Survival analyses correlate stanniocalcin 2 overexpression to poor prognosis of nasopharyngeal carcinomas

Abstract

Background: Stanniocalcin 2 (STC2) is overexpressed in several types of human cancers, and its overexpression positively correlates to tumor progression and poor prognosis. However, the clinical significance of STC2 overexpression in nasopharyngeal carcinomas (NPC) has not been investigated. This study examined STC2 expression in a cohort of 94 NPC samples, and explored its value in clinical diagnosis and prognosis.

Methods: Tumor samples from 94 patients diagnosed in 2008 were studied. All samples were obtained prior to treatment start. All cases were clinically diagnosed and pathologically confirmed to be poorly differentiated or undifferentiated NPC without distant metastasis, and have been treated with radical radiation therapy and followed-up for five years. Survival analyses were performed.

Results: Of the 94 NPC samples, STC2 overexpression (STC2+) was detected in 65 samples (69.1%). Overall survival rate of STC2 (+) patients is significantly lower than that of patients with normal STC2 levels (72.2% vs. 96.4%, respectively, P = 0.049). Moreover, STC2 (+) is also strongly predictive of a low progression-free survival and distant metastasis-free survival (63.0% vs 92.9%. P = 0.007; and 77.0% vs 96.4%. P = 0.028). Of the 54 patients treated with IMRT, residual tumors were found in 54.8% of STC2 positive patients (17/31), but only in 17.4% of STC2 negative ones (4/23), suggesting STC2 overexpression predicts a higher risk of residual tumors after IMRT.

Conclusions: STC2 overexpression correlates to poor prognosis for NPC and may be useful as a novel biomarker to predict NPC responses to radiation. Whether STC2 promotes NPC progression and metastasis remains to be investigated.

Figure 1

STC2 expression in tumor adjacent nasopharyngeal epithelia with normal morphology and carcinoma cells as determined by immunohistochemistry studies. A: STC2 expressed in local tumor (× 200). B: Traditional HE staining, NPC, (× 200). C: STC2 was overexpressed in the tumor zone (× 100). D: Negative Control: NPC tissue stained at the same conditions except that no specific antibody (anti-STC2) was added (× 100). Scale bar: 50 μm in A and B; 100 μm in C and D.

Figure 2

Criteria for STC2 expression intensity scoring. Representative micrographs were shown as labelled (× 200). All micrographs were taken and processed at identical conditions. Scale bar: 50 μm.

Figure 3

High STC2 expression predicts inferior outcomes in NPC patients. Survival data were analyzed and plotted using the Kaplan–Meier method. Patients were classified into STC2 negative or positive according to STC2 immunohistochemistry. *: P <0.05. A. Local regional failure-free survival (LRFS); B. Distant metastasis-free survival (DMFS); C. Overall Survival (OS); and D. Progression-free survival (PFS).