Figure 1. Immunohistochemistry of brain and glioblastoma multiforme IV WHO. A) Normal Brain, autopsy 3 (right parietal lobe); B) Glioblastoma multiforme IV WHO, case 1 (right parietal lobe); A and B hematoxylin counterstain; scale bar: 80 mm). protein may be used as a cell marker. Indeed, previous studies13,14 found the expression of PARP-1 in brain whit GBM, in normal brain and in nucleus and cytoplasm of human neu- rons, also Wharton et al. 200015 have observed expression of PARP-1 in multicellular tumour spheroids, derived from human glioma cell lines. PARP-1 gene plays a significant role in cell death both in cell necrosis and in apoptosis. Massive DNA damage that typically results from necrotic stimuli elicits a major increase of PARP-1 activity, which rapidly depletes the intracellular concentration of nicotine adenine dinucleotide (NAD+) and ATP. Increased con- sumption of ATP, in the effort to re-synthesize NAD+, leads to energy crisis culminating in cell death.16 This may in part justify the presence of PARP-1 protein in GBMs and in other tumors, such as ovarian, endometrial, lung, breast, skin cancers, and non-Hodgkin’s lym- phoma,11 as well as in a patients with Parkinson disease and multiple head and neck squamous cell in whom we recently reported an increased PARP-1 mRNA expression.17 The understanding of the mechanism that activates the expression of PARP-1 gene requires significant further work to character- ize its inter-domain interactions and its DNA- dependence, both at a structural and a func- tional level.18 Nonetheless, Eustermann and colleagues provided valuable insights into recognition of chromosomal DNA single-strand breaks, the crucial first step of the activation process, by PARP-1 DNA binding domain.18 In fact, PARP-1 is a highly abundant chromatin- associated enzyme present in all higher eukaryotic cell nuclei, where it plays key roles in maintenance of genomic integrity, chro- matin remodeling, and transcriptional control. PARP-1 gene product binds to DNA single- and double-strand breaks through an N-terminal region containing two zinc fingers, F1 and F2. The C-terminal catalytic domain of the PARP-1 protein is activated via an unknown mecha- nism, causing formation and addition of the poly (adenosine diphospho-ribose) complex to acceptor proteins including PARP-1 itself.19 Several reports from various laboratories indicate that inhibition or absence of PARP-1 provides remarkable protection in disease models, such as septic shock, diabetes, stroke, myocardial infarction, and ischemia, which are characterized predominantly by pro- grammed-necrotic cell death.20 In addition, PARP-1 activation has been causally connected to photoreceptor cell death;21 this observation has more recently been confirmed by other authors,22 who showed a causal involvement of PARP-1 in retinal degeneration, a neurodegen- erative diseases affecting photoreceptors and causing blindness in humans. Some authors, besides, observed that poly(ADP-ribose) poly- merase-1 inhibitor, increases the antitumor activity against intracranial melanoma, glioma, lymphoma, hematological neo- plasias;23-25 these data suggest the potential role that could have PARP-1 inhibitors in the therapy against glioblastoma. Activation of PARP-1 in response to DNA damage is an important mechanism to keep homeostasis or to trigger apoptosis. The expression and function of PARP-1 has been studied in primary human lung cell cultures from normal human bronchial epithelial cells (NHBEC) and peripheral lung cells (PLC) from lung cancer patients grown as explant cultures over a period of 12 weeks. PARP-1 protein was expressed in all the cell culture derived from bronchial epithelium explants.26 Overall, recent data on PARP-1 agree on the meaning of this gene expression in tumors. Accordingly, the results of this study indicate that PARP-1 gene may play a role in GBMs. In conclusion, PARP-1 protein (with this antibody) is detectable in the nuclei of all GBM cells, but is undetectable in normal cells. Given the role of PARP-1 protein in cell death (both necrosis and apoptosis) and in DNA repair mechanisms, it may be hypothesized that the presence of PARP-1 protein in the nucleus of the GBM is an attempt to trigger apoptosis in this type of tumor as well as in many other can- cers.11,17 In the context of the tumor biology, this may be envisioned as a defense mecha- nism regardless of the outcome on the progno- sis of patients with GBM. Finally, the evidence Brief Report that PARP-1 positive staining is exclusively present within the nucleus adds further evi- dence for the above-mentioned role played by this protein. References 1. Furnari FB, Fenton T, Bachoo RM, Mukasa A, Stommel JM, Stegh A et al. Malignant astrocytic glioma: genetics, biology, and paths to treatment. Genes Dev 2007;21:2683-10. 2. Lang FF, Miller DC, Koslow M, Newcomb EW. Pathways leading to glioblastoma mul- tiforme: a molecular analysis of genetic alterations in 65 astrocytic tumors. J Neurosurg 1994;81:427-36. 3. Kleihues P, Ohgaki H. Primary and second- ary glioblastomas: from concept to clinical diagnosis. Neuro-Oncol 1999;1:44-51. 4. Kleihues P, Burger PC, Scheithauer BW. The new WHO classification of brain tumors. Brain Pathol 1993;3:255-68. 5. Rasheed BK, Wiltshire RN, Bigner SH, Bigner DD. Molecular pathogenesis of malignant gliomas. Curr Opin Oncol 1999;11:162-67. 6. Grube K, Bürkle A. A Poly(ADP-ribose) polymerase activity in mononuclear leuko- cytes of 13 mammalian species correlates with species-specific life span. Proc Natl Acad Sci USA 1992;89:1175-63. 7. Yu SW, Wang H, Poitras MF, Coombs C, Bowers WJ, Federoff HJ. et al. Mediation of poly(ADP-ribose) polymerase-1-depend- ent cell death by apoptosis-inducing factor. Science 2002;297:259-63. 8. Andrabi SA, Kim NS, Yu SW. Poly(ADP- ribose) (PAR) polymer is a death signal.Proc Natl Acad Sci USA 2006;103:18308-13. 9. Yu SW, Andrabi SA, Wang H. Apoptosis- inducing factor mediates poly (ADP- ribose) (PAR) polymer-induced cell death. Proc Natl Acad Sci USA 2006;103:18314-9. 10. Hassa PO, Hottiger MO. The diverse bio- logical roles of mammalian PARPs, a small but powerful family of poly-ADP-ribose polymerases. Front Biosci 2008;13:3046- 82. 11. Ossovskaya V, Koo IC, Kaldjian EP, Alvares C, Sherman BM. Upregulation of poly(ADP-ribose) polymerase-1 (PARP1) in triple-negative breast cancer and other primary human tumor types. Genes Cancer 2010;8:812-21. 12. Salemi M, Calogero AE, Zaccarello G, Castiglione R, Cosentino A, Campagna C. et al. Expression of SPANX proteins in nor- mal prostatic tissue and in prostate cancer. Eur J Histochem 2010;54:e41. 13. Kase M, Vardja M, Lipping A, Asser T, Jaal [European Journal of Histochemistry 2012; 56:e9] [page 47]