Combining ferroptosis induction with MDSC blockade renders primary tumours and metastases in liver sensitive to immune checkpoint blockade

OBJECTIVE

Investigating the effect of ferroptosis in the tumour microenvironment to identify combinatory therapy for liver cancer treatment.

DESIGN

Glutathione peroxidase 4 (GPx4), which is considered the master regulator of ferroptosis, was genetically altered in murine models for hepatocellular carcinoma (HCC) and colorectal cancer (CRC) to analyse the effect of ferroptosis on tumour cells and the immune tumour microenvironment. The findings served as foundation for the identification of additional targets for combine therapy with ferroptotic inducer in the treatment of HCC and liver metastasis.

RESULTS

Surprisingly, hepatocyte-restricted GPx4 loss does not suppress hepatocellular tumourigenesis. Instead, GPx4-associated ferroptotic hepatocyte death causes a tumour suppressive immune response characterised by a CXCL10-dependent infiltration of cytotoxic CD8+ T cells that is counterbalanced by PD-L1 upregulation on tumour cells as well as by a marked HMGB1-mediated myeloid derived suppressor cell (MDSC) infiltration. Blocking PD-1 or HMGB1 unleashes T cell activation and prolongs survival of mice with Gpx4-deficient liver tumours. A triple combination of the ferroptosis inducing natural compound withaferin A, the CXCR2 inhibitor SB225002 and α-PD-1 greatly improves survival of wild-type mice with liver tumours. In contrast, the same combination does not affect tumour growth of subcutaneously grown CRC organoids, while it decreases their metastatic growth in liver.

CONCLUSION

Our data highlight a context-specific ferroptosis-induced immune response that could be therapeutically exploited for the treatment of primary liver tumours and liver metastases.

Circulating hypoxia marker carbonic anhydrase IX (CA9) in patients with hepatocellular carcinoma and patients with cirrhosis

BACKGROUND AND AIMS

Expression of carbonic anhydrase IX (CA9), an enzyme expressed in response to hypoxia, acidosis and oncogenic alterations, is reported to be a prognostic factor in HCC patients. Here we evaluated serum CA9 levels in HCC and cirrhosis patients.

METHODS

HCC and cirrhosis patients were prospectively recruited and CA9 levels were determined. CA9 levels were compared to stages of cirrhosis and HCC stages. The association of the CA9 levels and overall survival (OS) was assessed. Furthermore, immunohistochemical CA9 expression in HCC and cirrhosis was evaluated.

RESULTS

215 patients with HCC were included. The median serum CA9 concentration in patients with HCC was 370 pg/ml and significantly higher than in a healthy cohort. Patients with advanced cancer stages (BCLC and ALBI score) had hid significant higher levels of CA9 in the serum. HCC patients with high serum CA9 concentrations (>400 pg/ml) had an increased mortality risk (hazard ratio (HR) 1.690, 95% confidence interval (CI) 1.017-2.809, P = 0.043). Serum CA9 concentration in cirrhotic patients did not differ significantly from HCC patients. Higher CA9 levels in cirrhotic patients correlated with portal hypertension and esophageal varices. Patients with ethanol induced cirrhosis had the highest CA9 levels in both cohorts. Levels of CA9 did not correlate with immunohistochemical expression.

CONCLUSIONS

We conclude that a high CA9 level is a possible prognostic indicator for a poor outcome in HCC patients. The high CA9 levels are probably mainly associated with portal hypertension. Ductular reactions might be a possible source of serum CA9.

Canonical NF-κB signaling in myeloid cells promotes lung metastasis in a mouse breast cancer model

An inflammatory tumor microenvironment is a common characteristic of solid tumors. It is the result of a complex interplay between tumor cells, tumor infiltrating immune cells and other stromal cells. Myeloid cells in the tumor microenvironment are considered major drivers of tumor progression and metastasis and increased numbers of these cells are associated with poor prognosis in various cancer patients. The transcription factor NF-κB is considered the master regulator of inflammatory gene expression and immune cell function. Its activation in various cells of the tumor microenvironment contributes essentially to tumorigenesis. In the present study, the role of canonical NF-κB signaling in myeloid cells in metastatic breast cancer was addressed by myeloid-specific deletion of Ikkβ in the MMTV polyoma middle T (PyMT) mouse model. Ikkβ deletion in myeloid cells did not affect primary mammary tumor growth but significantly reduced lung metastasis. While dissemination from the primary tumor was unaltered, myeloid-specific Ikkβ loss resulted in a strong up-regulation of pro-inflammatory genes and changes in immune cell populations in the lung, creating a tumor-suppressive microenvironment at the distant site. Thus, canonical NF-κB signaling in myeloid cells creates a permissive lung microenvironment that supports breast to lung metastasis.

Myeloid Cell-Derived Reactive Oxygen Species Induce Epithelial Mutagenesis

Increased oxidative stress has been suggested to initiate and promote tumorigenesis by inducing DNA damage and to suppress tumor development by triggering apoptosis and senescence. The contribution of individual cell types in the tumor microenvironment to these contrasting effects remains poorly understood. We provide evidence that during intestinal tumorigenesis, myeloid cell-derived H₂O₂ triggers genome-wide DNA mutations in intestinal epithelial cells to stimulate invasive growth. Moreover, increased reactive oxygen species (ROS) production in myeloid cells initiates tumor growth in various organs also in the absence of a carcinogen challenge in a paracrine manner. Our data identify an intricate crosstalk between myeloid cell-derived ROS molecules, oxidative DNA damage, and tumor necrosis factor α-mediated signaling to orchestrate a tumor-promoting microenvironment causing invasive cancer.