Functional OCT4-specific CD4+ and CD8+ T cells in healthy controls and ovarian cancer patients

Tumor microenvironment of cancer stem cells: Perspectives on cancer stem cell targeting

There are few tumor cell subpopulations with stem cell characteristics in tumor tissue, defined as cancer stem cells (CSCs) or cancer stem-like cells (CSLCs), which can reconstruct neoplasms with malignant biological behaviors such as invasiveness via self-renewal and unlimited generation. The microenvironment that CSCs depend on consists of various cellular components and corresponding medium components. Among these factors existing at a variety of levels and forms, cytokine networks and numerous signal pathways play an important role in signaling transduction. These factors promote or maintain cancer cell stemness, and participate in cancer recurrence, metastasis, and resistance. This review aims to summarize the recent molecular data concerning the multilayered relationship between CSCs and CSC-favorable microenvironments. We also discuss the therapeutic implications of targeting this synergistic interplay, hoping to give an insight into targeting cancer cell stemness for tumor therapy and prognosis.

Anti-ovarian cancer actions and pharmacological targets of plumbagin

Ovarian cancer is a gynecological malignancy characterized with increasing death rate in the world. It is clinically reported that chemotherapy against ovarian cancer is still found with poor curative effect and potential side effect. Plumbagin is an emerging anti-cancer compound. Although some experimental findings of plumbagin anti-ovarian cancer activity are described, the pharmacological targets should be further explored. In this study, we aimed to investigate the underlying pharmacological activities and targets of plumbagin against ovarian cancer in vitro. As results, in silico docking analysis suggested plumbagin potently treating ovarian cancer through regulating pharmacological targets, including octamer-binding transcription factor 4 (OCT4) and Kruppel-like factor 4 (KLF4). The preliminary experimental data showed that plumbagin treatment inhibited cell growth and induced apoptosis in cancer cells. In addition, decreased mRNA expressions of intracellular OCT4, PCNA, and elevated KLF4 mRNA activation were detected in plumbagin-treated cancer cells. Furthermore, immunostaining determination showed reduced OCT4-positive cells and increased KLF4-positive cells were observed following plumbagin treatments. To sum up, our current findings have preliminarily showed the anti-ovarian cancer benefits of plumbagin, and the pharmacological targets may be identified as KLF4 and OCT4 pathway. Thus, we conclude that plumbagin may be a bioactive compound for ovarian cancer treatment.

Ovarian cancer stem cells: Critical roles in anti-tumor immunity

Ovarian cancer is a significant cause of cancer-related mortality in women. Over the past 3 decades, there has been a high incidence of recurrent chemoresistant disease, despite the relative effectiveness of current treatment strategies. This is partly attributed to cancer stem cells (CSC), a subpopulation that has acquired stem cell properties that allow these cells to evade standard chemotherapy and cause disease recurrence. Therefore, there is an urgent need for basic knowledge about CSC to develop innovative therapeutic approaches for ovarian cancer. These CSC subpopulations have been identified in ovarian cancer cell lines, tumors or ascites, and findings suggest that ovarian CSCs may be as heterogeneous as the disease itself. CSCs regulate the phenotype and function of immune cells involved in antitumor immunity, so a better understanding of the signaling pathways that interact between CSCs, immune cells and tumor cells will pave the way for the clinical application of CS in cancer immunotherapy. This review will focus on the markers currently used to identify and isolate these cells summarize current knowledge on the molecular and cellular mechanisms responsible for CSC-dependent regulation of antitumor immune responses. We will discuss the signaling pathways involved in CSC survival, replication, and differentiation as well as potential therapeutic targeting strategies.

Cancer stem-like cells evade CD8+CD103+ tumor-resident memory T (TRM) lymphocytes by initiating an epithelial-to-mesenchymal transition program in a human lung tumor model

Background

Cancer stem cells (CSC) define a population of rare malignant cells endowed with ‘stemness’ properties, such as self-renewing, multipotency and tumorigenicity. They are responsible for tumor initiation and progression, and could be associated with resistance to immunotherapies by negatively regulating antitumor immune response and acquiring molecular features enabling escape from CD8 T-cell immunity. However, the immunological hallmarks of human lung CSC and their potential interactions with resident memory T (T_RM) cells within the tumor microenvironment have not been investigated.

Methods

We generated a non-small cell lung cancer model, including CSC line and clones, and autologous CD8⁺CD103⁺ T_RM and CD8⁺CD103⁻ non-T_RM clones, to dissect out immune properties of CSC and their susceptibility to specific T-cell-mediated cytotoxic activity.

Results

Unlike their parental tumor cells, lung CSC are characterized by the initiation of an epithelial-to-mesenchymal transition program defined by upregulation of the SNAIL1 transcription factor and downregulation of phosphorylated-GSK-3β and cell surface E-cadherin. Acquisition of a CSC profile results in partial resistance to T_RM-cell-mediated cytotoxicity, which correlates with decreased surface expression of the CD103 ligand E-cadherin and human leukocyte antigen-A2-neoepitope complexes. On the other hand, CSC gained expression of intercellular adhesion molecule (ICAM)-1 and thereby sensitivity to leukocyte function-associated antigen (LFA)-1-dependent non-T_RM-cell-mediated killing. Cytotoxicity is inhibited by anti-ICAM-1 and anti-major histocompatibility complex class I neutralizing antibodies further emphasizing the role of LFA-1/ICAM-1 interaction in T-cell receptor-dependent lytic function.

Conclusion

Our data support the rational design of immunotherapeutic strategies targeting CSC to optimize their responsiveness to local CD8⁺CD103⁺ T_RM cells for more efficient anticancer treatments.

Immune evasion by cancer stem cells

Tumor immunity represents a new avenue for cancer therapy. Immune checkpoint inhibitors have successfully improved outcomes in several tumor types. In addition, currently, immune cell-based therapy is also attracting significant attention. However, the clinical efficacy of these treatments requires further improvement. The mechanisms through which cancer cells escape the immune response must be identified and clarified. Cancer stem cells (CSCs) play a central role in multiple aspects of malignant tumors. CSCs can initiate tumors in partially immunocompromised mice, whereas non-CSCs fail to form tumors, suggesting that tumor initiation is a definitive function of CSCs. However, the fact that non-CSCs also initiate tumors in more highly immunocompromised mice suggests that the immune evasion property may be a more fundamental feature of CSCs rather than a tumor-initiating property. In this review, we summarize studies that have elucidated how CSCs evade tumor immunity and create an immunosuppressive milieu with a focus on CSC-specific characteristics and functions. These profound mechanisms provide important clues for the development of novel tumor immunotherapies.

Immune Curbing of Cancer Stem Cells by CTLs Directed to NANOG

Cancer stem cells (CSCs) have been identified as the source of tumor growth and disease recurrence. Eradication of CSCs is thus essential to achieve durable responses, but CSCs are resistant to current anti-tumor therapies. Novel therapeutic approaches that specifically target CSCs will, therefore, be crucial to improve patient outcome. Immunotherapies, which boost the body's own immune system to eliminate cancerous cells, could be an alternative approach to target CSCs. Vaccines of dendritic cells (DCs) loaded with tumor antigens can evoke highly specific anti-tumor T cell responses. Importantly, DC vaccination also promotes immunological memory formation, paving the way for long-term cancer control. Here, we propose a DC vaccination that specifically targets CSCs. DCs loaded with NANOG peptides, a protein required for maintaining stem cell properties, could evoke a potent anti-tumor immune response against CSCs. We hypothesize that the resulting immunological memory will also control newly formed CSCs, thereby preventing disease recurrence.

Phenotypic characterization and anticancer capacity of CD8+ cytokine-induced killer cells after antigen-induced expansion

Cytokine-induced killer cells (CIK) have been used in clinic for adoptive immunotherapy in a variety of malignant tumors and have improved the prognosis of cancer patients. However, there are individual differences in the CIK cell preparations including the obvious differences in the ratio of effector CIK cells among different cancer patients. Infusion of such heterogeneous immune cell preparation is an important factor that would affect the therapeutic efficacy. We report here the enrichment and expansion of CD8+ cells from CIK cells cultured for one week using magnetic activated cell sorting (MACS). These enriched CD8+ CIK cells expressed T cell marker CD3 and antigen recognition receptor NKG2D. Phenotypic analysis showed that CD8+ CIK cells contained 32.4% of CD3+ CD56+ natural killer (NK)-like T cells, 23.6% of CD45RO+ CD28+, and 50.5% of CD45RA+ CD27+ memory T cells. In vitro cytotoxic activity assay demonstrated that the enriched CD8+ CIK cells had significant cytotoxic activity against K562 cells and five ovarian cancer cell lines. Intriguingly, CD8+ CIK cells had strong cytotoxic activity against OVCAR3 cells that has weak binding capability to NKG2D. Flow cytometry and quantitative RT-PCR analysis revealed that OVCAR3 cells expressed HLA-I and OCT4 and Sox2, suggesting that CD8+ CIK cells recognize surface antigen via specific T cell receptor and effectively kill the target cells. The results suggest that transplantation of such in vitro enriched and expanded OCT4-specific CD8+ CIK cells may improve the specific immune defense mechanism against cancer stem cells, providing a novel avenue of cancer stem cell targeted immunotherapy for clinical treatment of ovarian cancer.

Monitoring cancer stem cells: insights into clinical oncology

Cancer stem cells (CSCs) are a small, characteristically distinctive subset of tumor cells responsible for tumor initiation and progression. Several treatment modalities, such as surgery, glycolytic inhibition, driving CSC proliferation, immunotherapy, and hypofractionated radiotherapy, may have the potential to eradicate CSCs. We propose that monitoring CSCs is important in clinical oncology as CSC populations may reflect true treatment response and assist with managing treatment strategies, such as defining optimal chemotherapy cycles, permitting pretreatment cancer surveillance, conducting a comprehensive treatment plan, modifying radiation treatment, and deploying rechallenge chemotherapy. Then, we describe methods for monitoring CSCs.

Cellular immunotherapy in ovarian cancer: Targeting the stem of recurrence

Ovarian cancer is a devastating disease with a high relapse rate. Due to a mostly asymptomatic early stage and lack of early diagnostic tools, the disease is usually diagnosed in a late stage. Surgery and chemotherapy with taxanes and platinum compounds are very effective in reducing tumor burden. However, relapses occur frequently and there is a lack of credible second-line options. Therefore, new treatment modalities are eagerly awaited. The presence and influx of immune cells in the ovarian cancer tumor microenvironment are correlated with survival. High numbers of infiltrating T cells correlate with improved progression free and overall survival, while the presence of regulatory T cells and expression of T cell inhibitory molecules is correlated with a poor prognosis. These data indicate that immunotherapy, especially cell-based immunotherapy could be a promising novel addition to the treatment of ovarian cancer. Here, we review the available data on the immune contexture surrounding ovarian cancer and discuss novel strategies and targets for immunotherapy in ovarian cancer. In the end the addition of immunotherapy to existing therapeutic options could lead to a great improvement in the outcome of ovarian cancer, especially when targeting cancer stem cells.

Restoring immunosurveillance by dendritic cell vaccines and manipulation of the tumor microenvironment

Cancer cells evolve from normal cells throughout life and are usually recognized by our immune system and destroyed, a process called immunosurveillance. Unfortunately, in some instances cancer cells paralyze our immune system, resulting in outgrowth and spreading of the tumor. Understanding the complexity of immunomodulation by tumors is important for the development of therapeutical strategies. Nowadays, various approaches have been developed to enhance anti-tumor immune responses and abrogate the immune dampening effect of the tumor and its surrounding environment, including dendritic cell-based vaccines, therapies to counteract myeloid derived suppressor cell function within the tumor and antagonists of inhibitory signaling pathways to overcome 'immune checkpoints'. The challenge is now to find the right combination of immune based therapies to fully restore immune function and provide a more efficacious and enduring anti-tumor response.

The stem cell markers Oct4A, Nanog and c-Myc are expressed in ascites cells and tumor tissue of ovarian cancer patients

PURPOSE

The aim of this study was to examine the expression of established stem cell markers in ascites and tumor tissue obtained from ovarian cancer patients.

METHODS

Mononuclear cells present in ascites were collected by density gradient centrifugation. Intracellular flowcytometry was used to assess the putative presence of stem cell markers. RT-PCR was used to detect full length Oct4A, a splice variant Oct4B, implicated in glioma and breast cancer, Oct4 pseudogenes and c-Myc. Genes were cloned and sequenced to determine putative mutations. Confocal laser scanning microscopy was performed to localize the markers in ascites cells as well as in tumor tissue. Material from carcinomas other than epithelial ovarian carcinoma served as control.

RESULTS

A small quantity of cells in ascites and in tumor tissue of ovarian cancer patients was detected that expresses c-Myc, Oct4A and Nanog. Besides Oct4A, present in the nucleus, also the cytoplasmic resident Oct4B splice variant was detected. Remarkably, c-Myc was found partially in the cytoplasm. Since no mutations in c-Myc were found that could explain the cytoplasmic localization, we hypothesize that this is due an IL-6 induced c-Myc shuttle factor.

CONCLUSIONS

The expression of stem cell genes was detected in a small proportion of tumor cells present in ascites as well as in tumor tissue. IL-6 plays an important role in the induction of c-Myc.