Treatment Of Subcutaneous Tumors Research Articles

Stable Hybrid Nanocapsules with Gold Nanorods and Cyanine Dyes for Near‐Infrared Photothermal Ablation of Subcutaneous Tumor

AbstractGold nanorods and cyanine dyes are promising to be widely used in photothermal therapy due to their adjustable absorption wavelength and excellent photothermal conversion efficiency. However, it is unclear how gold nanorods differ from cyanine dyes in therapeutic effects. Nanocapsules are synthesized from hybrid silica encapsulated gold nanorods (AuNRs@YSiO2, hereafter GNR@YS). Composite nanocapsules (hereafter GNR@YS‐CyN) are prepared from GNR@YS loaded with CyN to treat subcutaneous tumor. Cyanine dye (CyCl) with similar absorption to gold nanorods is also synthesized to match the existing commercial 808 nm laser. The results show that both materials have good therapeutic effect, but differ in healing scabs on skin tissue surface after tumor ablation. GNR@YS‐CyN are superior to CyCl in the treatment of subcutaneous tumor. This may be the size effect of GNR@YS‐CyN has permeability and retention enhancement effect at the tumor site. GNR@YS‐CyN have no obvious dye diffusion phenomenon, which reduces the damage to normal tissue.

Abstract B44: Selective stimulation of RIG-I with a novel synthetic RNA induces strong anti-tumor immunity in mouse tumor models

Abstract We describe a novel immunotherapy approach in which a natural viral defense system is harnessed to stimulate anti-tumor immunity. Cancer immunotherapy has revolutionized oncology in recent years, yet many tumors become resistant or do not respond to current treatments such as checkpoint inhibitors. Stimulation of the innate immune system opens a new therapeutic strategy that could be combined effectively with other immunotherapeutic regimens. The ubiquitously expressed cytosolic RNA receptor retinoic acid inducible gene I (RIG-I) recognizes double-stranded RNA bearing a 5'-triphosphate. RIG-I plays a prominent role in antiviral defense. Its activation induces apoptosis preferentially in tumor cells and simultaneously activates the innate immune system via type I interferon (IFN) signaling. We developed an optimized, fully synthetic oligonucleotide, designated RGT100, which is a RIG-I selective ligand. RGT100 activates the RIG-I pathway leading to the induction of cytokines, including IFN-α and IFN-β. The treatment of tumor-bearing mice with RGT100 induced potent anti-tumor activity against large established B16 melanoma and CT26 colon carcinoma tumors. RGT100 also was efficacious in a spontaneous melanoma model. Histological and flow cytometric analysis of the tumors revealed infiltration and activation of immune cells after RGT100 treatment. RGT100 induced a strong and durable type I IFN response in tumors. Treatment of subcutaneous tumors by intratumor injection led to efficacy of both the treated tumors as well as untreated contralateral tumors. Furthermore, systemic delivery of RGT100 was efficacious against both local subcutaneous B16 melanoma as well as lung metastases. Data support both rapid natural killer (NK) cell-mediated and long-term T cell-mediated anti-tumor activities. Depletion of NK cells blocked the immediate anti-tumor activity of RGT100. In summary, Rigontec's RIG-I-selective ligand RGT100 shows strong anti-tumor activity in several clinically relevant mouse tumor models, while bearing an advantageous safety profile. RGT100 is rapidly progressing toward clinical evaluation in cancer patients. This agent will be evaluated both for single-agent activity as well as in combination with checkpoint inhibitors. Citation Format: Jim Barsoum, Marcel Renn, Christine Schuberth, Christopher Jakobs, Anna Schwickart, Martin Schlee, Jasper van den Boorn, Gunther Hartmann. Selective stimulation of RIG-I with a novel synthetic RNA induces strong anti-tumor immunity in mouse tumor models. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr B44.

Abstract A18: The integrin αvβ6 regulates PDAC cell growth and stromal cell behavior

Abstract Pancreatic adenocarcinoma (PDAC) is the fourth leading cause of cancer-related death in the UK. Five-year survival rates are less than 3% and haven’t improved over the last 40 years. Thus novel approaches are required urgently. We have found that over 90% of PDAC express αvβ6 and high expression of the integrin β6 gene (ITGB6) correlates with a significant reduction (Hazard Ratio 2.07; Logrank p=3.17x10-8) in overall survival from PDAC. Thus we have examined the biological functions mediated by αvβ6 in PDAC cell lines. A panel of human PDAC cell lines was incubated with αvβ6-blocking antibodies in order to define the role of αvβ6 in vitro. Some cell lines were driven into G2/M cell cycle arrest (Panc0403), whilst others died through apoptosis (CfPac1). Moreover, adhesion, migration and invasion through Matrigel were suppressed by blockade of αvβ6. Treatment of subcutaneous tumors composed of human αvβ6-positive cell lines in combination with human pancreatic stellate cells, with an αvβ6-blocking antibody resulted in significantly reduced tumor volume and growth rate in vivo, via modulation of the stromal compartment. In combination, these data suggested that targeting αvβ6 may be an effective therapeutic strategy in PDAC. To investigate the biological roles and molecular bases of αvβ6 in PDAC, cell lines were generated from PDAC tumors of a novel PDAC transgenic mouse. Two primary cell populations from PDAC tumors, abbreviated as KVC1 and KPCD3, demonstrated both epithelial and mesenchymal characteristics. Thus, cells were subsequently sorted by FACS to obtain high-αvβ6 expressing monoclonal cell lines. Resultant monoclonal cell lines expressed higher levels of αvβ6 than the parental line and expressed only epithelial markers. Transduction with lentivirus particles containing shRNA to itgb6 under a tetracycline-inducible promoter (SMARTvector, Dharmacon) was optimized for four high-αvβ6 expressing monoclonal cell lines, and doxycycline-induced knock-down of β6 protein was 70-80%, confirmed using FACS and western blotting. In vitro functional assays demonstrated that knock-down of itgb6 reduced invasion of Matrigel. To assess the role of αvβ6 in an assay that better reflected the PDAC environment, we developed 3D organotypic assays with inducible knockout PDAC combined with mouse embryo fibroblasts or mouse pancreatic stellate cells. Doxycycline treatment reduced PDAC tumor cell growth and invasion, but also reduced the contraction of the collagen-Matrigel gel matrix. Since αvβ6 activates TGFβ, and as TGFβ promotes fibroblast and stellate cell contractile propensity, current studies will determine whether this is the mechanism of how αvβ6 regulates stromal cell behavior. Citation Format: Claire S. Reader, Jennifer P. Morton, Owen J. Sansom, John F. Marshall.{Authors}. The integrin αvβ6 regulates PDAC cell growth and stromal cell behavior. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr A18.

Imaging‐Guided Combined Photothermal and Radiotherapy to Treat Subcutaneous and Metastatic Tumors Using Iodine‐131‐Doped Copper Sulfide Nanoparticles

Combining different therapeutic strategies to treat cancer by overcoming limitations of conventional cancer therapies has shown great promise in both fundamental and clinical studies. Herein, by adding 131I when making iodine‐doped CuS nanoparticles, CuS/[131I]I nanoparticles are obtained, which after functionalization with polyethylene glycol (PEG) are used for radiotherapy (RT) and photothermal therapy (PTT), by utilizing their intrinsic high near‐infrared absorbance and the doped 131I‐radioactivity, respectively. The combined RT and PTT based on CuS/[131I]I‐PEG is then conducted, achieving remarkable synergistic therapeutic effects as demonstrated in the treatment of subcutaneous tumors. In the meanwhile, as revealed by bimodal nuclear imaging and computed tomography (CT) imaging, it is found that CuS/[131I]I‐PEG nanoparticles after being injected into primary solid tumors could migrate to and retain in their nearby sentinel lymph nodes. Importantly, the combined RT and PTT applied on those lymph nodes to assist surgical resection of primary tumors results in remarkably inhibited cancer metastasis and greatly prolonged animal survival. In vivo toxicology studies further reveal that our CuS/I‐PEG is not obviously toxic to animals at fourfold of the treatment dose. This work thus demonstrates the potential of combining RT and PTT using a single nanoagent for imaging‐guided treatment of metastatic tumors.

In Situ Vaccination with CD204 Gene-Silenced Dendritic Cell, not Unmodified Dendritic Cell, Enhances Radiation Therapy of Prostate Cancer

Given the complexity of prostate cancer progression and metastasis, multimodalities that target different aspects of tumor biology, for example, radiotherapy in conjunction with immunotherapy, may provide the best opportunities for promoting clinical benefits in patients with high-risk localized prostate cancer. Here, we show that intratumoral administration of unmodified dendritic cells (DC) failed to synergize with fractionated radiotherapy. However, ionizing radiation combined with in situ vaccination with DCs, in which the immunosuppressive scavenger receptor A (SRA/CD204) has been downregulated by lentivirus-mediated gene silencing, profoundly suppressed the growth of two mouse prostate cancers (e.g., RM1 and TRAMP-C2) and prolonged the lifespan of tumor-bearing animals. Treatment of subcutaneous tumors with this novel combinatorial radioimmunotherapeutic regimen resulted in a significant reduction in distant experimental metastases. SRA/CD204-silenced DCs were highly efficient in generating antigen or tumor-specific T cells with increased effector functions (e.g., cytokine production and tumoricidal activity). SRA/CD204 silencing-enhanced tumor cell death was associated with elevated IFN-γ levels in tumor tissue and increased tumor-infiltrating CD8(+) cells. IFN-γ neutralization or depletion of CD8(+) cells abrogated the SRA/CD204 downregulation-promoted antitumor efficacy, indicating a critical role of IFN-γ-producing CD8(+) T cells. Therefore, blocking SRA/CD204 activity significantly enhances the therapeutic potency of local radiotherapy combined with in situ DC vaccination by promoting a robust systemic antitumor immunity. Further studies are warranted to test this novel combinatorial approach for translating into improved clinical outcomes in patients with prostate cancer.

Oncolytic recombinant herpes simplex virus for treatment of orthotopic liver tumors in nude mice

Cell-specific, replicating viruses are being developed as a new class of oncolytic agents. A novel approach to viral gene therapy with the use of replication-competent herpes simplex virus has been described; G92A is a replication-competent, multimutant oncolytic herpes simplex virus (HSV) that has been evaluated for anticancer effects and selectivity in the treatment of subcutaneous tumors. G92A replicates efficiently in albumin-producing tumor cell lines but not in non-albumin-producing tumor cell lines, whereas both types are equally susceptible to a non-tissue-specific recombinant HSV, hrR3. In this study, we analyzed the antitumoral efficacy of a single intrasplenic G92A or hrR3 injection in nude mice. In vivo, G92A replicated well in liver xenografts of human albumin-producing hepatoma cells (Hep3B) but not in liver xenografts of a non-albumin-producing malignant colon tumor cell line (HT29), whereas hrR3 replicated well in both tumor types. G92A effectively and selectively replicated throughout liver tumors without apparent hepatotoxicity and inhibited tumor growth, leading to a significantly increased survival time. By monitoring lacZ histochemical staining, we determined the oncolytic potential of recombinant HSV against liver tumors. Our results indicate that G92A warrants further investigation as a clinical therapy against malignant liver tumors.

The Course of Tissue Permeabilization Studied on a Mathematical Model of a Subcutaneous Tumor in Small Animals

One of the ways to potentiate antitumor effectiveness of chemotherapeutic drugs is by local application of short intense electric pulses. This causes an increase of the cell membrane permeability and is called electropermeabilization. In order to study the course of tissue permeabilization of a subcutaneous tumor in small animals, a mathematical model was built with the commercial program EMAS, which uses the finite element method. The model is based on the tissue specific conductivity values found in literature, experimentally determined electric field threshold values of reversible and irreversible tissue permeabilization, and conductivity changes in the tissues. The results obtained with the model were then compared to experimental results from the treatment of subcutaneous tumors in mice and a good agreement was obtained. Our results and the reversible and irreversible thresholds used coincide well with the effectiveness of the electrochemotherapy in real tumors where experiments show antitumor effectiveness for amplitudes higher than 900 V/cm ratio and pronounced antitumor effects at 1300 V/cm ratio.

Chemoimmunotherapy for melanoma with dacarbazine and 2,4-dinitrochlorobenzene: results from a murine tumour model.

An empirically established chemoimmunotherapy that combines the epifocal application of the contact sensitizer dinitrochlorobenzene (DNCB) to cutaneous metastases with the systemic administration of dacarbazine (DTIC) yields high response rates and results in prolonged survival. However, despite the fact that this therapy has been in clinical use for several years, the mode of action still remains elusive. In order to overcome this limitation we established a murine model system. B16 melanoma cells were implanted subcutaneously in syngeneic C57BL/6 mice and treatment was started 7 days after. In a first set of experiments mice received intraperitoneal injections of DTIC followed by epifocal applications of DNCB 24 h later. Treatment significantly decreased tumour growth. In contrast, no significant effect was induced by DTIC or DNCB alone. Using this regimen, with varying doses of either DTIC or DNCB, we demonstrated that the therapeutic effect is dose dependent. Furthermore, the treatment of subcutaneous tumours with DTIC and DNCB influenced the course of visceral metastases: the growth of pulmonary metastases was significantly inhibited if subcutaneous tumours were treated as described. In conclusion, we have established a model system that seems to be appropriate for both the optimization of this therapeutic regimen and the characterization of effector mechanisms.

A novel telomerase-specific gene therapy: gene transfer of caspase-8 utilizing the human telomerase catalytic subunit gene promoter.

Apoptosis is a genetically encoded cell death process and is a pathway that may be disrupted in tumor cells. Therefore, therapies that restore the ability to undergo apoptosis are promising for the treatment of tumor cells. We have demonstrated that the transfer of apoptosis-inducible genes inhibits the growth of tumors in vitro and in vivo through induction of apoptosis. However, to restrict induction of apoptosis to tumor cells, we need to explore a tumor-specific expression system of these genes. In the present study, we developed the telomerase-specific transfer system of apoptosis-inducible genes, utilizing the promoter of the human telomerase catalytic subunit (hTERT) gene. Approximately 90% of tumors have telomerase activity whereas most normal cells do not express the activity. These observations indicate that telomerase is a particularly attractive target for the tumor-specific expression system of vectors. We demonstrate here that by using the hTERT promoter-driven caspase-8 expression vector (hTERT/caspase-8), apoptosis is restricted to telomerase-positive tumor cells of wide range, and is not seen in normal fibroblast cells without telomerase activity. Furthermore, treatment of subcutaneous tumors in nude mice with the hTERT/caspase-8 construct inhibited tumor growth significantly because of induction of apoptosis (p < 0.01). The telomerase-specific expression of apoptosis-inducible genes afforded by the hTERT promoter, therefore, may be a novel and promising targeting approach for the treatment of tumors with telomerase activity.

Treatment of prostate cancer in vitro and in vivo with 2-5A-anti-telomerase RNA component.

Prostate cancer is the most common malignancy of elderly men in the United States. Since there is no curative treatment for advanced prostate cancer, exploration of novel modalities of treatment is essential. Telomerase, a ribonucleoprotein, is detected in the vast majority of prostate cancer, but not in normal or benign prostatic hyperplasia tissues. Thus, telomerase is expected to be a very strong candidate for targeted therapy of prostate cancer. In this study, we synthesized a 19-mer antisense oligonucleotide against the RNA component of human telomerase (hTR) linked to a 2-5A molecule (2-5A-anti-hTR) and examined its cytotoxic effect on prostate cancer cells. The 2-5A antisense strategy relies on the recruitment and activation of RNase L at the site of targeted RNA sequence. We here show that treatment with 2-5A-anti-hTR in the presence of a cationic liposome reduced cell viability of tumor cell lines tested to 9-18% within 6 days. In contrast, normal fibroblast cells were resistant to the treatment. Its effect was mainly due to induction of apoptosis by activated caspase family members. Furthermore, treatment of subcutaneous tumors in nude mice with 2-5A-anti-hTR significantly suppressed the tumor growth through induction of apoptosis (P<0.001). The treatment with 2-5A-anti-hTR may be a promising strategy for the treatment modality of prostate cancer with telomerase activity.

Mycobacterium vaccae (SRL172): a potential immunological adjuvant evaluated in rat prostate cancer.

To evaluate the potential of heat-killed Mycobacterium vaccae (SRL172) as a nonspecific immunostimulant and as an adjuvant to whole tumour cell vaccination in the rat model of prostate cancer. SRL172 was used as a vaccine in the prevention and treatment of subcutaneous tumours in rats. Prevention experiments were conducted using subcutaneous MAT-LyLu tumours in Copenhagen rats, comparing vaccination with SRL172 alone, SRL172 plus autologous cells, and bacille Calmette-Guèrin (BCG) plus autologous cells before tumour implantation. Treatment experiments were conducted using subcutaneous MAT-LyLu tumours in the Copenhagen rat and subcutaneous PAIII tumours in the Lobund-Wistar rat. Tumours were induced by subcutaneous injection with tumour cells. Animals were then vaccinated with autologous cells, autologous cells plus SRL172, or SRL172 alone. SRL172 was effective as an adjuvant to autologous whole tumour cell vaccination in the prevention of MAT-LyLu tumours and the survival benefit was equivalent to that provided when the adjuvant was live-attenuated BCG. SRL172 alone did not reduce tumour take or tumour growth in this model and neither strategy was effective in delaying the growth of established MAT-LyLu tumours. In the Lobund-Wistar rat vaccination with autologous whole tumour cells and SRL172 significantly delayed the growth of established tumours. Mycobacterium vaccae deserves further evaluation as an adjuvant to whole tumour cell vaccination in a phase I clinical trial in patients with prostate cancer.

Tumor cell-specific transgene expression prevents liver toxicity of the adeno-HSVtk/GCV approach.

Treatment of colorectal liver metastases with the HSVtk/GCV approach and adenoviral vectors is highly toxic. We present a nontoxic alternative using the cell type-specific CEA promoter instead of the widely used hCMV immediate-early promoter to drive tk gene expression in the context of a recombinant adenovirus. Analysis of CEA promoter-dependent tk gene expression showed significant activity of this promoter in several human and rat tumor-derived cell lines but not in rat primary hepatocytes and in mouse liver, whereas the CMV promoter was highly active in all cell types and tissues investigated. CEA promoter-dependent tk gene expression was sufficient to kill 100% of cancer cells in vitro, even if less than 10% were infected by the adenoviral vector, indicating a significant bystander effect. Moreover, treatment of subcutaneous tumors in SCID mice with Ad.CEA-tk led to a several-fold reduction of tumor growth, and tail vein injection of a high dose of Ad.CEA-tk caused no side-effects in the liver. The CMV promoter was more potent than the CEA promoter in mediating GCV sensitivity to cancer cells in vitro and in vivo, but even a 20-fold reduction of the dose of Ad.CMV-tk did not prevent its liver cell toxicity after systemic application to mice and still resulted in the death of all animals within 4 days after the start of GCV treatment. These results indicate that restriction of tk gene expression to tumor cells in the liver prevents systemic toxicity. Moreover, the CEA promoter is a safe and efficient tool for tumor cell-specific expression of suicide genes in the liver.

Antitumor and antimetastatic activity of interleukin 12 against murine tumors.

It has recently been demonstrated that in vivo administration of murine interleukin 12 (IL-12) to mice results in augmentation of cytotoxic natural killer (NK)/lymphocyte-activated killer cell activity, enhancement of cytolytic T cell generation, and induction of interferon gamma secretion. In this study, the in vivo activity of murine IL-12 against a number of murine tumors has been evaluated. Experimental pulmonary metastases or subcutaneous growth of the B16F10 melanoma were markedly reduced in mice treated intraperitoneally with IL-12, resulting in an increase in survival time. The therapeutic effectiveness of IL-12 was dose dependent and treatment of subcutaneous tumors could be initiated up to 14 d after injection of tumor cells. Likewise, established experimental hepatic metastases and established subcutaneous M5076 reticulum cell sarcoma and Renca renal cell adenocarcinoma tumors were effectively treated by IL-12 at doses which resulted in no gross toxicity. Local peritumoral injection of IL-12 into established subcutaneous Renca tumors resulted in regression and complete disappearance of these tumors. IL-12 was as effective in NK cell-deficient beige mice or in mice depleted of NK cell activity by treatment with antiasialo GM1, suggesting that NK cells are not the primary cell type mediating the antitumor effects of this cytokine. However, the efficacy of IL-12 was greatly reduced in nude mice suggesting the involvement of T cells. Furthermore, depletion of CD8+ but not CD4+ T cells significantly reduced the efficacy of IL-12. These results demonstrate that IL-12 has potent in vivo antitumor and antimetastatic effects against murine tumors and demonstrate as well the critical role of CD8+ T cells in mediating the antitumor effects against subcutaneous tumors.