Expression of HIF‑α and their association with clinicopathological parameters in clinical renal cell carcinoma

Abstract

Objectives: This study aimed to assess the cellular localization and expression levels of hypoxia-inducible factor (HIF) -α proteins (specifically HIF-1α, HIF-2α, and HIF-3α) that play a role in the hypoxia pathway and to determine their correlation with clinicopathological parameters and patient survival in renal cell carcinoma (RCC).

Materials and methods: Tissue microarray (TMA) with cores from 150 clear cell RCCs and 31 non-ccRCC samples. HIF-1α, HIF-2α, and HIF-3α antibodies were used for immunohistochemistry (IHC) of TMA to evaluate the cellular localization and expression levels of HIF-α proteins, specifically in relation to the hypoxia pathway.

Results: The expression levels of the HIF-α proteins were higher in the nucleus than in the cytoplasm. Furthermore, the nuclear expression levels of all HIF-α proteins were significantly higher in clear cell RCC (ccRCC) than in non-ccRCC. Cytoplasmic HIF-3α expression was also higher in ccRCC than in non-ccRCC, whereas cytoplasmic HIF-1α and HIF-2α expression levels were similar between the different RCC types. In ccRCC, nuclear HIF-1α expression levels correlated with both nuclear HIF-2α and HIF-3α levels, whereas cytoplasmic HIF-3α expression levels were associated with HIF-1α only.In non-ccRCC, there was a positive correlation observed between nuclear HIF-1α and HIF-3α expression, but no correlation was found with HIF-2α. In patients with ccRCC, the nuclear expressions of HIF-1α and HIF-3α was significantly associated with cancer-specific survival (CSS) in univariate analysis. This association was no longer evident in multivariate analysis. Notably, there was no correlation observed between nuclear HIF-2α expression and CSS in these patients. In contrast, cytoplasmic expression levels showed no association with CSS.

Conclusion: The expression levels of the three primary HIF-α proteins were found to be higher in the nucleus than in the cytoplasm. Furthermore, the results indicated that HIF-3α and HIF-1α expression levels were significant univariate factors associated with CSS in patients with clear cell RCC. These results highlight the critical role that HIF-3α and HIF-1α play in the hypoxia pathway.

Keywords: HIF-1α; HIF-2α; HIF-3α; and tumor stage; ccRCC; non-ccRCC; prognosis; renal cell carcinoma.

Figure 1

Box plots representation of expression levels of (A) nuclear HIF-1α, (B) cytoplasmic HIF-1α, (C) nuclear HIF-2α, (D) cytoplasmic HIF-2α (E) nuclear HIF-3α, and (F) cytoplasmic HIF-3α, in ccRCC patients compared with non-ccRCC; Representative stained tissues cores of ccRCC and non-ccRCC after IHC assay with (G and H) HIF-1α, (I and J) HIF-2α, (K and L) HIF-3α in ccRCC and non-ccRCC, respectively.

Figure 2

Box plots showing the comparison of expression levels of (A) nuclear HIF-1α and cytoplasmic HIF-1α, (B) nuclear HIF-2α and cytoplasmic HIF-2α, (C) nuclear HIF-3α and cytoplasmic HIF-3α in ccRCC patients; Box plots showing the comparison of expression levels of (D) nuclear HIF-1α and cytoplasmic HIF-1α, (E) nuclear HIF-2α and cytoplasmic HIF-2α, (F) nuclear HIF-3α and cytoplasmic HIF-3α in non-ccRCC patients.

Figure 3

Kaplan–Meier plots showing cancer-specific survival curves of ccRCC (A) nuclear HIF-1α, (B) cytoplasmic HIF-1α (cytoplasm), (C) nuclear HIF-2α, (D) cytoplasmic HIF-2α, (E) nuclear HIF-3α and (F) cytoplasmic HIF-3α.