Tiprl, also known as TOR signaling pathway regulator-like, is an important regulatory protein. It functions by impeding the activity of the catalytic subunits of PP2A and is involved in the TOR signaling pathway. Multiple serine/threonine protein phosphatases (PP)2A, PP4, and PP6 are part of the TOR signaling pathway in mammalian cells, and Tiprl plays a role in modulating this pathway [1]. It has been postulated to have various cellular functions, such as regulating the mechanistic target of rapamycin (mTOR) signaling, inhibiting apoptosis and biogenesis, and recycling of PP2A [1].

In lung cancer, Tiprl has been shown to have several functions. In lung cancer stem cells, upregulated Tiprl causes sustained activation of the calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2) signaling pathway by binding to CaMKK2, maintaining stemness and survival. Depletion of Tiprl sensitizes lung CSCs to afatinib-induced cell death and reduces distal metastasis in vivo [2]. In non-small cell lung cancer (NSCLC), Tiprl upregulation potentiates autophagy activity through the eIF2α-ATF4 pathway, conferring a survival advantage to cancer cells, while its depletion increases apoptosis by reducing autophagic clearance [3].

In gastric cancer, Tiprl acts as a metastasis suppressor. Decreased Tiprl expression in clinical specimens is correlated with more-advanced TNM stage, distant metastasis, and poor clinical outcome. Re-expression of Tiprl suppresses migratory and invasive capacities of gastric cancer cells by regulating the AMPK/mTOR signaling pathway [4].

In liver cancer, the level of Tiprl is significantly correlated with levels of LC3 and CD133, and its knockdown reduces expressions of LC3, CD133, stemness-related genes, as well as viability and stemness of liver cancer cell-lines. Tiprl can serve as a potential biomarker for early liver cancer [5].

In conclusion, Tiprl is a key regulator involved in multiple cellular processes and pathways. Its functions in different cancers, such as lung, gastric, and liver cancer, highlight its importance in tumorigenesis. Studies on Tiprl using in vivo models like the depletion experiments in lung CSCs and knockdown in liver cancer cell-lines have provided insights into its role in cancer-related biological processes, which may offer potential therapeutic targets for these diseases.