Melanoma Immunotherapy in Mice Using Genetically Engineered Pluripotent Stem Cells

Generation of immune cells from induced pluripotent stem cells (iPSCs): Their potential for adoptive cell therapy

Advances in human stem cell technologies enable induced pluripotent stem cells (iPSCs) to be explored as potent candidates for treating various diseases, such as malignancies, autoimmunity, immunodeficiencies, and allergic reactions. iPSCs with infinite self-renewal ability can be derived from different types of somatic cells without the ethical issues associated with embryonic stem cells. To date, numerous cell types, including various immune cell subsets [CD4+ and CD8+ T cells, gamma delta T (γδ T) cells, regulatory T cells, dendritic cells, natural killer cells, macrophages, and neutrophils] have successfully been generated from iPSCs paving the way for effective adoptive cell transfer therapy, drug development, and disease modeling. Herein, we review various iPSC-derived immune cells and their possible application in immunotherapy.

Genomic and T cell repertoire biomarkers associated with malignant mesothelioma survival

BACKGROUND

Malignant mesothelioma (MM) is an exceedingly rare tumor with poor prognosis due to the limited availability of effective treatment. Immunotherapy has emerged as a novel treatment approach for MM, but less than 40% of the patients benefit from it. Thus, it is necessary to identify accurate and effective biomarkers that can predict the overall survival (OS) and immunotherapy efficacy for MM.

METHODS

DNA sequencing was used to identify the genomic landscape based on the data from 86 Chinese patients. T cell receptor (TCR) sequencing was used to characterize MM TCR repertoires of 28 patients between October 2016 and April 2023.

RESULTS

Patients with TP53, NF2, or CDKN2A variants at the genomic level, as well as those exhibiting lower Shannon index (<6.637), lower evenness (<0.028), or higher clonality (≥0.194) according to baseline tumor tissue TCR indexes, demonstrated poorer OS. Furthermore, patients with TP53, CDKN2A, or CDKN2B variants and those with a lower evenness (<0.030) in baseline tumor tissue showed worse immunotherapy efficacy. The present study is the first to identify five special TCR Vβ-Jβ rearrangements associated with MM immunotherapy efficacy.

CONCLUSIONS

The present study reported the largest-scale genomic landscape and TCR repertoire of MM in Chinese patients and identified genomic and TCR biomarkers for the prognosis and immunotherapy efficacy in MM. The study results might provide new insights for prospective MM trials using specific genes, TCR indexes, and TCR clones as biomarkers and offer a reference for future antitumor drugs based on TCR-specific clones.

Predictive value of TCR Vβ-Jβ profile for adjuvant gefitinib in EGFR mutant NSCLC from ADJUVANT-CTONG 1104 trial

Herein, we characterize the landscape and prognostic significance of the T cell receptor (TCR) repertoire of early-stage non-small cell lung cancer (NSCLC) for patients with an epidermal growth factor receptor (EGFR) mutation. β Chain TCR sequencing was used to characterize the TCR repertoires of paraffin-preserved pretreatment tumor and tumor-adjacent tissues from 57 and 44 patients with stage II/III NSCLC with an EGFR mutation treated with gefitinib or chemotherapy in the ADJUVANT-CTONG 1104 trial. The TCR diversity was significantly decreased in patients with an EGFR mutation, and patients with high TCR diversity had a favorable overall survival (OS). A total of 10 TCR Vβ-Jβ rearrangements were significantly associated with OS. Patients with a higher frequency of Vβ5-6Jβ2-1, Vβ20-1Jβ2-1, Vβ24-1Jβ2-1, and Vβ29-1Jβ2-7 had significantly longer OS. Weighted combinations of the 4 TCRs were significantly associated with OS and disease-free survival (DFS) of patients, which could further stratify the high and low TCR diversity groups. Importantly, Vβ5-6Jβ2-1, Vβ20-1Jβ2-1, and Vβ24-1Jβ2-1 had a significant relationship with gefitinib treatment, while Vβ29-1Jβ2-7 was associated with chemotherapy. Four TCR Vβ-Jβ rearrangements related to favorable OS and DFS for adjuvant gefitinib and chemotherapy in patients with an EGFR mutation with stage II/III NSCLC; this may provide a novel perspective for the adjuvant setting for resectable NSCLC.

Stem Cell-Derived Viral Antigen-Specific T Cells Suppress HBV Replication through Production of IFN-γ and TNF-⍺

The viral antigen (Ag)-specific CD8⁺ cytotoxic T lymphocytes (CTLs) derived from pluripotent stem cells (PSCs), i.e., PSC-CTLs, have the ability to suppress hepatitis B virus (HBV) infection. After adoptive transfer, PSC-CTLs can infiltrate into the liver to suppress HBV replication. Nevertheless, the mechanisms by which the viral Ag-specific PSC-CTLs provoke the antiviral response remain to be fully elucidated. In this study, we generated the functional HBV surface Ag-specific CTLs from the induced PSC (iPSCs), i.e., iPSC-CTLs, and investigated the underlying mechanisms of the CTL-mediated antiviral replication in a murine model. We show that adoptive transfer of HBV surface Ag-specific iPSC-CTLs greatly suppressed HBV replication and prevented HBV surface Ag expression. We further demonstrate that the adoptive transfer significantly increased T cell accumulation and production of antiviral cytokines. These results indicate that stem cell-derived viral Ag-specific CTLs can robustly accumulate in the liver and suppress HBV replication through producing antiviral cytokines.

Stem Cell-Derived Viral Ag-Specific T Lymphocytes Suppress HBV Replication in Mice

Hepatitis B virus (HBV) infection is a global health issue. With over 350 million people affected worldwide, HBV infection remains the leading cause of liver cancer. This is a major concern, especially in developing countries. Failure of the immune system to mount an effective response against HBV leads to chronic infection. Although HBV vaccine is present and novel antiviral medicines are being created, eradication of virus-reservoir cells remains a major health topic. Described here is a method for the generation of viral antigen (Ag) -specific CD8⁺ cytotoxic T lymphocytes (CTLs) derived from induced pluripotent stem cells (iPSCs) (i.e., iPSC-CTLs), which have the ability to suppress HBV replication. HBV replication is efficiently induced in mice through hydrodynamic injection of an HBV expression plasmid, pAAV/HBV1.2, into the liver. Then, HBV surface Ag-specific mouse iPSC-CTLs are adoptively transferred, which greatly suppresses HBV replication in the liver and blood as well as prevents HBV surface Ag expression in hepatocytes. This method demonstrates HBV replication in mice after hydrodynamic injection and that stem cell-derived viral Ag-specific CTLs can suppress HBV replication. This protocol provides a useful method for HBV immunotherapy.

Adoptive Cell Transfer: Is it a Promising Immunotherapy for Colorectal Cancer?

The last decade has witnessed significant advances in the adoptive cell transfer (ACT) technique, which has been appreciated as one of the most promising treatments for patients with cancer. Utilization of ACT can enhance the function of the immune system or improve the specificity and persistence of transferred cells. Various immune cells including T lymphocytes, natural killer cells, dendritic cells, and even stem cells can be used in the ACT despite their different functional mechanisms. Colorectal cancer (CRC) is among the most common malignancies and causes millions of deaths worldwide every year. In this review, we discuss the status and perspective of the ACT in the treatment of CRC.

Protective Cancer Vaccine Using Genetically Modified Hematopoietic Stem Cells

Hematopoietic stem cells (HSCs) yield both the myeloid and lymphoid lineages of blood cells and can be reprogrammed into tumor antigen (Ag)-specific CD8⁺ cytotoxic T lymphocytes (CTLs) to prevent tumor growth. However, the optimal approach for differentiating tumor Ag-specific CTLs from HSCs, such as HSC-CTLs, remains elusive. In the current study, we showed that a combination of genetic modification of HSCs and in vivo T cell development facilitates the generation of Ag-specific CTLs that suppressed tumor growth. Murine HSCs, which were genetically modified with chicken ovalbumin (OVA)-specific T cell receptor, were adoptively transferred into recipient mice. In the following week, mice were administered with intraperitoneal injections of an agonist α-Notch 2 antibody and cytokines (rFlt3L and rIL-7) three times. After another two weeks, mice received a subcutaneous inoculation of B16-OVA melanoma cells that express OVA as a surrogate tumor Ag, before the anti-tumor activity of HSC-derived T cells was assessed. OVA-specific CTLs developed in vivo and greatly responded to OVA Ag stimulation ex vivo. In addition, mice receiving genetically modified HSCs and in vivo priming established anti-tumor immunity, resulting in the suppression of tumor growth. These results reported in this present study provide an alternative strategy to develop protective cancer vaccines by using genetically modified HSCs.

Development and characterization of naive single-type tumor antigen-specific CD8+ T lymphocytes from murine pluripotent stem cells

Optimal approaches to differentiate tumor antigen-specific cytotoxic T lymphocytes (CTLs) from pluripotent stem cells (PSCs) remain elusive. In the current study, we showed that combination of in vitro priming through Notch ligands and in vivo development facilitated the generation of tumor Ag-specific CTLs that effectively inhibited tumor growth. We co-cultured the murine induced PSCs (iPSCs) genetically modified with tyrosinase-related protein 2 (TRP2)-specific T cell receptors with OP9 cell line expressing both Notch ligands Delta-like 1 and 4 (OP9-DL1/DL4) for a week before adoptively transferred into recipient C67BL/6 mice. Three weeks later, B16 melanoma cells were inoculated subcutaneously, and the antitumor activity of the iPSC-derived T cells was assessed. We observed the development of the TRP2-specific iPSC-CD8⁺ T cells that responded to Ag stimulation and infiltrated into melanoma tissues, significantly inhibited the tumor growth, and improved the survival of the tumor-bearing mice. Thus, this approach may provide a novel effective strategy to treatment of malignant tumors.

Stem Cell-Derived Regulatory T Cells for Therapeutic Use in Arthritis

Pluripotent stem cells (PSCs) can be utilized to obtain a renewable source of healthy regulatory T cells (T_regs) to treat autoimmune arthritis as they have the ability to produce almost all cell types in the body, including T_regs. However, the right conditions for the development of antigen (Ag)-specific T_regs from PSCs (i.e., PSC-T_regs) remain unknown. An ongoing project will determine the mechanisms underlying the Ag-specific PSC-T_reg treatments that aim to modulate tolerance in autoimmune arthritis. The knowledge gained from these studies will provide new insights into cell-based therapies in autoimmune arthritis, and advance the understanding of fundamental mechanisms underlying T_reg differentiation.

Development of Auto Antigen-specific Regulatory T Cells for Diabetes Immunotherapy

CD4⁺ regulatory T cells (Tregs) are essential for normal immune surveillance, and their dysfunction can lead to the development of autoimmune diseases, such as type-1 diabetes (T1D). T1D is a T cell-mediated autoimmune disease characterized by islet β cell destruction, hypoinsulinemia, and severely altered glucose homeostasis. Tregs play a critical role in the development of T1D and participate in peripheral tolerance. Pluripotent stem cells (PSCs) can be utilized to obtain a renewable source of healthy Tregs to treat T1D as they have the ability to produce almost all cell types in the body, including Tregs. However, the right conditions for the development of antigen (Ag)-specific Tregs from PSCs (i.e., PSC-Tregs) remain undefined, especially molecular mechanisms that direct differentiation of such Tregs. Auto Ag-specific PSC-Tregs can be programmed to be tissue-associated and infiltrate to local inflamed tissue (e.g., islets) to suppress autoimmune responses after adoptive transfer, thereby avoiding potential overall immunosuppression from non-specific Tregs. Developing auto Ag-specific PSC-Tregs can reduce overall immunosuppression after adoptive transfer by accumulating inflamed islets, which drives forward the use of therapeutic PSC-Tregs for cell-based therapies in T1D.

Technical Considerations for the Generation of Adoptively Transferred T Cells in Cancer Immunotherapy

A significant function of the immune system is the surveillance and elimination of aberrant cells that give rise to cancer. Even when tumors are well established and metastatic, immune-mediated spontaneous regressions have been documented. While there are have been various forms of immunotherapy, one of the most widely studied for almost 40 years is adoptive cellular immunotherapy, but its success has yet to be fully realized. Adoptive cell transfer (ACT) is a therapeutic modality that has intrigued physicians and researchers for its many theoretical benefits. Preclinical investigations and human trials have utilized natural killer (NK) cells, dendritic cells (DC), macrophages, T-cells or B-cells for ACT with the most intense research focused on T-cell ACT. T-cells are exquisitely specific to the target of its T-cell receptor (TCR), thus potentially reducing the amount of collateral damage and off-target effects from treatment. T-cells also possess a memory subset that may reduce the risk of recurrence of a cancer after the successful treatment of the primary disease. There are several options for the source of T-cells used in the generation of cells for ACT. Perhaps the most widely known source is T-cells generated from tumor-infiltrating lymphocytes (TILs). However, studies have also employed peripheral blood mononuclear cells (PBMCs), lymph nodes, and even induced pluripotent stem cells (IPSCs) as a source of T-cells. Several important technical considerations exist regarding benefits and limitations of each source of T-cells. Unique aspects of T-cells factor into their ability to be efficacious in ACT including the total number of cells available for ACT, the anti-tumor efficacy on a per cell basis, the repertoire of TCRs specific to tumor cells, and their ability to traffic to various organs that harbor tumor. Current research is attempting to unlock the full potential of these cells to effectively and safely treat cancer.