Interactions between TGF-β type I receptor and hypoxia-inducible factor-α mediates a synergistic crosstalk leading to poor prognosis for patients with clear cell renal cell carcinoma

ABSTRACT

To investigate the significance of expression of HIF-1α, HIF-2α, and SNAIL1 proteins; and TGF-β signaling pathway proteins in ccRCC, their relation with clinicopathological parameters and patient’s survival were examined. We also investigated potential crosstalk between HIF-α and TGF-β signaling pathway, including the TGF-β type 1 receptor (ALK5-FL) and the intracellular domain of ALK5 (ALK5-ICD). Tissue samples from 154 ccRCC patients and comparable adjacent kidney cortex samples from 38 patients were analyzed for HIF-1α/2α, TGF-β signaling components, and SNAIL1 proteins by immunoblot. Protein expression of HIF-1α and HIF-2α were significantly higher, while SNAIL1 had similar expression levels in ccRCC compared with the kidney cortex. HIF-2α associated with poor cancer-specific survival, while HIF-1α and SNAIL1 did not associate with survival. Moreover, HIF-2α positively correlated with ALK5-ICD, pSMAD2/3, and PAI-1; HIF-1α positively correlated with pSMAD2/3; SNAIL1 positively correlated with ALK5-FL, ALK5-ICD, pSMAD2/3, PAI-1, and HIF-2α. Intriguingly, in vitro experiments performed under normoxic conditions revealed that ALK5 interacts with HIF-1α and HIF-2α, and promotes their expression and the expression of their target genes GLUT1 and CA9, in a VHL dependent manner. We found that ALK5 induces expression of HIF-1α and HIF-2α, through its kinase activity. Under hypoxic conditions, HIF-α proteins correlated with the activated TGF-β signaling pathway. In conclusion, we reveal that ALK5 plays a pivotal role in synergistic crosstalk between TGF-β signaling and hypoxia pathway, and that the interaction between ALK5 and HIF-α contributes to tumor progression.

KEYWORDS:

• ALK5
• clear cell renal cell carcinoma
• HIF-α
• SNAIL1
• transforming growth factor-β

Acknowledgments

We thank Ms. Britt-Inger Dahlin, Ms. Kerstin Almroth, the staff in Urology and Andrology at Umeå University Hospital for skillful technical assistance, and the participating patients for their cooperation.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Cancer Research Foundation in Northern Sweden [AMP 18-942]; Knut och Alice Wallenbergs Stiftelse [2012.0090]; Swedish Medical Research Council [K2016-02513]; The county of Västerbotten [ALF-VLL-464591]; The county of Västerbotten [ALF-VLL-73891]; Swedish Cancer Foundation [CAN 2017/544]. The funders did not play a role in manuscript design, data collection, data analysis, interpretation nor writing of the manuscript.