Gene Mutations in MDS Associating with Peripheral Blood Count Abnormalities

Recent data suggested that low levels of mutated myeloid genes could be detected in the peripheral blood of individuals with normal peripheral blood counts. While testing for MDS-related molecular abnormalities is not justified in individuals without a cytopenia, appreciating the linkage between abnormal peripheral blood counts and specific myeloid gene mutations would support the need for genetic testing. Furthermore, we found that approximately 50% of practicing hematologists and oncologists do not send MDS bone marrow specimens for conventional cytogenetic testing (Craig, et al. Leuk Res 2011), and even fewer order gene mutation profiling, despite the informative potential of results for diagnosis, prognosis and therapy. Hence, there is a gap in recognizing when to order genetic testing in MDS. To address this, bone marrow aspiration cells from patients with morphologically and clinically confirmed MDS were examined for genomic mutations by conventional cytogenetics and targeted next generation sequencing (NGS). Sequencing covered mutations in the following genes: TET2, SF3B1, ASXL1, DNMT3A, SRSF2, RUNX1, NRAS, ZRSR2, EZH2, ETV6, TP53, CBL, NPM1, JAK2, U2AF1, IDH1, KRAS, IDH2, FLT3, PTPN11, and SETBP1. The average depth of NGS was 10,000x and mutant allele frequency was >5%. Association between genomic mutations and peripheral blood counts were evaluated using the Kruskal-Wallis test. 147 patients with WHO-defined MDS were included in this study. 12/147 (8%) had very good cytogenetic risk disease, 104/147 (71%) were good risk, 22/147 (15%) were intermediate risk, 4/147 (3%) were poor risk, and 5/147 (3%) were very poor risk. Anemia was significantly associated with SF3B1 mutations (P=0.0017), while higher hemoglobin values were significantly associated with SRSF2 mutations (P=0.0051). Macrocytosis was associated with SF3B1 (P<0.0001) and ZRSR2 (P=0.0382) mutations. Thrombocytopenia (<100x10⁹/L) was associated with mutations in SRSF2 (P=0.0148), TP53 (P=0.0005), or U2AF1 (0.0434). Higher platelet counts were found in patients with SF3B1 mutations (P<0.0001). Higher total white blood cell counts (P<0.0001) and higher absolute neutrophil counts (P<0.0001) were noted in patients with SF3B1 mutations. Absolute monocyte counts were higher in patients with NRAS (P=0.0237) and SF3B1 (P=0.0122) mutations. TET2 mutations were associated with lower percentage of bone marrow blasts (P=0.0032). While patients with TP53 mutations tended to have higher IPSS-R score (P=0.0017), patients with SF3B1 mutations tended to have lower IPSS-R score (P=0.0133). Overall, patients with TP53 mutations were more likely to present with higher risk disease by IPSS-R than patients without TP53mutations. In patients with MDS, certain myeloid gene mutations significantly associated with peripheral blood count abnormalities (Table 1). Genetic testing of bone marrow samples is warranted in MDS patients showing abnormal peripheral blood counts.

Table 1. Summary of Significant Associations Between Peripheral Blood Count Abnormalities and Myeloid Gene Mutations in Patients with MDS.

 

Peripheral Blood Count Abnormality	Genetic Mutation
Anemia	SF3B1
Higher Hemoglobin	SRSF2
Macrocytosis	SF3B1, ZRSR2
Thrombocytopenia (<100x109/L)	SRSF2, TP53, U2AF1
Higher Platelet Count	SF3B1
Higher Total WBC count	SF3B1
Higher Absolute Neutrophil Count (ANC)	SF3B1
Higher Absolute Monocyte Count (AMC)	SF3B1, NRAS
Lower % BM blasts	TET2
Lower IPSS-R score	SF3B1
Higher IPSS-R score	TP53