Monoclonal antibodies cell transformation

Gauchat, J.F., Aversa, G., Gascan, H. and De-Vries, J.E. (1992a). Modulation of IL-4 induced germline epsilon RNA synthesis in human B cells by tumor necrosis factor-alpha, anti-CD40 monoclonal antibodies or transforming growth factor-beta correlates with levels of IgE production. Int. Immunol. 4, 397-406. 

Drebin JA, Link VC, Stem DF, et al. Down-modulation of an oncogene protein product and reversion of the transformed phenotype by monoclonal antibodies. Cell 1985, 41, 697-706. 

Bioprocess plants are an essential part of food, fine chemical and pharmaceutical industries. Use of microorganisms to transform biological materials for production of fermented foods, cheese and chemicals has its antiquity. Bioprocesses have been developed for an enoimous range of commercial products, as listed in Table 1.1. Most of the products originate from relatively cheap raw materials. Production of industrial alcohols and organic solvents is mostly originated from cheap feed stocks. The more expensive and special bioprocesses are in the production of antibiotics, monoclonal antibodies and vaccines. Industrial enzymes and living cells such as baker s yeast and brewer s yeast are also commercial products obtained from bioprocess plants. 

Monoclonal antibody technology entails isolation of such B-lymphocytes, with subsequent fusion of these cells with transformed (myeloma) cells. Many of the resultant hybrid cells retain immortal characteristics, while producing large quantities of the monospecific antibody. These hybridoma cells can be cultured long term to effectively produce an inexhaustible supply of the monoclonal antibody of choice. 

Abundant epidemiological data indicate that tumors that overexpress EGFR and/or HER-2 exhibit a worse outcome than tumors that do not overexpress these receptors. In addition, inhibition of these receptors with monoclonal antibodies has been shown to reverse transformation in preclinical models. Moreover, the measurable overexpression of EGFR and HER-2 in tumor diagnostic tissue and the lack of an obvious role for these tyrosine kinases in normal host tissues, all together, support the notion that these tumor cell surface molecules provide a therapeutic window that can be exploited in the treatment of carcinomas that overexpress EGFR and/or HER-2. 

Although Epstein-Barr virus (EBV) is capable of inducing cellular transformation, few antibody-producing B lymphocytes display the viral cell surface receptor. Most, therefore, are immune to EBV infection. Even upon successful transformation, most produce low-affinity IgM antibodies, and the cells are often unstable. Having said that, one monoclonal antibody approved for medical use (Humaspect, Table 10.4) is produced by a human lymphoblastoid cell line originally transformed by EBV. 

Anaphylactic and serum sickness reactions to ALG and murine monoclonal antibodies have been observed and usually require cessation of therapy. Complexes of host antibodies with horse ALG may precipitate and localize in the glomeruli of the kidneys. Even more disturbing has been the development of histiocytic lymphomas in the buttock at the site of ALG injection. The incidence of lymphoma as well as other forms of cancer is increased in kidney transplant patients. It appears likely that part of the increased risk of cancer is related to the suppression of a normally potent defense system against oncogenic viruses or transformed cells. The preponderance of lymphoma in these cancer cases is thought to be related to the concurrence of chronic immune suppression with chronic low-level lymphocyte proliferation. 

An immunogen induces antibodies from many B cell clones, producing a polyclonal antibody response. In contrast, the propagation of an isolated B cell clone produces an antibody of single specificity. However, the problem is that in tissue culture medium, B cells die within a few days of their isolation from, for example, a mouse spleen. To circumvent this problem, immortality can be conferred on B cells by means of viral transformation Epstein-Barr virus can be used. Alternatively, fusion to cancerous cells is carried out to generate hybrids or hybridomas. Generally, the former procedure is used to immortalize peripheral blood B cells and produce human monoclonal antibodies, while myeloma cells are used to produce murine monoclonal antibodies. 

The inherent features of monoclonal antibodies (mAbs), i.e., high specificity and generally low toxicity, make them ideal for targeting transformed cell surfaces. Upon binding, the mAbs could induce homo- or hetero-dimerization of the receptors, which in turn stimulate internalization into the target cells... 

Antibodies are expressed by hybridoma cells formed by cell fusion of sensitized animal or human B lymphocytes with myeloma cells, or they are generated by EBV (Epstein-Barr virus) transformation of sensitized B lymphocytes. Other heterologous expression systems such as bacteria, yeast, insect cells, and mammalian cells have also been used for expression of antibodies and their fragments. However, because of renaturation problems, glycosylation, and expression levels, mammalian cells are mostly used for the expression of monoclonal antibodies. More recently, technologies have been extensively developed for the expression of antibodies in transgenic animals and transgenic plants. 

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