Curcumin inhibits the activity of ubiquitin ligase Smurf2 to promote NLRP3-dependent pyroptosis in non-small cell lung cancer cells

Non-small cell lung cancer (NSCLC) is a malignant tumor of significant clinical relevance. Curcumin has been investigated for its potential anticancer properties, as it has been reported to act through multiple cancer-related targets and pathways. The present study aimed to explore the effects of curcumin in NSCLC using both in vitro and in vivo models. NSCLC cell lines (specifically, A549 and NCI-H1299 cells), and a mouse tumor model established through the subcutaneous injection of A549 cells, were utilized to evaluate the effects of curcumin intervention. The effects of treatment with curcumin on NOD-like receptor pyrin domain-containing 3 (NLRP3) ubiquitination, cell pyroptosis and pyroptosis-associated factors were also evaluated. In addition, Smad ubiquitination regulatory factor 2 (Smurf2) was analyzed via a series of knockdown and overexpression experiments, both in vitro and in vivo, aimed at investigating its association with curcumin and NLRP3. The results obtained from these experiments showed that curcumin inhibited NSCLC cell growth, promoted pyroptosis and reduced the level of NLRP3 ubiquitination. NLRP3 knockdown reversed the curcumin-induced increase in pyroptosis-associated factors both in vitro and in vivo. Additionally, Smurf2 interacted with NLRP3 and alterations in Smurf2 expression levels influenced NLRP3 ubiquitination and cell pyroptosis. Moreover, molecular docking analysis demonstrated that curcumin could bind directly to Smurf2, which subsequently led to an inhibition of Smurf2 activity. Knockdown of Smurf2 enhanced curcumin's ability to stabilize NLRP3 and to promote pyroptosis, whereas Smurf2 overexpression negated these effects. In the in vivo animal model, curcumin treatment led to reduced tumor volumes and weights, in addition to a decreased expression level of Ki67 and increased expression levels of NLRP3 and pyroptosis-associated factors. Similarly, these effects were enhanced or reversed by Smurf2 knockdown or overexpression, respectively. In conclusion, the findings of the present study showed that curcumin inhibited Smurf2 activity, thereby promoting NLRP3-dependent pyroptosis in NSCLC cells. In addition, these findings have provided mechanistic insights into the role of curcumin in NSCLC, opening an avenue for its potential therapeutic application.