Development of novel quality control material based on CRISPR/Cas9 editing and xenografts for MLH1 protein deficiency testing

A novel method for the preparation of reproducible, stable, and non-infectious quality control materials for Chlamydia trachomatis nucleic acid detection

Chlamydia trachomatis (CT) is a significant sexually transmitted pathogen known to evoke severe complications, including infertility. Nucleic acid amplification tests (NAATs) are recommended by the World Health Organization to detect CT infection. Furthermore, the establishment of methods, performance validation, internal quality control, and external quality assessment for CT NAATs necessitate the utilization of quality control materials (QCs). QCs are specimens or solutions that are analyzed for quality control purposes in a test system. In this study, we established a novel cell line that stably integrates CT amplification target sequences for producing QCs for CT NAATs. Utilizing clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 technology, we integrated the CT plasmid-mediated sequence (comprising the full length of the cryptic plasmid and the major outer membrane protein gene, 9,136 bp) into the MUC4 gene of HEK293T cells. Positive clones were screened through flow cytometric sorting, single-cell culture, and PCR-based identification, followed by the establishment of stable cell lines. These cells were then processed using optimized cell preservation procedures to prepare QCs. The sequence insertion copy number was confirmed by real-time quantitative PCR. This novel CT QCs demonstrate excellent clinical applicability, non-infectiousness, quantifiability, and stability. With an integrated sequence exceeding 9 kb in length, it offers exceptional flexibility for adapting to new kit developments. Furthermore, maintaining a well-defined copy number and stable shelf life, the QCs closely aligns with the quality control requirements of CT NAATs. This study presents an innovative method for preparing QCs for CT nucleic acid detection, making a valuable contribution to improving the performance of CT NAATs.IMPORTANCEUntreated CT infections impose significant burdens on individuals and communities, underscoring the importance of early and accurate testing via CT NAATs for disease control. QCs are instrumental in identifying testing process issues. Hence, we developed a cell line integrating CT-amplified target sequences as readily accessible non-infectious QCs. These QCs boast several advantages: the integration of over 9 kb of CT sequence allows for broad applicability, allowing flexible adaptation to the development of new kits. Confirming the CT sequence copy number provides a reliable basis for QC concentration preparation and kit detection limit evaluation. Optimized preservation protocol enhances QC stability during storage, facilitating convenient shipment to clinical laboratories at ambient temperatures. In summary, our novel CT QCs offer a powerful tool for improving CT NAAT performance and present a fresh perspective on QC preparation for detecting nucleic acids from intracellular parasitic pathogens.

Lentiviral vector–based xenograft tumors as candidate reference materials for detection of HER2-low breast cancer

The human epidermal growth factor receptor 2 (HER2) is an important biomarker that plays a pivotal role in therapeutic decision-making for patients with breast cancer (BC). Patients with HER2-low BC can benefit from new HER2 targeted therapy. For ensuring the accurate and reproducible detection of HER2-low cancer, reliable reference materials are required for monitoring the sensitivity and specificity of detection assays. Herein, a lentiviral vector was used to transduce the HER2 gene into MDA-MB-231 cells that exhibited low HER2 density, and the cells were characterized by droplet digital PCR to accurately determine the copy number variation. Then, the formalin-fixed paraffin-embedded (FFPE) samples from xenografts were prepared and evaluated for suitability as candidate reference materials by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). The FFPE reference materials were selected on the basis of IHC score of 2+ and negative FISH result to meet the requirement for HER2-low BC detection. Furthermore, the FFPE reference materials exhibited typical histological structures that resembled the clinical BC specimens. These novel FFPE reference materials displayed the high stability and homogeneity, and they were produced in high quantity. In summary, we generated high-quality reference materials for internal quality control and proficiency testing in HER2-low detection.