Hemopoietic Cell Kinase (HCK) belongs to the SRC family of non-receptor tyrosine kinase widely expressed in myeloid cells, most notably in macrophages. It is well established that macrophages play a role in creating an immunosuppressive, pro-tumoral and pro-angiogenic environment in cancers. Tumour associated macrophages (TAM) polarised to specific subtypes known as M2-like, alternative activated macrophages that are induced by T helper type 2 cells via interleukins such as IL4. HCK activity promotes polarisation of TAMs toward a tumour-promoting M2-like endotype thereby limiting infiltration and activation of immune effector cells and associated anti-tumour immune responses, including those elicited by immune checkpoint blockade.
We analysed scRNAseq from 1) Metastatic high grade ovarian cancer, and 2) Orthotopic lung cancer models established in either HCK Knock out (KO) and HCK wild type (WT) hosts. We looked at differential gene expression profiles in macrophages in these cancer models to seek for HCK-dependent, common gene signatures. Furthermore, we compared this dataset with bulk RNA sequencing of murine bone marrow-derived macrophages derived from HCK-KO and HCK-WT mice and stimulated in vitro by interleukin 4 (IL-4). Compared to immune cell subsets from HCK-WT host, in cells of HCK-KO hosts we observed consistent down-regulation of genes associated with pathways involved in cellular proliferation, receptor and integrin signalling and angiogenesis. By contrast, genes involved in regulation of T cell differentiation, cell population proliferation, intrinsic apoptotic signalling pathway, T cell mediated cytotoxicity, antigen processing via MHC class 1, humoral immune response, macrophage migration, type I and II interferon-mediated signalling pathway and negative regulation of apoptotic process were upregulated in cells of HCK-KO hosts. Importantly, there were significant differences in the extent of differential gene expression between the TAMs in these models and in vitro polarized cells suggesting the inability of IL-4 to recapitulate the exact conditions in cancer tumour microenvironment in vivo.
Our HCK-specific gene signatures in TAM will allow us in the future to assess the extent of HCK signalling in human tumours and to better identify patients most likely to benefit from anti-HCK therapies.