Arulkumaran Shanmugam

Endothelial progenitor cell biology in disease and tissue regeneration

Endothelial progenitor cells are increasingly being studied in various diseases ranging from ischemia, diabetic retinopathy, and in cancer. The discovery that these cells can be mobilized from their bone marrow niche to sites of inflammation and tumor to induce neovasculogenesis has afforded a novel opportunity to understand the tissue microenvironment and specific cell-cell interactive pathways. This review provides a comprehensive up-to-date understanding of the physiological function and therapeutic utility of these cells. The emphasis is on the systemic factors that modulate their differentiation/mobilization and survival and presents the challenges of its potential therapeutic clinical utility as a diagnostic and prognostic reagent.

Metastatic Phenotype Is Regulated by Estrogen in Thyroid Cells

BACKGROUND Over 200 million people worldwide are affected by thyroid proliferative diseases, including cancer, adenoma, and goiter, annually. The incidences of thyroid malignancies are three to four times higher in women, suggesting the possible involvement of estrogen. Based on this observed sex bias, we hypothesize that estrogen modulates the growth and metastatic propensity of thyroid cancer cells. METHODS In this study, two thyroid cell lines (Nthy-ori 3-1 and BCPAP) were evaluated for the presence of estrogen receptor (ER) by Western blot analysis and estrogen responsiveness by using a cell proliferation assay. In addition, the effect of estradiol (E(2)) on modulation of metastatic phenotype was determined by using in vitro adhesion, migration, and invasion assays. RESULTS Thyroid cells expressed a functionally active ER-alpha and ER-beta as evidenced by 50-150% enhancement of proliferation in the presence of E(2). E(2) also enhanced adhesion, migration, and invasion of thyroid cells in an in vitro experimental model system that, based on our results, is modulated by beta-catenin. CONCLUSION Our data provide evidence that the higher incidence of thyroid cancer in women is potentially attributed to the presence of a functional ER that participates in cellular processes contributing to enhanced mitogenic, migratory, and invasive properties of thyroid cells. These findings will enable and foster the possible development of antiestrogenic therapy targeting invasion and migration, thus affecting metastatic propensity.

Estrogen Induced Metastatic Modulators MMP-2 and MMP-9 Are Targets of 3,3′-Diindolylmethane in Thyroid Cancer

Background Thyroid cancer is the most common endocrine related cancer with increasing incidences during the past five years. Current treatments for thyroid cancer, such as surgery or radioactive iodine therapy, often require patients to be on lifelong thyroid hormone replacement therapy and given the significant recurrence rates of thyroid cancer, new preventive modalities are needed. The present study investigates the property of a natural dietary compound found in cruciferous vegetables, 3,3′-diindolylmethane (DIM), to target the metastatic phenotype of thyroid cancer cells through a functional estrogen receptor. Methodology/Principal Findings Thyroid cancer cell lines were treated with estrogen and/or DIM and subjected to in vitro adhesion, migration and invasion assays to investigate the anti-metastatic and anti-estrogenic effects of DIM. We observed that DIM inhibits estrogen mediated increase in thyroid cell migration, adhesion and invasion, which is also supported by ER-α downregulation (siRNA) studies. Western blot and zymography analyses provided direct evidence for this DIM mediated inhibition of E2 enhanced metastasis associated events by virtue of targeting essential proteolytic enzymes, namely MMP-2 and MMP-9. Conclusion/Significance Our data reports for the first time that DIM displays anti-estrogenic like activity by inhibiting estradiol enhanced thyroid cancer cell proliferation and in vitro metastasis associated events, namely adhesion, migration and invasion. Most significantly, MMP-2 and MMP-9, which are known to promote and enhance metastasis, were determined to be targets of DIM. This anti-estrogen like property of DIM may lead to the development of a novel preventive and/or therapeutic dietary supplement for thyroid cancer patients by targeting progression of the disease.

Synthetic Toll Like Receptor-4 (TLR-4) Agonist Peptides as a Novel Class of Adjuvants

Background Adjuvants serve as catalysts of the innate immune response by initiating a localized site of inflammation that is mitigated by the interactions between antigens and toll like receptor (TLR) proteins. Currently, the majority of vaccines are formulated with aluminum based adjuvants, which are associated with various side effects. In an effort to develop a new class of adjuvants, agonists of TLR proteins, such as bacterial products, would be natural candidates. Lipopolysaccharide (LPS), a major structural component of gram negative bacteria cell walls, induces the systemic inflammation observed in septic shock by interacting with TLR-4. The use of synthetic peptides of LPS or TLR-4 agonists, which mimic the interaction between TLR-4 and LPS, can potentially regulate cellular signal transduction pathways such that a localized inflammatory response is achieved similar to that generated by adjuvants. Methodology/Principal Findings We report the identification and activity of several peptides isolated using phage display combinatorial peptide technology, which functionally mimicked LPS. The activity of the LPS-TLR-4 interaction was assessed by NF-κB nuclear translocation analyses in HEK-BLUE™-4 cells, a cell culture model that expresses only TLR-4, and the murine macrophage cell line, RAW264.7. Furthermore, the LPS peptide mimics were capable of inducing inflammatory cytokine secretion from RAW264.7 cells. Lastly, ELISA analysis of serum from vaccinated BALB/c mice revealed that the LPS peptide mimics act as a functional adjuvant. Conclusions/Significance Our data demonstrate the identification of synthetic peptides that mimic LPS by interacting with TLR-4. This LPS mimotope-TLR-4 interaction will allow for the development and use of these peptides as a new class of adjuvants, namely TLR-4 agonists.

Estrogen activity as a preventive and therapeutic target in thyroid cancer

Thyroid cancer is the most common endocrine-related cancer with increasing incidences during the last five years. Interestingly, according to the American Thyroid Association, the incidences of thyroid proliferative diseases occur four to five times more in women than in men with the risk of developing thyroid disorders being one in every eight females. Several epidemiological studies have suggested a possible correlation between incidences of thyroid malignancies and hormones but the precise contribution of estrogen in thyroid proliferative disease initiation, and progression is not well understood. This review is an attempt to define the phenotypic and genotypic modulatory effects of estrogen on thyroid proliferative diseases. The significance and relevance of expression of estrogen receptors, α and β, in normal and malignant thyroid tissues and their effects on different molecular pathways involved in growth and function of the thyroid gland are discussed. These novel findings open up areas of developing alternative therapeutic treatments and preventive approaches which employ the use of antiestrogen to treat thyroid malignancies.

Estrogen-Mediated Angiogenesis in Thyroid Tumor Microenvironment Is Mediated Through VEGF Signaling Pathways

OBJECTIVES To explore the induction of a proangiogenic phenotype in endothelial cells in the thyroid tumor microenvironment by estrogen-treated thyroid cancer cells and to define the role of vascular endothelial growth factor (VEGF) in this interaction. DESIGN Cell-based in vitro systems analysis. SUBJECTS Thyroid tumor cell lines (BCPAP [papillary thyroid cancer] and ML-1 [follicular thyroid cancer]) were cultured with estradiol with and without an estrogen receptor (ER) inhibitor (fulvestrant or ICI) and used to treat human umbilical vein endothelial cells (HUVECs). INTERVENTIONS Immunofluorescence was used to confirm the presence of ERα and ERβ in BCPAP cells. Conditioned medium was then used to evaluate the induction of HUVEC tubulogenesis and migration. Secretion of VEGF in this medium was evaluated by Western blot analysis. The expression of phosphoinositide 3-kinase (PI3K), the initiator of a proangiogenic pathway, was evaluated with Western blot analysis of HUVEC lysates. The subsequent effects of an ER inhibitor (fulvestrant/ICI) and a neutralizing VEGF antibody were also observed. RESULTS Estrogen receptor α and ERβ are expressed in thyroid cancer cells. Estrogen-stimulated ML-1 cells secreted an increased amount of VEGF likely as a result of ER signaling. In contact with this environment, HUVECs demonstrate enhanced tubulogenesis and migration. Western blot analysis documented estrogen-mediated upregulation of PI3K in HUVECs. These effects were mitigated by an ER inhibitor (fulvestrant/ICI) and a neutralizing VEGF antibody. CONCLUSIONS Our data provide evidence that estrogen can induce a proangiogenic endothelial cell phenotype in the thyroid tumor microenvironment through ER and VEGF signaling. Our findings suggest that the effect of antiestrogenic therapy targeting tumor angiogenesis can be enhanced through VEGF inhibition.

Identification of PSA peptide mimotopes using phage display peptide library

Prostate cancer (PCa) is one of the most common types of cancer in men in the United States and is the second leading cause of cancer related death in men. Clinically, secreted prostate specific antigen (PSA) has gained recognition because of its proteolytic activity being directly linked to PCa cell proliferation leading to disease initiation and progression. Using phage display technology, we identified four distinct cyclical peptides. These peptides apart from differences in their amino acid sequence, elicited minimal cross reactive antibody responses against each other. One of the four peptides analyzed produced an antibody response that recognizes the PSA protein. We demonstrate that the synthetic PSA peptide mimics identified in our study are immunologically active and produce neutralizing activity and this has relevance and utility for prostate cancer disease progression.

Identification of peptide mimotopes of gp96 using single-chain antibody library

Heat shock proteins such as gp96 are immunogenic and are widely used as vaccines in immunotherapy of cancers. The present study focuses on the use of peptide mimotopes as immunotherapeutic vaccines for prostate cancer. To this end, we developed a 15-mer gp96 peptide mimotope specifically reactive to MAT-LyLu gp96–peptide complex using combinatorial single-chain antibody and peptide phage display library. The immunogenicity of the synthesized gp96 mimotope was analyzed initially in normal BALB/c mice in combination with various adjuvants such as complete Freund’s adjuvant (CFA), aluminum salts (ALUM), granulocyte-macrophage colony-stimulating factor (GM-CSF), and liposome, of which CFA served as a positive control. The antibody response was determined and found that the gp96 mimotope with ALUM showed a significant increase in antibody titer, followed by GM-CSF and liposomes. Further, the T cell (CD4+ and CD8+) populations from splenocytes, as well as IgG isotypes, interleukin-4, and interleukin-5 of gp96 mimotope with ALUM-immunized animals, were analyzed. The results suggest that the gp96 mimotope may elicit a potent and effective antitumor antibody response. Further, the study identifies ALUM and GM-CSF as adjuvant options to drive an appropriate protective immune response as these adjuvants have prior use in humans.

Abstract 304: Proinflammatory secretory chemokine CXCL8 regulates intercellular cross-talk in the breast cancer tumor microenvironment

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL The cellular composition of the tumor microenvironment (TME) and soluble effector molecules mediating intercellular cross-talk are important therapeutic and preventive targets for breast cancer. Chemokines released within the TME work in a synergistic and reciprocal manner to induce malignant progression of tumor cells. CXCL8, a proinflammatory CXC chemokine shown to be released within the TME, can act as a chemoattractant, angiogenic factor, and inflammatory factor via cellular receptors CXCR1 and CXCR2. However, the specific role of CXCL8 in the signaling cascades within the tumor microenvironment has yet to be fully classified and warrants further investigation. Treatment of human breast cancer cell lines MCF-7, MDA-MB-231, and T47D with 50nM exogenous CXCL8 enhanced the expression of CXCR2. The acquisition of chemokine receptors by tumor cells, in this case CXCR2, can mediate phenotypic changes that enhance migratory and invasive potential. Treatment of these human breast cancer cell lines with 50nM exogenous CXCL8 resulted in phenotypic morphology changes characteristic of an epithelial-to-mesenchymal transition (EMT), a phenomenon commonly exhibited by metastatic tumor cells. We validated this phenomenon with 50nM exogenous CXCL8 treatment, which led to enhanced expression of both Slug (Snail2) and Twist in all three human breast cancer cell lines. Furthermore, we observed that treatment with 50nM exogenous CXCL8 promoted the migration and invasion of these breast cancer cell lines in an in vitro modified Boyden chamber assay. These results suggest that CXCL2 secreted from cells within the TME act to induce characteristic changes in human breast cancer cells, propagating the transition to more aggressive tumors. Tumor-associated macrophages (TAMs) are an important component of the heterogeneous population of cells that make up the TME. Breast cancer cells exposed to conditioned media from human monocytic cell lines THP-1 and U937, previously differentiated with 12-O-tetradecanoylphorbol-13-acetate (TPA), exhibited distinct morphology changes characteristic of EMT and enhanced migratory and invasive ability, similar to exogenous CXCL8 treatment. Together, our results suggest that CXCL8 can have profound implications in determining the fate of tumor cells by engaging in extensive cross-talk within the TME, thus providing a potential target for the treatment and prevention of breast cancer tumor progression and metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 304. doi:1538-7445.AM2012-304

Abstract 1569: Multivalent melanoma vaccine using primary human melanoma cells and a vaccinia virus based antigen retrieval system

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Melanoma is the fifth most diagnosed cancer in men and seventh most diagnosed cancer in women and it is estimated that there will be over 70,000 new cases and 8,000 deaths in 2011. Prevention of both primary and secondary melanomas requires the development of a melanoma specific multi-valent vaccine. We have been involved in developing a vaccinia virus based vaccine consisting of melanoma cell membrane antigens and integrated vaccinia viral proteins, which serve as a potent adjuvant. This melanoma vaccine, referred to as viral membrane oncolysate (VMO), is composed of five primary cell lines derived from patient tumors each independently infected with vaccinia virus and has been shown to induce anti-cancer immune response in clinical trials. Notable results were obtained in node positive subsets of patients that showed a positive response in survival distribution function suggesting that this preparation is an active therapeutic immunogen but the mechanism of immune activation needs to be elucidated. In order for us to define the immunogens that impart the clinical efficacy of the this melanoma VMO vaccine, it is essential to characterize the primary cell lines with respect to their phenotypic characteristics as well as to define the melanoma antigen repertoire so that effective vaccine strategies can be designed that do not rely exclusively on tumor derived primary cells. Our study reveals that all the five primary cell lines expressed antigens, such as gp100, CD146, and tyrosinase, similar to several commercially available melanoma cell lines although at varying concentrations. In addition, the five primary cell lines demonstrated varying migratory/invasive properties using a Boyden Chamber assay and their tumorigenic potential is being tested in nude mice. The cells were also characterized with respect to BRAF mutations. We observed several similarities between the antigenic profile of the primary and established cell lines as well as some unique characteristics. We conclude that using a combination of defined antigens from primary tumor cells is useful in designing a pan-antigen immunotherapeutic vaccine. This melanoma pan antigen vaccine can be an effective tool in primary prevention of melanoma presumably having the highest clinical efficacy when combined with unique antigens from primary cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1569. doi:1538-7445.AM2012-1569