutations principally occur in codons 12 and 13 and less frequently in codons 61, 63, and 146. Population-based studies have suggested that these mutations might be associated with some tumor phenotypes [11,12]. Interestingly, recent study [13] indicated that the frequency of KRAS mutation was highest in caecal cancers among all subsites. The same group also proposed that luminal contents, including gut microbial communities and their metabolites, might trigger initiating molecular events or, alternatively, influence the tumour microenvironment and promote neoplastic progression [14]. When all these mutations are taken together, approximately 80 of patients have mutations in codon 12 whereas 18 have mutations in codon 13 [15]. Mutations in codons 61 and 146 have also been found to be oncogenic in KRAS, although these mutations occur at much lower prevalence (,5 of total KRAS mutations) than codon 12 and 13 mutations [16]. Mutations in codons 12 and 13 leads to alterations in encoded amino acids adjacent to the GDP/GTP binding pocket, reducing or abolishing the GTPase activity of KRAS after guanine nucleotide activating protein (GAP) binding and locking the protein in an active, GTPbound state [17]. Both codons 12 and 13 in KRAS WT encode the glycine residues. The incorporation of other amino acids, most commonly aspartate and valine at codon 12 and aspartate at codon 13 [18], brings about the projection of larger amino acid side chains into the GDP/GTP binding pocket of the protein, interfering with the steric hindrance in GTP hydrolysis [19]. As a consequence, the EGFR signaling pathway is out of control with constitutive activation of the KRAS protein because of these conformational and structural changes. With regard to anti-EGFR therapy, KRAS mutations conferring resistance to traditional anti-EGFR drugs have been reported [20,21]. Many studies demonstrate that a small number of patients with KRAS-mutated tumors (10 ) have responded to anti-EGFR therapy [22,23] and approximately 15 have long-term disease stabilization [24]. In these patients, codon 13 mutations w.
