Silybin suppresses ovarian cancer cell proliferation by inhibiting isocitrate dehydrogenase 1 activity.

Metabolic reprogramming is a sign of malignant tumors, and targeting the metabolism of tumor cells has become a promising therapeutic approach. Here, we report that Silybin (a nontoxic flavonoid commonly used for liver protection) exhibits prominent anti-tumor effects on human ovarian cancer cells. Treatment of an ovarian cancer cell line with Silybin interfered with glutamine metabolism and the tricarboxylic acid cycle. We applied the drug affinity responsive target stability approach to show that Silybin binds to isocitrate dehydrogenase 1 (IDH1). This combination leads to reduced phosphorylation of IDH1 and inhibits enzyme activity. IDH1 dysfunction significantly increases the ratio of NADP/NADPH in the cell, causing an increase in reactive oxygen species generation. Immunohistochemistry demonstrated that IDH1 was increased in ovarian cancer samples compared with normal para-tumoral tissues. Xenograft murine experiments indicated that Silybin administered orally suppressed the growth of the tumor formed by ovarian cancer cells. In combination, our data strongly suggest that Silybin targets IDH1 in ovarian cancer cells and may be a novel treatment candidate.

Inhibition of NOS1 promotes the interferon response of melanoma cells.

BACKGROUND: NOS1 expression predicts poor prognosis in patients with melanoma. However, the molecular function of NOS1 in the type I IFN response and immune escape of melanoma is still unknown. METHODS: The CRISPR/Cas9 system was used to generate NOS1-knockout melanoma cells and the biological characteristics of NOS1-knockout cells were evaluated by MTT assay, clonogenic assay, EdU assay, and flow cytometric assay. The effect on tumor growth was tested in BALB/c-nu and C57BL/6 mouse models. The gene expression profiles were detected with Affymetrix microarray and RNA-seq and KEGG (Kyoto Encyclopedia of Genes and Genomes) and CLUE GO analysis was done. The clinical data and transcriptional profiles of melanoma patients from the public database TCGA (The Cancer Genome Atlas) and GEO (Gene Expression Omnibus, GSE32611) were analyzed by Qlucore Omics Explorer. RESULTS: NOS1 deletion suppressed the proliferation of melanoma A375 cells in culture, blocked cell cycling at the G0/G1 phase, and decreased the tumor growth in lung metastasis nodes in a B16 melanoma xenograft mouse model. Moreover, NOS1 knockout increased the infiltration of CD3+ immune cells in tumors. The transcriptomics analysis identified 2203 differential expression genes (DEGs) after NOS1 deletion. These DEGs indicated that NOS1 deletion downregulated mostly metabolic functions but upregulated immune response pathways. After inhibiting with NOS1 inhibitor N-PLA, melanoma cells significantly increased the response to IFN[Formula: see text] by upregulation expression of IFN[Formula: see text] simulation genes (ISGs), especially the components in innate immune signaling, JAK-STAT, and TOLL-LIKE pathway. Furthermore, these NOS1-regulating immune genes (NOS1-ISGs) worked as a signature to predict poor overall survival and lower response to chemotherapy in melanoma patients. CONCLUSION: These findings provided a transcriptional evidence of NOS1 promotion on tumor growth, which is correlated with metabolic regulation and immune escape in melanoma cells.

A novel miR-200c/c-myc negative regulatory feedback loop is essential to the EMT process, CSC biology and drug sensitivity in nasopharyngeal cancer.

Overexpression of the c-Myc oncogene has been implicated in cancer stem cell - like (CSC) phenotypes and epithelial-to-mesenchymal transition (EMT) in cancer. However, the underlying molecular mechanism by which c-Myc regulates EMT and CSC potential in remains unclear. In the present study, we showed that the expression of c-Myc protein is inversely correlated with microRNA (miR)-200c expression in primary tumor samples from nasopharyngeal cancer (NPC) patients. We further demonstrated that Myc and miR-200c negatively regulate the expression each other in NPC cell lines. c-Myc transcriptionally repressed expression of miR-200c by directly binding to two E-box sites located within a 1 kb segment upstream of TSS of the miR-200c. In addition, miR-200c post-transcriptionally repressed expression of c-Myc by binding to its 3'-untranslated region, suggesting the existence of a negative feedback loop between Myc and miR-200c. Overexpression of c-Myc interfered with this feedback loop and activated the EMT program, induced CSC phenotypes, and enhanced drug sensitivity, whereas miR-200c could counteract these biological effects of c-Myc. Our results provide a novel mechanism governing c-Myc and miR-200c expression and indicate that either targeting c-Myc or restoring miR-200c expression would be a promising approach to overcome oncogenic role of c-Myc in NPC.

Microcystins-LR induced apoptosis via S-nitrosylation of GAPDH in colorectal cancer cells.

Microcystins-LR (MC-LR), a cyanobacterial toxins, initiate apoptosis in normal and tumor cells. Nitric oxide produced by iNOS is necessary for MC-LR-induced apoptosis. However, the underlying mechanism of NO mediated MC-LR cytotoxicity remains unclear. Here, we performed in vitro experiments on MC-LR cytotoxicity associated with NO induced S-nitrosyation of GAPDH in human colon cancer cells SW480. MTT assay indicated that MC-LR decreased the cellular viability by high concentration (>1 µM). Flow cytometer assay revealed that apoptosis was core mode for MC-LR cytotoxicity. Griess assay showed that MC-LR exposure increased the release of NO through the function of NOS1 and NOS2 in SW480 cells. In turn, NO stress induced the S-nitrosylated modification of GAPDH leading to its nuclear translocation following Siah1 binding. CHIP assay showed that the nuclear GADPH increased P53 transcript of a panner of apoptosis related genes. Moreover, apoptosis induced by MC-LR could be reduced by GAPDH or si-Siah1 or NOSs inhibitor, L-NAME. Thus, our study verified a molecular mechanism of NO/GAPDH/Siah1 cascade in MC-LR mediated apoptosis in colorectal cancer cells, providing a further understanding the in vitro molecular mechanism of MC-LR colorectal toxicity.

Mitochondrial NOS1 suppresses apoptosis in colon cancer cells through increasing SIRT3 activity.

Previous studies have suggested that nitric oxide (NO) which is synthetized by nitric oxide synthase (NOS) is closely related to the carcinogenesis and progression of colon cancer. However, the precise physiopathological role of NO on colon cancer remains unclear, and a lot of related studies focused on NOS2 and NOS3, but little on NOS1. Here, stable overexpression NOS1 of colon cancer cells were constructed to investigate whether NOS1 plays a special role in colon cancer. We observed that NOS1 protein was presented in mitochondria. Both the basal and cisplatin-induced mitochondrial superoxide were inhibited by NOS1, and the cisplatin-induced apoptosis was also inhibited by NOS1. Geldanamycin, a Hsp90 N-terminal inhibitor, was able to impede NOS1 translocation into mitochondria and reverse NOS1-induced apoptosis resistance. Importantly, SIRT3 activity was enhanced by NOS1, which contributes to the low level of mitochondrial superoxide and apoptosis resistance. Our data suggest a link between NOS1 and apoptosis resistance in colon cancer cells through mtNOS1-SIRT3-SOD2 axis. Furthermore, NOS1-induced apoptosis resistance could be reversed by inhibiting mitochondrial translocation of NOS1.

Nuclear ß-catenin accumulation is associated with increased expression of Nanog protein and predicts poor prognosis of non-small cell lung cancer.

BACKGROUND: Although the prognostic roles of ß-catenin expression in non-small cell lung cancer (NSCLC) have been reported in several immunohistochemical (IHC) studies, the results were not consistent because some studies lack sufficient number of the positive cases or did not evaluate the subcellular localization features of the protein. METHOD: In this study, we have evaluated the expression levels and subcellular localization of ß-catenin and Nanog proteins IHC staining in tissue specimens from 309 patients with NSCLC, and explored their association with clinicopathological features and patient outcome. RESULTS: We showed that patients with negative expression of membranous beta-catenin had a trend towards shorter survival (p=0.064) than those with positive expression. In contrast to previous studies, we found that increased expression of either cytoplasmic or nuclear ß-catenin was strongly associated with poor prognosis and was an independent prognosticator for overall survival (p <0.01). We further found that NSCLC cells frequently exhibited an abundance of nuclear Nanog protein which was significantly correlated with nuclear ß-catenin expression (p <0.01) and poor prognosis (p <0.01). Interestingly, immunofluorescent staining results revealed that increased expression of Nanog and nuclear translocation of ß-catenin occurred concomitantly in response to epidermal growth factor receptor(EGFR) signaling in A549 and H23 cells. Furthermore, western blot analysis show that nuclear ß-catenin rather than cytoplasmic ß-catenin expression in the A549 and H23 cells can be enhanced by adding EGF, Nanog expression in the A549 and H23 cells with knockdown of ß-catenin can not be obviously enhanced by adding EGF. CONCLUSION: We propose that evaluation of subcellular localization of ß-catenin and Nanog expression is of clinical significance for patients with NSCLC.

The stable traits of melanoma genetics: an alternate approach to target discovery.

BACKGROUND: The weight that gene copy number plays in transcription remains controversial; although in specific cases gene expression correlates with copy number, the relationship cannot be inferred at the global level. We hypothesized that genes steadily expressed by 15 melanoma cell lines (CMs) and their parental tissues (TMs) should be critical for oncogenesis and their expression most frequently influenced by their respective copy number. RESULTS: Functional interpretation of 3,030 transcripts concordantly expressed (Pearson's correlation coefficient p-value < 0.05) by CMs and TMs confirmed an enrichment of functions crucial to oncogenesis. Among them, 968 were expressed according to the transcriptional efficiency predicted by copy number analysis (Pearson's correlation coefficient p-value < 0.05). We named these genes, "genomic delegates" as they represent at the transcriptional level the genetic footprint of individual cancers. We then tested whether the genes could categorize 112 melanoma metastases. Two divergent phenotypes were observed: one with prevalent expression of cancer testis antigens, enhanced cyclin activity, WNT signaling, and a Th17 immune phenotype (Class A). This phenotype expressed, therefore, transcripts previously associated to more aggressive cancer. The second class (B) prevalently expressed genes associated with melanoma signaling including MITF, melanoma differentiation antigens, and displayed a Th1 immune phenotype associated with better prognosis and likelihood to respond to immunotherapy. An intermediate third class (C) was further identified. The three phenotypes were confirmed by unsupervised principal component analysis. CONCLUSIONS: This study suggests that clinically relevant phenotypes of melanoma can be retraced to stable oncogenic properties of cancer cells linked to their genetic back bone, and offers a roadmap for uncovering novel targets for tailored anti-cancer therapy.

IRF5 gene polymorphisms in melanoma.

BACKGROUND: Interferon regulatory factor (IRF)-5 is a transcription factor involved in type I interferon signaling whose germ line variants have been associated with autoimmune pathogenesis. Since relationships have been observed between development of autoimmunity and responsiveness of melanoma to several types of immunotherapy, we tested whether polymorphisms of IRF5 are associated with responsiveness of melanoma to adoptive therapy with tumor infiltrating lymphocytes (TILs). METHODS: 140 TILs were genotyped for four single nucleotide polymorphisms (rs10954213, rs11770589, rs6953165, rs2004640) and one insertion-deletion in the IRF5 gene by sequencing. Gene-expression profile of the TILs, 112 parental melanoma metastases (MM) and 9 cell lines derived from some metastases were assessed by Affymetrix Human Gene ST 1.0 array. RESULTS: Lack of A allele in rs10954213 (G > A) was associated with non-response (p < 0.005). Other polymorphisms in strong linkage disequilibrium with rs10954213 demonstrated similar trends. Genes differentially expressed in vitro between cell lines carrying or not the A allele could be applied to the transcriptional profile of 112 melanoma metastases to predict their responsiveness to therapy, suggesting that IRF5 genotype may influence immune responsiveness by affecting the intrinsic biology of melanoma. CONCLUSIONS: This study is the first to analyze associations between melanoma immune responsiveness and IRF5 polymorphism. The results support a common genetic basis which may underline the development of autoimmunity and melanoma immune responsiveness.

[A murine model of human primary hepatic lymphoma constructed by surgical orthotopic implantation of histologically intact human tumor tissue and in vivo continuous orthotopic passage].

OBJECTIVE: To establish a nude murine model of human primary hepatic lymphoma (PHL) with surgical orthotopic implantation of histologically intact human tumor tissue and in vivo continuous orthotopic passage. METHODS: Histologically intact lymphoma tissues harvested intraoperatively from a PHL patient were orthotopically transplanted into liver parenchyma of nude mice and in vivo continuous orthotopic passage in nude mice was used to develop a nude murine model mimicking the biological characteristics of PHL patients. Histopathology (light microscopy and immunohistochemistry), serological test, karyotypic analysis and flow cytometry were used to explore the tumorigenicity, invasion and metastasis. RESULTS: An orthotopic nude murine model of PHL, named HLBL-0102, was successfully developed. Histopathology of transplanted tumors showed primary hepatic lymphoma (diffuse large B cell) stained positive for CD20, CD79a and MUM1. Serological test in tumor-bearing mice indicated that alpha-fetal protein (AFP) was negative and hepatitis B surface antigen (HBsAg) positive. The serum level of lactate dehydrogenase (LDH) was elevated to an average of ((1223 ± 258) vs (124 ± 54) U/L, P < 0.01). The chromosomal number of transplanted tumors was between 55 and 59. The DNA index (DI) of 1.7 ± 0.2 indicated heteroploid. So far HLBL-0102 model has been passed for 42 generations in nude mice. A total of 320 nude mice were used for transplantation. The growth rate and resuscitation rate of liquid nitrogen cryopreservation of transplanted tumors were both 100%. The transplanted tumors grew invasively in the liver of nude mice and destroyed adjacent liver tissues and bile ducts, veins and arteries of portal area. There was no involvement of other tissues, organs and distal lymph nodes. CONCLUSION: An orthotopically transplanted model has been successfully established for human primary hepatic lymphoma in nude mice.

An immunologic portrait of cancer.

The advent of high-throughput technology challenges the traditional histopathological classification of cancer, and proposes new taxonomies derived from global transcriptional patterns. Although most of these molecular re-classifications did not endure the test of time, they provided bulk of new information that can reframe our understanding of human cancer biology. Here, we focus on an immunologic interpretation of cancer that segregates oncogenic processes independent from their tissue derivation into at least two categories of which one bears the footprints of immune activation. Several observations describe a cancer phenotype where the expression of interferon stimulated genes and immune effector mechanisms reflect patterns commonly observed during the inflammatory response against pathogens, which leads to elimination of infected cells. As these signatures are observed in growing cancers, they are not sufficient to entirely clear the organism of neoplastic cells but they sustain, as in chronic infections, a self-perpetuating inflammatory process. Yet, several studies determined an association between this inflammatory status and a favorable natural history of the disease or a better responsiveness to cancer immune therapy. Moreover, these signatures overlap with those observed during immune-mediated cancer rejection and, more broadly, immune-mediated tissue-specific destruction in other immune pathologies. Thus, a discussion concerning this cancer phenotype is warranted as it remains unknown why it occurs in immune competent hosts. It also remains uncertain whether a genetically determined response of the host to its own cancer, the genetic makeup of the neoplastic process or a combination of both drives the inflammatory process. Here we reflect on commonalities and discrepancies among studies and on the genetic or somatic conditions that may cause this schism in cancer behavior.

Circular RNA circ_001422 promotes the progression and metastasis of osteosarcoma via the miR-195-5p/FGF2/PI3K/Akt axis.

BACKGROUND: Circular RNAs (circRNAs) are involved in diverse processes that drive cancer development. However, the expression landscape and mechanistic function of circRNAs in osteosarcoma (OS) remain to be studied. METHODS: Bioinformatic analysis and high-throughput RNA sequencing tools were employed to identify differentially expressed circRNAs between OS and adjacent noncancerous tissues. The expression level of circ_001422 in clinical specimens and cell lines was measured using qRT-PCR. The association of circ_001422 expression with the clinicopathologic features of 55 recruited patients with OS was analyzed. Loss- and gain-of-function experiments were conducted to explore the role of circ_001422 in OS cells. RNA immunoprecipitation, fluorescence in situ hybridization, bioinformatics database analysis, RNA pulldown assays, dual-luciferase reporter assays, mRNA sequencing, and rescue experiments were conducted to decipher the competitive endogenous RNA regulatory network controlled by circ_001422. RESULTS: We characterized a novel and abundant circRNA, circ_001422, that promoted OS progression. Circ_001422 expression was dramatically increased in OS cell lines and tissues compared with noncancerous samples. Higher circ_001422 expression correlated with more advanced clinical stage, larger tumor size, higher incidence of distant metastases and poorer overall survival in OS patients. Circ_001422 knockdown markedly repressed the proliferation and metastasis and promoted the apoptosis of OS cells in vivo and in vitro, whereas circ_001422 overexpression exerted the opposite effects. Mechanistically, competitive interactions between circ_001422 and miR-195-5p elevated FGF2 expression while also initiating PI3K/Akt signaling. These events enhanced the malignant characteristics of OS cells. CONCLUSIONS: Circ_001422 accelerates OS tumorigenesis and metastasis by modulating the miR-195-5p/FGF2/PI3K/Akt axis, implying that circ_001422 can be therapeutically targeted to treat OS.

The role of S-nitrosylation of PFKM in regulation of glycolysis in ovarian cancer cells.

One of the malignant transformation hallmarks is metabolism reprogramming, which plays a critical role in the biosynthetic needs of unchecked proliferation, abrogating cell death programs, and immunologic escape. However, the mechanism of the metabolic switch is not fully understood. Here, we found that the S-nitrosoproteomic profile of endogenous nitrogen oxide in ovarian cancer cells targeted multiple components in metabolism processes. Phosphofructokinase (PFKM), one of the most important regulatory enzymes of glycolysis, was S-nitrosylated by nitric oxide synthase NOS1 at Cys351. S-nitrosylation at Cys351 stabilized the tetramer of PFKM, leading to resist negative feedback of downstream metabolic intermediates. The PFKM-C351S mutation decreased the proliferation rate of cultured cancer cells, and reduced tumor growth and metastasis in the mouse xenograft model. These findings indicated that S-nitrosylation at Cys351 of PFKM by NOS1 contributes to the metabolic reprogramming of ovarian cancer cells, highlighting a critical role of endogenous nitrogen oxide on metabolism regulations in tumor progression.

A liver-metastatic model of human primary gastric lymphoma in nude mice orthotopically constructed by using histologically intact patient specimens.

BACKGROUND AND OBJECTIVE: In recent years, incidence and mortality of lymphoma are markedly increasing worldwide. However, the pathogenesis and mechanism of invasion and metastasis for lymphoma are not yet fully clarified. It is mainly due to the lack of ideal animal models, which can precisely simulate the invasion and metastasis of lymphoma in the human body. So, it is very necessary to establish a highly metastatic nude mouse model of human lymphoma. This study developed a liver-metastatic model of primary gastric lymphoma in nude mice by using orthotopic surgical implantation of histologically intact patient specimens into the corresponding organs of the recipient small animals. METHODS: A histologically intact fragment of liver metastasis derived from a surgical specimen of a patient with primary gastric lymphoma was implanted into the submucosa of the stomach in nude mice. Tumorigenicity, invasion, metastasis, morphologic characteristics (via light microscopy, electron microscopy, and immunohistochemistry), karyotype analysis, and DNA content of the orthotopically transplanted tumors were studied. RESULTS: An orthotopic liver metastatic model of human primary gastric lymphoma in nude mice (termed HGBL-0304) was successfully established. The histopathology of the transplanted tumors showed primary gastric diffuse large B-cell lymphoma. CD19, CD20, CD22, and CD79alpha were positive, but CD3 and CD7 were negative. The serum level of lactate dehydrogenase (LDH) was elevated [(1010.56+/-200.85) U/L]. The number of chromosomes ranged from 75 to 89. The DNA index (DI) was 1.45+/-0.25 (that is, heteroploid). So far, the HGBL-0304 model has been passed on for 45 generations of nude mice. A total of 263 nude mice were used for the transplantation. Both the growth and resuscitation rates of liquid nitrogen cryopreservation of the transplanted tumors were 100%. The transplanted tumors autonomically invasively grew and damaged a whole layer in the stomach of nude mice. The metastasis rates of liver, spleen, lymph node, and peritoneal seeding were 100%, 94.3%, 62.6%, and 43.5%, respectively. CONCLUSIONS: The study successfully establishes an orthotopic liver metastatic model of human primary gastric lymphoma in nude mice. The HGBL-0304 model can completely simulate the natural clinical process of primary gastric lymphoma and provides an ideal animal model for the research on the biology of metastasis and antimetastatic experimental therapies of primary gastric lymphoma.

[Highly metastatic nude mouse model of human primary gastric lymphoma constructed by surgical orthotopic transplantation and in vivo continuous screening method].

OBJECTIVE: To develop a series of high metastatic models of human gastric malignant lymphoma in nude mice by orthotopic transplantation. METHODS: Two histologically intact primary and hepatic metastatic fragments derived from surgical specimen of a patient with primary gastric lymphoma were implanted into the submucosa of stomach in nude mice. Highly metastatic and specific organ metastatic models were screened by selective orthotopic passage in nude mice. Transplantability, invasion, metastasis, morphological characteristics (light microscopy, electron microscopy and immunohistochemistry), karyotypic analysis and DNA content of orthotopically transplanted tumors were studied. RESULTS: Primary and hepatic metastatic fragments of primary gastric lymphoma were successfully transplanted in nude mice. Two nude mouse models of human primary gastric lymphoma, termed HGBL-0304 (hepatic metastasis model) and HGBL-0305 (high metastasis model), were developed, exhibiting different metastasis biology. Histopathology of transplanted tumors showed primary gastric diffuse large B cell lymphoma. Two models have been maintained for 45 generations by orthotopic passage in nude mice. A total of 419 nude mice were used for transplantation. The growth rate and resuscitation rate of liquid nitrogen cryopreservation of transplanted tumors were both 100%. Significant difference in metastasis biology was exhibited in four aspects of metastasis time, organ metastatic rate, the extent of hepatic metastasis and survival of cancer-bearing mice. The metastatic rates of liver, spleen, lymph nodes and peritoneal seeding in HGBL-0304 and HGBL-0305 models were 100% and 69.5%, 94.3% and 55.6%, 62.6% and 45.7%, and 43.5% and 30.5%. The onset time for metastases of liver, spleen, lymph nodes and peritoneal seeding was 2 w and 5 w, 3 w and 6 w, 2 w and 3 w, 3 w and 6 w respectively. The extent of hepatic metastasis in HGBL-0304 and HGBL-0305 models displayed diffuse involvement of the whole liver and mainly right lobe invasion of liver respectively. The mean survival time of HGBL-0304 and HGBL-0305 models was 54.3d and 106.9 d respectively. CONCLUSION: Surgical orthotopic implantation combined with in vivo selective passage screening is an effective method for establishing highly metastatic and specific organ metastatic models of human malignant lymphoma in nude mice. The study is the first time to establish hepatic metastasis and high metastasis nude mouse models of human primary gastric lymphoma with the same original patient and different potentials of invasion and metastasis.

NOS1 expression promotes proliferation and invasion and enhances chemoresistance in ovarian cancer.

Nitric oxide (NO), an important chemical messenger, serves a dual role in tumor progression. Nitric oxide synthase isoform 1 (NOS1) was observed to be increasingly expressed in various types of cancer, and its expression has been associated with tumor progression. However, the level of NOS1 expression and the associated functions of NOS1 in human ovarian cancer remain undefined. Using gene expression profiles of ovarian cancer from the Gene Expression Omnibus (GEO) database, the present study revealed that NOS1 was increasingly expressed in ovarian cancer tissues. The present study investigated the level of NOS1 expression and its effects on in vitro cell function, including proliferation, migration and invasion as well as chemoresistance to cispatin (DDP) treatment in OVCAR3 cells. Reverse transcription-quantitative polymerase chain reaction demonstrated that the level of NOS1 mRNA expression varied in different ovarian cancer lines. However, immunoblotting indicated that the level of NOS1 protein expression was constitutively high in ovarian cancer cell lines. Treatment with NOS inhibitor NG-nitro-L-arginine methyl ester or transfection with NOS1 short hairpin RNA significantly inhibited cell proliferation, migration and invasion compared with the control, whereas the sensitivity of OVCAR3 cells to DDP treatment was increased. The results of the present study indicated that NOS1 promoted the function of ovarian cancer cells, including proliferation, invasion and chemoresistance, providing a potential target for ovarian cancer therapeutic.

The heterocyclic compound Tempol inhibits the growth of cancer cells by interfering with glutamine metabolism.

Tempol (4-hydroxy-2,2,6,6-Tetramethylpiperidine-1-oxyl, TPL), a nitroxide compound, inhibits proliferation and increases the vulnerability of cancer cells to apoptosis induced by cytotoxic agents. However, the molecular mechanism of TPL inhibiting cancer cell proliferation has not been fully understood. In this study, we evaluated the metabolic effect of TPL on cancer cells and explored its cancer therapeutic potential. Extracellular flow assays showed that TPL inhibited cellular basal and maximal oxygen consumption rates of mitochondrial. 13C metabolic flux analysis showed that TPL treatment had minimal effect on glycolysis. However, we found that TPL inhibits glutamine metabolism by interfering with the oxidative tricarboxylic acid cycle (TCA) process and reductive glutamine process. We found that the inhibitory effect of TPL on metabolism occurs mainly on the step from citrate to α-ketoglutarate or vice versa. We also found that activity of isocitrate dehydrogenase IDH1 and IDH2, the key enzymes in TCA, were inhibited by TPL treatment. In xenograft mouse model, TPL treatment reduced tumor growth by inhibiting cellular proliferation of xenograft tumors. Thus, we provided a mechanism of TPL inhibiting cancer cell proliferation by interfering with glutamine utilization that is important for survival and proliferation of cancer cells. The study may help the development of a therapeutic strategy of TPL combined with other anticancer medicines.

NOS1 upregulates ABCG2 expression contributing to DDP chemoresistance in ovarian cancer cells.

Nitric oxide synthase 1 (NOS1) has been reported to promote various cancer processes including chemoresistance. However, the role of NOS1 in chemoresistance has remained unclear. ATP-binding cassette, subfamily G, member 2 (ABCG2) has been identified as a molecular cause of multidrug resistance in a number of cancer types, including ovarian cancer. The present study observed that in ovarian cancer cells, the expression of ABCG2 was significantly upregulated in response to cis-diamminedichloroplatinum (cisplatin/DDP) treatment, in addition the expression of NOS1 exhibited an increasing trend. Additionally, the levels of NOS1 and ABCG2 in chemoresistant ovarian cancer profiles in Gene Expression Omnibus datasets (GSE26712 and GSE51373) were higher than in chemosensitive profiles. Furthermore, overexpression of NOS1 could upregulate ABCG2 expression, and expression of ABCG2 was inhibited by NOS1 selective inhibitor (N-PLA). In assays of cell survival, NOS1 appeared to increase the potential for DDP resistance, and this effect was reversed by addition of ABCG2 inhibitor (verapamil). The present study indicated that NOS1-induced chemoresistance was partly mediated by the upregulation of ABCG2 expression. This result suggests a link between the expression of NOS1 and the ABCG2-associated chemoresistance in ovarian cancer.

[Effect of the chemoprotectant tempol on anti-tumor activity of cisplatin].

OBJECTIVE: To investigate the effect of the chemoprotectant tempol on the anti-tumor activity of cisplatin (DDP). METHODS: The cellular toxicity of tempol in human colon cancer SW480 cells and mouse colon cancer CT26 cells were evaluated using MTT and cell counting kit-8 assays. CalcuSyn software analysis was used to determine the interaction between tempol and DDP in inhibition of the cell viability. A subcutaneous homograft mouse model of colon cancer was established. The mice were randomly divided into control group, tempol group, cisplatin group and tempol + DDP treatment group with intraperitoneal injections of the indicated agents. The tumor size, body weight and lifespan of the mice were measured, and HE staining was used to analyze the cytotoxic effect of the agents on the kidney and liver. Immunohistochemistry and Western blotting were performed to detect the expression of Bax and Bcl2 in the tumor tissue, and TUNEL staining was used to analyze the tumor cell apoptosis. The level of reactive oxygen species (ROS) in the tumor tissue was determined using flow cytometry. RESULTS: Tempol showed inhibitory effects on the viability of SW480 and CT26 cells. CalcuSyn software analysis showed that tempol had a synergistic anti-tumor effect with DDP (CI < 1). In the homograft mouse model, tempol treatment alone did not produce obvious anti-tumor effect. HE staining showed that the combined use of tempol and DDP alleviated DDP-induced fibrogenesis in the kidneys, but tempol also reduced the anti-tumor activity of DDP. Compared with the mice treated with DDP alone, the mice treated with both tempol and DDP had a significantly larger tumor size (P < 0.01) and a shorter lifespan (P < 0.05). Tempol significantly reversed DDP-induced expression of Bax and Bcl2 in the tumor tissue and tumor cell apoptosis (P < 0.001), and obviously reduced the elevation of ROS level in the tumor tissue induced by DDP treatment (P < 0.05). CONCLUSIONS: Tempol can attenuate the anti-tumor effect of DDP while reducing the side effects of DDP. Caution must be taken and the risks and benefits should be carefully weighed when considering the use of tempol as an anti-oxidant to reduce the toxicities of DDP.

Metformin attenuates hepatoma cell proliferation by decreasing glycolytic flux through the HIF-1α/PFKFB3/PFK1 pathway.

AIMS: Enhanced aerobic glycolysis is an essential hallmark of malignant cancer. Blocking the glycolytic pathway has been suggested as a therapeutic strategy to impair the proliferation of tumor cells. Metformin, a widely used anti-diabetes drug, exhibits anti-tumor properties. However, the underlying molecular mechanism of its action linking glucose metabolism with the suppression of proliferation has not been fully clarified. MAIN METHODS: Stable isotope tracing technology and gas chromatography-mass spectrometry method were utilized to analyze the effect of metformin on glycolytic flux in HCC cells. Western blot and immunohistochemistry were utilized to analyze the expression of phosphofructokinase-1 (PFK1) and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) in HCC cells or xenograft tumor tissues. Lactate measurement and glucose uptake assay were used to analyze the level of lactate and glucose in the presence of frucose-2,6-diphosphate (F2,6BP) in HCC cells treated with metformin. KEY FINDINGS: We found that metformin significantly impaired hepatoma cell proliferation by inhibiting the glycolytic flux via PFK1 blockade. Interestingly, activation of PFK1 by F2,6BP reverses the inhibitory effect of metformin on hepatoma cell proliferation and glycolysis. Mechanistically, PFKFB3，a potent allosteric activator of PFK1, was markedly suppressed through inhibiting hypoxia-induced factor 1 (HIF-1α) accumulation mediated by metformin. SIGNIFICANCE: Taken together these data indicate that HIF-1α/PFKFB3/PFK1 regulatory axis is a vital determinant of glucose metabolic reprogramming in hepatocellular carcinoma, which gives new insights into the action of metformin in combatting liver cancer.