Genetic Polymorphisms of the RANKL and OPG Genes Associated with Myeloma

Abstract 2911

The bone disease in myeloma is the result of the complex interactions between myeloma cells and the bone marrow osteoclasts plus other accessory cells and microenvironmental components. The receptor activator of NfkappaB (RANK) and osteoprotegerin (OPG) cascade system have been reported to be an essential pathway in the osteoclastogenesis. Genetic variations in the genes coding for RANK, RANK ligand (RANKL), and OPG are supposed to play a role in the susceptibility of myeloma.

In the present case control study genomic DNA was obtained in 217 myeloma patients including smoldering myeloma (age: mean 62, 33–88) and 516 healthy controls (healthy blood donors, HC; age mean: 44, 18–65). We studied six single-nucleotide-polymorphisms (SNPs) in the genes of RANK (2 SNPs, rs1805034, rs35211496), OPG (2 SNPs, rs3102735, rs2073618), and of RANKL (2 SNPs, rs9533156, rs2277438) using TaqMan assay guided polymerase chain reaction for the respective SNPs. The genotype and allelic frequencies comparing myeloma patients with HC were analyzed with χ2 test for 2×3 and 2×2 tables, respectively.

The genotype distributions of the SNP rs2277438 in the RANKL gene and SNP rs3102735 in the OPG gene differed highly significantly (p=0.0001 and p=0.005, respectively) between myeloma patients and HC (table 1 ). No significantly increased risk was detected in the other SNP analyzed in the study. A subgroup analysis of the myeloma patients stratified into beta2 microglobulin levels lower or higher than 3.5 mg/l showed lower values to be significantly associated with the minor allele of the SNP rs3102735 in the OPG gene (major vs. minor allele in myeloma vs. HC: 77/23% vs. 89/11%; OR 2.49; CI 1.38–4.49). Further stratification into gender, serum calcium levels, hemoglobin values at diagnosis showed no differences.

To the best of our knowledge, this is the first study reporting a highly significant association of the SNP rs2277438 of the RANKL gene and the SNP rs3102735 in the OPG gene, respectively, with the susceptibility to develop myeloma in the Caucasian population. Both SNPs are associated with an increased risk for myeloma. However, myeloma patients carrying the minor allele of OPG SNP rs3102735 developed lower levels of the proliferation marker beta2 microglobulin. The impact of the OPG SNP rs3102735 (location: promoter region, chromosome 8q24) or of the SNP rs2277438 located in intron 1 (chromosome 13q14.11), a potentially regulatory region of the RANKL gene, on the regulation of RANKL expression is unclear.