Syngeneic murine model for prostate cancer using RM1 cells transfected with gp100

Sialic acid blockade inhibits the metastatic spread of prostate cancer to bone

BACKGROUND

Bone metastasis is a common consequence of advanced prostate cancer. Bisphosphonates can be used to manage symptoms, but there are currently no curative treatments available. Altered tumour cell glycosylation is a hallmark of cancer and is an important driver of a malignant phenotype. In prostate cancer, the sialyltransferase ST6GAL1 is upregulated, and studies show ST6GAL1-mediated aberrant sialylation of N-glycans promotes prostate tumour growth and disease progression.

METHODS

Here, we monitor ST6GAL1 in tumour and serum samples from men with aggressive prostate cancer and using in vitro and in vivo models we investigate the role of ST6GAL1 in prostate cancer bone metastasis.

FINDINGS

ST6GAL1 is upregulated in patients with prostate cancer with tumours that have spread to the bone and can promote prostate cancer bone metastasis in vivo. The mechanisms involved are multi-faceted and involve modification of the pre-metastatic niche towards bone resorption to promote the vicious cycle, promoting the development of M2 like macrophages, and the regulation of immunosuppressive sialoglycans. Furthermore, using syngeneic mouse models, we show that inhibiting sialylation can block the spread of prostate tumours to bone.

INTERPRETATION

Our study identifies an important role for ST6GAL1 and α2-6 sialylated N-glycans in prostate cancer bone metastasis, provides proof-of-concept data to show that inhibiting sialylation can suppress the spread of prostate tumours to bone, and highlights sialic acid blockade as an exciting new strategy to develop new therapies for patients with advanced prostate cancer.

FUNDING

Prostate Cancer Research and the Mark Foundation For Cancer Research, the Medical Research Council and Prostate Cancer UK.

Tissue-resident glial cells associate with tumoral vasculature and promote cancer progression

Cancer cells are embedded within the tissue and interact dynamically with its components during cancer progression. Understanding the contribution of cellular components within the tumor microenvironment is crucial for the success of therapeutic applications. Here, we reveal the presence of perivascular GFAP+/Plp1+ cells within the tumor microenvironment. Using in vivo inducible Cre/loxP mediated systems, we demonstrated that these cells derive from tissue-resident Schwann cells. Genetic ablation of endogenous Schwann cells slowed down tumor growth and angiogenesis. Schwann cell-specific depletion also induced a boost in the immune surveillance by increasing tumor-infiltrating anti-tumor lymphocytes, while reducing immune-suppressor cells. In humans, a retrospective in silico analysis of tumor biopsies revealed that increased expression of Schwann cell-related genes within melanoma was associated with improved survival. Collectively, our study suggests that Schwann cells regulate tumor progression, indicating that manipulation of Schwann cells may provide a valuable tool to improve cancer patients' outcomes.

Hypoxia-inducible factor-1α inhibition augments efficacy of programmed cell death 1 antibody in murine prostatic cancer models

This study was designed to explore whether hypoxia-inducible factor-1α (HIF-1α) inhibitor could enhance immunotherapy efficacy in prostate cancer. Western blot was used to detect the expression of HIF-1α in the tumor and peritumor tissues from prostate cancer patients. The analysis from Cancer Genome Atlas database was used to show an association between HIF-1α expression and survival rate in prostate cancer patients. Murine prostate cell-derived xenograft (CDX) model was set up in both nude mice and BALB/c mice to observe the therapeutic effect of HIF-1α inhibitor IDF-11774. Protein expression of HIF-1α, as well as changes in the immune microenvironment, was detected. Moreover, the synergistic antitumor effect of IDF-11774 and PD-1 antibody was detected in another murine prostate cancer model. HIF-1α was found to have higher expression in prostate cancer tumor tissue than in peritumor tissue, and the expression level was negatively correlated with survival rate (P = 0.0157). HIF-1α inhibitor IDF-11774 reduced tumor volume and exhibited better efficacy in BALB/c mouse model (P < 0.0001) with normal immune system, with the same suppression level against HIF-1α. HIF-1α inhibitor reduced CD45+CD11b+Gr-1+ myeloid-derived suppressor cells (P = 0.0027) and CD45+ CD11b+F4/80+CD206hi M2 macrophages (P = 0.0059) but increased the abundance of CD45+CD3+CD8+ T cells (P = 0.0002) and CD45+CD3+CD4+ T cells (P = 0.0001) in tumor-infiltrating immune cells. The same synergistic effect was observed in RM-1 murine prostate CDX tumor model. HIF-1α inhibition augmented the antitumor efficacy of immune checkpoint inhibitor PD-1 antibody in murine prostate cancer models, probably through modulating the immunosuppressive microenvironment.

Immunotherapy for Metastatic Prostate Cancer: Current and Emerging Treatment Options

The advent of immunotherapy has revolutionized cancer treatment. Prostate cancer has an immunosuppressive microenvironment and a low tumor mutation burden, resulting in low neoantigen expression. The consensus was that immunotherapy would be less effective in prostate cancer. However, recent studies have reported that prostate cancer does have a high number of DNA damage and repair gene defects. Immunotherapies that have been tested in prostate cancer so far have been mainly vaccines and checkpoint inhibitors. A combination of genomically targeted therapies, with approaches to alleviate immune response and thereby make the tumor microenvironment immunologically hot, is promising.