Bis-indole-derived NR4A1 antagonists inhibit colon tumor and splenic growth and T-cell exhaustion

There is evidence that the orphan nuclear receptor 4A1 (NR4A1, Nur77) is overexpressed in exhausted CD8 + T cells and regulates PD-L1 in tumors. This study investigated the effects of potent bis-indole-derived NR4A1 antagonists on reversing T-cell exhaustion and downregulating PD-L1 in colon tumors/cells. NR4A1 antagonists inhibited colon tumor growth and downregulated expression of PD-L1 in mouse colon MC-38-derived tumors and cells. TILs from MC-38 cell-derived colon tumors and splenic lymphocytes exhibited high levels of the T-cell exhaustion markers including PD-1, 2B4, TIM3+ and TIGIT and similar results were observed in the spleen, and these were inhibited by NR4A1 antagonists. In addition, treatment with NR4A1 antagonists induced cytokine activation markers interferon γ, granzyme B and perforin mRNAs and decreased TOX, TOX2 and NFAT in TIL-derived CD8 + T cells. Thus, NR4A1 antagonists decrease NR4A1-dependent pro-oncogenic activity and PD-L1 expression in colon tumors and inhibit NR4A1-dependent T-cell exhaustion in TILs and spleen and represent a novel class of mechanism-based drugs that enhance immune surveillance in tumors.

Piperlongumine is a ligand for the orphan nuclear receptor 4A1 (NR4A1)

Piperlongumine and derivatives are being developed as anticancer agents which act primarily as inducers of reactive oxygen species (ROS) in cancer cell lines. Many of the anticancer activities of piperlongumine resemble those observed for bis-indole derived compounds that bind the orphan nuclear receptor 4A1 (NR4A1) and act as inverse receptor agonists to inhibit NR4A1-regulated pro-oncogenic pathways and genes. In this study we show that like other NR4A1 inverse agonists piperlongumine inhibited RKO, SW480 and HCT116 colon cancer cell growth migration and invasion and induced apoptosis. Piperlongumine also downregulated the pro-reductant isocitrate dehydrogenase 1 (IDH1) and thioredoxin domain-containing 5 (TXNDC5) gene products resulting in the induction of ROS as previously observed for other inverse NR4A1 agonists. ROS also induced sestrin2 and this resulted in activation of AMPK phosphorylation and inhibition of mTOR pathway signaling. It has previously been reported that these pathways/genes are also regulated by inverse NR4A1 agonists or by knockdown of NR4A1. We also observed that piperlongumine directly bound NR4A1, inhibited NR4A1-dependent transactivation and interactions of the NR4A1/Sp1 complex bound to the GC-rich promoter of the NR4A1-regulated G9a gene.

Flavonoids Quercetin and Kaempferol Are NR4A1 Antagonists and Suppress Endometriosis in Female Mice

Nuclear receptor 4A1 (NR4A1) plays an important role in endometriosis progression; levels of NR4A1 in endometriotic lesions are higher than in normal endometrium, and substituted bis-indole analogs (NR4A1) antagonists suppress endometriosis progression in mice with endometriosis. In addition, the flavonoids kaempferol and quercetin are natural products that directly bind NR4A1 and significantly repress the intrinsic NR4A1-dependent transcriptional activity in human endometriotic epithelial and stromal cells and Ishikawa endometrial cancer cells. NR4A1 knockdown and inhibition of NR4A1 by kaempferol and quercetin suppressed proliferation of human endometriotic epithelial cells and Ishikawa cells by inhibiting epidermal growth factor receptor/c-Myc/survivin-mediated growth-promoting and survival pathways, The mammalian target of rapamycin (mTOR) signaling and αSMA/CTGF/COL1A1/FN-mediated fibrosis signaling but increasing Thioredoxin domain Containing 5/SESN2-mediated oxidative/estrogen receptors stress signaling. In human endometriotic stromal cells, NR4A1 knockdown and inhibition of NR4A1 by kaempferol and quercetin primarily inhibited mTOR signaling by suppressing proliferation of human endometrial stromal cells. In addition, kaempferol and quercetin treatment also effectively suppressed the growth of endometriotic lesions in mice with endometriosis compared with the vehicle without any body weight changes. Therefore, kaempferol and quercetin are NR4A1 antagonists with potential as nutritional therapy for endometriosis.

Abstract 236: Nuclear receptor 4A1 ligands target T-cell exhaustion in colorectal cancer

Colorectal cancer (CRC) is a highly complex disease with multiple risk factors. The orphan nuclear receptor 4A1 (NR4A1) is overexpressed in several cancers and is a negative prognostic factor for cancer patient survival. Previous reports indicate a potential role for overexpression of NR4A1 in T-cell exhaustion and in this study, we aim to investigate the antitumorigenic activity of two bis-indole derived ligands (DIMs) that act as receptor antagonists. Immune competent C57BL/6 mice and mouse MC-38 colon cancer cells were used and tumor Infiltrating Lymphocytes (TILs) were isolated from mice either untreated or treated with CDIM/NR4A1 antagonists. FACS analysis and Real -Time PCR were performed to determine expression of exhaustion markers in these tumor T-cell population. 1,1-Bis(3΄-indolyl)-1-(3-bromo-5-trifluoromethoxyphenyl)methane (DIM-3-Br-5-OCF3) and the 3,5-dichlorophenyl analog (DIM-3,5-Cl2) at doses of 2.5 and 7.5 mg/kg/d inhibited tumor growth and downregulated expression of PD-L1, an NR4A1-regulated gene in MC-38 - derived tumors and cells. The mouse MC-38 colon cancer cell line was used in a syngeneic mouse model of colon cancer and tumor infiltrating lymphocytes (TILs) from MC-38 cell-derived colon tumors exhibited multiple markers of T-cell exhaustion in both CD8+ and CD4+ T-cells. Lymphocytes from an enlarged spleen in these tumor-bearing animals also exhibited markers of CD8+ and CD4+ T-cell exhaustion. Analysis of CD8+ cells from TILs showed that treatment with the NR4A1 antagonists modulated expression of several genes associated with T-cell exhaustion namely a decrease in TOX, TOX2 and NFAT mRNAs, activation of T-Bet. The percentage of CD8+ and CD4+ T-cells from tumors and spleen expressing PD-1, 2B4 and TIGIT was decreased in the treated vs control mice and TIM3 expression was also decreased in CD8+ (tumors and spleen) and CD4+ (tumors) T-cells. These findings suggest that NR4A1 antagonists are highly effective as anticancer agents in this mouse syngeneic colon tumor model by inactivating the pro-oncogenic activities of NR4A1 in tumors and by remediating NR4A1-regulated T-cell exhaustion in tumor and splenic lymphocytes.

Citation Format: Kumaravel Mohankumar, Gus Wright, Subhashree Kumaravel, Rupesh Shrestha, Lei Zhang, Maen Abdelrahim, Robert S. Chapkin, Stephen Safe. Nuclear receptor 4A1 ligands target T-cell exhaustion in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 236.

Nuclear receptor 4A1 (NR4A1) antagonists target paraspeckle component 1 (PSPC1) in cancer cells

Paraspeckles compound 1 (PSPC1) is a multifunctional protein that plays an important role in cancer cells, where PSPC1 is a master regulator of pro-oncogenic responses that includes activation of TGFβ (TGFβ1), TGFβ-dependent EMT, and metastasis. The pro-oncogenic activities of PSPC1 closely resembled those observed for the orphan nuclear receptor 4A1 (NR4A1, Nur77) and knockdown of NR4A1 decreased expression of PSPC1 in MDA-MB-231 breast, H1299 lung, and SNU449 liver cancer cells. Similar results were observed in these same cell lines after treatment with bisindole-derived (CDIMs) NR4A1 antagonists. Moreover, PSPC1-dependent regulation of TGFβ, genes associated with cancer stem cells and epithelial to mesenchymal transition (EMT) were also downregulated after NR4A1 silencing or treatment of breast, lung, and liver cancer cells with CDIM/NR4A1 antagonists. Results of chromatin immunoprecipitation (ChIP) assays suggest that NR4A1 regulates PSPC1 through interaction with an NBRE sequence in the PSPC1 gene promoter. These results coupled with in vivo studies showing that NR4A1 antagonists inhibit breast tumor growth and downregulate PSPC1 in tumors indicate that the pro-oncogenic nuclear PSPC1 factor can be targeted by CDIM/NR4A1 antagonists.

Orphan nuclear receptor 4A1 (NR4A1) and novel ligands

The nuclear receptor (NR) superfamily of transcription factors encodes expression of 48 human genes that are important for maintaining cellular homeostasis and in pathophysiology, and this has been observed for all sub-families including orphan receptors for which endogenous ligands have not yet been identified. The orphan NR4A1 (Nur77 and TR3) and other members of this sub-family (NR4A2 and NR4A3) are immediate early genes induced by diverse stressors, and these receptors play an important role in the immune function and are up-regulated in some inflammatory diseases including solid tumors. Although endogenous ligands for NR4A have not been identified, several different classes of compounds have been characterized as NR4A1 ligands that bind the receptor. These compounds include cytosporone B and structurally related analogs, bis-indole derived (CDIM) compounds, the triterpenoid celastrol and a number of other chemicals including polyunsaturated fatty acids. NR4A1 ligands bind different regions/surfaces of NR4A1 and exhibit selective NR4A1 modulator (SNR4AM) activities that are dependent on ligand structure and cell/tissue context. NR4A1 ligands exhibit pharmacologic activities in studies on cancer, endometriosis metabolic and inflammatory diseases and are promising agents with clinical potential for treating multiple diseases.

Flavonoids kaempferol and quercetin are nuclear receptor 4A1 (NR4A1, Nur77) ligands and inhibit rhabdomyosarcoma cell and tumor growth

BACKGROUND

Flavonoids exhibit both chemopreventive and chemotherapeutic activity for multiple tumor types, however, their mechanisms of action are not well defined. Based on some of their functional and gene modifying activities as anticancer agents, we hypothesized that kaempferol and quercetin were nuclear receptor 4A1 (NR4A1, Nur77) ligands and confirmed that both compounds directly bound NR4A1 with KD values of 3.1 and 0.93 μM, respectively.

METHODS

The activities of kaempferol and quercetin were determined in direct binding to NR4A1 protein and in NR4A1-dependent transactivation assays in Rh30 and Rh41 rhabdomyosarcoma (RMS) cells. Flavonoid-dependent effects as inhibitors of cell growth, survival and invasion were determined in XTT and Boyden chamber assays respectively and changes in protein levels were determined by western blots. Tumor growth inhibition studies were carried out in athymic nude mice bearing Rh30 cells as xenografts.

RESULTS

Kaempferol and quercetin bind NR4A1 protein and inhibit NR4A1-dependent transactivation in RMS cells. NR4A1 also regulates RMS cell growth, survival, mTOR signaling and invasion. The pro-oncogenic PAX3-FOXO1 and G9a genes are also regulated by NR4A1 and, these pathways and genes are all inhibited by kaempferol and quercetin. Moreover, at a dose of 50 mg/kg/d kaempferol and quercetin inhibited tumor growth in an athymic nude mouse xenograft model bearing Rh30 cells.

CONCLUSION

These results demonstrate the clinical potential for repurposing kaempferol and quercetin for clinical applications as precision medicine for treating RMS patients that express NR4A1 in order to increase the efficacy and decrease dosages of currently used cytotoxic drugs.

725 Immunomodulation by targeting PDL-1 in colon cancer using nuclear receptor 4A1 (NR4A1) antagonists

Background

The nuclear orphan receptor 4A1 (NR4A1, Nur77, TR3) is overexpressed in multiple solid tumors including colorectal tumors and is a negative prognostic factor for patient survival.1–3 NR4A1 is expressed in colon cancer cells and exhibit pro-oncogenic activity4 and results of examination of several colon cancer cell lines show that PD-L1 expression is limited and NR4A1 and PD-L1 are co-expressed in SW480 and RKO colon cancer cell lines. Previous studies showed that PD-L1 was regulated by NR4A1 which activates transcription factor Sp1 bound to the PD-L1 gene promoter.5–7 Knockdown of NR4A1 or Sp1 by RNA interference or treatment with mithramycin an inhibitor of Sp-mediated transcription decreased expression of PD-L1 in RKO and SW480 colon cancer cell lines.

Methods

SW480, RKO and MC-38 cells were used in this study. Cells were treated for 24 hrs with DIM series of compounds.

Results

Current data coupled with ongoing gene expression and PD-L1 promoter studies demonstrate that PD-L1 expression is regulated by NR4A1/Sp1 in colon cancer cells (figures 1–3). Bis-indole derived NR4A1 ligand that act as receptor antagonists have been developed in this laboratory and these compounds block pro-oncogenic NR4A1-regulated genes/pathways. Treatment of RKO and SW480 colon cancer cell lines with a series of potent 1,1-bis(3′-indolyl)-1-(3,5-disubstitutedphenyl) analogs decreased expression of PD-L1. These results show that bis-indole derived NR4A1 antagonists act as small molecule mimics of immunotherapeutics that target PD-L1. In vivo applications of NR4A1 ligands that target PD-L1 and their effects on tumor growth and immune surveillance are currently being investigated.

Conclusions

Bis-indole derived NR4A1 antagonists inhibit PD-L1 expression. NR4A1/SP1 regulates PD-L1 and is inhibited by NR4A1 antagonist. NR4A1 ligands such as DIM-3-Br-5-OCF3 were among the most potent of the substituted DIM compounds and ongoing in vivo studies show that this DIM compound also inhibits tumor growth in a syngenic mouse model (data not shown). Data from this study demonstrate the pro-oncogenic activity of NR4A1 and show that the synthetic buttressed analog DIM-3-Br-5-OCF3 acts as an NR4A1 antagonist and inhibits PD-L1 expression. These drugs can be developed for future clinical applications.

References

www.cancer.org/cancer/colon-rectal-cancer/about/key-statistics.html.

Garcia-Villatoro et al., Effects of high-fat diet and intestinal aryl hydrocarbon receptor deletion on colon carcinogenesis. Am J Physiol Gastrointest Liver Physiol 2020;318(3):G451–G463.

Safe S, Jin UH, Hedrick E, et al. Minireview: role of orphan nuclear receptors in cancer and potential as drug targets. Mol Endocrinol 2014;28(2):157–72.

Maxwell MA, Muscat GE. The NR4A subgroup: immediate early response genes with pleiotropic physiological roles. Nucl Recept Signal 2006;4:e002.

Lee SO, Li X, Hedrick E, et al. Diindolylmethane analogs bind NR4A1 and are NR4A1 antagonists in colon cancer cells. Mol Endocrinol 2014;28(10):1729–39.

Safe S, Kim K. Non-classical genomic estrogen receptor (ER)/specificity protein and ER/activating protein-1 signaling pathways. J Mol Endocrinol 2008;41(5):263–75.

Tao LH, Zhou XR, Li FC, Chen Q, Meng FY, Mao Y, et al. A polymorphism in the promoter region of PD-L1 serves as a binding-site for SP1 and is associated with PD-L1 overexpression and increased occurrence of gastric cancer. Cancer Immunol Immunother 2017;66(3):309–18.

Abstract 725 Figure 1

NR4A1 inactivation inhibits PD-L1 expression. SW480, RKO and MC-38 cells were transfected with siCtrl (non-specific oligonucleotide) and two oligonucleotides targeting NR4A1 (siNR4A1(1) and siNR4A1(2)) or PD-L1 (siPD-L1(1) and siPD-L1(2)) for 72 hrss. Protein expression from whole cell lysates were analyzed by western blots and effects on PD-L1 expression were determined

Abstract 725 Figure 2

Sp1 inactivation inhibits PD-L1 expression. SW480, RKO and MC-38 cells were transfected with siCtrl and oligonucleotides targeting Sp1 (siSp1(1) and siSp1(2)) for 72 hrs as well as treated with Mithrsamycin (150 and 300 nM) for 24 hrs. Protein expression from was analyzed by western blots and effects on PD-L1 levels were determined.

Abstract 725 Figure 3

Role of NR4A1/Sp in regulation of PD-L1. SW480, RKO and MC-38 cells were treated with DIM-3-Br-5-OCF3 for 24 hrss and protein interactions with the GC-rich PD-L1 promoter region were analyzed by ChIP using primers encompassing GC-rich region of the promoter

732 A novel nuclear receptor 4A1 (NR4A1) antagonists attenuates T-cell exhaustion in colorectal cancer

Background

Colorectal cancer (CRC) is a highly complex disease with multiple risk factors and both genetic and environmental components contribute to disease incidence.1 2 Cancer immunotherapy using immune-checkpoint blockades represents a major advance in treatment strategy.3 4 The orphan nuclear receptor 4A1 (NR4A1) is overexpressed in lung, colon, liver and breast cancers and in Rhabdomyosarcoma and is a negative prognostic factor for cancer patient survival.5–8 Previous studies in breast cancer cells showed that PD-L1 was regulated by NR4A1 which activates transcription factor Sp1 bound to the PD-L1 gene promoter. Genome-wide studies have identified NR4A1 as a key mediator of T-cell dysfunction and NR4A1 also plays an important role in regulating genes which are involved in tumor-induced T-cell exhaustion.9 Bis-indole derived NR4A1 ligand that act as receptor antagonists have been developed in this laboratory and these compounds block pro-oncogenic NR4A1-regulated genes/pathways.

Methods

Immune competent C57BL/6 mice and mouse MC-38 colon cancer cells were used and tumor Infiltrating Lymphocytes (TILs) were isolated from mice either untreated or treated with CDIM/NR4A1 antagonists. FACS analysis and Real -Time PCR were performed to determine expression of exhaustion markers in these tumor T-cell population.

Results

Two compounds:

1,1-bis(3′-indolyl)-1-(3-bromo-5-trifluoromethoxyphenyl)methane (DIM-3-Br-5-OCF3) and 3,5-dichlorophenyl analog (DIM-3,5-Cl2) inhibited tumor growth and weight at doses of 2.5 and 7.5mg/kg/day (figure 1). Tumor CD8+ T-cells isolated from mice treated with DIM-3,5-Cl2 and DIM-3-Br-5-OCF3 exhibited decreased mRNA expression of NR4A1 and high mobility group – box transcription factors NFAT, TOX and TOX2 and increased mRNA levels of Interferon-γ (IFNγ), granzyme β (GzB) and perforin compared to control animals (figure 2). As TOX and TOX2 cooperate with NR4A1 to modulate CD8+ T-cell exhaustion, we investigated the expression of several inhibitory receptors of T-cell exhaustion in CD8+ TILs, including PD-1, 2B4, TIGIT and TIM3. Following treatment with DIM-3,5-Cl2 or DIM-3-Br-5-OCF3, there was a significant decrease in the percentage of PD1 and 2B4 cells and a decrease in TIGIT and TIM3 (figure 3). These results indicate that NR4A1 antagonists reverses T-cell exhaustion.

Conclusions

NR4A1 plays a critical role in T-cell dysfunction, and this includes T-cell exhaustion.10 11 Our results demonstrate that the NR4A1 antagonists reverse many markers of T-cell exhaustion including activation of cytokines. The combined effects of NR4A1 antagonists in both tumors and T-cells result in inhibition of colon tumorigenesis by targeting pathways/genes in tumor cells and by enhancing immune surveillance via reversal of T-cell exhaustion.

References

Ahmed M. Colon cancer: a Clinician's perspective in 2019. Gastroenterology Res 2020;13(1):1–10. Epub 2020/02/26. doi: 10.14740/gr1239.

Keum N, Giovannucci E. Global burden of colorectal cancer: emerging trends, risk factors and prevention strategies. Nat Rev Gastroenterol Hepatol 2019;16(12):713–32. Epub 2019/08/29. doi: 10.1038/s41575-019-0189-8.

Pardoll DM. The blockade of immune checkpoints in cancer immunotherapy. Nat Rev Cancer 2012;12(4):252–64. Epub 2012/03/23. doi: 10.1038/nrc3239.

Ribas A, Wolchok JD. Cancer immunotherapy using checkpoint blockade. Science 2018;359(6382):1350–1355.

Yang et al. Distinct epigenetic features of tumor-reactive CD8+ T cells in colorectal cancer patients revealed by genome-wide DNA methylation analysis. Genome Biol 2019;21(1):2. doi: 10.1186/s13059-019-1921-y.

Safe S, Karki K. The paradoxical roles of orphan nuclear receptor 4A (NR4A) in cancer. Mol Can Res 2020. Epub 2020/10/28. doi: 10.1158/1541-7786.MCR-20-0707.

Lee SO, et al. Diindolylmethane analogs bind NR4A1 and are NR4A1 antagonists in colon cancer cells. Molecular Endocrinology. 2014;28(10):1729–39. doi: 10.1210/me.2014-1102.

Hedrick E, et al. The nuclear orphan receptor NR4A1 regulates β1-integrin expression in pancreatic and colon cancer cells and can be targeted by NR4A1 antagonists. Mol Carcinog 2017;56(9):2066–2075.

Liu X, et al. Genome-wide analysis identifies NR4A1 as a key mediator of T cell dysfunction. Nature 2019;567(7749):525–9. Epub 2019/03/01. doi: 10.1038/s41586-019-0979-8.

Chen J et al. NR4A transcription factors limit CAR T cell function in solid tumours. Nature. 2019;567(7749):530–4. Epub 2019/03/01. doi: 10.1038/s41586-019-0985-x. PubMed PMID: 30814732; PMCID: PMC6546093.

Seo H, et al. TOX and TOX2 transcription factors cooperate with NR4A transcription factors to impose CD8(+) T cell exhaustion. Proc Natl Acad Sci USA 2019;116(25):12410–5.

Ethics Approval

All animal studies were carried out according to the ethical procedures approved by the Texas A&M University Institutional Animal Care and Use Committee. Approval number is 2020-0138.

Abstract 732 Figure 1

CDIM/NR4A1 antagonists inhibit colon tumor growth. Model for regulation of genes with GC-rich promoters by NR4A1/SP1 (A). C57BL/6 mice bearing MC-38 cells as xenografts were treated for 21 days with corn oil (control), DIM-3-Br-5-OCF3 (2.5 and 7.5 mg/kg/d), DIM-3,5-Cl2 (2.5 and 7.5 mg/kg/d) and effects on tumor volume (B), and tumor weights (C) were determined.

Abstract 732 Figure 2

CDIM analogs alter transcription factors expression. FACS analysis and CD4 and CD8 – specific antibodies were used to determine T-cell population in tumors of mice treated with corn oil (control), DIM-3-Br-5-OCF3 (2.5 and 7.5 mg/kg/d) and DIM-3,5-Cl2 (2.5 and 7.5 mg/kg/d) (A). Real time PCR was used to determine expression of nuclear factors (B) and cytokine (C) mRNA levels in CD8+ T-cells isolated from tumors. Results are expressed as means ± SD replicates from each treatment group and significant (p<0.05) induction or inhibition is indicated (*)

Abstract 732 Figure 3

NR4A1 ligands decreases T-cell exhaustion markers. FACS analysis in tumors derived from mice treated with corn oil (control), DIM-3-Br-5-OCF3 (2.5 and 7.5 mg/kg/d) and DIM-3,5-Cl2 (2.5 and 7.5 mg/kg/d) using specific antibodies was carried out to determine percentage of CD8+ T-cells expressing T-cell exhaustion markers - PD1 (A), 2B4 (B), TIGIT (C) and TIM3 (D). Significant (p<0.05) induction or inhibition is indicated (*) and results are expressed as means ± SD for at least 4 separate mice per treatment group.

Transcription factors specificity protein and nuclear receptor 4A1 in pancreatic cancer

Specificity protein (Sp) transcription factors (TFs) Sp1, Sp3 and Sp4, and the orphan nuclear receptor 4A1 (NR4A1) are highly expressed in pancreatic tumors and Sp1 is a negative prognostic factor for pancreatic cancer patient survival. Results of knockdown and overexpression of Sp1, Sp3 and Sp4 in pancreatic and other cancer lines show that these TFs are individually pro-oncogenic factors and loss of one Sp TF is not compensated by other members. NR4A1 is also a pro-oncogenic factor and both NR4A1 and Sp TFs exhibit similar functions in pancreatic cancer cells and regulate cell growth, survival, migration and invasion. There is also evidence that Sp TFs and NR4A1 regulate some of the same genes including survivin, epidermal growth factor receptor, PAX3-FOXO1, α5- and α6-integrins, β1-, β3- and β4-integrins; this is due to NR4A1 acting as a cofactor and mediating NR4A1/Sp1/4-regulated gene expression through GC-rich gene promoter sites. Several studies show that drugs targeting Sp downregulation or NR4A1 antagonists are highly effective inhibitors of Sp/NR4A1-regulated pathways and genes in pancreatic and other cancer cells, and the triterpenoid celastrol is a novel dual-acting agent that targets both Sp TFs and NR4A1.

696 Are Group and Save Samples Necessary for Common Urological Procedures?

Aim

Blood tests are routinely performed as a part of pre-operative assessment (pre-op). We looked at the number of group and save (G+S) samples taken at pre-op and compared that to the number of patients needing blood transfusion having undergone common Urological procedures at our hospital. Our objective was to assess the utility of this invasive procedure in this clinical setting.

Method

Data was retrospectively collected from electronic patient records on 413 patients undergoing elective urological procedures 1st June 2020 to 30th September 2020 at Colchester General Hospital. Major procedures like radical prostatectomies, nephrectomies were excluded. Patients who had G+S samples done prior to surgery were checked. This was compared to the patients who required transfusions.

Results

Amongst 413 patients who underwent an elective urological procedure, 169(41%) were day-case endoscopic, 151(37%) were inpatient, and 93(22%) were penoscrotal procedures. 104(25%) patients had G+S taken, with only 5 patients (1.2%) requiring transfusion. 24(14.2%) patients undergoing day case procedures,79(52.3%) patients undergoing inpatient procedures and 1(1.1%) patient undergoing penoscrotal procedures had G+S tests done. Only 7(1.7%) patients had a baseline haemoglobin of less than 100.

Conclusions

Our data showed that many G+S samples were unnecessary. TURBTs (transurethral resection of bladder tumours) were most likely to need transfusion. Education was fed-back to those running pre-operative assessment clinics that G+S should be considered for TURBTs and those with Hb &lt; 100. We recommend running this audit again to further quantify the G+S tests which could be avoided.

Synthetic curcumin analog: inhibiting the invasion, angiogenesis, and metastasis in human laryngeal carcinoma cells via NF-kB pathway

BACKGROUND

Laryngeal carcinoma, the most common among head and neck squamous cell carcinoma (HNSCC), induces 1% of all cancer deaths. Curcumin the active constituent of turmeric, is shown to be effective in the treatment of various cancers. In the present study, we explored the mechanistic role of bis-demethoxy curcumin analog (BDMC-A) as a chemotherapeutic agent. We investigated its inhibitory effect on invasion, angiogenesis, and metastasis in human laryngeal carcinoma (Hep-2) cells in comparison with curcumin.

METHODS

The effect of curcumin and BDMC-A on transcription factors (NF-κB, p65, c-Jun, c-Fos, STAT3, 5, PPAR-γ, β-catenin, COX-2, MMP-9, VEGF, TIMP-2) involved in signal transduction cascade, invasion, and angiogenesis in Hep-2 cells were quantified using Western blotting and RT-PCR technique. ELISA was used to measure the pro-inflammatory markers in Hep-2 cells treated with curcumin and BDMC-A.

RESULTS

The results showed that BDMC-A inhibits the transcription factors NF-κB, p65, c-Jun, c-Fos, STAT3, STAT5, PPAR-γ and β-catenin, which are responsible for tumor progression and malignancy. Moreover, BDMC-A treatment downregulated MMP-9, VEGF, TGF- β, IL-6 and IL-8 and upregulated TIMP-2 levels. The effects were more significant compared to curcumin.

CONCLUSION

Our overall results revealed that BDMC-A more effectively inhibited the markers of invasion, angiogenesis and metastasis in comparison with curcumin.

Abstract 2428: NR4A1 ligands inhibits PSPC1 regulated EMT and stemness markers in breast, lung and liver cancer cells

The orphan nuclear receptor 4A1 (Nur77, TR3, NR4A1) is highly expressed in solid tumors and is a negative prognostic factor for survival of breast, lung, and liver cancer patients (1) and ongoing studies in our laboratory show that NR4A1 is pro-oncogenic in multiple tumor types. We have also identified a series of bis-indole derived compounds including 1,1-bis(3'-indolyl)-1-(p-hydroxyphenyl) methane (DIM-C-pPhOH; CDIM8) that act as NR4A1 antagonists that inhibit pro-oncogenic NR4A1-regulated genes and pathways in multiple cancer cell lines (2). Mechanistic studies show that many of the NR4A1-regulated genes involve interactions of NR4A1 with gene promoter DNA or with Sp-bound to GC-rich sequences and similar mechanisms have previously been observed for steroid hormone and other nuclear receptors. Our studies have identified paraspeckle component 1 (PSPC1) as an NR4A1 regulated gene in breast, lung and liver cancer cells and PSPC1 gene expression and protein levels are suppressed after treatment with C-DIM/NR4A1 antagonists. PSPC1 promotes tumorigenesis, epithelial-to-mesenchymal transition (EMT), stemness and metastasis and is a master activator of pro-metastatic switches and a potential target for anti-metastatic drugs. Knockdown of PSPC1 downregulates EMT and stemness markers in breast, lung and liver cancer cells. The novel buttressed analog of CDIM8 (DIM-C-pPhOH-3-Br-5-OCF3) at a concentration of 10 uM downregulates PSPC1 expression and its downstream targets (Snail, Slug, Nanog, OCT4, SOX2, c-myc). Knockdown of NR4A1 or SP1 inhibits PSPC1 expression in MDA-MB-231, H1299 and SNU449 cell lines respectively. These results identify PSPC1 as a novel gene that regulates EMT and invasion in these cancer cells and NR4A1 is an upstream regulator of PSPC1 gene expression. Thus, NR4A1 ligands act as an antimetastatic mimic by inhibiting PSPC1 and the mechanism of PSPC1 regulation involves ligand induced interactions of NR4A1/SP1 with a GC-rich region of the PSPC1 gene promoter.

References:1.Safe S, Jin UH, Hedrick E, Reeder A, Lee SO.

Minireview: Role of orphan nuclear receptors in cancer and potential as drug targets. Mol Endocrinol. 2014;28(2):157-72.

2.Mohankumar K, Li X, Sridharan S, Karki K, Safe S. Nuclear receptor 4A1 (NR4A1) antagonists induce ROS-dependent inhibition of mTOR signaling in endometrial cancer. Gynecol Oncol. 2019; 154(1):218-227.

Citation Format: Kumaravel Mohankumar, Rupesh Shrestha, Stephen Safe. NR4A1 ligands inhibits PSPC1 regulated EMT and stemness markers in breast, lung and liver cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2428.

Abstract 1149: Nuclear receptor 4A1 (NR4A1) antagonists target PD-L1 in colon cancer

The nuclear orphan receptor 4A1 (NR4A1, Nur77, TR3) is overexpressed in multiple solid tumors including colorectal tumors and is a negative prognostic factor for patient survival. NR4A1 is expressed in colon cancer cells and exhibit pro-oncogenic activity and results of examination of several colon cancer cell lines show that PD-L1 expression is limited and NR4A1 and PD-L1 are co-expressed in SW480 and RKO colon cancer cell lines. Previous studies in breast cancer cells showed that PD-L1 was regulated by NR4A1 which activates transcription factor Sp1 bound to the PD-L1 gene promoter. Knockdown of NR4A1 or Sp1 by RNA interference or treatment with mithramycin an inhibitor of Sp-mediated transcription decreased expression of PD-L1 in RKO and SW480 colon cancer cell lines. These data coupled with ongoing gene expression and PD-L1 promoter studies demonstrate that PD-L1 expression is regulated by NR4A1/Sp1 in colon cancer cells. Bis-indole derived NR4A1 ligand that act as receptor antagonists have been developed in this laboratory and these compounds block pro-oncogenic NR4A1-regulated genes/pathways. Treatment of RKO and SW480 colon cancer cell lines with a series of potent 1,1-bis(3′-indolyl)-1-(3,5-disubstitutedphenyl) analogs decreased expression of PD-L1. These results show that bis-indole derived NR4A1 antagonists act as small molecule mimics of immunotherapeutics that target PD-L1. In vivo applications of NR4A1 ligands that target PD-L1 and their effects on tumor growth and immune surveillance are currently being investigated.

Citation Format: Kumaravel Mohankumar, Keshav Karki, Stephen Safe, Maen Abdelrahim. Nuclear receptor 4A1 (NR4A1) antagonists target PD-L1 in colon cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1149.

Abstract 629: Flavonoids are NR4A1 antagonists and target PAX3-FOXO1 and G9a in alveolar rhabdomyosarcoma cells

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma that is primarily observed in children and adolescent, and accounts for 50% of soft tissue sarcomas in children. There are two major forms of RMS, namely embryonal RMS (ERMS) and alveolar RMS (ARMS) and these tumors are readily distinguished by their histological and genomic characteristics. ERMS patients have a better prognosis than ARMS patients and both groups undergo radiation, surgical and chemotherapeutic regiments. Many ARMS patients express different oncogenes including the histone methyltransferase G9a and the PAX3-FOXO1 fusion gene that contribute to ARMS cell growth, survival and migration/invasion. Studies in this laboratory have demonstrated that both G9a and PAX3-FOXO1 are regulated by the orphan nuclear receptor 4A1 (NR4A1) and can be targeted by bis-indole derived (CDIMs) NR4A1 antagonists. A recent study showed that the flavonoid kaempferol decreased G9a expression in gastric cancer cells and we hypothesized that kaempferol may be an NR4A1 ligand. Kamepferol and quercetin were used as models and both compounds bound NR4A1 at low μM concentrations and decreased NR4A1-dependent transactivation in ARMS cells. Functional studies showed that like CDIM/NR4A1 ligands, kaempferol and quercetin decrease ARMS cell growth, survival and migration/invasion, consistent with their activity as antagonists and inhibitors of NR4A1 regulated pro-oncogenic functions. In addition, kaempferol and quercetin also decreased expression of G9a, PAX3-FOXO1 and downstream genes regulated by them in ARMS cells further demonstrating their activity as NR4A1 antagonists. These results suggest that NR4A1-active flavonoids could be readily incorporated into chemotherapies used for treatment of ARMS patients to improve their efficacy and decrease the toxic side-effects of currently used cytotoxic drugs.

Citation Format: Rupesh Shrestha, Kumaravel Mohankumar, Gregory Martin, Stephen Safe. Flavonoids are NR4A1 antagonists and target PAX3-FOXO1 and G9a in alveolar rhabdomyosarcoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 629.

Flavonoids: structure-function and mechanisms of action and opportunities for drug development

Flavonoids are polyphenolic phytochemicals produced in fruits, nuts and vegetables and dietary consumption of these structurally diverse compounds is associated with multiple health benefits including increased lifespan, decreased cardiovascular problems and low rates of metabolic diseases. Preclinical studies with individual flavonoids demonstrate that these compounds exhibit anti-inflammatory and anticancer activities and they enhance the immune system. Their effectiveness in both chemoprevention and chemotherapy is associated with their targeting of multiple genes/pathways including nuclear receptors, the aryl hydrocarbon receptor (AhR), kinases, receptor tyrosine kinases and G protein-coupled receptors. However, despite the remarkable preclinical activities of flavonoids, their clinical applications have been limited and this is due, in part, to problems in drug delivery and poor bioavailability and these problems are being addressed. Further improvements that will expand clinical applications of flavonoids include mechanism-based precision medicine approaches which will identify critical mechanisms of action of individual flavonoids with optimal activities that can be used in combination therapies.

The Histone Methyltransferase Gene G9A Is Regulated by Nuclear Receptor 4A1 in Alveolar Rhabdomyosarcoma Cells

The histone methyltransferase G9A (EHMT2) gene catalyzes methylation of histone 3 lysine 9 (H3K9), and this gene silencing activity contributes to the tumor promoter-like activity of G9A in several tumor types including alveolar rhabdomyosarcoma (ARMS). Previous studies show the orphan nuclear receptor 4A1 (NR4A1, Nur77) is overexpressed in rhabdomyosarcoma and exhibits pro-oncogenic activity. In this study, we show that knockdown of NR4A1 in ARMS cells decreased expression of G9A mRNA and protein. Moreover, treatment of ARMS cells with several bis-indole-derived NR4A1 ligands (antagonists) including 1,1-bis(3'-indolyl)-1-(4-hydroxyphenyl)methane (CDIM8), 3,5-dimethyl (3,5-(CH₃)₂), and 3-bromo-5-methoxy (3-Br-5-OCH₃) analogs also decreased G9A expression. Furthermore, NR4A1 antagonists also decreased G9A expression in breast, lung, liver, and endometrial cancer cells confirming that G9A is an NR4A1-regulated gene in ARMS and other cancer cell lines. Mechanistic studies showed that the NR4A1/Sp1 complex interacted with the GC-rich 511 region of the G9A promoter to regulate G9A gene expression. Moreover, knockdown of NR4A1 or treatment with NR4A1 receptor antagonists decreased overall H3K9me2, H3K9me2 associated with the PTEN promoter, and PTEN-regulated phospho-Akt. In vivo studies showed that the NR4A1 antagonist (3-Br-5-OCH₃) inhibited tumor growth in athymic nude mice bearing Rh30 ARMS cells and confirmed that G9A was an NR4A1-regulated gene that can be targeted by NR4A1 receptor antagonists.

Indole Curcumin Reverses Multidrug Resistance by Reducing the Expression of ABCB1 and COX2 in Induced Multidrug Resistant Human Lung Cancer Cells

Background:

Drug resistance by the cancer cells towards current chemotherapeutic approaches poses a great challenge. In the present study, an indole analogue of a well-known plant derived anticancer molecule, curcumin, was tested for its Multidrug Resistance (MDR) reversing potential in induced multi drug resistant A549 cell line.

Materials and Methods:

Human lung cancer cell line A549 was made Multidrug Resistant (MDR) by prolonged treatment with low dosage of Docetaxel, an established anticancer drug. The MDR induction was confirmed by morphological evidence, Hoechst 33342 staining, MTT assay, Rhodamine123 staining and RT-PCR of ABCB1 gene. Protein expression studies were carried out using western blotting technique

Results and Discussions:

The induced MDR A549 cells exhibited significant increase in the gene expression of ABCB1 gene at the transcriptional level. Retention and efflux studies with Pglycoprotein (P-gp) substrate Rh123 indicated that indole curcumin inhibited P-gp mediated efflux of Rhodamine. Furthermore, treatment of MDR A549 cells with indole curcumin showed downregulation of gene expression of ABCB1 and COX 2. This was also confirmed from the decreased protein expression of COX 2.

Conclusion:

The results of the present study indicate that indole curcumin reverses multi drug resistance by downregulating the expression of ABCB1 and COX 2 genes. Thus, indole curcumin may act as a potent modulator for ABCB1 and COX 2 mediated MDR in lung cancer.

Bis-indole derived nuclear receptor 4A1 (NR4A1) antagonists inhibit TGFβ-induced invasion of embryonal rhabdomyosarcoma cells

Transforming growth factor β (TGFβ) enhances invasion of breast and lung cancer cells through phosphorylation-dependent nuclear export of the nuclear receptor 4A1 (NR4A1, Nur77). This response is inhibited by the NR4A1 antagonist 1,1-bis(3'-indoly)-1-(p-hydroxyphenyl) methane (CDIM8) and we hypothesized that similar effects would be observed in Rhabdomyosarcoma (RMS) cells. Although some kinase inhibitors block TGFβ-induced invasion of embryonal RMS (ERMS) cells, the mechanism differs from breast and lung cancer cells since NR4A1 is extranuclear in ERMS cells. However, CDIM8 blocks basal and TGFβ-induced invasion of RD and SMS-CTR ERMS cell lines but not Rh30 alveolar RMS (ARMS) cells. Moreover, this response in ERMS cells was independent of SMAD7 degradation or activation of SMAD2/SMAD3. β-Catenin silencing decreased ERMS cell invasion and CDIM8 induced proteasome-independent downregulation of β-catenin. The novel mechanism of CDIM8-mediated inhibition of basal and TGFβ-induced ERMS cell invasion was due to activation of the Bcl-2-NR4A1 complex, mitochondrial disruption, induction of the tumor suppressor-like cytokine interleukin-24 (IL-24) which in turn downregulates β-catenin expression. Thus, the NR4A1 antagonist inhibits TGFβ-induced invasion of ERMS cells through initial targeting of cytosolic NR4A1.

Bis-Indole-Derived Nuclear Receptor 4A1 (NR4A1, Nur77) Ligands as Inhibitors of Endometriosis

Endometriosis is an inflammatory disease that primarily affects women during their reproductive years, and since current hormonal therapies are of concern, new hormone-independent treatment regimens are needed. The orphan nuclear receptor 4A1 (NR4A1, Nur77) is expressed in patient-derived (stromal) endometriotic cells and also epithelial cell lines, and we observed that knockdown of NR4A1 in patient-derived ectopic endometrium-isolated ovarian endometrioma (ESECT)-7 and ESECT-40 cells decreased cell proliferation and induced apoptosis. Moreover, the treatment of these cells with bis-indole derived NR4A1 ligands 1,1-bis(3'-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH) and its buttressed 3-chloro-5-methoxy analog (DIM-C-pPhOH-3-Cl-5-OCH3) inhibited cell growth and induced apoptosis and related genes. The compounds exhibit NR4A1 antagonist activities in both functional and transactivation assays whereas these effects were not observed in normal endometrial cells. We also observed that NR4A1 knockdown and treatment with NR4A1 antagonists decreased fibrosis, α-smooth muscle actin, and related pro-fibrotic genes in ESECT-7 and ESECT-40 cells, and similar results were observed in epithelial-derived endometriotic cell lines. Moreover, in an endometriosis mouse model with auto-transplantation and also in severe combined immune deficiency mice transplanted with human endometriotic cells treatment with 25 mg/kg/day DIM-C-pPhOH-3-Cl-5-OCH3 significantly inhibited growth and expansion of endometriotic lesions. Thus, bis-indole-derived NR4A1 ligands represent a novel class of drugs as nonhormonal therapy for endometriosis.

Abstract B41: Bis-indole derived NR4A1 antagonist induces PD-L1 degradation and enhances antitumor immunity

PD-L1 is expressed in tumor cells and interaction with PD-1 in immune cells plays an important role in evading immune surveillance, and this can be overcome by immunotherapy using antibodies against PD-L1 or PD-1. This study reports a novel approach for targeting PD-L1. Results of RNA interference, chromatin immunoprecipitation, and mutational analysis show that in MDA-MB-231 and other human breast cancer cells and 4T1 mouse mammary tumor cells the PD-L1 expression is regulated by the nuclear receptor 4A1/NR4A1/Sp1 complex bound to the proximal GC-rich region of the PD-L1 gene promoter. Treatment breast cancer cells with bis-indole derived NR4A1 antagonists including 1,1-bis(3´-indolyl)-1-(3-chloro-4-hydroxy-5-methoxyphenyl)methane (ClOCH3) decreased expression of PD-L1 mRNA promoter-dependent luciferase activity and protein. In vivo studies using a syngeneic mouse model with Balb/c mice bearing orthotopically injected 4T1 cells showed that 2.5, 7.5, and 12.5 mg/kg/d of ClOCH3 decreased tumor growth and weight and inhibited lung metastasis. The NR4A1 antagonist ClOCH3 also decreased expression of CD+/CD4+/CD25+/FoxP3 regulatory T cells in tumor-infiltrating lymphocytes and increased Teff/Treg ratios. Thus, the potent anticancer activities of NR4A1 antagonists are also accompanied by enhanced antitumor immunity in breast cancer and represent a novel class of drugs that are immunotherapy mimics.

Note:This abstract was not presented at the conference.

Citation Format: Keshav Karki, Gus Wright, Jin Un-Ho, Kumaravel Mohankumar, Xing Zhang, Stephen Safe. Bis-indole derived NR4A1 antagonist induces PD-L1 degradation and enhances antitumor immunity [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B41.

A Bis-Indole-Derived NR4A1 Antagonist Induces PD-L1 Degradation and Enhances Antitumor Immunity

PD-L1 is expressed in tumor cells and its interaction with PD-1 plays an important role in evading immune surveillance; this can be overcome using PD-L1 or PD-1 immunotherapy antibodies. This study reports a novel approach for targeting PD-L1. In human breast cancer cell lines and 4T1 mouse mammary tumor cells, PD-L1 expression was regulated by the nuclear receptor NR4A1/Sp1 complex bound to the proximal germinal center (GC)-rich region of the PD-L1 gene promoter. Treatment of breast cancer cells with bis-indole-derived NR4A1 antagonists including 1,1-bis(3'-indolyl)-1-(3-chloro-4-hydroxy-5-methoxyphenyl)methane (Cl-OCH3) decreased expression of PD-L1 mRNA, promoter-dependent luciferase activity, and protein. In in vivo studies using a syngeneic mouse model bearing orthotopically injected 4T1 cells, Cl-OCH3 decreased tumor growth and weight and inhibited lung metastasis. Cl-OCH3 also decreased expression of CD3⁺/CD4⁺/CD25⁺/FoxP3⁺ regulatory T cells and increased the Teff/Treg ratio. Therefore, the potent anticancer activities of NR4A1 antagonists are also accompanied by enhanced antitumor immunity in PD-L1-expressing triple-negative breast cancer and thus represent a novel class of drugs that mimic immunotherapy. SIGNIFICANCE: These findings show that the orphan nuclear receptor NR4A1 controls PD-L1 expression and identify a chemical probe capable of disrupting this regulatory axis.

Nuclear receptor 4A2 (NR4A2) is a druggable target for glioblastomas

INTRODUCTION

The orphan nuclear receptor 4A2 (NR4A2) has been extensively characterized in subcellular regions of the brain and is necessary for the function of dopaminergic neurons. The NR4A2 ligand, 1,1-bis (3¹-indoly1)-1-(p-chlorophenyl)methane (DIM-C-pPhCl) inhibits markers of neuroinflammation and degeneration in mouse models and in this study we investigated expression and function of NR4A2 in glioblastoma (GBM).

METHODS

Established and patient-derived cell lines were used as models and the expression and functions of NR4A2 were determined by western blots and NR4A2 gene silencing by antisense oligonucleotides respectively. Effects of NR4A2 knockdown and DIM-C-pPhCl on cell growth, induction of apoptosis (Annexin V Staining) and migration/invasion (Boyden chamber and spheroid invasion assay) and transactivation of NR4A2-regulated reporter genes were determined. Tumor growth was investigated in athymic nude mice bearing U87-MG cells as xenografts.

RESULTS

NR4A2 knockdown and DIM-C-pPhCl inhibited GBM cell and tumor growth, induced apoptosis and inhibited migration and invasion of GBM cells. DIM-C-pPhCl and related analogs also inhibited NR4A2-regulated transactivation (luciferase activity) confirming that DIM-C-pPhCl acts as an NR4A2 antagonist and blocks NR4A2-dependent pro-oncogenic responses in GBM.

CONCLUSION

We demonstrate for the first time that NR4A2 is pro-oncogenic in GBM and thus a potential druggable target for patients with tumors expressing this receptor. Moreover, our bis-indole-derived NR4A2 antagonists represent a novel class of anti-cancer agents with potential future clinical applications for treating GBM.

Inhibition of NR4A1 Promotes ROS Accumulation and IL24-Dependent Growth Arrest in Rhabdomyosarcoma

Nuclear receptor 4A1 (NR4A1, Nur77) is overexpressed in rhabdomyosarcoma (RMS), and inactivation of NR4A1 (siNR4A1) or treatment with the NR4A1 antagonist 1,1-bis(3'-indoly)-1-(p-hydroxy-phenyl)methane (DIM-C-pPhOH) has antiproliferative and proapoptotic effects on RMS cells. However, the mechanism by which NR4A1 inhibition exerts these effects is poorly defined. Here, we report that NR4A1 silencing or inhibition resulted in accumulation of reactive oxygen species (ROS) and ROS-dependent induction of the tumor suppressor-like cytokine IL24 in RMS cells. Mechanistically, NR4A1 was found to regulate the expression of the proreductant genes thioredoxin domain-containing 5 (TXNDC5) and isocitrate dehydrogenase 1 (IDH1), which are downregulated in RMS cells following NR4A1 knockdown or inhibition. Silencing TXNDC5 and IDH1 also induced ROS accumulation and IL24 expression in RMS cells, suggesting that NR4A1 antagonists mediate their antiproliferative and apoptotic effects through modulation of proreductant gene expression. Finally, cotreatment with the antioxidant glutathione or IL24-blocking antibody reversed the effects of NR4A1 inhibition, demonstrating the importance of both ROS and IL24 in mediating the cellular responses. IMPLICATIONS: Overall, these data elucidate the mechanism by which NR4A1 inhibition functions to inhibit the proliferation, survival, and migration of RMS cells.

Potent inhibition of breast cancer by bis-indole-derived nuclear receptor 4A1 (NR4A1) antagonists

BACKGROUND

Nuclear receptor 4A1 (NR4A1) is overexpressed in mammary tumors, and the methylene-substituted bis-indole derivative 1,1-bis(3'-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH) acts as an NR4A1 antagonist (inverse agonist) and inhibits NR4A1-regulated pro-oncogenic pathways/genes in breast and other cancer cells.

METHODS

Buttressed analogs of DIM-C-pPhOH were synthesized by condensation of the substituted p-hydroxybenzaldehydes with indole. Breast cancer cell growth, survival, and migration assays were carried out by cell counting, Annexin V staining, and Boyden chamber assays, respectively. Changes in RNA and protein expression were determined by RT-PCR and western blots, respectively. Analysis of RNAseq results was carried out using Ingenuity Pathway Analysis, and in vivo potencies of NR4A1 antagonists were determined in athymic nude mice bearing MDA-MB-231 cells in an orthotopic model.

RESULTS

Ingenuity Pathway analysis of common genes modulated by NR4A1 knockdown or treatment with DIM-C-pPhOH showed that changes in gene expression were consistent with the observed decreased functional responses, namely inhibition of growth and migration and increased apoptosis. DIM-C-pPhOH is rapidly metabolized and the effects and potencies of buttressed analogs of DIM-C-pPhOH which contain one or two substituents ortho to the hydroxyl groups were investigated using NR4A1-regulated gene/gene products as endpoints. The buttressed analogs were more potent than DIM-C-pPhOH in both in vitro assays and as inhibitors of mammary tumor growth. Moreover, using 1,1-bis(3'-indolyl)-1-(3-chloro-4-hydroxy-5-methoxyphenyl)methane (DIM-C-pPhOh-3-Cl-5-OCH3) significant tumor growth inhibition was observed at doses as low as 2 mg/kg/d which was at least an order of magnitude more potent than DIM-C-pPhOH.

CONCLUSIONS

These buttressed analogs represent a more potent set of second generation NR4A1 antagonists as inhibitors of breast cancer.

Genetic Polymorphisms in the Open Reading Frame of the CCR5 gene From HIV-1 Seronegative and Seropositive Individuals From National Capital Regions of India

C-C chemokine receptor type 5 (CCR5) serves as a co-receptor for Human immunodeficiency virus (HIV), enabling the virus to enter human CD4 T cells and macrophages. In the absence of CCR5, HIV strains that require CCR5 (R5 or M-tropic HIV) fail to successfully initiate infection. Various natural mutations of the CCR5 gene have been reported to interfere with the HIV-CCR5 interaction, which influences the rate of AIDS progression. Genetic characterization of the CCR5 gene in individuals from the National Capital Regions (NCRs) of India revealed several natural point mutations in HIV seropositive/negative individuals. Furthermore, we identified novel frame-shifts mutations in the CCR5 gene in HIV seronegative individuals, as well as the well reported CCR5Δ32 mutation. Additionally, we observed a number of mutations present only in HIV seropositive individuals. This is the first report to describe the genetic variations of CCR5 in individuals from the NCRs of India and demonstrates the utility of investigating understudied populations to identify novel CCR5 polymorphisms.

Nuclear receptor 4A1 (NR4A1) antagonists induce ROS-dependent inhibition of mTOR signaling in endometrial cancer

OBJECTIVES

NR4A1 is overexpressed in many solid tumors, and the objectives of this study were to investigate the expression and functional role of this receptor in endometrial cancer cells and demonstrate that NR4A1 antagonist inhibit mTOR.

METHODS

Ishikawa and Hec-1B endometrial cells were used as models to investigate the parallel effects of NR4A1 knockdown by RNA interference (siNR4A1) and treatment with bis-indole-derived NR4A1 ligands (antagonists) on cell growth and survival by determining cell numbers and effects on Annexin V staining. Western blot analysis of whole cell lysates was used to determine effects of these treatments on expression of growth promoting, survival and apoptotic genes and mTOR signaling. Effects of NR4A1 antagonists on tumor growth were determined in athymic nude mice bearing Hec-1B cells as xenografts.

RESULTS

siNR4A1 or treatment with bis-indole-derived NR4A1 antagonists inhibited growth of endometrial cancer cells in vitro and endometrial tumors in vivo and this was accompanied by decreased expression of growth promoting and survival genes and mTOR inhibition.

CONCLUSIONS

NR4A1 exhibited pro-oncogenic activity in endometrial cells due, in part, to regulation of cell growth, survival and mTOR signaling, and all of these pathways and their associated gene products were inhibited after treatment with bis-indole-derived NR4A1 antagonists. Moreover, these compounds also blocked endometrial tumor growth in vivo demonstrating that NR4A1 is a potential novel drug target for treatment of endometrial cancer.

Gelatin-Based Matrices as a Tunable Platform To Study in Vitro and in Vivo 3D Cell Invasion

Hydrogels have been used as synthetic mimics of 3D extracellular matrices (ECM) and their physical properties like stiffness, degradability, and porosity have been known to influence the behavior of encapsulated cells. However, to understand the role of individual properties, the influence of biophysical cues should be decoupled from biochemical ones. In this study, we have used hydrogels as a tunable model matrix to develop a 3D cell culture platform for studying cell invasion. Inert polyethylene (glycol) diacrylate (PEGDA) and cell adhesive gelatin methacryloyl (GELMA) were blended in varying compositions, followed by UV-mediated photo polymerization to obtain hydrogels with varying stiffness, degradation, and cell adhesive properties. We developed two hydrogel matrix systems, namely, PEGDA-GELMA (containing a larger proportion of PEGDA) and GELMA-PEGDA (containing predominantly GELMA), and characterized them for differences in pore size, swelling ratio, storage modulus, degradability, and biocompatibility of the matrix. Both hydrogel systems had similar pore dimensions and swelling behavior, but PEGDA-GELMA was found to be stiffer and nondegradable, while GELMA-PEGDA was softer and degradable. Accordingly, MDA-MB-231 breast cancer cells encapsulated in these matrices showed a spheroidal morphology in PEGDA-GELMA hydrogels and were more spindle-shaped in GELMA-PEGDA hydrogels, confirming that size and extent of spreading of cells were influenced by the type of these hydrogels. The softer GELMA-PEGDA matrices readily allowed invasion of MDA-MB-231 cells in 3D and showed differences in epithelial-mesenchymal transition (EMT) gene expression of these cells. We further demonstrated the invasion and sprouting of endothelial cells using a chick aortic arch assay, exhibiting the utility of softer matrices to study 3D cell invasion for multiple applications. We also implanted these matrices in mice and showed that soft gelatin-based hydrogels allow cell infiltration in vivo. Results from our study highlight the tunability of this matrix system and the role of matrix constitution in influencing cell invasion in a 3D microenvironment.

Reactive Oxygen Species (ROS)-Inducing Triterpenoid Inhibits Rhabdomyosarcoma Cell and Tumor Growth through Targeting Sp Transcription Factors

Methyl 2-trifluoromethyl-3,11-dioxo-18β-olean-1,12-dien-3-oate (CF₃DODA-Me) is derived synthetically from glycyrrhetinic acid, a major component of licorice, and this compound induced reactive oxygen species (ROS) in RD and Rh30 rhabdomyosarcoma (RMS) cells. CF₃DODA-Me also inhibited growth and invasion and induced apoptosis in RMS cells, and these responses were attenuated after cotreatment with the antioxidant glutathione, demonstrating the effective anticancer activity of ROS in RMS. CF₃DODA-Me also downregulated expression of specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4 and prooncogenic Sp-regulated genes including PAX3-FOXO1 (in Rh30 cells). The mechanism of CF₃DODA-Me-induced Sp-downregulation involved ROS-dependent repression of c-Myc and cMyc-regulated miR-27a and miR-17/20a, and this resulted in induction of the miRNA-regulated Sp repressors ZBTB4, ZBTB10, and ZBTB34. The cell and tumor growth effects of CF₃DODA-Me further emphasize the sensitivity of RMS cells to ROS inducers and their potential clinical applications for treating this deadly disease. IMPLICATIONS: CF₃DODA-Me and HDAC inhibitors that induce ROS-dependent Sp downregulation could be developed for clinical applications in treating rhabdomyosarcoma.

Aryl Hydrocarbon Receptor (AhR) Ligands as Selective AhR Modulators: Genomic Studies

The aryl hydrocarbon receptor (AhR) binds structurally diverse ligands that vary from the environmental toxicant 2,3,7,8-tetrachlorodibenzo-B-dioxin (TCDD) to AhR- active pharmaceuticals and health-promoting phytochemicals. There are remarkable differences in the toxicity of TCDD and related halogenated aromatics (HAs) vs. health promoting AhR ligands, and genomic analysis shows that even among the toxic HAs, there are differences in their regulation of genes and pathways. Thus, like ligands for other receptors, AhR ligands are selective AhR modulators (SAhRMs) which exhibit variable tissue-, organ- and species-specific genomic and functional activities.

Interleukin-24 (IL24) Is Suppressed by PAX3-FOXO1 and Is a Novel Therapy for Rhabdomyosarcoma

Alveolar rhabdomyosarcoma (ARMS) patients have a poor prognosis, and this is primarily due to overexpression of the oncogenic fusion protein PAX3-FOXO1. Results of RNA-sequencing studies show that PAX3-FOXO1 represses expression of interleukin-24 (IL24), and these two genes are inversely expressed in patient tumors. PAX3-FOXO1 also regulates histone deacetylase 5 (HDAC5) in ARMS cells, and results of RNA interference studies confirmed that PAX3-FOXO1-mediated repression of IL24 is HDAC5-dependent. Knockdown of PAX3-FOXO1 decreases ARMS cell proliferation, survival, and migration, and we also observed similar responses in cells after overexpression of IL24, consistent with results reported for this tumor suppressor-like cytokine in other solid tumors. We also observed in double knockdown studies that the inhibition of ARMS cell proliferation, survival, and migration after knockdown of PAX3-FOXO1 was significantly (>75%) reversed by knockdown of IL24. Adenoviral-expressed IL24 was directly injected into ARMS tumors in athymic nude mice, and this resulted in decreased tumor growth and weight. Because adenoviral IL24 has already successfully undergone phase I in clinical trials, this represents an alternative approach (alone and/or combination) for treating ARMS patients who currently undergo cytotoxic drug therapies.

TGFβ-Induced Lung Cancer Cell Migration Is NR4A1-Dependent

TGFβ induces migration of lung cancer cells (A549, H460, and H1299), dependent on activation of c-Jun N-terminal kinase (JNK1), and is inhibited by the JNK1 inhibitor SP600125. Moreover, TGFβ-induced migration of the cells is also blocked by the nuclear export inhibitor leptomycin B (LMB) and the orphan nuclear receptor 4A1 (NR4A1) ligand 1,1-bis(3'-indolyl)-1-(p-hydroxyphenyl)methane (CDIM8), which retains NR4A1 in the nucleus. Subsequent analysis showed that the TGFβ/TGFβ receptor/PKA/MKK4 and -7/JNK pathway cascade phosphorylates and induces nuclear export of NR4A1, which in turn forms an active complex with Axin2, Arkadia (RNF111), and RNF12 (RLIM) to induce proteasome-dependent degradation of SMAD7 and enhance lung cancer cell migration. Thus, NR4A1 also plays an integral role in mediating TGFβ-induced lung cancer invasion, and the NR4A1 ligand CDIM8, which binds nuclear NR4A1, represents a novel therapeutic approach for TGFβ-induced blocking of lung cancer migration/invasion. IMPLICATIONS: Effective treatment of TGFβ-induced lung cancer progression could involve a number of agents including the CDIM/NR4A1 antagonists that block not only TGFβ-induced migration, but several other NR4A1-regulated prooncogenic genes/pathways in lung cancer cell lines.

Bis-Indole-Derived NR4A1 Ligands and Metformin Exhibit NR4A1-Dependent Glucose Metabolism and Uptake in C2C12 Cells

Treatment of C2C12 muscle cells with metformin or the NR4A1 ligand 1,1-bis(3'-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH) induced NR4A1 and Glut4 messenger RNA and protein expression. Similar results were observed with buttressed (3- or 3,5-substituted) analogs of DIM-C-pPhOH, including 1,1-bis(3'-indolyl)-1-(3-chloro-4-hydroxy-5-methoxyphenyl)methane (DIM-C-pPhOH-3-Cl-5-OCH3), and the buttressed analogs were more potent than DIM-C-pPhOH NR4A1 agonists. Metformin and the bis-indole substituted analogs also induced expression of several glycolytic genes and Rab4, which has previously been linked to enhancing cell membrane accumulation of Glut4 and overall glucose uptake in C2C12 cells, and these responses were also observed after treatment with metformin and the NR4A1 ligands. The role of NR4A1 in mediating the responses induced by the bis-indoles and metformin was determined by knockdown of NR4A1, and this resulted in attenuating the gene and protein expression and enhanced glucose uptake responses induced by these compounds. Our results demonstrate that the bis-indole-derived NR4A1 ligands represent a class of drugs that enhance glucose uptake in C2C12 muscle cells, and we also show that the effects of metformin in this cell line are NR4A1-dependent.

Impact of Genetic Variations in HIV-1 Tat on LTR-Mediated Transcription via TAR RNA Interaction

HIV-1 evades host defense through mutations and recombination events, generating numerous variants in an infected patient. These variants with an undiminished virulence can multiply rapidly in order to progress to AIDS. One of the targets to intervene in HIV-1 replication is the trans-activator of transcription (Tat), a major regulatory protein that transactivates the long terminal repeat promoter through its interaction with trans-activation response (TAR) RNA. In this study, HIV-1 infected patients (n = 120) from North India revealed Ser46Phe (20%) and Ser61Arg (2%) mutations in the Tat variants with a strong interaction toward TAR leading to enhanced transactivation activities. Molecular dynamics simulation data verified that the variants with this mutation had a higher binding affinity for TAR than both the wild-type Tat and other variants that lacked Ser46Phe and Ser61Arg. Other mutations in Tat conferred varying affinities for TAR interaction leading to differential transactivation abilities. This is the first report from North India with a clinical validation of CD4 counts to demonstrate the influence of Tat genetic variations affecting the stability of Tat and its interaction with TAR. This study highlights the co-evolution pattern of Tat and predominant nucleotides for Tat activity, facilitating the identification of genetic determinants for the attenuation of viral gene expression.

Heavy Metal Contamination in Groundwater around Industrial Estate vs Residential Areas in Coimbatore, India

INTRODUCTION

Water is the vital resource, necessary for all aspects of human and ecosystem survival and health. Depending on the quality, bore water may be used for human consumption, irrigation purposes and livestock watering. The quality of bore water can vary widely depending on the quality of ground water that is its source. Pollutants are being added to the ground water system through human and natural processes. Solid waste from industrial units is being dumped near the factories, which react with percolating rainwater and reaches the ground water. The percolating water picks up a large number of heavy metals and reaches the aquifer system and contaminates the ground water. The usage of the contaminated bore water causes the diseases. Mercury, Arsenic and Cadmium are used or released by many industries.

AIM

This study was conducted to investigate the pollution of bore water in the industrial region (Kurichi Industrial Cluster) of Coimbatore, in the state of Tamilnadu, India.

MATERIALS AND METHODS

Four samples were taken from residential areas around Kurichi Industrial Cluster and analysed to find the concentrations of Mercury, Arsenic and Cadmium. Four more samples were taken from other residential regions far from the industrial estate and served as control. Samples were analysed using Atomic absorption spectrophotometry method.

RESULTS

We found that the ground water of the areas surrounding the industrial cluster does not contain significant amount of those metals. Instead, Heavy metal contamination of ground water were observed in some residential areas of coimbatore.

CONCLUSION

The regulatory measures to contain and prevent ground water contamination by industries undertaken by Tamilnadu pollution control board may have lead to absence of heavy metal contamination in Kurichi Industrial cluster, Coimbatore, India.

Anti-proliferative and apoptosis-triggering potential of disulfiram and disulfiram-loaded polysorbate 80-stabilized PLGA nanoparticles on hepatocellular carcinoma Hep3B cell line

There is an emerging trend to restudy known drugs for their anti-cancer potential. One such anti-alcoholic drug, disulfiram, with significant anti-cancer potential was studied for its efficacy against Hep3B cell lines, an in vitro model of hepatocellular carcinoma. Simultaneously, we intended to study the effect of polysorbate 80-stabilized PLGA nanoparticles and its DSF-loaded counterpart. Cell and nuclear staining, comet assay, flow cytometry and Western blots were performed. Results suggest that cell proliferation was inhibited by DSF and its PLGA nanoparticles through cell cycle arrest, triggering activation of apoptotic pathways that culminates with cell death. DSF loaded nanoparticles when compared with free DSF, showed significantly lesser effect due to its sustained drug-releasing property, while empty nanoparticles showed negligible influence on Hep3B cells. Our results suggest that DSF alone contributes to cell death, while polysorbate 80-stabilized PLGA nanoparticles show sustained drug release patterns that would potentially lower dosage regimens.

Neuroprotective effect of Valeriana wallichii rhizome extract against the neurotoxin MPTP in C57BL/6 mice

Oxidative stress and inflammation are some of the contributing factors for dopaminergic neurodegeneration in Parkinson's disease (PD). Though Valeriana wallichii D.C. is known for its nervine activities its effect against PD is yet to be studied. This is the first report on the antioxidant and anti-inflammatory effect of V. wallichii rhizome extract (VWE) in MPTP induced PD mice. GC-MS analysis of VWE indicated the presence of phytoconstituents like isovaleric acid and acacetin. PD induced mice were treated orally with three different doses (50, 100 and 200mg/kg body weight (BW)) of VWE for 14 days and their behavioural changes were studied on days 0, 8, 13 and 21. The levels of striatal dopamine, mid brain tyrosine hydroxylase positive (TH(+)) cell count, TH protein expression, reactive oxygen species (ROS), lipid peroxidation (LPO), antioxidants and inflammatory cytokines were analysed. Mid brain glial fibrillary acidic protein (GFAP) expression was assessed by immunohistochemistry and western blotting. Also mid brain histopathological analysis was performed. VWE treatment significantly recuperated the altered behavioural test scores, striatal dopamine levels, mid brain TH(+) cell count and TH protein levels, increased GFAP expression and the histopathological changes observed in PD mice. Similarly, diminished levels of antioxidants, elevated levels of ROS, LPO and inflammatory cytokines were also significantly ameliorated following VWE treatment. The effective dose of VWE was found to be 200mg/kg BW. Conclusively, V. wallichii rhizome extract has the potential to mitigate oxidative stress and inflammatory damage in PD.

Hypoglycaemic role of wheatgrass and its effect on carbohydrate metabolic enzymes in type II diabetic rats

Diabetes mellitus (DM) is a leading cause of morbidity and mortality in the world. Insulin resistance and insulin insufficiency is the major factor for the prognosis of type II diabetes. Consistent high glucose level leads to multiple secondary complications in diabetic patients. Hence, hypoglycaemic drugs are of significance for reducing the risk of secondary complications in type II diabetes. Various hypoglycaemic drugs are already available in the market, but they are associated with several side effects. Therefore, traditional herbs have emerged as safer alternative for effective hypoglycaemic treatment. The juvenile grass of common wheat is known as wheatgrass (WG). It is commonly used as a health drink and has potent antioxidant efficacy. It has been used to cure DM in folk medicine. The current study was planned to test the hypoglycaemic effect and pathways regulated by WG on DM. We analysed the glucose and insulin levels in plasma, the activity of glucose oxidative enzymes, hexokinase and glucose 6 phosphate dehydrogenase, in serum and glycogen levels in liver of the male albino Wistar rats. Activity of glucose oxidative enzymes and the levels of insulin and liver glycogen were decreased in rats with diabetes, but they were reversed on treatment with WG. Hence, we conclude that WG can act as a potent anti-hyperglycaemic agent.

Activities of membrane bound phosphatases, transaminases and mitochondrial enzymes in white spot syndrome virus infected tissues of Fenneropenaeus indicus

Disease caused by viruses, especially white spot syndrome virus (WSSV), present the greatest challenge to shrimp aquaculture worldwide. Massive tissue disintegration occurs in WSSV-infected ectodermal and mesodermal tissues of penaeid shrimp. The activities of membrane bound phosphatases (Na(+)K(+)ATPase, Ca(2+)ATPase, Mg(2+)ATPase and Total ATPase), transaminases (alanine transaminase (ALT) and aspartate transaminase (AST)) and mitochondrial enzymes (isocitrate dehydrogenase (ICDH), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), alpha-ketoglutarate dehydrogenase (KGDH), NADH dehydrogenase, cytochrome C oxidase) in WSSV-infected tissues (hemolymph, hepatopancreas, gills and muscle) of Fenneropenaeus indicus were determined at intervals after WSSV infection (0, 24, 48, 72 and after 72 h (moribund)). The activities of phosphatases, transaminases and mitochondrial enzymes in healthy as compared with WSSV-infected hemolymph, hepatopancreas, gills and muscle showed marked divergence throughout the course of infection. WSSV infected hemolymph, hepatopancreas, gills and muscle exhibited significantly reduced activity of membrane bound phosphatases compared with the uninfected animals. Inactivation of these enzymes may occur due to increased production of free radicals, that cause conformational change by oxidation of 'SH' groups present at the active site. Significantly marked elevation in the activities of transaminases (ALT and AST) was observed in WSSV-infected hemolymph, hepatopancreas, gills and muscle compared to the uninfected tissues. This may be due to leakage of these enzymes from the damaged tissues. The activities of mitochondrial enzymes in WSSV-infected tissues were significantly decreased compared to the activities in uninfected animals. WSSV-infected animals showed reduced feeding that may have led to decreased oxidation of glucose via the TCA cycle. Excessive production of free radicals in WSSV-infected animals may have affected aerobic oxidation leading to lower production of ATP. It is concluded that membrane dynamics play a major role in the pathogenesis of WSSV infection.

White spot syndrome virus infection decreases the activity of antioxidant enzymes in Fenneropenaeus indicus

White spot syndrome virus (WSSV) is the causative agent of White Spot disease of shrimp, causing mass mortalities in aquaculture. WSSV infection causes oxidative stress by the release of reactive oxygen species (ROS) that are toxic to the cells. The antioxidant enzymes associated with oxidative stress during the process of pathogenesis of WSSV in the infected tissues (hemolymph, hepatopancreas, gills and muscle) of Fenneropenaeus indicus were quantitatively determined at different time intervals post infection (0, 24, 48, 72 and after 72 h (moribund)). The level of lipid peroxidation, the activities of superoxide dismutase, catalase, glutathione peroxidase, and also the activities of the non-enzymic antioxidants glutathione-S-transferase, reduced glutathione and glutathione reductase in healthy and WSSV-infected hemolymph, hepatopancreas, gills and muscle of F. indicus showed marked differences at different times during the course of infection. The level of lipid peroxidation was higher in WSSV-infected muscle, hemolymph, gills and hepatopancreas than in uninfected F. indicus. Significant reductions in the activities of superoxide dismutase, catalase, glutathione-S-transferase, reduced glutathione, glutathione peroxidase and glutathione reductase were observed in WSSV-infected compared with uninfected animals. The increased lipid peroxidation in WSSV-infected shrimp may be due to increased oxidative stress in the cells as a result of depletion of antioxidant scavenger systems. The reduced activity of antioxidant enzymes in WSSV-infected animals could be due to inactivation of antioxidant enzymes by oxidative stress thereby generating free radicals, which accumulate in the cells. Further understanding of the biochemical alterations induced by viral infections, including changes in the antioxidant status and oxidative stress, could help to advance the therapeutic armamentarium for control of WSSV in shrimp.

Dengue virus infection during post-epidemic period in Delhi, India

Dengue fever (DF) and dengue hemorrhagic fever (DHF) are major public health problems in India. During the period following an epidemic, a study was carried out using virological and serological tests for confirmation of suspected cases of dengue virus infection in fever cases presenting to the All India Institute of Medical Sciences. Serum samples of suspected DF/DHF cases were processed from January to December 1997. In 37 samples from patients with fever of less than 5-day duration, received on ice, virus isolation was attempted in C6/36 clone of Aedes albopictus cell line, followed by indirect fluorescent antibody staining with monoclonal antibodies to dengue viruses 1 to 4. One hundred and forty-three serum samples from patients with more than 5 days fever were tested for dengue specific IgM antibody by either MAC-ELISA or a rapid immunochromatographic assay. Dengue virus type 1 was demonstrated by culture in 8 (21.6%) of 37 serum samples and IgM antibody could be detected in 42 (29.4%) of the 143 serum samples by the serological methods. The peak of dengue virus infection was seen from September to November 1997.