INHIBITORS OF EPIDERMAL GROWTH-FACTOR RECEPTOR KINASE AND OF CYCLIN-DEPENDENT KINASE-2 ACTIVATION INDUCE GROWTH ARREST, DIFFERENTIATION, AND APOPTOSIS OF HUMAN PAPILLOMA-VIRUS 16-IMMORTALIZED HUMAN KERATINOCYTES

Human papilloma virus 16 (HPV 16) is associated with cervical cancer a nd is therefore considered a major health risk for women. Immortalizat ion of keratinocytes induced by HPV infection is largely due to the bi nding of p53 and Rb by the the viral oncoproteins E6 and E7, respectiv ely, and is driven to a large extent by a transforming growth factor a lpha/amphiregulin epidermal growth factor receptor autocrine loop. In this study, we show that the growth of HPV 16-immortalized human kerat inocytes can be blocked by a selective epidermal growth factor recepto r kinase inhibitor, AG 1478, and by AG 555, a blocker of cyclin-depend ent kinase 2 (Cdk2) activation. AG 1478 induces a massive increase in the Cdk2 protein inhibitors p27 and p21, whereas AG 555 appears to hav e a different mechanism of action, inhibiting the activation of Cdk2. Growth arrest induced by AG 1478 and AG 555 is accompanied by up to 20 % of cells undergoing apoptosis. Following AG 1478 treatment but not A G 555 treatment, up to 50% of cells undergo terminal keratinocyte diff erentiation as determined by filaggrin expression and by the decline i n the expression of cytokeratin 14. The growth-arresting properties of AG 1478 and AG 555 identifies them as possible lead antipapilloma age nts.