Serum High Expression of Micorna-214 Is a Novel Predictor for Myeloma Bone Disease and Poor Prognosis

Background: Multiple myeloma (MM) originates from clonal expansion of malignant plasma cells in bone marrow, leading to multiple destructive lytic bone lesions that occur in more than 80% of MM patients. MicroRNAs (miRNAs), such as miR-214, miR-34a and Mir-135 are reported to be involved in maintaining normal bone formation and development of metastatic bone lesions in cancers. Recent studies have demonstrated that miRNAs are stably expressed in human plasma and serum samples. And serum miRNAs have been used as biomarkers in diagnosis and prognosis of multiple cancers, including MM. However, the functional roles of miRNA in myeloma bone disease have not been elucidated yet.

Materials and methods: In the present study, the serum miRNA expression was assessed from 152 samples including 108 MM samples and 44 healthy donors (HD) of serum. Microarray-based assay and real-time PCR was used to determine differentially expressed miRNAs. The correlation of miRNA expression and bone disease detected by whole body X-ray scanning was evaluated by the receiver operating characteristic (ROC) curve and the area under the curve (AUC). Survival analysis was performed using the Kaplan-Meier method with a log-rank test and the generalized Wilcoxon procedure.

Results: We performed serum miRNA profiles from 7 newly diagnosed MMs and 5 normal donors using a microarray-based assay. Our results identified that twenty-seven miRNAs which were reported to be involved in maintaining normal bone formation and development of bone lesions were significantly dysregulated, 4 miRNAs were significantly up-regulated and 23 miRNAs were significantly down-regulated in patient serum. We further performed real-time PCR to verify the expression of miR-214, miR-135, miR-132 and miR-92a in a large cohort of 108 MM patients and 44 healthy donors. We found that miR-214 (0.43±0.17 vs. 2.3±0.14, p<0.0001) and miR-135 (-0.13±0.08 vs. 1.84±0.13, p=0.0022) levels were significantly increased, while serum levels of miR-92a (-0.19±0.20 vs. -1.03±0.11, p=0.0023) were significantly decreased in MM patients. However, we did not found that miR-132 was obviously altered between normal and patient serum. Furthermore, serum levels of miR-214 and miR-135 were notably increased in the patients with lytic bone lesions compared to those without bone disease (both p<0.0001), and a positive correlation was observed between the expression levels of miR-214 (r=0.455, p<0.0001) and miR-135 (r=0.404, p<0.001) with grades of lytic bone lesions. Receiver operating characteristic (ROC) analysis revealed that serum levels of miR-214 and miR-135 can be used to distinguish bone disease in myeloma patients with area under the curve (AUC) > 0.7. Moreover, patients had a significantly shortened OS with high levels of circulating miR-214 (50.0 months vs. NR (not reached); p=0.039) or miR-135 (34.0 months vs.NR; p=0.041) versus those patients with down-regulated levels of miR-214 and miR-135. Patients with higher serum levels of miR-214 were responsible to bisphosphonates with extended OS (NR comparing to 26.0 months, p=0.029), suggesting that bisphosphonates is suitable to treat patients with high expression of circulating miR-214.

Conclusion: Our findings reveal that the circulating miR-214 level is a biomarker for prediction of bone disease and prognosis in multiple myeloma. The detail mechanism how miR-214 involves in disease progression will be further explored. The result of this study also set the foundation for searching more circulating miRNA as biomarkers for metastatic bone lesions.