Potent antitumor activity of Oct4 and hypoxia dual-regulated oncolytic adenovirus against bladder cancer.

Most solid tumors undergo hypoxia, leading to rapid cell division, metastasis and expansion of a cell population with hallmarks of cancer stem cells (CSCs). Tumor-selective replication of oncolytic adenoviruses may be hindered by oxygen deprivation in tumors. It is desirable to develop a potent oncolytic adenovirus, retaining its antitumor activity even in a hypoxic environment. We have previously generated an Oct4-dependent oncolytic adenovirus, namely Ad9OC, driven by nine copies of the Oct4 response element (ORE) for specifically killing Oct4-overexpressing bladder tumors. Here, we developed a novel Oct4 and hypoxia dual-regulated oncolytic adenovirus, designated AdLCY, driven by both hypoxia response element (HRE) and ORE. We showed that hypoxia-inducible factor (HIF)-2α and Oct4 were frequently overexpressed in hypoxic bladder cancer cells, and HIF-2α was involved in HRE-dependent and Oct4 transactivation. AdLCY exhibited higher cytolytic activities than Ad9OC against hypoxic bladder cancer cells, while sparing normal cells. AdLCY exerted potent antitumor effects in mice bearing human bladder tumor xenografts and syngeneic bladder tumors. It could target hypoxic CD44- and CD133-positive bladder tumor cells. Therefore, AdLCY may have therapeutic potential for targeting hypoxic bladder tumors and CSCs. As Oct4 is expressed in various cancers, AdLCY may be further explored as a broad-spectrum anticancer agent.

Amelioration of experimental arthritis by intra-articular injection of an epidermal growth factor receptor tyrosine kinase inhibitor.

OBJECTIVES: Selectively targeting signalling pathways represents a promising pharmacological approach in rheumatoid arthritis (RA). Abundant levels of epidermal growth factor receptor (EGFR) are expressed in the synovial lining layers, and the anti-arthritis effect of erlotinib and lapatinib, small-molecule EGFR tyrosine kinase inhibitors (TKIs), has been demonstrated through the systemic administration on experimental arthritis models. Nevertheless, their therapeutic responses by the intra-articular (i.a.) route remain to be explored in rheumatoid joint. METHODS: The administration of an EGFR TKI (a gefitinib analogue) was explored in two in vivo models of collagen-induced arthritis (CIA) and in vitro experiments by using synovial fibroblasts (SF) from RA patients and CIA rats. RESULTS: There was a significant reduction of arthritis scores in CIA mice receiving the daily intraperitoneal injection. After the onset of arthritis in CIA rats, ankle joints receiving a single i.a. injection had significant lower articular indexes with reduced synovial inflammation, pannus formation and erosion on cartilage and bone as well as total histological scores by histopathological analyses. In CIASF or RASF, upon in vitro human EGF stimulation, there was a dose-dependent increase in cell proliferation and Akt activation with suppressed responses under the EGFR TKI treatment. CONCLUSIONS: These findings demonstrate the effect of i.a. injection of an EGFR TKI on amelioration of rheumatoid joint through the suppression of synovial inflammation, pannus formation and erosion on cartilage and bone in experimental arthritis, implicating targeting the i.a. EGFR signalling transduction as a pharmacological strategy.

Suppression of collagen-induced arthritis by intra-articular lentiviral vector-mediated delivery of Toll-like receptor 7 short hairpin RNA gene.

Knockdown of Toll-like receptors (TLRs) is a novel therapeutic strategy in treating patients with rheumatoid arthritis (RA). We examined the effects of lentiviral vector-mediated delivery of TLR7 short hairpin RNA gene (Lt.shTLR7) on collagen-induced arthritis (CIA). After being immunized on days 0 and 7, Sprague-Dawley rats received intra-articular (i.a.) injection of Lt.shTLR7 or scramble control vector on days 7 and 10. The therapeutic effects were evaluated by measuring ankle circumferences, articular index, and radiographic and histological scores on killing on day 16. Microvessel densities, vascular endothelial growth factor (VEGF) levels, pro-inflammatory cytokine concentrations and T-cell numbers within the synovial tissues were measured. Moreover, VEGF and pro-inflammatory cytokine concentrations in culture supernatants from TLR7-transfected synovial fibroblasts (SFs) stimulated with imiquimod or endogenous ligands were examined. There were significant reduction in ankle circumferences, articular indexes, and radiographic and histological scores. Microvessel densities, VEGF concentrations, interleukin (IL)-1ß and IL-6 levels and T-cell densities within synovial tissues were significantly lower. Induction of VEGF, IL-1ß and IL-6 production from stimulated SFs was significantly suppressed. Taken together, these data demonstrate the effects of i.a. lentiviral vector-mediated delivery of shTLR7 RNA gene on inhibition of CIA, and implicate the manipulation of TLR7 as a potential therapeutic strategy in RA patients.

Intra-articular lentivirus-mediated delivery of galectin-3 shRNA and galectin-1 gene ameliorates collagen-induced arthritis.

Different members of the galectin family may have inhibitory or stimulatory roles in controlling immune responses and regulating inflammatory reactions in autoimmune diseases such as rheumatoid arthritis (RA). A hypothetical model of a cross talk between galectin-1 and galectin-3 has been established in the circumstance of rheumatoid joints. As galectin-3 is a positive regulator and galectin-1 is a negative regulator of inflammation and autoimmune responses, in this study we evaluated the effects of local knockdown of galectin-3 or overexpression of galectin-1 on ameliorating collagen-induced arthritis (CIA) in rats. Lentiviral vectors encoding galectin-3 small hairpin RNA (shRNA) and galectin-1, as well as two control vectors expressing luciferase shRNA and green fluorescent protein, were individually injected intra-articularly into the ankle joints of rats with CIA, and their treatment responses were monitored by measuring the clinical, radiological and histological changes. Our results show that both knockdown of galectin-3 and overexpression of galectin-1 induced higher percentages of antigen-induced T-cell death in the lymph node cells from arthritic rats. Furthermore, these treatments significantly reduced articular index scores, radiographic scores and histological scores, accompanied with decreased T-cell infiltrates and reduced microvessel density in the ankle joints. Our findings implicate galectin-3 and galectin-1 as potential therapeutic targets for the treatment of RA.

Coexpression of Flt3 ligand and GM-CSF genes modulates immune responses induced by HER2/neu DNA vaccine.

DNA vaccine and dendritic cells (DCs)-based vaccine have emerged as promising strategies for cancer immunotherapy. Fms-like tyrosine kinase 3-ligand (Flt3L) and granulocyte-macrophage-colony-stimulating factor (GM-CSF) have been exploited for the expansion of DC. It was reported previously that combination of plasmid encoding GM-CSF with HER2/neu DNA vaccine induced predominantly CD4(+) T-cell-mediated antitumor immune response. In this study, we investigated the modulation of immune responses by murine Flt3L and GM-CSF, which acted as genetic adjuvants in the forms of bicistronic (pFLAG) and monocistronic (pFL and pGM) plasmids for HER2/neu DNA vaccine (pN-neu). Coexpression of Flt3L and GM-CSF significantly enhanced maturation and antigen-presentation abilities of splenic DC. Increased numbers of infiltrating DC at the immunization site, higher interferon-gamma production, and enhanced cytolytic activities by splenocytes were prominent in mice vaccinated with pN-neu in conjunction with pFLAG. Importantly, a potent CD8(+) T-cell-mediated antitumor immunity against bladder tumors naturally overexpressing HER2/neu was induced in the vaccinated mice. Collectively, our results indicate that murine Flt3L and GM-CSF genes coexpressed by a bicistronic plasmid modulate the class of immune responses and may be superior to those codelivered by two separate monocistronic plasmids as the genetic adjuvants for HER2/neu DNA vaccine.

Postoperative immuno-gene therapy of murine bladder tumor by in vivo administration of retroviruses expressing mouse interferon-gamma.

The murine MBT-2 bladder tumor model in syngeneic C3H/HeN mice was used to investigate the feasibility of gene therapy based on the delivery of interferon-gamma (IFN-gamma) in vivo by retroviral vectors. We constructed a recombinant retroviral vector pRUFneo/IFN-gamma, which was transfected into a retroviral packaging cell line psiCRE, to produce psiCRE/pRUFneo/IFN-gamma cells. The expressions of the neo and IFN-gamma genes were verified by reverse transcription-polymerase chain reaction and IFN-gamma was detected in the culture supernatant from psiCRE/pRUFneo/IFN-gamma cells. After receiving MBT-2 cells admixed with retroviral pRUFneoIFN-gamma supernatant, C3H/HeN mice exhibited lower tumor incidence, lower tumor mass, and higher survival rate, as well as higher antitumor responses compared to those injected with MBT-2 cells admixed with control retroviral supernatant. Moreover, the retroviral pRUFneoIFN-gamma supernatant was able to suppress the growth of rechallenged tumors in postoperated mice. Although the IFN-gamma protein secreted from psiCRE/pRUFneo/IFN-gamma cells partly contributes to the antitumor effect of retroviral pRUFneoIFN-gamma supernatant, the retroviruses carrying the IFN-gamma gene transduced MBT-2 cells in vivo, which may result in enhancing local IFN-gamma production from tumor cells. Because bladder is suitable for the intravesical instillation of therapeutic agents, in vivo administration of retroviral vectors encoding IFN-gamma may be explored for the treatment of bladder cancer.

Prothymosin alpha promotes cell proliferation in NIH3T3 cells.

Thymic hormones have immunomodulatory effects on T cells and hence have been used clinically to restore the immunity of immunodeficient patients as well as to enhance the cellular immunity of cancer patients. Prothymosin alpha, which is a member of the thymic hormone family, has recently been suggested to act as a nuclear protein participating in the stimulation of cell proliferation. To characterize the biological activities ofprothymosin alpha in vitro, we established NIH3T3 cell transformants that constitutively express higher prothymosin alpha protein and its mRNA compared with the wild-type counterpart. Cells that overexpressed prothymosin alpha increased the proliferative activity assayed by the [3H]-thymidine incorporation or by the cell cycle analysis with the fluorescent-activated cell sorter. The results provide direct evidence that prothymosin alpha plays a role in cell proliferation by shortening the duration of the G1 phase.

Modulation of the immunostimulating effect of autologous tumor vaccine by anti-TGF-beta antibody and interferon-alpha on murine MBT-2 bladder cancer.

UNLABELLED: Our aims were to: a) elucidate whether MBT-2 cells, lethally irradiated or nonirradiated, express TGF-beta 1 mRNA and secrete TGF-beta 1 protein, and b) to investigate whether the adverse effects from IRMBT-2-secreting TGF-beta 1 in the tumor vaccine can be abrogated by exogenous addition of monoclonal anti-TGF-beta 1 antibody and/or IFN-alpha. MATERIALS AND METHODS: using the Northern hybridization analysis and the two-antibody sandwich ELISA, we demonstrate that both irradiated IRMBT-2 and nonirradiated MBT-2 cells secrete TGF-beta 1. The effect of anti-TGF-beta and/or IFN-alpha were studied by an in vitro splenocyte proliferation assay and in vivo tumor rechallenge study on day 17-TBM. RESULTS: Both IRMBT-2 and splenocytes from day 17-TBM secrete TGF-beta 1 which can express suppression of the proliferation of the splenocytes from day 17-TBM. This suppression can be partially reversed by the simultaneous addition of both anti-TGF-beta and IFN-alpha, either alone being insufficient. The result of the in vivo tumor rechallenge study on day 17-TBM reveals that a lower tumor outgrowth incidence can be obtained in groups of mice treated with postoperative vaccination with anti-TGF-beta modified tumor vaccine with or without an additional administration of IFN-alpha. CONCLUSION: Apart from TGF-beta, MBT-2 cells, both irradiated and nonirradiated, may also secrete other suppressive factors that adversely downregulate the immune response of TBM which can not then be adequately reversed by IFN-alpha.

Antisense oligonucleotide specific for transforming growth factor-beta 1 inhibit both in vitro and in vivo growth of MBT-2 murine bladder cancer.

INTRODUCTION AND OBJECTIVES: TGF-beta is a potent immunosuppressive cytokine produced by many tumor cells. Secretion of TGF-beta by malignant cells may be a mechanism by which tumor cells escape destruction by tumor-specific T lymphocytes. In this study, we used a TGF-beta producing C3H/He-MBT-2 murine bladder tumor model to investigate the feasibility of antisense oligonucleotide (ODN) gene therapy strategy to block the production of TGF-beta from tumor cells and evaluate its influence on both in vitro tumor growth and in vivo tumor formation. MATERIALS AND METHODS: Using a plasmid, pRUFCD, we constructed a recombinant plasmid pRUFCD/TGF-beta 1(-) containing antisense TGF-beta ODN and then transfected in into MBT-2 cells by electroporation. Three transfectant clones were successfully obtained by their resistance to 5-fluorouracil and cytosine. RESULTS: The secretion of TGF-beta from the three obtained TGF-beta antisense-blocked MBT-2 cell clones, as assessed by ELISA, were all decreased. Moreover, they all exhibited smaller colony size in the in vitro anchorage-independent soft agar colony forming assay. Tumor growths in mice injected with these three clones were all inhibited compared with those injected with parental tumor cells. CONCLUSION: This study demonstrates that after reducing the secretion of TGF-beta 1 on tumor cells by TGF-beta 1 antisense, ODN can inhibit their in vitro growth and in vivo tumor formation suggesting that this approach can be a potentially useful strategy to abolish the adverse immunosuppression effect of TGF-beta 1 producing autologous tumor vaccine and therefore to enhance host antitumor immune response.

Immunization with TGF-beta antisense oligonucleotide-modified autologous tumor vaccine enhances the antitumor immunity of MBT-2 tumor-bearing mice through upregulation of MHC class I and Fas expressions.

The major purpose of this study was to define if the immunosuppressive effect of a transforming growth factor-beta (TGF-beta)-producing autologous tumor vaccine can be abrogated and rendered immunogenic by suppressing its TGF-beta secretion with antisense strategy. In this study, using a TGF-beta antisense gene modified MBT-2 tumor cell line [MBT-2/TGF-beta(-)#3] which we established by ourselves, we first demonstrated that the amounts of TGF-beta produced by irradiated (IR) and non-irradiated MBT-2/TGF-beta(-) #3 were both significantly decreased when detected after in vitro culture for 48 hours. The result of flow cytometry analysis reveals that decreased production of TGF-beta led to the increased expressions of MHC class I molecule and Fas on the surface of MBT-2 tumor cells. This finding may in part explain why the splenocytes obtained from day 17 tumor bearing mice (D17TBM) immunized with IRMBT-2/TGF-beta(-)#3 on day 26 expressed a higher in vitro cytotoxic activity against MBT-2 tumor cells and hence ensured a better survival of D17TBM when they were rechallenged with a two-fold higher amount of wild-type MBT-2 tumor cells, 48 hours after surgical removal of the primary tumor. Our result implies that decreasing the amount of TGF-beta secreted from the autologous tumor vaccine by antisense strategy may significantly improve its immunogenicity through up-regulation of both MHC class I and Fas expressions. Therefore, this could provide an alternative approach for future active immunotherapy.

Modulating the antitumor immunity of MBT-2 murine bladder tumor bearing mice by postoperative administration of interferon-alpha.

This study was conducted mainly to investigate the effect of interferon-alpha (IFN-alpha) on the antitumor immunity of a tumor bearing host (TBH) when postoperatively administrated with or without lethally irradiated autologous tumor cells. Using the C3H/He-MBT-2 murine bladder tumor model, a status of postoperative residual tumor was mimicked by rechallenging tumor cells 24 hours after resecting the day-17 tumor. Using immunohistochemical analysis we demonstrated that after treating with lethally irradiated MBT-2 tumor cells (IRMBT-2) + IL-2 cells of CD4+, CD8+, CD44+ and CD11b+ phenotypes prominently infiltrate the subcutaneous local injection sites. In contrast, only scanty immune responding cells could be seen locally if treated with IRMBT-2 + IFN-alpha 2b, albeit in the presence of interleukin-2 (IL-2). However, the spleens of D17TBM treated with IRMBT-2 + IFN-alpha 2b contained the highest percentage of CD44+ memory T cells and cells of the CD11b+ phenotype; moreover, their natural killer (NK), lymphokine activated killer (LAK) and cytotoxic T lymphocytes (CTL) activities were significantly augmented. The results of in vivo tumor rechallenge revealed that administration of IFN-alpha, either alone or combined with IRMBT-2, could both effectively suppress the outgrowth of perioperative rechallenged tumor cells as well as prolong the survival of TBH. We conclude that despite the presence of autologous tumor vaccine, postoperative administration of IFN-alpha can further enhance the antitumor immunity of TBH and therefore can be an effective adjuvant therapy to improve the therapeutic results of surgery on a tumor bearing host.

Hypoxia imaging predicts success of hypoxia-induced cytosine deaminase/5-fluorocytosine gene therapy in a murine lung tumor model.

Tc-99m-HL91 is a hypoxia imaging biomarker. The aim of this study was to investigate the value of Tc-99m-HL91 imaging for hypoxia-induced cytosine deaminase (CD)/5-fluorocytosine (5-FC) gene therapy in a murine lung tumor model. C57BL/6 mice were implanted with Lewis lung carcinoma cells transduced with the hypoxia-inducible promoter-driven CD gene (LL2/CD) or luciferase gene (LL2/Luc) serving as the control. When tumor volumes reached 100 mm(3), pretreatment images were acquired after injection of Tc-99m-HL91. The mice were divided into low and high hypoxic groups based on the tumor-to-non-tumor ratio of Tc-99m-HL91. They were injected daily with 5-FC (500 mg kg(-1)) or the vehicle for 1 week. When tumor volumes reached 1000 mm(3), autoradiography and histological examinations were performed. Treatment with 5-FC delayed tumor growth and enhanced the survival of mice bearing high hypoxic LL2/CD tumors. The therapeutic effect of hypoxia-induced CD/5-FC gene therapy was more pronounced in high hypoxic tumors than in low hypoxic tumors. This study provides the first evidence that Tc-99m-HL91 can serve as an imaging biomarker for predicting the treatment responses of hypoxia-regulated CD/5-FC gene therapy in animal tumor models. Our results suggest that hypoxia imaging using Tc-99m-HL91 has the predictive value for the success of hypoxia-directed treatment regimens.

Enhancement of antitumor activity of gammaretrovirus carrying IL-12 gene through genetic modification of envelope targeting HER2 receptor: a promising strategy for bladder cancer therapy.

The objective of this study was to develop an HER2-targeted, envelope-modified Moloney murine leukemia virus (MoMLV)-based gammaretroviral vector carrying interleukin (IL)-12 gene for bladder cancer therapy. It displayed a chimeric envelope protein containing a single-chain variable fragment (scFv) antibody to the HER2 receptor and carried the mouse IL-12 gene. The fragment of anti-erbB2scFv was constructed into the proline-rich region of the viral envelope of the packaging vector lacking a transmembrane subunit of the carboxyl terminal region of surface subunit. As compared with envelope-unmodified gammaretroviruses, envelope-modified ones had extended viral tropism to human HER2-expressing bladder cancer cell lines, induced apoptosis, and affected cell cycle progression despite lower viral titers. Moreover, animal studies showed that envelope-modified gammaretroviruses carrying IL-12 gene exerted higher antitumor activity in terms of retarding tumor growth and prolonging the survival of tumor-bearing mice than unmodified ones, which were associated with enhanced tumor cell apoptosis as well as increased intratumoral levels of IL-12, interferon-gamma, IL-1beta, and tumor necrosis factor-alpha proteins. Therefore, the antitumor activity of gammaretroviruses carrying the IL-12 gene was enhanced through genetic modification of the envelope targeting HER2 receptor, which may be a promising strategy for bladder cancer therapy.

Conditionally replicating E1B-deleted adenovirus driven by the squamous cell carcinoma antigen 2 promoter for uterine cervical cancer therapy.

Cervical cancer is the second most common type of malignant tumor among women worldwide. When the disease is confined locally, it can be controlled with surgical resection and radiotherapy. However, patients with recurrent or metastatic disease often have a poor prognosis. Measurement of serum levels of squamous cell carcinoma (SCC) antigens has been widely used as serological markers for SCC of uterine cervix. Recently, it has been demonstrated that cervical cancer patients with elevated squamous cell carcinoma antigen-2 (SCCA2) expression in tumor cells carry a poor prognosis. Here, by using a luciferase reporter assay, we show that SCCA2 promoter was active in SCCA2-producing human cervical cancer cell lines, including Cx, Cxwj, SiHa and HeLa cells, but relatively quiescent in normal cervical epithelial cells. We then developed a conditionally replicating adenovirus, designated Ad-KFH, under the transcriptional control of the SCCA2 promoter. This E1B-55 kDa-deleted oncolytic adenovirus replicated specifically in and lysed SCCA2-producing cervical cancer cells. Furthermore, in a peritoneal metastatic tumor model, Ad-KFH retarded Cxwj tumor growth in NOD/severe combined immunodeficient mice and prolonged survival of tumor-bearing mice, especially when combined with cisplatin. These results suggest that Ad-KFH may provide a new strategy of gene therapy for advanced or recurrent uterine cervical cancer.

Increased expression level of squamous cell carcinoma antigen 2 and 1 ratio is associated with poor prognosis in early-stage uterine cervical cancer.

Squamous cell carcinoma antigen (SCCA) is a tumor marker for patients with squamous cell carcinoma of uterine cervix, lung, and esophagus. It was encoded by two highly homologous genes, SCCA1 and SCCA2. However, the relevance of SCCA genes to squamous cell carcinogenesis and patient outcome remains far from clear. In this study, by using laser microdissection and real-time quantitative polymerase chain reaction procedures, the messenger RNA (mRNA) expression of the SCCA1 and SCCA2 genes in normal, dysplastic, and malignant squamous epithelia from uterine cervical tissues were analyzed and correlated with outcome of cancer patients. We found that the SCCA2/A1 mRNA ratios were progressively increased from normal, dysplastic, to cancer cells, and the mean ratio was significantly higher in cancer tissues than that in normal epithelium (P= 0.02). The SCCA2/A1 mRNA ratios were not significantly associated with types of human papillomavirus infection (P > 0.05). High SCCA2/SCCA1 mRNA ratios (ratio >1) were an independent predictor of disease recurrence (relative risk: 3.58; P= 0.003). Of the 38 patients with cervical cancer, 12 patients with high SCCA2/SCCA1 mRNA ratios had a significant lower 2-year disease-free survival of only 50%, while it was 92% in those with low SCCA2/SCCA1 mRNA ratios (P < 0.001). In conclusion, our study indicated that the ratios of SCCA2 to SCCA1 RNA were increased during the process of cervical carcinogenesis, and patients with elevated SCCA2/A1 ratio carried a higher risk for recurrence in early-stage uterine cervical cancer.

Mutated epitopes of hepatitis B surface antigen fused to the core antigen of the virus induce antibodies that react with the native surface antigen.

Fusion of peptide epitopes to the core antigen (HBcAg) of hepatitis B virus (HBV) enhances their immunogenicity, both quantitatively and qualitatively. In a number of vaccine-induced mutants of HBV, glycine145 of the surface antigen S polypeptide (HBsAg) has been replaced by arginine, resulting in loss of cross-reactivity with antibodies to normal (wild-type) HBsAg. HBcAg fusion proteins carrying the immunodominant epitope of HBsAg, in which glycine145 was replaced by arginine, glutamic acid, or lysine, were produced in Escherichia coli and formed particles that displayed HBc antigenicity and immunogenicity similar to that of HBcAg itself. The fusion proteins also elicited T-cell proliferative responsiveness to HBcAg and HBsAg. Fusions carrying either wild-type or mutated epitopes of HBsAG showed HBs antigenicity in immunoblot analysis and antigen-capture immunoradiometric assay, but both mutant and wild-type derivatives induced antibodies that cross-reacted with wild-type HBsAG. The results emphasise the potential for HBcAg fusion proteins in vaccines by broadening the antibody response in a way that could confer protection against both wild-type and variant form of HBV.

The inhibitory effect of Staphylococcus epidermidis slime on the phagocytosis of murine peritoneal macrophages is interferon-independent.

The extracellular slime produced by Staphylococcus epidermidis has been shown to interfere with several human neutrophil functions in vitro, such as chemotaxis, degranulation and phagocytosis. Slime production has been suggested as a useful marker for clinically significant infections with coagulase-negative Staphylococcus. Since the main role of macrophages in defense mechanisms is phagocytosis, the effect of slime on the phagocytic activity of macrophages was investigated. The phagocytic activity of murine peritoneal macrophages treated with slime in vitro decreased in a dose-dependent fashion. A similar decrease was also observed in macrophages isolated from mice that had previously received intraperitoneal injection of slime. To investigate whether interferon also plays a role in this process, mice were treated with interferon or an interferon inducer, polyinosinic-polycytidylic acid (poly I:C), together with slime before macrophage isolation. The slime-suppressed phagocytic activity of macrophages was partially relieved by both agents, and the recovery effect of poly I:C in slime-suppressed phagocytosis of macrophages in vivo might be attributed to the increased interferon level in peritoneal fluid and sera. However, when slime was given to poly I:C-pretreated mice, the phagocytic activity remained suppressed. Thus, it appears that slime is able to suppress the phagocytic activity of macrophages regardless of the state of macrophage activation by poly I:C. The results suggest that the inhibition of phagocytosis by S. epidermidis slime may be independent from the activation of interferon.

The core antigen of hepatitis B virus as a carrier for immunogenic peptides.

The core antigen of hepatitis B virus (HBcAg) made in Escherichia coli yields particles that closely resemble the viral nucleocapsid. Extensive modifications can be made to the primary structure of HBcAg without impairing particle assembly. This enables other peptide sequences, including very long sequences, to be added, substituted, or inserted into the nucleocapsid subunit while retaining the ability to form highly immunogenic particles. These also retain the T cell epitopes of HBcAg and constitute powerful delivery systems for a diverse range of immunogenic epitopes and have significant potential for development of multicomponent vaccines.

Retrovirus-mediated transfer of prothymosin gene inhibits tumor growth and prolongs survival in murine bladder cancer.

To explore the potential use of prothymosin alpha(ProT), a putative thymic hormone, in gene therapy for bladder cancer, we generated a replication-defective recombinant retroviral vector encoding ProT and tested its antitumor effect on the MBT-2 murine bladder cancer. C3H/HeN mice injected with MBT-2 cells in conjunction with retroviruses encoding ProT exhibited smaller tumor mass, lower tumor incidence and higher survival rate, as well as higher antitumor cytotoxic activities compared with those injected with control viruses. However, such effects were not observed in severe combined immunodeficiency mice, suggesting that ProT exerts antitumor effects through its immunomodulatory activities. Cell growth in monolayer culture and colony formation in soft agar were enhanced in ProT gene-modified MBT-2 clones, and such growth-promoting activities of ProT could be reversed if its nuclear localization signal (NLS) was deleted. To circumvent the proliferation-promoting effect of ProT on tumor cells, a retroviral vector encoding ProT lacking NLS was constructed. Our results showed that retroviruses encoding NLS-deleted ProT was more efficacious than those encoding wild-type ProT in prolonging survival of tumor-bearing mice. This is the first report indicating that ProT, in particular NLS-deleted ProT, delivered by retroviral vectors may be further explored for the treatment of bladder cancer.

Provision of positive and negative selections in retroviral vectors containing the cytosine deaminase gene.

The E. coli cytosine deaminase (CD) provides a negative selection system for suicide gene therapy as CD transfectants are eliminated following 5-fluorocytosine (5FC) treatment. Here we report a positive selection system for the CD gene using 5-fluorouracil (5FU) and cytosine in selection medium to screen for CD-positive transfectants. It is based on the relief of 5FU toxicity by uracil which is converted from cytosine via CD catalysis, as uracil competes with the toxic 5FU in subsequent pyrimidine metabolism. Hence, a retroviral vector containing the CD gene may provide both positive and negative selections after gene transfer. The CD transfectants selected with the positive selection system showed susceptibility to 5FC in subsequent negative selection in vitro and in vivo. Therefore, this dual selection system is useful not only for combination therapy with transgene and CD gene, but can also act to eliminate selectively transduced cells after the transgene has furnished its effects or upon undesired conditions if 5FC is applied for negative selection in vivo.