# Hypoxia-inducible factor 1α exerts dual roles in bladder cancer progression through TIMP3-mediated regulation of angiogenesis and invasion

## TL;DR

This study reveals that HIF-1α has a dual role in bladder cancer by influencing cell growth and angiogenesis through TIMP3 regulation.

## Contribution

The novel finding is that HIF-1α exerts dual roles in bladder cancer via TIMP3-mediated regulation of angiogenesis and invasion.

## Key findings

- Knockdown of HIF-1α increased bladder cancer cell proliferation, migration, invasion, and angiogenesis under hypoxia.
- TIMP3 overexpression reversed the effects of HIF-1α knockdown, highlighting TIMP3 as a key mediator.
- Clinical samples showed elevated HIF-1α levels in bladder cancer tissues.

## Abstract

Bladder cancer is one of the most prevalent malignancies of the urinary system, and its global incidence is rising, particularly among males. Hypoxia-inducible factor 1α (HIF-1α) plays a central role in enabling tumor cells to adapt to hypoxic conditions; however, its specific mechanisms of action in bladder cancer remain incompletely understood. This study aimed to investigate the effects of HIF-1α knockdown on bladder cancer cell proliferation, apoptosis, migration, invasion, and angiogenesis. The T24 and 5637 bladder cancer cell lines were employed. Specific si-HIF-1α plasmids were constructed and transfected into the cells. A series of functional assays were conducted, including MTT viability tests, flow cytometry for apoptosis analysis, Transwell migration and invasion assays, and in vitro angiogenesis experiments. Western blotting was performed to analyze the expression of tissue inhibitor of metalloproteinase 3 (TIMP3). Subsequent functional rescue experiments were carried out by overexpressing TIMP3. Additionally, clinical tissue samples were collected to assess the levels of HIF-1α and TIMP3. The results showed that under hypoxic conditions, knockdown of HIF-1α enhanced bladder cancer cell proliferation, migration, invasion, and angiogenesis while suppressing apoptosis. Furthermore, hypoxia was found to suppress TIMP3 expression in HIF-1α-knockdown cells. Notably, overexpression of TIMP3 reversed the alterations in bladder cancer cell behavior induced by HIF-1α knockdown. Analysis of clinical samples revealed that HIF-1α levels were significantly elevated in bladder cancer tissues. These findings uncover a complex regulatory role for HIF-1α in bladder cancer and identify TIMP3 as a critical mediator of its effects. Further studies are warranted to elucidate the transcriptional regulation of TIMP3 by HIF-1α and to validate its role in vivo, which may contribute to the advancement of targeted therapeutic strategies for bladder cancer.

The online version contains supplementary material available at 10.1038/s41598-026-39635-9.