Deciphering therapeutic potential of PEGylated recombinant PTEN-silver nanoclusters ensemble on 3D spheroids

The therapeutic application of recombinant proteins is limited due to their inherent structural complexity. Additionally, screening of therapeutic potential of protein products requires an appropriate testing platform to achieve biological relevance. Fabrication of three dimensional cultures bridges the gap between in vitro based monolayer cultures and clinical applications. In this perspective, glioblastoma U-87 MG and breast cancer MCF7 spheroids were generated to assess the therapeutic prospect of recombinant PTEN protein. PTEN bound to silver nanoclusters was encapsulated within PEG coating, which resulted in fabrication of spherical nanocarriers named as PTEN-nanocomposites. Internalization of PTEN-nanocomposites in the spheroids was confirmed by confocal microscopy. Upon uptake, PTEN-nanocomposites led to modulation of cyclins and apoptosis gene regulators culminating in cell cycle arrest and reduced cell viability as confirmed by calcein-AM/PI dual staining and alamar blue assay. Further, combination of tamoxifen and PTEN-nanocomposites on U-87 MG spheroids resulted in two-fold reduction of drug dosage. The study revealed that the monolayer culture results translated to the 3D culture as well, however higher dose of the recombinant PTEN was required for the spheroid system. The anti-proliferative role of PTEN-nanocomposites in a complex 3D environment augments its biological implication and paves the way for recombinant PTEN based therapeutic applications.