Growth inhibition of A549 human lung adenocarcinoma cells by L-canavanine is associated with p21/WAF1 induction

L-Canavanine (CAV) is a higher plant nonprotein amino acid and a potent L-a rginine antimetabolite, CAV can inhibit the proliferation of tumor cells in vitro and in vivo, but little is known regarding the molecular mechanisms mediating these effects, We demonstrated that the treatment of human lung a denocarcinoma A549 cells with CAV caused growth inhibition; G1 phase arrest is accompanied by accumulation of an incompletely phosphorylated form of t he retinoblastoma protein, whose phosphorylation is necessary for cell cycl e progression from G1 to S phase. Zn addition, CAV induces the expression o f p53 and subsequent expression of a cyclin-dependent kinase inhibitor, p21 /WAF1. The p53-dependent induction of p21/WAF1 and the following dephosphor ylation of the retinoblastoma protein by CAV could account for the observed CAV-mediated G1 phase arrest.