As far as we are aware, neither HOXA5 nor HOXA6 have been implicated in the regulation of ABCB1. However, another family member, HOXC6, has been found to activate the ABCB1 promoter, and its suppression in the paclitaxel-resistant squamous cell carcinoma line, FaDu/PTX, leads to a reversal of drug resistance46. This evidence concerns the gene ABCB1 and squamous cell carcinoma.