Verteporfin-loaded hydrogel targeting YAP-mediated MDSCs recruitment for the treatment of residual tumors after incomplete radiofrequency ablation

<b>Background:</b> Hepatocellular carcinoma (HCC), the major form of primary liver cancer, contributes markedly to cancer-related mortality worldwide and remains a serious global health concern, particularly affecting individuals with underlying chronic liver disorders. In hepatocellular carcinoma, insufficient radiofrequency ablation (iRFA) has been reported to drive local tumor relapse and distant spread, possibly by aggravating the immunosuppressive features of the tumor microenvironment. The present work seeks to clarify the underlying pathways driving the development of an immunosuppressive milieu after RFA and to identify potential therapeutic approaches to counteract this process. <b>Methods:</b> An injectable hydrogel composed of quaternized chitosan (QCS) and tannic acid (TA) was constructed to encapsulate verteporfin (VP), a well-established photosensitizer that has been clinically applied for treating neovascular retinal disorders such as age-related macular disease. Beyond its ophthalmologic application, VP has recently been reported to display anti-tumor activity through inhibition of oncogenic regulators such as Yes-associated protein (YAP), indicating its potential utility in cancer therapy. This hydrogel formulation is designed to target residual tumor tissue post-RFA, providing localized delivery and sustained release of VP to enhance anti-tumor immune responses. <b>Results:</b> Our findings identified YAP activation as a critical mediator of immunosuppression in residual tumors following RFA. Pharmacological inhibition of YAP significantly reduced the infiltration of myeloid-derived suppressor cells (MDSCs) and effectively reversed the immunosuppressive microenvironment conditions. Furthermore, the QCS/TA hydrogel enabled sustained local release of VP, resulting in enhanced antitumor immune responses via MDSC suppression. When administered as an adjuvant therapy following suboptimal RFA, the hydrogel markedly inhibited the progression of residual tumors, highlighting its therapeutic potential in improving post-RFA outcomes. <b>Conclusion:</b> Collectively, our data suggest YAP pathway inhibition as a promising immunomodulatory strategy to complement RFA in HCC management. This work demonstrates that the QCS/TA hydrogel-based delivery system can remodel the tumor immune milieu to overcome immunosuppression and delay post-ablation tumor recurrence, supporting its potential as a translational drug delivery strategy.