Sanjay Kumar Chauhan - Academia.edu (original) (raw)

Uploads

Papers by Sanjay Kumar Chauhan

Cell growth & differentiation : the molecular biology journal of the American Association for Cancer Research, 2002

To better understand androgen action in normal prostate cells, we characterized the androgen grow... more To better understand androgen action in normal prostate cells, we characterized the androgen growth response of an immortalized nontumorigenic rat prostate cell line called CA25 that had been stably transfected with androgen receptor (AR) cDNA. Surprisingly, we found that AR(+) CA25 cells grew slower in the presence of dihydrotestosterone (DHT), whereas the growth of AR(-) CA25 cells was not affected by the hormone. DHT-mediated growth inhibition of CA25 cells was not attributable to an increase in apoptosis but rather to a morphological conversion consistent with terminal differentiation. Specifically, we found that DHT treatment of CA25 cells resulted in a striking change in cell architecture, localization of desmoplakin to cell-cell boundaries, and an increase in alpha 6p integrin levels, a newly described marker of cell differentiation. Although no androgen-dependent changes were observed in the transcript levels of the mitochondrial aspartate aminotransferase or c-Myc genes by ...

Cell Adhesion and Cytoskeletal Molecules in Metastasis

The FERM domain protein EHM2 (EPB41L4B) was first isolated and characterized based on its elevate... more The FERM domain protein EHM2 (EPB41L4B) was first isolated and characterized based on its elevated expression in highly metastatic mouse melanoma cells. We recently found that human EHM2 is androgen-regulated in a cancer cell line model of steroid-induced cytoskeletal reorganization, and expression profiling analyses by others have shown that it is a primary steroidregulated gene in rat liver and human lung cells. Bioinformatic analysis of human EHM2 revealed that it is a member of a unique subfamily of FERM domain proteins that includes the Drosophila YURT gene. Analysis of YURT protein functions in Drosophila have shown that it is required for dorsal closure during embryogenesis and is involved in mediating epithelial cell migration. We have used immunostaining to analyze steroid-induced and ectopic expression of EHM2 in the human fibrosarcoma cell line HT-1080 and found that it is localized to the cell membrane and associated with cytoskeletal reorganization. We have also found that EHM2 is highly expressed in the metastatic prostate cancer cell lines LNCaP, DU-145 and PC-3 cells, and moreover, that EHM2 transcripts are present at significantly higher levels in human prostate tumors than in non-malignant prostate cells. Based on these data, we propose that elevated expression of EHM2 may enhance the metastatic properties of advanced prostate cancers.

The Prostate, 2006

BACKGROUND. Alterations of fibroblast growth factors and their receptors contribute to prostate c... more BACKGROUND. Alterations of fibroblast growth factors and their receptors contribute to prostate cancer progression by enhancing cell survival, motility, and proliferation. The expression of the FGFR-4 Arg 388 variant is correlated with the occurrence of pelvic lymph node metastasis and biochemical (PSA) recurrence in men undergoing radical prostatectomy. Ehm2 is an androgen-regulated gene that has been associated with metastasis in other systems, so we sought to determine if it is expressed in prostate cancer and if the FGFR-4 Arg 388 variant can increase its expression. METHODS. Expression of Ehm2 was examined by quantitative RT-PCR and Western blotting in prostate cell lines and by quantitative RT-PCR, in situ hybridization, and immunohistochemistry in prostate tissues. The effect of Ehm2 expression on collagen IV adhesion was tested by transient overexpression and RNA interference. RESULTS. Ehm2 expression is upregulated in prostate cancer cell lines and prostate cancer tissues. Expression of the FGFR-4 Arg 388 variant results in increased expression of Ehm2. Increased expression of Ehm2 leads to decreased adhesion to collagen IV, which has been associated with metastasis in cancers. Analysis of tissue microarrays revealed that increased Ehm2 expression is associated with biochemical recurrence after radical prostatectomy, which is indicative of more aggressive disease. CONCLUSIONS. Ehm2 is overexpressed in prostate cancer and may enhance disease progression and metastasis.

The Journal of Steroid Biochemistry and Molecular Biology, 2003

Molecular analysis of steroid-regulated gene expression in freshly isolated human eosinophils is ... more Molecular analysis of steroid-regulated gene expression in freshly isolated human eosinophils is difficult due to the inherent high rate of spontaneous apoptosis and elevated levels of endogenous ribonucleases. To circumvent these limitations, we determined if the human eosinophilic cell line EoL-1 could serve as an in vitro model of glucocorticoid signaling. We found by optimizing growth conditions in low serum-containing media that dexamethasone (Dex) treatment of EoL-1 cells induced an apoptotic pathway that was inhibited by interleukin-5 (IL-5). Moreover, gene expression profiling using RNA from untreated EoL-1 cells and from freshly isolated human eosinophils identified 380 commonly expressed genes, including the eosinophil markers granule major basic protein, prostaglandin-endoperoxide synthase 1 and arachidonate 15-lipoxygenase. Expression profiling was performed using EoL-1 cells that had been treated with dexamethasone for 0, 4, 12, 24 and 48 h identifying 162 genes as differentially expressed. Two of the most highly upregulated genes based on expression profiling were the transcription factor Ets-2 and the MHC Class II genes (Q, R, and P). Expression of these genes in EoL-1 cells was shown to be dexamethasone-induced at the RNA and protein levels which is consistent with the known function of Ets-2 in controlling cell cycle progression and the role of MHC Class II antigens in mediating eosinophil functions.

Journal of Plant Biochemistry and Biotechnology, 1996

An 8 kD in vivo turnover product of D1 polypeptide was identified using a C-terminal specific ant... more An 8 kD in vivo turnover product of D1 polypeptide was identified using a C-terminal specific anti-D1-antibody in thylakoids isolated from 5–10 days old seedlings of wheat (Triticum aestivum cv HD2329). Eight days old wheat seedlings grown under visible light were irradiated with UV-B (1 MW cm−2) alone (0–5h) and Tricine SDS-PAGE was run of the isolated thylakoids. UV-B exposure of intact wheat leaves generates a fragment of 24 kD and concomitant increase in 8 kD fragment was also observed. From these results it is concluded that in wheat visible light induces the breakdown of D1 polypeptide into an 8 kD C-terminal thylakold bound fragment and UV-B stress results in an increase in 8 kD breakdown fragment, thus suggesting that visible light/UV-B has a common hot spot on D1 protein in wheat.

Journal of Photochemistry and Photobiology B: Biology, 1997

The Journal provides a forum for the publication of papers relating to the various aspects of pho... more The Journal provides a forum for the publication of papers relating to the various aspects of photobiology, as wen as a means for communication in this munidisciplinary field. The scope includes bioluminescence, cllronobiology, DNA repair, environmental photobiology, photocarcinogenesis, photochemistry of biomolecules, photomedicine, photomorphogenesis. photomovement, photoreception, photosensttization, photosynthesis, phototechnology, spectroscopy of biological systems, UV and visible radiation effects and vision. Types of Contribution Invited review articles. Original papers not previously published. Rapid communications. Contributions to News and Views. Book reviews. Frequency Five volumes per year. Subscription Information 1997 Volumes 37-41, each volume containing 3 issues, are scheduled tor publication. Prices are available !rom the publishers upon request. Subscriptions are accepted on a prepaid basis only. Issues are sent by SAL (Surtace Air Lifted) mail wherever this service is available. Airmail rates are available upon request.

Journal of Biological Chemistry, 2003

We recently generated an HT-1080-derived cell line called HT-AR1 that responds to dihydrotestoste... more We recently generated an HT-1080-derived cell line called HT-AR1 that responds to dihydrotestosterone (DHT) treatment by undergoing cell growth arrest in association with cytoskeletal reorganization and induction of neuroendocrine-like cell differentiation. In this report, we show that DHT induces a dose-dependent increase in G 0 /G 1 growth-arrested cells using physiological levels of hormone. The arrested cells increase in cell size and contain a dramatic redistribution of desmoplakin, keratin 5, and chromogranin A proteins. DHTinduced cytoskeletal changes were also apparent from time lapse video microscopy that showed that androgen treatment resulted in the rapid appearance of neuronallike membrane extensions. Expression profiling analysis using RNA isolated from DHT-treated HT-AR1 cells revealed that androgen receptor activation leads to the coordinate expression of numerous cell signaling genes including RhoB, PTGF-␤, caveolin-2, Egr-1, myosin 1B, and EHM2. Because RhoB has been shown to have a role in tumor suppression and neuronal differentiation in other cell types, we investigated RhoB signaling functions in the HT-AR1 steroid response. We found that steroid induction of RhoB was DHT-specific and that newly synthesized RhoB protein was post-translationally modified and localized to endocytic vesicles. Moreover, treatment with a farnesyl transferase inhibitor reduced DHT-dependent growth arrest, suggesting that prenylated RhoB might function to inhibit HT-AR1 cell proliferation. This was directly shown by transfecting HT-AR1 cells with RhoB coding sequences containing activating or dominant negative mutations.

Current Microbiology, 2000

We report here a comparative analysis of the effect of blue (450 nm), red (660 nm), and white lig... more We report here a comparative analysis of the effect of blue (450 nm), red (660 nm), and white light (400-700 nm) on the protein profile of cyanobacteria Synechococcus sp. PCC 7942. In vivo labeling of cells with [ 35 S] methionine and their subsequent analysis by two-dimensional gel electrophoresis (2-DGE) showed that eight polypeptides were unique to dark adapted cells, ten were blue light specific, and four were specifically induced in red light. The results show that Synechococcus sp. respond to various light treatments rapidly and synthesize new polypeptides in dark and blue/red light.

Biochemical and Biophysical Research Communications, 2003

We have developed a cell model to investigate steroid control of differentiation using a subline ... more We have developed a cell model to investigate steroid control of differentiation using a subline of HT1080 cells (HT-AR1) that have been engineered to express the human androgen receptor. Dihydrotestosterone (DHT) treatment of HT-AR1 cells induced growth arrest and cytoskeletal reorganization that was associated with the expression of fibronectin and the neuroendocrine markers chromogranin A and neuron-specific enolase. Expression profiling analysis identified the human FERM domain-encoding gene EHM2 as uniquely induced in HT-AR1 cells as compared to 16 other FERM domain containing genes. Since FERM domain proteins control cytoskeletal functions in differentiating cells, and the human EHM2 gene has not been characterized, we investigated EHM2 steroid-regulation, genomic organization, and sequence conservation. We found that DHT, but not dexamethasone, induced the expression of a 3.8 kb transcript in HT-AR1 cells encoding a 504 amino acid protein, and moreover, that human brain tissue contains a 5.8 kb transcript encoding a 913 amino acid isoform. Construction of an unrooted phylogenetic tree using 98 FERM domain proteins revealed that the human EHM2 gene is a member of a distinct subfamily consisting of nine members, all of which contain a highly conserved 325 amino acid FERM domain.