(A) Northern analysis of primary human corneal epithelial (HCEKs) cells using specific probes for miR-184 and miR-205, showing expression of both of these miRNAs in untreated and control (Ir-antagomir) cells

(A) Northern analysis of primary human corneal epithelial (HCEKs) cells using specific probes for miR-184 and miR-205, showing expression of both of these miRNAs in untreated and control (Ir-antagomir) cells. associated with a marked increase in keratinocyte apoptosis and cell death. Aggressive squamous cell carcinoma (SCC) cells exhibited elevated levels of miR-205. This was associated with a concomitant reduction in SHIP2 levels. Partial knockdown of endogenous miR-205 in SCCs markedly decreased phosphorylated Akt and phosphorylated BAD levels and increased apoptosis. We were able to increase SHIP2 levels in SCC cells after inhibition of miR-205. Therefore, miR-205 might have diagnostic value in determining the aggressivity of SCCs. Blockage of miR-205 activity with an antagomir or via ectopic expression of miR-184 could be novel therapeutic methods for treating aggressive SCCs. MicroRNAs (miRNAs) are small, 20- to 24-nucleotide, noncoding RNAs found in diverse organisms. In animals, most miRNAs mediate posttranscriptional silencing by binding with partial complementarity to the 3 UTR of the target mRNA (1,2). These endogenous, silencing RNAs have been shown to play important roles in development and differentiation (36), cellular stress responses (7), and malignancy (811). The role of miRNAs in stratified squamous epithelia remains poorly comprehended. Inactivation of Dicer in mouse skin caused hair follicles to evaginate into the epidermis rather than invaginating downward, E6446 HCl thus forming cyst-like structures (12,13). These results underscore the importance of miRNAs in the regulation of epidermal and follicular development. miRNAs have also been extensively profiled in the corneal epithelium and show expression patterns that are regionally restricted (14). For example, miR-184 was the most abundant miRNA in the corneal epithelium; however, it was conspicuously absent from your limbal epithelium, an area enriched in corneal epithelial stem cells (1518). In contrast, miR-205 is E6446 HCl usually broadly expressed throughout all viable cell layers in nearly all stratified squamous epithelia including the corneal, limbal, and conjunctival epithelia of the eye (12,14). Thus, the corneal epithelium is unique in that it exhibits distinct as well as overlapping expression of miR-184 and miR-205 (14). miRNAs have been predicted to regulate thousands of mammalian genes (19); however, few targets have been experimentally validated for the great majority of these miRNAs. With the exception of a recent demonstration that a p63-related family member is negatively regulated by miR-203 (20), little is known about stratified squamous epithelial miRNA targets. We statement that miR-205 represses SH2-made up of phosphoinositide 5-phosphatase 2 (SHIP2). Our finding that miR-184 negatively modulates the activity of miR-205 to maintain SHIP2 levels is the first demonstration that a miRNA can interfere with another to ensure the expression of a target protein. We show (i) that SHIP2 levels can Edg3 be modulated in a variety of epithelial cells using gain- and loss-of-function experiments with miR-184 and miR-205 and (ii) that manipulating SHIP2 levels through miRNAs diminishes Akt signaling leading to decreased keratinocyte survival. Finally, we find a reciprocal relationship between miR-205 and SHIP2 expression in squamous cell carcinoma (SCC) cell lines and suggest that miR-205 may be viewed as a tumor promoter in the context of SCCs. == Results == == miR-205 Targets SHIP2. == We found miR-205 in all squamous epithelium that we examined (14). We also reported that miR-184 and miR-205 are the most abundant miRNAs in corneal epithelium and that miR-184 expression was restricted to the corneal epithelium (14). Bioinformatic analysis suggested that, in humans, the SHIP2 (Inppl1) 3 UTR is usually a putative target of both miR-184 and miR-205 (21) and is the only gene with overlapping binding sites to these two miRNAs. To test this prediction (Fig. 1A) we cotransfected HeLa cells with a miR-184 or miR-205 mimic and luciferase reporter constructs transporting the entire 3 UTR of SHIP2 mRNA (Fig. 1B). In cells treated with a miR-205 mimic, we found a marked reduction (50%) in luciferase activity [Fig. 1CandDandsupporting information (SI) Fig. S1B]; however, no reduction in luciferase activity was seen in transfectants expressing miR-184 (Fig. S1AandFig. 1D), suggesting that miR-184 does not inhibit SHIP2. To E6446 HCl confirm this result, we mutated the miR-205 binding site on SHIP2 3 UTR (Fig. 1B, SHIP2_mut1). The mutation prevented miR-205 from interfering with luciferase activity, indicating that the 3 UTR of SHIP2 is indeed a target of miR-205 (Fig. 1C). == Fig. 1. == miR-205 targets SHIP2 at 3 UTR and can be regulated by miR-184. (A) Sequence of the miR-205 and miR-184 binding sites within the human SHIP2 (INPPL1) 3 UTR. E6446 HCl Red nucleotides are overlapping binding sites. Shaded areas represent conserved complementary nucleotides of miR-184 and miR-205 seed sequences in various mammals (H.s, human; M.m, mouse; R.n, rat; C.f, chicken). (B) Schematic of the reporter constructs showing entire.