Widely used as anti-cancer and immunosuppressive agents, thiopurines have narrow therapeutic indices due to frequent toxicities, partly explained by TPMT genetic polymorphisms. Recent studies identified germline NUDT15 variation as another critical determinant of thiopurine intolerance, but the underlying molecular mechanisms and its clinical implications remain unknown. In 270 children enrolled in clinical trials for acute lymphoblastic leukemia in Guatemala, Singapore, and Japan, we identified 4 NUDT15 coding variants (p.Arg139Cys, p.Arg139His, p.Val18Ile, p.Val18_Val19insGlyVal) that resulted in 74.4%–100% loss of nucleotide diphosphatase activity. Loss-of-function NUDT15 diplotypes were consistently associated with thiopurine intolerance across three cohorts (P=0.021, 2.1×10−5, and 0.0054, respectively; meta-analysis P=4.45×10−8, allelic effect size=−11.5). Mechanistically, NUDT15 inactivated thiopurine metabolites and decreased its cytotoxicity in vitro, and patients with defective NUDT15 alleles showed excessive thiopurine active metabolites and toxicity. Taken together, our results indicate that a comprehensive pharmacogenetic model integrating NUDT15 variants may inform personalized thiopurine therapy.

Preliminary studies have demonstrated that some pituitary adenomas secrete immunoreactive interleukin-6 (irIL-6) when cultured in vitro. We have extended these studies by investigating 100 pituitary adenomas of different types measuring immunoreactive and bioactive IL-6. Tumors were cultured either as explants without fetal calf serum or as dispersed cells with 10% total calf serum. Fifty-three of the 100 (53%) pituitary cultures were found to release irIL-6 and in 44 adenomas examined, 32 (72.7%) secreted bioactive IL-6. In 61 explant cultures, 30 adenomas released IL-6, indicating autonomous secretion. The amount of IL-6 released by adenomas in cell culture was generally higher, although the incidence was similar to explant cultures. IrIL-6 was released by 7 of 14 prolactinomas, 15 of 27 somatotrophinomas, 5 of 7 corticotrophinomas (including 2 Nelson's adenomas), 1 of 1 thyrotrophinomas, 2 of 2 gonadotrophinomas, and 23 of 49 clinically non-functioning adenomas. Periadenomatous tissue removed from a patient with a corticotrophinoma was found to secrete IL-6 but in much lower concentration than from the adenoma tissue. Tumor necrosis factor-alpha and -gamma-interferon were not detected in the conditioned media. Four IL-6-secreting adenomas were examined by in situ hybridization for IL-6 messenger RNA, and three of these were positive with fluorescence present throughout the tissue examined. We have provided evidence that over half of pituitary adenomas secrete IL-6 which is bioactive and that IL-6 is synthesized within the tumor by the adenoma cells.

To assess whether NLRP3 gene promoter methylation was able to discriminate glucocorticoid (GC)‐resistant from GC‐sensitive idiopathic nephrotic syndrome (INS), patients with minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS), we measured the methylation level of NLRP3 promoter in DNA from peripheral blood cells of 10 adult patients with GC‐resistant FSGS already in hemodialysis and 18 patients with GC‐sensitive INS (13 MCD/5 FSGS) and in 21 pediatric patients with INS with MCD/FSGS before starting any treatment. Association of NLRP3 inflammasome with GC resistance was recapitulated in vitro in monocytic cell lines (THP‐1 and U937). In both adults and pediatric patients, NLRP3 promoter methylation was significantly reduced in GC‐resistant compared with GC‐sensitive patients. Indeed, NLRP3 methylation distinguished GC‐resistant and GC‐sensitive patients (area under the receiver operating characteristic curve [AUROC] 86.7% in adults, p = 0.00019, and 73.5% in children, p = 0.00097). NLRP3 knock‐down augmented sensitivity to GCs in THP‐1 cells, whereas NLRP3 inflammasome activation lowered GC receptor concentration, increasing GC resistance in U937 cells. Our results uncovered a new biological mechanism by which patients with INS may acquire GC resistance, that could be used in future as a novel noninvasive diagnostic tool. WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? ☑ Approximately 80% of patients with idiopathic nephrotic syndrome (INS) respond to glucocorticoids, with the remaining 20% being steroid‐resistant. WHAT QUESTION DID THIS STUDY ADDRESS? ☑ Whether NLRP3 gene promoter methylation was able to discriminate glucocorticoid‐resistant from glucocorticoid (GC)‐sensitive INS. WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? ☑ In both adults and children, NLRP3 promoter methylation was significantly reduced in leukocytes of patients with GC‐resistant compared with GC‐sensitive INS. NLRP3 inflammasome activation lowered GC receptor concentration and augmented GC resistance, whereas NLRP3 knockdown increased sensitivity to GCs in cell lines representative of monocytes (U937 and THP1). HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE? ☑ Our findings uncovered a new biological mechanism whereby patients with INS may develop resistance to GCs that could be used in the future as a novel noninvasive diagnostic tool.

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