Increased expression of h-prune is associated with tumor progression and poor survival in gastric cancer

Abstract

The human homolog of the Drosophila prune protein (from PRUNE, which encodes h-prune), which interacts with glycogen synthase kinase 3, promotes cellular motility. H-prune also interacts with nm23-H1, a suppressor of cancer metastasis. It has been reported that stimulation of cellular motility by h-prune is enhanced by its interaction with nm23-H1 in breast cancer cells. In the present study, we examined the expression of h-prune and nm23-H1 during tumor progression in gastric cancer (GC). PRUNE mRNA was overexpressed in 12 (32%) of 38 GC cases by quantitative reverse transcription-polymerase chain reaction. PRUNE mRNA levels correlated significantly with advanced T grade, N grade and tumor stage. Immunohistochemical analysis revealed that 43 (30%) of 143 GC cases were positive for h-prune, and h-prune-positive GC cases showed more advanced T grade, N grade and tumor stage than h-prune-negative GC cases. One hundred and twenty-four (87%) of 143 GC cases were positive for nm23-H1, and nm23-H1 was expressed in almost all (42 cases, 98%) h-prune-positive GC cases. Many GC cases positive for both h-prune and nm23-H1 showed more advanced T grade, N grade and tumor stage than other type GC cases. Patients with h-prune-positive GC had a significantly worse survival rate than patients with h-prune-negative GC. These findings indicate that overexpression of h-prune is associated with tumor progression and aggressiveness of GC. nm23-H1 may enhance motility of cancer cells by interacting with h-prune.

Figure 1

Expression of PRUNE mRNA in gastric cancer tissues. Each point represents the levels of PRUNE mRNA in an individual specimen. Horizontal bar represents the mean PRUNE mRNA expression level. (a) PRUNE mRNA expression levels were significantly higher in T3/4 cases than in T1/2 cases (P = 0.0156; Mann–Whitney U‐test). (b) The PRUNE mRNA expression levels were significantly higher in N1/2/3 cases than in N0 cases (P = 0.0122; Mann–Whitney U‐test). (c) The PRUNE mRNA expression levels were significantly higher in stage III/IV cases than in stage I/II cases (P = 0.0127; Mann–Whitney U‐test). (d) There was no clear association between PRUNE mRNA expression level and histological type.

Figure 2

Immunohistochemical analysis of h‐prune in gastric cancer (GC) tissues. (a) GC case in which h‐prune expression was strong at the invasive front (original magnification, ×40). (b,c,d) High magnification images of the fields indicated by boxes in panel (a). (b) In corresponding non‐neoplastic gastric mucosa, only weak or no staining of h‐prune was observed in epithelial and stromal cells (original magnification, ×100). (c) In the superficial layer of GC tissue, only weak or no staining of h‐prune was observed (original magnification, ×400). (d) In the invasive front of GC tissue, strong cytoplasmic staining of h‐prune was observed in GC cells (original magnification, ×400). (e) H‐prune‐positive intestinal‐type GC. Strong cytoplasmic staining of h‐prune was observed in GC cells (original magnification, ×400). (f) H‐prune‐positive diffuse‐type GC. Strong cytoplasmic staining of h‐prune was observed in GC cells (original magnification, ×400). (g) H‐prune‐positive diffuse‐type GC (so‐called scirrhous‐type GC). Strong cytoplasmic staining of h‐prune was observed in GC cells (original magnification, ×400).

Figure 3

Expression and distribution of h‐prune and nm23‐H1 in gastric cancer (GC) tissues. (a) Immunohistochemistry of h‐prune in h‐prune‐positive GC case. Staining for h‐prune was observed in diffuse‐type GC cells but not in signet ring cell carcinoma components (arrowhead) (original magnification, ×100). (b) Immunohistochemistry of nm23‐H1 in the same GC case as in panel (a). H‐prune and nm23‐H1 tended to be located in the same GC cells (original magnification, ×100). (c) Immunohistochemistry of h‐prune in h‐prune‐negative GC case (original magnification, ×100). (d) Immunohistochemistry of nm23‐H1 in the same GC case as in panel (c). Staining of nm23‐H1 was observed in GC cells (original magnification, ×100).

Figure 4

Correlation of h‐prune and nm23‐H1 expression with clinicopathologic features. Many gastric cancer (GC) cases positive for both h‐prune and nm23‐H1 showed advanced (a) T grade, (b) N grade and (c) tumor stage. There were no clear differences between h‐prune‐negative/nm23‐H1‐positive GC cases and h‐prune‐negative/nm23‐H1‐negative GC cases. There was only h‐prune‐positive/nm23‐H1‐negative GC among 143 GC cases. (d) The survival of patients with h‐prune‐positive GC was significantly worse in 84 patients with GC (P < 0.0001, log‐rank test). (e) There was no statistical difference between the survival rate of patients with nm23‐H1‐positive GC and that of patients with nm23‐H1‐negative GC (P = 0.6081, log‐rank test).