Si, Y. | bioRxiv Science

bioRxiv2019

Novel anti-somatostatin receptor 2 antibody-drug conjugate for neuroendocrine cancer therapy

Neuroendocrine (NE) cancers include a diverse spectrum of hormone-secreting neoplasms that arise from the endocrine and nervous systems. Current chemo- and radio- therapies have marginal curative benefits. This study aimed to develop an innovative antibody-drug conjugate (ADC) to effectively treat NE tumors (NETs). We first confirmed that somatostatin receptor 2 (SSTR2) is an ideal surface target by analyzing 38 patient-derived NET tissues, 33 normal organs, and 3 NET cell lines. We then developed a new monoclonal antibody (mAb, IgG1 and kappa) to target two extracellular domains of SSTR2, which showed strong and specific surface binding to NETs. The ADC was constructed by conjugating the anti-SSTR2 mAb and antimitotic monomethyl auristatin E. In vitro evaluations indicated that the ADC can effectively bind, internalize, release payload, and kill NET cells effectively. Finally, the ADC was evaluated in vivo using a NET xenografted mouse model to determine cancer targeting, maximal tolerated dosage, pharmacokinetics, and anti-cancer efficacy. The anti-SSTR2 ADC was able to exclusively target and kill NETs with minimal toxicity and high stability in vivo. This study demonstrates that the anti-SSTR2 mAb-based ADC has high therapeutic values for NET therapy.

bioengineering↗

bioRxiv2019

Scaffold subunits support associated subunit assembly in the Chlamydomonas ciliary nexin-dynein regulatory complex

The nexin-dynein regulatory complex (N-DRC) in motile cilia and flagella functions as a linker between neighboring doublet microtubules, acts to stabilize the axonemal core structure, and serves as a central hub for the regulation of ciliary motility. Although the N-DRC has been studied extensively using genetic, biochemical, and structural approaches, the precise arrangement of the eleven (or more) N-DRC subunits remains unknown. Here, using cryo-electron tomography, we have compared the structure of Chlamydomonas wild-type flagella to that of strains with specific DRC subunit deletions or rescued strains with tagged DRC subunits. Our results show that DRC7 is a central linker subunit that helps connect the N-DRC to the outer dynein arms. DRC11 is required for the assembly of DRC8, and DRC8/11 form a sub-complex in the proximal lobe of the linker domain that is required to form stable contacts to the neighboring B-tubule. Gold labeling of tagged subunits determines the precise locations of the previously ambiguous N-terminus of DRC4 which is now shown to contribute to the core scaffold of the N-DRC and C-terminus of DRC5. Our results reveal the overall architecture of N-DRC, with the three subunits, DRC1/2/4 forming a core complex that serves as the scaffold for the assembly of the \"functional subunits\" associate, namely DRC3/5-8/11. These findings shed light on N-DRC assembly and its role in regulating flagellar beating.\n\nSignificance StatementCilia and flagella are small hair-like appendages in eukaryotic cells that play essential roles in cell sensing, signaling, and motility. The highly conserved nexin-dynein regulatory complex (N-DRC) is one of the key regulators for ciliary motility. At least 11 proteins (DRC1-11) have been assigned to the N-DRC, but their precise arrangement within the large N-DRC structure is not yet known. Here, using cryo-electron tomography combined with genetic approaches, we have localized DRC7, the sub-complex DRC8/DRC11, the N-terminus of DRC4, and the C-terminus of DRC5. Our results provide insights into the N-DRC structure, its function in the regulation of dynein activity, and the mechanism by which n-drc mutations can lead to defects in ciliary motility that cause disease.

cell biology↗