Heme oxygenase-1 expressing macrophages in cancer Tumour associated macrophages (TAMs) are exquisitely polarized by the tumour microenvironment to adopt a range of specialized phenotypic subsets which facilitate tumour progression. The Arnold lab have been studying heme oxygenase-1 (HO-1) expressing macrophages and their role in metastasis and immune suppression within the tumour microenvironment. We have been studying HO-1+ TAMs cells in preclinical models of cancer, in particular the spontaneous MMTV-PyMT model, and applying scRNAseq and computation approaches to study the TAM subset and its interaction with other cells in the tumour microenvironment. We have also been using pharmacological inhibition and genetic inactivation of HO-1 to study the specific roles of the enzyme in disease progression. We have demonstrated that HO-1 activity plays an important role in both metastasis and suppressing anti-tumour immune responses.