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. 2023 Jun 20;83(19):3252–3263. doi: 10.1158/0008-5472.CAN-23-0282

Figure 4.

Figure 4. Depletion of the FTase targets RHEB and HRAS phenocopies tipifarnib treatment in PIK3CA/HRAS–dysregulated HNSCC cell lines. A, Graphical overview of the effect of tipifarnib on the membrane localization of HRAS and RHEB. Inhibition of FTase activity leads to defarnesylation of HRAS and RHEB and loss of membrane localization and activity. B–D, Immunoblots of HRAS, RHEB, LAMP1, and β-tubulin in the cytosol and membrane fractions of CAL33 (B), BICR22 (C), and SCC9 (D) cells treated with DMSO, 250 nmol/L alpelisib (24 hours), 1 μmol/L tipifarnib (48 hours), or the combination. E–G, Immunoblots of indicated signaling proteins in CAL33 (E), BICR22 (F), and SCC9 (G) cells treated with siRNAs to knock down RHEB and HRAS expression (vs. control nontargeting pool) for 48 hours prior to addition of 250 nmol/L alpelisib. Cells were collected and lysed after 0, 1, or 24 hours alpelisib treatment and immunoblot analysis performed.

Depletion of the FTase targets RHEB and HRAS phenocopies tipifarnib treatment in PIK3CA/HRAS–dysregulated HNSCC cell lines. A, Graphical overview of the effect of tipifarnib on the membrane localization of HRAS and RHEB. Inhibition of FTase activity leads to defarnesylation of HRAS and RHEB and loss of membrane localization and activity. B–D, Immunoblots of HRAS, RHEB, LAMP1, and β-tubulin in the cytosol and membrane fractions of CAL33 (B), BICR22 (C), and SCC9 (D) cells treated with DMSO, 250 nmol/L alpelisib (24 hours), 1 μmol/L tipifarnib (48 hours), or the combination. E–G, Immunoblots of indicated signaling proteins in CAL33 (E), BICR22 (F), and SCC9 (G) cells treated with siRNAs to knock down RHEB and HRAS expression (vs. control nontargeting pool) for 48 hours prior to addition of 250 nmol/L alpelisib. Cells were collected and lysed after 0, 1, or 24 hours alpelisib treatment and immunoblot analysis performed.