A Novel Prognostic Biomarker CCR8 for Gastric Cancer and Anti-CCR8 Blockade Attenuate the Immunosuppressive Capacity of Tregs In Vitro

CCR8 antagonist suppresses liver cancer progression via turning tumor-infiltrating Tregs into less immunosuppressive phenotype

BACKGROUND

Regulatory T cells (Tregs) are the main immunosuppressive cells in tumor immune microenvironment (TIME). However, systemic Treg depletion is not favored due to the crucial role of Tregs in the maintenance of immune homeostasis and prevention of autoimmunity. Recently, CCR8 has been identified as a key chemokine receptor expressed on tumor-infiltrating Tregs and targeted blockade of CCR8 exerts anticancer effect in several cancer types, but whether this pathway is involved in the progression of hepatocellular carcinoma (HCC) remains unclear.

METHODS

We determined the involvement of CCR8+ Tregs in HCC using human HCC tissues and TCGA database, and examined the anticancer effect and the underlying molecular mechanisms of the CCR8 antagonist, IPG0521m, which was developed in house, in murine liver cancer model with flow cytometry, bulk and single-cell RNA sequencing and Real-Time PCR.

RESULTS

Remarkable increase in CCR8+ Tregs was observed in human HCC tissues. Treatment of syngeneic liver cancer model with IPG0521m resulted in dramatic inhibition of tumor growth, associated with increased CD8+ T cells in tumor tissues. Bulk RNA sequencing analysis indicated that IPG0521m treatment resulted in remarkable increase in antitumor immunity. Furthermore, single-cell RNA sequencing analysis demonstrated that IPG0521m treatment resulted in a switch of Tregs from high immunosuppression to low immunosuppression phenotype, associated with elevated CD8+ T and NK cell proliferation and cytotoxicity, and decreased myeloid-derived suppressor cells and tumor-associated macrophages in the tumor tissues.

CONCLUSIONS

IPG0521m inhibited liver cancer growth via reducing the immunosuppressive function of Tregs, thereby boosting anti-cancer immunity. Our study paves the way for the clinical study of CCR8 antagonist in HCC and other cancers.

Development of a cellular model to study CCR8 signaling in tumor-infiltrating regulatory T cells

The human CC chemokine receptor 8 (CCR8) is specifically expressed on tumor-infiltrating regulatory T cells (TITRs) and is a promising drug target for cancer immunotherapy. However, the role of CCR8 signaling in TITR biology and the effectiveness of CCR8 small molecule antagonists as TITR-targeting immunotherapy remain subjects of ongoing debate. In this work, we generated a novel cellular model of TITRs by culturing peripheral blood mononuclear cell-derived regulatory T cells in medium containing tumor cell-conditioned medium, CD3/CD28 activator, interleukin-2 and 1α,25-dihydroxyvitamin D3. This cellular model (named TITR mimics) highly and stably expressed a series of TITR signature molecules, including CCR8, FOXP3, CD30, CD39, CD134, CD137, TIGIT and Tim-3. Moreover, TITR mimics displayed robust in vitro immunosuppressive activity. To unravel the functional role of CCR8 in TITR mimics, a chemotaxis assay was performed showing strong and CCR8-specific migration toward CCL1, the natural chemokine agonist of CCR8. However, either stimulation (with CCL1) or blocking (with the small molecule antagonist NS-15) of CCR8 signaling did not affect the immunosuppressive activity, proliferation and survival of TITR mimics. Collectively, our work provides a method for the generation of TITR mimics in vitro, which can be used to study TITR biology and to evaluate drug candidates targeting TITRs. Furthermore, our findings suggest that CCR8 signaling primarily regulates migration of these cells.

CC chemokine receptors are prognostic indicators of gastric cancer and are associated with immune infiltration

BACKGROUND

CC chemokine receptors are responsible for regulating the tumor microenvironment (TME) and participating in carcinogenesis and tumor advancement. However, no functional study has investigated CC chemokine receptors in gastric cancer (GC) prognosis, risk, immunotherapy, or other treatments.

METHODS

We conducted a bioinformatics analysis on GC data using online databases, including the Human Protein Atlas (HPA), Kaplan-Meier (KM) plotter, GeneMANIA, MethSurv, the University of ALabama at Birmingham CANcer (UALCAN) Data Analysis Portal, Gene Set Cancer Analysis (GSCA), cBioportal, and Tumor IMmune Estimation Resource (TIMER).

RESULTS

We noted that CC chemokine receptor expression correlated with survival in GC. CC chemokine receptor expression was also strongly linked to different tumor-infiltrating immune cells. Additionally, CC chemokine receptors were found to be broadly drug-resistant in GC.

CONCLUSION

Our study identifed CC chemokine receptor expression helped in predicting the prognosis of patients diagnosed with GC. The expression level of the CC chemokine receptors was also positively related to multiple tumor-infiltrating lymphocytes (TILs). These findings provide evidence to monitor patients with GC using CC chemokine receptors, which can be used as an effective biomarker for predicting the disease prognosis and be regarded as a therapeutic target for modulating the tumor immune microenvironment.