Signals of apoptotic pathways in several types of meningioma.

Meningiomas are intracranial tumour derived from meningothelial cells, which aggressive behaviour has been frequently associated to cell apoptosis. In this paper activation of several factors involved in apoptosis has been investigated on biopsies of primary, non recurrent meningiomas. Benign (meningotheliomatous, transitional, fibrous, angiomatous), atypical and anaplastic meningiomas were analysed by immunohistochemistry and western blot, to visualize the occurring of different apoptotic pathways and their association with clinical grading. Apoptotic cell have been detected by a double colorimetric staining for TUNEL and caspase-3 active form. Apoptotic signal positive cells have been detected in all type of meningiomas analysed, with exception of meningotheliomatous meningiomas. Differences have been found in the activation of apoptotic pathways between several types of grade I meningiomas and among benign, anaplastic and atypical meningiomas. An intense expression of several apoptotic inhibitor occurred in grade I meningiomas. The correlation among expression of apoptotic and inhibitory factors and cell proliferation index may suggest that in grade I meningiomas apoptosis may be related to mechanisms involved into tumor cells surviving. Instead in grade II and III meningiomas the same correlation seems indicate an high turnover of tumor cells that might be useful as index of cell proliferation and tumor mass growth.

Different apoptosis modalities in periprosthetic membranes.

This study reports on an investigation into apoptotic and proliferation signals in leukocyte and membrane fibroblasts in periprosthetic membranes collected during revision surgery for loosened total hip joint arthroplasty. Cementless and cemented prosthesis were studied under both aseptic and septic conditions. Fluorescence colocalization immunohistochemistry and colorimetric immunohistochemistry were used to investigate cell death signals. In aseptic cementless prosthesis macrophages and membrane fibroblasts show high bax signal, implying the occurrence of toxic/oxidative cell death caused by the debris of titanium alloy metal implant. Instead in aseptic cemented prosthesis only a moderate number of apoptotic leukocytes were observed, whilst the fibroblasts were affected by a diffuse apoptotic-like cell death, the Co-Cr ions debris released from cemented stem, may be at basis of apoptotic cell death induction. Furthermore cement debris is recognized to induce macrophages to produce cytokine, that may be responsible for the cell death observed and implant failure. The septic environment seems to protect leukocytes cell death. Septic cementless prosthesis showed only a few apoptotic leukocytes, instead fibroblasts remain affected by cell death signals. Similarly in septic cemented prosthesis, scanty apoptotic leukocytes were detected, whereas membrane fibroblasts showed an increase in proliferation index (Ki-67) along with caspase-3 activation. These findings indicate some kind of caspase-3 involvement in tissue proliferation, rather than in cell death pathway. Apoptotic periprosthetic sites have been interpreted as signs of inflammation resolution and normal tissue turnover. Nevertheless apoptosis may also be a sign of cell renewal associated to tissue proliferation.

Activation of caspase-8 triggers anoikis in human neuroblastoma cells.

Cells require appropriate interaction with extracellular matrix proteins mediated by integrins to grow, differentiate and survive. Many cell types including nervous cells undergo anoikis, a substrate-dependent apoptosis, when adhesion is impaired. Resistance of tumors to cytotoxic drugs is probably due to disturbed apoptosis programs. The proteolytic enzymes caspases are the main executioners of apoptosis. It was reported that caspase-8 expression is deficient in some neuroblastoma cells. We demonstrated that human neuroblastoma cell line SK-B-BE, differentiated with retinoic acid, expressed caspases 3, 8 and 9. Caspases 8 and 3, but not caspase-9 were activated in SK-N-BE cells cultured in suspension or on aspecific adhesive substrate. Cell positive to caspase-8 were classified into four stages, by morphometric and densitometric parameters. The use of the specific caspase-8 inhibitor Z-IETD-FMK dramatically reduced apoptosis, demonstrating that caspase-8 is the upstream initiator caspase during SK-N-BE cells anoikis. Among matrix proteins, type I collagen is the most effective and fibronectin the least in delaying anoikis. The activation of caspases 8 and 3 by unligated integrins was dependent on the state of neuronal differentiation, since the most differentiated cell was the most vulnerable to anoikis. These data show that activation of caspase-8 is specifically required to promote anoikis in SK-N-BE neuroblastoma cells.