Increase of BCNU sensitivity by wt-p53 gene therapy in glioblastoma lines depends on the administration schedule

In this article, we investigated the effect induced by the reintroduction o f wild-type p53 (wt-p53) protein on BCNU sensitivity in the ADF glioblastom a line. Using a wt-p53 recombinant adenovirus (Ad-p53), we demonstrated tha t exogenous wt-p53 expression was able to increase the sensitivity to BCNU in ADF cells. interestingly this effect was more evident when Ad-p53 infect ion was performed after BCNU treatment compared with the opposite sequence. To understand the biological basis of these different behaviors, we analyz ed the cell cycle of the differently treated cells. We found that Ad-p53 in fection induced a persistent accumulation of cells in the G0/G1 phase while , as expected, BCNU induced a block in the G2-M phase. Ad-p53-->BCNU sequen ce did not significantly modify the cell cycle profile in respect of Ad-p53 infected cells. In contrast, BCNU-->Ad-p53 sequence provoked G2-M arrest s imilar to that observed after treatment with BCNU alone, but prevented the later recovery of the cells through the cell cycle, by driving the cells to apoptotic death. These results demonstrate that the administration sequenc e is important to increase drug sensitivity. To generalize the phenomenon o bserved on ADF line, the antiproliferative effect of the two different sche dules was analyzed on other glioblastoma lines (A172, CRS-A2, U373MG) with different BCNU sensitivity and p53 status. The data obtained confirm that t he wt-p53 gene transfer enhances BCNU sensitivity in glioblastoma cells dep ending on the administration sequence.