Whole tumor cell vaccine with irradiated S180 cells as adjuvant

Cancer Vaccines in the Immunotherapy Era: Promise and Potential

Therapeutic vaccines are a promising alternative for active immunotherapy for different types of cancers. Therapeutic cancer vaccines aim to prevent immune system responses that are not targeted at the tumors only, but also boost the anti-tumor immunity and promote regression or eradication of the malignancy without, or with minimal, adverse events. Clinical trial data have pushed the development of cancer vaccines forward, and the US Food and Drug Administration authorized the first therapeutic cancer vaccine. In the present review, we discuss the various types of cancer vaccines and different approaches for the development of therapeutic cancer vaccines, along with the current state of knowledge and future prospects. We also discuss how tumor-induced immune suppression limits the effectiveness of therapeutic vaccinations, and strategies to overcome this barrier to design efficacious, long-lasting anti-tumor immune responses in the generation of vaccines.

The construction of a lymphoma cell-based, DC-targeted vaccine, and its application in lymphoma prevention and cure

In recent years, Non-Hodgkin lymphoma (NHL) has been one of the most fast-growing malignant tumor diseases. NHL poses severe damages to physical health and a heavy burden to patients. Traditional therapies (chemotherapy or radiotherapy) bring some benefit to patients, but have severe adverse effects and do not prevent relapse. The relevance of emerging immunotherapy options (immune-checkpoint blockers or adoptive cellular methods) for NHL remains uncertain, and more intensive evaluations are needed. In this work, inspired by the idea of vaccination to promote an immune response to destroy tumors, we used a biomaterial-based strategy to improve a tumor cell-based vaccine and constructed a novel vaccine named Man-EG7/CH@CpG with antitumor properties. In this vaccine, natural tumor cells are used as a vector to load CpG-ODN, and following lethal irradiation, the formulations were decorated with mannose. The study of the characterization of the double-improved vaccine evidenced the enhanced ability of DCs targeting and improved immunocompetence, which displayed an antitumor function. In the lymphoma prevention model, the Man-EG7/CH@CpG vaccine restrained tumor formation with high efficiency. Furthermore, unlike the non-improved vaccine, the double-improved vaccine elicited an enhanced antitumor effect in the lymphoma treatment model. Next, to improve the moderate therapeutic effect of the mono-treatment method, we incorporated a chemotherapeutic drug (doxorubicin, DOX) into the process of vaccination and devised a combination regimen. Fortunately, a tumor inhibition rate of ~85% was achieved via the combination therapy, which could not be achieved by mono-chemotherapy or mono-immunotherapy. In summary, the strategy presented here may provide a novel direction in the establishment of a tumor vaccine and is the basis for a prioritization scheme of immuno-chemotherapy in enhancing the therapeutic effect on NHL.

Overview of Current Immunotherapies Targeting Mutated KRAS Cancers

The occurrence of somatic substitution mutations of the KRAS proto-oncogene is highly prevalent in certain cancer types, which often leads to constant activation of proliferative pathways and subsequent neoplastic transformation. It is often seen as a gateway mutation in carcinogenesis and has been commonly deemed as a predictive biomarker for poor prognosis and relapse when conventional chemotherapeutics are employed. Additionally, its mutational status also renders EGFR targeted therapies ineffective owing to its downstream location. Efforts to discover new approaches targeting this menacing culprit have been ongoing for years without much success, and with incidences of KRAS positive cancer patients being on the rise, researchers are now turning towards immunotherapies as the way forward. In this scoping review, recent immunotherapeutic developments and advances in both preclinical and clinical studies targeting K-ras directly or indirectly via its downstream signal transduction machinery will be discussed. Additionally, some of the challenges and limitations of various K-ras targeting immunotherapeutic approaches such as vaccines, adoptive T cell therapies, and checkpoint inhibitors against KRAS positive cancers will be deliberated.

A Novel Self-Assembly Nanocrystal as Lymph Node-Targeting Delivery System: Higher Activity of Lymph Node Targeting and Longer Efficacy Against Lymphatic Metastasis

Mitoxantrone (MTO) is used to treat certain types of cancer, mostly metastatic cancer. While the drug has poor aqueous solubility and high side effects. Self-assembly nanocrystal is a novel lymphatic targeting delivery system. In our study, MTO self-assembly nanocrystal (MTO NC) was successfully prepared to improve lymphatic targeting ability and reduce its toxicity. MTO NCs had small size, stable potential, and uniform distribution. The average particle size of MTO NCs was less than 100 nm with the 0.218 PDI and - 6.6 mV the Zeta potential value. TEM images showed that MTO NCs had a sphere-like morphology with smooth surface and uniform distribution; Atomic force microscopy (AFM) images gave a 3D surface of MTO NCs. Polarizing microscope micrograph (PLM) of MTO NCs in lymph nodes demonstrated the crystal structure of MTO NCs when it was exposed to physiological condition. Transmission electron microscopy showed the presence of MTO NCs in mice lymph nodes. Pharmacokinetic parameters of MTO strongly demonstrated that MTO NCs could target the lymph nodes after subcutaneous injection. Moreover, tissue distribution results indicated that MTO NCs were mainly absorbed by the lymphatics and reduced system toxicity. Finally, a lymphatic metastasis mice model was established to precede the pharmacodynamics of MTO NCs, and using MTO liposomes as a reference preparation, the inhibitory effect of MTO NCs on lymphatic metastasis was markedly higher. Briefly, MTO NCs, as a novel self-assembled lymphatic targeting system, can accumulate in the metastatic lymph nodes and lead anticancer drug to kill cancer cells and control lymphatic metastasis with extremely low systemic toxicity.

Targeted delivery of pixantrone to neutrophils by poly(sialic acid)-p-octadecylamine conjugate modified liposomes with improved antitumor activity

Based on the knowledge that poly(sialic acid) is a critical element for tumour development and that the receptors for its monomer are expressed on neutrophils, which play important roles in the progression and invasion of tumours, a poly(sialic acid)-p-octadecylamine conjugate (PSA-p-ODA) was synthesised and used to modify the surface of liposomal pixantrone (Pix-PSL) to improve the delivery of Pix to peripheral blood neutrophils (PBNs). The liposomes were fabricated using a remote loading technology via a pH gradient, and were then assessed for particle size, encapsulation efficiency, in vitro release, in vitro cytotoxicity, and pharmacokinetics. Simultaneously, in vitro and in vivo cellular uptake studies demonstrated that Pix-PSL provided an enhanced accumulation of Pix in PBNs. An in vivo study showed that the anti-tumour activity of Pix-PSL was superior to that of other formulations, probably owing to the efficient targeting of PBNs by Pix-PSL, after which PBNs containing Pix-PSL (Pix-PSL/PBNs) in the circulatory system are recruited by the tumour microenvironment. These findings suggest that PSA-p-ODA-decorated liposomal Pix may provide a neutrophil-mediated drug delivery system (DDS) for the eradication of tumours, and thus represents a promising approach for the tumour targeting of chemotherapeutic treatments.

Thermosensitive Hydrogel System With Paclitaxel Liposomes Used in Localized Drug Delivery System for In Situ Treatment of Tumor: Better Antitumor Efficacy and Lower Toxicity

Intratumoral delivery of chemotherapeutic agents may provide drug localization within the tumor and divert the drug from nontarget organs to improve toxicity and increase efficacy. Thermosensitive injectable hydrogel system may be suitable for the treatment of pancreatic cancer. A study was carried out to examine the efficacy and toxicity of paclitaxel (PTX) liposome gel as a local chemotherapy system against pancreatic cancer in tumor-bearing mice model. The thermosensitive hydrogel we prepared had an appropriate sol-to-gel transition temperature and particle size and morphology study showed this new dosage form possessed physical stability of drug without precipitation and particle size growth of liposome. PTX-lip-gel release in vitro showed a much more slowly release than PTX-lip. The PTX-lip-gel system was proven to have a good retention inside of tumor tissue by intratumoral retention experiments. The in vivo trials showed a better balance between antitumor efficacy and systemic safety in PTX-lip-gel group than in other groups at the equal drug dose. In conclusion, the PTX-lip-gel we prepared in this study provided a high local PTX concentration, sustained and stable drug release, extend drug retention inside of tumor, and low toxicity to normal tissues.

Allogeneic tumor cell vaccines: the promise and limitations in clinical trials

The high mortality rate associated with cancer and its resistance to conventional treatments such as radiation and chemotherapy has led to the investigation of a variety of anti-cancer immunotherapies. The development of novel immunotherapies has been bolstered by the discovery of tumor-associated antigens (TAAs), through gene sequencing and proteomics. One such immunotherapy employs established allogeneic human cancer cell lines to induce antitumor immunity in patients through TAA presentation. Allogeneic cancer immunotherapies are desirable in a clinical setting due to their ease of production and availability. This review aims to summarize clinical trials of allogeneic tumor immunotherapies in various cancer types. To date, clinical trials have shown limited success due potentially to extensive degrees of inter- and intra-tumoral heterogeneity found among cancer patients. However, these clinical results provide guidance for the rational design and creation of more effective allogeneic tumor immunotherapies for use as monotherapies or in combination with other therapies.

Immune cells from SR/CR mice induce the regression of established tumors in BALB/c and C57BL/6 mice

Few experimental models are available for the study of natural resistance to cancer. One of them is the SR/CR (spontaneous regression/complete resistance) mouse model in which natural resistance to a variety of cancer types appeared to be inherited in SR/CR strains of BALB/c and C57BL/6 mice. The genetic, cellular, and molecular effector mechanisms in this model are largely unknown, but cells from the innate immune system may play a significant role. In contrast to previous observations, the cancer resistance was limited to S180 sarcoma cancer cells. We were unable to confirm previous observations of resistance to EL-4 lymphoma cells and J774A.1 monocyte-macrophage cancer cells. The cancer resistance against S180 sarcoma cells could be transferred to susceptible non-resistant BALB/c mice as well as C57BL/6 mice after depletion of both CD4+/CD8+ leukocytes and B-cells from SR/CR mice. In the responding recipient mice, the cancer disappeared gradually following infiltration of a large number of polymorphonuclear granulocytes and remarkably few lymphocytes in the remaining tumor tissues. This study confirmed that the in vivo growth and spread of cancer cells depend on a complex interplay between the cancer cells and the host organism. Here, hereditary components of the immune system, most likely the innate part, played a crucial role in this interplay and lead to resistance to a single experimental cancer type. The fact that leukocytes depleted of both CD4+/CD8+ and B cells from the cancer resistant donor mice could be transferred to inhibit S180 cancer cell growth in susceptible recipient mice support the vision of an efficient and adverse event free immunotherapy in future selected cancer types.

Whole cell vaccines--past progress and future strategies

Cancer vaccines have shown success in curing tumors in preclinical models. Accumulating evidence also supports their ability to induce immune responses in patients. In many cases, these responses correlate with improved clinical outcomes. However, cancer vaccines have not yet demonstrated their true potential in clinical trials. This is likely due to the difficulty in mounting a significant anti-tumor response in patients with advanced disease because of pre-existing tolerance mechanisms that are actively turning off immune recognition in cancer patients. This review will examine the recent progress being made in the design and implementation of whole cell cancer vaccines, one vaccine approach that simultaneously targets multiple tumor antigens to activate the immune response. These vaccines have been shown to induce antigen-specific T-cell responses. Preclinical studies evaluating these vaccines given in sequence with other agents and cancer treatment modalities support the use of immunomodulating doses of chemotherapy and radiation, as well as immune-modulating pathway-targeted monoclonal antibodies, to enhance the efficacy of cancer vaccines. Based on emerging preclinical data, clinical trials are currently exploring the use of combinatorial immune-based therapies for the treatment of cancer.

Cytotoxic T-cells as imaging probes for detecting glioma

Tumor vaccination using tumor-associated antigen-primed dendritic cells (DCs) is in clinical trials. Investigators are using patients’ own immune systems to activate T-cells against recurrent or metastatic tumors. Following vaccination of DCs or attenuated tumor cells, clinical as well as radiological improvements have been noted due to migration and accumulation of cytotoxic T-cells (CTLs). CTLs mediated tumor cell killing resulted in extended survival in clinical trails and in preclinical models. Besides administration of primed DCs or attenuated or killed tumors cells to initiate the generation of CTLs, investigators have started making genetically altered T-cells (CTLs) to target specific tumors and showed in vivo migration and accumulation in the implanted or recurrent tumors using different imaging modalities. Our groups have also showed the utilization of both in vivo and in vitro techniques to make CTLs against glioma and used them as imaging probes to determine the sites of tumors. In this short review, the current status of vaccination therapy against glioma and utilization of CTLs as in vivo imaging probes to determine the sites of tumors and differentiate recurrent glioma from radiation necrosis will be discussed.

Immunity to Trop-1, a newly identified breast cancer antigen, inhibits the growth of breast cancer in mice

This study describes the immunotherapeutic properties of vaccines that encode tumor-associated calcium signal transducer-1 (Trop-1), a newly identified breast cancer antigen, in mice with breast cancer. Previously we found that Trop-1 was over-expressed in cellular breast cancer vaccines that were highly enriched for cells that induced therapeutic CTL-mediated immune responses in mice with breast cancer, as compared with non-enriched vaccines. In this study, to determine if the expression of Trop-1 by cells in the enriched vaccine was responsible for its therapeutic benefits, an expression plasmid that specified the Trop-1 gene was transfected into the LM fibroblast cells, which was then used as a vaccine. To augment their immunogenic properties, the fibroblasts were genetically modified before Trop-1 DNA-transfer to secrete IL-2 and to express allogeneic MHC class I H-2K(b)-determinants. Mice with established breast cancer treated solely by immunization with fibroblasts modified to express Trop-1 developed CD8(+) cell-mediated immunity to the breast cancer cells. The immunity was sufficient to prolong the survival of mice with established breast cancer. In some instances, the immunity was sufficient to result in rejection of the tumor; the mice remained tumor free more than 60 days.