Spontaneous and therapy-induced immunity to pluripotency genes in humans: clinical implications, opportunities and challenges

RNA-loaded dendritic cells: more than a tour de force in cancer therapeutics

A wide array of therapeutic strategies has been implemented against cancers, yet their clinical benefit is limited. The lack of clinical efficacy of the conventional treatment options might be due to the inept immune competency of the patients. Dendritic cells (DCs) have a vital role in initiating and directing immune responses and have been frequently used as delivery vehicles in clinical research. The recent clinical data suggest the potential use of DCs pulsed with nucleic acid, especially with RNA holds a great potential as an immunotherapeutic measure with compare to other cancer therapeutics. This review mainly deals with the DCs and their role in transfection with RNA in cancer immunotherapy.

Therapeutic Cancer Vaccines

Cancer is one of the major leading death causes of diseases. Prevention and treatment of cancer is an important way to decrease the incidence of tumorigenesis and prolong patients' lives. Subversive achievements on cancer immunotherapy have recently been paid much attention after many failures in basic and clinical researches. Based on deep analysis of genomics and proteomics of tumor antigens, a variety of cancer vaccines targeting tumor antigens have been tested in preclinical and human clinical trials. Many therapeutic cancer vaccines alone or combination with other conventional treatments for cancer obtained spectacular efficacy, indicating the tremendously potential application in clinic. With the illustration of underlying mechanisms of cancer immune regulation, valid, controllable, and persistent cancer vaccines will play important roles in cancer treatment, survival extension and relapse and cancer prevention. This chapter mainly summarizes the recent progresses and developments on cancer vaccine research and clinical application, thus exploring the existing obstacles in cancer vaccine research and promoting the efficacy of cancer vaccine.

The Effect of MicroRNA-375 Overexpression, an Inhibitor of Helicobacter pylori-Induced Carcinogenesis, on lncRNA SOX2OT

Background

Helicobacter pylori is a major human pathogenic bacterium in gastric mucosa. Although the association between gastric cancer and H. pylori has been well-established, the molecular mechanisms underlying H. pylori-induced carcinogenesis are still under investigation. MicroRNAs (miRNAs) are small noncoding RNAs that modulate gene expression at the posttranscriptional level. Recently, studies have revealed that miRNAs are involved in immune response and host cell response to bacteria. Also, microRNA-375 (miR-375) is a key regulator of epithelial properties that are necessary for securing epithelium-immune system cross-talk. It has been recently reported that miR-375 acts as an inhibitor of H. pylori-induced gastric carcinogenesis. There are few reports on miRNA-mediated targeting long noncoding RNAs (lncRNAs).

Objectives

This study aimed to examine the possible effect of miR-375 as an inhibitor of H. pylori-induced carcinogenesis on the expression of lncRNA SOX2 overlapping transcript (SOX2OT) and SOX2, a master regulator of pluripotency of cancer stem cells.

Materials and Methods

In a model cell line, NT-2 was transfected with the constructed expression vector pEGFP-C1 contained miR-375. The RNA isolations and cDNA synthesis were performed after 48 hours of transformation. Expression of miR-375 and SOX2OT and SOX2 were quantified using real-time polymerase chain reaction and compared with control cells transfected with pEGFP-C1-Mock clone. Cell cycle modification was also compared after transfections using the flow cytometry analysis.

Results

Following ectopic expression of miR-375, SOX2OT and SOX2 expression analysis revealed a significant decrease in their expression level (P < 0.05) in NT-2 cells compared to the control. Cell cycle analysis following ectopic expression of miR-375 in the NT-2 cells using propidium iodine staining revealed significant extension in sub-G1 cell cycle.

Conclusions

This is the first report to show down-regulation of SOX2OT and SOX2 following induced expression of miR-375. This finding may suggest expression regulation potential between different classes of ncRNAs, for example between miR-375 and SOX2OT. This data not only extends our understanding of possible ncRNA interactions in cancers but also may open novel investigation lines towards elucidation of molecular mechanisms controlling H. pylori inflammation and carcinogenesis.

Antitumor DNA vaccination against the Sox2 transcription factor

As cancer stem cells (CSCs) are resistant to chemotherapy, radiotherapy and targeted molecular therapy, immunotherapy of tumors could be aimed at their elimination. Markers specific for CSCs have not been identified to date, but microarray analyses have shown that CSCs and embryonic stem cells use similar transcriptional programs, thus suggesting the production of shared transcription factors. In this study, we developed an experimental DNA vaccine against the transcription factor Sox2 that is important for self-renewal of stem cells and is overexpressed in numerous human cancers. The Sox2 gene was codon optimized for the expression in human cells, its sequences encoding two nuclear localization signals (NLSs) were mutagenized, and the sequence coding for the PADRE helper epitope was fused with its 5' terminus. While codon optimization did not increase Sox2 production and mutagenesis in NLSs only partially reduced nuclear localization of Sox2, the addition of the PADRE epitope was crucial for the enhancement of Sox2 immunogenicity. The antitumor effect was shown after immunization against mouse oncogenic TC-1/B7 cells derived from the lung cancer cell line TC-1 and characterized by high Sox2 production. Sox2-specific reactivity in an ELISPOT assay was further augmented by the depletion of regulatory T (Treg) cells, but this depletion did not enhance the antitumor effect. These data demonstrated the induction of immune responses against the Sox2 self-antigen, but did not confirm the usefulness of Treg depletion when combined with antitumor vaccination.

Therapeutic cancer vaccines: past, present, and future

Therapeutic vaccines represent a viable option for active immunotherapy of cancers that aim to treat late stage disease by using a patient's own immune system. The promising results from clinical trials recently led to the approval of the first therapeutic cancer vaccine by the U.S. Food and Drug Administration. This major breakthrough not only provides a new treatment modality for cancer management but also paves the way for rationally designing and optimizing future vaccines with improved anticancer efficacy. Numerous vaccine strategies are currently being evaluated both preclinically and clinically. This review discusses therapeutic cancer vaccines from diverse platforms or targets as well as the preclinical and clinical studies employing these therapeutic vaccines. We also consider tumor-induced immune suppression that hinders the potency of therapeutic vaccines, and potential strategies to counteract these mechanisms for generating more robust and durable antitumor immune responses.

Therapeutic cancer vaccines

Therapeutic cancer vaccines have the potential of being integrated in the therapy of numerous cancer types and stages. The wide spectrum of vaccine platforms and vaccine targets is reviewed along with the potential for development of vaccines to target cancer cell "stemness," the epithelial-to-mesenchymal transition (EMT) phenotype, and drug-resistant populations. Preclinical and recent clinical studies are now revealing how vaccines can optimally be used with other immune-based therapies such as checkpoint inhibitors, and so-called nonimmune-based therapeutics, radiation, hormonal therapy, and certain small molecule targeted therapies; it is now being revealed that many of these traditional therapies can lyse tumor cells in a manner as to further potentiate the host immune response, alter the phenotype of nonlysed tumor cells to render them more susceptible to T-cell lysis, and/or shift the balance of effector:regulatory cells in a manner to enhance vaccine efficacy. The importance of the tumor microenvironment, the appropriate patient population, and clinical trial endpoints is also discussed in the context of optimizing patient benefit from vaccine-mediated therapy.

Nestin expression throughout multistep pathogenesis of multiple myeloma

The stem cell marker nestin (NES) is found in dividing cells of developing and regenerating tissues. Upon terminal differentiation, NES expression is diminished but may be re-expressed following injury or in cancer. Surprisingly, we recently confirmed NES as a tumour-specific marker for mature CD138(+) 38(+) plasma cells (PC) in multiple myeloma (MM). The present study analysed NES expression throughout the spectrum of MM developmental stages, starting with individuals with no haematological malignancy, through monoclonal gammopathy of undetermined significance (MGUS) and MM to plasma cell leukaemia (PCL) and MM cell lines. NES was analysed in bone marrow PC of 163 MM, four PCL and nine MGUS patients, 10 individuals with no haematological malignancy and 6 myeloma cell lines (OPM-2, RPMI-8226, MOLP-8, U-266, EJM, NCI-H929) by flow cytometry and/or real-time polymerase chain reaction or immunochemistry. We observed a tendency of increased NES expression in parallel with disease progression. NES was evaluated as a reliable marker for accurate discrimination between MM patients and the control group. High NES levels were strongly associated with the presence of 1q21 gain. For the first time, NES was demonstrated to predict worse response to conventional therapy/novel agents. These results suggest that NES might become a useful clinical parameter with an important role in MM pathogenesis.

Therapeutic cancer vaccines: current status and moving forward

Concurrent with U.S. Food and Drug Administration (FDA) approval of the first therapeutic cancer vaccine, a wide spectrum of other cancer vaccine platforms that target a diverse range of tumor-associated antigens is currently being evaluated in randomized phase II and phase III trials. The profound influence of the tumor microenvironment and other immunosuppressive entities, however, can limit the effectiveness of these vaccines. Numerous strategies are currently being evaluated both preclinically and clinically to counteract these immunosuppressive entities, including the combined use of vaccines with immune checkpoint inhibitors, certain chemotherapeutics, small-molecule targeted therapies, and radiation. The potential influence of the appropriate patient population and clinical trial endpoint in vaccine therapy studies is discussed, as well as the potential importance of biomarkers in future directions of this field.

Patients with multiple myeloma develop SOX2-specific autoantibodies after allogeneic stem cell transplantation

The occurrence of SOX2-specific autoantibodies seems to be associated with an improved prognosis in patients with monoclonal gammopathy of undetermined significance (MGUS). However, it is unclear if SOX2-specific antibodies also develop in established multiple myeloma (MM). Screening 1094 peripheral blood (PB) sera from 196 MM patients and 100 PB sera from healthy donors, we detected SOX2-specific autoantibodies in 7.7% and 2.0% of patients and donors, respectively. We identified SOX2_211–230 as an immunodominant antibody-epitope within the full protein sequence. SOX2 antigen was expressed in most healthy tissues and its expression did not correlate with the number of BM-resident plasma cells. Accordingly, anti-SOX2 immunity was not related to SOX2 expression levels or tumor burden in the patients' BM. The only clinical factor predicting the development of anti-SOX2 immunity was application of allogeneic stem cell transplantation (alloSCT). Anti-SOX2 antibodies occurred more frequently in patients who had received alloSCT (n = 74). Moreover, most SOX2-seropositive patients had only developed antibodies after alloSCT. This finding indicates that alloSCT is able to break tolerance towards this commonly expressed antigen. The questions whether SOX2-specific autoantibodies merely represent an epiphenomenon, are related to graft-versus-host effects or participate in the immune control of myeloma needs to be answered in prospective studies.