Epigenetic inactivation of suppressors of cytokine signalling in Philadelphia‐negative chronic myeloproliferative disorders

Abstract

SummaryPh-negative chronic myeloproliferative disorders (CMPD) are characterized by constitutive Janus kinase-signal transducer and activator of transcription (JAK-STAT) activation. SOCS3, SOCS1 and PTPN6 (SHP1) are negative regulators of the JAK-STAT pathway. We investigated epigenetic and genetic inactivation of SOCS3, SOCS1 and PTPN6 in 112 CMPD and 20 acute myeloid leukaemia (AML) post-CMPD. SOCS3 methylation occurred at high frequency in both CMPD (46/112; 41AE1%) and AML post-CMPD (10/17; 58AE8%) and was associated with transcriptional silencing. In contrast, methylation of SOCS1 and PTPN6 was observed in only a fraction of CMPD (15/112, 13AE4% for SOCS1; and 8/112, 7AE1% for PTPN6) and AML post-CMPD (3/20, 15% for SOCS1; and 1/20, 5% for PTPN6). No somatic mutations of SOCS1 were found in CMPD. SOCS3, SOCS1 and PTPN6 methylation occurred in both JAK2V617F-positive (35AE1% for SOCS3; 14AE9% for SOCS1; 8AE1% for PTPN6) and JAK2V617F-negative (57AE1% for SOCS3; 14AE3% for SOCS1; and 9AE5% for PTPN6) CMPD. These data indicate that methylation of SOCS3 and, to a lesser extent, SOCS1 and PTPN6 is a frequent event in both JAK2V617F-positive and -negative CMPD and may act as an alternative or complementary mechanism to JAK2 mutations, enhancing cytokine signal transduction. The frequent inactivation of SOCS3 is a novel finding in CMPD with potential implications for the molecular pathology of these disorders.

SOCS-mediated downregulation of mutant Jak2 (V617F, T875N and K539L) counteracts cytokine-independent signaling

“…For example, mechanisms that were reported to interfere with SOCS function are methylation (Yoshikawa et al, 2001;Galm et al, 2003;Ekmekci et al, 2004), mutations (Melzner et al, 2005) and deletions (Melzner et al, 2006) of SOCS genes. It is important that epigenetic silencing of SOCS3 and SOCS1 was recently reported in B40% of patients with Ph-negative chronic myeloid disorders (Capello et al, 2008;Teofili et al, 2008). The mechanism of mutant Jak2 regulation that we report strongly suggests that the regulation and potential mutation of SOCS proteins could be important clinical parameters in patients carrying constitutively active Jak2 proteins.…”

Methylated Alteration of SHP1 Complements Mutation of JAK2 Tyrosine Kinase in Patients with Myeloproliferative Neoplasm

“…However, our data suggest SHP1 was methylated in 51/118 (43.2%) MPN patients. The frequency of methylation in our study is significantly higher than the results from Capello et al (2008) As reported that MSP may induce the false positive result, bisulfiteconverted DNA from K562 and 10 MPN patients with hypermethylation of SHP1 were performed sequencing. Our data suggest that sequence of CpG island in K562 and 10 MPN patients showed the expected nucleotide change.…”

“…Thus, our results are reliable. Although Capello et al reported hypermethylation of SOCS3 occurred in 46 of 112 (41.1%) MPN patients, Fourouclas and his colleage demonstrated hypermethylation of the SOCS3 promoter was only identified in 16 of 50 (32%) patients with IMF but not in patients with ET and PV (Capello et al, 2008). We speculate that the reason for this discrepancy may be the different selection of CpG island prediction methods, different PCR specificity and sensitivity, or a different patient selection criteria.…”

“…Inactivation of SHP1 and SOCS1/3 by epigenetic and other mechanism were frequently found in MPN and leukemia. SOCS3 was inactivated by DNA methylation in more than 40% MPN (Capello et al, 2008). Moreover, hyperphosphorylaiton of SOCS3 caused by JAK2V617F mutation rendered it unable to inhibit the mutant kinase (Hookham et al, 2007).…”

“…Although hypermethylation of SHP1 had been reported in leukemia, lymphoma (Oka et al, 2002), colon cancer (Xu et al, 2009) and high-risk myelodysplastic syndrome (Zhang et al, 2012), little data indicated whether SHP-1 was methylated in MPN especially in Chinese MPN patients. Capello et al (2008) found only fraction of MPN (8/112, 7.1%) showed methylation of SHP-1 using MSP. However, our data suggest SHP1 was methylated in 51/118 (43.2%) MPN patients.…”