Lack of insight into mechanisms governing breast cancer metastasis has precluded the development of curative therapies. Metastasis-initiating cancer cells (MICs) are uniquely equipped to establish metastases, causing recurrence and therapeutic resistance. Using various metastasis models, we discovered that certain primary tumours elicit a systemic inflammatory response involving interleukin-1β (IL-1β)-expressing innate immune cells that infiltrate distant MIC microenvironments. At the metastatic site, IL-1β maintains MICs in a ZEB1-positive differentiation state, preventing MICs from generating highly proliferative E-cadherin-positive progeny. Thus, when the inherent plasticity of MICs is impeded, overt metastases cannot be established. Ablation of the pro-inflammatory response or inhibition of the IL-1 receptor relieves the differentiation block and results in metastatic colonization. Among patients with lymph node-positive breast cancer, high primary tumour IL-1β expression is associated with better overall survival and distant metastasis-free survival. Our data reveal complex interactions that occur between primary tumours and disseminated MICs that could be exploited to improve patient survival.

Clinical trials involving anti-programmed cell death protein-1 (anti-PD-1) failed to demonstrate improved overall survival in glioblastoma (GBM) patients. This may be due to the expression of alternative checkpoints such as B- and T- lymphocyte attenuator (BTLA) on several immune cell types including regulatory T cells. Murine GBM models indicate that there is significant upregulation of BTLA in the tumor microenvironment (TME) with associated T cell exhaustion. We investigate the use of antibodies against BTLA and PD-1 on reversing immunosuppression and increasing long-term survival in a murine GBM model. C57BL/6 J mice were implanted with the murine glioma cell line GL261 and randomized into 4 arms: (i) control, (ii) anti-PD-1, (iii) anti-BTLA, and (iv) anti-PD-1 + anti-BTLA. Kaplan–Meier curves were generated for all arms. Flow cytometric analysis of blood and brains were done on days 11 and 16 post-tumor implantation. Tumor-bearing mice treated with a combination of anti-PD-1 and anti-BTLA therapy experienced improved overall long-term survival (60%) compared to anti-PD-1 (20%) or anti-BTLA (0%) alone ( P = .003). Compared to monotherapy with anti-PD-1, mice treated with combination therapy also demonstrated increased expression of CD4+ IFN-γ ( P < .0001) and CD8+ IFN-γ ( P = .0365), as well as decreased levels of CD4+ FoxP3+ regulatory T cells on day 16 in the brain ( P = .0136). This is the first preclinical investigation into the effects of combination checkpoint blockade with anti-PD-1 and anti-BTLA treatment in GBM. We also show a direct effect on activated immune cell populations such as CD4+ and CD8 + T cells and immunosuppressive regulatory T cells through this combination therapy.

Glioma is the most common tumor in the central nervous system that portends a poor prognosis. Key genes negatively related to survival may provide targets for therapy to improve the outcome of glioma. Here, we report a protein-coding gene CLEC5A, which is the top 1 gene by univariate Cox regression analysis of 524 primary GBM samples. Expression of CLEC5A is significantly correlated with decreased overall survival in patients with glioma via large-scale analysis. An analysis of 2589 patient samples showed that CLEC5A expression is higher in (1) glioblastoma than in lower-grade glioma and nontumor tissue, (2) in the mesenchymal subtype than in other subtypes, and (3) in IDH1-wild type glioblastoma than in IDH1-mutated glioblastoma. Notably, this tumor-associated biomarker is expressed preferentially on myeloid cells over glioma cells. And it shows a strong co-expression with M2 macrophage biomarker. Furthermore, CLEC5A-associated genes are enriched in immunosuppressive biological processes. The silico flow cytometry also showed CLEC5A expression related to less tumor purity and more tumor-promoting leukocytes infiltration. In conclusion, we proposed a new M2 biomarker expressed on myeloid cells that may decrease survival in patients with glioma through immunosuppressive mechanisms.