Simultaneously target of normal and stem cells-like gastric cancer cells via cisplatin and anti-CD133 CAR-T combination therapy

Angiogenesis causes and vasculogenic mimicry formation in the context of cancer stem cells

Tumor occurrence, development, invasion, and metastasis are regulated by multiple mechanisms. Among these, angiogenesis promotes tumor progression mainly by supplying tumor tissue and providing channels for tumor metastasis. Cancer stem cells (CSCs) are another important factor affecting tumor progression by involving in tumor initiation and development, while remaining insensitive to conventional antitumor treatments. Among treatment strategies for them, owing to the existence of alternative angiogenic pathways or the risk of damaging normal stem cells, the clinical effect is not ideal. Angiogenesis and CSCs may influence each other in this process. Tumor angiogenesis can support CSC self-renewal by providing a suitable microenvironment, whereas CSCs can regulate tumor neovascularization and mediate drug resistance to anti-angiogenic therapy. This review summarized the role of vascular niche formed by angiogenesis in CSC self-renewal and stemness maintenance, and the function of CSCs in endothelial progenitor cell differentiation and pro-angiogenic factor upregulation. We also elucidated the malignant loop between CSCs and angiogenesis promoting tumor progression. Additionally, we summarized and proposed therapeutic targets, including blocking tumor-derived endothelial differentiation, inhibiting pro-angiogenic factor upregulation, and directly targeting endothelial-like cells comprising CSCs. And we analyzed the feasibility of these strategies to identify more effective methods to improve tumor treatment.

Unraveling the triad of hypoxia, cancer cell stemness, and drug resistance

In the domain of addressing cancer resistance, challenges such as limited effectiveness and treatment resistance remain persistent. Hypoxia is a key feature of solid tumors and is strongly associated with poor prognosis in cancer patients. Another significant portion of the development of acquired drug resistance is attributed to tumor stemness. Cancer stem cells (CSCs), a small tumor cell subset with self-renewal and proliferative abilities, are crucial for tumor initiation, metastasis, and intra-tumoral heterogeneity. Studies have shown a significant association between hypoxia and CSCs in the context of tumor resistance. Recent studies reveal a strong link between hypoxia and tumor stemness, which together promote tumor survival and progression during treatment. This review elucidates the interplay between hypoxia and CSCs, as well as their correlation with resistance to therapeutic drugs. Targeting pivotal genes associated with hypoxia and stemness holds promise for the development of novel therapeutics to combat tumor resistance.

Breaking Immunosuppression to Enhance Cancer Stem Cell-Targeted Immunotherapy

Cancer stem cell (CSC)-targeted immunotherapy has emerged as a novel strategy in cancer treatment in the past decade. However, its efficacy is significantly limited due to the existence of host immune suppressive activity. Specifically, programmed cell death ligand-1 (PD-L1) is overexpressed in CSCs, and PD-L1 overexpressed CSCs create immunosuppressive milieu via interacting with various immune cells in tumor microenvironments (TME). Hence, novel immunotherapeutic strategies targeting CSCs with concurrent immunosuppression interruption will be promising in enhancing anti-CSC effects. These include dendritic cell (DC) and nanodisc (ND)-based vaccines to present CSC antigens in the forms of CSC lysate, CSC-marker proteins, and CSC-derived peptides to induce anti-CSC immunity. In addition, CSC-directed bispecific antibodies (BiAbs) and antibody drug conjugates (ADCs) have been developed to target CSCs effectively. Furthermore, chimeric antigen receptor (CAR)-T cell therapy and natural killer (NK) cell-based therapy targeting CSCs have achieved progress in both solid and hematologic tumors, and inhibition of CSC associated signaling pathways has proven successful. In this review, we aimed to outline the roles and regulatory mechanisms of PD-L1 in the properties of CSCs; the crosstalk between CSCs and immunosuppressive cells in TME, and recent progress and future promises of immunosuppression blockage to enhance CSC-targeted immunotherapy.

Therapeutic advantage of combinatorial chimeric antigen receptor T cell and chemotherapies

Chimeric antigen receptor (CAR) T cell therapies have transformed outcomes for many patients with hematological malignancies. However, some patients do not respond to CAR T cell treatment, and adapting CAR T cells for treatment of solid and brain tumors has been met with many challenges, including a hostile tumor microenvironment and poor CAR T cell persistence. Thus, it is unlikely that CAR T cell therapy alone will be sufficient for consistent, complete tumor clearance across patients with cancer. Combinatorial therapies of CAR T cells and chemotherapeutics are a promising approach for overcoming this because chemotherapeutics could augment CAR T cells for improved antitumor activity or work in tandem with CAR T cells to clear tumors. Herein, we review efforts toward achieving successful CAR T cell and chemical drug combination therapies. We focus on combination therapies with approved chemotherapeutics because these will be more easily translated to the clinic but also review nonapproved chemotherapeutics and drug screens designed to reveal promising new CAR T cell and chemical drug combinations. Overall, this review highlights the promise of CAR T cell and chemotherapy combinations with a specific focus on how combinatorial therapy overcomes challenges faced by either monotherapy and supports the potential of this therapeutic strategy to improve outcomes for patients with cancer. SIGNIFICANCE STATEMENT: Improving currently available CAR T cell products via combinatorial therapy with chemotherapeutics has the potential to drastically expand the types of cancers and number of patients that could benefit from these therapies when neither alone has been sufficient to achieve tumor clearance. Herein, we provide a thorough review of the current efforts toward studying CAR T and chemotherapy combinatorial therapies and offer perspectives on optimal ways to identify new and effective combinations moving forward.

CAR-T cell therapy: Advances in digestive system malignant tumors

Malignant tumors of the digestive system have had a notoriously dismal prognosis throughout history. Immunotherapy, radiotherapy, surgery, and chemotherapy are the primary therapeutic approaches for digestive system cancers. The rate of recurrence and metastasis, nevertheless, remains elevated. As one of the immunotherapies, chimeric antigen receptor T cell (CAR-T) therapy has demonstrated a promising antitumor effect in hematologic cancer. Despite undergoing numerous clinical trials, the ineffective antitumor effect and adverse effects of CAR-T cell therapy in the treatment of digestive system cancers continue to impede its clinical translation. It is necessary to surmount the restricted options for targeting proteins, the obstacles that impede CAR-T cell infiltration into solid tumors, and the limited survival time in vivo. We examined and summarized the developments, obstacles, and countermeasures associated with CAR-T therapy in digestive system cancers. Emphasis was placed on the regulatory functions of potential antigen targets, the tumor microenvironment, and immune evasion in CAR-T therapy. Thus, our analysis has furnished an all-encompassing comprehension of CAR-T cell therapy in digestive system cancers, which will generate tremendous enthusiasm for subsequent in-depth research into CAR-T-based therapies in digestive system cancers.

Novel immunotherapeutic approaches in gastric cancer

Gastric cancer is a malignant tumor that ranks third in cancer-related deaths worldwide. Early-stage gastric cancer can often be effectively managed through surgical resection. However, the majority of cases are diagnosed in advanced stages, where outcomes with conventional radiotherapy and chemotherapy remain unsatisfactory. Immunotherapy offers a novel approach to treating molecularly heterogeneous gastric cancer by modifying the immunosuppressive tumor microenvironment. Immune checkpoint inhibitors and adoptive cell therapy are regarded as promising modalities in cancer immunotherapy. Food and Drug Administration-approved programmed death-receptor inhibitors, such as pembrolizumab, in combination with chemotherapy, have significantly extended overall survival in gastric cancer patients and is recommended as a first-line treatment. Despite challenges in solid tumor applications, adoptive cell therapy has demonstrated efficacy against various targets in gastric cancer treatment. Among these approaches, chimeric antigen receptor-T cell therapy research is the most widely explored and chimeric antigen receptor-T cell therapy targeting claudin18.2 has shown acceptable safety and robust anti-tumor capabilities. However, these advancements primarily remain in preclinical stages and further investigation should be made to promote their clinical application. This review summarizes the latest research on immune checkpoint inhibitors and adoptive cell therapy and their limitations, as well as the role of nanoparticles in enhancing immunotherapy.

CAR-T cell therapy: Challenge and opportunity for effective treatment of small cell lung cancer

Small cell lung cancer (SCLC) is a devastating malignancy characterized by rapid metastasis, drug resistance, and frequent recurrence. Owing to the paucity of existing therapeutic options, the prognosis of SCLC remains poor. Recently, the combination of immune checkpoint inhibitors and chemotherapy has resulted in modest improvements in treatment responses. In this review, we characterize the biological signature of SCLC and outline the obstacles to current treatment, including impaired antigen presentation and T cell infiltration. These obstacles may potentially be overcome by chimeric antigen receptor (CAR)-T cell therapy. For the first time, we summarize the available data and discuss the future prospects of CAR-T cell therapy for the treatment of SCLC. Given the high heterogeneity and immunosuppressive tumor microenvironment of SCLC, structural modifications of CAR-T cells and combination therapy may be required to elicit a successful antitumor response. Further research, including clinical trials, is needed to determine the suitability of CAR-T cell therapy as a treatment for SCLC.

Beyond Conventional Treatments: Exploring CAR-T Cell Therapy for Cancer Stem Cell Eradication

BACKGROUND

For decades cancer remained the center of attention in the scientific community as its survival rates are low. Researchers from all around the world wanted to know the core of the problem as to what initiates cancer in a patient and helps with its progression. Many postulations came to light, but Cancer Stem Cells (CSC) was the most appealing and convincing.

MAIN BODY

In this review, we shed light on a potential solution to the problem by reviewing CAR-T cells (Chimeric antigen receptor T cells). These specialized T cells are designed to detect specific antigens on cancer cells. We analyse the steps of their formation from the collection of T cells from the patient's bloodstream and modifying it to exhibit specific CAR structures on their surfaces, to reinjecting them back and evaluating their efficacy. We thoroughly investigate the structure of the CAR design with improvements across different generations. The focus extends to the unique properties of CSCs as in how targeting specific markers on them can enhance the precision of cancer therapy.

CONCLUSION

Despite the successes, the review discusses the existing limitations and toxicities associated with CAR-derived therapies, highlighting the ongoing need for research and refinement. Looking ahead, we explore proposed strategies aimed at optimizing CAR-T cell therapy to mitigate adverse effects for improved cancer treatments.

Cancer Stem Cell markers: Symphonic masters of chemoresistance and immune evasion

Cancer Stem Cells (CSCs) are highly tumorigenic, chemoresistant, and immune evasive. They emerge as a central driver that gives rise to the bulk of tumoral mass, modifies the tumor microenvironment (TME), and exploits it, leading to poor clinical outcomes for patients with cancer. The existence of CSCs thus accounts for the failure of conventional therapies and immune surveillance. Identifying CSCs in solid tumors remains a significant challenge in modern oncology, with the use of cell surface markers being the primary strategy for studying, isolating, and enriching these cells. In this review, we explore CSC markers, focusing on the underlying signaling pathways that drive CSC self-renewal, which simultaneously makes them intrinsically chemoresistant and immune system evaders. We comprehensively discuss the autonomous and non-autonomous functions of CSCs, with particular emphasis on their interactions with the tumor microenvironment, especially immune cells. This reciprocal network enhances CSCs malignancy while compromising the surrounding niche, ultimately defining therapeutic vulnerabilities associated with each CSC marker. The most common CSCs surface markers addressed in this review-CD44, CD133, ICAM1/CD54, and LGR5-provide insights into the interplay between chemoresistance and immune evasion, two critically important phenomena in disease eradication. This new perspective on the state-of-the-art of CSCs will undoubtedly open new avenues for therapy.

MiR-21-5p Modulates Cisplatin-Resistance of CD44+ Gastric Cancer Stem Cells Through Regulating the TGF-β2/SMAD Signaling Pathway

Background

Cisplatin (DDP) resistance in gastric cancer (GC) is likely to come from gastric cancer stem cells (GCSC). It is a new idea to study the mechanism of the DDP-resistance in GCSC from miRNA.

Materials and Methods

CD44+ GCSCs and CD44- control cells were constructed based on the HGC27 gastric cancer cell line. DDP sensitivities in CD44+ and CD44- cells were detected via CCK-8 assay. The differential expression of miR-21-5p in these cell lines was detected by RT‒qPCR. The expression levels of downstream TGF-β2, SMAD2 and SMAD3 were determined through RT‒PCR and Western blotting. A luciferase assay was used to detect the relationship between miR-21-5p and TGFB2, and the TCGA database, clinical data from our centre, and vivo experiment were used for validation. Finally, we knocked down miR-21-5p to detect changes in cisplatin resistance in GCSCs and to verify changes in the levels of downstream pathways in GCSCs.

Results

CD44+ GCSCs induced cisplatin resistance compared with CD44- cells. miR-21-5p was highly expressed in GCSCs, and the TGF-β2/SMAD pathway was also highly expressed. TGFB2 was proven to be a downstream target gene of miR-21-5p and had a positive relationship with it in phenotype. After knockdown of miR-21-5p, the TGF-β2/SMAD pathway was also inhibited, and the resistance of GCSCs to cisplatin was specifically decreased.

Conclusion

MiR-21-5p promotes cisplatin resistance in gastric cancer stem cells by regulating the TGF-β2/SMAD signalling pathway.

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

Improvement of current immunotherapies with engineered oncolytic viruses that target cancer stem cells

The heterogeneity of the solid tumor microenvironment (TME) impairs the therapeutic efficacy of standard therapies and also reduces the infiltration of antitumor immune cells, all of which lead to tumor progression and invasion. In addition, self-renewing cancer stem cells (CSCs) support tumor dormancy, drug resistance, and recurrence, all of which might pose challenges to the eradication of malignant tumor masses with current therapies. Natural forms of oncolytic viruses (OVs) or engineered OVs are known for their potential to directly target and kill tumor cells or indirectly eradicate tumor cells by involving antitumor immune responses, including enhancement of infiltrating antitumor immune cells, induction of immunogenic cell death, and reprogramming of cold TME to an immune-sensitive hot state. More importantly, OVs can target stemness factors that promote tumor progression, which subsequently enhances the efficacy of immunotherapies targeting solid tumors, particularly the CSC subpopulation. Herein, we describe the role of CSCs in tumor heterogeneity and resistance and then highlight the potential and remaining challenges of immunotherapies targeting CSCs. We then review the potential of OVs to improve tumor immunogenicity and target CSCs and finally summarize the challenges within the therapeutic application of OVs in preclinical and clinical trials.

Targeted immunotherapy to cancer stem cells: A novel strategy of anticancer immunotherapy

Cancer is a major disease that endangers human health. Cancer drug resistance and relapse are the two main causes contributing to cancer treatment failure. Cancer stem cells (CSCs) are a small fraction of tumor cells that are responsible for tumorigenesis, metastasis, relapse, and resistance to conventional anticancer therapies. Therefore, CSCs are considered to be the root of cancer recurrence, metastasis, and drug resistance. Novel anticancer strategies need to face this new challenge and explore their efficacy against CSCs. Recently, immunotherapy has made rapid advances in cancer treatment, and its potential against CSCs is also an interesting area of research. Meanwhile, immunotherapy strategies are novel therapeutic modalities with promising results in targeting CSCs. In this review, we summarize the targeting of CSCs by various immunotherapy strategies such as monoclonal antibodies(mAb), tumor vaccines, immune checkpoint inhibitors, and chimeric antigen receptor-T cells(CAR-T) in pre-clinical and clinical studies. This review provides new insights into the application of these immunotherapeutic approaches to potential anti-tumor therapies in the future.

N6-methyladenosine reader hnRNPA2B1 recognizes and stabilizes NEAT1 to confer chemoresistance in gastric cancer

BACKGROUND

Chemoresistance is a major cause of treatment failure in gastric cancer (GC). Heterogeneous nuclear ribonucleoprotein A2B1 (hnRNPA2B1) is an N6-methyladenosine (m6A)-binding protein involved in a variety of cancers. However, whether m6A modification and hnRNPA2B1 play a role in GC chemoresistance is largely unknown. In this study, we aimed to investigate the role of hnRNPA2B1 and the downstream mechanism in GC chemoresistance.

METHODS

The expression of hnRNPA2B1 among public datasets were analyzed and validated by quantitative PCR (qPCR), Western blotting, immunofluorescence, and immunohistochemical staining. The biological functions of hnRNPA2B1 in GC chemoresistance were investigated both in vitro and in vivo. RNA sequencing, methylated RNA immunoprecipitation, RNA immunoprecipitation, and RNA stability assay were performed to assess the association between hnRNPA2B1 and the binding RNA. The role of hnRNPA2B1 in maintenance of GC stemness was evaluated by bioinformatic analysis, qPCR, Western blotting, immunofluorescence, and sphere formation assays. The expression patterns of hnRNPA2B1 and downstream regulators in GC specimens from patients who received adjuvant chemotherapy were analyzed by RNAscope and multiplex immunohistochemistry.

RESULTS

Elevated expression of hnRNPA2B1 was found in GC cells and tissues, especially in multidrug-resistant (MDR) GC cell lines. The expression of hnRNPA2B1 was associated with poor outcomes of GC patients, especially in those who received 5-fluorouracil treatment. Silencing hnRNPA2B1 effectively sensitized GC cells to chemotherapy by inhibiting cell proliferation and inducing apoptosis both in vitro and in vivo. Mechanically, hnRNPA2B1 interacted with and stabilized long noncoding RNA NEAT1 in an m6A-dependent manner. Furthermore, hnRNPA2B1 and NEAT1 worked together to enhance the stemness properties of GC cells via Wnt/β-catenin signaling pathway. In clinical specimens from GC patients subjected to chemotherapy, the expression levels of hnRNPA2B1, NEAT1, CD133, and CD44 were markedly elevated in non-responders compared with responders.

CONCLUSION

Our findings indicated that hnRNPA2B1 interacts with and stabilizes lncRNA NEAT1, which contribute to the maintenance of stemness property via Wnt/β-catenin pathway and exacerbate chemoresistance in GC.

Tumor cell stemness in gastrointestinal cancer: regulation and targeted therapy

The cancer stem cells are a rare group of self-renewable cancer cells capable of the initiation, progression, metastasis and recurrence of tumors, and also a key contributor to the therapeutic resistance. Thus, understanding the molecular mechanism of tumor stemness regulation, especially in the gastrointestinal (GI) cancers, is of great importance for targeting CSC and designing novel therapeutic strategies. This review aims to elucidate current advancements in the understanding of CSC regulation, including CSC biomarkers, signaling pathways, and non-coding RNAs. We will also provide a comprehensive view on how the tumor microenvironment (TME) display an overall tumor-promoting effect, including the recruitment and impact of cancer-associated fibroblasts (CAFs), the establishment of an immunosuppressive milieu, and the induction of angiogenesis and hypoxia. Lastly, this review consolidates mainstream novel therapeutic interventions targeting CSC stemness regulation.

Functional Roles of CD133: More than Stemness Associated Factor Regulated by the Microenvironment

CD133 protein has been one of the most used surface markers to select and identify cancer cells with stem-like features. However, its expression is not restricted to tumoral cells; it is also expressed in differentiated cells and stem/progenitor cells in various normal tissues. CD133 participates in several cellular processes, in part orchestrating signal transduction of essential pathways that frequently are dysregulated in cancer, such as PI3K/Akt signaling and the Wnt/β-catenin pathway. CD133 expression correlates with enhanced cell self-renewal, migration, invasion, and survival under stress conditions in cancer. Aside from the intrinsic cell mechanisms that regulate CD133 expression in each cellular type, extrinsic factors from the surrounding niche can also impact CD33 levels. The enhanced CD133 expression in cells can confer adaptive advantages by amplifying the activation of a specific signaling pathway in a context-dependent manner. In this review, we do not only describe the CD133 physiological functions known so far, but importantly, we analyze how the microenvironment changes impact the regulation of CD133 functions emphasizing its value as a marker of cell adaptability beyond a cancer-stem cell marker.

Cisplatin-Based Combination Therapy for Enhanced Cancer Treatment

Cisplatin, a primary chemotherapeutic drug, is of great value in the realm of tumor treatment. However, its clinical efficacy is strictly hindered by issues, such as drug resistance, relapse, poor prognosis, and toxicity to normal tissue. Cisplatin-based combination therapy has garnered increasing attention in both preclinical and clinical cancer research for its ability to overcome resistance, reduce toxicity, and enhance anticancer effects. This review examines three primary co-administration strategies of cisplatin-based drug combinations and their respective advantages and disadvantages. Additionally, seven types of combination therapies involving cisplatin are discussed, focusing on their main therapeutic effects, mechanisms in preclinical research, and clinical applications. This review also discusses future prospects and challenges, aiming to offer guidance for the development of optimal cisplatin-based combination therapy regimens for improved cancer treatment.

Can CD133 Be Regarded as a Prognostic Biomarker in Oncology: Pros and Cons

The CD133 cell membrane glycoprotein, also termed prominin-1, is expressed on some of the tumor cells of both solid and blood malignancies. The CD133-positive tumor cells were shown to exhibit higher proliferative activity, greater chemo- and radioresistance, and enhanced tumorigenicity compared to their CD133-negative counterparts. For this reason, CD133 is regarded as a potential prognostic biomarker in oncology. The CD133-positive cells are related to the cancer stem cell subpopulation in many types of cancer. Recent studies demonstrated the involvement of CD133 in the regulation of proliferation, autophagy, and apoptosis in cancer cells. There is also evidence of its participation in the epithelial-mesenchymal transition associated with tumor progression. For a number of malignant tumor types, high CD133 expression is associated with poor prognosis, and the prognostic significance of CD133 has been confirmed in a number of meta-analyses. However, some published papers suggest that CD133 has no prognostic significance or even demonstrate a certain correlation between high CD133 levels and a positive prognosis. This review summarizes and discusses the existing evidence for and against the prognostic significance of CD133 in cancer. We also consider possible reasons for conflicting findings from the studies of the clinical significance of CD133.

Update on immune-based therapy strategies targeting cancer stem cells

Accumulating data reveals that tumors possess a specialized subset of cancer cells named cancer stem cells (CSCs), responsible for metastasis and recurrence of malignancies, with various properties such as self-renewal, heterogenicity, and capacity for drug resistance. Some signaling pathways or processes like Notch, epithelial to mesenchymal transition (EMT), Hedgehog (Hh), and Wnt, as well as CSCs' surface markers such as CD44, CD123, CD133, and epithelial cell adhesion molecule (EpCAM) have pivotal roles in acquiring CSCs properties. Therefore, targeting CSC-related signaling pathways and surface markers might effectively eradicate tumors and pave the way for cancer survival. Since current treatments such as chemotherapy and radiation therapy cannot eradicate all of the CSCs and tumor relapse may happen following temporary recovery, improving novel and more efficient therapeutic options to combine with current treatments is required. Immunotherapy strategies are the new therapeutic modalities with promising results in targeting CSCs. Here, we review the targeting of CSCs by immunotherapy strategies such as dendritic cell (DC) vaccines, chimeric antigen receptors (CAR)-engineered immune cells, natural killer-cell (NK-cell) therapy, monoclonal antibodies (mAbs), checkpoint inhibitors, and the use of oncolytic viruses (OVs) in pre-clinical and clinical studies. This review will mainly focus on blood malignancies but also describe solid cancers.

Targeted delivery of a PD-1-blocking scFv by CD133-specific CAR-T cells using nonviral Sleeping Beauty transposition shows enhanced antitumour efficacy for advanced hepatocellular carcinoma

BACKGROUND

CD133 is considered a marker for cancer stem cells (CSCs) in several types of tumours, including hepatocellular carcinoma (HCC). Chimeric antigen receptor-specific T (CAR-T) cells targeting CD133-positive CSCs have emerged as a tool for the clinical treatment of HCC, but immunogenicity, the high cost of clinical-grade recombinant viral vectors and potential insertional mutagenesis limit their clinical application.

METHODS

CD133-specific CAR-T cells secreting PD-1 blocking scFv (CD133 CAR-T and PD-1 s cells) were constructed using a sleeping beauty transposon system from minicircle technology, and the antitumour efficacy of CD133 CAR-T and PD-1 s cells was analysed in vitro and in vivo.

RESULTS

A univariate analysis showed that CD133 expression in male patients at the late stage (II and III) was significantly associated with worse progression-free survival (PFS) (P = 0.0057) and overall survival (OS) (P = 0.015), and a multivariate analysis showed a trend toward worse OS (P = 0.041). Male patients with advanced HCC exhibited an approximately 20-fold higher PD-L1 combined positive score (CPS) compared with those with HCC at an early stage. We successfully generated CD133 CAR-T and PD-1 s cells that could secrete PD-1 blocking scFv based on a sleeping beauty system involving minicircle vectors. CD133 CAR-T and PD-1 s cells exhibited significant antitumour activity against HCC in vitro and in xenograft mouse models. Thus, CD133 CAR-T and PD-1 s cells may be a therapeutically tractable strategy for targeting CD133-positive CSCs in male patients with advanced HCC.

CONCLUSIONS

Our study provides a nonviral strategy for constructing CAR-T cells that could also secrete checkpoint blockade inhibitors based on a Sleeping Beauty system from minicircle vectors and revealed a potential benefit of this strategy for male patients with advanced HCC and high CD133 expression (median immunohistochemistry score > 2.284).

Novel insights into cancer stem cells targeting: CAR-T therapy and epigenetic drugs as new pillars in cancer treatment

Cancer stem cells (CSCs) represent the most aggressive subpopulation present in the tumor bulk retaining invasive capabilities, metastatic potential and high expression levels of drug efflux pumps responsible for therapy resistance. Cancer is still an incurable disease due to the inefficacy of standard regimens that spare this subpopulation. Selective targeting of CSCs is still an unmet need in cancer research field. Aberrant epigenetic reprogramming promotes the initiation and maintenance of CSCs, which are able to escape the immune system defense. Promising therapeutic approaches able to induce the selective inhibition of this stem-like small subset include immunotherapy alone or in combination with epigenetic compounds. These strategies are based on the specific expression of epitopes and/or epigenetic alterations present only in the CSC and not in the other cancer cells or normal cells. Thus, the combined approach utilizing CAR-T immunotherapy along with epigenetic probes may overcome the barriers of treatment ineffectiveness towards a more precision medicine approach in patients with known specific alterations of CSCs. In this perspective article we will shed new lights on the future applications of epi-immunotherapy in tumors enriched in CSCs, along with its potential side-effects, limitations and the development of therapy resistance.

Current progress and challenges of immunotherapy in gastric cancer: A focus on CAR-T cells therapeutic approach

Gastric cancer (GC) is a severe malignancy, accounting for the third most common cancer death worldwide. Despite the development of chemo-radiation therapy, there has not been sufficient survival advantage in patients with GC who were treated by these methods. GC immunogenicity is hampered by a highly immunosuppressive microenvironment; therefore, further understanding of the molecular biology of GC is the potential to achieve new therapeutic strategies in GC therapy, including specific immunotherapy. Current immunotherapies are mainly based on cytokines, immune checkpoints, monoclonal antibodies (mAb), bispecific antibodies (BisAbs), antibody-drug conjugates (ADCs), and chimeric antigen receptor (CAR). Immunotherapy has made significant progress in the treatment of GC, so that studies show that nivolumab as a programmed death 1 (PD1) inhibitor has proper safety and effectiveness as a third-line treatment for GC patients. Multiple monoclonal antibodies like ramucirumab and claudiximab were effective in treating GC patients, especially in combination with other treatments. Despite the challenges of CAR therapy in solid tumors, CAR therapy targets various GC cells targets; among them, intercellular adhesion molecule (ICAM)-1 CAR-T cell and CLDN18.2 CAR-T cell have shown promising results. Although responses to all these treatments are encouraging and in some cases, durable, these successes are not seen in all treated patients. The present review represents the development of various immunotherapies especially CAR-T cell therapy, its current use, clinical data in GC, and their limitations.

Immunotargeting of Cancer Stem Cells

The generally accepted view is that CSCs hijack the signaling pathways attributed to normal stem cells that regulate the self-renewal and differentiation processes. Therefore, the development of selective targeting strategies for CSC, although clinically meaningful, is associated with significant challenges because CSC and normal stem cells share many important signaling mechanisms for their maintenance and survival. Furthermore, the efficacy of this therapy is opposed by tumor heterogeneity and CSC plasticity. While there have been considerable efforts to target CSC populations by the chemical inhibition of the developmental pathways such as Notch, Hedgehog (Hh), and Wnt/β-catenin, noticeably fewer attempts were focused on the stimulation of the immune response by CSC-specific antigens, including cell-surface targets. Cancer immunotherapies are based on triggering the anti-tumor immune response by specific activation and targeted redirecting of immune cells toward tumor cells. This review is focused on CSC-directed immunotherapeutic approaches such as bispecific antibodies and antibody-drug candidates, CSC-targeted cellular immunotherapies, and immune-based vaccines. We discuss the strategies to improve the safety and efficacy of the different immunotherapeutic approaches and describe the current state of their clinical development.

Cancer cell targeting by CAR-T cells: A matter of stemness

Chimeric antigen receptor (CAR)-T cell therapy represents one of the most innovative immunotherapy approaches. The encouraging results achieved by CAR-T cell therapy in hematological disorders paved the way for the employment of CAR engineered T cells in different types of solid tumors. This adoptive cell therapy represents a selective and efficacious approach to eradicate tumors through the recognition of tumor-associated antigens (TAAs). Binding of engineered CAR-T cells to TAAs provokes the release of several cytokines, granzyme, and perforin that ultimately lead to cancer cells elimination and patient's immune system boosting. Within the tumor mass a subpopulation of cancer cells, known as cancer stem cells (CSCs), plays a crucial role in drug resistance, tumor progression, and metastasis. CAR-T cell therapy has indeed been exploited to target CSCs specific antigens as an effective strategy for tumor heterogeneity disruption. Nevertheless, a barrier to the efficacy of CAR-T cell-based therapy is represented by the poor persistence of CAR-T cells into the hostile milieu of the CSCs niche, the development of resistance to single targeting antigen, changes in tumor and T cell metabolism, and the onset of severe adverse effects. CSCs resistance is corroborated by the presence of an immunosuppressive tumor microenvironment (TME), which includes stromal cells, cancer-associated fibroblasts (CAFs), tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), and immune cells. The relationship between TME components and CSCs dampens the efficacy of CAR-T cell therapy. To overcome this challenge, the double strategy based on the use of CAR-T cell therapy in combination with chemotherapy could be crucial to evade immunosuppressive TME. Here, we summarize challenges and limitations of CAR-T cell therapy targeting CSCs, with particular emphasis on the role of TME and T cell metabolic demands.

Tumor microenvironment-mediated immune tolerance in development and treatment of gastric cancer

Tumor microenvironment is the general term for all non-cancer components and their metabolites in tumor tissue. These components include the extracellular matrix, fibroblasts, immune cells, and endothelial cells. In the early stages of tumors, the tumor microenvironment has a tumor suppressor function. As the tumor progresses, tumor immune tolerance is induced under the action of various factors, such that the tumor suppressor microenvironment is continuously transformed into a tumor-promoting microenvironment, which promotes tumor immune escape. Eventually, tumor cells manifest the characteristics of malignant proliferation, invasion, metastasis, and drug resistance. In recent years, stress effects of the extracellular matrix, metabolic and phenotypic changes of innate immune cells (such as neutrophils, mast cells), and adaptive immune cells in the tumor microenvironment have been revealed to mediate the emerging mechanisms of immune tolerance, providing us with a large number of emerging therapeutic targets to relieve tumor immune tolerance. Gastric cancer is one of the most common digestive tract malignancies worldwide, whose mortality rate remains high. According to latest guidelines, the first-line chemotherapy of advanced gastric cancer is the traditional platinum and fluorouracil therapy, while immunotherapy for gastric cancer is extremely limited, including only Human epidermal growth factor receptor 2 (HER-2) and programmed death ligand 1 (PD-L1) targeted drugs, whose benefits are limited. Clinical experiments confirmed that cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), vascular endothelial growth factor receptor (VEGFR) and other targeted drugs alone or in combination with other drugs have limited efficacy in patients with advanced gastric cancer, far less than in lung cancer, colon cancer, and other tumors. The failure of immunotherapy is mainly related to the induction of immune tolerance in the tumor microenvironment of gastric cancer. Therefore, solving the immune tolerance of tumors is key to the success of gastric cancer immunotherapy. In this study, we summarize the latest mechanisms of various components of the tumor microenvironment in gastric cancer for inducing immune tolerance and promoting the formation of the malignant phenotype of gastric cancer, as well as the research progress of targeting the tumor microenvironment to overcome immune tolerance in the treatment of gastric cancer.

Tumor buster - where will the CAR-T cell therapy 'missile' go?

Chimeric antigen receptor (CAR) T cell (CAR-T cell) therapy based on gene editing technology represents a significant breakthrough in personalized immunotherapy for human cancer. This strategy uses genetic modification to enable T cells to target tumor-specific antigens, attack specific cancer cells, and bypass tumor cell apoptosis avoidance mechanisms to some extent. This method has been extensively used to treat hematologic diseases, but the therapeutic effect in solid tumors is not ideal. Tumor antigen escape, treatment-related toxicity, and the immunosuppressive tumor microenvironment (TME) limit their use of it. Target selection is the most critical aspect in determining the prognosis of patients receiving this treatment. This review provides a comprehensive summary of all therapeutic targets used in the clinic or shown promising potential. We summarize CAR-T cell therapies' clinical trials, applications, research frontiers, and limitations in treating different cancers. We also explore coping strategies when encountering sub-optimal tumor-associated antigens (TAA) or TAA loss. Moreover, the importance of CAR-T cell therapy in cancer immunotherapy is emphasized.

Advances in CAR T-cell therapy in bile duct, pancreatic, and gastric cancers

Bile duct, pancreatic, and gastric cancers are deadly digestive system tumors with high malignancy and poor patient prognosis. The efficiencies of conventional surgical treatment, radiation therapy, and chemotherapy are limited. In contrast, chimeric antigen receptor (CAR) T-cell therapy represents a landmark therapeutic approach to antitumor immunity with great efficacy in treating several hematological malignancies. CAR T-cell therapy involves genetically engineering the expression of specific antibodies based on the patient's T-cell surface and amplifying these antibodies to identify and target tumor-associated antigens. CAR T-cell therapy can effectively inhibit disease progression and improve the survival of patients with bile duct, pancreatic, and gastric cancers. The effectiveness of CAR T cells in tumor therapy can be validated using xenograft models, providing a scientific testing platform. In this study, we have reviewed the progress in CAR T-cell production and its development, focusing on the current status and optimization strategies for engineered CAR T cells in the bile duct, pancreatic, and gastric cancers.

Therapeutic strategies for gastric cancer targeting immune cells: Future directions

Gastric cancer (GC) is a malignancy with a high incidence and mortality, and the emergence of immunotherapy has brought survival benefits to GC patients. Compared with traditional therapy, immunotherapy has the advantages of durable response, long-term survival benefits, and lower toxicity. Therefore, targeted immune cells are the most promising therapeutic strategy in the field of oncology. In this review, we introduce the role and significance of each immune cell in the tumor microenvironment of GC and summarize the current landscape of immunotherapy in GC, which includes immune checkpoint inhibitors, adoptive cell therapy (ACT), dendritic cell (DC) vaccines, reduction of M2 tumor-associated macrophages (M2 TAMs), N2 tumor-associated neutrophils (N2 TANs), myeloid-derived suppressor cells (MDSCs), effector regulatory T cells (eT_regs), and regulatory B cells (B_regs) in the tumor microenvironment and reprogram TAMs and TANs into tumor killer cells. The most widely used immunotherapy strategies are the immune checkpoint inhibitor programmed cell death 1/programmed death-ligand 1 (PD-1/PD-L1) antibody, cytotoxic T lymphocyte–associated protein 4 (CTLA-4) antibody, and chimeric antigen receptor T (CAR-T) in ACT, and these therapeutic strategies have significant anti-tumor efficacy in solid tumors and hematological tumors. Targeting other immune cells provides a new direction for the immunotherapy of GC despite the relatively weak clinical data, which have been confirmed to restore or enhance anti-tumor immune function in preclinical studies and some treatment strategies have entered the clinical trial stage, and it is expected that more and more effective immune cell–based therapeutic methods will be developed and applied.

Targeting Gastric Cancer Stem Cells to Enhance Treatment Response

Gastric cancer (GC) was the fourth deadliest cancer in the world in 2020, and about 770,000 people died from GC that year. The death of patients with GC is mainly caused by the metastasis, recurrence, and chemotherapy resistance of GC cells. The cancer stem cell theory defines cancer stem cells (CSCs) as a key factor in the metastasis, recurrence, and chemotherapy resistance of cancer. It considers targeting gastric cancer stem cells (GCSCs) to be an effective method for the treatment of GC. For GCSCs, genes or noncoding RNAs are important regulatory factors. Many experimental studies have found that some drugs can target the stemness of gastric cancer by regulating these genes or noncoding RNAs, which may bring new directions for the clinical treatment of gastric cancer. Therefore, this review mainly discusses related genes or noncoding RNAs in GCSCs and drugs that target its stemness, thereby providing some information for the treatment of GC.

A promising antitumor method: Targeting CSC with immune cells modified with CAR

Tumors pose a great threat to human health; as a subgroup of tumor cells, cancer stem cells (CSCs) contribute to the genesis, development, metastasis, and recurrence of tumors because of their enhanced proliferation and multidirectional differentiation. Thus, a critical step in tumor treatment is to inhibit CSCs. Researchers have proposed many methods to inhibit or reduce CSCs, including monoclonal antibodies targeting specific surface molecules of CSCs, signal pathway inhibitors, and energy metabolic enzyme inhibitors and inducing differentiation therapy. Additionally, immunotherapy with immune cells engineered with a chimeric antigen receptor (CAR) showed favorable results. However, there are few comprehensive reviews in this area. In this review, we summarize the recent CSC targets used for CSC inhibition and the different immune effector cells (T cells, natural killer (NK) cells, and macrophages) which are engineered with CAR used for CSC therapy. Finally, we list the main challenges and options in targeting CSC with CAR-based immunotherapy. The design targeting two tumor antigens (one CSC antigen and one mature common tumor antigen) should be more reasonable and practical; meanwhile, we highlight the potential of CAR-NK in tumor treatment.

From Anti-HER-2 to Anti-HER-2-CAR-T Cells: An Evolutionary Immunotherapy Approach for Gastric Cancer

Current Therapeutic modalities provide no survival advantage to gastric cancer (GC) patients. Targeting the human epidermal growth factor receptor-2 (HER-2) is a viable therapeutic strategy against advanced HER-2 positive GC. Antibody-drug conjugates, small-molecule tyrosine kinase inhibitors (TKIs), and bispecific antibodies are emerging as novel drug forms that may abrogate the resistance to HER-2-specific drugs and monoclonal antibodies. Chimeric antigen receptor-modified T cells (CAR-T) targeting HER-2 have shown considerable therapeutic potential in GC and other solid tumors. However, due to the high heterogeneity along with the complex tumor microenvironment (TME) of GC that often leads to immune escape, the immunological treatment of GC still faces many challenges. Here, we reviewed and discussed the current progress in the research of anti-HER-2-CAR-T cell immunotherapy against GC.

Mathematical Modeling of Tumor and Cancer Stem Cells Treated with CAR-T Therapy and Inhibition of TGF- β

The stem cell hypothesis suggests that there is a small group of malignant cells, the cancer stem cells, that initiate the development of tumors, encourage its growth, and may even be the cause of metastases. Traditional treatments, such as chemotherapy and radiation, primarily target the tumor cells leaving the stem cells to potentially cause a recurrence. Chimeric antigen receptor (CAR) T-cell therapy is a form of immunotherapy where the immune cells are genetically modified to fight the tumor cells. Traditionally, the CAR T-cell therapy has been used to treat blood cancers and only recently has shown promising results against solid tumors. We create an ordinary differential equations model which allows for the infusion of trained CAR-T cells to specifically attack the cancer stem cells that are present in the solid tumor microenvironment. Additionally, we incorporate the influence of TGF-β which inhibits the CAR-T cells and thus promotes the growth of the tumor. We verify the model by comparing it to available data and then examine combinations of CAR-T cell treatment targeting both non-stem and stem cancer cells and a treatment that reduces the effectiveness of TGF-β to determine the scenarios that eliminate the tumor.

Antitumor responses in gastric cancer by targeting B7H3 via chimeric antigen receptor T cells

Background

Gastric cancer (GC) has a poor prognosis and limited therapeutic options. As a new promising cancer therapeutic approach, chimeric antigen receptor (CAR)-T cells represent a potential GC treatment. We investigated the antitumor activity of CAR-T cells target-B7H3 in GC.

Methods

In our study, expression of B7H3 was examined in GC tissues and explored the tumoricidal potential of B7H3-targeting CAR-T cells in GC. B7H3-directed CAR-T cells with a humanized antigen-recognizing domain was generated. The anti-tumor effects of this CAR-T cell were finally investigated in vitro and in vivo.

Results

Our results show that B7H3-directed CAR-T cells efficiently killed GC tumor cells. In addition, we found that B7H3 is correlated with tumor cell stemness, and anti-B7H3 CAR-T can simultaneously target stem cell-like GC cells to improve the treatment outcome.

Conclusions

Our study indicates that B7H3 is an attractive target for GC therapy, and B7H3 has high potential for clinical application.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02471-8.

Emerging roles of CD133 in the treatment of gastric cancer, a novel stem cell biomarker and beyond

Gastric cancer (GC) is an aggressive disease with one of the highest mortality rates in the world. In the early stage, most patients are asymptomatic and early diagnosis is difficult. Recently, cancer stem cells (CSCs) have been highlighted as crucial emerging factors in the initiation or invasiveness of solid tumors. CD133, a CSC marker, is highly expressed in various tumors including gastric cancer. CD133-positive cells showed elevated malignant biological behaviors and CD133 upregulation is related to chemoresistance, cancer relapse, and poor prognosis. CD133 also plays an important role in the progression of tumors and metastasis. This review summarizes the current knowledge of the role of CD133 expression in GC and aims to contribute at identifying promising new strategies for treatment and management of gastric cancer.