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Background: Autocrine motility factor (AMF) is secreted by cancer cells and acts in an autocrine or paracrine fashion to bind to its receptor, AMFR, at the cell surface of tumor cells. The AMF-AMFR pathway has been shown to promote proliferation, anti-apoptosis, motility and migration, invasion, and metastasis pathways in various cancers. However, our understanding of the AMF-AMFR pathway in breast cancer is limited. We propose that the AMF signaling pathway is an unexplored mechanism for breast cancer tumor aggression and its receptor, AMFR, may be a potential therapeutic target. Methods: Tumor tissue obtained from consented female (n = 31) and male (n = 1) patients were analyzed by the Affymetrix OncoscanTM genome-wide microarray platform and examined for somatic copy-number alterations (SCNAs) of AMFR. cBioPortal was used to investigate SCNA of AMFR and gene expression of AMF on primary breast cancer tumors from METABRIC (n = 1,784) and TCGA Pan-Cancer Atlas (n = 981) datasets. In vitro, AMF and AMFR gene expression in luminal A (MCF-7) and triple-negative breast cancer (MDA-MB-231) cell lines were assessed by qPCR. Cell migration assays were performed on MDA-MB-231 cells to investigate their migration towards AMF with AMFR present or knocked down by siRNA. Results: Microarray analysis of 32 tumors revealed that a single-copy loss of AMFR occurred 79% of the time in luminal A tumors (n = 19); 67% of the time in luminal B tumors (n = 6); 33% of the time in ER+, PR+, HER2+ tumors (n = 3); and 0% of the time in triple-negative breast cancer (TNBC) tumors (n = 4), suggesting that the loss of AMFR results in less aggressive tumors that have good overall prognosis. To extend our findings to a larger patient cohort, SCNA analysis of the METABRIC and TCGA Pan-Cancer Atlas datasets revealed that single-copy loss of AMFR occurred in 64.53% and 68.14% of luminal A tumors, 58.51% and 59.90% of luminal B tumors, 23.62% and 48.72% of HER2 overexpression tumors, and 29.80% and 39.77% of TNBC tumors, respectively. Therefore, AMFR appears most frequently deleted in the tumor genomes of good prognosis breast cancer molecular subtypes (luminal tumors). Gene expression analysis of AMF in the METABRIC (using z-scores) and TCGA Pan-Cancer Atlas (using batch-normalized numbers) datasets revealed median mRNA expressions of -0.3351 and 4862 in luminal A tumors, -0.05415 and 5841 in luminal B tumors, 0.5758 and 9390 in HER2 overexpression tumors, and 0.754 and 8798 in TNBC tumors, respectively, suggesting that the AMF-AMFR pathway is more active in aggressive breast cancers. Similarly, we observed that AMF and AMFR are transcriptionally overexpressed by 7-fold and 16-fold, respectively, in the TNBC cell line MDA-MB-231 compared to the luminal A breast cancer cell line MCF-7. When AMFR is knocked down in MDA-MB-231 cells, focused migration towards AMF is abolished. Conclusion: AMF-AMFR pathway activity correlates with aggressive cancer cell behavior and enhanced migration in breast cancer. Single-copy loss of AMFR in tumor genomes is associated with less aggressive tumors with better overall prognosis. AMFR may be an attractive therapeutic target. Citation Format: Liu C, Price JD, Maroni D, Stevens JM, VanDyke AZ, Althof PA, Mondal P, Sanmann JN, Thayer SP. Autocrine motility factor signaling pathway promotes aggressive behavior and migration in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-03-09.

Autocrine motility factor (AMF) enhances invasion by breast cancer cells, but how its secretion and effector signaling are controlled in the tumor microenvironment is not fully understood. In this study, we investigated these issues with a chimeric AMF that is secreted at high levels through a canonical endoplasmic reticulum (ER)/Golgi pathway. Using this tool, we found that AMF enhances tumor cell motility by activating AKT/ERK, altering actin organization, and stimulating β-catenin/TCF and activating protein 1 transcription. EGF enhanced secretion of AMF through its casein kinase II–mediated phosphorylation. RNA interference–mediated attenuation of AMF expression inhibited EGF-induced invasion by suppressing extracellular signal–regulated kinase signaling. Conversely, exogenous AMF overcame the inhibitory effect of EGF receptor inhibitor gefitinib on invasive motility by activating HER2 signaling. Taken together, our findings show how AMF modulates EGF-induced invasion while affecting acquired resistance to cytotoxic drugs in the tumor microenvironment. Cancer Res; 74(8); 2229–37. ©2014 AACR.

Phosphoglucose isomerase/autocrine motility factor (PGI/AMF) plays an important role in glycolysis and gluconeogenesis and is associated with invasion and metastasis of cancer cells. We have previously shown its role in the induction of epithelial-mesenchymal transition (EMT) in breast cancer cells, which led to increased aggressiveness; however, the molecular mechanism by which PGI/AMF regulates EMT is not known. Here we show, for the first time, that PGI/AMF overexpression led to an increase in the DNA-binding activity of NF-κB, which, in turn, led to increased expression of ZEB1/ZEB2. The microRNA-200s (miR-200s) miR-200a, miR-200b, and miR-200c are known to negatively regulate the expression of ZEB1/ZEB2, and we found that the expression of miR-200s was lost in PGI/AMF overexpressing MCF-10A cells and in highly invasive MDA-MB-231 cells, which was consistent with increased expression of ZEB1/ZEB2. Moreover, silencing of PGI/AMF expression in MDA-MB-231 cells led to overexpression of miR-200s, which was associated with reversal of EMT phenotype (i.e., mesenchymal-epithelial transition), and these findings were consistent with alterations in the relative expression of epithelial (E-cadherin) and mesenchymal (vimentin, ZEB1, ZEB2) markers and decreased aggressiveness as judged by clonogenic, motility, and invasion assays. Moreover, either reexpression of miR-200 or silencing of PGI/AMF suppressed pulmonary metastases of MDA-MB-231 cells in vivo, and anti-miR-200 treatment in vivo resulted in increased metastases. Collectively, these results suggest a role of miR-200s in PGI/AMF-induced EMT and thus approaches for upregulation of miR-200s could be a novel therapeutic strategy for the treatment of highly invasive breast cancer. Cancer Res; 71(9); 3400–9. ©2011 AACR.

Phosphoglucose isomerase/autocrine motility factor (PGI/AMF) is a housekeeping gene product/cytokine that catalyzes a step in glycolysis and gluconeogenesis, and acts as a multifunctional cytokine associated with aggressive tumors. PGI/AMF has been correlated significantly with breast cancer progression and poor prognosis in breast cancer. We show here that ectopic expression of PGI/AMF induced epithelial-to-mesenchymal transition (EMT) in MCF10A normal human breast epithelial cells, and inhibition of PGI/AMF expression triggered mesenchymal-to-epithelial transition (MET) in aggressive mesenchymal-type human breast cancer MDA-MB-231 cells. EMT in MCF10A cells was shown by morphologic changes and loss of E-cadherin/β-catenin–mediated cell-cell adhesion, which is concomitant with the induction of the E-cadherin transcriptional repressor Snail and proteosome-dependent degradation of β-catenin protein. Molecular analysis showed that PGI/AMF suppressed epithelial marker expressions and enhanced mesenchymal marker expressions. Silencing of PGI/AMF expression by RNA interference in MDA-MB-231 cells induced the reverse processes of EMT including altered cell shape, gain of epithelial marker, and reduction of mesenchymal marker, e.g., MET. Taken together, the results show the involvement of PGI/AMF in both EMT and MET: overexpression of PGI/AMF induces EMT in normal breast epithelial cells and reduction of PGI/AMF expression led to MET in aggressive breast cancer cells. These results suggest for the first time that PGI/AMF is a key gene to both EMT in the initiating step of cancer metastasis and MET in the later stage of metastasis during breast cancer progression. [Cancer Res 2009;69(13):5349–56]

Phosphoglucose isomerase (PGI; EC 5.3.1.9) is a ubiquitous cytosolic enzyme essential for glycolysis and gluconeogenesis. PGI is a multifunctional dimeric protein that extracellularly acts as a cytokine [autocrine motility factor (AMF)] eliciting mitogenic, motogenic, and differentiation functions through binding to its cell surface receptor gp78/AMF receptor (AMFR). AMFR contains a seven-transmembrane domain with RING-H2 and leucine zipper motifs showing ubiquitin protein ligase (E3) activity and is exposed on the endoplasmic reticulum surface. Augmented expressions of both PGI/AMF and AMFR have been implicated in tumor progression and metastasis, and an intracellular binding partner of PGI/AMF is expected to regulate in part its diverse biological functions. Thus, we screened a cDNA library using a yeast two-hybrid system to search for interacting protein(s) and report on the finding of poly(ADP-ribose) polymerase-14 (PARP-14) to be a binding partner with PGI/AMF. PARP-14–PGI/AMF interaction was confirmed by coimmunoprecipitation and immunolocalization. We also report that PGI/AMF degradation is mainly regulated by the ubiquitin-lysosome system and RNA interference experiments revealed that PARP-14 inhibits PGI/AMF ubiquitination, thus contributing to its stabilization and secretion. This newly characterized PARP-14 protein should assist in understanding the regulation of PGI/AMF intracellular function(s) and may provide a new therapeutic target for inhibition of PGI/AMF inducing tumor cell migration and invasion during metastasis. [Cancer Res 2007;67(18):8682–9]

Overexpression of HER2 (ErbB2) oncoprotein is associated with approximately 25% of aggressive breast carcinoma. Although a humanized monoclonal antibody (Trastuzumab) against HER2 is currently considered one of the most effective treatments, a significant number of patients are initially or eventually become resistant to Trastuzumab based therapy. Here, we demonstrate that secreted phosphoglucose isomerase (PGI)/ autocrine motility factor (AMF), an orphan -CXXC- cytokine directly binds to HER2 and activates PI3K and MAPK through HER2 autophosphorylation, and also induces immediately HER2 cleavage in metalloprotease dependent fashion. We therefore speculate that AMF/HER2 signaling pathways play a physiological role in HER2 overexpressing breast cancer cells and contribute to Trastuzumab resistance and propose that AMF can be a novel therapeutic target in Trastuzumab resistant breast cancer. 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 1079. doi:1538-7445.AM2012-1079

Phosphoglucose isomerase/autocrine motility factor (PGI/AMF) is a multifunctional protein that intracellularly catalyzes the interconversion of glucose 6-phosphate and fructose 6-phosphate in both glycolytic and gluconeogenesis pathways and extracellularly acts as a cytokine associated with aggressive tumor phenotype. Secreted PGI/AMF promotes cancer cell invasion and metastasis by stimulating cell motility via an autocrine manner following binding to its seven-transmembrane glycoprotein receptor gp78/AMFR. Gp78/AMFR also demonstrates an additional function in the endoplasmic reticulum (ER) as ubiquitin ligase (E3). Thus, gp78/AMFR represents a potential link between ubiquitination, ER-associated degradation (ERAD) and metastasis. We questioned if gp78/AMFR is involved in the ubiquitination of PGI/AMF, and whether the ubiquitinated PGI/AMF can be related to cancer progression and metastasis. In this study, we found that indeed PGI/AMF can be ubiquitinated and gp78/AMFR is involved in this process. PGI/AMF was predominantly ubiquitinated via K29-linked ubiquitin chains. Monoubiquitinated PGI/AMF increases the secretion of PGI/AMF and this is the first report to show that monoubiquitinated PGI/AMF is secreted out of the cells. As secretion of PGI/AMF plays a significant role in tumor cell migration and invasion during metastasis, these studies assist in understanding the regulation of PGI/AMF and the mechanisms of its secretion, which may provide a new therapeutic target for tumor 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 212. doi:1538-7445.AM2012-212