YC-1 [3-(5′-hydroxymethyl-2′-furyl)-1-benzyl indazole] exhibits a novel antiproliferative effect and arrests the cell cycle in G ₀-G₁ in human hepatocellular carcinoma cells

This study delineates the antiproliferative activities and in vivo efficacy of YC-1 [3-(5′-hydroxymethyl-2′-furyl)-1-benzyl indazole] in human hepatocellular carcinoma cells. YC-1 inhibited the growth of HA22T and Hep3B cells in a concentration-dependent manner without significant cytotoxicity. YC-1 induced G₁ phase arrest in the cell cycle, as detected by an increase in the proportion of cells in the G₁ phase using FAC-Scan flow cytometric analysis. It was further shown that cGMP, p42/p44 mitogen-activated protein kinase, or AKT kinase-mediated signaling pathways did not contribute to the YC-1-induced effect. Of note, YC-1 induced a dramatic increase in the expression of cyclin-dependent kinase (CDK)-inhibitory protein, p21^CIP1/WAP1, and a modest increase in p27^KIP1. The association of p21^CIP1/WAP1 with CDK2 was markedly increased in cells responsive to YC-1. YC-1 did not modify the expression of cyclin D1, cyclin E, CDK2, or CDK4. In a corollary in vivo study, YC-1 induced dose-dependent inhibition of tumor growth in mice inoculated with HA22T cells. Immunohistochemical analysis revealed an inverse relationship between the staining of p21^CIP1/WAF and the staining of Ki-67, a cell proliferation marker. Based on the results reported herein, we suggest that YC-1 induces cell cycle arrest and inhibits tumor growth both in vitro and in vivo via the up-regulation of p21^CIP1/WAP1 expression in HA22T cells. Because of this, YC-1 is a potential anti-tumor agent worthy of further investigation.