FJ-5002

Subcutaneous cell-line-derived xenograft (CDX) models are established by implanting cultured human cancer cell lines into immunodeficient mice, where the injected cells form localized tumors that can be monitored in vivo as a measure of tumorigenic potential, growth kinetics, and treatment response. These models are widely used in oncology research because they allow reproducible tumor formation and enable comparative assessment of tumor growth between different cell lines or genetic manipulations in a controlled in vivo microenvironment. Subcutaneous implantation of cancer cells in immunodeficient mice is a standard approach for evaluating tumor growth behavior and therapeutic response across multiple cancer types, including prostate, esophageal, pancreatic, and colon cancer models.

Senescence-associated β-galactosidase staining detects β-galactosidase activity that is histochemically visible at pH 6. 0 in senescent cells, where X-gal cleavage produces an insoluble blue precipitate observable by bright-field microscopy. This activity reflects increased lysosomal β-galactosidase/lysosomal mass rather than a senescence-essential enzyme, because GLB1 depletion or genetic lysosomal β-galactosidase deficiency can abolish SA-β-gal staining while cells still undergo senescence. SA-β-gal was originally reported in senescent but not presenescent fibroblasts and keratinocytes, absent from quiescent fibroblasts and terminally differentiated keratinocytes, and increased with donor age in human skin samples. Because SA-β-gal can also appear in some non-senescent or tissue-specific contexts, interpretation should be paired with experimental controls and, when possible, independent senescence markers.