ABSTRACT
OBJECTIVE: This investigation aims to explore the expression levels of serine protease 8 (PRSS8) in gefitinib-resistant Non-Small Cell Lung Cancer (NSCLC) cell lines (PC9/GR) and elucidate its mechanism of action. METHODOLOGY: We measured PRSS8 expression in gefitinib-resistant (PC9/GR) and sensitive (PC9) NSCLC cell lines using Western blot analysis. PRSS8-specific small interfering RNA (PRSS8-siRNA), a recombinant plasmid, and a corresponding blank control were transfected into PC9/GR cells. Subsequently, Western blot analyses were conducted to assess the expression levels of PRSS8, phosphorylated AKT (p-AKT), AKT, phosphorylated mTOR (p-mTOR), mTOR, and various apoptosis-related proteins within each group. Additionally, a cell proliferation assay utilizing Cell Counting Kit-8 (CCK8) was performed on each group treated with gefitinib. RESULT: PRSS8 expression was markedly higher in PC9/GR cells compared to PC9 cells (p < 0.05). The group treated with PRSS8-siRNA exhibited significantly reduced protein expression levels of PRSS8, p-AKT, p-mTOR, ß-catenin, and BCL-2 compared to the control siRNA (Con-siRNA) group, whereas expressions of Caspase9 and Bax were significantly increased. In the untransfected PC9/GR cells, protein expressions of PRSS8, p-AKT, pmTOR, and BCL-2 were significantly elevated when compared with the plasmid-transfected group, which also showed a significant reduction in Bax expression. The proliferative activity of the PRSS8-siRNA group postgefitinib treatment was significantly diminished at 24, 48, and 72 hours in comparison to the Con-siRNA group. CONCLUSION: The findings indicate that PRSS8 contributes to the acquisition of resistance to gefitinib in NSCLC, potentially through regulation of the AKT/mTOR signaling pathway.
ABSTRACT
Drug resistance is a major cause of treatment failure and post-treatment disease progression in patients with cancer. This study aimed to investigate the mechanisms of chemoresistance to gemcitabine (GEM) plus cisplatin (cis-diamminedichloroplatinum, DDP) combination therapy in stage IV lung squamous cell carcinoma (LSCC). It also examined the functional role of lncRNA ASBEL and lncRNA Erbb4-IR in the malignant progression of LSCC. The expression of lncRNA ASBEL, lncRNA Erbb4-IR, miR-21, and LZTFL1 mRNA was examined in human stage IV LSCC tissues and adjacent normal tissues, human LSCC cells and normal human bronchial epithelial cells using qRT-PCR. Furthermore, LZTFL1 protein levels were also examined using western blots. Cell proliferation, cell migration and invasion, and cell cycle progression and apoptosis were evaluated in vitro using the CCK-8, transwell, and flow cytometry assays, respectively. Based on the treatment response, LSCC tissues were classified as GEM-, DDP-, and GEM+DDP-sensitive/resistant. The MTT assay was performed to assess the chemoresistance of human LSCC cells to GEM, DDP, and GEM+DDP following transfection experiments. The results showed that lncRNA ASBEL, lncRNA Erbb4-IR, and LZTFL1 were down-regulated in human LSCC tissues and cells, whereas miR-21 was up-regulated. In stage IV human LSCC tissues, miR-21 levels were negatively correlated with those of lncRNA ASBEL, lncRNA Erbb4-IR, and LZTFL1 mRNA. The overexpression of lncRNA ASBEL and lncRNA Erbb4-IR inhibited cell proliferation, migration, and invasion. It also blocked cell cycle entry and accelerated apoptosis. These effects were mediated by the miR-21/LZTFL1 axis and reduced chemoresistance to GEM+DDP combination therapy in stage IV human LSCC. These findings indicate that lncRNA ASBEL and lncRNA Erbb4-IR function as tumor suppressors in stage IV LSCC and attenuate chemoresistance to GEM+DDP combination therapy via the miR-21/LZTFL1 axis. Hence, lncRNA ASBEL, lncRNA Erbb4-IR, and LZTFL1 may be targeted to enhance the efficacy of GEM+DDP combination chemotherapy against LSCC.