Involvement of cell surface TG2 in the aggregation of K562 cells triggered by gluten.

Gluten-induced aggregation of K562 cells represents an in vitro model reproducing the early steps occurring in the small bowel of celiac patients exposed to gliadin. Despite the clear involvement of TG2 in the activation of the antigen-presenting cells, it is not yet clear in which compartment it occurs. Herein we study the calcium-dependent aggregation of these cells, using either cell-permeable or cell-impermeable TG2 inhibitors. Gluten induces efficient aggregation when calcium is absent in the extracellular environment, while TG2 inhibitors do not restore the full aggregating potential of gluten in the presence of calcium. These findings suggest that TG2 activity is not essential in the cellular aggregation mechanism. We demonstrate that gluten contacts the cells and provokes their aggregation through a mechanism involving the A-gliadin peptide 31-43. This peptide also activates the cell surface associated extracellular TG2 in the absence of calcium. Using a bioinformatics approach, we identify the possible docking sites of this peptide on the open and closed TG2 structures. Peptide docks with the closed TG2 structure near to the GTP/GDP site, by establishing molecular interactions with the same amino acids involved in stabilization of GTP binding. We suggest that it may occur through the displacement of GTP, switching the TG2 structure from the closed to the active open conformation. Furthermore, docking analysis shows peptide binding with the ß-sandwich domain of the closed TG2 structure, suggesting that this region could be responsible for the different aggregating effects of gluten shown in the presence or absence of calcium. We deduce from these data a possible mechanism of action by which gluten makes contact with the cell surface, which could have possible implications in the celiac disease onset.

Adenosine-induced cardiac arrest in complex cerebral aneurysms surgery: an Italian single-center experience.

AIM: Even if endovascular techniques are improving, treatment of complex intracranial aneurysms still remains a neurosurgeon challenge. Adenosine administration, producing a brief and profound systemic hypotension, seems to improve surgical aneurysm visualization facilitating its exclusion with less risks of rupture. In our retrospective study we confirmed that adenosine advantages could be determinant for an optimal surgical result. METHODS: We retrospectively reviewed all unruptured complex cerebral aneurysms surgically treated in our institution between August 2009 and April 2012. Treatment of those aneurysms was surgical, with proximal temporary artery occlusion or adenosine induced flow arrest. We compared the two different techniques, evaluating intra- and postoperative data; a three-month follow-up including a neurological assessment, cerebral angiography and echocardiography for the adenosine group was performed. RESULTS: Twenty-four patients were collected in our study. Eleven patients underwent traditional temporary proximal clipping while in 13 patients intraoperative adenosine was used. Most common location was paraclinoid region. We did not observe any complication in the adenosine group. Adenosine was well tolerated, spontaneous recovery of sinusal cardiac rhythm was observed even at high and subsequent doses. The Intensive Care Unit and Hospital length of stay were shorter in adenosine group. A three-month follow-up did not show cardiac abnormalities with good angiographic aneurysms exclusion. CONCLUSION: We observed that adenosine administration allowed an easier clipping thanks to a reduced wall tension in a clearer surgical field without cardiological adverse events. In our opinion adenosine induced arrest technique could be an efficacious, harmless and reliable alternative strategy for surgical treatment of complex cerebral aneurysms.

Transglutaminases: future perspectives.

This is the third special issue focused on "Transglutaminases" that is now available on this journal and dedicated to one of the pioneers of these enzymes, John Edward Folk, who died December 2010 [see in this issue Beninati et al. 2012a]. The first edition, "Polyamines and Transglutaminases" was published in Amino Acids, vol 26, no. 4, 2004, with the contribution of two prestigious Guest Editors as Alberto Abbruzzese and Mauro Piacentini. This editorial initiative was followed by the second special issue published in occasion of the 50th years of the discovery of transglutaminase. Indeed, "Transglutaminase 2: 50th Anniversary of the Discovery" Amino Acids, vol 36, no. 4, 2009, was published with the valuable collaboration of Carlo Maria Bergamini and Mauro Piacentini (Beninati et al. 2009). To continue with this editorial tradition, on this occasion, an outstanding board of Guest Editors composed by Francesco Facchiano and Mauro Piacentini has also been invited to promote this initiative and recruit a selected panel of Authors, many of who participated in the first and second edition of the Gordon Conference on Transglutaminases: "Transglutaminases in Human Diseases Processes" chaired by Rickard L Eckert and Kapil Mehta on July 18-23, 2010, and by Kapil Mehta and Mauro Piacentini on July 15-20, 2012, held at Davidson College, NC, USA. In this Amino Acids special issue, the manuscripts were selected to reflect the progress and the future perspectives of transglutaminases.

γ-Tocopherol inhibits human prostate cancer cell proliferation by up-regulation of transglutaminase 2 and down-regulation of cyclins.

To establish a system to study differentiation therapy drugs, we used the androgen-independent human prostate PC-3 tumor cell line as a target and α- and γ-tocopherol as inducers. Effects of α- and γ-tocopherol on the cell cycle, proliferation and differentiation, were examined. A more significant growth inhibition activity for γ- than for α-tocopherol was observed. Flow cytometry analysis of α- and γ-tocopherol-treated prostate carcinoma PC3 cells showed decreased progression into the S-phase. This effect, particularly evident for γ-tocopherol, was associated with an up-regulation and increased activity of transglutaminase 2 (TG2), a reduced DNA synthesis and a remarkable decreased levels of cyclin D1 and cyclin E. Activation of TG2 suggests that γ-tocopherol has an evident differentiative capacity on PC3 cells, leading to an increased expression of TG2, and reduced cyclin D1 and cyclin E levels, affecting cell cycle progression. It is feasible that up-regulation and activation of TG2, associated with a reduced proliferation, are parts of a large-scale reprogramming that can attenuate the malignant phenotype of PC3 cells in vitro. These data suggest further investigation on the potential use of this γ-form of vitamin E as a differentiative agent, in combination with the common cytotoxic treatments for prostate cancer therapy.

Does polyamine oxidase activity influence the oxidative metabolism of children who suffer of diabetes mellitus?

Diabetes mellitus is a metabolic disease characterized by inadequate secretion of insulin. Polyamine oxidase (PAO), a FAD-containing enzyme is involved in the biodegradation of Sp and Spd, catalyzing the oxidative deamination of Sp and Spd, resulting in production of ammonia (NH(3)), corresponding amino aldehydes and H(2)O(2). Malondialdehyde (MDA) and acrolein (CH2=CHCHO), potentially toxic agents, which induce oxidative stress in mammalian cells, are then spontaneously formed from aminoaldehydes. The main signs of oxidative stress in diabetic children were the values of HbA1c and MDA levels. Polyamines have an insulin-like action. Antiglycation property of spermine and spermidine has been recently confirmed. There are no data in the literature about plasma polyamine oxidase (PAO) activities in children with type 1 diabetes. The idea of this study was to evaluate the polyamine metabolism through the estimation of polyamine oxidase activity. We have study children with newly diagnosed type 1 diabetes mellitus (n = 35, age group of 5-16 years, as well as age-matched healthy control subjects (n = 25). The biochemical investigations were done on diabetic children who have the pathological values of glucose (9.11-17.33 mmol/l) and glycosylated Hb (7.57-14.49% HbA(1c)). The children in the control group have referent values of glucose and glycated hemoglobin (4.11-5.84 mmol/L and HbA(1c) 4.22-6.81% of the total Hb. Glucose levels in blood plasma and glycosylated hemoglobin in erythrocythes hemolysates (HbA1c) were measured by using standard laboratory methods. PAO activity in venous blood plasma and the amount of malondialdehyde (MDA) were measured by the spectrophotometric methods. PAO activity, glycemia, HbA1c and MDA were significantly increased in diabetic children compared to the control subjects. PAO activity in children with type 1 diabetes mellitus was very high. The findings of higher blood HbA(1C) and MDA levels confirm the presence of oxidant stress in children with type 1 diabetes mellitus and demonstrate that PAO activity may participate in these circumstances.

Role of transglutaminase 2 in quercetin-induced differentiation of B16-F10 murine melanoma cells.

Flavonoids belong to the class of plant polyphenolic compounds with over 6,000 individual structures known. These phytochemicals have attracted the interest of the scientists, because they possess a remarkable spectrum of biological activities, such as antiallergic, antiinflammatory, antioxidant, antimutagenic and anticarcinogenic. In this work, we compared the anticancer potential of two flavonoids, quercetin and pelargonidin, on highly metastatic B16-F10 melanoma murine cells. We have evaluated different parameters related to cell proliferation and differentiation, such as cell number, toxicity, intracellular content of polyamines and transglutaminase (TG, EC 2.3.2.13) activity. The higher inhibition of tumor cell growth, with respect to control, was obtained with quercetin cell treatment, i.e. 32% reduction after 48 h and 39% reduction after 72 h of incubation (P < 0.001). In parallel, quercetin-treated cells showed a similar decrease in polyamine content. TG activity was fourfold increased, with respect to control, after 48 h and twofold increased after 72 h (P < 0.001). Pelargonidin treatment did not show significant antiproliferative effects and any increase in TG activity. Proteomic approach was used to investigate changes in protein expression profiles in tumor cells following quercetin treatment. Changes in expression of 60 proteins were detected, i.e. 8 proteins were down-regulated, 35 up-regulated, 11 "de novo" synthetized proteins and 6 suppressed proteins were present in treated cells. A 80 kDa spot, identified as TG type 2 by Western blot analysis, presented a fourfold increase in intensity, confirming the key role played by TG in the induction of cancer cell differentiation.

Protein-polyamine conjugates by transglutaminase 2 as potential markers for antineoplastic screening of natural compounds.

The role of post-translational modification of cell proteins with polyamines, a reaction catalyzed by a tissue tranglutaminase (TG, EC 2.3.2.13), in the induction of cell differentiation, represents an intriguing strategy to control cell proliferation and metastatic ability of different tumor cell lines. In this review, we focus our attention on the metabolic aspects of some natural compounds (methylxantines, retinoids and flavonoids) responsible of their antitumor effects exerted through the induction of TG activity in cancer cells.

In vivo evaluation of type 2 transglutaminase contribution to the metastasis formation in melanoma.

One of the most relevant problems in tumour treatment resides on the ability of the tumour to form metastasis and disseminate among the organism. The formation of metastases is a complex process, which requires the action of various effectors, not yet completely identified. The analysis of various types of tumours revealed a complex picture about the relationship between type 2 transglutaminase (TG2) expression and outcome and/or metastatic potential of the tumour itself. In some tumours, the transition to a highly invasive state is paralleled by an up-regulation of TG2 expression and/or activity while in some other a down-regulation has been reported. In addition, host tissues seem to react to tumour invasion by up-regulating TG2 expression. In order to analyse whether TG2 might be involved in the metastatic process in melanoma, we studied the metastases formation and development by means of the B16-F10 murine melanoma cell line and with TG2(-/-) mice as experimental model. Our results indicate that TG2 absence in the host is a favouring condition for the formation and development of the metastasis, while the presence of TG2 in the tumour's cell might be requested for the development of the metastasis.

Long-term follow-up of patients with hyperthyroidism due to Graves' disease treated with methimazole. Comparison of usual treatment schedule with drug discontinuation vs continuous treatment with low methimazole doses: a retrospective study.

Antithyroid drugs may be proposed as the firstline therapy for hyperthyroidism due to Graves' disease since some patients undergo prolonged remission after drug withdrawal. On the other hand, some studies, though controversial, indicated that methimazole (MMI) has some immunomodulating activity. We retrospectively analyzed 384 consecutive patients newly diagnosed with Graves' disease in the years 1990-2002 to ascertain whether long-term therapy with low doses of MMI may prevent relapse of thyrotoxicosis. Two hundred and forty-nine patients were included in our study. The date of reduction of MMI dose to 5 mg/day was considered time 0 for survival analysis. In 121 MMI was discontinued in less than 15 months after time 0 (group D), while in the remaining 128 a daily MMI 2.5-5 mg dose was maintained (group M). One hundred and thirty-five patients were excluded for inadequate response to MMI, relapse of thyrotoxicosis that could be related to an improper withdrawal or reduction of MMI, inadequate or too short followup, iodide contamination, steroid or interferon therapy, pregnancy or post-partum. D and M groups did not differ for clinical and hormonal parameters except age, which was lower in D (p=0.019). Age > vs < 35 yr was relevant in survival analysis; therefore patients were divided in 2 groups according to this age cut-off. In younger patients relapse of thyrotoxicosis occurred in 15 patients of group D 2.4-39.6 months (median 19.0) after time 0, and 8 M after 5.9-40.0 (21.3) months, while 14 D and 5 M maintained euthyroidism until the end of the observation after 31.8-95.3 (56.6) months and 30.4-62.1 (46.5) months, respectively. Survival analysis indicated that the risk of relapse was similar in group D and M. In older patients relapse of thyrotoxicosis occurred in 40 patients of group D after 8.2-65.8 (25.4) months and 29 M after 5.8-62.5 (22.4) months, while 52 D and 86 M maintained euthyroidism until the end of the observation, 20.1-168.0 (46.7) months and 24.1-117.4 (53.4) months respectively. Survival analysis indicated that the risk of relapse was increased in group D. Therefore long-term treatment with low doses of MMI seems to prevent relapse in Graves' disease in patients above 35 yr of age. This should be confirmed in a prospective study.

Impairment of the metastatic activity of melanoma cells by transglutaminase-catalyzed incorporation of polyamines into laminin and Matrigel.

Previously published evidences highlighted the effect of transglutaminase (TG, EC 2.3.2.13) activation on the reduction of the in vitro adhesive and invasive behaviour of murine B16-F10 melanoma cells, as well as in vivo. Here, we investigated the influence of spermidine (SPD) incorporation by TG into basement membrane components i.e. laminin (LN) or Matrigel (MG), on the adhesion and invasion of B16-F10 melanoma cells by these TG/SPD-modified substrates. The adhesion assays showed that cell binding to the TG/SPD-modified LN was reduced by 30%, when compared to untreated LN, whereas the reduction obtained using TG/SPD-modified MG was 35%. Similarly, tumor cell invasion by the Boyden chamber system through TG/SPD modified LN or MG was respectively reduced by 45%, and by 69%. Evaluation of matrix metalloproteinase (gelatinases MMP-2 and MMP-9) activities by gel-zymography showed that MMP-2 activity was unaffected, while MMP-9 activity was reduced by about 32% using TG/SPD-modified substrate. These results strongly suggest that the observed antiinvasive effect of TG activation in the host may be ascribed to the covalent incorporation of polyamines, which led to the post-translational modification of some components of the cell basement membrane. This modification may interfere with the metastatic property of melanoma cells, affecting the proteolytic activity necessary for their migration and invasion activities.

Glucocorticoids and oxidative stress.

Glucocorticoids (GC) are used widely for the treatment of patients with various disorders, including autoimmune diseases, allergies, and lymphoproliferative disorders. Glucocorticoid therapy is often limited by several adverse reactions associated with GC excess. Excess GC can elicit a variety of symptoms and signs, including growth retardation in children; immunosuppression; cardiovascular disorders like hypertension and atherosclerosis; osteoporosis; myopathy; and diabetes mellitus. Currently, attention is focused on oxidative stress as one of the major determinants of endothelial dysfunction and cardiovascular senescence. The main reason for all unwanted effects of GC is that dexamethasone induces the overproduction of reactive oxygen species, causing dysregulation of physiological processes. Humans and animals with GC-induced hypertension exhibit reduced nitric oxide levels; patients with excess GC levels also suffer from depression as a consequence of low levels of serotonin and melatonin. The common cofactor for the production of these vasoactive molecules is tetrahydrobiopterin (BH4), which is required for nitric oxide synthesis.

Role of the FAD-dependent polyamine oxidase in the selective formation of N(1),N(8)-bis(gamma-glutamyl)spermidine protein cross-links(1).

Protein-bound gamma-glutamylpolyamines have highlighted a new pathway in polyamine metabolism. Human foreskin keratinocytes offer a suitable model for this study. Indeed, they develop polymerized envelopes, as they differentiate, rich in epsilon-(gamma-glutamyl)lysine and N(1),N(8)-bis(gamma-glutamyl)spermidine cross-links. We have found that the selective oxidation of N(1)-(gamma-glutamyl)spermidine and N-(gamma-glutamyl)spermine by FAD-dependent polyamine oxidase (PAO) may be one of the cellular mechanisms regulating the preferential formation of a sterically defined bis(gamma-glutamyl)spermidine cross-link. The significance of this finding is unknown, but it suggests that the target of this PAO-modulation is to achieve the biochemical prerequisite for production of a normal epidermal stratum corneum.

Somatostatin analogues, a series of tissue transglutaminase inducers, as a new tool for therapy of mesenchimal tumors of the gastrointestinal tract.

Imatinib, a tyrosine kinase inhibitor directed against the enzymatic domain of KIT protein, was found to produce dramatic clinical responses in metastatic gastrointestinal stromal tumors (GISTs). However, resistance usually develops thus determining treatment failure. The present study was performed to analyse the expression of somatostatin receptor (SSTR) subtypes, modulators of tissue transglutaminase, in a series of GISTs and leiomyosarcomas by immunohistochemistry to identify a new potential therapeutic target. Sixteen cases (8 males and 8 females, age range: 38-73; 11 GISTs, 4 leiomyosarcomas, 1 leiomyoma) were studied. Immunohistochemical detection of the relevant SSTRs was performed on paraffin-embedded tissue sections, stained with polyclonal antibodies directed against the five somatostatin receptor subtypes. We found 7 out of 16 (44%) tumors expressing all SSTRs and 14 out of 16 (87%) tumors positive for at least 3 subtypes. SSTR2A was the most represented subtype in the tumors studied, being expressed in approximately 70% of cases exhibiting an intense labeling in most of these cases. The significant expression of SSTRs shown in this series of GISTs and gastrointestinal leiomyosarcomas suggests a potential therapeutic target to be explored alone and/or in combination with other therapeutic agents in the setting of refractory GI stromal tumors.

The role of L-arginine in toxic liver failure: interrelation of arginase, polyamine catabolic enzymes and nitric oxide synthase.

The existing interrelation in metabolic pathways of L-arginine to polyamines, nitric oxide (NO) and urea synthesis could be affected in sepsis, inflammation, intoxication and other conditions. The role of polyamines and NO in the toxic effect of mercury chloride on rat liver function was studied. Administration of mercury chloride for 24 h led to significantly elevated plasma activities of Alanine transaminase (ALT) and Aspartate transaminase (AST). Malondyaldehyde (MDA) levels were unaffected (p > 0.05) and arginase activity was significantly decreased (p < 0.05) while nitrate/nitrite production was significantly elevated (p < 0.001) in liver tissue. Polyamine oxidase (PAO) and diamine oxidase (DAO) activities, enzymes involved in catabolism of polyamines, were decreased. L-arginine supplementation to intoxicated rats potentiated the effect of mercury chloride on NO production and it was ineffective on arginase activity. Results obtained in this study show that mercury chloride-induced toxicity leads to abnormally high levels of ALT and AST that may indicate liver damage with the involvement of polyamine catabolic enzymes and NO.

Enhancement of transglutaminase activity and polyamine depletion in B16-F10 melanoma cells by flavonoids naringenin and hesperitin correlate to reduction of the in vivo metastatic potential.

The in vitro and in vivo effects of two flavonons, naringenin (NG) and hesperitin (HP) on the proliferation rate of highly metastatic murine B16-F10 melanoma cell were investigated. NG or HP treatment of melanoma cells produced a remarkable reduction of cell proliferation, paralleled with both the lowering of the intracellular levels of polyamine, spermidine and spermine and the enhancement of transglutaminase (TGase, EC 2.3.2.13) activity. Orally administered NG or HP in C57BL6/N mice inoculated with B16-F10 cells affected the pulmonary invasion of melanoma cells in an in vivo metastatic assay. The number of lung metastases detected by a computerized image analyzer was reduced, compared to untreated animals, by about 69% in NG-treated mice and by about 36% in HP-treated mice. Survival studies showed that 50% of the NG-treated animals died 38 +/- 3.1 days after tumor cell injection (control group: 18 +/- 1.5 days) and HP-treated mice died 27 +/- 2.3 days after cell inoculation. Taken together, these findings provide further evidences for the potential anticancer properties of dietary flavonoids as chemopreventive agents against malignant melanoma.

Selenomethionine induces polyamine biosynthesis in regenerating rat liver tissue.

Our study was undertaken to elucidate the effects of selenomethionine (SeMet) on polyamine metabolism in regenerating rat liver tissue, as useful model of rapidly growing normal tissue. We have examined the levels of spermine, spermidine and putrescine in liver tissue. At the same time we have evaluated the activities of polyamine oxidase (PAO) and diamine oxidase (DAO), the catabolic enzymes of polyamine metabolism. The obtained results suggest that polyamine levels in regenerating liver tissue, at 7(th) day after two-thirds partial hepatectomy, were higher in comparison with control group. The administration of selenomethionine to hepatectomized animals during seven days, in a single daily dose of 2.5 microg/100 g body weight, increases the amount of spermine and spermidine; the level of putrescine does not change under the influence of SeMet in regenerating rat liver tissue.PAO activity is lower in regenerating hepatic tissue than in control group. Supplementation of hepatectomized animals with SeMet significantly decreases the activity of this enzyme. DAO activity was significantly higher in hepatectomized and in operated animals treated with SeMet compared to the sham-operated and control ones. The differential sensitivity observed in our model of highly proliferating normal tissue to SeMet, compared with the reported anticancer activity of this molecule is discussed.

Alternative therapy of earth elements increases the chondroprotective effects of chondroitin sulfate in mice.

The administration of mineral sulphur water is an alternative experimental approach for the treatment of rheumatic diseases, such as osteoarthritis (OA), that cause the degeneration of bone and cartilage and sufferance to the patients. Chondroitin sulfate (CS) is a symptomatic slow acting nutropeucital agent currently used in molecular therapy of OA. Therefore, we have studied the role and efficacy of the selective soil paste from the mineral sulphur enriched spring (mud)-therapy alone or in combination with CS in the treatment of OA. The study was performed on 40 C57 Black 6N mice, an experimental model which spontaneously develop an osteoarthritic process. The animals were divided in 4 groups and were treated with the single agents or with the combination. After 30 days of treatment all the mice were sacrificed and right knees and blood were collected. It was found that CS determined a reduction of radiological and histological features of chondrodegeneration and that mud-therapy increased the effects of CS in the animal group treated with the combination. However, the effects of thermal therapy alone were not statistically significant. Since OA is characterized by an increase of the production of nitric oxide (NO) by chondrocytes in extracellular matrix with its consequent elevation in serum and synovial fluid, we have evaluated the effects of the treatments on serum NO levels. CS alone induced a statistically significant reduction of NO serum levels (90+/-13 micromM vs 219+/-60 microM of control group, P<0.05) while mud-therapy alone induced a not statistically significant reduction of serum NO (170+/-62 microM, P>0.05). However, the latter strongly potentiated the decrease of serum NO induced by CS (31+/-1.5 microM) with a high statistical significance if compared to both the control group (P<0.01) and the CS-treated group (P<0.05). In conclusion, this study demonstrates that mud-therapy with sulphur mineral water could represent an important phase of the therapeutic strategy of OA. This experimental strategy could integrate and potentiate the standard pharmacological tools. Moreover, we have set a valid experimental in vivo model for the study of the thermal effects on the development of OA.

Protein-polyamine conjugation by transglutaminase in cancer cell differentiation: review article.

Considerable and intense progress has been made in the understanding of the chemistry, molecular biology and cell biology of transglutaminases (TGases: EC 2.3.2.13). The knowledge that very different processes such as cell growth, reproduction and death are dependent on the presence of adequate levels of these enzymes and that the amount of both free and protein-conjugated polyamines, formed by the enzyme, are capable of modulating the differentiation and proliferative capability of several cell types, has prompted a multitude of researchers to study the role of these fascinating molecules in cancer cell differentiation.

The transglutaminase family: an overview: minireview article.

The knowledge that very different processes such as normal and neoplastic cell growth, reproduction and death are dependent on the presence of adequate levels of transglutaminases (TGase: EC 2.3.2.13) and that they are capable of affecting the differentiation and proliferative capability of several cell types, has prompted a multitude of researchers to study these fascinating molecules. In the following overview we intend to summarize the currently known information on the biological significance of these enzymes.

Translational and post-translational modifications of proteins as a new mechanism of action of alpha-interferon: review article.

Interferon-alpha (IFNalpha) is a recombinant protein widely used in the therapy of several neoplasms such as myeloma, renal cell carcinoma, epidermoid cervical and head and neck tumours and melanoma. IFNalpha, the first cytokine to be produced by recombinant DNA technology, has emerged as an important regulator of cancer cell growth and differentiation, affecting cellular communication and signal transduction pathways. However, the way by which tumour cell growth is directly suppressed by IFNalpha is not well known. Wide evidence exists on the possibility that cancer cells undergo apoptosis after the exposure to the cytokine. Here we will discuss data obtained by us and others on the post-translational regulation of the expression of proteins involved in the occurrence of apoptotic process such as tissue transglutaminase (tTG) or in the modulation of cell cycle such as the cyclin-dependent kinase inhibitor p27. This new way of regulation of p27 and tTG occurs through the modulation of their proteasome-dependent degradation induced by the cytokine. We will also review the involvement of protein synthesis machinery in the induction of cell growth inhibition by IFNalpha. In details, we will describe the effects of IFNalpha on the expression and activity of the protein kinase dependent from dsRNA (PKR) and on the eukaryotic initiation factor of protein synthesis 5A (eIF-5A) and their correlations with the regulation of cancer cell growth. These data strongly suggest that the antitumour activity of IFNalpha against human tumours could involve still unexplored mechanisms based on post-translational and translational control of the expression of proteins that regulate cell proliferation and apoptosis.