Ganfeng Xie

Synergistic antitumor effect of dichloroacetate in combination with 5-fluorouracil in colorectal cancer.

Dichloroacetate (DCA), an inhibitor of pyruvate dehydrogenase kinase (PDK), has been recently demonstrated as a promising nontoxic antineoplastic agent that promotes apoptosis of cancer cells. In the present study, we aimed to investigate the antitumor effect of DCA combined with 5-Fluorouracil (5-FU) on colorectal cancer (CRC) cells. Four human CRC cell lines were treated with DCA or 5-FU, or a combination of DCA and 5-FU. The cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The interaction between DCA and 5-FU was evaluated by the median effect principle. Immunocytochemistry with bromodeoxyuridine (BrdU) was carried out to determine the proliferation of CRC cells. Cell cycle and apoptosis were measured by flow cytometry, and the expression of apoptosis-related molecules was assessed by western blot. Our results demonstrated that DCA inhibited the viability of CRC cells and had synergistic antiproliferation in combination with 5-FU. Moreover, compared with 5-FU alone, the apoptosis of CRC cells treated with DCA and 5-FU was enhanced and demonstrated with the changes of Bcl-2, Bax, and caspase-3 proteins. Our results suggest that DCA has a synergistic antitumor effect with 5-FU on CRC cell lines in vitro.

Knock-down of glutaminase 2 expression decreases glutathione, NADH, and sensitizes cervical cancer to ionizing radiation.

Phosphate-activated mitochondrial glutaminase (GLS2) is suggested to be linked with elevated glutamine metabolism. It plays an important role in catalyzing the hydrolysis of glutamine to glutamate. The present study was to investigate the potent effect of GLS2 on radioresistance of cervical carcinoma. GLS2 was examined in 144 cases of human cervical cancer specimens (58 radioresistant specimens, 86 radiosensitive specimens) and 15 adjacent normal cervical specimens with immunohistochemistry. HeLa cells were treated with a cumulative dose of 50Gy X-rays, over 6months, yielding the resistant sub-line HeLaR. The expressions of GLS2 were measured by Western blot. Radioresistance was tested by colony survival assay. Apoptosis was determined by flow cytometry. The levels of glutathione (GSH), reactive oxygen species (ROS), NAD(+)/NADH ratio and NADP(+)/NADPH ratio were detected by quantization assay kit. Xenografts were used to confirm the effect of GLS2 on radioresistance in vivo. The expressions of GLS2 were significantly enhanced in tumor tissues of radioresistant patients compared with that in radiosensitive patients. In vitro, the radioresistant cell line HeLaR exhibited significantly increased GLS2 levels than its parental cell line HeLa. GLS2 silenced radioresistant cell HeLaR shows substantially enhanced radiosensitivity with lower colony survival and higher apoptosis in response to radiation. In vivo, xenografts with GLS2 silenced HeLaR were more sensitive to radiation. At the molecular level, knock-down of GLS2 increased the intracellular ROS levels of HeLaR exposed to irradiation by decreasing the productions of antioxidant GSH, NADH and NADPH. GLS2 may have an important role in radioresistance in cervical cancer patients.

Overexpression of MicroRNA-122 Re-sensitizes 5-FU-Resistant Colon Cancer Cells to 5-FU Through the Inhibition of PKM2 In Vitro and In Vivo

Abstract 5-Fluorouracil (5-FU) is one of the most commonly used anticancer drugs in the treatment of colon cancer. However, acquired chemoresistance is becoming one of the major challenges for patients with advanced stages of colon cancer. Currently, the mechanisms underlying cancer cell resistance to 5-FU are not fully understood. MicroRNAs (miRNA) have been suggested to play important roles in tumorigenesis and drug resistance in colon cancer. In this study, we generated 5-FU-resistant colon cancer cell lines from which we found that miR-122 was downregulated in 5-FU-resistant cells compared with sensitive cells. Meanwhile, the glucose metabolism is significantly upregulated in 5-FU-resistant cells. We report that PKM2 is a direct target of miR-122 in colon cancer cell. Importantly, overexpression of miR-122 in 5-FU-resistant cells resensitizes 5-FU resistance through the inhibition of PKM2 both in vitro and in vivo. In summary, these findings reveal that the dysregulated glucose metabolism contributes to 5-FU resistance, and glycolysis inhibition by miR-122 might be a promising therapeutic strategy to overcome 5-FU resistance.

Loss of Abhd5 Promotes Colorectal Tumor Development and Progression by Inducing Aerobic Glycolysis and Epithelial-Mesenchymal Transition

How cancer cells shift metabolism to aerobic glycolysis is largely unknown. Here, we show that deficiency of α/β-hydrolase domain-containing 5 (Abhd5), an intracellular lipolytic activator that is also known as comparative gene identification 58 (CGI-58), promotes this metabolic shift and enhances malignancies of colorectal carcinomas (CRCs). Silencing of Abhd5 in normal fibroblasts induces malignant transformation. Intestine-specific knockout of Abhd5 in Apc(Min/+) mice robustly increases tumorigenesis and malignant transformation of adenomatous polyps. In colon cancer cells, Abhd5 deficiency induces epithelial-mesenchymal transition by suppressing the AMPKα-p53 pathway, which is attributable to increased aerobic glycolysis. In human CRCs, Abhd5 expression falls substantially and correlates negatively with malignant features. Our findings link Abhd5 to CRC pathogenesis and suggest that cancer cells develop aerobic glycolysis by suppressing Abhd5-mediated intracellular lipolysis.

High Expression of Testes-Specific Protease 50 Is Associated with Poor Prognosis in Colorectal Carcinoma

Background Testes-specific protease 50 (TSP50) is normally expressed in testes and abnormally expressed in breast cancer, but whether TSP50 is expressed in colorectal carcinoma (CRC) and its clinical significance is unclear. We aimed to detect TSP50 expression in CRC, correlate it with clinicopathological factors, and assess its potential diagnostic and prognostic value. Methodology/Principal Findings TSP50 mRNAs and proteins were detected in 7 CRC cell lines and 8 CRC specimens via RT-PCR and Western blot analysis. Immunohistochemical analysis of TSP50, p53 and carcinoembryonic antigen (CEA) with tissue microarrays composed of 95 CRCs, 20 colorectal adenomas and 20 normal colorectal tissues were carried out and correlated with clinicopathological characteristics and disease-specific survival for CRC patients. There was no significant correlation between the expression levels of TSP50 and p53 (P = 0.751) or CEA (P = 0.663). Abundant expression of TSP50 protein was found in CRCs (68.4%) while it was poorly expressed in colorectal adenomas and normal tissues (P<0.0001). Thus, CRCs can be distinguished from them with high specificity (92.5%) and positive predictive value (PPV, 95.6%). The survival of CRC patients with high TSP50 expression was significantly shorter than that of the patients with low TSP50 expression (P = 0.010), specifically in patients who had early-stage tumors (stage I and II; P = 0.004). Multivariate Cox regression analysis indicated that high TSP50 expression was a statistically significant independent risk factor (hazard ratio  = 2.205, 95% CI = 1.214–4.004, P = 0.009). Conclusion Our data demonstrate that TSP50 is a potential effective indicator of poor survival for CRC patients, especially for those with early-stage tumors.

Fibronectin extra domain A (EDA) sustains CD133(+)/CD44(+) subpopulation of colorectal cancer cells.

Fibronectin is a major extracellular matrix glycoprotein with several alternatively spliced variants, including extra domain A (EDA), which was demonstrated to promote tumorigenesis via stimulating angiogenesis and lymphangiogenesis. Given that CD133(+)/CD44(+) cancer cells are critical in tumorigenesis of colorectal cancer (CRC), we hypothesize that fibronectin EDA may promote tumorigenesis by sustaining the properties of CD133(+)/CD44(+) colon cancer cells. We found that tumor tissue and serum EDA levels are substantially higher in advanced versus early stage human CRC. Additionally we showed that tumor tissue EDA levels are positively correlated with differentiation status and chemoresistance, and correlated with a poor prognosis of CRC patients. We also showed that in colon cancer cells SW480, CD133(+)/CD44(+) versus CD133(-)/CD44(-) cells express significantly elevated EDA receptor integrin α9β1. Silencing EDA in SW480 cells reduces spheroid formation and cells positive for CD133 or CD44, which is associated with reduced expressions of embryonic stem cell markers and increased expressions of differentiation markers. Blocking integrin α9β1 function strongly reversed the effect of EDA overexpression. We also provided evidence suggesting that EDA sustains Wnt/β-catenin signaling activity via activating integrin/FAK/ERK pathway. In xenograft models, EDA-silenced SW480 cells exhibit reduced tumorigenic and metastatic capacity. In conclusion, EDA is essential for the maintenance of the properties of CD133(+)/CD44(+) colon cancer cells.

The extra domain A of fibronectin increases VEGF-C expression in colorectal carcinoma involving the PI3K/AKT signaling pathway.

The extra domain A (EDA)-containing fibronectin (EDA-FN), an alternatively spliced form of the extracellular matrix protein fibronectin, is predominantly expressed in various malignancies but not in normal tissues. In the present study, we investigated the potential pro-lymphangiogenesis effects of extra domain A (EDA)-mediated vascular endothelial growth factor-C (VEGF-C) secretion in colorectal carcinoma (CRC). We detected the expressions of EDA and VEGF-C in 52 human colorectal tumor tissues and their surrounding mucosae by immunohistochemical analysis, and further tested the correlation between the expressions of these two proteins in aforementioned CRC tissues. Both EDA and VEGF-C were abundantly expressed in the specimens of human CRC tissues. And VEGF-C was associated with increased expression of EDA in human CRC according to linear regression analysis. Besides, EDA expression was significantly correlated with lymph node metastasis, tumor differentiation and clinical stage by clinicopathological analysis of tissue microarrays containing tumor tissues of 115 CRC patients. Then, human CRC cell SW480 was transfected with lentivectors to elicit expression of shRNA against EDA (shRNA-EDA), and SW620 was transfected with a lentiviral vector to overexpress EDA (pGC-FU-EDA), respectively. We confirmed that VEGF-C was upregulated in EDA-overexpressed cells, and downregulated in shRNA-EDA cells. Moreover, a PI3K-dependent signaling pathway was found to be involved in EDA-mediated VEGF-C secretion. The in vivo result demonstrated that EDA could promote tumor growth and tumor-induced lymphangiogenesis in mouse xenograft models. Our findings provide evidence that EDA could play a role in tumor-induced lymphangiogenesis via upregulating autocrine secretion of VEGF-C in colorectal cancer, which is associated with the PI3K/Akt-dependent pathway.

Macrophage ABHD5 promotes colorectal cancer growth by suppressing spermidine production by SRM

Metabolic reprogramming in stromal cells plays an essential role in regulating tumour growth. The metabolic activities of tumour-associated macrophages (TAMs) in colorectal cancer (CRC) are incompletely characterized. Here, we identify TAM-derived factors and their roles in the development of CRC. We demonstrate that ABHD5, a lipolytic co-activator, is ectopically expressed in CRC-associated macrophages. We demonstrate in vitro and in mouse models that macrophage ABHD5 potentiates growth of CRC cells. Mechanistically, ABHD5 suppresses spermidine synthase (SRM)-dependent spermidine production in macrophages by inhibiting the reactive oxygen species-dependent expression of C/EBPɛ, which activates transcription of the srm gene. Notably, macrophage-specific ABHD5 transgene-induced CRC growth in mice can be prevented by an additional SRM transgene in macrophages. Altogether, our results show that the lipolytic factor ABHD5 suppresses SRM-dependent spermidine production in TAMs and potentiates the growth of CRC. The ABHD5/SRM/spermidine axis in TAMs might represent a potential target for therapy.

Melatonin regulates PARP1 to control the senescence‐associated secretory phenotype (SASP) in human fetal lung fibroblast cells

Cellular senescence is an important tumor‐suppressive mechanism. However, acquisition of a senescence‐associated secretory phenotype (SASP) in senescent cells has deleterious effects on the tissue microenvironment and, paradoxically, promotes tumor progression. In a drug screen, we identified melatonin as a novel SASP suppressor in human cells. Strikingly, melatonin blunts global SASP gene expression upon oncogene‐induced senescence (OIS). Moreover, poly(ADP‐ribose) polymerase‐1 (PARP‐1), a sensor of DNA damage, was identified as a new melatonin‐dependent regulator of SASP gene induction upon OIS. Here, we report two different but potentially coherent epigenetic strategies for melatonin regulation of SASP. The interaction between the telomeric repeat‐containing RNA (TERRA) and PARP‐1 stimulates the SASP, which was attenuated by 67.9% (illustrated by the case of IL8) by treatment with melatonin. Through binding to macroH2A1.1, PARP‐1 recruits CREB‐binding protein (CBP) to mediate acetylation of H2BK120, which positively regulates the expression of target SASP genes, and this process is interrupted by melatonin. Consequently, the findings provide novel insight into melatonins epigenetic role via modulating PARP‐1 in suppression of SASP gene expression in OIS‐induced senescent cells. Our studies identify melatonin as a novel anti‐SASP molecule, define PARP‐1 as a new target by which melatonin regulates SASP, and establish a new epigenetic paradigm for a pharmacological mechanism by which melatonin interrupts PARP‐1 interaction with the telomeric long noncoding RNA(lncRNA) or chromatin.

EZH2 promotes colorectal cancer stem-like cell expansion by activating p21 cip1 -Wnt/β-catenin signaling

Because colorectal cancer (CRC) stem-like cells (CCS-like cells) contribute to poor patient prognosis, these cells are a potential target for CRC therapy. However, the mechanism underlying the maintenance of CCS-like cell properties remains unclear. Here, we found that patients with advanced stage CRC expressed high levels of polycomb group protein enhancer of zeste homologue 2 (EZH2). High expression of EZH2 in tumor tissues correlated with poor patient prognosis. Conversely, silencing EZH2 reduced CRC cell proliferation. Surprisingly, EZH2 was more highly expressed in the CCS-like cell subpopulation than in the non-CCS-like cell subpopulation. EZH2 knockdown significantly reduced the CD133+/CD44+ subpopulation, suppressed mammosphere formation, and decreased the expression of self-renewal-related genes and strongly impaired tumor-initiating capacity in a re-implantation mouse model. Gene expression data from 433 human CRC specimens from TCGA database and in vitro results revealed that EZH2 helped maintain CCS-like cell properties by activating the Wnt/β-catenin pathway. We further revealed that p21cip1–mediated arrest of the cell cycle at G1/S phase is required for EZH2 activation of the Wnt/β-catenin pathway. Moreover, the specific EZH2 inhibitor EPZ-6438, a clinical trial drug, prevented CRC progression. Collectively, these findings revealed EZH2 maintaining CCS-like cell characteristics by arresting the cell cycle at the G1/S phase. These results indicate a new approach to CRC therapy.