Anshu Mittal Roy

Vascular endothelial growth factor reduces tamoxifen efficacy and promotes metastatic colonization and desmoplasia in breast tumors.

Clinical studies have shown that decreased tamoxifen effectiveness correlates with elevated levels of vascular endothelial growth factor (VEGF)-A(165) in biopsy samples of breast cancers. To investigate the mechanisms underlying tamoxifen resistance and metastasis, we engineered the estrogen receptor (ER)-positive MCF-7 human breast cancer cell line to express VEGF to clinically relevant levels in a doxycycline-regulated manner. Induction of VEGF expression in orthotopically implanted xenografts that were initially tamoxifen responsive and noninvasive resulted in tamoxifen-resistant tumor growth and metastasis to the lungs. Lung metastases were also observed in a VEGF-dependent manner following tail vein injection of tumor cells. At both primary and metastatic sites, VEGF-overexpressing tumors exhibited extensive fibroblastic stromal content, a clinical feature called desmoplasia. VEGF-induced metastatic colonies were surrounded by densely packed stromal cells before detectable angiogenesis, suggesting that VEGF is involved in the initiation of desmoplasia. Because expression of VEGF receptors R1 and R2 was undetectable in these tumor cells, the observed VEGF effects on reduction of tamoxifen efficacy and metastatic colonization are most likely mediated by paracrine signaling that enhances tumor/stromal cell interactions and increases the level of desmoplasia. This study reveals new roles for VEGF in breast cancer progression and suggests that combination of antiestrogens and VEGF inhibitors may prolong tamoxifen sensitivity and prevent metastasis in patients with ER-positive tumors.

Abstract 5154: Serotonin signaling as a novel target of tumor angiogenesis

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Angiogenesis is a well-controlled process that is regulated by multiple factors that are secreted by the cancer cells as well as other cells within the tumor microenvironment. Angiogenesis inhibitors are showing therapeutic efficacy in an increasing number of human cancers. However, in both preclinical and clinical settings, the benefits are transitory and are followed by resistance and a restoration of tumor growth and progression. Therefore, novel anti-angiogenic strategies with complementary mechanisms are needed to maximize efficacy and minimize resistance to current angiogenesis inhibitors. Activation of platelets and blood coagulation frequently occurs in cancer patients. Apart from VEGF, platelets contain several other angiogenic growth factors and inhibitors that are released upon activation and promote tumor neoangiogenesis. Although considerable attention has been focused on platelet peptide growth factors, little is known about the mitogenic effects of nonpeptide platelet products such s serotonin (5-HT), considering that 99% of 5-HT in blood is found in platelets and is released at blood clotting sites. In previous studies, we have shown that endothelial cells express 5-HT receptors and 5-HT has growth stimulatory effcts on multiple types of endothelial cells. We have also demonstrated that 5-HT binds to inhibitory type of G-protein coupled receptors and stimulates the phosphorylation of PYK2/PI3K/AKT/mTOR signaling pathway, the same signaling pathway, which has been activated by most angiogenic factors, including VEGF. In our recent studies, we explored angiogenic promoting activity of 5-HT in the mouse matrigel plug assay (in vivo angiogenesis model system) and antiangiogenic potential of antagonists against 5-HT receptors in xenograft-CAM assay (ex vivo tumor angiogenesis model system). The most importantly, an antagonist against a specific 5-HT receptor demonstrated the synergistic effect in blocking tumor-induced new blood vessel formation when it was applied in combination with Sutent, a FDA approved antiangiogenic drug against VEGF receptor. The results of this study suggest that 5-HT signaling pathway constitute a novel target of tumor angiogenesis in anticancer therapeutic development. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5154. doi:10.1158/1538-7445.AM2011-5154

Abstract 2333: Serotonin: A known neurotransmitter functions as an angiokine to support cancer progression

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Platelet aggregation leads to significant serotonin release from its major storage and results in increasing of serotonin levels at injury site and thrombotic tumor environment. Many studies have shown that platelet activation plays a crucial role in tumor progression; however, the role of serotonin in angiogenesis and tumor progression has not been well studied. In this study, we have tested the hypothesis that 5-HT promotes angiogenesis, and antagonizing 5-HT activity has anti-angiogenic benefit in controlling tumor growth. Real time PCR and western blot studies showed that endothelial cell expressed 5-HT receptor 1B (HTR1B) in higher level than other 5-HT receptors. Endothelial cell proliferation and tube formation were significantly affected by blocking HTR1B and the cAMP and IP1 assays have revealed the HTR1B as the inhibitory type of GPCR. Stimulation of endothelial cell with 5-HT or HTR1B agonist has led to activation of two individual signaling pathways: ERK and Akt / mTOR. In further studies, p70S6K was recognized as the merging point of these signaling. These kinases have been also activated by known angiogenic factors (VEGF and FGF) but the mechanism of activation was different from serotonin and it was through their tyrosine kinase receptors. In contrast, pretreatment of endothelial cell with a selective HTR1B antagonist have led to blockade of the 5-HT induced kinases’ activation. We also demonstrated angiogenic promoting activity of 5-HT with a mouse Matrigel plug (in vivo angiogenesis model system) and antiangiogenic potential of antagonists against HTR1B with an ex vivo tumor angiogenesis model (xenograft CAM assay) and xenograft mice model of human ovary cancer (SKOV-3). Selective HTR1B antagonist displayed the synergistic effect (combination index analysis) in blocking tumor-induced new blood vessel formation when it was applied in combination with Sutent (VEGFR2 antagonist). HTR1B antagonist also showed preclinical efficacy in the xenograft model of human ovary cancer by reducing over 50% in tumor size and blood vessel density marker.The results of this study enhanced our understanding of the serotonin-signaling pathway in human endothelial cells during angiogenesis. This research also revealed the potential of 5-HT signaling as the new target for antiangiogenic development. 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 2333. doi:1538-7445.AM2012-2333

Abstract 4265: Bithionol as an inhibitor of tumor angiogenesis

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Tumor progression depends on angiogenesis. The clinical successes in recent years have demonstrated that antiangiogenic agents can be developed as effective treatment for cancer patients. However, the resistance to the current FDA approved antiangiogenic therapies is emerging, which presents challenges in cancer research and urgent needs for novel angiogenesis inhibitors with different mechanisms of drug actions to overcome the resistance. In our previous studies, we have identified a small molecule bithionol as a potential antiangiogenic agent through a chemical diversity library screening with a cell-based angiogenesis assay. Bithionol is a FDA approved and current clinically used anthelmintics, which has been found to directly inhibit activity of autotaxin, a secreted enzyme that catalyzes lysophosphatidic acid (LPA) production. LPA, as a lipid signaling molecule, is a potent angiogenic and cancer cell motility stimulating factor. Therefore, autotaxin plays important role in tumor angiogenesis and metastasis and has been recently identified as an attractive angiogenesis and cancer target. Our recent studies have shown that autotaxin is expressed at high levels in human endothelial and number of human cancer cell lines. Bithionol has demonstrated inhibitory activities against human endothelial cell proliferation, migration, and tube-formation as the three key cellular steps in angiogenesis process. The effect of bithionol on inhibition of tumor angiogenesis was also evaluated with an ex vivo xenograft chicken embryo chorioallantoic membrane (xenograft-CAM) model system. Bithionol is able to inhibit tumor-induced new blood vessel formation in a dose dependent manner and has demonstrated an additive inhibitory activity when it is applied in combination with Sutent, a current clinically used antiangiogenic drug. The results of this research suggest that bithionol provide a unique promising opportunity in developing new combinational treatment to increase the anticancer efficacy and minimize the resistance in cancer patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4265. doi:10.1158/1538-7445.AM2011-4265

Abstract 5474: Targeting endothelial tubulogenesis for anticancer therapeutic development

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC The clinical successes of VEGF-targeted agents in recent years have demonstrated that antiangiogenic therapy can be developed as effective anti-cancer treatment. However, the field of oncology is facing a new challenge of overcoming the resistance to VEGF-targeted therapy; therefore, novel angiogenesis inhibitors are required for new therapeutic development. During the growth of new blood capillaries, following proliferation and migration, endothelial cells undergo morphological changes and adhere to each other forming tubular structures as a process of tubulogenesis, which presents a unique target for inhibitory action of antiangiogenic agents. Southern Research angiogenesis research team has identified a structurally related series of heterocyclic compounds SRI-24637 and its analogs as a new class of antiangiogenic agents. SRI-24637 demonstrated selective potent inhibition of endothelial tube-formation and significant activity in blocking tumor-induced blood vessel formation using an ex vivo human cancer xenograft-CAM assay model system. The mechanism of action of SRI-24637 is different from the clinical VEGF-targeted drugs; therefore, it may provide a complementary mechanism to overcome the resistance to VEGF-targeted therapies. Bioavailability studies showed that SRI-24637 dosed at 40 mg/kg in DMSO/PEG400 reached systemic concentration levels much higher than the IC50 concentration for in vitro endothelial tube-formation. Comparing with the clinical VEGF-targeted drug Sunitinib, the cytotoxic activities of SRI-24637 against normal human fibroblast and epithelial cells suggest that the toxic side effects of SRI-24637 may be within a tolerable range. Ongoing preclinical efficacy studies with animal tumor models will aid in the development of SRI-24637 as an anti-cancer drug. Based on the outcome of these studies, further lead optimization will be done if required, before entering it into the clinical Phase I and II trials using protocols similar to those employed for Sunitinib and Sorafenib, or other investigational small molecules targeting tumor angiogenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5474.

Abstract 563: Novel role of VEGF and neuropilin-1 in breast cancer tumor-stromal interactions

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Human breast cancers contain high levels of fibroblastic stroma as a critical feature of desmoplasia. The complex interactions between tumor and stromal cells play important roles in tumor growth, metastasis and resistance to anticancer treatments. Our previous in vivo studies showed that increased levels of tumor-released VEGF were associated with increased desmoplastic responses and resulted in a hormonal resistance phenotype of ER+ breast tumor. Based on our findings, a clinical trial conducted at UAB with a new combinational treatment targeting both ER and VEGF signalings has achieved significant objective response in ER+ breast cancer patients. In our current studies, we further studied the role of VEGF in mediating tumor-stromal interactions and initiation of desmoplasia. Our results have shown that tumor released VEGF interacts with stromal fibroblasts which express VEGF receptors R1, R2 and Neuropilin-1 (NRP1), thereby stimulating their infiltration to promote desmoplastic response. Down regulation of NRP1 expression by siRNA significantly abolished the fibroblast chemo-attractive motility towards VEGF, while the VEGFR1 and VEGFR2 blocking antibodies had no effects on their migration mobility, suggesting that NRP1 expressed in fibroblast is involved in tumor-stroma cell interactions in breast cancer. Our studies using breast cancer xenograft mouse model with regulated tumor VEGF expression revealed that tumor VEGF expression was positively correlated with expression of NRP1 and alpha smooth muscle actin (α-SMA, a transformed/myo fibroblast marker) in the tumor stroma. In addition, levels of tumor VEGF, stromal NRP1 and α-SMA were all positively correlated with level of tumor stromal content and tumor growth. Blocking tumor VEGF with a neutralizing antibody (Avastin) as a treatment modality in xenograft mice reversed the VEGF increased desmoplasia. Our study results reveal a novel role of VEGF and NRP1 in tumor-stromal interactions and desmoplasia, indicating NRP1 can be a therapeutic target for breast cancer treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 563.

Abstract 2390: Serotonin signal transduction in human endothelial cells

Angiogenesis is a highly regulated biological complex process, which consist of endothelial cells proliferation, migration, and tubulogenesis as key cellular steps to form new blood capillaries from preexisting vessels. Imbalance in angiogenesis contributes to a variety of human diseases. Tumor growth depends on angiogenesis and antiangiogenic agents have been developed as effective anti-cancer medicine. Recently, we have demonstrated that serotonin (5-HT), a well-recognized neurotransmitter, has a promoting effect on endothelial cells proliferation, migration and tubulogenesis, suggesting serotonin plays a role in regulation of angiogenesis. To study the role of serotonin in angiogenesis, we examined the expression of serotonin receptor isoforms in human endothelial cells. Real time PCR studies have showed that, serotonin receptor 1B (HTR1B), 1D (HTR1D), 1A (HTR1A) and 2B (HTR2B) are expressed in primary human endothelial cell lines. Blocking serotonin 1B receptor had significant inhibitory effect on endothelial cells proliferation and tubulogenesis. We have further explored the 1B-mediated signal transduction in endothelial cells. The results have revealed that the serotonin 1B receptor as a G protein-coupled receptor (GPCR) is coupled to Gi protein and decreased intracellular cAMP level upon its receptor binding. Both serotonin and 1B receptor agonist were able to activate ERK, p38, Akt, RhoA, Rac1 and PYK2/FAK signaling in endothelial cells. In contrast, a selective antagonist for serotonin 1B receptor blocks the serotonin-stimulated Akt and PYK2/FAK activation. Experiments with pertussis toxin (general Gi blocker) further demonstrated that heterotrimeric Gi-protein is required for the activation of Akt and PYK2/FAK by serotonin. These findings suggest that Akt and PYK2/FAK are involved in signaling transduction in serotonin-activated endothelial cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2390.