[Clinical Characteristic of "triple-negative" Essential Thrombocythaemia Patients and Mutation Analysis by Targeted Sequencing].

BACKGROUND: Essential thrombocythemia is a subgroup of myeloproliferative neoplasms. Previous studies identified mutations of JAK2, CALR, and MPL that are closely related with the pathogenesis of myeloproliferative neoplasms. All these mutations contribute to the hyperactivation of JAK2/STAT pathway. However, a small proportion of essential thrombocythemia patients does not display such mutations. The pathogenesis of "triple-negative" form of essential thrombocythemia remains unknown. OBJECTIVE: To investigate the clinical characteristics of triple-negative essential thrombocythemia and related mutation genes. METHODS: To identify the mutations associated with triple-negative essential thrombocythemia, next-generation sequencing was used to conduct targeted sequencing of 360 genes in samples from 68 patients. RESULTS: At least one missense mutation was detected in all the patients and all the detected genes. After screening the data, it was observed that 10 genes with the 10 highest mutation were follows: FLT3, SH2B3, ASXL1, ADAMTS1, TET2, TP53, EGFR, CUX1, GATA2, and MPL.When only rare genes (i.e., with a frequency in Asian populations lower than 5%, as estimated by the 1000 Genomes Project) were analyzed, the most frequently mutated genes in the patients were TET2 (33.82%), SH2B3(29.41%), and ASXL1 (23.53%). Our study identified some mutations that did not previously reported. Although all these mutations need further validation, high incidence rates may indicate relevance of the respective mutations to essential thrombocythemia pathogenesis. Some of the detected mutations have been previously reported; these mutations were also found in a large proportion of our subjects. CONCLUSION: whole-exon sequencing can provide a higher level of accuracy for gene mutation analysis and assist in identifying mutations that contribute to illustrate the pathogenesis of essential thrombocythemia.

ASXL1 mutations in Chinese patients with essential thrombocythemia.

Essential thrombocythemia (ET) is characterized by thrombotic and hemorrhagic events. The association of clinical characteristics of Chinese ET patients and additional sex combs like 1 (ASXL1) mutations in these patients has remained to be elucidated. In the present study, 72 newly diagnosed Chinese ET patients were enrolled to determine ASXL1 mutations. Mutations in ASXL1, Janus kinase (JAK)2, calreticulin (CALR) and myeloproliferative leukemia (MPL) genes were detected using Sanger sequencing, and data were statistically analyzed. The frequencies of ASXL1, JAK2 V617F, CALR and MPL W515 mutations in ET patients were 19.4% (14/72), 29.2% (21/72), 31.9% (23/72) and 0% (0/72), respectively. Of note, 28 ET patients (38.9%) were negative for JAK2, CALR and MPL mutations; these patients were classified as triple-negative (TN). The frequency of ASXL1 mutations in patients with JAK2 V617F, CALR and TN mutations was 23.8% (5/21), 21.7% (5/23) and 14.3% (4/28), respectively. ASXL1-mutant patients exhibited significant propensities for thrombotic events compared with the ASXL1 wild-type (wt) cohort (42.9 vs. 12.1%; P=0.021). In addition, JAK2 V617F-mutant patients had a higher mean age compared with CALR-mutant (64.76 vs. 52.96 years; P=0.008) or TN patients (64.76 vs. 51.14 years; P=0.002). Furthermore, more white blood cells in the peripheral blood (PB) were observed in JAK2 V617F-mutant patients compared with those in TN patients (12.40 vs. 8.20×109/l; P=0.02). In addition, CALR-mutant patients exhibited more platelets (PLT) in PB than JAK2 V617F-mutant patients (787.91 vs. 562.17×109/l; P=0.047). TN patients had a significantly lower incidence of clinical symptoms, including dizziness, palpitation and chest congestion compared with CALR- or JAK2 V617F-mutant patients (14.1 vs. 39.1%; P=0.043 and 14.1 vs. 38.1%; P=0.050). No significant difference in progression-free survival was observed between ASXL1-mutant and ASXL1-wt patients (P=0.590). In conclusion, ASXL1-mutant ET patients are prone to experiencing thrombotic events. There was no significant difference in the occurrence of thrombotic events among CARL-mutant, JAK2 V617F-mutant and TN patients. Furthermore, ASXL1-mutant/TN patients exhibited a higher number of PLT than ASXL1/JAK2 V617F-double mutant patients. Therefore, ASXL1 mutations may be a risk factor for the occurrence of thrombotic events in ET patients.

[Clinical Characteristics and Long-Term Outcome of 125 Chinese Young Patients with Essential Thrombocythemia].

OBJECTIVE: To investigate the clinical characteristics and long-term outcome of Chinese young patients (≤40 years) with essential thrombocythemia(ET), and to develop a thrombosis predicting model specific for young patients with ET, so as to provide a new evidence for risk stratification and treatment. METHODS: Medical records of 125 Chinese young patients with newly diagnosed of ET were retrospectively analyzed. RESULTS: The median age at diagnosis was 32 (18-40) years old, with 37 males and 88 females. During follow-up, 18 patients (14.4%) experienced major thrombotic events. JAK2 V617F (HR=8.895, P=0.001), history of thrombosis (HR=8.001, P<0.001) and WBC≥12.0×109/L (HR=5.225, P=0.002) were independent risk factors for thrombosis. The incidence of thrombosis and risk factors in young patients were different from that in general ET population, so a thrombosis predicting model specific for young patients with ET was developed. In this model, JAK2 V617F (score 2), history of thrombosis (score 2) and WBC≥12.0×109/L (score 1) were used to divide the patients into low risk (score 0), intermediate risk (score 1-2) and high risk (score≥3) groups. These 3 groups exhibited significantly different thrombosis-free survival (χ2=32.223, P<0.001). Antiplatelet treatment could prevent the occurrence of thrombosis (HR=0.081, P<0.001), while cytoreductive agents significantly decreased the risk of thrombosis only in intermediate and high risk groups (14.3% vs 36.4%, χ2=4.416, P=0.036). Seven patients (5.6%) evolved to myelofibrosis, and one of them finally progressed in to acute leukemia. The only risk factor for evolution was WBC≥15.0×109/L (χ2=5.434, P=0.020). Neither antiplatelet treatment nor cytoreductive agents could prevent disease progression. CONCLUSION: The incidence of thrombosis and risk factors in young patients with ET are different from that in general ET population. The thrombosis-predicting model specific for young patients with ET is useful for guiding therapeutic decisions.