Cytokine-induced killer cells efficiently kill stem-like cancer cells of nasopharyngeal carcinoma via the NKG2D-ligands recognition

ThermomiR-377-3p-induced suppression of Cirbp expression is required for effective elimination of cancer cells and cancer stem-like cells by hyperthermia

BACKGROUND

In recent years, the development of adjunctive therapeutic hyperthermia for cancer therapy has received considerable attention. However, the mechanisms underlying hyperthermia resistance are still poorly understood. In this study, we investigated the roles of cold‑inducible RNA binding protein (Cirbp) in regulating hyperthermia resistance and underlying mechanisms in nasopharyngeal carcinoma (NPC).

METHODS

CCK-8 assay, colony formation assay, tumor sphere formation assay, qRT-PCR, Western blot were employed to examine the effects of hyperthermia (HT), HT + oridonin(Ori) or HT + radiotherapy (RT) on the proliferation and stemness of NPC cells. RNA sequencing was applied to gain differentially expressed genes upon hyperthermia. Gain-of-function and loss-of-function experiments were used to evaluate the effects of RNAi-mediated Cirbp silencing or Cirbp overexpression on the sensitivity or resistance of NPC cells and cancer stem-like cells to hyperthermia by CCK-8 assay, colony formation assay, tumorsphere formation assay and apoptosis assay, and in subcutaneous xenograft animal model. miRNA transient transfection and luciferase reporter assay were used to demonstrate that Cirbp is a direct target of miR-377-3p. The phosphorylation levels of key members in ATM-Chk2 and ATR-Chk1 pathways were detected by Western blot.

RESULTS

Our results firstly revealed that hyperthermia significantly attenuated the stemness of NPC cells, while combination treatment of hyperthermia and oridonin dramatically increased the killing effect on NPC cells and cancer stem cell (CSC)‑like population. Moreover, hyperthermia substantially improved the sensitivity of radiation‑resistant NPC cells and CSC‑like cells to radiotherapy. Hyperthermia noticeably suppressed Cirbp expression in NPC cells and xenograft tumor tissues. Furthermore, Cirbp inhibition remarkably boosted anti‑tumor‑killing activity of hyperthermia against NPC cells and CSC‑like cells, whereas ectopic expression of Cirbp compromised tumor‑killing effect of hyperthermia on these cells, indicating that Cirbp overexpression induces hyperthermia resistance. ThermomiR-377-3p improved the sensitivity of NPC cells and CSC‑like cells to hyperthermia in vitro by directly suppressing Cirbp expression. More importantly, our results displayed the significantly boosted sensitization of tumor xenografts to hyperthermia by Cirbp silencing in vivo, but ectopic expression of Cirbp almost completely counteracted hyperthermia-mediated tumor cell-killing effect against tumor xenografts in vivo. Mechanistically, Cirbp silencing-induced inhibition of DNA damage repair by inactivating ATM-Chk2 and ATR-Chk1 pathways, decrease in stemness and increase in cell death contributed to hyperthermic sensitization; conversely, Cirbp overexpression-induced promotion of DNA damage repair, increase in stemness and decrease in cell apoptosis contributed to hyperthermia resistance.

CONCLUSION

Taken together, these findings reveal a previously unrecognized role for Cirbp in positively regulating hyperthermia resistance and suggest that thermomiR-377-3p and its target gene Cirbp represent promising targets for therapeutic hyperthermia.

Hairy gene homolog increases nasopharyngeal carcinoma cell stemness by upregulating Bmi-1

B-cell-specific Moloney murine leukemia virus integration site 1 (Bmi-1) is overexpressed in various cancer types. We found that Bmi-1 mRNA levels were elevated in nasopharyngeal carcinoma (NPC) cell lines. In immunohistochemical analyses, high Bmi-1 levels were observed in not only 5 of 38 non-cancerous nasopharyngeal squamous epithelial biopsies, but also in 66 of 98 NPC specimens (67.3%). High Bmi-1 levels were detected more frequently in T3-T4, N2-N3 and stage III-IV NPC biopsies than in T1-T2, N0-N1 and stage I-II NPC samples, indicating that Bmi-1 is upregulated in advanced NPC. In 5-8F and SUNE1 NPC cells, stable depletion of Bmi-1 using lentiviral RNA interference greatly suppressed cell proliferation, induced G1-phase cell cycle arrest, reduced cell stemness and suppressed cell migration and invasion. Likewise, knocking down Bmi-1 inhibited NPC cell growth in nude mice. Both chromatin immunoprecipitation and Western blotting assays demonstrated that Hairy gene homolog (HRY) upregulated Bmi-1 by binding to its promoter, thereby increasing the stemness of NPC cells. Immunohistochemistry and quantitative real-time PCR analyses revealed that HRY expression correlated positively with Bmi-1 expression in a cohort of NPC biopsies. These findings suggested that HRY promotes NPC cell stemness by upregulating Bmi-1, and that silencing Bmi-1 can suppress NPC progression.

Cross-talk between cancer stem cells and immune cells: potential therapeutic targets in the tumor immune microenvironment

Ongoing research has revealed that the existence of cancer stem cells (CSCs) is one of the biggest obstacles in the current cancer therapy. CSCs make an influential function in tumor progression, recurrence and chemoresistance due to their typical stemness characteristics. CSCs are preferentially distributed in niches, and those niche sites exhibit characteristics typical of the tumor microenvironment (TME). The complex interactions between CSCs and TME illustrate these synergistic effects. The phenotypic heterogeneity within CSCs and the spatial interactions with the surrounding tumor microenvironment led to increased therapeutic challenges. CSCs interact with immune cells to protect themselves against immune clearance by exploiting the immunosuppressive function of multiple immune checkpoint molecules. CSCs also can protect themselves against immune surveillance by excreting extracellular vesicles (EVs), growth factors, metabolites and cytokines into the TME, thereby modulating the composition of the TME. Therefore, these interactions are also being considered for the therapeutic development of anti-tumor agents. We discuss here the immune molecular mechanisms of CSCs and comprehensively review the interplay between CSCs and the immune system. Thus, studies on this topic seem to provide novel ideas for reinvigorating therapeutic approaches to cancer.

Immune evader cancer stem cells direct the perspective approaches to cancer immunotherapy

Exploration of tumor immunity leads to the development of immune checkpoint inhibitors and cell-based immunotherapies which improve the clinical outcomes in several tumor types. However, the poor clinical efficacy of these treatments observed for other tumors could be attributed to the inherent complex tumor microenvironment (TME), cellular heterogeneity, and stemness driven by cancer stem cells (CSCs). CSC-specific characteristics provide the bulk tumor surveillance and resistance to entire eradication upon conventional therapies. CSCs-immune cells crosstalk creates an immunosuppressive TME that reshapes the stemness in tumor cells, resulting in tumor formation and progression. Thus, identifying the immunological features of CSCs could introduce the therapeutic targets with powerful antitumor responses. In this review, we summarized the role of immune cells providing CSCs to evade tumor immunity, and then discussed the intrinsic mechanisms represented by CSCs to promote tumors' resistance to immunotherapies. Then, we outlined potent immunotherapeutic interventions followed by a perspective outlook on the use of nanomedicine-based drug delivery systems for controlled modulation of the immune system.

Liver-specific over-expression of Cripto-1 in transgenic mice promotes hepatocyte proliferation and deregulated expression of hepatocarcinogenesis-related genes and signaling pathways

In this study, we investigated the role of embryonic gene Cripto-1 (CR-1) in hepatocellular carcinoma (HCC) using hepatocyte-specific CR-1-overexpressing transgenic mice. The expression of truncated 1.7-kb CR-1 transcript (SF-CR-1) was significantly higher than the full-length 2.0-kb CR-1 transcript (FL-CR-1) in a majority of HCC tissues and cell lines. Moreover, CR-1 mRNA and protein levels were significantly higher in HCC tissues than adjacent normal liver tissues. Hepatocyte-specific over-expression of CR-1 in transgenic mice enhanced hepatocyte proliferation after 2/3 partial hepatectomy (2/3 PHx). CR-1 over-expression significantly increased in vivo xenograft tumor growth of HCC cells in nude mice and in vitro HCC cell proliferation, migration, and invasion. CR-1 over-expression in the transgenic mouse livers deregulated HCC-related signaling pathways such as AKT, Wnt/β-catenin, Stat3, MAPK/ERK, JNK, TGF-β and Notch, as well as expression of HCC-related genes such as CD5L, S100A8, S100A9, Timd4, Orm2, Orm3, PDK4, DMBT1, G0S2, Plk2, Plk3, Gsta1 and Gsta2. However, histological signs of precancerous lesions, hepatocyte dysplasia or HCC formation were not observed in the livers of 3-, 6- or 8-month-old hepatocyte-specific CR-1-overexpressing transgenic mice. These findings demonstrate that liver-specific CR-1 overexpression in transgenic mice deregulates signaling pathways and genes associated with HCC.

Reporter gene systems for the identification and characterization of cancer stem cells

Cancer stem cells (CSCs) are tumor cells that share functional characteristics with normal and embryonic stem cells. CSCs have increased tumor-initiating capacity and metastatic potential and lower sensitivity to chemo- and radiotherapy, with important roles in tumor progression and the response to therapy. Thus, a current goal of cancer research is to eliminate CSCs, necessitating an adequate phenotypic and functional characterization of CSCs. Strategies have been developed to identify, enrich, and track CSCs, many of which distinguish CSCs by evaluating the expression of surface markers, the initiation of specific signaling pathways, and the activation of master transcription factors that control stemness in normal cells. We review and discuss the use of reporter gene systems for identifying CSCs. Reporters that are under the control of aldehyde dehydrogenase 1A1, CD133, Notch, Nanog homeobox, Sex-determining region Y-box 2, and POU class 5 homeobox can be used to identify CSCs in many tumor types, track cells in real time, and screen for drugs. Thus, reporter gene systems, in combination with in vitro and in vivo functional assays, can assess changes in the CSCs pool. We present relevant examples of these systems in the evaluation of experimental CSCs-targeting therapeutics, demonstrating their value in CSCs research.

Selectively targeting cancer stem cells: Current and novel therapeutic strategies and approaches in the effective eradication of cancer

Cancer stem cells (CSCs) are a subgroup of cells in malignant cancers, which possess self-renewal capacity, tumor-initiating capability, and pluripotency, as well as being responsible for tumor maintenance, metastasis, relapse, and chemoresistance. The treatment modalities previously established for cancer included surgery, chemotherapy, and radiotherapy. The majority of tumor cells of non-CSCs could be eradicated using conventional chemotherapy and radiotherapy. Therefore, novel and promising therapeutic strategies that selectively target CSCs are of great importance. In this review, we described different therapeutic strategies such as immunotherapy, metabolism-based therapeutic strategies, and additional potential therapeutic approaches (targeting microRNAs [miRNAs], histone deacetylase, and DNA methyl transferase) against CSCs. Taken together, due to the inefficiency of anticancer single therapies, targeting CSCs through their metabolism and using immunotherapy and miRNAs besides classical chemo- and radiotherapy may exert better therapeutic effects.

Immunotherapy: A Potential Approach to Targeting Cancer Stem Cells

Tumor recurrence and drug resistance are two of the key factors affecting the prognosis of cancer patients. Cancer stem cells (CSCs) are a group of cells with infinite proliferation potential which are not sensitive to traditional therapies, including radio- and chemotherapy. These CSCs are considered to be central to tumor recurrence and the development of drug resistance. In addition, CSCs are important targets in cancer immunotherapy because of their expression of novel tumorassociated antigens, which result from mutations in cancer cells over the course of treatment. Emerging immunotherapies, including cancer vaccines, checkpoint blockade therapies, and transferred immune cell therapies, have all been shown to be more effective when they selectively target CSCs. Such therapies may also provide novel additions to the current therapeutic milieu and may offer new therapeutic combinations for treatment. This review summarizes the relationships between various immunotherapies and CSCs and provides novel insights into potential therapeutic applications for these approaches in the future.

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.

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Cancer stem cells (CSCs) play a central role in multiple aspects of malignant tumors.

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Immune evasion is a fundamental feature of CSCs.

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Immune evasion mechanisms must be precisely clarified to improve tumor immunotherapy.

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CSCs are promising targets for tumor immunotherapy.

Natural killer cells efficiently target multiple myeloma clonogenic tumor cells

The multiple myeloma (MM) landscape has changed in the last few years, but most patients eventually relapse because current treatment modalities do not target clonogenic stem cells, which are drug-resistant and can self-renew. We hypothesized that side population (SP) cells represent myeloma clonogenic stem cells and, searching for new treatment strategies, analyzed the anti-myeloma activity of natural killer (NK) cells against clonogenic cells. Activated and expanded NK cells (NKAE) products were obtained by co-culturing NK cells from MM patients with K562-mb15-41BBL cell line and characterized by flow cytometry. Functional experiments against MM cells were performed by Eu-TDA release assays and methylcellulose clonogenic assays. Side population was detected by Dye Cycle Violet labeling and then characterized by flow cytometry and RNA-Seq. Self-renewal capacity was tested by clonogenic assays. Sorting of both kind of cells was performed for time-lapse microscopy experiments. SP cells exhibited self-renewal potential and overexpressed genes involved in stem cell metabolism. NK cells from MM patients exhibited dysregulation and had lower anti-tumor potential against clonogenic cells than healthy donors’ NK cells. Patients’ NK cells were activated and expanded. These cells recovered cytotoxic activity and could specifically destroy clonogenic myeloma cells. They also had a highly cytotoxic phenotype expressing NKG2D receptor. Blocking NKG2D receptor decreased NK cell activity against clonogenic myeloma cells, and activated NK cells were able to destroy SP cells, which expressed NKG2D ligands. SP cells could represent the stem cell compartment in MM. This is the first report describing NK cell activity against myeloma clonogenic cells.

Cellular Immunotherapy Targeting Cancer Stem Cells: Preclinical Evidence and Clinical Perspective

The term “cancer stem cells” (CSCs) commonly refers to a subset of tumor cells endowed with stemness features, potentially involved in chemo-resistance and disease relapses. CSCs may present peculiar immunogenic features influencing their homeostasis within the tumor microenvironment. The susceptibility of CSCs to recognition and targeting by the immune system is a relevant issue and matter of investigation, especially considering the multiple emerging immunotherapy strategies. Adoptive cellular immunotherapies, especially those strategies encompassing the genetic redirection with chimeric antigen receptors (CAR), hold relevant promise in several tumor settings and might in theory provide opportunities for selective elimination of CSC subsets. Initial dedicated preclinical studies are supporting the potential targeting of CSCs by cellular immunotherapies, indirect evidence from clinical studies may be derived and new studies are ongoing. Here we review the main issues related to the putative immunogenicity of CSCs, focusing on and highlighting the existing evidence and opportunities for cellular immunotherapy approaches with T and non-T antitumor lymphocytes.

Glycoengineering of NK Cells with Glycan Ligands of CD22 and Selectins for B-Cell Lymphoma Therapy

CD22, a member of Siglec family of sialic acid binding proteins, has restricted expression on B cells. Antibody-based agents targeting CD22 or CD20 on B lymphoma and leukemia cells exhibit clinical efficacy for treating these malignancies, but also attack normal B cells leading to immune deficiency. Here, we report a chemoenzymatic glycocalyx editing strategy to introduce high-affinity and specific CD22 ligands onto NK-92MI and cytokine-induced natural killer cells to achieve tumor-specific CD22 targeting. These CD22-ligand modified cells exhibited significantly enhanced tumor cell binding and killing in vitro without harming healthy B cells. For effective lymphoma cell killing in vivo, we further functionalized CD22 ligand-modified NK-92MI cells with the E-selectin ligand sialyl Lewis X to promote trafficking to bone marrow. The dual-functionalized cells resulted in the efficient suppression of B lymphoma in a xenograft model. Our results suggest that natural killer cells modified with glycan ligands to CD22 and selectins promote both targeted killing of B lymphoma cells and improved trafficking to sites where the cancer cells reside, respectively.

Impact of FAK Expression on the Cytotoxic Effects of CIK Therapy in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a special subtype of breast cancer in which several common diagnostic biomarkers are lost. Due to the loss of expression of receptors, treatment options for TNBC are limited. Therefore, finding safe and effective treatments for patients with TNBC is a major objective for clinicians. Previous studies suggested that cytokine-induced killer (CIK) cells may be beneficial for patients with a variety of tumor types. However, CIK therapy is not effective for all patients. In this study, we found that focal adhesion kinase (FAK), a non-receptor protein tyrosine kinase that regulates several cellular functions in different cells, has the potential to regulate tumor cells sensitized to CIK cells. Knockdown of FAK expression in TNBC cells or the treatment of TNBC cells with a FAK inhibitor followed by coculture with CIK cells increases death of TNBC cells, suggesting that FAK plays important roles in sensitizing tumor cells to CIK cells. This phenomenon could be regulated by a FAK-programmed death-ligand 1 (PD-L1)-related mechanism. Overall, our findings provide new insights into the cytotoxic effect of CIK cell therapy in TNBC treatment, and show that CIK cell therapy combined with FAK inhibitors may be a novel therapeutic strategy for patients with TNBC.

miR-26a promotes hepatocellular carcinoma invasion and metastasis by inhibiting PTEN and inhibits cell growth by repressing EZH2

A previous study revealed that therapeutic miR-26a delivery suppresses tumorigenesis in a murine liver cancer model, whereas we found that forced miR-26a expression increased hepatocellular carcinoma (HCC) cell migration and invasion, which prompted us to characterize the causes and mechanisms underlying enhanced invasion due to ectopic miR-26a expression. Gain-of-function and loss-of-function experiments demonstrated that miR-26a promoted migration and invasion of BEL-7402 and HepG2 cells in vitro and positively modulated matrix metalloproteinase (MMP)-1, MMP-2, MMP-9, and MMP-10 expression. In addition, exogenous miR-26a expression significantly enhanced the metastatic ability of HepG2 cells in vivo. miR-26a negatively regulated in vitro proliferation of HCC cells, and miR-26a overexpression suppressed HepG2 cell tumor growth in nude mice. Further studies revealed that miR-26a inhibited cell growth by repressing the methyltransferase EZH2 and promoted cell migration and invasion by inhibiting the phosphatase PTEN. Furthermore, PTEN expression negatively correlated with miR-26a expression in HCC specimens from patients with and without metastasis. Thus, our findings suggest for the first time that miR-26a promotes invasion/metastasis by inhibiting PTEN and inhibits cell proliferation by repressing EZH2 in HCC. More importantly, our data also suggest caution if miR-26a is used as a target for cancer therapy in the future.

Epithelial ovarian cancer stem‑like cells are resistant to the cellular lysis of cytokine‑induced killer cells via HIF1A‑mediated downregulation of ICAM‑1

Epithelial ovarian cancer (EOC) is the most lethal of all gynecologic tumors. Cancer spheroid culture is a widely used model to study cancer stem cells. Previous studies have demonstrated the effectiveness of cytokine‑induced killer (CIK) cell‑based therapies against cancer and cancer stem cells. However, it is not clear how EOC spheroid cells respond to CIK‑mediated cellular lysis, and the mechanisms involved have never been reported before. A flow cytometry‑based method was used to evaluate the anti‑cancer effects of CIK cells against adherent A2780 cells and A2780 spheroids. To demonstrate the association between hypoxia inducible factor‑1α (HIF1A) and intercellular adhesion molecule‑1 (ICAM‑1), two HIF1A short hairpin RNA (shRNA) stable transfected cell lines were established. Furthermore, the protein expression levels of hypoxia/HIF1A‑associated signaling pathways were evaluated, including transforming growth factor‑β1 (TGF‑β1)/mothers against decapentaplegic homologs (SMADs) and nuclear factor‑κB (NF‑κB) signaling pathways, comparing A2780 adherent cells and cancer spheroids. Flow cytometry revealed that A2780 spheroid cells were more resistant to CIK‑mediated cellular lysis, which was partially reversed by an anti‑ICAM‑1 antibody. HIF1A was significantly upregulated in A2780 spheroids compared with adherent cells. Using HIF1A shRNA stable transfected cell lines and cobalt chloride, it was revealed that hypoxia/HIF1A contributed to downregulation of ICAM‑1 in A2780 spheroid cells and adherent cells. Furthermore, hypoxia/HIF1A‑associated signaling pathways, TGF‑β1/SMADs and NF‑κB, were activated in A2780 spheroid cells by using western blotting. The findings indicate that EOC stem‑like cells resist the CIK‑mediated cellular lysis via HIF1A‑mediated downregulation of ICAM‑1, which may be instructive for optimizing and enhancing CIK‑based therapies.

Recent Advances in Cancer Stem Cell-Targeted Immunotherapy

Cancer stem cells (CSCs) are one of the reasons for the relapse of cancer cells and metastasis. They have drug resistance against most chemotherapeutic agents. CSCs are also responsible for tumor cell heterogeneity and cause minimal residual disease. In order to achieve complete regression of tumors, CSCs have to be targeted. Recent advances in immunotherapies have shown promising outcomes in curing cancer, which are also applicable to target CSCs. CSCs express immune markers and exhibit specific immune characteristics in various cancers, which can be used in immunotherapies to target CSCs in the tumor microenvironment. Recently, various strategies have been used to target CSCs. Adaptive T-cells, dendritic cell (DC)-based vaccines, oncolytic viruses, immune checkpoint inhibitors, and combination therapies are now being used to target CSCs. Here, we discuss the feasibility of these immunological approaches and the recent trends in immunotherapies to target CSCs.

Direct conversion of pig fibroblasts to chondrocyte-like cells by c-Myc

Unexpectedly, we found that c-Myc-expressing porcine embryonic fibroblasts (PEFs) subcutaneously implanted into nude mice formed cartilage-like tissues in vivo, while previous studies revealed the direct conversion of mouse and human somatic cells into chondrocytes by the combined use of several defined factors, including c-Myc, which prompted us to explore whether PEFs can be reprogrammed to become pig induced chondrocyte-like cells (piCLCs) via ectopic expression of c-Myc alone. In this study, c-Myc-expressing PEFs, designated piCLCs, which exhibited a significantly enhanced proliferation ability in vitro, displayed a chondrogenic phenotypes in vitro, as shown by the cell morphology, toluidine blue staining, alcian blue staining and chondrocyte marker gene expression. Additionally, piCLCs with a polygonal chondrocyte-like morphology were readily and efficiently converted from PEFs by enforced c-Myc expression within 10 days, while piCLCs maintained the chondrocytic phenotype and normal karyotype during long-term subculture. piCLC-derived single clones with a chondrogenic phenotype in vitro exhibited homogeneity in cell morphology and staining intensity compared with mixed piCLCs. Although the mixtures of cartilaginous tissues and tumorous tissues accounted for ~12% (6/51) of all xenografts (51), piCLCs generated stable, homogenous, hyaline cartilage-like tissues without tumour formation at 45 out of the 51 injected sites when subcutaneously injected into nude mice. The hyaline cartilage-like tissues remained for at least 16 weeks. Taken together, these findings demonstrate for the first time the direct induction of chondrocyte-like cells from PEFs with only c-Myc.

Total HLA Class I Antigen Loss with the Downregulation of Antigen-Processing Machinery Components in Two Newly Established Sarcomatoid Hepatocellular Carcinoma Cell Lines

Limited information is currently available concerning HLA class I antigen abnormalities in sarcomatoid hepatocellular carcinoma (sHCC). Here, we have analyzed the growth characteristics and HLA class I antigen status of four sHCC cell lines (sHCC29, sHCC63, sHCC74, and SAR-HCV); the first three were newly established in this study. Among the four, sHCC29 showed the highest growth rate in vitro and tumorigenicity in NOD-SCID mice. Unlike sHCC74 and SAR-HCV, both sHCC29 and sHCC63 had no detectable surface HLA class I antigen expression, alongside undetected intracellular β₂-microglobulin (β₂m) and marked HLA class I heavy chain and selective antigen-processing machinery (APM) component downregulation. The loss of β₂m in sHCC29 and sHCC63 was caused by a >49 kb deletion across the B2M locus, while their downregulation of APM components was transcriptional, reversible by IFN-γ only in several components. β₂m was also undetected in the primary HCC lesions of the patients involved, indicating its in vivo relevance. We report for the first time HLA class I antigen loss with underlying B2M gene deficiency and APM defects in 50% (2 of 4) of the sHCC cell lines tested. These findings may have implications for a proper design of T cell immunotherapy for the treatment of sHCC patients.

Clinical Effect of Adjuvant Cytokine-Induced Killer Cells Immunotherapy in Patients with Stage II-IVB Nasopharyngeal Carcinoma after Chemoradiotherapy: A propensity score analysis

As an adjuvant immunotherapy, cytokine-induced killer cells (CIKs) infusion has been demonstrated to exert potent effectiveness in several types of cancer patients who received curative treatment. However, controversy exists regarding whether nasopharyngeal carcinoma (NPC) patients can benefit from additional treatment after radical radiotherapy or chemoradiotherapy to improve their distant control and survival. In this retrospective study, we aimed to evaluate the efficacy of adjuvant CIK cells therapy in NPC patients with stage II-IVB after curative treatment. From January 1, 2005 to December 31, 2012, 85 pairs of NPC patients matching by propensity score matching (PSM) method to balance prognostic factors were included in this study: 85 cases underwent radical treatment, 85 cases received radical treatment and sequential CIKs infusion. We found that disease-free survival (DFS) and overall survival (OS) were significantly better in the CIK group than that in the control group (P = 0.009, P < 0.001, respectively). Adjuvant CIK cells immunotherapy was showed to be an independent prognostic factor for survival of the patients in further multivariate analysis. In subgroup analyses, the DFS and OS of patients with T3/4, III and IV A-B TNM (tumor-node-metastasis) stages were significantly enhanced in CIK group compared to control group. Nevertheless, both NPC patients with high and low EBV DNA benefited from adjuvant CIK cells immunotherapy. In conclusion, CIKs infusion is an effective adjuvant immunotherapy for enhancing the prognosis of NPC patients who have received the standard treatment, particularly for those with more aggressive tumor (T3/4) or advanced TNM stage.

Cytokine-induced killer cells as a feasible adoptive immunotherapy for the treatment of lung cancer

Most of the patients with lung cancer are diagnosed at advanced stage, and they often lose the opportunity of surgical therapy, most of whom fail to reach good prognosis after chemotherapy. Recently, a few clinical studies have confirmed the role of adoptive T-cell transfer in the maintenance therapy of cancer patients. Here, we provided statistical insights into the role of CIKs in advanced lung cancer from three different levels, cell model (in vitro co-culture system), mice model (in situ lung cancer), and clinical research (in lung cancer patients of different progression stages). We optimized the components of supplements and cytokines on activating and expanding CIK cells. Based on this, we explored a new serum-free medium for in vitro activation and expansion of CIK cells. Moreover, we found that activated CIK cells could efficiently kill lung cancer cells in cell-to-cell model in vitro and significantly reduce the tumor growth in mice. For the clinical research, the OS rates of patients received combination of chemotherapy and CIK treatment were significantly improved compared to the OS rates of patients only received chemotherapy. Additionally, CIK therapy represented good toleration in our study. All the results suggested that combination of immunotherapy with traditional therapy will be a feasible and promising method for the treatment of lung cancer.

Reporter Systems to Study Cancer Stem Cells

Cancer stem cells have been identified in primary tumors, patient derived xenografts, and established cancer cell lines. The development of reporters has enabled investigators to rapidly enrich for these cells and more importantly track these cells in real time. Here we describe the current state of the reporter field and their use and limitations in multiple cancers.

Klf4 reduces stemness phenotype, triggers mesenchymal-epithelial transition (MET)-like molecular changes, and prevents tumor progression in nasopharygeal carcinoma

The reprogramming factor Krüppel-like factor 4 (Klf4), one of the Yamanaka's reprogramming factors, plays an essential role in reprogramming somatic cells into induced pluripotent stem cells (iPSCs). Klf4 is dysregulated and displays divergent functions in multiple malignancies, but the biological roles of Klf4 in nasopharyngeal carcinoma (NPC) remain unknown. The present study revealed that Klf4 downregulation in a cohort of human NPC biopsies is significantly associated with invasive and metastatic phenotypes of NPC. Our results showed exogenous expression of Klf4 significantly inhibited cell proliferation, decreased stemness, triggered mesenchymal-epithelial transition (MET)-like molecular changes, and suppressed migration and invasion of NPC cells, whereas depletion of endogeneous Klf4 by RNAi reversed the aforementioned biological behaviors and characheristics. Klf4 silencing significantly enhanced the metastatic ability of NPC cells in vivo. In addition, CHIP assay confirmed that E-cadherin is a transcriptional target of Klf4 in NPC cells. Additional studies demonstrated that Klf4-induced MET-like cellular marker alterations, and reduced motility and invasion of NPC cells were mediated by E-cadherin. This study revealed the clinical correlation between Klf4 expression and epithelial-mesenchymal transition (EMT) biomarkers (including its target gene E-cadherin) in a cohort of NPC biopsies. Taken together, our findings suggest, for what we believe is the first time, that Klf4 functions as a tumor suppressor in NPC to decrease stemness phenotype, inhibit EMT and prevent tumor progression, suggesting that restoring Klf4 function may provide therapeutic benefits in NPC.

Enhanced antitumor activity of gemcitabine by polysaccharide-induced NK cell activation and immune cytotoxicity reduction in vitro/vivo

The polysaccharide SEP has been reported to activate NK and T cells via TLR2/4. Here, the combination of gemcitabine (GEM) and SEP against HepG-2 was investigated. SEP apparently enhanced antitumor activity of gemcitabine against liver cancer through stimulating NKG2D and DAP10/Akt pathway to activate NK cells. The NKG2D upregulation could improve the sensitivity of NK-92 cells targeting to its ligand MICA expressed on HepG-2 cells. Meanwhile, GEM up-regulated MICA expression and attenuated soluble MICA secretion through inhibiting ADAM10 expression, which in turn enhanced the cytotoxicity of NK-92 cells against cancer cells. SEP remarkably enhanced GEM antitumor activity with an inhibitory rate of 79.1% in an H22-bearing mouse model. Moreover, SEP reversed atrophy and apoptosis caused by GEM in both spleen and bone marrow through suppressing ROS secretion in vivo. The data indicated that the combination of SEP and GEM is a potential chemo-immunotherapy strategy for liver cancer treatment clinically.

Efficient killing of radioresistant breast cancer cells by cytokine-induced killer cells

Recurrence of breast cancer after radiotherapy may be partly explained by the presence of radioresistant cells. Thus, it would be desirable to develop an effective therapy against radioresistant cells. In this study, we demonstrated the intense antitumor activity of cytokine-induced killer cells against MCF-7 and radioresistant MCF-7 cells, as revealed by cytokine-induced killer-mediated cytotoxicity, tumor cell proliferation, and tumor invasion. Radioresistant MCF-7 cells were more susceptible to cytokine-induced killer cell killing. The stronger cytotoxicity of cytokine-induced killer cells against radioresistant MCF-7 cells was dependent on the expression of major histocompatibility complex class I polypeptide-related sequence A/B on radioresistant MCF-7 cells after exposure of cytokine-induced killer cells to sensitized targets. In addition, we demonstrated that cytokine-induced killer cell treatment sensitized breast cancer cells to chemotherapy via the downregulation of TK1, TYMS, and MDR1. These results indicate that cytokine-induced killer cell treatment in combination with radiotherapy and/or chemotherapy may induce synergistic antitumor activities and represent a novel strategy for breast cancer.

Dendritic cells infected by Ad-sh-SOCS1 enhance cytokine-induced killer (CIK) cell immunotherapeutic efficacy in cervical cancer models

BACKGROUND AIMS

Cervical cancer constitutes a major problem in women's health worldwide, but the efficacy of the standard therapy is unsatisfactory. Cytokine-induced killer (CIK) cells exhibit antitumor activity against a variety of malignancies in preclinical models and have proven safe and effective in clinical trials. However, current CIK therapy has limitations and needs to be improved to meet the clinical requirements. The aim of this study was to investigate whether suppressing the expression of cytokine signaling 1 (SOCS1) in dendritic cells (DCs) can shorten in vitro CIK culture time and improve its antitumor efficacy.

METHODS

DCs were pre-cultured for 3 days before infected with adenovirus-mediated-SOCS1 short hairpin RNA (Ad-sh-SOCS1) and pulsed with CTL epitope peptides E7. The DCs infected by Ad-sh-SOCS1 (gmDCs) and CIKs were then co-cultured for 5 or 9 days, and CIK proliferation and antitumor activity were evaluated both in vitro and in vivo.

RESULTS

Our data show that gmDCs significantly stimulated the expansion of co-cultured CIKs and increased the secretion of interferon-γ and interleukin-12. Moreover, gmDCs-activated CIKs showed higher cytotoxic activity against TC-1 cells expressing HPV16E6 and E7. Our in vivo study showed that the mice infused with gmDCs-activated CIKs on day 10 had an increased survival rate and prolonged survival time compared with the controls.

CONCLUSIONS

Taken together, these results indicate that DCs modified by adenovirus-mediated SOCS1 silencing can promote CIKs expansion and enhance the efficacy of antitumor immunotherapy both in vitro and in vivo, which represents an effective therapeutic approach for cervical cancer and other tumors.

Simple and rapid determination of homozygous transgenic mice via in vivo fluorescence imaging

Setting up breeding programs for transgenic mouse strains require to distinguish homozygous from the heterozygous transgenic animals. The combinational use of the fluorescence reporter transgene and small animal in-vivo imaging system might allow us to rapidly and visually determine the transgenic mice homozygous for transgene(s) by the in vivo fluorescence imaging. RLG, RCLG or Rm17LG transgenic mice ubiquitously express red fluorescent protein (RFP). To identify homozygous RLG transgenic mice, whole-body fluorescence imaging for all of newborn F2-generation littermates produced by mating of RFP-positive heterozygous transgenic mice (F1-generation) derived from the same transgenic founder was performed. Subsequently, the immediate data analysis of the in vivo fluorescence imaging was carried out, which greatly facilitated us to rapidly and readily distinguish RLG transgenic individual(s) with strong fluorescence from the rest of F2-generation littermates, followed by further determining this/these RLG individual(s) showing strong fluorescence to be homozygous, as strongly confirmed by mouse mating. Additionally, homozygous RCLG or Rm17LG transgenic mice were also rapidly and precisely distinguished by the above-mentioned optical approach. This approach allowed us within the shortest time period to obtain 10, 8 and 2 transgenic mice homozygous for RLG, RCLG and Rm17LG transgene, respectively, as verified by mouse mating, indicating the practicality and reliability of this optical method. Taken together, our findings fully demonstrate that the in vivo fluorescence imaging offers a visual, rapid and reliable alternative method to the traditional approaches (i.e., mouse mating and real-time quantitative PCR) in identifying homozygous transgenic mice harboring fluorescence reporter transgene under the control of a ubiquitous promoter in the situation mentioned in this study.

Adjuvant immunotherapy with autologous cytokine-induced killer cells for hepatocellular carcinoma patients after curative resection, a systematic review and meta-analysis

BACKGROUND

Cytokine-induced killer cells have been used as an adjuvant treatment for hepatocellular carcinoma with curative treatment. However, the outcomes remain controversial.

AIM

We conducted this meta-analysis to assess the safety and efficacy of cytokine-induced killer cells.

METHODS

Randomized controlled trials on cytokine-induced killer cells for hepatocellular carcinoma after curative treatments were identified by electronic searches. A meta-analysis was carried out to examine disease-free survival, overall survival rate and adverse effect.

RESULTS

Six randomized controlled trials with 844 patients (85.9% with hepatitis B or C) were included. Our meta-analysis showed that cytokine-induced killer cells can not only improve the 1-year (RR=1.23, P<0.001), 2-year (RR=1.37, P<0.001) and 3-year (RR=1.35, P=0.004) disease-free survival, but also improve the 1-year (RR=1.08, P=0.001), 2-year (RR=1.14, P<0.001) and 3-year (RR=1.15, P=0.02) overall survival. However, it failed to affect the 4-year and 5-year disease-free survival and overall survival (P>0.05). At the same time, cytokine-induced killer cells treatment was proved to be a safe strategy with the comparable adverse events comparing to the control group (P=0.39).

CONCLUSIONS

This review provides the best available evidence that adjuvant cytokine-induced killer cells treatment can be safely used to improve the early disease-free survival and survival of hepatitis B or C related hepatocellular carcinoma.

MiR-17-5p promotes cancer cell proliferation and tumorigenesis in nasopharyngeal carcinoma by targeting p21

MicroRNAs (miRNAs) may act as either tumor suppressors or oncogenes in various types of cancers. Previous studies have indicated that miR‐17‐5p is involved in the initiation and development of human tumors. However, its mechanism and function in nasopharyngeal carcinoma (NPC) remain largely unclear. In this study, we evaluated the expression profiles of miR‐17‐5p and p21 in NPC cell lines and tissues by quantitative real‐time PCR (qRT‐PCR). For the analysis, we have established a stable overexpression or depletion of miR‐17‐5p NPC cell lines for analyzing the effects of cell proliferation by MTT, colony formation, and cell cycle assay. A nude mice xenograft model was used to verify the tumor growth in vivo. MiR‐17‐5p was overexpressed, whereas the expression of p21 was downregulated in NPC cell lines and tissues. The miR‐17‐5p expression level was inversely correlated with the p21 mRNA level in NPC samples. Furthermore, analysis of 2^−ΔΔCt value in 81 NPC patients suggested that the elevated expression level of miR‐17‐5p or the downregulated expression level of p21 was significantly correlated with tumor size (T classification) and tumor stage, and Kaplan–Meier survival analysis revealed a correlation between miR‐17‐5p or p21 expression level and overall survival times in 81 NPC patients. MiR‐17‐5p promoted cell growth in vivo and in vitro by directly targeting p21. Our results indicate that miR‐17‐5p can promote the occurrence of NPC and it may serve as a potential novel diagnostic maker or therapeutic target for NPC in the future.

Efficient Killing of High Risk Neuroblastoma Using Natural Killer Cells Activated by Plasmacytoid Dendritic Cells

High-risk neuroblastoma (NB) remains a major therapeutic challenge despite the recent advent of disialoganglioside (GD2)-antibody treatment combined with interleukin (IL)-2 and granulocyte monocyte-colony stimulating factor (GM-CSF). Indeed, more than one third of the patients still die from this disease. Here, we developed a novel approach to improve the current anti-GD2 immunotherapy based on NK cell stimulation using toll-like receptor (TLR)-activated plasmacytoid dendritic cells (pDCs). We demonstrated that this strategy led to the efficient killing of NB cells. When the expression of GD2 was heterogeneous on NB cells, the combination of pDC-mediated NK-cell activation and anti-GD2 treatment significantly increased the cytotoxicity of NK cells against NB cells. Activation by pDCs led to a unique NK-cell phenotype characterized by increased surface expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), with increased expression of CD69 on CD56dim cytotoxic cells, and strong interferon-γ production. Additionally, NB-cell killing was mediated by the TRAIL death-receptor pathway, as well as by the release of cytolytic granules via the DNAX accessory molecule 1 pathway. NK-cell activation and lytic activity against NB was independent of cell contact, depended upon type I IFN produced by TLR-9-activated pDCs, but was not reproduced by IFN-α stimulation alone. Collectively, these results highlighted the therapeutic potential of activated pDCs for patients with high-risk NB.

R/L, a double reporter mouse line that expresses luciferase gene upon Cre-mediated excision, followed by inactivation of mRFP expression

The Cre/loxP system has become an important tool for the conditional gene knockout and conditional gene expression in genetically engineered mice. The applications of this system depend on transgenic reporter mouse lines that provide Cre recombinase activity with a defined cell type-, tissue-, or developmental stage-specificity. To develop a sensitive assay for monitoring Cre-mediated DNA excisions in mice, we generated Cre-mediated excision reporter mice, designated R/L mice (R/L: mRFP(monomeric red fluorescent protein)/luciferase), express mRFP throughout embryonic development and adult stages, while Cre-mediated excision deletes a loxP-flanked mRFP reporter gene and STOP sequence, thereby activating the expression of the second reporter gene luciferase, as assayed by in vivo and ex vivo bioluminescence imaging. After germ line deletion of the floxed mRFP and STOP sequence in R/L mice by EIIa-Cre mice, the resulting luciferase transgenic mice in which the loxP-mRFP-STOP-loxP cassette is excised from all cells express luciferase in all tissues and organs examined. The expression of luciferase transgene was activated in liver of RL/Alb-Cre double transgenic mice and in brain of RL/Nestin-Cre double transgenic mice when R/L reporter mice were mated with Alb-Cre mice and Nestin-Cre mice, respectively. Our findings reveal that the double reporter R/L mouse line is able to indicate the occurrence of Cre-mediated excision from early embryonic to adult lineages. Taken together, these findings demonstrate that the R/L mice serve as a sensitive reporter for Cre-mediated DNA excision both in living animals and in organs, tissues, and cells following necropsy.

Ectopic expression of Cripto-1 in transgenic mouse embryos causes hemorrhages, fatal cardiac defects and embryonic lethality

Targeted disruption of Cripto-1 in mice caused embryonic lethality at E7.5, whereas we unexpectedly found that ectopic Cripto-1 expression in mouse embryos also led to embryonic lethality, which prompted us to characterize the causes and mechanisms underlying embryonic death due to ectopic Cripto-1 expression. RCLG/EIIa-Cre embryos displayed complex phenotypes between embryonic day 14.5 (E14.5) and E17.5, including fatal hemorrhages (E14.5-E15.5), embryo resorption (E14.5-E17.5), pale body surface (E14.5-E16.5) and no abnormal appearance (E14.5-E16.5). Macroscopic and histological examination revealed that ectopic expression of Cripto-1 transgene in RCLG/EIIa-Cre embryos resulted in lethal cardiac defects, as evidenced by cardiac malformations, myocardial thinning, failed assembly of striated myofibrils and lack of heartbeat. In addition, Cripto-1 transgene activation beginning after E8.5 also caused the aforementioned lethal cardiac defects in mouse embryos. Furthermore, ectopic Cripto-1 expression in embryonic hearts reduced the expression of cardiac transcription factors, which is at least partially responsible for the aforementioned lethal cardiac defects. Our results suggest that hemorrhages and cardiac abnormalities are two important lethal factors in Cripto-1 transgenic mice. Taken together, these findings are the first to demonstrate that sustained Cripto-1 transgene expression after E11.5 causes fatal hemorrhages and lethal cardiac defects, leading to embryonic death at E14.5-17.5.

Interleukin-15 enhances cytokine induced killer (CIK) cytotoxic potential against epithelial cancer cell lines via an innate pathway

CIK cells are a subset of effector lymphocytes endowed with a non-MHC restricted anti-tumor activity making them an appealing and promising cell population for adoptive immunotherapy. CIK are usually generated ex-vivo by initial priming with Interferon-γ (IFN-γ) and monoclonal antibody against CD3 (anti-CD3), followed by culture in medium containing Interleukin-2 (IL-2). Interleukin-15 (IL-15) shares with IL-2 similar biological functions and recently it has been reported to induce CIK with increased anti-leukemic potential. The aim of the study was to compare the killing efficacy of CIK generated by IL-2 alone or IL-2 and IL-15 toward tumor targets of different origins, leukemic cells and malignant cells from epithelial solid tumors. CIK bulk cultures were examined for cell proliferation, surface phenotype and cytotoxic potential against tumor cell lines K562, HL60, HeLa and MCF-7. The results showed that IL-15 is able to induce a selective expansion of CIK cells, but it is less effective in sustaining CIK cell proliferation compared to IL-2. Conversely, our data confirm and reinforce the feature of IL-15 to induce CIK cells with a potent cytotoxic activity mostly against tumor cells from epithelial solid malignancies via NKG2D-mediated mechanism.

Targeted Disruption of miR-17-92 Impairs Mouse Spermatogenesis by Activating mTOR Signaling Pathway

The miR-17-92 cluster and its 6 different mature microRNAs, including miR-17, miR-18a, miR-19a, miR-20a, miR-19b-1, and miR-92a, play important roles in embryo development, immune system, kidney and heart development, adipose differentiation, aging, and tumorigenicity. Currently, increasing evidence indicates that some members of miR-17-92 cluster may be critical players in spermatogenesis, including miR-17, miR-18a, and miR-20a. However, the roles and underlying mechanisms of miR-17-92 in spermatogenesis remain largely unknown. Our results showed that the targeted disruption of miR-17-92 in the testes of adult mice resulted in severe testicular atrophy, empty seminiferous tubules, and depressed sperm production. This phenotype is partly because of the reduced number of spermatogonia and spermatogonial stem cells, and the significantly increased germ cell apoptosis in the testes of miR-17-92-deficient mice. In addition, overactivation of the mammalian target of rapamycin signaling pathway and upregulation of the pro-apoptotic protein Bim, Stat3, c-Kit, and Socs3 were also observed in miR-17-92-deficient mouse testes, which might be, at least partially if not all, responsible for the aforementioned phenotypic changes in mutant testes. Taken together, these findings suggest that miR-17-92 is essential for normal spermatogenesis in mice.

Immune-based Therapy Clinical Trials in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related mortality and continues to increase. Current standard of care for patients with HCC only provides limited therapeutic benefit. Development of innovative strategies is urgently needed. Experience with immunotherapy in HCC is quite early, but rapidly rise in the recent 15 years. Multifaceted immune-based approaches have shown efficacy in achieving disease regression, representing the most promising new treatment approach. Here, we classify the ongoing or completed clinical trials in HCC in terms of the immune strategies to be used and assess their clinical outcomes. The generated information may be helpful in the design of future immune-based therapies for achieving ideal tumor control and maximizing anti-tumor immunity.