EGFR pathway in colo-rectal cancer Ahmed Allam A.H. Mohammed. Ass. Lecturer, Clinical oncology and Nuclear med. Depart. Assiut University Hospitals
EGFR is a transmembrane glycoprotein tyrosine kinase receptor that belongs to the ErbB family of cell membrane receptors. In addition to EGFR (also known as HER1 and ErbB-1), other receptors in this family include HER2/c-neu (ErbB-2), Her 3 (ErbB-3), and Her 4 (ErbB-4). All of these receptors contain an extracellular ligand-binding region, a single membrane-spanning region, and a cytoplasmic tyrosine kinase-containing domain. EGFR is expressed in a variety of human tumors, including gliomas and carcinomas of the lung, colon, head and neck, pancreas, breast, ovary, bladder, and kidney. There are at least 16 different EGF family ligands that bind ErbB receptors, for example:TGF-Alpha (Transforming Growth Factor- Alpha), which bind specifically to ErbB1
Ligand binding induces dimerization of the receptor with formation of homodimers and heterodimers, which leads to the activation of tyrosine kinase. The intracellular tyrosine kinase residues then become autophosphorylated, inducing activation of multiple signal transduction pathways.
Two main intracellular pathways activated by EGFR are the mitogen activated protein kinase (MAPK) pathway and the phosphatidylinositol 3-kinase- (PI3K-) protein kinase B (AKT) pathway. These pathways lead to the activation of various transcription factors that then impact cellular responses such as proliferation, migration, differentiation, and apoptosis
The EGFR Pathway and Colorectal Carcinogenesis EGFR Protein Expression EGFR expression (or overexpression), typically determined by immunohistochemistry Although EGFR has been reported to be overexpressed in anywhere from 25% to 82% of colorectal cancers, some recent studies report protein overexpression (defined as 2+ and/or 3+ staining or in >50% of cells) in 35 to 49% of cases.N. S. Goldstein and M. Armin, “Epidermal growth factor receptor immunohistochemical reactivity in patients with American Joint Committee on Cancer Stage IV colonadenocarcinoma: implications for a standardized scoring system,” Cancer, vol. 92, pp. 1331–1346, 2001.J. P. Spano, R. Fagard, J. C. Soria, O. Rixe, D. Khayat, and G. Milano, “Epidermal growth factor receptor signaling in colorectal cancer: preclinical data and therapeuticperspectives,” Annals of Oncology, vol. 16, no. 2, pp. 189–194, 2005.
EGFR Protein Expression (cont’d) Prognostic: the clinical significance of EGFR overexpression in colorectal cancer is uncertain.While one study of 249 colorectal cancers demonstrated an association of EGFR overexpression with tumor grade (poor differentiation) (P = .014) [J. A. McKay,2002], another group found no association with grade in 134 tumors [M. B. Resnick 2004]. Similarly, some studies have found an association between EGFR overexpression (defined as 2+ or 3+ intensity) and reduced survival [M. B. Resnick 2004], while others have not [J. P. Spano,2005].J. A. McKay, L. J. Murray, S. Curran et al., “Evaluation of the epidermal growth factor receptor (EGFR) in colorectal tumours and lymph node metastases,” European Journal ofCancer, vol. 38, no. 17, pp. 2258–2264, 20M. B. Resnick, J. Routhier, T. Konkin, E. Sabo, and V. E. Pricolo, “Epidermal growth factor receptor, c-MET, β-catenin, and p53 expression as prognostic indicators in stage IIcolon cancer: a tissue microarray study,” Clinical Cancer Research, vol. 10, no. 9, pp. 3069–3075, 2004.J. P. Spano, R. Fagard, J. C. Soria, O. Rixe, D. Khayat, and G. Milano, “Epidermal growth factor receptor signaling in colorectal cancer: preclinical data and therapeuticperspectives,” Annals of Oncology, vol. 16, no. 2, pp. 189–194, 2005.
EGFR Protein Expression (cont’d) Predictive : Due to the known expression of EGFR in colorectal cancer, a phase II trial of cetuximab, an anti-EGFR monoclonal antibody, in patients with refractory EGFR-positive (assessed by immunohistochemistry) colorectal cancer was undertaken [L. B. Saltz,2004]. The results of this trial, reported in 2004, were promising. . It was soon discovered, however, that there was no correlation between EGFR expression in the tumor and response to therapy In the study by Chung et al., 4 of 16 (25%) patients with EGFR- negative tumors who received cetuximab-plus-irinotecan therapy achieved a partial response with a greater than 50% reduction in the size of measurable lesions, other trials did show the same results, As a result, cetuximab is now administered as indicated without the need for EGFR testing.L. B. Saltz, N. J. Meropol, P. J. Loehrer Sr., M. N. Needle, J. Kopit, and R. J. Mayer, “Phase II trial of cetuximab in patients with refractory colorectal cancer that expresses the epidermalgrowth factor receptor,” Journal of Clinical Oncology, vol. 22, no. 7, pp. 1201–1208, 2004K. Y. Chung, J. Shia, N. E. Kemeny et al., “Cetuximab shows activity in colorectal cancer patients with tumors that do not express the epidermal growth factor receptor byimmunohistochemistry,” Journal of Clinical Oncology, vol. 23, no. 9, pp. 1803–1810, 2005.
EGFR Protein Expression (cont’d) The wide range of EGFR expression in colorectal cancer reported in the literature, as well as the uncertain significance of EGFR expression as a prognostic indicator, may be related to the methodology used to detect EGFR. Most studies use immunohistochemistry to detect EGFR expression in colorectal cancers. As demonstrated by the experience of HER2 expression in breast cancer, immunohistochemistry is highly dependent on the antibody clone that is used, staining protocols, selection of scoring methods, and selection of cutoff values. Until a standard method of EGFR staining and reporting is adopted, the significance of EGFR protein expression in colorectal cancer remains controversialAlyssa M. Krasinskas EGFR Signaling in Colorectal Carcinoma, SAGE-Hindawi Access to Research Pathology Research International Volume 2011, Article ID 932932,doi:10.4061/2011/932932
- EGFR Gene Amplification, and Copy Number. The significance of EGFR gene amplification/increased EGFR copy number is difficult to summarize. Some studies report that EGFR gene amplification (assessed by in situ hybridization methods) is uncommon in colorectal cancer* . In contrast, in recent studies on chemo refractory colon cancers, it appears that modest increases in copy number (three- to fivefold) are present in up to 50% of cases** It appears, however, that increased EGFR protein expression does not always translate into increased EGFR gene dosage . For example, a study by Shia et al. found that only a small fraction (17 of 124 or 14%) of EGFRpositive (defined as 1+, 2+, or 3+) colorectal carcinomas detected by immunohistochemistry were associated with EGFR gene amplification (defined as >5 gene copies/nucleus).****K. L. Spindler, J. Lindebjerg, J. N. Nielsen et al., “Epidermal growth factor receptor analyses in colorectal cancer: a comparison o fmethods,” International Journal of Oncology, vol. 29, no. 5,pp. 1159–1165, 2006.**F. Cappuzzo, G. Finocchiaro, E. Rossi et al., “EGFR FISH assay predicts for response to cetuximab in chemotherapy refractory colorectal cancer patients,” Annals of Oncology, vol. 19, no. 4, pp.717–723, 2008.***J. Shia, D. S. Klimstra, A. R. Li et al., “Epidermal growth factor receptor expression and gene amplification in colorectal carcinoma: an immunohistochemical and chromogenic in situhybridization study,” Modern Pathology, vol. 18, no. 10, pp. 1350–1356, 2005
- EGFR Gene Amplification, and Copy Number.(cont’d) the predictive significance of EGFR gene amplification is also confusing and uncertain. One study of 47 patients with metastatic colorectal cancer treated with a cetuximab-based regimen showed that EGFR gene copy gain, as assessed by fluorescence in situ hybridization, had no correlation with objective response rate, disease control rate, progression-free survival, or overall survival* Conversely, another study of 173 patients with K-RAS WT metastatic colorectal cancer treated with a cetuximab based regimen found that EGFR amplification/increased EGFR copy number, present in 17.7% of patients, was associated with response to anti-EGFR therapy** These conflicting results may be related to the fact that there are no established guidelines for EGFR gene amplification. But since there are no guidelines, testing for EGFR gene amplification in colorectal cancer is not routinely performed.*A. Italiano, P. Follana, F. X. Caroli et al., “Cetuximab shows activity in colorectal cancer patients with tumors for which FISH analysis does not detect an increase in EGFR gene copynumber,” Annals of Surgical Oncology, vol. 15, no. 2, pp. 649– 654, 2008**P. Laurent-Puig, A. Cayre, G. Manceau et al., “Analysis of PTEN, BRAF, and EGFR status in determining benefit from cetuximab therapy in wild-type KRAS metastatic coloncancer,” Journal of Clinical Oncology, vol. 27, no. 35, pp. 5924– 5930, 2009.
The EGFR Pathway and Colorectal Carcinogenesis
K-RAS Mutations The RAS family of proto-oncogenes include H-RAS, K-RAS, and N-RAS. K-RAS (Kirsten ras sarcoma viral oncogene) is a guanosine triphosphate-(GTP-) binding protein downstream of the EGFR and is a central component of the mitogen activated protein kinase (MAPK) pathway Somatic K-RAS mutations are found in many cancers, including 30%– 40% of colorectal cancers, and are an early event in carcinogenesis. K-RAS mutations lead to constitutive activation of the K- RAS protein by abrogating GTPase activity. These mutations result in unregulated downstream signaling that will not be blocked by antibodies that target the EGFR receptor.** Roughly 40% of colorectal cancers are characterized by a mutationin the K-RAS gene *, about 90% of these mutations occur in codons 12 and 13 in exon 2 of the K-RAS gene, with the remaining mutations occurring in codons 61 and 146 (roughly 5% each)*** KRAS mutation status heterogeneity between primary tumors, lymph nodes and distant metastases in 5– 10% of patients has been reported, with mixed responses to antiEGFR monoclonal antibody therapy in those with metastatic CRC. Because of this, some clinicians have called for a reassessment of K-RAS mutation status on metastatic foci in situations where only the primary tumor was assessed for K-RAS status*R. G. Amado, M. Wolf, M. Peeters et al., “Wild-type KRAS is required for panitumumab efficacy in patients with metastatic colorectal cancer,” Journal of Clinical Oncology, vol. 26, no. 10,pp. 1626–1634, 2008.**C. J. Allegra, J. M. Jessup, M. R. Somerfield et al., “American society of clinical oncology provisional clinical opinion: testing for KRAS gene mutations in patients with metastatic colorectalcarcinoma to predict response to anti-epidermal growth factor receptor monoclonal antibody therapy,” Journal of Clinical Oncology, vol. 27, no. 12, pp. 2091–2096, 2009.***W. De Roock, B. Claes, D. Bernasconi et al., “Effects of KRAS, BRAF, NRAS, and PIK3CA mutations on the efficacyof cetuximab plus chemotherapy in chemotherapy-refractory metastatic colorectal cancer: a retrospective consortium analysis,” The Lancet Oncology, vol. 11, no. 8, pp. 753–762, 2010.
K-RAS Mutations (cont’d) The prognostic significance of KRAS mutations is controversial. K-RAS mutation status is associated with shorter survival in some studies *’**, but not others ***The results of one study, which showed increased mortality with codon 13 G-A mutations but not with K-RAS mutations in general, suggest that prognosis may be related to specific mutations in the KRAS gene*****W. S. Samowitz, K. Curtin, D. Schaffer, M. Robertson, M. Leppert, and M. L. Slattery, “Relationship of Ki-ras mutations in colon cancers to tumor location, stage, and survival: a .population-based study,” Cancer Epidemiology Biomarkers and Prevention, vol. 9, no. 11, pp. 1193–1197, 2000**H. J. N. Andreyev, A. R. Norman, D. Cunningham et al., “Kirsten ras mutations in patients with colorectal cancer: the ’RASCAL II’ study,” British Journal of Cancer, vol. 85, no. 5,pp. 692–696, 2001*** A. D. Roth, S. Tejpar, M. Delorenzi et al., “Prognostic role of KRAS and BRAF in stage II and III resected colon cancer: results of the translational study on the PETACC-3,EORTC 40993, SAKK 60-00 trial,” Journal of Clinical Oncology, vol. 28, no. 3, pp. 466–474, 2010.****W. S. Samowitz, K. Curtin, D. Schaffer, M. Robertson, M. Leppert, and M. L. Slattery, “Relationship of Ki-ras mutations in colon cancers to tumor location, stage, and survival:a population-based study,” Cancer Epidemiology Biomarkers and Prevention, vol. 9, no. 11, pp. 1193–1197, 2000.
K-RAS Mutations (cont’d) Although not predictive of outcome with standard chemotherapy, K-RAS mutation status is a strong predictive marker of resistance to EGFRtargeted therapy in patients with metastatic colorectal cancer (i.e., KRAS mutations predict a lack of response to anti-EGFR monoclonal antibodies cetuximab and panitumumab) The effectiveness of cetuximab was significantly associated with K-RAS mutation status. In patients with wild type K-RAS tumors, treatment with cetuximab as compared with supportive care alone significantly improved overall survival (median, 9.5 vs. 4.8 months, P<0.001) and progression-free survival (median, 3.7 months vs. 1.9 months; P<0.001). Among patients with mutated K-RAS tumors, there was no significant difference between those who were treated with cetuximab and those who received supportive care alone with respect to overall survival (hazard ratio, 0.98; P = 0.89) or progression-free survival (hazard ratio, 0.99; P = 0.96). In the group of patients receiving best supportive care alone, the mutation status of the K-RAS gene was not significantly associated with overall survival (hazard ratio for death, 1.01; P = 0.97).**C. S. Karapetis, S. Khambata-Ford, D. J. Jonker et al., “Kras mutations and benefit from cetuximab in advanced colorectal cancer,” The New England Journal of Medicine, vol. 359, no.17, pp. 1757–1765, 2008 .
K-RAS Mutations (cont’d) Amado et al. assessed the predictive role of K-RAS mutational status in a randomized phase III trial comparing panitumumab monotherapy with best supportive care (BSC) in patients with chemotherapy refractory metastatic CRC* KRAS status was ascertained in 427 (92%) of 463 patients (208 panitumumab, 219 BSC). KRAS mutations were found in 43% of patients. The treatment effect on PFS in the wild-type (WT) KRAS group was significantly greater (P .0001) than in the mutant group. Median PFS in the WT K-RAS group was 12.3 weeks for panitumumab and 7.3 weeks for BSC. Response rates to panitumumab were 17% and 0%, for theWT and mutant groups, respectively. **R. G. Amado, M. Wolf, M. Peeters et al., “Wild-type KRAS is required for panitumumab efficacy in patients with metastatic colorectal cancer,” Journal of Clinical Oncology, vol.26, no. 10, pp. 1626–1634, 2008
B-RAF Mutations The B- RAF gene encodes a serine-threonine protein kinase that is downstream of K-RAS in the MAPK signaling pathway. B-RAF mutations occur in 5–22% of all colorectal cancers The most frequently reported B-RAF mutation is a valine-to-glutamic acid amino acid (V600E) substitution. Unlike K-RAS mutations, B-RAF mutations do have an impact on prognosis and survival, Patients with a B-RAF mutation in a microsatellite-stable colon cancer have significantly poorer survival than those without the mutation, but the B-RAF status does not affect survival of patients with micro satellite unstable tumors* BRAF status also predicts response to anti-EGFR therapy. Of metastatic colorectal cancers that are found to be K-RAS wild type at codons 12/13, 5% to 15% can harbor BRAF mutations and show resistance to anti-EGFR therapy***A. D. Roth, S. Tejpar, M. Delorenzi et al., “Prognostic role of KRAS and BRAF in stage II and III resected colon cancer: results of the translational study on the PETACC-3, EORTC 40993, SAKK 60-00 trial,” Journal of Clinical Oncology, vol. 28, no. 3, pp. 466–474, 2010.**W. de Roock, B. Claes, D. Bernasconi et al., “Effects of KRAS, BRAF, NRAS, and PIK3CA mutations on the efficacy of cetuximab plus chemotherapy in chemotherapy-refractorymetastatic colorectal cancer: a retrospective consortium analysis,” Lancet Oncology, vol. 11, pp. 753–762, 2010
The EGFR Pathway and Colorectal Carcinogenesis
The PI3K Pathway The PI3K-AKT pathway can be deregulated by activating mutations in the PIK3CA gene (p110 subunit), by inactivation of the phosphatase and tensin homolog (PTEN) gene, or by activation of AKT. PI3k is composed of an regulatory subunit and a catalytic subunit. The protein encoded by by the PIK3CA gene represents the catalytic subunit, Mutations in PIK3CA occur in 14% to 18% of colon cancers, As a prognostic marker, PIK3CA mutations are associated with shorter cancer-specific survival, but this effect may be limited to patients with K-RAS wild-type tumors*. Briefly, as a predictive marker, only PIK3CA exon 20 mutations appear to be associated with worse outcome after cetuximab***S. Ogino, K. Nosho, G. J. Kirkner et al., “PIK3CA mutation is associated with poor prognosis among patients with curatively resected colon cancer,” Journal of Clinical Oncology, vol. 27, no.9, pp. 1477–1484, 2009.**W. de Roock, B. Claes, D. Bernasconi et al., “Effects of KRAS, BRAF, NRAS, and PIK3CA mutations on the efficacy of cetuximab plus chemotherapy in chemotherapy-refractory metastaticcolorectal cancer: a retrospective consortium analysis,” Lancet Oncology, vol. 11, pp. 753–762, 2010
The PI3K Pathway (cont’d) Phosphatase and tensin homolog (PTEN) is a protein that is encoded by the PTEN gene, that dephosphorylates phosphatidylinositol- 3,4,5 triphosphate (PIP3) into PIP2. and thereby inhibits PI3K function. Loss of PTEN results in constitutive activation of the PI3K-AKT pathway. PTEN mutations and loss of heterozygosity (LOH) of the PTEN locus have been reported in 13%–18% and 17%–19% of colon cancers, respectively. Loss of PTEN protein expression (assessed by IHC) is associated with shorter overall survival in patients with K- RAS wild-type tumors.* PTEN protein inactivation may also be a negative predictor of response to anti-EGFR therapy**.*A. Bardelli and S. Siena, “Molecular mechanisms of resistance to cetuximab and panitumumab in colorectal cancer,” Journal of Clinical Oncology, vol. 28, no. 7, pp. 1254–1261, 2010**P. Laurent-Puig, A. Cayre, G. Manceau et al., “Analysis of PTEN, BRAF, and EGFR status in determining benefit from cetuximab therapy in wild-type KRAS metastatic colon cancer,”Journal of Clinical Oncology, vol. 27, no. 35, pp. 5924– 5930, 2009.
The PI3K Pathway (cont’d) AKT is a major downstream effector of PI3K, also known as protein kinase B (PKB) is a serine/theronine-specific protien kinase. A recen study examined the role of activated (phosphorylated) AKT expression in a large cohort of colorectal cancers * They demonstrated that p-AKT expression is associated with early stage disease and good prognosis, It is possible that p-AKT expression could serve as positive prognostic marker in patients with colorectal cancer.*Y. Baba, K. Nosho, K. Shima et al., “Phosphorylated AKT expression is associated with PIK3CAmutation, low stage, and favorable outcome in 717 colorectal cancers,” Cancer.
The same one who did this!!!!!!!!!!! Adolf Hitler
Fascism is a form of radical authoritarian nationalism. Fascists seek to unify their nation based upon suprapersonal connections of ancestry and culture through a totalitarian state that seeks the mass mobilization of the national community through discipline, indoctrination, and physical training. Fascism utilizes a vanguard party to initiate a revolution to organize the nation upon fascist principles. The fascist party and state is led by a supreme leader who exercises a dictatorship over the party, the government and other state institutions. Fascism views direct action including political violence and war, as a means to achieve national rejuvenation, spirit and vitality.* ANY CORRELATION WITH WAT IS GOING ON NOW IN EGYPT????? *En.wikipedia.
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