Modulation of drug cytotoxicity by reintroduction of wild-type p53 gene (Ad5CMV-p53) in human pancreatic cancer

Abstract

Chemotherapy does not significantly improve prognosis in pancreatic cancer. New therapeutical approaches involving p53 gene replacement appear to be very encouraging due to the key role of p53 in the cell response to DNA damage. Here, we have evaluated the effectiveness of combining wild-type p53 (wt-p53) gene reintroduction (Ad5CMV-p53) and exposure to two genotoxic drugs, gemcitabine and cisplatin, in several human pancreatic cell lines. The efficiency of the combinations was clearly dependent upon timing, as assessed by cell survival determinations. Although wt-p53 transduction before drug treatment induced chemoresistance, p53 transduction in cells treated previously with gemcitabine increased cytotoxicity. Cell cycle profiles showed significant decreases in the percentage of cells in the S phase as a consequence of arrests provoked by the expression of exogenous p53, reducing the number of cells susceptible to the drug. The sensitivity of cells to cisplatin, which has a lower degree of S-phase specificity, was not modified as much by p53 gene replacement. In contrast, the recognition of the previous drug-induced DNA damage by the newly expressed wt-p53 elicited increases in sub-G 1 populations, consistent with the annexin determinations and bax/bcl-2 ratios observed. Experiments on subcutaneous pancreatic xenografts corroborated the effectiveness of this approach in vivo. Thus, the combination of p53 transduction and chemotherapy, under a correct schedule of administration, appears to be a very promising therapy for human pancreatic cancer. Cancer Gene Therapy (2000) 7, 545-556

Expression of a non‐functional p53 affects the sensitivity of cancer cells to gemcitabine

“…Moreover, other authors have reported that transfection of p53-null cells with wt-p53 expression vector enhanced the sensitivity of the cells to gemcitabine. 19,31 Conversely Merlin, 32 as well as Rieger, 33 have suggested that gemcitabine cytotoxicity does not require wt-p53 activity because they found no difference in the susceptibility to gemcitabine between cell lines with wt-p53 and cell lines with mutant or deleted p53. It is also possible that there are tissue-specific differences in the relationship between p53 status and sensitivity to gemcitabine.…”

“…17 Finally, alterations of apoptosis-regulating genes such as p53 also appear to be involved in the sensitivity of tumor cells to the cytotoxic effect of gemcitabine. 18,19 The effect of p53 status on sensitivity of cancer cells to chemotherapeutic agents depends on the dual role of p53 protein as a guardian of genome integrity and as a key intermediate of apoptosis. 20 p53 is markedly upregulated after DNA damage and blocks the cell cycle at the G1/S checkpoint or leads to apoptosis of the damaged cells.…”

Cooperative effect of adenoviral p53 gene therapy and standard chemotherapy in ovarian cancer cells independent of the endogenous p53 status

“…Recent reports demonstrated that p53 missense mutants markedly reduced DNA binding of wild-type p53 Previous reports have demonstrated that the combination of adenoviral p53 and cisplatin was cooperative in ovarian, breast, lung, pancreatic, prostate, head and neck cancer cells expressing mutant p53. [10][11][12][26][27][28] Furthermore adenoviral p53 might enhance the effect of taxanes in lung and ovarian cancer. 9,10,12,29 Although it appears that p53 is not involved in paclitaxel-dependent apoptosis, 30 it may enhance adenoviral transduction efficiency.…”

“…p53 gene mutations occur even more frequently in recurrent ovarian cancer and may affect response to chemotherapy. 8 Gene transfer of a wild-type p53 gene is intended to reverse the loss of normal p53 function and has been demonstrated to reduce proliferation of tumor cells alone or in combination with chemotherapy in vitro and in vivo among different types of tumors, such as breast, 9,10 head and neck, 9,10 prostate, 9,10 pancreas, 11 lung, 12 as well as ovarian cancer. 9,10,13,14 At least three major issues remain unclear when this therapeutic strategy is applied to ovarian cancer: the efficiency of the adenoviral transduction in ovarian cancer cells, the effect of adenoviral p53 on tumor cells with endogenous wild-type p53, the efficacy of the combination of current standard paclitaxel/carboplatin chemotherapy with adenoviral p53 gene transfer, systematically analyzed with regard to the mutational status.…”

Adenovirus-mediated wt- p16 reintroduction induces cell cycle arrest or apoptosis in pancreatic cancer

“…At 2 days after virus administration, X -gal staining showed that the expression of -galactosidase was restricted to patches of -gal -expressing cells around the injection points in the tumors. 44 No more than 20% of reduction in tumor growth was observed in animals treated with Ad -lacZ at the same dose as for Ad -p16 (data not shown ).…”