Despite aggressive surgery, radiotherapy and chemotherapy, malignant gliomas remain uniformly fatal. To progress, these tumours stimulate the formation of new blood vessels through processes driven primarily by vascular endothelial growth factor (VEGF). However, the resulting vessels are structurally and functionally abnormal, and contribute to a hostile microenvironment (low oxygen tension and high interstitial fluid pressure) that selects for a more malignant phenotype with increased morbidity and mortality. Emerging preclinical and clinical data indicate that anti-VEGF therapies are potentially effective in glioblastoma — the most frequent primary brain tumour — and can transiently normalize tumour vessels. This creates a window of opportunity for optimally combining chemotherapeutics and radiation.

Angiogenesis in brain tumours

Carey, Hannah V., Matthew T. Andrews, and Sandra L. Martin. Mammalian Hibernation: Cellular and Molecular Responses to Depressed Metabolism and Low Temperature. Physiol Rev 83: 1153-1181, 2003; 10....

https://www.physiology.org/doi/pdf/10.1152/physrev.00008.2003

Mammalian Hibernation: Cellular and Molecular Responses to Depressed Metabolism and Low Temperature

Numerous genetic and environmental insults impede the ability of cells to properly fold and posttranslationally modify secretory and transmembrane proteins in the endoplasmic reticulum (ER), leading to a buildup of misfolded proteins in this organelle—a condition called ER stress. ER-stressed cells must rapidly restore protein-folding capacity to match protein-folding demand if they are to survive. In the presence of high levels of misfolded proteins in the ER, an intracellular signaling pathway called the unfolded protein response (UPR) induces a set of transcriptional and translational events that restore ER homeostasis. However, if ER stress persists chronically at high levels, a terminal UPR program ensures that cells commit to self-destruction. Chronic ER stress and defects in UPR signaling are emerging as key contributors to a growing list of human diseases, including diabetes, neurodegeneration, and cancer. Hence, there is much interest in targeting components of the UPR as a therapeutic strategy t...

The Role of Endoplasmic Reticulum Stress in Human Pathology

Having accumulated mutations that overcome cell-cycle and apoptotic checkpoints, the main obstacle to survival faced by a cancer cell is the restricted supply of nutrients and oxygen. These conditions impinge on protein folding in the endoplasmic reticulum and activate a largely cytoprotective signalling pathway called the unfolded protein response. Prolonged activation of this response can, however, terminate in apoptosis. Recent delineation of the components of this response, coupled with several clinical studies, indicate that it is uniquely poised to have a role in regulating the balance between cancer cell death, dormancy and aggressive growth, as well as altering the sensitivity of solid tumours to chemotherapeutic agents.

The role of the unfolded protein response in tumour development: friend or foe?

Hypoxia profoundly influences tumor development and response to therapy. While progress has been made in identifying individual gene products whose synthesis is altered under hypoxia, little is known about the mechanism by which hypoxia induces a global downregulation of protein synthesis. A critical step in the regulation of protein synthesis in response to stress is the phosphorylation of translation initiation factor eIF2alpha on Ser51, which leads to inhibition of new protein synthesis. Here we report that exposure of human diploid fibroblasts and transformed cells to hypoxia led to phosphorylation of eIF2alpha, a modification that was readily reversed upon reoxygenation. Expression of a transdominant, nonphosphorylatable mutant allele of eIF2alpha attenuated the repression of protein synthesis under hypoxia. The endoplasmic reticulum (ER)-resident eIF2alpha kinase PERK was hyperphosphorylated upon hypoxic stress, and overexpression of wild-type PERK increased the levels of hypoxia-induced phosphorylation of eIF2alpha. Cells stably expressing a dominant-negative PERK allele and mouse embryonic fibroblasts with a homozygous deletion of PERK exhibited attenuated phosphorylation of eIF2alpha and reduced inhibition of protein synthesis in response to hypoxia. PERK(-/-) mouse embryo fibroblasts failed to phosphorylate eIF2alpha and exhibited lower survival after prolonged exposure to hypoxia than did wild-type fibroblasts. These results indicate that adaptation of cells to hypoxic stress requires activation of PERK and phosphorylation of eIF2alpha and suggest that the mechanism of hypoxia-induced translational attenuation may be linked to ER stress and the unfolded-protein response.

Regulation of protein synthesis by hypoxia via activation of the endoplasmic reticulum kinase perk and phosphorylation of the translation initiation factor eif2alpha

The Mr 78,000 glucose-regulated protein (GRP78) can be induced by physiological stresses such as glucose deprivation and hypoxia. In solid tumors, hypoxia can promote malignant progression and confer resistance to irradiation and chemotherapy by altering gene expression. Here, we investigated the molecular mechanisms and signaling pathway involved in the late and prolonged induction of the GRP78 gene by hypoxia in a human gastric cancer cell line, MKN28. Nuclear run-on assays and mRNA stability measurements revealed that transcriptional activation, not stabilization of mRNA, contributed to the dramatic induction of GRP78 gene under hypoxia. Induction of GRP78 by chronic hypoxia was completely abolished by pretreatment with PD98059 [a specific inhibitor of mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase (MEK1)] or by overexpression of a dominant-negative MEK1 mutant, demonstrating a direct involvement of ERK in the induction of transcription at the GRP78 promoter under these conditions. Furthermore, hypoxia increased the transcriptional activity of a 12-O-tetradecanoylphorbol-13-acetate response element-like motif on the GRP78 promoter and increased the abundance and DNA binding activity of AP-1 complex composed of c-Jun and c-Fos. A selective protein kinase C (PKC) inhibitor, GF109203X, inhibited the induction of GRP78 gene expression as well as the activities of both ERK and Raf-1. Among six PKC isoforms expressed in MKN28 cells, PKC-e expression level and kinase activity were increased by hypoxia. Transfection of MKN28 cells with a dominant-negative PKC-e blocked the induction of GRP78 through ERK by hypoxia, indicating that PKC-e directly participated in GRP78 induction under hypoxia. Taken together, this study shows that a PKC-e-Raf-1-MEK-ERK-AP1 signaling cascade acts on a 12-O-tetradecanoylphorbol-13-acetate response element-like element to mediate hypoxia-induced GRP78 expression in human gastric cancer cells. We also confirmed in vivo the overexpression of GRP78 in surgical specimens of human primary gastric tumors.

https://cancerres.aacrjournals.org/content/canres/61/22/8322.full.pdf

Induction of glucose-regulated protein 78 by chronic hypoxia in human gastric tumor cells through a protein kinase C-ε/ERK/AP-1 signaling cascade

The Wnt/beta-catenin signaling pathway is activated during the malignant transformation of keratinocytes that originate from the human uterine cervix. Dkk1, 2 and 4 have been shown to modulate the Wnt-induced stabilization of the beta-catenin signaling pathway. However, the function of Dkk3 in this pathway is unknown. Comparison of the Dkk3 gene expression profiles in cervical cancer and normal cervical tissue by cDNA microarray and subsequent real-time PCR revealed that the Dkk3 gene is frequently downregulated in the cancer. Methylation studies showed that the promoter of Dkk3 was methylated in cervical cancer cell lines and 22 (31.4%) of 70 cervical cancer tissue specimens. This promoter methylation was associated with reduced expression of Dkk3 mRNA in the paired normal and tumor tissue samples. Further, the reintroduction of Dkk3 into HeLa cervical cancer cells resulted in reduced colony formation and retarded cell growth. The forced expression of Dkk3 markedly attenuated beta-catenin-responsive luciferase activity in a dose-dependent manner and decreased the beta-catenin levels. By utilizing a yeast two-hybrid screen, betaTrCP, a negative regulator of beta-catenin was identified as a novel Dkk3-interacting partner. Coexpression with betaTrCP synergistically enhanced the inhibitory function of Dkk3 on beta-catenin. The stable expression of Dkk3 blocks the nuclear translocation of beta-catenin, resulting in downregulation of its downstream targets (VEGF and cylcin D), whereas knockdown of Dkk3 abrogates this blocking. We conclude from our finding that Dkk3 is a negative regulator of beta-catenin and its downregulation contribute to an activation of the beta-catenin signaling pathway.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ijc.23913

Dkk3, downregulated in cervical cancer, functions as a negative regulator of β‐catenin

Bcl-2 is involved in the progression of human malignancies, but the precise role and mechanism of Bcl-2 for tumor invasion and metastasis remains unclear. In this study, we have investigated the role and mechanism of Bcl-2 on tumor cell invasion and metastasis by using Bcl-2 overexpressing non-small cell lung cancer cells. Matrix metalloproteinases (MMPs) are important proteins involved in the processes of tumor invasion and metastasis. In vitro Matrigel invasion assays showed that Bcl-2 overexpression increased tumor cell invasion by 15-fold. Moreover, Bcl-2 overexpression enhanced in vivo lung metastasis by 4-fold. Consistent with its effect on invasion and metastasis, Bcl-2 overexpression induced not only MMP-2 mRNA and its protein expression, but this also activated the pro-MMP-2 protein to its active form. To explore the induction mechanism of MMP-2 by Bcl-2, we investigated the effects of Bcl-2 overexpression on MMP-2 transcriptional regulation. Nuclear run-on assays showed a 6-fold increase in the transcription rate of MMP-2 mRNA in the Bcl-2 transfectants (H157/Bcl-2) compared with that of the H157/vector control cells (H157/C). Overexpression of Bcl-2 induced the nuclear transcription factor activator protein 1 family, including the c-Jun, JunD, c-Fos, FosB, and Fra-1 proteins. Reporter assays combined with deletion mutagenesis analysis and gel shift assays showed the involvement of activator protein 1 in the activation of MMP-2 promoter activity by Bcl-2. Taken together, we have shown that Bcl-2 promotes tumor invasion and lung metastasis by inducing MMP-2 gene expression through the combined action of transcriptional and posttranslational mechanisms.

http://cancerres.aacrjournals.org/content/canres/65/13/5554.full.pdf

Bcl-2 Promotes Invasion and Lung Metastasis by Inducing Matrix Metalloproteinase-2

Ovarian cancer is a leading cause of death in women. Early detection of ovarian cancer is essential to decrease mortality. However, the early diagnosis of ovarian cancer is difficult due to a lack of clinical symptoms and suitable molecular diagnostic markers. Thus, identification of meaningful tumor biomarkers with potential clinical application is clearly needed. To search for a biomarker for the early detection of ovarian cancer, we identified human anterior gradient 2 (AGR2) from our systematic analysis of paired normal and ovarian tumor tissue cDNA microarray. We noted a marked overexpression of AGR2 mRNA and protein in early stage mucinous ovarian tumors compared to normal ovarian tissues and serous type ovarian tumors by Western blot analysis and immunohistochemistry. To further elucidate the role of AGR2 in ovarian tumorigenesis, stable 2774 human ovarian cancer cell lines overexpressing AGR2 were established. Forced expression of AGR2 in 2774 cells enhanced the growth and migration of ovarian cancer cells. AGR2 protein was detected in the serum of mucinous ovarian cancer patients by Western blot and ELISA analysis. Thus, AGR2 is a potential biomarker for the diagnosis of mucinous ovarian cancer and an ELISA assay may facilitate the early detection of mucinous ovarian cancer using patient serum.

/pdf/agr2-a-mucinous-ovarian-cancer-marker-promotes-cell-bzpwk20ylz.pdf

AGR2, a mucinous ovarian cancer marker, promotes cell proliferation and migration.

Induction of glucose-regulated proteins (GRPs) is a ubiquitous intracellular response to stresses such as hypoxia, glucose starvation and acidosis. The induction of GRPs offers some protection against these stresses in vitro, but the specific role of GRPs in vivo remains unclear. Hibernating bats present a good in vivo model to address this question. The bats must overcome local high oxygen demand in tissue by severe metabolic stress during arousal thermogenesis. We used brain tissue of a temperate bat Rhinolopus ferrumequinum to investigate GRP induction by high metabolic oxygen demand and to identify associated signaling molecules. We found that during 30 min of arousal, oxygen consumption increased from nearly zero to 11.9/kg/h, which was about 8.7-fold higher than its active resting metabolic rate. During this time, body temperature rose from 7 degrees C to 35 degrees C, and levels of TNF-alpha and lactate in brain tissue increased 2-2.5-fold, indicating a high risk of oxygen shortage. Concomitantly, levels of GRP75, GRP78 and GRP94 increased 1.5-1.7-fold. At the same time, c-Jun N-terminal protein kinase (JNK) activity increased 6.4-fold, and extracellular signal-regulated protein kinase (ERK) activity decreased to a similar degree (6.1-fold). p38 MAPK activity was very low and remained unchanged during arousal. In addition, survival signaling molecules protein kinase B (Akt) and protein kinase C (PKC) were activated 3- and 5-fold, respectively, during arousal. Taken together, our results showed that bat brain undergoes high oxygen demand during arousal from hibernation. Up-regulation of GRP proteins and activation of JNK, PKCgamma and Akt may be critical for neuroprotection and the survival of bats during the repeated process.

Kyoungsook Park

Papers

Induction of glucose-regulated protein 78 by chronic hypoxia in human gastric tumor cells through a protein kinase C-ε/ERK/AP-1 signaling cascade

Dkk3, downregulated in cervical cancer, functions as a negative regulator of β‐catenin

Bcl-2 Promotes Invasion and Lung Metastasis by Inducing Matrix Metalloproteinase-2

AGR2, a mucinous ovarian cancer marker, promotes cell proliferation and migration.

Activation of stress signaling molecules in bat brain during arousal from hibernation.