Lisam Shanjukumar Singh

Lysophosphatidic Acid Is Constitutively Produced by Human Peritoneal Mesothelial Cells and Enhances Adhesion, Migration, and Invasion of Ovarian Cancer Cells

Lysophosphatidic acid (LPA) is both a potential marker and a therapeutic target for ovarian cancer. It is critical to identify the sources of elevated LPA levels in ascites and blood of patients with ovarian cancer. We show here that human peritoneal mesothelial cells constitutively produce LPA, which accounts for a significant portion of the chemotactic activity of the conditioned medium from peritoneal mesothelial cells to ovarian cancer cells. Both production of LPA by peritoneal mesothelial cells and the chemotactic activity in the conditioned medium can be blocked by HELSS [an inhibitor of the calcium-independent phospholipase A(2) (iPLA(2))] and AACOCF(3) [an inhibitor of both cytosolic PLA(2) (cPLA(2)) and iPLA(2)]. Moreover, cell-based enzymatic activity assays for PLA(2) indicate that peritoneal mesothelial cells have strong constitutive PLA(2) activity. Receptors for LPA, LPA(2), and LPA(3) are involved in the conditioned medium-induced chemotactic activity. Invasion of ovarian cancer cells into peritoneal mesothelial cells has also been analyzed and shown to require PLA(2), LPA receptors, and the mitogen-activated protein/extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase signaling pathway. Thus, we show here, for the first time, that human peritoneal mesothelial cells constitutively produce bioactive lipid signaling molecules, such as LPA, via iPLA(2) and/or cPLA(2) activities. Conditioned medium from peritoneal mesothelial cells stimulate migration, adhesion, and invasion of ovarian cancer cells, and may play similar roles in vivo.

KiSS1 suppresses metastasis in human ovarian cancer via inhibition of protein kinase C alpha

Metastasis is a vital target for cancer treatment, since the majority of cancer patients die from metastatic, rather than the primary disease. KiSS1 has been identified as a metastasis suppressor gene in melanoma and breast carcinomas. We show here that KiSS1 is also a metastasis suppressor in human ovarian cancer. Overexpression of KiSS1 in ovarian cancer cells inhibits cell migration induced by serum or lysophosphatidic acid (LPA), and colonization in soft agar, but not cell proliferation, representing the characteristics of a metastasis suppressor gene. Furthermore, using an experimental metastatic mouse model, we show that expression of KiSS1 in SKOV3 ovarian cancer cells suppresses >50% metastatic colonization in mice (P < 0.0001). We find that activating protein kinase C (PKC) reverses about 80% of the inhibited cell migration induced by KiSS1, while down-regulation of PKCα with shRNA restores KiSS1 effect, providing evidence that inhibiting PKCα may be an important mechanism of the effect of KiSS1. These results suggest that KiSS1 is a metastasis suppressor of ovarian cancer and may be a potential molecular target for the treatment.

The contribution of amino acid region Asp695-Tyr698 of factor V to procofactor activation and factor Va function

There is strong evidence that a functionally important cluster of amino acids is located on the COOH-terminal portion of the heavy chain of factor Va, between amino acid residues 680 and 709. To ascertain the importance of this region for cofactor activity, we have synthesized five overlapping peptides representing this amino acid stretch (10 amino acids each, HC1-HC5) and tested them for inhibition of prothrombinase assembly and function. Two peptides, HC3 (spanning amino acid region 690-699) and HC4 (containing amino acid residues 695-704), were found to be potent inhibitors of prothrombinase activity with IC50 values of ∼12 and ∼10 μm, respectively. The two peptides were unable to interfere with the binding of factor Va to active site fluorescently labeled Glu-Gly-Arg human factor Xa, and kinetic analyses showed that HC3 and HC4 are competitive inhibitors of prothrombinase with respect to prothrombin with Ki values of ∼6.3 and ∼5.3 μm, respectively. These data suggest that the peptides inhibit prothrombinase because they interfere with the incorporation of prothrombin into prothrombinase. The shared amino acid motif between HC3 and HC4 is composed of Asp695-Tyr-Asp-Tyr-Gln699 (DYDYQ). A pentapeptide with this sequence inhibited both prothrombinase function with an IC50 of 1.6 μm (with a KD for prothrombin of 850 nm), and activation of factor V by thrombin. Peptides HC3, HC4, and DYDYQ were also found to interact with immobilized thrombin. A recombinant factor V molecule with the mutations Asp695 → Lys, Tyr696 → Phe, Asp697 → Lys, and Tyr698 → Phe (factor V2K2F) was partially resistant to activation by thrombin but could be readily activated by RVV-V activator (factor VaRVV2K2F) and factor Xa (factor VaXa2K2F). Factor VaRVV2K2F and factor VaXa2K2F had impaired cofactor activity within prothrombinase in a system using purified reagents. Our data demonstrate for the first time that amino acid sequence 695-698 of factor Va heavy chain is important for procofactor activation and is required for optimum prothrombinase function. These data provide functional evidence for an essential and productive contribution of factor Va to the activity of prothrombinase.

Abnormalities in Osteoclastogenesis and Decreased Tumorigenesis in Mice Deficient for Ovarian Cancer G Protein-Coupled Receptor 1

Ovarian cancer G protein-coupled receptor 1 (OGR1) has been shown to be a proton sensing receptor in vitro. We have shown that OGR1 functions as a tumor metastasis suppressor gene when it is over-expressed in human prostate cancer cells in vivo. To examine the physiological functions of OGR1, we generated conditional OGR1 deficient mice by homologous recombination. OGR1 deficient mice were viable and upon gross-inspection appeared normal. Consistent with in vitro studies showing that OGR1 is involved in osteoclastogenesis, reduced osteoclasts were detected in OGR1 deficient mice. A pH-dependent osteoclasts survival effect was also observed. However, overall abnormality in the bones of these animals was not observed. In addition, melanoma cell tumorigenesis was significantly inhibited in OGR1 deficient mice. OGR1 deficient mice in the mixed background produced significantly less peritoneal macrophages when stimulated with thioglycolate. These macrophages also showed altered extracellular signal-regulated kinases (ERK) activation and nitric oxide (NO) production in response to lipopolysaccharide. OGR1-dependent pH responses assessed by cAMP production and cell survival in macrophages or brown fat cells were not observed, presumably due to the presence of other proton sensing receptors in these cells. Our results indicate that OGR1s role in osteoclastogenesis is not strong enough to affect overall bone development and its role in tumorigenesis warrants further investigation. The mice generated can be potentially used for several disease models, including cancers or osteoclast-related diseases.

Purification and characterization of intestinal adenosine deaminase from mice.

Adenosine deaminase (ADA) was isolated from small intestine of mice and purified to utmost homogeneity. SDS-PAGE of purified ADA gave a molecular weight of 41 kDa. Western blot analyses gave a single reactive band at 41 kDa and the other band was an associated ADA binding protein. The purified enzyme was more stable in the alkaline pH. The optimum pH and the pI values were about 7.0 and 4.96, respectively. Km values of the small intestinal ADA for adenosine and 2′-deoxyadenosine were 23 and 16μM, respectively. Purine riboside was a competitive inhibitor with Ki of 5 μM, whereas 2′-3′-o-isopropylidene adenosine acted as an uncompetitive inhibitor (Ki 66 μM). Activity of ADA was inhibited by the presence of theophylline (-40%), caffeine (-30%), and L-cysteine (-50%). Significantly, Hg2+ (100 μM) inhibited 98% of the initial ADA activity. In addition, various purine analogs such as inosine, purine, α-adenosine and adenine showed variable inhibitions on the activity of ADA. Relative ADA activity towards 3′-deoxyadenosine and 6-chloropurine riboside was lower by 30% and 40%, respectively. However, the activity towards 2′-o-methyl adenosine was higher (30%) compared to the activity obtained using adenosine.

Role of OGR1 in myeloid-derived cells in prostate cancer

Ovarian cancer G-protein-coupled-receptor-1 (OGR1) is a tumor metastasis suppressor in prostate cancer (PCa). OGR1 knockout mice (ogr1−/−) are grossly normal under physiological conditions, however, reduced melanoma tumorigenesis has been observed, with the mechanisms of this reduction completely unknown. In this work, we demonstrated that OGR1 deficiency in host cells significantly reduced tumorigenesis of PCa in mice. Adoptive transfer of WT CD11b+ Gr1+ double positive (DP) cells, but not T cells, was sufficient to allow tumor development in ogr1−/− mice. The expression of an M1 macrophage marker, inducible nitric oxide synthase (iNOS) was higher and expression of an M2 macrophage marker, arginase-1 (Arg 1) was lower in tumors from ogr1−/− mice compared with WT mice. Furthermore, coinjection of transgenic adenocarcinoma mouse prostate (TRAMP)-C2 cells with WT, but not ogr1−/− macrophages, increased tumor incidence in ogr1−/− mice. T-cell depletion experiments suggested that T cells were required for tumor rejection in ogr1−/−mice, although OGR1 expression in T cells may not be necessary. In summary, the expression of OGR1 in myeloid-derived cells, especially in DP cells, was required for PCa tumor cell-induced immunosuppression.

Anticancer properties and enhancement of therapeutic potential of cisplatin by leaf extract of Zanthoxylum armatum DC.

BackgroundClinical use of chemotherapeutic drug, cisplatin is limited by its toxicity and drug resistance. Therefore, efforts continue for the discovery of novel combination therapies with cisplatin, to increase efficacy and reduce its toxicity. Here, we screened 16 medicinal plant extracts from Northeast part of India and found that leaf extract of Zanthoxylumarmatum DC. (ZALE) induced cytotoxicity as well as an effect on the increasing of the efficiency of chemotherapeutic drugs (cisplatin, mitomycin C and camptothecin). This work shows detail molecular mechanism of anti-cancer activity of ZALE and its potential for combined treatment regimens to enhance the apoptotic response of chemotherapeutic drugs.ResultsZALE induced cytotoxicity, nuclear blebbing and DNA fragmentation in HeLA cells suggesting apoptosis induction in human cervical cell line. However, the apoptosis induced was independent of caspase 3 activation and poly ADP ribose polymerase (PARP) cleavage. Further, ZALE activated Mitogen-activated protein kinases (MAPK) pathway as revealed by increased phosphorylation of extracellular-signal-regulated kinases (ERK), p38 and c-Jun N-terminal kinase (JNK). Inhibition of ERK activation but not p38 or JNK completely blocked the ZALE induced apoptosis suggesting an ERK dependent apoptosis. Moreover, ZALE generated DNA double strand breaks as suggested by the induction γH2AX foci formation. Interestingly, pretreatment of certain cancer cell lines with ZALE, sensitized the cancer cells to cisplatin and other chemotherapeutic drugs. Enhanced caspase activation was observed in the synergistic interaction among chemotherapeutic drugs and ZALE.ConclusionPurification and identification of the bio-active molecules from the ZALE or as a complementary treatment for a sequential treatment of ZALE with chemotherapeutic drugs might be a new challenger to open a new therapeutic window for the novel anti-cancer treatment.

Evaluation of Risk Factors for Nasopharyngeal Carcinoma in a High-risk Area of India, the Northeastern Region

Northeastern India is a major nasopharyngeal carcinoma (NPC) high risk-area although the rest of the country has very low incidence. A case-control study of 105 NPC cases and 115 controls was conducted to identify the potential risk factors for NPC development in this region. Information was collected by interviewer about socio-demographic characteristics, cigarette smoking, alcohol consumption, dietary history, occupational history, and a family history of cancer. Epstein-Barr viral load was assayed from the blood DNA by real time PCR. Associations between GSTs genotypes, cytochrome P450 family including CYP1A1, CYP2E1 and CYP2A6 polymorphisms and susceptibility to relationship between the diseases were studied using PCR-RFLP assay. Results indicate that Epstein-Barr virus load was significantly higher in patients compared to controls (p<0.0001). Furthermore, concentration of blood EBV-DNA was significantly higher in advanced stage disease (Stage III and IV) than in early stage disease (Stage I and II) (p<0.05). Presence of CYP2A6 variants that reduced the enzyme activity was significantly less frequent in cases than controls. Smoked meat consumption, exposure to smoke, living in poorly ventilated house and alcohol consumption were associated with NPC development among the population of Northeastern India. Thus, overall our study revealed that EBV viral load and genetic polymorphism of CYP2A6 along with living practices which include smoked meat consumption, exposure to smoke, living in poorly ventilated houses and alcohol consumption are the potential risk factors of NPC in north eastern region of India. Understanding of the risk factors and their role in the etiology of NPC are helpful forpreventive measures and screening.

Developmental expression and corticosterone inhibition of adenosine deaminase activity in different tissues of mice

The activity expression and corticosterone inhibition of adenosine deaminase (ADA) were studied in the spleen, stomach, and liver of mice at various postnatal ages. The specific activity of ADA is very low in the spleen and stomach of 5- and 10-day-old mice, and increases significantly (2.5- to 3.0-fold) in 20- and 30-day-old animals. Its level shows a further increase in the spleen of 60-day-old mice while stomach increase of ADA is not significant. In contrast, the activity of ADA is significantly higher in the liver of 5- and 10-day-old mice, decreases markedly (2.5-fold) in 20- and 30-day-old animals and shows a sharp increase in the liver of 60-day-old mice. Corticosterone administration brings a marked inhibition in the activity of ADA at all ages studied in the spleen and stomach whereas it inhibits the liver ADA only at 30 and 60 days postnatal age. These findings suggest an age- and tissue-specific expression of ADA activity and also indicate corticosterone as an inhibitory regulator of this enzyme.

Prevalence of Drug Resistance Associated Mutations Among the Anti Retroviral Therapy Exposed HIV-1 Infected Individuals in Manipur, Northeast India

Background: Manipur is one of the highest HIV prevalence states of India because of its geographical location at the international border near the golden triangle of South-East Asia, but no study on drug resistance associated mutations (DRAMs) has been reported yet. Objective: A population-based study on DRAMs of HIV-1 among the anti-retroviral therapy (ART) exposed HIV-1 infected individuals of Manipur was conducted. Methods: 110 HIV-1 positive individuals who had initially exposed to first line anti-HIV drugs were recruited for the surveillance of DRAMs. Reverse transcriptase and protease genes of HIV-1 were amplified, sequenced and analyzed. Results: Significant prevalence of DRAMs of HIV-1 was found among the ART exposed HIV-1 infected individuals of Manipur. The results revealed that 37%, 29% and 7% individuals harbor HIV-1 strains mutated at the target sites of nonnucleoside reverse transcriptase inhibitors, nucleoside reverse transcriptase inhibitors and protease inhibitors respectively. Predominant DRAMs at RT genes were M184V, T215Y, M41L and V108I and H221Y while at PR genes were M46I and I47V. Among the high risk groups, intravenous drug users have the highest number of DRAMs followed by heterosexual individuals. Analysis of viral subtype based on pol gene revealed 83% subtype C, 11.8% recombinant forms and 5.2% subtype B. Conclusion: DRAMs at the target sites of reverse transcriptase inhibitors are high and these were found to have developed resistance to the primary ART drugs that are used in Manipur. The findings of this study will help the clinicians to guide patients during the course of ART treatment regimes.