Author Correction: FGL2 promotes tumor progression in the CNS by suppressing CD103+ dendritic cell differentiation.

The original version of this Article contained errors in the author affiliations. Qingnan Zhao, Xueqing Xia, Longfei Huo and Shulin Li were incorrectly associated with Beijing Institute for Brain Disorders, 100069, Beijing, China.This has now been corrected in both the PDF and HTML versions of the Article.

FGL2 promotes tumor progression in the CNS by suppressing CD103+ dendritic cell differentiation.

Few studies implicate immunoregulatory gene expression in tumor cells in arbitrating brain tumor progression. Here we show that fibrinogen-like protein 2 (FGL2) is highly expressed in glioma stem cells and primary glioblastoma (GBM) cells. FGL2 knockout in tumor cells did not affect tumor-cell proliferation in vitro or tumor progression in immunodeficient mice but completely impaired GBM progression in immune-competent mice. This impairment was reversed in mice with a defect in dendritic cells (DCs) or CD103+ DC differentiation in the brain and in tumor-draining lymph nodes. The presence of FGL2 in tumor cells inhibited granulocyte-macrophage colony-stimulating factor (GM-CSF)-induced CD103+ DC differentiation by suppressing NF-κB, STAT1/5, and p38 activation. These findings are relevant to GBM patients because a low level of FGL2 expression with concurrent high GM-CSF expression is associated with higher CD8B expression and longer survival. These data provide a rationale for therapeutic inhibition of FGL2 in brain tumors.

Tonic B-cell receptor signaling in diffuse large B-cell lymphoma.

We used clustered regularly interspaced short palindromic repeats/Cas9-mediated genomic modification to investigate B-cell receptor (BCR) signaling in cell lines of diffuse large B-cell lymphoma (DLBCL). Three manipulations that altered BCR genes without affecting surface BCR levels showed that BCR signaling differs between the germinal center B-cell (GCB) subtype, which is insensitive to Bruton tyrosine kinase inhibition by ibrutinib, and the activated B-cell (ABC) subtype. Replacing antigen-binding BCR regions had no effect on BCR signaling in GCB-DLBCL lines, reflecting this subtype's exclusive use of tonic BCR signaling. Conversely, Y188F mutation in the immunoreceptor tyrosine-based activation motif of CD79A inhibited tonic BCR signaling in GCB-DLBCL lines but did not affect their calcium flux after BCR cross-linking or the proliferation of otherwise-unmodified ABC-DLBCL lines. CD79A-GFP fusion showed BCR clustering or diffuse distribution, respectively, in lines of ABC and GCB subtypes. Tonic BCR signaling acts principally to activate AKT, and forced activation of AKT rescued GCB-DLBCL lines from knockout (KO) of the BCR or 2 mediators of tonic BCR signaling, SYK and CD19. The magnitude and importance of tonic BCR signaling to proliferation and size of GCB-DLBCL lines, shown by the effect of BCR KO, was highly variable; in contrast, pan-AKT KO was uniformly toxic. This discrepancy was explained by finding that BCR KO-induced changes in AKT activity (measured by gene expression, CXCR4 level, and a fluorescent reporter) correlated with changes in proliferation and with baseline BCR surface density. PTEN protein expression and BCR surface density may influence clinical response to therapeutic inhibition of tonic BCR signaling in DLBCL.

Mature adipocytes in bone marrow protect myeloma cells against chemotherapy through autophagy activation.

A major problem in patients with multiple myeloma is chemotherapy resistance, which develops in myeloma cells upon interaction with bone marrow stromal cells. However, few studies have determined the role of bone marrow adipocytes, a major component of stromal cells in the bone marrow, in myeloma chemotherapy resistance. We reveal that mature human adipocytes activate autophagy and upregulate the expression of autophagic proteins, thereby suppressing chemotherapy-induced caspase cleavage and apoptosis in myeloma cells. We found that adipocytes secreted known and novel adipokines, such as leptin and adipsin. The addition of these adipokines enhanced the expression of autophagic proteins and reduced apoptosis in myeloma cells. In vivo studies further demonstrated the importance of bone marrow-derived adipocytes in the reduced response of myeloma cells to chemotherapy. Our findings suggest that adipocytes, adipocyte-secreted adipokines, and adipocyte-activated autophagy are novel targets for combatting chemotherapy resistance and enhancing treatment efficacy in myeloma patients.

Anti-ß2-microglobulin monoclonal antibodies overcome bortezomib resistance in multiple myeloma by inhibiting autophagy.

Our previous studies showed that anti-ß2M monoclonal antibodies (mAbs) have strong and direct apoptotic effects on multiple myeloma (MM) cells, suggesting that anti-ß2M mAbs might be developed as a novel therapeutic agent. In this study, we investigated the anti-MM effects of combination treatment with anti-ß2M mAbs and bortezomib (BTZ). Our results showed that anti-ß2M mAbs enhanced BTZ-induced apoptosis of MM cell lines and primary MM cells. Combination treatment could also induce apoptosis of BTZ-resistant MM cells, and the enhanced effect depended on the surface expression of ß2M on MM cells. BTZ up-regulated the expression of autophagy proteins, whereas combination with anti-ß2M mAbs inhibited autophagy. Sequence analysis of the promoter region of beclin 1 identified 3 putative NF-κB-binding sites from -615 to -789 bp. BTZ treatment increased, whereas combination with anti-ß2M mAbs reduced, NF-κB transcription activities in MM cells, and combination treatment inhibited NF-κB p65 binding to the beclin 1 promoter. Furthermore, anti-ß2M mAbs and BTZ combination treatment had anti-MM activities in an established MM mouse model. Thus, our studies provide new insight and support for the clinical development of an anti-ß2M mAb and BTZ combination treatment to overcome BTZ drug resistance and improve MM patient survival.

p38 MAPK inhibits breast cancer metastasis through regulation of stromal expansion.

p38 MAPK signaling controls cell growth, proliferation and the cell cycle under stress conditions. However, the function of p38 activation in tumor metastasis is still not well understood. We report that p38 activation in breast cancer cells inhibits tumor metastasis but does not substantially modulate primary tumor growth. Stable p38 knockdown in breast cancer cells suppressed NF-κB p65 activation, inhibiting miR-365 expression and resulting in increased IL-6 secretion. The inhibitory effect of p38 signaling on metastasis was mediated by suppression of mesenchymal stem cell (MSC) migration to the primary tumor and sites of metastasis, where MSCs can differentiate into cancer-associated fibroblasts to promote tumor metastasis. The migration of MSCs to these sites relies on CXCR4-SDF1 signaling in the tumor microenvironment. Analysis of human primary and metastatic breast cancer tumors showed that p38 activation was inversely associated with IL-6 and vimentin expression. This study suggests that combination analysis of p38 MAPK and IL-6 signaling in patients with breast cancer may improve prognosis and treatment of metastatic breast cancer.

MAPK11 in breast cancer cells enhances osteoclastogenesis and bone resorption.

Breast cancer cells frequently metastasize to bone and induce osteolytic bone destruction in patients. These metastases cause severe bone pain, high risk of fractures and hypercalcemia, and are essentially incurable and fatal. Recent studies show that breast cancer cells in bone activate osteoclastogenesis and bone resorption. However the underlying mechanism is poorly understood. This study shows that the p38 MAPK (p38) isoform MAPK11 (p38ß) is expressed in breast cancer cells. By using specific small hairpin RNAs for MAPK11, we demonstrated that p38ß-mediated p38 activity in breast cancer cells is responsible for breast cancer-induced osteolytic bone destruction. The addition of conditioned media from breast cancer cell lines MDA-MB-231 and MDA-MB-468, which have high expression of p38ß, induced osteoclast differentiation and bone resorption. In contrast, knockdown of p38ß in breast cancer cells reduced osteoclast differentiation in vitro and reduced bone destruction in severe combined immunodeficiency (SCID) mouse models. The knockdown of p38ß did not affect tumor growth or survival or the ability of cancer cells to home to bone. Furthermore, our results showed that p38ß upregulated the expression and secretion of monocyte chemotactic protein-1 (MCP-1) in breast cancer cells, and upregulated MCP-1 activates osteoclast differentiation and activity. This study elucidates a novel molecular mechanism of breast cancer cell-induced osteolytic bone destruction. This study also indicates that targeting breast cancer cell p38ß and its product MCP-1 may be a viable approach to treat or prevent bone destruction in patients with bone-metastatic breast cancer.

A critical role of autocrine sonic hedgehog signaling in human CD138+ myeloma cell survival and drug resistance.

Hedgehog (Hh) signaling plays an important role in the oncogenesis of B-cell malignancies such as multiple myeloma (MM). However, the source of Hh ligand sonic hedgehog (SHH) and its target cells remains controversial. Previous studies showed that stromally induced Hh signaling is essential for the tumor cells and that CD19(+)CD138(-) MM stem cells are the target cells of Hh signaling. Here we demonstrate that SHH was mainly secreted by human myeloma cells but not by stromal cells in MM bone marrow. Autocrine SHH enhanced CD138(+) myeloma cell proliferation and protected myeloma cells from spontaneous and stress-induced apoptosis. More importantly, autocrine SHH protected myeloma cells against chemotherapy-induced apoptosis in vitro and in vivo. Combinational treatment with chemotherapy and SHH-neutralizing antibody displayed synergistic antimyeloma effects. Mechanistic studies showed that SHH signaling activated the SHH/GLI1/BCL-2 axis, leading to the inhibition of myeloma cell apoptosis. Thus, this study identifies the myeloma autocrine Hh signaling pathway as a potential target for the treatment of MM. Targeting this pathway may improve the efficacy of chemotherapy in MM patients.

Human osteoclasts are inducible immunosuppressive cells in response to T cell-derived IFN-γ and CD40 ligand in vitro.

Osteoclasts (OCs) are bone resorbing cells whose activity can be regulated by activated T cells and their cytokines. However, the immune function of OCs is largely unknown. In this study, we found that as bystanders, human OCs effectively suppressed T-cell proliferation induced by allogeneic, microbial antigenic, and T-cell receptor stimuli in vitro. Mechanism studies revealed that T cell-derived IFN-γ and CD40 ligand (CD40L) induced the expression of indoleamine 2,3-dioxygenase (IDO) in OCs, which mediated the immunosuppressive function on T-cell proliferation through depleting tryptophan. Neutralizing IFN-γ and blocking CD40L, or silencing or inhibiting IDO in OCs restored T-cell proliferation in the presence of OCs. Our data reveal a novel function of human OCs as inducible immunosuppressive cells, and a feedback loop between OCs and activated T cells. Thus, this study provides new insight into the mechanism of the immunosuppressive function of OCs, and may be helpful for developing novel therapeutic strategies for human diseases involving both the bone and immune systems.

Bone marrow stromal cells derived MCP-1 reverses the inhibitory effects of multiple myeloma cells on osteoclastogenesis by upregulating the RANK expression.

Multiple myeloma (MM) cells are responsible for aberrant osteoclast (OC) activation. However, when cocultured monocytes, but not OC precursors, with MM cells, we made a novel observation that MM cells inhibited receptor activator of nuclear factor κB ligand (RANKL)-induced increase of OC differentiation, OC gene expression, signaling pathways and bone resorption activity. Our results showed that MM cells produced multiple inhibitory cytokines of osteoclastogenesis, such as IL-10, which activated STAT3 signaling and induce OC inhibition. However, cocultures of bone marrow stromal cells (BMSCs) reversed MM-induced OC inhibition. We found that MM cells increased production of MCP-1 from BMSCs and BMSC-derived MCP-1 enhanced OC formation. Mechanistic studies showed that IL-10 downregulated RANK expression in monocytes and thus, inhibited RANKL-induced OC formation. In contrast, MCP-1 upregulated RANK expression and thus, enhanced OC formation. Overall, our studies for the first time demonstrated that MM cell have inhibitory effects on osteoclastogenesis by producing inhibitory cytokines. Our results further indicate that activation of osteoclastogenesis in bone marrow requests the crosstalk of MM cells, BMSCs and their produced cytokines. Thus, our studies provide evidences that targeting bone marrow microenvironmental cells and/or cytokines may be a new approach to treating MM bone destruction.

p38 MAPK in myeloma cells regulates osteoclast and osteoblast activity and induces bone destruction.

p38 mitogen-activated protein kinase (MAPK), which is constitutively activated in human myeloma, has been implicated in bone destruction by this cancer, but the processes it recruits are obscure. In this study, we show that p38 activity in myeloma inhibits osteoblast differentiation and bone formation, but also enhances osteoclast maturation and bone resorption. p38 regulated the expression and secretion of the Wnt pathway antagonist DKK-1 and the monocyte chemoattractant MCP-1. Attenuating p38, DKK-1, or MCP-1 were each sufficient to reduce bone lesions in vivo. Although it is well known that DKK-1 inhibits osteoblast differentiation, we found that together with MCP-1, it could also promote osteoclast differentiation and bone resorption. The latter effects were mediated by enhancing expression of RANK in osteoclast progenitor cells and by upregulating secretion of its ligand RANKL from stromal cells and mature osteoblasts. In summary, our study defined the mechanisms by which p38 signaling in myeloma cells regulates osteoblastogenesis, osteoclastogenesis, and bone destruction. Our findings, which may have implications for bone invasion by other cancers where p38 is elevated, strongly suggests that targeting p38 for inhibition may offer an effective therapeutic approach to treat osteolytic bone lesions in patients with myeloma.

Th9 cells promote antitumor immune responses in vivo.

Th9 cells are a subset of CD4+ Th cells that produce the pleiotropic cytokine IL-9. IL-9/Th9 can function as both positive and negative regulators of immune response, but the role of IL-9/Th9 in tumor immunity is unknown. We examined the role of IL-9/Th9 in a model of pulmonary melanoma in mice. Lack of IL-9 enhanced tumor growth, while tumor-specific Th9 cell treatment promoted stronger antitumor responses in both prophylactic and therapeutic models. Th9 cells also elicited strong host antitumor CD8+ CTL responses by promoting Ccl20/Ccr6-dependent recruitment of DCs to the tumor tissues. Subsequent tumor antigen delivery to the draining LN resulted in CD8+ T cell priming. In agreement with this model, Ccr6 deficiency abrogated the Th9 cell-mediated antitumor response. Our data suggest a distinct role for tumor-specific Th9 cells in provoking CD8+ CTL-mediated antitumor immunity and indicate that Th9 cell-based cancer immunotherapy may be a promising therapeutic approach.

RACK1 promotes breast carcinoma migration/metastasis via activation of the RhoA/Rho kinase pathway.

We aimed to gain a mechanistic understanding of the role of RACK1 in breast carcinoma migration/metastasis. Migration assays were conducted in breast carcinoma cell lines. siRNA targeting RACK1 as well as the Rho kinase inhibitor were also applied. Immunoprecipitation and immunofluorescence were used to study the RACK1/RhoA interaction. GTP-Rho pull-down assays were performed to assess the activation of RhoA. We also conducted immunohistochemistry in 160 breast carcinoma samples. Experiments in vitro showed that RACK1 promotes migration via interaction with RhoA and activation of the RhoA/Rho kinase pathway. Immunohistochemistry in 160 samples revealed that RACK1 is strongly correlated with accepted tumor spread indicators and RhoA (all P < 0.05). Kaplan-Meier survival analysis indicated a correlation between higher RACK1 expression and shorter survival times (P < 0.001). RACK1 is a prognostic factor that promotes breast carcinoma migration/metastasis by interacting with RhoA and activating the RhoA/Rho kinase pathway.

Connexin 26 expression correlates with less aggressive phenotype of intestinal type-gastric carcinomas.

Connexin 26 (Cx26), one of the gap junction-forming family members, is more controversial than other members, as a tumor suppressor. Here, we assessed Cx26 expression in gastric carcinoma, which has not been investigated before, and its clinical significance including survival analyses. Cx26 expression was assessed in 205 tissue samples from gastric carcinoma by immunohistochemistry. Of 205 gastric carcinoma cases, 79 (38.5%) were positive for Cx26 with mainly cytoplasmic localization compared to sporadic membranous staining in normal epithelium, and the expression levels were confirmed by Western blotting and real-time PCR. Negative associations were revealed between Cx26 expression and most clinicopathologic features (all P<0.05). Notably, high Cx26 expression was associated with histological intestinal-type (P=0.017) and early stage of gastric carcinoma. The multivariate regression analysis revealed that positive Cx26 expression was an independent prognostic predictor of intestinal-type GC (P=0.023, HR=2.019). Our findings suggest that aberrant expression of Cx26 in cytoplasm plays a tumor-suppressor role in gastric carcinoma and is an independent biomarker for favorable prognosis in intestinal-type gastric carcinoma.

RACK1 promotes breast carcinoma proliferation and invasion/metastasis in vitro and in vivo.

A yeast two-hybrid system was utilized to identify novel PI3K p110alpha-interacting proteins, of which receptor of activated protein kinase C1 (RACK1) was chosen for successive detailed analyses. Our aim was to investigate the function(s) of RACK1 and its involvement in mechanisms of breast carcinoma proliferation and invasion/metastasis. Experiments in breast carcinoma cell lines stably transfected with RACK1, as well as nude mouse models, showed that RACK1 promotes breast carcinoma proliferation and invasion/metastasis in vitro and in vivo. Conversely, knockdown of RACK1 by siRNA in vitro inhibited proliferation, migration, and invasion. In cell lines stably transfected with RACK1, p-AKT, cyclin D1, cyclin D3, and CD147 expression, as well as MMP2 activity, were elevated. RACK1-induced migration could be inhibited by the addition of Rho-kinase inhibitor. In 160 breast carcinoma cases, survival analyses established that RACK1 is an independent prognostic factor for poor outcome (P < 0.001). In conclusion, RACK1 is an independent prognosis-related factor and promotes breast carcinoma proliferation and invasion/metastasis in vitro and in vivo.

RACK1: A superior independent predictor for poor clinical outcome in breast cancer.

We aimed to investigate the expression of RACK1 in breast cancer, evaluate its role in predicting prognosis and compare with commonly used biomarkers: Ki67, ER, PR and HER-2 for patients with breast cancer. The RACK1 expression and its clinical significance were examined in 160 breast carcinoma patients using immunohistochemistry. Correlations of RACK1 expression with other commonly used biomarkers and survival analyses were assessed. Immunohistochemistry results showed that the number of RACK1 cases scoring 0, 1, and 2 were 66, 54, and 40, respectively. RACK1 staining was strongly related to clinical stage, histological grade, Ki67, ER, PR and HER-2 (all p < 0.05). Consistently, all of the cases exhibiting RACK1 staining score 0 were survivors, whereas the majority (55.0%) of those exhibiting RACK1 staining score 2 were deaths. Kaplan-Meier survival analysis of 160 cases revealed a correlation between higher RACK1 expression levels and shorter overall survival times (p < 0.001). Univariate and multivariate analyses revealed that RACK1, tumor size, lymph node metastasis, and HER-2 were independent prognostic factors (all p < 0.05). Interestingly, receiver operator characteristic (ROC) curves showed that the ROC areas for RACK1, Ki67, ER, PR and HER-2 were 0.833, 0.766, 0.446, 0.387, and 0.689, respectively, and the superiority of RACK1 in sensitivity and specificity as biomarker was demonstrated. To our knowledge, it is the first time to investigate the expression of RACK1, and identified that RACK1 is a superior independent biomarker for diagnosis and prognosis comparing with currently widely used diagnostic index in breast carcinoma.

Overexpression and involvement of special AT-rich sequence binding protein 1 in multidrug resistance in human breast carcinoma cells.

Special AT-rich sequence binding protein (SATB) 1 has been proposed to act as a determinant for the acquisition of metastatic activity by controlling expression of a specific set of genes that promote metastatic activity. Here we found that SATB1 expression is upregulated in multidrug-resistant breast cancer cells that exhibit higher invasive potential than the parental cells. Apart from accelerating metastasis and inducing epithelial-mesenchymal transition, SATB1 was demonstrated to confer resistance to both P-glycoprotein-related and P-glycoprotein-non-related drugs on MCF7 cells, which was accompanied by decreasing accumulation of adriamycin in SATB1-overexpressing transfectants. SATB1 depletion could partially reverse the multidrug resistance (MDR) phenotype of MCF7/ADR in vitro and in vivo. The SATB1-induced P-glycoprotein-mediated MDR could be reversed by treatment with anti-P-glycoprotein mAb. Moreover, SATB1 plays an important role in anti-apoptotic activity in MCF7/ADR cells in response to adriamycin treatment, which suggests another mechanism contributing to SATB1-related MDR of breast cancers. These data provide new insights into the mode by which breast tumors acquire the MDR phenotype and also imply a role for SATB1 in this process.

Twist1-mediated adriamycin-induced epithelial-mesenchymal transition relates to multidrug resistance and invasive potential in breast cancer cells.

PURPOSE: Besides its therapeutic effects, chemotherapeutic agents also enhance the malignancy of treated cancers in clinical situations. Recently, epithelial-mesenchymal transition (EMT) has attracted attention in studies of tumor progression. We aimed to test whether transient Adriamycin treatment induces EMT and apoptosis simultaneously in cancer cells, clarify why the same type of cells responds differentially (i.e., apoptosis, EMT) to Adriamycin treatment, and elucidate the role of Twist1, the master regulator of EMT, in this process. EXPERIMENTAL DESIGN: In unsynchronized MCF7 cells or cells synchronized at different phases, apoptosis, EMT, and concurrent events [multidrug resistance (MDR) and tumor invasion] after Adriamycin or/and Twist1 small interfering RNA treatment were examined in vitro and in vivo. The Adriamycin-induced Twist1 expression and the interaction of Twist1 with p53-Mdm2 were examined by immunoblotting and immunoprecipitation, respectively. RESULTS: We showed in vitro that Adriamycin induced EMT and apoptosis simultaneously in a cell cycle-dependent manner. Only the cells undergoing EMT displayed enhanced invasion and MDR. Twist1 depletion completely blocked the mesenchymal transformation, partially reversed MDR, and greatly abolished invasion induced by Adriamycin. Also, we confirmed in vivo that Twist1 RNA interference improved the efficacy of Adriamycin for breast cancers. Further, Twist1 reduction in Adriamycin-treated cells promoted p53-dependent p21 induction and disrupted the association of p53 with Mdm2. CONCLUSIONS: Our studies show the diverse responses to Adriamycin treatment in cells at different phases, suggest an unrecognized role of EMT in regulating MDR and invasion, and show the efficacy of Twist1 RNA interference in Adriamycin-based chemotherapies for breast cancer.

Comparison of chromosomal aberrations between primary tumors and their synchronous lymph-node metastases in intestinal-type gastric carcinoma.

Lymph-node metastasis is a main factor causing poor prognosis of patients with gastric cancer (GC). In order to determine the genes involved in lymph-node metastasis, we compared primary tumors with their synchronous lymph-node metastases for DNA sequence copy number aberrations (DSCNAs) in 20 patients diagnosed as having intestinal-type GC using comparative genomic hybridization (CGH). The results showed that some DSCNAs (gains at 8q, 13q, 5p, 7 and X, and losses at 1p, 17p, 19, 21q and 22q) were frequently found in both primary tumors and their metastases. However, metastases often contained DSCNAs that were not found in corresponding primary tumors, and gain at 20q12-13 and losses at 21qcen-21, 4q and 14q22-ter were significantly more frequently observed in metastatic lesions than in their primary tumors (10:2, 9:0, 6:0, and 7:0 between metastases and corresponding primary tumors, respectively). Our data indicate that gain at 20q12-13 and losses at 21qcen-21, 4q, and 14q22-ter are involved in lymph-node metastases, and that these chromosomal regions may contain the genes related to lymph-node metastases in intestinal-type GC.

Over-expression of ubiquitin carboxy terminal hydrolase-L1 induces apoptosis in breast cancer cells.

Ubiquitin carboxy terminal hydrolase-L1 (UCH-L1) belongs to the UCH proteases family that deubiquitinates ubiquitin-protein conjugates in the ubiquitin-proteasome system. Previous research showed that UCH-L1 was expressed in mouse retinal cells and testicular germ cells, and its function was associated with apoptosis. But it is still unclear whether UCH-L1 is concerned with apoptosis in tumor cells. In order to clarify the role of UCH-L1 in tumor cells, multi-drug resistance (MDR) human breast carcinoma cell line MCF7/Adr, that expresses relatively high UCH-L1, and its parental cell line MCF7, that expresses relatively low UCH-L1, were chosen for this study. We transfected pcDNA3.1-UCH-L1 plasmid and UCH-L1 siRNA into MCF7 and MCF7/Adr cells, respectively. Using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, western blot, Hoechst 33258 staining assay and flow cytometry, we found that over-expression of UCH-L1 in MCF7 cells induced apoptosis. On the other hand, silencing of UCH-L1 in MCF7/Adr cells led to the opposite effect. Moreover, to explore the mechanism underling these observations, we further investigated the expression of phospho-Akt and its downstream signal phospho-IkB-alpha and other signal molecules including Fas, Fas-L, Trail, DR4, DR5, Bax, cytochrome C, active caspase-3, phospho-p53, phospho-Mdm-2, Bcl-2, Bcl-xL, p21 and p27. The results indicated that the process of apoptosis triggered by UCH-L1 is, at least in part, probably through Phosphoinositide 3-kinase (PI3K)/Akt signal pathway. Our findings suggest that modulating the ubiquitination and deubiquitination pathway could be a novel method for tumor therapy.