Non-metastatic Tumor Cells Research Articles

Understanding the mechano and chemo response of retinoblastoma tumor cells

IntroductionCellular homeostasis with its environment is bidirectional and dynamic in nature. Extracellular matrix plays an important role in retinoblastoma tumor cell's response to chemotherapeutic drugs. The present study was designed to investigate the effect of mechanotransduction along with the chemotherapeutic effect on RB cells grown on three-dimensional matrices. MethodsMatrigels of varying stiffness (low and high) were prepared and characterized. Drug sensitivity of RB cells on various matrigel stiffness was measured using cytotoxicity (MTT) assay and IC50 value was found for carboplatin and etoposide. Further, the effect on the proliferation and migration of RB cells in various stiffness matrigels was investigated. FindingsThe results showed that drug sensitivity decreased with an increase in matrix stiffness when compared to RB cells grown in suspension. In higher stiffness, the drug sensitivity decreases with an increase in cell proliferation. Data from a gene expression study revealed that Vinculin was variably regulated between metastatic and non-metastatic tumor cells, and upregulated RhoA was altered in different stiffness gradient matrigel during drug treatment. InterpretationThese results enhance the understanding of the fundamental molecules responding to drug sensitivity in a stiffness-altering environment. Additionally, it provides a new avenue for understanding how RB cells respond to chemotherapeutic intervention.

Cystathionine β-synthase overexpression drives metastatic dissemination in pancreatic ductal adenocarcinoma via inducing epithelial-to-mesenchymal transformation of cancer cells

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest of all cancer types with a constant rise in global incidence. Therefore, better understanding of PDAC biology, in order to design more efficient diagnostic and treatment modalities, is a priority.Here we found that the expression levels of cystathionine β-synthase (CBS), a transsulfuration enzyme, is markedly elevated in metastatic PDAC cells compared to cell lines isolated from non-metastatic primary tumors. On human immunohistochemical samples from PDAC patients we also found higher CBS staining in cancerous ductal cells compared to in non-tumor tissue, which was further elevated in the lymph node metastasis of the same patients. In mice, orthotopically injected CBS-silenced T3M4 cells induced fewer liver metastases compared to control cells indicating important roles for CBS in PDAC cancer cell invasion and malignant transformation. Wound healing and colony formation assays in cell culture confirmed that CBS-deficient metastatic T3M4 and non-metastatic BxPC3 primary tumor cells migrate slower and have impaired anchorage-independent growth capacities compared to control T3M4 cells. CBS silencing in T3M4 cells lowered WNT5a and SNAI1 gene expression down to levels that were observed in BxPC3 cells as well as resulted in an increase in E-cadherin and a decrease in Vimentin signals in mouse tumors when injected orthotopically. These observations suggested a primary role for the epithelial to mesenchymal transformation of cancer cells in CBS-mediated tumor aggressiveness. Under normal conditions, STAT3, an upstream regulator of Wnt signaling pathways, was less phosphorylated and more oxidized in shCBS T3M4 and BxPC3 compared to control T3M4 cells, which is consistent with decreased transcriptional activity at lower CBS levels due to less protection against oxidation. Sulfur metabolome analyses suggested that this CBS-mediated protection against oxidative modifications is likely to be related to persulfide/sulfide producing activities of the enzyme rather than its canonical function to produce cystathionine for cysteine synthesis. Taken together, CBS overexpression through regulation of the EMT plays a significant role in PDAC cancer cell invasion and metastasis.

Abstract P130: P-cadherin activates metabolic coupling in the tumor-mesothelial niche: From glycolysis through lactate to lipogenesis

Abstract Peritoneal metastasis affects >70% ovarian cancer patients, and its effective management is an unmet medical goal. Successful adhesion to the peritoneal mesothelium is a key rate-limiting step for metastasis formation, but it is unclear the selective advantage of why ovarian cancer cells colonize specifically to the unique mesothelial environment. Metabolic reprogramming is a hallmark of cancers. Still their role in peritoneal metastasis remains to be fully understood. To overcome the limitations of a lack of tightly controlled experimental model to pinpoint key molecules causing metastasis, we have established an isogenic model of spontaneous human ovarian cancer metastasis. Metabolism is characterized using RNA-seq, RT-PCR, real-time cell metabolic assay, targeted lipidomic analysis and neutral lipid staining. Using coculture, we showed that HM but not NM specifically activated peritoneal mesothelium in a P-cadherin-dependent manner compared to other cadherins, suggesting that there is a unique role for P-cadherin. RNA-seq revealed distinct regulation of lipogenic pathway in non-specific or P-cadherin siRNA treated HM. For these, we have confirmed that P-cadherin could promote the expression of lipogenic genes ACLY, FASN and ACAT2 in HM. Concomitantly, P-cadherin activated glycolysis (HK2, Gpi and PGK1) in the mesothelial cells. Targeted lipidomic analysis further showed that lactate acid that was enriched in the mesothelium was shuttled from the mesothelium to the HM to fuel de novo lipid synthesis in HM, revealing a feed-forward positive loop. Suppressing lactate uptake by using a monocarboxylate transporter 1 inhibitor could abolish the metabolic crosstalk and subsequent metastatic outgrowth. Together, these findings reveal the metabolic differences between metastatic versus non-metastatic tumor cells in understanding ovarian cancer metastasis to the mesothelium, and suggest targeting P-cadherin could be a promising therapeutic approach (RGC17105919). Citation Format: Kun Wang, Jing Ma, Carmen C. L. Wong, Chi Bun Chan, Alice S. T. Wong. P-cadherin activates metabolic coupling in the tumor-mesothelial niche: From glycolysis through lactate to lipogenesis [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P130.

CD8+ T cells from experimental in situ breast carcinoma interfere with bone homeostasis.

Before bone colonization, immune cells primed by breast primary tumor cells actively modify the bone microenvironment, disturbing the complex and tightly homeostatic signaling network regulated by osteoblasts and osteoclasts. Indeed, we have shown that RANKL+ CD4+ T cells specific for the 4T1 mammary carcinoma cell line, arrive at the bone marrow (BM) before metastatic cells and set the pre-metastatic niche. In the absence of RANKL expressed by T cells, there is no pre-metastatic osteolytic disease and bone metastases are blocked. Adding to the role of T cells, we have recently demonstrated that dendritic cells (DCs) provide a positive feedback loop to the osteolytic profile induced by the metastatic tumor. In this setting, DCs are able to differentiate into potent bone resorbing osteoclast-like cells keeping their antigen-presenting cell (APC) properties to maintain RANKL+ CD4+ Th17 T cells activities, via IL-23 expression. Here we show that 67NR non-metastatic tumor cells, a sibling of 4T1 tumor cell line, induce an increase in trabecular bone mass on day 11 post-tumor implant. This observation was associated with an expansion of the osteoblastic lineage cells accompanied by a reduction of osteoclasts numbers. Moreover, BM derived CD8+ T cells from 67NR tumor-bearing mice, express an anti-osteoclastogenic cytokine milieu enriched by IFN-γ, IL-10 and producing low levels of RANKL. The frequency of BM derived CD8+ FoxP3+ regulatory T cells, known as potent suppressors of osteoclastogenesis both in vitro and in vivo, was also increased in such animals. This milieu was capable to suppress 4T1 tumor-specific CD4+ T cells phenotype in vivo and in vitro and strongly inhibited bone metastases establishment, restoring trabecular bone mass volume. We concluded that the 67NR+ tumor derived CD8+ T cells phenotypes, either contributing to bone homeostasis and/or control of 4T1 breast tumor pre-metastatic disease, interfere with osteoclasts and osteoblasts activities inside BM. Our study highlights the opposing roles of subverted tumor CD4+ and CD8+ T cell subtypes in directing breast cancer progression and bone metastases establishment. For non-metastatic tumors, the role of T cells regarding bone remodeling has never been addressed before. As far as we know, this is the first description that an in situ carcinoma can modify distant sites. In the case showed here, modification of the distant bone site disfavors pre-metastatic bone niche formation.

MicroRNA-710 regulates multiple pathways of carcinogenesis in murine metastatic breast cancer.

Prior research has shown that critical differences between non-metastatic and metastatic tumor cells are at the level of microRNA. Consequently, harnessing these molecules for the treatment of metastatic cancer could have significant clinical impact. In the present study, we set out to identify metastasis-specific microRNAs which drive metastatic colonization of distant organs. Using a murine model of metastatic breast cancer, we employed a directed approach in which we screened for microRNAs that are differentially expressed between the primary tumors and metastatic lesions but concordantly expressed in all of the metastatic lesions irrespective of the tissue that is colonized. Of the identified targets, we focused on miR-710, which was consistently and significantly downregulated in the metastatic lesions relative to the primary tumors. The level of downregulation was independent of the distant organ that is involved, suggesting that miR-710 plays a fundamental role in metastatic colonization. Computational target prediction suggested a pleiotropic role for miR-710 in apoptosis, migration and invasion, and stemness. Using a previously validated oligonucleotide delivery system, we introduced miR-710 mimics into 4T1 metastatic breast adenocarcinoma cells and assessed the resultant phenotypic effects. We demonstrated significant inhibition of cell viability, migration, and invasion. We also showed that the treatment profoundly enhanced cell senescence, reduced stemness, and influenced markers of epithelial to mesenchymal transition, as evidenced by enhanced E-cadherin and reduced vimentin expression. This knowledge represents a first step towards harnessing a similar approach to discover novel microRNA targets with therapeutic potential in metastasis.

Mammary tumor and mastectomy synergistically promote neuroinflammation in a breast cancer survivor model

Understanding why breast cancer survivors are at an increased risk for cognitive and affective disorders is essential for developing targeted treatment plans and improving quality of life. Microglia priming results in chronic neuroinflammation and can contribute to neuronal degeneration and dysfunction, thereby offering a potential mechanism for altered brain function that persists after tumor removal. This study examined whether mammary tumors alter microglia and augment the inflammatory profile and behavior of mice. To test this, non-metastatic mammary tumor cells (67NR) were injected orthotopically into the mammary glands of BALB/c mice, allowed to grow for 16 days, and then the tumors were removed via mastectomy. Following a 14-day surgical recovery, the mice were challenged with lipopolysaccharide (LPS), and then central and peripheral inflammation, anxiety, and depressive-like behavior were evaluated. Here we show that major central and peripheral inflammatory markers were not altered by tumor growth nor mastectomy surgery alone. However, hippocampal mRNA expression of major proinflammatory cytokines IL-1β and TNFα was increased in tumor removal animals, persisting past surgical recovery. Nonetheless, the immune and behavioral responses following LPS administration were comparable among groups. In sum, these data demonstrate that the combination of tumor and mastectomy promotes neuroinflammation; however, immune challenge did not elucidate this inflammation as maladaptive for the host.

New Directions in the Study and Treatment of Metastatic Cancer.

Traditional cancer therapy has relied on a strictly cytotoxic approach that views non-metastatic and metastatic tumor cells as identical in terms of molecular biology and sensitivity to therapeutic intervention. Mounting evidence suggests that, in fact, non-metastatic and metastatic tumor cells differ in key characteristics that could explain the capacity of the metastatic cells to not only escape the primary organ but also to survive while in the circulation and to colonize a distant organ. Here, we lay out a framework for a new multi-pronged therapeutic approach. This approach involves modifying the local microenvironment of the primary tumor to inhibit the formation and release of metastatic cells; normalizing the microenvironment of the metastatic organ to limit the capacity of metastatic tumor cells to invade and colonize the organ; remediating the immune response to tumor neoantigens; and targeting metastatic tumor cells on a systemic level by restoring critical and unique aspects of the cell’s phenotype, such as anchorage dependence. Given the limited progress against metastatic cancer using traditional therapeutic strategies, the outlined paradigm could provide a more rational alternative to patients with metastatic cancer.

Abstract 446: Differential effects of folate depletion on metabolic reprogramming and oxidative stress in nonmetastatic and metastatic claudin-low breast cancer cells

Abstract Folate coenzymes play an important role in biosynthesis and methylation reactions. Aberrant folate metabolism has been implicated in the development of several cancer types, though mechanisms underlying folate metabolism and cancer development remain unclear. We previously showed that a folate-restricted diet can exert differential effects on metastatic versus nonmetastatic murine claudin-low breast cancer cells in vivo. Specifically, folate restriction increased growth and invasion of orthotopically transplanted M-Wnt (nonmetastatic) tumor cells, but decreased growth and lung metastases of transplanted metM-Wnt cells, a metastatic subclone of M-Wnt cells. The current study set out to explore the underlying mechanism. To examine the effect of long-term folate depletion (LFD) on M-Wnt and metM-Wnt cell metabolism, oxidative stress and autophagic flux in vitro, the two cell lines were grown in standard and folate-depleted media for 14 days. metM-Wnt cells showed higher oxidative stress, as measured by ROS staining and Nrf2 expression, and phosphorylation of the key nutrient sensor, AMPK, compared to M-Wnt cells when grown in standard growth medium. LFD M-Wnt cells showed an increased dependence on glycolysis compared to those cultured in standard medium. Both M-Wnt and metM-Wnt cells displayed a high autophagy level in LFD, measured by LC3B cleavage, and AMPK phosphorylation. However, LFD metM-Wnt cells showed low viability, increased apoptosis and loss of redox defense, as measured by cleaved-caspase 3 and Nrf2 expressions. These results suggest that non-metastatic M-Wnt cells undergo metabolic reprogramming, including a shift from oxidative phosphorylation to glycolysis that may fuel cell growth and proliferation. Further, an elevated autophagic flux may mitigate nutrient stress induced by folate depletion, which allows them to withstand LFD and which may contribute to a more invasive primary tumor in response to folate restriction. In contrast, metM-Wnt cells are unable to undergo this metabolic adaptation, and display increased oxidative stress and cell death in response to LFD, preventing the development of metastatic lesions in vitro. This study highlights different responses of primary and metastatic breast cancer cells to folate depletion. The results provide additional rationale for targeting folate metabolism as a potential strategy for treating metastatic breast cancer. Citation Format: Xuewen Chen, Ciara H. O'Flanagan, Stephen D. Hursting. Differential effects of folate depletion on metabolic reprogramming and oxidative stress in nonmetastatic and metastatic claudin-low breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 446. doi:10.1158/1538-7445.AM2017-446

Melatonin and IL-25 modulate apoptosis and angiogenesis mediators in metastatic (CF-41) and non-metastatic (CMT-U229) canine mammary tumour cells.

Melatonin has oncostatic actions and IL-25 is active in inflammatory processes that induce apoptosis in tumor cells AIM: The aim of this study was to evaluate melatonin and IL-25 in metastatic (CF-41) and non-metastatic (CMT-U229) canine mammary tumor cells cultured as monolayers and tridimensional structures. The cells were treated with melatonin, IL-25 and IL-17B silencing gene and performed cell viability, gene and protein expression of caspase-3 and VEGFA (Vascular endothelial growth factor A) and an apoptosis membrane protein array. Treatment with 1 mM of melatonin reduced cell viability of both tumor cell lines, all treatments alone and combined significantly increased caspase-3 cleaved and proteins involved in the apoptotic pathway and reduced pro-angiogenic VEGFA, confirming the effectiveness of these potential promising treatments. This is the first study evaluating the potential use of these strategies in CF-41 and CMT-U229 cell lines and together encourages subsequent in vitro and in vivo studies for further exploration of clinical applications.

Abstract C41: Altered control of intracellular androgen availability by glucuronidation contributes to loss of androgen dependence in prostate tumor cells

Abstract Locally advanced and metastatic cancers are frequently treated by androgen deprivation therapy. Tumors that recur despite this treatment, termed castration resistant prostate cancer, are highly aggressive and have acquired the capacity to survive and expand in conditions of low circulating androgens. Prostate epithelial cells control the potency and overall availability of androgen hormones in part by inactivation and excretion of excess quantities. The enzymes that catalyze inactivation, specifically by covalently modifying the hormone with a glucuronate adduct, are called UDP-glucuronosyltransferases (UGT). Genetic mutations that reduce levels of the UGT isozymes needed to eliminate excess androgens from the prostate have been correlated with prostate cancer incidence. The ability to alter androgen elimination at the level of individual cells within a tumor is one mechanism by which tumors become heterogeneous with respect to molecular features and therapeutic resistance. UDP-glucose dehydrogenase (UGDH) catalyzes the NAD+-dependent oxidation of UDP-glucose to UDP-glucuronate, an essential precursor for androgen inactivation by the prostate glucuronidation enzymes UGT2B15 and UGT2B17. Our laboratory has found that non-metastatic prostate tumor cell lines express UGDH in an androgen sensitive manner, that its expression increases the level of UDP-glucuronate, and that these precursors are then channeled to the UGT-catalyzed glucuronidation pathway. The level of UGDH is androgen controlled and serves to regulate tumor cell growth, inversely to its expression. Loss of androgen stimulated UGDH, or pharmacological antagonism of its activity, translated to increased proliferation rate, specifically of androgen dependent tumor cells. We knocked down expression of UGDH in androgen dependent cells to test the role of UGDH in driving cellular glucuronate levels, intratumoral steroid availability, and response to androgen. Flux of UDP sugar metabolites and levels of androgen glucuronide accumulation were compared in control and UGDH knockdown lines by liquid chromatography and mass spectrometry analysis. Effects on androgen sensitive gene expression were monitored by western analysis. Selection of manipulated cells in decremental DHT levels that simulated androgen deprivation was found to reduce steady state UGDH expression, thereby activating the UGT-driven steroid clearance mechanism, as reflected in increased PSA levels and de-repression of UGT2B17. Whereas restimulation of control transfectants with physiological levels of DHT could only increase UGDH expression and maintain full androgen sensitivity in cells experiencing complete androgen loss, the knockdown of UGDH permitted cells to accumulate UDP-glucuronate pools, and decreased UGT-driven glucuronidation of DHT and androsterone. These results support a model in which maintenance of partial UGDH activity through gradual androgen deprivation facilitates loss of sensitivity in androgen elimination pathways and suggests adjuvant UGDH inhibition could prevent or delay onset of castration resistant recurrence. Citation Format: Michelle Palmer, Linlin Ma, Trevor Romsdahl, Qin Wei, Eileen Loughman, Jonathan Markham, Joseph Barycki, Melanie A. Simpson. Altered control of intracellular androgen availability by glucuronidation contributes to loss of androgen dependence in prostate tumor cells. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr C41.

Abstract 1839: Analysis of cell cycle-related gene expressions in MDM2-transfected LNCaP-MST cells after inhibition of HSP90

Abstract MDM2 gene is a cellular proto-oncogene amplified in 25-40% of all human cancers and regulates cell proliferation, senescence, and apoptosis through targeting p53. It is widely speculated that MDM2 protein is not only responsible for tumorigenesis via p53 inactivation, but also for increasing the metastatic ability of originally non-metastatic tumor cells. HSP90 is a molecular chaperone that regulates the maturation, activation and stability of critical signaling proteins that drive the development and progression of prostate cancer. 17-Allyamino-17-demethoxygeldanamycin (17-AAG) is an inhibitor of HSP90, which causes proteasomal degradation of client proteins such as AR, HER2, Akt etc., leading to cell cycle arrest and substantial growth inhibition. HSP90 is also believed to be involved in the stabilization of MDM2 and therefore, inhibition of HSP90 is expected to accelerate degradation of MDM2 and disrupt its function. Hence, our study was designed to determine the expression profile of the genes in the cell cycle pathway following treatment of MDM2 overexpressing LNCaP-MST prostate cancer cells with 17-AAG (10 μM at 24 hrs). In the present study, Human cell cycle PCR array was used to examine the alterations in gene expression pattern following exposure to the 17-AAG in MDM2 overexpressed prostate cancer cells. In our experiments we observed that the genes impacted by MDM2 overexpression were reversed by HSP90 inhibition. The expression of genes such as CDC25A, CDC25C, AURKB and Survivin levels were significantly down-regulated after 17-AAG treatment, while p21 and GADD45A were up-regulated compared to the control LNCaP-MST. A heat map and scatterplot analysis clearly confirmed the alterations in the expression levels of these genes following 17-AAG treatment. It is expected that more thorough understanding of the consequences of HSP90 blockade, particularly those that are independent of its role as a regulator of p53, will reveal its therapeutic significance. Our results offer convincing evidence to suggest that the inhibition of HSP90 can induce cell cycle arrest in LNCaP-MST cells. (The financial support from the Royal Dames of Cancer Research Inc., Ft. Lauderdale, Florida is gratefully acknowledged). Citation Format: Thiagarajan Venkatesan, Ali Alaseem, Khalid Alhazzani, Priya Dondapati, Saad Alobid, Appu Rathinavelu. Analysis of cell cycle-related gene expressions in MDM2-transfected LNCaP-MST cells after inhibition of HSP90. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1839.

Differentiating Metastatic and Non-metastatic Tumor Cells from Their Translocation Profile through Solid-State Micropores.

Cancer treatment, care, and outcomes are much more effective if started at early stages of the disease. The presence of malignant cancer cells in human samples such as blood or biopsied tissue can be used to reduce overtreatment and underdiagnosis as well as for prognosis monitoring. Reliable quantification of metastatic tumor cells (MTCs) and non-metastatic tumor cells (NMTCs) from human samples can help in cancer staging as well. We report a simple, fast, and reliable approach to identify and quantify metastatic and non-metastatic cancer cells from whole biological samples in a point-of-care manner. The metastatic (MDA MB-231) and non-metastatic (MCF7) breast cancer cells were pushed through a solid-state micropore made in a 200 nm thin SiO2 membrane while measuring current across the micropore. The cells generated very distinctive translocation profiles. The translocation differences stemmed from their peculiar mechanophysical properties. The detection efficiency of the device for each type of tumor cells was ∼75%. MTCs showed faster translocation (36%) and 34% less pore blockage than NMTCs. The micropore approach is simple, exact, and quantitative for metastatic cell detection in a lab-on-a chip setting, without the need for any preprocessing of the sample.

CD8 Memory Cells Develop Unique DNA Repair Mechanisms Favoring Productive Division.

Immune responses are efficient because the rare antigen-specific naïve cells are able to proliferate extensively and accumulate upon antigen stimulation. Moreover, differentiation into memory cells actually increases T cell accumulation, indicating improved productive division in secondary immune responses. These properties raise an important paradox: how T cells may survive the DNA lesions necessarily induced during their extensive division without undergoing transformation. We here present the first data addressing the DNA damage responses (DDRs) of CD8 T cells in vivo during exponential expansion in primary and secondary responses in mice. We show that during exponential division CD8 T cells engage unique DDRs, which are not present in other exponentially dividing cells, in T lymphocytes after UV or X irradiation or in non-metastatic tumor cells. While in other cell types a single DDR pathway is affected, all DDR pathways and cell cycle checkpoints are affected in dividing CD8 T cells. All DDR pathways collapse in secondary responses in the absence of CD4 help. CD8 T cells are driven to compulsive suicidal divisions preventing the propagation of DNA lesions. In contrast, in the presence of CD4 help all the DDR pathways are up regulated, resembling those present in metastatic tumors. However, this up regulation is present only during the expansion phase; i.e., their dependence on antigen stimulation prevents CD8 transformation. These results explain how CD8 T cells maintain genome integrity in spite of their extensive division, and highlight the fundamental role of DDRs in the efficiency of CD8 immune responses.

CXCR3 as a molecular target in breast cancer metastasis: inhibition of tumor cell migration and promotion of host anti-tumor immunity.

Chemokines and chemokine receptors have critical roles in cancer metastasis and have emerged as one of the targeting options in cancer therapy. However, the treatment efficacy on both tumor and host compartments needs to be carefully evaluated. Here we report that targeting CXCR3 decreased tumor cell migration and at the same time improved host anti-tumor immunity. We observed an increased expression of CXCR3 in metastatic tumor cells compared to those from non-metastatic tumor cells. Knockdown (KD) of CXCR3 in metastatic tumor cells suppressed tumor cell migration and metastasis. Importantly, CXCR3 expression in clinical breast cancer samples correlated with progression and metastasis. For the host compartment, deletion of CXCR3 in all host cells in 4T1 mammary tumor model significantly decreased metastasis. The underlying mechanisms involve a decreased expression of IL-4, IL-10, iNOs, and Arg-1 in myeloid cells and an increased T cell response. IFN-γ neutralization diminished the metastasis inhibition in the CXCR3 knockout (KO) mice bearing 4T1 tumors, suggesting a critical role of host CXCR3 in immune suppression. Consistently, targeting CXCR3 using a small molecular inhibitor (AMG487) significantly suppressed metastasis and improved host anti-tumor immunity. Our findings demonstrate that targeting CXCR3 is effective in both tumor and host compartments, and suggest that CXCR3 inhibition is likely to avoid adverse effects on host cells.

IL17 Promotes Mammary Tumor Progression by Changing the Behavior of Tumor Cells and Eliciting Tumorigenic Neutrophils Recruitment.

The aggressiveness of invasive ductal carcinoma (IDC) of the breast is associated with increased IL17 levels. Studying the role of IL17 in invasive breast tumor pathogenesis, we found that metastatic primary tumor-infiltrating T lymphocytes produced elevated levels of IL17, whereas IL17 neutralization inhibited tumor growth and prevented the migration of neutrophils and tumor cells to secondary disease sites. Tumorigenic neutrophils promote disease progression, producing CXCL1, MMP9, VEGF, and TNFα, and their depletion suppressed tumor growth. IL17A also induced IL6 and CCL20 production in metastatic tumor cells, favoring the recruitment and differentiation of Th17. In addition, IL17A changed the gene-expression profile and the behavior of nonmetastatic tumor cells, causing tumor growth in vivo, confirming the protumor role of IL17. Furthermore, high IL17 expression was associated with lower disease-free survival and worse prognosis in IDC patients. Thus, IL17 blockade represents an attractive approach for the control of invasive breast tumors.

Abstract 1130: AKT-mediated phosphorylation is responsible for TWIST1-mediated tumor growth and metastasis

Abstract Cancer cells show epithelial-mesenchymal transition (EMT) during cell migration, invasion and dissemination. Although it has been shown by numerous publications that the evolutionary conserved basic helix-loop-helix (b-HLH) transcription factor TWIST1 plays pivotal role during EMT the molecular mechanism responsible for TWIST1 function is not fully understood. Here we show that Twist1 binds to and phosphorylated by AKT/protein kinase-B at S42, T121 and S123. While conversion of S42, T121 and S123 to phosphorylation-mimicking Aspartic or glutamic acids created active Twist1, Alanin mutants of the same sites diminished the DNA-binding and transctivating functions of Twist1. In line with this, Glutamic Acids mutants suppressed the expression of E-Cadherin, whose expression is negatively regulated by active TWIST1, Alanin mutants induced the expression of E-Cadherin. Similarly, we tested the impact of above mentioned mutants on cell migration and proliferation. Our results demonstrated that while Glutamic acid mutants accelerated, Alanin mutants suppressed the migration and proliferation of 293T cells. Our in vitro results prompted us to test our mutants under in vivo conditions using breast cancer as a model. We transfected non-metastatic mouse mammary tumor cell line, 67NR, with Glutamic acid mutants, and metastatic mouse mammary tumor cell line, 4T1, with Alanin mutants of mouse TWIST1 and selected the Neo-resistant populations. We injected 1 million 67NR cells over-expressing wild type or Glutamic acid mutants of Twist1, and 100.000 4T1 cells over-expressing wild type or Alanin mutants of Twist1 into the breast tissue of female inbred BalBC mice, and animals were monitored for metastasis. At the end of the 4th week, we sacrifised and examined the animals for tumor growth and metastasis. Although 67NR cells over-expressing wild type Twist1 did not show any metastasis, cells over-expressing 1E (S42E) and 2E (S42E, T121E) mutants of Twist1 showed 15-20 macroscopic metastasis to liver and Lungs. Paralel to this, 4T1 cells expressing 1A (S42A) and 2A (S42A, T121A) mutants of TWIST1 showed no macroscopic metastasis. Our results clearly indicate that phosphorylation of S42 and T121 by AKT is essential for TWIST1-mediated tumor growth and metastasis. Citation Format: Osman N. Ozes, Suray Pehivanoglu, Gokhan Ertosun, Gokhan Gorgisen, Nuray Erin, Duygu Unal, Gamze Tanriover. AKT-mediated phosphorylation is responsible for TWIST1-mediated tumor growth and metastasis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1130. doi:10.1158/1538-7445.AM2014-1130

P62. Effectiveness of melatonin, IL-25 and siRNA IL-17B in growth control of breast cancer cell lines

Interleukin (IL)-25, a cytokine active in inflammatory processes and production of proinflammatory cytokines, is secreted by mammary epithelial non-malignant cells and induces apoptosis in tumour cells by differential expression of its receptor IL-17RB, highly expressed in malignant cells and lower expressed in non-malignant epithelial cells. It is known that another ligand (IL-17B) compete for the same site of action in tumour cells, contributing to its tumorigenic potential. The melatonin hormone acts in several activities, among them the immune system regulation, proliferation, differentiation and apoptosis process in tumour cells. The aim of this study was to evaluate the effects of treatment with IL-25, silencing gene (siRNA) of cytokine IL-17B and melatonin in human mammary tumour cells for the control of cell proliferation and induction of apoptosis. Non-metastatic mammary tumour cells (MCF-7), metastatic (MDA-MB-231) and a human normal mammary epithelial cells (MCF-10A) were cultured and divided into five treatment groups: group I control, group II treated with IL-25 protein, group III treated with siRNA IL-17B, group IV treated with melatonin and group V joint treatments. The gene silencing was standardised by real-time PCR (qPCR), cell viability assessed by MTT assay and protein expression of caspase-3, apoptotic marker, by immunocytochemistry and subsequent quantification by optical densitometry. After 24 hours of incubation with IL-25 at concentrations of 1, 10 and 50 ng/mL was found a significant decrease in cell viability at 1 ng/mL (38.5 % for MCF-7 cells and 74.0 % for MDA-MB-231 cells; p<0.05) compared with control group, and increased expression of caspase-3 (p<0.001) in both lineage cells. The treatment with siRNA IL-17B at 10nM significantly decreased cell viability (80.0% for MCF-7 cells and 86.0% for MDA-MB-231 cells, p<0.05), and showed a slight increase in the expression of caspase-3. When treated with melatonin at concentrations from 0.001 to 1 mM was observed a significant decreased in cell viability at 1 mM (70.0% for MCF-7 cells and 41.0% for MDA-MB-231 cells; p<0.05) and high expression of caspase-3 (p<0.001) in both lineage cells. For MCF-10A cells, there was no decrease in cell viability to treatments proposed, enabling the use of these therapeutic agents. The joint treatments showed synergic action in reducing the cell viability and induction apoptosis. Our results reinforce the anti-proliferative properties of these agents in breast cancer, establishing new therapeutic strategies. In addition, understanding the role of these factors in immune modulating highlights the growing connection between the contribution of the immune system to combat cancer progression.

β3 Integrin Promotes TGF-β1/H2O2/HOCl-Mediated Induction of Metastatic Phenotype of Hepatocellular Carcinoma Cells by Enhancing TGF-β1 Signaling

In addition to being an important mediator of migration and invasion of tumor cells, β3 integrin can also enhance TGF-β1 signaling. However, it is not known whether β3 might influence the induction of metastatic phenotype of tumor cells, especially non-metastatic tumor cells which express low level of β3. Here we report that H2O2 and HOCl, the reactive oxygen species produced by neutrophils, could cooperate with TGF-β1 to induce metastatic phenotype of non-metastatic hepatocellular carcinoma (HCC) cells. TGF-β1/H2O2/HOCl, but not TGF-β1 or H2O2/HOCl, induced β3 expression by triggering the enhanced activation of p38 MAPK. Intriguingly, β3 in turn promoted TGF-β1/H2O2/HOCl-mediated induction of metastatic phenotype of HCC cells by enhancing TGF-β1 signaling. β3 promoted TGF-β1/H2O2/HOCl-induced expression of itself via positive feed-back effect on p38 MAPK activation, and also promoted TGF-β1/H2O2/HOCl-induced expression of α3 and SNAI2 by enhancing the activation of ERK pathway, thus resulting in higher invasive capacity of HCC cells. By enhancing MAPK activation, β3 enabled TGF-β1 to augment the promoting effect of H2O2/HOCl on anoikis-resistance of HCC cells. TGF-β1/H2O2/HOCl-induced metastatic phenotype was sufficient for HCC cells to extravasate from circulation and form metastatic foci in an experimental metastasis model in nude mice. Inhibiting the function of β3 could suppress or abrogate the promoting effects of TGF-β1/H2O2/HOCl on invasive capacity, anoikis-resistance, and extravasation of HCC cells. These results suggest that β3 could function as a modulator to promote TGF-β1/H2O2/HOCl-mediated induction of metastatic phenotype of non-metastatic tumor cells, and that targeting β3 might be a potential approach in preventing the induction of metastatic phenotype of non-metastatic tumor cells.

Abstract 3862: Mechanistic studies of the metastasis suppressor prostaglandin E2 receptor EP1 in breast cancer.

Abstract Prostaglandin E2 (PGE2), the chief cyclooxygenase-2 enzyme (COX-2) product in tumors, is the predominant protumorigenic prostanoid and mediates biological effects by binding to each of four EP receptors (EP1-4). Each receptor is coupled to different intracellular signaling pathways with EP1 coupled to calcium mobilization and PKC. EP4, expressed on malignant breast cells, promotes metastasis, but a role for EP1 in metastasis has not been investigated. Our published studies indicate that EP1 was detected in the cytoplasm and nucleus of benign ducts and malignant cells in invasive ductal carcinomas, and overall survival for women with tumors negative for nuclear EP1 was significantly worse than for women with EP1 expression. Pharmacologic antagonism and reduction of EP1 expression increased metastatic capacity in our murine model of metastatic breast cancer. These data support our hypothesis that EP1 functions as a metastasis suppressor. We now report that murine metastatic mammary tumor cell lines 410.4 and 66.1 have decreased EP1 mRNA expression compared to the non-metastatic cell line 410. We have also identified the presence of a variant EP1 (EP1v) transcript. EP1v has been identified previously in murine mast cell line MC/9 and rat uterus but not in malignant cells. EP1v has a pattern of mRNA expression different than full-length EP1. Compared to the cell line 410, EP1v expression is slightly increased in 410.4 and decreased in 66.1 cell lines. In order to determine the underlying mechanism in which EP1 suppresses metastasis, a metastasis gene array was performed comparing gene expression in EP1-vector, and EP1-silenced 66.1 cell lines and several candidate genes were identified including Fn1, whose protein is altered during epithelial-to-mesenchymal transition. qPCR analysis of Fn1 expression in EP1-silenced and overexpression cell lines revealed an inverse relationship between EP1 and Fn1 expression. A decrease in EP1 expression led to a 4-5 fold increase in Fn1 expression; whereas, increased EP1 expression resulted in a 0.50 fold decrease in Fn1 expression. Like full length EP1, overexpression of EP1v also resulted in a decrease in Fn1 expression. Bioinformatic analysis of the EP1 gene identified several CpG islands. DNA methylation analysis revealed hypermethylation of the CpG island nearest to the promoter in normal, non-metastatic and metastatic murine mammary tumor cell lines. In the quest to identify a clinically relevant strategy to increase expression of this protective receptor, we treated 410.4 and 66.1 cells with demethylating agent 5-azacytidine which resulted in an increase in EP1 expression. Our published studies show that EP1 acts to suppress metastasis and we are currently exploring the contribution of EP1v to this mechanism. These findings suggest that EP1 has the potential to be a new therapeutic target in reducing breast cancer metastasis and increasing overall cancer survival. Citation Format: Jocelyn C. Reader, Xinrong Ma, Namita Kundu, Olga Goloubeva, Amy Fulton. Mechanistic studies of the metastasis suppressor prostaglandin E2 receptor EP1 in breast cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3862. doi:10.1158/1538-7445.AM2013-3862

Regulation of COX2 Expression in Mouse Mammary Tumor Cells Controls Bone Metastasis and PGE2-Induction of Regulatory T Cell Migration

BackgroundThe targeting of the immune system through immunotherapies to prevent tumor tolerance and immune suppression are at the front lines of breast cancer treatment and research. Human and laboratory studies have attributed breast cancer progression and metastasis to secondary organs such as the bone, to a number of factors, including elevated levels of prostaglandin E2 (PGE2) and the enzyme responsible for its production, cyclooxygenase 2 (COX2). Due to the strong connection of COX2 with immune function, we focused on understanding how variance in COX2 expression manipulates the immune profile in a syngeneic, and immune-competent, mouse model of breast cancer. Though there have been correlative findings linking elevated levels of COX2 and Tregs in other cancer models, we sought to elucidate the mechanisms by which these immuno-suppressive cells are recruited to breast tumor and the means by which they promote tumor tolerance.Methodology/Principal FindingsTo elucidate the mechanisms by which exacerbated COX2 expression potentiates metastasis we genetically manipulated non-metastatic mammary tumor cells (TM40D) to over-express COX2 (TM40D-COX2). Over-expression of COX2 in this mouse breast cancer model resulted in an increase in bone metastasis (an observation that was ablated following suppression of COX2 expression) in addition to an exacerbated Treg recruitment in the primary tumor. Interestingly, other immune-suppressive leukocytes, such as myeloid derived suppressor cells, were not altered in the primary tumor or the circulation. Elevated levels of PGE2 by tumor cells can directly recruit CD4+CD25+ cells through interactions with their EP2 and/or EP4 receptors, an effect that was blocked using anti-PGE2 antibody. Furthermore, increased Treg recruitment to the primary tumor contributed to the greater levels of apoptotic CD8+ T cells in the TM40D-COX2 tumors.Conclusion/SignificanceDue to the systemic effects of COX2 inhibitors, we propose targeting specific EP receptors as therapeutic interventions to breast cancer progression.