Xinjian Lin

Purpose Glutamine (Gln) is essential for the proliferation of most cancer cells, making it an appealing target for cancer therapy. However, the role of Gln in gastric cancer (GC) metabolism is unknown and Gln-targeted therapy against GC remains scarce. The aim of this study was to investigate the relevance of Gln in GC growth and targeting. Methods Expression of Gln transporter ASCT2 and glutamine synthetase (GS) in the parental and molecularly engineered GC cells or in human GC specimens was determined by RT-PCR and western blot analysis or immunohistochemistry. Cell proliferation and survival was assessed by CCK-8 assay and colony formation assay. Intracellular Gln content was measured by a HPLC system. Effects of ASCT2 and/or GS inhibitor on tumor growth were investigated in xenograft models. Results A significant heterogeneity of GC cells was observed with respect to their response to the treatment of ASCT2 inhibitor benzylserine (BenSer). Gln deprivation did not affect the BenSer-resistant cell growth due to endogenous GS expression, whose inhibition remarkably reduced cell proliferation. The differential in vitro sensitivity correlated with overall intracellular Gln content. Combined therapy with both ASCT2 and GS inhibitors produced a greater therapeutic efficacy than the treatment of either inhibitor alone. Furthermore, 77% human GC tissues were found to express moderate and high levels of ASCT2, 12% of which also co-expressed relatively high levels of GS. Conclusion Gln mediates GC growth and the therapeutic efficacy of Gln-targeted treatment relies on distinct ASCT2 and GS expression pattern in specific gastric cancer groups.

Purpose: Gossypol and its analogs, through their ability to bind to and inactivate BH3 domain-containing antiapoptotic proteins, have been shown to inhibit the growth of various human cancer cells in culture and xenograft models. Here, we evaluated the antitumor efficacy of a novel gossypol derivative and BH3 mimetic ch282-5 (2-aminoethanesulfonic acid sodium-gossypolone) in colon cancer models. Several innovative combination strategies were also explored and elaborated. Experimental Design: Ch282-5 was synthesized by modifying the active aldehyde groups and R groups of gossypol according to a computer-aided drug design program. The stability of ch282-5 was examined by high-performance liquid chromatography, and cytotoxic effects of ch282-5 on colon cancer cells were assessed by MTS assay. Activation of mitochondrial apoptotic pathway by ch282-5 was evidenced with a series of molecular biology techniques. In vivo antitumor activity of ch282-5 and its combination with chloroquine, rapamycin, oxaliplatin, and ABT-263 was also evaluated in colon cancer xenograft models and experimental liver metastasis models. Results: Ch282-5 showed antiproliferative and pro-cell death activity against colon cancer cells both in vitro and in vivo, and the response to the drug correlated with inhibition of antiapoptotic Bcl-2 proteins, induction of mitochondria-dependent apoptotic pathway, and disruption of mitophagy and mTOR pathway. Ch282-5 also suppressed liver metastasis produced by intrasplenic injection of colon cancer cells. Furthermore, ch282-5 could potentiate the effectiveness of oxaliplatin and rescue ABT-263 efficacy by downregulation of Mcl-1 and elevation of platelet number. Conclusions: These findings provide a rational basis for clinical investigation of this highly promising BH3 mimetic in colon cancer. Clin Cancer Res; 22(6); 1445–58. ©2015 AACR.

The intracellular level of reactive oxygen species (ROS) is closely associated with chemosensitivity of cancer cells. Overexpression of ATP binding cassette transporter MRP1 is correlated with resistance to platinum drugs. In this study, we tested the hypothesis that emodin, a potent ROS generator, may increase sensitivity of cisplatin-(cDDP-) resistant ovarian carcinoma cells to cDDP cytotoxicity via ROS-mediated suppression of MRP1 expression. Using the isogenic pair of the human ovarian carcinoma cell line COC1 and its cDDP resistant variant COC1/DDP, we found that ROS level in the cDDP-sensitive ovarian cancer cells was significantly higher than that in the cDDP-resistant cells. Emodin enhanced ROS production in COC1/DDP cells and consequently sensitized them to cDDP-induced apoptosis. These effects were reversed by addition of the antioxidant N-acetyl-L-cysteine (NAC). Cotreatment with emodin and cDDP inhibited the tumor growthin vivoby increasing tumor cell apoptosis. The emodin-enhanced cDDP cytotoxicity was attributable to downregulation of multidrug resistance-related protein 1 (MRP1) expression. Together, these results suggest that emodin could act as an adjunct to enhance the anticancer effect of cDDP likely through ROS-related downregulation of MRP1 expression, and may be of therapeutic potential in cDDP-refractory ovarian carcinomas.

The EphA2 receptor, which is expressed in many types of cancer, is activated by two different mechanisms. Activation by engagement with one of its ephrin ligands is anti-oncogenic whereas phosphorylation of S897 by AKT increases migration, invasion and metastasis. Down-regulation of claudin-4 (CLDN4) produces a loss of E-cadherin and increased ?-catenin signaling and a phenotype similar to that produced by oncogenic activation of EphA2, suggesting that CLDN4 may serve to restrain the pro-oncogenic signaling of EphA2. We found that constitutive knockdown of CLDN4 was associated with a 4.5-fold increase in EphA2 mRNA and a 2.5-fold increase in EphA2 protein which was reversible by re-expression of CLDN4. Knockdown of EphA2 blocked the migratory phenotype induced by loss of CLDN4. Knockdown of CLDN4 resulted in a 5.8-fold increase in pEphA(S897), the oncogenic form of the receptor, as well as partial mislocalization of the excess EphA2 to the interior of the cell. Forced expression of E-cadherin did not reduce total EphA2 or pEphA(S897) whereas re-expression of CLDN4 restored localization and reduced EphA2 and pEphA(S897) even in cells not expressing E-cadherin. Transient siRNA-mediated knockdown of EphA2 and ?-catenin, and inhibition of PI3K by LY294002, demonstrated that increased pEphA(S897) in the CLDN4 knockdown cells was attributable to an increase in the level of active dephospho-?-catenin upstream of PI3K and AKT. We conclude that CLDN4 serves to restrain pro-oncogenic signaling from EphA2 by limiting the activity of ?-catenin and PI3K and preventing phosphorylation of EphA2 on S897 by AKT. This suggests that interventions directed at enhancing the level or functional activity of CLDN4 may be of therapeutic interest.

Background and Purpose: Conventional MRI is often difficult to distinguish between primary central nervous system lymphomas (PCNSLs), high‐grade gliomas and brain metastases due to the similarity of their appearance. The aim of this study was to investigate whether the susceptibility‐weighted imaging (SWI) has higher sensitivity than conventional MRI in detecting hemorrhage between PCNSLs, high‐grade gliomas and brain metastases, and can be used to differentiate the diagnosis between these tumors.Methods: The number of lesions with hemorrhage was quantified by both the conventional MR imaging and SWI. The number of micro‐hemorrhage and vessels within lesions were counted on SWI.Results: The detection rate of hemorrhage on SWI was significantly higher than that on the conventional MR imaging. The intralesional hemorrhagic burden and the number of the vessels within lesions detected by SWI were significantly higher in high‐grade gliomas and brain metastases than those in PCNSLs. There was no significant difference in these two parameters between high‐grade gliomas and brain metastases. The best predictor to differentiate PCNSLs from high‐grade gliomas and brain metastases was intralesional vessel number that yielded the best ROC characteristics and highest classification accuracy.Conclusions: SWI is useful in differentiating of PCNSLs from high‐grade gliomas and brain metastases.

Reactive oxygen species (ROS) can drive the de‑differentiation of tumor cells leading to the process of epithelial-to-mesenchymal transition (EMT) to enhance invasion and metastasis. The invasive and metastatic phenotype of malignant cells is often linked to loss of E-cadherin expression, a hallmark of EMT. Recent studies have demonstrated that hypoxic exposure causes HIF-1-dependent repression of E-cadherin. However, the mechanism by which ROS and/or HIF suppresses E-cadherin expression remains less clear. In the present study, we found that ROS accumulation in ovarian carcinoma cells upregulated HIF-1α expression and subsequent transcriptional induction of lysyl oxidase (LOX) which repressed E-cadherin. Loss of E-cadherin facilitated ovarian cancer (OC) cell migration in vitro and promoted tumor growth in vivo. E-cadherin immunoreactivity correlated with International Federation of Gynecology and Obstetrics (FIGO) stage, tumor differentiation and metastasis. Negative E-cadherin expression along with FIGO stage, tumor differentiation and metastasis significantly predicted for a lower 5-year survival rate. These findings suggest that ROS play an important role in the initiation of metastatic growth of OC cells and support a molecular pathway from ROS to aggressive transformation which involves upregulation of HIF-1α and its downstream target LOX to suppress E-cadherin expression leading to an increase in cell motility and invasiveness.

Glioblastoma multiforme (GBM) is the most aggressive and invasive brain tumor, for which novel prognostic markers and predictors of therapeutic response are urgently needed. We reported previously that levels of peptide-O-linked mannose β-1,2-N-acetylglucosaminyltransferase 1 (PomGnT1) in glioma specimens correlated with tumor grade. However, the prognostic significance of PomGnT1 in glioma patients and its function in GBM progression remain unknown. Clinical relevance of PomGnT1 in GBM patients' prognosis was analyzed both in a clinically annotated expression dataset of 446 GBM tumor specimens and in 82 GBM tumor samples collected at our institution. The function of PomGnT1 in glioma growth and invasion, and the underlying mechanisms of PomGnT1 regulation were explored in vitro and in vivo. PomGnT1 expression in GBM tissues was closely associated with poor prognosis in GBM patients. Forced overexpression of PomGnT1 in glioblastoma cells impaired cell adhesion and increased their proliferation and invasion in vitro. Subsequent in vivo experiments showed that overexpression of PomGnT1 promoted tumor growth and shortened the survival time of tumor-bearing mice in an orthotopic model. Conversely, stable short hairpin RNA–mediated knockdown of PomGnT1 expression produced opposite effects both in vitro and in vivo. Mechanistic studies revealed that activation of epidermal growth factor receptor (EGFR) resulted in EGFR/extracellular signal-regulated kinase–dependent upregulation of PomGnT1, downregulation of receptor-type protein tyrosine phosphatase β, and activation of β-catenin pathway signaling. These findings suggest that PomGnT1 promotes GBM progression via activation of β-catenin and may serve as a prognostic factor for glioma patient survival as well as a novel molecular target for anticancer therapy in malignant glioma.

The αV integrin is expressed in most cancer cells where it regulates a diverse array of cellular functions essential to the initiation, progression and metastasis of solid tumors. However, little is known about how αV integrin modulates cellular sensitivity to chemotherapeutic agents, particularly the platinum drugs. In this study, we found that down-regulation of αV sensitized human M21 cells to cisplatin (cDDP) through up-regulation of the copper influx transporter CTR1. Cells selected for low αV integrin expression (M21L) were more sensitive to cDDP, accompanied by increase in CTR1 mRNA and CTR1 protein levels, more intracellular cDDP accumulation and cDDP DNA adduct formation. Basal copper (Cu) content, Cu uptake, and Cu cytotoxicity were also increased. Transfection of a luciferase reporter construct containing the hCTR1 promoter sequence revealed an increase of the hCTR1 transcription activity in M21L cells. The basis for the increased hCTR1 transcription was related to an increase in the steady-state level of Sp1, a transcription factor known to drive hCTR1 expression. These results indicate that the αV integrin modulates sensitivity of human cells to the cytotoxic effect of cDDP by regulating expression of the Cu transporter CTR1, and introduce the concept that αV expression is linked to Cu homeostasis.