HOTTIP and cancer: We established a Transwell co-culture system in which cancer cells were in the upper chamber and THP-1-derived M0 macrophages were in the lower chamber, which revealed that HOTTIP-overexpressed FaDu cells promoted, while HOTTIP-knockdown Hep-2 cells decreased, the number of CD11b+iNOS+ M1 macrophages after 72 h (Fig. 6A).