title: Inhibition of the prenylation of K-Ras, but not H- or N-Ras, is highly resistant to CAAX peptidomimetics and requires both a farnesyltransferase and a geranylgeranyltransferase I inhibitor in human tumor cell lines.
abstract: The farnesyltransferase (FTase) inhibitor FTI-277 is highly effective at blocking oncogenic H-Ras but not K-Ras4B processing and signaling. While inhibition of processing and signaling of oncogenic K-Ras4B is more sensitive to the geranylgeranyltransferase I (GGTase I) inhibitor GGTI-286 than it is to FTI-277 in K-Ras4B-transformed NIH3T3 cells, the sensitivity of K-Ras as well as H- and N-Ras to the CAAX peptidomimetics in human tumor cell lines is not known. Here, we report that a panel of five human carcinoma cell lines from pancreatic, pulmonary, and bladder origins all express H-, N-, and K-Ras, and their respective prenylation sensitivities to the FTase and GGTase I inhibitors is variable. In all of the cell lines investigated, the prenylation of N-Ras was highly sensitive to FTI-277, and in two of the cell lines, N-Ras showed slight sensitivity to GGTI-298, an analog of GGTI-286. Although the prenylation of H-Ras was also sensitive to FTI-277, complete inhibition of H-Ras processing even at high concentrations of FTI-277 and/or GGTI-298 was never achieved. The prenylation of K-Ras, on the other hand, was highly resistant to FTI-277 and GGTI-298. Most significantly, treatment of human tumor cell lines with both inhibitors was required for inhibition of K-Ras prenylation. In one cell line, the human lung adenocarcinoma A-549, prenylation of K-Ras was highly resistant even when co-treated with both inhibitors. Furthermore, soft agar experiments demonstrated that in all the human tumor cell lines tested inhibition of K-Ras prenylation was not necessary for inhibition of anchorage-independent growth. In addition, although GGTI-298 had very little effect on soft agar growth, the combination of FTI-277 and GGTI-298 resulted in significant growth inhibition. Therefore, the results demonstrate that while FTI-277 inhibits N-Ras and H-Ras processing in the human tumor cell lines evaluated, inhibition of K-Ras processing requires both an FTase inhibitor as well as a GGTase I inhibitor, and that inhibition of human tumor growth in soft agar does not require inhibition of oncogenic K-Ras processing.
authors.affiliation: Department of Pharmacology, University of Pittsburgh, Pennsylvania 15261, USA.
authors.forename: E C
authors.initials: EC
authors.lastname: Lerner
authors.forename: T T
authors.initials: TT
authors.lastname: Zhang
authors.forename: D B
authors.initials: DB
authors.lastname: Knowles
authors.forename: Y
authors.initials: Y
authors.lastname: Qian
authors.forename: A D
authors.initials: AD
authors.lastname: Hamilton
authors.forename: S M
authors.initials: SM
authors.lastname: Sebti
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors*; D001549:Benzamides / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D051231:Farnesyltranstransferase; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D011905:Genes, ras; D006801:Humans; D008715:Methionine / Q000031:analogs & derivatives / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D017368:Protein Prenylation / Q000187:drug effects; D014407:Tumor Cells, Cultured; D020668:rap GTP-Binding Proteins; D018631:ras Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
chemical_list: D001549:Benzamides; D004791:Enzyme Inhibitors; C096856:FTI 277; C102521:GGTI 298; D010455:Peptides; D008715:Methionine; D019883:Alkyl and Aryl Transferases; C083291:geranylgeranyltransferase type-I; D051231:Farnesyltranstransferase; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins; D018631:ras Proteins