Fig. 1

In vitro time course reflects clinical evolution of cetuximab response and evolution of acquired resistance. Intrinsic cetuximab-sensitive HNSCC cell line SCC25 was treated with cetuximab (red) or PBS (black) for 11 generations to develop acquired resistance. Proliferation assay (flow) of cetuximab treatment (red line) and PBS-treated cells (black line) measured cetuximab response for all SCC25 generations. While proliferation of the PBS generations was stable throughout the 11 weeks, proliferation of the CTX generations progressively increased over each week. Relative to the untreated controls, the growth of the treated cells was initially (CTX-G1) inhibited until CTX-G3. Starting at CTX-G4, the cells became resistant to the anti-proliferative effects of cetuximab and gained stable growth advantages compared to the untreated controls