Therapeutic Antitumor Efficacy of Cancer Stem Cell-Derived DRibble Vaccine on Colorectal Carcinoma

Crosstalk between colorectal CSCs and immune cells in tumorigenesis, and strategies for targeting colorectal CSCs

Cancer immunotherapy has emerged as a promising strategy in the treatment of colorectal cancer, and relapse after tumor immunotherapy has attracted increasing attention. Cancer stem cells (CSCs), a small subset of tumor cells with self-renewal and differentiation capacities, are resistant to traditional therapies such as radiotherapy and chemotherapy. Recently, CSCs have been proven to be the cells driving tumor relapse after immunotherapy. However, the mutual interactions between CSCs and cancer niche immune cells are largely uncharacterized. In this review, we focus on colorectal CSCs, CSC-immune cell interactions and CSC-based immunotherapy. Colorectal CSCs are characterized by robust expression of surface markers such as CD44, CD133 and Lgr5; hyperactivation of stemness-related signaling pathways, such as the Wnt/β-catenin, Hippo/Yap1, Jak/Stat and Notch pathways; and disordered epigenetic modifications, including DNA methylation, histone modification, chromatin remodeling, and noncoding RNA action. Moreover, colorectal CSCs express abnormal levels of immune-related genes such as MHC and immune checkpoint molecules and mutually interact with cancer niche cells in multiple tumorigenesis-related processes, including tumor initiation, maintenance, metastasis and drug resistance. To date, many therapies targeting CSCs have been evaluated, including monoclonal antibodies, antibody‒drug conjugates, bispecific antibodies, tumor vaccines adoptive cell therapy, and small molecule inhibitors. With the development of CSC-/niche-targeting technology, as well as the integration of multidisciplinary studies, novel therapies that eliminate CSCs and reverse their immunosuppressive microenvironment are expected to be developed for the treatment of solid tumors, including colorectal cancer.

Immunotherapy for colorectal cancer: Rational strategies and novel therapeutic progress

There are increasing incidences and mortality rates for colorectal cancer in the world. It is common for chemotherapy and radiation given to patients with colorectal cancer to cause toxicities that limit their effectiveness and cause cancer cells to become resistant to these treatments. Additional targeted treatments are needed to improve patient's quality of life and outcomes. Immunotherapy has rapidly emerged as an incredibly exciting and promising avenue for cancer treatment in recent years. This innovative approach provides novel options for tackling solid tumors, effectively establishing itself as a new cornerstone in cancer treatment. Specifically, in the realm of colorectal cancer (CRC), there is great promise in developing new drugs that target immune checkpoints, offering a hopeful and potentially transformative solution. While immunotherapy of CRC has made significant advances, there are still obstacles and limitations. CRC patients have a poor response to treatment because of the immune-suppressing function of their tumor microenvironment (TME). In addition to blocking inhibitory immune checkpoints, checkpoint-blocking antibodies may also boost immune responses against tumors. The review summarizes recent advances in immune checkpoint inhibitors (ICIs) for CRC, including CTLA-4, PD-1, PD-L1, LAG-3, and TIM-3.

Efficacy of Whole Cancer Stem Cell-Based Vaccines: A Systematic Review of Preclinical and Clinical Studies

BACKGROUND

Despite the conventional cancer therapeutic, cancer treatment remains a medical challenge due to neoplasm metastasis and cancer recurrence; therefore, new approaches promoting therapeutic strategies are highly desirable. As a new therapy, the use of whole neoplastic stem cells or cancer stem cell (CSC)-based vaccines is one strategy to overcome these obstacles. We investigated the effects of whole CSC-based vaccines on the solid tumor development, metastasis, and survival rate.

METHODS

Primary electronic databases (PubMed/MEDLINE, Scopus, Embase, and Web of Science) and a major clinical registry were searched. Interventional studies of whole CSC-based vaccines in rodent cancer models (38 studies) and human cancer patients (11 studies) were included; the vaccine preparation methodologies, effects, and overall outcomes were evaluated.

RESULTS

Preclinical studies were divided into 4 groups: CSC-lysates/ inactivated-CSC-based vaccines, CSC-lysate-loaded dendritic cell (CSC-DC) vaccines, cytotoxic T-cell (CTL) vaccines generated with CSC-DC (CSC-DC-CTL), and combinatorial treatments carried out in the prophylactic and therapeutic experimental models. The majority of preclinical studies reported a promising effect on tumor growth, survival rate, and metastasis. Moreover, whole CSC-based vaccines induced several antitumor immune responses. A small number of clinical investigations suggested that the whole CSC-based vaccine treatment is beneficial; however, further research is required.

CONCLUSIONS

This comprehensive review provides an overview of the available methods for assessing the efficacy of whole CSC-based vaccines on tumor development, metastasis, and survival rate. In addition, it presents a set of recommendations for designing high-quality clinical studies that may allow to determine the efficacy of whole CSC-based-vaccines in cancer therapy.

Current understanding of cancer stem cells: Immune evasion and targeted immunotherapy in gastrointestinal malignancies

As a relatively rare population of cancer cells existing in the tumor microenvironment, cancer stem cells (CSCs) possess properties of immune privilege to evade the attack of immune system, regulated by the microenvironment of CSCs, the so-called CSCs niche. The bidirectional interaction of CSCs with tumor microenvironment (TME) components favors an immunosuppressive shelter for CSCs' survival and maintenance. Gastrointestinal cancer stem cells (GCSCs) are broadly regarded to be intimately involved in tumor initiation, progression, metastasis and recurrence, with elevated tumor resistance to conventional therapies, which pose a major hindrance to the clinical efficacy for treated patients with gastrointestinal malignancies. Thus, a multitude of efforts have been made to combat and eradicate GCSCs within the tumor mass. Among diverse methods of targeting CSCs in gastrointestinal malignancies, immunotherapy represents a promising strategy. And the better understanding of GCSCs immunomodulation and immunoresistance mechanisms is beneficial to guide and design novel GCSCs-specific immunotherapies with enhanced immune response and clinical efficacy. In this review, we have gathered available and updated information to present an overview of the immunoevasion features harbored by cancer stem cells, and we focus on the description of immune escape strategies utilized by CSCs and microenvironmental regulations underlying CSCs immuno-suppression in the context of gastrointestinal malignancies. Importantly, this review offers deep insights into recent advances of CSC-targeting immunotherapeutic approaches in gastrointestinal cancers.

Colorectal cancer vaccines: The current scenario and future prospects

Colorectal cancer (CRC) is one of the most common cancers worldwide. Current therapies such as surgery, chemotherapy, and radiotherapy encounter obstacles in preventing metastasis of CRC even when applied in combination. Immune checkpoint inhibitors depict limited effects due to the limited cases of CRC patients with high microsatellite instability (MSI-H). Cancer vaccines are designed to trigger the elevation of tumor-infiltrated lymphocytes, resulting in the intense response of the immune system to tumor antigens. This review briefly summarizes different categories of CRC vaccines, demonstrates the current outcomes of relevant clinical trials, and provides particular focus on recent advances on nanovaccines and neoantigen vaccines, representing the trend and emphasis of CRC vaccine development.