Telomere length in myelodysplastic syndromes

Abstract

The relationship between telomere length (TL) and predisposition to myelodysplastic syndromes (MDS) remains unclear. We compared peripheral blood leukocyte (PBL) TL among cases of histologically confirmed MDS (n = 65) who were treatment-naive with no prior cancer history to age-matched controls (n = 63). Relative TL was measured in PBLs and saliva by quantitative polymerase chain reaction (PCR) and in CD15+ and CD19+ cells by flow cytometry-fluorescence in situ hybridization (flow-FISH). Human telomerase reverse transcriptase gene (hTERT) mutations were assessed by PCR. After adjustment for age and sex, relative TLs were reduced in PBLs (p = 0.02), CD15+ (p = 0.01), CD19+ (p = 0.25), and saliva (p = 0.13) in MDS cases versus controls, although only the PBL and CD15+ results were statistically significant. Among MDS cases, CD15+ and CD19+ cell TLs were positively correlated (p = 0.03). PBL TL was reduced among those occupationally exposed to paints and pesticides, but was not associated with hTERT genotype. Future studies are needed to further investigate constitutional telomere attrition as a possible predisposing factor for MDS.

Figure 1. Telomere length measured in peripheral blood leukocytes (PBL) and saliva samples among MDS cases and controls

Using quantitative PCR, telomere lengths were measured in (A) PBL from 65 MDS cases and 63 controls and (B) in saliva from 17 MDS cases and 14 controls. Telomere lengths measured in both PBL and saliva were shorter in MDS cases compared to controls. After adjustment for age and sex, the case-control difference was statistically significant for telomere lengths measured in PBL (p= 0.02) but not saliva (p= 0.13).

Figure 2. Telomere length measured in CD15+ and CD19+ in MDS cases and controls by flow-FISH

Telomere length by flow FISH. (A) Flow cytometry plots showing PBLs from one exemplary patient mixed with 1301 cells. (i) Forward and side scatter plots of the cells for gating: Region 1 (R1) contains 1301 cells, R2 myeloid cells, and R3 lymphocytes. (ii)Gating of R2, was used to identify the CD15 positive myeloid population. Gating of R3 (lymphocyte gate) was used to identify CD19 positive B cells. A sample containing only Alexa 546 and APC secondary antibodies was used as a negative control for CD15 and CD19 staining (not shown). (iii) G0/G1 cells of the CD15 positive, CD19 positive, and 1301 cells were identified by DAPI staining. (iv) G0/G1 gated cells were analyzed for telomere length in the presence (solid red histograms) and absence (open blue histograms) of the FITC labeled telomere PNA probe. The assay was performed in duplicate to demonstrate low inter assay variability. Telomere length fluorescence intensity of cells from MDS patients was compared to that of Jurkat 1301 leukemia T cell line. (B) The telomere length relative to 1301 was calculated in B cells and myeloid cells from 15 MDS patients and 18 healthy controls. Telomere lengths were shorter in MDS cases compared to controls, whether telomere length was measured in CD15+ (p=0.01) or CD19+ cells (p=0.25). (C) Telomere length in B cells (y-axis) was positively correlated with the telomere length in myeloid cells (x-axis) for MDS cases and controls combined (r=0.64, p<0.0001).