Expression of pigment epithelial derived factor is reduced in non-small cell lung cancer and is linked to clinical outcome

Abstract

Angiogenesis is under the exquisite control of a network of angiogenic factors and anti-angiogenic factors. PEDF (pigment epithelial derived factor) is one of the known anti-angiogenesis factors and is naturally occurring in the body. There has been studies to show that the factor plays an important role in negating the angiogenic process in pathological conditions in the eye. However, little is known about its expression in solid tumors. The current study examined PEDF expression at protein and message levels and investigated its critical link with cancer progression and prognosis in patients with non-small cell lung cancer (NSCLC). We used immunohistochemistry to examine the protein expression of PEDF and to evaluate the microvessel density (MVD) in a cohort of 91 NSCLC patients. In addition, real-time quantitative PCR was used to measure levels of the PEDF transcript. PEDF was positively stained in cytoplasm of cancer cells, but at a lower level, compared with normal cells in the lung tissues. Low levels of PEDF were seen in 57.1% patients. The levels of PEDF appeared to be associated with MVD, in that patients with reduced PEDF had a significantly high MVD count (28.50), compared with patients with high levels of PEDF who had a 16.98 MVD count (p<0.0005). In univariate but not multivariate analysis PEDF was an independent prognostic factor. In real-time PCR analysis, PEDF mRNA level of cancer tissue was significantly lower than normal tissue (0.55+/-0.36 vs 0.72+/-0.26, p=0.024, paired t-test). PEDF mRNA level in cancer tissue was negatively associated with TNM stage and the tumor size (p<0.05, independent t-test). Finally, low levels of PEDF in lung tumor tissues was associated with a significantly shorter survival (p=0.038) using Kaplan-Meier and Cox analyses. In this first study, PEDF was reduced at both protein and mRNA level in NSCLC tumors compared with normal lung tissues. This reduction is associated with an increase in microvessel density in tumors and significantly associated with TNM stage, tumor size and the overall survival. PEDF is an important factor in NSCLC development and may be a of prognostic value for NSCLC patients.