Increased expression of SSEA-4 on TKI-resistant non-small cell lung cancer with EGFR-T790M mutation.

Non-small cell lung cancer (NSCLC), a major life-threatening disease accounting for 85% of all lung cancer cases, has been treated with tyrosine kinase inhibitors (TKIs), but often resulted in drug resistance, and approximately 60% of TKI-resistant cases are due to acquired secondary (epithelial growth factor receptor) EGFR-T790M mutation. To identify alternative targets for TKI-resistant NSCLC with EGFR-T790M mutation, we found that the three globo-series glycosphingolipids are increasingly expressed on this type of NSCLC cell lines, and among them, the increase of stage-specific embryonic antigen-4 (SSEA-4) expression is the most significant. Compared to TKI-sensitive cell lines, SSEA-4 and the key enzyme ß3GalT5 responsible for the synthesis of SSEA3 are more expressed in TKI-resistant NSCLC cell lines with EGFR-T790M mutation, and the expression levels strongly correlate with poor survival in patients with EGFR mutation. In addition, we demonstrated that a SSEA-4 targeted monoclonal antibody, especially the homogeneous glycoform with well-defined Fc glycan designed to improve effective functions, is highly effective against this subpopulation of NSCLC in cell-based and animal studies. These findings provide a direction for the prediction of tumor recurrence and treatment of TKI-resistant NSCLC with EGFR-T790M mutation.

Synthesis of a dendritic cell-targeted self-assembled polymeric nanoparticle for selective delivery of mRNA vaccines to elicit enhanced immune responses.

Recent development of SARS-CoV-2 spike mRNA vaccines to control the pandemic is a breakthrough in the field of vaccine development. mRNA vaccines are generally formulated with lipid nanoparticles (LNPs) which are composed of several lipids with specific ratios; however, they generally lack selective delivery. To develop a selective delivery method for mRNA vaccine formulation, we reported here the synthesis of polymeric nanoparticles (PNPs) composed of a guanidine copolymer containing zwitterionic groups and a dendritic cell (DC)-targeted aryl-trimannoside ligand for encapsulation and selective delivery of an mRNA to dendritic cells. A DC-targeted SARS-CoV-2 spike mRNA-PNP vaccine was shown to elicit a stronger protective immune response in mice compared to the traditional mRNA-LNP vaccine and those without the selective delivery design. It is anticipated that this technology is generally applicable to other mRNA vaccines for DC-targeted delivery with enhanced immune response.

Use of phase plate cryo-EM reveals conformation diversity of therapeutic IgG with 50 kDa Fab fragment resolved below 6 Å.

While cryogenic electron microscopy (cryo-EM) is fruitfully used for harvesting high-resolution structures of sizable macromolecules, its application to small or flexible proteins composed of small domains like immunoglobulin (IgG) remain challenging. Here, we applied single particle cryo-EM to Rituximab, a therapeutic IgG mediating anti-tumor toxicity, to explore its solution conformations. We found Rituximab molecules exhibited aggregates in cryo-EM specimens contrary to its solution behavior, and utilized a non-ionic detergent to successfully disperse them as isolated particles amenable to single particle analysis. As the detergent adversely reduced the protein-to-solvent contrast, we employed phase plate contrast to mitigate the impaired protein visibility. Assisted by phase plate imaging, we obtained a canonical three-arm IgG structure with other structures displaying variable arm densities co-existing in solution, affirming high flexibility of arm-connecting linkers. Furthermore, we showed phase plate imaging enables reliable structure determination of Fab to sub-nanometer resolution from ab initio, yielding a characteristic two-lobe structure that could be unambiguously docked with crystal structure. Our findings revealed conformation diversity of IgG and demonstrated phase plate was viable for cryo-EM analysis of small proteins without symmetry. This work helps extend cryo-EM boundaries, providing a valuable imaging and structural analysis framework for macromolecules with similar challenging features.