Split-Cas9-based targeted gene editing and nanobody-mediated proteolysis-targeting chimeras optogenetically coordinated regulation of Survivin to control the fate of cancer cells.

Background: Precise regulation of partial critical proteins in cancer cells, such as anti-apoptotic proteins, is one of the crucial strategies for treating cancer and discovering related molecular mechanisms. Still, it is also challenging in actual research and practice. The widely used CRISPR/Cas9-based gene editing technology and proteolysis-targeting chimeras (PROTACs) have played an essential role in regulating gene expression and protein function in cells. However, the accuracy and controllability of their targeting remain necessary.

Methods: Construction of UMUC-3-EGFP stable transgenic cell lines using the Sleeping Beauty system, Flow cytometry, quantitative real-time PCR, western blot, fluorescence microplate reader and fluorescence inverted microscope analysis of EGFP intensity. Characterization of Survivin inhibition was done by using Annexin V-FITC/PI apoptosis, calcein/PI/DAPI cell viability/cytotoxicity assay, cloning formation assay and scratch assay. The cell-derived xenograft (CDX) model was constructed to assess the in vivo effects of reducing Survivin expression.

Results: Herein, we established a synergistic control platform that coordinated photoactivatable split-Cas9 targeted gene editing and light-induced protein degradation, on which the Survivin gene in the nucleus was controllably edited by blue light irradiation (named paCas9-Survivin) and simultaneously the Survivin protein in the cytoplasm was degraded precisely by a nanobody-mediated target (named paProtacL-Survivin). Meanwhile, in vitro experiments demonstrated that reducing Survivin expression could effectively promote apoptosis and decrease the proliferation and migration of bladder cancerous cells. Furthermore, the CDX model was constructed using UMUC-3 cell lines, results from animal studies indicated that both the paCas9-Survivin system and paProtacL-Survivin significantly inhibited tumour growth, with higher inhibition rates when combined.

Conclusions: In short, the coordinated regulatory strategies and combinable technology platforms offer clear advantages in controllability and targeting, as well as an excellent reference value and universal applicability in controlling the fate of cancer cells through multi-level regulation of key intracellular factors.