Changes of plasma GARP-LTGFβ1 complex during chemoradiotherapy may predict survival in non-small cell lung cancer (NSCLC)

Abstract

Background: Glycoprotein-A repetitions predominant protein (GARP), a cell surface docking and activating receptor for latent transforming growth factor β1 (LTGFβ1), has been implicated in promoting oncogenesis. We report recently that GARP-LTGFβ can be clipped by thrombin but its clinical significance remains unclear. Herein, we hypothesized that 1) the baseline plasma GARP-LTGFβ1 complex is associated with clinical stage of cancers; 2) the baseline and/or changes of plasma GARP-LTGFβ1 complex during chemo-radiotherapy is associated with overall survival (OS) in patients with NSCLC. Methods: This is a correlative study for patients with stage I-III NSCLC receiving chemo-radiotherapy. Levels of GARP-LTGFβ1 complex in platelet-poor plasma were determined by a modified ELISA at pre-RT, 2,4 weeks during-RT and post-RT. Values were calculated based on the following formula: (OD test -OD negative control )/OD postive control -OD negative control ). The primary endpoint was OS, analyzed using the Kaplan-Meier method and Cox proportional hazard model. Platelet-poor plasma samples from healthy subjects were used as normal controls. Results: A total of 155 patients were included: 41 stage I-II, 111 stage III. There were 115 male, 50 female with a median age of 66 years. Compared to 13 normal controls (0.638, 95% CI:0.477-0.799), NSCLC patients had a significantly higher plasma GARP-LTGFβ1 (0.965, 95%CI: 0.881-1.048, p = 0.014). The same trend was observed for stage, higher level in more advanced stage (1.037, 95%CI: 0.930-1.145) vs for stage I-II (0.854, 95%CI: 0.720-0.988) (p = 0.0375). Univariate analysis demonstrated that age, gender, clinical stage, smoking history, histology, KPS, and radiation dose were significantly associated with OS. Post/pre RT GARP-LTGFβ1 complex (high vs. low HR = 0.384, p = 0.043) instead of pre-RT (p = 0.538), during RT (p = 0.739 for 2 weeks, p = 0.570 for 4 weeks) or post-RT (p = 0.507) plasma GARP-LTGFβ1 complex during the course of radiation therapy correlated significantly with OS under univariate analysis. On multivariate Cox regression models after adjusting for above significant clinical factors, the changes of plasma GARP-LTGFβ1 level had significance in correlating with OS (HR = 0.359, p = 0.0087). Conclusions: Baseline plasma GARP-LTGFβ1 were significantly associated with presence of cancer and advanced stages in NSCLC patients. Changes of GARP-LTGFβ1 level in plasma could be useful to predict outcomes and reflect the changes of immune status after chemoradiation.