Hypoxia inducible factor-1alpha correlates with vascular endothelial growth factor A and C indicating worse prognosis in clear cell renal cell carcinoma

Abstract

Background: The role of angiogenesis in the pathogenesis of renal cell carcinoma is well recognized, however, the influence of tumor cells in this activity has not yet been fully clarified. The aim of this study was to analyze the expression of hypoxia inducible factor-1alpha (HIF-1alpha), a regulatory factor of angiogenic switch, in comparison to vascular endothelial growth factor A and C (VEGF-A and VEGF-C), recognized to be involved in blood and lymph vessel neoangiogenesis, with potential association in the prognosis of patients with renal cell carcinoma.

Methods: Ninety-four patients with diagnosis of clear cell renal cell carcinomas (CCRCC), all clinicopathological characteristics and overall survival were unrolled in this study. Immunohistochemicaly VEGF-A, VEGF-C, HIF-1alpha and Ki67 were detected on tumor cells and the staining was performed on tissue microarrays (TMA). The staining was evaluated as a percentage of cytoplasmic or nuclear positive tumor cells.

Results: Variable expression of all three proteins was confirmed. Both angiogenic factors demonstrated perimembranous or diffuse cytoplasmic staining, with diffuse pattern positively associated (p < 0.001). Nuclear HIF-1alpha expression (nHIF-1alpha) showed inverse correlation with diffuse cytoplasmic VEGF-A (p = 0.002) and VEGF-C (p = 0.053), while cytoplasmic HIF-1alpha expression (cHIF-1alpha) showed positive correlation with diffuse staining of both angiogenic factors (p < 0.001; p < 0.001, respectively). In comparison to clinicopathological characteristics, a higher nuclear grade (p = 0.006; p < 0.001, respectively), larger tumor size (p = 0.009; p = 0.015, respectively), higher stage (p = 0.023; p = 0.027, respectively) and shorter survival (p = 0.018; p = 0.024, respectively) were associated with overexpression of cHIF-1alpha and diffuse cytoplasmic VEGF-A expression. In contrary, overexpression of nHIF-1alpha was associated with better diagnostic parameters i.e. lower nuclear grade (p = 0.006), smaller tumor size (p = 0.057), and longer survival (p = 0.005).

Conclusion: Overexpression of VEGF-A and cHIF-1alpha in tumor cells highlights a more aggressive subtype of CCRCC that might have some clinical implications. The significance of nHIF-1alpha expression associated with better differentiated tumors should be further elucidated.

Figure 1

Immunohistochemical staining of HIF-1α, VEGF-A and VEGF-C in normal renal tissue (A-C) and clear cell renal cell carcinoma (CCRCC) (D-F). A homogeneous cytoplasmic staining of tubular cells and weak staining in glomerules was observed with HIF-1α (A), while VEGF-A and VEGF-C were positive in tubular cells, glomerular mesangium and interstitial macrophages (B and C). In CCRCC, HIF-1α immmunoreactivity was nuclear and/or cytoplasmic (D), while it was perimembranous and/or diffuse cytoplasmic for VEGF-A and VEFG-C (E and F). (magnification ×200).

Figure 2

Kaplan-Meier cumulative survival analysis according to staining for nuclear and cytoplasmic HIF-1α, VEGF-A and VEGF-C. The log-rank test showed significantly shorter overall survival in patients with tumors showing low nHIF-1α (p = 0.005) (A) and low pVEGF-C (p = 0.008) (D). The 5-year survival rate was 32% for patients whose tumors showed low nHIF-1α vs. 65% for patients whose tumors showed high nHIF-1α (A); and 40% for patients whose tumors showed low pVEGF-C vs. 61% for patients whose tumors showed high pVEGF-C (D). The log-rank test showed significantly shorter overall survival in patients with tumors showing high cHIF-1α (p = 0.018) (B) and high dVEGF-A (p = 0.024) (C). The 5-year survival rate was 60% for patients whose tumors showed low cHIF-1α vs. 40% for patients whose tumors showed high cHIF-1α (B); and 59% for patients whose tumors showed low dVEGF-A vs. 40% for patients whose tumors showed high dVEGF-A (C).