Receptor tyrosine kinases (RTKs) such as epidermal growth factor receptor (EGFR) and hepatocyte growth factor receptor (MET) are the best-known therapeutic targets in lung adenocarcinoma. Previously, we have revealed that stratifin (SFN, 14-3-3 sigma) acts as a novel oncogene, accelerating tumor initiation and progression of lung adenocarcinoma and interacts with ubiquitin-specific protease 8 (USP8) (IJC 2011, Mol Cancer 2015). USP8 is one of the deubiquitination enzymes that stabilize specific protein substrates by removing ubiquitin from the proteins, and is known to target receptor tyrosine kinases (RTKs). In this study, we investigated the molecular mechanism underlying the binding of SFN to USP8 in lung adenocarcinoma cells, as the role of this interaction in RTK stabilization was considered a promising avenue for identifying a useful therapeutic target for lung adenocarcinoma. Expressions of USP8 and SFN in human lung adenocarcinoma tissues (n=193) were examined by immunohistochemistry and statistically analyzed with clinicopathological features of patients. Functional analysis of USP8 and SFN such as cellular proliferation assay, apoptosis assay, and wound healing assay was examined after siRNA-USP8 or SFN transfection. Regulation mechanism of USP8 and SFN on RTKs stabilization was demonstrated using co-immunoprecipitation, western blot analysis, and immunofluorescence. USP8 specifically bound to SFN in lung adenocarcinoma cells. Both USP8 and SFN showed higher expression in human lung adenocarcinoma than in normal lung tissue, and their expression was mutually correlated. Expression of SFN, but not that of USP8, was significantly associated with histological subtype, pathological stage, and patient’s prognosis. In vitro, USP8 binds SFN at the early- and late-endosome in immortalized adenocarcinoma in situ (AIS) cells. Moreover, USP8 or SFN knockdown led to down-regulation of tumor cell proliferation, RTK expression, and expression of downstream factors including AKT and STAT3, as well as accumulation of ubiquitinated RTKs leading to lysosomal degradation. Additionally, transfection with mutant USP8 and mutant SFN, which are unable to interact each other, reduced the expression of RTKs and their downstream factors, indicating that interaction with SFN is important for USP8-mediated stabilization of RTKs via deubiquitination. RTKs are regulated by ubiquitin-lysosome system, and aberrant stabilization of RTKs contributes to the proliferative activity of many human cancers, including NSCLC. Here, we demonstrate SFN induces aberrant activation of USP8 and subsequently protects RTKs from lysosomal degradation, resulting in hyperactivation of these signaling pathways. SFN may be central to the development of a useful therapeutic strategy for both early and advanced lung adenocarcinomas.