Biomedical advances from tissue culture

The demonstration that the “dedifferentiation” of cells commonly observed in the early days of tissue culture was due to selective overgrowth of fibroblasts led to enrichment culture techniques (alternate animal and culture passage) designed to give a selective advantage to functionally differentiated tumor cells. These experiments resulted in the derivation of a large number of functionally differentiated clonal strains of a range of cell types. These results gave rise to the hypothesis that cells in culture accurately represent cells in vivo but without the complex in vivo environment. This concept has been strengthened with the development of hormonally defined culture media in combination with functionally differentiated clonal cell lines, which have augmented the potential of tissue culture studies. The use of hormonally defined media in place of serum-supplemented media demonstrates that hormonal responses and dependencies can be discovered in culture. Discoveries of hormonal dependencies of cancer cells has led to therapies targeting intracellular signaling pathways while discoveries of hormonal responses of pluripotent cells are helping to identify the potential application of stem cells. In these and other ways tissue culture technology will continue to contribute to solving problems of human health.     

Interaction of antibodies with ErbB receptor extracellular regions

Antibodies to the extracellular region of the ErbB receptors have played key roles in the development of a mechanistic understanding of this family of receptor tyrosine kinases. An extensively studied class of such antibodies inhibits activation of ErbB receptors, and these antibodies have been the focus of intense development as anti-cancer agents. In this review we consider the properties of ErbB receptors antibodies in light of the current structure-based model for ErbB receptor homo- and hetero-dimerization and activation. Crystal structures of the Fab fragments from five different inhibitory antibodies in complex with the extracellular regions of EGFR and ErbB2 have been determined. These structures highlight several different modes of binding and mechanisms of receptor inhibition. Information about antibody interactions with the structurally well-characterized soluble extracellular regions of ErbB receptors can be combined with the rich knowledge of the effects of these antibodies in cultured cells, and in vivo, to provide insights into the conformation and activation of ErbB receptors at the cell surface.     

The ErbB/HER receptor protein-tyrosine kinases and cancer

The ErbB/HER protein-tyrosine kinases, which include the epidermal growth factor receptor, consist of a growth-factor-binding ectodomain, a single transmembrane segment, an intracellular protein-tyrosine kinase catalytic domain, and a tyrosine-containing cytoplasmic tail. The genes for the four members of this family, ErbB1-ErbB4, are found on different human chromosomes. Null mutations of any of the ErbB family members result in embryonic lethality. ErbB1 and ErbB2 are overexpressed in a wide variety of tumors including breast, colorectal, ovarian, and non-small cell lung cancers. The structures of the ectodomains of the ErbB receptors in their active and inactive conformation have shed light on the mechanism of receptor activation. The extracellular component of the ErbB proteins consists of domains I-IV. The activating growth factor, which binds to domains I and III, selects and stabilizes a conformation that allows a dimerization arm to extend from domain II to interact with an ErbB dimer partner. As a result of dimerization, protein kinase activation, trans-autophosphorylation, and initiation of signaling occur. The conversion of the inactive to active receptor involves a major rotation of the ectodomain. The ErbB receptors are targets for anticancer drugs. Two strategies for blocking the action of these proteins include antibodies directed against the ectodomain and drugs that inhibit protein-tyrosine kinase activity. A reversible ATP competitive inhibitor of ErbB1 (ZD1839, or Iressa) and an ErbB1 ectodomain directed antibody (IMC-C225, or Erbitux) have been approved for the treatment of non-small cell lung cancer and colorectal cancer, respectively. An ErbB2/HER2 ectodomain directed antibody (trastuzumab, or Herceptin) has also been approved for the treatment of breast cancer. Current research promises to produce additional agents based upon these approaches.     

2nd PEGS Annual Symposium on Antibodies for Cancer Therapy: April 30–May 1, 2012, Boston,USA

The 2nd Annual Antibodies for Cancer Therapy symposium, organized again by Cambridge Healthtech Institute as part of the Protein Engineering Summit, was held in Boston, USA from April 30^th to May 1^st, 2012. Since the approval of the first cancer antibody therapeutic, rituximab, fifteen years ago, eleven have been approved for cancer therapy, although one, gemtuzumab ozogamicin, was withdrawn from the market.  The first day of the symposium started with a historical review of early work for lymphomas and leukemias and the evolution from murine to human antibodies. The symposium discussed the current status and future perspectives of therapeutic antibodies in the biology of immunoglobulin, emerging research on biosimilars and biobetters, and engineering bispecific antibodies and antibody-drug conjugates. The tumor penetration session was focused on the understanding of antibody therapy using ex vivo tumor spheroids and the development of novel agents targeting epithelial junctions in solid tumors. The second day of the symposium discussed the development of new generation recombinant immunotoxins with low immunogenicity, construction of chimeric antigen receptors, and the proof-of-concept of ‘photoimmunotherapy’. The preclinical and clinical session presented antibodies targeting Notch signaling and chemokine receptors.  Finally, the symposium discussed emerging technologies and platforms for therapeutic antibody discovery.     

2nd PEGS Annual Symposium on Antibodies for Cancer Therapy

The 2nd Annual Antibodies for Cancer Therapy symposium, organized again by Cambridge Healthtech Institute as part of the Protein Engineering Summit, was held in Boston, USA from April 30^th to May 1^st, 2012. Since the approval of the first cancer antibody therapeutic, rituximab, fifteen years ago, eleven have been approved for cancer therapy, although one, gemtuzumab ozogamicin, was withdrawn from the market. The first day of the symposium started with a historical review of early work for lymphomas and leukemias and the evolution from murine to human antibodies. The symposium discussed the current status and future perspectives of therapeutic antibodies in the biology of immunoglobulin, emerging research on biosimilars and biobetters, and engineering bispecific antibodies and antibody-drug conjugates. The tumor penetration session was focused on the understanding of antibody therapy using ex vivo tumor spheroids and the development of novel agents targeting epithelial junctions in solid tumors. The second day of the symposium discussed the development of new generation recombinant immunotoxins with low immunogenicity, construction of chimeric antigen receptors, and the proof-of-concept of ‘photoimmunotherapy’. The preclinical and clinical session presented antibodies targeting Notch signaling and chemokine receptors. Finally, the symposium discussed emerging technologies and platforms for therapeutic antibody discovery.