Attenuated Listeria monocytogenes as a cancer vaccine vector for the delivery of CD24, a biomarker for hepatic cancer stem cells

Exploiting bacteria for cancer immunotherapy

Immunotherapy has revolutionized the treatment of cancer but continues to be constrained by limited response rates, acquired resistance, toxicities and high costs, which necessitates the development of new, innovative strategies. The discovery of a connection between the human microbiota and cancer dates back 4,000 years, when local infection was observed to result in tumour eradication in some individuals. However, the true oncological relevance of the intratumoural microbiota was not recognized until the turn of the twentieth century. The intratumoural microbiota can have pivotal roles in both the pathogenesis and treatment of cancer. In particular, intratumoural bacteria can either promote or inhibit cancer growth via remodelling of the tumour microenvironment. Over the past two decades, remarkable progress has been made preclinically in engineering bacteria as agents for cancer immunotherapy; some of these bacterial products have successfully reached the clinical stages of development. In this Review, we discuss the characteristics of intratumoural bacteria and their intricate interactions with the tumour microenvironment. We also describe the many strategies used to engineer bacteria for use in the treatment of cancer, summarizing contemporary data from completed and ongoing clinical trials. The work described herein highlights the potential of bacteria to transform the landscape of cancer therapy, bridging ancient wisdom with modern scientific innovation.

Harnessing Bacterial Membrane Components for Tumor Vaccines: Strategies and Perspectives

Tumor vaccines stand at the vanguard of tumor immunotherapy, demonstrating significant potential and promise in recent years. While tumor vaccines have achieved breakthroughs in the treatment of cancer, they still encounter numerous challenges, including improving the immunogenicity of vaccines and expanding the scope of vaccine application. As natural immune activators, bacterial components offer inherent advantages in tumor vaccines. Bacterial membrane components, with their safer profile, easy extraction, purification, and engineering, along with their diverse array of immune components, activate the immune system and improve tumor vaccine efficacy. This review systematically summarizes the mechanism of action and therapeutic effects of bacterial membranes and its derivatives (including bacterial membrane vesicles and hybrid membrane biomaterials) in tumor vaccines. Subsequently, the authors delve into the preparation and advantages of tumor vaccines based on bacterial membranes and hybrid membrane biomaterials. Following this, the immune effects of tumor vaccines based on bacterial outer membrane vesicles are elucidated, and their mechanisms are explained. Moreover, their advantages in tumor combination therapy are analyzed. Last, the challenges and trends in this field are discussed. This comprehensive analysis aims to offer a more informed reference and scientific foundation for the design and implementation of bacterial membrane-based tumor vaccines.

Bacteria-driven cancer therapy: Exploring advancements and challenges

Cancer, a serious fatal disease caused by the uncontrolled growth of cells, is the biggest challenge flagging around medicine and health fields. Conventionally, various treatments-based strategies such as radiotherapy, chemotherapy, and alternative cancer therapies possess drugs that cannot reach the cancerous tissues and make them toxic to noncancerous cells. Cancer immunotherapy has made outstanding achievements in reducing the chances of cancer. Our considerable attention towards cancer-directed immune responses and the mechanisms behind which immune cells kill cancer cells have progressively been helpful in the advancement of new therapies. Among them, bacteria-based cancer immunotherapy has achieved much more attention due to smart and robust mechanisms in activating the host anti-tumor response. Moreover, bacterial-based therapy can be utilized as a single monotherapy or in combination with multiple anticancer immunotherapies to accelerate productive clinical results. Herein, we comprehensively reviewed recent advancements, challenges, and future perspectives in developing bacterial-based cancer immunotherapies.

Listeria monocytogenes: a promising vector for tumor immunotherapy

Cancer receives enduring international attention due to its extremely high morbidity and mortality. Immunotherapy, which is generally expected to overcome the limits of traditional treatments, serves as a promising direction for patients with recurrent or metastatic malignancies. Bacteria-based vectors such as Listeria monocytogenes take advantage of their unique characteristics, including preferential infection of host antigen presenting cells, intracellular growth within immune cells, and intercellular dissemination, to further improve the efficacy and minimize off-target effects of tailed immune treatments. Listeria monocytogenes can reshape the tumor microenvironment to bolster the anti-tumor effects both through the enhancement of T cells activity and a decrease in the frequency and population of immunosuppressive cells. Modified Listeria monocytogenes has been employed as a tool to elicit immune responses against different tumor cells. Currently, Listeria monocytogenes vaccine alone is insufficient to treat all patients effectively, which can be addressed if combined with other treatments, such as immune checkpoint inhibitors, reactivated adoptive cell therapy, and radiotherapy. This review summarizes the recent advances in the molecular mechanisms underlying the involvement of Listeria monocytogenes vaccine in anti-tumor immunity, and discusses the most concerned issues for future research.

Advances in anti-tumor based on various anaerobic bacteria and their derivatives as drug vehicles

Cancer therapies, such as chemotherapy and radiotherapy, are often unsatisfactory due to several limitations, including drug resistance, inability to cross biological barriers, and toxic side effects on the body. These drawbacks underscore the need for alternative treatments that can overcome these challenges and provide more effective and safer options for cancer patients. In recent years, the use of live bacteria, engineered bacteria, or bacterial derivatives to deliver antitumor drugs to specific tumor sites for controlled release has emerged as a promising therapeutic tool. This approach offers several advantages over traditional cancer therapies, including targeted drug delivery and reduced toxicity to healthy tissues. Ongoing research in this field holds great potential for further developing more efficient and personalized cancer therapies, such as E. coli, Salmonella, Listeria, and bacterial derivatives like outer membrane vesicles (OMVs), which can serve as vehicles for drugs, therapeutic proteins, or antigens. In this review, we describe the advances, challenges, and future directions of research on using live bacteria or OMVs as carriers or components derived from bacteria of delivery systems for cancer therapy.

Phage for cancer therapy

Cancer is currently a global health challenge, characterized by dysfunction of organs due to the uncontrolled growth of cells exponentially. The therapies used to treat cancer in patients so far are widely used. However, there are also some problems, such as the high cost of surgery and chemotherapy. Thus, there are many barriers to care for patients with cancer, especially in low and middle-income countries. In addition, the many risks and adverse effects of radiation treatment. Therefore, to reduce mortality in patients with the disease, we need a newer therapy with more targeted treatment, fewer side effects, and cheaper cost. The application of bacteria in cancer treatment was first developed in 1983. Currently, this therapy is attracting the attention of scientists due to its great potential in cancer treatment. This chapter discusses the successful research on the bacteriophage for cancer, the mechanism and its potential. In addition, some types of bacteria that are most important for cancer treatment and limitations on the widespread application of this therapy were also mentioned. Reviewing all the researches on bacteriotherapy in cancer are essential to increase the knowledge in this area and make this therapy more optimal in the future.

CD24 blockade as a novel strategy for cancer treatment

The CD24 protein is a heat-stable protein with a small core that undergoes extensive glycosylation. It is expressed on the surface of various normal cells, including lymphocytes, epithelial cells, and inflammatory cells. CD24 exerts its function by binding to different ligands. Numerous studies have demonstrated the close association of CD24 with tumor occurrence and progression. CD24 not only facilitates tumor cell proliferation, metastasis, and immune evasion but also plays a role in tumor initiation, thus, serving as a marker on the surface of cancer stem cells (CSCs). Additionally, CD24 induces drug resistance in various tumor cells following chemotherapy. To counteract the tumor-promoting effects of CD24, several treatment strategies targeting CD24 have been explored, such as the use of CD24 monoclonal antibodies (mAb) alone, the combination of CD24 and chemotoxic drugs, or the combination of these drugs with other targeted immunotherapeutic techniques. Regardless of the approach, targeting CD24 has demonstrated significant anti-tumor effects. Therefore, the present study focuses on anti-tumor therapy and provides a comprehensive review of the structure and fundamental physiological function of CD24 and its impact on tumor development, and suggests that targeting CD24 may represent an effective strategy for treating malignant tumors.

Bacterial-Mediated Tumor Therapy: Old Treatment in a New Context

Targeted therapy and immunotherapy have brought hopes for precision cancer treatment. However, complex physiological barriers and tumor immunosuppression result in poor efficacy, side effects, and resistance to antitumor therapies. Bacteria-mediated antitumor therapy provides new options to address these challenges. Thanks to their special characteristics, bacteria have excellent ability to destroy tumor cells from the inside and induce innate and adaptive antitumor immune responses. Furthermore, bacterial components, including bacterial vesicles, spores, toxins, metabolites, and other active substances, similarly inherit their unique targeting properties and antitumor capabilities. Bacteria and their accessory products can even be reprogrammed to produce and deliver antitumor agents according to clinical needs. This review first discusses the role of different bacteria in the development of tumorigenesis and the latest advances in bacteria-based delivery platforms and the existing obstacles for application. Moreover, the prospect and challenges of clinical transformation of engineered bacteria are also summarized.

Portal vein tumor thrombosis in hepatocellular carcinoma: molecular mechanism and therapy

Portal vein tumor thrombosis (PVTT), a common complication of advanced hepatocellular carcinoma (HCC), remains the bottleneck of the treatments. Liver cancer cells potentially experienced multi-steps during PVTT process, including cancer cells leave from cancer nest, migrate in extracellular matrix, invade the vascular barrier, and colonize in the portal vein. Accumulated evidences have revealed numerous of molecular mechanisms including genetic and epigenetic regulation, cancer stem cells, immunosuppressive microenvironment, hypoxia, et al. contributed to the PVTT formation. In this review, we discuss state-of-the-art PVTT research on the potential molecular mechanisms and experimental models. In addition, we summarize PVTT-associated clinical trials and current treatments for PVTT and suppose perspectives exploring the molecular mechanisms and improving PVTT-related treatment for the future.

Cancer Stem Cells in Hepatocellular Carcinoma: Intrinsic and Extrinsic Molecular Mechanisms in Stemness Regulation

Hepatocellular carcinoma (HCC) remains the most predominant type of liver cancer with an extremely poor prognosis due to its late diagnosis and high recurrence rate. One of the culprits for HCC recurrence and metastasis is the existence of cancer stem cells (CSCs), which are a small subset of cancer cells possessing robust stem cell properties within tumors. CSCs play crucial roles in tumor heterogeneity constitution, tumorigenesis, tumor relapse, metastasis, and resistance to anti-cancer therapies. Elucidation of how these CSCs maintain their stemness features is essential for the development of CSCs-based therapy. In this review, we summarize the present knowledge of intrinsic molecules and signaling pathways involved in hepatic CSCs, especially the CSC surface markers and associated signaling in regulating the stemness characteristics and the heterogeneous subpopulations within the CSC pool. In addition, we recapitulate the effects of crucial extrinsic cellular components in the tumor microenvironment, including stromal cells and immune cells, on the modulation of hepatic CSCs. Finally, we synopsize the currently valuable CSCs-targeted therapy strategies based on intervention in these intrinsic and extrinsic molecular mechanisms, in the hope of shedding light on better clinical management of HCC patients.

Recombinant Listeria ivanovii strain expressing listeriolysin O in place of ivanolysin O might be a potential antigen carrier for vaccine construction

Listeria monocytogenes (LM) induces efficient and specific T-cell immune responses in the host. Listeriolysin O (LLO) is the main virulence protein of LM. LLO helps LM escape from the lysosome. However, the pronounced pathogenicity of LM limits its practical application as a live bacterial vector. Listeria ivanovii (LI) also displays intracellular parasitic abilities, cell to cell transfer, and other LM properties, with an elevated biosafety relative to LM. We have confirmed that LI can be used as a viable bacterial vaccine vector. However, we have also observed in vivo that LI vector vaccine candidates survive in the immune organ (spleen) for a shorter time compared with the survival time of LM and elicit weaker immune responses compared with LM. Studies have confirmed that hemolysin correlates with some important biological properties of Listeria, including cell invasion, intracellular proliferation, and the ability to induce immune responses. We speculated that the weaker immunogenicity of LI compared to LM may be related to the function of ivanolysin O (ILO). Here, we established a hemolysin gene deletion strain, LIΔilo, and a modified strain, LIΔilo:hly, whose ilo was replaced by hly. The hemolysin-modified strain was attenuated; however, it led to significantly improved invasive and proliferative activities of antigen-presenting cells, including those of RAW 264.7 macrophages, compared with the effects of LI. Mice immunized twice with LIΔilo:hly showed higher cytokine levels and better challenge protection rates than LI-immunized mice. This is the first description in Listeria carrier vaccine research of the modification of LI hemolysin to obtain a better vaccine carrier than LI. The recombinant strain LIΔilo:hly showed good biosafety and immunogenicity, and thus appears to be a good vector strain for vaccine development.

Bacterial-Based Methods for Cancer Treatment: What We Know and Where We Are

A severe disease, cancer is caused by the exponential and uncontrolled growth of cells, leading to organ dysfunction as well as disorders. This disease has been recognized as one of the significant challenges to health and medicine. Various treatment procedures for cancer are associated with diverse side effects; the most conventional cancer treatments include chemotherapy, surgery, and radiotherapy, among others. Numerous adverse and side effects, low specificity and sensitivity, narrow therapeutic windows, and, recently, the emergence of tumor cells resistant to such treatments have been documented as the shortcomings of conventional treatment strategies. As a group of prokaryotic microorganisms, bacteria have great potential for use in cancer therapy. Currently, utilizing bacteria for cancer treatment has attracted the attention of scientists. The high potential of bacteria to become non-pathogenic by genetic manipulation, their distinguished virulence factors (which can be used as weapons against tumors), their ability to proliferate in tissues, and the contingency to control their population by administrating antibiotics, etc., have made bacteria viable candidates and live micro-medication for cancer therapies. However, the possible cytotoxicity impacts of bacteria, their inability to entirely lyse cancerous cells, as well as the probability of mutations in their genomes are among the significant challenges of bacteria-based methods for cancer treatment. In this article, various available data on bacterial therapeutics, along with their pros and cons, are discussed.

Safety and efficacy of prophylactic and therapeutic vaccine based on live-attenuated Listeria monocytogenes in hepatobiliary cancers

Primary liver cancer (PLC) comprising hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) represents the third deadliest cancer worldwide with still insufficient treatment options. We have previously found that CD4 T helper 1 (Th1) response is indispensable for the protection against PLC. In the present research, we aimed to test the potent inducers of Th1 responses, live-attenuated Listeria monocytogenes ∆actA/∆inlB strain as preventive/therapeutic vaccine candidate in liver fibrosis, HCC, and CCA. Studies were performed using autochthonous models of HCC and CCA, highly reflecting human disease. L. monocytogenes ∆actA/∆inlB demonstrated strong safety/efficacy in premalignant and malignant liver diseases. The protective mechanism relied on the induction of strong tumor-specific immune responses that keep the development of hepatobiliary cancers under control. Combination therapy, comprising Listeria vaccination and a checkpoint inhibitor blockade significantly extended the survival of HCC-bearing mice even at the advanced stages of the disease. This is the first report on the safety and efficacy of Listeria-based vaccine in liver fibrosis, as well as the first proof of principle study on Listeria-based vaccines in CCA. Our study paves the way for the use of live-attenuated Listeria as safe and efficient vaccine and a potent inducer of protective immune responses in liver fibrosis and hepatobiliary malignancies.

Protective immune mechanism induced by live-attenuated double-deleted L. monocytogenes ∆actA/∆inlB vaccine strain delivering tumor antigens keeps hepatobiliary malignancies under control. Live-attenuated, double-deleted L. monocytogenes ∆actA/∆inlB strain expressing model tumor antigen was used in both, prophylactic and therapeutic vaccination settings. Vaccination was safe and led to: (i) induction of protective tumor-specific Th1 immune responses in premalignant and malignant stages and strong increase of tumor-specific IFN-ɣ⁺ CD4 and CD8 T cells; (ii) decrease of T regulatory cells; (iii) downregulation of several tumor-promoting ICI molecules (PD-1, CD160, LAG3, 4-1BBL) on CD4/CD8 T lymphocytes; (iv) decrease of tumor-specific IgG in serum, and (v) decrease of B lymphocytes, DC and MΦ locally in livers. iCCA, intrahepatic cholangiocarcinoma.

Bacteria and bacterial derivatives as delivery carriers for immunotherapy

There is growing interest in the role of microorganisms in human health and disease, with evidence showing that new types of biotherapy using engineered bacterial therapeutics, including bacterial derivatives, can address specific mechanisms of disease. The complex interactions between microorganisms and metabolic/immunologic pathways underlie many diseases with unmet medical needs, suggesting that targeting these interactions may improve patient treatment. Using tools from synthetic biology and chemical engineering, non-pathogenic bacteria or bacterial products can be programmed and designed to sense and respond to environmental signals to deliver therapeutic effectors. This review describes current progress in biotherapy using live bacteria and their derivatives to achieve therapeutic benefits against various diseases.

Hemolysin function of Listeria is related to biofilm formation: transcriptomics analysis

Listeriolysin O (LLO) is the main virulence protein of Listeria monocytogenes (LM), that helps LM escape lysosomes. We previously found that the cellular immune response elicited by L.ivanovii (LI) is weaker than that elicited by LM. We speculated that this may be related to the function of ivanolysin O (ILO). Here, we constructed hemolysin gene deletion strain, LIΔilo, and a modified strain, LIΔilo::hly, in which ilo was replaced by hly. Prokaryotic transcriptome sequencing was performed on LI, LIΔilo, and LIΔilo::hly. Transcriptome differences between the three strains were compared, and genes and pathways with significant differences between the three strains were analyzed. Prokaryotic transcriptome sequencing results revealed the relationship of ilo to the ribosome, quorum sensing, and phosphotransferase system (PTS) pathways, etc. LIΔilo exhibited attenuated biofilm formation ability compared to LI. Biofilm formation was significantly recovered or even increased after replenishing hly. After knocking out ilo, the relative expression levels of some virulence genes, including sigB, prfA, actA, smcL, and virR, were up-regulated compared to LI. After replenishing hly, these genes were down-regulated compared to LIΔilo. The trend and degree of such variation were not completely consistent when cultured in media containing only monosaccharides or disaccharides. The results confirmed that hemolysin is related to some important biological properties of Listeria, including biofilm formation and virulence gene expression levels. This is the first comprehensive study on ILO function at the transcriptomic level and the first evidence of a relationship between Listeria hemolysin and biofilm formation.

Bacteria-based immune therapies for cancer treatment

Engineered bacterial therapies that target the tumor immune landscape offer a new class of cancer immunotherapy. Salmonella enterica and Listeria monocytogenes are two species of bacteria that have been engineered to specifically target tumors and serve as delivery vessels for immunotherapies. Therapeutic bacteria have been engineered to deliver cytokines, gene silencing shRNA, and tumor associated antigens that increase immune activation. Bacterial therapies stimulate both the innate and adaptive immune system, change the immune dynamics of the tumor microenvironment, and offer unique strategies for targeting tumors. Bacteria have innate adjuvant properties, which enable both the delivered molecules and the bacteria themselves to stimulate immune responses. Bacterial immunotherapies that deliver cytokines and tumor-associated antigens have demonstrated clinical efficacy. Harnessing the diverse set of mechanisms that Salmonella and Listeria use to alter the tumor-immune landscape has the potential to generate many new and effective immunotherapies.

Optimized Doxycycline-Inducible Gene Expression System for Genetic Programming of Tumor-Targeting Bacteria

PURPOSE

In the programming of tumor-targeting bacteria, various therapeutic or reporter genes are expressed by different gene-triggering strategies. Previously, we engineered pJL87 plasmid with an inducible bacterial drug delivery system that simultaneously co-expressed two genes for therapy and imaging by a bidirectional tet promoter system only in response to the administration of exogenous doxycycline (Doxy). In this multi-cassette expression approach, tetA promoter (P_tetA) was 100-fold higher in expression strength than tetR promoter (P_tetR). In the present study, we developed pJH18 plasmid with novel Doxy-inducible gene expression system based on a tet promoter.

PROCEDURES

In this system, Tet repressor (TetR) expressed by a weak constitutive promoter binds to tetO operator, resulting in the tight repression of gene expressions by P_tetA and P_tetR, and Doxy releases TetR from tetO to de-repress P_tetA and P_tetR.

RESULTS

In Salmonella transformed with pJH18, the expression balance of bidirectional tet promoters in pJH18 was remarkably improved (P_tetA:P_tetR = 4~6:1) compared with that of pJL87 (P_tetA:P_tetR = 100:1) in the presence of Doxy. Also, the expression level by novel tet system was much higher in Salmonella transformed with pJH18 than in those with pJL87 (80-fold in rluc8 and 5-fold in clyA). Interestingly, pJH18 of the transformed Salmonella was much more stably maintained than pJL87 in antibiotic-free tumor-bearing mice (about 41-fold), because only pJH18 carries bom sequence with an essential role in preventing the plasmid-free population of programmed Salmonella from undergoing cell division.

CONCLUSIONS

Overall, doxycycline-induced co-expression of two proteins at similar expression levels, we exploited bioluminescence reporter proteins with preclinical but no clinical utility. Future validation with clinically compatible reporter systems, for example, suitable for radionuclide imaging, is necessary to develop this system further towards potential clinical application.

CD24, A Review of its Role in Tumor Diagnosis, Progression and Therapy

CD24, is a mucin-like GPI-anchored molecules. By immunohistochemistry, it is widely detected in many solid tumors, such as breast cancers, genital system cancers, digestive system cancers, neural system cancers and so on. The functional roles of CD24 are either fulfilled by combination with ligands or participate in signal transduction, which mediate the initiation and progression of neoplasms. However, the character of CD24 remains to be intriguing because there are still opposite voices about the impact of CD24 on tumors. In preclinical studies, CD24 target therapies, including monoclonal antibodies, target silencing by RNA interference and immunotherapy, have shown us brighten futures on the anti-tumor application. Nevertheless, evidences based on clinical studies are urgently needed. Here, with expectancy to spark new ideas, we summarize the relevant studies about CD24 from a tumor perspective.

Bacteria-mediated cancer therapies: opportunities and challenges

In recent years, cancer therapy strategies utilizing live tumor-targeting bacteria have presented unique advantages. Engineered bacteria have the particular ability to distinguish tumors from normal tissues with less toxicity. Live bacteria are naturally capable of homing to tumors, resulting in high levels of local colonization because of insufficient oxygen and low pH in the tumor microenvironment. Bacteria initiate their antitumor effects by directly killing the tumor or by activating innate and adaptive antitumor immune responses. The bacterial vectors can be reprogrammed following advanced DNA synthesis, sophisticated genetic bioengineering, and biosensors to engineer microorganisms with complex functions, and then produce and deliver anticancer agents based on clinical needs. However, because of the lack of knowledge on the mechanisms and side effects of microbial cancer therapy, developing such smart microorganisms to treat or prevent cancer remains a significant challenge. In this review, we summarized the potential, status, opportunities and challenges of this growing field. We illustrated the mechanism of tumor regression induced by engineered bacteria and discussed the recent advances in the application of bacteria-mediated cancer therapy to improve efficacy, safety and drug delivery. Finally, we shared our insights into the future directions of tumor-targeting bacteria in cancer therapy.

Combination immunotherapy with two attenuated Listeria strains carrying shuffled HPV-16 E6E7 protein causes tumor regression in a mouse tumor model

Cervical cancer continues to impose a heavy burden worldwide, and human papilloma virus (HPV) infection, especially persistent infection with type 16 (HPV-16), is known to be the primary etiological factor. Therapeutic vaccines are urgently needed because prophylactic vaccines are ineffective at clearing pre-existing HPV infection. Here, two recombinant Listeria strains (LMΔ-E6E7 & LIΔ-E6E7) with deletions of the actA and plcB genes, expressing the shuffled HPV-16 E6E7 protein were constructed. The strains were delivered into the spleen and liver by intravenous inoculation, induced antigen-specific cellular immunity and were eliminated completely from the internal organs several days later. Intravenously treating with single strain for three times, or with both strains alternately for three times significantly reduced the tumor size and prolonged the survival time of model mice. Combination immunotherapy with two strains seemed more effective than immunotherapy with single strain in that it enhanced the survival of the mice, and the LMΔ-E6E7-prime-LIΔ-E6E7-boost strategy showed significant stronger efficacy than single treatment with the LIΔ-E6E7 strain. The antitumor effect of this treatment might due to its ability to increase the proportion of CD8⁺ T cells and reduce the proportion of T regulatory cells (Tregs) in the intratumoral milieu. This is the first report regarding Listeria ivanovii-based therapeutic vaccine candidate against cervical cancer. Most importantly we are the first to confirm that combination therapy with two different recombinant Listeria strains has a more satisfactory antitumor effect than administration of a single strain. Thus, we propose a novel prime-boost treatment strategy.

Identification and evaluation of a panel of strong constitutive promoters in Listeria monocytogenes for improving the expression of foreign antigens

Attenuated Listeria monocytogenes could be a potential vaccine vector for the immunotherapy of tumors or pathogens. However, the lack of reliable promoters has limited its ability to express foreign antigens. In the present study, 21 promoters were identified from Listeria monocytogenes through RNA-seq analysis under two pH conditions of pH 7.4 and pH 5.5. Based on the constructed fluorescence report system, 7 constitutive promoters exhibited higher strength than P_help (1.8-fold to 5.4-fold), a previously reported strong promoter. Furthermore, the selected 5 constitutive promoters exhibited higher UreB production activity than P_help (1.1-fold to 8.3-fold). Notably, a well-characterized constitutive promoter P₁₈ was found with the highest activity of fluorescence intensity and UreB production. In summary, the study provides a panel of strong constitutive promoters for Listeria monocytogenes and offers a theoretical basis for mining constitutive promoters in other organisms. KEY POINTS: • Twenty-one promoters were identified from L. monocytogenes through RNA-seq. • Fluorescent tracer of L. monocytogenes (P₁₈) was performed in vitro and in vivo. • A well-characterized constitutive promoter P₁₈ could improve the expression level of a foreign antigen UreB in L. monocytogenes.

Cell primitive-based biomimetic functional materials for enhanced cancer therapy

Cell primitive-based functional materials that combine the advantages of natural substances and nanotechnology have emerged as attractive therapeutic agents for cancer therapy. Cell primitives are characterized by distinctive biological functions, such as long-term circulation, tumor specific targeting, immune modulation etc. Moreover, synthetic nanomaterials featuring unique physical/chemical properties have been widely used as effective drug delivery vehicles or anticancer agents to treat cancer. The combination of these two kinds of materials will catalyze the generation of innovative biomaterials with multiple functions, high biocompatibility and negligible immunogenicity for precise cancer therapy. In this review, we summarize the most recent advances in the development of cell primitive-based functional materials for cancer therapy. Different cell primitives, including bacteria, phages, cells, cell membranes, and other bioactive substances are introduced with their unique bioactive functions, and strategies in combining with synthetic materials, especially nanoparticulate systems, for the construction of function-enhanced biomaterials are also summarized. Furthermore, foreseeable challenges and future perspectives are also included for the future research direction in this field.

One Single Site Clinical Study: To Evaluate the Safety and Efficacy of Immunotherapy With Autologous Dendritic Cells, Cytokine-Induced Killer Cells in Primary Hepatocellular Carcinoma Patients

Dendritic cells (DCs) and cytokine-induced killer (CIK) cells play an important role in the anti-tumor immune response. In this study, we evaluated the clinical effectiveness of DC/CIK-CD24 immunotherapies to primary hepatocellular carcinoma patients who received radical resection. 36 resected primary hepatocellular carcinoma (HCC) patients were enrolled from August 2014 to December 2015. All patients received two or four times of DC/CIK immunotherapy after radical resection. 1-4 years patients' survival rates were evaluated during the follow-up. The 4-year survival rate of patients who received two times of immunotherapy was 47.1%, and the rate of those who received four times of immunotherapies was 52.6%. Compared to baseline, after receiving the DC/CIK-CD24 autotransfusion, the serum Treg concentration of the patients decreased, while CD3+, CD4+, CD56+ increased slightly. The adverse effect of immunotherapy was I-II° transient fever and could be tolerable. DC/CIK-CD24 immunotherapy can delay the relapse time.

Draft Genome Sequences of 171 Listeria monocytogenes Isolates from Food-Related Listeriosis Outbreaks in California from 2007 to 2017

This publication reports the availability of draft genome sequences of 171 Listeria monocytogenes strains isolated from various food-related sources from California between 2007 and 2017. All isolates contain at least two antimicrobial resistance genes.

This publication reports the availability of draft genome sequences of 171 Listeria monocytogenes strains isolated from various food-related sources from California between 2007 and 2017. All isolates contain at least two antimicrobial resistance genes.

Immunological evaluation of virulence-deficient Listeria monocytogenes strains in C57BL/6 mice

Attenuated Listeria monocytogenes (L. monocytogenes), which has unique advantages in presenting foreign antigens, was widely used in tumor immunotherapy research. As a live vaccine vector, attenuated L. monocytogenes was required to not only have certain invasiveness but also ensure safety, while the lack of different virulence factors may cause L. monocytogenes to show different safety and invasiveness. To evaluate the potential of virulence-deficient L. monocytogenes strains as a vaccine vector, four mutant strains EGD-eΔactA, EGD-eΔactA/inlB, EGD-eΔhly, and EGD-eΔprfA were used to infect C57BL/6 mice for determining related immune indexes. Compared with EGD-e, mutant strains showed significantly decreased invasion in C57BL/6 mice and caused relatively minor damage to spleen and liver. However, EGD-eΔactA and EGD-eΔactA/inlB were superior to EGD-eΔhly and EGD-eΔprfA in the comprehensive evaluation of inflammatory factor transcription level, immune cell differentiation and antibody level, which proved that they have a stronger adjuvant effect as a vaccine vector.

Attenuated Listeria monocytogenes as a Vaccine Vector for the Delivery of OMPW, the Outer Membrane Protein of Aeromonas hydrophila

Listeria monocytogenes (LM) is a gram-positive facultative intracellular pathogen that could stimulate host to produce inflammatory response, cell-mediated immunity, and humoral immunity. In this study, an attenuated live vector vaccine for Aeromonas hydrophila (AH) named EGDeABdd-dat-ompW was successfully constructed using an attenuated vector named EGDeABdd, in which dal, dat, actA, and inlB genes were deleted from wild-type LM-EGDe. To construct EGDeABdd-dat-ompW, a recombinant plasmid pERL3-dat-ompW obtained by inserting the dat gene from EGDe and outer membrane protein gene ompW from AH into pERL3 plasmid was transformed into EGDeABdd cell. The safety and immunogenicity of EGDeABdd-dat-ompW as an attenuated vector vaccine for delivery of OMPW were assessed through analyzing invasion to Caco-2 cells and mice, cytokine production of macrophagocyte and mouse splenocytes, and T-cell proliferation of mouse splenocytes. Serum titers against AH and the immunoprotective effect of the vaccine to mice were also measured after intravenous injection with vaccine for four times. The results showed that the live vector vaccine EGDeABdd-dat-ompW for AH exhibited high attenuation in invading Caco-2 cells and mice than did EGDe. Real-time PCR (RT-PCR) showed that cytokines (e.g., TNF-α, IL-6, and IL-1β from macrophages; and IL-6 and IFN-γ from mouse splenocytes) had significantly increased after immunization by EGDeABdd-dat-ompW. Meanwhile, the vaccine could induce the production of CD3⁺CD4⁺ and CD3⁺CD8⁺ T-cell proliferation of mice and generate effective immunoprotection against lethal challenge of 20 × LD₅₀ AH. All these results indicated that the attenuated EGDeABdd-dat could be used as a live vector for the delivery of the exogenous gene, not only possessing safety but also providing high immunogenicity. The successful application in the AH vaccine further showed that it could be used in other fields such as vaccines in cancer or infectious diseases.

Design of Outer Membrane Vesicles as Cancer Vaccines: A New Toolkit for Cancer Therapy

Cancer vaccines have been extensively studied in recent years and have contributed to exceptional achievements in cancer treatment. They are some of the most newly developed vaccines, although only two are currently approved for use, Provenge and Talimogene laherparepvec (T-VEC). Despite the approval of these two vaccines, most vaccines have been terminated at the clinical trial stage, which indicates that although they are effective in theory, concerns still exist, including low antigenicity of targeting antigens and tumor heterogeneity. In recent years, with new understanding of the biological function and vaccine potential of outer membrane vesicles (OMVs), their potential application in cancer vaccine design deserves our attention. Therefore, this review focuses on the mechanisms, advantages, and prospects of OMVs as antigen-carrier vaccines in cancer vaccine development. We believe that OMV-based vaccines present a safe and effective cancer therapeutic option with broad application prospects.

Coating With Chitooligosaccharides Enhances the Cytokine Induction of Listeria ivanovii-Based Vaccine Strain

Listeria ivanovi (LI) is an available live bacterial vaccine vector. This work attempted to coat LI-based vaccine candidates (LI-Rv0129c) with chitooligosaccharides (COSs) as an adjuvant to enhance the cellular immune responses induced. COS-bacteria composite was achieved by mixing the bacteria suspension with equal volume of COS solution, and this process accompanied with the increase of bacteria superficial zeta potential and formation of special superficial configurations. COS coating improved the ratio swallowed by the macrophage-like RAW264.7 cells from 0.54% to 2.88% (p < 0.001). In vivo, the COS-coated LI-Rv0129c strain did elicit significantly higher specific CD4⁺ IFN-γ, CD4⁺ TNF-α or CD8⁺ IFN-γ secretion (0.91%, 1.00%, 0.30%, respectively) than naked LI-Rv0129c (0.32%, 0.38%, 0.07%, respectively) (p < 0.01). These results demonstrated that COS is a promising adjuvant to enhance the protective cellular immune responses induced by LI-based vaccine strains. Our work provided a notion for developing adjuvant for Listeria and other bacterial vector-based vaccines.

Fabrication of Cell-Derived Biomimetic Drug Delivery System

Functional biomaterials that are capable of effectively carrying therapeutic agents and specifically delivering therapeutics to pathological sites have been widely investigated over decades. Recently, cellular carriers and cell derivative-based bio-hybrid delivery systems have drawn extensive attention as a promising branch of therapeutic delivery systems, owing to their low immunogenicity and intriguing biomimetic capabilities. Various approaches for the fabrication of these biomimetic carriers have been developed, and some products have already been commercialized as well. In this review, we summarized various processing methods for engineering cell-derived biomimetic drug delivery systems, and discussed their future outlooks.

Polysaccharides from Chinese Herbal Lycium barbarum Induced Systemic and Local Immune Responses in H22 Tumor-Bearing Mice

Lycium barbarum polysaccharide (LBP) is isolated from the fruit of Chinese herbal Lycium barbarum. Previous studies had demonstrated that LBP could inhibit tumor growth and enhance the immunity in mice. However, the effect of LBP on systemic and local immune responses in vivo, especially on phenotypic and functional changes of T cells, is still largely unknown. In the present study, we investigated the effects of LBP on systemic and local T cell-dependent antitumor immune responses in H22 tumor-bearing mice. The results showed that LBP could inhibit the solid tumor growth in mice, but showed little effect on the body weight or spleen index. Furthermore, LBP could maintain high levels of T cells in peripheral blood (PB), tumor draining lymph node (TDLN), and tumor tissue, prevent the increase of Tregs while promote infiltration of CD8+ T cells in tumor tissue, inhibit the production of TGF-β1 and IL-10 in serum, decrease the exhaustion phenotype of T cells, and maintain cytotoxicity of lymphocytes. Taken together, our results demonstrated that LBP simultaneously induced systemic and local immune responses in H22 tumor-bearing mice by alleviating immunosuppression and maintaining antitumor immune responses in mice.

IFI44L is a novel tumor suppressor in human hepatocellular carcinoma affecting cancer stemness, metastasis, and drug resistance via regulating met/Src signaling pathway

BACKGROUND

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death worldwide. The disease recurrent rate is relatively high resulted in poor 5-year survival in advanced HCC. Cancer stem cells (CSCs) have been considered to be one of the main mechanisms for chemoresistance, metastasis, and recurrent disease. Interferon-induced protein 44-like (IFI44L) gene is a type I interferon-stimulated gene (ISG) and belongs to the IFI44 family. Previous reports indicated antiviral activity against HCV in IFI44L, however, its precise role and function in HCC has not been unveiled.

METHODS

To explore the characteristics of hepatic CSCs, we successfully enriched hepatic cancer stem-like cells from three established liver cancer cell lines (Hep3B, HepG2, and PLC lines). Parental Hep3B and HepG2 cells and their sphere cells were treated with doxorubicin for 48 h and cell viability was measured by MTT assay. HCC tissue blocks from 217 patients were sampled for tissue microarray (TMA). Follow-up information and histopathological and clinical data including age, gender, tumor grade, advanced stages, HBV, HCV, tumor number, tumor size, relapse-free survival, and overall survival were obtained from the cancer registry and medical charts. The liver TMA was evaluated for IFI44L expression using immunohistochemical staining and scores.

RESULTS

These hepatic cancer stem-like cells possess important cancer stemness characteristics including sphere-forming abilities, expressing important HCC cancer stem cell markers, and more chemoresistant. Interestingly, we found that overexpression of IFI44L decreased chemoresistance towards doxorubicin and knockdown of IFI44L restored chemoresistance as well as promoted sphere formation. Furthermore, we found that depletion of IFI44L enhanced migration, invasion, and pulmonary metastasis through activating Met/Src signaling pathway. Clinically, the expression level of IFI44L significantly reduced in HCC tumor tissues. Low expression of IFI44L levels also correlated with larger tumor size, disease relapse, advanced stages, and poor clinical survival in HCC patients.

CONCLUSION

Taken together, we first demonstrated that IFI44L is a novel tumor suppressor to affect cancer stemness, metastasis, and drug resistance via regulating Met/Src signaling pathway in HCC and can be serve as an important prognostic marker.

Prospects and progress of Listeria-based cancer vaccines

INTRODUCTION

The development of an effective therapeutic vaccine to induce cancer-specific immunity remains problematic. Recently, a species of intracellular pathogen known as Listeria monocytogenes (Lm) has been used to transfer DNA, RNA and proteins into tumour cells as well as elicit an immune response against tumour-specific antigens. Areas covered: Herein, the authors provide the mechanisms of different Listeria monocytogenes strains, which are potential therapeutic cancer vaccine vectors, in addition to their preclinical and clinical development. They also speculate on the future of Lm-based tumour immunotherapies. The article is based on literature published on PubMed and data reported in clinical trials. Expert opinion: Attenuated strains of Listeria monocytogenes have safely been applied as therapeutic bacterial vectors for the delivery of cancer vaccines. These vectors stimulate MHCI and MHCII pathways as well as the proliferation of antigen-specific T lymphocytes. Several preclinical studies have demonstrated the potency of Lm in intracellular gene and protein delivery in vitro and in vivo. They have also indicated safety and efficiacy in clinical trials. Readers should be aware that the ability of attenuated Lm strains to induce potent immune responses depends on the type of deleted or inactivated Lm virulent gene or genes.

A suicidal strain of Listeria monocytogenes is effective as a DNA vaccine delivery system for oral administration

In this study we determined the in vivo activity of model ovalbumin vaccines delivered by direct intramuscular delivery of plasmid DNA or oral delivery using a recombinant suicidal Listeria monocytogenes strain (rsΔ2). In a previous report we described how rsΔ2 is capable of delivering luciferase, as protein or DNA, in vitro, into non-dividing intestinal epithelial cells (Kuo et al., 2009). This is achieved by engineering a dual expression shuttle vector, pDuLX-Luc, that replicates in E. coli and rsΔ2 and drives gene expression from the Listeria promoter (Phly) as well as the eukaryotic cytomegalovirus promoter (CMV), thereby delivering both protein and plasmid DNA to the cell cytoplasm. For the current in vivo study rsΔ2 containing pDuLX-OVA was used to deliver both ovalbumin protein and the mammalian expression plasmid by the oral route. Controls were used to investigate the activity of this system versus positive and negative controls, as well as quantifying activity against direct intramuscular injection of expression plasmids. Oral administration of rsΔ2(pDuLX-OVA) produced significant titres of antibody and was effective at inducing targeted T-cell lysis (approximately 30% lysis relative to an experimental positive control, intravenous OVA-coated splenocytes+lipopolysaccharide). Intramuscular injection of plasmids pDuLX-OVA or p3L-OVA (which lacks the prokaryotic promoter) also produced significant CTL-mediated cell lysis. The delivery of the negative control rsΔ2 (pDuLX-Luc) confirmed that the observed activity was induced specifically by the ovalbumin vaccination. The data suggest that the oral activity of rsΔ2(pDuLX-OVA) is explained by delivery of OVA protein, expressed in rsΔ2 from the prokaryotic promoter present in pDuLX-OVA, but transfection of mammalian cells in vivo may also play a role. Antibody titres were also produced by oral delivery (in rsΔ2) of the p3L-OVA plasmid in which does not include a prokaryotic promoter.

A Genetically Modified attenuated Listeria Vaccine Expressing HPV16 E7 Kill Tumor Cells in Direct and Antigen-Specific Manner

Attenuated Listeria monocytogenes (L. monocytogenes, LM) induces specific CD8⁺ and CD4⁺ T cell responses, and has been identified as a promising cancer vaccine vector. Cervical cancer is the third most common cancer in women worldwide, with human papillomavirus (HPV), particularly type 16, being the main etiological factor. The therapeutic HPV vaccines are urgently needed. The E7 protein of HPV is necessary for maintaining malignancy in tumor cells. Here, a genetically modified attenuated LM expressing HPV16 E7 protein was constructed. Intraperitoneal vaccination of LM4Δhly::E7 significantly reduced tumor size and even resulted in complete regression of established tumors in a murine model of cervical cancer. We provided evidence that recombinant LM strains could enter the tumor tissue and induce non-specific tumor cell death, probably via activation of reactive oxygen species and increased intracellular Ca²⁺ levels. LM4Δhly::E7 effectively triggered a strong antigen-specific cellular immunity in tumor-bearing mice, and elicited significant infiltration of T cells in the intratumoral milieu. In summary, these data showed LM4Δhly::E7 to be effective in a cervical cancer model and LM4Δhly::E7 induced an antitumor effect by antigen-specific cellular immune responses and direct killing of tumor cells, indicating a potential application against cervical cancer.

Regulator Versus Effector Paradigm: Interleukin-10 as Indicator of the Switching Response

The interleukin-10 (IL-10) is generally considered as the most important cytokine with anti-inflammatory properties and one of the key cytokines preventing inflammation-mediated tissue damage. In this respect, IL-10 producing cells play a crucial role in the outcome of infections, allergy, autoimmune reactions, tumor development, and transplant tolerance. Based on recent findings with regard to the mentioned clinical conditions, this review attempts to shed some light on the IL-10 functions, considering this cytokine as inherent inducer of the switching immunity. While acute infections and vaccinations are associated by IL-10 enhanced during few weeks, chronic parasitoses, tumor diseases, allergen-specific immunotherapy, transplants, and use of immune-suppressor drugs show an increased IL-10 level along months or years. With regard to autoimmune pathologies, the IL-10 increase is prevalently observed during early stages, whereas the successive stages are characterized by reaching of immune equilibrium independently to disease's activity. Together, these findings indicate that IL-10 is mainly produced during transient immune conditions and the persistent IL-10-related effect is the indication/prediction (and maybe effectuation) of the switching immunity. Actual knowledge emphasizes that any manipulation of the IL-10 response for treatment purposes should be considered very cautiously due to its potential hazards to the immune system. Probably, the IL-10 as potential switcher of immunity response should be used in association with co-stimulatory immune effectors that are necessary to determine the appropriate deviation during treatment of respective pathologies. Hopefully, further findings would open new avenues to study the biology of this "master switch" cytokine and its therapeutic potential.

State-of-the-art of regulatory dendritic cells in cancer

Dendritic cells (DCs) with robust immunosuppressive activity are commonly found in the microenvironment of advanced solid tumors. These innate immune cells are generically termed regulatory DCs and include various subsets such as plasmacytoid, conventional and monocyte-derived/inflammatory populations whose normal function is subverted by tumor-derived signals. This review summarizes recent findings on the nature and function of regulatory DCs, their relationship with other myeloid subsets and unique therapeutic opportunities to abrogate malignant progression through their targeting.

Enhancing vaccine effectiveness with delivery technology

Vaccines stand as a very powerful means of disease prevention and treatment. Fundamental to the success of vaccination is the efficient delivery of antigenic cargo needed to trigger an effective immune response. In this article, we will review recent advances in delivery technology with a focus on devices designed to optimally maximize responses to antigen cargo. Included with the review is an overview of traditional vaccine applications and how these approaches can benefit by well-designed delivery methods.

The attenuated hepatocellular carcinoma-specific Listeria vaccine Lmdd-MPFG prevents tumor occurrence through immune regulation of dendritic cells

Immunotherapy is a promising treatment for liver cancer. Here, we tested the ability of the attenuated hepatocellular carcinoma-specific Listeria vaccine (Lmdd-MPFG) to treat hepatocellular carcinoma (HCC) in a mouse model. Immunization with the vaccine caused a strong anti-tumor response, especially in mice reinfused with dendritic cells (DCs). In mice that were also administered DCs, tumor suppression was accompanied by the strongest cytotoxic T lymphocyte response of all treatment groups and by induced differentiation of CD4+ T cells, especially Th17 cells. Additionally, the Lmdd-MPFG vaccine caused maturation of DCs in vitro. We demonstrated the synergistic effect of TLR4 and NLRP3 or NOD1 signaling pathways in LM-induced DC activation. These results suggest that the Lmdd-MPFG vaccine is a feasible strategy for preventing HCC.

CD24 promotes HCC progression via triggering Notch-related EMT and modulation of tumor microenvironment

CD24 is known as a cell surface molecule in hematopoiesis and also described as a diagnostic marker for tumors. Previous studies suggested the important role of CD24 in hepatocellular carcinoma (HCC) pathogenesis. However, precise functions of CD24 in HCC are still unknown. Here, we found that CD24 is highly expressed in HCC both in mRNA and protein levels. Further, the epithelial-mesenchymal transition (EMT) and Notch1 signaling activations mediated by CD24 were elucidated as potential mechanisms of HCC promotion in Hepa1-6/Hepa1-6-CD24 cell models. Additionally, possible systemic immune reaction was explored through immune cells and Hepa1-6/Hepa1-6-CD24 cell co-culture. We demonstrated that the EMT process of HCC cell was effectively induced by CD24; also, the tumor immune microenvironment was changed by facilitating Notch-related EMT in vivo. These results reveal the underlying link between the HCC processes mediated by CD24. Moreover, as a clear tumor promoter, CD24 is considered a potential new target for HCC treatment.

Live-Attenuated Bacterial Vectors: Tools for Vaccine and Therapeutic Agent Delivery

Genetically attenuated microorganisms, including pathogenic and commensal bacteria, can be engineered to carry and deliver heterologous antigens to elicit host immunity against both the vector as well as the pathogen from which the donor gene is derived. These live attenuated bacterial vectors have been given much attention due to their capacity to induce a broad range of immune responses including localized mucosal, as well as systemic humoral and/or cell-mediated immunity. In addition, the unique tumor-homing characteristics of these bacterial vectors has also been exploited for alternative anti-tumor vaccines and therapies. In such approach, tumor-associated antigen, immunostimulatory molecules, anti-tumor drugs, or nucleotides (DNA or RNA) are delivered. Different potential vectors are appropriate for specific applications, depending on their pathogenic routes. In this review, we survey and summarize the main features of the different types of live bacterial vectors and discussed the clinical applications in the field of vaccinology. In addition, different approaches for using live attenuated bacterial vectors for anti-cancer therapy is discussed, and some promising pre-clinical and clinical studies in this field are outlined.

Improving cell-based therapies by nanomodification

Cell-based therapies are emerging as a promising approach for various diseases. Their therapeutic efficacy depends on rational control and regulation of the functions and behaviors of cells during their treatments. Different from conventional regulatory strategy by chemical adjuvants or genetic engineering, which is restricted by limited synergistic regulatory efficiency or uncertain safety problems, a novel approach based on nanoscale artificial materials can be applied to modify living cells to endow them with novel functions and unique properties. Inspired by natural "nano shell" and "nano compass" structures, cell nanomodification can be developed through both external and internal pathways. In this review, some novel cell surface engineering and intracellular nanoconjugation strategies are summarized. Their potential applications are also discussed, including cell protection, cell labeling, targeted delivery and in situ regulation. It is believed that these novel cell-material complexes can have great potentials for biomedical applications.

Trial watch: Naked and vectored DNA-based anticancer vaccines

One type of anticancer vaccine relies on the administration of DNA constructs encoding one or multiple tumor-associated antigens (TAAs). The ultimate objective of these preparations, which can be naked or vectored by non-pathogenic viruses, bacteria or yeast cells, is to drive the synthesis of TAAs in the context of an immunostimulatory milieu, resulting in the (re-)elicitation of a tumor-targeting immune response. In spite of encouraging preclinical results, the clinical efficacy of DNA-based vaccines employed as standalone immunotherapeutic interventions in cancer patients appears to be limited. Thus, efforts are currently being devoted to the development of combinatorial regimens that allow DNA-based anticancer vaccines to elicit clinically relevant immune responses. Here, we discuss recent advances in the preclinical and clinical development of this therapeutic paradigm.

Engineering nanoparticle-coated bacteria as oral DNA vaccines for cancer immunotherapy

Live attenuated bacteria are of increasing importance in biotechnology and medicine in the emerging field of cancer immunotherapy. Oral DNA vaccination mediated by live attenuated bacteria often suffers from low infection efficiency due to various biological barriers during the infection process. To this end, we herein report, for the first time, a new strategy to engineer cationic nanoparticle-coated bacterial vectors that can efficiently deliver oral DNA vaccine for efficacious cancer immunotherapy. By coating live attenuated bacteria with synthetic nanoparticles self-assembled from cationic polymers and plasmid DNA, the protective nanoparticle coating layer is able to facilitate bacteria to effectively escape phagosomes, significantly enhance the acid tolerance of bacteria in stomach and intestines, and greatly promote dissemination of bacteria into blood circulation after oral administration. Most importantly, oral delivery of DNA vaccines encoding autologous vascular endothelial growth factor receptor 2 (VEGFR2) by this hybrid vector showed remarkable T cell activation and cytokine production. Successful inhibition of tumor growth was also achieved by efficient oral delivery of VEGFR2 with nanoparticle-coated bacterial vectors due to angiogenesis suppression in the tumor vasculature and tumor necrosis. This proof-of-concept work demonstrates that coating live bacterial cells with synthetic nanoparticles represents a promising strategy to engineer efficient and versatile DNA vaccines for the era of immunotherapy.

Establishment and characterization of a novel cell line derived from thymoma with myasthenia gravis patients

Background

Thymoma is a cancer with rare incidence, but it is a major malignancy in adult anterior mediastinum, occurring in about 40% of patients with myasthenia gravis. Because of the lack of thymic epithelial tumor cell lines, thymoma has lagged far behind other tumors in cytological studies. It is, therefore, quite necessary to establish a new thymic epithelial tumor cell line from Chinese patients to study the pathogenic mechanism and therapeutic methods.

Methods

Twenty-three samples of tumor tissues were collected from thymoma and thymic carcinoma patients for primary culture by tissue explant, suspension cell culture method, and collagenase digestion. We detected the biological characteristics and origin of the cell line after the establishment of a novel thymoma cell line.

Results

A novel cell line, designed as Thy0517, was established from thymoma type AB with myasthenia gravis patients by tissue explant. As an immortalized cell line, it always has a stable growth cycle, and there is no change in characteristics and morphology after culturing for 18 months and passing 160 generations in vitro. The experimental data demonstrate that the cell line exhibits the growth characteristics of tumor cells, the doubling time of 37 hours, with tumorigenicity in vitro and chromosome abnormality. Immunocytochemistry indicated that the cell line positive expression of CK7, CK8/18, CK19, CK-pan, CD24, BCL-2, P63, Vimentin, epithelial membrane antigen and epidermal growth factor receptor, lymphocyte related antigen CD99, and TdT were negatively expressed.

Conclusions

The newly established thymic epithelial tumor cell line from Chinese patients provides a model in the study of thymoma and molecularly targeted therapies.

Role of liver stem cells in hepatocarcinogenesis

Liver cancer is an aggressive disease with a high mortality rate. Management of liver cancer is strongly dependent on the tumor stage and underlying liver disease. Unfortunately, most cases are discovered when the cancer is already advanced, missing the opportunity for surgical resection. Thus, an improved understanding of the mechanisms responsible for liver cancer initiation and progression will facilitate the detection of more reliable tumor markers and the development of new small molecules for targeted therapy of liver cancer. Recently, there is increasing evidence for the “cancer stem cell hypothesis”, which postulates that liver cancer originates from the malignant transformation of liver stem/progenitor cells (liver cancer stem cells). This cancer stem cell model has important significance for understanding the basic biology of liver cancer and has profound importance for the development of new strategies for cancer prevention and treatment. In this review, we highlight recent advances in the role of liver stem cells in hepatocarcinogenesis. Our review of the literature shows that identification of the cellular origin and the signaling pathways involved is challenging issues in liver cancer with pivotal implications in therapeutic perspectives. Although the dedifferentiation of mature hepatocytes/cholangiocytes in hepatocarcinogenesis cannot be excluded, neoplastic transformation of a stem cell subpopulation more easily explains hepatocarcinogenesis. Elimination of liver cancer stem cells in liver cancer could result in the degeneration of downstream cells, which makes them potential targets for liver cancer therapies. Therefore, liver stem cells could represent a new target for therapeutic approaches to liver cancer in the near future.