Xuejun Hu

Arsenic trioxide induces apoptosis and G2/M phase arrest by inducing Cbl to inhibit PI3K/Akt signaling and thereby regulate p53 activation

Arsenic trioxide (ATO) strongly induces apoptosis in acute promyelocytic leukemia (APL), but it induces cell cycle arrest in most solid tumors. In this study, we investigated the mechanism of ATO action on APL-derived NB4 cells and gastric cancer cell lines. ATO decreased the viability of both cell lines, but gastric cancer cells were much less susceptible. ATO-induced G2/M phase arrest and p53 degradation in gastric cancer MGC803 cells. In contrast, ATO-induced apoptosis in NB4 cells without degradation of p53. Both processes were accompanied by transient activation of Akt. The PI3K/Akt inhibitor LY294002 significantly increased the amount of p53 protein and ATO-induced apoptosis in both cell lines and decreased G2/M phase arrest of MGC803 cells. In addition, ATO up-regulated the expression of Cbl proteins in both cell lines. Inhibition of Cbl with the proteasome inhibitor Ps341 decreased apoptosis in NB4 cells and increased the G2/M phase arrest of MGC803 cells, and it also prolonged the activation of PI3K/Akt by ATO. Consistent results with those in MGC803 cells were showed in gastric cancer cell BGC823 and SGC7901 after ATO treatment. These results demonstrate that inhibition of PI3K/Akt signaling by Cbl is involved in both ATO-induced apoptosis of NB4 cells and ATO-induced G2/M phase arrest of gastric cancer cells. Cbl achieved these effects probably via its regulating PI3K/Akt pathway, and thereby modulated p53 activation.

Oxaliplatin enhances TRAIL-induced apoptosis in gastric cancer cells by CBL-regulated death receptor redistribution in lipid rafts

Tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL) is a member of the tumor necrosis factor family that selectively induces apoptosis in cancer cells. However, gastric cancer cells are insensitive to TRAIL. In the present study, we show that oxaliplatin enhanced TRAIL‐induced apoptosis of MGC803, BGC823, and SGC7901 cells. Oxaliplatin promoted death receptor 4 (DR4) and death receptor 5 (DR5) clustering into aggregated lipid rafts, while the cholesterol‐sequestering agent nystatin partially prevented lipid raft aggregation, DR4 and DR5 clustering, and reduced apoptosis. Furthermore, the expression of the casitas B‐lineage lymphoma (Cbl) family was downregulated by oxaliplatin. Transfection of c‐Cbl or Cbl‐b partially reversed oxaliplatin‐induced lipid raft aggregation. These results indicated that oxaliplatin enhanced TRAIL‐induced gastric cancer cell apoptosis at least partially through Cbl‐regulated death receptor redistribution in lipid rafts.

Reversal of P-glycoprotein-mediated multi-drug resistance by the E3 ubiquitin ligase Cbl-b in human gastric adenocarcinoma cells†

P‐glycoprotein (P‐gp)‐mediated multi‐drug resistance (MDR) is a major barrier to the effective chemotherapy of many cancers. Recent studies have shown that inhibition of the PI3K/Akt signalling pathway can reverse P‐gp‐mediated MDR. We investigated the expression of activated Akt (p‐Akt) in 124 human gastric carcinoma tissue samples. Ubiquitous p‐Akt expression was recorded in the majority (88/124). There was a significant correlation between p‐Akt expression and the expression of P‐gp. In the adriamycin‐resistant MDR gastric carcinoma cell line SGC7901/ADR, p‐Akt expression was increased in comparison with the parental cell line SGC7901. Treatment of SGC7901/ADR cells with the PI3K inhibitor LY294002 reduced the expression of both p‐Akt and P‐gp. To explore the role of ubiquitin ligase Cbl‐b in this regulatory pathway, SGC7901/ADR cells were transfected with a plasmid overexpressing wild‐type Cbl‐b. This down‐regulated the expression of both p‐Akt and P‐gp. Furthermore, resistance to chemotherapeutic drugs was partially reversed. These results demonstrate an important role for Cbl‐b in reversing P‐gp‐mediated gastric cancer MDR through suppression of the PI3K/Akt signalling pathway and the down‐regulation of P‐gp expression. Copyright

miR-103/107 modulates multidrug resistance in human gastric carcinoma by downregulating Cav-1.

MicroRNAs (miRNAs) are a class of non-protein-coding small RNAs with the capacity to regulate fundamental biological processes essential for cancer initiation and progression. In the present study, we analyzed miRNA expression levels between multidrug-resistant gastric carcinoma cell line SGC7901/ADR and its parent cell line SGC7901 using a miRNA microarray. MiR-103/107 was downregulated compared with parental SGC7901 cells. Overexpression of miR-103/107 sensitized SGC7901/ADR cells to doxorubicin (DOX), as demonstrated by in vitro and in vivo drug sensitivity assay. We further confirmed that miR-103/107 inhibited P-gp function in gastric cancer SGC7901/ADR cells. Finally, we verified that caveolin-1 (Cav-1), a critical component of lipid rafts, was a target of miR-103/107.

β‐Elemene induces apoptosis as well as protective autophagy in human non‐small‐cell lung cancer A549 cells

Objectives  β‐Elemene, a novel traditional Chinese medicine, has been shown to be effective against a wide range of tumours. In this study, the antitumour effect of β‐elemene on human non‐small‐cell lung cancer (NSCLC) A549 cells and the mechanism involved have been investigated.

Tumor response and survival in patients with advanced non-small-cell lung cancer: the predictive value of chemotherapy-induced changes in fibrinogen

BackgroundHyperfibrinogenemia is a common problem associated with various carcinomas, and is accompanied by hypercoagulablity. In advanced non-small-cell lung cancer (NSCLC) it remains unclear whether or not chemotherapy-induced changes in fibrinogen level relate to chemotherapeutic response and prognosis. The purposes of this study were to: 1) analyze the association between chemotherapy-induced changes in plasma fibrinogen level and the chemotherapeutic response after the first two courses of standard first-line platinum-based chemotherapy; and 2) evaluate the prognostic significance of the basal plasma fibrinogen level in patients with advanced NSCLC.MethodsIn this retrospective study, the data from 160 patients with advanced NSCLC were collected. The association between the changes in fibrinogen and the response to chemotherapy, or between the pre-and post-chemotherapy fibrinogen levels and patient clinical characteristics, were analyzed using SPSS software. In addition, the prognostic value of pre-chemotherapy fibrinogen levels was assessed.ResultsThe median pre-chemotherapy plasma fibrinogen level was 4.4 g/L. Pre-chemotherapy plasma fibrinogen levels correlated significantly with gender (p = 0.041). Post-chemotherapy plasma fibrinogen levels correlated with gender (p = 0.023), age (p = 0.018), ECOG (p = 0.002) and tumor response (p = 0.049). Plasma fibrinogen levels markedly decreased after chemotherapy in 98 (61.25 %) patients with pre-chemotherapy hyperfibrinogenemia (p = 0.008); and in this population there was a significant link between the decrease in fibrinogen level, and initial partial response (PR; p = 0.017) and stable disease (SD; p = 0.031). Univariate and multivariate analysis revealed that higher levels of fibrinogen (≥4.4 g/L) and ECOG 1 were positively associated with shorter overall survival (OS). CEA and CA125 also decreased significantly (p =0.015, p =0.000) in DCR group after chemotherapy.ConclusionsThis study showed that the reduction in plasma fibrinogen levels induced by chemotherapy might be as a promising biomarker as CEA and CA125 for evaluating the efficacy of chemotherapy in advanced NSCLC. In addition, basal plasma fibrinogen levels could be used as an independent prognostic parameter for the OS of patients with advanced NSCLC.

Synergistic antitumor effect of β-elemene and etoposide is mediated via induction of cell apoptosis and cell cycle arrest in non-small cell lung carcinoma cells

β-Elemene, an anticancer agent, was isolated from the traditional Chinese medicine plant, curcuma aromatica. In this study, we investigated the synergistic antitumor effect of β-elemene and etoposide phosphate (VP-16) in A549 non-small cell lung carcinoma cells. The cells were treated with β-elemene (20 or 50 µg/ml), VP-16 (15 µg/ml) or the combination of both for 24 h. Compared to the treatment with β-elemene or VP-16 alone, an increased antitumor activity was observed with the combination of both, which was mediated by the cleavage of PARP, the up-regulation of Bax, p53 and p21, and the suppression of cyclin D1. These results suggest that the combination of β-elemene and VP-16 may be a promising therapeutic option for lung cancer.

TRAIL-activated EGFR by Cbl-b-regulated EGFR redistribution in lipid rafts antagonises TRAIL-induced apoptosis in gastric cancer cells

Most gastric cancer cells are resistant to tumour necrosis factor-related apoptosis-inducing ligand (TRAIL). Since TRAIL resistance is associated with lipid rafts, in which both death receptors and epidermal growth factor receptors (EGFR) are enriched, our aim is to identify how lipid raft-regulated receptor redistribution influences the sensitivity of TRAIL in gastric cancer cells. In TRAIL-resistant gastric cancer cells, TRAIL did not induce effective death-inducing signalling complex (DISC) formation in lipid rafts, accompanied with EGFR translocation into lipid rafts, and activation of EGFR pathway. Knockdown of casitas B-lineage lymphoma-b (Cbl-b) enhanced TRAIL-induced apoptosis by promoting DISC formation in lipid rafts. However, knockdown of Cbl-b also enhanced EGFR translocation into lipid rafts and EGFR pathway activation induced by TRAIL. Either using inhibitors of EGFR or depletion of EGFR with small interfering RNA (siRNA) prevented EGFR pathway activation, and thus increased TRAIL-induced apoptosis, especially in Cbl-b knockdown clones. Taken together, TRAIL-induced EGFR activation through Cbl-b-regulated EGFR redistribution in lipid rafts antagonised TRAIL-induced apoptosis. The contribution of DISC formation and the inhibition of EGFR signal triggered in lipid rafts are both essential for increasing the sensitivity of gastric cancer cells to TRAIL.

Cbl-regulated Akt and ERK signals are involved in β-elemene-induced cell apoptosis in lung cancer cells

β-elemene is an active component of a natural plant-derived antineoplastic agent. Although the anticancer activity of β-elemene has been reported, its antitumor mechanism has not been elucidated. The aim of the present study was to investigate how Cbl-regulated Akt and ERK affect β-elemene-induced cell apoptosis in lung cancer cells. In the present study, β-elemene induced cell apoptosis in a dose-dependent manner in A549 cells. Moreover, β-elemene decreased bcl-2 expression, increased bax expression and caused the cleavage of PARP. However, β-elemene also induced the phosphorylation of Akt and ERK in a short period of time. The inhibition of Akt and ERK activation rapidly enhanced β-elemene-induced apoptosis, and the up-regulation of c-Cbl and Cbl-b expression was also detected. These results suggest that Cbl-regulated Akt and ERK signals are involved in β-elemene-induced cell apoptosis in lung cancer cells.

Ubiquitin ligase Cbl-b sensitizes leukemia and gastric cancer cells to anthracyclines by activating the mitochondrial pathway and modulating Akt and ERK survival signals

The present study reported that the ubiquitin ligase Cbl‐b was up‐regulated during anthracycline‐induced apoptosis in two cell lines, RBL‐2H3 leukemia cells and MGC803 gastric cancer cells. Overexpression of Cbl‐b strongly promoted the cytotoxic and apoptosis‐inducing effects of anthracyclines, while a dominant negative (DN) Cbl‐b mutation abolished these effects in both cell lines. Further investigation revealed that mitochondrial depolarization was enhanced by Cbl‐b and decreased by Cbl‐b (DN) in RBL‐2H3 cells. Moreover, overexpression of Cbl‐b significantly suppressed ERK activation, and Cbl‐b (DN) strongly enhanced both ERK and Akt activation. Altogether, these results indicate that Cbl‐b sensitized both leukemia and gastric cancer cells to anthracyclines by activating the mitochondrial apoptotic pathway and modulating the ERK and Akt survival pathways.