RESUMO
BACKGROUND: MicroRNAs (miRNAs or miRs) are post-transcriptional regulators of eukaryotic cells and knowledge of differences in miR levels may provide new approaches to diagnosis and therapy. METHODS: The present study measured the levels of nine miRs in head and neck squamous cell carcinomas (HNSCC) and determined whether clinical pathological features are associated with differences in miR levels. SET (I2PP2A) and PTEN protein levels were also measured, since their levels can be regulated by miR-199b and miR-21, respectively. Nine miRs (miR-15a, miR-21, miR-29b, miR-34c, miR-100, miR-125b, miR-137, miR-133b and miR-199b) were measured by real time qRT-PCR in HNSCC samples from 32 patients and eight resection margins. SET (I2PP2A) and PTEN protein levels were estimated by immunohistochemistry in paired HNSCC tissues and their matched resection margins. RESULTS: In HNSCC, the presence of lymph node invasion was associated with low miR-15a, miR-34c and miR-199b levels, whereas the presence of perineural invasion was associated with low miR-199b levels. In addition, miR-21 levels were high whereas miR-100 and miR-125b levels were low in HNSCC compared to the resection margins. When HNSCC line HN12, with or without knockdown of SET, were transfected with miR-34c inhibitor or miR-34c mimic, the miR-34c inhibitor increased cell invasion capacity while miR-34c mimic decreased the cell invasion. CONCLUSIONS: We showed that the levels of specific miRs in tumor tissue can provide insight into the maintenance and progression of HNSCC. GENERAL SIGNIFICANCE: MiRNAs are up- or down-regulated during cancer development and progression; they can be prognosis markers and therapeutic targets in HNSCC.
RESUMO
Dysfunctional clock signaling is observed in a variety of pathological conditions. Many members of the clock gene family are upregulated in tumor cells. Here, we explored the consequences of a commonly disrupted signaling pathway in head and neck cancer on the regulation of circadian clock genes. PTEN is a key molecular controller of the PI3K signaling, and loss of PTEN function is often observed in a variety of cancers. Our main goal was to determine whether PTEN regulates circadian clock signaling. We found that oxidation-driven loss of PTEN function resulted in the activation of mTOR signaling and activation of the core clock protein BMAL1 (also known as ARNTL). The PTEN-induced BMAL1 upregulation was further confirmed using small interference RNA targeting PTEN, and in vivo conditional depletion of PTEN from the epidermis. We observed that PTEN-driven accumulation of BMAL1 was mTOR-mediated and that administration of Rapamycin, a specific mTOR inhibitor, resulted in in vivo rescue of normal levels of BMAL1. Accumulation of BMAL1 by deletion of PER2, a Period family gene, was also rescued upon in vivo administration of mTOR inhibitor. Notably, BMAL1 regulation requires mTOR regulatory protein Raptor and Rictor. These findings indicate that mTORC1 and mTORC2 complex plays a critical role in controlling BMAL1, establishing a connection between PI3K signaling and the regulation of circadian rhythm, ultimately resulting in deregulated BMAL1 in tumor cells with disrupted PI3K signaling.
