Publicação
Identification of the Saccharomyces cerevisiae target of Cetuximab-Erbitux, the anti-EGFR antibody used in the treatment of colorectal cancer
| Resumo: | Colorectal cancer (CRC) is one of the most common malignancies affecting mankind. CRC cells over-express epidermal growth factor receptor (EGFR), which usually correlates with disease poor prognosis and reduced response to therapy. Hence, several therapeutic agents against EGFR were developed, viz. the monoclonal antibody cetuximab/Erbitux®. Such drug competes with EGFR ligands for binding to L2/III domain, which results in EGFR internalization and subsequent degradation, leading to inhibition of cell growth and angiogenesis, and induction of apoptosis. Yet, cancer patients may display or acquire resistance-inducing mutations in EGFR, as well as in its downstream effectors. These contribute to a significant degree of ineffectiveness of treatment, being one of the most prominent problems in CRC clinical assessment. Given the high degree of conservation of eukaryotic cellular processes, yeast has been a model of choice for research in many human pathologies. In this line, this work aimed at the identification of S. cerevisiae surface target of cetuximab, ultimately seeking for the possible EGFR yeast counterpart. Two different strategies were used: (1) in silico sequence and structure homology search, and (2) immune recognition in a cetuximab-based Western blot. The first approach pointed to proteins from the yeast Sporulation specific family, especially Sps2p and Sps22p. These have some structural resemblance with EGFR leucin-rich L-domains, along with cell-surface localization. Conversely, the Western blot clearly identified the Pdc1p (pyruvate decarboxylase isoform 1) as cetuximab antigen. The subsequent detailed analysis of protein features revealed that Pdc1p, as well as its close homologue Pdc5p, present some similarity with EGFR epitope sequence. Moreover, Pdc and EGFR also present some functional pathway overlapping, more evident in malignantly transformed cells. The recognition of Pdc1/5p as cetuximab antigen, combined with its extracellular localization described before, suggests that Pdc1p may have distinct functions beyond glycolytic catalysis/regulation. The double deletion of Sps and Pdc, and the use of diploid genetic background, will be needed to devise the true existence of growth phenotypes induced by cetuximab. However, this work opens a large window as to future research in novel pathways in yeast, beyond the continued exploration of yeast for the aim of generating a tool for CRC patients’ theranostics. |
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| Autores principais: | Puga, Sónia Andreia Silva |
| Ano: | 2013 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Colorectal cancer (CRC) is one of the most common malignancies affecting mankind. CRC cells over-express epidermal growth factor receptor (EGFR), which usually correlates with disease poor prognosis and reduced response to therapy. Hence, several therapeutic agents against EGFR were developed, viz. the monoclonal antibody cetuximab/Erbitux®. Such drug competes with EGFR ligands for binding to L2/III domain, which results in EGFR internalization and subsequent degradation, leading to inhibition of cell growth and angiogenesis, and induction of apoptosis. Yet, cancer patients may display or acquire resistance-inducing mutations in EGFR, as well as in its downstream effectors. These contribute to a significant degree of ineffectiveness of treatment, being one of the most prominent problems in CRC clinical assessment. Given the high degree of conservation of eukaryotic cellular processes, yeast has been a model of choice for research in many human pathologies. In this line, this work aimed at the identification of S. cerevisiae surface target of cetuximab, ultimately seeking for the possible EGFR yeast counterpart. Two different strategies were used: (1) in silico sequence and structure homology search, and (2) immune recognition in a cetuximab-based Western blot. The first approach pointed to proteins from the yeast Sporulation specific family, especially Sps2p and Sps22p. These have some structural resemblance with EGFR leucin-rich L-domains, along with cell-surface localization. Conversely, the Western blot clearly identified the Pdc1p (pyruvate decarboxylase isoform 1) as cetuximab antigen. The subsequent detailed analysis of protein features revealed that Pdc1p, as well as its close homologue Pdc5p, present some similarity with EGFR epitope sequence. Moreover, Pdc and EGFR also present some functional pathway overlapping, more evident in malignantly transformed cells. The recognition of Pdc1/5p as cetuximab antigen, combined with its extracellular localization described before, suggests that Pdc1p may have distinct functions beyond glycolytic catalysis/regulation. The double deletion of Sps and Pdc, and the use of diploid genetic background, will be needed to devise the true existence of growth phenotypes induced by cetuximab. However, this work opens a large window as to future research in novel pathways in yeast, beyond the continued exploration of yeast for the aim of generating a tool for CRC patients’ theranostics. |
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