P11 (S100A10) as a potential biomarker of psychiatric patients at risk of suicide

Although suicide represents 1.8% of the global burden of disease, there are few objective assays for suicide risk. Being associated with depressive disorders, which have a high risk of suicide, the proteins P11, P2RX7, and S100β may be biomarkers for a suicidal disposition. We measured levels of p11 and P2RX7 mRNA in peripheral blood mononuclear cells (PBMCs) of 26 psychiatric patients (11 suicide attempters, 15 suicide non-attempters) with post-traumatic stress disorder (PTSD) and major depressive disorder (MDD), and 14 normal controls, using quantitative real-time PCR. We also conducted a meta-analysis of microarray data of p11, P2RX7 and S100β from post-mortem prefrontal cortex (PFC) of patients who committed suicide (n = 56) and non-suicide controls (n = 61). We found that PBMC p11 mRNA levels were significantly lower in suicide attempters and higher in suicide non-attempters, when compared to normal controls. The PFC p11 mRNA levels in suicide completers were also lower than non-suicide controls (adjusted p = 0.007). Unlike p11, PBMC P2RX7 mRNA levels were significantly lower than normal controls in all patients including suicide attempters, suicide non-attempters, and suicide completers. In addition, levels of S100β in PFC did not differ between suicide completers and non-suicide controls. These results suggest that PBMC p11 mRNA levels may be a potential adjunctive biomarker for the assessment of suicide risk in mental disorders and warrants a larger translational study to determine its clinical utility.