Heat induced expression of CD95 and its correlation with the activation of apoptosis upon heat shock in rat histiocytic tumor cells

AbstractThe heat shock response is a universal phenomenon and is among the most highly conserved cellular responses. However, BC-8, a rat histiocytoma, fails to mount a heat shock response unlike all other eukaryotic cells. In the absence of induction of heat shock proteins, apoptotic cell death is activated in BC-8 tumor cells upon heat shock. We demonstrate here that stable transformants of BC-8 tumor cells transfected with hsp70 cDNA constitutively express hsp70 protein and are transiently protected from heat induced apoptosis for 6–8 h. In addition heat stress induces CD95 gene expression in these tumor cells. There is a delay in CD95 expression in hsp70 transfected cells suggesting a correlation between the cell surface expression of CD95 and the time of induction of apoptosis in this tumor cell line. Also expression of CD95 antigen appears to inhibit the interaction between heat shock factors and heat shock elements in these cells resulting in the lack of heat shock response

Apoptosis: An Overview

58-72Apoptosis, a highly ordered cascade of enzymatic events that culminates in cell death and entails the autolytic degradation of cellular components, is characterized by blebbing of cell membrane, nuclear and cytoplasmic condensation, protein fragmentation and DNA degradation followed by rapid engulfment of cell corpses by neighbouring cells. It is essential for maintenance of cellular homeostasis and deregulation of this process leads to a spectrum of pathological manifestations. Caspases, which form the proteolytic network within the cell are among the critical components of cell death process. They bring about the cleavage and degradation of a number of proteins that result in cell demise. Mitochondria are regarded as the central control point in the execution of apoptosis. They release a potent cocktail of pro-apoptotic proteins into the cytosol, which results in the amplification of the death cascade, the most prominent one being cytochrome c. The mechanism by which cytochrome c is released into the cytosol is controversial but seems to be regulated by the Bcl-2 family of proteins

Enzyme-linked immunolysis assay for tumour-specific surface antigens

Expression of the activity of the cytosolic enzyme lactate dehydrogenase released on cell lysis by tumour specific antibodies in the presence of complement was investigated by direct assay of the expression of the occluded enzyme tumour cell suspensions. This method, called Enzyme Linked Immunolysis assay (ELILA) was shown to be more sensitive than conventional cytotoxic assays. The data fit well in the linear regression model, so that the technique can be used for quantitation of the antibody titres

Dendritic cells as natural adjuvants and modulators of immune response in cancer immunotherapy

363-367Dendritic cells (DCs) are potent antigen presenting cells. Mature DCs activate antigen specific naїve T cells B cells and NK cells. Under certain conditions, DCs even silence T cell immune responses in vivo, thus, modulating the 'immune response. This special function of DCs could be exploited in the treatment of cancer, autoimmune disorder and chronic viral infections

Differential modulation of nitric oxide production by curcumin in host macrophages and NK cells

AbstractCurcumin, the yellow pigment from Curcuma longa, has been shown to possess tumoricidal activity. We have earlier reported the induction of apoptosis in AK-5, rat histiocytic cells by curcumin leading to the inhibition of tumor growth in vivo. In this study we have observed differential activation status in host macrophages and NK cells induced by curcumin during the spontaneous regression of subcutaneously transplanted AK-5 tumors. Closer scrutiny of the cytokine profile and nitric oxide (NO) production by immune cells showed an initial downregulation of Th1 cytokine response and NO production by macrophages, and their upregulation in NK cells, which picked-up upon prolonged treatment with curcumin, culminating in a stronger tumoricidal effect. These studies suggest that the host macrophages and NK cells play an important modulatory role in the remission of AK-5 tumor

Downregulation of phospho-tyrosine phosphatases in a macrophage tumor

AbstractWe provide evidence for the downregulation of phospho-tyrosine phosphatases (PTPases) in malignancy. AK-5, a rat macrophage tumor, shows the downregulation of the transcripts of two non-receptor-type PTPases, PTP-1 and PTP-S. Though downregulated fourfold, the genomic organization of PTP-S is unaltered. There is no gross alteration of the PTPase activity in AK-5 as compared to macrophages. Immunoblot analysis reveals no significant change in the total phospho-tyrosine levels in AK-5, but there is a qualitative difference in the pattern between AK-5 and macrophages. Our results lend credence to the conjecture that PTPases also might be involved in malignancy

Activating and inhibitory receptors and their role in Natural Killer cell function

291-299Last decade has seen a significant advancement in our understanding of the Natural Killer (NK) cell biology and function. Several receptors present on NK cells have been identified, which are involved in either their activation or inhibition. Similarly, a large number of interacting ligands have been identified on the target cells that upon interaction transmit either activating or inhibitory signals. This review is oriented towards understanding the role of these receptors on the NK cells, which are considered as the first line of defense

Subcellular localization and physiological consequences of introducing a mitochondrial matrix targeting signal sequence in bax and its mutants

Bax, a proapoptotic member of the Bcl-2 family of proteins, resides in the cytosol and translocates to the mitochondrial membrane upon induction of apoptosis. It has been proposed that Bax does not translocate to mitochondria under normal physiological conditions, due to interaction between amino (ART) and carboxy (TM) terminal domains. Here, we report the physiological consequences of introducing a matrix targeting mitochondrial signal sequence (Su9) at the amino terminus of Bax and its mutants lacking ART, TM, or both segments. In vitro mitochondrial protein import assays of the fusion proteins suggests localization to the mitochondrial matrix. When expressed in Cos-1 cells, Su9 could target Bax to mitochondria in the absence of an apoptotic stimulus. However, mitochondrial localization did not result in apoptosis. When ART, TM, or both segments of Bax were deleted, expression of fusion proteins containing Su9 resulted in apoptosis via cytochrome c release. Cell death was inhibited by the pan-caspase inhibitor zVAD-fmk. We thus demonstrate that an effective mitochondrial matrix targeting signal can override the inhibition of import of Bax to the organelle, presumed to arise as a result of interaction between ART and TM segments, in the absence of apoptotic stimulus. We also demonstrate the ability of truncated variants of Bax to cause apoptosis when targeted to mitochondria by cytochrome c release from an ectopic environment