Hypoxia-inducible factor-1alpha expression in the gastric carcinogenesis sequence and its prognostic role in gastric and gastro-oesophageal adenocarcinomas

Downregulation of malic enzyme 3 facilitates progression of gastric carcinoma via regulating intracellular oxidative stress and hypoxia-inducible factor-1α stabilization

BACKGROUND

Gastric cancer (GC) is one of the most malignant cancers worldwide. Metabolism disorder is a critical characteristic of malignant tumors related to tumor progression and metastasis. However, the expression and molecular mechanism of malic enzyme 3 (ME3) in GC are rarely reported. In this study, we aim to investigate the molecular mechanism of ME3 in the development of GC and to explore its potential value as a prognostic and therapeutic target in GC.

METHOD

ME3 mRNA and protein expression were evaluated in patients with GC using RT-qPCR, WB, and immunohistochemistry, as well as their correlation with clinicopathological indicators. The effect of ME3 on proliferation and metastasis was evaluated using Cell Counting Kit-8 (CCK-8), 5-ethynyl-20-deoxyuridine (EdU) assay, transwell assay, wound healing assay, and subcutaneous injection or tail vein injection of tumor cells in mice model. The effects of ME3 knockdown on the level of metabolites and hypoxia-inducible factor-1α (HIF-1α) protein were determined in GC cells. Oxidative phosphorylation was measured to evaluate adenosine triphosphate (ATP) production.

RESULTS

ME3 was downregulated in human GC tissues (P < 0.001). The decreased ME3 mRNA expression was associated with younger age (P = 0.02), pathological staging (P = 0.049), and lymph node metastasis (P = 0.001), while low ME3 expression was associated with tumor size (P = 0.048), tumor invasion depth (P < 0.001), lymph node metastasis (P = 0.018), TNM staging (P < 0.001), and poor prognosis (OS, P = 0.0206; PFS P = 0.0453). ME3 knockdown promoted GC cell malignancy phenotypes. Moreover, α-ketoglutarate (α-KG) and NADPH/NADP+ ratios were reduced while malate was increased in the ME3 knockdown group under normoxia. When cells were incubated under hypoxia, the NADPH/NADP+ ratio and α-KG decreased while intracellular reactive oxygen species (ROS) increased significantly. The ME3 knockdown group exhibited an increase in ATP production and while ME3 overexpression group exhibited oppositely. We discovered that ME3 and HIF-1α expression were negatively correlated in GC cells and tissues, and proposed the hypothesis: downregulation of ME3 promotes GC progression via regulating intracellular oxidative stress and HIF-1α.

CONCLUSION

We provide evidence that ME3 downregulation is associated with poor prognosis in GC patients and propose a hypothesis for the ME3 regulatory mechanism in GC progression. The present study is of great scientific significance and clinical value for exploring the prognostic and therapeutic targets of GC, evaluating and improving the clinical efficacy of patients, reducing recurrence and metastasis, and improving the prognosis and quality of life of patients.

Impact of high-altitude hypoxia on Helicobacter pylori-induced gastritis pathological manifestations and inflammatory responses

BACKGROUND

Chronic gastritis caused by Helicobacter pylori (Hp) infection is a common gastrointestinal disorder. Despite the high prevalence of Hp infection and chronic gastritis in the Tibetan Plateau, there is a lack of studies elucidating the influence of plateau hypoxia on Hp-induced gastritis. This study aimed to investigate the impact of high-altitude hypoxia on Hp-induced gastritis, particularly focusing on pathological manifestations and inflammatory responses.

METHODS

This study was conducted from July 2023 to March 2024 at the Department of Gastroenterology, Affiliated Hospital of Qinghai University. Ninety patients diagnosed with chronic gastritis were enrolled in the study and divided into four groups based on their residential altitude and Hp infection status. Data on endoscopic and pathological characteristics were collected, along with serum oxidative stress and inflammatory markers.

RESULTS

Patients with Hp gastritis exhibit distinctive features in the gastric mucosa, including diffuse erythema, enlarged folds, and white turbid mucus during endoscopy. Notably, individuals with Hp gastritis at high altitudes show a higher prevalence of diffuse erythema and enlarged folds. Pathological analysis reveals that these patients have elevated gastric mucosal inflammation scores and increased chronic and active inflammation. Furthermore, individuals with Hp gastritis at high altitudes demonstrate elevated levels of serum TNF-α, IL-1β, IL-6, and MDA, as well as reduced serum SOD and GSH-Px activities.

CONCLUSIONS

High-altitude hypoxia may exacerbate gastric mucosal damage by enhancing oxidative stress and inflammatory response induced by Hp infection.

HIF1A protein expression is correlated with clinical features in gastric cancer: an updated systematic review and meta-analysis

To elucidate the correlation of HIF1A with clinicopathologic characteristics in patients with gastric cancer (GC), we conducted a systematic review and meta-analysis. We searched PubMed, Embase and Web of Science for studies on GC and HIF1A, covering studies published until January 31st, 2022. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) for clinical characteristics based on high and low HIF1A protein levels. We used random-effects and fixed-effects meta-analysis methods to determine mean effect sizes of ORs and evaluated publication heterogeneity with τ2, I2, and Q values. Additionally, we generated funnel plots to inspect publication bias. Our meta-analysis included 20 publications with 3416 GC patients to estimate the association between high or low HIF1A expression and clinical characteristics. Positive HIF1A expression was significantly associated with T stage progression (OR: 2.46; 95% CI 1.81-3.36; P < 0.01), TNM stage progression (OR: 2.50; 95% CI 1.61-3.87; P < 0.01), lymph node metastasis (OR: 2.06; 95% CI 1.44-2.94; P < 0.01), undifferentiated status (OR: 1.83; 95% CI 1.45-2.32; P < 0.01), M stage progression (OR: 2.34; 95% CI 1.46-3.77; P < 0.01), Borrmann stage progression (OR: 1.48; 95% CI 1.02-2.15; P = 0.04), larger tumor size (OR: 1.27; 95% CI 1.06-1.52; P < 0.01), vascular invasion (OR: 1.94; 95% CI 1.38-2.72; P < 0.01), and higher vascular endothelial growth factor (VEGF) protein expression (OR: 2.61; 95% CI 1.79-3.80; P < 0.01) in our meta-analysis. GC Patients highly expressing HIF1A protein might be prone to tumor progression, poorly differentiated GC cell types, and a high VEGF expression.

RUVBL1 in Clear-Cell Renal Cell Carcinoma: Unraveling Prognostic Significance and Correlation with HIF1A

This study investigates the roles of RUVBL1 and HIF1A in ccRCC development and explores their clinical significance as prognostic biomarkers. mRNA and protein expressions were analyzed using TCGA data and an institutional tissue cohort, respectively. Correlations with clinicopathological parameters and patient outcomes were assessed. TCGA data revealed significantly elevated RUVBL1 mRNA expression in ccRCC tissues, associated with advanced histological grade, T stage, lymph node metastasis, and clinical stage. High RUVBL1 mRNA expression correlated with inferior overall survival and served as an adverse prognostic factor. Similarly, HIF1A mRNA expression was significantly higher in ccRCC tissues, correlating with worse overall survival and acting as an adverse prognostic factor for treatment outcomes. Simultaneous evaluation of RUVBL1 and HIF1A mRNA expression demonstrated enhanced prognostic capacity, surpassing the predictive power of individual markers. Immunohistochemical staining confirmed substantial upregulation of both RUVBL1 and HIF-1α proteins in ccRCC tissues. Furthermore, high expression of both RUVBL1 and HIF-1α proteins was significantly associated with shorter patient survival time. Our findings underscore the significance of RUVBL1 and HIF-1α as potential prognostic markers in ccRCC, paving the way for further research to translate these insights into clinically relevant applications.

The hypoxia-inducible factor-1α in stemness and resistance to chemotherapy in gastric cancer: Future directions for therapeutic targeting

Hypoxia-inducible factor-1α (HIF-1α) is a crucial mediator of intra-tumoral heterogeneity, tumor progression, and unresponsiveness to therapy in tumors with hypoxia. Gastric tumors, one of the most aggressive tumors in the clinic, are highly enriched in hypoxic niches, and the degree of hypoxia is strongly correlated with poor survival in gastric cancer patients. Stemness and chemoresistance in gastric cancer are the two root causes of poor patient outcomes. Based on the pivotal role of HIF-1α in stemness and chemoresistance in gastric cancer, the interest in identifying critical molecular targets and strategies for surpassing the action of HIF-1α is expanding. Despite that, the understanding of HIF-1α induced signaling in gastric cancer is far from complete, and the development of efficacious HIF-1α inhibitors bears various challenges. Hence, here we review the molecular mechanisms by which HIF-1α signaling stimulates stemness and chemoresistance in gastric cancer, with the clinical efforts and challenges to translate anti-HIF-1α strategies into the clinic.

Non-canonical approaches to targeting hypoxic tumors

Hypoxia is a common characteristic in solid cancers. Hypoxia-inducible factors (HIFs) are involved in various aspects of cancer, such as angiogenesis, metastasis and therapy resistance. Targeting the HIF pathway has been regarded as a challenging but promising strategy in cancer treatment with recent FDA approval of a HIF2α-inhibitor. During the past several decades, numerous efforts have been made to understand how HIFs participate in cancer development and progression along with how HIF signaling can be modulated to achieve anti-cancer effect. In this chapter, we will provide an overview of the role of hypoxia and HIFs in cancer, summarize the oxygen-dependent and independent mechanisms of HIF-1α regulation, and discuss emerging approaches targeting hypoxia and HIF signaling which possess therapeutic potential in cancer. We will emphasize on two signaling pathways, involving cyclin-dependent kinases (CDKs) and heat shock protein 90 (HSP90), which contribute to HIF-1α (and HIF-2α) stabilization in an oxygen-independent manner. Through reviewing their participation in malignant progression and the potential targeting strategies, we discuss the non-canonical approaches to target HIF signaling in cancer therapy.

Influence of high altitude on the expression of HIF-1 and on the prognosis of Ecuadorian patients with gastric adenocarcinoma

Since the incidence of gastric adenocarcinoma (GA) is high in populations living at high altitudes, we evaluated the influence of altitude on the expression of HIF-1 and survival of Ecuadorian GA patients. Method: 155 GA cases were studied: 56 from coastal (GAC) and 99 from mountainous regions (GAM), and 74 non-GA controls (25 coast and 49 mountain). The expression of HIF-1/HER2 was analyzed by immunohistochemistry. Analyses were performed using Fisher's exact and Breslow-Day tests for homogeneity and Kaplan-Meier curves and restricted median survival time ΔRMST. Results: HIF-1 was overexpressed in normal/inflamed gastric mucosa, especially in mountainous non-GA patients (p = 0.001). There was no difference between GAC and GAM in terms of age/gender, HIF-1/HER2 expression, stage/tumor location. Median survival at 120 months was significantly higher among GAC, with a difference (ΔRMST) of 43.7 months (95% CI 29.5, 57.8) (p < 0.001) and those with positive HIF-1 expression: ΔRMST 26.6 months (95% CI 11.0, 42.1) (p < 0.001). Positive HIF-1 expression was associated with better GAM survival, with ΔRMST 33.6 months (95% CI 14.2, 52.9) (p < 0.001). Conclusion: Despite the limitations of this retrospective study, GA patients in the coastal region and those who expressed HIF-1 exhibited a better prognosis, but this factor was associated with better survival only in the mountain region.

The HIF-1α as a Potent Inducer of the Hallmarks in Gastric Cancer

Hypoxia is the principal architect of the topographic heterogeneity in tumors. Hypoxia-inducible factor-1α (HIF-1α) reinforces all hallmarks of cancer and donates cancer cells with more aggressive characteristics at hypoxic niches. HIF-1α potently induces sustained growth factor signaling, angiogenesis, epithelial-mesenchymal transition, and replicative immortality. Hypoxia leads to the selection of cancer cells that evade growth suppressors or apoptotic triggers and deregulates cellular energetics. HIF-1α is also associated with genetic instability, tumor-promoting inflammation, and escape from immunity. Therefore, HIF-1α may be an important therapeutic target in cancer. Despite that, the drug market lacks safe and efficacious anti-HIF-1α molecules, raising the quest for fully unveiling the complex interactome of HIF-1α in cancer to discover more effective strategies. The knowledge gap is even wider in gastric cancer, where the number of studies on hypoxia is relatively low compared to other well-dissected cancers. A comprehensive review of the molecular mechanisms by which HIF-1α induces gastric cancer hallmarks could provide a broad perspective to the investigators and reveal missing links to explore in future studies. Thus, here we review the impact of HIF-1α on the cancer hallmarks with a specific focus on gastric cancer.

Prognostic value of HIF-1α in digestive system malignancies: evidence from a systematic review and meta-analysis

Aim

This meta-analysis aimed to evaluate the association of HIF-1α expression with clinicopathological features and overall survival (OS) of patients with digestive system malignancies.

Background

Numerous studies have demonstrated that hypoxia-inducible factor-1α (HIF-1α) is abnormally expressed in various solid tumors. However, the clinicopathological features and prognostic value of HIF-1α expression in patients with digestive system malignancies remain controversial.

Methods

A literature search in PubMed, Web of Science, and Scopus databases was performed to identify all relevant studies published in English until 15 October 2020. The pooled effect was calculated to evaluate the association between HIF-1α expression and clinicopathological features and overall survival in cancer patients. Pooled odds ratios (ORs) or hazard ratios (HRs) with a 95% confidence interval (CI) were calculated using fixed- or random-effects model based on between-study heterogeneity.

Results

A total of 44 eligible studies with 5,964 patients were included. The pooled results indicated a positive association of HIF-1α overexpression with poor overall survival (OS) (HR=1.990, 95% CI: 1.615-2.453, p<0.001) and disease-free survival (DFS) (HR=1.90, 95% CI: 1.084-3.329, p=0.043). Meta-analysis results showed that HIF-1α level expression was significantly associated with positive lymph node metastasis (OR=1.869, 95% CI: 1.488-2.248, p<0.001), distance metastasis (OR=2.604, 95% CI: 1.500-4.519, p<0.001), tumor stage (OR=1.801, 95% CI: 1.437-2.257, p<0.001) and tumor size (OR=1.392. 95% CI: 1.068-1.815, p=0.014).

Conclusion

This meta-data suggest that HIF-1α expression might serve as an independent prognostic marker and a promising therapeutic target in patients with digestive system malignancies.

Prognostic features of the tumour microenvironment in oesophageal adenocarcinoma

Oesophageal adenocarcinoma (OAC) is a disease with an incredibly poor survival rate and a complex makeup. The growth and spread of OAC tumours are profoundly influenced by their surrounding microenvironment and the properties of the tumour itself. Constant crosstalk between the tumour and its microenvironment is key to the survival of the tumour and ultimately the death of the patient. The tumour microenvironment (TME) is composed of a complex milieu of cell types including cancer associated fibroblasts (CAFs) which make up the tumour stroma, endothelial cells which line blood and lymphatic vessels and infiltrating immune cell populations. These various cell types and the tumour constantly communicate through environmental cues including fluctuations in pH, hypoxia and the release of mitogens such as cytokines, chemokines and growth factors, many of which help promote malignant progression. Eventually clusters of tumour cells such as tumour buds break away and spread through the lymphatic system to nearby lymph nodes or enter the circulation forming secondary metastasis. Collectively, these factors need to be considered when assessing and treating patients clinically. This review aims to summarise the ways in which these various factors are currently assessed and how they relate to patient treatment and outcome at an individual level.

Hypoxia‑induced lactate dehydrogenase A protects cells from apoptosis in endometriosis

The pathological expression and function of lactate dehydrogenase A (LDHA), a key enzyme that converts pyruvate into lactic acid during glycolysis, remains unknown in endometriosis. In the present study, LDHA expression in tissue samples was determined by immunohistochemistry. To examine whether LDHA was induced by hypoxia, primary cultured endometrial stromal cells (ESCs) and glandular epithelial Ishikawa cells were exposed to 1% O₂ (hypoxia) or 21% O₂ (normoxia). Cellular functions were assessed by flow cytometry, Transwell and Cell Counting Kit-8 assays in LDHA-silenced ESCs and Ishikawa cells. Mitochondrial functions were evaluated using mitochondrial membrane potential JC-1 staining, reactive oxygen species flow cytometric analysis and ATP detection. Additionally, lactic acid production was examined and western blotting was used to evaluate the expression levels of proteins associated with apoptosis, cell cycle and glycolysis, as well as regulatory proteins involved in epithelial-mesenchymal transformation and glycolytic pathways. LDHA was localized to endometrial glandular cells and stromal cells. However, LDHA protein expression was higher in endometriotic lesions compared with that in normal and eutopic endometria. LDHA expression levels in ectopic glandular cells were higher during the proliferative stage compared with during the secretory stage. Hypoxia treatment of Ishikawa cells and ESCs markedly induced the mRNA and protein expression of LDHA. Silencing of LDHA expression in Ishikawa cells and THESC cells significantly promoted impaired mitochondrial function and apoptosis while inhibiting migration and glycolysis. However, it had no obvious effect on proliferation. In conclusion, the present study revealed that LDHA was highly expressed in endometriotic tissues, where it may serve a notable role in the occurrence and development of endometriosis.

Hypoxia and its impact on the tumour microenvironment of gastroesophageal cancers

The malfeasant role of the hypoxic tumour microenvironment (TME) in cancer progression was recognized decades ago but the exact mechanisms that augment the hallmarks of cancer and promote treatment resistance continue to be elucidated. Gastroesophageal cancers (GOCs) represent a major burden of worldwide disease, responsible for the deaths of over 1 million people annually. Disentangling the impact of hypoxia in GOCs enables a better overall understanding of the disease pathogenesis while shining a light on novel therapeutic strategies and facilitating precision treatment approaches with the ultimate goal of improving outcomes for patients with these diseases. This review discusses the underlying principles and processes of the hypoxic response and the effect of hypoxia in promoting the hallmarks of cancer in the context of GOCs. We focus on its bidirectional influence on inflammation and how it drives angiogenesis, innate and adaptive immune evasion, metastasis, and the reprogramming of cellular bioenergetics. The contribution of the hypoxic GOC TME to treatment resistance is examined and a brief overview of the pharmacodynamics of hypoxia-targeted therapeutics is given. The principal methods that are used in measuring hypoxia and how they may enhance prognostication or provide rationale for individually tailored management in the case of tumours with significant hypoxic regions are also discussed.

HIF-1α expression in liver metastasis but not primary colorectal cancer is associated with prognosis of patients with colorectal liver metastasis

Background

The role of hypoxia-inducible factor-1α (HIF-1α) in primary colorectal cancer (CRC) and colorectal liver metastasis (CRLM) has remained unclear. The aim of this study was to investigate HIF-1α expression and its association with prognosis in patients with CRLM with a focus on hepatic stellate cells (HSCs).

Methods

Colon cancer cells were cultured in HSC-conditioned medium (CM), and HIF-1α expression and cell migration were analyzed. Seventy-five patients with CRLM who underwent an initial curative hepatectomy were enrolled. We examined HIF-1α expressions and patient prognosis between primary CRCs and the matched liver metastatic specimens.

Results

Activated HSCs induced HIF-1α mRNA and protein expression in colon cancer cells (p < 0.01) and promoted cell migration (p < 0.01). The positive rates of HIF-1α expression in primary CRCs and liver metastases were 68.0 and 72.0%, respectively. There were no differences in overall (OS) and disease-free survival (DFS) of HIF-1α expression in primary CRC. However, HIF-1α expression in liver metastasis correlated to poor prognosis in both OS and DFS. Furthermore, patients with HIF-1α positive expression in liver metastasis had poor prognosis.

Conclusion

HIF-1α expression in liver metastasis determines poor prognosis of CRLM patients. HSCs might play a key role in aggressive phenotypes of tumor cells.

High-performance reoxygenation from PLGA-PEG/PFOB emulsions: a feedback relationship between ROS and HIF-1α

Background

Hypoxemia is one of the most common pathological processes in various clinical diseases.

Methods

A novel emulsion of poly(lactide-co-glycolide)-poly(ethylene glycol)/perfluorooctyl bromide has been developed to improve arterial hypoxemia through pulmonary drug delivery. Hypoxia-reoxygenation experiment was used to investigate the ability of the emulsion to supply oxygen and the saline lavage acute lung injury model was established to evaluate oxygen supply of the emulsion.

Results

It has been demonstrated that an apparent increase has been detected in the cytotoxicity test of the emulsion, indicating its lower cell toxicity. A hypoxia-reoxygenation experiment uncovered the fact that notable cell growth was observed after reoxygenation with poly(lactide-co-glycolide)-poly(ethylene glycol)/perfluorooctyl bromide emulsion because of the ability of the emulsion to supply oxygen adequately and reasonably. Moreover, the level of intracellular reactive oxygen species was significantly enhanced during hypoxia, which further influenced the concentration and activity of hypoxia-inducible factor-1α (HIF-1α). Furthermore, the upregulated expression of HIF-1α during hypoxia has verified that certain emulsions can increase HIF-1α content and relieve hypoxia, which further indicates HIF-1α plays an essential role in improving cell viability. Afterwards, the saline lavage acute lung injury model was established to evaluate oxygen supply of the emulsion and the result shows considerable improvement of lung ventilation of rabbits.

Conclusion

We recommend that the feedback relationship between reactive oxygen species and HIF-1 plays an essential role in improving cell viability. It is anticipated that the emulsion will be applied in the field of alleviating hypoxemia.

Acetylation-mediated Siah2 stabilization enhances PHD3 degradation in Helicobacter pylori-infected gastric epithelial cancer cells

Gastric epithelial cells infected with Helicobacter pylori acquire highly invasive and metastatic characteristics. The seven in absentia homolog (Siah)2, an E3 ubiquitin ligase, is one of the major proteins that induces invasiveness of infected gastric epithelial cells. We find that p300-driven acetylation of Siah2 at lysine 139 residue stabilizes the molecule in infected cells, thereby substantially increasing its efficiency to degrade prolyl hydroxylase (PHD)3 in the gastric epithelium. This enhances the accumulation of an oncogenic transcription factor hypoxia-inducible factor 1α (Hif1α) in H. pylori-infected gastric cancer cells in normoxic condition and promotes invasiveness of infected cells. Increased acetylation of Siah2, Hif1α accumulation, and the absence of PHD3 in the infected human gastric metastatic cancer biopsy samples and in invasive murine gastric cancer tissues further confirm that the acetylated Siah2 (ac-Siah2)-Hif1α axis is crucial in promoting gastric cancer invasiveness. This study establishes the importance of a previously unrecognized function of ac-Siah2 in regulating invasiveness of H. pylori-infected gastric epithelial cells.-Kokate, S. B., Dixit, P., Das, L., Rath, S., Roy, A. D., Poirah, I., Chakraborty, D., Rout, N., Singh, S. P., Bhattacharyya, A. Acetylation-mediated Siah2 stabilization enhances PHD3 degradation in Helicobacter pylori-infected gastric epithelial cancer cells.

Regulation of SIRT3 signal related metabolic reprogramming in gastric cancer by Helicobacter pylori oncoprotein CagA

Injection of the Helicobacter pylori cytotoxin-associated gene A (CagA) is closely associated with the development of chronic gastritis and gastric cancer. Individuals infected with H. pylori possessing the CagA protein produce more reactive oxygen species (ROS) and show an increased risk of developing gastric cancer. Sirtuins (SIRTs) are nicotinamide adenine dinucleotide (NAD⁺)-dependent deacetylases and mitochondrial SIRT3 is known to be a tumor suppressor via its ability to suppress ROS and hypoxia inducible factor 1α (HIF-1α). However, it is unclear whether increased ROS production by H. pylori is regulated by SIRT3 followed by HIF-1α regulation and whether intracellular CagA acts as a regulator thereof. In this study, we investigated correlations among SIRT3, ROS, and HIF-1α in H. pylori-infected gastric epithelial cells. We observed that SIRT3-deficient AGS cells induce HIF-1α protein stabilization and augmented transcriptional activity under hypoxic conditions. In CagA⁺H. pylori infected cells, CagA protein localized to mitochondria where it subsequently suppressed SIRT3 proteins. CagA⁺H. pylori infection also increased HIF-1α activity through the ROS production induced by the downregulated SIRT3 activity, which is similar to the hypoxic condition in gastric epithelial cells. In contrast, overexpression of SIRT3 inhibited the HIF-1α protein stabilization and attenuated the increase in HIF-1α transcriptional activity under hypoxic conditions. Moreover, CagA⁺H. pylori attenuated HIF-1α stability and decreased transcriptional activity in SIRT3-overexpressing gastric epithelial cells. Taken together, these findings provide valuable insights into the potential role of SIRT3 in CagA⁺H. pylori-mediated gastric carcinogenesis and a possible target for cancer prevention via inhibition of HIF-1α.

Molecular mechanisms of hypoxia in cancer

PURPOSE

Hypoxia is a condition of insufficient oxygen to support metabolism which occurs when the vascular supply is interrupted, or when a tumour outgrows its vascular supply. It is a negative prognostic factor due to its association with an aggressive tumour phenotype and therapeutic resistance. This review provides an overview of hypoxia imaging with Positron emission tomography (PET), with an emphasis on the biological relevance, mechanism of action, highlighting advantages, and limitations of the currently available hypoxia radiotracers.

METHODS

A comprehensive PubMed literature search was performed, identifying articles relating to biological significance and measurement of hypoxia, MRI methods, and PET imaging of hypoxia in preclinical and clinical settings, up to December 2016.

RESULTS

A variety of approaches have been explored over the years for detecting and monitoring changes in tumour hypoxia, including regional measurements with oxygen electrodes placed under CT guidance, MRI methods that measure either oxygenation or lactate production consequent to hypoxia, different nuclear medicine approaches that utilise imaging agents the accumulation of which is inversely related to oxygen tension, and optical methods. The advantages and disadvantages of these approaches are reviewed, along with individual strategies for validating different imaging methods. PET is the preferred method for imaging tumour hypoxia due to its high specificity and sensitivity to probe physiological processes in vivo, as well as the ability to provide information about intracellular oxygenation levels.

CONCLUSION

Even though hypoxia could have significant prognostic and predictive value in the clinic, the best method for hypoxia assessment has in our opinion not been realised.

HIF1/2α mediates hypoxia-induced LDHA expression in human pancreatic cancer cells

Glycolysis is a typical conduit for energy metabolism in pancreatic cancer (PC) due to the hypoxic microenviroment. Lactate dehydrogenase A (LDHA) catalyzes the conversion of pyruvate to lactate and is considered to be a key checkpoint of anaerobic glycolysis. The aim of the present study was to explore the mechanism of interactions between hypoxia, HIF-1/2α and LDHA, and the function of LDHA on PC cells by analyzing 244 PC and paratumor specimens. It was found that LDHA was over-expressed and related to tumor stages. The result of in vitro study demonstrated that hypoxia induced LDHA expression. To explore the relationship between HIF and LDHA, chromatin immunoprecipitation assay and luciferase assay were performed. The result showed that HIF-1/2α bound to LDHA at 89bp under the hypoxic condition. Furthermore, knockdown of endogenous HIF-1α and HIF-2α decreased the LDHA expression even in the hypoxic condition, which was accompanied with a significant decrease in lactate production and glucose utilization (p < 0.01). Immunofluorescence in the 244 specimens showed that HIF-1/2α was over-expressed and associated with LDHA over-expression (p < 0.0001). Forced expression of LDHA promoted the growth and migration of PC cells, while knocking down the expression of LDHA inhibited the cell growth and migration markedly. In summary, the present study proved that HIF1/2α could activate LDHA expression in human PC cells, and high expression of LDHA promoted the growth and migration of PC cells.

Clinical significance of HIF-1α expression in gastric malignant transformation in people from high altitude area of Qinghai

AIM

To detect the expression of hypoxia inducible factor-1α (HIF-1α) in gastric malignant transformation in people from high altitude area of Qinghai, China.

METHODS

RT-PCR was used to detect the expression of HIF-1α gene in 7 cell lines and 27 pairs of GC and matched tumor adjacent normal gastric mucosa tissues. Using tissue microarray including 57 normal gastric mucosa tissues, 37 chronic atrophic gastritis tissues, 34 intestinal metaplasia tissues, and 146 gastric cancer (GC) tissues, immunohistochemistry (IHC) was performed to detect the level of HIF-1α protein expression.

RESULTS

The expression of HIF-1α at the mRNA level was different in GC cell lines. HIF-1αexpression in AGS, SGC7901, and N87 cells was higher than that in MGC803, BGC823, PAMC82 and MKN45 cells. The level of HIF-1α expression was significantly higher in GC tissues (66.6%, 18/27) compared with normal gastric mucosa tissues (26.3%, 15/57; P < 0.001). IHC data showed that the positive rate of HIF-1α was 64.8% (24/37) in chronic atrophic gastritis tissues, 61.7% (21/34) in intestinal metaplasia tissues, and 56.8% (83/146) in GC tissues, all of which were significantly higher than that in normal tissues (26.3%, 15/57). Expression of HIF-1α was positively associated with age in GC (P < 0.05). Kaplan-Meier analysis showed that patients with a low level of HIF-1α had apparently better survival than those with a high level (P < 0.0001). HIF-1α protein (RR = 3.229, 95%CI: 2.024-5.151) was identified to be an independent risk factor for the outcome of GC patients.

CONCLUSION

High HIF-1α expression is associated with gastric malignant transformation and poor prognosis in high altitude areas.

Hypoxia and HIF-1 activation in bacterial infections

For most of the living beings, oxygen is one of the essential elements required to sustain life. Deprivation of oxygen causes tissue hypoxia and this severely affects host cell and organ functions. Tissue hypoxia is a prominent microenvironmental condition occurring in infections and there is a body of evidence that hypoxia and inflammation are interconnected with each other. The primary key factor mediating the mammalian hypoxic response is hypoxia inducible factor (HIF)-1, which regulates oxygen homeostasis on cellular, tissue and organism level. Recent studies show that HIF-1 plays a central role in angiogenesis, cancer and cardiovascular disease but also in bacterial infections. Activation of HIF-1 depends on the nature of the pathogen and the characteristics of infections in certain hosts. Up to date, it is not completely clear whether the phenomenon of HIF-1 activation in infections has a protective or detrimental effect on the host. In this review, we give an overview of whether and how hypoxia and HIF-1 affect the course of infections.

Hostile takeover: Manipulation of HIF-1 signaling in pathogen-associated cancers (Review)

Hypoxia-inducible factor (HIF)-1 is a central regulator in the adaptation process of cell response to hypoxia (low oxygen). Emerging evidence has demonstrated that HIF-1 plays an important role in the development and progression of many types of human diseases, including pathogen-associated cancers. In the present review, we summarize the recent understandings of how human pathogenic agents including viruses, bacteria and parasites deregulate cellular HIF-1 signaling pathway in their associated cancer cells, and highlight the common molecular mechanisms of HIF-1 signaling activated by these pathogenic infection, which could act as potential diagnostic markers and new therapeutic strategies against human infectious cancers.

Annexin A1 sustains tumor metabolism and cellular proliferation upon stable loss of HIF1A

Despite the approval of numerous molecular targeted drugs, long-term antiproliferative efficacy is rarely achieved and therapy resistance remains a central obstacle of cancer care. Combined inhibition of multiple cancer-driving pathways promises to improve antiproliferative efficacy. HIF-1 is a driver of gastric cancer and considered to be an attractive target for therapy. We noted that gastric cancer cells are able to functionally compensate the stable loss of HIF-1α. Via transcriptomics we identified a group of upregulated genes in HIF-1α-deficient cells and hypothesized that these genes confer survival upon HIF-1α loss. Strikingly, simultaneous knock-down of HIF-1α and Annexin A1 (ANXA1), one of the identified genes, resulted in complete cessation of proliferation. Using stable isotope-resolved metabolomics, oxidative and reductive glutamine metabolism was found to be significantly impaired in HIF-1α/ANXA1-deficient cells, potentially explaining the proliferation defect. In summary, we present a conceptually novel application of stable gene inactivation enabling in-depth deconstruction of resistance mechanisms. In theory, this experimental approach is applicable to any cancer-driving gene or pathway and promises to identify various new targets for combination therapies.

Expression and significance of HIF-1α and HIF-2α in pancreatic cancer

The expression levels of hypoxia-inducible factor 1alpha (HIF-1α) and HIF-2α in pancreatic cancer (PC) and their association with clinicopathologic characteristics were investigated in order to elucidate their roles in the development of PC. HIF-1α and HIF-2α mRNA levels in 20 patients with PC were detected by quantitative real-time polymerase chain reaction. The expression of HIF-1α and HIF-2α protein in samples from other 90 patients with PC was measured by immunohistochemistry. Correlations between the expression of HIF-1α or HIF-2α and clinicopathologica features and prognosis were analyzed. The expression of both HIF-1α and HIF-2α mRNA was up-regulated in most cancer tissues (P<0.05). HIF-1α staining was weakly positive in most cancer tissues and strongly positive in adjacent pancreas tissues (P<0.05). Clinicopathologic analysis revealed that relatively strong HIF-1α expression in cancer tissues was related to greater invasion (P<0.05), higher tumor pathologic stage (P<0.05), higher American Joint Committee on Cancer (AJCC) stage (P<0.05) and shorter overall survival time (P<0.05). Conversely, HIF-2α staining was strongly positive in most cancer tissues and weakly positive in adjacent pancreas tissues. Clinicopathologic analysis revealed that relatively strong HIF-2α expression in cancer tissues was related to less invasion (P<0.05), lower tumor pathologic stage (P<0.05), lower AJCC stage (P<0.05) and longer overall survival time (P<0.05). Moreover, the HIF-1α(high)/HIF-2α(low) group showed a shorter survival time than the HIF-1α(low)/HIF-2α(high) group. In conclusion, although HIF-1α and HIF-2α mRNA expression patterns are the same, their protein expression patterns are significantly different and they play different roles in PC. Combined analysis of HIF-1α and HIF-2α expression might be useful to predict the prognosis of patients with PC.

Implication of Leptin-Signaling Proteins and Epstein-Barr Virus in Gastric Carcinomas

We investigated the clinicopathological implications of leptin-signaling proteins and Epstein-Barr virus (EBV)-infection status in gastric carcinomas. Immunohistochemistry for leptin signalling-related proteins (leptin, leptin-receptor, pSTAT3, ERK, pAkt, mTOR and HIF-1 alpha), and in situ hybridization for EBV-encoded small RNAs was performed in 343 cases of gastric carcinomas. The siRNA against leptin-receptor was transfected into three stomach cancer cell lines, and western blot for caspase 3 was performed. The TNM stage was a prognostic factor in all 343 patients, and was negatively correlated with expression of leptin, pSTAT3, ERK, pAkt, mTOR and HIF-1 alpha (P < 0.05). Leptin-receptor expression was correlated with poor survival in 207 patients of the advanced gastric cancer (AGC) subgroup, 139 of the Lauren diffuse group, and in 160 patients with lymph node metastasis (P < 0.05, respectively). Additionally, in stomach cancer cells, cleaved caspase 3 level increased by leptin-receptor inhibition, that is, apoptosis increased. Interestingly, EBV-positive AGC (n = 29) tended to show better survival of patients than EBV-negative AGC (n = 178) (P = 0.06). pAkt expression was related with a good survival of 32 patients (9%) in the EBV-positive subgroup, but was not an independent prognostic factor. Among, leptin signaling-related proteins, expressions of leptin-receptor and mTOR were different between EBV-positive subgroup and EBV-negative subgroup (P < 0.05, respectively). In conclusion, leptin-signaling proteins and EBV status show different significance on patient survival, according to subsets of gastric carcinomas. The leptin-receptor may predict poor patient prognosis in the AGC, Lauren diffuse and lymph node metastasis subgroups, while EBV-positive status can show a good prognosis in the AGC. Each leptin signaling-related protein may be differently involved in carcinogenesis of EBV-negative and EBV-positive subsets.

The potential predictive role of nuclear NHERF1 expression in advanced gastric cancer patients treated with epirubicin/oxaliplatin/capecitabine first line chemotherapy

Cellular resistance in advanced gastric cancer (GC) might be related to function of multidrug resistance (MDR) proteins. The adaptor protein NHERF1 (Na(+)/H(+) exchanger regulatory factor) is an important player in cancer progression for a number of solid malignancies, even if its role to develop drug resistance remains uncertain. Herein, we aimed to analyze the potential association between NHERF1 expression and P-gp, sorcin and HIF-1α MDR-related proteins in advanced GC patients treated with epirubicin/oxaliplatin/capecitabine (EOX) chemotherapy regimen, and its relation to response. Total number of 28 untreated patients were included into the study. Expression and subcellular localization of all proteins were assessed by immunohistochemistry on formalin-fixed paraffin embedded tumor samples. We did not found significant association between NHERF1 expression and the MDR-related proteins. A trend was observed between positive cytoplasmic NHERF1 (cNHERF1) expression and negative nuclear HIF-1α (nHIF-1α) expression (68.8% versus 31.3% respectively, P = 0.054). However, cytoplasmic P-gp (cP-gp) expression was positively correlated with both cHIF-1α and sorcin expression (P = 0.011; P = 0.002, respectively). Interestingly, nuclear NHERF1 (nNHERF1) staining was statistically associated with clinical response. In detail, 66.7% of patients with high nNHERF1 expression had a disease control rate, while 84.6% of subjects with negative nuclear expression of the protein showed progressive disease (P = 0.009). Multivariate analysis confirmed a significant correlation between nNHERF1 and clinical response (OR 0.06, P = 0.019). These results suggest that nuclear NHERF1 could be related to resistance to the EOX regimen in advanced GC patients, identifying this marker as a possible independent predictive factor.

Hypoxia and free radicals: role in tumor progression and the use of engineering-based platforms to address these relationships

Hypoxia is a feature of all solid tumors, contributing to tumor progression and therapy resistance. Through stabilization of the hypoxia-inducible factor 1 alpha (HIF-1α), hypoxia activates the transcription of a number of genes that sustain tumor progression. Since the seminal discovery of HIF-1α as a hypoxia-responsive master regulator of numerous genes and transcription factors, several groups have reported a novel mechanism whereby hypoxia mediates stabilization of HIF-1α. This process occurs as a result of hypoxia-generated reactive oxygen species (ROS), which, in turn, stabilize the expression of HIF-1α. As a result, a number of genes regulating tumor growth are expressed, fueling ongoing tumor progression. In this review, we outline a role for hypoxia in generating ROS and additionally define the mechanisms contributing to ROS-induced stabilization of HIF-1α.We further explore how ROS-induced HIF-1α stabilization contributes to tumor growth, angiogenesis, metastasis, and therapy response. We discuss a future outlook, describing novel therapeutic approaches for attenuating ROS production while considering how these strategies should be carefully selected when combining with chemotherapeutic agents. As engineering-based approaches have been more frequently utilized to address biological questions, we discuss opportunities whereby engineering techniques may be employed to better understand the physical and biochemical factors controlling ROS expression. It is anticipated that an improved understanding of the mechanisms responsible for the hypoxia/ROS/HIF-1α axis in tumor progression will yield the development of better targeted therapies.

Interaction of sonic hedgehog (SHH) pathway with cancer stem cell genes in gastric cancer

Gastric cancer may appear by frequent genetic or epigenetic changes in oncogenes, tumor suppressor or DNA mismatch repair genes. Molecular studies show the possibility of involvement of certain cancer pathways in gastric cancer. In this respect, DNA methylation is one of the most important epigenetic alterations in gastric cancer and identifying the signaling mechanism and also methylation of some genes that are involved in gastric cancer can help to improve treatment strategies. Relatively, there are many reported methylation alteration of genes in stem cells in all kinds of tumors with some of these genes having a key role in tumor development. Correspondingly, KLF5, CDX1/2, WNT1 and FEM1A are considerable genes in gastric cancer, although many researches and studies have illustrated that sonic hedgehog and expression of its signaling cascade proteins are related in gastric cancer. Relatively, modification in these genes causes many eclectic cancers such as rhabdomyosarcoma and diverse kinds of digestive system tumor development. Conspicuously, these master genes have a noticeable role in stem cell's growth regulation as well as other kinds of cancer such as breast cancer and leukemia. Hence, we concluded that research and studies on methylation and expression of these genes and also the investigation of molecular signaling in gastric cancer can acquire impressive conclusions in order to control and treat this common place and serious problem.

Hypoxia inducible factor-1 alpha as a therapeutic target in multiple myeloma

The increasing importance of hypoxia-inducible factor-1α (HIF-1α) in tumorigenesis raises the possibility that agents which specifically inhibit this transcription factor, would provide significant therapeutic benefit. The constitutive expression of HIF-1α in about 35% of Multiple Myeloma (MM) patients suggests HIF-1α suppression might be part of a therapeutic strategy. Accordingly, we explored the effect of EZN-2968, a small 3rd generation antisense oligonucleotide against HIF-1α, in a panel of MM cell lines and primary patients samples. Here, we demonstrated that EZN-2968 is highly specific for HIF-1α mRNA and that exposure of MM cells to EZN-2968 resulted in an efficient and homogeneous loading of the cells showing a long lasting low HIF-1α protein level. In MM cells, HIF-1α suppression induced a permanent cell cycle arrest by prolonging S-phase through cyclin A modulation and in addition it induced a mild apoptotic cell death. Moreover, HIF-1α suppression caused a metabolic shift that leaded to increased production of ATP by oxidative phosphorylation (i.e. Warburg effect reversion), that was confirmed by the observed mitochondrial membrane potential decrease. These results show that HIF-1α is an important player in MM homeostasis and that its inhibition by small antisense oligonucleotides provides a rationale for novel therapeutic strategy to improving MM treatment.

Molecular insight in gastric cancer induction: an overview of cancer stemness genes

Gastric cancer is one of the most outgoing human cancers in the world. Two main functional types were described: Intestinal adenocarcinoma and diffuse one. The most important purpose of this review is to analyze and investigate the main genetic factors involved in tumorogenesis of stomach and the molecular mechanism of their expression regulation alongside with the importance of cancer stem cells and their relationship with gastric cancer. It is evident that proper diagnosis of molecular case of cancer may lead to absolute treatment and at least reduction in the disease severity. However, stemness factors such as Sox2, Oct3/4, and Nanog were related with induced pluripotent stem cells, proposing a correlation between these stemness factors and cancer stem cells. Moreover, aberrant induction by Helicobacter pylori of the intestinal-specific homeobox transcription factors, CDX1 and CDX2, also plays an important role in this modification. There are some genes which are directly activated by CDX1 in gastric cancer and distinguished stemness-related reprogramming factors like SALL4 and KLF5. Correspondingly, we also aimed to present the main important epigenetic changes such as DNA methylation, histone modification, and chromatin modeling of stemness genes in disease development. Remarkably, a better understanding of molecular bases of cancer may lead to novel diagnostic, therapeutic, and preventive approaches by some genetic and epigenetic changes such as gene amplifications, gene silencing by DNA methylation, losses of imprinting, LOH, and mutations. Consequently, genome-wide searches of gene expression are widely important for surveying the proper mechanisms of cancer emergence and development. Conspicuously, this review explains an outline of the molecular mechanism and new approaches in gastric cancer.

Risk prediction for malignant conversion of oral epithelial dysplasia by hypoxia related protein expression

AIMS

Increased aerobic glycolysis is a unique finding in cancers and hypoxia-related proteins are associated with aerobic glycolysis. Therefore, we aimed to investigate whether hypoxia-related proteins can be predictive markers for malignant conversion of oral premalignant lesions with epithelial dysplasia (OED).

METHODS

Expression of HIF-1α, Glut-1 and CA9 were detected in clinical samples of eight normal oral mucosa, 85 transitional areas of oral squamous cell carcinoma (OSCC) and 28 OED with or without malignant conversion using immunohistochemistry and were also comparatively detected in immortalised human oral keratinocyte (IHOK) and OSCC cell lines under hypoxia using immunoblotting.

RESULTS

Sequential expression of HIF-1α, Glut-1 and CA9 was found both in transitional areas of OSCC and cell lines of IHOK and OSCC under hypoxia, supporting hypoxia-aerobic glycolysis-acidosis axis. Expression of all proteins showed significant association with malignant conversion of OED and CA9 was an independent risk factor of malignant transformation of OED. But the predictability of malignant transformation was improved when all three proteins were applied together.

CONCLUSION

High expression of CA9 was an independent predictive marker of malignant conversion. Moreover, the combined application of these three proteins may be useful to assess the risk of malignant conversion of OED.

Hypoxia-inducible factor 1 alpha (HIF-1α) as a prognostic indicator in patients with gastric tumors: a meta-analysis

BACKGROUND AND OBJECTIVE

Though researched for years, the prognostic role of hypoxia-inducible factor 1 alpha (HIF-1α) in gastric cancer is still controversial. We thus undertook a systematic review to assess the relationship.

METHOD

A systematically literature search of Pubmed, Embase, Web of Science, China Biological Medicine Disc and Cochrane Library was undertaken in February 2013, and the reference lists of articles were retrieved.

RESULTS

12 trials (1,555 participants) were included to assess the association between HIF-1α expression and survival. Summary hazard ratios (HRs) were calculated. HIF-1α expression was significantly correlated with poor overall survival of gastric cancer patients (HR=1.34, 95%CI: 1.13-1.58; P=0.0009), but not with poor disease free survival of gastric cancer patients (HR=1.67, 95%CI: 0.99-2.82; P=0.06).

CONCLUSION

HIF-1α was associated with poor OS, but not DFS, especially for Asian patients. But studies evaluating relationships of HIF- 1α with OS and DFS in non-Asian gastric cancer patients appear needed.

OCT-1 overexpression is associated with poor prognosis in patients with well-differentiated gastric cancer

Octamer transcription factor-1 (OCT-1) is a well-known transcription factor that is reportedly overexpressed in intestinal metaplasia and gastric carcinoma in the intestine. In this study, we investigated OCT-1 overexpression as a prognostic factor for gastric cancer. The association between OCT-1 overexpression (detected using immunohistochemistry) and clinicopathological features including survival was evaluated. In vitro gain-of-function approaches were utilized to assess the function of OCT-1 in malignancy. Analysis of OCT-1 expression in patients with gastric cancer with well-differentiated carcinoma as per the World Health Organization classification showed that OCT-1 overexpression was correlated with advanced tumor invasion (58.8 % of patients with advanced tumor invasion vs. 21.2 % of patients with early tumor invasion; p<0.01), lymph node metastasis (63.9 % of patients with metastasis vs. 24.1 % of those without; p=0.015), and cancer recurrence (83.3 % of patients with recurrence vs. 25.4 % of those without; p<0.01), as well as a lower survival rate (62.8 vs. 87.9 Mo; p<0.01). However, there were no significant differences in the levels of OCT-1 expression in gastric cancer patients with other carcinoma types (p>0.05). Furthermore, we found that the proliferation rate of OCT-1-overexpressing MKN-45 cells was higher than that of the control cells. OCT-1 overexpression may be a marker for poor prognosis in patients with well-differentiated gastric adenocarcinoma.

Prognostic value and clinicopathological differences of HIFs in colorectal cancer: evidence from meta-analysis

Background

The prognostic value of HIFs in colorectal cancer was evaluated in a large number of studies, but the conclusions were inconclusive. Meanwhile, clinicopathologic differences of HIF-1α and HIF-2α were rarely compared in recent studies.

Methodology

Identical search strategies were used to search relevant literatures in the PubMed and Web of Science databases. The prognostic significances and clinicopathological differences of HIFs in CRC were analyzed.

Principal Findings

A total of 23studies comprising 2984 CRC patients met the inclusion criteria. The results indicated that overexpressed HIFs were significantly associated with increase of mortality risk, including overall survival (OS) (HR 2.06 95%CI 1.55–2.74) and disease free survival (HR 2.84, 95%CI 1.87–4.31). Subgroup analysis revealed that both overexpressed HIF-1α and HIF-2α had correlations with worse prognosis. The pooled HRs were 2.01 (95% CI: 1.55–2.6) and 2.07(95% CI: 1.01–4.26). Further subgroup analysis on HIF-1α was performed by study location, number of patients, quality score and cut-off value. The results showed that HIF-1α overexpression was significantly associated with poor OS, particularly in Asian countries (HR 2.3, 95% CI: 1.74–3.01), while not in European or other countries. In addition, overexpression of HIF-1α was closely related with these clinicopathological features, including Dukes' stages (OR 0.39, 95% CI: 0.17–0.89), UICC stages (OR 0.42 95% CI: 0.3–0.59), depth of invasion (OR 0.71, 95% CI: 0.51–0.99), lymphnode status (OR 0.49, 95% CI: 0.32–0.73) and metastasis (OR 0.29, 95% CI: 0.11–0.81). While overexpression of HIF-2α was only associated with grade of differentiation (OR 0.48, 95% CI: 0.29–0.81).

Conclusions

This study showed that both HIF-1α and HIF-2α overexpression were associated with an unfavorable prognosis. HIF-1α overexpression seemed to be associated with worse prognosis in Asian countries. Additionally, HIF-1α and HIF-2α indicated distinct clinicopathologic features.

Prognostic value of HIF-1α expression in patients with gastric cancer

The role of hypoxia-inducible factors-1 alpha (HIF-1α) expression in gastric cancer remains controversial. We performed a systematic review of the literature with meta-analysis. Electronic databases were used to identify published studies before December 1, 2012. Pooled hazard ratio (HR) or odds ratio (OR) with 95 % confidence interval (95 % CI) was used to estimate the strength of the association between HIF-1α expression and survival of gastric cancer patients. Heterogeneity and publication bias were also assessed. Final analysis of 1,268 patients from 9 eligible studies was performed. High HIF-1α expression was significantly correlated with poor overall survival (OS) of gastric cancer patients (HR = 2.14, 95 % CI = 1.32-3.48). Subgroup analysis indicated that HIF-1α over-expression had an unfavorable impact on OS in Asian patients (HR = 2.35, 95 % CI = 1.41-3.92). Moreover, up-regulation of HIF-1α was significantly associated with the depth of invasion (OR = 2.49, 95 % CI = 1.28-4.83), lymph node metastasis (OR = 2.15, 95 % CI = 1.27-3.66), and vascular invasion (OR = 2.23, 95 % CI = 1.20-4.14). HIF-1α expression might be a predicative factor of poor prognosis for gastric cancer particularly in Asia.

The association between HIF-1α polymorphism and cancer risk: a systematic review and meta-analysis

Epidemiological studies have assessed the association between HIF-1α polymorphisms and cancer risk. However, the results remained conflicting rather than conclusive. Therefore, we performed a systematic review to provide a complete picture and conducted a meta-analysis to derive a precise estimation. We searched PubMed, Embase, and China National Knowledge Infrastructure (CNKI) databases until July 2013 to identify eligible studies. Data sets (43) from 39 studies with a total of 10,841 cases and 14,682 controls were included. The most commonly investigated polymorphism was C1772T, followed by G1790A, C111A, and rs2057482. Overall, C1772T and G1790A but not rs2057482 were associated with increased risk for cancer. When stratified by cancer type, C1772T was associated with increased risk for cervical cancer (T/T vs. C/T+C/C: OR = 8.80, 95 % CI = 2.30-33.70), prostate cancer (T vs. C: OR = 1.54, 95 % CI = 1.04-2.30), and other cancers (T vs. C: OR = 1.42, 95 % CI = 1.07-1.89), but not oral, breast, colorectal, endometrial, lung, and bladder cancers or renal cell carcinoma. G1790A was associated with marginal but insignificant risk for prostate cancer (A vs. G: OR = 1.46, 95 % CI = 1.00-2.13, P = 0.056) and with increased risk for oral (A vs. G: OR = 9.66, 95 % CI = 1.31-71.15), lung (A vs. G: OR = 2.27, 95 % CI = 1.74-2.96), and other cancers (A vs. G: OR = 2.06, 95 % CI = 1.26-3.37) and renal cell carcinoma (A/A vs. G/A+G/G: OR = 3.05, 95 % CI = 1.36-6.84), but not breast, colorectal, cervical, or bladder cancer. Furthermore, we detected increased cancer risk in haplotypes TA and CA and in those carrying at least one risk allele, and decreased cancer risk in haplotype TG regarding C1772T and G1790A polymorphisms. Further well-designed studies on various cancer types are warranted to verify our findings.

Oxygen sensing, hypoxia-inducible factors, and disease pathophysiology

Hypoxia-inducible factors (HIFs) are transcriptional activators that function as master regulators of oxygen homeostasis, which is disrupted in disorders affecting the circulatory system and in cancer. The role of HIFs in these diseases has been elucidated by clinical studies and by analyses of mouse models. HIFs play a protective role in the pathophysiology of myocardial ischemia due to coronary artery disease, limb ischemia due to peripheral arterial disease, pressure-overload heart failure, wound healing, and chronic rejection of organ transplants. In contrast, HIFs contribute to the pathogenesis of pulmonary arterial hypertension, systemic hypertension associated with sleep apnea, ocular neovascularization, hereditary erythrocytosis, and cancer.

Investigation of the esophageal Rho-kinase expression in patients with Barrett's esophagus

The mechanisms responsible for the malignant transformation in Barrett's esophagus (BE) are still poorly understood. The authors have evaluated the role of Rho-kinase (ROCK1 and ROCK2) expressions in patients with BE. All patients underwent upper gastrointestinal system endoscopy, which was confirmed histologically. Real-time PCR revealed no marked change in gene expressions of ROCK1 and ROCK2 at mRNA levels in BE when compared to controls. Immunohistochemical and western blot analyses showed no change in ROCK1 and ROCK2 protein expressions in BE. This study demonstrates that Rho-kinase gene and protein expressions are not modified in BE.

Signaling pathways in the molecular pathogenesis of adenocarcinomas of the esophagus and gastroesophageal junction

Esophageal adenocarcinoma develops in response to severe gastroesophageal reflux disease through the precursor lesion Barrett esophagus, in which the normal squamous epithelium is replaced by a columnar lining. The incidence of esophageal adenocarcinoma in the United States has increased by over 600% in the past 40 years and the overall survival rate remains less than 20% in the community. This review highlights some of the signaling pathways for which there is some evidence of a role in the development of esophageal adenocarcinoma. An increasingly detailed understanding of the biology of this cancer has emerged recently, revealing that in addition to the well-recognized alterations in single genes such as p53, p16, APC, and telomerase, there are interactions between the components of the reflux fluid, the homeobox gene Cdx2, and the Wnt, Notch, and Hedgehog signaling pathways.

Hypoxia stimulates the EMT of gastric cancer cells through autocrine TGFβ signaling

Epithelial mesenchymal transition (EMT) is considered to be correlated with malignancy of cancer cells and responsible for cancer invasion and metastasis. We previously reported that distant metastasis was associated with hypoxia in gastric cancer. We therefore investigated the effect of hypoxic condition on EMT of gastric cancer cells. Gastric cancer cells were cultured in normoxia (21% O₂) or hypoxia (1% O₂) for 24 h. EMT was evaluated as the percentage of spindle-shaped cells in total cells. Effect of transforming growth factor β1 (TGFβ1) or tyrosine kinase inhibitors on the EMT was evaluated. The expression level of TGFβ1 and TGFβR was evaluated by real time RT-PCR. The TGFβ1 production from cancer cells was measured by ELISA. Hypoxia stimulated EMT of OCUM-2MD3 and OCUM-12 cells, but not that of OCUM-2M cells. The expression level of TGFβ1 mRNA under hypoxia was significantly higher than that under normoxia in all of three cell lines. The expression level of TGFβR mRNA was significantly increased by hypoxia in OCUM-2MD3 cells, but not in OCUM-2M cells. TGFβR inhibitor, SB431542 or Ki26894, significantly suppressed EMT of OCUM-2MD3 and OCUM-12. TGFβ1 production from OCUM-2MD3 and OCUM-12 cells was significantly increased under hypoxia in comparison with that under normoxia. These findings might suggest that hypoxia stimulates the EMT of gastric cancer cells via autocrine TGFβ/TGFβR signaling.

Hypoxia-inducible factor-1 as a therapeutic target in cancer

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that immortalizes tumors by inducing key genes in cancer biology, including angiogenesis, glycolysis, invasion, and metastasis. Overexpression of HIF-1α is thus associated with resistance to cancer chemotherapy and increased patient mortality in several cancer phenotypes. In the present review, we summarize the role of intratumoral hypoxia and bioactive lipids in enhancing HIF-1 activity, critically discussing the potential for HIF-1α inhibitors in cancer chemotherapy. Considering preclinical studies, HIF-1 inhibitors appear to have antitumor effects and thus represent a novel therapeutic strategy.

The Critical Impact of HIF-1a on Gastric Cancer Biology

Hypoxia inducible factor-1 (HIF-1) monitors the cellular response to the oxygen levels in solid tumors. Under hypoxia conditions, HIF-1α protein is stabilized and forms a heterodimer with the HIF-1β subunit. The HIF-1 complex activates the transcription of numerous target genes in order to adapt the hypoxic environment in human cancer cells. In gastric cancer patients, HIF-1α activation following extended hypoxia strongly correlates with an aggressive tumor phenotype and a poor prognosis. HIF-1α activation has been also reported to occur via hypoxia-independent mechanisms such as PI3K/AKT/mTOR signaling and ROS production. This article argues for the critical roles of HIF-1α in glucose metabolism, carcinogenesis, angiogenesis, invasion, metastasis, cell survival and chemoresistance, focusing on gastric cancer.

Clinicopathological implications of the expression of hypoxia-related proteins in gastric cancer

OBJECTIVES

Tumor hypoxia confers poor prognosis of a wide range of solid tumors due to increased malignancy, increased likelihood of metastasis and treatment resistance. The aim of this study was to assess the significance of the expression of HIF-1α and HIF-1α-inducible proteins in gastric cancer and their impact on prognosis.

MATERIALS AND METHODS

The expression of HIF-1α, GLUT-1, CA-9, and iNOS proteins was analyzed by immunohistochemistry in 193 gastric adenocarcinomas (GAs) and 20 normal gastric mucosa.

RESULTS

HIF-1α, GLUT-1, CA-9 and iNOS were expressed in 52.3%, 43.0%, 57.0%, and 43.0% of GAs, respectively, which are higher than the normal counterparts except for CA-9. HIF-1α expression was positively correlated with the expression of GLUT-1, CA-9 and iNOS. GLUT-1 expression was higher in the intestinal type (p = 0.012); however, iNOS expression was higher in the less-differentiated type and the diffuse type (p = 0.006, p = 0.032, respectively). The expression of HIF-1α and GLUT-1 was significantly correlated with lymph node metastasis (p = 0.009, p = 0.008, respectively), while the expression of GLUT-1 and iNOS was significantly correlated with the depth of invasion and advanced stage (p = 0.044, p = 0.004; p = 0.009, p = 0.008, respectively). Overall survival was shorter in patients with GLUT-1 expression than in those without GLUT-1 expression, which was statistically significant by univariate analysis (p = 0.042). On multivariate analysis, however, stage was determined as the only independent prognostic marker (p < 0.001).

CONCLUSIONS

Our data suggest that overexpression of HIF-1α, GLUT-1, and iNOS may play an important role in gastric cancer progression. GLUT-1 is a potential candidate for predicting patient survival.

Hypoxia enhances colon cancer migration and invasion through promotion of epithelial-mesenchymal transition

BACKGROUND

A hypoxic environment exists in most solid tumors because in rapidly growing tumors, the development of angiogenic vasculature is heterogenous, usually not enough to overcome the necessary oxygen supply. In an ischemic condition, cancer cells develop escape mechanisms to survive and leave the unfavorable environment. That result in the acquisition of increased potential for local invasion and evasion to distant organs. However, the escape mechanisms of cancer cells from hypoxic stress have not been fully characterized.

MATERIALS AND METHODS

The human colon cancer cell line LoVo was cultured in hypoxia, and the adhesive and migratory properties were analyzed. The expression of cell surface and cytoplasmic molecules was also investigated.

RESULTS

Under hypoxic conditions, cells developed epithelial-mesenchymal transition. The expression levels of α2, α5, and β1 integrins were significantly upregulated and, as a consequence, the ability to adhere to and migrate on collagen and fibronectin was increased. On the other hand, the expression of 67-kDa laminin receptor and the abilities to adhere to and migrate on laminin were decreased. Additionally, the expression of CXCR4 was significantly increased on cells cultured in hypoxia, and the chemotactic activity to stromal cell-derived factor 1α was remarkably increased.

CONCLUSIONS

Hypoxic stress induced active epithelial-mesenchymal transition in colon cancer cells, with the typical morphologic and functional changes. These morphologic and functional changes of β1 integrins, the 67-kDa laminin receptor, and CXCR4 may be essential for the acquisition of the invasive and metastatic features in colorectal cancer.

Deficiency of the complex I of the mitochondrial respiratory chain but improved adenylate control over succinate-dependent respiration are human gastric cancer-specific phenomena

The purpose of study was to comparatively characterize the oxidative phosphorylation (OXPHOS) and function of respiratory chain in mitochondria in human gastric corpus mucosa undergoing transition from normal to cancer states and in human gastric cancer cell lines, MKN28 and MKN45. The tissue samples taken by endobiopsy and the cells were permeabilized by saponin treatment to assess mitochondrial function in situ by high-resolution oxygraphy. Compared to the control group of endobiopsy samples, the maximal capacity of OXPHOS in the cancer group was almost twice lower. The respiratory chain complex I-dependent respiration, normalized to complex II-dependent respiration, was reduced that suggests deficiency of complex I, but the respiratory control by ADP in the presence of succinate was increased. Similar changes were observed also in mucosa adjacent to cancer tissue. The respiratory capacity of MKN45 cells was higher than that of MKN28 cells, but both types of cells exhibited a deficiency of complex I of the respiratory chain which appears to be an intrinsic property of the cancer cells. In conclusion, human gastric cancer is associated with decreased respiratory capacity, deficiency of the respiratory complex I of mitochondria, and improved coupling of succinate oxidation to phosphorylation in tumor tissue and adjacent atrophic mucosa. Detection of these changes in endobiopsy samples may be of diagnostic value.

Optical detection of preneoplastic lesions of the central airways

Current routine diagnosis of premalignant lesions of the central airways is hampered due to a limited sensitivity (white light bronchoscopy) and resolution (computer tomography (CT), positron emission tomography (PET)) of currently used techniques. To improve the detection of these subtle mucosal abnormalities, novel optical imaging bronchoscopic techniques have been developed over the past decade. In this review we highlight the technological developments in the field of endoscopic imaging, and describe their advantages and disadvantages in clinical use.

Clinicopathological significance of hypoxia-inducible factor-1 alpha (HIF-1α) expression in gastric cancer

BACKGROUND

Hypoxia is a common feature of rapidly growing solid tumors. Therefore, cellular adaptation to hypoxia and altered glucose metabolism are fundamental to the biology of cancer cells. Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor for more than 60 genes recognized to control the delivery of oxygen and nutrients through the induction of angiogenesis and glycolysis under hypoxic conditions. Therefore, inhibition of the expression of HIF-1α can be expected to be potentially tumor-specific molecular target-based therapy. In this study, we evaluated the significance of HIF-1α expression in relationship to clinicopathological factors, prognosis, vascular endothelial growth factor (VEGF) expression, and microvessel density (MVD).

METHODS

Paraffin-embedded tumor specimens from 128 patients who underwent gastrectomy at Kurume University from 2004 to 2005 were used to assess the clinical significance of HIF-1α expression. We used the ABC method to perform an immunohistochemical analysis of the HIF-1α and VEGF expression.

RESULTS

Eighty-four (65.6%) of gastric cancer specimens were positive for HIF-1α expression. Multivariate analysis showed that histology, depth of invasion, VEGF expression, and MVD were significantly associated with HIF-1α expression. On relapse-free and overall survival curves, the HIF-1α-negative group was significantly higher than the HIF-1α-positive group. Moreover, HIF-1α(+)/VEGF(+) patients had the worst prognosis. HIF-1α expression was identified as a significant predictor of relapse-free survival and overall survival by multivariate Cox's proportional hazard analyses.

CONCLUSION

Overexpression of HIF-1α was found to be an indicator of poor prognosis for patients with gastric cancer and was significantly correlated with histology, depth of invasion, VEGF, and MVD.