The anti-glioma effect of suicide gene therapy using BMSC expressing HSV/TK combined with overexpression of Cx43 in glioma cells

Abstract

The disseminated neoplastic foci of malignant gliomas are essentially responsible for the limited efficacy of current available therapeutic modalities. Bone marrow-derived stem cells (BMSCs) have the ability to migrate into these tumors and even track infiltrating tumor cells, making them to be promising cellular vehicles for delivering therapeutic agents to glioma cells. The herpes simplex virus thymidine kinase (HSV-TK)/ganciclovir (GCV) suicide gene therapy with a potent bystander effect has been considered as one of the most promising therapeutic strategies for malignant gliomas. In this study, we evaluate the anti-glioma effect of suicide gene therapy using BMSCs expressing HSV-TK combined with overexpression of connexin 43 (Cx43), which can restore the gap junction of intercellular communication and may enhance the bystander effect of suicide gene therapy. To assess the potential of BMSCs to track glioma cells, a spheroid co-culture system in matrigel was used to show that some BMSCs migrated to C6 glioma cell microspheres. Transwell assay showed the tumor tropic property of BMSCs. In addition, BrdU-labeled BMSCs injected directly into the cerebral hemisphere opposite to the established C6 rat gliomas were capable of migrating into the xenograft gliomas. C6 cell growth was more intensively inhibited by HSV-TK/GCV treatment mediated by BMSCs, and could be further enhanced by combination with Cx43 transfection into glioma cells. The same result was observed in vivo by the growth of C6 gliomas and the survival analysis of rats bearing C6 glioma. In conclusion, Cx43 combined with HSV-TK/GCV gene therapy using BMSCs as vehicles was highly effective in a rat glioma model and therefore hold great potential as a novel approach for the gene therapy of human malignant gliomas.

Stem Cell-Mediated Delivery of Therapies in the Treatment of Glioma

“…HSV-1-tk/GCV treatment mediated by MSC inhibited C6 cell growth and this effect was enhanced after transfection of the tumoral cells with Cx43. The therapeutic gains were confirmed in vivo: BrdU-labeled MSC injected controlateral to the C6 glioma tumor mass in rats could migrate to the tumour xenograft and inhibit its growth [14]. Adult MSC engineered with HSV-1-tk can exert a bystander toxic effect on murine 9L glioma cells as well [28].…”

“…Upon administration of 5-fluorocytosine (5-FC), CD/IFN-beta-expressing NSC exerted a bystander effect on human glioma cells in vitro. The bystander effect occurs by two major mechanisms: one involves cell-to-cell transfer of toxic metabolites through intercellular gap junctions; the other involves uptake of toxic metabolites by target cells through apoptotic vesicles produced by bystanding cells [2,14]. In nude mice bearing orthotopic gliomas, infusion of the CD/IFN-beta-expressing NSC produced partial remission of the tumour upon administration of 5-FC and survival of animals was significantly increased (Fig.…”

“…Mice receiving GCV after HACtk-hMSC injection showed a partial reduction of the glioma mass [25]. Similar suicide gene therapy using MSC expressing HSV-1-tk combined with overexpression of connexin 43 (Cx43), which can restore the gap junction of intercellular communication and may enhance the bystander effect of glioma therapy has been described [14]. Co-culture experiments and transwell assays were used to assess the ability of MSC to migrate to C6 glioma tumour cells in vitro.…”

Adeno-associated virus-mediated cancer gene therapy: Current status

“…Connexin is an important GJIC molecule generally expressed in the cytosol. Some study groups have demonstrated that overexpression of connexin43 restored GJIC in tumor cells and thereby resulted in the increased antitumor effect of the HSV- tk /GCV system [62, 63]. Recently, a novel family of GJIC named Pannexin (Panx) [64]may play the same roles as the connexins[65].…”

Regulation of gap junction channels by infectious agents and inflammation in the CNS

“…Therefore, combining HSV-tk therapy with induced expression of Cx43 should be a more effective eliminator of undetectable malignant gliomas after resection. Using a rat model in which C6 glioma cells transfected to express Cx43 were injected into the caudate nucleus, followed by injection of BMSC-tk cells into the tumor site and GCV intraperitoneal injection, animals were able to live six times longer and reduced tumor volume by a quarter of the original size was observed (Huang et al, 2010). Therefore, bystander killing of tumor cells induced by the expression of Cx43 shows promise in combination with current therapies.…”