Transforming “cold” tumors into “hot” ones <i>via</i> immunogenic cell death by bufadienolides for reverse immunosuppressive TME in HCC

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. Unfortunately, the inherently immunosuppressive tumor microenvironment (TME) severely limits the anti-tumor efficacy of conventional therapies. Immunogenic cell death (ICD) is a rare immunostimulatory form of cell death and can activate adaptive immune responses as a way to remodel the immunosuppressive tumor microenvironment. In this study, we found that bufadienolide-based nanocrystalline formulations (HBE NCs) can reshape the tumor microenvironment by inducing an ICD, thereby achieving superior anti-tumor efficacy. HBE NCs could effectively induce Hepa1-6 cells to release damage-associated molecular patterns, such as CRT as an "eat me" signal, HMGB1 as a "danger" signal and ATP as a "find me" signal to an active immune system. HBE NCs improved the maturation of dendritic cells, enhanced the infiltration of CD4⁺T and CD8⁺T cells, depleted the number of immunosuppressive MDSCs and Treg cells, and successfully reconstructed immunosuppressed "cold" tumors into immune-activated "hot" tumors in HCC mice. Notably, dying Hepa1-6 cells treated with HBE NCs can be used as an <i>in vivo</i> "inactivated vaccine" to effectively enhance the ability of mice to resist the challenge of a live tumor. Our study demonstrates a promising strategy for remodeling the immunosuppressive TME of liver cancer.