Gene expression profiling during treatment of COLO205 cells with selumetinib

Here, we investigate gene expression response of the BRAFV600E mutant cell line COLO205 to the MEK inhibitor selumetinib / AZD6244 / ARRY-142886. Although selumetinib causes long term G1 arrest, we observe cells stochastically entering the cell cycle without re-activation of ERK and initiation of a normal proliferative gene expression programme. Genes encoding DNA replication and repair factors are downregulated during G1 arrest, but many of these are transiently induced when cells escaping arrest enter S and G2. Nonetheless, mRNAs encoding key DNA replication factors including the MCM replicative helicase complex, PCNA and TIPIN remain at very low abundance. 1) An mRNA-seq timecourse of COLO205 cells across 48 hours selumetinib treatment. 2) COLO205 cells either untreated or treated 24 hours with 1 µM selumetinib were glyoxal fixed and stained for CCNB1 then flow sorted into CCNB1 positive and CCNB1 negative fractions, RNA extracted and mRNA-seq performed. Equivalent cell populations were pulsed for 4 hours with EdU, stained and sorted into EdU negative and positive cohorts that were then used for mRNA-seq.