lncRNA AL445238.2‑USP4 axis regulates cell survival and stemness in colon cancer.

Local progression and metastasis remain the foremost impediments to long‑term survival among patients with colorectal cancer (CRC). long non‑coding RNAs (lncRNAs) have a pivotal role in the advancement of colorectal malignancies. The aim of the present study was to elucidate the functional role and underlying molecular mechanisms of the lncRNA AL445238.2 in CRC progression. In the present study, overexpression/knockdown lentiviral vectors, protein half‑life assays and co‑immunoprecipitation assays were used to explore the regulatory relationship among AL445238.2, ubiquitin‑specific protease 4 (USP4) and BCL2, combined with Transwell assays, sphere formation assays and subcutaneous xenograft models to demonstrate their effects on colon cancer proliferation and stemness both in vitro and in vivo. The experimental findings revealed that AL445238.2 was highly expressed in CRC cells. AL445238 overexpression significantly enhanced the proliferation of DLD1 and SW480 cells, reduced extracellular lactate dehydrogenase release, diminished apoptotic activity and increased cellular stemness, as evidenced by increased CD133 expression and augmented tumor sphere formation, together with enhanced mitochondrial activity. RNA pulldown and immunofluorescence assays further demonstrated a direct interaction between AL445238.2 and USP4, with the two synergistically modulating the expression of the anti‑apoptotic protein Bcl2 and the pro‑apoptotic protein BAX to suppress apoptosis. Moreover, in in vivo assays, USP4 independently promoted cell proliferation, sustained stemness and enhanced mitochondrial function, thereby increasing tumor growth. Collectively, the findings of the present study revealed that AL445238.2, through its interaction with USP4, orchestrated the regulation of cell proliferation, apoptosis, stemness maintenance and migration in CRC cells, offering novel insights into the role of lncRNAs in cancer progression and highlighting potential therapeutic targets.