The AMPK-activator AICAR in thyroid cancer: effects on CXCL8 secretion and on CXCL8-induced neoplastic cell migration.

PURPOSE: The AMPK-activator AICAR recently raised great interest for its anti-cancer properties. With specific regard to thyroid cancer, AICAR reduces cancer cell growth, invasion and metastasis. CXCL8, a chemokine with several recognized tumorigenic effects, is abundantly secreted in thyroid cancer microenvironment. The aim of this study was to investigate if AICAR could inhibit the basal and the TNFα-induced CXCL8 secretion in normal human thyroid cells (NHT) and in thyroid cancer cell lines TPC-1 and BCPAP (RET/PTC and BRAFV600e mutated, respectively). METHODS: The effect of AICAR on basal and CXCL8-induced cell migration was assessed. Cells were incubated with AICAR (0.05, 0.5, 1, 2 mM) alone or in combination with TNF-α (10 ng/ml) for 24 h. CXCL8 concentrations were measured in cell supernatants. Transwell migration assays were performed in NHT, TPC-1 and BCPAP, basally and after treatment with AICAR (2 mM) and rh-CXCL8 (50 ng/ml) alone or in combination. RESULTS: AICAR dose dependently inhibited the basal secretion of CXCL8 in TPC-1 (F = 4.26; p < 0.007) and BCPAP (F = 6.75; p < 0.0001) but not in NHT. TNFα-induced CXCL8 secretion was dose dependently reduced by AICAR in NHT (F = 9.99; p < 0.0001), TPC-1 (F = 9.25; p < 0.0001) and BCPAP (F = 6.82; p < 0.0001). AICAR significantly reduced the basal migration of TPC-1 and BCPAP but not of NHT. CONCLUSIONS: CXCL8-induced cell migration was inhibited in NHT, TPC-1 and BCPAP. This is the first demonstration of the inhibition of CXCL8 secretion exerted by AICAR in TPC-1 and BCPAP indicating that the anti-cancer properties of AICAR are, at least in part, mediated by its ability to reduce the pro-tumorigenic effects of CXCL8.

Differential clinical effects of different mutation subtypes in CALR-mutant myeloproliferative neoplasms.

A quarter of patients with essential thrombocythemia or primary myelofibrosis carry a driver mutation of CALR, the calreticulin gene. A 52-bp deletion (type 1) and a 5-bp insertion (type 2 mutation) are the most frequent variants. These indels might differentially impair the calcium binding activity of mutant calreticulin. We studied the relationship between mutation subtype and biological/clinical features of the disease. Thirty-two different types of CALR variants were identified in 311 patients. Based on their predicted effect on calreticulin C-terminal, mutations were classified as: (i) type 1-like (65%); (ii) type 2-like (32%); and (iii) other types (3%). Corresponding CALR mutants had significantly different estimated isoelectric points. Patients with type 1 mutation, but not those with type 2, showed abnormal cytosolic calcium signals in cultured megakaryocytes. Type 1-like mutations were mainly associated with a myelofibrosis phenotype and a significantly higher risk of myelofibrotic transformation in essential thrombocythemia. Type 2-like CALR mutations were preferentially associated with an essential thrombocythemia phenotype, low risk of thrombosis despite very-high platelet counts and indolent clinical course. Thus, mutation subtype contributes to determining clinical phenotype and outcomes in CALR-mutant myeloproliferative neoplasms. CALR variants that markedly impair the calcium binding activity of mutant calreticulin are mainly associated with a myelofibrosis phenotype.