Anti-cancer Peptides from Ras-P21 and P53 Proteins

Abstract

We have employed computer-based molecular modeling approaches to design peptides from the ras-p21 and p53 proteins that either induce tumor cell reversion to the untransformed phenotype or induce tumor cell necrosis without affecting normal cells. For rasp21, we have computed and superimposed the average low energy structures for the wild-type protein and oncogenic forms of this protein and found that specific domains change conformation in the oncogenic proteins. We have synthesized peptides corresponding to these and found that ras peptides, 35-47 (PNC-7) and 96-110 (PNC-2), block oncogenic ras-p21-induced oocyte maturation but have no effect on insulin-induced oocyte maturation that requires activation of endogenous wild-type ras-p21. These results show signal transduction pathway differences between oncogenic and activated wild-type ras-p21. Both peptides, attached to a membrane-penetrating peptide (membrane residency peptide or MRP), either induce phenotypic reversion to the untransformed phenotype or tumor cell necrosis of several ras-transformed cell lines, but have no effect on the growth of normal cells. Using other computational methods, we have designed two peptides, PNC-27 and 28, containing HDM-2-protein-binding domain sequences from p53 linked on their C-termini to the MRP that induce pore formation in the membranes of a wide range of cancer cells but not any normal cells tested. This is due to the expression of HDM-2 in the cancer cell membrane that does not occur in normal cells. These peptides eradicate a highly malignant tumor in nude mice with no apparent side effects. Both ras and p53 peptides show promise as anti-tumor agents in humans.

Anticancer peptide PNC-27 adopts an HDM-2-binding conformation and kills cancer cells by binding to HDM-2 in their membranes

“…None of these sets of cells was induced to undergo apoptosis as revealed by the absence of enhanced caspase activity above background (Fig. S2B), consistent with our prior findings that PNC-27 induces tumor cell necrosis and not apoptosis (1)(2)(3)(4)(5). Control peptide PNC-29 (200 μg∕ml), had no effect on either LDH release or the viability of any of the four sets of transfected cells, suggesting that PNC-27 binds specifically to HDM-2 on the cell membrane, allowing for its cytotoxicity.…”

“…We have found previously that the peptide PNC-27, containing the HDM-2-binding domain of p53, residues 12-26, attached to a transmembrane-penetrating or membrane residency peptide (MRP) on its carboxyl terminal end, and PNC-28 (p53 residues 17-26-MRP) induce tumor cell necrosis by forming pores in cancer cell membranes but have no effects on a number of untransformed cells, including human stem cells from cord blood (1)(2)(3)(4), and eradicate tumors in nude mice (5). The p53-HDM-2 complex results in the catabolism of p53 (6).…”

Novel compound cedrelone inhibits hepatocellular carcinoma progression via PBLD and Ras/Rap1

“…Ras is encoded by oncogene las. Humans have three Ras genes, H-Ras, K-Ras and N-Ras that are distributed on different chromosomes, encoding protein p21 (23,24). Ras-p21 binds to guanine nucleotides (GTP and GDP) and the GTP enzyme (hydrolysis of GTP to GDP) (25).…”

Inhibition of regulated cell death by cell-penetrating peptides

“…It has long been speculated that direct reactivation of the endogenous tumor suppressor p53 in cancer cells will be therapeutically beneficial. So far, many different p53-derived peptides conjugated to various CPPs like penetratin or Tat have been demonstrated to restore the tumor suppressor function of p53 in cancer cells (reviewed in [ 98 ]). The group of Steven Dowdy demonstrated in 2004 that a retro-inverse version of the parental p53 peptide linked to the Tat-domain of HIV (named RI-Tatp53C) restored p53 function specifically in cancer cells but not in normal cells [ 99 ].…”