# Rhaponitin Reverses Cisplatin Resistance and Impairs Cancer Stemness Through HIF‐1α/MCT4/Wnt Pathway in Tongue Squamous Cell Carcinoma

## TL;DR

Rhaponitin reduces cisplatin resistance and cancer stemness in tongue cancer by targeting the HIF-1α/MCT4/Wnt pathway.

## Contribution

Rhaponitin's novel role in reversing cisplatin resistance and impairing cancer stemness via HIF-1α/MCT4/Wnt signaling in TSCC is demonstrated.

## Key findings

- Rhaponitin repressed growth and stemness of cisplatin-resistant TSCC cells in vitro and in vivo.
- Rhaponitin enhanced cisplatin sensitivity by suppressing Wnt/β-catenin signaling through the HIF-1α/MCT4 axis.
- HIF-1α overexpression reversed rhaponitin-induced apoptosis and stemness inhibition in resistant cells.

## Abstract

Rhaponitin (Rha) possesses anti‐tumor activity and mediates the transcriptional activity of hypoxia‐inducible factor (HIF)‐1α that affects cisplatin (Cis) resistance. However, whether Rha can lessen Cis resistance in tongue squamous cell carcinoma (TSCC) by mediating HIF‐1α activity is unclear. Cis‐resistant SCC9 (SCC9‐CisR) cells were treated with Cis, Rha, or Cis plus Rha to explore the effect of Rha on Cis resistance using a cell counting kit‐8, flow cytometry, and tumor sphere formation assays. Stemness markers CD44 and SOX2 and HIF‐1α mRNA levels were detected by quantitative PCR. The GSE115119 database and plugin iRegulon were employed to select target genes mediated by HIF‐1α. Protein levels of HIF‐1α, monocarboxylate transporter 4 (MCT4), and the Wnt/β‐catenin pathway were measured by western blot. Subcutaneous xenograft models were constructed to explore the efficacy of Rha in combating Cis resistance. Rha repressed the growth and stemness of SCC9‐CisR cells in vitro and in vivo. HIF‐1α protein levels were markedly elevated in SCC9‐CisR cells, yet Rha treatment attenuated the transcriptional activity of HIF‐1α but not HIF‐1α mRNA levels. Rha plus Cis repressed the viability and stemness of SCC9‐CisR cells, but not HIF‐1α‐knockdown SCC9‐CisR cells, compared with Cis alone. Rha‐induced stemness inhibition and apoptosis in SCC9‐CisR cells were overridden after HIF‐1α overexpression. Rha inhibited the Wnt/β‐catenin signaling by regulating the HIF‐1α/MCT4 axis. In conclusion, Rha reduced cell stemness and enhanced Cis sensitivity in TSCC, which was achieved possibly via suppressing the Wnt/β‐catenin signaling through mediation of the HIF‐1α/MCT4 axis.