IRAK2 is associated with systemic lupus erythematosus risk

A CD40 variant is associated with systemic bone loss among patients with rheumatoid arthritis

OBJECTIVES

Little is known about genes predisposing to systemic bone loss (SBL) in rheumatoid arthritis (RA). Therefore, we examined the association between SBL and variants of genes playing a critical role in both immune response and bone homeostasis among patients with RA.

METHODS

IRAK-1 rs3027898, IRAK-2 rs3844283, IRAK-2 rs708035, IFIH1 rs1990760, CD40 rs48104850, TNFAIP3 rs2230926, and miR146-a rs2910164 were genotyped in 176 adult RA patients. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DXA).

RESULTS

Low BMD was observed in 116 (65.9%) patients. Among them, 60 (34.1%) had low femoral neck (FN) Z score, 72 (40.9%) had low total femur (TF) Z score, and 105 (59.6%) had low lumbar spine (LS) Z score. Among all the SNPs assessed, only CD40 rs4810485 was found to be associated with reduced TF Z score with the CD40 rs4810485 T allele protecting against reduced TF Z score (OR = 0.40, 95% CI = 0.23-0.68, p = 0.0005). This association was confirmed in the multivariate logistic regression analysis (OR = 0.31, 95% CI = 0.16-0.59, p = 3.84 × 10^-4). Moreover, median FN BMD was reduced among RA patients with CD40 rs4810485 GG genotype compared to RA patients harbouring CD40 rs4810485 TT and GT genotypes (0.788 ± 0.136 versus 0.826 ± 0.146 g/cm², p = 0.001). IRAK-1 rs3027898, IRAK-2 rs3844283, rs708035, IFIH rs1990760, TNFAIP3 rs2230926, and miR146-a rs2910164 were not found to be associated with SBL.

CONCLUSION

This study for the first time ever demonstrated an association between a CD40 genetic variant and SBL among patients with RA.

KEY POINTS

• CD40 rs4810485 GG genotype is associated with decreased BMD among patients with RA. • CD40 rs4810485 might serve as a genetic marker for SBL in RA. • CD40 genetic variations might be integrated in future development of more effective therapeutic interventions for prevention of SBL in RA.

IRAK2, an IL1R/TLR Immune Mediator, Enhances Radiosensitivity via Modulating Caspase 8/3-Mediated Apoptosis in Oral Squamous Cell Carcinoma

Predicting and overcoming radioresistance are crucial in radiation oncology, including in managing oral squamous cell carcinoma (OSCC). First, we used RNA-sequence to compare expression profiles of parent OML1 and radioresistant OML1-R OSCC cells in order to select candidate genes responsible for radiation sensitivity. We identified IRAK2, a key immune mediator of the IL-1R/TLR signaling, as a potential target in investigating radiosensitivity. In four OSCC cell lines, we observed that intrinsically low IRAK2 expression demonstrated a radioresistant phenotype (i.e., OML1-R and SCC4), and vice versa (i.e., OML1 and SCC25). Next, we overexpressed IRAK2 in low IRAK2-expression OSCC cells and knocked it down in high IRAK2-expression cells to examine changes of irradiation response. After ionizing radiation (IR) exposure, IRAK2 overexpression enhanced the radiosensitivity of radioresistant cells and synergistically suppressed OSCC cell growth both in vitro and in vivo, and vice versa. We found that IRAK2 overexpression restored and enhanced radiosensitivity by enhancing IR-induced cell killing via caspase-8/3-dependent apoptosis. OSCC patients with high IRAK2 expression had better post-irradiation local control than those with low expression (i.e., 87.4% vs. 60.0% at five years, P = 0.055), showing that IRAK2 expression was associated with post-radiation recurrence. Multivariate analysis confirmed high IRAK2 expression as an independent predictor for local control (HR, 0.11; 95% CI, 0.016 – 0.760; P = 0.025). In conclusion, IRAK2 enhances radiosensitivity, via modulating caspase 8/3-medicated apoptosis, potentially playing double roles as a predictive biomarker and a novel therapeutic target in OSCC.