Proteomic signatures corresponding to histological classification and grading of soft-tissue sarcomas

We performed a global protein expression study on soft-tissue sarcoma in order to develop novel diagnostic biomarkers and allow molecular classification. 2-D difference gel electrophoresis was used to generate the global protein expression profiles of 80 soft-tissue sarcoma samples with seven different histological backgrounds. We found that 67 protein spots distinguished the subtypes of soft-tissue sarcoma. Hierarchical clustering with these 67 protein spots resulted in the grouping of all 80 sarcoma samples corresponding to the histological classification. We found that the expression pattern of tropomyosin isoforms was different in conventional and pleomorphic leiomyosarcomas. We also identified five proteins, including alpha-1-antitrypsin, alpha-actinin 1, HSP27, and elongation factor 2, that could differentiate between malignant fibrous histiocytomas and leiomyosarcomas in grade III into low-risk and high-risk groups, which differed significantly with respect to survival. These results establish proteomics as a powerful tool to develop novel biomarkers for diagnosis and molecular classification of soft-tissue sarcomas. Identification of proteins associated with survival in grade III sarcoma will allow delineation of a high-risk group that may benefit from adjuvant therapy and the exclusion of low-risk patients in whom additional therapies are unlikely to exhibit clinical benefit.     

Enrichment of regulatory CD4(+)CD25(+) T cells by inhibition of phospholipase D signaling

Antigen stimulation of lymphocytes induces upregulation of phospholipase D (PLD) activity, but the biological significance of PLD-mediated signaling in T cells has not been well established. Here we demonstrate that PLD signaling is essential for proliferation of mouse CD8(+) T cells and CD4(+)CD25(-) T cells, but is not required for proliferation of CD4(+)CD25(+) regulatory T cells. We exploited this observation to develop an efficient method to enrich for regulatory T cells starting from preparations of total CD4(+) T lymphocytes. Inhibition of PLD signaling blocked effector T-cell proliferation after T cell-antigen receptor (TCR) engagement, but had no significant effect on the proliferation of CD4(+)CD25(+) T cells with regulatory functions. Consequently, cells expanded in vitro for one week by antigen receptor stimulation with PLD signal inhibition were markedly enriched for regulatory T cells.     

Low growth ability of recent influenza clinical isolates in MDCK cells is due to their low receptor binding affinities

Madin Darby canine kidney (MDCK) cells have generally been used to isolate influenza viruses from patients. However, in recent years, most fresh isolates of the H3N2 subtype have shown poor growth in MDCK cell cultures. Such low-growth viruses were often converted to high-growth viruses after several passages through MDCK cell cultures. In the present study, viruses were found to lose a potential glycosylation site near the receptor-binding pocket of hemagglutinin (HA), at the same time as they acquired the high-growth property. The growth curves of viruses in MDCK cell cultures revealed that multi-cycle replication did not function well in the low-growth viruses. However, the production of progeny viruses within a single cycle of growth did not differ much between the low- and high-growth viruses. The high-growth viruses showed higher infection efficiency in MDCK cell cultures than the low-growth viruses. The HA genes of both low- and high-growth viruses were separately cloned into the SV40 vector to compare their receptor binding affinities. The HA of high-growth viruses showed a much higher receptor binding affinity than that of low-growth viruses, when assayed by hemadsorption and the release kinetics of erythrocytes with bacterial neuraminidase. Reverse genetics studies demonstrated that HA was a crucial determinant for multi-cycle replication in MDCK cell cultures. Taken together, these results demonstrate that inefficient multi-cycle growth of fresh isolates is due to their low receptor binding affinities.     

Hydrogen peroxide-induced apoptosis in HL-60 cells requires caspase-3 activation

Apoptosis has been associated with oxidative stress in biological systems. Caspases have been considered to play a pivotal role in the execution phase of apoptosis. However, which caspases function as executioners in reactive oxygen species (ROS)-induced apoptosis is not known. The present study was performed to identify the major caspases acting in ROS-induced apoptosis. Treatment of HL-60 cells with 50 μM hydrogen peroxide (H₂O₂) for 4 h induced the morphological changes such as condensed and/or fragmented nuclei, increase in caspase-3 subfamily protease activities, reduction of the procaspase-3 and a DNA fragmentation. To determine the role of caspases in H₂O₂-induced apoptosis, caspase inhibitors, acetyl-Tyr-Val-Ala-Asp-chloromethyl ketone(Ac-YVAD-cmk), acetyl-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO) and acetyl-Val-Glu-lle-Aspaldehyde (Ac-VEID-CHO), selective for caspase-1 subfamily, caspase-3 subfamily and caspase-6, respectively, were loaded into the cells using an osmotic lysis of pinosomes method. Of these caspase inhibitors, only Ac-DEVD-CHO completely blocked morphological changes, caspase-3 subfamily protease activation and DNA ladder formation in H₂O₂-treated HL-60 cells. This inhibitory effect was dose-dependent. These results suggest that caspase-3, but not caspase-1 is required for commitment to ROS-triggered apoptosis.     

The introduction of dominant-negative p53 mutants suppresses temperature shift-induced senescence in immortal human fibroblasts expressing a thermolabile SV40 large T antigen

Immortal human fibroblasts, SVts8 cells, which express a heat-labile SV40 large T antigen, induces a senescence-like phenomenon in response to upward shift in temperature. Cells with arrested division show strong induction of senescence-associated beta-galactosidase. We examined how p53 and pRB are involved in this phenomenon since they are major targets of the T antigen. Transfection of cells with plasmids encoding the wild-type T antigen or human papilloma virus type 16 E6/E7 proteins completely abolished the arrest in cell division, a plasmid encoding the E6 protein suppressed it markedly, while a plasmid encoding E7 had no effect. Plasmids encoding dominant-negative p53 mutants also suppressed the arrest in cell division to various degrees. Upon temperature shift, p21 mRNA was upregulated 10-fold in SVts8 cells, but only slightly in clones expressing the wild-type T antigen or dominant-negative p53 mutants. These data demonstrate that p53 plays a major role in this senescence-like phenomenon.     

Reconstitution of Btk signaling by the atypical tec family tyrosine kinases Bmx and Txk

Bruton's tyrosine kinase (Btk) is mutated in X-linked agammaglobulinemia patients and plays an essential role in B cell receptor signal transduction. Btk is a member of the Tec family of nonreceptor protein-tyrosine kinases that includes Bmx, Itk, Tec, and Txk. Cell lines deficient for Btk are impaired in phospholipase C-gamma2 (PLCgamma2)-dependent signaling. Itk and Tec have recently been shown to reconstitute PLCgamma2-dependent signaling in Btk-deficient human cells, but it is not known whether the atypical Tec family members, Bmx and Txk, can reconstitute function. Here we reconstitute Btk-deficient DT40 B cells with Bmx and Txk to compare their function with other Tec kinases. We show that in common with Itk and Tec, Bmx reconstituted PLCgamma2-dependent responses including calcium mobilization, extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) activation, and apoptosis. Txk also restored PLCgamma2/calcium signaling but, unlike other Tec kinases, functioned in a phosphatidylinositol 3-kinase-independent manner and failed to reconstitute apoptosis. These results are consistent with a common role for Tec kinases as amplifiers of PLCgamma2-dependent signal transduction, but suggest that the pleckstrin homology domain of Tec kinases, absent in Txk, is essential for apoptosis.