Chloroethylating nitrosoureas in cancer therapy: DNA damage, repair and cell death signaling.

Chloroethylating nitrosoureas (CNU), such as lomustine, nimustine, semustine, carmustine and fotemustine are used for the treatment of malignant gliomas, brain metastases of different origin, melanomas and Hodgkin disease. They alkylate the DNA bases and give rise to the formation of monoadducts and subsequently interstrand crosslinks (ICL). ICL are critical cytotoxic DNA lesions that link the DNA strands covalently and block DNA replication and transcription. As a result, S phase progression is inhibited and cells are triggered to undergo apoptosis and necrosis, which both contribute to the effectiveness of CNU-based cancer therapy. However, tumor cells resist chemotherapy through the repair of CNU-induced DNA damage. The suicide enzyme O6-methylguanine-DNA methyltransferase (MGMT) removes the precursor DNA lesion O6-chloroethylguanine prior to its conversion into ICL. In cells lacking MGMT, the formed ICL evoke complex enzymatic networks to accomplish their removal. Here we discuss the mechanism of ICL repair as a survival strategy of healthy and cancer cells and DNA damage signaling as a mechanism contributing to CNU-induced cell death. We also discuss therapeutic implications and strategies based on sequential and simultaneous treatment with CNU and the methylating drug temozolomide.

Cerebrospinal fluid ferritin--unspecific and unsuitable for disease monitoring.

BACKGROUND AND PURPOSE: Subarachnoid hemorrhage is sometimes difficult to diagnose radiologically. Cerebrospinal fluid (CSF) ferritin has been proposed to be highly specific and sensitive to detect hemorrhagic central nervous system (CNS) disease. We analyzed here the specificity of CSF ferritin in a large series of various CNS diseases and the influence of serum ferritin. MATERIALS AND METHODS: CSF ferritin, lactate, protein and total cell count were analyzed in 141 samples: neoplastic meningitis (n=62), subarachnoid hemorrhage (n=20), pyogenic infection (n=10), viral infection (n=10), multiple sclerosis (n=10), borreliosis (n=5) and normal controls (n=24). Cerebrospinal fluid ferritin was measured with a microparticle immunoassay. In addition, serum and CSF ferritin were compared in 18 samples of bacterial and neoplastic meningitis. RESULTS: In CNS hemorrhage, median ferritin was 51.55µg/L (sensitivity: 90%) after the second lumbar puncture. In neoplastic meningitis, the median CSF ferritin was 16.3µg/L (sensitivity: 45%). Interestingly, ferritin was higher in solid tumors than that in hematological neoplasms. In 90% of pyogenic inflammation, ferritin was elevated with a median of 53.35µg/L, while only 50% of patients with viral infection had elevated CSF ferritin. In ventricular CSF, median ferritin was 163µg/L, but only 20.6µg/L in lumbar CSF. Ferritin was normal in multiple sclerosis and borreliosis. CONCLUSIONS: Ferritin was elevated not only in hemorrhagic disease, but also in neoplastic and infectious meningitis. Ferritin was not a reliable marker of the course of disease. The influence of serum ferritin on CSF ferritin is negligible. We conclude that elevated CSF ferritin reliably, but unspecifically indicates severe CNS disease.

Temozolomide dosing regimens for glioma patients.

Even in modern times of high-precision brain surgery and irradiation, malignant gliomas belong to the deadliest types of cancer. Due to a marked primary and presumably also acquired resistance, the beneficial effects of cytotoxic chemotherapy are limited. Only one randomized clinical trial demonstrated a significant impact on overall survival with temozolomide. Ever since, there have been attempts to improve the efficacy of alkylating chemotherapy by modulating the distribution of dose in time aiming at a better treatment success. Apart from higher cumulative doses per cycle, better efficacy by depletion of the anti-alkylating O6-methylguanine-DNA methyltransferase (MGMT) protein has been a major goal of these regimens. After promising results of single-arm pilot studies, however, randomized studies have been disappointing so far. In this overview, the different strategies of dose-dense temozolomide regimen are highlighted and results of clinical trials put into perspective.

Reduced cortisol levels in cerebrospinal fluid and differential distribution of 11beta-hydroxysteroid dehydrogenases in multiple sclerosis: implications for lesion pathogenesis.

Relapses during multiple sclerosis (MS) are treated by administration of exogenous corticosteroids. However, little is known about the bioavailability of endogenous steroids in the central nervous system (CNS) of MS patients. We thus determined cortisol and dehydroepiandrosterone (DHEA) levels in serum and cerebrospinal fluid (CSF) samples from 34 MS patients, 28 patients with non-inflammatory neurological diseases (NIND) and 16 patients with other inflammatory neurological diseases (OIND). This revealed that MS patients - in sharp contrast to patients with OIND - show normal cortisol concentrations in serum and lowered cortisol levels in the CSF during acute relapses. This local cortisol deficit may relate to poor local activation of cortisone via 11beta-hydroxysteroid dehydrogenase type 1 (11bHSD1) or to inactivation via 11bHSD2. Accordingly, 11bHSD2 was found to be expressed within active plaques, whereas 11bHSD1 was predominantly detected in surrounding "foamy" macrophages. Our study thus provides new insights into the impaired endogenous CNS cortisol regulation in MS patients and its possible relation to MS lesion pathogenesis. Moreover, an observed upregulation of 11bHSD1 in myelin-loaded macrophages in vitro suggests an intriguing hypothesis for the self-limiting nature of MS lesion development. Finally, our findings provide an attractive explanation for the effectivity of high- vs. low-dose exogenous corticosteroids in the therapy of acute relapses.

Galectin-1 expression in human glioma cells: modulation by ionizing radiation and effects on tumor cell proliferation and migration.

Galectins are evolutionarily conserved beta-galactoside-binding lectins which recognize specific glycoconjugates on the cell surface and the extracellular matrix. Accumulating evidence indicates that these proteins are involved in a variety of physiological and pathological processes including tumor growth and metastasis. Up-regulated expression of galectin-1 is a hallmark of a variety of malignant tumors. Here, we examined the expression of galectin-1 in glioma cell lines, the influence of ionizing irradiation and the intracellular and extracellular effects of this protein on tumor cell proliferation and migration. Galectin-1 was detected in both A172 and U118 glioma cells by immunoblot analysis. Ionizing irradiation induced a statistically significant up-regulation in glioma cell lines. RNA-interference-mediated silencing resulted in a significant suppression of the proliferation of the A172 cells, while the addition of recombinant galectin-1 had no effect. On the other hand, the migratory capacity of both cell lines was reduced after galectin-1 down-regulation, and up-regulated by the addition of exogenous galectin-1. Our results provide evidence of a role for galectin-1 in the regulation of glioma cell proliferation and migration. While an intracellular mechanism seemed to prevail in galectin-1-mediated regulation of tumor cell proliferation, the control of cell migration was exerted by both intracellular and extracellular mechanisms. In addition, this protein was up-regulated by ionizing radiation, indicating that the blockade of this protein should be performed before radiotherapy to avoid any undesired stimulating effects. Given the multifactorial role of galectin-1 in the regulation of tumor escape and metastasis, we conclude that targeting galectin-1 may have therapeutic benefits in the treatment of malignant glioma.

Models of monocytic invasion into glioma cell aggregates.

BACKGROUND: In order to investigate why human gliomas are abundantly infiltrated by monocytic cells without signs of antitumor activity, experimental models were established in vitro and in vivo. MATERIALS AND METHODS: Peripheral human blood monocytes were added to A172 or U118 glioma cell spheroids and probes analyzed after 72 h by immunohistochemistry. Fluorescence-labelled peritoneal macrophages were administered to syngeneic RG2-glioma-bearing Fischer rats by intravenous or intracarotid injection. RESULTS: Spheroids of both cell lines were infiltrated by monocytes, which took on a chronic inflammatory phenotype with co-expression of MRP8 and MAC 387/MRP14 and positivity to 25F9, but not to 27E10. After both intra-arterial and intravenous injection, labelled monocytes accumulated within the tumor parenchyma of the rat gliomas, while the surrounding brain was only sparsely infiltrated. CONCLUSION: The experimental models described here allow for further investigation of the interactions between monocytes and glioma cells, both in vitro and in vivo. Moreover, monocytes that infiltrate from the peripheral blood into brain tumors may serve as carriers for targeted therapies.

Immune cell infiltration of intrinsic and metastatic intracranial tumours.

BACKGROUND: Immune escape is one prerequisite for the formation of neoplasms that is reflected by the pattern of immune cell infiltration. Abundant monocytic infiltration without apparent phagocytic activity is well known in human gliomas, while other types of human intracranial tumours have not yet been investigated. MATERIALS AND METHODS: We analysed LCA-positive lymphocytes and CD68-positive macrophages/microglia by immunohistochemistry in 67 intracranial neoplasms: 18 glioblastomas (GBM), 14 primitive neuroectodermal tumours and medulloblastomas (PNET), metastases of 9 adenocarcinomas and of 8 malignant melanomas, and 18 benign meningiomas. RESULTS: Levels of monocytic infiltration in GBM and adenocarcinomas were higher than in PNET and meningiomas. Lymphocytes were rare in all tested tumours. No differences were found between all malignant neoplasms and benign meningiomas and between primary intracranial and metastatic tumours. CONCLUSION: Malignancy or primary intracranial origin seem not to be major determinants of immune cell infiltration. Different patterns of cytokine production may explain the differences in single tumour entities.

Clinical response following adjuvant Temozolomide in a patient with primary cerebral lymphoma.

A 69-year-old female patient was treated for primary CNS-lymphoma (PCNSL) starting from August 2002. As her general condition allowed no high-dose methotrexate (MTX) therapy, radiotherapy was administered as a first-line treatment. CSF involvement could be managed by intrathecal Ara-C. Her general condition and cognitive status stabilized, but did not improve for 3 months. Therefore, oral chemotherapy with Temozolomide 200 mg/m2 was initiated. After two courses, which were tolerated without any problems, the patient's Karnofsky performance index had improved from 40% to 50%, the Mini-Mental Status rose from 16 to 27/30. The CSF-cell count was elevated again to 23 cells/l without signs of meningeal relapse. Unfortunately, the patient died unexpectedly from suspected pulmonary embolism. We conclude that adjuvant Temozolomide chemotherapy can improve the general condition and cognition in patients with PCNSL even when the general condition is poor. Long-term effects and neurotoxicity remain to be analysed in prospective trials, as well as the efficacy in leptomeningeal disease.

Glycobiology in malignant gliomas: expression and functions of galectins and possible therapeutic options.

Malignant gliomas, the most common malignant primary brain tumors, have a deleterious clinical prognosis of approximately 12 months in unselected series. The resistance against antineoplastic therapy is apparently not only associated with a high proliferative potential, marked antiapoptotic resistance and high migratory capacity. Effective mechanisms to escape the immune response of the organism and an intense neoangiogenesis also contribute to the aggressive growth of these neoplasms. In addition to a number of molecular mechanisms, the group of glycohydrate-binding galectins seems to contribute to the aggressive growth of malignant gliomas. Galectin-1, -3, -4 and -8 have been shown to be overexpressed in malignant gliomas. Galectin-1 is known to be involved in glioma cell migration and possibly also in proliferation. In this review, various aspects of glioma biology and their therapeutic relevance is discussed. The role of galectins in apoptosis-resistance, immune response and angiogenesis is discussed and explained why these molecules are interesting targets of glioma therapy.