We have previously reported30 the development of EGFR-targeted lipopolyplexes for the delivery of pDNA encoding an EGFR biosensor.31 This allowed us to monitor EGFR activity in a breast cancer model in vivo, before and after separate treatment with a TKI, Mo-IPQA.30 As well as successfully demonstrating the inhibition of tyrosine phosphorylation by EGFR in vivo, and showing a significant degree of intratumoral heterogeneity in EGFR activity, our results showed that small molecule TKIs have a very poor uptake in cancer cells, and that the uptake is unselective. The gene discussed is EGFR; the disease is breast cancer.