Transformation by [Hras.sup.G12V] is consistently associated with mutant allele copy gains and is reversed by farnesyl transferase inhibition

• Published in: Oncogene Vol. 33; no. 47; p. 5442
• Main Authors: Chen, X, Makarewicz, J.M, Knauf, J.A, Johnson, L.K, Fagin, J.A
• Format: Journal Article
• Language: English
• Published: Nature Publishing Group 20-11-2014
• Subjects: Carcinogenesis; Enzymes; Gene mutations; Genetic aspects; Health aspects; Regulation
• ISSN: 0950-9232
• DOI: 10.1038/onc.2013.489

RAS-driven malignancies remain a major therapeutic challenge. The two-stage 7,12-dimethylbenz(a)anthracene (DMBA)/12-o- tetradecanoylphorbol-13-acetate (TPA) model of mouse skin carcinogenesis has been used to study mechanisms of epithelial tumor development by oncogenic Hras. We used mice with an [Hras.sup.G12V] knock-in allele to elucidate the early events after Hras activation, and to evaluate the therapeutic effectiveness of farnesyltransferase inhibition (FTI). Treatment of Caggs-Cre/[FR- Hras.sup.G,12V] mice with TPA alone was sufficient to trigger papilloma development with a shorter latency and an ~ 10-fold greater tumor burden than DMBA/TPA-treated WT-controls. [Hras.sup.G12V] allele copy number was increased in all papillomas induced by TPA. DMBA/TPA treatment of [Hras.sup.G12V] knock-in mice induced an even greater incidence of papillomas, which either harbored [Hras.sup.G12V] amplification or developed an [Hras.sup.Q61L] mutation in the second allele. Laser-capture microdissection of normal skin, hyperplastic skin and papillomas showed that amplification occurred only at the papilloma stage. HRAS-mutant allelic imbalance was also observed in human cancer cell lines, consistent with a requirement for augmented oncogenic HRAS signaling for tumor development. The FTI SCH66336 blocks HRAS farnesylation and delocalizes it from the plasma membrane. NRAS and KRAS are not affected as they are alternatively prenylated. When tested in lines harboring HRAS, NRAS or KRAS mutations, SCH66336 delocalized, inhibited signaling and preferentially inhibited growth only of HRAS-mutant lines. Treatment with SCH66336 also induced near-complete regression of papillomas of TPA-treated [Hras.sup.G12V] knock-in mice. These data suggest that farnesyl transferase inhibitors should be reevaluated as targeted agents for human HRAS-driven cancers, such as those of bladder, thyroid and other epithelial lineages. Oncogene (2014) 33, 5442-5449; doi: 10.1038/onc.2013.489; published online 18 November 2013 Keywords: RAS; papilloma; farnesyl transferase inhibitor