miR-21 microRNA acts as an oncogene promoting cell transformation.

<p>Time evolution of NF-κB, Lin28, Let-7, IL6 and STAT3 is shown in the presence of an overexpression of miR-21 (panel A for t>100 h), and in the presence of an overexpression of miR-21 together with an inhibition of Lin28 (panel B for t>100 h). For t<100 h, normal condition, non-transformed state of the cell characterized by a high level of Let-7 and low levels of Lin28, NF-κB, IL6 and STAT3. (A) The overexpression of miR-21, <i>V</i>_SMIR21 = 4000, triggers cell transformation. (B) The same overexpression of miR-21 does not trigger cell transformation if Lin28 is inhibited, <i>V</i>_SLIN28 = 0.008 instead of 0.012. Other parameter values are as in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003455#pcbi-1003455-g003" target="_blank">Fig. 3</a> with <i>V</i>_SLET7 = 3, <i>V</i>_SMPTEN = 0.1, <i>Src</i> = 0.00001.