Liver X receptors (LXRs) contribute not only to maintain cholesterol homeostasis but also to control cell growth. However, the molecular mechanisms behind the LXR-mediated anti-proliferative effects are largely unknown. Here we show, by immunohistochemistry, that LXRα and LXRβ are differentially distributed in oral stratified squamous epithelia. By immunohistochemical and Western blot analyses, we also reveal that LXRα is abundantly expressed in human oral squamous cell carcinoma (HOSCC) tissues and cell lines. Cell counting, BrdU labeling and cell cycle assay indicated that LXR stimulation led to significant reduction of proliferation in HOSCC cells. Importantly, our study highlights, by using RNA interference, that the ATP-binding cassette transporter A1 (ABCA1)-accelerated cholesterol efflux is critical for the growth inhibitory action of LXRs in HOSCC cells. Moreover, we demonstrate that LXR activation reduces the growth of xenograft tumour of HOSCC cells in mice accompanied by the upregulation of ABCA1 expression and the decline of cholesterol levels in the tumour. These findings strongly suggested that targeting the LXR-regulated cholesterol transport, yielding in lowering intracellular cholesterol levels, could be a promising therapeutic option for certain types of cancers.

Background Tumors in the parapharyngeal space are rare, and preoperative diagnosis is difficult because of anatomical and histological complexity. Methods To evaluate the usefulness of preoperative diagnosis, we compared the classification of tumor localization in the prestyloid and retrostyloid compartments by imaging and preoperative cytological diagnosis by fine‐needle aspiration cytology with the postoperative histopathological diagnosis in 120 patients with tumors in the parapharyngeal space. Results Tumors were located in the prestyloid and retrostyloid compartments in 68 and 52 patients, respectively. The majority of histopathological diagnoses in the prestyloid and retrostyloid compartments were pleomorphic adenoma and schwannoma, respectively. All malignant tumors were in the prestyloid compartment. The preoperative cytological diagnostic rate for benign or malignant tumor was 95.2%, which was not inferior to that for other head and neck lesions. Conclusion Our results suggested that the preoperative classification of tumor localization and cytological diagnosis improved the accuracy of presumptive diagnosis.

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