Clinical significance of mTOR, ZEB1, ROCK1 expression in lung tissues of pulmonary fibrosis patients

Abstract

Background: Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease of unknown causes. Three proteins (mammalian target of rapamycin, mTOR; zinc finger E-box-binding homeobox 1, ZEB1; Rho-associated, coiled-coil containing protein kinase 1, ROCK1) may be related to pulmonary fibrosis. However, they have not been assessed in human pulmonary fibrosis. We assessed the clinical significance of mTOR, ZEB1, and ROCK1 expression in human pulmonary fibrosis of usual interstitial pneumonia (UIP) pattern.

Methods: The mTOR, ZEB1, and ROCK1 expression was evaluated by immunohistochemical staining of 30 surgical lung biopsy tissues from 26 IPF and 4 UIP pattern connective tissue disease related interstitial lung disease (CTD-ILD) patients. The expression scores correlated with the clinical features.

Results: The mTOR, ZEB1 and ROCK1 mainly expressed in alveolar epithelial cells of UIP lungs. The histological fibrosis scores and lung function decline in the strong mTOR expression group were higher than those in the weak and intermediate expression group. Patients with positive ZEB1 expression had higher fibrosis scores and greater decline in carbon monoxide diffusion capacity (DLCO) than patients with negative ZEB1 expression. Patients with positive mTOR or ZEB1 expression had poorer prognosis than that of patients with negative mTOR or ZEB1 expression, although it was not statistically significant. ROCK1 was not associated with the studied clinicopathological features.

Conclusions: The mTOR and ZEB1 expression in pulmonary fibrosis patients significantly correlated with the fibrosis score and lung function decline, indicating that it may be related to the prognosis of pulmonary fibrosis. Further studies involving large numbers of homogeneous IPF patients are warranted.

Figure 1

Representative lung tissue sections of usual interstitial pneumonia patients exemplifying the two principal grades of fibrosis and expression levels observed with the different markers. Low-power images showing grade of fibrosis (A, grade 1 fibrosis; B, grade 7 fibrosis; hematoxylin and eosin staining, 40× magnification) The mTOR and ZEB1 expressed in hyperplastic alveolar epithelial cells and some mesenchymal cells from fibrotic areas (C, mTOR intermediate; D, mTOR strong; E, ZEB1 intermediate; F, ZEB1 strong). ROCK1 expressed in hyperplastic alveolar epithelial cells, mesenchymal cells, macrophages and lymphocytes of the UIP patients (G, ROCK1 intermediate; H, ROCK1 strong). (C-H); immunohistochemical staining, brown color, 400× magnification.

Figure 2

Representative lung tissue sections from healthy individuals and patients with usual interstitial pneumonia (UIP), stained for mTOR, ZEB1, and ROCK1. The mTOR, ZEB1 and ROCK1 expression was not detected in alveolar epithelial cells of control normal lung tissue (Figure 2A, E, I, immunohistochemical staining, brown color, 200× magnification). Staining was weak or absent in normal area of UIP lungs (Figure 2B, F, J, 400× magnification). Cells overlying fibroblastic foci showed weak staining, however mesenchymal cells of the fibroblastic foci did not show mTOR, ZEB1 and ROCK1 expression (Figure 2C, G, K; arrows denote location of fibroblastic focus, 400× magnification). Expression of mTOR, ZEB1 and ROCK1 was compared in same fibrotic area (Figure 2D, H, L, 400× magnification).

Figure 3

Association of mTOR(A), ZEB1(B), and ROCK1(C) expression with fibrosis score.

Figure 4

Patient survival in association with the expression of mTOR(A), ZEB1(B) and ROCK1(C) expression; (-) represents negative expression group and (+) represents intermediate and strong expression group.