Two-Drug Regimen Containing Darunavir: Metabolic Evaluation of an Old Dual Therapy.

Regimens containing darunavir are one of the first one with two drugs that demonstrated good efficacy as a simplification strategy. We wanted to describe the characteristics of patients followed in our center on a dual therapy regimen containing darunavir evaluating the metabolic aspects during follow-ups. We collected data from 208 patients switching to lamivudine plus darunavir with either ritonavir or cobicistat between 2010 and 2019. In all patients we found an increase in low-density lipoprotein (LDL), with no rising in creatinine, total cholesterol, or triglycerides. Twenty-five patients reached 120 weeks of follow-up. In these patients, no significant metabolic changes were described without concomitant treatment with drugs for dyslipidemia. These regimens seem to be more tolerable in metabolic profile compared with the data concerning three-drug therapies, leading only to a slight increase in LDL. The main reason for discontinuation was for a single-tablet therapy. None of the patients started treatment for dyslipidemia.

Cardiovascular Disease Risk in a Cohort of Virologically Suppressed People Living with HIV Switching to Doravirine: Preliminary Data from the Real Life.

Aim of this study is to assess the impact of doravirine (DOR)-based regimens on cardiovascular risk in treatment-experienced people living with HIV (PLWHIV). We retrospectively analyzed a cohort of 40 treatment-experienced PLWHIV switching to a DOR-based three-drug regimen, evaluating 10-year risk of manifesting clinical cardiovascular diseases (CD) through the Framingham Risk Score at baseline, 12, and 24 weeks of follow-up. At baseline, median predicted 10-year risk of cardiovascular disease (10Y-CD) was 8.0% (interquartile range 4.0-13.0). After 12 weeks, we observed a significant reduction in 10Y-CD (mean decrease -2.21, p = .012); similarly, we observed a nonsignificant reduction at week 24 (p = .336). Regarding metabolic parameters, after 24 weeks we observed a significant reduction in total cholesterol (median change -8.8 mg/dL, p = .018), low-density lipoprotein cholesterol (median -9.5 mg/dL, p = .007), and triglycerides (median -19.8 mg/dL, p < .001). Our results show a favorable metabolic impact of DOR-based regimens along with a promising reduction in 10-year risk of cardiovascular disease.

Are we ready for long-acting? A feasibility evaluation of long-acting cabotegravir-rilpivirine in clinical practice.

Cabotegravir and rilpivirine are the first drugs to be approved as injectable therapy to treat individuals with HIV. Despite encouraging results, the guidelines specify strict criteria for eligibility that could limit the feasibility of this strategy. We collected the clinical data of HIV-positive patients who were being treated at a single, third-level center in Italy. All patients were on stable therapy and showed suppressed viral load on their most recent analyses. We performed a cross-sectional analysis of the clinical and viro-immunological characteristics of this population and excluded patients who had previous virological failures, resistance-associated mutations (RAMs) to rilpivirine or integrase inhibitors in the historical genotype, hepatitis B infection, absence of previous genotypes, and the coexistence of HIV-subtype A and obesity. Our aim was to evaluate the proportion of patients who could be eligible for switching to this strategy. one thousand seven hundred fifty-two patients were eligible. One hundred and forty-eight were excluded because of a detectable viral load. With regard to the exclusion criteria, 48 patients had coinfection with hepatitis B virus, and 744 had a history of previous virological failures. Of the 896 patients with at least one genotypic resistance test, 161 had one or more RAMs to rilpivirine and 3 had RAMs to cabotegravir. None of the patients presented the combination of obesity and the A viral subtype. Overall, 31.2% of the patients were ineligible for cabotegravir-rilpivirine, and the proportion increased to 47.3% when we considered only patients with all available information concerning resistance tests. Approximately half of our cohort of patients did not fulfill the criteria and even more patients were potentially ineligible for cabotegravir-rilpivirine due to the lack of genotypic resistance tests. Also, fertile women had to be excluded due to the lack of data about this combination during pregnancy and breastfeeding.

Viral Encephalitis in Adults: A Narrative Review.

Viral infections of the central nervous system cause frequent hospitalization. The pathogenesis of viral encephalitis involves both the direct action of invading pathogens and the damage generated by the inflammatory reaction they trigger. The type of signs and symptoms presented by the patient depends on the severity and location of the ongoing inflammatory process. Most of the viral encephalitides are characterized by an acute development, fever, variable alterations in consciousness (confusion, lethargy, even coma), seizures (focal and generalized) and focal neurologic signs. The specific diagnosis of encephalitis is usually based on lumbar puncture. Cerebrospinal fluid examination should be performed in all patients unless absolutely contraindicated. Also, electroencephalogram and neuroimaging play a prominent role in diagnosis. Airway protection, ventilatory support, the management of raised intracranial pressure and correction of electrolyte disorders must be immediately considered in a patient with altered mental status. The only therapy strictly recommended is acyclovir in HSV encephalitis. The use of adjunctive glucocorticoids has poor-quality evidence in HSV, EBV, or VZV encephalitis. The role of antiviral therapy in other types of viral encephalitis is not well defined.

Evaluation of doravirine-based regimen population target in a large Italian clinical center.

BACKGROUND: Doravirine (DOR) is a non-nucleoside reverse transcriptase inhibitor (NNRTI) approved for HIV-1 infection treatment. Because of its genetic barrier, DOR appears to be a good alternative in switch strategies compared to other NNRTI. Our aim was to evaluate the percentage of people living with HIV (PLWHIV) followed in our center who could be eligible to a DOR-based regimen. METHODS: We collected data from all treatment-experienced PLWHIV, never exposed to DOR and with a demonstrated virological suppression. We analyzed previous genotypic analyses, clinical history, and previous exposure to NNRTIs. RESULTS: We analyzed data from 653 patients, whose characteristics are shown in Table 1. 59% of them presented no resistance mutation (RAM) at genotypic analysis. The most common DOR-related RAM were V106A, Y181V, and Y188L. We also analyzed RAM that can possibly interfere with combination therapy (mostly K65R and M184V). In the end, 81.8% of our patients results to be eligible for a DOR-based therapy regimen. CONCLUSIONS: DOR represents a good option for switch strategies in virological suppressed PLWHIV. It seems to have a higher genetic barrier and a lower risk for resistance mutation development compared to other NNRTI. In our cohort, we found 81.8% of patients who could be eligible for a regimen containing DOR and almost 2/3 of patients who can be treated with the fixed-dose combination DOR/3TC/TDF.

Short Communication: Comparing Lamivudine+Dolutegravir and Bictegravir/Emtricitabine/Tenofovir Alafenamide as Switch Strategies: Preliminary Results from Clinical Practice.

We tried to investigate and compare the safety of a dual therapy (DT) with dolutegravir+lamivudine (DTG +3TC) versus bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF). We performed a retrospective analysis in a cohort of virologically suppressed HIV+ pts switching to DT or BIC in our center. Primary endpoint was to evaluate time to treatment discontinuation (TD) for any cause. Survival analysis was employed to determine time to TD and its predictors were analyzed by Cox regression. Moreover, we collected viro-immunological parameters as well as markers of renal function and lipid profile at baseline and after 24 weeks and assessed changes through nonparametric tests. We analyzed 476 patients: 350 starting a DT and 126 starting BIC. Overall, we registered 21 TD: 15 in the DT group during 170 patient-years of follow-up (PYFU) (a rate of 8.8 per 100 PYFU) and 6 in the BIC one during 48 PYFU (12.5 per 100 PYFU). Estimated probabilities of maintaining study regimen after 24 weeks were 95.5% [standard deviation (SD) ±1.1] in the DT group and 94.9% (SD ±2.0) in the BIC group, with no significant differences between them (log-rank p = .639). Concerning metabolic profile, in the DT group, after 24 weeks, triglycerides decreased significantly (median change -14 mg/dL, p < .001), whereas high-density lipoprotein cholesterol increased (+3 mg/dL, p = .031). In the BIC group, meanwhile, we observed a significant decrease in low-density lipoprotein cholesterol after 24 weeks (-13 mg/dL, p = .026). Both optimization strategies showed high tolerability in the short term in experienced pts, with few differences between them. Further studies are needed to properly assess the matter.

FKBP51s signature in peripheral blood mononuclear cells of melanoma patients as a possible predictive factor for immunotherapy.

The inhibitory immune checkpoint PD-L1/PD1 promotes the alternative splicing of the FKBP5 gene, resulting in increased expression of its variant 4 in the peripheral blood mononuclear cells of melanoma patients. The variant 4 transcript is translated into the truncated FKBP51s protein. Given the importance of co-inhibitory signalling in tumour immune escape, here we tested the potential for using FKBP51s expression to predict immunotherapy outcomes. To do this, we immunophenotyped PBMCs from 118 melanoma patients and 77 age- and sex-matched healthy controls. Blood samples were collected before patients underwent ipilimumab treatment. In 64 of the 118 patients, FKBP51s expression was also assessed in regulatory T cells (Tregs). We found that each PBMC subset analysed contained an FKBP51spos fraction, and that this fraction was greater in the melanoma patients than healthy controls. In CD4 T lymphocytes, the FKBP51sneg fraction was significantly impaired. Tregs count was increased in melanoma patients, which is in line with previous studies. Also, by analyses of FKBP51s in Tregs, we identified a subgroup of ipilimumab nonresponder patients (p = 0.002). In conclusion, FKBP51s-based immunophenotyping of melanoma patients revealed several profiles related to a negative immune regulatory control and identified an unknown Treg subset. These findings are likely to be useful in the selection of the patients that are candidate for immunotherapy.

Effects Of Glycoprotein IIb/IIIa Antagonists: Anti Platelet Aggregation And Beyond.

BACKGROUND: The use of inhibitors of glycoprotein IIb/IIIa (GPIIb/IIIa) has provided dramatic results in terms of the prevention of acute stent thrombosis and a reduction in major adverse coronary events in patients subjected to percutaneous coronary intervention. GPIIb/IIIa or αIIbß3 is a member of the ß3 subfamily of integrins, which also includes αVß3. GPIIb/IIIa functions as a receptor for fibrinogen and several adhesion proteins sharing an arginine-glycine-aspartic acid (RGD) sequence. GPIIb/IIIa antagonists, through blockade of the receptor, prevent platelet aggregation. Among the three GPIIb/IIIa antagonists used in therapy, abciximab is an anti-ß3 monoclonal antibody, while tirofiban and eptifibatide mimic the binding sequence of the fibrinogen ligand. Although antiplatelet aggregation represents the central function of GPIIb/IIIa inhibitors, further actions have been documented for these compounds. OBJECTIVE: The aim of the present article is to review the structures and functions of GPIIb/IIIa antagonists and to highlight the clinical outcomes and results of randomized trials with these compounds. Hypotheses on the unexplored potential of GPIIb/IIIa antagonists will be put forward. CONCLUSION: GPIIb/IIIa inhibitors were developed to prevent platelet aggregation, however, these compounds can exert further biological functions, both platelet- and non-platelet-related. Large-scale studies comparing the efficacy and safety of GPIIb/IIIa antagonists are lacking. More insights into the functions of these compounds may lead to generation of novel small molecules able to antagonize platelet aggregation while promoting vascular repair.

Tirofiban counteracts endothelial cell apoptosis through the VEGF/VEGFR2/pAkt axis.

Tirofiban is used in the treatment of patients with acute coronary syndrome submitted to percutaneous coronary intervention (PCI). We have, previously, shown that tirofiban stimulates VEGF expression and promotes proliferation of endothelial cells. VEGF is a well known inhibitor of endothelial cell apoptosis. TNF-α is a pro-apoptotic cytokine released in the site of a vascular injury, including balloon angioplasty. We thought to investigate whether tirofiban was able to protect endothelial cells from cell death induced by TNF-α. For this study, we used human umbilical vein endothelial cells (HUVEC). Analysis of apoptosis was performed by propidium iodide incorporation, annexin V staining and measure of active caspase 3 levels. Western blot served for a semiquantitative measure of Akt activation, VEGF, and the pro-apoptotic Bim and Bak. Our results show that TNF-α was unable to activate caspase 3 and produce cell death in the presence of tirofiban. Activation of apoptosis was preceded by upregulation of Bim and Bak that resulted decreased after addition of tirofiban. The anti-apoptosis effect of tirofiban was reproduced by VEGF and counteracted by VEGFR2 blockade and the cation chelating agent ethylene glycol tetraacetic acid (EGTA). The use of p-Akt inhibitor, BEZ235,and Akt knockdown, suggested that pAkt mediated the prosurvival effect of tirofiban. In conclusion, tirofiban protects endothelial cells from apoptosis stimulated by TNF-α, due to its ability to stimulate VEGF production.

FKBP51 employs both scaffold and isomerase functions to promote NF-κB activation in melanoma.

Melanoma is the most aggressive skin cancer; its prognosis, particularly in advanced stages, is disappointing largely due to the resistance to conventional anticancer treatments and high metastatic potential. NF-κB constitutive activation is a major factor for the apoptosis resistance of melanoma. Several studies suggest a role for the immunophilin FKBP51 in NF-κB activation, but the underlying mechanism is still unknown. In the present study, we demonstrate that FKBP51 physically interacts with IKK subunits, and facilitates IKK complex assembly. FKBP51-knockdown inhibits the binding of IKKγ to the IKK catalytic subunits, IKK-α and -ß, and attenuates the IKK catalytic activity. Using FK506, an inhibitor of the FKBP51 isomerase activity, we found that the IKK-regulatory role of FKBP51 involves both its scaffold function and its isomerase activity. Moreover, FKBP51 also interacts with TRAF2, an upstream mediator of IKK activation. Interestingly, both FKBP51 TPR and PPIase domains are required for its interaction with TRAF2 and IKKγ, whereas only the TPR domain is involved in interactions with IKKα and ß. Collectively, these results suggest that FKBP51 promotes NF-κB activation by serving as an IKK scaffold as well as an isomerase. Our findings have profound implications for designing novel melanoma therapies based on modulation of FKBP51.

Molecular Aspects of FKBP51 that Enable Melanoma Dissemination.

FKBP51 (FKBP5 Official Symbol) is large molecular weight member of the FK506 binding protein family, a subfamily of the immunophilin proteins. FKBP51 exerts multiple biological functions in the cell, including modulation of steroid hormone response, immune regulation, cell proliferation, regulation of pAkt levels and control of NF-κB activation. Several lines of evidence support a role for this protein in cancer biology, especially in resistance to chemo- and radio-therapy. Recent research studies highlighted functions of FKBP51 in promoting the epithelial to mesenchymal transition (EMT) transdifferentiation program in melanoma. This process, which is classically regulated by Transforming Growth Factor (TGF)-ß, enables cancer cells to disseminate from primary tumors and spread to distant locations, acquiring resistance to therapy and self-renewal capability. This last, in turn, is crucial to their subsequent expansion at sites of dissemination. The aim of the present article is to review recent literature data that involve FKBP51 in the mechanisms that switch the TGF-ß from a tumor suppressor to a pro-metastatic invader.

Immunomodulatory pathways regulate expression of a spliced FKBP51 isoform in lymphocytes of melanoma patients.

FKBP51 (gene FKBP5) is an immunophilin capable of immunosuppression expressed in melanoma and lymphocytes. We found increased levels of a spliced FKBP5 variant in the PBMCs of 124 patients with melanoma. This variant encodes for an unknown isoform (FKBP51s). We hypothesized that FKBP51s resulted from tumour interaction with immune cells, through PDL-1/PD-1. To address this issue, we performed melanoma/PBMC cocultures. Furthermore, the immunohistochemistry of 76 melanoma specimens served to investigate whether FKBP51s stained tumour infiltrating lymphocytes. Our results showed that PBMCs expressed FKBP51s when cocultured with melanoma. Tumour PDL-1 knockdown or anti-PD-1 reduced FKBP51s expression in cocultured PBMCs. IHC showed a strong FKBP51s signal in tumour infiltrating lymphocytes, and lymphocytes of the invasion front of the tumour, along with melanoma PDL-1 expression. When overexpressed in melanoma, FKBP51s facilitated PDL-1 expression on the cell surface. In conclusion, our study shows that FKBP51s marks the PBMCs of patients with melanoma and is exploited by the tumour to immunomodulate through PDL-1.

Pleiotropic roles in cancer biology for multifaceted proteins FKBPs.

BACKGROUND: FK506 binding proteins (FKBP) are multifunctional proteins highly conserved across the species and abundantly expressed in the cell. In addition to a well-established role in immunosuppression, FKBPs modulate several signal transduction pathways in the cell, due to their isomerase activity and the capability to interact with other proteins, inducing changes in conformation and function of protein partners. Increasing literature data support the concept that FKBPs control cancer related pathways. SCOPE OF THE REVIEW: The aim of the present article is to review current knowledge on FKBPs roles in regulation of key signaling pathways associated with cancer. MAJOR CONCLUSIONS: Some family members appear to promote disease while others are protective against tumorigenesis. GENERAL SIGNIFICANCE: FKBPs family proteins are expected to provide new biomarkers and small molecular targets, in the near future, increasing diagnostic and therapeutic opportunities in the cancer field. This article is part of a Special Issue entitled Proline-Directed Foldases: Cell Signaling Catalysts and Drug Targets.

Tirofiban induces VEGF production and stimulates migration and proliferation of endothelial cells.

Tirofiban is a fibrinogen receptor antagonist, generated using the tripeptide Arg-Gly-Asp (RGD) as a template. RGD activates integrin receptors and integrin-mediated signals are necessary for normal cells to promote survival and stimulate cell cycle progression. We investigated whether tirofiban activated growth-stimulatory signals in endothelium. For this study human umbilical vein endothelial cells (HUVEC) and human aortic endothelial cells (HAEC) were used. Analysis of cell proliferation, by cell counts, showed that the number of endothelial cells doubled after 72 h of culture in the absence of tirofiban, while they were tripled and even quadrupled, in the presence of increasing doses of the drug. Moreover, tirofiban-stimulated cells had a greater ability to migrate through the transwell filters of Boyden chamber, compared to unstimulated cells. The scratch assay, which mimics cell migration during wound healing, showed that tirofiban stimulated HUVECs to migrate into the leading hedge of the scratch. Western blot showed that tirofiban increased the expression levels of VEGF and the downstream effectors Erk and cyclin D. An inhibitor of VEGFR2 counteracted tirofiban-induced-proliferation, suggesting a role for VEGF in such effect. Our study shows that tirofiban stimulates the migration and proliferation of endothelial cells suggesting that it can promote endothelial repair. Ex vivo cultures of arterial rings confirmed the growth stimulatory effect of tirofiban on endothelium. Thus, the benefits of tirofiban in those with acute coronary syndromes undergoing PTCA may be due to rapid endothelization of damaged vessel, besides antiplatelet effects.

FKBP51 increases the tumour-promoter potential of TGF-beta.

BACKGROUND: FKBP51 (FKBP5 Official Symbol) is a large molecular weight component of the family of FK506 binding proteins (FKBP). In recent years, research studies from our laboratory highlighted functions for FKBP51 in the control of apoptosis and melanoma progression. FKBP51 expression correlated with the invasiveness and aggressiveness of melanoma. Since a role for TGF-ß in the enhanced tumorigenic potential of melanoma cells is widely described, we hypothesized a cooperative effect between FKBP51 and TGF-ß in melanoma progression. METHODS: SAN and A375 melanoma cell lines were utilized for this study. Balb/c IL2γ NOD SCID served to assess the ability to colonize organs and metastasize of different cell lines, which was evaluated by in vivo imaging. Realtime PCR and western blot served for measurement of mRNA and protein expression, respectively. RESULTS: By comparing the metastatic potential of two melanoma cell lines, namely A375 and SAN, we confirmed that an increased capability to colonize murine organs was associated with increased levels of FKBP51. A375 melanoma cell line expressed FKBP51 mRNA levels 30-fold higher in comparison to the SAN mRNA level and appeared more aggressive than SAN melanoma cell line in an experimental metastasis model. In addition, A375 expressed, more abundantly than SAN, the TGF-ß and the pro angiogenic TGF-ß receptor type III (TßRIII) factors. FKBP51 silencing produced a reduction of TGF-ß and TßRIII gene expression in A375 cell line, in accordance with previous studies. We found that the inducing effect of TGF-ß on Sparc and Vimentin expression was impaired in condition of FKBP51 depletion, suggesting that FKBP51 is an important cofactor in the TGF-ß signal. Such a hypothesis was supported by co immunoprecipitation assays, showing that FKBP51 interacted with either Smad2,3 and p300. In normal melanocytes, FKBP51 potentiated the effect of TGF-ß on N-cadherin expression and conferred a mesenchymal-like morphology to such round-shaped cells. CONCLUSIONS: Overall, our findings show that FKBP51 enhances some pro oncogenic functions of TGF-ß, suggesting that FKBP51-overexpression may help melanoma to take advantage of the tumor promoting activities of the cytokine.

Cellular and molecular background underlying the diversity in therapeutic responses between primary tumours and metastases.

Metastasis, also called secondary neoplastic disease, is a tumour newly formed in a site different from that of origin, as a consequence of cancer progression and dissemination largely through blood and lymphatic vessels. The ability to form metastases is the main property that distinguishes malignant from benign tumours. Treatments for metastatic cancer are similar in practice to those for primary tumours, but such treatments are mostly palliative; indeed, almost all deaths caused by solid tumours occur in the metastatic phase. Increasing evidence supports the concept that therapies for primary tumours are inadequate to treat metastasis and can even promote formation of metastases, while exerting local growth control. Furthermore, recurrent tumours, which are denoted by increased aggressiveness and therapy resistance in comparison with the primary tumour, have an increased metastatic potential. Genetic modifications occurring during tumour progression lead to substantial differences between the primary and metastatic tumours. This emphasises the importance of designing novel therapies for metastasis. In the last decade, a number of studies have contributed to the understanding of the genetic rearrangements underlying the conversion of cancer cells into the metastasis founder cells. The present article aims at reviewing recent advances in metastasis research and attempts to discuss the reasons for which the therapeutic strategies against primary tumours may not satisfactorily address their metastatic counterparts.

Synergy between enzastaurin doxorubicin in inducing melanoma apoptosis.

Melanoma is resistant to most standard chemotherapeutics. We analysed the combined effect of doxorubicin and enzastaurin on cell death of four melanoma cell lines, namely G361, SK-MEL3, A375 and SAN. Enzastaurin IC50 was calculated by measure of growth inhibition with MTS assay and corresponded to 2 µM; the half maximal cytotoxicity of doxorubicin was obtained at 3 µM dose. Evaluation of combination index showed synergism (CI > 1) or additive effect (CI = 1) with all melanoma cell lines, with enzastaurin doses ≥0.6 µM and doxorubicin doses ≥1 µM. Combination of the two drugs resulted in increase in caspase 3 and 8 activation, in comparison with activation by single agents. Caspase 8 activation was impaired by TNFR-1 blocking. Our results show doxorubicin-stimulated production of TNFα, whereas enzastaurin-stimulated TNFR-1 expression on plasma membrane. The effect on TNFR-1 appeared to be mediated by PKCζ inhibition. Taken together, our findings suggest that enzastaurin increases doxorubicin-induced apoptosis of melanoma by a mechanism involving, at least in part, activation of the TNF-α signal.

Toxoplasma gondii Dense Granule Antigen 1 stimulates apoptosis of monocytes through autocrine TGF-ß signaling.

Monocyte/macrophages represent the first line of defense against protozoan parasites. Different mechanisms of monocyte suppression by Toxoplasma gondii that sustain parasite invasion and persistence have been described, including apoptosis. In the present study, we investigated the effect of microbial excretory­secretory polypeptides, namely the microneme protein MIC3 and the dense granule antigen GRA1, on apoptosis of monocytes from patients with congenital toxoplasmosis and healthy individuals. We found that GRA1 but not MIC3 could induce apoptosis of monocytes, observing the effect in samples from both Toxoplasma-infected and uninfected individuals, thus ruling out involvement of mechanisms of apoptosis linked to adaptive immunity or a cellular context related to infection. Selective inhibition of TGF-ß type I receptors reversed GRA1-induced apoptosis, indicating that this apoptosis involved canonical TGF-ß signaling. By using TGF-ß-neutralizing antibodies, we showed that monocyte apoptosis required endogenous TGF-ß and that GRA1 stimulation activated TGF-ß transcription and expression in monocytes but not lymphocytes, suggesting involvement of an autocrine TGF-ß-mediated mechanism in GRA1-induced apoptosis.

The effect of FK506 on transforming growth factor beta signaling and apoptosis in chronic lymphocytic leukemia B cells.

BACKGROUND: Loss of response to transforming growth factor-beta (TGF-beta ) is thought to contribute to the progression of chronic lymphocytic leukemia. Recent findings of over-activation of the TGF-beta signal in FKBP12-knockout mouse prompted us to investigate whether FK506, the canonical ligand of FKBP, can activate the TGF-beta signal in chronic lymphocytic leukemia. DESIGN AND METHODS: We studied 62 chronic lymphocytic leukemia samples from patients with Rai/Binet stage 0 to 4 disease. The TGF-beta signal was investigated by western blotting and flow cytometry. The levels of Bcl2-family members and death-associated-protein kinase were also investigated by western blotting, whereas apoptosis was studied in flow cytometry. Down-modulation of FKBP12 was obtained by gene silencing with short interfering RNA. RESULTS: Twenty-two out of 62 chronic lymphocytic leukemia samples were sensitive to TGF-beta-induced apoptosis. All but two of the responsive samples underwent apoptosis also when cultured with FK506, but not with cyclosporine. Thirteen samples that were not sensitive to TGF-beta were sensitive to FK506. Overall, response to FK506 occurred in 33 samples. FK506 induced Smad2 phosphorylation and nuclear translocation. Accordingly, death-associated-protein kinase, a transcriptional target of Smad, was induced. At the same time, Bcl-2 and Bcl-xL levels decreased whereas the levels of Bim and Bmf increased. A loss of mitochondrial membrane potential preceded caspase activation and cell death. FK506 removed FKBP12 from its binding to the TGF-beta-receptor. FKBP12 release activated the receptor-kinase activity as suggested by the enhanced levels of phospho-Smad found in cells depleted of FKBP12. CONCLUSIONS: Our study shows that most chronic lymphocytic leukemia cells escape the homeostatic control of TGF-beta and that FK506 restores the TGF-beta signal in a proportion of non-responsive samples. We demonstrated that FK506 activates TGF-beta receptor I kinase activity in chronic lymphocytic leukemia, which transduces apoptosis by a mitochondrial-dependent pathway.