GTMB 7 - Gene Therapy & Molecular Biology

Jekunen et al: Strategy of sensitizing tumor cells with adenovirus-p53 transfectionthat CPT-11 and 5-fluorouracil may be useful asanticancer agents for use in a combination therapyregimen, using wild-type p53 gene transfer. These resultsindicate that CPT-11, as well as cisplatin, is a candidatefor the combination of chemotherapy and gene therapy forNSCLC. Adeno-p53 and DNA-damaging agents, cisplatin,etoposide and CPT-11 showed synergistic effects inNSCLC, but, in contrast had additive effects withantitubulin agents such as paclitaxel and docetaxel (Horio,Hasegawa et al, 2000). Perdomo et al, (Perdomo et al,1998) have demonstrated that human NSCLC cells havinga mutant form of p53 grow faster in vivo than wild-typep53 cell lines and the treatment with cisplatin or radiationdoes not reduce the size of mutant p53 tumors, althoughwild-type p53 tumors regress markedly. Apoptosisoccurred in mutant p53 cell types only at high cisplatindoses and not at the magnitude detected in wild-typetumors.III. In vivo evidence ofchemosensitization by adenovirus p53These observations have been extended to in vivomodels. Tumors have been treated in vivo withreplication-defective p53 adenovirus and chemotherapy.Nguyen et al, have reported convincing in vivo studies, inwhich p53null H1299 lung tumor xenografts were giveni.p. cisplatin before, concurrently with, or afterintratumoral adenovirus p53 (Nguyen et al, 1996). Themost effective dosing regimen was cisplatin given twodays before p53 therapy. Cisplatin and CPT-11 had asignificant antitumoral effect on lung cancer H157 cellxenografts of nude mice in vivo. Human head and neckcancer and colon cancer (Gjerset et al, 1997) and prostatecancer (Gjerset and Mercola 2000) in nude mice models invivo have been found to exhibit a similar sensitizationeffect with adenovirus plus cisplatin as in studies in vitro.Gjerset et al, demonstrated increased sensitivity tocisplatin cytotoxicity in p53mut T98G glioblastoma andp53 mut H23 small cell lung carcinoma cells transducedwith p53 expression vectors one or two days beforeexposure to cisplatin (Gjerset et al, 1995). These resultsare consistent with other in vivo studies in animal modelsshowing 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). Gjersetand Mercola are convinced that these results support theclinical application of adenovirus p53 combinationapproaches to tumors expressing mutant p53 (Gjerset andMercola 2000). Chemosensitization by p53 has also beenstudied using ex vivo modified cells in an orthotopicmodel of glioblastoma in Fisher rats (Dorigo et al, 1998).The combination of p53 with 5-fluorouracil andtopotecan has been studied in p53mut SW480 colorectaltumor cells transfected with an inducible p53 construct(Yang et al, 1996). Dose-dependent enhancement ofcytotoxicity was observed with these drugs by theconcurrent expression of wild-type p53. Increasedcytotoxicity has been reported in p53mut SkBr3 mammarytumor cells when transduction with p53 was followed 8 hrlater by doxorubicin or mitomycin-C, but not byvincristine (Blagosklonny and El-Deiry 1996).In the p53 null SK-OV-2 xenograft model of ovariancancer, 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 with2774 human ovarian cancer cells (mutated p53), theresponse to adeno-p53 gene therapy showed significantsurvival duration, with a survival time greater than that ofuntreated animals. However, no statistically significantsurvival advantage was observed between adeno-p53- andadenovirus-βgal-treated mice (von Gruenigen et al, 1998).In another ovarian cancer study using nude mice, theadeno-p53 treatment effectively suppressed the growth ofperitoneal tumors and prolonged the survival of the treatedgroup, especially when the tumor burden was small (Kimet al, 1999). Greater combined efficacy was observed inthe p53null DU-145 prostate, p53Mut MDA-MB-468breast, and p53met MDA-MB-231 breast cancer xenograftmodels in vivo. The authors concluded that their data,taken together, offer the possibility of enhanced antitumoractivity with lower than normal doses of paclitaxel andadenovirus p53, when the two drugs are administered incombination (Nielsen et al, 1998). They noted that thiscould potentially decrease the chemotherapy-induced sideeffects, increasing the quality of life of the patients and,perhaps, reducing the overall expense of a complete courseof cancer treatment.IV. Clinical results of adenovirus p53transfection with chemotherapyThe first evidence of the efficacy of p53 gene therapyfor cancer was given by a pilot study in which retroviralp53 expression vectors were directly injected into smallendobronchial lesions of NSCLC patients (Roth et al,1996). Tumor regression was noted in three patients out ofnine, and tumor growth stabilized in three other patients.The safety and feasibility of the intratumoral injection ofadenoviral wild-type p53 expression vectors have beenestablished in NSCLC patients, with clear evidence fortransgenic expression, and possibly induction of apoptosis(Swisher et al, 1999; see Table 1). The antitumor activityin this trial was consistent with the activity of retroviralp53 injection in NSCLC patients. Twenty-four patientsreceived intratumor injections of adenovirus p53 and twopatients achieved a partial response, while 17 patientsachieved stable disease as the best clinical response.A nonrandomized, phase I, dose-escalating study byClayman et al expanded these findings into head and necksquamous cell carcinoma (Clayman et al, 1998). Patientswith incurable recurrent local or regionally metastaticHNSCC received multiple intratumoral injections ofadeno-p53, either with or without tumor resection. P53expression was detected in tumor biopsies despiteantibody responses after injections. prevent the appearanceof adeno-p53 in blood and urine. were seen in the study Asexpected, almost Neither dose-limiting effects nor serious30