Chemotherapeutic agents sensitize osteogenic sarcoma cells, but not normal human bone cells, to Apo2L/TRAIL-induced apoptosis

Inflammatory T cells rapidly induce differentiation of human bone marrow stromal cells into mature osteoblasts

Activated T cells secrete multiple osteoclastogenic cytokines which play a major role in the bone destruction associated with rheumatoid arthritis. While the role of T cells in osteoclastogenesis has received much attention recently, the effect of T cells on osteoblast formation and activity is poorly defined. In this study, we investigated the hypothesis that in chronic inflammation activated T cells contribute to enhanced bone turnover by promoting osteoblastic differentiation. We show that T cells produce soluble factors that induce alkaline phosphatase activity in bone marrow stromal cells and elevated expression of mRNA for Runx2 and osteocalcin. This data indicate that T cell derived factors have the capacity to stimulate the differentiation of bone marrow stromal cells into the osteoblast phenotype. RANKL mRNA was undetectable under any conditions in highly purified bone marrow stromal cells. In contrast, RANKL was constitutively expressed in primary osteoblasts and only moderately up-regulated by activated T cell conditioned medium. Interestingly, both bone marrow stromal cells and osteoblasts expressed mRNA for RANK, which was strongly up-regulated in both cell types by activated T cell conditioned medium. Although, mRNA for the RANKL decoy receptor, osteoprotegerin, was also up-regulated by activated T cell conditioned medium, it's inhibitory effects may be mitigated by a simultaneous rise in the osteoprotegerin competitor TNF-related apoptosis-inducing ligand. Based on our data we propose that during chronic inflammation, T cells regulate bone loss by a dual mechanism involving both direct stimulation of osteoclastogenesis, by production of osteoclastogenic cytokines, and indirectly by induction of osteoblast differentiation and up-regulation of bone turnover via coupling.

Localization of TRAIL/TRAILR in fetal pancreas

AIM: To observe the localization of TRAIL/TRAIR (DR4, DR5, DcR1, DcR2) in the fetal pancreas.

METHODS: Fetal pancreas of 32 wk of pregnancy were obtained from induced abortions, embedded in paraffin, and 4-μm sections were prepared. The localization of TRAIL/TRAILR in fetal pancreas was investigated by fluorescence immunohistochemical method combined with laser scanning confocal microscopy.

RESULTS: TRAIL immunoreactive cells were mainly located on the periphery of the pancreas islets. There were a few DcR1 and DcR2 positive cells whereas there were no immunoreactive cells of DR4 and DR5 in the pancreas islets. In the acini and the ducts of the exocrine pancreas there were no TRAIL/TRAILR immunoreactive cells.

CONCLUSION: This study not only describes the distribution of TRAIL/TRAILR in the fetal pancreas, but also provides a morphological basis for deducing the function of TRAIL/TRAILR in pancreas, suggesting that in normal pancreatic islets, the pancreatic cells are resistant towards apoptosis too.

In vivo selective and distant killing of cancer cells using adenovirus-mediated decorin gene transfer

Decorin is a well-known, ubiquitous proteoglycan that is a normal component of the ECM. Upon transgenic expression of decorin, tumor cells with diverse histogenetic background overexpress p21WAF1, a potent inhibitor of cyclin-dependent kinase activity, become arrested in G1, and fail to generate tumors in immunocompromised animals. Because decorin is a secreted protein, it has been recently suggested that decorin could act as an autocrine and paracrine regulator of tumor growth. Here, we demonstrate that adenovirus (Ad)-mediated transfer and expression of human decorin cDNA induced in vivo apoptosis of xenograft tumor cells in nude mice. This oncolytic activity was observed when the Ad vector encoding the decorin cDNA was injected intratumorally (i.t.) or i.v. Importantly, i.t. injection of the decorin Ad vector led to growth inhibition of the injected tumor associated with similar growth inhibition of a distant contralateral tumor, demonstrating a distant decorin antitumoral effect. Immunochemistry against human decorin and decorin quantitation in tumors confirmed that decorin migrated to the tumor distant site. Furthermore, decorin effect was specific to tumor cells, because neither apoptosis nor growth inhibition were observed in nontumoral human cells such as hepatocytes, endothelial cells, and fibroblasts, despite p21 overexpression.

Human osteoblasts are resistant to Apo2L/TRAIL-mediated apoptosis

Apo2 ligand (Apo2L/TRAIL) is a member of the tumor necrosis factor (TNF) cytokine family. Apo2L/TRAIL can selectively induce programmed cell death in transformed cells, although its wide tissue distribution suggests potential physiological roles. We have investigated the expression, in human osteoblast-like cells (NHBC), of Apo2L/TRAIL and the known Apo2L/TRAIL death receptors, DR4 and DR5, and the Apo2L/TRAIL decoy receptors, DcR-1, DcR-2, and osteoprotegerin (OPG). NHBC expressed abundant mRNA corresponding to each of these molecular species. Immunofluorescence staining demonstrated that Apo2L/TRAIL protein was abundant within the cytoplasm of NHBC and OPG was strongly expressed at the cell surface. DR5 and DcR-2 were present in the cell membrane and cytoplasm and DcR-1 was confined to the nucleus. DR4 staining was weak. Neither Apo2L/TRAIL alone, nor in combination with chemotherapeutic agents of clinical relevance to treatment of osteogenic sarcoma, induced cell death in NHBC, as assessed morphologically and by activation of caspase-3. In contrast, the human osteogenic sarcoma cell lines, BTK-143 and G-292, were sensitive to exogenous Apo2L/TRAIL alone, and to the combined effect of Apo2L/TRAIL/cisplatin and Apo2L/TRAIL/doxorubicin treatments, respectively. In NHBC, we observed strong associations between the levels of mRNA corresponding to the pro-apoptotic molecules, Apo2L/TRAIL, DR4, and DR5, and those corresponding to pro-survival molecules, DcR-1, DcR-2, OPG, and FLIP, suggesting that the balance between pro-survival and pro-apoptotic molecules is a mechanism by which NHBC can resist Apo2L/TRAIL-mediated apoptosis. In contrast, osteogenic sarcoma cells had low or absent levels of DcR-1 and DcR-2. These results provide a foundation to explore the role of Apo2L/TRAIL in osteoblast physiology. In addition, they predict that therapeutic use of recombinant Apo2L/TRAIL, in combination with chemotherapeutic agents to treat skeletal malignancies, would have limited toxic effects on normal osteoblastic cells.

[Haptoglobin and orosomucoid in the blood in a case of congenital afibrinogenemia and in the family of the patient]

Background

TRAIL (tumor necrosis factor related apoptosis inducing ligand) is an apoptosis inducing ligand with high specificity for malignant cell systems. Combined treatment modalities using TRAIL and cytotoxic drugs revealed highly additive effects in different tumour cell lines. Little is known about the efficacy and underlying mechanistic effects of a combined therapy using TRAIL and ionising radiation in solid tumour cell systems. Additionally, little is known about the effect of TRAIL combined with radiation on normal tissues.

Methods

Tumour cell systems derived from breast- (MDA MB231), lung- (NCI H460) colorectal- (Colo 205, HCT-15) and head and neck cancer (FaDu, SCC-4) were treated with a combination of TRAIL and irradiation using two different time schedules. Normal tissue cultures from breast, prostate, renal and bronchial epithelia, small muscle cells, endothelial cells, hepatocytes and fibroblasts were tested accordingly. Apoptosis was determined by fluorescence microscopy and western blot determination of PARP processing. Upregulation of death receptors was quantified by flow cytometry.

Results

The combined treatment of TRAIL with irradiation strongly increased apoptosis induction in all treated tumour cell lines compared to treatment with TRAIL or irradiation alone. The synergistic effect was most prominent after sequential application of TRAIL after irradiation. Upregulation of TRAIL receptor DR5 after irradiation was observed in four of six tumour cell lines but did not correlate to tumour cell sensitisation to TRAIL. TRAIL did not show toxicity in normal tissue cell systems. In addition, pre-irradiation did not sensitise all nine tested human normal tissue cell cultures to TRAIL.

Conclusions

Based on the in vitro data, TRAIL represents a very promising candidate for combination with radiotherapy. Sequential application of ionising radiation followed by TRAIL is associated with an synergistic induction of cell death in a large panel of solid tumour cell lines. However, TRAIL receptor upregulation may not be the sole mechanism by which sensitation to TRAIL after irradiation is induced.