Cancer-inducible transgene expression by the Grp94 promoter: spontaneous activation in tumors of various origins and cancer-associated macrophages (original) (raw)
Related papers
Glucose-regulated proteins in cancer: molecular mechanisms and therapeutic potential
Nature Reviews Cancer, 2014
The glucose-regulated proteins (GRPs) GRP78 (also known as BiP and HSPA5), GRP94 (also known as GP96 and HSP90B1), GRP170 (also known as ORP150 and HYOU1) and GRP75 (also known as mortalin and HSPA9) are stress-inducible molecular chaperones that belong to the heat shock protein (HSP) family (BOX 1). Unlike most of the HSPs, which reside mainly in the cytosol and the nucleus, these GRPs are found in the endoplasmic reticulum (ER) or the mitochondria, which are important organelles for the regulation of protein quality control and metabolic balance 1-4. In their traditional chaperone roles, these GRPs facilitate protein folding and assembly, as well as the export of misfolded proteins for degradation. Coupled with their Ca 2+ binding functions, they maintain the integrity and homeo stasis of the ER and the mitochondria under physiological and pathological conditions. GRP overexpression is widely reported in cancer cell lines and is associated with aggressive growth and invasive properties 5,6 (see Supplementary information S1 (table)). During the past decade, exciting discoveries have been made in identifying common and distinctive functions of these GRPs in cancer. GRP78 regulates the balance between cancer cell viability and apoptosis by sustaining ER protein folding capacity and by maintaining ER stress sensors and ER-associated pro-apoptotic machineries in their inactive state 7. GRP94 is essential for the processing of proteins that have been implicated in tumorigenesis, such as insulin-like growth factor 1 (IGF1), Toll-like receptors (TLRs) and integrins 4. GRP170, which has an ADP-ATP exchange function, is both a co-chaperone for GRP78 and an independent chaperone, and it is crucial for vascular endothelial growth factor A (VEGFA) processing and maturation 2,8,9. GRP75 interacts with the tumour suppressor p53, thereby inactivating the capacity of p53 to function as a transcription factor and inducing apoptosis 10. Furthermore, these GRPs, which are traditionally thought to exclusively reside in the ER lumen, can be actively translocated to other cellular locations and can be secreted, and they have additional functions that control signalling, proliferation, invasion, apoptosis, inflammation and immunity 11-14. ER stress, as well as the development of therapeutic resistance, actively promotes the cell surface expression of GRP78, which functions as an upstream regulator of the PI3K-AKT oncogenic signalling pathway 15-17. GRP78 is also a downstream target of AKT activation 18,19. At the cell surface, GRP94 and GRP170 function in antigen presentation, and their secreted forms have the ability to elicit innate and adaptive immune responses, which could be useful in the development of cancer vaccines 1,2,20. Through the use of cancer cell lines, xenografts and conditional knockout mouse models, the important roles of these GRPs in cancer are being established 5,20,21. Promising therapeutics that are specifically directed against the GRPs, including conjugated peptides and toxins, antibodies, small molecules and microRNAs, are being developed 5,20,22. Thus, these GRPs represent novel
Cancer Research, 2008
The unfolded protein response (UPR) is an evolutionarily conserved mechanism that activates both proapoptotic and survival pathways to allow eukaryotic cells to adapt to endoplasmic reticulum (ER) stress. Although the UPR has been implicated in tumorigenesis, its precise role in endogenous cancer remains unclear. A major UPR protective response is the induction of the ER chaperone GRP78/BiP, which is expressed at high levels in a variety of tumors and confers drug resistance in both proliferating and dormant cancer cells. To determine the physiologic role of GRP78 in in situ-generated tumor and the consequence of its suppression on normal organs, we used a genetic model of breast cancer in the Grp78 heterozygous mice where GRP78 expression level was reduced by about half, mimicking anti-GRP78 agents that achieve partial suppression of GRP78 expression. Here, we report that Grp78 heterozygosity has no effect on organ development or antibody production but prolongs the latency period and significantly impedes tumor growth. Our results reveal three major mechanisms mediated by GRP78 for cancer progression: enhancement of tumor cell proliferation, protection against apoptosis, and promotion of tumor angiogenesis. Importantly, although partial reduction of GRP78 in the Grp78 heterozygous mice substantially reduces the tumor microvessel density, it has no effect on vasculature of normal organs. Our findings establish that a key UPR target GRP78 is preferably required for pathophysiologic conditions, such as tumor proliferation, survival, and angiogenesis, underscoring its potential value as a novel therapeutic target for dual antitumor and antiangiogenesis activity. [Cancer Res 2008; 68(2):498-505] Requests for reprints: Amy S. Lee,
PloS one, 2014
This study was designed to investigate the activation of the unfolded protein response (UPR) in tumor associated endothelial cells (TECs) and its association with chemoresistance during acidic pH stress. Endothelial cells from human oral squamous cell carcinomas (OSCC) were excised by laser capture microdissection (LCM) followed by analysis of UPR markers (Grp78, ATF4 and CHOP) using quantitative PCR. Grp78 expression was also determined by immunostaining. Acidic stress was induced in primary human dermal microvascular endothelial cells (HDMECs) by treatment with conditioned medium (CM) from tumor cells grown under hypoxic conditions or by adjusting medium pH to 6.4 or 7.0 using lactic acid or hydrochloric acid (HCl). HDMEC resistance to the anti-angiogenic drug Sunitinib was assessed with SRB assay. UPR markers, Grp78, ATF4 and CHOP were significantly upregulated in TECs from OSCC compared to HDMECs. HDMECs cultured in acidic CM (pH 6.0-6.4) showed increased expression of the UPR m...
Macrophage migration and gene expression in response to tumor hypoxia
International Journal of Cancer, 2005
Monocytes are recruited into tumors from the circulation along defined chemotactic gradients and they then differentiate into tumor-associated macrophages (TAMs). Recent evidence has shown that large numbers of TAMs are attracted to and retained in avascular and necrotic areas, where they are exposed to tumor hypoxia. At these sites, TAMs appear to undergo marked phenotypic changes with activation of hypoxia-inducible transcription factors, dramatically upregulating the expression of a large number of genes encoding mitogenic, proangiogenic and prometastatic cytokines and enzymes. As a consequence, high TAMs density has been correlated with increased tumor growth and angiogenesis in various tumor types. Since hypoxia is a hallmark feature of malignant tumors and hypoxic tumor cells are relatively resistant to radio- and chemotherapy, these areas have become a target for novel forms of anticancer therapy. These include hypoxia-targeted gene therapy in which macrophages are armed with therapeutic genes that are activated by hypoxia-responsive promoter elements. This restricts transgene expression to hypoxic areas, where the gene product is then released and acts on neighboring hypoxic tumor cells or proliferating blood vessels. In this way, the responses of macrophages to tumor hypoxia can be exploited to deliver potent antitumor agents to these poorly vascularized, and thus largely inaccessible, areas of tumors. © 2005 Wiley-Liss, Inc.
Breast cancer research …, 2000
The 78 kDa glucose-regulated stress protein GRP78 is induced by physiological stress conditions such as hypoxia, low pH, and glucose deprivation which often exist in the microenvironments of solid tumors. Activation of this stress pathway occurs in response to several pro-apoptotic stimuli. In vitro studies have demonstrated a correlation between induced expression of GRP78 and resistance to apoptotic death induced by topoisomerase II-directed drugs. We were interested in characterizing this protein in human breast lesions for potential implications in chemotherapeutic intervention. Surgical specimens of human breast lesions and paired normal tissues from the same patients were flash frozen for these studies. Total RNA and/or protein were extracted from these tissues and used in northern and/or western blot analyses, respectively, to quantify the relative expression of GRP78. Northern blot analysis indicated that 0/5 benign breast lesions, 3/5 estrogen receptor positive (ER+) breast tumors, and 6/9 estrogen receptor negative (ER−) breast tumors exhibited overexpression of GRP78 mRNA compared to paired normal tissues, with fold overexpressions ranging from 1.8 to 20. Western blot analyses correlated with these findings since 0/5 benign breast lesions, 4/6 ER+ breast tumors, and 3/3 ER− breast tumors overexpressed GRP78 protein with fold overexpressions ranging from 1.8 to 19. Immunohistochemical analysis of these tissues demonstrated that the expression of GRP78 was heterogeneous among the cells comprising different normal and malignant glands, but confirmed the overexpression of GRP78 in most of the more aggressive ER− tumors. These results suggest that some breast tumors exhibit adverse microenvironment conditions that induce the overexpression of specific stress genes that may play a role in resistance to apoptosis and decreased chemotherapeutic efficacy.
Cancer Cell, 2004
We have recently identified glucose-regulated protein-78 (GRP78) as a relevant molecular target expressed in metastatic tumors by fingerprinting the circulating repertoire of antibodies from cancer patients. Here we design and evaluate a ligand-receptor system based on the tumor cell membrane expression of GRP78. We show that GRP78 binding peptide motifs target tumor cells specifically in vivo and in human cancer specimens ex vivo. Moreover, synthetic chimeric peptides composed of GRP78 binding motifs fused to a programmed cell death-inducing sequence can suppress tumor growth in xenograft and isogenic mouse models of prostate and breast cancer. Together, these preclinical data validate GRP78 on the tumor cell surface as a functional molecular target that may prove useful for translation into clinical applications.
International Journal of Cancer, 2013
GTP cyclohydrolase (GCH1) is the key-enzyme to produce the essential enzyme cofactor, tetrahydrobiopterin. The byproduct, neopterin is increased in advanced human cancer and used as cancer-biomarker, suggesting that pathologically increased GCH1 activity may promote tumor growth. We found that inhibition or silencing of GCH1 reduced tumor cell proliferation and survival and the tube formation of human umbilical vein endothelial cells, which upon hypoxia increased GCH1 and endothelial NOS expression, the latter prevented by inhibition of GCH1. In nude mice xenografted with HT29-Luc colon cancer cells GCH1 inhibition reduced tumor growth and angiogenesis, determined by in vivo luciferase and near-infrared imaging of newly formed blood vessels. The treatment with the GCH1 inhibitor shifted the phenotype of tumor associated macrophages from the proangiogenic M2 towards M1, accompanied with a shift of plasma chemokine profiles towards tumor-attacking chemokines including CXCL10 and RANTES. GCH1 expression was increased in mouse AOM/DSS-induced colon tumors and in high grade human colon and skin cancer and oppositely, the growth of GCH1-deficient HT29-Luc tumor cells in mice was strongly reduced. The data suggest that GCH1 inhibition reduces tumor growth by (i) direct killing of tumor cells, (ii) by inhibiting angiogenesis, and (iii) by enhancing the antitumoral immune response.
Cancer Research, 2005
Therapeutic targeting of the tumor vasculature that destroys preexisting blood vessels of the tumor and antiangiogenesis therapy capitalize on the requirement of tumor cells on an intact vascular supply for oxygen and nutrients for growth, expansion and metastasis to the distal organs. Whereas these classes of agents show promise in delaying tumor progression, they also create glucose and oxygen deprivation conditions within the tumor that could trigger unintended prosurvival responses. The glucose-regulated protein GRP78, a major endoplasmic reticulum chaperone, is inducible by severe glucose depletion, anoxia, and acidosis. Here we report that in a xenograft model of human breast cancer, treatment with the vascular targeting agent, combretastatin A4P, or the antiangiogenic agent, contortrostatin, promotes transcriptional activation of the Grp78 promoter and elevation of GRP78 protein in surviving tumor cells. We further show that GRP78 is overexpressed in a panel of human breast c...
Cancer research, 1993
Tumor cells undergo self-destruction when incubated with cytotoxic T-cells (CTL) consistent with the observation that suppression of target protein synthesis causes resistance to apoptosis. Resistance to CTL is also induced by stress, suggesting that pathways exist suppressing apoptosis. Here we examine whether stress induced lysis resistance to CTL and tumor necrosis factor alpha involves stress proteins GRP78 and GRP94. We show that inhibition of GRP78 synthesis by transfection of cells with grp78 antisense vector pRSV-78WO leads to inability to induce resistance to CTL or tumor necrosis factor alpha. Resistance induced in untransfected cells is reversible upon stress removal and correlates with GRP78 rephosphorylation, consistent with the notion that phosphorylated GRP78 is nonfunctional. The possibility that GRP78 plays a role in defense against CTL mediated apoptosis is supported by the finding that CTL but not CD4+ cells express a high level of unphosphorylated GRP78.