Aquaporin 3 (AQP3) and phospholipase D2 (PLD2) are abnormally expressed and/or localized in squamous cell carcinoma (SCC). AQP3 transports glycerol to PLD2 for the synthesis of lipid second messenger, which can mediate the effect of the AQP3/PLD2 signaling module in the regulation of keratinocyte proliferation and differentiation. However, the role of the AQP3/PLD2 signaling module in the pathogenesis of SCC remains to be fully elucidated. In the present study, the expression levels of AQP3 and PLD2 in tissue samples were examined using immunohistochemistry, it was found that the expression levels of AQP3 and PLD2 in tissue samples of actinic keratosis (AK), Bowen's disease (BD) and SCC were significantly increased. AQP3 small interfering RNA (siRNA) and PLD2 siRNA were constructed and used for transfection into the human A431 SCC cell line, and their anticancer effect on SCC was examined. The mRNA expression and protein expression levels of AQP3 and PLD2 were significantly downregulated following siRNA transfection. AQP3 siRNA and PLD2 siRNA inhibited the proliferation and promoted the apoptosis of A431 cells. Taken together, the findings of the present study suggested that increased levels of AQP3 and PLD2 were correlated with tumor progression and development in SCC. AQP3 siRNA and PLD2 siRNA significantly downregulated the mRNA and protein levels of AQP3 and PLD2 in the A431 cells; inhibiting proliferation and promoting apoptosis in vitro. The concomitant effects of AQP3/PLD2 signaling by inhibiting the expression of siRNA may be important for the treatment of SCC in the future.
Our previous study demonstrated that ultraviolet radiation upregulated Toll-like receptor 2 and Toll-like receptor 4 expression in Langerhans cells. Ultraviolet radiation also upregulated mitogen-activated protein kinases and nuclear factor-κB/p65 expression via Toll-like receptor 2 and Toll-like receptor 4, and upregulated interferon regulatory factor-3 expression partially via Toll-like receptor 4. So we conclude that ultraviolet radiation can directly or indirectly activate keratinocytes to induce endogenous ligands which stimulate Toll-like receptor 2- or Toll-like receptor 4-dependent signaling cascade in Langerhans cells, sequentially influence innate and adaptive immune responses.
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