Analysis of Polymorphism in the Genes TLR3, TLR4 and TLR9 in Patients with Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a bone marrow malignancy characterized by uncontrolled proliferation of transformed myeloid precursors. It is the most common acute leukemia and is a highly heterogeneous disease. AML leads to impaired hematopoiesis, which may result in increased risk of infection. Toll-like receptors (TLRs) are major elements of the innate immune system which recognize pathogen-associated molecular patterns. They also have a role in autoimmune diseases and cancer through their recognition of endogenous danger-associated molecular patterns. Various TLRs were found to be expressed in AML cells, and their expression was found to affect growth, differentiation, and immunostimulatory capacity in AML.

We retrospectively analysed 90 patients (48 females and 42 males) with diagnosis of AML, hospitalized in Department and Clinic of Hematology, Blood Neoplasms and Bone Marrow Transplantation of Wroclaw Medical University. The median age of patients was 62 (range:18-81). Infectious complications after induction chemotherapy occurred in 62 patients. In the present study, we detected the effect of seven single nucleotide polymorphisms (SNPs) located in the genes coding for TLR3 (rs5743305, rs3775296, 3775291), TLR4 (rs4986791, rs4986790) and TLR9 (rs187084, rs5743836). DNA was isolated from samples of peripheral blood taken on EDTA. Melting curve genotyping with the use of LightSNiP asays(TIB MOLBIOL, Germany) was employed to determining TLR3, TLR4 and TLR9 genotypes, and the reactions were performed LightCycler 480 device (Roche Applied Science, Germany).Statistical analyses were performer using Real Statistics Resource Pack for Microsoft Excel.

We found that TLR3 rs5743305 AA homozygosity was more common in AML patients with infectious complications than in patients unaffected by infections (p=0.015). TLR4 rs4986791 C and TLR9 rs5743836 C were associated with lower levels of the inflammation marker CRP (p=0.015 and p=0.048, for rs4986791 and rs5743836, respectively), TLR4 rs4986791 C and was less frequently detected among patients with CRP>5 (p=0.028). We also found TLR9 rs187084 C to be more common in patients with adverse cytogenetic risk according to ELN criteria (0.012). Additionally, a trend for higher prevalence of extramedullary disease was observed for carriers of TLR3 rs3775296 T (p=0.054), TLR3 3775291 GG (p=0.068), TLR4 rs4986790 G (p=0.078), as well as TLR9 rs187084 TT (p=0.053).

In conclusion, our results suggest that SNPs in the genes coding for TLR3, TLR4 and TLR9 may be implicated in clinical outcome of AML and is related with increased risk of infectious complications.