Toxicity Evaluation of a Novel Magnetic Resonance Imaging Marker, CoCl2-N-Acetylcysteine, in Rats.

C4 (cobalt dichloride-N-acetylcysteine [1% CoCl2:2% NAC]) is a novel magnetic resonance imaging contrast marker that facilitates visualization of implanted radioactive seeds in cancer brachytherapy. We evaluated the toxicity of C4. Rats were assigned to control (0% CoCl2:NAC), low-dose (0.1% CoCl2:2% NAC), reference-dose (C4), and high-dose (10% CoCl2:2% NAC) groups. Agent was injected into the left quadriceps femoris muscle of the rats. Endpoints were organ and body weights, hematology, and serum chemistry and histopathologic changes of tissues at 48 hours and 28 and 63 days after dosing. Student's t tests were used. No abnormalities in clinical signs, terminal body and organ weights, or hematologic and serum chemistry were noted, and no gross or histopathologic lesions of systemic tissue toxicity were found in any treatment group at any time point studied. At the site of injection, concentration-dependent acute responses were observed in all treatment groups at 48 hours after dosing and were recovered by 28 days. No myofiber degeneration or necrosis was observed at 28 or 63 days in any group. In conclusion, a single intramuscular dose of C4 produced no acute or chronic systemic toxicity or inflammation in rats, suggesting that C4 may be toxicologically safe for clinical use in cancer brachytherapy.

Erratum to: Pharmacokinetic evaluation of nanoparticle albumin-bound paclitaxel delivered via hepatic arterial infusion in patients with predominantly hepatic metastases.

In the original article, corresponding author's given name and family name are flipped. It should be "Siqing Fu" rather than "Fu Siqing".

Pharmacokinetic evaluation of nanoparticle albumin-bound paclitaxel delivered via hepatic arterial infusion in patients with predominantly hepatic metastases.

PURPOSE: Cancer patients with predominantly hepatic metastases have poor outcomes and limited options. Hepatic arterial infusion (HAI) of a therapeutic agent may be an appropriate option for producing increased drug concentrations at the tumor sites while reducing systemic adverse effects in normal tissues. METHODS: Patients with predominantly hepatic metastases (n = 48) were placed in 6 groups according to nanoparticle albumin-bound paclitaxel (nab-paclitaxel) dose level using a 3 + 3 design plus dose expansion for responsive tumor types. We evaluated the toxicity, antitumor activity, and pharmacokinetics of nab-paclitaxel delivered via HAI. RESULTS: Thirty-eight and ten patients underwent HAI over 1 and 4 h, respectively, at doses of up to 300 mg/m(2). The treatment was safe and exhibited antitumor activity. Pharmacokinetic analyses revealed that HAI of nab-paclitaxel over 4 h resulted in markedly lower peak drug concentrations (C max) and longer times to peak concentration (T max) than that over 1 h. The self-control pharmacokinetic studies showed that HAI of nab-paclitaxel led to much lower C max and areas under the curve (AUC), compared with intravenous infusion. CONCLUSIONS: HAI of nab-paclitaxel at up to 300 mg/m(2) over 4 h was well tolerated. Pharmacokinetic evaluation of C max, T max, and AUC implied that 4-h HAI enhanced hepatic extraction of nab-paclitaxel. Further preclinical and clinical studies are required to develop reliable methods of evaluation of hepatic extraction (clinicaltrials.gov registration number NCT00732836, first registered on August 8, 2008, and last updated on October 27, 2014).

Physical and chemical stability of proflavine contrast agent solutions for early detection of oral cancer.

BACKGROUND AND PURPOSE: Proflavine hemisulfate solution is a fluorescence contrast agent to visualize cell nuclei using high-resolution optical imaging devices such as the high-resolution microendoscope. These devices provide real-time imaging to distinguish between normal versus neoplastic tissue. These images could be helpful for early screening of oral cancer and its precursors and to determine accurate margins of malignant tissue for ablative surgery. Extemporaneous preparation of proflavine solution for these diagnostic procedures requires preparation in batches and long-term storage to improve compounding efficiency in the pharmacy. However, there is a paucity of long-term stability data for proflavine contrast solutions. METHODS: The physical and chemical stability of 0.01% (10 mg/100 ml) proflavine hemisulfate solutions prepared in sterile water was determined following storage at refrigeration (4-8℃) and room temperature (23℃). Concentrations of proflavine were measured at predetermined time points up to 12 months using a validated stability-indicating high-performance liquid chromatography method. RESULTS: Proflavine solutions stored under refrigeration were physically and chemically stable for at least 12 months with concentrations ranging from 95% to 105% compared to initial concentration. However, in solutions stored at room temperature increased turbidity and particulates were observed in some of the tested vials at 9 months and 12 months with peak particle count reaching 17-fold increase compared to baseline. Solutions stored at room temperature were chemically stable up to six months (94-105%). CONCLUSION: Proflavine solutions at concentration of 0.01% were chemically and physically stable for at least 12 months under refrigeration. The solution was chemically stable for six months when stored at room temperature. We recommend long-term storage of proflavine solutions under refrigeration prior to diagnostic procedure.

An Oral Formulation of YK-4-279: Preclinical Efficacy and Acquired Resistance Patterns in Ewing Sarcoma.

Ewing sarcoma is a transcription factor-mediated pediatric bone tumor caused by a chromosomal translocation of the EWSR1 gene and one of several genes in the ETS family of transcription factors, typically FLI1 or ERG. Full activity of the resulting oncogenic fusion protein occurs only after binding RNA helicase A (RHA), and novel biologically targeted small molecules designed to interfere with that interaction have shown early promise in the preclinical setting. Herein, we demonstrate marked preclinical antineoplastic activity of an orally bioavailable formulation of YK-4-279 and identify mechanisms of acquired chemotherapy resistance that may be exploited to induce collateral sensitivity. Daily enteral administration of YK-4-279 led to significant delay in Ewing sarcoma tumor growth within a murine model. In advance of anticipated early-phase human clinical trials, we investigated both de novo and acquired mechanism(s) by which Ewing sarcoma cells evade YK-4-279-mediated cell death. Drug-resistant clones, formed by chronic in vitro exposure to steadily increased levels of YK-4-279, overexpressed c-Kit, cyclin D1, pStat3(Y705), and PKC isoforms. Interestingly, cross-resistance to imatinib and enzastaurin (selective inhibitors of c-Kit and PKC-ß, respectively), was observed and the use of YK-4-279 with enzastaurin in vitro led to marked drug synergy, suggesting a potential role for combination therapies in the future. By advancing an oral formulation of YK-4-279 and identifying prominent mechanisms of resistance, this preclinical research takes us one step closer to a shared goal of curing adolescents and young adults afflicted by Ewing sarcoma.

A Phase I/II Study of the mTOR Inhibitor Everolimus in Combination with HyperCVAD Chemotherapy in Patients with Relapsed/Refractory Acute Lymphoblastic Leukemia.

PURPOSE: Previous studies suggest a potential therapeutic role for mTOR inhibition in lymphoid malignancies. This single-center phase I/II study was designed to test the safety and efficacy of the mTOR inhibitor everolimus in combination with HyperCVAD chemotherapy in relapsed/refractory acute lymphoblastic leukemia (ALL). EXPERIMENTAL DESIGN: Twenty-four patients were treated; 15 received everolimus 5 mg/day and 9 received 10 mg/day with HyperCVAD. RESULTS: The median age of patients was 25 years (range, 11-64) and median number of prior treatments was 2 (range, 1-7). Grade 3 mucositis was the dose-limiting toxicity and the maximum tolerated everolimus dose was 5 mg/day. Responses included complete remission (CR) in 6 patients (25%), CR without platelet recovery (CRp) in 1 (4%), and CR without recovery of counts (CRi) in 1 (4%), for an overall response rate of 33%. In addition, partial response (PR) was noted in 2 patients (8%). Seven of 11 patients treated in first salvage achieved CR/CRp (64%). The median OS was 29 weeks for patients in first salvage versus 15 weeks for patients in second salvage and beyond (P ≤ 0.001). A response was noted in 5 of 10 (50%) heavily pretreated T-ALL patients (median of 4 prior salvage regimens). Everolimus significantly inhibited phosphorylation of S6RP, but this did not correlate with response. No significant decreases in p4EBP1 and pAkt levels were noted. Responders had higher everolimus dose-adjusted area under the curve (P = 0.025) and lower clearance (P = 0.025) than nonresponders. CONCLUSIONS: The combination of HyperCVAD and everolimus is well tolerated and moderately effective in relapsed ALL, specifically T-ALL.

SU2C phase Ib study of paclitaxel and MK-2206 in advanced solid tumors and metastatic breast cancer.

BACKGROUND: There is preclinical synergism between taxanes and MK-2206. We aim to determine the maximum tolerated dose, safety, and activity of combining MK-2206 and paclitaxel in metastatic cancer. METHODS: Patients received weekly doses of paclitaxel at 80mg/m2 on day 1, followed by MK-2206 orally on day 2 escalated at 90mg, 135mg, and 200mg. Treatment continued until progression, excessive toxicity, or patient request. Blood and tissue were collected for pharmacokinetic and pharmacodynamics markers. A cycle consisted of three weeks of therapy. Dose-limiting toxicity (DLT) was defined as unacceptable toxicity during the first cycle. All statistical tests were two-sided. RESULTS: Twenty-two patients were treated, nine in dose escalation and 13 in dose expansion. Median age was 55 years. Median number of cycles was four. Dose escalation was completed with no DLT. CTCAE Grade 3 or higher adverse events were fatigue (n = 2), rash (n = 2), hyperglycemia (n = 1), and neutropenia (n = 7). Four patients in the expansion phase required MK-2206 dose reduction. Phase II recommended dose was established as paclitaxel 80mg/m2 weekly on day 1, and MK-2206 135mg weekly on day 2. Paclitaxel systemic exposure was similar in the presence or absence of MK-2206. Plasma MK-2206 concentrations were similar to data from previous phase I monotherapy. There was a statistically significant decrease in expression of pAKT S473 (P = .01) and pAKT T308 (P = .002) after therapy. PI3K/AKT/mTOR downregulation in tumor tissues and circulating markers did not correlate with tumor response or clinical benefit. There were five objective responses, and nine patients had stable disease. CONCLUSION: MK-2206 was well tolerated with paclitaxel. Preliminary antitumor activity was documented.

Dual inhibition of the vascular endothelial growth factor pathway: a phase 1 trial evaluating bevacizumab and AZD2171 (cediranib) in patients with advanced solid tumors.

BACKGROUND: The current study was conducted to evaluate the safety and biological activity of dual inhibition of the vascular endothelial growth factor (VEGF) pathway with combined bevacizumab and cediranib (a VEGF receptor tyrosine kinase inhibitor). METHODS: This was a 3 + 3 dose escalation study in patients with advanced solid tumors. Cediranib was given orally daily for 21 days and bevacizumab intravenously every 2 weeks. Pharmacokinetics and correlates (nitric oxide synthase, nitrate oxide, and circulating tumor cells) were assessed. RESULTS: Fifty-one patients were treated. Dose-limiting toxicities (DLTs) (grade 3-4; graded according to the National Cancer Institute Common Terminology Criteria of Adverse Events [version 3.0]) observed included 1 patient with chest pain, 1 patient with fatigue, 2 patients with thrombocytopenia, 3 patients with hypertension (1 with intracranial hemorrhage), and 1 patient with grade 5 hemoptysis. Moreover, 2 patients presented with grade 3 intracranial bleeding beyond the DLT window. Dose level 2 (cediranib at a dose of 20 mg/day and bevacizumab at a dose of 5 mg/kg every 2 weeks) was selected as the recommended phase 2 dose (RP2D); 17 patients were treated at dose level 2 with 1 DLT and no intracranial bleeding or severe hypertension reported. Pharmacokinetics of cediranib at dose level 3 demonstrated a 46% to 77% increase in area under the curve (0-24 hours) on cycle 1 day 1 compared with historical controls. Four patients attained partial remissions: inflammatory breast cancer (-54%), basal cell carcinoma (-33%), alveolar soft part sarcoma (-33%), and synovial sarcoma (-32%). Patients with a lower circulating tumor cell count (< 30) at the predose period had a longer time to tumor progression (P = .024, log-rank test). CONCLUSIONS: Cediranib at a dose of 20 mg/day and bevacizumab at a dose of 5 mg/kg every 2 weeks was found to be the RP2D. Activity in several tumor types was noted. Central nervous system bleeding and severe hypertension were observed at doses above the RP2D.

Physical and chemical stability of high-dose ifosfamide and mesna for prolonged 14-day continuous infusion.

PURPOSE: Ifosfamide plus mesna have been used recently in a high-dose regimen that allows this chemotherapy to be given to outpatients with less toxicity over 14 days using a portable pump. However, there is a need for published stability information. The aim of this study was to investigate the physicochemical stability of ifosfamide with mesna in normal saline at room temperature over a prolonged period of 14 days. METHODS: Infusion solutions of 1:1 ifosfamide and mesna at final concentrations of 10, 20 and 30 mg/mL were prepared with 0.9% sodium chloride in PVC bags. Solutions were stored at room temperature. Concentrations of ifosfamide and mesna were measured at 0 and 1, 3, 7 and 14 days using a stability-indicating reversed phase high-performance liquid chromatography (HPLC) assay with ultraviolet detection. RESULTS: Ifosfamide and mesna were both physicochemically stable (>94%) for 14 days in all tested infusion solutions (10, 20 and 30 mg/mL). CONCLUSIONS: Our stability data indicate that ifosfamide and mesna (1:1) combination can be administered as a prolonged continuous infusion with portable pump in an outpatient setting without replacement of the infusion bag. We suggest 20 mg/mL as a reasonable concentration for infusion rates of about 2-4 cc/hr over prolonged periods of time.

Phase I study of the combination of sorafenib and temsirolimus in patients with metastatic melanoma.

PURPOSE: This phase I clinical trial was conducted to determine the safety, efficacy, and molecular effects of sorafenib with temsirolimus in patients with advanced melanoma. PATIENTS AND METHODS: Patients with stage IV or unresectable or recurrent stage III melanoma and Eastern Cooperative Oncology Group performance status of 0 to 1 were eligible. Sorafenib was given orally once or twice daily and temsirolimus was given i.v. weekly, both starting on day 1, with a 4-week cycle. Responses were assessed every 2 cycles per Response Evaluation Criteria in Solid Tumors criteria. Consenting patients with accessible tumors underwent optional tumor biopsies before treatment and after the second infusion of temsirolimus. Tumor biopsies were analyzed for activating mutations in BRAF and NRAS, and for expression of P-extracellular signal-regulated kinase (P-ERK) and P-S6 proteins. RESULTS: A total of 25 patients were accrued to the study. The maximum tolerated doses were sorafenib 400 mg every morning and 200 mg every evening and temsirolimus 25 mg i.v. weekly. Dose-limiting toxicities included thrombocytopenia, hand-foot syndrome, serum transaminase elevation, and hypertriglyceridemia. There were no complete or partial responses with the combination; 10 patients achieved stabilization of disease as their best response. The median progression-free survival was 2.1 months. Matching pretreatment and day 15 tumor biopsies showed marked inhibition of P-S6 with treatment in 3 of 4 evaluable patients, but minimal inhibition of P-ERK. CONCLUSIONS: Combination therapy with sorafenib and temsirolimus resulted in significant toxicity at higher dose levels, failed to achieve any clinical responses in genetically unselected patient population, and did not inhibit P-ERK.

Busulfan and metronidazole: an often forgotten but significant drug interaction.

OBJECTIVE: To report the case of a clinically significant drug interaction between intravenous busulfan and oral metronidazole observed through busulfan therapeutic drug monitoring (TDM). CASE SUMMARY: A 7-year-old boy with a history of myelodysplasia that progressed to acute myeloid leukemia received busulfan with therapeutic drug monitoring (TDM), clofarabine, and thiotepa as a pretransplant conditioning regimen for a cord blood transplant. The patient received metronidazole the day after a busulfan test dose of 0.5 mg/kg was administered. On the day of the first busulfan therapeutic dose, TDM was performed and the clearance of busulfan was significantly decreased by 46%. After 2 doses of busulfan therapy, the course area under the curve was exceeded, requiring discontinuation of busulfan. Metronidazole is not known to affect glutathione or the glutathione S-transferase A1 (GSTA1) enzyme system or cytochrome P450 (CYP) 3A4. DISCUSSION: Busulfan is a bifunctional alkylating agent widely used in pretransplant conditioning regimens in patients undergoing stem cell transplantation for hematologic malignancies. Busulfan metabolism is best described by hepatic conjugation to glutathione by GSTA1, although some CYP-dependent pathways have been described. Currently there is 1 publication describing the drug interaction between oral busulfan and oral metronidazole, in which concomitant use of metronidazole resulted in higher busulfan trough concentrations and higher risk of veno-occlusive disease. Our case represents a possible drug interaction based on the Horn Drug Interaction Probability Scale. CONCLUSIONS: Though the mechanistic basis for this interaction is unknown, the risks and benefits of using metronidazole during and in close proximity to busulfan should be carefully considered and therapeutic alternatives to metronidazole should be used when appropriate.

Phase I trial of hepatic arterial infusion of nanoparticle albumin-bound paclitaxel: toxicity, pharmacokinetics, and activity.

Because liver involvement in patients with metastatic cancer has limited options and poor outcomes, we conducted a phase I study to determine the safety, activity, and pharmacokinetic characteristics of hepatic arterial infusion of nanoparticle albumin-bound paclitaxel (HAI nab-paclitaxel). Cohorts of three patients having predominant hepatic metastases received HAI nab-paclitaxel at three dose levels (180, 220, and 260 mg/m(2), respectively) infused for more than 1 hour every 3 weeks (3 + 3 design). Some patients participated in comparative pharmacokinetic studies (i.v. vs. HAI), receiving their first course i.v., to determine peak concentrations and effect of first-pass hepatic extraction compared with subsequent courses administered by HAI. The highest dose level was expanded to determine the safety and activity of HAI nab-paclitaxel. Thirty-eight patients were treated. There were no dose-limiting toxicities at doses up to 260 mg/m(2). Common adverse events included alopecia, fatigue, myelosuppresion, nausea, and vomiting. Three patients had stable disease for 4 or more months and 2 patients (1 of 12 with breast cancer and 1 of 1 with cervical cancer) achieved a partial response lasting for 5 and 15 months, respectively. Peak concentrations were lower (∼50%) with greater hepatic extraction of drug (∼42%) following HAI than i.v. infusion based on area under the curve comparison of drug exposure. HAI nab-paclitaxel showed partial hepatic extraction. At doses 260 mg/m(2) or less given for 1 hour every 3 weeks, the treatment was well-tolerated and showed activity in advanced cancer patients with predominant liver metastases.

Phase 2 study of dasatinib in the treatment of head and neck squamous cell carcinoma.

BACKGROUND: Treatment options for patients with advanced head and neck squamous cell carcinoma (HNSCC) are scarce. This phase 2 study was conducted to evaluate the safety, tolerability, pharmacokinetics, and efficacy of dasatinib in this setting. METHODS: Patients with recurrent and/or metastatic HNSCC after platinum-based therapy were treated with dasatinib either orally or via percutaneous feeding gastrostomy (PFG). Primary endpoints were 12-week progression-free survival (PFS) and objective response rate with a 2-stage design and early withdrawal if the 12-week PFS rate was ≤20% and no patients had an objective response (OR). Forty-nine serum cytokines and angiogenic factors (CAFs) were analyzed from treated patients. RESULTS: Of the 15 patients enrolled, 12 were evaluable for response, and all patients were evaluable for toxicity. No OR was observed and 2 patients (16.7%) had stable disease (SD) at 8 weeks. The median treatment duration was 59 days, the median time to disease progression was 3.9 weeks, and the median survival was 26 weeks. One patient required a dose reduction, 3 patients required dose interruptions, and 4 patients were hospitalized for toxicity. Dasatinib inhibited c-Src both when administered orally and via PFG. Greater mean drug exposure, decreased half-life, and greater maximum concentration were observed in patients receiving dasatinib via PFG. Eleven baseline CAFs were associated with treatment outcome and 1 CAF, macrophage migration inhibitory factor, was found to be differentially modulated in correlation with SD versus disease progression. CONCLUSIONS: Single-agent dasatinib failed to demonstrate significant activity in patients with advanced HNSCC, despite c-Src inhibition. The toxicity profile was consistent with that reported in other solid tumors, and the drug can be given via PFG tube.

Phase II randomized, placebo-controlled trial of green tea extract in patients with high-risk oral premalignant lesions.

Epidemiologic and preclinical data support the oral cancer prevention potential of green tea extract (GTE). We randomly assigned patients with high-risk oral premalignant lesions (OPL) to receive GTE at 500, 750, or 1,000 mg/m(2) or placebo thrice daily for 12 weeks, evaluating biomarkers in baseline and 12-week biopsies. The OPL clinical response rate was higher in all GTE arms (n = 28; 50%) versus placebo (n = 11; 18.2%; P = 0.09) but did not reach statistical significance. However, the two higher-dose GTE arms [58.8% (750 and 1,000 mg/m(2)), 36.4% (500 mg/m(2)), and 18.2% (placebo); P = 0.03] had higher responses, suggesting a dose-response effect. GTE treatment also improved histology (21.4% versus 9.1%; P = 0.65), although not statistically significant. GTE was well tolerated, although higher doses increased insomnia/nervousness but produced no grade 4 toxicity. Higher mean baseline stromal vascular endothelial growth factor (VEGF) correlated with a clinical (P = 0.04) but not histologic response. Baseline scores of other biomarkers (epithelial VEGF, p53, Ki-67, cyclin D1, and p16 promoter methylation) were not associated with a response or survival. Baseline p16 promoter methylation (n = 5) was associated with a shorter cancer-free survival. Stromal VEGF and cyclin D1 expression were downregulated in clinically responsive GTE patients and upregulated in nonresponsive patients at 12 weeks (versus at baseline). An extended (median, 27.5 months) follow-up showed a median time to oral cancer of 46.4 months. GTE may suppress OPLs, in part through reducing angiogenic stimulus (stromal VEGF). Higher doses of GTE may improve short-term (12-week) OPL outcome. The present results support longer-term clinical testing of GTE for oral cancer prevention.

T cell CD3 receptor zeta (TCRzeta)-chain expression in children with idiopathic nephrotic syndrome.

Children with idiopathic nephrotic syndrome (INS) have an increased risk of developing life-threatening infections. Several studies have demonstrated functional abnormalities in the T lymphocytes of patients with nephrotic syndrome. Although T cells are activated in INS during relapse, as indicated by an increased expression of interleukin (IL)-2 receptor, these cells have a decreased ability to proliferate. The T-cell receptor (TCR) plays an important role in signal transduction and T cell activation, with the TCR-zeta (TCRzeta) chain being a key element in early signaling. We measured the expression of the TCRzeta chain in patients with INS (steroid resistant and steroid sensitive) during relapse and remission by flow cytometry and by PCR ELISA. The results showed a significant decrease in the expression of the TCRzeta chain at both the protein and mRNA level in INS patients during relapse as compared with normal controls (p < 0.05). In contrast, when patients with INS achieved remission, the expression of TCRzeta normalized and was similar to that expressed in normal controls. Therefore, a decreased expression of the TCRzeta chain may explain the abnormal function of T cells in patients with INS, and it may also contribute to the increased risk for infections seen in these patients.

Decreased expression of CD3zeta and nuclear transcription factor kappa B in patients with pulmonary tuberculosis: potential mechanisms and reversibility with treatment.

BACKGROUND: The protective immune response against Mycobacterium tuberculosis relies both on antigen-presenting cells and on T lymphocytes. In patients with different forms of tuberculosis, varying degrees of T cell function--ranging from positive delayed-type hypersensitivity, in asymptomatic infected healthy individuals, to the absence of the response, in patients with miliary or pulmonary tuberculosis (PTB)--have been reported. The decreased expression of CD3zeta reported in T cells from patients with either cancer or leprosy has provided possible explanations for the altered immune response observed in these diseases. METHODS: The present study aimed to compare the expression of CD3zeta , nuclear transcription factor- kappa B (NF- kappa B), arginase activity, and cytokine production in 20 patients with PTB, in 20 tuberculin-positive asymptomatic subjects, and in 14 tuberculin-negative control subjects. RESULTS: Compared with those in tuberculin (purified protein derivative)-negative control subjects, peripheral-blood T lymphocytes from patients with active PTB had significantly (P < .001) decreased expression of CD3zeta and absence of the p65/p50 heterodimer of NF- kappa B. These alterations were reversed only in patients who responded to treatment. Also reported here for the first time is that the presence of arginase activity in peripheral-blood mononuclear-cell lysates of patients with PTB parallels high production of interleukin-10. CONCLUSIONS: The presence of arginase could, in part, explain the decreased expression of CD3zeta . These findings provide a novel mechanism that may explain the T cell dysfunction observed in patients with PTB.

L-Arginine modulates CD3zeta expression and T cell function in activated human T lymphocytes.

Engagement of the T cell receptor (TCR) by antigen or anti-CD3 antibody results in a cycle of internalization and re-expression of the CD3zeta. Following internalization, CD3zeta is degraded and replaced by newly synthesized CD3zeta on the cell surface. Here, we provide evidence that availability of the amino acid L-arginine modulates the cycle of internalization and re-expression of CD3zeta and cause T cell dysfunction. T cells stimulated and cultured in presence of L-arginine, undergo the normal cycle of internalization and re-expression of CD3zeta. In contrast, T cells stimulated and cultured in absence of L-arginine, present a sustained down-regulation of CD3zeta preventing the normal expression of the TCR, exhibit a decreased proliferation, and a significantly diminished production of IFNgamma, IL5, and IL10, but not IL2. The replenishment of L-arginine recovers the expression of CD3zeta. The decreased expression of CD3zeta is not caused by a decreased CD3zeta mRNA, an increased CD3zeta degradation or T cell apoptosis.

L-arginine consumption by macrophages modulates the expression of CD3 zeta chain in T lymphocytes.

L-Arginine plays a central role in the normal function of several organs including the immune system. It is metabolized in macrophages by inducible nitric oxide synthase to produce nitric oxide, important in the cytotoxic mechanisms, and by arginase I (ASE I) and arginase II (ASE II) to synthesize L-ornithine and urea, the first being the precursor for the production of polyamines needed for cell proliferation. L-Arginine availability can modulate T cell function. Human T cells stimulated and cultured in the absence of L-arginine lose the expression of the TCR zeta-chain (CD3zeta) and have an impaired proliferation and a decreased cytokine production. The aim of this work was to test whether activated macrophages could modulate extracellular levels of L-arginine and alter T cell function, and to determine which metabolic pathway was responsible for this event. The results show that macrophages stimulated with IL-4 + IL-13 up-regulate ASE I and cationic amino acid transporter 2B, causing a rapid reduction of extracellular levels of L-arginine and inducing decreased expression of CD3zeta and diminished proliferation in normal T lymphocytes. Competitive inhibitors of ASE I or the addition of excess L-arginine lead to the re-expression of CD3zeta and recovery of T cell proliferation. In contrast, inducible nitric oxide synthase or ASE II failed to significantly reduce the extracellular levels of L-arginine and modulate CD3zeta expression. These results may provide new insights into the mechanisms leading to T cell dysfunction and the down-regulation of CD3zeta in cancer and chronic infectious diseases.

Regulation of T cell receptor CD3zeta chain expression by L-arginine.

L-Arg plays a central role in the normal function of several organ systems including the immune system. L-Arg can be depleted by arginase I produced by macrophages and hepatocytes in several disease states such as trauma and sepsis and following liver transplantation. The decrease in L-Arg levels induces a profound decrease in T cell function through mechanisms that have remained unclear. The data presented here demonstrate that Jurkat T cells cultured in medium without L-Arg (L-Arg-free RPMI) have a rapid decrease in the expression of the T cell antigen receptor zeta chain (CD3zeta), the principal signal transduction element in this receptor, and a decrease in T cell proliferation. This phenomenon is completely reversed by the replenishment of L-Arg but not other amino acids. These changes are not caused by cell apoptosis; instead, the diminished expression of CD3zeta protein is paralleled by a decrease in CD3zeta mRNA. This change in CD3zeta mRNA expression is not caused by a decrease in the transcription rate but rather by a significantly shorter CD3zeta mRNA half-life. This mechanism is sensitive to cycloheximide. Therefore, the regulation of L-Arg concentration in the microenvironment could represent an important mechanism to modulate the expression of CD3zeta and the T cell receptor and consequently of T cell function.