Rapid eradication of colon carcinoma by Clostridium perfringens Enterotoxin suicidal gene therapy

Background Bacterial toxins have evolved to an effective therapeutic option for cancer therapy. The Clostridium perfringens enterotoxin (CPE) is a pore- forming toxin with selective cytotoxicity. The transmembrane tight junction proteins claudin-3 and -4 are known high affinity CPE receptors. Their expression is highly upregulated in human cancers, including breast, ovarian and colon carcinoma. CPE binding to claudins triggers membrane pore complex formation, which leads to rapid cell death. Previous studies demonstrated the anti-tumoral effect of treatment with recombinant CPE-protein. Our approach aimed at evaluation of a selective and targeted cancer gene therapy of claudin-3- and/or claudin-4- expressing colon carcinoma in vitro and in vivo by using translation optimized CPE expressing vector. Methods In this study the recombinant CPE and a translation optimized CPE expressing vector (optCPE) was used for targeted gene therapy of claudin-3 and/or -4 overexpressing colon cancer cell lines. All experiments were performed in the human SW480, SW620, HCT116, CaCo-2 and HT-29 colon cancer and the isogenic Sk-Mel5 and Sk-Mel5 Cldn-3-YFP melanoma cell lines. Claudin expression analysis was done at protein and mRNA level, which was confirmed by immunohistochemistry. The CPE induced cytotoxicity was analyzed by the MTT cytotoxicity assay. In addition patient derived colon carcinoma xenografts (PDX) were characterized and used for the intratumoral in vivo gene transfer of the optCPE expressing vector in PDX bearing nude mice. Results Claudin-3 and -4 overexpressing colon carcinoma lines showed high sensitivity towards both recCPE application and optCPE gene transfer. The positive correlation between CPE cytotoxicity and level of claudin expression was demonstrated. Transfection of optCPE led to targeted, rapid cytotoxic effects such as membrane disruption and necrosis in claudin overexpressing cells. The intratumoral optCPE in vivo gene transfer led to tumor growth inhibition in colon carcinoma PDX bearing mice in association with massive necrosis due to the intratumoral optCPE expression. Conclusions This novel approach demonstrates that optCPE gene transfer represents a promising and efficient therapeutic option for a targeted suicide gene therapy of claudin-3 and/or claudin-4 overexpressing colon carcinomas, leading to rapid and effective tumor cell killing in vitro and in vivo

Oncoleaking gene therapy: a new suicide approach for treatment of pancreatic cancer

Bakterielle Toxine stellen eine wirkungsvolle und effektive Alternative zur Therapie von Tumorerkrankungen dar. Das vom Clostridium perfringens Typ A produzierte Clostridium perfringens enterotoxin (CPE) gehört zu der Gruppe der porenbildenden Toxine und weist eine rezeptorspezifische zytotoxische Wirkung auf, welche über die Membranrezeptoren Cldn3 und Cldn4 entfaltet wird. Diese liegen vor allem in Epithelialkarzinomen wie dem Brust-, Prostata-, oder Kolon-, sowie dem Pankreaskarzinom (PK) stark hochreguliert vor. Ziel dieser Arbeit war die Anwendung des neuen selektiven und effizienten „Onkoleaking“ Suizid-Gentherapie Konzepts für die Behandlung von Cldn3 / 4 überexprimierender PK unter Verwendung eines nicht-viralen translations-optimierten CPE exprimierenden Vektors (optCPE). Weiterhin sollte in dieser Arbeit der genaue molekulare Mechanismus der CPE-vermittelten Zytotoxizität in vitro und auch in vivo analysiert werden. Für die in vitro Analysen wurden verschiedene humane PK Zelllinien, Patienten abgeleitete Xenotransplantate (PDX) und deren abgeleiteten Zellen bezüglich ihrer Cldn3 / 4 Expression und Sensitivität sowohl gegenüber rekombinantem CPE (rekCPE) als auch nach optCPE Gentransfer untersucht. Es konnte eine positive Korrelation zwischen der Effizienz CPE vermittelter Zytotoxizität und der Höhe der Cldn3 / 4 Überexpression gezeigt werden. Des Weiteren wurde die Verfügbarkeit und Zugänglichkeit der CPE Rezeptoren für die Toxinbindung als kritischer Faktor für die durch Porenbildung induzierte Zytotoxizität beschrieben. Auch eine detaillierte Analyse verschiedener apoptotischer und nekrotischer Signalwege und deren Schlüsselmoleküle waren vom besonderen Interesse. Von noch größerer Wichtigkeit war jedoch die Anwendbarkeit und der Nachweis der antitumoralen Wirksamkeit der optCPE-basierten Suizid-Gentherapie mit Hilfe des intratumoralen Jet-Injektion Gentransfers in verschiedenen Luziferase-exprimierenden CDX und PDX Modellen des PK. Alle in vivo Studien zeigten eine selektive optCPE vermittelte Verminderung der Tumorvitalität in Verbindung mit Nekrose, die in fast allen Fällen mit einer Reduktion des Tumorvolumens einher ging. Die tierexperimentellen Studien belegen damit die Effektivität der CPE-basierten Gentherapie im Pankreaskarzinom. Mit diesen neu gewonnenen Erkenntnissen zum „Onkoleaking“ Konzept der CPE Suizid-Gentherapie und deren Wirkungsmechanismen sind Kombinationen mit konventionellen Therapien möglich.Bacterial toxins have evolved to an effective therapeutic option for cancer therapy and numerous studies demonstrated their antitumoral potential. The Clostridium perfringens enterotoxin (CPE), produced by the anaerobic Clostridium perfringes bacteria, is a pore-forming (oncoleaking) toxin, which binds to its receptors claudin-3 and -4 (Cldn3 / 4) and exerts a selective, receptor-dependent cytotoxicity. The transmembrane tight junction proteins Cldn3 and Cldn4 are known CPE receptors and are highly upregulated in several human epithelial cancers such as breast, colon, ovarian and pancreatic cancer. This study aimed at the evaluation of the potential of oncoleaking gene therapy using a non-viral translation optimized CPE vector (optCPE) as a new suicide approach for the treatment of Cldn3  /  4 overexpressing pancreatic cancer (PC) in vitro and in vivo. We demonstrated the successful in vitro use of optCPE gene transfer in a panel of human PC cells and more importantly patient derived PC xenograft (PDX) derived cells. We showed significant reduction of cell viability in all Cldn3 / 4 overexpressing PC cells after optCPE transfection. Furthermore a positive correlation between CPE cytotoxicity and level of claudin expression was shown. We revealed accessibility of CPE receptors for toxin binding as determining for optCPE mediated cytotoxicity. Since investigation of optCPE induced cell death mechanism was of particular interest, detailed analyses of apoptotic and necrotic key players were performed. By this, caspase dependent- and independent apoptosis and necrosis activation after gene transfer was demonstrated, which was dependent on amount of expressed optCPE and accessibility of Cldn. More importantly, this study demonstrated the applicability and antitumoral efficacy of optCPE gene therapy by the non-viral intratumoral jet-injection gene transfer in vivo in different luciferase-expressing CDX and PDX pancreatic cancer models. The animal experiments demonstrated the selective CPE mediated tumor growth inhibition, associated with reduced tumor viability and effective induction of tumor necrosis. This further corroborated the advantages of this novel oncoleaking strategy. With this gain of knowledge about our new oncoleaking concept of suicidal gene therapy and its mechanism of action, novel combinations with conventional therapies are possible to further improve therapeutic efficacy and to overcome resistance in pancreas carcinoma

Effective Oncoleaking Treatment of Pancreatic Cancer by Claudin-Targeted Suicide Gene Therapy with Clostridium perfringens Enterotoxin (CPE)

Pancreatic cancer (PC) is one of the most lethal cancers worldwide, associated with poor prognosis and restricted therapeutic options. Clostridium perfringens enterotoxin (CPE), is a pore-forming (oncoleaking) toxin, which binds to claudin-3 and -4 (Cldn3/4) causing selective cytotoxicity. Cldn3/4 are highly upregulated in PC and represent an effective target for oncoleaking therapy. We utilized a translation-optimized CPE vector (optCPE) for new suicide approach of PC in vitro and in cell lines (CDX) and patient-derived pancreatic cancer xenografts (PDX) in vivo. The study demonstrates selective toxicity in Cldn3/4 overexpressing PC cells by optCPE gene transfer, mediated by pore formation, activation of apoptotic/necrotic signaling in vitro, induction of necrosis and of bystander tumor cell killing in vivo. The optCPE non-viral intratumoral in vivo jet-injection gene therapy shows targeted antitumoral efficacy in different CDX and PDX PC models, leading to reduced tumor viability and induction of tumor necrosis, which is further enhanced if combined with chemotherapy. This selective oncoleaking suicide gene therapy improves therapeutic efficacy in pancreas carcinoma and will be of value for better local control, particularly of unresectable or therapy refractory PC

Additional file 4: Figure S3. of Rapid eradication of colon carcinoma by Clostridium perfringens Enterotoxin suicidal gene therapy

Influence of optCPE in vivo gene transfer on body weight. Body weight of Co7515* PDX bearing mice was measured during tumor growth inhibition. In all animals no systemic toxicities, such as body weight loss, were observed, which strongly indicates the safety of this gene therapeutic approach. (JPG 283 kb

Additional file 2: Figure S1. of Rapid eradication of colon carcinoma by Clostridium perfringens Enterotoxin suicidal gene therapy

Knockdown of claudin-3 and -4 leads to reduced CPE activity in human colon cancer cells. a Sequences of used short interfering RNA (siRNA) targeting claudin-3 and -4. b Western blot analysis for claudin-3 and claudin-4 gene expression in human colon cancer cell lines SW480 (left panel) and HCT116 (right panel) 72 h after siRNA treatment, showing an efficient down-regulation of both with two independent siRNA compared to control (siCo). c Specific toxin responsiveness of claudin-3 and -4 down-regulated colon cancer cells. 72 h after siRNA transfection tumor cells were treated with recCPE at indicated concentrations for another 72 h. The cytotoxicity was determined by MTT assay and compared to siCo treated cells. A significantly reduced responsiveness (*** P < 0.0001) was demonstrated in both colon cancer cell lines, SW480 (left panel) and HCT116 (right panel). All assays were performed in two independent experiments and are expressed as mean percent of untreated control. Bars: SD. Level of significance was calculated by 2way-ANOVA (Bonferroni posttest). b Cytotoxicity of optCPE gene transfer in siRNA treated colon cancer cells and proof of claudin specificity. The siCldn3 + siCldn4 treated SW480 and HCT116 cells were transfected with optCPE construct 72 h after siRNA treatment. MTT assay was performed 72 h after CPE treatment and a significantly reduced CPE mediated cytotoxicity was observed in down-regulated SW480 (left panel) and also in HCT116 (right panel) cells compared to siCo treated cells. All assays were performed in two independent experiments and expressed as survival in optical density [OD]. Bars: SD. Level of significance was calculated by nonparametric, unpaired students t-test, *** P < 0.0001. Both assays demonstrate high selectivity of CPE on claudin-3 and -4 as down-regulated cells remain unaffected. (JPG 600 kb