Immunity, virus evolution, and effectiveness of SARS-CoV-2 vaccines.

Phylogenetic and pathogenesis studies of the severe acute respiratory syndrome-related coronaviruses (SARS-CoVs) strains have highlighted some specific mutations that could confer the RNA genome fitness advantages and immunological resistance for their rapid spread in the human population. The analyses of 30 kb RNA SARS-CoVs genome sequences, protein structures, and functions have provided us a perspective of how host-virus protein-protein complexes act to mediate virus infection. The open reading frame (ORF)1a and ORF1b translation yields 16 non-structural (nsp1-16) and 6 accessory proteins (p6, p7a, p8ab, p9b) with multiple functional domains. Viral proteins recruit over 300 host partners forming hetero-oligomeric complexes enabling the viral RNA synthesis, packing, and virion release. Many cellular host factors and the innate immune cells through pattern-recognition receptors and intracellular RNA sensor molecules act to inhibit virus entry and intracellular replication. However, non-structural ORF proteins hijack them and suppress interferon synthesis and its antiviral effects. Pro-inflammatory chemokines and cytokines storm leads to dysfunctional inflammation, lung injury, and several clinical symptoms in patients. During the global pandemic, COVID-19 patients were identified with non-synonymous substitution of G614D in the spike protein, indicating virus co-evolution in host cells. We review findings that suggest that host RNA editing and DNA repair systems, while carrying on recombination, mutation, and repair of viral RNA intermediates, may facilitate virus evolution. Understanding how the host cell RNA replication process may be driven by SARS-CoV-2 RNA genome fitness will help the testing of vaccines effectiveness to multiple independent mutated coronavirus strains that will emerge.

Genes up- and down-regulated by dermcidin in breast cancer: a microarray analysis.

Dermcidin (DCD) is a human gene mapped to chromosome 12q13 region, which is co-amplified with multiple oncogenes with a well-established role in the growth, survival and progression of breast cancers. Here, we present a summary of a DNA microarray-based study that identified the genes that are up- and down-regulated in a human MDA-361 pLKO control clone and three clones expressing short hairpin RNA against three different regions of DCD mRNA. A list of 235 genes was differentially expressed among independent clones (> 3-fold change and p < 0.005). The gene expression of 208 was reduced and of 27 was increased in the three DCD-RNAi clones compared to pLKO control clone. The expression of 77 genes (37%) encoding for enzymes involved in amino acid metabolism, glucose metabolism and oxidoreductase activity and several genes required for cell survival and DNA repair were decreased. The expression of EGFR/ErbB-1 gene, an important predictor of outcome in breast cancer, was reduced together with the genes for betacellulin and amphiregulin, two known ligands of EGFR/ErbB receptors. Many of the 27 genes up-regulated by DCD-RNAi expression have not yet been fully characterized; among those with known function, we identified the calcium-calmodulin-dependent protein kinase-II delta and calcineurin A alpha. We compared 132 up-regulated and 12 down-regulated genes in our dataset with those genes up- and down-regulated by inhibitors targeting various signaling pathway components. The analysis showed that the genes in the DCD pathway are aligned with those functionally influenced by the drugs sirolimus, LY-294002 and wortmannin. Therefore, DCD may exert its function by activating the PI3K/AKT/mTOR signaling pathway. Together, these bioinformatic approaches suggest the involvement of DCD in the regulation of genes for breast cancer cell metabolism, proliferation and survival.

A mechanistic view of mitochondrial death decision pores.

Mitochondria increase their outer and inner membrane permeability to solutes, protons and metabolites in response to a variety of extrinsic and intrinsic signaling events. The maintenance of cellular and intraorganelle ionic homeostasis, particularly for Ca2+, can determine cell survival or death. Mitochondrial death decision is centered on two processes: inner membrane permeabilization, such as that promoted by the mitochondrial permeability transition pore, formed across inner membranes when Ca2+ reaches a critical threshold, and mitochondrial outer membrane permeabilization, in which the pro-apoptotic proteins BID, BAX, and BAK play active roles. Membrane permeabilization leads to the release of apoptogenic proteins: cytochrome c, apoptosis-inducing factor, Smac/Diablo, HtrA2/Omi, and endonuclease G. Cytochrome c initiates the proteolytic activation of caspases, which in turn cleave hundreds of proteins to produce the morphological and biochemical changes of apoptosis. Voltage-dependent anion channel, cyclophilin D, adenine nucleotide translocase, and the pro-apoptotic proteins BID, BAX, and BAK may be part of the molecular composition of membrane pores leading to mitochondrial permeabilization, but this remains a central question to be resolved. Other transporting pores and channels, including the ceramide channel, the mitochondrial apoptosis-induced channel, as well as a non-specific outer membrane rupture may also be potential release pathways for these apoptogenic factors. In this review, we discuss the mechanistic models by which reactive oxygen species and caspases, via structural and conformational changes of membrane lipids and proteins, promote conditions for inner/outer membrane permeabilization, which may be followed by either opening of pores or a rupture of the outer mitochondrial membrane.

Prediction and biochemical characterization of intrinsic disorder in the structure of proteolysis-inducing factor/dermcidin.

Proteolysis-inducing factor/dermcidin (PIF/DCD) is a novel human gene, located on chromosome 12, locus 12q13.1, that encodes a secreted 110-amino acid protein. Two transcripts for the protein have been identified in normal skin, breast, placenta and brain, and in various primary and metastatic tumor cells. The putative native-state structure of PIF/DCD has not been resolved. Here, we describe some biochemical features of the soluble recombinant 11-kDa protein produced in Escherichia coli. The native 11-kDa polypeptide displayed an anomalous mobility on 1% SDS-PAGE under reduced conditions and appeared as a single approximately 16-kDa band. Under nonreduced conditions, we detected by mass spectrometry, the presence of multiple peaks corresponding to m/z values of 21 kDa, which we confirmed as a dimeric form with a disulfide bridge between cysteine 34 of each 11-kDa monomer. The native protein exhibited an unusually high susceptibility to proteolytic attack by trypsin, and up to 13 peptides derived from its C-terminus were produced after 5 min of incubation. The secondary structure analysis of PIF/DCD native protein in aqueous solution, by circular dichroism spectroscopy, revealed regions with non-well-defined secondary structure but that acquired alpha-helix and beta-sheet secondary structures in the presence of TFE/water mixtures and micellar and non-micellar SDS molecules. By using PONDR, DisEMBL, DisProt, and GlobPlot computational predictors, we identified a long disorder region at the N-terminus of PIF/DCD amino acid sequence. This segment (from 19-50 residues) is critical for some of its biological activities, including neuron survival. This result is coherent with successive failure of crystallization of the protein. Taken together, these data suggest that the disorder and order transition may be relevant for some biological functions of PIF/DCD.

Interleukin 1, interleukin 6, tumor necrosis factor, and transforming growth factor beta increase cell resistance to tumor necrosis factor cytotoxicity by growth arrest in the G1 phase of the cell cycle.

During infection, inflammation, immune responses, and neoplastic growth, various cytokines are produced affecting both susceptibility to and protection from cellular death. We have studied the protective effect of pretreatment of the L929 fibroblast cell line with interleukin 1 beta (IL-1 beta), IL-6, tumor necrosis factor alpha (TNF-alpha), or transforming growth factor beta 1 (TGF-beta) on subsequent TNF/actinomycin D-induced cytotoxicity. The protective effects of these cytokines on TNF cytotoxicity were time and concentration dependent. TGF-beta was the most effective cytokine, followed by TNF, IL-1 beta, and IL-6. Activators of protein kinase C also afforded protection, and TGF-beta acted synergistically with either phorbol 12-myristate 13-acetate or the calcium ionophore A-23187. TGF-beta-induced protection against TNF was observed in cells subjected to prolonged treatment with phorbol 12-myristate 13-acetate. Cells pretreated with prostaglandin E2 or cholera toxin amplified the sensitivity to TNF and inhibited TGF-beta-mediated resistance, whereas indomethacin enhanced the protective effect of TGF-beta. Cells cultured in the presence of IL-1 beta, IL-6, TNF-alpha, or TGF-beta for 6 h inhibited DNA synthesis, and this was associated with concomitant growth arrest in the G1 phase of the cell cycle. On the other hand, prostaglandin E2 or cholera toxin stimulated the progression of cells from G1 toward G2 + M which was associated with increased TNF sensitivity. We conclude that these cytokines protect against death by arresting growth in the G1 phase of the cell cycle.

Immunity, virus evolution, and effectiveness of SARS-CoV-2 vaccines

Phylogenetic and pathogenesis studies of the severe acute respiratory syndrome-related coronaviruses (SARS-CoVs) strains have highlighted some specific mutations that could confer the RNA genome fitness advantages and immunological resistance for their rapid spread in the human population. The analyses of 30 kb RNA SARS-CoVs genome sequences, protein structures, and functions have provided us a perspective of how host-virus protein-protein complexes act to mediate virus infection. The open reading frame (ORF)1a and ORF1b translation yields 16 non-structural (nsp1-16) and 6 accessory proteins (p6, p7a, p8ab, p9b) with multiple functional domains. Viral proteins recruit over 300 host partners forming hetero-oligomeric complexes enabling the viral RNA synthesis, packing, and virion release. Many cellular host factors and the innate immune cells through pattern-recognition receptors and intracellular RNA sensor molecules act to inhibit virus entry and intracellular replication. However, non-structural ORF proteins hijack them and suppress interferon synthesis and its antiviral effects. Pro-inflammatory chemokines and cytokines storm leads to dysfunctional inflammation, lung injury, and several clinical symptoms in patients. During the global pandemic, COVID-19 patients were identified with non-synonymous substitution of G614D in the spike protein, indicating virus co-evolution in host cells. We review findings that suggest that host RNA editing and DNA repair systems, while carrying on recombination, mutation, and repair of viral RNA intermediates, may facilitate virus evolution. Understanding how the host cell RNA replication process may be driven by SARS-CoV-2 RNA genome fitness will help the testing of vaccines effectiveness to multiple independent mutated coronavirus strains that will emerge.

Induction of apoptosis in cancer cells by tumor necrosis factor and butyrolactone, an inhibitor of cyclin-dependent kinases.

Induction of apoptosis by tumor necrosis factor (TNF) is modulated by changes in the expression and activity of several cell cycle regulatory proteins. We examined the effects of TNF (1-100 ng/ml) and butyrolactone I (100 microM), a specific inhibitor of cyclin-dependent kinases (CDK) with high selectivity for CDK-1 and CDK-2, on three different cancer cell lines: WEHI, L929 and HeLa S3. Both compounds blocked cell growth, but only TNF induced the common events of apoptosis, i.e., chromatin condensation and ladder pattern of DNA fragmentation in these cell lines. The TNF-induced apoptosis events were increased in the presence of butyrolactone. In vitro phosphorylation assays for exogenous histone H1 and endogenous retinoblastoma protein (pRb) in the total cell lysates showed that treatment with both TNF and butyrolactone inhibited the histone H1 kinase (WEHI, L929 and HeLa) and pRb kinase (WEHI) activities of CDKs, as compared with the controls. The role of proteases in the TNF and butyrolactone-induced apoptosis was evaluated by comparing the number and expression of polypeptides in the cell lysates by gel electrophoresis. TNF and butyrolactone treatment caused the disappearance of several cellular protein bands in the region between 40-200 kDa, and the 110-90- and 50-kDa proteins were identified as the major substrates, whose degradation was remarkably increased by the treatments. Interestingly, the loss of several cellular protein bands was associated with the marked accumulation of two proteins apparently of 60 and 70 kDa, which may be cleavage products of one or more proteins. These findings link the decrease of cyclin-dependent kinase activities to the increase of protease activities within the growth arrest and apoptosis pathways induced by TNF.

Steroid receptors in a group of Brazilian melanoma patients.

Melanoma biopsies from 22 Brazilian patients were evaluated for estrogen (ER), progesterone (PR) and glucocorticoid receptors (GR) by the dextran-coated charcoal method. Fifty percent (11/22) of the tumors exhibited specific estrogen and progesterone binding activities ranging from 5 to 25 fmol/mg protein for ER and from 18 to 200.75 fmol/mg protein for PR; 20/22 (90%) of the biopsies displayed significant quantities of GR, which ranged from 10.0 to 362.5 fmol/mg protein. The incidence and concentration of positive receptors in melanoma samples from Brazilian patients are similar to those of countries with populations of Caucasian origin.

Glutathione depletion sensitizes cisplatin- and temozolomide-resistant glioma cells in vitro and in vivo.

Malignant glioma is a severe type of brain tumor with a poor prognosis and few options for therapy. The main chemotherapy protocol for this type of tumor is based on temozolomide (TMZ), albeit with limited success. Cisplatin is widely used to treat several types of tumor and, in association with TMZ, is also used to treat recurrent glioma. However, several mechanisms of cellular resistance to cisplatin restrict therapy efficiency. In that sense, enhanced DNA repair, high glutathione levels and functional p53 have a critical role on cisplatin resistance. In this work, we explored several mechanisms of cisplatin resistance in human glioma. We showed that cellular survival was independent of the p53 status of those cells. In addition, in a host-cell reactivation assay using cisplatin-treated plasmid, we did not detect any difference in DNA repair capacity. We demonstrated that cisplatin-treated U138MG cells suffered fewer DNA double-strand breaks and DNA platination. Interestingly, the resistant cells carried higher levels of intracellular glutathione. Thus, preincubation with the glutathione inhibitor buthionine sulfoximine (BSO) induced massive cell death, whereas N-acetyl cysteine, a precursor of glutathione synthesis, improved the resistance to cisplatin treatment. In addition, BSO sensitized glioma cells to TMZ alone or in combination with cisplatin. Furthermore, using an in vivo model the combination of BSO, cisplatin and TMZ activated the caspase 3-7 apoptotic pathway. Remarkably, the combined treatment did not lead to severe side effects, while causing a huge impact on tumor progression. In fact, we noted a remarkable threefold increase in survival rate compared with other treatment regimens. Thus, the intracellular glutathione concentration is a potential molecular marker for cisplatin resistance in glioma, and the use of glutathione inhibitors, such as BSO, in association with cisplatin and TMZ seems a promising approach for the therapy of such devastating tumors.

Mitochondrial swelling and incipient outer membrane rupture in preapoptotic and apoptotic cells.

Outer mitochondrial membrane (OMM) rupture was first noted in isolated mitochondria in which the inner mitochondrial membrane (IMM) had lost its selective permeability. This phenomenon referred to as mitochondrial permeability transition (MPT) refers to a permeabilized inner membrane that originates a large swelling in the mitochondrial matrix, which distends the outer membrane until it ruptures. Here, we have expanded previous electron microscopic observations that in apoptotic cells, OMM rupture is not caused by a membrane stretching promoted by a markedly swollen matrix. It is shown that the widths of the ruptured regions of the OMM vary from 6 to 250 nm. Independent of the perforation size, herniation of the mitochondrial matrix appeared to have resulted in pushing the IMM through the perforation. A large, long focal herniation of the mitochondrial matrix, covered with the IMM, was associated with a rupture of the OMM that was as small as 6 nm. Contextually, the collapse of the selective permeability of the IMM may precede or follow the release of the mitochondrial proteins of the intermembrane space into the cytoplasm. When the MPT is a late event, exit of the intermembrane space proteins to the cytoplasm is unimpeded and occurs through channels that transverse the outer membrane, because so far, the inner membrane is impermeable. No channel within the outer membrane can expose to the cytoplasm a permeable inner membrane, because it would serve as a conduit for local herniation of the mitochondrial matrix.

CaSPredictor: a new computer-based tool for caspase substrate prediction.

MOTIVATION: In vitro studies have shown that the most remarkable catalytic features of caspases, a family of cysteineproteases, are their stringent specificity to Asp (D) in the S1 subsite and at least four amino acids to the left of scissile bound. However, there is little information about the substrate recognition patterns in vivo. The prediction and characterization of proteolytic cleavage sites in natural substrates could be useful for uncovering these structural relationships. RESULTS: PEST-like sequences rich in the amino acids Ser (S), Thr (T), Pro (P), Glu or Asp (E/D), including Asn (N) and Gln (Q) are adjacent structural/sequential elements in the majority of cleavage site regions of the natural caspase substrates described in the literature, supporting its possible implication in the substrate selection by caspases. We developed CaSPredictor, a software which incorporated a PEST-like index and the position-dependent amino acid matrices for prediction of caspase cleavage sites in individual proteins and protein datasets. The program predicted successfully 81% (111/137) of the cleavage sites in experimentally verified caspase substrates not annotated in its internal data file. Its accuracy and confidence was estimated as 80% using ROC methodology. The program was much more efficient in predicting caspase substrates when compared with PeptideCutter and PEPS software. Finally, the program detected potential cleavage sites in the primary sequences of 1644 proteins in a dataset containing 9986 protein entries. AVAILABILITY: Requests for software should be made to Dr José E. Belizário SUPPLEMENTARY INFORMATION: Supplementary information is available for academic users at site http://icb.usp.br/~farmaco/Jose/CaSpredictorfiles.

Bioactivity of skeletal muscle proteolysis-inducing factors in the plasma proteins from cancer patients with weight loss.

We determined the circulating level of bioactivity for skeletal muscle proteolysis-inducing factors (PIF) in the blood samples from cancer patients whose body weight loss was greater than 10%. The level of bioactivity was estimated by measurement of tyrosine release from isolated 1at diaphragm muscles incubated with an ultrafiltered fraction of plasma or serum proteins containing molecules from 0 to 25 kDa in molecular weight. Significant levels of bioactivity were detected in 25 of the 50 cancer samples. No activity was found in 18 of the samples from healthy human blood donors. The ability of 13 of the cancer samples to induce muscle proteolysis was significantly inhibited by incubation of muscles in presence of indomethacin (10 microM). The neutralisation of 12 of the cancer samples with the antibodies to recombinant human interleukin-1 (IL-1), alpha and beta forms, partially abrogated the activity in five samples. These results suggest that the accelerated breakdown of proteins induced by the cancer plasma factors is at least in part mediated by IL-1 in cooperation with other active factors not yet defined. Additionally, we have shown that the increased breakdown of proteins induced by PIF in the crude supernatant derived from activated mouse peritoneal macrophages is prevented by the treatment of muscles with either indomethacin or quin-2 (1 microM). These observations provide indirect evidence for a possible causal relationship between the production of PIF and the body-weight loss of cancer patients.

Cleavage of caspases-1, -3, -6, -8 and -9 substrates by proteases in skeletal muscles from mice undergoing cancer cachexia.

A prominent feature of several type of cancer is cachexia. This syndrome causes a marked loss of lean body mass and muscle wasting, and appears to be mediated by cytokines and tumour products. There are several proteases and proteolytic pathways that could be responsible for the protein breakdown. In the present study, we investigated whether caspases are involved in the proteolytic process of skeletal muscle catabolism observed in a murine model of cancer cachexia (MAC16), in comparison with a related tumour (MAC13), which does not induce cachexia. Using specific peptide substrates, there was an increase of 54% in the proteolytic activity of caspase-1, 84% of caspase-8, 98% of caspase-3 151% to caspase-6 and 177% of caspase-9, in the gastrocnemius muscle of animals bearing the MAC16 tumour (up to 25% weight loss), in relation to muscle from animals bearing the MAC13 tumour (1-5% weight loss). The dual pattern of 89 kDa and 25 kDa fragmentation of poly (ADP-ribose) polymerase (PARP) occurred in the muscle samples from animals bearing the MAC16 tumour and with a high amount of caspase-like activity. Cytochrome c was present in the cytosolic fractions of gastrocnemius muscles from both groups of animals, suggesting that cytochrome c release from mitochondria may be involved in caspase activation. There was no evidence for DNA fragmentation into a nucleosomal ladder typical of apoptosis in the muscles of either group of mice. This data supports a role for caspases in the catabolic events in muscle involved in the cancer cachexia syndrome.

Caffeine potentiates the lethality of tumour necrosis factor in cancer cells.

In this study we have investigated the interaction of caffeine, a prototypic methylxanthine, and TNF on the induction of cell death in mouse and human cell lines during progression from G1 to successive phases of the cell cycle. Exposure of cells to TNF (0.1-100 ng ml-1) as single agent for 48 h caused low or no lethality. The rates of cell death increased significantly when cells cultured with TNF for 24 h were exposed to caffeine (2.5-20 mM). The magnitude of the enhancement by caffeine was TNF and caffeine dose-dependent. The most effective response to this combination was observed in the mouse cell lines, WEHI and L929, followed by the human cell lines, HeLa, A375 and MCF-7, respectively. In L929 cells, TNF treatment did not inhibit DNA synthesis during the first S phase of the cell cycle (20-24 h), but it did block the progress toward a second S phase, indicating the cells were arrested at G2 phase or mitosis. Caffeine had great enhancer effect on L929 cells exposed to TNF for 24 h, but the effect was reduced in cells with either less than 24 h or greater than 28 h of exposure. L929 cells stimulated with TNF died via apoptosis, as judged by both morphological criteria and the occurrence of internucleosomal DNA cleavage. Exposure of TNF-treated cells to caffeine caused a greater increase in the proportion of apoptotic cells as well as the extent of internucleosomal DNA fragmentation.

A mechanistic view of mitochondrial death decision pores

Mitochondria increase their outer and inner membrane permeability to solutes, protons and metabolites in response to a variety of extrinsic and intrinsic signaling events. The maintenance of cellular and intraorganelle ionic homeostasis, particularly for Ca2+, can determine cell survival or death. Mitochondrial death decision is centered on two processes: inner membrane permeabilization, such as that promoted by the mitochondrial permeability transition pore, formed across inner membranes when Ca2+ reaches a critical threshold, and mitochondrial outer membrane permeabilization, in which the pro-apoptotic proteins BID, BAX, and BAK play active roles. Membrane permeabilization leads to the release of apoptogenic proteins: cytochrome c, apoptosis-inducing factor, Smac/Diablo, HtrA2/Omi, and endonuclease G. Cytochrome c initiates the proteolytic activation of caspases, which in turn cleave hundreds of proteins to produce the morphological and biochemical changes of apoptosis. Voltage-dependent anion channel, cyclophilin D, adenine nucleotide translocase, and the pro-apoptotic proteins BID, BAX, and BAK may be part of the molecular composition of membrane pores leading to mitochondrial permeabilization, but this remains a central question to be resolved. Other transporting pores and channels, including the ceramide channel, the mitochondrial apoptosis-induced channel, as well as a non-specific outer membrane rupture may also be potential release pathways for these apoptogenic factors. In this review, we discuss the mechanistic models by which reactive oxygen species and caspases, via structural and conformational changes of membrane lipids and proteins, promote conditions for inner/outer membrane permeabilization, which may be followed by either opening of pores or a rupture of the outer mitochondrial membrane.

Prediction and biochemical characterization of intrinsic disorder in the structure of proteolysis-inducing factor/dermcidin

Proteolysis-inducing factor/dermcidin (PIF/DCD) is a novel human gene, located on chromosome 12, locus 12q13.1, that encodes a secreted 110-amino acid protein. Two transcripts for the protein have been identified in normal skin, breast, placenta and brain, and in various primary and metastatic tumor cells. The putative native-state structure of PIF/DCD has not been resolved. Here, we describe some biochemical features of the soluble recombinant 11-kDa protein produced in Escherichia coli. The native 11-kDa polypeptide displayed an anomalous mobility on 1% SDS-PAGE under reduced conditions and appeared as a single ~16-kDa band. Under nonreduced conditions, we detected by mass spectrometry, the presence of multiple peaks corresponding to m/z values of 21 kDa, which we confirmed as a dimeric form with a disulfide bridge between cysteine 34 of each 11-kDa monomer. The native protein exhibited an unusually high susceptibility to proteolytic attack by trypsin, and up to 13 peptides derived from its C-terminus were produced after 5 min of incubation. The secondary structure analysis of PIF/DCD native protein in aqueous solution, by circular dichroism spectroscopy, revealed regions with non-well-defined secondary structure but that acquired á-helix and â-sheet secondary structures in the presence of TFE/water mixtures and micellar and non-micellar SDS molecules. By using PONDR®, DisEMBL™, DisProt, and GlobPlot™ computational predictors, we identified a long disorder region at the N-terminus of PIF/DCD amino acid sequence. This segment (from 19-50 residues) is critical for some of its biological activities, including neuron survival. This result is coherent with successive failure of crystallization of the protein. Taken together, these data suggest that the disorder and order transition may be relevant for some biological functions of PIF/DCD.

Induction of apoptosis in cancer cells by tumor necrosis factor and butyrolactone, an inhibitor of cyclin-dependent kinases

Induction of apoptosis by tumor necrosis factor (TNF) is modulated by changes in the expression and activity of several cell cycle regulatory proteins. We examined the effects of TNF (1-100 ng/ml) and butyrolactone I (100 µM), a specific inhibitor of cyclin-dependent kinases (CDK) with high selectivity for CDK-1 and CDK-2, on three different cancer cell lines: WEHI, L929 and HeLa S3. Both compounds blocked cell growth, but only TNF induced the common events of apoptosis, i.e., chromatin condensation and ladder pattern of DNA fragmentation in these cell lines. The TNF-induced apoptosis events were increased in the presence of butyrolactone. In vitro phosphorylation assays for exogenous histone H1 and endogenous retinoblastoma protein (pRb) in the total cell lysates showed that treatment with both TNF and butyrolactone inhibited the histone H1 kinase (WEHI, L929 and HeLa) and pRb kinase (WEHI) activities of CDKs, as compared with the controls. The role of proteases in the TNF and butyrolactone-induced apoptosis was evaluated by comparing the number and expression of polypeptides in the cell lysates by gel electrophoresis. TNF and butyrolactone treatment caused the disappearance of several cellular protein bands in the region between 40-200 kDa, and the 110- 90- and 50-kDa proteins were identified as the major substrates, whose degradation was remarkably increased by the treatments. Interestingly, the loss of several cellular protein bands was associated with the marked accumulation of two proteins apparently of 60 and 70 kDa, which may be cleavage products of one or more proteins. These findings link the decrease of cyclin-dependent kinase activities to the increase of protease activities within the growth arrest and apoptosis pathways induced by TNF.

Bioactivity of skeletal muscle proteolysis-inducing factors in the plasma proteins from cancer patients with weight loss

We determined the circulating level of bioactivity for skeletal muscle proteolysis-inducing factors (PIF) in the blood samples from cancer patients whose body weight loss was greater than 10%. The level of bioactivity was estimated by measurement of tyrosine release from isolated rat diagphragm muscles incubated with an ultrafiltered fraction of plasma or serum proteins containing molecules from 0 to 25 kDa in molecular weight. Significant levels of bioactivity were detected in 25 of the 50 cancer samples. No activity was found in 18 of the samples from healthy human blood donors. The ability of 13 of the cancer samples to induce muscle proteolysis was significantly inhibited by incubation of muscles in presence of indomethacin (10 gM). The neutralisation of 12 of the cancer samples with the antibodies to recombinant human interleukin-I (IL-1), a and P forms, partially abrogated the activity in five samples. These results suggest that the accelerated breakdown of proteins induced by the cancer plasma factors is at least in part mediated by IL-1 in cooperation with other active factors not yet defined. Additionally, we have shown that the increased breakdown of proteins induced by PIF in the crude supernatant derived from activated mouse peritoneal macrophages is prevented by the treatment of muscles with either indomethacin or quin-2 (1 juM). These observations provide indirect evidence for a possible causal relationship between the production of PIF and the body-weight loss of cancer patients.