Expression of insulin-like growth factor II mRNA-binding protein 3 (IMP3) in sacral chordoma

Sacral chordoma is a rare and aggressive tumor, with a high rate of local recurrence even when the tumor is radically resected. The fundamental knowledge of its biological behavior remains unknown. Insulin-like growth factor II mRNA-binding protein 3 (IMP3) is one of the RNA binding proteins and is expressed during embryogenesis and in various malignant tumors. This study evaluated expression of IMP3 in sacral chordoma for association with patient's clinicopathological factors. A total of 32 patients with sacral chordoma (17 male and 15 female) and 10 samples of distant normal tissues were collected for analysis of IMP3 expression using immuno-histochemistry. Association between IMP3 expression and clinicopathological factors (such as patient's age, gender, tumor location, tumor size, surrounding muscle invasion, Ki-67 expression, and tumor recurrence) were statistically analyzed. IMP3 was expressed in 20 (62.5 %) patients, whereas there was no expression in the 10 distant normal tissues. IMP3 expression was associated with tumor invasion into the surrounding muscle (P = 0.028), high levels of Ki-67 expression (P = 0.009), and tumor recurrence (P = 0.012). The log-rank test revealed that patients with positive IMP3 expression had a shorter continuous disease-free survival time than those with negative IMP3 expression (P = 0.016). IMP3 expression was independent of age, gender, tumor location and tumor size. These results indicate that IMP3 was overexpressed in sacral chordoma and this expression was associated with tumor invasion and recurrence; thus, IMP3 may play an important role in tumor progression and could serve as a prognostic biomarker for sacral chordoma and IMP3 could be used as a potential therapeutic target for the treatment of sacral chordoma.