BACKGROUND: Around 50% of cutaneous melanomas harbor the BRAF V600E mutation and can be treated with BRAF inhibitors. DNA carrying this mutation can be released into circulation as cell-free BRAF

Human leukocyte antigen-G (HLA-G) is a low polymorphic nonclassical HLA-I molecule restrictively expressed and with suppressive functions. HLA-G gene products are quite complex, with seven HLA-G isoforms, four membrane bound, and other three soluble isoforms that can suffer different posttranslational modifications or even complex formations. In addition, HLA-G has been described included in exosomes. In this review we will focus on HLA-G biochemistry with special emphasis to the mechanisms that regulate its expression and how the protein modifications affect the quantification in biological fluids.

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The most common cause of organic fasting hypoglycemia in adults is the presence of an insulin-producing pancreatic adenoma, but when high insulin levels are not found, the differential diagnosis is challenging. Misdiagnosis can lead to an unnecessary pancreatectomy. Insulin concentrations may be low in some cases despite a clinical history suggestive of insulinoma. In these cases, a proinsulinoma should be suspected, although the rarity of this condition requires an extensive workup before reaching a final diagnosis. We describe an unusual case of a 38-year-old man with a severe hypoglycemic syndrome due to a proinsulin-secreting pancreatic adenoma. Insulin was measured by the specific assay and suppressed under the lower detection limit during fasting hypoglycemia. Serum proinsulin and C-peptide levels were abnormally elevated, and further tests revealed an islet cell tumor. The tumor was surgically removed, relieving the fasting hypoglycemia. Histopathological study showed a conventional well-differentiated neuroendocrine tumor with high immunoreactivity against proinsulin and with lesser intensity against insulin. Interestingly, GS-9A8 antibody clone used for immunostaining proinsulin did not cross-react with human insulin or C-peptide, providing an unbiased picture of proinsulin secretion. The resolution of symptoms, the fall of proinsulin concentrations after tumor removal and the histopathology study confirmed the diagnosis of proinsulinoma.

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9074 Background: MIA and S-100 have been proposed as tumor markers for patients with melanoma, but they are not widely accepted. BRAF V600E mutation has been reported in more than 50% of melanomas. Recently, selective BRAF inhibitors have proved to be more active than DTIC in first line treatment of BRAF V600E melanoma patients. The aim of the present work is to evaluate the utility of MIA and S-100 during iBRAF treatment. Methods: BRAF V600E mutation was analyzed in 77 patients with metastatic melanoma by automated direct sequencing in tumor DNA. Tumor markers (MIA, S-100 and LDH) were studied in serum from all patients. Sixteen of these patients received iBRAF therapy (11 Vemurafenib, 5 Dabrafenib) and tumor markers were analyzed sequentially: baseline, best response and progression. MIA and S-100 were determined by immunometric methods and LDH by a spectrophotometric assay. The cut-off points were MIA=9 ug/L, S-100=0.1 ug/L, and LDH=290 U/L. Non-parametric statistical analysis was performed. Results: Forty-three patients had BRAF V600E mutation and 34 were wild type (WT). The percentage of cases with MIA above the cut-off in patients with V600E mutation was significantly higher than in the WT group (76.3% vs. 52.9%; p<0.05), while the frequency of elevated S-100 and LDH was similar. Among patients treated with iBRAF, the response rate was 87.5% (5 CR, 9PR). In responding patients, MIA and S100 levels decreased dramatically, but not LDH (Table). At the time of this report, thirteen patients have progressed. Upon progression, MIA and S-100 increased significantly above levels achieved at best response (Table). Conclusions: Serum MIA and S-100 are potentially useful markers in the clinical and follow-up management of patients receiving iBRAF therapy. Validation in a larger series is needed. [Table: see text]