Bacterial protein-oleate complexes induce ferroptosis-like cell death in colorectal cancer cells by disrupting cell membranes and inhibiting the β-catenin-GPX4 axis.

The tumoricidal activity of human α-lactalbumin complexes, such as HAMLET and its α-helical domain with sodium oleate, is well-documented. However, the potential of bacterial α-helical proteins to form analogous anticancer complexes remains unexplored. In the current study, we demonstrate that α-helical proteins of bacterial origin can form tumoricidal complexes with sodium oleate. Using non-hemolytic toxin A (NheA), an inactive component of the native tripartite (NheABC) toxin complex from Bacillus thuringiensis, we show that NheA, upon mixing with sodium oleate (NheA-O), forms potent tumoricidal complexes against colorectal cancer cells. The NheA-O complex binds to the plasma membrane of tumor cells, disrupting the function of cellular organelles and ultimately causing cell death. Mechanistically, NheA-O induces ACSL4 and suppresses GPX4 expression, which ultimately leads to the accumulation of lipid peroxidation, following suppression of β-catenin signaling. The suppression of β-catenin signaling and its target proteins ultimately leads to suppression of colorectal cancer tumorigenesis. Functionally, NheA-O inhibits tumor cell migration, spheroid formation, clonogenic potential, ATP production and induces lipid peroxidation. These findings establish that bacterial α-helical proteins, like their human counterparts, can be engineered to form tumoricidal complexes with sodium oleate. Our work highlights NheA-O as a novel candidate that causes activation of ferroptosis-like cell death in target cancer cells, leading to intracellular organelles dysfunction. Moreover, NheA-O activity synergizes with RSL3, and NheA-O mediated cell death is antagonized by Fer-1, indicating the role of NheA-O in inducing ferroptosis-like cell death. Overall, these results describe NheA-O as a novel therapeutic agent to combat tumorigenesis by targeting tumor cell membrane and proteasomal degradation of GPX4 to trigger ferroptosis-like cell death and expands the paradigm of tumoricidal protein-lipid complexes functionality across biological kingdoms.