Although viral infection also resulted in cyclin D1, CDK4, and CDK6 down-regulation on protein level (Fig. 4A), the level of down-regulation is not as robust as that of cyclin D3, and their protein levels could not be rescued by protease and calpain inhibitor when compared with cyclin D3 (Fig. 4B). The gene discussed is CCND3; the disease is viral infectious disease.