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. Author manuscript; available in PMC: 2020 Feb 1.
Published in final edited form as: Semin Cancer Biol. 2018 Feb 9;54:174–182. doi: 10.1016/j.semcancer.2018.02.006

Fig. 2.

Fig. 2

The RAS-dependent mouse embryonic fibroblast (MEF) system. Panel a shows a schematic for the production of RAS-dependent MEF lines, starting with untreated MEFs which lack HRAS and NRAS alleles and have floxed KRAS. When treated with 4-hydroxytamoxifen (4-OHT), the cells lose KRAS and enter G1 arrest. Transduction with lentiviruses carrying single alleles of RAS isoforms (KRAS G12D mutant and HRAS wild type are shown here as an example) allows a return to growth, now dependent entirely on the added RAS transgene. Clones can be selected from these pools and subject to rigorous QC as described. Panel b shows a set of dose-response curves using the two single-isoform RAS-dependent MEF lines. The Y-axis readout is cell viability based on Cell-Titer Glo assay. Dactolsib (left) is an PI3K inhibitor which should have no differential effect on different RAS isoforms. Tipifarnib (right) is a farnesyltransferase inhibitor which is expected to be highly selective for inhibition of HRAS over KRAS.