# Curcumol Induces G1 Phase Arrest in SK-Hep-1 Cells by Targeting SKP2-Mediated p27 Degradation

## TL;DR

Curcumol stops liver cancer cells from dividing by targeting SKP2, which normally helps break down a protein that controls the cell cycle.

## Contribution

This study reveals that curcumol induces G1 phase arrest by inhibiting SKP2-mediated p27 degradation in hepatocellular carcinoma cells.

## Key findings

- Curcumol modulates SKP2, CDK4, CDK6, Cyclin D1, and p27 expression in hepatocellular carcinoma cells.
- Overexpression of SKP2 reduces curcumol's antitumor and cell cycle arrest effects.
- Curcumol disrupts the interaction between SKP2 and p27, preventing p27 degradation and inducing G1 arrest.

## Abstract

Context: S-phase kinase-associated protein 2 (SKP2) is an oncogene and cell cycle regulator that mediates the ubiquitination of cell cycle regulators. Curcumol, a sesquiterpene natural product, has been reported to regulate SKP2-mediated ubiquitination degradation to overcome drug resistance in cancer cells. However, whether the cell cycle arrest effect of curcumol is related to SKP2’s function in cancer cells and its mechanisms are still unclear. Objective: To investigate the role of SKP2 in curcumol-induced cell cycle arrest and its underlying mechanisms. Materials and Methods: Transcriptomic and proteomic analyses were used to screen the ubiquitination-related factors in curcumol treated hepatocellular carcinoma cells. Lentiviral overexpression, co-immunoprecipitation assays, ubiquitination analysis, and cell-line-derived xenograft (CDX) models were used to dissect the role and mechanisms of the identified ubiquitination-related factor in the cell cycle arrest effect of curcucmol. Results: Curcumol modulated the expression of CDK4, CDK6, Cyclin D1, p27 and SKP2. SKP2 was one candidate target of curcumol selected by multi-omics. Overexpressed SKP2 partially reversed curcumol-induced growth inhibition and G1-phase arrest. The increased expression of p27 induced by curcumol was attenuated by overexpressed SKP2. Curcumol impaired the interaction between SKP2 and p27, and led to the ubiquitination and degradation of p27. In vivo, curcumol effectively reduced tumor growth, and its antitumor effect was significantly mitigated by SKP2 overexpression. Discussion and Conclusions: Curcumol reduced SKP2 expression, weakened the interaction between SKP2 and p27, inhibited degradation of p27, and then induced G1 phase cell-cycle arrest in SK-Hep-1 cells.