Transcriptional control of the tumor- and hypoxia-marker carbonic anhydrase 9: A one transcription factor (HIF-1) show?

Targeting CAIX with [64Cu]XYIMSR-06 Small Molecular Radiotracer Enables Noninvasive PET Imaging of Malignant Glioma in U87 MG Tumor Cell Xenograft Mice

Carbonic anhydrase IX (CAIX) plays an important role in glioma cell proliferation, invasion, metastasis, and resistance to radiotherapy and chemotherapy. An effective and noninvasive PET molecular imaging agent targeting CAIX would help its diagnosis and treatment but is not currently available. Recently, a low-molecular-weight (LMW) CAIX targeting agent, [⁶⁴Cu]XYIMSR-06, was reported to have significantly improved properties for targeting clear cell renal cell carcinoma (ccRCC). We are encouraged to investigate the feasibility of adapting this agent for the diagnosis and treatment of CAIX-overexpressing malignant glioma. In vitro cell uptake and binding affinity assays were used to verify the binding capacity of [⁶⁴Cu]XYIMSR-06 to U87 MG tumor cells in which CAIX overexpression was confirmed. The U87 MG tumor-bearing mouse (in situ and subcutaneous) model was built, and mice were injected with the radiotracer and/or coinjected with acetazolamide (0.2 g/kg) as a blocking agent for noninvasive micro-PET imaging. Micro-PET imaging was performed at 2, 4, and 8 h postinjection. ROI (region of interest)-based semiquantification was performed in an orthotopic glioma tumor model. Biodistribution throughout each organ was performed at 2, 4, 4 h block, 8, and 24 h postinjection. Hematoxylin and eosin (HE) staining and immunofluorescence or immunohistochemistry (IF/IHC) staining were implemented postimaging to assess the expression of CAIX in tumor organs. In vitro, [⁶⁴Cu]XYIMSR-06 exhibits greater uptake in glioma cells (high CAIX expression) than in HCT116 cells (low CAIX expression). The binding affinity of [⁶⁴Cu]XYIMSR-06 to U87 MG cell lines reaches up to 4.22 nM. Both orthotopic and subcutaneous tumors were clearly visualized at 2-8 h postinjection. Biodistribution studies demonstrated a maximum tumor uptake of 3.13% ID/g at 4 h postinjection, and the tumor to brain ratio (T/brain) was 6.51 at 8 h postinjection. The ROI-based T/brain values were 7.03 and 5.46 at 2 and 8 h postinjection, respectively. Histopathological analysis confirmed the overexpression of CAIX in gliomas, and the area of CAIX-positive IF staining is extremely consistent with the morphology on micro-PET imaging. In this study, [⁶⁴Cu]XYIMSR-06 demonstrated specific accumulation in CAIX-expressing U87 MG glioma tumors, indicating that the radiotracer has the potential for noninvasively monitoring and guiding personalized treatment of malignant glioma and other tumors overexpressing CAIX.

3,17β-Bis-sulfamoyloxy-2-methoxyestra-1,3,5(10)-triene and Nonsteroidal Sulfamate Derivatives Inhibit Carbonic Anhydrase IX: Structure-Activity Optimization for Isoform Selectivity

3,17β-Bis-sulfamoyloxy-2-methoxyestra-1,3,5(10)-triene (STX140), a bis-sulfamate derivative of the endogenous steroid 2-methoxyestradiol, has shown promising anticancer potency both in vitro and in vivo, with excellent bioavailability. Its activity against taxane-resistant xenografts makes it a potential drug candidate against triple-negative breast cancer (TNBC). These properties are linked to the ability of STX140 to act in a multitargeting fashion in vivo as a microtubule disruptor, leading to cell cycle arrest and with both proapoptotic and anti-angiogenic activities. Carbonic anhydrase IX (CA IX) is a well-established biomarker for aggressive cancers, including TNBC. This study reports, for the first time, the inhibitory activities of a series of steroidal and nonsteroidal sulfamate derivatives against CA IX in comparison to the ubiquitous CA II, with some compounds demonstrating 100-200-fold selectivity for CA IX over CA II. X-ray crystallographic studies of four of the most promising compounds reveal that isoform-specific residue interactions are responsible for the high specificity.

Evaluation of Radiolabeled Girentuximab In Vitro and In Vivo

Girentuximab (cG250) targets carbonic anhydrase IX (CAIX), a protein which is expressed on the surface of most renal cancer cells (RCCs). cG250 labeled with 177Lu has been used in clinical trials for radioimmunotherapy (RIT) of RCCs. In this work, an extensive characterization of the immunoconjugates allowed optimization of the labeling conditions with 177Lu while maintaining immunoreactivity of cG250, which was then investigated in in vitro and in vivo experiments. cG250 was conjugated with S-2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (DOTA(SCN)) by using incubation times between 30 and 90 min and characterized by mass spectrometry. Immunoconjugates with five to ten DOTA(SCN) molecules per cG250 molecule were obtained. Conjugates with ratios less than six DOTA(SCN)/cG250 had higher in vitro antigen affinity, both pre- and postlabeling with 177Lu. Radiochemical stability increased, in the presence of sodium ascorbate, which prevents radiolysis. The immunoreactivity of the radiolabeled cG250 tested by specific binding to SK-RC-52 cells decreased when the DOTA content per conjugate increased. The in vivo tumor uptake was < 10% ID/g and independent of the total amount of protein in the range between 5 and 100 µg cG250 per animal. Low tumor uptake was found to be due to significant necrotic areas and heterogeneous CAIX expression. In addition, low vascularity indicated relatively poor accessibility of the CAIX target.

Hypoxia increases chemoresistance in human medulloblastoma DAOY cells via hypoxia‑inducible factor 1α‑mediated downregulation of the CYP2B6, CYP3A4 and CYP3A5 enzymes and inhibition of cell proliferation

Medulloblastomas are among the most frequently diagnosed pediatric solid tumors, and drug resistance remains as the principal cause of treatment failure. Hypoxia and the subsequent activation of hypoxia-inducible factor 1α (HIF-1α) are considered key factors in modulating drug antitumor effectiveness, but the underlying mechanisms in medulloblastomas have not yet been clearly understood. The aim of the present study was to determine whether hypoxia induces resistance to cyclophosphamide (CPA) and ifosfamide (IFA) in DAOY medulloblastoma cells, whether the mechanism is dependent on HIF-1α, and whether involves the modulation of the expression of cytochromes P450 (CYP)2B6, 3A4 and 3A5 and the control of cell proliferation. Monolayer cultures of DAOY medulloblastoma cells were exposed for 24 h to moderate (1% O₂) or severe (0.1% O₂) hypoxia, and protein expression was evaluated by immunoblotting. Cytotoxicity was studied with the MTT assay and by Annexin V/PI staining and flow cytometry. Cell proliferation was determined by the trypan-blue exclusion assay and cell cycle by propidium iodide staining and flow cytometry. Hypoxia decreased CPA and IFA cytotoxicity in medulloblastoma cells, which correlated with a reduction in the protein levels of CYP2B6, CYP3A4 and CYP3A5 and inhibition of cell proliferation. These responses were dependent on hypoxia-induced HIF-1α activation, as evidenced by chemical inhibition of its transcriptional activity with 2-methoxyestradiol (2-ME), which enhanced the cytotoxic activity of CPA and IFA and increased apoptosis. Our results indicate that by stimulating HIF-1α activity, hypoxia downregulates the expression of CYP2B6, CYP3A4 and CYP3A5, that in turn leads to decreased conversion of CPA and IFA into their active forms and thus to diminished cytotoxicity. These results support that the combination of HIF-1α inhibitors and canonical antineoplastic agents provides a potential therapeutic alternative against medulloblastoma.

Blocking HIF signaling via novel inhibitors of CA9 and APE1/Ref-1 dramatically affects pancreatic cancer cell survival

Pancreatic ductal adenocarcinoma (PDAC) has reactive stroma that promotes tumor signaling, fibrosis, inflammation, and hypoxia, which activates HIF-1α to increase tumor cell metastasis and therapeutic resistance. Carbonic anhydrase IX (CA9) stabilizes intracellular pH following induction by HIF-1α. Redox effector factor-1 (APE1/Ref-1) is a multifunctional protein with redox signaling activity that converts certain oxidized transcription factors to a reduced state, enabling them to upregulate tumor-promoting genes. Our studies evaluate PDAC hypoxia responses and APE1/Ref-1 redox signaling contributions to HIF-1α-mediated CA9 transcription. Our previous studies implicated this pathway in PDAC cell survival under hypoxia. We expand those studies, comparing drug responses using patient-derived PDAC cells displaying differential hypoxic responses in 3D spheroid tumor-stroma models to characterize second generation APE1/Ref-1 redox signaling and CA9 inhibitors. Our data demonstrates that HIF-1α-mediated CA9 induction differs between patient-derived PDAC cells and that APE1/Ref-1 redox inhibition attenuates this induction by decreasing hypoxia-induced HIF-1 DNA binding. Dual-targeting of APE1/Ref-1 and CA9 in 3D spheroids demonstrated that this combination effectively kills PDAC tumor cells displaying drastically different levels of CA9. New APE1/Ref-1 and CA9 inhibitors were significantly more potent alone and in combination, highlighting the potential of combination therapy targeting the APE1-Ref-1 signaling axis with significant clinical potential.

Circulating hypoxia marker carbonic anhydrase IX (CA9) in patients with hepatocellular carcinoma and patients with cirrhosis

BACKGROUND AND AIMS

Expression of carbonic anhydrase IX (CA9), an enzyme expressed in response to hypoxia, acidosis and oncogenic alterations, is reported to be a prognostic factor in HCC patients. Here we evaluated serum CA9 levels in HCC and cirrhosis patients.

METHODS

HCC and cirrhosis patients were prospectively recruited and CA9 levels were determined. CA9 levels were compared to stages of cirrhosis and HCC stages. The association of the CA9 levels and overall survival (OS) was assessed. Furthermore, immunohistochemical CA9 expression in HCC and cirrhosis was evaluated.

RESULTS

215 patients with HCC were included. The median serum CA9 concentration in patients with HCC was 370 pg/ml and significantly higher than in a healthy cohort. Patients with advanced cancer stages (BCLC and ALBI score) had hid significant higher levels of CA9 in the serum. HCC patients with high serum CA9 concentrations (>400 pg/ml) had an increased mortality risk (hazard ratio (HR) 1.690, 95% confidence interval (CI) 1.017-2.809, P = 0.043). Serum CA9 concentration in cirrhotic patients did not differ significantly from HCC patients. Higher CA9 levels in cirrhotic patients correlated with portal hypertension and esophageal varices. Patients with ethanol induced cirrhosis had the highest CA9 levels in both cohorts. Levels of CA9 did not correlate with immunohistochemical expression.

CONCLUSIONS

We conclude that a high CA9 level is a possible prognostic indicator for a poor outcome in HCC patients. The high CA9 levels are probably mainly associated with portal hypertension. Ductular reactions might be a possible source of serum CA9.

Hypoxia-targeted gold nanorods for cancer photothermal therapy

Tumor hypoxia is a well-recognized driver of resistance to traditional cancer therapies such as chemotherapy and radiation therapy. We describe development of a new nanoconstruct composed of gold nanorods (GNRs) conjugated to carbonic anhydrase IX (CAIX) antibody that specifically binds to CAIX, a biomarker of hypoxia, to facilitate targeting tumor hypoxic areas for focused photothermal ablation. Physicochemical characterization studies confirmed the size, shape, monodispersity, surface charge, and serum stability of the GNRs. Enzyme-linked immunosorbent assays and cellular binding and uptake studies confirmed successful conjugation of antibody to the GNRs and specificity for CAIX. Near-infrared irradiation of CAIX-overexpressing cells treated with GNR/anti-CAIX resulted in significantly higher cell death than cells treated with control GNRs. In vivo biodistribution studies using hyperspectral imaging and inductively coupled plasma mass spectrometry confirmed intravenous administration results not only in greater accumulation of GNR/anti-CAIX in tumors than control GNRs but also greater penetration into hypoxic areas of tumors. Near-infrared ablation of these tumors showed no tumor regression in the sham-treated group, regression but recurrence in the non-targeted-GNR group, and complete tumor regression in the targeted-GNR group. GNR/anti-CAIX nanoconstructs show promise as hypoxia targeting and photothermal ablation agents for cancer treatment.

Carbonic anhydrase IX is a critical determinant of pulmonary microvascular endothelial cell pH regulation and angiogenesis during acidosis

Carbonic anhydrase IX (CA IX) is highly expressed in rapidly proliferating and highly glycolytic cells, where it serves to enhance acid-regulatory capacity. Pulmonary microvascular endothelial cells (PMVECs) actively utilize aerobic glycolysis and acidify media, whereas pulmonary arterial endothelial cells (PAECs) primarily rely on oxidative phosphorylation and minimally change media pH. Therefore, we hypothesized that CA IX is critical to PMVEC angiogenesis because of its important role in regulating pH. To test this hypothesis, PMVECs and PAECs were isolated from Sprague-Dawley rats. CA IX knockout PMVECs were generated using the CRISPR-Cas9 technique. During serum-stimulated growth, mild acidosis (pH 6.8) did not affect cell counts of PMVECs, but it decreased PAEC cell number. Severe acidosis (pH 6.2) decreased cell counts of PMVECs and elicited an even more pronounced reduction of PAECs. PMVECs had a higher CA IX expression compared with PAECs. CA activity was higher in PMVECs compared with PAECs, and enzyme activity was dependent on the type IX isoform. Pharmacological inhibition and genetic ablation of CA IX caused profound dysregulation of extra- and intracellular pH in PMVECs. Matrigel assays revealed impaired angiogenesis of CA IX knockout PMVECs in acidosis. Lastly, pharmacological CA IX inhibition caused profound cell death in PMVECs, whereas genetic CA IX ablation had little effect on PMVEC cell death in acidosis. Thus CA IX controls PMVEC pH necessary for angiogenesis during acidosis. CA IX may contribute to lung vascular repair during acute lung injury that is accompanied by acidosis within the microenvironment.

Expression of HIF-1α in medullary thyroid cancer identifies a subgroup with poor prognosis

Background

Medullary thyroid cancer (MTC) comprises only 4% of all thyroid cancers and originates from the parafollicular C-cells. HIF-1α expression has been implied as an indicator of worse prognosis in various solid tumors. However, whether expression of HIF-1α is a prognosticator in MTC remained unclear. Our aim was to evaluate the prognostic value of HIF-1α in patients with MTC.

Methods

All patients with MTC who were operated on between 1988 and 2014 in five tertiary referral centers in The Netherlands were included. A tissue microarray was constructed in which 111 primary tumors could be analyzed for expression of HIF-1α, CAIX, Glut-1, VEGF and CD31 and correlated with clinicopathologic variables and survival.

Results

The mean age of patients was 46.3 years (SD 15.6), 59 (53.2%) were male. Of the 111 primary tumors, 49 (44.1%) were HIF-1α negative and 62 (55.9%) were HIF-1α positive. Positive HIF-1α expression was an independent negative indicator for progression free survival (PFS) in multivariate cox regression analysis (HR 3.1; 95% CI 1.3 – 7.3). Five-years survival decreased from 94.0% to 65.9% for the HIF-1α positive group (p=0.007). Even within the group of patients with TNM-stage IV disease, HIF-1α positivity was associated with a worse prognosis, shown by a decrease in 5-years survival of 88.0% to 49.3% (p=0.020).

Conclusion

Expression of HIF-1α is strongly correlated with adverse prognosis of MTC. This could open up new ways for targeted systemic therapy of MTC.

Correlation of High-Risk Soft Tissue Sarcoma Biomarker Expression Patterns with Outcome following Neoadjuvant Chemoradiation

BACKGROUND

Sarcoma mortality remains high despite adjuvant chemotherapy. Biomarker predictors of treatment response and outcome could improve treatment selection.

METHODS

Tissue microarrays (TMAs) were created using pre- and posttreatment tumor from two prospective trials (MGH pilot and RTOG 9514) of neoadjuvant/adjuvant MAID chemotherapy and preoperative radiation. Biomarkers were measured using automated computerized imaging (AQUA or ACIS). Expression was correlated with disease-free survival (DFS), distant disease-free survival (DDFS), and overall survival (OS).

RESULTS

Specimens from 60 patients included 23 pretreatment (PRE), 40 posttreatment (POST), and 12 matched pairs (MPs). In the MP set, CAIX, GLUT1, and PARP1 expression significantly decreased following neoadjuvant therapy, but p53 nuclear/cytoplasmic (N/C) ratio increased. In the PRE set, no biomarker expression was associated with DFS, DDFS, or OS. In the POST set, increased p53 N/C ratio was associated with a significantly decreased DFS and DDFS (HR 4.13, p=0.017; HR 4.16, p=0.016), while increased ERCC1 and XPF expression were associated with an improved DFS and DDFS. No POST biomarkers were associated with OS.

CONCLUSIONS

PRE biomarker expression did not predict survival outcomes. Expression pattern changes after neoadjuvant chemoradiation supports the concepts of tumor reoxygenation, altered HIF-1α signaling, and a p53 nuclear accumulation DNA damage response.

CLINICAL TRIAL REGISTRATION

NRG Oncology RTOG 9514 is registered with ClinicalTrials.gov. The ClinicalTrials.gov Identifier is NCT00002791.

The two glycolytic markers GLUT1 and MCT1 correlate with tumor grade and survival in clear-cell renal cell carcinoma

Background

Clear-cell renal cell carcinoma (ccRCC) is the most common type of kidney cancer. Although ccRCC is characterized by common recurrent genetic abnormalities, including inactivation of the von Hippel-Lindau (vhl) tumor suppressor gene resulting in stabilization of hypoxia-inducible factors (HIFs), the tumor aggressiveness and outcome of ccRCC is variable. New biomarkers are thus required to improve ccRCC diagnosis, prognosis and therapeutic options. This work aims to investigate the expression of HIF and proteins involved in metabolism and pH regulation. Their correlation to histoprognostic parameters and survival was analyzed.

Methods

ccRCC of 45 patients were analyzed. HIF-1α, HIF-2α, HAF, GLUT1, MCT1, MCT4, CAIX and CAXII expression was assessed by immunohistochemistry in a semi-quantitative and qualitative manner. The GLUT1, MCT1, MCT4, CAIX and CAXII mRNA levels were analyzed in an independent cohort of 43 patients.

Results

A significant correlation was observed between increased GLUT1, MCT1, CAXII protein expression and a high Fuhrman grade in ccRCC patients. Moreover, while HIF-1α, HIF-2α and HAF expression was heterogenous within tumors, we observed and confirmed that HIF-2α co-localized with HAF.

We confirmed, in an independent cohort, that GLUT1, MCT1 and CAXII mRNA levels correlated with the Fuhrman grade. Moreover, we demonstrated that the high mRNA level of both MCT1 and GLUT1 correlated with poor prognosis.

Conclusions

This study demonstrates for the first time a link between the aggressiveness of high- Fuhrman grade ccRCC and metabolic reprogramming. It also confirms the role of HIF-2α and HAF in tumor invasiveness. Finally, these results demonstrate that MCT1 and GLUT1 are strong prognostic markers and promising therapeutic targets.

Bicarbonate Recycling by HIF-1-Dependent Carbonic Anhydrase Isoforms 9 and 12 Is Critical in Maintaining Intracellular pH and Viability of Nucleus Pulposus Cells

Intervertebral disc degeneration is a ubiquitous condition closely linked to chronic low-back pain. The health of the avascular nucleus pulposus (NP) plays a crucial role in the development of this pathology. We tested the hypothesis that a network comprising HIF-1α, carbonic anhydrase (CA) 9 and 12 isoforms, and sodium-coupled bicarbonate cotransporters (NBCs) buffer intracellular pH through coordinated bicarbonate recycling. Contrary to the current understanding of NP cell metabolism, analysis of metabolic-flux data from Seahorse XF analyzer showed that CO2 hydration contributes a significant source of extracellular proton production in NP cells, with a smaller input from glycolysis. Because enzymatic hydration of CO2 is catalyzed by plasma membrane-associated CAs we measured their expression and function in NP tissue. NP cells robustly expressed isoforms CA9/12, which were hypoxia-inducible. In addition to increased mRNA stability under hypoxia, we observed binding of HIF-1α to select hypoxia-responsive elements on CA9/12 promoters using genomic chromatin immunoprecipitation. Importantly, in vitro loss of function studies and analysis of discs from NP-specific HIF-1α null mice confirmed the dependency of CA9/12 expression on HIF-1α. As expected, inhibition of CA activity decreased extracellular acidification rate independent of changes in HIF activity or lactate/H+ efflux. Surprisingly, CA inhibition resulted in a concomitant decrease in intracellular pH that was mirrored by inhibition of sodium-bicarbonate importers. These results suggested that extracellular bicarbonate generated by CA9/12 is recycled to buffer cytosolic pH fluctuations. Importantly, long-term intracellular acidification from CA inhibition lead to compromised cell viability, suggesting that plasma-membrane proton extrusion pathways alone are not sufficient to maintain homeostatic pH in NP cells. Taken together, our studies show for the first time that bicarbonate buffering through the HIF-1α-CA axis is critical for NP cell survival in the hypoxic niche of the intervertebral disc. © 2017 American Society for Bone and Mineral Research.

Hypoxia and hypoxia inducible factor-1α are required for normal endometrial repair during menstruation

Heavy menstrual bleeding (HMB) is common and debilitating, and often requires surgery due to hormonal side effects from medical therapies. Here we show that transient, physiological hypoxia occurs in the menstrual endometrium to stabilise hypoxia inducible factor 1 (HIF-1) and drive repair of the denuded surface. We report that women with HMB have decreased endometrial HIF-1α during menstruation and prolonged menstrual bleeding. In a mouse model of simulated menses, physiological endometrial hypoxia occurs during bleeding. Maintenance of mice under hyperoxia during menses decreases HIF-1α induction and delays endometrial repair. The same effects are observed upon genetic or pharmacological reduction of endometrial HIF-1α. Conversely, artificial induction of hypoxia by pharmacological stabilisation of HIF-1α rescues the delayed endometrial repair in hypoxia-deficient mice. These data reveal a role for HIF-1 in the endometrium and suggest its pharmacological stabilisation during menses offers an effective, non-hormonal treatment for women with HMB.

Intermittent, low dose carbon monoxide exposure enhances survival and dopaminergic differentiation of human neural stem cells

Exploratory studies using human fetal tissue have suggested that intrastriatal transplantation of dopaminergic neurons may become a future treatment for patients with Parkinson's disease. However, the use of human fetal tissue is compromised by ethical, regulatory and practical concerns. Human stem cells constitute an alternative source of cells for transplantation in Parkinson's disease, but efficient protocols for controlled dopaminergic differentiation need to be developed. Short-term, low-level carbon monoxide (CO) exposure has been shown to affect signaling in several tissues, resulting in both protection and generation of reactive oxygen species. The present study investigated the effect of CO produced by a novel CO-releasing molecule on dopaminergic differentiation of human neural stem cells. Short-term exposure to 25 ppm CO at days 0 and 4 significantly increased the relative content of β-tubulin III-immunoreactive immature neurons and tyrosine hydroxylase expressing catecholaminergic neurons, as assessed 6 days after differentiation. Also the number of microtubule associated protein 2-positive mature neurons had increased significantly. Moreover, the content of apoptotic cells (Caspase3) was reduced, whereas the expression of a cell proliferation marker (Ki67) was left unchanged. Increased expression of hypoxia inducible factor-1α and production of reactive oxygen species (ROS) in cultures exposed to CO may suggest a mechanism involving mitochondrial alterations and generation of ROS. In conclusion, the present procedure using controlled, short-term CO exposure allows efficient dopaminergic differentiation of human neural stem cells at low cost and may as such be useful for derivation of cells for experimental studies and future development of donor cells for transplantation in Parkinson's disease.

The ERβ4 variant induces transformation of the normal breast mammary epithelial cell line MCF-10A; the ERβ variants ERβ2 and ERβ5 increase aggressiveness of TNBC by regulation of hypoxic signaling

Triple negative breast cancer (TNBC) still remains a challenge to treat in the clinic due to a lack of good targets for treatment. Although TNBC lacks expression of ERα, the expression of ERβ and its variants are detected quite frequently in this cancer type and can represent an avenue for treatment. We show that two of the variants of ERβ, namely ERβ2 and ERβ5, control aggressiveness of TNBC by regulating hypoxic signaling through stabilization of HIF-1α. RNA-seq of patient derived xenografts (PDX) from TNBC shows expression of ERβ2, ERβ4 and ERβ5 variants in more than half of the samples. Furthermore, expression of ERβ4 in the immortalized, normal mammary epithelial cell line MCF-10A that is resistant to tumorsphere formation caused transformation and development of tumorspheres. By contrast, ERβ1, ERβ2 or ERβ5 were unable to support tumorsphere formation. We have previously shown that all variants except ERβ1 stabilize HIF-1α but only ERβ4 appears to have the ability to transform normal mammary epithelial cells, pointing towards a unique property of ERβ4. We propose that ERβ variants may be good diagnostic tools and also serve as novel targets for treatment of breast cancer.

[Is Oxygen Deficiency Always Harmful?]

Is Oxygen Deficiency Always Harmful? Abstract. The role of the cardiovascular circulation is to supply tissue with oxygen and nutrients. Oxygen deficiency (hypoxia) is considered life-threatening, since cells die, either through apoptotic or necrotic processes. Tissue tries to counteract this by means of evolutionary signalling pathways, such as the nuclear hypoxia-inducible factor, which protects the tissue by promoting cell survival strategies and simultaneously intervening in angiogenesis, haematogenesis and metabolic processes. Recent findings indicate that these conserved signalling pathways can also function as therapeutic approaches in wound healing of bones and skin, as well as in the regeneration of tissues, e.g. in the liver, and in the hematopoietic system.

Addition of carbonic anhydrase 9 inhibitor SLC-0111 to temozolomide treatment delays glioblastoma growth in vivo

Tumor microenvironments can promote stem cell maintenance, tumor growth, and therapeutic resistance, findings linked by the tumor-initiating cell hypothesis. Standard of care for glioblastoma (GBM) includes temozolomide chemotherapy, which is not curative, due, in part, to residual therapy-resistant brain tumor-initiating cells (BTICs). Temozolomide efficacy may be increased by targeting carbonic anhydrase 9 (CA9), a hypoxia-responsive gene important for maintaining the altered pH gradient of tumor cells. Using patient-derived GBM xenograft cells, we explored whether CA9 and CA12 inhibitor SLC-0111 could decrease GBM growth in combination with temozolomide or influence percentages of BTICs after chemotherapy. In multiple GBMs, SLC-0111 used concurrently with temozolomide reduced cell growth and induced cell cycle arrest via DNA damage in vitro. In addition, this treatment shifted tumor metabolism to a suppressed bioenergetic state in vivo. SLC-0111 also inhibited the enrichment of BTICs after temozolomide treatment determined via CD133 expression and neurosphere formation capacity. GBM xenografts treated with SLC-0111 in combination with temozolomide regressed significantly, and this effect was greater than that of temozolomide or SLC-0111 alone. We determined that SLC-0111 improves the efficacy of temozolomide to extend survival of GBM-bearing mice and should be explored as a treatment strategy in combination with current standard of care.

Impact of tumoral carbonic anhydrase IX and Ki-67 expression on survival in oral squamous cell carcinoma patients

Oral squamous cell carcinoma (OSCC) is the most commonly diagnosed type of head and neck cancer, accounting for ~300,000 new cases worldwide annually. Carbonic anhydrase IX (CAIX) and Ki-67 have been associated with reduced disease-specific survival (DSS) in patients with OSCC. We previously proposed a combined CAIX and Ki-67 signature of 'functional hypoxia' and sought to replicate this association in a larger independent cohort of patients with OSCC at the Fred Hutchinson Cancer Research Center (FHCRC) in Seattle. The study population included patients with incident primary OSCC treated at the University of Washington Medical Center and the Harborview Medical Center in Seattle between December 2003 and February 2012. Archived tumor blocks were obtained with tissue samples from 189 patients, and triplicate 0.6 mm cores were assembled into tissue microarrays (TMAs). Fluorescence immunohistochemistry and AQUAnalysis® were used to quantify the expression of tumoral CAIX (tCAIX) and stromal CAIX (sCAIX) and tumoral Ki-67 for each TMA core. Hazard ratios for DSS were calculated using Cox proportional hazards analysis. High tCAIX and sCAIX expression levels were associated with reduced DSS (aHR=1.003, 95% CI:1.00-1.01 and aHR=1.010, 95% CI:1.001-1.019, per AQUA score unit, respectively). Ki-67 expression was not associated with survival (aHR=1.01, 95% CI:0.99-1.02) in the FHCRC cohort. DSS for patients with high sCAIX and low Ki-67 did not differ from that of other patient groups. Elevated tCAIX was associated with reduced DSS as a continuous and as a dichotomized (75%) variable. sCAIX was associated with DSS as a continuous variable but not when dichotomized (75%). However, the previously proposed 'functional hypoxia' signature was not replicated in the current FHCRC study. The failure to replicate our prior observation of poorer survival in patients with combined high sCAIX and low tumoral Ki-67 was likely due to the absence of an association between tumoral Ki-67 and DSS in this cohort. However, the association between DSS and tCAIX and sCAIX supports a role for CAIX in OSCC clinical outcomes.

Increased expression of stemness markers and altered tumor stroma in hepatocellular carcinoma under TACE-induced hypoxia: A biopsy and resection matched study

Background

Hepatocellular carcinomas (HCCs) expressing stemness markers are characterized by an aggressive behavior, which might be promoted by an altered tumor stroma. Transarterial chemoembolization (TACE) induces severe hypoxia, and its effect on stemness and tumor stroma of HCCs remains unclear. The purpose of this study was to evaluate the sequential changes of stemness and tumor stroma under TACE-induced hypoxia using biopsy and resection-matched HCCs.

Methods

Forty-six biopsy and resection matched HCCs including 10 cases with and 36 cases without preoperative TACE were selected. Immunohistochemistry for stemness (keratin 19 [K19], epithelial cell adhesion molecule [EpCAM], and CD133), hypoxia (carbonic anhydrase IX [CAIX] and vascular endothelial growth factor [VEGF]), and tumor stromal (α-smooth muscle actin [α-SMA] and fibroblast activation protein [FAP]) markers were performed and compared in matched biopsied and resected HCCs with and without TACE.

Results

The accuracy of K19, EpCAM, CD133, CAIX, VEGF, α-SMA and FAP detected on biopsied HCCs was 64% ∼ 86%, using the expression status in resected HCCs as a reference standard in non-TACE group. The sequential change of hypoxia, stemness and stromal marker expression in matched biopsied and resected HCC was greater in TACE group than in non-TACE group (P < 0.05 for all). The degree of stemness marker expression was well correlated with those of tumor stromal markers, and the degree of CAIX expression was well correlated with that of K19 (P < 0.05).

Conclusions

Stemness marker expression is considered to be increased along with tumor stromal alteration under TACE-induced hypoxia, which might promote the aggressive biology of HCC.

Preferential activation of HIF-2α adaptive signalling in neuronal-like cells in response to acute hypoxia

Stroke causes severe neuronal damage as disrupted cerebral blood flow starves neurons of oxygen and glucose. The hypoxia inducible factors (HIF-1α and HIF-2α) orchestrate oxygen homeostasis and regulate specific aspects of hypoxic adaptation. Here we show the importance of HIF-2α dependant signalling in neuronal adaptation to hypoxic insult. PC12 and NT2 cells were differentiated into neuronal-like cells using NGF and retinoic acid, and exposed to acute hypoxia (1% O₂). Gene and protein expression was analysed by qPCR and immunoblotting and the neuronal-like phenotype was examined. PC12 and NT2 differentiation promoted neurite extension and expression of neuronal markers, NSE and KCC2. Induction of HIF-1α mRNA or protein was not detected in hypoxic neuronal-like cells, however marked induction of HIF-2α mRNA and protein expression was observed. Induction of HIF-1α target genes was also not detected in response to acute hypoxia, however significant induction of HIF-2α transcriptional targets was clearly evident. Furthermore, hypoxic insult dramatically reduced both neurite number and length, and attenuated expression of neuronal markers, NSE and KCC2. This correlated with an increase in expression of the neural progenitor and stem cell-like markers, CD44 and vimentin, suggesting HIF-2α molecular mechanisms could potentially promote regression of neuronal-like cells to a stem-like state and trigger neuronal recovery following ischaemic insult. Our findings suggest the HIF-2α pathway predominates over HIF-1α signalling in neuronal-like cells following acute hypoxia.

Cancer metabolism: New insights into classic characteristics

Initial studies of cancer metabolism in the early 1920s found that cancer cells were phenotypically characterized by aerobic glycolysis, in that these cells favor glucose uptake and lactate production, even in the presence of oxygen. This property, called the Warburg effect, is considered a hallmark of cancer. The mechanism by which these cells acquire aerobic glycolysis has been uncovered. Acidic extracellular fluid, secreted by cancer cells, induces a malignant phenotype, including invasion and metastasis. Cancer cells survival depends on a critical balance of redox status, which is regulated by amino acid metabolism. Glutamine is extremely important for oxidative phosphorylation and redox regulation. Cells highly dependent on glutamine and that cannot survive with glutamine are called glutamine-addicted cells. Metabolic reprogramming has been observed in cancer stem cells, which have the property of self-renewal and are resistant to chemotherapy and radiotherapy. These findings suggest that studies of cancer metabolism can reveal methods of preventing cancer recurrence and metastasis.

Depletion of carbonic anhydrase IX abrogates hypoxia-induced overexpression of stanniocalcin-1 in triple negative breast cancer cells

Carbonic anhydrase IX (CAIX) is a pH-regulating enzyme that plays a key role in maintaining an alkaline intracellular pH under hypoxic conditions. It is overexpressed in a variety of solid cancers, including breast cancer (BC), and has been implicated in the migration, invasion and stemness of breast cancer cells. Therefore, CAIX recently emerged as a novel therapeutic target for the treatment of BC. To gain an insight into the mechanism of action of CAIX inhibitors, we investigated the impact of CAIX knock-down on the transcriptional response to hypoxia in 2 BC cell lines - MCF7 and MDA-MB-231, by performing a global gene expression analysis. This showed that CAIX knock-down had a relatively minor effect on the global transcriptional response to hypoxia, however it blocked hypoxia-induced upregulation of stanniocalcin-1 (STC1), a secreted glycoprotein that has been shown to promote tumor progression and metastasis in BC. Kaplan-Meier survival analysis showed that high STC1 expression is significantly associated with poor survival in patients with basal-type breast cancer but not luminal A and HER2+ subtypes. Moreover, the association was particularly high in a subgroup of basal-type BC patients with TP53 mutations thus revealing a putative cooperation of STC1 with mutated TP53 in generating highly aggressive BC subgroup. Taken together, these findings show that CAIX inhibitors at least partially act through blocking STC1 induction in BC cells and reveal a subgroup of BC patients, who potentially would benefit most from the treatment with CAIX inhibitors.

Exploiting the Ref-1-APE1 node in cancer signaling and other diseases: from bench to clinic

Reduction-oxidation factor 1-apurinic/apyrimidinic endonuclease (Ref-1/APE1) is a critical node in tumor cells, both as a redox regulator of transcription factor activation and as part of the DNA damage response. As a redox signaling protein, Ref-1/APE1 enhances the transcriptional activity of STAT3, HIF-1α, nuclear factor kappa B, and other transcription factors to promote growth, migration, and survival in tumor cells as well as inflammation and angiogenesis in the tumor microenvironment. Ref-1/APE1 is activated in a variety of cancers, including prostate, colon, pancreatic, ovarian, lung and leukemias, leading to increased aggressiveness. Transcription factors downstream of Ref-1/APE1 are key contributors to many cancers, and Ref-1/APE1 redox signaling inhibition slows growth and progression in a number of tumor types. Ref-1/APE1 inhibition is also highly effective when paired with other drugs, including standard-of-care therapies and therapies targeting pathways affected by Ref-1/APE1 redox signaling. Additionally, Ref-1/APE1 plays a role in a variety of other indications, such as retinopathy, inflammation, and neuropathy. In this review, we discuss the functional consequences of activation of the Ref-1/APE1 node in cancer and other diseases, as well as potential therapies targeting Ref-1/APE1 and related pathways in relevant diseases. APX3330, a novel oral anticancer agent and the first drug to target Ref-1/APE1 for cancer is entering clinical trials and will be explored in various cancers and other diseases bringing bench discoveries to the clinic.

Overcoming the Limits of Hypoxia in Photodynamic Therapy: A Carbonic Anhydrase IX-Targeted Approach

A major challenge in photodynamic cancer therapy (PDT) is avoiding PDT-induced hypoxia, which can lead to cancer recurrence and progression through activation of various angiogenic factors and significantly reduce treatment outcomes. Reported here is an acetazolamide (AZ)-conjugated BODIPY photosensitizer (AZ-BPS) designed to mitigate the effects of PDT-based hypoxia by combining the benefits of anti-angiogenesis therapy with PDT. AZ-BPS showed specific affinity to aggressive cancer cells (MDA-MB-231 cells) that overexpress carbonic anhydrase IX (CAIX). It displayed enhanced photocytotoxicity compared to a reference compound, BPS, which is an analogous PDT agent that lacks an acetazolamide unit. AZ-BPS also displayed an enhanced in vivo efficacy in a xenograft mouse tumor regrowth model relative to BPS, an effect attributed to inhibition of tumor angiogenesis by both PDT-induced ROS generation and CAIX knockdown. AZ-BPS was evaluated successfully in clinical samples collected from breast cancer patients. We thus believe that the combined approach described here represents an attractive therapeutic approach to targeting CAIX-overexpressing tumors.

Regulation of HIF1α under Hypoxia by APE1/Ref-1 Impacts CA9 Expression: Dual Targeting in Patient-Derived 3D Pancreatic Cancer Models

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related mortality in the United States. Aggressive treatment regimens have not changed the disease course, and the median survival has just recently reached a year. Several mechanisms are proposed to play a role in PDAC therapeutic resistance, including hypoxia, which creates a more aggressive phenotype with increased metastatic potential and impaired therapeutic efficacy. AP Endonuclease-1/Redox Effector Factor 1 (APE1/Ref-1) is a multifunctional protein possessing a DNA repair function in base excision repair and the ability to reduce oxidized transcription factors, enabling them to bind to their DNA target sequences. APE1/Ref-1 regulates several transcription factors involved in survival mechanisms, tumor growth, and hypoxia signaling. Here, we explore the mechanisms underlying PDAC cell responses to hypoxia and modulation of APE1/Ref-1 redox signaling activity, which regulates the transcriptional activation of hypoxia-inducible factor 1 alpha (HIF1α). Carbonic anhydrase IX (CA9) is regulated by HIF1α and functions as a part of the cellular response to hypoxia to regulate intracellular pH, thereby promoting cell survival. We hypothesized that modulating APE1/Ref-1 function will block activation of downstream transcription factors, STAT3 and HIF1α, interfering with the hypoxia-induced gene expression. We demonstrate APE1/Ref-1 inhibition in patient-derived and established PDAC cells results in decreased HIF1α-mediated induction of CA9. Furthermore, an ex vivo three-dimensional tumor coculture model demonstrates dramatic enhancement of APE1/Ref-1-induced cell killing upon dual targeting of APE1/Ref-1 and CA9. Both APE1/Ref-1 and CA9 are under clinical development; therefore, these studies have the potential to direct novel PDAC therapeutic treatment. Mol Cancer Ther; 15(11); 2722-32. ©2016 AACR.

Optical imaging probes in oncology

Cancer is a complex disease, characterized by alteration of different physiological molecular processes and cellular features. Keeping this in mind, the possibility of early identification and detection of specific tumor biomarkers by non-invasive approaches could improve early diagnosis and patient management.Different molecular imaging procedures provide powerful tools for detection and non-invasive characterization of oncological lesions. Clinical studies are mainly based on the use of computed tomography, nuclear-based imaging techniques and magnetic resonance imaging. Preclinical imaging in small animal models entails the use of dedicated instruments, and beyond the already cited imaging techniques, it includes also optical imaging studies. Optical imaging strategies are based on the use of luminescent or fluorescent reporter genes or injectable fluorescent or luminescent probes that provide the possibility to study tumor features even by means of fluorescence and luminescence imaging. Currently, most of these probes are used only in animal models, but the possibility of applying some of them also in the clinics is under evaluation.The importance of tumor imaging, the ease of use of optical imaging instruments, the commercial availability of a wide range of probes as well as the continuous description of newly developed probes, demonstrate the significance of these applications. The aim of this review is providing a complete description of the possible optical imaging procedures available for the non-invasive assessment of tumor features in oncological murine models. In particular, the characteristics of both commercially available and newly developed probes will be outlined and discussed.

CRLX101 nanoparticles localize in human tumors and not in adjacent, nonneoplastic tissue after intravenous dosing

Nanoparticle-based therapeutics are being used to treat patients with solid tumors. Whereas nanoparticles have been shown to preferentially accumulate in solid tumors of animal models, there is little evidence to prove that intact nanoparticles localize to solid tumors of humans when systemically administered. Here, tumor and adjacent, nonneoplastic tissue biopsies are obtained through endoscopic capture from patients with gastric, gastroesophageal, or esophageal cancer who are administered the nanoparticle CRLX101. Both the pre- and postdosing tissue samples adjacent to tumors show no definitive evidence of either the nanoparticle or its drug payload (camptothecin, CPT) contained within the nanoparticle. Similar results are obtained from the predosing tumor samples. However, in nine of nine patients that were evaluated, CPT is detected in the tumor tissue collected 24-48 h after CRLX101 administration. For five of these patients, evidence of the intact deposition of CRLX101 nanoparticles in the tumor tissue is obtained. Indications of CPT pharmacodynamics from tumor biomarkers such as carbonic anhydrase IX and topoisomerase I by immunohistochemistry show clear evidence of biological activity from the delivered CPT in the posttreatment tumors.

MRI with hyperpolarised [1-13C]pyruvate detects advanced pancreatic preneoplasia prior to invasive disease in a mouse model

OBJECTIVES

Pancreatic cancer (PCa) is treatable by surgery when detected at an early stage. Non-invasive imaging methods able to detect both established tumours and their precursor lesions are needed to select patients for surgery. We investigated here whether pancreatic preneoplasia could be detected prior to the development of invasive cancers in genetically engineered mouse models of PCa using metabolic imaging.

DESIGN

The concentrations of alanine and lactate and the activities of lactate dehydrogenase (LDH) and alanine aminotransferase (ALT) were measured in extracts prepared from the pancreas of animals at different stages of disease progression; from pancreatitis, through tissue with predominantly low-grade and then high-grade pancreatic intraepithelial neoplasia and then tumour. (13)C magnetic resonance spectroscopic imaging ((13)C-MRSI) was used to measure non-invasively changes in (13)C labelling of alanine and lactate with disease progression, following injection of hyperpolarised [1-(13)C]pyruvate.

RESULTS

Progressive decreases in the alanine/lactate concentration ratio and ALT/LDH activity ratio with disease progression were accompanied by a corresponding decrease in the [1-(13)C]alanine/[1-(13)C]lactate signal ratio observed in (13)C-MRSI images of the pancreas.

CONCLUSIONS

Metabolic imaging with hyperpolarised [1-(13)C]pyruvate enables detection and monitoring of the progression of PCa precursor lesions. Translation of this MRI technique to the clinic has the potential to improve the management of patients at high risk of developing PCa.

Circulating Carbonic Anhydrase IX and Antiangiogenic Therapy in Breast Cancer

INTRODUCTION

Carbonic anhydrase IX (CAIX) is a hypoxia regulated metalloenzyme integral to maintaining cellular pH. Increased CAIX expression is associated with poor prognosis in breast cancer. To explore CAIX as a biomarker for breast cancer therapies, we measured plasma CAIX levels in healthy control subjects and in breast cancer patients.

METHODS

In control subjects we evaluated plasma CAIX stability via commercially available ELISA. We then similarly quantified plasma CAIX levels in (1) locally advanced breast cancer (LABC) patients treated with neoadjuvant paclitaxel + sunitinib (T + S) followed by doxorubicin and cyclophosphamide (AC); (2) metastatic breast cancer (MBC) patients treated with systemic chemotherapy.

RESULTS

Plasma CAIX levels were stable at room temperature for at least 48 hours in control subjects. Mean baseline plasma CAIX levels were lower in controls compared to patients with LABC or MBC. In LABC, CAIX levels rose significantly in response to administration of antiangiogenic therapy (T + S) (p = 0.02) but not AC (p = 0.37). In patients with MBC treated without an antiangiogenic agent CAIX levels did not change with therapy.

CONCLUSIONS

Our results suggest that CAIX may be an easily obtained, stable measure of tumor associated hypoxia as well as a useful pharmacodynamic biomarker for antiangiogenic therapy.

Histological Characterization of the Tumorigenic "Peri-Necrotic Niche" Harboring Quiescent Stem-Like Tumor Cells in Glioblastoma

BACKGROUND

Characterization of the niches for stem-like tumor cells is important to understand and control the behavior of glioblastomas. Cell-cycle quiescence might be a common mechanism underlying the long-term maintenance of stem-cell function in normal and neoplastic stem cells, and our previous study demonstrated that quiescence induced by hypoxia-inducible factor (HIF)-1α is associated with a high long-term repopulation capacity of hematopoietic stem cells. Based on this, we examined human astrocytoma tissues for HIF-1α-regulated quiescent stem-like tumor cells as a candidate for long-term tumorigenic cells and characterized their niche histologically.

METHODS

Multi-color immunohistochemistry was used to visualize HIF-1α-expressing (HIF-1α+) quiescent stem-like tumor cells and their niche in astrocytoma (WHO grade II-IV) tissues. This niche was modeled using spheroids of cultured glioblastoma cells and its contribution to tumorigenicity was evaluated by sphere formation assay.

RESULTS

A small subpopulation of HIF-1α+ quiescent stem-like tumor cells was found in glioblastomas but not in lower-grade astrocytomas. These cells were concentrated in the zone between large ischemic necroses and blood vessels and were closer to the necrotic tissues than to the blood vessels, which suggested that a moderately hypoxic microenvironment is their niche. We successfully modeled this niche containing cells of HIF-1α+ quiescent stem-like phenotype by incubating glioblastoma cell spheroids under an appropriately hypoxic condition, and the emergence of HIF-1α+ quiescent stem-like cells was shown to be associated with an enhanced sphere-forming activity.

CONCLUSIONS

These data suggest that the "peri-necrotic niche" harboring HIF-1α+ quiescent stem-like cells confers a higher tumorigenic potential on glioblastoma cells and therefore may be a therapeutic target to control the behavior of glioblastomas.

Hypoxia biomarkers in squamous cell carcinoma of the uterine cervix

Background

There is significant evidence that severe tumor hypoxia may cause resistance to chemoradiotherapy and promote metastatic spread in locally advanced carcinoma of the uterine cervix. Some clinical investigations have suggested that high expression of hypoxia-inducible factor-1α (HIF-1α) and/or its target gene carbonic anhydrase IX (CAIX) may be useful biomarkers of tumor hypoxia and poor outcome in cervical cancer. Here, we challenged this view by investigating possible associations between HIF-1α expression, CAIX expression, fraction of hypoxic tissue, and lymph node metastasis in experimental human tumors.

Methods

Tumors of two cervical carcinoma xenograft lines (CK-160 and TS-415) were included in the study. Pimonidazole was used as a hypoxia marker, and tumor hypoxia, HIF-1α expression, and CAIX expression were detected by immunohistochemistry. Metastatic status was assessed by examining external lymph nodes in the inguinal, axillary, interscapular, and submandibular regions and internal lymph nodes in the abdomen and mediastinum.

Results

Tissue regions staining positive for pimonidazole, HIF-1α, or CAIX were poorly colocalized, both in CK-160 and TS-415 tumors. The expression of HIF-1α or CAIX did not correlate with the fraction of hypoxic tissue in any of the two tumor lines. Furthermore, clinically relevant associations between HIF-1α or CAIX expression and lymph node metastasis were not found.

Conclusion

Because significant associations between HIF-1α expression, CAIX expression, fraction of hypoxic tissue, and incidence of lymph node metastases could not be detected in any of two preclinical models of human cervical cancer, it is not realistic to believe that high expression of HIF-1α or CAIX can be useful biomarkers of tumor hypoxia and poor outcome in a highly heterogeneous disease like cervical carcinoma.

Tumor Microenvironment in Head and Neck Squamous Cell Carcinomas

Recent studies about solid tumors demonstrated that tumor microenvironment has an important role in tumor progression, aggressivity, and metastasis process, in addition to genetic aberrations and molecular alterations of cancer cells. Therefore, the crosstalks between cancerous and noncancerous cells and metabolic changes in tumor microenvironment cause significant detrimental effects. The purpose of this review is to present the role and effect of noncancerous cells and their crosstalks with cancer cells, metabolic changes in tumor microenvironment, and to discuss the clinical significance of all these factors with respect to the current literature.

Bortezomib attenuates HIF-1- but not HIF-2-mediated transcriptional activation

Bortezomib is the first proteasomal inhibitor (PI) to be used therapeutically for treating relapse cases of multiple myeloma and mantle cell lymphoma. A proposed mechanism for its action is that it prevents the proteasomal degradation of proapoptotic proteins, leading to enhanced apoptosis. Although the α subunit of hypoxia-inducible factor (HIF)-1 is not degraded with bortezomib treatment, the heterodimeric HIF-1 fails to transactivate target genes. HIF-1 and HIF-2 are related hypoxia-inducible transcription factors that are important for the survival of hypoxic tumor cells. The majority of reports have focused on the effects of bortezomib on the transcriptional activities of HIF-1, but not HIF-2. The present study investigated the effects of bortezomib on HIF-2 activity in cancer cells with different levels of HIF-1α and HIF-2α subunits. HIF-α subunit levels were detected using specific antibodies, while HIF transcriptional activities were evaluated using immunodetection, reverse transcription-polymerase chain reaction and luciferase reporter assay. Bortezomib treatment was found to suppress the transcription and expression of CA9, a HIF-1-specific target gene; however, it had minimal effects on EPO and GLUT-1, which are target genes of both HIF-1 and HIF-2. These data suggest that bortezomib attenuates the transcriptional activity only of HIF-1, and not HIF-2. This novel finding on the lack of an inhibitory effect of bortezomib on HIF-2 transcriptional activity has implications for the improvement of design and treatment modalities of bortezomib and other PI drugs.

Evaluation of a hypoxia regulated gene panel in ovarian cancer

A panel of nine hypoxia regulated genes, selected from a previously published fifty gene panel, was investigated for its ability to predict hypoxic ovarian cancer phenotypes. All nine genes including vascular endothelial growth factor A, glucose transporter 1, phosphoglycerate mutase 1, lactate dehydrogenase A, prolyl 4-hydroxylase, alpha-polypeptide 1, adrenomedullin, N-myc downstream regulated 1, aldolase A, and carbonic anhydrase 9 were upregulated in the HEY and OVCAR-3 human ovarian cell lines cultured in vitro under hypoxic compared to normoxic conditions as measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The gene panel was also elevated in HEY xenograft tumor tissue compared to HEY cells cultured in normoxia. The HEY xenograft tissue demonstrated heterogeneous positive immunohistochemical staining for the exogenous hypoxia biomarker pimonidazole, and the hypoxia regulated protein carbonic anhydrase IX. A quantitative nuclease protection assay (qNPA) was developed which included the nine hypoxia regulated genes. The qNPA assay provided similar results to those obtained using qRT-PCR for cultured cell lines. The qNPA assay was also evaluated using paraffin embedded fixed tissues including a set of five patient matched primary and metastatic serous cancers and four normal ovaries. In this small sample set the average gene expression was higher in primary and metastatic cancer tissue compared to normal ovaries for the majority of genes investigated. This study supports further evaluation by qNPA of this gene panel as an alternative or complimentary method to existing protein biomarkers to identify ovarian cancers with a hypoxic phenotype.

Assessment of carbonic anhydrase IX expression and extracellular pH in B-cell lymphoma cell line models

The expression of carbonic anhydrase IX (CA IX) and its relationship to acidosis in lymphomas has not been widely studied. We investigated the protein expression of CA IX in a human B-cell lymphoma tissue microarray, and in Raji, Ramos and Granta 519 lymphoma cell lines and tumor models, while also investigating the relationship with hypoxia. An imaging method, acidoCEST magnetic resonance imaging (MRI), was used to estimate lymphoma xenograft extracellular pH (pHe). Our results showed that clinical lymphoma tissues and cell line models in vitro and in vivo had moderate CA IX expression. Although in vitro studies showed that CA IX expression was induced by hypoxia, in vivo studies did not show this correlation. Untreated lymphoma xenograft tumor pHe had acidic fractions, and an acidity score was qualitatively correlated with CA IX expression. Therefore, CA IX is expressed in B-cell lymphomas and is qualitatively correlated with extracellular acidosis in xenograft tumor models.

Expression of hypoxic marker carbonic anhydrase IX predicts poor prognosis in resectable hepatocellular carcinoma

Carbonic anhydrase IX (CA-IX), a hypoxia marker, correlates with tumor progression in a variety of human cancers. However, the role of CA-IX in hepatocellular carcinomas (HCCs) remains largely unknown. We examined the expression of 277 unifocal, resectable, primary HCC tumors using immunohistochemistry. The CA-IX protein was expressed in 110 of the 227 (48.5%) HCC tumors. The expression of CA-IX correlated with younger age (P = 0.0446), female sex (P = 0.0049), high serum α-fetoprotein levels (P<1x10^-6), larger tumor size (P = 0.0031), high tumor grade P<1x10^-6) and high tumor stage (P = 1.5x10^-6). Patients with HCC tumors that expressed CA-IX were more likely to have lower 5-year disease-free survival (DFS; P = 0.0001) and 5-year overall survival (OS; P<1x10^-6). The multivariate analysis indicated that CA-IX expression was an independent predictor for high tumor stage (P = 0.0047) and DFS (P = 0.0456), and a borderline predictor for OS (P = 0.0762). Furthermore, CA-IX expression predicted poor DFS and OS in patients with high tumor stage (P = 0.0004 and P<1x10^-6, respectively). Interestingly, CA-IX expression might contribute to the worse prognosis of female patients with advanced HCCs. Our study indicates the expression of the CA-IX protein is a crucial predictor of poor prognosis in resectable HCC, and it is also an unfavorable prognostic predictor in HCC patients with high tumor stage.

Histopathological determinants of tumor resistance: a special look to the immunohistochemical expression of carbonic anhydrase IX in human cancers

Intrinsic and acquired drug resistance of tumor cells still causes the failure of treatment regimens in advanced human cancers. It may be driven by intrinsic tumor cells features, or may also arise from micro environmental influences. Hypoxia is a microenvironment feature associated with the aggressiveness and metastasizing ability of human solid cancers. Hypoxic cancer cells overexpress Carbonic Anhydrase IX (CA IX). CA IX ensures a favorable tumor intracellular pH, while contributing to stromal acidosis, which facilitates tumor invasion and metastasis. The overexpression of CA IX is considered an epiphenomenon of the presence of hypoxic, aggressive tumor cells. Recently, a relationship between CA IX overexpression and the cancer stem cells (CSCs) population has been hypothesized. CSCs are strictly regulated by tumor hypoxia and drive a major non-mutational mechanism of cancer drug-resistance. We reviewed the current data concerning the role of CA IX overexpression in human malignancies, extending such information to the expression of the stem cells markers CD44 and nestin in solid cancers, to explore their relationship with the biological behavior of tumors. CA IX is heavily expressed in advanced tumors. A positive trend of correlation between CA IX overexpression, tumor stage/grade and poor outcome emerged. Moreover, stromal CA IX expression was associated with adverse events occurrence, maybe signaling the direct action of CA IX in directing the mesenchymal changes that favor tumor invasion; in addition, membranous/cytoplasmic co-overexpression of CA IX and stem cells markers were found in several aggressive tumors. This suggests that CA IX targeting could indirectly deplete CSCs and counteract resistance of solid cancers in the clinical setting.

Carbonic anhydrase IX: regulation and role in cancer

Tumor microenvironment substantially influences the process of tumorigenesis. In many solid tumors, imbalance between the demand of rapidly proliferating cancer cells and the capabilities of the vascular system generates areas with insufficient oxygen supply. In response to tumor hypoxia, cancer cells modulate their gene expression pattern to match the requirements of the altered microenvironment. One of the most significant adaptations to this milieu is the shift towards anaerobic glycolysis to keep up the energy demands. This oncogenic metabolism is often maintained also in aerobic cells. Lactic acid, its metabolic end-product, accumulates hand-in-hand with carbon dioxide, leading to acidification of the extracellular environment. Carbonic anhydrase IX (CA IX) is the most widely expressed gene in response to hypoxia. Its crucial role in intracellular pH maintenance represents the means by which cancer cells adapt to the toxic conditions of the extracellular milieu. Furthermore, the activity of CA IX stimulates the migratory pathways of cancer cells and is connected with the increase of the aggressive/invasive phenotype of tumors. CA IX expression in many types of tumors indicates its relevance as a general marker of tumor hypoxia. Moreover, its expression is closely related to prognosis of the clinical outcome in several tumor types. All above mentioned facts support the strong position of CA IX as a potential drug therapy target. Here, we summarize the state-of-the-art knowledge on its regulation and role in cancer development.

c-Myc-mediated repression of miR-15-16 in hypoxia is induced by increased HIF-2α and promotes tumor angiogenesis and metastasis by upregulating FGF2

Previous studies have established the link between aberrant microRNA (miRNA) expression and hypoxia in various neoplasms. However, how these hypoxia-related miRNAs modulate tumor progression is still unclear. Therefore, the patterns of miRNA in colorectal carcinoma cell lines in response to hypoxia or not were first screened and the hypoxia-induced repression of the miR-15-16 cluster was confirmed. Then, this repression was found to be associated with high tumor stage and poor prognosis in colorectal carcinoma and is shown to promote tumor angiogenesis and metastasis by the loss of restriction of its target gene, fibroblast growth factor-2 (FGF2). Moreover, the general and alterative promoters of the miR-15-16 host (deleted in lymphocytic leukemia 2, DLEU2) were mapped, and three c-Myc/Max binding sites in response to the hypoxia-induced repression of miR-15-16 were further identified. Finally, an enhanced stability of c-Myc/Max heterodimer promoted by increased hypoxia-inducible factor-2α (HIF-2α) was validated, and we also verified that the enhancement contributed to the hypoxia-induced repression of miR-15-16. In brief, the c-Myc-mediated transcriptional repression of miR-15-16 in hypoxia is induced by increased HIF-2α and promoted tumor angiogenesis and hematogenous metastasis by the further loss of post-transcriptional inhibition of FGF2. Our study provides a better understanding of the coping mechanisms in response to tumor hypoxia and may be helpful in developing an effective prognostic marker or treatment target against solid tumors.

A comparison of the imaging characteristics and microregional distribution of 4 hypoxia PET tracers

We compared the imaging characteristics and hypoxia selectivity of 4 hypoxia PET radiotracers ((18)F-fluoromisonidazole [(18)F-FMISO], (18)F-flortanidazole [(18)F-HX4], (18)F-fluoroazomycin arabinoside [(18)F-FAZA], and (64)Cu-diacetyl-bis(N4-methylsemicarbazone) [(64)Cu-ATSM]) in a single murine xenograft tumor model condition using small-animal PET imaging and combined ex vivo autoradiography and fluorescence immunohistochemistry.

METHODS

Nude mice bearing SQ20b xenograft tumors were administered 1 of 4 hypoxia PET tracers and images acquired 80-90 min after injection. Frozen sections from excised tumors were then evaluated for tracer distribution using digital autoradiography and compared with histologic markers of tumor hypoxia (pimonidazole, carbonic anydrase 9 [CA9]) and vascular perfusion (Hoechst 33342).

RESULTS

The highest tumor uptake was observed with (64)Cu-ATSM (maximum standardized uptake values [SUV(max)], 1.26 ± 0.13) and the lowest with (18)F-FAZA (SUVmax, 0.41 ± 0.24). (18)F-FMISO and (18)F-HX4 had similar intermediate tumor uptake (SUV(max), 0.76 ± 0.38 and 0.65 ± 0.19, respectively). Digital autoradiographs of hypoxia tracer distribution were compared pixel by pixel with images of immunohistochemistry stains. The fluorinated nitroimidazoles all showed radiotracer uptake increasing with pimonidazole and CA9 staining. (64)Cu-ATSM showed the opposite pattern, with highest radiotracer uptake observed in regions with the lowest pimonidazole and CA9 staining.

CONCLUSION

The fluorinated nitroimidazoles showed similar tumor distributions when compared with immunohistochemistry markers of hypoxia. Variations in tumor standardized uptake value and normal tissue distribution may determine the most appropriate clinical setting for each tracer. (64)Cu-ATSM showed the highest tumor accumulation and little renal clearance. However, the lack of correlation between (64)Cu-ATSM distribution and immunohistochemistry hypoxia markers casts some doubt on the hypoxia selectivity of (64)Cu-ATSM.

Interaction of HIF-1α and Notch3 Is Required for the Expression of Carbonic Anhydrase 9 in Breast Carcinoma Cells

Expression of carbonic anhydrase 9 (CA9) is associated with poor prognosis and increased tumor aggressiveness and does not always correlate with HIF-1α expression. Presently, we analyzed the regulation of CA9 expression during hypoxia by HIF-1α, Notch3, and the von Hippel-Lindau (VHL) in breast carcinoma cells. Both HIF-1α and Notch3 were absolutely required for the expression of CA9 mRNA, protein, and reporter. Reciprocal co-immunoprecipitation of HIF-1α, Notch3 intracellular domain (NICD3), and pVHL demonstrated their association. The presence of common consensus prolyl hydroxylation and pVHL binding motifs (L(XY)LAP);LLPLAP(2191) suggested an oxygen-dependent regulation for NICD3. However, unlike the HIF-1α protein, NICD3 protein levels were not modulated with hypoxia or hypoxia-mimetic agents. Surprisingly, mutations of the common prolyl hydroxylation and pVHL binding domain lead to the loss of CA9 mRNA, protein, and reporter activity. Chromatin immunoprecipitation assay demonstrated the association of NICD3, HIF-1α, and pVHL at the CA9 promoter. Further, the NICD3 mutant defective in prolyl hydroxylation and subsequent pVHL binding caused a reduction in cell proliferation of breast carcinoma cells. We show here for the first time that the interaction of HIF-1α with NICD3 is important for the regulation of CA9 expression. These findings suggest that although CA9 is a hypoxia-responsive gene, its expression is modulated by the interaction of HIF-1α, Notch3, and VHL proteins. Targeting the expression of CA9 by targeting upstream regulators could be useful in cancer/stem cell therapy.

Carbonic anhydrase IX as an imaging and therapeutic target for tumors and metastases

Carbonic anhydrase IX (CAIX) which is a zinc containing metalloprotein, efficiently catalyzes the reversible hydration of carbon dioxide. It is constitutively up-regulated in several cancer types and has an important role in tumor progression, acidification and metastasis. High expression of CAIX generally correlates with poor prognosis and is related to a decrease in the disease-free interval following successful therapy. Therefore, it is considered as a prognostic indicator in oncology.In this review, we describe CAIX regulation and its role in tumor hypoxia, acidification and metastasis. In addition, the molecular imaging of CAIX and its potential for use in cancer detection, diagnosis, staging, and for use in following therapy response is discussed. Both antibodies and small molecular weight compounds have been used for targeted imaging of CAIX expression. The use of CAIX expression as an attractive and promising candidate marker for systemic anticancer therapy is also discussed.

Beta-catenin/HuR post-transcriptional machinery governs cancer stem cell features in response to hypoxia

Hypoxia has been long-time acknowledged as major cancer-promoting microenvironment. In such an energy-restrictive condition, post-transcriptional mechanisms gain importance over the energy-expensive gene transcription machinery. Here we show that the onset of hypoxia-induced cancer stem cell features requires the beta-catenin-dependent post-transcriptional up-regulation of CA9 and SNAI2 gene expression. In response to hypoxia, beta-catenin moves from the plasma membrane to the cytoplasm where it binds and stabilizes SNAI2 and CA9 mRNAs, in cooperation with the mRNA stabilizing protein HuR. We also provide evidence that the post-transcriptional activity of cytoplasmic beta-catenin operates under normoxia in basal-like/triple-negative breast cancer cells, where the beta-catenin knockdown suppresses the stem cell phenotype in vitro and tumor growth in vivo. In such cells, we unravel the generalized involvement of the beta-catenin-driven machinery in the stabilization of EGF-induced mRNAs, including the cancer stem cell regulator IL6. Our study highlights the crucial role of post-transcriptional mechanisms in the maintenance/acquisition of cancer stem cell features and suggests that the hindrance of cytoplasmic beta-catenin function may represent an unprecedented strategy for targeting breast cancer stem/basal-like cells.

Progress in research of hypoxia and angiogenesis in pancreatic cancer

Pancreatic cancer remains one of the most lethal solid tumors of the gastrointestinal tract. Hypoxia is the driving force behind angiogenesis in cancer. Angiogenesis is an essential factor for tumors to grow and metastasize. Studies in recent years have demonstrated that hypoxia and angiogenesis play important roles in the pathogenesis of pancreatic cancer. In this paper we will review recent advances in understanding the role of hypoxia and angiogenesis in the pathogenesis of pancreatic cancer.

The prognostic impact of a combined carbonic anhydrase IX and Ki67 signature in oral squamous cell carcinoma

Background:

Tumour hypoxia is associated with impaired apoptosis, resistance to therapy and poor prognosis. We previously reported that high stromal expression of the endogenous marker of hypoxia, carbonic anhydrase IX (CAIX), is associated with significantly reduced survival in oral squamous cell carcinoma (OSCC). In addition to hypoxia, CAIX expression is regulated by proliferation-associated signalling. We hypothesised that incorporating Ki67, a proliferation marker, into our existing CAIX-based stratification of OSCC would identify patients with the least favourable prognosis.

Methods:

Surgically resected tumours from 60 OSCC patients were analysed for CAIX, Ki67 and BAX expression using fluorescence immunohistochemistry and automated quantitative analysis (AQUA).

Results:

In patients expressing high stromal CAIX (sCAIX), stratification by tumour Ki67 expression revealed significantly distinct survival outcomes (P=0.005). In our OSCC cohort, below-median Ki67 and top-quartile sCAIX expression (Ki67^losCAIX^hi) were associated with significantly worse disease-specific survival in univariate (HR 7.2 (2.5–20.4), P=0.001) and multivariate (HR 4.2 (1.4–12.8), P=0.011) analyses. Hypoxia is associated with decreased BAX expression; the Ki67^losCAIX^hi group was more strongly associated with low BAX expression than high sCAIX alone.

Conclusion:

These data suggest that combined analysis of tumour Ki67 and sCAIX expression may provide a more clinically relevant assessment of tumour hypoxia in OSCC.

Prognostic assessment of hypoxia and metabolic markers in cervical cancer using automated digital image analysis of immunohistochemistry

BACKGROUND

Hypoxia inducible factor-1 alpha (HIF-1α), induced by tumor hypoxia, regulates tumor cell metabolism and metastasis by up-regulation of c-Met, carbonic anhydrase 9 (CA9) and glucose transporter 1 (GLUT1). The prognostic significance of hypoxia and metabolic markers is not clearly defined in cervical cancer. Here, we have examined the primary players in the hypoxia signaling pathway, by immunohistochemistry, but confirming their interactions, as well as defining which proteins are associated with outcome.

METHODS

The study subjects were comprised of cervical intraepithelial neoplasia (CIN, n = 209), carcinoma in situ (CIS, n = 74), cervical cancer (n = 179), and matched nonadjacent normal tissues (n = 357). Immunohistochemistry (IHC) was performed to identify HIF-1α, c-Met, CA9, and GLUT1. IHC scoring was performed using automated digital image analysis and the association of hypoxic markers with prognostic outcome was evaluated.

RESULTS

HIF-1α, c-Met, CA9 and GLUT1 expression were higher in cervical cancer than in CIN and normal cervix (all P < 0.001). Among these markers, expression of HIF-1α and c-Met were significantly different in FIGO stage (P < 0.001 and P = 0.019, respectively) and patients with lymph node metastasis (P < 0.001 and P = 0.010, respectively). HIF-1α expression was correlated with c-Met expression in cervical cancer (P < 0.001). High expression of HIF-1α and c-Met showed worse 5-year overall survival rate (P = 0.047 and P = 0.005, respectively) than low expression group, but CA9 and GLUT1 did not show significant survival difference. After adjusting the prognostic covariates, c-Met was found to be an independent risk factor (HR=3.27; 95% CI, 1.05-10.23, P = 0.041) for overall survival in cervical cancer.

CONCLUSIONS

We demonstrate that c-Met correlates with HIF-1α and is a poor prognostic factor in survival in cervical cancer.