K13 induces CCL20 expression in HUVEC and PEL cell lines. (A) HUVECs stably expressing a control vector or K13-ER^TAM were mock-treated or treated with 4-OHT (50 nM) for 48 hours after which RNA was extracted and used for quantitative RT-PCR. The results of the quantitative RT-PCR analysis were confirmed by agarose gel electrophoresis (bottom panel). (B) Supernatants from cells treated in panel A were used for the measurement of CCL20 protein by ELISA. (C) Quantitative RT-PCR analysis showing increased expression of CCL20 mRNA in BCBL-1 and K562 cells stably transduced with a Flag-K13–expressing retroviral vector (top panel). The expression of Flag-tagged K13 in cell lysates was confirmed by immunoblotting (bottom panel). (D) Quantitative RT-PCR analyses showing down-regulation of K13 and CCL20 mRNAs in BCBL-1 cells infected with a K13 shRNA-expressing lentiviral vector compared with cells infected with a control shRNA vector.