Cancer immunotherapy using tumor cryoablation

KCl enhances the cryoablation-induced antitumor immune response: A hepatocellular carcinoma murine model research

Cryoablation is a valuable treatment for liver cancer. To investigate the effect of KCl solution on the immunological response post cryoablation, we created a tumor-bearing mice model by subcutaneously implanting Hepal-6 cells in adult Balb/c mice. Subsequently, the mice were randomly assigned to three groups: group A (sham cryoablation), group B (cryoablation), and group C (cryoablation plus KCl solution). Mice were sacrificed on days 0, 7, and 14 post-treatment. Immune cell populations were assessed using flow cytometry. Blood samples were analyzed for serum IL-4, HSP70, and TGF-β1 levels with ELISA assays. Ablated tissues stained with immunohistochemistry were utilized to evaluate Ki67 expression at the margins of the ablation site. Our findings revealed higher HSP70 expression levels in groups B and C compared to group A. Cryoablation triggered an immune response, which was enhanced by KCl. On days 0, 7, and 14, the percentages of CD4+ T cells, CD8+ T cells, and NK cells in the spleen of group C were significantly increased compared with groups A and B. Additionally, the Th1/Th2 ratio was significantly increased in group C. Serum TGF-β1 expression was elevated after cryoablation, but KCl solution reduced the high TGF-β1 expression after cryoablation and decreased the invasiveness of cancer cells. Finally, the proliferative activity of untreated tumor tissue was significantly reduced in group C compared to groups A and B. In summary, Cryoablation triggered a systemic immune response in tumor-bearing mice, which was further boosted by combining cryoablation with a KCl solution.

Intratumoural immunotherapy plus focal thermal ablation for localized prostate cancer

Major advances have been made in the use of immunotherapy for the treatment of solid tumours, including the use of intratumourally injected immunotherapy instead of systemically delivered immunotherapy. The success of immunotherapy in prostate cancer treatment has been limited to specific populations with advanced disease, which is thought to be a result of prostate cancer being an immunologically 'cold' cancer. Accordingly, combining intratumoural immunotherapy with other treatments that would increase the immunological heat of prostate cancer is of interest. Thermal ablation therapy is currently one of the main strategies used for the treatment of localized prostate cancer and it causes immunological activation against prostate tissue. The use of intratumoural immunotherapy as an adjunct to thermal ablation offers the potential to elicit a systemic and lasting adaptive immune response to cancer-specific antigens, leading to a synergistic effect of combination therapy. The combination of thermal ablation and immunotherapy is currently in the early stages of investigation for the treatment of multiple solid tumour types, and the potential for this combination therapy to also offer benefit to prostate cancer patients is exciting.

Abscopal downstaging of intermediate stage hepatocellular via combination cryoablation and immunotherapy with complete pathologic response

The abscopal effect is a rare phenomenon characterized by disease regression in distant sites after tumoral locoregional therapy. Locoregional therapy, such as cryoablation, can induce an antitumor immunological response, potentially improving outcomes in cancer patients receiving immunotherapy. This report describes a patient with multifocal hepatocellular carcinoma who progressed through multiple locoregional therapies, was initially unresponsive to immunotherapy, and later achieved rapid and sustained disease regression with a combination cryoablation and immunotherapy. A 5-year sustained complete tumor response successfully bridged to liver transplantation.

Cryoablation for the treatment of breast cancer: immunological implications and future perspectives. Utopia or reality?

Cryoablation is a minimally invasive technique currently employed in breast cancer care, that uses freeze and thaw cycles to treat benign breast lesions, small breast cancers or focal sites of metastatic disease in patients not eligible for surgery. The final goal of this procedure is to destroy breast cancer cells using extreme cold. In addition, several studies have shown that this technique seems to have an enhancing effect on the immune response, especially by increasing the expression of tumor neoantigens specific to tumor cells, which are then attacked and destroyed. Exploiting this effect, cryoablation in combination with immunotherapy could be the key to treating early-stage breast cancers or patients who are unsuitable for surgery. According to some recent studies, there are other potential tools that could be used to enhance the therapeutic effect of cryoablation, such as FE3O4 nanoparticles or the manipulation of aquaporin expression. The aim of this narrative review is to summarize the current evidence regarding the use, indications, advantages and disadvantages of cryoablation in the treatment of breast cancer.

In-situ cryo-immune engineering of tumor microenvironment with cold-responsive nanotechnology for cancer immunotherapy

Cancer immunotherapy that deploys the host's immune system to recognize and attack tumors, is a promising strategy for cancer treatment. However, its efficacy is greatly restricted by the immunosuppressive (i.e., immunologically cold) tumor microenvironment (TME). Here, we report an in-situ cryo-immune engineering (ICIE) strategy for turning the TME from immunologically "cold" into "hot". In particular, after the ICIE treatment, the ratio of the CD8+ cytotoxic T cells to the immunosuppressive regulatory T cells is increased by more than 100 times in not only the primary tumors with cryosurgery but also distant tumors without freezing. This is achieved by combining cryosurgery that causes "frostbite" of tumor with cold-responsive nanoparticles that not only target tumor but also rapidly release both anticancer drug and PD-L1 silencing siRNA specifically into the cytosol upon cryosurgery. This ICIE treatment leads to potent immunogenic cell death, which promotes maturation of dendritic cells and activation of CD8+ cytotoxic T cells as well as memory T cells to kill not only primary but also distant/metastatic breast tumors in female mice (i.e., the abscopal effect). Collectively, ICIE may enable an efficient and durable way to leverage the immune system for combating cancer and its metastasis.

Transarterial Embolization Modulates the Immune Response within Target and Nontarget Hepatocellular Carcinomas in a Rat Model

Background Transarterial embolization (TAE) is the most common treatment for hepatocellular carcinoma (HCC); however, there remain limited data describing the influence of TAE on the tumor immune microenvironment. Purpose To characterize TAE-induced modulation of the tumor immune microenvironment in a rat model of HCC and identify factors that modulate this response. Materials and Methods TAE was performed on autochthonous HCCs induced in rats with use of diethylnitrosamine. CD3, CD4, CD8, and FOXP3 lymphocytes, as well as programmed cell death protein ligand-1 (PD-L1) expression, were examined in three cohorts: tumors from rats that did not undergo embolization (control), embolized tumors (target), and nonembolized tumors from rats that had a different target tumor embolized (nontarget). Differences in immune cell recruitment associated with embolic agent type (tris-acryl gelatin microspheres [TAGM] vs hydrogel embolics) and vascular location were examined in rat and human tissues. A generalized estimating equation model and t, Mann-Whitney U, and χ2 tests were used to compare groups. Results Cirrhosis-induced alterations in CD8, CD4, and CD25/CD4 lymphocytes were partially normalized following TAE (CD8: 38.4%, CD4: 57.6%, and CD25/CD4: 21.1% in embolized liver vs 47.7% [P = .02], 47.0% [P = .01], and 34.9% [P = .03], respectively, in cirrhotic liver [36.1%, 59.6%, and 4.6% in normal liver]). Embolized tumors had a greater number of CD3, CD4, and CD8 tumor-infiltrating lymphocytes relative to controls (191.4 cells/mm2 vs 106.7 cells/mm2 [P = .03]; 127.8 cells/mm2 vs 53.8 cells/mm2 [P < .001]; and 131.4 cells/mm2 vs 78.3 cells/mm2 [P = .01]) as well as a higher PD-L1 expression score (4.1 au vs 1.9 au [P < .001]). A greater number of CD3, CD4, and CD8 lymphocytes were found near TAGM versus hydrogel embolics (4.1 vs 2.0 [P = .003]; 3.7 vs 2.0 [P = .01]; and 2.2 vs 1.1 [P = .03], respectively). The number of lymphocytes adjacent to embolics differed based on vascular location (17.9 extravascular CD68+ peri-TAGM cells vs 7.0 intravascular [P < .001]; 6.4 extravascular CD68+ peri-hydrogel embolic cells vs 3.4 intravascular [P < .001]). Conclusion Transarterial embolization-induced dynamic alterations of the tumor immune microenvironment are influenced by underlying liver disease, embolic agent type, and vascular location. © RSNA, 2022 Online supplemental material is available for this article. See also the editorials by Kennedy et al and by White in this issue.

Cryoablation reshapes the immune microenvironment in the distal tumor and enhances the anti-tumor immunity

As one of the local treatments, cryoablation plays an increasingly important role in the comprehensive treatment of malignant tumors with its advantages of less trauma, high reproducibility, and minimally invasive. Activation of anti-tumor immunity, another characteristic of cryoablation, has attracted more and more attention with the extensive application of immunotherapy. Unfortunately, the mechanism by which cryoablation enhances anti-tumor immunity is still unclear. In this study, we applied a multi-omics approach to investigate the effects of local cryoablation in the distal tumor microenvironment. The results revealed that large amounts of tumor antigens were released post-cryoablation, leading to a sterile inflammatory response in distant tumors. During this period, activated lysosome-related pathways result in over-expression of SNAP23 (Synaptosome associated protein 23) and STXBP2 (Syntaxin binding protein 2), activation of immune effector cells, suppression of the release of immunosuppressive factors, and finally enhancement of anti-tumor immunity, which shows a broad prospect in combined immunotherapy.

Case Report: Antiangiogenic Therapy Plus Immune Checkpoint Inhibitors Combined With Intratumoral Cryoablation for Hepatocellular Carcinoma

Background

Hepatocellular carcinoma (HCC) is a common gastrointestinal malignancy with high incidence and poor prognosis. Common treatment methods include surgery, transcatheter arterial chemoembolization (TACE), ablation, and targeted therapy. In recent years, combination treatment with antiangiogenic therapy and immune checkpoint inhibitors has made great progress in the treatment of advanced HCC. Here, we report the case of a patient with HCC who achieved a durable benefit from anti-vascular therapy and immune checkpoint inhibitors combined with intratumoral cryoablation.

Main Body

A 38-year-old male patient initially presented with severe abdominal pain that was identified as an HCC rupture and hemorrhage by computed tomography (CT). The patient underwent emergency surgery and postoperative pathology confirmed HCC. The patient received prophylactic TACE after surgery. Unfortunately, three months after surgery, the patient developed multiple liver metastases. Subsequently, he received systemic anti-vascular therapy and immune checkpoint inhibitors combined with intratumoral cryoablation. After treatment, the patient achieved extensive tumor necrosis and the disease was effectively controlled.

Conclusions

Anti-angiogenic therapy and immune checkpoint inhibitors combined with cryoablation can induce a powerful and effective systemic anti-tumor immune response, which is worthy of further research.

Thermal ablation in non-small cell lung cancer: a review of treatment modalities and the evidence for combination with immune checkpoint inhibitors

Lung cancer is the leading cause of cancer death worldwide, with approximately 1.6 million cancer related deaths each year. Prognosis is best in patients with early stage disease, though even then five-year survival is only 55% in some groups. Median survival for advanced non-small cell lung cancer (NSCLC) is 8–12 months with conventional treatment. Immune checkpoint inhibitor (ICI) therapy has revolutionised the treatment of NSCLC with significant long-term improvements in survival demonstrated in some patients with advanced NSCLC. However, only a small proportion of patients respond to ICI, suggesting the need for further techniques to harness the potential of ICI therapy. Thermal ablation utilizes the extremes of temperature to cause tumour destruction. Commonly used modalities are radiofrequency ablation (RFA), cryoablation and microwave ablation (MWA). At present thermal ablation is reserved for curative-intent therapy in patients with localized NSCLC who are unable to undergo surgical resection or stereotactic ablative body radiotherapy (SABR). Limited evidence suggests that thermal ablative modalities can upregulate an anticancer immune response in NSCLC. It is postulated that thermal ablation can increase tumour antigen release, which would initiate and upregulated steps in the cancer immunity cycle required to elicit an anticancer immune response. This article will review the current thermal ablative techniques and their ability to modulate an anti-cancer immune response with a view of using thermal ablation in conjunction with ICI therapy.

Establishment of a modified percutaneous CT-guided paraspinal intramuscular VX-2 squamous cell carcinoma dual tumor model in rabbits

Background

The rabbit VX-2 tumor model is a commonly used transplanted tumor model and is widely used in surgical, radiological, and interventional studies. Most of the known tumor models for each site are single solid tumors. This study aimed to establish an accurate and stable intramuscular dual tumor model guided by computed tomography (CT).

Methods

In this study, we compared three different inoculation methods to select the most appropriate dual tumor model. Six New Zealand White rabbits were used as tumor-carrying rabbits for tumor harvesting. Thirty rabbits were divided into three groups as experimental rabbits. Group A applied the tumor cell suspension method, in which the suspension was injected into the designated location with a syringe under CT guidance. Groups B and C used tumor tissue strips obtained in vivo or under direct in vitro vision. The tumor tissue strips were implanted into the designated locations using a guide needle under CT guidance. The differences in tumorigenic rate, the size difference between bilateral tumors, and metastasis between the three methods were compared.

Results

It was found that group A obtained a 100% tumor survival rate, but the size of the tumor was more variable, and needle tract implantation metastasis occurred in 5 cases. In group B, tumor tissue strips were taken in vivo for implantation, in which one case failed to survive. Tumor tissue strips in group C were obtained in vitro under direct vision. The tumor tissue strips obtained in vitro by puncture using a biopsy needle in group C had a 100% tumorigenicity rate and stable tumor size. No significant needle tract implantation metastases were found in either group B or C. The variance of tumor size obtained in group A was significantly higher than in groups B and C. The variance of tumor size in group C was the smallest. Group C had high tumorigenicity and a more stable size and morphology of the formed tumors.

Conclusion

The results showed that the method of obtaining tumor tissue strips using in vitro direct vision puncture and implanting them into the muscle with CT guidance and guide needles can establish an accurate and stable dual tumor model. This dual tumor model can provide substantial support for relevant preclinical studies.

The efficacy of radiofrequency ablation versus cryoablation in the treatment of single hepatocellular carcinoma: A population-based study

BACKGROUND

Radiofrequency ablation (RFA) is an effective treatment for single hepatocellular carcinoma (HCC), but it is difficult to use against tumors in some locations and often leads to incomplete ablation as a result of the heat-sink effect. This study was conducted to evaluate the efficacy of cryoablation compared with that of RFA in the treatment of single HCC.

METHODS

This retrospective study was conducted based on the Surveillance, Epidemiology, and End Results (SEER) database. From 2004 to 2015, patients aged 40 to 79 diagnosed with HCC were included in the study. A propensity score matching (PSM) model was used to reduce selection biases.

RESULTS

Before PSM, the median overall survival (mOS) and median cancer-specific survival (mCSS) in the RFA group were slightly longer than those in the cryoablation group (p > 0.05). In the subgroup analysis, the mOS and mCSS of patients with tumor sizes <3, 3-5, and >5 cm who received RFA treatment were longer than those of patients given cryoablation treatment, but there was no significant difference (p > 0.05). Similar results were presented in patients at American Joint Committee on Cancer (AJCC) stages I and II. After PSM, the mOS and mCSS were slightly better in the RFA group than the cryoablation group but without significant differences. Univariate and multivariate analysis showed that cryoablation treatment was not an unfavorable factor for OS and CSS before or after PSM (p > 0.05). In the multivariable competing risk model, non-cancer-specific death was taken as a competing factor and cryoablation was also not unfavorable for the survival of patients before and after PSM (p > 0.05).

CONCLUSION

Cryoablation is non-inferior to RFA therapy for single HCC patients without lymph node invasion or distant metastasis.

Exceptional Response of Cryoablation Followed by Pembrolizumab in a Patient with Metastatic Cervical Carcinosarcoma with High Tumor Mutational Burden: A Case Report

Cervical carcinosarcoma is an extremely rare type of neoplasm that lacks standard of care. Preclinical and clinical evidence has suggested that cryoablation in combination with immunotherapy may result in a synergistic effect, generating a more robust immune response to distant lesions. A few clinical trials have evaluated the efficacy of such combination treatment in a variety of solid tumors, but with conflicting results. This report describes the first clinical efficacy of cryoablation followed by pembrolizumab observed in a patient with tumor mutational burden (TMB)-high metastatic cervical carcinosarcoma that was negative for programmed cell death protein 1 expression, microsatellite instability stable, and had mutations in DNA polymerase epsilon (POLE). She had achieved complete response (CR) after 3 months of pembrolizumab treatment and had maintained CR as of the time of submission of this manuscript, with a progression-free survival of 11 months and counting. The case exhibited an exceptional response to cryoablation followed by pembrolizumab, potentially attributed to mutations in POLE, which lead to an extremely high TMB. This report paves the avenue for establishing treatment regimens for patients with TMB-high cervical carcinosarcoma. KEY POINTS: Owing to its rarity, cervical carcinosarcoma has not been well characterized, and currently, there is no standard of care for this disease. This report describes the first case of clinical efficacy of cryoablation followed by pembrolizumab observed in a patient with tumor mutational burden-high metastatic cervical carcinosarcoma. The case exhibited an exceptional response (maintained CR as of the time of submission of this article: 11 months) to cryoablation followed by pembrolizumab. This is the first POLE-mutated cervical carcinosarcoma case.

Cryoablation In The Management Of Breast Cancer: Evidence To Date

Cryoablation has been successfully used to treat various type of solid tumors, including breast carcinomas. This ablation method has the advantage of being a minimally invasive procedure useful in various clinical situations, including early breast cancer and metastatic breast cancer, when co-morbidities preclude the use of surgical treatment. However, due to the small sample size of the available studies, reliable and definitive conclusions on the usefulness of cryoablation in patients with breast cancer could not be drawn. In fact, many aspects necessitate to be elucidated, regarding technical issues, indications, efficacy, imaging follow-up, and possible advantages over other percutaneous ablative methods. This review article has the aim to clarify the current evidence supporting cryoablation of breast cancer, and discuss the future perspectives, including those arising from the new studies on immunological effects related to cryoablation.

The renaissance of anti-neoplastic immunity from tumor cell demise

Cancer therapies can temporarily reduce tumor burdens by inducing malignant cell death. However, cancer cure is still far from realization because tumors often gain resistance to current treatment and eventually relapse. Accumulating evidence suggests that successful cancer interventions require anti-tumor immunity. Therapy-induced cell stress responses ultimately result in one or more cell death modalities, including apoptosis, autophagy, necroptosis, and pyroptosis. These irreversible dying processes are accompanied by active or passive release of cell death-associated molecular patterns (CDAMPs), which can be sensed by corresponding pattern recognition receptors (PRR) on tumor-infiltrating immune cells. This crosstalk with the immune system can reawaken immune surveillance in the tumor microenvironment (TME). This review focuses on immune-modulatory properties of anti-cancer regimens and CDAMP-mediated communications between cell stress responses and the immune contexture of TME. In addition, we describe how immunogenic cell death can elicit strong and durable anti-tumor immune responses.

Immunological Aspects of Cryoablation of Non-Small Cell Lung Cancer: A Comprehensive Review

In cryoimmunotherapy, target tumors are treated with cryoablation to generate antitumor immune responses. Because immune checkpoint inhibitors have demonstrated that lung cancer can be an immunotherapy-responsive disease, there has been renewed interest in the immunological aspects of cryoablation of lung cancer. Herein, we review preclinical and clinical trials of cryoablation of primary lung tumors. We examine the magnitude of cryoablation-induced antitumor immune responses and the synergy between cryoablation and either other immunotherapies or molecular targeted therapies to improve treatment responses in advanced lung cancer. We further discuss a rationale for the addition of cryoablation to immune checkpoint inhibitors for the treatment of advanced lung cancer, which is currently under clinical investigation.

Cryoablation inhibition of distant untreated tumors (abscopal effect) is immune mediated

Cryoablation is moderately effective against prostate cancer. Of note, the off-target or enlarged therapeutic effect after cryoablation is reported in routine clinical practice. To uncover it, we constructed a bilateral inguinal transplantation model of prostate cancer. All the mice were randomly subdivided into three groups: Group A (Control group), Group B (Surgery group), and Group C (Cryoablation group). All the procedures in three groups were conducted only for tumors in the target region (right groin). The tumors in untargeted region (left groin) received no treatment. We measured the growth of untargeted tumors and lung metastasis rate, and then explored the changes in a series of immune cells and danger signals. First, our results revealed the protective effect of cryoablation treatment against the abscopal tumor. The possible mechanism was mediated by an increase in the number of CD4⁺ T cells, CD8⁺ T cells, ratio T helper 1 (Th1)/Th2, the killing activity of cytotoxic T lymphocytes and NK cells. Hsp70 may be involved in the modulation of the immune response. The combination of weakened Ki67 activity and activated immune response delayed spectator tumor growth, decreased the pulmonary metastasis rate, and prolonged animal survival, with an inducible abscopal effect.

Laparotomy Cryoablation in Rabbit VX2 Pancreatic Carcinoma

OBJECTIVE

The aim of this study was to establish a suitable rabbit model and select the optimal protocol for laparotomy cryoablation of pancreatic carcinoma.

METHODS

VX2 tumor tissues were inoculated into rabbit pancreases to build the pancreatic carcinoma model; then, the tumor-bearing rabbits were randomly divided into 4 groups: control, treatment A (the cryoablated-iceball diameter was bigger than the tumor), treatment B (iceball was as big as the tumor), and treatment C (iceball was smaller than the tumor). Related laboratory tests were conducted, and survival time was recorded.

RESULTS

The VX2 pancreatic carcinoma model was successfully established, and serum neuron-specific enolase levels increased continuously after inoculation. Compared with controls, rabbits in treatments A and C groups had no significant survival benefit (P > 0.05), but treatment B significantly prolonged the survival time (P < 0.01).

CONCLUSIONS

VX2 pancreatic cancer model was successfully established with neuron-specific enolase as biomarker. Treatment B may be the optimal protocol for pancreatic carcinoma and a new treatment option for patients with unresectable pancreatic cancer.

Effect of Transcatheter Arterial Chemoembolization Combined with Argon-Helium Cryosurgery System on the Changes of NK Cells and T Cell Subsets in Peripheral Blood of Hepatocellular Carcinoma Patients

Hepatocellular carcinoma (HCC) is one of the most aggressive tumors in humans. T lymphocytes and natural killer (NK) cells are the body's first line of defense to prevent tumor cell growth. Previous studies have demonstrated that transcatheter arterial chemoembolization (TACE) combined with argon-helium cryosurgery system (AHCS) can effectively treat liver cancer. However, the mechanism of the treatment is unclear yet. In the current study, we investigated the effects of TACE combined with AHCS on the changes of T cell subsets and NK cells in peripheral blood of HCC. Our data show that alpha-fetoprotein (AFP) levels in peripheral blood were significantly up-regulated in HCC patients before treatment when compared with healthy people and reduced after TACE combined with AHCS treatment (P < 0.01). In addition, we found that CD4+ cells and NK cells decreased (P < 0.05) and CD8+ cells increased (P < 0.05) in HCC patients when compared with healthy people. After treatment, the CD4+ cells, CD4+/CD8+ ratio, and NK cells were dramatically increased in HCC patients (P < 0.05). In contrast, CD8+ cells were significantly decreased (P < 0.05). TACE combined with AHCS treatment significantly prolonged 1-year survival rate of HCC patients and did not show significant side effects. Taken together, our data indicate that TACE combined with AHCS treatment improves patients' immune system. It is a feasible and effective therapeutic method for HCC patients.

The Application of Cytidyl Guanosyl Oligodeoxynucleotide Can Affect the Antitumor Immune Response Induced by a Combined Protocol of Cryoablation and Dendritic Cells in Lewis Lung Cancer Model

BACKGROUND Recently, several combined therapeutic strategies and targeted agents have been under investigation for their potential role in lung cancer. The combined administration of dendritic cells (DCs) and immune-adjuvant cytidyl guanosyl oligodeoxynucleotide (CpG-ODN) after cryosurgery has proven to be an effective strategy for treating lung cancer. However, whether the application of CpG-ODN could affect the therapeutic results remained to be further explored. MATERIAL AND METHODS The Lewis lung cancer (LLC)-bearing mice received cryoablation and injection of ex vivo-cultured DCs into the peritumoral zone. Subsequently, CpG-ODN was administered to experimental animals 6 hours, 12 hours, and 24 hours after DC injection. The mice in the control group received coadministration of DCs and CpG-ODN simultaneously. Therapeutic effects were evaluated by survival rates. The resistance to rechallenge of LLC cell was assessed by lung metastasis and in vitro cytotoxicity of splenocytes. Furthermore, T-cell subsets and multiple cytokines (interleukin [IL]-4, -10, and-12; interferon [IFN]-γ; tumor necrosis factor [TNF]-α) in the blood were assessed to elucidate the underlying mechanisms. RESULTS Higher ratios of CD4+ and CD8+ T cells and higher levels of IL-12, IFN-γ, and TNF-α were found in the blood of the mice that received CpG-ODN therapy 12 h after DC injection. The cytotoxicity potency of the splenocytes of these mice was significantly higher compared with the mice in other groups. Moreover, the mice receiving CpG-ODN therapy 12 h after DC injection showed significantly better resistance to rechallenge. Compared with the mice in other groups, the mice receiving CpG-ODN therapy 12 h after DC injection were superior in survival rates and antimetastatic effects. CONCLUSIONS Our study suggested that the therapeutic efficacy was closely associated with CpG-ODN administration in the combined therapeutic protocol of cryoablation, DCs, and immune adjuvant. In situ administration of CpG-ODN 12 h after DC injection might be considered the optimum application.

Ultrasound induced cancer immunotherapy

Recently, the use of ultrasound (US) has been shown to have potential in cancer immunotherapy. High intensity focused US destruction of tumors may lead to immunity forming in situ in the body by immune cells being exposed to the tumor debris and immune stimulatory substances that are present in the tumor remains. Another way of achieving anti-cancer immune responses is by using US in combination with microbubbles and nanobubbles to deliver genes and antigens into cells. US leads to bubble destruction and the forces released to direct delivery of the substances into the cytoplasm of the cells thus circumventing the natural barriers. In this way tumor antigens and antigen-encoding genes can be delivered to immune cells and immune response stimulating genes can be delivered to cancer cells thus enhancing immune responses. Combination of bubbles with cell-targeting ligands and US provides an even more sophisticated delivery system whereby the therapy is not only site specific but also cell specific. In this review we describe how US has been used to achieve immunity and discuss the potential and possible obstacles in future development.