Yiwei Chu

Differential Expression of CXCR4 Is Associated with the Metastatic Potential of Human Non–Small Cell Lung Cancer Cells

Purpose: To evaluate the relation between CXCR4 expression and the presence of metastatic disease in human non–small cell lung cancer (NSCLC) patients and investigate whether modulation of CXCR4 expression could serve as a potential pathway in preventing metastasis of NSCLC. Experimental Design: CXCR4 expression in 36 patients with NSCLC and 10 normal lung tissues was detected by real-time PCR and immunohistochemistry. CXCR4 expression in two human NSCLC clones (95C and 95D) with different metastatic potential was determined by real-time PCR and flow cytometry. 95C and 95D cells were transfected with the plasmid DNA containing CXCR4 coding gene or CXCR4 antisense nucleotide fragment, respectively, and the effects on in vitro cell migration, invasion, and adhesion and in vivo metastasis were measured. Results: Up-regulated expression of CXCR4 was detected in 34 tumors, which were further divided into 17 high expression cancers and 17 low expression cancers by their staining intensities. High CXCR4 tumors (13 of 17) were more prone to clinical metastasis in comparison with low expression tumors. CXCR4 was differentially expressed in 95C and 95D cells with low or high metastatic potential, and the surface expression of CXCR4 were 50% up-regulated or down-regulated following the stable transfection. The metastatic potential of NSCLC in vitro, such as migration, invasion, and adhesion, were significantly enhanced or impaired. In addition, neutralizing the interactions of stromal cell–derived factor-1/CXCR4 in vitro with CXCR4-specific antibodies inhibited the CXCR4-dependent migration, invasion, and adhesion. Furthermore, s.c. inoculation of lung cancer cells with low expression of CXCR4 in nude mice showed 0- to 2-fold decrease in lung metastatic foci than that with high expression of CXCR4. Conclusions: Differential expression of CXCR4 is associated with the metastatic potential of human NSCLC, raising the possibility that blockade of CXCR4/stromal cell–derived factor-1 interaction may lead the way to design novel therapeutic tools for the treatment of metastatic NSCLC patients.

Involvement of cellular death in TRAIL/DR5-dependent suppression induced by CD4 + CD25 + regulatory T cells

CD4+CD25+ regulatory T cells (Treg) are potent immunosuppressive cells active in controlling normal pathological immune responses. The mechanisms of this suppression have been investigated under various conditions. In this report, tumor necrosis factor-related apoptosis inducing ligand (TRAIL)/death receptor 5 (DR5) was explored as one of the pivotal factors for the suppression and cytotoxicity induced by CD4+CD25+ Treg. Cell death was involved in the suppression induced by activated CD4+CD25+ Treg in vitro. The induction of CD4+ T cell death was not mediated by the CD95/CD95L pathway, but rather depended upon the upregulation of TRAIL in the Treg. Blocking the TRAIL/DR5 pathway resulted in a significant reduction of the suppressive activity as well as the cytotoxic effects of Treg in vitro. Activated Treg displayed TRAIL-dependent cytotoxicity against CD4+ T cells in vivo. The prolonged survival of allogeneic skin grafts induced by Treg was inhibited by DR5-blocking antibodies. Our findings suggest that the TRAIL/DR5 pathway is one of the mechanisms used by Treg to regulate immune responses both in vitro and in vivo.

Interleukin-7-Dependent Expansion and Persistence of Melanoma-Specific T Cells in Lymphodepleted Mice Lead to Tumor Regression and Editing

Active-specific immunotherapy with dendritic cells loaded with peptide derived from the melanoma antigen, gp100, failed to mediate regression of established B16F10 melanoma in normal mice. Dendritic cell vaccination induced activation and subsequent deletion of adoptively transferred naive CD8+ T-cell receptor transgenic (pmel-1) T cells specific for gp100 in normal mice. In lymphodepleted mice, dendritic cell vaccination produced greater T-cell expansion, long-term persistence of memory T cells, and tumor regression. Most tumors that persisted in the presence of functional memory T cells had either lost or exhibited reduced expression of MHC class I or gp100 proteins. In contrast to other naive T cells, pmel-1 T cells adoptively transferred to lymphodepleted mice exhibited faster proliferation and a more differentiated phenotype after exposure to peptide-pulsed dendritic cells. Proliferation and persistence of pmel-1 T cells was highly dependent on interleukin-7 (IL-7) in irradiated mice, and IL-15 when IL-7 was neutralized, two critical homeostatic cytokines produced in response to the irradiation-induced lymphodepletion.

Differential impairment of regulatory T cells rather than effector T cells by paclitaxel-based chemotherapy.

Characterized as a mitotic inhibitor, paclitaxel has gained importance as a promising agent for the treatment of advanced non-small cell lung cancer (NSCLC). However, whether paclitaxel has immune modulatory effects remains unclear. In this study, we analyzed 55 peripheral blood samples from NSCLC patients who underwent paclitaxel-based chemotherapy. We found that among the lymphocyte subsets, paclitaxel selectively decreased the size of the regulatory T cell (Treg) population rather than other subsets including effector T cells (Teff). Apoptosis by upregulating the expression of the cell death receptor Fas (CD95) contributed to the reduced cell number of Treg. Importantly, the inhibitory function of Treg was significantly impaired, while the production of Th1 cytokines IFN-gamma and IL-2 and the expression of the activation marker CD44 among CD4(+) and CD8(+) T cells were augmented after paclitaxel treatment. These results strongly demonstrated that paclitaxel-based chemotherapy played important roles in modulating immune responses.

TLR1/TLR2 agonist induces tumor regression by reciprocal modulation of effector and regulatory T cells.

Using TLR agonists in cancer treatment can have either beneficial or detrimental effects. Therefore, it is important to determine their effect on the tumor growth and understand the underlying mechanisms in animal tumor models. In this study, we report a general immunotherapeutic activity of a synthetic bacterial lipoprotein (BLP), a TLR1/TLR2 agonist, on established lung carcinoma, leukemia, and melanoma in mice. Systemic treatment of 3LL tumor-bearing mice with BLP, but not LPS, led to a dose-dependent tumor regression and a long-lasting protective response against tumor rechallenge. The BLP-mediated tumor remission was neither mediated by a direct tumoricidal activity nor by innate immune cells, because it lacked therapeutic effect in immunodeficient SCID mice. Instead, BLP treatment reduced the suppressive function of Foxp3+ regulatory T cells (Tregs) and enhanced the cytotoxicity of tumor-specific CTL in vitro and in vivo. Furthermore, adoptive cotransfer of BLP-pretreated but not untreated CTL and Tregs from wild-type but not from TLR2−/− mice was sufficient to restore antitumor immunity in SCID mice by reciprocally modulating Treg and CTL function. These results demonstrate that the TLR1/TLR2 agonist BLP may have a general tumor therapeutic property involving reciprocal downregulation of Treg and upregulation of CTL function. This property may play an important role in the development of novel antitumor strategies.

Overactivated Neddylation Pathway as a Therapeutic Target in Lung Cancer

BACKGROUND A number of oncoproteins and tumor suppressors are known to be neddylated, but whether the neddylation pathway is entirely activated in human cancer remains unexplored. METHODS NEDD8-activating enzyme (NAE) (E1) and NEDD8-conjugating enzyme (E2) expression and global-protein neddylation were examined by immunohistochemistry, immunoblotting, and real-time polymerase chain reaction analysis. Cell proliferation, clonogenic survival, migration, and motility in vitro, as well as tumor formation and metastasis in vivo, were determined upon neddylation inhibition by MLN4924, an investigational NEDD8-activating enzyme inhibitor. Survival was analyzed with Kaplan-Meier methods and compared by the log-rank test. All statistical tests were two-sided. RESULTS The entire neddylation pathway, including NEDD8-activating enzyme E1, NEDD8-conjugating enzyme E2, and global-protein neddylation, is overactivated in both lung adenocarcinoma and squamous-cell carcinoma. Compared with lung adenocarcinoma patients with low expression, those with high expression had worse overall survival (NEDD8-activating enzyme E1 subunit 1 [NAE1]: hazard ratio [HR] = 2.07, 95% confidence interval [CI] = 0.95 to 4.52, P = .07; ubiquitin-conjugating enzyme E2M (UBC12): HR = 13.26, 95% CI = 1.77 to 99.35, P = .01; global protein neddylation: HR = 3.74, 95% CI = 1.65 to 8.47, P = .002). Moreover, inhibition of neddylation by the NAE inhibitor MLN4924 statistically significantly suppressed proliferation, survival, migration, and motility of lung cancer cells in vitro and tumor formation and metastasis in vivo. At the molecular level, MLN4924 inactivated Cullin-RING E3 ligases, led to accumulation of tumor-suppressive Cullin-RING E3 ligase substrates and induced phorbol-12-myristate-13-acetate-induced protein 1 (NOXA)-dependent apoptosis or cellular senescence. CONCLUSIONS Our study highlights the overactivated neddylation pathway in lung cancer development and as a promising therapeutic target.

Glucocorticoids inhibit lipopolysaccharide-mediated inflammatory response by downregulating microRNA-155: a novel anti-inflammation mechanism.

Glucocorticoids (GCs) are among the most widely used and effective therapies for many chronic inflammatory diseases. Although attempts have been made to identify important protein-coding genes and pathways involved in the anti-inflammatory effect of GCs, knowledge of genomic aberrations associated with noncoding genes, such as micro-RNAs (miRNAs), and their contributions is relatively limited. In this study, a systematic screening of the miRNA expression profile by microarray showed that GCs inhibited the expression of miR-155 in lipopolysaccharide (LPS)-induced macrophage inflammatory responses. Overexpression of miR-155 markedly reversed the suppressive action of GCs, whereas inhibition of miR-155 exhibited an effect similar to that of GCs on LPS-treated RAW264.7 cells, indicating miR-155 to be a functional regulator in the anti-inflammatory effect of GCs. Furthermore, GCs inhibited miR-155 expression in a GC receptor- and NF-κB-dependent manner. Bioinformatics analysis and luciferase assay revealed that the NF-κB binding site located in the promoter region of the B-cell integration cluster was important in mediating the GC-driven suppression of miR-155 in response to LPS stimulation. In addition, the combination of treatment with GCs and inhibition of miR-155 enhanced the anti-inflammatory effect of GCs on LPS-stimulated RAW264.7 cells. Therefore, we identify miR-155 to be a novel target through which GCs exert their anti-inflammatory effect on the LPS-induced macrophage inflammatory response. These findings may provide a basic rationale for new approaches in the effort to develop anti-inflammatory therapeutics.

Efficacy of GM-CSF-producing Tumor Vaccine after Docetaxel Chemotherapy in Mice Bearing Established Lewis Lung Carcinoma

In this report, we evaluated the efficacy of a GM-CSF-producing tumor vaccine given before and after docetaxel in mice bearing established lung tumors. Mice bearing established 3LL tumors were treated with docetaxel and tumor vaccines transduced with either control or GM-CSF adenoviral vectors. Docetaxel (5–20 mg/kg) treatment alone had only a minimal effect on growth of established 3LL tumors in vivo, although docetaxel was cytotoxic to 3LL cells in vitro. When mice bearing established 3LL tumors were pretreated with docetaxel followed by vaccination with irradiated GM-CSF- transduced 3LL tumor cells, significant tumor regression and prolonged survival were observed compared with chemotherapy alone. Delaying docetaxel treatment until after tumor vaccination abrogated the vaccines anti-tumor effects. Mice that survived treatment were able to resist a lethal rechallenge of 3LL tumor cells. Memory CTL specific for an epitope (MUT-1) derived from 3LL were detected in surviving mice. Docetaxel induced a mild lymphodepletion in mice, both CD4 and CD8 subsets were reduced in LN and spleens. Interestingly, docetaxel also diminished the number of memory CD8+ T cells (CD122+) and possible CD4+CD25+Foxp3+ natural Treg cells. Docetaxel treatment did not affect antigen-driven proliferation of naive T cells but significantly promoted survival of activated T cells. Thus, augmentation of vaccine induced antitumor immunity in docetaxel-treated mice primarily due to the enhanced survival of antigen-experienced T cells.

SIRT1 Limits the Function and Fate of Myeloid-Derived Suppressor Cells in Tumors by Orchestrating HIF-1α–Dependent Glycolysis

Myeloid-derived suppressor cells (MDSC) display an immature phenotype that may assume a classically activated (M1) or alternatively activated phenotype (M2) in tumors. In this study, we investigated metabolic mechanisms underlying the differentiation of MDSCs into M1 or M2 myeloid lineage and their effect on cancer pathophysiology. We found that SIRT1 deficiency in MDSCs directs a specific switch to M1 lineage when cells enter the periphery from bone marrow, decreasing the suppressive function in favor of a proinflammatory M1 phenotype associated with tumor cell attack. Glycolytic activation through the mTOR-hypoxia-inducible factor-1α (HIF-1α) pathway was required for differentiation to the M1 phenotype, which conferred protection against tumors. Our results define the essential nature of a SIRT1-mTOR/HIF-1α glycolytic pathway in determining MDSC differentiation, with implications for metabolic reprogramming as a cancer therapeutic approach.

Induction of autophagy and senescence by knockdown of ROC1 E3 ubiquitin ligase to suppress the growth of liver cancer cells

Regulator of Cullins-1 (ROC1) or RING box protein-1 (RBX1) is an essential RING component of Cullin-RING ligase (CRL). Our previous studies showed that ROC1 is required for the growth of several cancer cell lines while ROC1 siRNA silencing inactivates CRL, leading to cell cycle arrest, cell senescence and/or apoptosis. However, it is completely unknown whether ROC1 knockdown triggers autophagic response by inactivating CRL. Moreover, the role of ROC1 in liver cancer remains elusive. In this study, we reported that ROC1 knockdown significantly inhibited the growth of liver cancer cells by sequentially and independently inducing autophagy and p21-dependent cell senescence. Mechanism analysis revealed that ROC1 silencing triggered autophagy by inhibition of mammalian target of rapamycin (mTOR) activity due to accumulation of mTOR-inhibitory protein Deptor, a substrate of CRL. Consistently, Deptor knockdown significantly blocked autophagy response upon ROC1 silencing. Biologically, autophagy response upon ROC1 silencing was a survival signal, and blockage of autophagy pathway sensitized cancer cells to apoptosis. Finally, we demonstrated that ROC1 was overexpressed in hepatocellular carcinomas, which is associated with poor prognosis of liver cancer patients. These findings suggest that ROC1 is an appealing drug target for liver cancer and provide a proof-of-concept evidence for a novel drug combination of ROC1 inhibitor and an autophagy inhibitor for effective treatment of liver cancer by enhancing apoptosis.