Expression of 58-kD Microspherule Protein (MSP58) is Highly Correlated with PET Imaging of Tumor Malignancy and Cell Proliferation in Glioma Patients

Abstract

Background/Aims: The nucleolar 58-kDa microspherule protein (MSP58) has important transcriptional regulation functions and plays a crucial role in the tumorigenesis and progression of cancers. 3'-deoxy-3'-[¹⁸F]fluorothymidine (FLT) has emerged as a promising positron emission tomography (PET) tracer for evaluating tumor malignancy and cell proliferation. Methods: In the present study, the expression of MSP58 was evaluated by immunohistochemistry and the corresponding PET image was examined using FLT-PET in 55 patients with various grades of gliomas. Results: The immunoreactivity score (IRS) of MSP58 increased with tumor grade with grade IV gliomas exhibiting the highest expression and showed a highly significant positive correlation with the Ki-67 index (r = 0.65, P < 0.001). The IRS of MSP58 in the tumor showed a highly significant positive correlation with corresponding FLT uptake value (r = 0.61, P < 0.001). The correlation between MSP58 expression and glioma malignancy was also confirmed by immunofluorescence, RT-PCR and western blot analysis. FLT uptake value also exhibited a highly significant positive correlation with the Ki-67 index (r = 0.59, P < 0.001). Kaplan-Meier analysis revealed that MSP58 expression has a significant prognostic ability for the overall survival time similar to that found in the uptake value of FLT-PET. Conclusion: These results indicate that MSP58 plays an important role in cell proliferation and will be one of the potential candidates of molecular therapy targeting proliferation. FLT-PET might be used as an early measure of treatment response in the proliferation-targeted therapy.