Unformatted text preview: osis: The Bcl-2 Family
The third gene identified as a key regulator of programmed cell death in C.
elegans, ced-9, was found to be closely related to a mammalian gene called
bcl-2, which was first identified in 1985 as an oncogene that contributed to
the development of human B cell lymphomas (cancers of B lymphocytes).
In contrast to other oncogene proteins, such as Ras, that stimulate cell proliferation (see Molecular Medicine, Chapter 15), Bcl-2 was found to inhibit
apoptosis. Ced-9 and Bcl-2 were thus similar in function, and the role of Bcl2 as a regulator of apoptosis first focused attention on the importance of cell
survival in cancer development. As discussed further in the next chapter,
we now recognize that cancer cells are generally defective in the normal
process of programmed cell death and that their inability to undergo apoptosis is as important as their uncontrolled proliferation in the development
of malignant tumors.
Mammals encode a family of approximately 20 proteins related to Bcl-2,
which are divided into three functional groups (Figure 17.6). Some members of the Bcl-2...
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