Unexpectedly, we found that 3‐Cl‐AHPC, a synthetic ligand of RARγ and a potent cancer inhibitor, strongly induced the formation of matriptase/HAI‐1 complex in breast cancer cell MCF‐7, skin cancer cell A431 and colon cancer cell SW620 (Figure 1). The gene discussed is SPINT1; the disease is skin neoplasm.