Effects of electrogenetherapy with p53wt combined with cisplatin on curvival of human tumor cell lines with different p53 status

The aim of our study was to evaluate electrogenetherapy with p53wt alone or combined with cisplatin on two colorectal (HT-29 and LoVo) and two prostatic (PC-3 and Du145) carcinoma cell lines with different p53 status. In addition, the feasibility of electrogenetherapy with p53wt was tested also in vivo on PC-3 prostatic cancer xenografts. Electrogenetherapy with p53wt was dependent on the p53 status of the cell lines used. Electrogenetherapy was the most effective on the PC-3 (p53 null) and Du145 (p53mt) cells, and to the much lesser extent in LoVo cells (p53wt). The exception was the HT-29 cell line with overexpressed mutated p53, where electrogenetherapy with p53wt was the least effective. Sensitivity of the cell lines to cisplatin was independent of the p53 status. Furthermore, the presence of exogenous p53 due to electrogenetherapy did not enhance cisplatin cytotoxicity, since the combination of these therapies resulted in additive cytotoxic effect. The effectiveness of electrogenetherapy with p53wt was also demonstrated in vivo by successful treatment of subcutaneous PC-3 tumors in mice. In conclusion, our study shows that electrogenetherapy with p53wt is feasible, and resulted in comparable cytotoxic and antitumor effectiveness to viral-mediated p53wt gene therapy. This therapy was effective and dependent on the p53 status of the tumor cell lines. Combination of electrogenetherapy and cisplatin resulted in additional cell kill by cisplatin, and was not dependent on the p53 status.     

Electrochemotherapy of Mouse Sarcoma Tumors Using Electric Pulse Trains with Repetition Frequencies of 1 Hz and 5 kHz

Electrochemotherapy is an efficient local treatment of tumors that combines administration of a chemotherapeutic drug with the subsequent application of electric pulses to the tumor. Although no difference in clinical response of the treated tumors to the electrochemotherapy when using 1 Hz or 5 kHz repetition frequency was observed, it is mandatory to be aware of possible differences in the effectiveness of electrochemotherapy when using suboptimal doses of the drugs. Therefore, this study compares the antitumor effectiveness of electrochemotherapy using electric pulse trains with repetition frequencies of 1 Hz and 5 kHz at suboptimal drug doses of bleomycin or cisplatin. Electrochemotherapy of fibrosarcoma SA-1 subcutaneous tumors transplanted in A/J mice resulted in good antitumor effectiveness, but antitumor effectiveness was significantly better at 1 Hz repetition frequency than at 5 kHz. The platinum content was higher in tumors treated with a 1 Hz repetition frequency. The application of electric pulses to the tumors at a 5 kHz repetition frequency induced an immediate reduction in tumor perfusion, comparable to the reduction at 1 Hz but with faster reperfusion. The greater effectiveness of electrochemotherapy using electric pulse trains of 1 Hz compared to 5 kHz is due to the greater electroporative effect and longer time in which electroporated tumors are exposed to the two chemotherapeutic drugs. These differences are observed at suboptimal drug doses, whereas at optimal drug doses of bleomycin or cisplatin the antitumor effectiveness is the same, as demonstrated in clinical trials.     

In vivo imaging of tumor growth after electrochemotherapy with cisplatin

Imaging methods can give both temporal and spatial dimensions to characterize the processes in progression of and/or treatment of specific disease Subcutaneous tumors can be cured after electrochemotherapy (ECT). Growth and reduction of tumors as a result of cytotoxic therapy can be followed by fluorescence video imaging directly on the same animal after treatment. Imaging of tumors should bring more information on the cellular effects of ECT. Green fluorescent protein (eGFP) expressing B16F10 and LPB tumors implanted in C57Bl/6 mice were treated with ECT with cisplatin. The growth or regression of the tumors was monitored either classically by using a caliper or by a manual definition of the region of interest where critical fluorescence levels were detected on the animals. A very good correlation between the two methods was observed. The eGFP mean fluorescence emission was only slightly affected by ECT with intravenously injected cisplatin. Ex vivo observations under a fluorescence microscope showed that eGFP was only detected on the outer layer of the tumor. No fluorescence was detected in the central part of the tumors, which were necrotic.     

Withaferin A Alone and in Combination with Cisplatin Suppresses Growth and Metastasis of Ovarian Cancer by Targeting Putative Cancer Stem Cells

Currently, the treatment for ovarian cancer entails cytoreductive surgery followed by chemotherapy, mainly, carboplatin combined with paclitaxel. Although this regimen is initially effective in a high percentage of cases, unfortunately within few months of initial treatment, tumor relapse occurs because of platinum-resistance. This is attributed to chemo-resistance of cancer stem cells (CSCs). Herein we show for the first time that withaferin A (WFA), a bioactive compound isolated from the plant Withania somnifera, when used alone or in combination with cisplatin (CIS) targets putative CSCs. Treatment of nude mice bearing orthotopic ovarian tumors generated by injecting human ovarian epithelial cancer cell line (A2780) with WFA and cisplatin (WFA) alone or in combination resulted in a 70 to 80% reduction in tumor growth and complete inhibition of metastasis to other organs compared to untreated controls. Histochemical and Western blot analysis of the tumors revealed that inclusion of WFA (2 mg/kg) resulted in a highly significant elimination of cells expressing CSC markers - CD44, CD24, CD34, CD117 and Oct4 and downregulation of Notch1, Hes1 and Hey1 genes. In contrast treatment of mice with CIS alone (6 mg/kg) had opposite effect on those cells. Increase in cells expressing CSC markers and Notch1 signaling pathway in tumors exposed to CIS may explain recurrence of cancer in patients treated with carboplatin and paclitaxel. Since, WFA alone or in combination with CIS eliminates putative CSCs, we conclude that WFA in combination with CIS may present more efficacious therapy for ovarian cancer.     

Combined effects of adenovirus-mediated wild-type p53 transduction, temozolomide and poly (ADP-ribose) polymerase inhibitor in mismatch repair deficient and non-proliferating tumor cells.

Lack of p53 or mismatch repair (MR) function and scarce cell proliferation are commonly associated with tumor cell resistance to antineoplastic agents. Recently, inhibition of poly(ADP-ribose) polymerase (PARP) has been considered as a tool to overcome resistance of MR-deficient tumors to methylating agents. In the present study we demonstrated that infection with p53 expressing adenovirus (Ad-p53), enhances chemosensitivity of MR-deficient tumor cell lines to the methylating agent temozolomide (TZM), either used as single agent or, more efficiently, when combined with PARP inhibitor. Moreover, the association of Ad-p53 with drug treatment induced a more pronounced growth inhibitory effect than that provoked by Ad-p53 infection only. Cells, growth arrested by p53 transduction, and then subsequently exposed to the drugs, were still highly susceptible to cytotoxicity induced by TZM and PARP inhibitor. The results suggested that this drug combination might be effective even in non-proliferating tumor cells. It is conceivable to envisage future possible strategies to enhance cytostatic or cytotoxic effects induced by Ad-p53, based on the use of TZM, alone or combined with PARP inhibitor for the therapy of resistant tumors.     

AdDelta24 and the p53-expressing variant AdDelta24-p53 achieve potent anti-tumor activity in glioma when combined with radiotherapy

BACKGROUND: The conditionally replicating adenovirus (CRAd) AdDelta24-p53 replicates selectively in Rb mutant cells, and encodes the p53 suppressor protein. It has shown improved oncolytic potency compared to the parental control AdDelta24. As exogenous p53 has been shown to enhance radiosensitivity, the combination of AdDelta24-p53 and AdDelta24 with radiotherapy was assessed in vitro and in vivo against the therapy resistant gliomas. METHODS: In glioma cells, multicellular spheroids and animal xenografts the efficacy of combination therapy was assessed. P53 phosphorylation, induction of apoptosis and viral replication were determined following single or combination therapies. RESULTS: In vitro, AdDelta24-p53 was more effective against glioma cells than the control AdDelta24. Addition of irradiation equally increased the efficacy of both AdDelta24-p53 and AdDelta24 resulting in improved oncolysis compared to single agent treatment. Radiotherapy did not significantly change the replication kinetics of AdDelta24-p53 or AdDelta24. No detectable increase in p53 phosphorylation was observed but combination of radiotherapy and AdDelta24-p53 caused an increase in the percentage of apoptotic cells. In vivo, combination therapy with either AdDelta24 or AdDelta24-p53 significantly increased the number of mice demonstrating tumor regression (100%) as well as long-term survival (50%). No differences between viruses were noted. CONCLUSIONS: Exogenous p53 expression does not appear to increase the synergistic interaction of CRAds combined with radiotherapy. These results however do indicate that radiotherapy provides the time frame in which AdDelta24 and AdDelta24-p53 can eradicate established tumors that would otherwise escape treatment, and establishes the need to combine these modalities to form an effective anti-cancer treatment.     

Inhibition of SA-1 tumor growth in mice by human leukocyte interferon alpha combined with low-level direct current

A preliminary study of the antitumor effect of partially purified human interferon alpha (IFN-alpha) and low-level direct current (DC) was carried out using a murine subcutaneous SA-1 experimental tumor model. Tumor-bearing animals were treated with 5 x 10(4) IU IFN-alpha peritumorally, or with 0.6 mA DC current for 15 minutes daily, for 6 consecutive days. Antitumor effect was manifested 2 days after the beginning of each treatment modality. Combined treatment with DC current applied immediately after IFN-alpha application was more effective than IFN-alpha treatment alone (P less than 0.005), but not significantly better than DC current treatment (P less than 0.5). The results indicate that the combined treatment with IFN-alpha and DC current can be effective in tumor therapy; however, further work is required to determine optimal scheduling.     

Antitumor activity of Herceptin in combination with STEALTH liposomal cisplatin or nonliposomal cisplatin in a HER2 positive human breast cancer model

Single agent antitumor activity of Herceptin, a humanized monoclonal antibody directed against HER2, has been demonstrated in numerous preclinical and clinical studies. Additionally, combination therapy with Herceptin and chemotherapy (CRx) has demonstrated additive antitumor activity in both preclinical models and early clinical trials. STEALTH (pegylated) liposomal (PL) cisplatin, also known as SPI-077, is currently in clinical trials for a variety of solid tumors. The three studies reported here discuss the antitumor activity of the combination of Herceptin and nonliposomal cisplatin or PL-cisplatin in two xenograft tumor models, initiated from the cell lines, BT474 and MDA453, that overexpress the oncogene, HER2. Herceptin alone had significant antitumor activity in all three experiments (p < 0.0001). Nonliposomal cisplatin and PL-cisplatin were both effective antitumor agents but, at tolerable dose levels, PL-cisplatin was superior to nonliposomal cisplatin (p < 0.0003). The effect of combining Herceptin with the chemotherapeutic cisplatin or PL-cisplatin, was most significant at moderate doses of H (0.5 mg/kg, p < 0.0001), but tended to be greater than either agent alone in all experiments. The combination of PL-cisplatin with Herceptin had statistically similar antitumor activity to that of nonliposomal cisplatin with Herceptin in all experiments. We conclude that combination therapy with PL-cisplatin and Herceptin results in significant antitumor activity with the potential for reducing toxicity in metastatic breast cancer patients.     

Inhibition of AMP-activated protein kinase sensitizes cancer cells to cisplatin-induced apoptosis via hyper-induction of p53

Cisplatin is one of the most effective and widely used chemotherapeutic agents. However, one of the most salient limitations to the clinical application of cisplatin is the acquired or intrinsic drug resistance exhibited by some tumors. In the present study, we have assessed the potential of an intracellular energy balancing system as a target for augmentation of cisplatin sensitivity in tumors. AMP-activated protein kinase (AMPK) regulates the energy balance system by monitoring intracellular energy status. Here we demonstrate that AMPK is rapidly activated by cisplatin in AGS and HCT116 cancer cells. The inhibition of AMPK in those cells and in xenografts of HCT116 resulted in a remarkable increase in cisplatin-induced apoptosis, which was associated with hyper-induction of the tumor suppressor p53. We further showed that ERK, but not ATM (ataxia telangiectasia mutated) and ATR (ATM- and Rad3-related) kinases, was involved in the hyper-induction of p53 by the inhibition of cisplatin-induced AMPK. By way of contrast, cisplatin did not induce AMPK activation in HeLa cells, which appear to have a relatively high sensitivity to cisplatin-induced cytotoxicity, but expression of the constitutive active form of AMPK in HeLa cells resulted in a significant increase of cell viability after cisplatin treatment. Collectively, our data suggest that AMPK performs a pivotal function for protection against the cytotoxic effect of cisplatin, thereby implying that AMPK is one of the cellular factors determining the cellular sensitivity to cisplatin. On the basis of these observations, we propose that a strategy combining cisplatin and AMPK inhibition could be developed into a novel chemotherapeutic modality.     

Inflammasome Modulation by Chemotherapeutics in Malignant Mesothelioma

Malignant mesothelioma (MM) is a fatal disease in dire need of therapy. The role of inflammasomes in cancer is not very well studied, however, literature supports both pro-and anti-tumorigenic effects of inflammasomes on cancer depending upon the type of cancer. Asbestos is a causative agent for MM and we have shown before that it causes inflammasome priming and activation in mesothelial cells. MM tumor cells/tissues showed decreased levels of inflammasome components like NLRP3 and caspase-1 as compared to human mesothelial cells or normal tissue counterpart of tumor. Based on our preliminary findings we hypothesized that treatment of MMs with chemotherapeutic drugs may elevate the levels of NLRP3 and caspase-1 resulting in increased cell death by pyroptosis while increasing the levels of IL-1β and other pro-inflammatory molecules. Therefore, a combined strategy of chemotherapeutic drug and IL-1R antagonist may play a beneficial role in MM therapy. To test our hypothesis we used two human MM tumor cell lines (Hmeso, H2373) and two chemotherapeutic drugs (doxorubicin, cisplatin). Through a series of experiments we showed that both chemotherapeutic drugs caused increases in NLRP3 levels, caspase-1 activation, pyroptosis and pro-inflammatory molecules released from MM cells. In vivo studies using SCID mice and Hmeso cells showed that tumors were smaller in combined treatment group of cisplatin and IL-1R antagonist (Anakinra) as compared to cisplatin alone or untreated control groups. Taken together our study suggests that chemotherapeutic drugs in combination with IL-1R antagonist may have a beneficial role in MM treatment.     

ADP sensitizes ZL55 cells to the activity of cisplatin

Malignant pleural mesothelioma (MPM) is an aggressive malignant tumor in which cisplatin therapy is commonly used, although its effectiveness is limited. It follows that research efforts dedicated to identify promising combinations that can synergistically kill cancer cells are needed. Because we recently demonstrated that ADP inhibits the proliferation of ZL55 cells, an MPM-derived cell line obtained from bioptic samples of asbestos-exposed patients. Our objective in this study was to investigate the hypothesis that ADP also potentiates the cytotoxic activity of cisplatin. Results show that in ZL55 cells ADP enhanced (a) the cytotoxicity of cisplatin by 12-fold, (b) the restraint of cell clonogenic potential cisplatin-mediated, and (c) the number of apoptotic cells. Cisplatin, but not ADP, caused caspases activation; nevertheless, poly(ADP-ribose) polymerase-1 was not only cleaved in cisplatin-treated cells but also in cells treated with ADP alone. Furthermore, ADP, but not cisplatin, decreased mTOR and 6SK phosphorylations. Both ADP and cisplatin increased p53 protein, but ADP was also able to enhance p53 messenger RNA. P53 silencing resulted in a very large decrement of cell death induced by ADP or by cisplatin and reverted ADP effects on mTOR/S6K phosphorylation, suggesting that activated p53 may act as a negative regulator of mTOR. Consistently, the inhibition of mTOR by rapamycin also sensitized cells to cisplatin, and the effects of cisplatin plus rapamycin were identical to those obtained with cisplatin plus ADP. These findings suggest that the combination of ADP and cisplatin may be a promising strategy for the clinical treatment of cisplatin-resistant MPM.     

Advantage of combining NLCQ-1 (NSC 709257) with radiation in treatment of human head and neck xenografts

NLCQ-1 (NSC 709257), a hypoxia-selective cytotoxin that targets DNA through weak intercalation, was investigated for efficacy in combination with single or fractionated radiotherapy of human head and neck xenografts. A staged tumor experiment was performed in tumor-bearing female athymic nude mice that were locally irradiated with or without NLCQ-1. Tumor hypoxia was assessed by immunohistochemistry for pimonidazole adducts in tumors of varying weight. Fractionated radiation, depending on the dose, was administered either once daily for 4 days or once daily for 4 days followed by a 7-day rest and repeat. NLCQ-1 was administered i.p. at 15 mg/kg alone or 45 min before each radiation dose. Hypoxia (1-52%) was detected in all tumors and was positively correlated with tumor size. NLCQ-1 alone resulted in about 10 days of tumor growth delay, measured at sixfold the tumor's original size, without causing toxicity. All combination treatments with NLCQ-1 were more effective than treatments with radiation alone. Radiation at 1 Gy given once daily for 4 days on days 20 and 30 caused 3.5 days of tumor growth delay, whereas in combination with NLCQ-1 it caused 14.5 days of growth delay. Radiation at 5 Gy given in two doses 10 days apart resulted in 3.5 days of tumor growth delay, whereas more than 20 additional days of delay were observed in combination with NLCQ-1. Radiation given as a single dose of 10 Gy resulted in about 7 days of tumor growth delay, whereas in combination with NLCQ-1 about 30 additional days of delay were seen. These results suggest a significant advantage in combining radiation with NLCQ-1 in treatment of human head and neck tumors, which are known to have hypoxic areas.     

p53 gene status and chemosensitivity in ovarian cancer.

Recent studies suggest that drug induced apoptosis relates to the sensitivity. p53 gene, which has a pivotal role in inducing apoptosis, frequently mutates in ovarian cancer. Therefore, p53 gene status and chemosensitivity in epithelial ovarian cancer is discussed. Nonresponders to chemotherapy had mutations of the p53 gene more frequently (83% for nonresponders vs. 16% for responders) in patients with epithelial ovarian cancer undergoing platinum-base chemotherapy. Apoptotic index was significantly greater in tumors with wild-type p53 gene than those without the gene. p53 gene transduction markedly enhanced the sensitivity to cisplatin (CDDP) and CDDP-induced apoptosis, but did not affect the sensitivity to paclitaxel (PTX) nor PTX-induced apoptosis in ovarian cancer cells without p53 gene. The combination treatment with a recombinant adenovirus carrying a wild-type p53 gene (AxCAp53) and CDDP significantly suppressed tumor growth of ovarian cancer cells with and without p53 gene, compared with a single treatment of either AxCAp53 or CDDP in ovarian cancer xenograft. Apoptotic index was significantly higher and proliferating cell nuclear antigen labeling index was relatively lower in an ovarian cancer xenograft without p53 gene receiving combination treatment, compared with a single treatment of either CDDP or AxCAp53, suggesting that the transduction of p53 gene induces apoptosis, but does not enhance the DNA repair system. A significant survival advantage was observed in the combination treatment compared with other treatments in carcinoma peritonitis models. In conclusion, p53 gene status contributes the sensitivity to CDDP in ovarian cancer. Additionally, combination treatment of p53 gene transduction and CDDP may be an effective therapeutic modality for ovarian cancer without wild-type p53 gene.     

Effects of granulocyte-colony-stimulating factor and interleukin-2 on ascites formation and the survival time of nude mice bearing human ovarian cancer cells

 The aim of this study was to elucidate the effect of intraperitoneal (i.p.) instillations of granulocyte-colony-stimulating factor (G-CSF) and/or interleukin-2 (IL-2) on ascites formation and the survival time of nude mice with malignant ascites, produced by i.p. inoculation of human ovarian cancer cells. When the nude mice were treated with medium alone, ascites was observed in all mice 28 days after tumor inoculation. When the mice were treated with cis-diamminedichloroplatinum(II) (cisplatin) alone, G-CSF alone or IL-2 alone, it took 35 days for the ascites to form in all mice. When cisplatin was combined with G-CSF or IL-2, one of ten mice did not form ascites during the observation period. Surprisingly, when G-CSF and IL-2 were simultaneously administered, ascites formation was not observed in any mice. Although i.p. treatment with cisplatin alone significantly prolonged the survival time, compared to medium alone, the lytic activity of spleen cells against HRA cells was significantly suppressed. When G-CSF or IL-2 was combined with cisplatin, the suppression by cisplatin was eliminated and subsequently resulted in a prolongation of the survival time. When G-CSF was combined with IL-2, both the peritoneal and splenic macrophages/monocytes were stimulated and the splenic lytic activity was about double that following treatment with G-CSF alone on IL-2 alone, suggesting that complete inhibition of ascites formation results not only from a significant increase of the peritoneal macrophages but also from enhancement of the lytic activity. Two mice, died from dissemination of tumor in the abdominal cavity, but eight mice survived without tumor for more than 90 days. As confirmed by monitoring body weight and hematocrit, G-CSF and IL-2 seemed to have no adverse effect. From these results, we conclude that a combination therapy with G-CSF and IL-2 might be of clinical use for inhibiting large amounts of ascites, which may inhibit therapeutic effects for ovarian cancer patients. Received: 20 May 1996 / Accepted: 19 September 1996     

a controlled trial of intratumoral ONYX-015, a selectively-replicating adenovirus, in combination with cisplatin and 5-fluorouracil in patients with recurrent head and neck cancer

ONYX-015 is an adenovirus with the E1B 55-kDa gene deleted, engineered to selectively replicate in and lyse p53-deficient cancer cells while sparing normal cells. Although ONYX-015 and chemotherapy have demonstrated anti-tumoral activity in patients with recurrent head and neck cancer, disease recurs rapidly with either therapy alone. We undertook a phase II trial of a combination of intratumoral ONYX-015 injection with cisplatin and 5-fluorouracil in patients with recurrent squamous cell cancer of the head and neck. There were substantial objective responses, including a high proportion of complete responses. By 6 months, none of the responding tumors had progressed, whereas all non-injected tumors treated with chemotherapy alone had progressed. The toxic effects that occurred were acceptable. Tumor biopsies obtained after treatment showed tumor-selective viral replication and necrosis induction.     

Interleukin-2: hope in cases of cisplatin-resistant tumours

 To establish whether or not local low-dose recombinant interleukin-2 (rIL-2) therapy might result in therapeutic benefit for ovarian cancer patients treated with cisplatin, the antitumour effects of rIL-2 and of combined treatment with cisplatin and rIL-2 in a mouse ovarian tumour (MOT) model were studied. In addition, some possible mechanistic aspects underlying the observed antitumour responses were analysed. MOT cells were injected i.p. into syngeneic, immunocompetent, female C3HeB mice. Tumour-bearing mice received i.p. treatment with cisplatin, rIL-2 or both. The MOT tumour appeared to be hardly responsive to treatment with cisplatin only or rIL-2 only. In contrast, combined local treatment with low doses of cisplatin (1 and 5 mg/kg body weight) and rIL-2 (60 000 U/day) resulted in an effective antitumour response in MOT-bearing mice. Complete rejection of the i.p. (local) tumour occurred in up to 60% of the cases. In vitro studies showed that cisplatin and rIL-2 do not have cumulative direct toxic effects on MOT cells. Mice cured after combined treatment with cisplatin and rIL-2 were not able to reject a rechallenge with tumour cells, indicating that these mice had not developed immunity to the tumour. Analysis of tumour-associated leucocytes, however, showed that combined treatment with cisplatin and rIL-2 did result in enhanced non-specific cytolytic activity of peritoneal leucocytes. We have thus demonstrated that, in the MOT model, combined local treatment with low doses of cisplatin and of rIL-2 is far more effective than therapy with cisplatin alone. Non-specific cytotoxicity of leucocytes appears to be involved in antitumour responses induced by combined treatment with cisplatin and rIL-2. These results suggest that, in human ovarian carcinoma, much better results may be obtained with the combined treatment of cisplatin and low (non-toxic) doses of rIL-2 than with cisplatin only. This may also apply to cisplatin-resistant ovarian carcinoma. Received: 6 March 1997 / Accepted: 30 October 1997     

Antineoplastic effect of mer-trichlorobisdimethylsulphoxideaminorutheniumIII against murine tumors: comparison with cisplatin and with ImH[RuIm2Cl4

An asymmetric rutheniumIII complex containing dimethylsulphoxide ligands, namely mer-trichlorobisdimethylsulphoxideaminorutheniumIII (BBR2382), has been tested in mice bearing solid metastasizing tumors. The effects of i.p. treatment with BBR2382 on primary tumor growth and on the survival time of hosts carrying s.c. or i.m. tumors have been compared to those of cisplatin and of a rutheniumIII complex with imidazole ligands, ImH[RuIm2Cl4], described as a potent antitumor agent in a number of experimental models of murine neoplasms. In mice bearing Lewis lung carcinoma, BBR2382 results as effective as cisplatin on s.c. primary tumor growth and more potent than cisplatin on the prolongation of host survival time. The combined treatment of mice bearing Lewis lung carcinoma with cisplatin and BBR2382 causes a reduction of s.c. tumors higher than that caused by each single agent; the effects on host survival time are similar to those caused by BBR2382 alone but significantly superior to those caused by cisplatin alone. In CBA mice bearing MCa mammary carcinoma, the effects of BBR2382 are slightly lower than those of cisplatin on i.m. tumors but are equivalent on host survival time. The comparison of the antineoplastic action of BBR2382 with that of ImH[RuIm2Cl4] is always in favor of the former, independently of the parameter chosen and of the tumor system used. Qualitatively, the antitumor action of BBR2382 seems different from that of cisplatin and of ImH[RuIm2Cl4]; it is supposed that this agent, like other "rutheniumIII dimethylsulphoxide" complexes, could have a particular efficacy for tumors localized in the lungs.     

Intratumoral spread and increased efficacy of a p53-VP22 fusion protein expressed by a recombinant adenovirus

In vitro experiments have demonstrated intercellular trafficking of the VP22 tegument protein of herpes simplex virus type 1 from infected cells to neighboring cells, which internalize VP22 and transport it to the nucleus. VP22 also can mediate intercellular transport of fusion proteins, providing a strategy for increasing the distribution of therapeutic proteins in gene therapy. Intercellular trafficking of the p53 tumor suppressor protein was demonstrated in vitro using a plasmid expressing full-length p53 fused in-frame to full-length VP22. The p53-VP22 chimeric protein induced apoptosis both in transfected tumor cells and in neighboring cells, resulting in a widespread cytotoxic effect. To evaluate the anti-tumor activity of p53-VP22 in vivo, we constructed recombinant adenoviruses expressing either wild-type p53 (FTCB) or a p53-VP22 fusion protein (FVCB) and compared their effects in p53-resistant tumor cells. In vitro, treatment of tumor cells with FVCB resulted in enhanced p53-specific apoptosis compared to treatment with equivalent doses of FTCB. However, in normal cells there was no difference in the dose-related cytotoxicity of FVCB compared to that of FTCB. In vivo, treatment of established tumors with FVCB was more effective than equivalent doses of FTCB. The dose-response curve to FVCB was flatter than that to FTCB; maximal antitumor responses could be achieved using FVCB at doses 1 log lower than those obtained with FTCB. Increased antitumor efficacy was correlated with increased distribution of p53 protein in FVCB-treated tumors. This study is the first demonstration that VP22 can enhance the in vivo distribution of therapeutic proteins and improve efficacy in gene therapy.