Proto-oncogene expression in cloned T lymphocytes: mitogens and growth factors induce different patterns of expression.

We have compared the effects of a mitogenic lectin, concanavalin A (Con A), and a growth factor, interleukin-2 (IL-2), on the expression of the c-myc, c-fos, and c-myb proto-oncogenes in cloned T lymphocytes. Accumulation of c-myc mRNA was induced by both ConA and IL-2 in these cells. In contrast, expression of c-fos was stimulated primarily by ConA, and accumulation of c-myb mRNA was induced predominantly by IL-2. Thus, ConA and IL-2 induce expression of overlapping, but non-identical, sets of proto-oncogenes in T lymphocytes. Investigations with several different cloned T cells revealed that: (1) c-myb is not induced in all T cells stimulated to grow, indicating that its expression may not be absolutely required for their proliferation; and (2) expression of c-myc, even in combination with c-fos, can be insufficient for growth, demonstrating functional differences between cellular and viral oncogenes in T cells. These observations provide insight into the roles of the c-myc, c-fos, and c-myb proto-oncogenes in normal T cell responses.