engleski

The role of ΔNp73α in response to genotoxic stress in normal human fibroblasts

p73 exists in multiple isoforms which could be divided into two groups: one containing transactivation domain (TA) and another amino- terminally truncated (ΔN) isoforms. While TAp73 isoforms show tumor-suppressive functions similar to those of wild-type p53, ΔNp73 isoforms inhibit wild-type p53 as well as TAp63 and TAp73, and are considered as potential oncogenes. ΔNp73 isoforms are overexpressed in many tumors correlating with enhanced chemoresistance and poorer disease outcome. The aim of our work is to investigate how ΔNp73α overexpression (OE) affects cell cycle regulation and DNA damage response in normal human cells. To this end we infected wild-type human dermal fibroblasts (HDF-WT) as well as HDF expressing human papilloma virus HPV16-E6 oncoprotein (HDF- E6), which promotes p53 degradation, with retroviral vectors carrying ΔNp73α gene. Preliminary results show that HDF cells overexpressing ΔNp73α are more prone to entry into mitosis compared to control ones after treatment with ICRF-193 which causes G2 arrest or delay, obtained by video-microscopy. In accordance with this result, the lower expression of p21 is observed in cells with ΔNp73α compared to control ones after ICRF-193 treatment. In order to investigate whether ΔNp73α has specific role at the G2/M checkpoint, HDF and HDF E6 cells were synchronized by hydroxyurea in G1/S. Released cells were γ-irradiated (12 Gy) and analysed by FACS. As no significant difference could be seen between cells expressing ΔNp73α and control cells, detailed analysis of the number of cells that manage to enter mitosis needs to be taken. Further investigation could contribute to understanding the mechanisms by which ΔNp73 isoforms carry out its oncogenic function in normal cells, shedding new light on the process of tumorigenesis in general.

p73; cell cycle; DNA damage

nije evidentirano