HPK1 Inhibition Enhancing HFRT Anti-Tumor Immune Response

Abstract

Radiation therapy, as one of the canonical treatments for classic tumors, results in impressive clinical responses. Stereotactic body radiotherapy (SBRT) has been increasingly used as one main therapy in early-stage non-small-cell lung cancer (NSCLC). SBRT affords good local tumor control, however, recurrence and metastasis are still the main causes of treatment failure. With the continuous deepening of the relationship between radiotherapy (RT) and immunity, reversing RT induced immunosuppression is considered to be a promising strategy to improve radiotherapy efficacy. Hematopoietic progenitor kinase 1 (HPK1) is mainly expressed in immune cells while rarely expressed in tumor cells. It has been proven to play a negative regulatory role in T cell receptor (TCR) signal. Therefore, we hypothesized that the combination of HPK1 inhibitor with SBRT would boost local and systemic anti-tumor immune responses by potentiating the anti-tumor effects of SBRT. Using Digital Spatial Profiler (DSP), we analyzed HPK1 expression in the tumor specimens of 39 NSCLC patients treated with SBRT. By establishing mice subcutaneous tumor models, we assessed the combination of a HPK1 inhibitor and local hyper-fractionated radiotherapy (HFRT) on local and systemic tumor control and mouse survival. Using Single-cell RNA sequencing, Flow cytometry and pharmacological treatment, we analyzed and verified Tumor-infiltrating lymphocytes (TILs), and excavated the specific mechanism of the HPK1 inhibitor enhancing HFRT -induced anti -tumor immune response. In the tumor specimens of NSCLC patients treated with SBRT, we found that high expression HPK1 in TILs predicted poor progression-free survival (PFS). Among the C57BL/6 mice model, HFRT combined with a HPK1 inhibitor promoted local response, and improved the survival rate of mice, showing better anti-tumor curative effects. We further showed that HFRT promoted CD8+ T cell cytotoxic activity, and also aggravated CD8+ T cell exhaustion. After the intervention of HPK1 small molecular inhibitors, the proportion of exhaustion CD8+T cells was significantly reduced, while CD8+T cell cytotoxic activity was further enhanced in the later period. Single-cell RNA sequencing and pharmacological inhibition of HPK1 revealed that HPK1 mediated the exhaustion of CD8+T cells by regulating RGS16. In abscopal effects preclinical models, BGB-15025 induced obvious abscopal effect. Thus, we demonstrate that HPK1 mediates HFRT-induced CD8+T cell exhaustion by regulating RGS16, and HPK1 is an attractive drug target for enhancing local and systemic radiotherapy.