Jekunen et al: Strategy of sensitizing tumor cells with adenovirus-p53 transfection that CPT-11 and 5-fluorouracil may be useful as anticancer agents for use in a combination therapy regimen, using wild-type p53 gene transfer. These results indicate that CPT-11, as well as cisplatin, is a candidate for the combination of chemotherapy and gene therapy for NSCLC. Adeno-p53 and DNA-damaging agents, cisplatin, etoposide and CPT-11 showed synergistic effects in NSCLC, but, in contrast had additive effects with antitubulin agents such as paclitaxel and docetaxel (Horio, Hasegawa et al, 2000). Perdomo et al, (Perdomo et al, 1998) have demonstrated that human NSCLC cells having a mutant form of p53 grow faster in vivo than wild-type p53 cell lines and the treatment with cisplatin or radiation does not reduce the size of mutant p53 tumors, although wild-type p53 tumors regress markedly. Apoptosis occurred in mutant p53 cell types only at high cisplatin doses and not at the magnitude detected in wild-type tumors.
III. In vivo evidence chemosensitization by adenovirus p53
later by doxorubicin or mitomycin-C, but not by vincristine (Blagosklonny and El-Deiry 1996). In the p53 null SK-OV-2 xenograft model of ovarian cancer, a dosing schedule of the p53 therapy that, by itself, had a relatively minimal effect on the tumor burden (16%) caused a much greater decrease in tumor burden (55%) when combined with paclitaxel (Nielsen et al, 1998). Further, in nude mice implanted intraperitoneally with 2774 human ovarian cancer cells (mutated p53), the response to adeno-p53 gene therapy showed significant survival duration, with a survival time greater than that of untreated animals. However, no statistically significant survival advantage was observed between adeno-p53- and adenovirus-!gal-treated mice (von Gruenigen et al, 1998). In another ovarian cancer study using nude mice, the adeno-p53 treatment effectively suppressed the growth of peritoneal tumors and prolonged the survival of the treated group, especially when the tumor burden was small (Kim et al, 1999). Greater combined efficacy was observed in the p53null DU-145 prostate, p53Mut MDA-MB-468 breast, and p53met MDA-MB-231 breast cancer xenograft models in vivo. The authors concluded that their data, taken together, offer the possibility of enhanced antitumor activity with lower than normal doses of paclitaxel and adenovirus p53, when the two drugs are administered in combination (Nielsen et al, 1998). They noted that this could potentially decrease the chemotherapy-induced side effects, increasing the quality of life of the patients and, perhaps, reducing the overall expense of a complete course of cancer treatment.
of
These observations have been extended to in vivo models. Tumors have been treated in vivo with replication-defective p53 adenovirus and chemotherapy. Nguyen et al, have reported convincing in vivo studies, in which p53null H1299 lung tumor xenografts were given i.p. cisplatin before, concurrently with, or after intratumoral adenovirus p53 (Nguyen et al, 1996). The most effective dosing regimen was cisplatin given two days before p53 therapy. Cisplatin and CPT-11 had a significant antitumoral effect on lung cancer H157 cell xenografts of nude mice in vivo. Human head and neck cancer and colon cancer (Gjerset et al, 1997) and prostate cancer (Gjerset and Mercola 2000) in nude mice models in vivo have been found to exhibit a similar sensitization effect with adenovirus plus cisplatin as in studies in vitro. Gjerset et al, demonstrated increased sensitivity to cisplatin cytotoxicity in p53mut T98G glioblastoma and p53 mut H23 small cell lung carcinoma cells transduced with p53 expression vectors one or two days before exposure to cisplatin (Gjerset et al, 1995). These results are consistent with other in vivo studies in animal models showing a combined benefit of p53 and chemotherapy (Badie et al, 1998), (Fujiwara et al, 1994), (Miyake et al, 1998), (Nielsen et al, 1998), (Nguyen et al, 1996). Gjerset and Mercola are convinced that these results support the clinical application of adenovirus p53 combination approaches to tumors expressing mutant p53 (Gjerset and Mercola 2000). Chemosensitization by p53 has also been studied using ex vivo modified cells in an orthotopic model of glioblastoma in Fisher rats (Dorigo et al, 1998). The combination of p53 with 5-fluorouracil and topotecan has been studied in p53mut SW480 colorectal tumor cells transfected with an inducible p53 construct (Yang et al, 1996). Dose-dependent enhancement of cytotoxicity was observed with these drugs by the concurrent expression of wild-type p53. Increased cytotoxicity has been reported in p53mut SkBr3 mammary tumor cells when transduction with p53 was followed 8 hr
IV. Clinical results of adenovirus p53 transfection with chemotherapy The first evidence of the efficacy of p53 gene therapy for cancer was given by a pilot study in which retroviral p53 expression vectors were directly injected into small endobronchial lesions of NSCLC patients (Roth et al, 1996). Tumor regression was noted in three patients out of nine, and tumor growth stabilized in three other patients. The safety and feasibility of the intratumoral injection of adenoviral wild-type p53 expression vectors have been established in NSCLC patients, with clear evidence for transgenic expression, and possibly induction of apoptosis (Swisher et al, 1999; see Table 1). The antitumor activity in this trial was consistent with the activity of retroviral p53 injection in NSCLC patients. Twenty-four patients received intratumor injections of adenovirus p53 and two patients achieved a partial response, while 17 patients achieved stable disease as the best clinical response. A nonrandomized, phase I, dose-escalating study by Clayman et al expanded these findings into head and neck squamous cell carcinoma (Clayman et al, 1998). Patients with incurable recurrent local or regionally metastatic HNSCC received multiple intratumoral injections of adeno-p53, either with or without tumor resection. P53 expression was detected in tumor biopsies despite antibody responses after injections. prevent the appearance of adeno-p53 in blood and urine. were seen in the study As expected, almost Neither dose-limiting effects nor serious
30