High expression of metabotropic glutamate receptor 4: correlation with clinicopathologic characteristics and prognosis of osteosarcoma.

PURPOSE

Analyze protein and gene expression of mGluRs (mGluR1, mGluR5, mGluR4) in osteosarcoma tissues and discuss the relation between expression level and clinical characteristics of osteosarcoma, and study the clinical significance.

METHODS

Detect protein and mRNA expression level of mGluRs (mGluR1, mGluR5, mGluR4) in 40 osteosarcoma tissues and the corresponding adjacent normal tissues by Western blot and RT-PCR accordingly. Immunohistochemistry was adopted to detect the expression of mGluRs (mGluR1, mGluR5, mGluR4) in 118 paraffin embedded osteosarcoma tissues and eight normal bone tissues. Then, the correlation between the expression and clinical characteristics of patients was analyzed. Furthermore, survival analysis of osteosarcoma was performed to study the relation between expression level of mGluRs and patient prognosis.

RESULTS

No correlation of mGluR1 and mGluR5 with clinicopathologic characteristics of osteosarcoma was found. Statistical analysis demonstrated that the expression level of mGluR4 shared no significant correlation with gender, age, histologic type and tumor location of patient, but was related to Enneking stage and tumor metastasis (P < 0.05). High mGluR4 expression is more frequently noted in the osteosarcoma tissues with higher Enneking stage and metastasis. The results of Western blot and RT-PCR indicated a significantly increased expression level of mGluR4 gene and protein in osteosarcoma tissues compared with normal tissues. Though higher gene and protein expression of mGluR5 and mGluR1 were also indicated in osteosarcoma tissues compared with normal tissues, no statistical significance was noted for the difference (P > 0.05). According to the survival analysis of 118 osteosarcoma patients, cases in the mGluR4 high-expression group showed inferior disease-free survival rate and poorer overall survival rate.

CONCLUSION

High expression of mGluR4 in osteosarcoma tissues is related to poor prognosis, thus holding certain reference value for estimating prognosis of osteosarcoma patients.