Decrease of autophagy activity promotes malignant progression of tongue squamous cell carcinoma.

ABSTRACT

BACKGROUND: Autophagy is a catabolic process involving the degradation of cells' own unnecessary, injured, or aged proteins and recycling of degraded products to maintain hemostasis. Recently, studies indicated that autophagy plays a crucial role in cancer development. However, the role of autophagy in tongue squamous cell carcinoma (TSCC) has not been well documented. This study aims to assess the expression of autophagy-related protein and investigate its effect on TSCC. MATERIALS AND METHODS: Archival 50 TSCC samples were enrolled. Immunohistochemistry were performed to examine the expression of Beclin1 and LC3. Statistical analyses were carried out to assess the associations among clinicopathologic parameters. In vitro, cells were treated with rapamycin or 3-MA. Then, qPCR, western blot and immunofluorescence were performed to detect the expression of Beclin1 and LC3. Transmission electron microscopy was utilized to identify autophagsomes. For functional analysis, cell proliferation and cell cycle were evaluated with MTT assay and flow cytometer, respectively. At last, cell migration and invasion potentials were assessed by wound healing assay and transwell assay. RESULTS: We confirmed that down-regulation of Beclin1 and LC3 is a frequent event in TSCC. Then, we demonstrated that decreased expression of Beclin1 was associated with T stage, clinical stage and differentiation. Furthermore, we showed that activation of autophagy by rapamycin suppressed proliferation, migration and invasion while inhibition of autophagy by 3-MA promoted proliferation, migration and invasion in TSCC cells. CONCLUSION: Taken together, these data suggest that autophagy plays a pivotal role in the progression of TSCC.