Appeal No. 2001-1293 Page 3
Application No. 08/464,271
substance that is toxic to the cells (C), are eliminated from the
original cell population. In this manner, the toxic potential of the cell
(C) is actualized, thus allowing specific cell (C) types within the
transgenic cell population to be negatively selected for, i.e., to be
ablated. In addition, by controlling the amount of expression of
gene (G) in cell (C), which can be done, for example, by linking the
gene (G) to a “weak” or a “strong” tissue-specific promoter, and by
controlling the rate, dose and/or timing of the exposure of cell (C) to
the non-toxic drug compounds, it is possible to control the degree
and timing of the resulting genetic ablation.
Id., page 10.
The specification discloses several exemplary tissue-specific promoters
suitable for use in the disclosed method. See page 8. The specification also
discloses that the exogenous enzyme can be herpes simplex virus thymidine
kinase (HSV-TK). See, e.g., pages 16-17. No other examples of suitable
exogenous genes or enzymes are disclosed, although the specification notes
that “[o]ther enzymes which can be used in the practice of the present invention
are non-mammalian, i.e., enzymes which are not native to the host cells
contemplated for the generation of a transgenic cell population.” Page 15.
The specification discloses that the method “makes it possible to progress
from mild cellular degeneration to almost complete destruction of a specific cell
line, thus providing the ability to (1) create valuable animal models with which to
study lineage formation and cell function; (2) treat diseased individuals by
selective ablation of disease cells, and (3) selectively ablate any cell line.”
Specification, page 19.
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