Kristiina Nordfors

Expression of Carbonic Anhydrase IX in Astrocytic Tumors Predicts Poor Prognosis

Purpose: Carbonic anhydrase IX (CA IX) is a hypoxia-inducible enzyme, which is associated with neoplastic growth. Ectopic CA IX expression has been observed in several tumors, whose normal counterparts do not express this enzyme. Normal human brain tissue shows only slight or no expression of CA IX. Experimental Design: We describe CA IX expression in human diffusely infiltrating astrocytomas. The association of CA IX is evaluated with clinicopathologic and molecular factors including cell proliferation and apoptosis as well as the expression of p53 and epidermal growth factor receptor. Results: CA IX immunopositivity was observed in 284 cases of 362 (78%) tumors. The positive areas were often located in close proximity to necrotic regions (P < 0.001). The CA IX immunoreactivity showed strong association with tumor malignancy grades (P < 0.0001). CA IX showed no association with p53 expression nor did it correlate with epidermal growth factor receptor–amplification, apoptosis, or cell proliferation. CA IX intensity had significant prognostic value in univariate (P=0.0011, log-rank test) and multivariate survival analysis (P = 0.038, Cox analysis). Conclusions: CA IX expression is common in diffusely infiltrating high-grade astrocytomas. Our results suggest that CA IX is a useful biomarker for predicting poor prognosis of astrocytic tumors. It may also be a promising target molecule for the improvement of therapeutic interventions in astrocytomas.

Identification of an alternatively spliced isoform of carbonic anhydrase XII in diffusely infiltrating astrocytic gliomas

Carbonic anhydrase XII (CA XII) is a transmembrane enzyme that is associated with neoplastic growth. CA XII has been proposed to be involved in acidification of the extracellular milieu, creating an appropriate microenvironment for rapid tumor growth. Because RNA sequence databases have indicated that two isoforms of CA XII might exist in human tissues, and because alternatively spliced protein forms have been linked to aggressive behavior of cancer cells, we designed a study to evaluate the presence of the two forms of CA XII in diffuse astrocytomas, a tumor type known for its aggressive and often noncurable behavior. Reverse transcription PCR of tumor samples surprisingly revealed that CA XII present in diffuse astrocytomas is mainly encoded by a shorter mRNA variant. We further showed by Western blotting that anti-CA XII antibody recognized both isoforms in the glioblastoma cell lines, and we then evaluated the expression of CA XII in astrocytomas using immunohistochemistry and correlated the results with various clinicopathological and molecular factors. Of 370 diffusely infiltrating astrocytomas, 363 cases (98%) showed immunoreactions for CA XII. Importantly, CA XII expression correlated with poorer patient prognosis in univariate (p = 0.010, log-rank test) and multivariate survival analyses (p = 0.039, Cox analysis). From these results, we conclude that CA XII is commonly expressed in diffuse astrocytomas and that it might be used as a biomarker of poor prognosis. The absence of 11 amino acids in the shorter isoform, which seems to be common in astrocytomas, may affect the normal quaternary structure and biological function of CA XII.

Carbonic anhydrase II in the endothelium of glial tumors: A potential target for therapy

Carbonic anhydrase isozyme II (CA II) is a cytosolic enzyme that is highly expressed in most organs, including the brain, where it is mainly located in the oligodendrocytes. Recent studies have shown that its expression is induced in the endothelium of neovessels in melanoma and esophageal, renal, and lung cancer. Immunological studies further indicate that CA II represents a major target antigen stimulating an autoantibody response in melanoma patients. These results prompted us to investigate endothelial CA II expression in two types of brain cancer: oligodendrogliomas and astrocytomas. A series of 255 astrocytoma and 71 oligodendroglial tumor specimens was immunostained for CA II. The staining results were correlated with a number of different clinicopathological factors and survival data. CA II showed weak or no expression in low-grade tumors, while grade 3 mixed oligoastrocytoma and glioblastoma multiforme were the most positively stained tumor types. Survival analysis indicated that endothelial CA II staining is significantly associated with a poor prognosis in patients with astrocytomas. About 17% of patients with CA II-negative tumors (weak or no endothelial signal) were still alive at the end of the follow-up period of five years. The presence of CA II in the tumor endothelium suggests that it may play an important functional role in tumor metabolism. From a clinical perspective, the results also open new avenues for selecting tumor types for dendritic cell therapy trials.

The tumour-associated carbonic anhydrases CA II, CA IX and CA XII in a group of medulloblastomas and supratentorial primitive neuroectodermal tumours: an association of CA IX with poor prognosis

BackgroundMedulloblastomas (MBs) and supratentorial primitive neuroectodermal tumours (PNETs) are the most common highly aggressive paediatric brain tumours. In spite of extensive research on these tumours, there are only few known biomarkers or therapeutic target proteins, and the prognosis of patients with these tumours remains poor. Our aim was to investigate whether carbonic anhydrases (CAs), enzymes commonly overexpressed in various tumours including glioblastomas and oligodendrogliomas, are present in MBs and PNETs, and whether their expression can be correlated with patient prognosis.MethodsWe determined the expression of the tumour-associated carbonic anhydrases CA II, CA IX and CA XII in a series of MB/PNET specimens (n = 39) using immunohistochemistry.ResultsEndothelial CA II, cytoplasmic CA II, CA IX and CA XII were expressed in 49%, 73%, 23% and 11% of the tumours, respectively. CA II was detected in the neovessel endothelium and the tumour cell cytoplasm. CA IX was mainly expressed in the tumour cells located in perinecrotic areas. CA XII showed the most homogenous distribution within the tumours. Importantly, CA IX expression predicted poor prognosis in both univariate (p = 0.041) and multivariate analyses (p = 0.016).ConclusionsWe suggest that CA IX should be considered a potential prognostic and therapeutic target in MBs and PNETs.

Twist predicts poor outcome of patients with astrocytic glioma

Aims and methods Epithelial-mesenchymal transition (EMT) has previously been linked to glioma invasion and progression. To determine whether EMT regulators, Twist and Zeb1, had clinical significance in astrocytic gliomas, the association of Twist and Zeb1 with clinicopathological and molecular factors was studied in 269 astrocytoma samples. Results Twist and Zeb1 were widely expressed in astrocytic gliomas, but the expression of the former did not correlate with that of the latter. Stronger Twist expression levels were associated with higher WHO grades (p=0.001), whereas Zeb1 did not correlate with WHO grades. We found no association between Twist and proliferation activity (Ki67/MIB-1), p53 status, epidermal growth factor receptor (EGFR) amplification or neural cell adhesion molecule (NCAM) expression. There was no significant difference in Twist or Zeb1 expression when primary and secondary gliomas were analysed. Tumours with high Twist expression were IDH1 negative (p=0.009). High hypoxia-inducible factor-1α expression correlated significantly with positive Twist expression (p<0.001), whereas it was not associated with Zeb1 expression. Zeb1 expression did not correlate with proliferation, EGFR or IDH1. Nevertheless, we did find a correlation between high Zeb1 expression and low p53 expression levels (p=0.027). Positive NCAM expression was significantly associated with Zeb1 positivity (p=0.022). Zeb1 had no association with patient survival, whereas positive Twist expression predicted poor survival for patients in both univariate (p<0.001) and multivariable analyses (p=0.027). Conclusions EMT regulators, Twist and Zeb1, are common features of infiltrating astrocytomas, and Twist is upregulated in glioblastomas in particular. Twist may be a novel marker for poor prognosis in glioma patients.

Peroxiredoxins and antioxidant enzymes in pilocytic astrocytomas

OBJECTIVE Peroxiredoxins are antioxidant enzymes (AOEs), which are redox-regulated thiol proteins with potential effects on the growth, invasion and drug resistance of neoplastic cells. In this study, their biology and clinical significance were examined in pilocytic astrocytomas (PAs). MATERIAL AND METHODS The expression of peroxiredoxins (Prx I-VI) was investigated in 105 PAs by the means of immunohistochemistry and compared with the expression of selected other antioxidant enzymes, cell proliferation, angiogenesis, apoptosis, p53, histopathology and patient survival. RESULTS Peroxiredoxins were strongly expressed in general suggesting that oxidative damage and consequent defense takes place during the progression of pilocytic astrocytomas. In agreement with this hypothesis, several other AOEs correlated with the degenerative features and angiogenesis possibly associated with reactive oxygen species-derived cellular damage. Moreover, the expression of the AOEs was associated with each other indicating a concurrent activation of the enzymes. With the exception of manganese superoxide dismutase (MnSOD), a strong expression of AOEs was generally associated with higher cell proliferation. Prx VI seemed to have a positive association with a longer recurrence-free interval while other AOEs had no association with patient survival. Many AOEs, such as MnSOD, induce chemo- and radioresistance and are highly elevated in aggressive malignancies. PAs lack this confounding factor, and these tumors are treated only by surgery. CONCLUSIONS Taken together, the results of this study on pilocytic astrocytomas suggest that the levels of Prxs and other AOEs and their related thiol proteins are generally strongly expressed in these tumors. At least Prx VI can contribute to tumor behavior which can make it a potential prognostic factor.

Expression of claudins relates to tumour aggressivity, location and recurrence in ependymomas.

The aim of our study was to assess the nature and importance of claudin expression in grade I-III ependymomas. The expression of claudins 2-5, 7, 10, TWIST, and ZEB1 were investigated in a series of 61 ependymomas using immunohistochemistry. All the claudins were expressed in ependymomas, except for CLDN4. CLDN5 positive tumours were associated with higher grade (p=0.049), whereas CLDN10 was lower in higher grade tumours (p=0.039). CLDN5 and CLDN3 were overexpressed in ependymomas of cerebral location (p=0.036, p=0.007, respectively). CLDN5 positive tumours showed more nuclear atypia, endothelial proliferation, mitosis, and hypercellularity (p=0.007, p=0.018, p=0.041, p=0.010, respectively). CLDN5 positivity correlated to higher proliferation (p=0.015). CLDN7 was more often positive in primary tumours (p=0.041). Positive ZEB1 expression was associated with CLDN2 negativity (p=0.031). TWIST-negative tumours were more often also CLDN5 and 10 negative (p=0.013, p=0.017, respectively). CLDN5 was related to more aggressive tumours compared to CLDN2 and 10, which tended to display a better degree of differentiation and a better prognosis. CLDN2 and CLDN5 were expressed commonly in ependymomas, while the parental ependymal cells in the central nervous system were usually negative. Evidently, claudins influence growth and differentiation in ependymomas.

Polysialic acid is associated with better prognosis and IDH1-mutation in diffusely infiltrating astrocytomas

BackgroundThe aim of the study was to assess the localization of Polysialic acid (polySia) and Neural cell adhesion molecule (NCAM) in grade I–IV astrocytomas by confocal microscopy, and also to clarify and compare their relationship to conventional clinicopathological features in these tumors.MethodsStudy material was stained immunohistochemically for polySia, NCAM and IDH1-R132H point mutation. Confocal microscopy of polySia and NCAM staining was performed on tissue micro-array samples (TMA) of 242 diffusely infiltrating astrocytomas (grade II: 28; grade III: 33; grade IV: 181) and 82 pilocytic astrocytomas. The results were statistically correlated to clinicopathological factors and survival data.ResultsPolySia was observed in 45 cases (19%) and NCAM positivity in 92 cases (38%). All 45 tumors with polySia positivity were also positive for NCAM whereas there were 47 tumors which contained positive staining for NCAM but not for polySia. The simultaneous expression was concomitant and colocalized suggesting polysialyated NCAM (polySia-NCAM). PolySia expression was significantly stronger in IDH1 mutated tumors than in IDH1 non-mutated (p = 0.001, chi-square test). There were no significant differences in polySia-NCAM between primary tumors or recurrences (p = n.s., chi-square test). PolySia positivity was associated with longer patient survival in relation to total tumor material (p = 0.020, log-rank test). Furthermore, when only glioblastomas were assessed, patients with positive polySia had significantly better prognosis (p = 0.006, log-rank test). In multivariate survival analysis, polySia was found to be an independent prognostic factor. PolySia was nearly absent in grade I pilocytic astrocytomas (1 immunopositive tumor of 82).ConclusionsExpression of polySia is common in adult grade II–IV astrocytomas, whereas it is nearly absent in pediatric grade I pilocytic astrocytomas. PolySia positivity is associated with longer survival rates in patients with a grade II–IV astrocytomas and also grade IV glioblastomas assessed separately. The results of this study suggest that IDH1 mutation may be associated with polySia expression pathways in malignant gliomas.

Peroxiredoxins and their expression in ependymomas

Aims Peroxiredoxins I–VI (Prxs) have recently been shown to have a role in the tumorigenesis of astrocytic brain tumours. In some tumour types they are associated with Nrf2 (transcription factor NF-E2-related factor), a sensor of oxidative stress, and DJ-1 (also known as PARK7), a protein known to stabilise Nrf2. Methods We investigated the immunohistochemical expression of Prxs I–VI, Nrf2 and DJ-1 in a total of 76 ependymomas and their relationship with clinicopathological features of these tumours. Results There was a significant expression of all Prxs except Prx IV in the ependymomas. Strong nuclear and cytoplasmic expression of Nrf2 could be detected in these tumours. Prx I expression was significantly associated with cytoplasmic and nuclear Nrf2 expression. Prx I expression was also associated with tumour site, with cerebellar ependymomas having a lower expression of Prx I than other tumours. DJ-1 did not associate with Prxs but nuclear DJ-1 had an inverse association with nuclear Nrf2. Cytoplasmic DJ-1 associated with worse survival in ependymoma patients. Conclusions This study indicates that oxidative mechanisms as reflected by Nrf2 expression are highly activated in ependymomas. Prxs, especially Prx I, were associated with Nrf2 expression, suggesting a role for Nrf2 in Prx I synthesis in ependymomas. While DJ-1 did not associate with any of the Prxs, its expression was associated with worsened patient survival and could have a role as a prognostic marker in ependymomas.

Carbonic Anhydrase IX in Adult and Pediatric Brain Tumors

Carbonic anhydrases (CAs) are zinc-containing metalloenzymes present in prokaryotes and eukaryotes (Sly and Hu 1995). CAs have been investigated since 1930 s (Meldrum and Roughton 1933). They are important in normal human physiology, e.g., in gluconeogenesis, lipogenesis, ureagenesis, bone resorption, and formation of gastric juice and cerebrospinal fluid (Sly and Hu 1995, Pastorekova et al. 2004). There are at least 15 members in human alphaCA family: Five active family members are cytosolic (CA I-III, VII, and XIII), four are membrane associated (CA IV, IX, XII, and XIV), two are mitochondrial (CA VA and VB), and one is a secretory form (CA VI). In addition, there are three acatalytic forms, which are called CArelated protein (CARPs). CAs can be categorized to catalytically active or inactive, intracellular or extracellular, and wide-spread or restricted to few tissues.