Practice question

Anchorage-dependent cells require physical attachment to solid substratum coated with extracellular matrix proteins such as collagen type I, fibronectin, or laminin to progress through cell cycle. Attachment occurs via transmembrane integrin heterodimers α and β binding to RGD sequences in matrix, clustering into focal adhesions recruiting focal adhesion kinase autophosphorylation at Y397, Src recruitment, and downstream activation of PI3K-Akt survival pathway and Ras-MAPK mitogenic cascade inducing cyclin D1 transcription. Without this signaling, normal cells arrest in G1 and undergo anoikis form of apoptosis mediated by Bcl-2 family proteins and caspase activation. Laboratory provision includes tissue culture treated polystyrene with increased hydrophilicity, collagen-coated dishes, or microcarriers for bioreactors. Liquid nitrogen storage, simple suspension culture with agitation, or shaking without substrate does not satisfy requirement, causing loss of viability for anchorage-dependent lines. Transformation to malignancy often releases cells from dependence allowing colony formation in semi-solid agar, hallmark of tumorigenicity assays. Stiffness sensing via YAP mechanotransduction links matrix elasticity to proliferation decisions in tissue engineering. This knowledge strengthens laboratory safety, protocol reproducibility, and regulatory compliance critical for translational research and clinical applications, ensuring reliable data and workforce protection.