The p53
tumor suppressor is mutated in over 50% of human
cancers. Mutations resulting in
amino acid changes within p53 result in a loss of activity and consequent changes in expression of genes that regulate DNA repair and cell cycle progression. Replacement of p53 using
protein therapy would restore p53 function in p53-deficient
tumor cells, with a consequence of
tumor cell death and
tumor regression. p53 functions in a tetrameric form in vivo. Here, we refolded a wild-type, full-length p53 from inclusion bodies expressed in Escherichia coli as a stable tetramer. The tetrameric p53 binds to p53-specific
DNA and, when transformed into a p53-deficient
cancer cell line, induced apoptosis of the transformed cells. Next, using the same expression and refolding technology, we produced a stable tetramer of recombinant
gonadotropin-releasing hormone-p53 fusion
protein (GnRH-p53), which traverses the plasma membrane, slows proliferation, and induces apoptosis in p53-deficient,
GnRH-receptor-expressing
cancer cell lines. In addition, we showed a time-dependent binding and internalization of GnRH-p53 to a receptor-expressing cell line. We conclude that the GnRH-p53 fusion strategy may provide a basis for constructing an effective
cancer therapeutic for patients with
tumors in
GnRH-receptor-positive tissue types.