Suicide gene therapy for graft-versus-host disease

Gene and virotherapy for hematological malignancies

Recent years have seen a transformation in the treatment of hematological malignancies. Advances in gene therapy and molecular techniques and significant gains in computational abilities have supported the rapid development of safer and better tolerated therapies for many patients with hematologic cancers. In this review, we discuss novel applications of gene therapy, including immunomodulation and gene silencing, and report on the rise of oncolytic viruses for use in the treatment of malignancies arising in cells of the blood, lymph, and marrow. We discuss the relationship of the tropism of wildtype viruses and their oncolytic behavior as well as the tumoricidal and immunostimulatory properties of a number of attenuated and recombinant viruses currently in clinical development in countries around the world. While we have focused on promising virotherapy applications for future development, we also present a historical perspective and identify areas of potential clinical and regulatory practice change. We outline several of the virus systems being developed for applications in hematology, and summarize efficacy data in the context of ongoing or future human clinical testing. We also present the advantages and limitations of gene and virus therapy, including challenges and opportunities for improved treatment tolerability and outcomes for patients with hematologic malignancies.

Cancer suicide gene therapy with TK.007: superior killing efficiency and bystander effect

Suicide gene therapy is a promising concept in oncology. We have recently introduced a novel suicide gene, TK.007, which was shown to excel established herpes simplex virus thymidine kinase (HSVtk) variants when used for donor-lymphocyte modification in adoptive immunotherapy models. Here, the potential of TK.007 in killing cancer cells was studied. Initially, we transduced tumour cell lines derived from different neoplasias (glioblastoma, melanoma, lung cancer, colon cancer) with lentiviral LeGO vectors encoding TK.007 or the splice-corrected (sc)HSVtk together with an eGFP/Neo-marker. Based on direct in vitro comparison, we found that TK.007 facilitates more efficient tumour cell killing at significantly lower ganciclovir doses in all tumour cell lines tested. Also, using different readout systems, we found a significantly stronger bystander effect of TK.007 as compared to scHSVtk. Importantly, in vitro data were confirmed in vivo using a subcutaneous G62 glioblastoma model in NOD/SCID mice. In mice transplanted with scHSVtk-positive tumours, treatment with low (10 mg/kg) or standard (50 mg/kg) ganciclovir doses resulted only in short-term growth inhibition or transient tumour remission, respectively. In striking contrast, in the TK.007 group, all animals achieved continuous complete remission after both standard and low-dose ganciclovir. Finally, a substantial bystander effect for TK.007 was also confirmed with the G62 model in vivo, where significantly prolonged survival for mice bearing tumours containing only 10% or 50% TK.007-expressing cells was observed. In summary, our data indicate strongly improved anti-tumour activity of TK.007 as compared to conventional HSVtk. We therefore suppose that TK.007 is an excellent candidate for cancer suicide gene therapy.