Reduced Tumor Growth Rate Research Articles

Molecular Characterization of Macbecin as an Hsp90 Inhibitor

Macbecin compares favorably to geldanamycin as an Hsp90 inhibitor, being more soluble, stable, more potently inhibiting ATPase activity (IC50 = 2 microM) and binding with higher affinity (Kd = 0.24 microM). Structural studies reveal significant differences in their Hsp90 binding characteristics, and macbecin-induced tumor cell growth inhibition is accompanied by characteristic degradation of Hsp90 client proteins. Macbecin significantly reduced tumor growth rates (minimum T/C: 32%) in a DU145 murine xenograft. Macbecin thus represents an attractive lead for further optimization.

IFN-β-Dependent Inhibition of Tumor Growth by the Vascular Disrupting Agent 5,6-Dimethylxanthenone-4-Acetic Acid (DMXAA)

By attacking established tumor vasculature, vascular disrupting agents (VDAs) represent an alternative approach to the treatment of cancer. One such VDA, 5,6-dimethylxanthenone-4-acetic acid (DMXAA), is scheduled for phase III trials for prostate and lung cancer in combination with conventional chemotherapies. In this work, we identify interferon-beta (IFN-beta) as a central mediator in the host's response to DMXAA. In mice bearing Lewis lung adenocarcinomas, a single intraperitoneal dose of DMXAA was shown to effect a highly significant reduction in tumor growth rate in wild-type mice that was not seen in IFN-beta-null mice. Moreover, intratumoral cytokine expression was shown to be dependent on host-derived IFN-beta, as DMXAA-treated IFN-beta-null mice demonstrated a lack of induction of not only IFN-beta but also the antiangiogenic cytokine, IP-10, in excised tumor tissue. These results support the conclusion that DMXAA derives its potent anticancer properties in part through elicitation of IFN-beta expression by host-derived elements.

Smad3 Is Overexpressed in Advanced Human Prostate Cancer and Necessary for Progressive Growth of Prostate Cancer Cells in Nude Mice

The purpose of this study was to investigate the potential role of Smad3, a key mediator of transforming growth factor-beta signaling, in progression of prostate cancer. Expression of Smad proteins was determined in human prostate cancer tissue array and cell lines. Growth and metastasis of cells overexpressing dominant-negative Smad3 (Smad3D) were studied to determine its role in tumor progression in mice. Cell growth, apoptosis, and expression of angiogenic molecules in tumor lesions were studied to determine potential pathways that Smad3 promotes tumor progression. Smad3 was overexpressed in human prostate cancer, which correlated with Gleason score and expression of proliferating cell nuclear antigen. Androgen-independent PC-3MM2 and DU145 cells expressed much higher levels of Smad3 than did androgen-dependent LNCaP, 22Rv1, and LAPC-4 cells. Overexpression of Smad3D in PC-3MM2 cells (PC-3MM2-Smad3D) had minimal direct effects on cell growth but attenuated effects of transforming growth factor-beta1 on gene expression and cell growth. Overexpression of Smad3D did not significantly alter tumor incidence but reduced tumor growth rate and metastasis incidence. Most cells in the control tumors, but not PC-3MM2-Smad3D tumors, were positively stained by an antibody to proliferating cell nuclear antigen. Microvessels and expression of angiogenic molecule interleukin-8 were significantly reduced in tumors from PC-3MM2-Smad3D cells. PC-3MM2-Smad3D tumors also expressed lower levels of vascular endothelial growth factor and platelet-derived growth factor. These data suggest that Smad3, through regulating angiogenic molecule expression in tumor cells, is critical for progression of human prostate cancer.

Antitumor effects of non-replicative herpes simplex vectors expressing antiangiogenic proteins and thymidine kinase on Lewis lung carcinoma establishment and growth

There is growing evidence that combinations of antiangiogenic proteins with other antineoplastic treatments such as chemo- or radiotherapy and suicide genes-mediated tumor cytotoxicity lead to synergistic effects. In the present work, we tested the activity of two non-replicative herpes simplex virus (HSV)-1-based vectors, encoding human endostatin::angiostatin or endostatin::kringle5 fusion proteins in combination with HSV-1 thymidine kinase (TK) molecule, on endothelial cells (ECs) and Lewis lung carcinoma (LLC) cells. We observed a significant reduction of the in vitro growth, migration and tube formation by primary ECs upon direct infection with the two recombinant vectors or cultivation with conditioned media obtained from the vector-infected LLC cells. Moreover, direct cytotoxic effect of HSV-1 TK on both LLC and ECs was demonstrated. We then tested the vectors in vivo in two experimental settings, that is, LLC tumor growth or establishment, in C57BL/6 mice. The treatment of pre-established subcutaneous tumors with the recombinant vectors with ganciclovir (GCV) induced a significant reduction of tumor growth rate, while the in vitro infection of LLC cells with the antiangiogenic vectors before their implantation in mice flanks, either in presence or absence of GCV, completely abolished the tumor establishment.

A nanoemulsion of an anti-oxidant synergy formulation reduces tumor growth rate in neuroblastoma-bearing nude mice

A nanoemulsion of an anti-oxidant synergy formulation reduces tumor growth rate in neuroblastoma-bearing nude mice

A nanoemulsion of an anti‐oxidant synergy formulation reduces tumor growth rate in neuroblastoma‐bearing nude mice.

Neuroblastoma, the most common form of childhood cancer, may arise from a biochemical block of cellular differentiation and a resultant continuation of a proliferative state. Neuroblastoma often spontaneously reverts by undergoing partial differentiation and ultimate degeneration and may be associated with the generation of reactive oxygen species (ROS). We have recently reported in neuroblastoma cell culture studies that an anti-oxidant synergy formulation (ASF) can induce differentiation and buffer neuronal degeneration and oxidative stress in cultured cortical neurons and in central nervous system tissue of apolipoprotein E-deficient mice. The objective of the present study was to investigate whether a subcutaneous injection and/or transdermal application of a nanoemulsion preparation of ASF would reduce tumor growth rate in a neuroblastoma xenograph mouse model. The results indicate that whereas suspensions of ASF were ineffective in decreasing tumor growth rate in the neuroblastoma mouse model, tumor growth rate was similarly reduced an average 65% by either subcutaneous injection or transdermal application of an ASF nanoemulsion preparation to the tumor. In conclusion, the data suggest that subcutaneous and/or transdermal application of an ASF nanoemulsion preparation is effective in reducing tumor growth rate in this neuroblastoma mouse model.

Short hairpin RNA knockdown of the androgen receptor attenuates ligand-independent activation and delays tumor progression: Cheng H, Snoek R, Ghaidi F, Cox ME, Rennie PS, The Prostate Center at Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada

Progression to androgen independence is the lethal end stage of prostate cancer. We used expression of androgen receptor (AR)-targeted short hairpin RNAs (shRNA) to directly test the requirement for AR in ligand-independent activation of androgen-regulated genes and hormone-independent tumor progression. Transient transfection of LNCaP human prostate cancer cells showed that AR shRNA decreased R1881 induction of the prostate-specific antigen (PSA)-luciferase reporter by 96%, whereas activation by forskolin, interleukin-6, or epidermal growth factor was inhibited 48% to 75%. Whereas the antiandrogen bicalutamide provided no further suppression, treatment with the mitogen-activated protein kinase (MAPK) inhibitor U0126 completely abrogated the residual activity, indicating a MAPK-dependent, AR-independent pathway for regulating the PSA promoter. Expression of doxycycline-inducible AR shRNA expression in LNCaP cells resulted in decreased levels of AR and PSA as well as reduced proliferation in vitro. When these cells were grown as xenografts in immunocompromised mice, induction of AR shRNA decreased serum PSA to below castration nadir levels and significantly retarded tumor growth over the entire 55-day experimental period. This is the first demonstration that, by inducibly suppressing AR expression in vivo, there is an extensive delay in progression to androgen independence as well as a dramatic inhibition of tumor growth and decrease in serum PSA, which exceeds that seen with castration alone. Based on these findings, we propose that suppressing AR expression may provide superior therapeutic benefit in reducing tumor growth rate than castration and may additionally be very effective in delaying progression to androgen independence.

Short Hairpin RNA Knockdown of the Androgen Receptor Attenuates Ligand-Independent Activation and Delays Tumor Progression

Progression to androgen independence is the lethal end stage of prostate cancer. We used expression of androgen receptor (AR)-targeted short hairpin RNAs (shRNA) to directly test the requirement for AR in ligand-independent activation of androgen-regulated genes and hormone-independent tumor progression. Transient transfection of LNCaP human prostate cancer cells showed that AR shRNA decreased R1881 induction of the prostate-specific antigen (PSA)-luciferase reporter by 96%, whereas activation by forskolin, interleukin-6, or epidermal growth factor was inhibited 48% to 75%. Whereas the antiandrogen bicalutamide provided no further suppression, treatment with the mitogen-activated protein kinase (MAPK) inhibitor U0126 completely abrogated the residual activity, indicating a MAPK-dependent, AR-independent pathway for regulating the PSA promoter. Expression of doxycycline-inducible AR shRNA expression in LNCaP cells resulted in decreased levels of AR and PSA as well as reduced proliferation in vitro. When these cells were grown as xenografts in immunocompromised mice, induction of AR shRNA decreased serum PSA to below castration nadir levels and significantly retarded tumor growth over the entire 55-day experimental period. This is the first demonstration that, by inducibly suppressing AR expression in vivo, there is an extensive delay in progression to androgen independence as well as a dramatic inhibition of tumor growth and decrease in serum PSA, which exceeds that seen with castration alone. Based on these findings, we propose that suppressing AR expression may provide superior therapeutic benefit in reducing tumor growth rate than castration and may additionally be very effective in delaying progression to androgen independence.

CD32B, the human inhibitory Fc-γ receptor IIB, as a target for monoclonal antibody therapy of B-cell lymphoma

AbstractHuman CD32B (FcγRIIB), the low-affinity inhibitory receptor for IgG, is the predominant Fc receptor (FcR) present on B cells. Immunohistochemical and expression studies have identified CD32B expression in a variety of B-cell malignancies, suggesting that CD32B is a potential immunotherapeutic target for B-cell malignancies. A high-affinity monoclonal antibody (mAb 2B6), from a novel panel of anti–human CD32B–specific mAbs, was chimerized (ch2B6) and humanized (hu2B6-3.5). Both ch2B6 and hu2B6-3.5 were capable of directing cytotoxicity by peripheral blood mononuclear cells and monocyte-derived macrophages against B-lymphoma lines in vitro. In a human B-cell lymphoma mouse xenograft model, administration of ch2B6 or hu2B6-3.5 reduced tumor growth rate and improved tumor-free survival. Both the in vitro and in vivo activities of 2B6 required an intact Fc, suggesting an FcR-mediated mechanism of action. These data support the hypothesis that CD32B is a viable target for mAb treatment of B-cell lymphoproliferative disorders.

Anticancer effects of amooranin in human colon carcinoma cell line in vitro and in nude mice xenografts

Amooranin (AMR), a natural triterpenoid drug isolated and characterized from Amoora rohituka stem bark, is cytotoxic to SW620 human colon carcinoma cell line with an IC(50) value of 2.9 microg/ml. This novel compound caused depolarization of mitochondrial membrane and decrease of membrane potential, indicating initial signal of apoptosis induction. The percentage of cells with decreased mitochondrial potential ranged from 7.4% at 1 microg/ml to 60.5% at 100 microg/ml AMR. Flow cytometric analysis of apoptosis using Annexin-V-FITC staining showed that the percentage of apoptotic cells ranged from 7.5% at 1 microg/ml to 59.2% at 100 microg/ml AMR. AMR-induced apoptosis was accompanied by redistribution of cytochrome c from mitochondria to cytosol as well as down regulation of Bcl-2 and Bcl-X(L) proteins in a dose-dependent manner. SW620 human colon carcinoma xenograft mice treated with AMR showed significant reduction in tumor growth rates compared to saline- and doxorubicin-treated groups. The reduction in tumor growth rate was better in xenografts treated with 2 mg/kg AMR than 5 and 10 mg/kg treated mice. The analysis of global gene expression changes induced by AMR in xenograft tumors by microarray hybridization revealed that several genes involved in energy pathways, transport, apoptosis, immune response, nucleic acid metabolism, protein metabolism, cell growth and/or maintenance, signal transduction and cell communication, were affected by this natural cancer drug. These results suggest that the anticancer properties of AMR in SW620 human colon carcinoma cell line are mediated through its effects on functional genomics, targeting the apoptotic process.

Particle-Mediated Cytokine Gene Therapy Leads to Antitumor and Antimetastatic Effects in Mouse Carcinoma Models

We investigated the effects of continuous cancer gene therapy including (antigen-presenting cell) (APC) engineering and local stimulation of the immune system. Lewis lung carcinomas and B16 melanomas, intradermally established on C57/Bl6 mice, were shot using a gene gun every 4th day with a combination of plasmids. The first therapy group received plasmids coding the genes for interleukin (IL)-12 and IL-2. The second therapy group was treated with plasmids coding for B7.1 interferon-gamma (IFN-gamma)/IL-12 alternated by a plasmid coding IL-2. Control were mice without any therapy or treatment with the empty plasmid. Gene therapy led to reduced tumor sizes in the therapy groups of both models (significant for the Lewis lung carcinoma). We found an enhanced survival and reduced tumor growth rate in the therapy groups; however, the effects were not significant. IL- 12/IL-2 therapy was more effective, compared to B7.1/IFN-gamma/IL-12 and IL-2. Cytokine gene transfer let to a significantly lower metastasis rate in Lewis lung carcinoma. Continuous particle-mediated gene transfer is easy to handle and shows good results. Gene therapy combining the genes coding for IL-12 and IL-2 was superior to additional IFN-gamma/B7.1. APC engineering does not appear to be sufficient in these poorly antigenic tumors.

Attenuation of Proteasome-Induced Proteolysis in Skeletal Muscle by β-Hydroxy-β-Methylbutyrate in Cancer-Induced Muscle Loss

Abstract Loss of skeletal muscle is an important determinant of survival in patients with cancer-induced weight loss. The effect of the leucine metabolite β-hydroxy-β-methylbutyrate (HMB) on the reduction of body weight loss and protein degradation in the MAC16 model of cancer-induced weight loss has been compared with that of eicosapentaenoic acid (EPA), a recognized inhibitor of protein degradation. HMB was found to attenuate the development of weight loss at a dose greater than 0.125 g/kg accompanied by a small reduction in tumor growth rate. When EPA was used at a suboptimal dose level (0.6 g/kg) the combination with HMB seemed to enhance the anticachectic effect. Both treatments caused an increase in the wet weight of soleus muscle and a reduction in protein degradation, although there did not seem to be a synergistic effect of the combination. Proteasome activity, determined by the “chymotrypsin-like” enzyme activity, was attenuated by both HMB and EPA. Protein expression of the 20S α or β subunits was reduced by at least 50%, as were the ATPase subunits MSS1 and p42 of the 19S proteasome regulatory subunit. This was accompanied by a reduction in the expression of E214k ubiquitin-conjugating enzyme. The combination of EPA and HMB was at least as effective or more effective than either treatment alone. Attenuation of proteasome expression was reflected as a reduction in protein degradation in gastrocnemius muscle of cachectic mice treated with HMB. In addition, HMB produced a significant stimulation of protein synthesis in skeletal muscle. These results suggest that HMB preserves lean body mass and attenuates protein degradation through down-regulation of the increased expression of key regulatory components of the ubiquitin-proteasome proteolytic pathway, together with stimulation of protein synthesis.

Dickkopf-3/REIC functions as a suppressor gene of tumor growth

To identify putative tumor suppressor genes in hepatocarcinogenesis, we combined the representational difference analysis and reverse northern blot identifying downregulated genes in human hepatoma tissues. One of them was Dkk-3/REIC. Dkk-3/REIC was downregulated in 11 out of the 20 human hepatoma tissues as compared to their counterparts of noncancerous liver tissues by northern blot analysis. It was also downregulated in 29 out of 48 human cancer samples including the kidney, urinary bladder, prostate, pancreas and lung cancers. Its gene product, Dkk-3/REIC, was found to be N-glycosylated and have two isoforms, the 55 kDa in the cytosol and 50 kDa secreted in the medium. Ectopic expression of Dkk-3/REIC in HeLa, Hep3B and Huh 7 cells led to suppression of cell growth, which was primarily attributable to induction of cell apoptosis. The suppression phenomenon was found to be cell-type related (most prominent in HeLa and least in Hep3B cells) and cell-density dependent (attenuated as the cell density increased). Transduction of Dkk-3/REIC into HeLa and Hep3B cells caused suppression on colony formation in vitro and reduced tumor growth rate in inoculated athymic nude mice. In conclusion, these data indicate that Dkk-3/REIC functions as a suppressor for human tumor growth.

Combined effect of recombinant CD19xCD16 diabody and thalidomide in a preclinical model of human B cell lymphoma

Combining different treatment strategies offers the possibility of improving treatment results for cancer patients. The aim of our study was therefore to investigate the combination of treatment of established s.c. human B non-Hodgkin's lymphoma in severe immune deficient mice using a recombinant bispecific CD19 x CD16 diabody (targeting natural killer cells to CD19 cells) and the angiogenesis inhibitor thalidomide. Monotherapy with either thalidomide or diabody caused an approximate 50% reduction in tumor growth rate. The combined treatment showed evidence for a synergistic effect resulting in a 74% reduction in median tumor size. In the combined treatment group, two of five animals had complete remissions of their s.c. tumor. These results suggest that a combination treatment with recombinant diabodies and angiogenesis inhibition represents a useful approach in cancer therapy.

Oral recombinant human Lactoferrin (rhLF) slows tumor growth in metastatic NSCLC and other advanced incurable cancers: Results of a Phase II study

3140 Background: RhLF, a novel immunomodulatory agent, was previously shown to have anti-tumor activity in a variety of animal models, and was safe and well tolerated in Phase I human trials. Methods: 33 patients with advanced solid tumors that had progressed on previous chemotherapy regimens, or who had no effective chemotherapy regimens available, will be scheduled to receive oral rhLF monotherapy in cycles of 2 weeks on, 2 weeks off, until tumor progression. Following an initial dose escalation, patients were randomized between the two highest rhLF doses (4.5 or 9 g/day). Tumor response was followed by periodic CT scans using RECIST criteria. Results: We have enrolled 27 patients to date–9 with NSCLC, 4 each with renal and colon cancer, and 3 or fewer with seven other tumor types. RhLF was safe and well tolerated, with no drug-related SAEs or DLTs. A total of 22 patients were evaluable radiologically. We observed one (5%) partial response and 12 (55%) stable disease. In NSCLC patients, the largest group, 5 patients (53%) had stable disease. In patients with renal cancer, we had one (25%) partial response and 3 (75%) stable disease. Colon cancer patients had 50% stable disease. We also observed a substantial decrease in the growth rate of target lesions before and after start of rhLF. The average tumor growth rate dropped by 68% (p<0.05) from 5.2% to 1.7% per week. A reduction in tumor growth rate could potentially result in increased survival. The NSCLC patients (88% tumor rate reduction; p<0.05) already appear to demonstrate a survival benefit. The median survival to date among the 9 NSCLC patients is 8 months (with only one death), which compares favorably to the 4.6 months expected median for pretreated patients with metastatic lung cancer. Updated survival and response data will be presented. Conclusions: RhLF is safe and well tolerated, shows promise in salvage therapy of NSCLC and renal cancer, and should be evaluated in larger Phase II trials. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Agennix, Inc. Agennix, Incorporated

Oral recombinant human Lactoferrin (rhLF) slows tumor growth in metastatic NSCLC and other advanced incurable cancers: Results of a Phase II study

3140 Background: RhLF, a novel immunomodulatory agent, was previously shown to have anti-tumor activity in a variety of animal models, and was safe and well tolerated in Phase I human trials. Methods: 33 patients with advanced solid tumors that had progressed on previous chemotherapy regimens, or who had no effective chemotherapy regimens available, will be scheduled to receive oral rhLF monotherapy in cycles of 2 weeks on, 2 weeks off, until tumor progression. Following an initial dose escalation, patients were randomized between the two highest rhLF doses (4.5 or 9 g/day). Tumor response was followed by periodic CT scans using RECIST criteria. Results: We have enrolled 27 patients to date–9 with NSCLC, 4 each with renal and colon cancer, and 3 or fewer with seven other tumor types. RhLF was safe and well tolerated, with no drug-related SAEs or DLTs. A total of 22 patients were evaluable radiologically. We observed one (5%) partial response and 12 (55%) stable disease. In NSCLC patients, the largest group, 5 patients (53%) had stable disease. In patients with renal cancer, we had one (25%) partial response and 3 (75%) stable disease. Colon cancer patients had 50% stable disease. We also observed a substantial decrease in the growth rate of target lesions before and after start of rhLF. The average tumor growth rate dropped by 68% (p<0.05) from 5.2% to 1.7% per week. A reduction in tumor growth rate could potentially result in increased survival. The NSCLC patients (88% tumor rate reduction; p<0.05) already appear to demonstrate a survival benefit. The median survival to date among the 9 NSCLC patients is 8 months (with only one death), which compares favorably to the 4.6 months expected median for pretreated patients with metastatic lung cancer. Updated survival and response data will be presented. Conclusions: RhLF is safe and well tolerated, shows promise in salvage therapy of NSCLC and renal cancer, and should be evaluated in larger Phase II trials. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Agennix, Inc. Agennix, Incorporated

Tumor cells engineered with IL-12 and IL-15 genes induce protective antibody responses in nude mice.

IL-12 and IL-15 stimulate T, B, and NK cell functions through independent mechanisms, and cooperative effects of these cytokines have been reported. The human MHC class I-negative small cell lung cancer cell line, N592, genetically engineered to secrete IL-15, N592/IL-15, showed a reduced tumor growth rate, while N592 cells engineered with IL-12, N592/IL-12, grew similarly to the wild-type N592, N592 parental cells (N592pc), in nude mice. However, N592 cells coexpressing both cytokines, N592/IL-12/IL-15 cells, were completely rejected by 100% of nude mice. Here we show that 60% of nude mice rejecting N592/IL-12/IL-15 cells were resistant to N592pc rechallenge. SCID mice rejected N592/IL-12/IL-15 cells, but did not develop resistance to N592pc rechallenge, suggesting a role of Ab responses. Among nude mice rejecting N592/IL-12/IL-15 cells, those developing resistance to N592pc rechallenge had significantly higher titers of anti-N592 IgG2b Abs than nonresistant nude mice. Induction of an Ig class switch in nude mice was related to the expression of IFN-gamma and CD40 ligand in the draining lymph nodes. An IgG2b, anti-N592 mAb, derived from N592/IL-12/IL-15-immunized nude mice splenocytes induced significant protection against N592pc, while an IgM mAb was ineffective. The protective IgG2b mAb, but not the IgM mAb, triggered Ab-dependent cell-mediated cytotoxicity by nude mouse splenocytes against N592pc. These data indicate that IL-12 and IL-15 synergistically trigger innate, immunity-mediated, anti-tumor effects, resulting in cytotoxic IgG Ab responses in T cell-deficient mice. Protective Ab responses may relate to both direct actions of IL-12 and IL-15 on B cells and to the activation of an innate immunity-B cell cross-talk.

Modeling human breast cancer metastasis in mice: maspin as a paradigm.

Breast cancer is the most common cancer detected in women, accounting for nearly one out of every three cancers diagnosed in the United States. Most cancer patients do not die from the primary tumor but die due to metastasis. Therefore, the study of metastasis is of most importance both to the clinician and patient. In the past, animal models have been used in breast cancer research and mammary gland biology. Our group has also established several animal models to address the function of a novel tumor suppressor gene maspin in breast tumor progression. Maspin was initially isolated from normal mammary epithelial cells. Its expression was down regulated in breast tumors. To test the protective role of maspin overexpression in mammary tumor progression, we crossed maspin overexpression transgenic mice (WAP-maspin) with a strain of oncogenic WAP-SV40 T antigen mice. The bitransgenic mice had reduced tumor growth rate and metastasis. Maspin overexpression increased the rate of apoptosis of both preneoplastic and carcinomatous mammary epithelial cells. Maspin reduced tumor growth through a combination of reduced angiogenesis and increased apoptosis. In a separate animal experiment, maspin overexpressing mammary tumor cells (TM40D) were implanted into the fat pad of syngeneic mice. TM40D tumor cells were very invasive and metastatic. However, both primary tumor growth and metastasis were significantly blocked in TM40D cells that overexpress maspin as a consequence of plasmid or retrovirus infection. These evidences demonstrate that maspin function to inhibit primary tumor growth as well as invasion and metastasis. Elucidating the molecular mechanism of maspin action will shed light on our understanding of breast cancer invasion and metastasis.

Molecular imaging of gene expression and efficacy following adenoviral-mediated brain tumor gene therapy.

Cancer gene therapy is an active area of research relying upon the transfer and subsequent expression of a therapeutic transgene into tumor cells in order to provide for therapeutic selectivity. Noninvasive assessment of therapeutic response and correlation of the location, magnitude, and duration of transgene expression in vivo would be particularly useful in the development of cancer gene therapy protocols by facilitating optimization of gene transfer protocols, vector development, and prodrug dosing schedules. In this study, we developed an adenoviral vector containing both the therapeutic transgene yeast cytosine deaminase (yCD) along with an optical reporter gene (luciferase). Following intratumoral injection of the vector into orthotopic 9 L gliomas, anatomical and diffusion-weighted MR images were obtained over time in order to provide for quantitative assessment of overall therapeutic efficacy and spatial heterogeneity of cell kill, respectively. In addition, bioluminescence images were acquired to assess the duration and magnitude of gene expression. MR images revealed significant reduction in tumor growth rates associated with yCD/5-fluorocytosine (5FC) gene therapy. Significant increases in mean tumor diffusion values were also observed during treatment with 5FC. Moreover, spatial heterogeneity in tumor diffusion changes were also observed revealing that diffusion magnetic resonance imaging could detect regional therapeutic effects due to the nonuniform delivery and/or expression of the therapeutic yCD transgene within the tumor mass. In addition, in vivo bioluminescence imaging detected luciferase gene expression, which was found to decrease over time during administration of the prodrug providing a noninvasive surrogate marker for monitoring gene expression. These results demonstrate the efficacy of the yCD/5FC strategy for the treatment of brain tumors and reveal the feasibility of using multimodality molecular and functional imaging for assessment of gene expression and therapeutic efficacy.

Molecular Imaging of Gene Expression and Efficacy following Adenoviral-Mediated Brain Tumor Gene Therapy

Cancer gene therapy is an active area of research relying upon the transfer and subsequent expression of a therapeutic transgene into tumor cells in order to provide for therapeutic selectivity. Noninvasive assessment of therapeutic response and correlation of the location, magnitude, and duration of transgene expression in vivo would be particularly useful in the development of cancer gene therapy protocols by facilitating optimization of gene transfer protocols, vector development, and prodrug dosing schedules. In this study, we developed an adenoviral vector containing both the therapeutic transgene yeast cytosine deaminase (yCD) along with an optical reporter gene (luciferase). Following intratumoral injection of the vector into orthotopic 9 L gliomas, anatomical and diffusion-weighted MR images were obtained over time in order to provide for quantitative assessment of overall therapeutic efficacy and spatial heterogeneity of cell kill, respectively. In addition, bioluminescence images were acquired to assess the duration and magnitude of gene expression. MR images revealed significant reduction in tumor growth rates associated with yCD/5-fluorocytosine (5FC) gene therapy. Significant increases in mean tumor diffusion values were also observed during treatment with 5FC. Moreover, spatial heterogeneity in tumor diffusion changes were also observed revealing that diffusion magnetic resonance imaging could detect regional therapeutic effects due to the nonuniform delivery and/or expression of the therapeutic yCD transgene within the tumor mass. In addition, in vivo bioluminescence imaging detected luciferase gene expression, which was found to decrease over time during administration of the prodrug providing a noninvasive surrogate marker for monitoring gene expression. These results demonstrate the efficacy of the yCD/5FC strategy for the treatment of brain tumors and reveal the feasibility of using multimodality molecular and functional imaging for assessment of gene expression and therapeutic efficacy.