Overall Survival in Patients with JAK2 and ASXL1 Positive Myeloproliferative Neoplasms
Authors: Al-Khabori Murtadha , Al-Zadjali Shoaib , Al Noumani Iman , Al Farsi Khalil , Al-Kindi Salam , Al Huneini Mohamed , Fawaz Naglaa , Sulayma Al Lamki , Al Bulushi Mahdiya Pir , Al Hashmi Khalid , Al Tarshi Muna , Almusalhi Muhanna 
Published: November 2019

Objectives: Mutations in additional sex combs-like transcriptional regulator 1 (ASXL1) have been previously described in myeloid neoplasms (21% in non-Myeloproliferative [MPN; Tefferi A, Leukemia, 2010) and have been associated with a more aggressive disease [Rocquain J et al, BMC Cacer, 2010]. They can also be found in patients with JAK2 positive MPN [Abdel-Wahab O et al, Cancer Research, 2010). Disruption of ASXL1 gene leads to MPN phenotype in zebrafish model (Gjini E, Dis Model Mech, 2019). The co-expression and the prognostic significance of ASXL1 in patients with JAK2 positive MPN are not yet fully defined. We therefore planned to define the prognostic impact of ASXL1 mutations on the Overall Survival (OS) of patients with JAK2 positive MPN.
Methods: We included patients with JAK2 V617F positive MPN diagnosed according to the World Health Organization 2016 criteria and treated at the three largest hematology centers in Oman. The entire coding region of ASXL1 gene was sequenced using Next Generation Sequencing (NGS; Ion PGM Sequencer; Thermo Fisher Scientific®). The library was constructed and the templates were prepared using the PGM tool and the variants were annotated using the ClinVar database and the prediction from the Scale-Invariant Feature Transform (SIFT) and or Polymorphism Phenotyping (Polyphen) algorithms. The NGS analysis was done on the frozen diagnostic bone marrow samples. The survival probability was estimated using Kaplan-Meier estimator and Cox regression was used to assess the impact of predictors on the OS outcome. An alpha threshold of 0.05 was used. The R program (version 3.1.2) was used for all statistical analyses.
Results: A total of 58 patients with JAK2 V617F positive MPN were included. All of these patients were found to have mutated ASXL1 using the NGS (ASXL1 p.Leu815Pro was found in all patients). The median age of this cohort was 62 years (InterQuartile Range [IQR]: 44 - 70) and female to male ratio was 25:33. The median hemoglobin, hematocrit, white blood cell count and platelet count was 14.7 g/dL, 58%, 11.5 x109/L and 518 x109/L respectively. Out of the 58 patients included, 28 had polycythemia vera, 20 had essential thrombocythemia, 8 had myelofibrosis and 2 had MPN-Unclassified. The median time from diagnosis to last follow up or death was 13 months (IQR: 3-39). During this period, 5 patients died. The probability of OS at 3 years was 88%. The median OS was not reached. In the univariable analysis, age was a statistically significant predictor of OS (p = 0.0355) but not gender (p = 0.434) and MPN subtype (p = 0.7). In the multivariable analysis model of the previous three factors, age remained statistically significant (Hazard ratio = 1.13, p = 0.041).
Conclusions: ASXL1 is mutated in high proportion of patients with JAK2 positive MPN. Despite the negative impact of ASXL1 in patients with non-MPN myeloid neoplasms, the patients with combined positivity of JAK2 and ASXL1 in this study had a very good OS probability. Age was a predictor of OS in the univariable and multivariable models. We recommend the development and the assessment of ASXL1 inhibitors as therapeutic strategies in patients with MPN.

Disclosures
Al-Khabori: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; NovoNardisk: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees; Shire (Takeda): Membership on an entity's Board of Directors or advisory committees; SOBI: Honoraria; AstraZeneca: Honoraria; Abbvie: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees.