PCSK9 and neoplasm: Furthermore, in a mouse model bearing a 4MOSC1 syngeneic tumor, PCSK9 inhibition increased the infiltration of CD8 + T cells, decreased the number of myeloid-derived suppressor cells (MDSCs), and improved the antitumor efficacy of anti-PD-1 (programmed cell death-1 (PD-1)) immune checkpoint blockade (ICB) therapy.