FAM3C (family with sequence similarity 3 member C), also known as interleukin-like EMT inducer (ILEI), is a secreted cytokine-like protein that plays critical roles in cancer progression and metabolism regulation 1. The protein promotes epithelial-to-mesenchymal transition and is overexpressed in multiple cancer types, including breast and lung cancers, where it correlates with poor patient prognosis and enhanced metastatic potential 12. FAM3C functions through several molecular mechanisms: it activates the YY1-HSF1-Akt-Cyclin D1 signaling pathway to promote breast cancer cell proliferation and migration 3, and interacts with RalA to trigger Src/Stat3 signaling cascades in lung cancer 2. In the tumor microenvironment, FAM3C is produced by cancer-associated adipocytes in response to TGFβ signaling, where it supports tumor cell survival and reduces fibrosis 4. The protein can be transported via tumor-derived extracellular vesicles, facilitating metastatic colonization 2. Clinically, elevated circulating FAM3C levels are associated with metastatic breast cancer 4, and therapeutic inhibition of FAM3C represents a promising treatment strategy. Interestingly, FAM3C expression is transcriptionally downregulated in Alzheimer's disease brains, where it may function as an endogenous suppressor of amyloid-β production 5.