Dna Methylation in Esophageal Diseases Including Cancer: Special Reference to hMLH1 Gene Promoter Status

Aims and Background

Chronic inflammation leading to malignancy in the esophagus may be due to errors in mismatch repair (MMR) genes such as hMLH1. Promoter hypermethylation has been suggested as the main cause of hMLH1 silencing. In this study we assessed hMLH1 promoter hypermethylation in a range of esophageal diseases. Further, we evaluated the role of factors affecting the methylation cycle: (1) methyt-enetetrahydrofolate reductase (MTHFR) C677T mutation and (2) serum homocysteine levels.

Methods

We endoscopically and histologically categorized 124 paired tissue and blood samples from patients into cancer, precancer, reflux esophagitis, other inflammatory esophagitis and controls (endoscopically normal). Restriction enzyme-based methylation analysis was carried out to assess hMLH1 promoter hypermethylation.

Results and Conclusions

hMLH1 promoter hypermethylation in tissue was seen in 63.5% of patients with cancer and 53.8% of those with precancer, which was significantly increased when compared with controls (P <0.001). There appears to be an increasing degree of hMLH1 hypermethylation with disease progression. Patients with gastroesophageal reflux disease (GERD) showed a high degree of hMLH1 hypermethylation (88.8%), indicating that local environment due to reflux may be promoting hypermethylation. We suggest that GERD is a progressive condition with an increased risk for developing into cancer. Only 14.5% of cases exhibited hypermethylation both in tissue and blood. Hence, we conclude that hMLH1 promoter hypermethylation is a tissue-specific change in the esophagus and blood testing cannot be used as a noninvasive tool to assess it. DNA methylation is dependent on the methylation cycle; MTHFR is a major enzyme in this pathway. MTHFR mutations did not correlate with hypermethylation or clinical pathology (P >0.5). Elevated homocysteine levels, independent of MTHFR mutation, correlated significantly with hMLH1 hypermethylation in tissue (P <0.005). Our study shows that hMLH1 hypermethylation in tissue may be the primary event caused by endogenous/exogenous factors in esophageal diseases, aiding disease progression.

Mechanism of Anti-rotavirus Synergistic Activity by Epigallocatechin Gallate and a Proanthocyanidin-Containing Nutraceutical

Epigallocatechin gallate (EGCG) of green tea and the nutraceutical CystiCran^®-40 (containing 40% proanthocyanidins) of the cranberry plant have been associated with antiviral activity. The purpose of this work was to determine the mechanism of antiviral synergy between each compound. Coliphage T4II (phage T4) and the rotavirus strain SA-11(RTV) were used as model virus systems. Individual and combined flavonoids structural and molecular weight analyses were performed by NMR and HPCL/MS, respectively. A suboptimal concentration of EGCG or C-40 alone or in combination reduced phage infectivity by ≤10%. Similarly, EGCG (30 µg/ml) and C-40 (25 µg/ml), respectively, reduced RTV titers by 3 and 13%. However, RTV titers were reduced by 32% (p < .05) with both flavonoids used in combination. RTV was not recognized in host cells by electron microscopy 24-h post-inoculation. NMR and HPLC/MS findings revealed significant structural and potential changes in molecular weight of the flavonoids in complex.

Involvement of nitric oxide synthase in matrix metalloproteinase-9- and/or urokinase plasminogen activator receptor-mediated glioma cell migration

BACKGROUND

Src tyrosine kinase activates inducible nitric oxide synthase (iNOS) and, in turn, nitric oxide production as a means to transduce cell migration. Src tyrosine kinase plays a key proximal role to control α9β1 signaling. Our recent studies have clearly demonstrated the role of α9β1 integrin in matrix metalloproteinase-9 (MMP-9) and/or urokinase plasminogen activator receptor (uPAR)-mediated glioma cell migration. In the present study, we evaluated the involvement of α9β1 integrin-iNOS pathway in MMP-9- and/or uPAR-mediated glioma cell migration.

METHODS

MMP-9 and uPAR shRNAs and overexpressing plasmids were used to downregulate and upregulate these molecules, respectively in U251 glioma cells and 5310 glioma xenograft cells. The effect of treatments on migration and invasion potential of these glioma cells were assessed by spheroid migration, wound healing, and Matrigel invasion assays. In order to attain the other objectives we also performed immunocytochemical, immunohistochemical, RT-PCR, Western blot and fluorescence-activated cell sorting (FACS) analysis.

RESULTS

Immunohistochemical analysis revealed the prominent association of iNOS with glioblastoma multiforme (GBM). Immunofluorescence analysis showed prominent expression of iNOS in glioma cells. MMP-9 and/or uPAR knockdown by respective shRNAs reduced iNOS expression in these glioma cells. RT-PCR analysis revealed elevated iNOS mRNA expression in either MMP-9 or uPAR overexpressed glioma cells. The migration potential of MMP-9- and/or uPAR-overexpressed U251 glioma cells was significantly inhibited after treatment with L-NAME, an inhibitor of iNOS. Similarly, a significant inhibition of the invasion potential of the control or MMP-9/uPAR-overexpressed glioma cells was noticed after L-NAME treatment. A prominent reduction of iNOS expression was observed in the tumor regions of nude mice brains, which were injected with 5310 glioma cells, after MMP-9 and/or uPAR knockdown. Protein expressions of cSrc, phosphoSrc and p130Cas were reduced with simultaneous knockdown of both MMP-9 and uPAR.

CONCLUSIONS

Taken together, our results from the present and earlier studies clearly demonstrate that α9β1 integrin-mediated cell migration utilizes the iNOS pathway, and inhibition of the migratory potential of glioma cells by simultaneous knockdown of MMP-9 and uPAR could be attributed to the reduced α9β1 integrin and iNOS levels.

Abstract 4907: Knockdown of MMP-9 inhibits radiation-induced invasive phenotype, angiogenesis and tumor growth in glioma cancer stem cells

Gliomas contain a small number of treatment-resistant glioma stem cells (GSCs). It is thought that tumor regrowth or recurrence originates from GSCs, thus rendering GSCs an attractive target for novel treatment approaches. GSCs are also resistant to conventional chemotherapy and radiation therapy, and a low dose of ionizing radiation can induce stem cell-like properties in heterogeneous cancer cells. In the present study, an isolated glioma stem cell population exhibited a significant differential expression of MMP-9 and a low dose of irradiation enhanced MMP-9 expression levels. Transfection of GSCs with pMMP-9-Si inhibited radiation-induced MMP-9 activity and protein levels as well as cell proliferation. The sphere de-differentiating and invasive ability of GSCs were also reduced in MMP-9 knockdown cells when compared with mock and pSV controls. MMP-9 knockdown led to the induction of apoptotic cell death as determined by FACS and TUNEL analyses, and caspase-3 and poly (ADP-ribose) polymerase (PARP) cleavage. pMMP-9-Si transfection also inhibited radiation-induced angiogenesis in vitro and in vivo in GSCs. Further, pMMP-9-Si treatment inhibited pre-established glioma tumor growth in an intracranial model. In addition, GSC xenograft tissue sections from mice that were treated with MMP-9 siRNA showed reduced expression of VEGF and the angiogenic marker, CD31. Indeed, TUNEL analysis of tumor sections collected from the combination group of pMMP-9-Si and irradiation revealed more apoptotic cells. These results validate the usefulness of targeting MMP-9 and provide a novel perspective in the treatment of the cancer stem cell population with its higher resistance to radiotherapy.

Citation Format: Chandramu Chetty, Shivani Ponnala, Meena Gujrati, Jasti S. Rao. Knockdown of MMP-9 inhibits radiation-induced invasive phenotype, angiogenesis and tumor growth in glioma cancer stem cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4907. doi:10.1158/1538-7445.AM2013-4907

Abstract 461: Involvement of α9β1 integrin-iNOS pathway in matrix metalloproteinase-9 and/or urokinase plasminogen activator receptor-mediated glioma cell migration

Src tyrosine kinase activates inducible nitric oxide synthase (iNOS) and, in turn, nitric oxide (NO) production as a means to transduce cell migration. Src tyrosine kinase plays a key proximal role to control α9β1 signaling. Our recent studies have clearly demonstrated the role of α9β1 integrin in matrix metalloproteinase-9 (MMP-9) and/or urokinase plasminogen activator receptor (uPAR)-mediated glioma cell migration. In the present study, we aimed to investigate the involvement of α9β1 integrin-iNOS pathway in MMP-9- and/or uPAR-mediated glioma cell migration. Immunohistochemical analysis of the glioblastoma multiforme (GBM) tissue array revealed the prominent presence of iNOS in several clinical GBM samples. In addition, immunofluorescence analysis of U251 glioma cell lines and 5310 glioma xenograft cells showed a prominent expression of iNOS. Transcriptional inactivation of MMP-9 and/or uPAR by respective shRNA reduced iNOS expression in both U521 and 5310 glioma cells. RT-PCR analysis revealed elevated iNOS mRNA expression in these glioma cells after transfection with MMP-9- or uPAR-overexpressing plasmids. Wound healing and spheroid migration assays showed a significant inhibition of the migration potential of MMP-9- or uPAR-overexpressed U251 glioma cells after treatment with L-NAME, an inhibitor of iNOS. Similarly, Matrigel invasion assay revealed a significant inhibition of the invasion potential of the control or MMP-9/uPAR-overexpressed U251 and 5310 glioma cells after L-NAME treatment. Further, we noticed a prominent reduction of iNOS expression in the tumor regions of nude mice brains, which were injected with 5310 glioma cells, after MMP-9 and/or uPAR knockdown. Integrin α9β1 regulates iNOS activity via Src tyrosine kinase; Src coordinates subsequent signaling pathways through activation of FAK and tyrosine phosphorylation of the adaptor protein p130Cas. Western blot analysis of MMP-9 and/or uPAR shRNA treated U251 and 5310 glioma cells revealed significant reductions in the protein expression of cSrc, phosphoSrc, FAK and p130Cas after simultaneous downregulation of both MMP-9 and uPAR. Taken together, our results from the present and earlier studies clearly demonstrate that α9β1 integrin-mediated cell migration utilizes the iNOS pathway, and inhibition of the migratory potential of these glioma cells by simultaneous knockdown of MMP-9 and uPAR could be attributed to the reduced α9β1 integrin and iNOS levels. Therefore, our results highlight the possible involvement of α9β1 integrin-iNOS pathway in MMP-9- and/or uPAR-mediated glioma cell migration.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 461. doi:1538-7445.AM2012-461

Abstract 240: Transcriptional knockdown of urokinase-type plasminogen activator receptor (uPAR) induces apoptosis in glioblastoma xenograft cells via activation of p53

Elevated levels of urokinase plasminogen activator receptor (uPAR), a glycoprotein tethered to the cell membrane with a glycosylphosphotidylinositol (GPI) anchor, is associated with tumor malignancy in a variety of cancers including glioblastoma (GBM). In this study, we show that inhibition of uPAR via RNA interference (puPAR-Si) induced p53-mediated massive cell death in human GBM xenograft cell lines, 4910 and 5310. Induction of Fas expression and cleavage of caspases-8, -9 and -3 and PARP (poly (ADP-ribose) polymerase) revealed induction of the extrinsic apoptotic pathway. Inhibition of Fas death receptor blocked puPAR-Si-induced apoptosis. Further, uPAR inhibition induced the expression of tumor suppressor p53 and its downstream target gene p21. Transcriptional knockdown of p53 rescued cells from apoptosis, thereby indicating that p53 was critical for induction of apoptosis. Moreover, puPAR-Si treatment inhibited pre-established tumor growth in an intracranial model. Indeed, histological analysis of tumor sections collected from mice that were treated with uPAR siRNA revealed increased immunoreactivity of phosphorylated p53, Fas, active caspase 3 and induction of programmed cell death. These data suggest a novel function of uPAR acting as a survival factor for GBM by downregulating p53; inhibition of uPAR induces a pro-apoptotic signaling pathway via p53. These findings may offer new treatment strategies for GBM.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 240. doi:1538-7445.AM2012-240

Abstract 1118: Protease-integrin regulates mitochondrial biogenesis in glioma xenograft cells

Various studies have described mitochondrial dysfunction and its association with several diseases, including cancer. Regulation of mitochondrial biogenesis via mitochondrial-nuclear genome encoded protein signaling has been identified in recent literature. In the present study, we explored whether matrix metalloproteinase-9 (MMP-9) shRNA mediates mitochondrial biogenesis and alters glioma proliferation. We found that MMP-9 shRNA initiated mitochondrial biogenesis in glioma cells by increasing the expression of mitochondrial transcription factor (mtTFA). MMP-9 silencing elevated nuclear respiratory factor-1 (NRF1) and -2 (NRF2), which are involved in transcription regulation of mtTFA. Mitochondrial localization of mtTFA was more evident in MMP-9-treated glioma cells as compared to untreated cells. In addition, MMP-9 suppression significantly increased the binding of mtTFA to light strand and heavy strand promoter of mitochondrial genome as determined by mitochondrial chromatin immunoprecipitation assay. MMP-9 transcriptional suppression decreased the expression of phospho Akt and PI3K while increasing PTEN expression in glioma xenograft cells. We also show that dominant negative Akt increased mtTFA, NRF1 and NRF2, and decreased PI3K, integrin αv and integrin β3. Further, MMP-9 and Akt suppression increased the nuclear and mitochondrial expression of mtTFA. As indicated by increased copy number of displacement (D) loop, mitochondrial replication was observed in both MMP-9- and Akt-downregulated glioma cells. As confirmed by immunoprecipitation analysis, interaction of αvβ3 integrin with MMP-9 decreased. Studies with functional blocking of αvβ3 integrin indicated elevation of mtTFA, a decrease in phospho Akt, and overexpression of D-loop; these data indicate MMP-9 mediates mitochondrial biogenesis via αvβ3 integrin-Akt/PTEN, which led to increased mtTFA expression. Earlier studies from our lab also showed apoptosis induction in these glioma cells by MMP-9 shRNA. Moreover, 4910 and 5310 glioma xenograft tissue sections from mice treated with MMP-9 shRNA showed reduced expression of phospho Akt, and elevated PTEN and mtTFA levels. Decreased co-localization of αvβ3 integrin and MMP-9 was associated with MMP-9-suppressed tumor sections. Further, RT-PCR and western blot analyses showed increased expression of proteins involved in mitochondrial biogenesis encoded both by mitochondrial and nuclear genome in MMP-9 shRNA-treated glioma cells. Elevated levels of reactive oxygen species and the results of the FACS analysis show increased mitochondrial organelle stain in MMP-9-silenced glioma cells. Taken together, these data provide new insight into MMP-9-mediated glioma proliferation inhibition by mitochondrial biogenesis induced cell death.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1118. doi:1538-7445.AM2012-1118

Role of MDR1 C3435T and GABRG2 C588T gene polymorphisms in seizure occurrence and MDR1 effect on anti-epileptic drug (phenytoin) absorption

AIMS

To assess the role of MDR1 and gamma-aminobutyric acid receptor-gamma 2 sub unit (GABRG2) gene polymorphism in seizure susceptibility in generalized seizure (GS) and febrile seizure (FS) patients and to evaluate MDR1 C3435T gene polymorphism's role in absorption of the anti-epileptic drug, phenytoin (PHT) in a cohort of patients.

METHODS

One hundred twenty-seven cases of seizure (86 GS and 41 FS) patients were analyzed for MDR1 C3435T and GABRG2 C588T gene polymorphisms using restriction fragment length polymorphism-polymerase chain reaction. Serum PHT levels were analyzed.

RESULTS

The T allele of MDR1 C3435T and GABRG2 C588T gene polymorphism was higher in GS in the Indian population compared with controls. From the data in GS, CT and TT genotype carriers of the MDR1 gene and TT genotype carriers of the GABRG2 gene had more recurrent seizures compared with others. MDR1 T allele carriers in the seizure reoccurrence (SR) group of GS and FS were high compared with the well-controlled seizure group (with no seizures after treatment). TT genotype carriers in SR group were high in FS (with regard to MDR1 gene polymorphism) and GS (with regard to GABRG2 gene polymorphism) compared with a well-controlled seizure group. MDR1 C3435T gene polymorphism affects serum PHT levels (p<0.015). Association of dose PHT ratio and genotype groups of MDR1 C3435T gene polymorphism showed a significant association (p<0.05). MDR1*CC genotype was more common in cases with low serum PHT levels.In addition, it is evident that CT and TT genotype carriers have a high percentage of SR with elevated serum PHT levels.

CONCLUSIONS

Our results show that the MDR1 3435T and GABRG2 588T alleles play a role in seizure occurrence. Moreover, the MDR1 3435T allele also affects PHT absorption. We suggest MDR1 C3435T and GABRG2 C588T genotyping would be of value in order to lower the risk of concentration-dependent drug toxicity and for better patient management.

Metabolic remodeling precedes mitochondrial outer membrane permeabilization in human glioma xenograft cells

Glioma cancer cells adapt to changing microenvironment and shift from mitochondrial oxidative phosphorylation to aerobic glycolysis for their metabolic needs irrespective of oxygen availability. In the present study, we show that silencing MMP-9 in combination with uPAR/cathepsin B switch the glycolytic metabolism of glioma cells to oxidative phosphorylation (OXPHOS) and generate reactive oxygen species (ROS) to predispose glioma cells to mitochondrial outer membrane permeabilization. shRNA for MMP-9 and uPAR (pMU) as well as shRNA for MMP-9 and cathepsin B (pMC) activated complexes of mitochondria involved in OXPHOS and inhibited glycolytic hexokinase expression. The decreased interaction of hexokinase 2 with mitochondria in the treated cells indicated the inhibition of glycolysis activation. Overexpression of Akt reversed the pMU- and pMC-mediated OXPHOS to glycolysis switch. The OXPHOS un-coupler oligomycin A altered the expression levels of the Bcl-2 family of proteins; treatment with pMU or pMC reversed this effect and induced mitochondrial outer membrane permeabilization. In addition, our results show changes in mitochondrial pore transition to release cytochrome c due to changes in the VDAC-Bcl-XL and BAX-BAK interaction with pMU and pMC treatments. Taken together, our results suggest that pMU and pMC treatments switch glioma cells from the glycolytic to the OXPHOS pathway through an inhibitory effect on Akt, ROS induction and an increase of cytosolic cytochrome c accumulation. These results demonstrate the potential of pMU and pMC as therapeutic candidates for the treatment of glioma.

Regulation of DNA repair mechanism in human glioma xenograft cells both in vitro and in vivo in nude mice

BACKGROUND

Glioblastoma Multiforme (GBM) is the most lethal form of brain tumor. Efficient DNA repair and anti-apoptotic mechanisms are making glioma treatment difficult. Proteases such as MMP9, cathepsin B and urokinase plasminogen activator receptor (uPAR) are over expressed in gliomas and contribute to enhanced cancer cell proliferation. Non-homologous end joining (NHEJ) repair mechanism plays a major role in double strand break (DSB) repair in mammalian cells.

METHODOLOGY/PRINCIPAL FINDINGS

Here we show that silencing MMP9 in combination with uPAR/cathepsin B effects NHEJ repair machinery. Expression of DNA PKcs and Ku70/80 at both mRNA and protein levels in MMP9-uPAR (pMU) and MMP9-cathepsin B (pMC) shRNA-treated glioma xenograft cells were reduced. FACS analysis showed an increase in apoptotic peak and proliferation assays revealed a significant reduction in the cell population in pMU- and pMC-treated cells compared to untreated cells. We hypothesized that reduced NHEJ repair led to DSBs accumulation in pMU- and pMC-treated cells, thereby initiating cell death. This hypothesis was confirmed by reduced Ku70/Ku80 protein binding to DSB, increased comet tail length and elevated γH2AX expression in treated cells compared to control. Immunoprecipitation analysis showed that EGFR-mediated lowered DNA PK activity in treated cells compared to controls. Treatment with pMU and pMC shRNA reduced the expression of DNA PKcs and ATM, and elevated γH2AX levels in xenograft implanted nude mice. Glioma cells exposed to hypoxia and irradiation showed DSB accumulation and apoptosis after pMU and pMC treatments compared to respective controls.

CONCLUSION/SIGNIFICANCE

Our results suggest that pMU and pMC shRNA reduce glioma proliferation by DSB accumulation and increase apoptosis under normoxia, hypoxia and in combination with irradiation. Considering the radio- and chemo-resistant cancers favored by hypoxia, our study provides important therapeutic potential of MMP9, uPAR and cathepsin B shRNA in the treatment of glioma from clinical stand point.

Integrin α9β1-mediated cell migration in glioblastoma via SSAT and Kir4.2 potassium channel pathway

The α9β1 integrin accelerates cell migration through binding of the α9 cytoplasmic domain to SSAT, which catalyzes the catabolism of higher order polyamines, spermidine and spermine, to the lower order polyamine, putrescine. SSAT levels were downregulated at both the mRNA and protein levels by shRNA-mediated simultaneous knockdown of MMP-9 and uPAR/cathepsin B. In addition, we noted a prominent reduction in the expression of SSAT with MMP-9 and uPAR/cathepsin B knockdown in the tumor regions of 5310 injected nude mice brains. Further, SSAT knockdown in glioma xenograft cells significantly reduced their migration potential. Interestingly, MMP-9, uPAR and cathepsin B overexpression in these xenograft cells significantly elevated SSAT mRNA and protein levels. The migratory potential of MMP-9/uPAR/cathepsin B-overexpressed 4910 and 5310 cells was not affected by either glybenclamide (Kir 6.x inhibitor) or tertiapin-Q (Kir 1.1 and 3.x inhibitor) but instead was significantly inhibited by either barium or Kir4.2 siRNA treatments. Co-localization of α9 integrin with Kir4.2 was observed in both 4910 and 5310 xenograft cells. However, MMP-9 and uPAR/cathepsin B knockdown in these cells prominently reduced the co-localization of α9 with Kir4.2. Taken together, our results clearly demonstrate that α9β1 integrin-mediated cell migration utilizes SSAT and the Kir4.2 potassium channel pathway, and inhibition of the migratory potential of these glioma xenograft cells by simultaneous knockdown of MMP-9 and uPAR/cathepsin B could be attributed to the reduced SSAT levels and co-localization of α9 integrin with Kir4.2 inward rectifier potassium channels.

Abstract 1391: Simultaneous knockdown of MMP-9 and uPAR/cathepsin B retards α9β1 integrin-mediated cell migration via SSAT and potassium channel pathway in glioma xenografts

The α9β1 integrin accelerates cell migration through the binding of α9 cytoplasmic domain to spermidine/spermine-N1-acetyltransferase (SSAT), which catalyzes the catabolism of higher order polyamines, spermidine and spermine, to the lower order polyamine, putrescine. Our recent studies have clearly demonstrated the role of α9β1 integrin in MMP-9, uPAR and cathepsin B-mediated cell migration in glioma xenograft cells (4910 and 5310). In the present study, we aimed to investigate the underlying mechanisms through which MMP-9 and uPAR/cathepsin B knockdown inhibits α9β1 integrin-mediated migration in glioma xenograft cells. Western blot, RT-PCR and immunofluorescence analyses revealed downregulation of SSAT levels both at the mRNA and protein levels by siRNA-mediated simultaneous knockdown of MMP-9 and uPAR/cathepsin B. In addition, we noted a prominent reduction in the expression of SSAT with MMP-9 and uPAR/cathepsin B knockdown in the tumor regions of 5310 injected nude mice brains. Co-localization of α9 integrin with kir4.2, an inward rectifier potassium channel, was observed in both 4910 and 5310 xenograft cells. However, MMP-9 and uPAR/cathepsin B knockdown in these cells prominently reduced the co-localization of α9 with kir4.2. Interestingly, MMP-9, uPAR and cathepsin B overexpression in these xenograft cells significantly elevated SSAT mRNA and protein levels. Further, the migratory potential of MMP-9/uPAR/cathepsin B overexpressed 4910 and 5310 cells was not affected by either glybenclamide or tertiapin-Q but instead was significantly inhibited by either barium or kir4.2 siRNA treatments. Taken together, our results from the present and earlier studies clearly demonstrate that α9β1 integrin-mediated cell migration utilizes SSAT and kir4.2 potassium channel pathway, and inhibition of the migratory potential of these glioma xenograft cells by simultaneous knockdown of MMP-9 and uPAR/cathepsin B could be attributed to the reduced SSAT levels and co-localization of α9 integrin with kir4.2 potassium channels. Based on these findings, we conclude that the simultaneous knockdown of MMP-9 and uPAR/cathepsin B retards SSAT and potassium channel pathway-mediated cell migration through the α9β1 integrin.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1391. doi:10.1158/1538-7445.AM2011-1391

Abstract 5503: Anti-proliferative role of MMP-9 and uPAR/cathepsin B knockdown in negative regulation of DNA repair mechanisms in human glioma xenografts

Glioblastoma multiforme (GBM) is one of the most lethal forms of brain tumors. Efficient repair of DNA damage, especially double strand breaks (DSBs) and anti-apoptotic mechanisms associated with GBM, makes treating GBM challenging. In the present study, siRNA-mediated transcriptional silencing of MMP-9 and uPAR (MU) and MMP-9 and cathepsin B (MC) in 4910 and 5310 glioma xenograft cells had significant anti-proliferative effect as assessed by BrdU, MTT and clonogenic assays. FACS analysis revealed cells were in sub-G0-G1 phase after xenograft cells were treated with MU or MC. We also investigated the role of MU or MC knockdown in reducing DNA damage response (DDR), which eventually leads to apoptosis in glioma xenograft cells. RT-PCR and Western blot analyses revealed downregulation of DNA PKcs and Ku70/80 levels, which are responsible for non-homologous end joining (NHEJ) DNA repair. Elevated γH2AX protein expression and increased comet tail length indicated that the reduced NHEJ DNA repair led to accumulation of DSBs in MU and MC knocked down cells. The binding efficiency of Ku70 and Ku80 to DSB was significantly reduced in glioma cells treated with MU or MC. In addition, we noticed a reduced γH2AX and Ku70/Ku80 colocalization at DSBs in MU- and MC-treated xenograft cells. Moreover, MU and MC knockdown in these xenograft cells resulted in the downregulation of several other proteins involved in DNA damage response and the survival pathway (e.g., ATM, Rad 51, CHK2, EGFR, Akt, and ERK). Immunohistochemistry of the brain sections of xenografts injected into nude mice showed a reduced expression of DNA PKcs in animals treated with MU and MC siRNA. Taken together, our results clearly demonstrate that silencing via MU and MC not only negatively regulates DNA damage response, but also downregulates the proteins associated with the survival pathway. Based on these findings, it appears that silencing MU or MC in addition to radiation could be an effective strategy to treat radioresistant high-grade gliomas, where treatment usually fails due to the enhanced repair of DSBs induced by radiation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5503. doi:10.1158/1538-7445.AM2011-5503

Abstract 1493: Tumor-associated soluble uPAR enhances endothelial cell migration by staffing into lipid rafts

The expression of urokinase plasminogen activator receptor (uPAR), a heavily glycosylated glycosyl-phosphatidylinositol (GPI)-anchored cell surface receptor, induces cell migration, and its expression correlates with the malignant phenotype of various cancers. The soluble form of uPAR (s-uPAR), which is found in the circulation of cancer patients, is associated with tumor malignancy and serves as a prognostic marker for various cancers. As such, in the current study, we analyzed the effect of s-uPAR from glioblastoma tumor cell conditioned medium (TCM) on endothelial cell migration. Here, we present evidence that s-uPAR from tumor cells augments migration and invasion on vitronectin and fibronectin matrices of human umbilical vein endothelial cells (HUVEC). The membrane fraction of HUVEC, which were cultured on TCM, had increased amounts of s-uPAR recruited into the membranes of endothelial cells. Co-localization studies for GM1 ganglioside receptor (a lipid raft marker) and uPAR further demonstrated s-uPAR recruitment into lipid rafts of HUVEC. Further, western blot analysis for uPAR in lipid raft fractions from HUVEC cells grown on TCM confirmed s-uPAR recruiting onto HUVEC cell membranes. Moreover, the addition of functional blocking uPAR antibodies to TCM mitigated s-uPAR-enhanced HUVEC migration and invasion. Our data suggest that s-uPAR from tumor cells might be involved in the recruitment of endothelial cells in the tumor microenvironment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1493. doi:10.1158/1538-7445.AM2011-1493

MMP-9, uPAR and cathepsin B silencing downregulate integrins in human glioma xenograft cells in vitro and in vivo in nude mice

BACKGROUND

Involvement of MMP-9, uPAR and cathepsin B in adhesion, migration, invasion, proliferation, metastasis and tumor growth has been well established. In the present study, MMP-9, uPAR and cathepsin B genes were downregulated in glioma xenograft cells using shRNA plasmid constructs and we evaluated the involvement of integrins and changes in their adhesion, migration and invasive potential.

METHODOLOGY/PRINCIPAL FINDINGS

MMP-9, uPAR and cathepsin B single shRNA plasmid constructs were used to downregulate these molecules in xenograft cells. We also used MMP-9/uPAR and MMP-9/cathepsin B bicistronic constructs to evaluate the cumulative effects. MMP-9, uPAR and cathepsin B downregulation significantly inhibits xenograft cell adhesion to several extracellular matrix proteins. Treatment with MMP-9, uPAR and cathepsin B shRNA of xenografts led to the downregulation of several alpha and beta integrins. In all the assays, we noticed more prominent effects with the bicistronic plasmid constructs when compared to the single plasmid shRNA constructs. FACS analysis demonstrated the expression of alphaVbeta3, alpha6beta1 and alpha9beta1 integrins in xenograft cells. Treatment with bicistronic constructs reduced alphaVbeta3, alpha6beta1 and alpha9beta1 integrin expressions in xenograft injected nude mice. Migration and invasion were also inhibited by MMP-9, uPAR and cathepsin B shRNA treatments as assessed by spheroid migration, wound healing, and Matrigel invasion assays. As expected, bicistronic constructs further inhibited the adhesion, migration and invasive potential of the xenograft cells as compared to individual treatments.

CONCLUSIONS/SIGNIFICANCE

Downregulation of MMP-9, uPAR and cathespin B alone and in combination inhibits adhesion, migration and invasive potential of glioma xenografts by downregulating integrins and associated signaling molecules. Considering the existence of integrin inhibitor-resistant cancer cells, our study provides a novel and effective approach to inhibiting integrins by downregulating MMP-9, uPAR and cathepsin B in the treatment of glioma.

Effect of polyunsaturated fatty acids on diphenyl hydantoin-induced genetic damage in vitro and in vivo

Phenytoin sodium/diphenyl hydantoin (DPH) is used by a major segment of epileptics and neuro surgery patients with head injury to prevent seizures. DPH is a known mutagen, carcinogen, and teratogen. Essential fatty acids (EFAs) are critical for various tissues and were reported to act as anti-mutagenic agents. In the present study we assessed the effect of five EFAs on DPH-induced genetic damage both in vitro and in vivo. DPH induced significant genetic damage. Of all the EFAs (linoleic acid, alpha-linolenic acid, gamma-linolenic acid, arachidonic acid, dihomo-gamma-linolenic acid, and eicosapentaenoic acid) studied, all except eicosapentaenoic acid showed significant decrease in DPH induced genetic damage as assessed by micronucleus (MN) test. However, gamma-linolenic acid (GLA) was found to be the most effective in reducing the number of MN containing lymphocytes both in vitro and in vivo to control values. EFAs when tested alone produced insignificant increase in the amount of genetic damage but when tested in combination with DPH the number of micronuclei containing lymphocytes was reduced; but the DNA ladder pattern, an indication of DNA damage, was increased. This apparently paradoxical action of EFAs, especially of GLA, suggests that, in all probability, fatty acids induce apoptosis of cells that harbor significant DNA damage. Based on these results we suggest that GLA functions as a unique endogenous molecule that protects cells from accumulating genetic damage.

Role of shigella infection in endometriosis: A novel hypothesis

Endometriosis is the presence of endometrial cells and stroma at ectopic sites outside the uterine cavity. The natural history of endometriosis is uncertain, its etiology unknown, the clinical presentation inconsistent, diagnosis difficult and the treatment poorly standardized. It causes significant morbidity due to pelvic pain and infertility among 15-25% of women during their reproductive age. The benign disease causes peritoneal inflammation, fibrosis, adhesions and ovarian cysts but displays features of malignancy, like neo-vascularization, local invasion and distant metastasis. Mechanical, hormonal, immunological, environmental and genetic factors have been implicated in its etiology but provide inconclusive explanations. Present study was carried out on ectopic and eutopic endometriotic tissue specimens collected during laproscopy/laprotomy from cases of endometriosis. mRNA was isolated from the tissues and converted to cDNA by RT and subsequently subjected to differential display Polymerase Chain Reaction using seven sets of arbitrary primers. A unique band was identified only in the ectopic endometriotic tissue, which was sequenced. BLAST search results revealed sequence homology to shigella bacterial DNA leading us to hypothesize that infection may be playing a role in the etiology of endometriosis. This is the first report implicating the role of bacterial infection in the etiology of endometriosis. Shigella is known to invade the mucosa of the colon through the feco-oral route causing Shigellosis. The pathogenesis of shigellosis involves inflammation, ulceration, haemorrhage, tissue destruction and fibrosis of the colonic mucosa resulting in abdominal pain and diarrhoea/dysentery, this is similar to the pathogenesis of endometriosis which also involves inflammation, haemorrhage, tissue destruction and fibrotic adhesions of the pelvic peritoneum resulting in abdominal pain and infertility. The non-motile shigella bacteria invade the deeper mucosal layers by travelling from cell to cell of colonic epithelium, reaching the lamina propria of the colonic mucosa. We propose that, by the same mechanism, the bacteria travel across the colon wall to reach the outer peritoneal surface of the colon, which is in close proximity to the posterior uterine surface in the Pouch of Douglas, the site which incidentally happens to be the commonest site of early endometriosis. Our hypothesis therefore proposes that shigella or shigella-like organisms may be the trigger for the initiation of immunological changes in the pelvic peritoneum causing endometriosis. Once the endometrial cells are implanted at ectopic sites they are sustained by hormones and angiogenic factors. Hence "Infection hypothesis" provides a novel explanation for the etiopathogenesis of endometriosis.

Chromosome 11 aneusomy in esophageal cancers and precancerous lesions- an early event in neoplastic transformation: An interphase fluorescence in situ hybridization study from south India

AIM: To detect aneusomic changes with respect to chromosome 11 copy number in esophageal precancers and cancers wherein the generation of cancer-specific phenotypes is believed to be associated with specific chromosomal aneuploidies.

METHODS: We performed fluorescence in situ hybridization (FISH) on esophageal tissue paraffin sections to analyze changes in chromosome 11 copy number using apotome-generated images by optical sectioning microscopy. Sections were prepared from esophageal tumor tissue, tissues showing preneoplastic changes and histologically normal tissues (control) obtained from patients referred to the clinic for endoscopic evaluation.

RESULTS: Our results demonstrated that aneusomy was seen in all the cancers and preneoplastic tissues, while none of the controls showed aneusomic cells. There was no increase in aneusomy from precancers to cancers.

CONCLUSION: Our results suggest that evaluation of chromosome 11 aneusomy in esophageal tissue using FISH with an appropriate signal capture-analysis system, can be used as an ancillary molecular marker predictive of early neoplastic changes. Future studies can be directed towards the genes on chromosome 11, which may play a role in the neoplastic transformation of esophageal precancerous lesions to cancers.