title: Toward understanding recurrent meningioma: the potential role of lysosomal cysteine proteases and their inhibitors.
abstract: OBJECTIVE
  The first aim of this study was to diagnose more aggressive and potentially recurrent meningiomas using an in vitro embryonic chick heart invasiveness assay in which lysosomal enzyme cathepsin B was used as the invasiveness marker. The second aim was to confirm if cathepsin B and/or cathepsin L and their endogenous inhibitors were also prognostic parameters in the clinical study of 119 patients with meningioma.
  
  
  METHODS
  Primary meningioma cultured spheroids were "confronted" with embryonic chick heart spheroids in vitro, and cathepsin B was used as molecular marker to immunolabel the invasive tumor cells. In vitro invasion assays of the malignant meningioma cells were used to assess the invasive potential related to the cysteine cathepsins. As to the second aim, the possible association of cathepsin B along with selected molecular markers, cathepsin L, and endogenous cysteine protease inhibitors (stefins A and B and cystatin C) with meningioma malignancy was determined using enzyme-linked immunosorbent assays in tumor homogenates. Univariate and multivariate analyses were used to compare these parameters with established biological markers of meningioma recurrence in 119 patients with meningiomas.
  
  
  RESULTS
  The more invasive tumors, which characteristically overgrew the normal tissue, were identified even within a group of histologically benign meningiomas. More intensive staining of cathepsin B in these tumors was not only found at the tumor front, but also in the invading pseudopodia of a single migrating tumor cells. Matrigel invasion of malignant meningioma cells was significantly altered by modulating cathepsin B activity and by stefin B silencing. In the clinical samples of meningioma, the levels of cathepsins B and L, stefin B, and cystatin C were highest in the tumors of higher histological grades, whereas stefin A and progesterone receptor were the only markers that were significantly increased and decreased, respectively, in WHO Grade III lesions. With respect to the prognosis of relapse, cathepsin L (p = 0.035), stefin B (p = 0.007), cystatin C (p = 0.008), and progesterone receptor (p = 0.049) levels were significant, whereas cathepsin B was not a prognosticator. As expected, WHO grade, age, and Simpson grade (complete tumor resection) were prognostic, with Simpson grade only relevant in the short term (up to 90 months) but not in longer-term follow-up. Of note, the impact of all these parameters was lost in multivariate analysis, due to overwhelming prognostic impact of stefin B (p = 0.039).
  
  
  CONCLUSIONS
  The data indicate that the cysteine cathepsins and their inhibitors are involved in a process related to early meningioma recurrence, regardless of their histological classification. Of note, the known tumor invasiveness marker cathepsin B, measured in whole-tumor homogenates, was not prognostic, in contrast to its endogenous inhibitor stefin B, which was highly significant and the only independent prognostic factor to predict meningioma relapse in multivariate analysis and reported herein for the first time. Stefin B inhibition of local invasion was confirmed by in vitro invasion assay, although its other functions cannot be excluded.
authors.affiliation: Department of Genetic Toxicology and Cancer Biology, National Institute of Biology, Ljubljana, Slovenia. tamara.lah@nib.si
authors.forename: Tamara T
authors.initials: TT
authors.lastname: Lah
authors.forename: Isabelle
authors.initials: I
authors.lastname: Nanni
authors.forename: Miha
authors.initials: M
authors.lastname: Trinkaus
authors.forename: Philipe
authors.initials: P
authors.lastname: Metellus
authors.forename: Christophe
authors.initials: C
authors.lastname: Dussert
authors.forename: Leo
authors.initials: L
authors.lastname: De Ridder
authors.forename: Uros
authors.initials: U
authors.lastname: Rajcević
authors.forename: Andrej
authors.initials: A
authors.lastname: Blejec
authors.forename: Pierre-Marie
authors.initials: PM
authors.lastname: Martin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology*; D002401:Cathepsin B / Q000235:genetics; D055312:Cystatin A / Q000235:genetics; D055313:Cystatin B / Q000235:genetics; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use*; D005260:Female; D020868:Gene Silencing; D006801:Humans; D008247:Lysosomes / Q000187:drug effects*; D008297:Male; D008579:Meningioma / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology*; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D009367:Neoplasm Staging; D019635:Neurosurgical Procedures; D014944:World Health Organization; D055815:Young Adult
chemical_list: C524994:CSTB protein, human; D055312:Cystatin A; D015853:Cysteine Proteinase Inhibitors; D055313:Cystatin B; C533912:CTSB protein, human; D002401:Cathepsin B