A naturally occurring reishi protein (Ganoderma resinaceum) called FIP-Gre can directly block cancer growth and activate clean cell death pathways without harming healthy cells. FIP-Gre killed human lung cancer cells in lab culture at 21 µg/mL, while showing no toxicity to normal kidney cells even above 100 µg/mL. At 8 µg/mL, it triggered programmed cancer cell death, increasing tumor-kill signals 2–4× and reducing survival signals by about 40% in these cells.