Comprehensive Analysis and Experimental Validation of TLL2 as a Potential New Prognostic Biomarker Associated with Immune Infiltration in Lung Adenocarcinoma

Background: The precise function of Tolloid Like 2 (TLL2) remains uncertain within the context of Lung Adenocarcinoma (LUAD). Objective: The primary objective of this investigation was to conduct a thorough analysis. Methods: To assess its diagnostic utility, data from The Cancer Genome Atlas (TCGA) database were used to assess TLL2 expression in pan-cancer and LUAD. The study has also investigated the correlation between TLL2 expression levels and LUAD symptoms and prognosis. Furthermore, the study has explored possible regulatory networks involving TLL2, including its association with immune infiltration, tumor stemness index (mRNAsi), and drug sensitivity in LUAD. We have explored TLL2 expression in single-cell sequencing of LUAD and the genomic variation and clinical significance of TLL2 in LUAD. The expression of TLL2 has been validated in GSE87340 and cell lines by quantitative Real-time PCR (qRT-PCR). Results: An abnormal expression of TLL2 has been found in pan-cancer and LUAD. In LUAD patients, elevated levels of TLL2 were significantly related to the T stage (p = 0.046) and the pathological stage (p = 0.016). The expression of TLL2 in patients with LUAD was significantly associated with poorer Overall Survival (OS) (p < 0.001). The expression of TLL2 was determined to be an independent predictor of poorer OS (p = 0.042). TLL2 was associated with ribosome, neuroactive ligand-receptor interaction, allograft rejection, ECM receptor interaction, asthma, porphyrin and chlorophyll metabolism, focal adhesion, pentose and glucuronate inter-conversions, and ascorbate and aldarate metabolism. The expression of TLL2 in LUAD was correlated with immune infiltration and mRNAsi. The expression of TLL2 was significantly and negatively correlated with TAK-715, XMD13-2, STF-62247, OSI-930, and EHT-1864 in LUAD. The TLL2 gene was up- -regulated in multiple individual LUAD cells. LUAD patients with altered TLL2 had a shorter PFS as opposed to those with unaltered TLL2. The expression of TLL2 was significantly increased in LUAD cells. Conclusion: For patients with LUAD, TLL2 may serve as an immunotherapeutic target and a useful prognosis biomarker.