Combined cyclin D1 overexpression and zinc deficiency disrupts cell cycle and accelerates mouse forestomach carcinogenesis.

Overexpression of cyclin D1 and disruption of cell cycle control in G(1) occur frequently in human esophageal cancer. Transgenic (TG) mice with cyclin D1 overexpression targeted to the oral-esophageal tissue by the EBV ED-L2 promoter showed increased severity in esophageal dysplasia without cancer development, after multiple doses of N-nitrosomethylbenzylamine (NMBA). Dietary zinc deficiency (ZD) in mice enhances cellular proliferation in esophagus/forestomach and susceptibility to NMBA-induced carcinogenesis. We investigated whether cyclin D1 overexpression in TG mice, together with ZD, might lead to unchecked cell proliferation and accelerated NMBA-induced tumorigenesis. Five-week-old TG and wild-type (WT) mice were fed a ZD- or -sufficient (ZS) diet, forming four groups: ZD:TG; ZS:TG; ZD:WT; and ZS:WT. After 4 weeks, animals were given a single intragastric NMBA dose and were sacrificed 25 and 77 days later. Without NMBA, cell proliferation was greatest in ZD:TG esophagus/forestomach, followed by ZD:WT, and then ZS:TG>/=ZS:WT. The high rate of cell proliferation was accompanied by overexpression of cell cycle progression and tumorigenesis biomarkers, including proliferating cell nuclear antigen, cyclin D1, cyclin-dependent kinase 4, p53, cytokeratin 14, epidermal growth factor receptor, and by a reduced rate of apoptosis. ZD substantially increased forestomach tumor incidence in TG mice: 85% of ZD:TG versus 14% of ZS:TG mice had forestomach tumors (P < 0.001), with progression to malignancy occurring only in ZD:TG tumors. Additionally, 14% of ZD:TG mice developed esophageal tumors and esophageal intestinal metaplasia at 77 days. Thus, cyclin D1 overexpression, in cooperation with ZD, decontrols cell proliferation, ensuring cell expansion, a prerequisite for cancer development.