Since the beginning of the project, we have firmly confirmed the role of host cells, specifically macrophages and mesenchymal stromal cells, in promotion of the disease progression of metastatic hormone refractory prostate cancer using our novel tumour model. A novel cell culture method has also been developed in the laboratory to mimic interaction between tumour cells and mesenchymal stromal cells (MSCs). In this assay, MSCs can significantly promote anti-androgen resistance of PC cells. Several compounds have been identified in a screening using this new method. More studies are needed to further confirm these findings in a low-throughput assay and in vivo in order to understand disease mechanism and identify potential therapeutic approaches.
Furthermore, we have uncovered a set of potential molecular mechanisms by analysing the gene expression profile of tumour cells and host macrophages. We have developed computational biology algorisms and confirmed some of our experimental findings in publicly available patient gene expression datasets.
Part of these results were published recently in the Journal of Experimental Medicine titled: Macrophages promote anti-androgen resistance in prostate cancer bone disease (J Exp Med. 2023 Apr 3; 220(4): e20221007). This study identified that the macrophage is the major microenvironmental component of bone-metastatic PC in patients. Using a novel in vivo model, we demonstrated that macrophages were critical for enzalutamide resistance through induction of a wound-healing–like response of ECM–receptor gene expression. Mechanistically, macrophages drove resistance through cytokine activin A that induced fibronectin (FN1)-integrin alpha 5 (ITGA5)–tyrosine kinase Src (SRC) signaling cascade in PC cells. This novel mechanism was strongly supported by bioinformatics analysis of patient transcriptomics datasets. Furthermore, macrophage depletion or SRC inhibition using a novel specific inhibitor significantly inhibited resistant growth. Together, our findings elucidated a novel mechanism of macrophage-induced anti-androgen resistance of metastatic PC and a promising therapeutic approach to treat this deadly disease. We have presented these results in multiple conferences including: Keystone Symposia - the Resistant Tumor Microenvironment (2023.5) Asian 3 conference of Molecular Imaging (2023.01) EACR-MRS Virtual Conference on Seed and Soil: In Vivo Models of Metastasis (2022.01).
We are currently working on additional ECM-receptor pairs identified in the gene expression profile described above. In addition, we have performed scRNAseq analysis on bone metastasis samples of MycCaP-Bo cells and illustrated the dynamic alteration of the cellular landscape of the bone metastasis microenvironment alone the course of disease progression from naïve to responsive and to resistant. Part of this alteration include changes of hematopoietic progenitor cells. We are now using in vitro colony formation assays to confirm these changes. Furthermore, we have also used Stereo-seq spatial transcriptomics technology on MycCaP-Bo bone metastasis samples. We are in the process of analysing these data in order to determine the spatial location of different cell types and sub-types within the bone metastasis microenvironment and potential molecular interactions among them.
