Low electric field enhanced chemotherapy can cure mice with CT-26 colon carcinoma and induce anti-tumour immunity

Tamibarotene-Loaded PLGA Microspheres for Intratumoral Injection Administration: Preparation and Evaluation

Tamibarotene (Am80) has good curative effect on advanced hepatocellular carcinoma (HCC). To improve the therapeutic efficacy furtherly, we prepared tamibarotene-loaded PLGA microspheres (Am80-PLGA-MS) for intratumoral injection. Firstly, Am80-PLGA-MS were prepared by emulsion-solvent evaporation method. Subsequently, microspheres were characterized by particle size analysis, drug loading (DL), and entrapment efficiency (EE). Finally, the drug release characteristics in vitro, pharmacokinetic, and pharmacodynamics were studied separately. According to results obtained, microspheres were spherical with a uniform particle size 7.04 ± 0.03 μm and its EE and DL were 82.23 ± 0.74 and 11.74 ± 0.11%, respectively. In vitro, Am80-PLGA-MS can release drug for 14 days and its release behavior was fitted with the Higuchi equation. In pharmacokinetic studies, the t1/2β, MRT, and AUC of microspheres were 15.43-fold, 8.62-fold, and 9.98-fold those of Am80 solution, respectively, which revealed that the utilization of drug was improved obviously. The pharmacodynamics studies showed that the tumor doubling time, growth inhibition rate, and specific growth rate of tumor of Am80-PLGA-MS were 1.34 times, 2.63 times, and 0.72 times those of drug solution, respectively, indicating that the inhibitory effect on tumor by the microspheres was significantly improved. In summary, Am80-PLGA-MS are promising carrier to enhance the inhibitory effect on tumor, which will provide significantly clinical value for treatment of HCC.

Synergistic combinations of short high-voltage pulses and long low-voltage pulses enhance irreversible electroporation efficacy

Irreversible electroporation (IRE) uses ~100 μs pulsed electric fields to disrupt cell membranes for solid tumor ablation. Although IRE has achieved exciting preliminary clinical results, implementing IRE could be challenging because of volumetric limitations at the ablation region. Combining short high-voltage (SHV: 1600V, 2 μs, 1 Hz, 20 pulses) pulses with long low-voltage (LLV: 240-480 V, 100 μs, 1 Hz, 60-80 pulses) pulses induces a synergistic effect that enhances IRE efficacy. Here, cell cytotoxicity and tissue ablation were investigated. The results show that combining SHV pulses with LLV pulses induced SKOV3 cell death more effectively, and compared to either SHV pulses or LLV pulses applied alone, the combination significantly enhanced the ablation region. Particularly, prolonging the lag time (100 s) between SHV and LLV pulses further reduced cell viability and enhanced the ablation area. However, the sequence of SHV and LLV pulses was important, and the LLV + SHV combination was not as effective as the SHV + LLV combination. We offer a hypothesis to explain the synergistic effect behind enhanced cell cytotoxicity and enlarged ablation area. This work shows that combining SHV pulses with LLV pulses could be used as a focal therapy and merits investigation in larger pre-clinical models and microscopic mechanisms.

Tumor ablation by intratumoral Ra-224-loaded wires induces anti-tumor immunity against experimental metastatic tumors

INTRODUCTION

The current systemic anti-metastatic treatment is chemotherapy. Chemotherapy reacts mostly against replicating cells, which makes this therapy not specific. Moreover, resting cancer cells will not be destroyed. A better alternative is an engagement of the host immune system to react against tumor-associated antigens. An efficient immune-stimulating technique is an ablation of the tumor that results in the release of tumor antigens. Our ablation strategy is an innovative alpha-radiation-based technology, diffusing alpha-emitters radiation therapy (DaRT), which efficiently destroys local tumors and provides thereby an antigenic supply for antigen-presenting cells to stimulate T cells.

METHODS

Mice bearing weakly immunogenic DA3 adenocarcinoma or highly immunogenic CT26 colon carcinoma were treated by DaRT. Anti-tumor immune responses following tumor destruction were evaluated by (1) the resistance to a tumor challenge; (2) scanning by a CT imaging device for elimination of lung metastases; (3) improved tumor control when combining DaRT with an immunoadjuvant (CpG).

RESULTS

CT26 model: 63-77 % of DaRT-treated mice became resistant to a re-inoculated tumor compared to 29-33 % resistant mice in the control. DA3 model: (1) The growth rate of challenge tumors was the lowest in mice which their primary tumor was treated by DaRT. (2) Most (93 %) mice in the control group developed lung metastases compared to 56 % in the DaRT group. (3) Combining DaRT with CpG resulted in a better control of the primary tumor. Our study offers a technique to eliminate local and distant malignant cells, regardless of their replication status, by stimulating specific anti-tumor immunity through the supply of tumor antigens from the destroyed tumor.

Ablation of experimental colon cancer by intratumoral 224Radium-loaded wires is mediated by alpha particles released from atoms which spread in the tumor and can be augmented by chemotherapy

PURPOSE

We developed (224)Ra-loaded wires, which release by recoil alpha emitting nuclei into solid tumors and cause tumor cell killing. This research examined if the major damage was inflicted by alpha particles emitted from these atoms or by direct gamma and beta emissions from the inserted wires. We also examined the efficacy of this treatment against colon cancer in combination with chemotherapy.

MATERIALS AND METHODS

Mouse colon carcinomas (CT-26 xenografts), treated by intra-tumoral radioactive wires loaded with (224)Ra atoms were monitored for effects on tumor growth, intratumoral tissue damage and distribution of alpha emitting atoms. The effects were compared with those of (224)Ra-loaded wires coated with poly methyl methacrylate (PMMA), which blocks atom recoil. Similar experiments were performed with radioactive wires combined with systemic 5-FU.

RESULTS

(224)Ra-loaded wires inhibited tumor growth and formed necrotic areas inside the tumor. PMMA coated wires did not inhibit tumor growth, and caused minor intratumoral damage. Autoradiography images of tumors treated with (224)Ra-loaded wires revealed a spread of alpha emitters over several mm, whereas PMMA-coated wires showed no such spread. Injection of 5-FU with (224)Ra-loaded wires augmented tumor growth retardation and cure.

CONCLUSIONS

(224)Ra-loaded wires ablate solid tumors by the release of alpha-particle emitting atoms inside the tissue, an effect that can be enhanced by combining this method with chemotherapy.

Activation of local and systemic anti-tumor immune responses by ablation of solid tumors with intratumoral electrochemical or alpha radiation treatments

Cancer, the most devastating chronic disease affecting humankind, is treated primarily by surgery, chemotherapy, and radiation therapy. Surgery and radiotherapy are mainly used for debulking the primary tumor, while chemotherapy is the most efficient anti-metastatic treatment. To control better metastatic cancer, the host immune system should be stimulated. Yet, successful specific stimulation of the immune system against tumors was seldom achieved even in antigenic tumors. Our working hypothesis is that aggressive in situ tumor ablation can release tumor antigens and danger signals, which will enhance anti-tumor T cell responses resulting in the destruction of residual malignant cells in primary tumors and distant metastases. We developed two efficient in situ ablation treatments for solid cancer, which can be used to destroy the primary tumors and stimulate anti-tumor immune responses. The first treatment, electrochemical ablation, is applied through intratumoral electrodes, which deliver unipolar-pulsed electric currents. The second treatment, diffusing alpha-emitters radiation therapy (DaRT), is based on intratumoral (224)Ra-loaded wire(s) that release by recoil its daughter atoms. These short-lived alpha-emitting atoms spread in the tumor and spray it with lethal alpha particles. It was confirmed that these treatments effectively destroy various malignant animal and human primary solid tumors. As a consequence of such tumor ablation, tumor-derived antigenic material was released and provoked systemic T cell-dependent anti-tumor immunological reactions. These reactions conferred protection against a secondary tumor challenge and destroyed remaining malignant cells in the primary tumor as well as in distant metastases. Such anti-tumor immune responses could be further amplified by the immune adjuvant, CpG. Electrochemical ablation or DaRT together with chemotherapy and immunostimulatory agents can serve as treatment protocols for solid metastatic tumors and can be applied instead of or in combination with surgery.

Enhanced delivery of macromolecules into cells by electroendocytosis

Transfer of exogenous material into the cytosol of cells is one of the main challenges in drug delivery. We present a novel physical approach for efficient incorporation of macromolecules into living cells, based on exposing them to a train of unipolar electric field pulses, possessing much lower amplitude than used for electroporation. The exposure of cells to a low electric field (LEF) alters the cell surface, leading to enhanced adsorption of macromolecules and their subsequent uptake by stimulated endocytosis. The macromolecules are initially encapsulated in membrane vesicles and then, at a later stage, are released into the cytosol and interact with intracellular targets. The uptake of fluorescently labeled macromolecules is monitored using confocal microscopy and flow cytometry. The biological activities of the incorporated macromolecules are determined by biochemical methods.

Effective treatment of mouse metastatic prostate cancer by low electric field enhanced chemotherapy

BACKGROUND

We developed a new anti-cancer treatment, which is a combination of chemotherapeutic agents and low electric field. In the present study we investigated its efficacy against prostate metastatic transgenic adenocarcinoma of mice (TRAMP).

METHODS

Mice with 5, 10, and 13 mm in diameter intracutaneous tumors received Low Electric Field Cancer Treatment-Enhanced Chemotherapy (LEFCT-EC) with doxorubicin (10 mg/kg), and monitored for survival, and primary and metastatic tumors growth.

RESULTS

The electric field increased the uptake of doxorubicin by TRAMP cells in vitro. In vivo use of LEFCT-EC reduced tumor size, prolonged survival, and cured 36-93% of the animals, dependent on treated tumor size. LEFCT-EC was more effective than surgery with or without chemotherapy. Part of the cured animals developed anti-tumor immunity and immunosuppression, significantly decreased the effectiveness of the treatment.

CONCLUSION

Our results suggest that LEFCT-EC is an effective method for the destruction of metastatic prostate tumors.

Involvement of the immune response in the cure of metastatic murine CT-26 colon carcinoma by low electric field-enhanced chemotherapy

Low electric field cancer treatment-enhanced chemotherapy (LEFCT-EC) is a new treatment modality that combines chemotherapeutic agents and low electric field stimulation. LEFCT-EC was found to destroy malignant mouse tumors and cause massive death of tumor cells. This may enable the immune system cells to efficiently recognize and eliminate tumor cells at the primary tumor site and at metastatic foci. Mice with 15 mm diameter intracutaneous colon carcinomas (CT-26) were injected with BCNU (35 mg/kg), and 2 min later the tumors were exposed to low electric fields (intensity 40 V/cm, pulse duration 180 micros, frequency 500 Hz) for 12 min (LEFCT-EC). We found that treatment with LEFCT-EC achieved complete cure of 93% of the animals. In comparison, electric fields alone (13% cure), chemotherapy alone (0%), surgery (15%) or a combination of surgery and bis-chloroethyl-nitrosurea, carmustine (BCNU; 84%) treatments resulted in lower cure rates. After treatment and cure with LEFCT-EC, 50% of the cured mice developed resistance to a tumor challenge (surgery + BCNU only 15%). Furthermore, splenocytes from cured animals protected naive animals from a tumorigenic dose of tumor cells. Separation of spleen cells into lymphocyte subpopulations indicated a major role for CD4 and CD8 T cells in this protection. FACS analysis revealed restoration of normal splenocyte subpopulation proportions impaired by cytotoxic chemotherapy. Our results suggest that LEFCT-EC can directly destroy primary tumors and facilitate the destruction of metastatic disease by enforcement of antitumor immune responses.