James J. Kowalczyk

Direct Demonstration of Geranylgeranylation and Farnesylation of Ki-Ras in Vivo

It has recently been reported that Ki-Ras protein can be modified in vitro by farnesylation or geranylgeranylation. However, a previous analysis of Ki-Ras prenylationin vivo found only farnesylated Ki-Ras. In this report it is shown that under normal conditions, Ki-Ras is farnesylated in vivo and when cells are treated with the farnesyl transferase inhibitors B956 or B957, farnesylation is inhibited and Ki-Ras becomes geranylgeranylated in a dose dependent manner. These results have strong implications in the design of anticancer drugs based on inhibition of prenylation.

Cysteine and methionine linked by carbon pseudopeptides inhibit farnesyl transferase

Compounds in which cysteine and methionine have been linked by amino acids replacing the A1A2 portion of the CA1A2X box template inhibit farnesyl and geranylgeranyl transferases. The expected specificity for FTase over GGTase I is observed. A variety of linkers are accepted with the most potent compounds possessing a hydrophobic substituent at C-2 of the A1A2 replacement.

Antitumor activity of ER-51785, a new peptidomimetic inhibitor of farnesyl transferase: synergistic effect in combination with paclitaxel.

Inhibitors of ras farnesylation have been extensively studied in the preclinical stage, and some of them are being developed in the clinic. Herein, we describe the antitumor activity of a new farnesyl transferase inhibitor, ER-51785. In vitro, ER-51785 selectively inhibited farnesyl transferase activity (IC50 = 77 nM) compared with geranylgeranyl transferase I activity (IC50 = 4200 nM). In cells, ER-51785 inhibited posttranslational processing of H-ras with IC50 = 28 nM, but not that of rap 1A at concentrations up to 50 microM. This compound also strongly inhibited colony formation of H-ras-transformed NIH 3T3 fibroblasts and EJ-1 bladder carcinoma cells. In vivo, ER-51785 showed potent tumor regression activity against EJ-1 xenografts but only modest activity against MIA PaCa-2 xenografts. Treatment of ER-51785 in combination with paclitaxel exhibited synergistic effects against colony formation and tumor growth of MIA PaCa-2 cells. The results presented herein support the idea that farnesyl transferase inhibitors alone and in combination with other chemotherapeutic agents have the potential to be developed as therapies for tumors expressing H-ras or K-ras oncogenes.

Phenolic replacements for cysteine in farnesyl transferase inhibitors based on CVFM

Abstract Compounds in which cysteine of the tetrapeptide CVFM has been replaced with a phenolic benzyl substituent inhibit farnesylation of H-ras protein by farnesyl transferase (FTase). In the most potent inhibitors (e.g., 5-chloro-2-hydroxybenzyl-VFM, IC 50 = 0.5 μM, approx. 8 times less active than CVFM) the phenolic hydroxyl is ortho to the methylene linker. Inhibitory activity is influenced by substitution on the phenol ring.