Single-Cell Profiling of Apoptotic Resistance in Patient-Derived Xenografts and Primary Circulating Tumor Cells Using TetherChip.

Circulating tumor cells (CTCs) must escape the primary tumor and spread to distant organs through harsh, nonadherent blood, and lymphatic microenvironments, where over 99% perish. Some CTCs survive by resisting extracellular matrix (ECM) detachment-induced apoptosis (anoikis). CTC enumeration has already been directly linked to poor patient outcomes. Single-cell profiling of the anoikis resistance phenotype of CTCs could improve our diagnostic capabilities; however, there remain technical limitations to isolating and characterizing live, nonadherent tumor cells. To address this gap in knowledge, our group developed a cell tethering nanosurface, TetherChip, that enables high-resolution microscopy over extended time periods of live, nonadherent single cells within minutes to hours of detachment and/or isolation. This study leveraged optically clear microfluidic slides with the TetherChip nanosurface to develop an anoikis resistance profiling assay that combines real-time cell tracking with caspase activation to assess apoptotic resistance in nonadherent conditions. This assay was first optimized in cultured breast and lung cancer cell lines and subsequently extended to clinically applicable patient-derived xenograft (PDX) and patient CTC samples as a proof-of-concept for translational feasibility. This platform integrated AI-assisted analysis techniques and implemented fluorescent multiplexing to ultimately enable an efficient tumor-specific, single-cell analysis for TetherChip anoikis resistance profiling of live, nonadherent tumor cells.