Knockout of the caspase 8-associated protein 2 gene improves recombinant protein expression in HEK293 cells through up-regulation of the cyclin-dependent kinase inhibitor 2A gene

Time and Cost-Effective Genome Editing Protocol for Simultaneous Caspase 8 Associated Protein 2 Gene Knock in/out in Chinese Hamster Ovary Cells Using CRISPR-Cas9 System

Background

CHO cells are preferred for producing biopharmaceuticals, and genome editing technologies offer opportunities to enhance recombinant protein production. Targeting apoptosis-related genes, such as Caspases 8-Associated Protein 2 (CASP8AP2), improves CHO cell viability and productivity. Integrating robust strategies with the CRISPR-Cas9 system enables its application in CHO cell engineering.

Objectives

This study was performed to develop a cost-effective protocol using the CRISPR-Cas9 system combined with the HITI strategy for simultaneous CASP8AP2 gene deletion/insertion in CHO cells and to assess its impact on cell viability and protein expression.

Materials and Methods

We developed an efficient protocol for CHO cell engineering by combining CRISPR/Cas9 with the HITI strategy. Two distinct sgRNA sequences were designed to target the 3' UTR region of the CASP8AP2 gene using CHOPCHOP software. The gRNAs were cloned into PX459 and PX460-1 vectors and transfected into CHO cells using the cost-effective PEI reagent. A manual selection system was employed to streamline the process of single-cell cloning. MTT assays assessed gene silencing and cell viability at 24, 48, and 72 hours. Flow cytometry evaluated protein expression in CASP8AP2-silenced CHO cells.

Results

The study confirmed the robustness of combining CRISPR-Cas9 with the HITI strategy, achieving a high 60% efficiency in generating knockout clones. PEI transfection successfully delivered the constructs to nearly 65% of the clones, with the majority being homozygous. The protocol proved feasible for resource-limited labs, requiring only an inverted fluorescent microscope. CASP8AP2 knockout (CHO-KO) cells exhibited significantly extended cell viability compared to CHO-K1 cells when treated with NaBu, with IC50 values of 7.28 mM and 14.25 mM at 48 hours, respectively (P-value 24 hours ≤ 0.0001, 48 hours ≤ 0.0001, P-value 72 hours = 0.0007). CHO CASP8AP2-silenced cells showed a 1.3-fold increase in JRed expression compared to native cells.

Conclusions

CRISPR-Cas9 and HITI strategy was used to efficiently engineer CHO cells for simultaneous CASP8AP2 gene deletion/insertion, which improved cell viability and protein expression.

State-of-the-Art Approaches to Heterologous Expression of Bispecific Antibodies Targeting Solid Tumors

Bispecific antibodies (bsAbs) are some of the most promising biotherapeutics due to the versatility provided by their structure and functional features. bsAbs simultaneously bind two antigens or two epitopes on the same antigen. Moreover, they are capable of directing immune effector cells to cancer cells and delivering various compounds (radionuclides, toxins, and immunologic agents) to the target cells, thus offering a broad spectrum of clinical applications. Current review is focused on the technologies used in bsAb engineering, current progress and prospects of these antibodies, and selection of various heterologous expression systems for bsAb production. We also discuss the platforms development of bsAbs for the therapy of solid tumors.

Knockout of caspase-7 gene improves the expression of recombinant protein in CHO cell line through the cell cycle arrest in G2/M phase

Background

Chinese hamster ovary cell line has been used routinely as a bioproduction factory of numerous biopharmaceuticals. So far, various engineering strategies have been recruited to improve the production efficiency of this cell line such as apoptosis engineering. Previously, it is reported that the caspase-7 deficiency in CHO cells reduces the cell proliferation rate. But the effect of this reduction on the CHO cell productivity remained unclear. Hence, in the study at hand the effect of caspase-7 deficiency was assessed on the cell growth, viability and protein expression. In addition, the enzymatic activity of caspase-3 was investigated in the absence of caspase-7.

Results

Findings showed that in the absence of caspase-7, both cell growth and cell viability were decreased. Cell cycle analysis illustrated that the CHO knockout (CHO-KO) cells experienced a cell cycle arrest in G2/M phase. This cell cycle arrest resulted in a 1.7-fold increase in the expression of luciferase in CHO-KO cells compared to parenteral cells. Furthermore, in the apoptotic situation the enzymatic activity of caspase-3 in CHO-KO cells was approximately 3 times more than CHO-K1 cells.

Conclusions

These findings represented that; however, caspase-7 deficiency reduces the cell proliferation rate but the resulted cell cycle arrest leads to the enhancement of recombinant protein expression. Moreover, increasing in the caspase-3 enzymatic activity compensates the absence of caspase-7 in the caspase cascade of apoptosis.

Affecting HEK293 Cell Growth and Production Performance by Modifying the Expression of Specific Genes

The HEK293 cell line has earned its place as a producer of biotherapeutics. In addition to its ease of growth in serum-free suspension culture and its amenability to transfection, this cell line’s most important attribute is its human origin, which makes it suitable to produce biologics intended for human use. At the present time, the growth and production properties of the HEK293 cell line are inferior to those of non-human cell lines, such as the Chinese hamster ovary (CHO) and the murine myeloma NSO cell lines. However, the modification of genes involved in cellular processes, such as cell proliferation, apoptosis, metabolism, glycosylation, secretion, and protein folding, in addition to bioprocess, media, and vector optimization, have greatly improved the performance of this cell line. This review provides a comprehensive summary of important achievements in HEK293 cell line engineering and on the global engineering approaches and functional genomic tools that have been employed to identify relevant genes for targeted engineering.