Jian-Bin Wang

How does cancer cell metabolism affect tumor migration and invasion

Cancer metastasis is the major cause of cancer-associated death. Accordingly, identification of the regulatory mechanisms that control whether or not tumor cells become “directed walkers” is a crucial issue of cancer research. The deregulation of cell migration during cancer progression determines the capacity of tumor cells to escape from the primary tumors and invade adjacent tissues to finally form metastases. The ability to switch from a predominantly oxidative metabolism to glycolysis and the production of lactate even when oxygen is plentiful is a key characteristic of cancer cells. This metabolic switch, known as the Warburg effect, was first described in 1920s, and affected not only tumor cell growth but also tumor cell migration. In this review, we will focus on the recent studies on how cancer cell metabolism affects tumor cell migration and invasion. Understanding the new aspects on molecular mechanisms and signaling pathways controlling tumor cell migration is critical for development of therapeutic strategies for cancer patients.

Involvement of Drp1 in hypoxia-induced migration of human glioblastoma U251 cells

Glioblastoma is one of the most aggressive brain tumors with high morbidity and mortality. Hypoxia is often the common characteristic of tumor microenvironment, and hypoxia-inducible factor-1α (HIF-1α) is an essential factor regulating the migratory activity of cancer cells including glioblastoma. Recently, mitochondrial dynamics was found to be involved in the aggression of cancer cells. However, whether dynamin-related protein 1 (Drp1) contributes to the migration of human glioblastoma cells under hypoxia remains unknown. In the present study, hypoxia was found to upregulate the transcription and expression of Drp1, and stimulated mitochondrial fission in glioblastoma U251 cells. Inhibition of HIF-1α with echinomycin blocked hypoxia‑induced expression of Drp1. Notably, Drp1 inhibitor Mdivi-1 efficiently attenuated hypoxia-induced mitochondrial fission and migration of U251 cells. In addition, three U251 stable cell lines expressing GFP, GFP-Drp1 and dominant negative GFP-Drp1‑K38A were established to examine the direct role of Drp1 in hypoxia-induced migration. MTT assay showed that there was no significant difference in proliferation of three cell lines. Compared with the GFP cell line, exogenously expressed GFP-Drp1-K38A inhibited hypoxia-induced migration of U251 cells, while stable expression of GFP-Drp1 enhanced the migration of U251 cells under hypoxia. Therefore, this study indicates the involvement of Drp1 in hypoxia-induced migration of human glioblastoma U251 cells, and suggests Drp1 to be a potential therapeutic target to suppress the aggression of glioblastoma in the future.

Mitochondrial dynamics regulates hypoxia-induced migration and antineoplastic activity of cisplatin in breast cancer cells

Mitochondria are high dynamic organelles with frequent fission and fusion. Here, we found hypoxia stimulated Drp1 expression, mitochondrial fission and migration in metastatic MDA-MB‑231 cells, but not in non-metastatic MCF-7 cells. Inhibition of Drp1-dependent mitochondrial fission by Mdivi-1 or silencing Drp1 attenuated hypoxia-induced mitochondrial fission and migration in MDA-MB‑231 cells. On the other hand, cisplatin induced significant apoptosis and mitochondrial fission in MDA-MB‑231 cells, but not in MCF-7 cells. Mdivi-1 and silencing Drp1 also efficiently prevented cisplatin-induced MMP decrease, ROS production and apoptosis in MDA-MB‑231 cells. Our data suggest that Drp1-dependent mitochondrial fission not only regulates hypoxia-induced migration of breast cancer cells, but also facilitates its sensitivity to chemotherapeutic agents. Thus, targeting Drp1-dependent mitochondrial dynamics may provide a novel strategy to suppress breast cancer metastasis and improve the chemotherapeutic effect in the future.

TRIM59 Promotes the Proliferation and Migration of Non-Small Cell Lung Cancer Cells by Upregulating Cell Cycle Related Proteins

TRIM protein family is an evolutionarily conserved gene family implicated in a number of critical processes including inflammation, immunity, antiviral and cancer. In an effort to profile the expression patterns of TRIM superfamily in several non-small cell lung cancer (NSCLC) cell lines, we found that the expression of 10 TRIM genes including TRIM3, TRIM7, TRIM14, TRIM16, TRIM21, TRIM22, TRIM29, TRIM59, TRIM66 and TRIM70 was significantly upregulated in NSCLC cell lines compared with the normal human bronchial epithelial (HBE) cell line, whereas the expression of 7 other TRIM genes including TRIM4, TRIM9, TRIM36, TRIM46, TRIM54, TRIM67 and TRIM76 was significantly down-regulated in NSCLC cell lines compared with that in HBE cells. As TRIM59 has been reported to act as a proto-oncogene that affects both Ras and RB signal pathways in prostate cancer models, we here focused on the role of TRIM59 in the regulation of NSCLC cell proliferation and migration. We reported that TRIM59 protein was significantly increased in various NSCLC cell lines. SiRNA-induced knocking down of TRIM59 significantly inhibited the proliferation and migration of NSCLC cell lines by arresting cell cycle in G2 phase. Moreover, TRIM59 knocking down affected the expression of a number of cell cycle proteins including CDC25C and CDK1. Finally, we knocked down TRIM59 and found that p53 protein expression levels did not upregulate, so we proposed that TRIM59 may promote NSCLC cell growth through other pathways but not the p53 signaling pathway.

Dihydromyricetin ameliorates oleic acid-induced lipid accumulation in L02 and HepG2 cells by inhibiting lipogenesis and oxidative stress.

AIMS Dihydromyricetin (DMY), a flavonoid component isolated from Ampelopsis grossedentata, was recently reported to ameliorate nonalcoholic fatty liver disease (NAFLD) in patients. However, the underlying mechanisms of this action remain unknown. Here, we evaluate the effect of DMY on an in vitro model of NAFLD and investigate the signal transduction pathways underlying DMY treatment. MAIN METHODS Oleic acid (OA) induced hepatic steatosis was established in L02 and HepG2 cells as in vitro model of NAFLD. Cell apoptosis, lipid accumulation and oxide stress were evaluated by flow cytometry, oil red O staining, and cellular biochemical assays, respectively. Signaling pathways involved in lipid metabolism including PPARγ, AMPK, and AKT were investigated by Western blot and RT-qPCR. KEY FINDINGS DMY protected cells against apoptosis and lipid accumulation induced by oleic acid. DMY decreased the levels of cellular triglycerides (TG), cholesterol (TC) and malondialdehyde (MDA), while at the same time increasing the level of superoxide dismutase (SOD). DMY suppressed the expression of PPARγ and the phosphorylation of AKT, and promoted the phosphorylation of AMPK. SIGNIFICANCE Our study suggests that DMY ameliorates OA-induced hepatic steatosis by inhibiting cell apoptosis, lipid accumulation and oxide stress. Furthermore, the effect of DMY is likely associated with its role in the regulating of PPARγ, AMPK and AKT signaling pathways.

Inhibition of mitochondrial glutaminase activity reverses acquired erlotinib resistance in non-small cell lung cancer

The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) erlotinib has been approved based on the clinical benefit in non-small cell lung cancer (NSCLC) patients over the past decade. Unfortunately, cancer cells become resistant to this agent via various mechanisms, and this limits the improvement in patient outcomes. Thus, it is urgent to develop novel agents to overcome erlotinib resistance. Here, we propose a novel strategy to overcome acquired erlotinib resistance in NSCLC by inhibiting glutaminase activity. Compound 968, an inhibitor of the glutaminase C (GAC), when combined with erlotinib potently inhibited the cell proliferation of erlotinib-resistant NSCLC cells HCC827ER and NCI-H1975. The combination of compound 968 and erlotinib not only decreased GAC and EGFR protein expression but also inhibited GAC activity in HCC827ER cells. The growth of erlotinib-resistant cells was glutamine-dependent as proved by GAC gene knocked down and rescue experiment. More importantly, compound 968 combined with erlotinib down-regulated the glutamine and glycolysis metabolism in erlotinib-resistant cells. Taken together, our study provides a valuable approach to overcome acquired erlotinib resistance by blocking glutamine metabolism and suggests that combination of EGFR-TKI and GAC inhibitor maybe a potential treatment strategy for acquired erlotinib-resistant NSCLC.

A novel glutaminase inhibitor-968 inhibits the migration and proliferation of non-small cell lung cancer cells by targeting EGFR/ERK signaling pathway

Metabolic reprogramming is critical for cancer cell proliferation. Glutaminolysis which provides cancer cells with bioenergetics and intermediates for macromolecular synthesis have been intensively studied in recent years. Glutaminase C (GAC) is the first and rate-limiting enzyme in glutaminolysis and plays important roles in cancer initiation and progression. We previously screened a small molecule named 968, a specific inhibitor of GAC, to block the proliferation of human breast cancer cells. In this study, we found that 968 effectively inhibited NSCLC cell proliferation and migration and arrested G0/G1 phase of cell cycle. Furthermore, we demonstrated that 968 inhibited the EGFR/ERK pathway via decreasing the expression of EGFR and phospho-ERK. Apart from this, we discovered that 968 treatment induced autophagy to protect cells against apoptosis and the combination of 968 with autophagy inhibitor Chloroquine (CQ) had synergistic effects on the growth of NSCLC cells. Thus, our study pointed out a new therapeutic strategy for NSCLC treatment by combination of 968 with CQ.

COMMD9 promotes TFDP1/E2F1 transcriptional activity via interaction with TFDP1 in non-small cell lung cancer

COMMD protein family is an evolutionarily conserved gene family implicated in a number of critical processes including inflammation, copper homeostasis, sodium balance, endosomal sorting and cancer. In an effort to profile the expression pattern of COMMD family in several non-small cell lung cancer (NSCLC) cell lines, we found that compared with that in human bronchial epithelial (HBE) cells, the mRNA expression levels of five COMMD genes including COMMD3, COMMD4, COMMD5, COMMD6 and COMMD8 were significantly down-regulated, whereas COMMD9 was up-regulated in NSCLC cell lines. Here we reported that the expression of COMMD9 protein was significantly increased in various NSCLC cell lines and tissue samples. SiRNA-induced knocking down of COMMD9 inhibited proliferation and migration, arrested cell cycle at G1/S transition and induced autophagy in NSCLC cells. Mechanistically, COMMD9 interacted with the TFDP1 through COMM domain, and DNA-binding domain of TFDP1 was required for this interaction. Moreover, decreased expression COMMD9 attenuated TFDP1/E2F1 activation accompanied with enhanced p53 signaling pathway. Taken together, these findings demonstrate that COMMD9 participates in TFDP1/E2F1 activation and plays a critical role in non-small cell lung cancer.

Cdc42 induces EGF receptor protein accumulation and promotes EGF receptor nuclear transport and cellular transformation

Cdc42 is a Ras‐related small GTP‐binding protein. A previous study has shown that Cdc42 binding to the γ subunit of the coatomer protein complex (γCOP) is essential for Cdc42‐regulated cellular transformation, but the molecular mechanism involved is not well understood. Here, we demonstrate that constitutively‐active Cdc42 binding to γCOP induced the accumulation of epithelial growth factor receptor (EGFR) in the cells, sustained EGF‐stimulated extracellular signal‐regulated kinase (ERK), JUN amino‐terminal kinase (JNK) and phosphoinositide 3‐kinase (PI3K) signaling and promoted cell division. Moreover, constitutive Cdc42 activity facilitated the nuclear translocation of EGFR, and this indicates a novel mechanism through which Cdc42 might promote cellular transformation.

Phosphorylation of glutaminase by PKCε is essential for its enzymatic activity and critically contributes to tumorigenesis

Glutamine metabolism plays an important role in cancer development and progression. Glutaminase C (GAC), the first enzyme in glutaminolysis, has emerged as an important target for cancer therapy and many studies have focused on the mechanism of enhanced GAC expression in cancer cells. However, little is known about the post-translational modification of GAC. Here, we report that phosphorylation is a crucial post-translational modification of GAC, which is responsible for the higher glutaminase activity in lung tumor tissues and cancer cells. We identify the key Ser314 phosphorylation site on GAC that is regulated by the NF-κB-PKCε axis. Blocking Ser314 phosphorylation by the S314A mutation in lung cancer cells inhibits the glutaminase activity, triggers genetic reprogramming, and alleviates tumor malignancy. Furthermore, we find that a high level of GAC phosphorylation correlates with poor survival rate of lung cancer patients. These findings highlight a previously unappreciated mechanism for activation of GAC by phosphorylation and demonstrate that targeting glutaminase activity can inhibit oncogenic transformation.