Carbonic anhydrase-9 expression levels and prognosis in human breast cancer: association with treatment outcome

Imaging hypoxia in gliomas

Hypoxia plays a central role in tumour development, angiogenesis, growth and resistance to treatment. Owing to constant developments in medical imaging technology, significant advances have been made towards in vitro and in vivo imaging of hypoxia in a variety of tumours, including gliomas of the central nervous system. The aim of this article is to review the literature on imaging approaches currently available for measuring hypoxia in human gliomas and provide an insight into recent advances and future directions in this field. After a brief overview of hypoxia and its importance in gliomas, several methods of measuring hypoxia will be presented. These range from invasive monitoring by Eppendorf polarographic O(2) microelectrodes, positron electron tomography (PET) tracers based on 2-nitroimidazole compounds [(18)F-labelled fluoro-misonidazole ((18)F-MISO) or 1-(2-[((18))F]fluoro-1-[hydroxymethyl]ethoxy)methyl-2-nitroimidazole (FRP-170)], (64)Cu-ATSM Cu-diacetyl-bis(N4-methylthiosemicarbazone) (Cu-ATSM) or (99m)Tc- and (68)Ga-labelled metronidazole (MN) agents to advanced MRI methods, such as blood oxygenation level dependent (BOLD) MRI, oxygen-enhanced MRI, diffusion-weighted MRI (DWI-MRI), dynamic contrast-enhanced MRI (DCE-MRI) and (1)H-magnetic resonance spectroscopy.

Comparative genomics of esophageal adenocarcinoma and squamous cell carcinoma

BACKGROUND

Esophageal cancer consists of two major histologic types: esophageal squamous cell carcinoma (ESCC), predominant globally, and esophageal adenocarcinoma (EAC), which has a higher incidence in westernized countries. Five-year overall survival is 15%. Clinical trials frequently combine histologic types although they are different diseases with distinct origins. In the evolving era of personalized medicine and targeted therapies, we hypothesized that ESCC and EAC have genomic differences important for developing new therapeutic strategies for esophageal cancer.

METHODS

We explored DNA copy number abnormalities in 70 ESCCs with publicly available array data and 189 EACs from our group. All data was from single nucleotide polymorphism arrays. Analysis was performed using a segmentation algorithm. Log ratio thresholds for copy number gain and loss were set at ±0.2 (approximately 2.3 and 1.7 copies, respectively).

RESULTS

The ESCC and EAC genomes showed some copy number abnormalities with similar frequencies (eg, CDKN2A, EGFR, KRAS, MYC, CDK6, MET) but also many copy number abnormalities with different frequencies between histologic types, most of which were amplification events. Some of these regions harbor genes for which targeted therapies are currently available (VEGFA, ERBB2) or for which agents are in clinical trials (PIK3CA, FGFR1). Other regions contain putative oncogenes that may be targeted in the future.

CONCLUSIONS

Using single nucleotide polymorphism arrays we compared genomic abnormalities in a large cohort of EACs and ESCCs. We report here the similar and different frequencies of copy number abnormalities in ESCC and EAC. These results may allow development of histology-specific therapeutic agents for esophageal cancer.

Role of zinc in catalytic activity of carbonic anhydrase IX

The carbonic anhydrases (CAs) in the α class are zinc-dependent metalloenzymes. Previous studies have reported that recombinant forms of carbonic anhydrase IX (CAIX), a membrane-bound form of CA expressed in solid tumors, appear to be activated by low levels of zinc independent of its well-studied role at the catalytic site. In this study, we sought to determine if CAIX is stimulated by zinc in its native environment. MDA-MB-231 breast cancer cells express CAIX in response to hypoxia. We compared CAIX activity associated with membrane ghosts isolated from hypoxic cells with that in intact hypoxic cells. We measured CA activity directly using (18)O exchange from (13)CO(2) into water determined by membrane inlet mass spectrometry. In membrane ghosts, there was little effect of zinc at low concentrations on CAIX activity, although at high concentration zinc was inhibitory. In intact cells, zinc had no significant effect on CAIX activity. This suggests that there is an appreciable decrease in sensitivity to zinc when CAIX is in its natural membrane milieu compared to the purified forms.

Carbonic anhydrase IX is a predictive marker of doxorubicin resistance in early-stage breast cancer independent of HER2 and TOP2A amplification

Background:

In early-stage breast cancer, adjuvant chemotherapy is associated with significant systemic toxicity with only a modest survival benefit. Therefore, there is considerable interest in identifying predictive markers of response to therapy. Doxorubicin, one of the most common drugs used to treat breast cancer, is an anthracycline chemotherapeutic agent, a class of drugs known to be affected by hypoxia. Accordingly, we examined whether expression of the endogenous hypoxia marker carbonic anhydrase IX (CA IX) is predictive of outcome in early-stage breast cancer patients treated with doxorubicin.

Methods:

We obtained 209 early-stage pre-treatment surgically-resected breast tumours from patients, who received doxorubicin in their chemotherapeutic regimen and had >10 years of follow-up. Immunohistochemistry was used to detect CA IX, and we used fluorescence in situ hybridisation to detect both human epidermal growth factor receptor (HER2) and DNA topoisomerase II-alpha (TOP2A) gene amplification.

Results:

Carbonic anhydrase IX intensity was significantly correlated with progression-free survival (PFS) and overall survival (OS) in patients receiving 300 mg m⁻² of doxorubicin (HR=1.82 and 3.77; P=0.0014 and 0.010, respectively). There was a significant, inverse correlation between CA IX score and oestrogen receptor expression, but no significant correlations were seen with either HER2 or TOP2A ratio.

Conclusion:

We demonstrate that CA IX expression is correlated with worse PFS and OS for breast cancer patients treated with doxorubicin, independent of HER2 or TOP2A gene amplification. This study provides evidence that using CA IX to detect hypoxia in surgically-resected breast tumours may be of clinical use in choosing an appropriate chemotherapy regimen.

Noninvasive detection of breast cancer lymph node metastasis using carbonic anhydrases IX and XII targeted imaging probes

PURPOSE

To develop targeted molecular imaging probes for the noninvasive detection of breast cancer lymph node metastasis.

EXPERIMENTAL DESIGN

Six cell surface or secreted markers were identified by expression profiling and from the literature as being highly expressed in breast cancer lymph node metastases. Two of these markers were cell surface carbonic anhydrase isozymes (CAIX and/or CAXII) and were validated for protein expression by immunohistochemistry of patient tissue samples on a breast cancer tissue microarray containing 47 normal breast tissue samples, 42 ductal carcinoma in situ, 43 invasive ductal carcinomas without metastasis, 46 invasive ductal carcinomas with metastasis, and 49 lymph node macrometastases of breast carcinoma. Targeted probes were developed by conjugation of CAIX- and CAXII-specific monoclonal antibodies to a near-infrared fluorescent dye.

RESULTS

Together, these two markers were expressed in 100% of the lymph node metastases surveyed. Selectivity of the imaging probes were confirmed by intravenous injection into nude mice-bearing mammary fat pad tumors of marker-expressing cells and nonexpressing cells or by preinjection of unlabeled antibody. Imaging of lymph node metastases showed that peritumorally injected probes detected nodes harboring metastatic tumor cells. As few as 1,000 cells were detected, as determined by implanting, under ultrasound guidance, a range in number of CAIX- and CAXII-expressing cells into the axillary lymph nodes.

CONCLUSION

These imaging probes have potential for noninvasive staging of breast cancer in the clinic and elimination of unneeded surgery, which is costly and associated with morbidities.

Prognostic significance of carbonic anhydrase IX (CA-IX), endoglin (CD105) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in breast cancer patients

The aim of this study was to examine the prognostic significance of carbonic anhydrase IX (CA-IX), an endogenous marker for tumor hypoxia; endoglin (CD105), a proliferation-associated and hypoxia-inducible glycoprotein and 8-hydroxy-2'-deoxyguanosine (8-OHdG), an oxidative DNA lesion, in breast cancer patients. Immunohistochemical expressions of CA-IX, CD105 and 8-OHdG, analyzed on paraffin-embedded tumor tissues from forty female breast cancer patients, were used to assess their prognostic implication on overall survival (OS) and relapse-free survival (RFS). Patients with high CA-IX expression (above cut-off value) had a higher occurrence of relapse (P = = 0.002). High CA-IX expression was significantly associated with shorter RFS (P < 0.001, hazard ratio (HR) 0.21) and shorter OS (P < 0.001, HR 0.19). Lymph node negative patients with high CA-IX expression had worse RFS (P = 0.031, HR 0.14) and OS (P = 0.005, HR 0.05). Patients with grade I&II tumors and high CA-IX expression showed shorter RFS (P = 0.028, HR 0.28) and OS (P = 0.008, HR 0.20). Worse OS (P = 0.046, HR 0.28) was found in subgroup of patients with grade II tumors and high CA-IX expression. Among all three markers, only high CA-IX expression was strong independent prognostic indicator for shorter OS (HR 4.14, 95% CI 1.28-13.35, P = 0.018) and shorter RFS (HR 3.99, 95% CI 1.38-11.59, P = 0.011). Elevated expression of CA-IX was an independent prognostic factor for decreased RFS and OS and a significant marker for tumor aggressiveness. CD105 had week prognostic value; whereas, 8-OHdG, in this study, did not provide sufficient evidence as a prognostic indicator in breast cancer patients.

Gene expression and hypoxia in breast cancer

Hypoxia is a feature of most solid tumors and is associated with poor prognosis in several cancer types, including breast cancer. The master regulator of the hypoxic response is the Hypoxia-inducible factor 1α (HIF-1α). It is becoming clear that HIF-1α expression alone is not a reliable marker of tumor response to hypoxia, and recent studies have focused on determining gene and microRNA (miRNA) signatures for this complex process. The results of these studies are likely to pave the way towards the development of a robust hypoxia signature for breast and other cancers that will be useful for diagnosis and therapy. In this review, we outline the existing markers of hypoxia and recently identified gene and miRNA expression signatures, and discuss their potential as prognostic and predictive biomarkers. We also highlight how the hypoxia response is being targeted in the development of cancer therapies.

Tribbles homolog 3 denotes a poor prognosis in breast cancer and is involved in hypoxia response

Introduction

Hypoxia in solid tumors is associated with treatment resistance, resulting in poor prognosis. Tribbles homolog 3 (TRIB3) is induced during hypoxia and is involved in multiple cellular pathways involved in cell survival. Here, we investigated the role of TRIB3 in breast cancer.

Methods

TRIB3 mRNA expression was measured in breast tumor tissue from 247 patients and correlated with clinicopathological parameters and clinical outcome. Furthermore, we studied TRIB3 expression regulation in cell lines, xenografts tissues and human breast cancer material using Reverse transcriptase, quantitative polymerase chain reaction (RT-qPCR) and immunohistochemical staining. Finally, the effect of small interfering RNA (siRNA) mediated TRIB3 knockdown on hypoxia tolerance was assessed.

Results

Breast cancer patients with low, intermediate or high TRIB3 expression exhibited a mean disease free survival (DFS) of 80 (95% confidence interval [CI] = 74 to 86), 74 (CI = 67 to 81), and 63 (CI = 55 to 71) months respectively (P = .002, Mantel-Cox log-rank). The prognostic value of TRIB3 was limited to those patients that had received radiotherapy as part of their primary treatment (n = 179, P = .005) and remained statistically significant after correction for other clinicopathological parameters (DFS, Hazard Ratio = 1.90, CI = 1.17 to 3.08, P = .009). In breast cell lines TRIB3 expression was induced by hypoxia, nutrient starvation, and endoplasmic reticulum stress in an hypoxia inducible factor 1 (HIF-1) independent manner. TRIB3 induction after hypoxia did not increase with decreasing oxygen levels. In breast tumor xenografts and human breast cancer tissues TRIB3 co-localized with the hypoxic cell marker pimonidazole. The induction of TRIB3 by hypoxia was shown to be regulated via the PERK/ATF4/CHOP pathway of the unfolded protein response and knockdown of TRIB3 resulted in a dose-dependent increase in hypoxia sensitivity.

Conclusions

TRIB3 is independently associated with poor prognosis of breast cancer patients, possibly through its association with tumor cell hypoxia.

Catalysis and pH control by membrane-associated carbonic anhydrase IX in MDA-MB-231 breast cancer cells

Carbonic anhydrase IX (CAIX) is a membrane-bound, tumor-related enzyme whose expression is often considered a marker for hypoxia, an indicator of poor prognosis in the majority of cancer patients, and is associated with acidification of the tumor microenvironment. Here, we describe for the first time the catalytic properties of native CAIX in MDA-MB-231 breast cancer cells that exhibit hypoxia-inducible CAIX expression. Using (18)O exchange measured by membrane inlet mass spectrometry, we determined catalytic activity in membrane ghosts and intact cells. Exofacial carbonic anhydrase activity increases with exposure to hypoxia, an activity which is suppressed by impermeant sulfonamide CA inhibitors. Inhibition by sulfonamide inhibitors is not sensitive to reoxygenation. CAIX activity in intact cells increases in response to reduced pH. Data from membrane ghosts show that the increase in activity at reduced pH is largely due to an increase in the dehydration reaction. In addition, the kinetic constants of CAIX in membrane ghosts are very similar to our previous measurements for purified, recombinant, truncated forms. Hence, the activity of CAIX is not affected by the proteoglycan extension or membrane environment. These activities were measured at a total concentration for all CO(2) species at 25 mm and close to chemical equilibrium, conditions which approximate the physiological extracellular environment. Our data suggest that CAIX is particularly well suited to maintain the extracellular pH at a value that favors the survival fitness of tumor cells.

Role of hypoxia and EGF on expression, activity, localization and phosphorylation of carbonic anhydrase IX in MDA-MB-231 breast cancer cells

Carbonic anhydrase IX (CAIX) is a zinc metalloenzyme that catalyzes the reversible hydration of CO(2). CAIX is overexpressed in many types of cancer, including breast cancer, but is most frequently absent in corresponding normal tissues. CAIX expression is strongly induced by hypoxia and is significantly associated with tumor grade and poor survival. Herein, we show that hypoxia induces a significant increase in CAIX protein in MDA-MB-231 breast cancer cells. Using a unique mass spectrophotometric assay, we demonstrate that CAIX activity in plasma membranes isolated from MDA-MB-231 is correlated with CAIX content. We also show that CAIX exists predominantly as a dimeric, high-mannose N-linked glycoprotein. While there is some evidence that the dimeric form resides specifically in lipid rafts, our data do not support this hypothesis. EGF, alone, did not affect the distribution of CAIX into lipid rafts. However, acute EGF treatment in the context of hypoxia increased the amount of CAIX in lipid rafts by about 5-fold. EGF did not stimulate tyrosine phosphorylation of CAIX, although EGFR and down-stream signaling pathways were activated by EGF. Interestingly, hypoxia activated Akt independent of EGF action. Together, these data demonstrate that the active form of CAIX in the MDA-MB-231 breast cancer cell line is dimeric but that neither lipid raft localization nor phosphorylation are likely required for its dimerization or activity.

Brain tumor hypoxia: tumorigenesis, angiogenesis, imaging, pseudoprogression, and as a therapeutic target

Hypoxia is implicated in many aspects of tumor development, angiogenesis, and growth in many different tumors. Brain tumors, particularly the highly aggressive glioblastoma multiforme (GBM) with its necrotic tissues, are likely affected similarly by hypoxia, although this involvement has not been closely studied. Invasion, apoptosis, chemoresistance, resistance to antiangiogenic therapy, and radiation resistance may all have hypoxic mechanisms. The extent of the influence of hypoxia in these processes makes it an attractive therapeutic target for GBM. Because of their relationship to glioma and meningioma growth and angiogenesis, hypoxia-regulated molecules, including hypoxia inducible factor-1, carbonic anhydrase IX, glucose transporter 1, and vascular endothelial growth factor, may be suitable subjects for therapies. Furthermore, other novel hypoxia-regulated molecules that may play a role in GBM may provide further options. Emerging imaging techniques may allow for improved determination of hypoxia in human brain tumors to better focus therapeutic treatments; however, tumor pseudoprogression, which may be prompted by hypoxia, poses further challenges. An understanding of the role of hypoxia in tumor development and growth is important for physicians involved in the care of patients with brain tumors.

The key hypoxia regulated gene CAIX is upregulated in basal-like breast tumours and is associated with resistance to chemotherapy

Basal-like tumours account for 15% of invasive breast carcinomas and are associated with a poorer prognosis and resistance to therapy. We hypothesised that this aggressive phenotype is because of an intrinsically elevated hypoxic response. Microarrayed tumours from 188 patients were stained for hypoxia-inducible factor (HIF)-1α, prolyl hydroxylase (PHD)1, PHD2, PHD3 and factor inhibiting HIF (FIH)-1, and carbonic anhydrase (CA) IX stained in 456 breast tumours. Tumour subtypes were correlated with standard clincopathological parameters as well as hypoxic markers. Out of 456 tumours 62 (14%) tumours were basal-like. These tumours were positively correlated with high tumour grade (P<0.001) and were associated with a significantly worse disease-free survival compared with luminal tumours (P<0.001). Fifty percent of basal-like tumours expressed HIF-1α, and more than half expressed at least one of the PHD enzymes and FIH-1. Basal-like tumours were nine times more likely to be associated with CAIX expression (P<0.001) in a multivariate analysis. Carbonic anhydrase IX expression was positively correlated with tumour size (P=0.005), tumour grade (P<0.001) and oestrogen receptor (ER) negativity (P<0.001). Patients with any CAIX-positive breast tumour phenotype and in the basal tumour group had a significantly worse prognosis than CAIX-negative tumours when treated with chemotherapy (P<0.001 and P=0.03, respectively). The association between basal phenotype and CAIX suggests that the more aggressive behaviour of these tumours is partly due to an enhanced hypoxic response. Further, the association with chemoresistance in CAIX-positive breast tumours and basal-like tumours in particular raises the possibility that targeted therapy against HIF pathway or downstream genes such as CAs may be an approach to investigate for these patients.

Clinical biomarkers for hypoxia targeting

Tumor hypoxia or a reduction of the tissue oxygen tension is a key microenvironmental factor for tumor progression and treatment resistance in solid tumors. Because hypoxic tumor cells have been demonstrated to be more resistant to ionizing radiation, hypoxia has been a focus of laboratory and clinical research in radiation therapy for many decades. It is believed that proper detection of hypoxic regions would guide treatment options and ultimately improve tumor response. To date, most clinical efforts in targeting tumor hypoxia have yielded equivocal results due to the lack of appropriate patient selection. However, with improved understanding of the molecular pathways regulated by hypoxia and the discovery of novel hypoxia markers, the prospect of targeting hypoxia has become more tangible. This chapter will focus on the development of clinical biomarkers for hypoxia targeting.

Low CAIX expression and absence of VHL gene mutation are associated with tumor aggressiveness and poor survival of clear cell renal cell carcinoma

We attempted to describe, in a series of clear cell renal cell carcinoma (RCC), the relationship between CAIX expression, VHL gene mutations, tumor characteristics and outcome. Radical nephrectomy was performed in 100 patients. Genomic DNA was extracted from frozen tumor samples. Four amplimers covering the whole coding sequence of the VHL gene were synthesized by PCR and sequenced. The monoclonal antibody M75 was used to evaluate CAIX protein expression immunohistochemically. VHL mutations were identified in 58 patients (58%) and high CAIX expression (>85%) was observed in 78 (78%). Tumors with VHL mutation showed higher CAIX expression than those without (p = 0.02). Low CAIX expression and absence of VHL mutation were associated with a more advanced tumors e.g., higher T stages and presence of metastases. VHL mutation and high CAIX expression predicted longer progression-free survival (p = 0.037) and disease-specific survival (p = 0.001), respectively. In combination, they defined three prognostic groups (p = 0.002): (i) good prognosis, defined as VHL mutation and high CAIX (2-year survival: 86%), (ii) intermediate prognosis with either VHL mutation or high CAIX (69%), and (iii) poor prognosis with no VHL mutation and low CAIX (45%, median survival 18 months). CAIX expression, but not VHL mutational status, was an independent prognostic factor in multivariate analysis. Taken together, CAIX expression and VHL mutational status are able to stratify patients with clear cell RCC into distinct groups with regards to clinicopathological variables and prognosis, with low CAIX expression and absence of VHL mutation being associated with a poor clinicopathological phenotype and diminished survival.

Molecular aspects of tumour hypoxia

Hypoxia is an important feature of the microenvironment of a wide range of solid tumours. Its critical role in radio- and chemoresistance and its significance as an adverse prognostic factor have been well established over the last decades. On a cellular level, hypoxia evokes a complex molecular response with a central role for the HIF-1 pathway. The cellular processes under control of HIF-1 contain important prognostic information and comprise potential candidates for directing hypoxia-modifying therapies. This review will provide an overview of the current knowledge on the molecular aspects of tumour hypoxia and the link to clinical practice.

The potential role of intrinsic hypoxia markers as prognostic variables in cancer

Tumor hypoxia is related to tumor progression and therapy resistance, which leads to poor patient outcome. It has been suggested that measuring the hypoxic status of a tumor helps to predict patient outcome and to select more targeted treatment. However, current methods using needle electrodes or exogenous markers have limitations due to their invasiveness or necessity for preinjection. Recent studies showed that hypoxia-regulated genes could be alternatively used as endogenous hypoxia markers. This is a review of 15 hypoxia-regulated genes, including hypoxia-inducible factor-1 and its targets, and their correlation with tumor hypoxia and patient outcome from 213 studies. Though most of the studies showed significance of these genes in predicting prognosis, there was no definitive prognostic and hypoxia marker. In conclusion, this review suggests the need for further studies with standardized methods to examine gene expression, as well as the use of multiple gene expressions.

CA9 gene expression in conventional renal cell carcinoma: a potential marker for prediction of early metastasis after nephrectomy

About 30-40% of patients with renal cell carcinoma (RCC) will develop metastasis after curative nephrectomy. There is a strong need to identify the early metastasis with conventional and molecular risk factors. The present study aimed to test if analysis of the CA9 gene can provide useful information to predict early metastasis after nephrectomy. This study included 63 patients with a conventional RCC. Ten tumors were N+ or/and M+ at diagnosis. The mean follow-up was 43 months (range, 4-67 months). About 11 M0N0 patients were found to have a metastasis during the follow-up. Quantitative RT-PCR of CA9 gene expression was performed. The metastasis-free survival curve was established according to the Kaplan-Meier method with comparison by the Log-Rank test. At diagnosis, the average of CA9 gene expression was significantly lower (p = 0.004) in metastatic tumors (N+ or/and M+) than in non-metastatic tumors (N0M0). For the follow-up of M0N0 patients, the metastasis-free survival rate was significantly higher (p = 0.005) in the high CA9 group than in the low-CA9 group. When combined with CA9, the metastasis-free survival rates, in terms of stage (p = 0.015) or grade (p = 0.010) were significantly different. When the stage, grade, and CA9 were combined, there was a significant difference (p = 0.004) in metastasis-free survival rates (T1T2 + G1G2 + high expression of CA9 versus T3 + G3G4 + low expression of CA9). Finally, the multivariate regression analysis identified CA9 expression (p = 0.036) as an independent predictor of early metastasis. Our study confirms that the expression level of CA9 gene in conventional RCC is related to metastasis. CA9 may be a potential marker for the prediction of early metastasis after nephrectomy and to guide post-operative follow-up and treatment.

HIF-1α and CA IX staining in invasive breast carcinomas: Prognosis and treatment outcome

Hypoxia stabilizes HIF-1alpha (Hypoxia Inducible Factor-1alpha), which then triggers the expression of several genes involved in many aspects of cancer progression, including metabolic adaptation, cell survival and angiogenesis. The aim of our study was to evaluate the impact of HIF-1alpha and CA IX (carbonic anhydrase IX) (one of its target genes) expression on prognosis and treatment outcome of patients with breast cancer. Because of the extreme O2-dependent instability of the protein, we first validated HIF-1alpha staining using xenograft tumours that were subjected to experimental conditions mimicking surgical clamping or sitting at room temperature under normoxic conditions after surgical excision but before fixation. Afterwards, the immunohistochemical staining of HIF-1alpha and CA IX was evaluated in 132 invasive breast carcinomas with a 10-year follow-up, and correlated to classical clinicopathological parameters and response to adjuvant therapy. No significant correlation was found between tumour size or nodal status and the expression of HIF-1alpha or CA IX. Statistically significant association was found between HIF-1alpha or CA IX staining and the grade, hormonal receptors loss and the presence of carcinoma in situ. Overexpression of HIF-1alpha and CA IX correlates with a poor prognosis in breast cancer. We show that HIF-1alpha is an independent prognostic factor for distant metastasis-free survival and disease-free survival in multivariate analysis. Furthermore, overexpression of HIF-1alpha or CA IX correlates with a poor outcome after conventional adjuvant therapy. CA IX is, however, a weaker prognostic and predictive factor than HIF-1alpha, and its association with HIF-1alpha does not modify the survival curve neither response to therapy, compared to HIF-1alpha alone.

CA IX is an independent prognostic marker in premenopausal breast cancer patients with one to three positive lymph nodes and a putative marker of radiation resistance

PURPOSE

Hypoxia in breast cancer is associated with poor prognosis and down-regulation of the estrogen receptor. Carbonic anhydrase IX (CA IX) is a hypoxia-inducible gene that has been associated with poor outcome in many epithelial cancers. Previous studies of CA IX in breast cancer have been carried out on mixed cohorts of premenopausal and postmenopausal patients with locally advanced disease and varying treatment regimens. We examined the potential prognostic and predictive role of CA IX in premenopausal breast cancer patients.

EXPERIMENTAL DESIGN

Using tissue microarrays, we analyzed CA IX expression in 400 stage II breast cancers from premenopausal women. The patients had previously participated in a randomized control trial comparing 2 years of tamoxifen to no systemic adjuvant treatment. Median follow-up was 13.9 years.

RESULTS

CA IX expression correlated positively with tumor size, grade, hypoxia-inducible factor 1alpha, Ki-67, cyclin E, and cyclin A2 expression. CA IX expression correlated negatively with cyclin D1, estrogen receptor, and progesterone receptor. CA IX expression was associated with a reduced relapse-free survival (P=0.032), overall survival (P=0.022), and breast cancer-specific survival (P=0.005). Multivariate analysis revealed that CA IX was an independent prognostic marker in untreated patients with one to three positive lymph nodes (hazard ratio, 3.2; 95% confidence interval, 1.15-9.13; P=0.027).

CONCLUSION

CA IX is marker of poor prognosis in premenopausal breast cancer patients and it is an independent predictor of survival in patients with one to three positive lymph nodes. As all these patients received locoregional radiation therapy, CA IX may be associated with resistance to radiotherapy.

Tumor-associated carbonic anhydrases and their clinical significance

Carbonic anhydrases (CAs) are physiologically important enzymes that catalyze a reversible conversion of carbon dioxide to bicarbonate and participate in ion transport and pH control. Two human isoenzymes, CA IX and CA XII, are overexpressed in cancer and contribute to tumor physiology. Particularly CA IX is confined to only few normal tissues but is ectopically induced in many tumor types mainly due to its strong transcriptional activation by hypoxia accomplished via HIF-1 transcription factor. Therefore, CA IX can serve as a surrogate marker of hypoxia and a prognostic indicator. CA IX appears implicated in cell adhesion and in balance of pH disturbances caused by tumor metabolism. Both tumor-related expression pattern and functional involvement in tumor progression make it a suitable target for anticancer treatment. Here we summarize a current knowledge on CA IX and CA XII, and discuss possibilities of their exploitation for cancer detection, diagnostics, and therapy.

Hypoxia in breast cancer: role of blood flow, oxygen diffusion distances, and anemia in the development of oxygen depletion

Heterogeneously distributed hypoxic areas are a characteristic property of locally advanced breast cancers. Hypoxia results from an imbalance between the supply and consumption of oxygen (O2). Major pathogenetic mechanisms for the emergence of hypoxia are (i) structural and functional abnormalities in the tumor microvasculature, (ii) an adverse diffusion geometry, and (iii) tumor-related and therapy-induced anemia leading to a reduced O2 transport capacity of the blood. There is pronounced intertumor variability in the extent of hypoxia, which is independent of clinical size, stage, histology and grade. Hypoxia is intensified in anemic patients, especially in tumor (areas) with low perfusion rates. Tumor hypoxia is a therapeutic problem since it makes solid tumors resistant to sparsely ionizing radiation, some forms of chemotherapy, and photodynamic therapy. However, besides more direct mechanisms involved in the development of therapeutic resistance, there are, in addition, indirect machineries that can cause barriers to therapies. These include hypoxia-mediated alterations in gene expression, proteomic and genomic changes, and clonal selection. These in turn can drive subsequent events that are known to further increase resistance to therapy in addition to critically affecting long-term prognosis.

Hypoxia in the tumorigenesis of gliomas and as a potential target for therapeutic measures

✓ In this article, the author provides a brief description of the role of hypoxia in the tumorigenesis of gliomas and suggests potential ways of exploiting this role to design treatment modalities. Tumor hypoxia predicts the likelihood of metastases, tumor recurrence, resistance to chemotherapy and radiation therapy, invasive potential, and decreased patient survival for many human malignancies. Various methods of measurement of tumor hypoxia are discussed, including direct measurement and imaging methods.

The role of hypoxia-responsive molecules, especially hypoxia-inducible factor-1 (HIF-1), in glioma tumorigenesis is explored. Treatment modalities regulated by hypoxia are proposed and some potential strategies reviewed. The progression of a low-grade astrocytoma to a glioblastoma multiforme may be mediated by hypoxia-induced phenotypic changes and subsequent clonal selection of cells that overexpress hypoxia-responsive molecules, such as HIF-1. In this model, intratumoral hypoxia causes genetic changes that produce a microenvironment that selects for cells of a more aggressive phenotype.

Detection of carbonic anhydrase 9-expressing tumor cells in the lymph nodes of vulvar carcinoma patients by RT-PCR

Regional lymph node status is an important prognostic factor for vulvar cancer. The goal of our study was to elaborate a reliable test for detecting micrometastases, undetectable by traditional methods, in the lymph nodes of vulvar squamous carcinoma patients. For this purpose, carbonic anhydrase-9 (CA9) was investigated as a cancer-related marker by RT-PCR. Firstly, primary carcinoma specimens were examined for CA9 expression by immunohistochemistry with M75 monoclonal antibody. All 19 tissues exhibited a variable degree of staining, which was mostly confined to the plasma membranes of tumor cells. Correspondingly, all primary tumor specimens and the control A-431 vulvar cancer cell line gave a positive signal in the nested RT-PCR assay designed to detect CA9-expressing cells with a high sensitivity. Analysis of 77 lymph node specimens from 20 patients revealed a full correlation between RT-PCR results and standard hematoxylin-eosin staining in 75% of samples, whereas 25% of specimens were negative by the standard method and positive for CA9 mRNA, accounting for 28% of all histologically negative lymph nodes. There were no false-negatives with RT-PCR. A positive inguinal lymph node with a negative sentinel node was observed in the same groin only once in 38 specimens. Our findings clearly indicate potential value of CA9 as a molecular marker for the assessment of regional lymph node status in vulvar cancer patients and support a possible utility of our RT-PCR assay in the detection of micrometastases.

Lessons to be learned from primary renal cell carcinomas: novel tumor antigens and HLA ligands for immunotherapy

The lack of sufficient well-defined tumor-associated antigens is still a drawback on the way to a cytotoxic T-lymphocyte-based immunotherapy of renal cell carcinoma (RCC). We are trying to define a larger number of such targets by a combined approach involving HLA ligand characterization by mass spectrometry and gene expression profiling by oligonucleotide microarrays. Here, we present the results of a large-scale analysis of 13 RCC specimens. We were able to identify more than 700 peptides, mostly from self-proteins without any evident tumor association. However, some HLA ligands derived from previously known tumor antigens in RCC. In addition, gene expression profiling of tumors and a set of healthy tissues revealed novel candidate RCC-associated antigens. For several of them, we were able to characterize HLA ligands after extraction from the tumor tissue. Apart from universal RCC antigens, some proteins seem to be appropriate candidates in individual patients only. This underlines the advantage of a personalized therapeutic approach. Further analyses will contribute additional HLA ligands to this repertoire of universal as well as patient-individual tumor antigens.

Vascularization and expression of hypoxia-related tissue factors in intracranial ependymoma and their impact on patient survival

We investigated angiogenic patterns and expression of hypoxia-related tissue factors and their prognostic impact in 100 cases of intracranial ependymoma. Angiogenic patterns were evaluated by anti-CD34 immunolabeling. Hypoxia-related factors carbonic anhydrase 9 (CA9) and hypoxia-inducible factor 1 alpha (HIF-1alpha) were visualized by immunohistochemistry, and vascular endothelial growth factor (VEGF) mRNA by in situ hybridization. Expression patterns of VEGF and CA9 are similar with regard to distribution (perinecrotic) and extent. HIF-1alpha expression occurs in a significantly smaller fraction of cases and only in a few tumor cells without clear association with necrosis. Expression of VEGF and CA9, but not HIF-1alpha, is associated with a bizarre angiogenic subtype. Combined expression of two or three hypoxia markers (high hypoxia score) associates with presence of necrosis, high proliferation index, bizarre vascular pattern, and increased cellularity. Univariate analysis indicated that patients with high hypoxia score had significantly shorter survival. On multivariate analysis, only proliferation index and extent of resection remained independent predictive factors. We conclude that bizarre vascular pattern, necrosis and high hypoxia score are frequently detectable in intracranial ependymoma, but seem less important for patient outcome than tumor cell proliferation.

Colocalization of Carbonic Anhydrase 9 Expression and Cell Proliferation in Human Head and Neck Squamous Cell Carcinoma

Purpose: Tumor cells undergo a variety of biological changes under sustained hypoxic conditions, allowing cells to survive and retain their clonogenic potential. The purpose of this study is to relate the expression of the hypoxia marker carbonic anhydrase 9 (CA9) to the uptake of iododeoxyuridine (IdUrd), a marker of proliferation, in head and neck squamous cell carcinomas. Colocalization of IdUrd and CA9 may identify an important subpopulation of tumor cells that might be responsible for repopulation and disease progression.

Experimental Design: Expression of CA9, IdUrd labeling, and colocalization between IdUrd and CA9 was examined by immunohistochemistry in biopsies of head and neck squamous cell carcinomas. Biopsies were taken from 51 patients recruited between 1998 and 2001 after administration of the proliferation marker IdUrd.

Results: A large variation was observed between the tumors in CA9 expression (range 0-39%), IdUrd labeling (range 0-81%), and colocalization between IdUrd and CA9 [FId(CA9); range 0-53%]. FId(CA9), the fraction of IdUrd-labeled cells positive for CA9, was highest at an intermediate distance from the blood vessels (100-150 μm). IdUrd labeling was higher in T4 carcinomas relative to lower stage tumors (P = 0.04). High FId(CA9) correlated with the worst disease-free survival rates (P = 0.04).

Conclusions: Colocalization between IdUrd labeling and CA9 expression was observed in head and neck squamous cell carcinomas, suggesting the presence of a population of tumor cells under intermediate hypoxic conditions which still has proliferative capacity. The size of this subpopulation may be indicative of tumor aggressiveness and is associated with the worst disease-free survival rates.

Prognostic predictor with multiple fuzzy neural models using expression profiles from DNA microarray for metastases of breast cancer

Gene expression profiling data from DNA microarray were analyzed using the fuzzy neural network (FNN) modeling method for predicting the distant metastases of breast cancer. The best model consisting of five genes was able to predict metastases of breast cancer with 94% accuracy. Furthermore, 100% accuracy was achieved by majoritarian decision using only 25 genes from five noninferior models which were constructed independently. From the constructed model, gene expression rules, which may cause distant metastases, were explicitly extracted and 60% of the metastases cases could be explained by this rule. The FNN modeling method described in this paper enables precise extraction of significant biological markers affecting prognosis without prior knowledge.