Lars Boenicke

Bcl-XL protects pancreatic adenocarcinoma cells against CD95- and TRAIL-receptor-mediated apoptosis

In this study we sought to clarify the role of the pro-apoptotic potential of mitochondria in the death pathway emanating from the TRAIL (APO-2L) and CD95 receptors in pancreatic carcinoma cells. We focused on the role of the Bcl-2 family member Bcl-XL, using three pancreatic carcinoma cell lines as a model system, two of which have high (Panc-1, PancTuI) and one has low (Colo357) Bcl-XL expression. In these cell lines, the expression of Bcl-XL correlated with sensitivity to apoptosis induced by TRAIL or anti-CD95. Flow cytometric analysis revealed cell surface expression of TRAIL-R1 and TRAIL-R2 on PancTuI and Colo357, and TRAIL-R2 on Panc-1 cells. In Colo357 cells retrovirally transduced with Bcl-XL, caspase-8 activation in response to treatment with TRAIL or anti-CD95 antibody was not different from parental cells and EGFP-transfected controls, however, apoptosis was completely suppressed as measured by the mitochondrial transmembrane potential Δψm, caspase-3 activity (PARP cleavage) and DNA-fragmentation. Inhibition of Bcl-XL function by overexpression of Bax or administration of antisense oligonucleotides against Bcl-XL mRNA resulted in sensitization of Panc-1 cells to TRAIL and PancTuI cells to anti-CD95 antibody-induced cell death. The results show that Bcl-XL can protect pancreatic cancer cells from CD95- and TRAIL-mediated apoptosis. Thus, in these epithelial tumour cells the mitochondrially mediated ‘type II’ pathway of apoptosis induction is not only operative regarding the CD95 system but also regarding the TRAIL system.

Transduction of human pancreatic tumor cells with vesicular stomatitis virus G-pseudotyped retroviral vectors containing a herpes simplex virus thymidine kinase mutant gene enhances bystander effects and sensitivity to ganciclovir

We examined the suitability of Moloney murine leukemia virus (MLV) 4070A-, cat endogenous virus (CEV) RD114-, or vesicular stomatitis virus G (VSV-G)-pseudotyped retroviruses containing the humanized enhanced green fluorescent protein (hEGFP) or one of two herpes simplex virus thymidine kinase (HSV-TK) genes to transduce and provide gene expression in human pancreatic tumor cells. Fluorescence-activated cell sorter analysis demonstrated that VSV-G-pseudotyped hEGFP vector infected a greater percentage of cells and generated more robust gene expression than MLV 4070A- or CEV RD114-pseudotyped vectors. Dot blot and Southern blot analysis of genomic DNA revealed up to 10-fold more gene copies in G418-selected VSV-G hEGFP vector-transduced cells compared with genomic DNA from cells transduced with MLV 4070A or CEV RD114 pseudotypes. Cells transduced with VSV-G pseudotypes of HSV-TKWT or the HSV-TK30 vectors were 5- to 10-fold more sensitive to ganciclovir (GCV) than other pseudotype-transduced cells. A 40- to 61-fold difference in sensitivity to GCV was observed between cells transduced with VSV-G HSV-TK30 vector and cells transduced with MLV 4070A HSV-TKWT vector in vitro. A 13-fold reduction in tumor volume was observed in severe combined immunodeficient mice inoculated with PancTuITK30 cells compared with mice inoculated with PancTuITKWT cells during GCV treatment. We conclude that the choice of glycoprotein envelope and the potency of a particular suicide gene were therapeutically additive and increased the number of HSV-TK-positive cells and sensitivity toward GCV in human pancreatic tumors cells for prodrug gene therapy.

Wortmannin inhibits growth of human non-small-cell lung cancer in vitro and in vivo

Abstract Background and aims. Recently we demonstrated that phosphatidylinositol 3-kinase (PI3K) is overexpressed in human lung cancer. This study evaluated whether the PI3K inhibiting agent wortmannin affects proliferation of human lung cancer cells in vitro and in vivo. Methods. Effects of exposure of human non-small-cell lung cancer (NSCLC) cells (KNS-62, Colo-699) to wortmannin were investigated in vitro by proliferation, cytotoxicity, and DNA fragmentation assays. In vivo we examined the effects of blocking PI3K by wortmannin prior to xenotransplantation of human NSCLC cells into SCID-bg mice and the effect of systemic wortmannin administration following intrapulmonary xenotransplantation of human NSCLC. Results. Exposure of KNS-62 and Colo-699 lung cancer cells to wortmannin inhibited proliferation in correlation to concentration in vitro. In vivo the blocking of PI3K by wortmannin prior to xenotransplantation caused a significant delay in the growth of subcutaneously induced tumors. Systemic wortmannin administration increased mean survival after intrapulmonary xenotransplantation of human NSCLC significantly by 38% and 47%. Conclusions. These data suggest inhibition of PI3K activity as a potential target for treatment of human NSCLC. Systemic toxicity of wortmannin requires development of improved PI3K inhibitors with favorable pharmacological properties.

Ganciclovir prodrug therapy is effective in a murine xenotransplant model of human lung cancer

BACKGROUND Therapy failures have been reported for retroviral gene transfer of herpes simplex virus thymidine kinase (HSV-TK) gene followed by systemic ganciclovir application in human lung cancer. Use of the HSV-TK mutant TK30 in combination with a VSV-G pseudotyped retroviral vector was found to enhance the efficacy of prodrug therapy. The present study evaluated this therapeutic strategy in human non-small cell lung cancer cell lines in a preclinical murine xenotransplant model. METHODS Intrathoracally induced by HSV-TK30 transduced non-small cell lung cancer cell lines Colo 699 (adenocarcinoma) and KNS 62 (squamous cell carcinoma) were monitored for local tumor growth, survival, and metastases. So-called bystander effects were investigated in tumors consisting of as little as 25% TK30 transfected cells and by analysis of gap junctional protein connexin-43 expression. RESULTS Survival was significantly prolonged, and tumor growth and pleural metastases were reduced in HSV-TK30-positive tumors of both cell lines. A significant therapeutic effect in bystander experiments was observed in squamous cell carcinoma. This was correlated with higher expression of connexin-43. CONCLUSIONS Delivery of HSV-TK30 in a VSV-G pseudotyped retroviral vector and subsequent ganciclovir application provided therapeutic efficacy. Despite of low transduction rates achievable in gene transfer in situ, prodrug therapy appears to be feasible in tumor cells with efficient bystander effects.

Efficient dose-dependent and time-dependent protein transduction of pancreatic carcinoma cells in vitro and in vivo using purified VP22-EGFP fusion protein.

We constructed a prokaryotic vector expressing a truncated VP22-EGFP gene and purified this fusion protein from Escherichia coli cultures using nickel resin. Application of purified VP22-EGFP protein to human pancreatic carcinoma cells showed a highly efficient time-dependent and dose-dependent uptake and resulted in green fluorescence predominantly located in the nuclei of treated cells. Purified VP22-EGFP efficiently translocated into deeper layers of pancreatic tumor cell spheroids. Homogeneous uptake into the whole tumor was observed after peritumoral injection in human pancreatic tumors in SCID mice. We conclude that the direct application of purified VP22 fusion proteins offers a new, peptide-mediated and potentially systemic therapy for pancreatic cancer. This opens the possibility of achieving specific antitumor effects induced by fused apoptosis-enhancing proteins.

Enhanced Retroviral Transduction Efficiency of Pancreatic Tumor Cell Lines Using Different Envelope Glycoproteins

Since the overall prognosis for pancreatic cancer remains poor, there is an urgent need to develop additional therapeutic strategies. The genetic alteration of human pancreatic tumor cells by recombinant retroviral vectors capable of delivering therapeutic genes is essential for experimental and clinical investigation. During retroviral infection, virus binding and entry into the target cell is mediated by the interaction of the viral envelope glycoprotein with specific receptors located on the cell surface.1 Most gene therapy protocols using recombinant retroviruses employ the amphotropic murine leukemia virus (MLV) envelope glycoprotein, which binds to a phosphate transporter on the host membrane.2 Since it has been shown by others that the expression of these transporters can be inadequate for succesful transduction, we investigated the ability of virions possessing different envelope glycoproteins to infect pancreatic tumors. We constructed a retroviral vector containing the humanized enhanced green fluorescent protein (hEGFP) gene, pseudotyped it with either the amphotropic MLV-4070A envelope, the cat endogenous virus (CEV) envelope RD114 or the rhabdovirus vesicular stomatitis virus glycoprotein (VSV-G), and used the generated virions to transduce three pancreatic tumor cell lines. Transduction efficiency was measured by fluorescence-activated cell sorter (FACS) analysis and by differences in delivered gene copy number as determined by dot blot analysis. We tested the possible influence of different media components on the transduction efficiency and gene expression of transduced cells.