Mechanisms of checkpoint inhibition-induced adverse events

Immune checkpoint inhibition has revolutionized the treatment of several solid cancers, most notably melanoma and non-small-cell lung cancer (NSCLC). Drugs targeting cytotoxic T lymphocyte antigen (CTLA)-4 and programmed cell death 1 (PD-1) have made their way into routine clinical use; however, this has not been without difficulties. Stimulation of the immune system to target cancer has been found to result in a reduction of self-tolerance, leading to the development of adverse effects that resemble autoimmunity. These adverse effects are erratic in their onset and severity and can theoretically affect any organ type. Several mechanisms for immune-related toxicity have been investigated over recent years; however, no consensus on the cause or prediction of toxicity has been reached. This review seeks to examine reported evidence for possible mechanisms of toxicity, methods for prediction of those at risk and a discussion of future prospects within the field.

Nuclear transport of the human aryl hydrocarbon receptor and subsequent gene induction relies on its residue histidine 291

The aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor involved in the metabolism of physiological substances and xenobiotics, representing an interesting target in both toxicology and pharmacology. In this study, we investigated the ligand-dependent conjunction of nuclear import of the human AHR in living cells and target gene induction. Our findings strengthen the theory that the AHR triggers a precisely defined and rapid reaction upon binding to endogenous ligands, while the xenobiotic β-naphthoflavone only induces rather unspecific and slow effects. To better illuminate the ligand-mediated responses of the human AHR, we applied site-directed mutagenesis and identified histidine 291 as key residue for AHR functionality, essential for both nuclear import and target gene induction. Contrary, replacing histidine at position 291 by alanine did not affect nucleo-cytoplasmic shuttling, showing that permanent endogenous import and ligand-induced import of the AHR into the nucleus are two independent and differently regulated processes. Combining these observations with our structural investigations using a homology model of the AHR-PAS B domain, we suggest a dual role of histidine 291: (1) a major role for shaping the ligand binding site including direct interactions with ligands and, (2) an essential role for the conformational dynamics of a PAS B loop, which most likely influences the association of the AHR with the AHR nuclear translocator through interference with their protein-protein interface.

Binding characteristics of [3H]-JSM10292: a new cell membrane-permeant non-peptide bradykinin B2 receptor antagonist

BACKGROUND AND PURPOSE

A (3) H-labelled derivative of the novel small-molecule bradykinin (BK) B(2) receptor antagonist JSM10292 was used to directly study its binding properties to human and animal B(2) receptors in intact cells and to closely define its binding site.

EXPERIMENTAL APPROACH

Equilibrium binding, dissociation and competition studies with various B(2) receptor ligands and [(3) H]-JSM10292 were performed at 4°C and 37°C. The experiments were carried out using HEK293 cells stably (over)expressing wild-type and mutant B(2) receptors of human and animal origin.

KEY RESULTS

[(3) H]-JSM10292 bound to B(2) receptors at 4°C and at 37°C with the same high affinity. Its dissociation strongly depended on the temperature and increased when unlabelled B(2) receptor agonists or antagonists were added. [(3) H]-JSM10292 is cell membrane-permeant and thus also bound to intracellular, active B(2) receptors, as indicated by the different 'nonspecific' binding in the presence of unlabelled JSM10292 or of membrane-impermeant BK. Equilibrium binding curves with [(3) H]-JSM10292 and competition experiments with unlabelled JSM10292 and [(3) H]-BK showed a different affinity profile for the wild-type B(2) receptor in different species (man, cynomolgus, rabbit, mouse, rat, dog, pig, guinea pig). Characterization of B(2) receptor mutants and species orthologues combined with homology modelling, using the CXCR4 as template, suggests that the binding site of JSM10292 is different from that of BK but overlaps with that of MEN16132, another small non-peptide B(2) receptor ligand.

CONCLUSIONS AND IMPLICATIONS

[(3) H]-JSM10292 is a novel, cell membrane-permeant, high-affinity B(2) receptor antagonist that allows direct in detail studies of active, surface and intracellularly located wild-type and mutant B(2) receptors.

The role of PET-CT in the follow-up of patients with urothelial cancer diagnosis

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Background: Positron emission tomography (PET) is an imaging technique whose principle is the detection of metabolic activity of tumor cells but in urology its use had been restricted due to urinary excretion of the radiotracer and overlap with urological structures, the use of hybrid PET (PET-CT) would allow its use for monitoring patients with urothelial tumors.

Methods: Between 2007 and 2010 we performed PET-TC images in consecutive patients with suspected recurrences in CT scan or MRI. All patients had renal, bladder and uretral cancer and were treated with urothelial cancer diagnosis. We evaluate the usefulness of FDG PET-CT and its impact on behavior therapy in suspected recurrence in patients with urothelial carcinoma, compared with conventional studies.

Results: 17 patients were studied for suspected recurrence. All patients had positive images previously on CT scan and MRI; positive PET-TC was observed in 14 and 3 studies were negative. The positive PET-CT showed more number of lesions and change the medical and surgical strategy. Of the three studies negative on PET- CT none had recurrence and remain disease free. PET/CT is in a great benefit to the detection recurrence in the follow up of patients with urothelial cancer diagnosis. These results showed an increased sensitivity and specificity over previous work with conventional PET technology. In the series studied, the implementation of PET-CT (FDG) in the follow up of patients with urothelial tumors were an useful tool.

Conclusions: PET/CT is in a great benefit to the detection recurrence in the follow up of patients with urothelial cancer diagnosis. These results showed an increased sensitivity and specificity over previous work with conventional PET technology. In the series studied, the implementation of PET-CT (FDG) in the follow up of patients with urothelial tumors were an useful tool. However, multicenter studies and more patients are required to define its role.

No significant financial relationships to disclose.

Genotype and allele frequencies of polymorphic cytochromes P450 CYP1A2 and CYP2E1 in Mexicans

CYP1A2 and CYP2E1 are two of the main cytochrome P450 isoforms involved in the metabolism of commonly used drugs and xenobiotic compounds considered to be responsible for or possible participants in the development of several human diseases. Individual susceptibility to developing these pathologies relies, among other factors, on genetic polymorphism which depends on ethnic differences, as the frequency of mutant genotypes varies in different human populations. Thus the aim of this study was to investigate the frequency of CYP1A2 5'-flanking region and CYP2E1 Rsa I/Pst I polymorphisms in Mexicans by PCR-RFLP methods. The DNA of 159 subjects was analysed and mutant allele frequencies of 30% for CYP2E1 Rsa I/Pst I sites and 43% for CYP1A2 5'-flanking region were found. These frequencies are higher than those previously reported for other human populations.

Allogeneic PBPC transplantation in children

BACKGROUND

While PBPC are being used increasingly as a source of stem cells in allotransplantation, the published experience in pediatric donor-recipient pairs is limited. Our aim was to evaluate the mobilization of PBPC in healthy child donors and the outcome of child recipients undergoing allogeneic PBSC transplant.

METHODS

Eight children with malignancies AML (one), refractory anemia with excess blasts in transformation (RAEBt) (one), ALL (four), NHL (one) and neuroblastoma (one)] were grafted with PBPC from HLA-identical sibling donors (seven patients) or from a 2-antigen mismatched donor (one case). Donors, aged 1-15 years underwent leukapheresis after mobilization with G-CSF (10-15 g/kg/day, 4 days). The extracorporeal line was primed in five cases (four with HSA). Peripheral venous access was used in all except one infant. The harvests were cryopreserved in six cases. GvHD prophylaxis consisted of CsA plus MTX or methylprednisolone.

RESULTS

No adverse effects related to G-CSF administration, nor procedure-related complications were observed. Median number of CD34(+) cells harvested was 5.18 x 10(6)/kg (range, 2.56-6.40), after one (five cases) or two (three cases) leukaphereses. All patients engrafted. The median time to achieve an ANC > 0.5 x 10(9)/L was 11 days (range 9-13) and a platelet count of > 50 x 10(9)/L was 18 days (range 13-45). Six patients did not develop any acute GvHD and three developed chronic GvHD. After a median follow-up of 18 months (14-44 months), six patients are alive and five in complete remission.

DISCUSSION

Allogeneic PBPC transplantation has shown to be a safe and successful procedure for pediatric donor and recipient pairs.

N-palmitoylphosphatidylethanolamine stabilizes liposomes in the presence of human serum: effect of lipidic composition and system characterization

Liposomes containing negatively-charged phospholipid, N-palmitoylphosphatidylethanolamine (NPPE) were examined for stability in the presence of human serum, using the release of the entrapped 5,6-carboxyfluorescein as an aqueous marker. Either small unilamellar vesicles (SUV) or large unilamellar vesicles (LUV) were used. Incorporation of NPPE into PC SUV decreases leakage in the presence of serum or phosphate-buffered saline, no strictly related to size increase observed and to the surface negative charge present. The stabilizing effect of NPPE and Chol were synergistic. Inhibition of destabilization induced by serum of PC/Chol liposomes was observed when NPPE concentrations were above 12 mol%. Change in the membrane fluidity or incorporation of a monosialoganglioside into liposomes do not significantly change the half-life of liposomes in the presence of a high NPPE concentration. Incorporation of NPPE into PC/Chol liposomes increases membrane rigidity which does not change after serum incubation. The presence of NPPE in liposomes decreases lipid transfer/exchange between liposomes and lipoproteins although the same amount of serum proteins were incorporated as in PC/Chol liposomes. As expected, these proteins are accessible to trypsin digestion. In accordance with these results, the liposome agglutination assay shows no steric barrier activity. As a whole, the results obtained in this paper suggest a complex mechanism for stabilization of NPPE containing liposomes in human serum.

Controlled trial of external negative pressure ventilation in patients with severe chronic airflow obstruction

The effect of intermittent external negative pressure ventilation (ENPV) with the Emerson Pulmowrap ventilator upon leg cycle endurance time (ET), maximal transdiaphragmatic pressure (Pdimax), breathing pattern as expressed by the tension time index (TTdi), and sense of well being was studied in 16 patients with severe chronic airflow obstruction (CAO). The patients were randomized to 3 wk of in-hospital pulmonary rehabilitation (Group I, seven patients) or the same program plus ENPV (Group II, nine patients). Both groups were similar in terms of age (65 +/- 8 versus 61 +/- 13 yr), severity of CAO (FEV1 of 0.64 +/- 0.14 versus 0.59 +/- 0.18 L), and PaCO2 (44 +/- 9 versus 45 +/- 7 mm Hg). Blood theophylline levels and nutritional status were also similar in both groups. Baseline ET (2.9 +/- 0.6 versus 3.8 +/- 1.6 min) and Pdimax (45 +/- 15 versus 56 +/- 18 cm H2O) were decreased in both groups. Baseline TTdi was high but similar in both groups; at rest the values were 0.15 +/- 0.05 versus 0.16 +/- 0.04, and at end-exercise they were 0.17 +/- 0.06 versus 0.21 +/- 0.12. After treatment FEV1 and Pdimax remained unchanged, but the patients in both groups manifested clinical improvement and had a significant increase in mean ET (Group I from 2.9 to 6.9 and Group II from 3.8 to 6 min, p less than 0.01). TTdi decreased both at rest (0.14 +/- 0.07 versus 0.13 +/- 0.04) and at end-exercise (0.14 +/- 0.06 versus 0.15 +/- 0.09) with no difference between groups.(ABSTRACT TRUNCATED AT 250 WORDS)