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. 2025 Sep 9;151(9):243. doi: 10.1007/s00432-025-06300-z

Inhibition of dipeptidyl peptidase 9 improves sorafenib sensitivity by inducing ferroptosis in hepatocellular carcinoma

Qing Li 1, Yang Wang 2,✉, Jun Zou 3
PMCID: PMC12417342  PMID: 40921831

Abstract

Objective

Dipeptidyl peptidase 9 (DPP9) not only regulates tumor progression and drug sensitivity, but also modifies oxidative stress mediated ferroptosis. This study aimed to investigate the effect of DPP9 inhibition on sorafenib sensitivity and its interaction with ferroptosis in hepatocellular carcinoma (HCC).

Methods

Two HCC cell lines (Huh7 and MHCC-97H) were transfected with DPP9 siRNA, followed by detection of reactive oxygen species (ROS), ferrous iron (Fe2+), malondialdehyde (MDA), and ferroptosis-related proteins, and treated by 0–16 μM sorafenib to calculate half-maximal inhibitory concentration (IC50) for sensitivity assessment. Moreover, ferrostatin-1 (Fer-1) was added with or without DPP9 siRNA, followed by the above detections.

Results

Inhibition of DPP9 improved sorafenib sensitivity reflected by a lower sorafenib IC50 value, and it increased ROS fluorescence intensity, Fe2+ level, and MDA level, which also upregulated ACSL4 expression but downregulated NRF2 and SLC7A11 expressions. Fer-1 treatment decreased ROS fluorescence intensity, Fe2+ level, MDA level, and reduced sorafenib sensitivity reflected by a higher sorafenib IC50 value. Moreover, Fer-1 treatment weakened the effect of DPP9 inhibition on ROS fluorescence intensity, Fe2+ level, MDA level, most of the ferroptosis-related proteins, and sorafenib sensitivity reflected by sorafenib IC50 value.

Conclusion

Inhibition of DPP9 improves sorafenib sensitivity by promoting ferroptosis in HCC, which provides novel evidence for DPP9 as an HCC treatment target synergizing with sorafenib.

Keywords: Hepatocellular carcinoma, Dipeptidyl peptidase 9, Sorafenib sensitivity, Oxidative stress, Ferroptosis

Introduction

Liver cancer is the sixth top prevalent cancer and third top deadly cancer globally (Bray et al. 2024); and in China, the condition is even worse that liver cancer ranks the fourth in incidence and second in cancer deaths (Han et al. 2024). As the predominant type of liver cancer, hepatocellular carcinoma (HCC) patients present an unfavorable prognosis, especially those patients at advanced stages who lose the chance of curative treatments (Dopazo et al. 2024; Cappuyns et al. 2024). Sorafenib is a multi-kinase inhibitor commonly applied for the treatment of advanced HCC via repressing tumor angiogenesis and proliferation (Raoul et al. 2018; Vogel et al. 2025). However, sorafenib resistance is becoming a critical issue that even worsens the prognosis of HCC, which is reported to be related to the STAT3 dysregulation, cancer stemness, hypoxia, autophagy, ferroptosis, immune environment, etc. (Yousef et al. 2025; Liang 2024; Zhang et al. 2025). Among these mechanisms, ferroptosis is a newly proposed research hotspot implicating in the sorafenib resistance (Liu et al. 2024; Wang et al. 2024).

Solute carrier family 7-member 11 (SLC7A11) is a key component of the cystine/glutamate antiporter system (System Xc⁻) and plays a central role in ferroptosis, which mediates cystine uptake into cells for glutathione (GSH) synthesis, maintaining antioxidant capacity. When SLC7A11 is inhibited (e.g., by Erastin) or downregulated, reduced cystine import leads to GSH depletion, glutathione peroxidase 4 (GPX4) inactivation, and reactive oxygen species (ROS) accumulation, ultimately triggering ferroptosis (Li et al. 2023; Dixon and Olzmann 2024). Moreover, Acyl-CoA synthetase long-chain family member 4 (ACSL4), as another key factor in ferroptosis, drives ferroptosis by activating and incorporating polyunsaturated fatty acids (PUFAs) like arachidonic acid into membranes, promoting lipid peroxidation; meanwhile, high ACSL4 levels increase sensitivity to ferroptosis inducers, while its inhibition protects cells (Dixon and Olzmann 2024; Ding et al. 2023).

Dipeptidyl peptidase 9 (DPP9), as a member of the dipeptidyl peptidase family, functions as a proline-specific protease that hydrolyzes peptide bonds following penultimate proline residues at the N-terminus, whose biological significance spans multiple critical processes, such as inflammation control, genomic stability maintenance, cell cycle regulation, and metabolic balance (Zolg et al. 2024; Nguyen et al. 2025). Inspiringly, the oncogene role of DPP9 is observed by recent researches (Tang et al. 2017; Huang et al. 2025). For example, DPP9 is upregulated in non-small-cell lung cancer (NSCLC) tissues and predicts unsatisfied 5-year survival, whose inhibition reduces NSCLC proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) while induces apoptosis (Tang et al. 2017). DPP9 conditional deletion improves energy metabolism and inhibits HCC development via regulating tumor autophagy and growth suppression (Huang et al. 2025). In addition, DPP9 promotes drug resistance via oxidative stress and ferroptosis in several types of cancers including HCC, colorectal cancer and renal cancer (Zhou et al. 2024; Saso et al. 2020; Chang et al. 2023). Based on the above information, this study hypothesized that DPP9 might be related to ferroptosis regulation then implicated in the drug sensitivity of sorafenib in HCC.

Therefore, this study aimed to investigate the effect of DPP9 inhibition on sorafenib sensitivity and its interaction with ferroptosis in HCC.

Methods

Cell culture

Huh7 and MHCC-97H cell lines were acquired from iCell (Shanghai, China). Cells were cultured with Dulbecco's Modified Eagle Medium plus 10% fetal bovine serum and 1% antibiotic (Servicebio, China), and maintained in a 37 °C and 5% CO2 incubator.

Small interfering RNA (siRNA) transfection

DPP9 knockdown was achieved in Huh7 and MHCC-97H cells using siRNA (GenePharma, China) with the following sequences (5′–3′): siDPP9 (sense: GAGAACUCCCUCCUCUACUTT; antisense: AGUAGAGGAGGGAGUUCUCTT) and non-targeting control siRNA (siNC) (sense: UUCUCCGAACGUGUCACGUTT; antisense: ACGUGACACGUUCGGAGAATT). Transient transfections were conducted with siRNA-MATE Plus Reagent (GenePharma, China), referring to the kit's protocol for 48 h. Untransfected cells were cultured as the control group. Cells were harvested post-transfection and employed for Western blot, sorafenib sensitivity, ROS, ferrous iron (Fe2+), and malondialdehyde (MDA) assays.

Ferrostatin-1 (Fer-1) treatment

Firstly, Huh7 and MHCC-97H cells were treated with 1 µM Fer-1 (ferroptosis inhibitor; MCE, China) for 24 h, and untreated cells served as the control group. The concentration of Fer-1 was selected in accordance with a previous study (Bai et al. 2019). ROS, Fe2+, MDA and sorafenib sensitivity were subsequently assessed.

Secondly, cells were transfected with siNC and siDPP9, then divided into three groups, including siDPP9, Fer-1, and siDPP9+Fer-1 groups. In brief, the siDPP9 group was transfected with siDPP9. The Fer-1 group was transfected with siNC and treated with 1 µM Fer-1. The siDPP9+Fer-1 group was transfected with siDPP9 and exposed to 1 µM Fer-1. After 24 h of treatment, cells were employed for ROS, Fe2+, MDA, Western blot, and sorafenib sensitivity assays.

Western blot

Proteins were extracted via RIPA Reagent (Servicebio, China) containing protease inhibitors (Servicebio, China). Proteins were collected by centrifugation and quantified via a BCA Kit (Servicebio, China). Proteins were separated via 4–20% Gradient SDS-PAGE Precast Gels (Willget, China), then transferred to nitrocellulose membranes (Pall, USA). Membranes were blocked, then incubated with primary antibodies (Affinity, China), including DPP9 (1:1000), NRF2 (1:500), SLC7A11 (1:1000), ACSL4 (1:1000), and GAPDH (1:10,000), for 1.5 h at room temperature (RT). After that, membranes were exposed to secondary antibody (1:20,000, Servicebio, China) for 0.5 h. Bands were visualized using Enhanced Chemiluminescence Kit (Servicebio, China) and quantified with ImageJ (NIH, USA).

Sorafenib sensitivity assay

Sorafenib (MCE, China) was diluted with medium to prepare drug-containing medium at different concentrations (0, 1, 2, 4, 8, and 16 μM). Meanwhile, Huh7 and MHCC-97H cells were replated to 96-well plates (1 × 104 cells/well) and cultivated for 24 h in different concentrations of the drug-containing medium. After that, 10 μL of Cell Counting Kit-8 (CCK-8) buffer (Servicebio, China) was added for 2 h, followed by detection with the microplate reader (Huadong Electronics, China). The half-maximal inhibitory concentration (IC50) was determined via the sigmoidal dose–response function (Tian et al. 2020).

ROS assay

Huh7 and MHCC-97H cells were replated into 6-well plates (3 × 105 cells/well) for 24 h, then exposed to 10 μM of 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) (Beyotime, China) for 0.5 h at RT. After washing with serum-free medium, the images were captured by an inverted fluorescence microscope (Motic, China), and the mean fluorescence intensity of ROS was assessed with ImageJ software. The fluorescence intensity was analyzed according to the method described in a previous study (Jensen 2013).

Fe2+ assay

Intracellular Fe2+ level was assessed using Ferrous Iron Assay Kit (Servicebio, China). In brief, Huh7 and MHCC-97H cells were lysed for 10 min. The lysates were incubated with working solution added in a 96-well plate for 10 min, followed by detection at 593 nm with the microplate reader.

Lipid peroxidation analysis

The MDA, a marker of lipid peroxidation, was analyzed with a commercial kit (Beyotime, China). To complete the analysis, the cells were lysed by the RIPA Reagent and quantified by the BCA Kit. Then, the MDA test working solution was prepared. The MDA of cells were analyzed by the MDA test working solution. The kit’s protocols were strictly followed.

Statistical analysis

Data are shown as mean ± standard deviation. Differences among multiple groups was evaluated via one-way analysis of variance (ANOVA) and Tukey's test. Differences between two groups were analyzed using t-test. All analyses were carried out via GraphPad Prism 9.0 (GraphPad Software, USA). P < 0.05 was considered statistically significant.

Results

Inhibition of DPP9 improved sorafenib sensitivity in HCC

After transfection of siRNAs, DPP9 expression was largely downregulated in siDPP9 group compared with siNC group in Huh7 cells (Fig. 1A); afterwards, sorafenib sensitivity was improved in siDPP9 group compared to siNC group, suggested by a lower IC50 value of sorafenib in Huh7 cells (Fig. 1B). Similar findings were observed in MHCC-97H cells for validation (Fig. 1C, D).

Fig. 1.

Fig. 1

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Inhibition of DPP9 and sorafenib sensitivity. DPP9 expression (A), cell viability under 0–16 μM sorafenib treatment and corresponding IC50 value of sorafenib (B), among three groups in Huh7 cell line. DPP9 expression (C), cell viability under 0–16 μM sorafenib treatment and corresponding IC50 value of sorafenib (D), among three groups in MHCC-97H cell line

Inhibition of DPP9 induced ferroptosis in HCC

ROS fluorescence intensity, Fe2+ level, and MDA level were elevated in siDPP9 group compared with siNC group in Huh7 cells (Fig. 2A–C); moreover, NRF2 expression and SLC7A11 expression were downregulated, but ACSL4 expression was upregulated in siDPP9 group compared to siNC group in Huh7 cells (Fig. 2D). Similar findings were observed in MHCC-97H cells for validation, except that ACSL4 expression was not different between siDPP9 group and siNC group (Fig. 2E–H).

Fig. 2.

Fig. 2

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Inhibition of DPP9 and ferroptosis. ROS fluorescence intensity (A), Fe2+ level (B), MDA level (C), expressions of NRF2, SLC7A11, and ACSL4 (D), among three groups in Huh7 cell line. ROS fluorescence intensity (E), Fe2+ level (F), MDA level (G), expressions of NRF2, SLC7A11, and ACSL4 (H), among three groups in MHCC-97H cell line

Ferroptosis regulated sorafenib sensitivity in HCC

After treatment, ROS fluorescence intensity, Fe2+ level, and MDA level were all lower in Fer-1 group compared with control group in Huh7 cells (Fig. 3A–C); in addition, sorafenib sensitivity was reduced in Fer-1 group compared to control group, indicated by a higher IC50 value of sorafenib in Huh7 cells (Fig. 3D). Similar findings were discovered in MHCC-97H cells for validation (Fig. 3E–H).

Fig. 3.

Fig. 3

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Ferroptosis and sorafenib sensitivity. ROS fluorescence intensity (A), Fe2+ level (B), MDA level (C), cell viability under 0–16 μM sorafenib treatment and corresponding IC50 value of sorafenib (D) between two groups in Huh7 cell line. ROS fluorescence intensity (E), Fe2+ level (F), MDA level (G), cell viability under 0–16 μM sorafenib treatment and corresponding IC50 value of sorafenib (H) between two groups in MHCC-97H cell line

Fer-1 weakened the effect of DPP9 inhibition on sorafenib sensitivity in HCC

Importantly, sorafenib sensitivity was decreased in siDPP9 + Fer-1 group compared with siDPP9 group, suggested by an increased IC50 value of sorafenib in Huh7 cells (Fig. 4A) and MHCC-97H cells (Fig. 4B). ROS fluorescence intensity, Fe2+ level, and MDA level were decreased in siDPP9+Fer-1 group compared with siDPP9 group in Huh7 cells (Fig. 5A–C); furthermore, NRF2 expression and SLC7A11 expression were elevated, but ACSL4 expression was reduced in siDPP9+Fer-1 group compared to siDPP9 group in Huh7 cells (Fig. 5D). ROS fluorescence intensity, Fe2+ level, and MDA level were also lower in siDPP9+Fer-1 group compared with siDPP9 group in MHCC-97H cells (Fig. 5E–G). However, NRF2 expression and ACSL4 expression did not vary between siDPP9+Fer-1 group and siDPP9 group, while SLC7A11 expression was increased in siDPP9+Fer-1 group compared to siDPP9 group in MHCC-97H cells (Fig. 5H).

Fig. 4.

Fig. 4

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DPP9 inhibition, Fer-1 treatment, and sorafenib sensitivity. Cell viability under 0–16 μM sorafenib treatment and corresponding IC50 value of sorafenib (A) among three groups in Huh7 cell line (A) and MHCC-97H cell line (B)

Fig. 5.

Fig. 5

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DPP9 inhibition, Fer-1 treatment, and ferroptosis. ROS fluorescence intensity (A), Fe2+ level (B), MDA level (C), expressions of NRF2, SLC7A11, and ACSL4 (D), among three groups in Huh7 cell line. ROS fluorescence intensity (E), Fe2+ level (F), MDA level (G), expressions of NRF2, SLC7A11, and ACSL4 (H), among three groups in MHCC-97H cell line

Mechanism schematic diagram

Combining the above findings, a mechanism schematic diagram was proposed (Fig. 6). Separately, siRNA inhibited DPP9; DPP9 positively regulated NRF2 and SLC7A11 while negatively modified ACSL4, Fe2+, and ROS; ROS promoted ferroptosis; Fer-1 repressed ROS and ferroptosis; finally, ferroptosis facilitated sorafenib sensitivity in HCC. Collectively, inhibition of DPP9 induced ferroptosis (indicated by NRF2, SLC7A11, ACSL4, Fe2+, and ROS) to improve sorafenib sensitivity in HCC.

Fig. 6.

Fig. 6

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Mechanism schematic diagram

Discussion

Despite of the tumor-promoting effect of DPP9 (Tang et al. 2017; Huang et al. 2025, 2021), it’s also discovered to engage in the sensitivity of anti-tumor drug (Zhou et al. 2024; Saso et al. 2020; Chang et al. 2023; Bettecken et al. 2023). DPP9 upregulates NQO1 and downregulates ROS to enhance the resistance of chemotherapy in HCC (Zhou et al. 2024), and its inhibition promotes the sensitivity of chemotherapy in colorectal cancer (Saso et al. 2020). Moreover, inhibition of DPP9 improves tamoxifen sensitivity in breast cancer, which may be related to its regulation of autophagy (Bettecken et al. 2023). In addition, DPP9 enhances resistance of sorafenib via stabilizing NRF2 in renal cancer (Chang et al. 2023). This study found that inhibition of DPP9 increases sorafenib sensitivity in Huh7 cell line, and further validated in MHCC-97H cell line, indicating inhibition of DPP9 increases HCC sorafenib sensitivity. The reasons for the above finding may be: DPP9 is previous reported to regulate NQO1, ROS, autophagy, or NRF2 to regulate drug sensitivity (Zhou et al. 2024; Saso et al. 2020; Chang et al. 2023; Bettecken et al. 2023), therefore it’s hypothesized that DPP9 may regulate sorafenib sensitivity via these ways, but further verifications are needed; moreover, DPP9 may regulate ferroptosis to modify sorafenib sensitivity as observed in our subsequent experiments.

A study reported that DPP9 was positively correlated with NRF2 and genes encoding for antioxidant enzymes, but negatively associated with genes encoding for ROS (Castillo-Izquierdo et al. 2022). Another study stated that DPP9 reduced ROS, which was related to its function on chemoresistance in HCC (Zhou et al. 2024). Oxidative stress is an important trigger and actor for ferroptosis (Li et al. 2024; Piccolo et al. 2024), and the latter is implicated in the sorafenib resistance in HCC (Liu et al. 2024; Wang et al. 2024). Interestingly, a recent study found that DPP9 could decrease ferroptosis in renal cancer (Chang et al. 2023). This study further observed that inhibition of DPP9 promoted ferroptosis (indicated by NRF2, SLC7A11, ACSL4, Fe2+, and ROS) in Huh7 cell line and MHCC-97H cell line, indicating inhibition of DPP9 enhanced HCC ferroptosis. The reasons for the above finding may be the regulation of DPP9 on oxidative stress and NRF2 (Liu et al. 2024; Wang et al. 2024; Zhou et al. 2024; Chang et al. 2023; Castillo-Izquierdo et al. 2022; Li et al. 2024; Piccolo et al. 2024).

Ferroptosis is a type of iron-dependent, lipid peroxide accumulation-driven regulated cell death form widely participants in human health and various diseases (Berndt et al. 2024). Ferroptosis has been considered to be a tumor inhibitor that represses HCC growth and invasion, and modifies tumor microenvironment to regulate HCC progression (Tu et al. 2025; Mo et al. 2024). Moreover, ferroptosis can also improve treatment sensitivity in HCC, including sorafenib sensitivity (Liu et al. 2024; Zhao et al. 2022). This study observed that anti-ferroptosis treatment by Fer-1 reduced sorafenib sensitivity in Huh7 cell line and MHCC-97H cell line, indicating the involvement of ferroptosis in HCC sorafenib sensitivity. In addition, Fer-1 not only attenuated the effect of DPP9 inhibition on ferroptosis, but also weakened the effect of DPP9 inhibition on sorafenib sensitivity in Huh7 cell line and MHCC-97H cell line, indicating the effect of DPP9 on HCC sorafenib sensitivity was related to ferroptosis mediation. In details, this study observed that Fer-1 attenuated the effect of DPP9 inhibition on ROS level, SLC7A11 expression, and ACSL4 expression significantly, but less affected the NRF2 expression (showed a tendency but not statistically significant). We consider this phenomenon may result from that Fer-1 cannot direct regulate NRF2, and NRF2 is at the upstream of the target of Fer-1. Moreover, whether ferroptosis is the primary contributor to sorafenib resistance needs further verifications.

Despite of the interesting findings, this study existed some limitations. Firstly, the detailed mechanism between DPP9 and ferroptosis was not comprehensively explored, which could be considered in future studies. Secondly, the study findings were not validated in an animal experiment, which could be performed in future for verification. Thirdly, clinical validation of the relationship among DPP9, ferroptosis and sorafenib sensitivity in HCC was not accessible in this study, which could be performed in future clinical studies. Fourthly, normal control or negative control was not set in the siDPP9 plus Fer-1 treatment related experiments, which should be considered in future studies.

In conclusion, this study summarizes that inhibition of DPP9 improves sorafenib sensitivity via inducing ferroptosis in HCC. This study provides novel evidence for DPP9 as a synergistic treatment target of sorafenib in HCC; however, further verifications are needed.

Acknowledgements

None.

Author contributions

YW contributed to the study conception and design. Material preparation, data collection and analysis were performed by QL and JZ. The first draft of the manuscript was written by JZ and all authors reviewed and revised the manuscript. All authors read and approved the final manuscript.

Funding

None.

Data availability

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

Declarations

Conflict of interest

The authors declare no competing interests.

Ethical approval

This article does not contain any studies with human participants performed by any of the author.

Consent to participate

Not applicable.

Consent for publication

Not applicable.

Footnotes

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

  1. Bai T, Lei P, Zhou H, Liang R, Zhu R, Wang W, Zhou L, Sun Y (2019) Sigma-1 receptor protects against ferroptosis in hepatocellular carcinoma cells. J Cell Mol Med 23(11):7349–7359. 10.1111/jcmm.14594 [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Berndt C, Alborzinia H, Amen VS, Ayton S, Barayeu U, Bartelt A, Bayir H, Bebber CM, Birsoy K, Bottcher JP, Brabletz S, Brabletz T, Brown AR, Brune B, Bulli G, Bruneau A, Chen Q, DeNicola GM, Dick TP, Distefano A, Dixon SJ, Engler JB, Esser-von Bieren J, Fedorova M, Friedmann Angeli JP, Friese MA, Fuhrmann DC, Garcia-Saez AJ, Garbowicz K, Gotz M, Gu W, Hammerich L, Hassannia B, Jiang X, Jeridi A, Kang YP, Kagan VE, Konrad DB, Kotschi S, Lei P, Le Tertre M, Lev S, Liang D, Linkermann A, Lohr C, Lorenz S, Luedde T, Methner A, Michalke B, Milton AV, Min J, Mishima E, Muller S, Motohashi H, Muckenthaler MU, Murakami S, Olzmann JA, Pagnussat G, Pan Z, Papagiannakopoulos T, Pedrera Puentes L, Pratt DA, Proneth B, Ramsauer L, Rodriguez R, Saito Y, Schmidt F, Schmitt C, Schulze A, Schwab A, Schwantes A, Soula M, Spitzlberger B, Stockwell BR, Thewes L, Thorn-Seshold O, Toyokuni S, Tonnus W, Trumpp A, Vandenabeele P, Vanden Berghe T, Venkataramani V, Vogel FCE, von Karstedt S, Wang F, Westermann F, Wientjens C, Wilhelm C, Wolk M, Wu K, Yang X, Yu F, Zou Y, Conrad M (2024) Ferroptosis in health and disease. Redox Biol 75:103211. 10.1016/j.redox.2024.103211 [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Bettecken A, Hess L, Holzen L, Reinheckel T (2023) Dipeptidyl-aminopeptidases 8 and 9 regulate autophagy and tamoxifen response in breast cancer cells. Cells. 10.3390/cells12162031 [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Bray F, Laversanne M, Sung H, Ferlay J, Siegel RL, Soerjomataram I, Jemal A (2024) Global cancer statistics 2022: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin 74(3):229–263. 10.3322/caac.21834 [DOI] [PubMed] [Google Scholar]
  5. Cappuyns S, Corbett V, Yarchoan M, Finn RS, Llovet JM (2024) Critical appraisal of guideline recommendations on systemic therapies for advanced hepatocellular carcinoma: a review. JAMA Oncol 10(3):395–404. 10.1001/jamaoncol.2023.2677 [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Chang K, Chen Y, Zhang X, Zhang W, Xu N, Zeng B, Wang Y, Feng T, Dai B, Xu F, Ye D, Wang C (2023) DPP9 stabilizes NRF2 to suppress ferroptosis and induce sorafenib resistance in clear cell renal cell carcinoma. Cancer Res 83(23):3940–3955. 10.1158/0008-5472.CAN-22-4001 [DOI] [PubMed] [Google Scholar]
  7. Del Castillo-Izquierdo A, Moreno-Navarrete JM, Latorre J, Arnoriaga-Rodriguez M, Ballanti M, Monteleone G, Alessandro Paoluzi O, Mingrone G, Puig J, Ramos R, Garre-Olmo J, Jove M, Pamplona R, Portero-Otin M, Sol J, Lefebvre P, Staels B, Federici M, Fernandez-Real JM, Mayneris-Perxachs J (2022) DPP9 as a potential novel mediator in gastrointestinal virus infection. Antioxidants (Basel). 10.3390/antiox11112177 [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Ding K, Liu C, Li L, Yang M, Jiang N, Luo S, Sun L (2023) Acyl-CoA synthase ACSL4: an essential target in ferroptosis and fatty acid metabolism. Chin Med J (Engl) 136(21):2521–2537. 10.1097/CM9.0000000000002533 [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Dixon SJ, Olzmann JA (2024) The cell biology of ferroptosis. Nat Rev Mol Cell Biol 25(6):424–442. 10.1038/s41580-024-00703-5 [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Dopazo C, Soreide K, Rangelova E, Mieog S, Carrion-Alvarez L, Diaz-Nieto R, Primavesi F, Stattner S (2024) Hepatocellular carcinoma. Eur J Surg Oncol 50(1):107313. 10.1016/j.ejso.2023.107313 [DOI] [PubMed] [Google Scholar]
  11. Han B, Zheng R, Zeng H, Wang S, Sun K, Chen R, Li L, Wei W, He J (2024) Cancer incidence and mortality in China, 2022. J Natl Cancer Center 4(1):47–53. 10.1016/j.jncc.2024.01.006 [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Huang JC, Emran AA, Endaya JM, McCaughan GW, Gorrell MD, Zhang HE (2021) DPP9: comprehensive in silico analyses of loss of function gene variants and associated gene expression signatures in human hepatocellular carcinoma. Cancers (Basel). 10.3390/cancers13071637 [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Huang JC, Tong XL, Xiang MSW, Boumelhem BB, Foulis DP, Zhang M, McKenzie CA, McCaughan GW, Reinheckel T, Zhang HE, Gorrell MD (2025) Dipeptidyl peptidase 9 (DPP9) depletion from hepatocytes in experimental primary liver cancer. Biochimica Et Biophysica Acta (BBA) 1871(5):167819. 10.1016/j.bbadis.2025.167819 [Google Scholar]
  14. Jensen EC (2013) Quantitative analysis of histological staining and fluorescence using ImageJ. Anat Rec (Hoboken) 296(3):378–381. 10.1002/ar.22641 [DOI] [PubMed] [Google Scholar]
  15. Li P, Yu J, Huang F, Zhu YY, Chen DD, Zhang ZX, Xie ZC, Liu ZY, Hou Q, Xie N, Peng TH, Chen X, Li L, Xie W (2023) SLC7A11-associated ferroptosis in acute injury diseases: mechanisms and strategies. Eur Rev Med Pharmacol Sci 27(10):4386–4398. 10.26355/eurrev_202305_32444 [DOI] [PubMed] [Google Scholar]
  16. Li K, Fan C, Chen J, Xu X, Lu C, Shao H, Xi Y (2024) Role of oxidative stress-induced ferroptosis in cancer therapy. J Cell Mol Med 28(10):e18399. 10.1111/jcmm.18399 [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Liang Y (2024) Mechanisms of sorafenib resistance in hepatocellular carcinoma. Clin Res Hepatol Gastroenterol 48(8):102434. 10.1016/j.clinre.2024.102434 [DOI] [PubMed] [Google Scholar]
  18. Liu R, Cui H, Li D, Guo X, Zhang Z, Tan S, Zhu X (2024) Roles and mechanisms of ferroptosis in Sorafenib resistance for hepatocellular carcinoma. J Hepatocell Carcinoma 11:2493–2504. 10.2147/JHC.S500084 [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Mo Y, Zou Z, Chen E (2024) Targeting ferroptosis in hepatocellular carcinoma. Hepatol Int 18(1):32–49. 10.1007/s12072-023-10593-y [DOI] [PubMed] [Google Scholar]
  20. Nguyen JMH, Zolg S, Geiss-Friedlander R, Gorrell MD (2025) The multifunctional regulatory post-proline protease dipeptidyl peptidase 9 and its inhibitors: new opportunities for therapeutics. Cell Mol Life Sci 82(1):187. 10.1007/s00018-025-05719-4 [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Piccolo M, Ferraro MG, Iazzetti F, Santamaria R, Irace C (2024) Insight into iron, oxidative stress and ferroptosis: therapy targets for approaching anticancer strategies. Cancers (Basel). 10.3390/cancers16061220 [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Raoul JL, Kudo M, Finn RS, Edeline J, Reig M, Galle PR (2018) Systemic therapy for intermediate and advanced hepatocellular carcinoma: sorafenib and beyond. Cancer Treat Rev 68:16–24. 10.1016/j.ctrv.2018.05.006 [DOI] [PubMed] [Google Scholar]
  23. Saso K, Miyoshi N, Fujino S, Sasaki M, Yasui M, Ohue M, Ogino T, Takahashi H, Uemura M, Matsuda C, Mizushima T, Doki Y, Eguchi H (2020) Dipeptidyl peptidase 9 increases chemoresistance and is an indicator of poor prognosis in colorectal cancer. Ann Surg Oncol 27(11):4337–4347. 10.1245/s10434-020-08729-7 [DOI] [PubMed] [Google Scholar]
  24. Tang Z, Li J, Shen Q, Feng J, Liu H, Wang W, Xu L, Shi G, Ye X, Ge M, Zhou X, Ni S (2017) Contribution of upregulated dipeptidyl peptidase 9 (DPP9) in promoting tumoregenicity, metastasis and the prediction of poor prognosis in non-small cell lung cancer (NSCLC). Int J Cancer 140(7):1620–1632. 10.1002/ijc.30571 [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Tian S, Lou L, Tian M, Lu G, Tian J, Chen X (2020) MAPK4 deletion enhances radiation effects and triggers synergistic lethality with simultaneous PARP1 inhibition in cervical cancer. J Exp Clin Cancer Res 39(1):143. 10.1186/s13046-020-01644-5 [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Tu S, Zou Y, Yang M, Zhou X, Zheng X, Jiang Y, Wang H, Chen B, Qian Q, Dou X, Bao J, Tian L (2025) Ferroptosis in hepatocellular carcinoma: mechanisms and therapeutic implications. Biomed Pharmacother 182:117769. 10.1016/j.biopha.2024.117769 [DOI] [PubMed] [Google Scholar]
  27. Vogel A, Chan SL, Dawson LA, Kelley RK, Llovet JM, Meyer T, Ricke J, Rimassa L, Sapisochin G, Vilgrain V, Zucman-Rossi J, Ducreux M (2025) Hepatocellular carcinoma: ESMO clinical practice guideline for diagnosis, treatment and follow-up. Ann Oncol 36(5):491–506. 10.1016/j.annonc.2025.02.006 [DOI] [PubMed] [Google Scholar]
  28. Wang Z, Zhou C, Zhang Y, Tian X, Wang H, Wu J, Jiang S (2024) From synergy to resistance: navigating the complex relationship between sorafenib and ferroptosis in hepatocellular carcinoma. Biomed Pharmacother 170:116074. 10.1016/j.biopha.2023.116074 [DOI] [PubMed] [Google Scholar]
  29. Yousef EH, El Gayar AM, El-Magd NFA (2025) Insights into Sorafenib resistance in hepatocellular carcinoma: mechanisms and therapeutic aspects. Crit Rev Oncol Hematol 212:104765. 10.1016/j.critrevonc.2025.104765 [DOI] [PubMed] [Google Scholar]
  30. Zhang W, Hong X, Xiao Y, Wang H, Zeng X (2025) Sorafenib resistance and therapeutic strategies in hepatocellular carcinoma. Biochimica Et Biophysica Acta (BBA) 1880(3):189310. 10.1016/j.bbcan.2025.189310 [Google Scholar]
  31. Zhao S, Zheng W, Yu C, Xu G, Zhang X, Pan C, Feng Y, Yang K, Zhou J, Ma Y (2022) The role of ferroptosis in the treatment and drug resistance of hepatocellular carcinoma. Front Cell Dev Biol 10:845232. 10.3389/fcell.2022.845232 [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Zhou Y, Chen Y, Xuan C, Li X, Tan Y, Yang M, Cao M, Chen C, Huang X, Hu R (2024) DPP9 regulates NQO1 and ROS to promote resistance to chemotherapy in liver cancer cells. Redox Biol 75:103292. 10.1016/j.redox.2024.103292 [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Zolg S, Donzelli L, Geiss-Friedlander R (2024) N-terminal processing by dipeptidyl peptidase 9: cut and go! Biochimie 226:180–192. 10.1016/j.biochi.2024.03.002 [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

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