Structure-based analysis of heme oxygenase subtype-selective inhibition activity of tumor-initiating cell near-infrared probe: a promising therapeutic agent for metastatic lung cancer.

Heme oxygenase-2 (HMOX-2) is overexpressed in various cancers and is a key target in metastasis. Recently, tumor-initiating cell near-infrared probe (TiNIR) was identified as a selective HMOX-2 inhibitor, yet its molecular mechanism and selectivity remain unexplored. This study elucidates TiNIR's HMOX-2 selective binding mechanism by integrating molecular modeling and in-vitro assays. In-vitro assays directly measured binding affinity of TiNIR to HMOX-1 and HMOX-2; structural differences were analyzed through molecular-docking, pharmacophore-modeling, and molecular-dynamics (MD) simulations. Selective binding of TiNIR to HMOX-2 was experimentally confirmed, and molecular docking results indicated that TiNIR exhibited a binding affinity comparable to or higher than that of heme in HMOX-2. In contrast, binding affinity to HMOX-1 was relatively low. Pharmacophore modeling analysis revealed that open binding-pocket of HMOX-2 facilitates stable TiNIR binding, whereas spatial constraints in HMOX-1 restrict its interaction with TiNIR. Furthermore, MD simulations demonstrated that interaction between TiNIR and HMOX-2 is dynamically stable. In conclusion, TiNIR exhibited high binding affinity and selectivity for HMOX-2, providing structural evidence for its potential as a previously unrecognized HMOX-2 selective probe. The findings of this study suggest that TiNIR could serve as a theranostic agent targeting HMOX-2 in metastatic cancer and establish a structural foundation for TiNIR-based therapeutics.