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T C Thompson

Publications and source records attributed to T C Thompson.

At least 19 recordsLinked to original sources
PubMed2006

Cooperative effects of adenoviral vector-mediated interleukin 12 gene therapy with radiotherapy in a preclinical model of metastatic prostate cancer.

We investigated the potential benefits of combining adenoviral vector mediated in situ interleukin-12 (AdmIL-12) gene therapy with radiation therapy (XRT) to enhance therapeutic efficacy. In a metastatic mouse prostate cancer cell line, 178-2 BMA, AdmIL-12+XRT demonstrated enhanced therapeutic activities in vitro as determined by clonogenic survival, apoptosis, and mIL-12 levels. At the molecular level, increased expression of tumor necrosis factor-alpha mRNA was specific for the combined therapy. In a subcutaneous 178-2 BMA in vivo model, the combination of AdmIL-12+XRT produced statistically significant tumor growth suppression compared to control vector Adbetagal, Adbetagal XRT, or AdmIL-12 as monotherapy. In addition, significant prolongation of survival was demonstrated for the combination of AdmIL-12+XRT. The combination of AdmIL-12+XRT significantly suppressed both spontaneous and pre-established lung metastases, and led to a prolonged elevation of serum IL-12 and significantly increased natural killer (NK) activities. Importantly, in vivo depletion of NK cells resulted in significant attenuation of the antimetastatic activities of AdmIL-12 alone or AdmIL-12+XRT. These combined effects suggest that AdIL-12 gene therapy together with radiotherapy may achieve maximal tumor control (both local and systemic) in selected prostate cancer patients via radio-gene therapy induced local cytotoxicity and local and systemic antitumor immunity.

Adenoviridae↗
PubMed2006

Adenoviral vector-mediated RTVP-1 gene-modified tumor cell-based vaccine suppresses the development of experimental prostate cancer.

We previously identified a novel p53 target gene, RTVP-1, that possesses unique cytotoxic and immunostimulatory activities which make it potentially useful for cancer gene therapy. To test the therapeutic potential of RTVP-1 in a gene-modified tumor cell-based vaccine model, we used an adenoviral vector capable of efficient transduction and expression of RTVP-1 (AdRTVP-1), together with a highly metastatic mouse prostate cancer cell line (178-2 BMA). A vaccine was prepared with 178-2 BMA cells transduced with AdRTVP-1 or a control adenoviral vector expressing beta-galactosidase (Adbetagal). After irradiation of the cells, syngeneic 129/Sv mice were vaccinated three times at weekly intervals. After 3 weeks, they were challenged with orthotopic 178-2 BMA cells. After 21 days, fewer than 60% of the RTVP-1-cell-vaccinated mice developed tumors compared to 100% of the control mice. The RTVP-1-cell vaccine significantly reduced primary tumor wet weight compared with control Adbetagal-cell vaccine (P<0.0001 at 7 and 14 days). Experimental metastasis to lung was also significantly reduced (P=0.0377), and survival significantly increased (P=0.0002). In addition, significantly increased NK and CTL activities were demonstrated in the AdRTVP-1-cell-vaccinated mice. These findings indicate that RTVP-1 gene-modified cell-based vaccines may be useful in the prevention of recurrent prostate cancer.

Adenoviridae↗
PubMed2006

Therapeutic effects of adoptive splenocyte transfer following in situ AdIL-12 gene therapy in a mouse prostate cancer model.

We developed a preclinical prostate cancer model to study the feasibility of adoptive immunotherapy for residual tumor following neo-adjuvant in situ adenoviral-vector-mediated interleukin 12 (AdIL-12) gene therapy. Splenocytes were obtained from mice with orthotopic 178-2 BMA metastatic mouse prostate cancers treated previously with AdIL-12, or a vector with the IL-12 genes plus the costimulatory gene B7-1 (AdIL-12/B7), or a control gene (Adbetagal). The splenocytes were subsequently injected intravenously into syngeneic mice bearing orthotopic 178-2 BMA tumors generated 3 days previously. Significant orthotopic tumor growth suppression was achieved with splenocytes derived from mice whose tumors had been injected with AdIL-12 compared to splenocytes from control Adbetagal mice (P = 0.0005) and splenocytes from AdIL-12/B7-treated mice significantly suppressed spontaneous lung metastases compared to splenocytes from control mice (P = 0.0356). Adoptive transfer of splenocytes from either AdIL-12 (P = 0.004) or AdIL-12/B7 (P = 0.009)-treated mice significantly prolonged survival relative to controls. Transfer of NK and tumor-specific CTL activities was detected and depletion of CD4+ and CD8+ T cells by in vitro antibody-mediated complement lysis of the splenocytes prior to injection abrogated the effects. Systemic IL-12 administration delivered by intramuscular AdIL-12 injection enhanced the antitumor effects of adoptive splenocyte transfer and boosted the CTL response. Our data provide evidence that this form of adoptive immunotherapy can enhance the effectiveness of neo-adjuvant in situ IL-12 gene therapy in cases of persistent malignancy.

Adoptive Transfer↗
PubMed2005

The emerging role of the PI3-K-Akt pathway in prostate cancer progression.

The PI3-K-Akt pathway plays a central role in the development and progression of prostate cancer and other malignancies. We review original studies and summarize relevant sections of previous reviews concerning the relationships between abnormalities in the PI3-K-Akt pathway and prostate cancer progression. We discuss laboratory and clinical data that indicate gene perturbation and dysregulation of PI3-K-Akt pathway is common in prostate cancer and other malignancies. We further discuss the critical role of the PI3-K-Akt pathway in the oncogenic signaling network and provide examples that establish the PI3-K-Akt pathway as a focal point for the future development of informative biomarkers and effective therapies for prostate cancer.

Biomarkers, Tumor↗
PubMed2002

Gene therapy for prostate cancer: toxicological profile of four HSV-tk transducing adenoviral vectors regulated by different promoters.

Adenoviral vector delivery of the Herpes simplex virus thymidine kinase (HSV-tk) gene in combination with the prodrug ganciclovir (GCV) has been tested in phase I clinical trials for prostate cancer and found to exhibit a satisfactory toxicity profile. We have developed additional adenoviral vectors with differing promoters to optimize the expression profile and in the present study evaluate the potential systemic toxicity of these vectors. Four recombinant adenoviral vectors that express the HSV-tk gene were generated using three different promoters: CMV (leftward orientation); RSV (both rightward and leftward orientation); and the mouse caveolin-1 (cav-1) promoter (leftward orientation). Efficacy was determined in vitro by cytotoxicity assays in a mouse prostate cancer cell line, RM-9, and in vivo by treating orthotopic tumors. Potential toxicity was evaluated from liver histology and apoptotic cell counts and enzyme levels in the serum following intravenous adenoviral vector injection. Although there were differences in HSV-tk expression at the protein level among the four vectors there were no significant differences in in-vitro cytotoxicity studies with GCV or in vivo in tumor growth suppression of an orthotopic mouse prostate cancer model in GCV treated mice. Intravenous delivery of high doses of all adenoviral vectors lead to abnormalities in liver function as measured by specific serum markers and histological evaluation of liver tissue and increased levels of apoptosis in the liver. These abnormalities were most prevalent with the vector containing the CMV promoter and the rightward oriented RSV promoter. They were least prevalent in the vector regulated by the cav-1 promoter. Upregulation of specific chemokines, MIP-2 and MIP-1beta was correlated with apoptotic counts. Our results demonstrate that comprehensive toxicological analysis of adenoviral vectors provides internally consistent information that can differentiate vectors with comparable efficacy based on toxicity. In these studies vectors with the cav-1 promoter-driven and leftward RSV-driven HSV-tk gene demonstrated minimal toxicities with cytotoxic effectiveness comparable to more toxic vectors. Our studies further suggest that promoter selection can influence the toxic effects of an adenoviral gene therapy vector.

Adenocarcinoma↗
PubMed2001

Enhanced therapeutic effect of multiple injections of HSV-TK + GCV gene therapy in combination with ionizing radiation in a mouse mammary tumor model.

PURPOSE: Standard therapies for breast cancer lack tumor specificity and have significant risk for recurrence and toxicities. Herpes simplex virus-thymidine kinase (HSV-tk) gene therapy combined with radiation therapy (XRT) may be effective because of complementary mechanisms and distinct toxicity profiles. HSV-tk gene therapy followed by systemic administration of ganciclovir (GCV) enhances radiation-induced DNA damage by generating high local concentrations of phosphorylated nucleotide analogs that increase radiation-induced DNA breaks and interfere with DNA repair mechanisms. In addition, radiation-induced membrane damage enhances the "bystander effect" by facilitating transfer of nucleotide analogs to neighboring nontransduced cells and by promoting local and systemic immune responses. This study assesses the effect of single and multiple courses of HSV-tk gene therapy in combination with ionizing radiation in a mouse mammary cancer model. METHODS AND MATERIALS: Mouse mammary TM40D tumors transplanted s.c. in syngeneic immunocompetent BALB-c mice were treated with either adenoviral-mediated HSV-tk gene therapy or local radiation or the combination of gene and radiation therapy. A vector consisting of a replication-deficient (E1-deleted) adenovirus type 5 was injected intratumorally to administer the HSV-tk gene, and GCV was initiated 24 h later for a total of 6 days. Radiation was given as a single dose of 5 Gy 48 h after the HSV-tk injection. A metastatic model was developed by tail vein injection of TM40D cells on the same day that the s.c. tumors were established. Systemic antitumor effect was evaluated by counting the number of lung nodules after treating only the primary tumors with gene therapy, radiation, or the combination of gene and radiation therapy. To assess the therapeutic efficacy of multiple courses of this combinatorial approach, one, two, and three courses of HSV-tk + GCV gene therapy, in combination with radiation, were compared to HSV-tk or XRT alone and to sham-treated animals. (Treatments were repeated at 7-day intervals from the HSV-tk injection.) RESULTS: Both single-therapy modalities reduced tumor growth by 11% compared to controls, while the combined therapy resulted in a decrease of 29%. Median survival was 36 days in the combined therapy group, compared to 33 days in the monotherapy groups and 26 days in the control group. In the metastatic model, the number of lung nodules was reduced by 59.5% after HSV-tk gene therapy, whereas radiotherapy had no effect on metastatic growth. Combined therapy led to an additional 66.7% reduction in lung colonization. Compared to controls, local tumor growth was maximally suppressed by three courses of combined therapy (51.5%), followed by two courses of combined therapy (37.2%), and three sessions of XRT alone (35.6%). Median survival was also significantly prolonged to 58 days with the three courses of combined therapy, followed by two courses, to 45 days. All other treatment groups demonstrated median survival times between 26 and 35 days, while controls had a median survival of 24 days. CONCLUSIONS: These results indicate that multiple courses of HSV-tk therapy in combination with radiation improve the therapeutic efficacy of this approach and may provide therapeutic implications for the treatment of human breast cancer and other solid tumors.

Adenoviridae↗
PubMed2001

Prostate-specific antigen response and systemic T cell activation after in situ gene therapy in prostate cancer patients failing radiotherapy.

In an extended phase I/II study we evaluated 36 prostate cancer patients with local recurrence after radiotherapy who received single or repeated cycles of replication-deficient adenoviral vector (ADV)-mediated herpes simplex virus-thymidine kinase (HSV-tk) plus ganciclovir (GCV) in situ gene therapy with respect to serum PSA levels, alterations in immune cells, and numbers of apoptotic cells in needle biopsies. An initial cycle of HSV-tk plus GCV gene therapy caused a significant prolongation of the mean serum PSA-doubling time (PSADT) from 15.9 to 42.5 months (p = 0.0271) and in 28 of the injected patients (77.8%) there was a mean PSA reduction (PSAR) of 28%. It took a mean of 8.5 months for the PSA to return to the initial PSA (TR-PSA) value. A repeated cycle of gene therapy failed to significantly extend PSADT but did result in significant increases in PSAR (29.4%) and TR-PSA (10.5 months). Moderately increased serum adenovirus antibody titers were generally observed 2 weeks after initial vector injection. Also at this time there was a statistically significant increase in the mean percent of CD8(+) T cells positive for the HLA-DR marker of activation in peripheral blood (p = 0.0088). Studies using prostate biopsies obtained at the same time point demonstrated that vector DNA was detectable by PCR in most samples yet all patients remained positive for prostate cancer in at least one biopsy core. Further analysis demonstrated a correlation between the level of CD8(+) cells and the number of apoptotic cells in biopsies containing cancer cells (p = 0.042). We conclude that repeated cycles of in situ HSV-tk plus GCV gene therapy can be administered to prostate cancer patients who failed radiotherapy and have a localized recurrence. Biological responses to this experimental therapy including increases in PSADT, PSAR, and TR-PSA, and activated CD8(+) T cells present in the peripheral blood, were demonstrated. Interestingly, the density of CD8(+) cells in posttreatment biopsies correlated with the number of apoptotic cells.

Adenoviridae↗
PubMed2001

LAPSER1: a novel candidate tumor suppressor gene from 10q24.3.

Numerous LOH and mutation analysis studies in different tumor tissues, including prostate, indicate that there are multiple tumor suppressor genes (TSGs) present within the human chromosome 8p21-22 and 10q23-24 regions. Recently, we showed that LZTS1 (or FEZ1), a putative TSG located on 8p22, has the potential to function as a cell growth modulator. We report here the cloning, gene organization, cDNA sequence characterization and expression analysis of LAPSER1, an LZTS1-related gene. This gene maps within a subregion of human chromosome 10q24.3 that has been reported to be deleted in various cancers, including prostate tumors, as frequently as the neighboring PTEN locus. The complete LAPSER1 cDNA sequence encodes a predicted protein containing various domains resembling those typically found in transcription factors (P-Box, Q-rich and multiple leucine zippers). LAPSER1 is expressed at the highest levels in normal prostate and testis, where multiple isoforms are seen, some of which are either undetectable or differentially expressed in some prostate tumor tissues and cell lines. Over-expression of LAPSER1 cDNA strongly inhibited cell growth and colony-forming efficiencies of most cancer cells assessed. Together these data suggest that LAPSER1 is another gene involved in the regulation of cell growth whose loss of function may contribute to the development of cancer.

Amino Acid Sequence↗
PubMed2001

Functional identification of LZTS1 as a candidate prostate tumor suppressor gene on human chromosome 8p22.

Deletions in the 8p21-22 region of the human genome are among the most common genetic alterations in prostate carcinomas. Several studies in different tumor tissues, including prostate, indicate that there are probably multiple tumor suppressor genes (TSGs) present in this region. To identify candidate TSGs on 8p22 a YAC contig spanning this region was assembled and YAC clones retrofitted with a selectable marker (neo) were transferred into rat prostate AT6.2 cells. Two overlapping YAC clones showed greatly reduced colony-forming efficiency, indicating they may carry a TSG. Two BAC clones encompassing the overlapping region also appeared to exert suppressive effects on the growth of AT6.2 cells. Database searches for genes mapped to the critical region identified a gene known as FEZ1 (LZTS1) as a potential candidate suppressor gene. Subsequent experiments showed that over-expression of LZTS1 cDNA inhibited stable colony-forming efficiencies of AT6.2, HEK-293 and LNCaP cells. In contrast, LZTS1-transfected Rat-1 and RM1 cells were growth-stimulated. Database searches also identified additional isoforms of the LZTS1 mRNA, as well as LZTS1 protein domains reminiscent of those found in transcription factors. Together these data suggest that the LZTS1 gene is involved in the regulation of cell growth and its loss of function may contribute to the development of prostatic carcinomas, as well as other cancers.

Animals↗
PubMed2001

Inhibition of murine prostate tumor growth and activation of immunoregulatory cells with recombinant canarypox viruses.

BACKGROUND: Immunization with modified tumor cells carrying recombinant immunomodulatory genes is being explored as cancer immunotherapy. In this study, we examine whether canarypox ALVAC viruses carrying immunostimulatory cytokine genes (granulocyte-macrophage colony-stimulating factor, interleukin 2, interleukin 12, and tumor necrosis factor-alpha) can induce antitumor immunity (to rechallenge) in the RM-1 model of a highly aggressive, weakly immunogenic murine prostate cancer. METHODS: For antitumor activity studies, RM-1 murine prostate cancer cells were infected with the parental ALVAC virus or one or two recombinant ALVAC-cytokine viruses and then injected into male C57BL/6 mice. For rechallenge studies, other mice were first given an injection subcutaneously with irradiated (nonproliferating) recombinant ALVAC-infected RM-1 cells and then (10 days later) with untreated RM-1 cells. For the determination of which immune cells were required for antitumor activity, mice were immunodepleted of CD4, CD8, or natural killer (NK) NK1.1 cells with the corresponding monoclonal antibodies and were then given an injection of ALVAC-cytokine-infected RM-1 cells. For all experiments, tumor outgrowth and animal survival were monitored. RESULTS: After subcutaneous injection into mice, RM-1 cells infected with one (except ALVAC-interleukin 2) or two ALVAC-cytokine recombinants had statistically significantly greater antitumor activity than RM-1 cells infected with parental ALVAC (P<.001 for all; two-sided test). The antitumor activity of RM-1 cells infected with any two ALVAC-cytokine recombinants was greater than, but not statistically significantly different from, that of RM-1 cells infected with any one ALVAC-cytokine recombinant. NK1.1 cells were necessary for antitumor activity, but tumor-specific CD4(+) regulatory T cells were also induced that inhibited CD8(+) RM-1-specific cytotoxic T cells, resulting in the lack of immunity to a rechallenge by RM-1 cells. DISCUSSION: Canarypox viruses can transfer immunostimulatory cytokine genes into RM-1 prostate cancer cells. When such cells were injected into mice, the cytokines induced an antitumor response against this highly aggressive, weakly immunogenic tumor. This response, however, did not protect the mouse against a rechallenge with RM-1 cells because suppressor CD4(+) T cells were induced that inhibited tumor-specific CD8(+) cytotoxic T cells.

Animals↗
PubMed2001

Caveolin-1 mediates testosterone-stimulated survival/clonal growth and promotes metastatic activities in prostate cancer cells.

Previously, we demonstrated that up-regulation of caveolin-1 (cav-1) was associated with prostate cancer metastasis, biochemical recurrence after radical prostatectomy, and androgen insensitivity. The objective of this study was to characterize the regulation of cav-1 by testosterone (T) and to test the effects of cav-1 on prostate cancer cell survival/clonal growth and metastatic activities. Our results demonstrated that T up-regulated cav-1 protein levels in part through transcriptional regulation and significantly enhanced survival of prostate cancer cell lines ABAC3 and LNCaP after serum starvation (>40% and >60% increased viability, respectively) and in an extended clonogenic assay (approximately 4-fold and 6-fold increase in colonies, respectively). Importantly, antisense cav-1 inhibited the survival effects of T in these assay systems. Modest but not high levels of adenoviral vector-mediated cav-1 expression alone also significantly increased viability (>40%) and clonal growth (10-fold increase in colonies) after serum starvation. Analysis of spontaneous metastasis in stably transfected antisense cav-1 mouse prostate cancer cell clones demonstrated reduction of spontaneous lymph node metastasis incidence (13%), spontaneous lymph node metastasis volume (46%), and experimental lung metastasis incidence (40%) compared with vector control cell clones. Surgical castration further reduced spontaneous lymph node metastasis incidence and volume (18% and 28%, respectively) in antisense cancer cell clones, but not in vector control clones. Our studies demonstrate that cav-1 is a downstream effector of T-mediated prostate cancer cell survival/clonal growth and that modest levels of cav-1 can independently promote prostate cancer cell survival/clonal growth and metastatic activities.

Animals↗
PubMed2001

Secreted caveolin-1 stimulates cell survival/clonal growth and contributes to metastasis in androgen-insensitive prostate cancer.

Caveolin-1 is an integral protein of caveolae, known to play important roles in signal transduction and lipid transport. We demonstrate that caveolin-1 expression is significantly increased in primary and metastatic human prostate cancer after androgen ablation therapy. We also show that caveolin-1 is secreted by androgen-insensitive prostate cancer cells, and that this secretion is regulated by steroid hormones. Significantly, caveolin-1 was detected in the MDL(3) fraction of serum specimens from patients with advanced prostate cancer and to a lesser extent in normal subjects. Conditioned media from high passage caveolin-1 secreting, androgen-insensitive, LNCaP cells stimulated increased viability and clonal growth of low passage, caveolin-1-negative, androgen-sensitive, LNCaP cells in vitro, and this effect was blocked by treating the media with caveolin-1 antibody. i.p. injections of caveolin-1 antibody suppressed the orthotopic growth and spontaneous metastasis of highly metastatic, androgen-insensitive caveolin-1-secreting mouse prostate cancer. Overall, our results establish caveolin-1 as an autocrine/paracrine factor that is associated with androgen-insensitive prostate cancer. We demonstrate the potential for caveolin-1 as a therapeutic target for this important malignancy.

Androgen Antagonists↗
PubMed2001

In vivo surgical resection plus adjuvant gene therapy in the treatment of mammary and prostate cancer.

Adenoviral-mediated gene therapy delivery, combining the herpes simplex virus thymidine kinase gene (Ad-tk) with gancyclovir, has been evaluated as a treatment modality for numerous tumors in the laboratory and in the clinics. As a single modality, gene therapy has shown some promising local and systemic results but no curative success. Surgery is the standard of care for many solid tumors. However, minor residual tumor following surgical resection can lead to local recurrence, and surgery is neither efficient nor plausible for metastatic disease. In this study, two tumor models were used to evaluate the effects of Ad-tk gene therapy as an adjuvant to surgery. Subcutaneous mammary- and prostate-derived tumors were produced in syngeneic mice. To evaluate systemic effects, tumor cells were injected intravenously, with subsequent formation of lung nodules. The subcutaneous tumors were surgically resected and the tumor bed was bathed with saline or Ad-tk. The animals were evaluated for toxicity, local tumor recurrence, survival, and lung nodule formation. No evidence of additional toxicity was observed. In the less aggressive mammary model, the time to recurrence was increased from 11.7 (+/-1.0) days to 22.7 (+/-5.5) days. In the prostate model, recurrence went from a mean of 17.3 (+/-5.6) to 22.6 (+/-6.8) days. Survival was also improved from a mean of 19.7 (+/-1.1) to 32.3 (+/-4.8) and 26.1 (+/-5.0) to 34.1 (+/-6.1) days in the mammary and prostate models, respectively. Evidence of systemic benefits from the use of adjuvant Ad-tk therapy was demonstrated by a significant reduction in lung nodules from a mean of 17 to 3.5. These results suggest that Ad-tk gene therapy may be a useful adjuvant for patients undergoing surgery for treatment of cancer.

Adenoviridae↗
PubMed2001

Enhanced therapeutic effect of HSV-tk+GCV gene therapy and ionizing radiation for prostate cancer.

Standard therapies for prostate cancer including radiation, prostatectomy, and hormone ablation have significant toxicities and recurrence risk. HSV-tk gene therapy may be effective in combination with radiation therapy due to complementary mechanisms and distinct toxicity profiles. Mouse prostate tumors transplanted subcutaneously were treated by either gene therapy involving intratumoral injection of AdV-tk followed by systemic ganciclovir or local radiation therapy or the combination of gene and radiation therapy. Both single-therapy modalities showed a 38% decrease in tumor growth compared to controls. The combined treatment resulted in a decrease of 61%. In addition the combined-therapy group had a mean survival of 22 days versus 16.6 days for single therapy and 13.8 days for nontreated controls. To analyze systemic anti-tumor activity, lung metastases were generated by tail vein injection of RM-1 prostate cancer cells on the same day that they were injected subcutaneously. The primary tumors were treated as before with AdV-tk followed by ganciclovir, radiation, or the combination. The number of lung nodules was reduced by 37% following treatment with AdV-tk, whereas radiotherapy alone had no effect on metastatic growth. The combination led to an additional 50% reduction in lung colonization. Primary tumors that received the combination therapy had a marked increase in CD4 T cell infiltrate. This is the first report showing a dramatic systemic effect following the local combination treatment of radiation and AdV-tk. A clinical study using this strategy has been initiated and patient accrual is ongoing.

Adenoviridae↗
PubMed2001

Combination gene therapy with adenoviral vector-mediated HSV-tk+GCV and IL-12 in an orthotopic mouse model for prostate cancer.

We previously demonstrated significant therapeutic activities associated with adenoviral vector-mediated Herpes Simplex Virus/thymidine kinase (AdHSV-tk) with ganciclovir (GCV) in situ gene therapy in the RM-1 orthotopic mouse prostate cancer model and interleukin-12 (AdmIL-12) in situ gene therapy in the RM-9 orthotopic mouse prostate model for prostate cancer. In both protocols, local cytotoxicity and activities against pre-established lung metastases were demonstrated. To test whether combined AdHSV-tk+GCV+IL-12 gene therapy would lead to enhanced therapeutic effects when compared to either treatment alone, we used RM-9 mouse prostate cancer cells in both orthotopic and pre-established lung metastases models of prostate cancer. Combined treatment with a single injection of optimal doses of AdHSV-tk+GCV or AdmIL-12 led to significantly increased suppression of orthotopic tumor growth. IL-12 gene therapy alone was more effective than AdHSV-tk+GCV in suppressing spontaneous lymph node metastases and pre-established lung metastases but combination gene therapy did not result in additional anti-metastatic activities. Combination gene therapy also did not achieve significantly better animal survival compared to AdHSV-tk+GCV or AdmIL-12 alone. Analysis of localized antitumor activities demonstrated that AdHSV-tk+GCV therapy induced higher levels of necrosis compared to AdmIL-12 or combination therapy. However, both treatments alone and combination therapy produced similar increases in apoptotic index. To address the possible mechanisms of locally co-operative cytotoxic activities, we analyzed the systemic natural killer (NK) response and the numbers of tumor-infiltrating immune cells using quantitative immunohistochemical analysis. AdHSV-tk+GCV therapy alone led to detectable increases in iNOS-positive cells, CD4+and CD8+T-cells and moderately increased numbers of F4/80 (macrophage selective)-positive cells within treated tumors. In contrast, AdmIL-12 elicited a highly robust pattern of tumor infiltration for all four of these immune cells that was in general mimicked by combination therapy. Further analysis of the accumulation of transforming growth factor-beta1 (TGF-beta1) immunohistochemical staining demonstrated that AdHSV-tk+GCV treatment, but not AdmIL-12 treatment, produced cancer cell-associated increases in this cytokine relative to control Ad-beta-gal injections. Interestingly, local injection with AdHSV-tk+GCV induced significant splenocyte-derived NK cell cytolytic activities with maximal response 7 days following treatment, whereas AdmIL-12 injection produced significantly higher NK activity with maximal response 2 days following injection. The combined treatment produced a higher systemic NK response over the 14-day treatment period. Depletion of NK cells in vivo demonstrated that this immunocyte subpopulation was responsible for early locally cytotoxic activities induced by AdHSV-tk+GCV but not AdmIL-12 and that NK activities were largely responsible for activities against pre-established metastases generated by both gene therapy protocols. Prostate Cancer and Prostatic Diseases (2001) 4, 44-55

Journal Article↗
PubMed2001

In situ gene therapy for prostate cancer: immunomodulatory approaches.

The development of effective treatments for prostate cancer is thwarted by the natural history of the disease. The biological and clinical potential of most individual cancers is uncertain. In many cases the disease will not progress to clinical significance but experimental and clinical studies indicate that prostate cancer can and may metastasis early in the course of the disease from relatively small foci (i.e., not necessarily the largest or index cancer). Localised prostate cancer is potentially curable with localised therapies (radical prostatectomy or irradiation therapy). However, there are no curative therapies for metastatic prostate cancer. Gene therapy, especially those approaches with an immunomodulatory component, may provide additional therapeutic options with the potential to affect both localised and systemic disease. We have pioneered the development and application of in situ gene therapy protocols using adenoviral vectors to transduce specific genes that generate cytotoxic activity and/or a systemic antitumour immune response. In addition we have completed initial studies that demonstrate the therapeutic potential of adenoviral vector-mediated gene modified cell-based vaccines. Our review discusses preclinical studies focused on the development of immunostimulatory in situ gene therapy approaches that hopefully will provide novel and effective treatments for localised and metastatic prostate cancer.

Animals↗
PubMed2001

In situ prostate cancer gene therapy using a novel adenoviral vector regulated by the caveolin-1 promoter.

Caveolin-1, a structural component of caveolae, is overexpressed in metastatic and androgen-resistant prostate cancer and highly expressed in tumor-associated endothelial cells. The mouse cav-1 promoter was cloned and placed upstream of the HSV-tk gene in an adenoviral vector (Adcav-1tk) and compared with a cytomegalovirus (CMV) or Rous sarcoma virus (RSV) promoter-driven HSV-tk, AdCMVtk and AdRSVtk vectors, respectively. Mouse and human prostate cancer cells and mouse endothelial cells were infected with Adcav-1tk, AdCMVtk or control vectors without the HSV-tk gene (Adcav-1 and AdCMV) and subsequently treated with ganciclovir (GCV). GCV-mediated in vitro cytotoxicity induced by the Adcav-1tk vector was comparable to that for AdCMVtk in multiple mouse and human prostate cancer cell lines. To evaluate the activity of Adcav-1tk in vivo, orthotopic mouse prostate cancer tumors were generated with RM-9 cells and injected in situ with Adcav-1tk, AdCMVtk, AdRSVtk, or AdCMVbetagal (control) and treated with GCV. All three HSV-tk transducing vectors produced statistically significant reductions in wet weight and increased apoptotic indices compared with the control vector. However, only Adcav-1tk produced significant necrosis, and only Adcav-1tk and AdRSVtk caused significant decreases in microvessel density. In conclusion, Adcav-1tk demonstrated efficacy in vitro and in vivo in preclinical models of prostate cancer. Our results suggest that the cav-1 promoter may have unique benefits in targeting gene therapy to prostate cancer and its associated vasculature.

Adenoviridae↗