The ATG4A knockout HT29 polyclonal cells are a CRISPR/Cas9-mediated gene-disrupted polyclonal cell population derived from the human colorectal adenocarcinoma HT29 cell line. This product provides a loss-of-function model for studying the autophagy-related cysteine protease ATG4A in a colon cancer background. The polyclonal format ensures a diverse genetic landscape, enabling robust population-level phenotypic analyses while avoiding clonal artifacts inherent to single-cell clones.
HT29 is a widely used human epithelial colorectal adenocarcinoma cell line originally isolated from a primary tumor of a 44-year-old Caucasian female. Under standard culture, HT29 cells exhibit an undifferentiated epithelial morphology; however, they can undergo enterocytic differentiation in response to appropriate stimuli such as glucose deprivation or sodium butyrate treatment. As a model for colon cancer, HT29 is employed in studies of tumor biology, drug sensitivity, and metastasis. The p53-mutant status of HT29 contributes to its resistance to apoptosis, making it a relevant system for evaluating autophagy-mediated survival mechanisms.
ATG4A is a cysteine protease that plays an essential role in autophagy by processing the pro-forms of LC3 and GABARAP family proteins, exposing C-terminal glycine residues for conjugation to phosphatidylethanolamine (PE). This lipidation generates LC3-II and GABARAP-II, which are critical for autophagosome elongation and closure. Additionally, ATG4A mediates the delipidation of LC3-II on mature autophagosomes, recycling LC3 for subsequent rounds of autophagosome formation. ATG4A activity is regulated by mTORC1, which integrates signals from nutrient deprivation, hypoxia, and AMPK. Upstream of ATG4A, the ULK1 complex initiates autophagy upon mTORC1 inhibition. ATG4A directly interacts with LC3/GABARAP family members, ATG7, ATG3, BECN1, and the ATG12-ATG5 conjugate. Its downstream targets include MAP1LC3A, MAP1LC3B, MAP1LC3C, GABARAP, GABARAPL1, and GABARAPL2. Thus, ATG4A sits at a pivotal node in autophagic flux, coupling proteolytic processing to membrane expansion.
In the HT29 colorectal adenocarcinoma model, ATG4A-mediated autophagy contributes to tumor cell adaptation to metabolic stress, hypoxia, and therapeutic insults. Loss of ATG4A disrupts autophagosome formation and LC3/GABARAP lipidation, impairing the cell??s ability to recycle damaged organelles and maintain energy homeostasis. This makes the ATG4A knockout HT29 polyclonal cells a valuable tool for dissecting autophagy-dependent tumorigenic processes, including chemoresistance, invasion, and metastatic potential. The model is particularly suited for studying cross-talk between autophagy and pathways frequently dysregulated in colorectal cancer, such as mTOR signaling and TP53-mediated responses.
Researchers can employ this knockout model for diverse mechanistic and phenotypic assays. Autophagy flux can be quantified by western blotting for the LC3-II/LC3-I ratio in the presence or absence of lysosomal inhibitors, or by immunofluorescence detection of LC3 puncta. A tandem mCherry-GFP-LC3 reporter enables real-time monitoring of autophagic flux. Gene-disruption efficacy can be confirmed via RT-qPCR for ATG4A transcript levels or sequencing of the targeted locus. Functional studies may include MTT or colony formation assays to assess proliferation, and transwell invasion assays to evaluate metastatic behavior under nutrient deprivation or drug treatment. This polyclonal population is ideal for investigating autophagy-related drug resistance in colorectal cancer and for screening autophagy modulators. For additional information or custom applications, please contact Ascent Research.
