Correlation between FOXP3 Gene Polymorphisms in Donors, and the Severity of Acute Graft-Versus-Host Disease in Patients after Related Allogeneic Stem Cell Transplantation.

INTRODUCTION: Acute Graft-versus-host disease (aGVHD) is a major complication of allogeneic stem cell transplantation (alloSCT). Risk factors include patient age, sex matching, CMV status and degree of match. Regulatory T cells are critical for immune tolerance processes such as aGVHD, and express the transcription factor FOXP3, a member of the forkhead/winged-helix family, identified as a key regulatory gene required for the development and activity of these cells. It has been suggested that genetic expression of FOXP3 is inversely correlated with the severity of the GVHD. We studied donor’s DNA looking for 5 polymorphisms on the promoter region of the FOXP3 gene, and we tried to correlate them with presence and degree of aGVHD.

PATIENTS AND METHODS: We studied donors of stem cells for allogeneic stem cell transplants. We looked for the presence of the following polymorphisms by PCR: POL01 −5906 T/A rs2869211; POL03 −3279 A/C rs3761548 ; POL04 −2383 C/T rs3761549 ; POL05 −1383 C/T rs2232364 ; POL06 −924 A/G rs2232365.

RESULTS: Our sample consisted of 31 donors, all siblings. In them we found only 2 of the 5 FOXP3 polymorphisms, either as homozygous or heterozygous. These polymorphisms were found in 15/31 donors, with 12 being homozygous (38.7%), and 3 heterozygous (9.7%). These genes polymorphisms were POL03 y POL06. The most observed polymorphism was POL-06 with 9 cases, while POL-03 was found in 6 donors. Only sex difference and CMV status had an elevated hazard ratio for developing GVHD (HR=1.18, CI95%: 0.18 to 7.64; p=0.85) and (HR=3.0, CI95%: 0.07 to 126; p=0.46) respectively. We found no statistically significant difference in the incidence of GVHD between patients who had received cells from donor with or without a FOXP3 polymorphism (p=0.87). When we analyzed the risk of presenting GVHD, results suggest that having one of the 2 positive polymorphisms of the FOXP3 gene could have a protective effect for the patient. For POL03 HR=0.87, CI95%:0.18 to 4.14; p=0.86, and for POL06, HR=1, CI95%: 0.37 to 2.64, p=0.67.

CONCLUSIONS: Even though our sample is still small to make conclusive remarks, we believe that our results point toward some level of “protection” from acute GVHD in patients receiving cells from donors expressing POL03 and POL06. It is also worthwhile mentioning the relatively high frequency of these polymorphisms, as well as the absence of the other 3.