Atezolizumab plus bevacizumab versus lenvatinib or sorafenib in non-viral unresectable hepatocellular carcinoma: an international propensity score matching analysis.

BACKGROUND: A growing body of evidence suggests that non-viral hepatocellular carcinoma (HCC) might benefit less from immunotherapy. MATERIALS AND METHODS: We carried out a retrospective analysis of prospectively collected data from consecutive patients with non-viral advanced HCC, treated with atezolizumab plus bevacizumab, lenvatinib, or sorafenib, in 36 centers in 4 countries (Italy, Japan, Republic of Korea, and UK). The primary endpoint was overall survival (OS) with atezolizumab plus bevacizumab versus lenvatinib. Secondary endpoints were progression-free survival (PFS) with atezolizumab plus bevacizumab versus lenvatinib, and OS and PFS with atezolizumab plus bevacizumab versus sorafenib. For the primary and secondary endpoints, we carried out the analysis on the whole population first, and then we divided the cohort into two groups: non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH) population and non-NAFLD/NASH population. RESULTS: One hundred and ninety patients received atezolizumab plus bevacizumab, 569 patients received lenvatinib, and 210 patients received sorafenib. In the whole population, multivariate analysis showed that treatment with lenvatinib was associated with a longer OS [hazard ratio (HR) 0.65; 95% confidence interval (CI) 0.44-0.95; P = 0.0268] and PFS (HR 0.67; 95% CI 0.51-0.86; P = 0.002) compared to atezolizumab plus bevacizumab. In the NAFLD/NASH population, multivariate analysis confirmed that lenvatinib treatment was associated with a longer OS (HR 0.46; 95% CI 0.26-0.84; P = 0.0110) and PFS (HR 0.55; 95% CI 0.38-0.82; P = 0.031) compared to atezolizumab plus bevacizumab. In the subgroup of non-NAFLD/NASH patients, no difference in OS or PFS was observed between patients treated with lenvatinib and those treated with atezolizumab plus bevacizumab. All these results were confirmed following propensity score matching analysis. By comparing patients receiving atezolizumab plus bevacizumab versus sorafenib, no statistically significant difference in survival was observed. CONCLUSIONS: The present analysis conducted on a large number of advanced non-viral HCC patients showed for the first time that treatment with lenvatinib is associated with a significant survival benefit compared to atezolizumab plus bevacizumab, in particular in patients with NAFLD/NASH-related HCC.

Nonalcoholic steatohepatitis in hepatocarcinoma: new insights about its prognostic role in patients treated with lenvatinib.

BACKGROUND: Hepatocellular carcinoma (HCC) treatment remains a big challenge in the field of oncology. The liver disease (viral or not viral) underlying HCC turned out to be crucial in determining the biologic behavior of the tumor, including its response to treatment. The aim of this analysis was to investigate the role of the etiology of the underlying liver disease in survival outcomes. PATIENTS AND METHODS: We conducted a multicenter retrospective study on a large cohort of patients treated with lenvatinib as first-line therapy for advanced HCC from both Eastern and Western institutions. Univariate and multivariate analyses were performed. RESULTS: Among the 1232 lenvatinib-treated HCC patients, 453 (36.8%) were hepatitis C virus positive, 268 hepatitis B virus positive (21.8%), 236 nonalcoholic steatohepatitis (NASH) correlate (19.2%) and 275 had other etiologies (22.3%). The median progression-free survival (mPFS) was 6.2 months [95% confidence interval (CI) 5.9-6.7 months] and the median overall survival (mOS) was 15.8 months (95% CI 14.9-17.2 months). In the univariate analysis for OS NASH-HCC was associated with longer mOS [22.2 versus 15.1 months; hazard ratio (HR) 0.69; 95% CI 0.56-0.85; P = 0.0006]. In the univariate analysis for PFS NASH-HCC was associated with longer mPFS (7.5 versus 6.5 months; HR 0.84; 95% CI 0.71-0.99; P = 0.0436). The multivariate analysis confirmed NASH-HCC (HR 0.64; 95% CI 0.48-0.86; P = 0.0028) as an independent prognostic factor for OS, along with albumin-bilirubin (ALBI) grade, extrahepatic spread, neutrophil-to-lymphocyte ratio, portal vein thrombosis, Eastern Cooperative Oncology Group (ECOG) performance status and alpha-fetoprotein. An interaction test was performed between sorafenib and lenvatinib cohorts and the results highlighted the positive predictive role of NASH in favor of the lenvatinib arm (P = 0.0047). CONCLUSION: NASH has been identified as an independent prognostic factor in a large cohort of patients with advanced HCC treated with lenvatinib, thereby suggesting the role of the etiology in the selection of patients for tyrosine kinase treatment. If validated, this result could provide new insights useful to improve the management of these patients.

Identification of lenvatinib prognostic index via recursive partitioning analysis in advanced hepatocellular carcinoma.

BACKGROUND: After the advent of new treatment options for advanced hepatocellular carcinoma (HCC), the identification of prognostic factors is crucial for the selection of the most appropriate therapy for each patient. PATIENTS AND METHODS: With the aim to fill this gap, we applied recursive partitioning analysis (RPA) to a cohort of 404 patients treated with lenvatinib. RESULTS: The application of RPA resulted in a classification based on five variables that originated a new prognostic score, the lenvatinib prognostic index (LEP) index, identifying three groups: low risk [patients with prognostic nutritional index (PNI) >43.3 and previous trans-arterial chemoembolization (TACE)]; medium risk [patients with PNI >43.3 but without previous TACE and patients with PNI <43.3, albumin-bilirubin (ALBI) grade 1 and Barcelona Clinic Liver Cancer stage B (BCLC-B)]; high risk [patients with PNI <43.3 and ALBI grade 2 and patients with PNI <43.3, albumin-bilirubin (ALBI) grade 1 and Barcelona Clinic Liver Cancer stage C (BCLC-C)]. Median overall survival was 29.8 months [95% confidence interval (CI) 22.8-29.8 months] in low risk patients (n = 128), 17.0 months (95% CI 15.0-24.0 months) in medium risk (n = 162) and 8.9 months (95% CI 8.0-10.7 months) in high risk (n = 114); low risk hazard ratio (HR) 1 (reference group), medium risk HR 1.95 (95% CI 1.38-2.74), high risk HR 4.84 (95% CI 3.16-7.43); P < 0.0001. The LEP index was validated in a cohort of 127 Italian patients treated with lenvatinib. While the same classification did not show a prognostic value in a cohort of 311 patients treated with sorafenib, we also show a possible predictive role in favor of lenvatinib in the low risk group. CONCLUSIONS: LEP index is a promising, easy-to-use tool that may be used to stratify patients undergoing systemic treatment of advanced HCC.

N-3 polyunsaturated fatty acids in heart failure: mechanisms and recent clinical evidence.

Over the past 20 years, there has been significant progress in our knowledge of the pathophysiology of heart failure (HF) with consequent considerable development of both pharmacological and non pharmacological approaches. Despite improved therapeutic strategies, HF still remains burdensome in terms of mortality, quality of life, and hospitalization costs. A new and promising medical treatment to improve survival in HF patients stems from the recent results of the Italian study, Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico-Heart Failure (GISSI-HF). GISSI-HF was a randomized, large scale, double-blind, placebo-controlled trial showing that n-3 PUFA (850-882 mg/d) reduced mortality and admission to the hospital for cardiovascular reasons in patients with chronic heart failure (HF) who were already receiving recommended therapies. The clinical benefit observed in GISSI-HF seemed to be mediated prominently by the antiarrhythmic effects of n-3 PUFA, though an effect on mechanisms related to HF progression cannot be excluded. This article presents the results of GISSI-HF study and reviews the previous clinical evidence on n-3 PUFA and risk of heart failure and discusses in depth the potential mechanisms through which n-3 PUFA treatment can improve clinical outcome in HF patients.

Angiogenesis modifications related with cetuximab plus irinotecan as anticancer treatment in advanced colorectal cancer patients.

INTRODUCTION: Angiogenesis has been correlated with increased invasion and metastases in a variety of human neoplasms. Inadequate inhibition of the growth of tumor microvessels by anticancer agents may result in treatment failure, rated clinically as progressive or stable disease. We designed this trial to investigate the modification of the vascular endothelial growth factor (VEGF) and interferon-gamma (IFN-gamma) in advanced colorectal cancer patients during treatment with a weekly combination of cetuximab plus irinotecan. MATERIALS AND METHODS: Forty-five metastatic colorectal cancer patients were prospectively evaluated for circulating levels of VEGF and IFN-gamma during the treatment with cetuximab (initial dose of 400 mg/m(2), followed by weekly infusions of 250 mg/m(2)) plus weekly irinotecan (90 mg/m(2)). The circulating levels of the cytokines were assessed at the following time points: just before and at 1, 21, 50 and 92 days after the start of cetuximab plus irinotecan treatment. RESULTS: Basal serum VEGF median levels were significantly decreased just at the first day (after the first treatment infusion (P = 0.016). The VEGF persisted at the following time points reaching the highest statistical significance 92 days after the first infusion (P < 0.0001). On the contrary, IFN-gamma values showed a statistical significant increase one day after the first infusion (P < 0.0001). This effect persisted 21 days after the treatment start (P = 0.001), but was no more evident at the following time points. Moreover, a linear regression model with variance analysis showed a significant negative correlation between VEGF and IFN-gamma values 1, 21 and 50 days after the treatment beginning (P = 0.002, 0.001 and 0.047, respectively). CONCLUSIONS: This study suggests that a cetuximab may induce a modulation of VEGF circulating levels. The reduction of VEGF serum levels is a sudden and long lasting phenomenon. Moreover, in our study we identified a IFN-gamma increase, even if the specific role of this behavior remains to be investigated.

Cell cycle alterations and lung cancer.

It is now widely accepted that human carcinogenesis is a multi-step process and phenotypic changes during cancer progression reflect the sequential accumulation of genetic alterations in cells. The recent progress of scientific research has notably increased knowledge about biological events involved in lung cancer pathogenesis and progression, thanks to the use of molecular biology and immunohistochemistry techniques. Lots of the genetic alteration found in small cells lung cancer (SCLC) and in not small cells lung cancer (NSCLC) concern the expression of cell cycle genes, actually recognized as onco-suppressor genes and the lack of equilibrium between oncogenes and oncosuppressor genes. The present review of literature widely describes the cell cycle control, the lung cancer molecular pathogenesis, the catalog of known genetic alterations and the recent advances in global expression profiles in lung tumors, on the basis of the various hystological types too. Such data suggest the potential use of this knowledges in clinical practice both as prognostic factors and innovative therapeutic possibilities and they impose the necessity of new studies about cell cycle control and lung carcinogenesis.

Antiarrhythmic mechanisms of n-3 PUFA and the results of the GISSI-Prevenzione trial.

The purpose of this paper is twofold: on the one hand, to confirm the positive results on n-3 PUFA from the overall results Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GlSSI)-Prevenzione trial; on the other, to summarize and describe how the results of an important trial can help generate hypotheses either on mechanisms of action or on differential results in particular subgroups of patients, as well as test the pathophysiological hypotheses that have accompanied in the years the story of the hypothesized mechanisms of action of a drug. GISSI-Prevenzione was conceived as a pragmatic population trial on patients with recent myocardial infarction and it was conducted in the framework of the Italian public health system. In GISSI-Prevenzione, 11,323 patients were enrolled in a clinical trial aimed at testing the effectiveness of n-3 polyunsaturated fatty acids (PUFA) and vitamin E. Patients were invited to follow Mediterranean dietary habits, and were treated with up-to-date preventive pharmacological interventions. Long-term n-3 PUFA at 1 g daily, but not vitamin E at 300 mg daily, was beneficial for death and for combined death, non-fatal myocardial infarction, and stroke. All the benefit, however, was attributable to the decrease in risk for overall (-20%), cardiovascular (-30%), and sudden death (-45%). At variance from the orientation of a scientific scenario largely dominated by the "cholesterol-heart hypothesis", GISSI-Prevenzione results indicate n-3 PUFA (virtually devoid of any cholesterol-lowering effect) as a relevant pharmacological treatment for secondary prevention after myocardial infarction.

CtBP/BARS induces fission of Golgi membranes by acylating lysophosphatidic acid.

Membrane fission is essential in intracellular transport. Acyl-coenzyme As (acyl-CoAs) are important in lipid remodelling and are required for fission of COPI-coated vesicles. Here we show that CtBP/BARS, a protein that functions in the dynamics of Golgi tubules, is an essential component of the fission machinery operating at Golgi tubular networks, including Golgi compartments involved in protein transport and sorting. CtBP/BARS-induced fission was preceded by the formation of constricted sites in Golgi tubules, whose extreme curvature is likely to involve local changes in the membrane lipid composition. We find that CtBP/BARS uses acyl-CoA to selectively catalyse the acylation of lysophosphatidic acid to phosphatidic acid both in pure lipidic systems and in Golgi membranes, and that this reaction is essential for fission. Our results indicate a key role for lipid metabolic pathways in membrane fission.

Molecular cloning and functional characterization of brefeldin A-ADP-ribosylated substrate. A novel protein involved in the maintenance of the Golgi structure.

Brefeldin A (BFA) is a fungal metabolite that disassembles the Golgi apparatus into tubular networks and causes the dissociation of coatomer proteins from Golgi membranes. We have previously shown that an additional effect of BFA is to stimulate the ADP-ribosylation of two cytosolic proteins of 38 and 50 kDa (brefeldin A-ADP-riboslyated substrate (BARS)) and that this effect greatly facilitates the Golgi-disassembling activity of the toxin. In this study, BARS has been purified from rat brain cytosol and microsequenced, and the BARS cDNA has been cloned. BARS shares high homology with two known proteins, C-terminal-binding protein 1 (CtBP1) and CtBP2. It is therefore a third member of the CtBP family. The role of BARS in Golgi disassembly by BFA was verified in permeabilized cells. In the presence of dialyzed cytosol that had been previously depleted of BARS or treated with an anti-BARS antibody, BFA potently disassembled the Golgi. However, in cytosol complemented with purified BARS, or even in control cytosols containing physiological levels of BARS, the action of BFA on Golgi disassembly was strongly inhibited. These results suggest that BARS exerts a negative control on Golgi tubulation, with important consequences for the structure and function of the Golgi complex.

Role of brefeldin A-dependent ADP-ribosylation in the control of intracellular membrane transport.

The fungal toxin brefeldin A (BFA) dissociates coat proteins from Golgi membranes, causes the rapid disassembly of the Golgi complex and potently stimulates the ADP-ribosylation of two cytosolic proteins of 38 and 50 kDa. These proteins have been identified as the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and a novel guanine nucleotide binding protein (BARS-50), respectively. The role of ADP-ribosylation in mediating the effects of BFA on the structure and function of the Golgi complex was analyzed by several approaches including the use of selective pharmacological blockers of the reaction and the use of ADP-ribosylated cytosol and/or enriched preparations of the BFA-induced ADP-ribosylation substrates, GAPDH and BARS-50. A series of blockers of the BFA-dependent ADP-ribosylation reaction identified in our laboratory inhibited the effects of BFA on Golgi morphology and, with similar potency, the ADP-ribosylation of BARS-50 and GAPDH. In permeabilized RBL cells, the BFA-dependent disassembly of the Golgi complex required NAD+ and cytosol. Cytosol that had been previously ADP-ribosylated (namely, it contained ADP-ribosylated GAPDH and BARS-50), was instead sufficient to sustain the Golgi disassembly induced by BFA. Taken together, these results indicate that an ADP-ribosylation reaction is part of the mechanism of action of BFA and it might intervene in the control of the structure and function of the Golgi complex.

Possible role of BARS-50, a substrate of brefeldin A-dependent mono-ADP-ribosylation, in intracellular transport.

Brefeldin A (BFA), a fungal metabolite that inhibits membrane transport, potently stimulates an endogenous ADP-ribosylation reaction that selectively modifies two cytosolic proteins of 38 and 50 kDa on an amino acid residue different from those used by all known mADPRTs. The 38-kDa substrate was identified as the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH), whereas the 50-kDa substrate (BARS-50) was characterized as a novel guanine nucleotide binding protein. Thus, BARS-50 is able to bind GTP and its ADP-ribosylation is inhibited by the beta gamma subunit of GTP-binding (G) proteins. Moreover, BARS-50 was demonstrated to be a group of closely related proteins that appear to be different from all the known G proteins. A partially purified BARS-50 was obtained from rat brain cytosol, which was then used for microsequencing and in functional studies. A similar procedure led to the purification of native (non-ADP-ribosylated) BARS-50. The possible role of the BFA-dependent ADP-ribosylation and of BARS-50 in the maintenance of Golgi structure and function was addressed by examining which of the effects of BFA may be modified by inhibiting this reaction. We find that the BFA-dependent transformation of the Golgi stacks into a tubular reticular network is prevented when the BFA-dependent ADP-ribosylation activity was blocked by specific inhibitors thus indicating that BFA-dependent ADP-ribosylation of cytosolic proteins participate in the dynamic regulation of intracellular transport.

Modulatory role of GTP-binding proteins in the endogenous ADP-ribosylation of cytosolic proteins.

The endogenous ADP-ribosylation of cytosolic proteins and the pattern of NAD degradation were analyzed in subcellular fractions of rat liver in order to investigate the modulation of these reactions by GTP-binding (G) proteins. We could show that intracellular membranes from rat liver have a guanine nucleotide- and divalent cation-dependent pyrophosphatase activity able to rapidly degrade NAD to AMP. This enzymatic activity was investigated by two different approaches: the degradation of [32P]-NAD in the presence of intracellular membranes and the mono-ADP-ribosylation of cytosolic proteins. Divalent cations, preferentially Zn2+ and Mn2+, were required for the pyrophosphatase activity, since in the presence of the Zn2+ chelator TPEN (N,N,N',N'-tetrakis(2-pyridyl-methyl)ethylenediamine) or EDTA, the NAD degradation was inhibited by about 50%. Accordingly, in the presence of TPEN the endogenous ADP-ribosylation of cytosolic proteins was enhanced, whereas Zn2+ caused a significant inhibition of this reaction. GDP beta S was able to strongly activate the mono-ADP-ribosylation of cytosolic proteins. This effect was abolished by GTP gamma S, suggesting that a G protein, or rather one of the subunits of a heterotrimeric G protein, is involved in the modulation of the pyrophosphatase and consequently, of endogenous ADP-ribosylation. We propose that a regulatory pathway involving a heterotrimeric G protein modulates enzymes affecting the NAD turnover and availability of NAD for endogenous mADPRTs.

Role of NAD+ and ADP-ribosylation in the maintenance of the Golgi structure.

We have investigated the role of the ADP- ribosylation induced by brefeldin A (BFA) in the mechanisms controlling the architecture of the Golgi complex. BFA causes the rapid disassembly of this organelle into a network of tubules, prevents the association of coatomer and other proteins to Golgi membranes, and stimulates the ADP-ribosylation of two cytosolic proteins of 38 and 50 kD (GAPDH and BARS-50; De Matteis, M.A., M. DiGirolamo, A. Colanzi, M. Pallas, G. Di Tullio, L.J. McDonald, J. Moss, G. Santini, S. Bannykh, D. Corda, and A. Luini. 1994. Proc. Natl. Acad. Sci. USA. 91:1114-1118; Di Girolamo, M., M.G. Silletta, M.A. De Matteis, A. Braca, A. Colanzi, D. Pawlak, M.M. Rasenick, A. Luini, and D. Corda. 1995. Proc. Natl. Acad. Sci. USA. 92:7065-7069). To study the role of ADP-ribosylation, this reaction was inhibited by depletion of NAD+ (the ADP-ribose donor) or by using selective pharmacological blockers in permeabilized cells. In NAD+-depleted cells and in the presence of dialized cytosol, BFA detached coat proteins from Golgi membranes with normal potency but failed to alter the organelle's structure. Readdition of NAD+ triggered Golgi disassembly by BFA. This effect of NAD+ was mimicked by the use of pre-ADP- ribosylated cytosol. The further addition of extracts enriched in native BARS-50 abolished the ability of ADP-ribosylated cytosol to support the effect of BFA. Pharmacological blockers of the BFA-dependent ADP-ribosylation (Weigert, R., A. Colanzi, A. Mironov, R. Buccione, C. Cericola, M.G. Sciulli, G. Santini, S. Flati, A. Fusella, J. Donaldson, M. DiGirolamo, D. Corda, M.A. De Matteis, and A. Luini. 1997. J. Biol. Chem. 272:14200-14207) prevented Golgi disassembly by BFA in permeabilized cells. These inhibitors became inactive in the presence of pre-ADP-ribosylated cytosol, and their activity was rescued by supplementing the cytosol with a native BARS-50-enriched fraction. These results indicate that ADP-ribosylation plays a role in the Golgi disassembling activity of BFA, and suggest that the ADP-ribosylated substrates are components of the machinery controlling the structure of the Golgi apparatus.

Evidence that the 50-kDa substrate of brefeldin A-dependent ADP-ribosylation binds GTP and is modulated by the G-protein beta gamma subunit complex.

Brefeldin A, a fungal metabolite that inhibits membrane transport, induces the mono(ADP-ribosyl)ation of two cytosolic proteins of 38 and 50 kDa as judged by SDS/PAGE. The 38-kDa substrate has been previously identified as glyceraldehyde-3-phosphate dehydrogenase (GAPDH). We report that the 50-kDa BFA-induced ADP-ribosylated substrate (BARS-50) has native forms of 170 and 130 kDa, as determined by gel filtration of rat brain cytosol, indicating that BARS-50 might exist as a multimeric complex. BARS-50 can bind GTP, as indicated by blot-overlay studies with [alpha-32P]GTP and by photoaffinity labeling with guanosine 5'-[gamma-32P] [beta,gamma-(4-azidoanilido)]triphosphate. Moreover, ADP-ribosylation of BARS-50 was completely inhibited by the beta gamma subunit complex of G proteins, while the ADP-ribosylation of GAPDH was unmodified, indicating that this effect was due to an interaction of the beta gamma complex with BARS-50, rather than with the ADP-ribosylating enzyme. Two-dimensional gel electrophoresis and immunoblot analysis shows that BARS-50 is a group of closely related proteins that appear to be different from all the known GTP-binding proteins.

Signalling pathways involved in the mitogenic action of lysophosphatidylinositol.

Lysophosphatidylinositol has been previously shown to stimulate cell proliferation in differentiated and in K-ras transformed thyroid cells. Increased levels of lysophosphatidylinositol, but not lysophosphatidylcholine or lysophosphatidylethanolamine, are present in thyroid as well as in other ras-transformed cell lines. We have now investigated the mechanism of action of this lysolipid by analysing its effects in a differentiated thyroid cell line. Lysophosphatidylinositol did not increase the levels of cAMP, the main stimulator of cell proliferation in the thyroid, whereas it stimulated phosphoinositide breakdown, mobilization of cytosolic Ca2+ and arachidonic acid release, suggesting that it activates both phospholipases C and A2. None of the effects of lysophosphatidylinositol were prevented by pretreatment of cells with pertussis toxin. Instead, the tyrosine kinase inhibitors, tyrphostins AG18 and AG561, completely blocked its mitogenic action. The effects of lysophosphatidylinositol were distinguishable from those of the well known mitogen lysophosphatidic acid, which affected differently the signalling pathways analysed and was not mitogenic in ras-transformed cells. These results suggest that the mitogenic activity of lysophosphatidylinositol is associated with the activation of phospholipase C and phospholipase A2 and is relatively specific for ras-transformed cells.

Physiological concentrations of thyrotropin increase cytosolic calcium levels in primary cultures of human thyroid cells.

The activity of TSH, the main regulator of growth and differentiation in the thyroid, has been mainly related to the activation of the adenylyl cyclase cascade. TSH also activates phospholipase-C and -A2; these effects, however, have been reported to require concentrations of the hormone up to 1000-fold higher than those effective on adenylyl cyclase, suggesting that the main physiological mechanism involved in the action of TSH is the activation of this enzyme. Using primary cultures of human thyroids, we here show that physiological concentrations of TSH (0.01-10 mU/L) are also able to increase intracellular Ca2+ levels. Cells were loaded with the fluorescent Ca2+ probe fura-2 and analyzed by single cell Ca2+ recording. The basal Ca2+ level was 105 +/- 30 nmol/L, and physiological concentrations of TSH increased it by 2- to 7-fold. The Ca2+ increase was transient and lasted up to 10 min. It is also shown that the TSH-dependent Ca2+ increase involves both the activation of phospholipase-C and the entry of extracellular Ca2+. TSH (100-10000 mU/L) increased cAMP levels by up to 20-fold in parallel experiments performed on the same cell preparations. These data demonstrate that physiological concentrations of TSH are able to increase cytosolic Ca2+ levels, indicating that this second messenger might directly mediate the action of this hormone in the thyroid.