Gladys N. Nangami

The impact of low-dose carcinogens and environmental disruptors on tissue invasion and metastasis

The purpose of this review is to stimulate new ideas regarding low-dose environmental mixtures and carcinogens and their potential to promote invasion and metastasis. Whereas a number of chapters in this review are devoted to the role of low-dose environmental mixtures and carcinogens in the promotion of invasion and metastasis in specific tumors such as breast and prostate, the overarching theme is the role of low-dose carcinogens in the progression of cancer stem cells. It is becoming clearer that cancer stem cells in a tumor are the ones that assume invasive properties and colonize distant organs. Therefore, low-dose contaminants that trigger epithelial-mesenchymal transition, for example, in these cells are of particular interest in this review. This we hope will lead to the collaboration between scientists who have dedicated their professional life to the study of carcinogens and those whose interests are exclusively in the arena of tissue invasion and metastasis.

Fetuin-A associates with histones intracellularly and shuttles them to exosomes to promote focal adhesion assembly resulting in rapid adhesion and spreading in breast carcinoma cells

The present analyses were undertaken to define the mechanisms by which fetuin-A modulates cellular adhesion. FLAG-tagged fetuin-A was expressed in breast carcinoma and HEK-293T cells. We demonstrated by confocal microscopy that fetuin-A co-localizes with histone H2A in the cell nucleus, forms stable complexes with histones such as H2A and H3 in solution, and shuttles histones to exosomes. The rate of cellular adhesion and spreading to either fibronectin or laminin coated wells was accelerated significantly in the presence of either endogenous fetuin-A or serum derived protein. More importantly, the formation of focal adhesion complexes on surfaces coated by laminin or fibronectin was accelerated in the presence of fetuin-A or histone coated exosomes. Cellular adhesion mediated by histone coated exosomes was abrogated by heparin and heparinase III. Heparinase III cleaves heparan sulfate from cell surface heparan sulfate proteoglycans. Lastly, the uptake of histone coated exosomes and subsequent cellular adhesion, was abrogated by heparin. Taken together, the data suggest a mechanism where fetuin-A, either endogenously synthesized or supplied extracellularly can extract histones from the nucleus or elsewhere in the cytosol/membrane and load them on cellular exosomes which then mediate adhesion by interacting with cell surface heparan sulfate proteoglycans via bound histones.

Reduced annexin A6 expression promotes the degradation of activated epidermal growth factor receptor and sensitizes invasive breast cancer cells to EGFR-targeted tyrosine kinase inhibitors

BackgroundThe expression of annexin A6 (AnxA6) in AnxA6-deficient non-invasive tumor cells has been shown to terminate epidermal growth factor receptor (EGFR) activation and downstream signaling. However, as a scaffolding protein, AnxA6 may stabilize activated cell-surface receptors to promote cellular processes such as tumor cell motility and invasiveness. In this study, we investigated the contribution of AnxA6 in the activity of EGFR in invasive breast cancer cells and examined whether the expression status of AnxA6 influences the response of these cells to EGFR-targeted tyrosine kinase inhibitors (TKIs) and/or patient survival.ResultsWe demonstrate that in invasive BT-549 breast cancer cells AnxA6 expression is required for sustained membrane localization of activated (phosho-Y1068) EGFR and consequently, persistent activation of MAP kinase ERK1/2 and phosphoinositide 3- kinase/Akt pathways. Depletion of AnxA6 in these cells was accompanied by rapid degradation of activated EGFR, attenuated downstream signaling and as expected enhanced anchorage-independent growth. Besides inhibition of cell motility and invasiveness, AnxA6-depleted cells were also more sensitive to the EGFR-targeted TKIs lapatinib and PD153035. We also provide evidence suggesting that reduced AnxA6 expression is associated with a better relapse-free survival but poorer distant metastasis-free and overall survival of basal-like breast cancer patients.ConclusionsTogether this demonstrates that the rapid degradation of activated EGFR in AnxA6-depleted invasive tumor cells underlies their sensitivity to EGFR-targeted TKIs and reduced motility. These data also suggest that AnxA6 expression status may be useful for the prediction of the survival and likelihood of basal-like breast cancer patients to respond to EGFR-targeted therapies.

Fetuin-A (α2HS-glycoprotein) is a serum chemo-attractant that also promotes invasion of tumor cells through Matrigel

The present study was conducted to determine whether fetuin-A, a dominant serum protein plays a role in chemo-attraction and chemo-invasion of carcinoma cells in vitro. Serum is normally used as positive chemotaxis control in Boyden chamber motility assays, prompting the need to identify the factor/s in serum that contributes the bulk of chemo-taxis and invasion. Serum has a plethora of chemotactic factors including stromal derived factor 1 also known as CXCL12. Using highly purified fetuin-A, we compared its chemo-attraction potential to culture medium containing 10% fetal bovine serum. We also investigated its ability to attract tumor cells through a bed of Matrigel (invasion assay). We demonstrated, using similar concentration range of fetuin-A found in blood, that it robustly supports both directed chemo-attraction and invasion of breast tumor cells. More importantly, we showed that at low concentrations (fetuin-A coated wells) itinteracts synergistically with CXCL12 to promote chemotaxis. The presence of plasminogen (PL) blunted the fetuin-A mediated chemotaxis. Taken together, the data suggest an in vivo chemotaxis/invasion role for fetuin-A.

Fetuin-A (alpha 2HS glycoprotein) modulates growth, motility, invasion, and senescence in high-grade astrocytomas

Glioblastomas (high‐grade astrocytomas) are highly aggressive brain tumors with poor prognosis and limited treatment options. In the present studies, we have defined the role of fetuin‐A, a liver‐derived multifunctional serum protein, in the growth of an established glioblastoma cell line, LN229. We hereby demonstrate that these cells synthesize ectopic fetuin‐A which supports their growth in culture in the absence of serum. We have demonstrated that a panel of tissue microarray (TMA) of glioblastomas also express ectopic fetuin‐A. Knocking down fetuin‐A using shRNA approach in LN229, significantly reduced their in vitro growth as well as growth and invasion in vivo. The fetuin‐A knockdown subclones of LN229 (A and D) also had reduced motility and invasive capacity. Treatment of LN229 cells with asialofetuin (ASF), attenuated their uptake of labeled fetuin‐A, and induced senescence in them. Interestingly, the D subclone that had ~90% reduction in ectopic fetuin‐A, underwent senescence in serum‐free medium which was blunted in the presence of purified fetuin‐A. Uptake of labeled exosomes was attenuated in fetuin‐A knockdown subclones A and D. Taken together, the studies demonstrate the impact of fetuin‐A as significant node of growth, motility, and invasion signaling in glioblastomas that can be targeted for therapy.

Impact of Fetuin-A (AHSG) on Tumor Progression and Type 2 Diabetes

Fetuin-A is the protein product of the AHSG gene in humans. It is mainly synthesized by the liver in adult humans and is secreted into the blood where its concentration can vary from a low of ~0.2 mg/mL to a high of ~0.8 mg/mL. Presently, it is considered to be a multifunctional protein that plays important roles in diabetes, kidney disease, and cancer, as well as in inhibition of ectopic calcification. In this review we have focused on work that has been done regarding its potential role(s) in tumor progression and sequelae of diabetes. Recently a number of laboratories have demonstrated that a subset of tumor cells such as pancreatic, prostate and glioblastoma multiform synthesize ectopic fetuin-A, which drives their progression. Fetuin-A that is synthesized, modified, and secreted by tumor cells may be more relevant in understanding the pathophysiological role of this enigmatic protein in tumors, as opposed to the relatively high serum concentrations of the liver derived protein. Lastly, auto-antibodies to fetuin-A frequently appear in the sera of tumor patients that could be useful as biomarkers for early diagnosis. In diabetes, solid experimental evidence shows that fetuin-A binds the β-subunit of the insulin receptor to attenuate insulin signaling, thereby contributing to insulin resistance in type 2 diabetes mellitus (T2DM). Fetuin-A also may, together with free fatty acids, induce apoptotic signals in the beta islets cells of the pancreas, reducing the secretion of insulin and further exacerbating T2DM.

Extracellular histones are the ligands for the uptake of exosomes and hydroxyapatite‐nanoparticles by tumor cells via syndecan‐4

The mechanisms by which exosomes (nano‐vesicular messengers of cells) are taken up by recipient cells are poorly understood. We hypothesized that histones associated with these nanoparticles are the ligands which facilitate their interaction with cell surface syndecan‐4 (SDC4) to mediate their uptake. We show that the incubation with fetuin‐A (exosome‐associated proteins) and histones mediates the uptake of exosomes that are normally not endocytosed. Similarly, hydroxyapatite‐nanoparticles incubated with fetuin‐A and histones (FNH) are internalized by tumor cells, while nanoparticles incubated with fetuin‐A alone (FN) are not. The uptake of exosomes and FNH, both of which move to the perinuclear region of the cell, is attenuated in SDC4‐knockdown cells. Data show that FNH can compete with exosomes for uptake and that both use SDC4 as uptake receptors.

Abstract B09: Fetuin-A, an emerging biomarker for breast and prostate cancer

We hypothesized that fetuin-A, a liver derived glycoprotein would be a useful biomarker to follow for the progression of prostate and breast cancer particularly in African American patients. For many years, conflicting reports have appeared in the literature regarding the role of fetuin-A in the progression of a number of solid tumors. The majority of the studies have reported that the serum levels of fetuin-A drops as tumors progress, suggesting a tumor suppressive role for the protein. We on the other hand, demonstrated that it is a significant tumor growth promoter in vitro. In the recent past, a number of laboratories, including ours, have indicated that fetuin-A is actively synthesized by high grade tumors. In the present study, we investigated the appearance of fetuin-A autoantibodies in the sera of 12 prostate and breast cancer patients, 60% of whom were African Americans. We demonstrated the presence of fetuin-A auto antibodies in all except two of the tumor serum specimens. Blood of normal tumor free individuals do not show fetuin-A autoantibodies. We also subjected tissue microarrays of prostate and breast tumors to immune-histochemical analysis of fetuin-A. Our data show a dramatic increase in the synthesis of fetuin-A in the TMA particularly in high grade tumors. Taken together, these results suggest that as tumors become more aggressive they may synthesize fetuin-A which then presents as a new antigen in the blood that provokes the synthesis of auto-antibodies, which could be a biomarker of advanced or metastatic disease. Furthermore, the study suggests that fetuin-A itself could be a significant surrogate marker of aggressive tumors of the prostate or breast particularly in African Americans. Citation Format: Gladys Nangami, Josiah Ochieng, Ebenezer Appah, Philip E. Lammers. Fetuin-A, an emerging biomarker for breast and prostate cancer. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr B09.