NFKB1 and neoplasm: The results showed that significantly more activation of p65 subunit was observed in HCT116 high density tumor microenvironment co-cultures compared to control HCT116 high density mono-cultures and 5-FU-induced p65/p50 phosphorylation in a concentration-dependent manner (Fig. 5:b). Indeed, curcumin blocked 5-FU-induced phosphorylation of p65/p50 subunits in a concentration-dependent manner.