Project description:Ell3 is a RNA polymerase II transcription elongation factor that is enriched in testis. The C-terminal domain of Ell3 shows strong similarities to that of Ell (eleven-nineteen lysine-rich leukemia gene), which acts as a negative regulator of p53 and regulates cell proliferation and survival. Recent studies in our laboratory showed that Ell3 induces the differentiation of mouse embryonic stem cells by protecting differentiating cells from apoptosis via the promotion of p53 degradation. In this study, we evaluated the function of Ell3 in breast cancer cell lines. MCF7 cell lines overexpressing Ell3 were used to examine cell proliferation and cancer stem cell properties. Ectopic expression of Ell3 in breast cancer cell lines induces proliferation and 5-FU resistance. In addition, Ell3 expression increases the cancer stem cell population, which is characterized by CD44 (+) or ALDH1 (+) cells. Mammosphere-forming potential and migration ability were also increased upon Ell3 expression in breast cancer cell lines. Through biochemical and molecular biological analyses, we showed that Ell3 regulates proliferation, cancer stem cell properties and drug resistance in breast cancer cell lines partly through the MEK-extracellular signal-regulated kinase signaling pathway. Murine xenograft experiments showed that Ell3 expression promotes tumorigenesis in vivo. The transcription elongation factor Ell3 induces chemosensitization of MCF7 cells to the chemotherapeutic agent cis-diamminedichloroplatinum (II) (CDDP) by stabilizing p53. Interestingly, Ell3 induced p53 stabilization in response to CDDP by promoting binding of p53 to NADH quinoneoxidoreductase 1 (NQO1), which is linked to an ubiquitin-independent degradation pathway, as well as by suppressing a MDM2 mediated ubiquitin-dependent degradation pathway. Furthermore, Ell3 enhanced interleukin-20 (IL-20) expression leading to the activation of the ERK1/2 signaling pathway. By analyzing the suppressive effects of IL-20 and ERK signaling in the Ell3 expressing MCF7 cells, we confirmed that the IL-20 mediated ERK1/2 signaling pathway is the main cause of p53 stabilization after CDDP exposure in MCF7 cells. Ell3-overexpressing breast cancer cell lines were established using the chromosomal integration of an Ell3 expression plasmid, which was constructed by cloning PCR-amplified Ell3 cDNA into pcDNA3.1 vectors (Invitrogen, Carlsbad, CA; https://www.lifetechnologies.com). Three independent Ell3 overexpressing cell lines were generated. The gene expression profiles of wild type MCF7 and Ell3 overexpressing cell line were compared using Affymetrix PrimeView arrays.

Project description:Ell3 is a RNA polymerase II transcription elongation factor that is enriched in testis. The C-terminal domain of Ell3 shows strong similarities to that of Ell (eleven-nineteen lysine-rich leukemia gene), which acts as a negative regulator of p53 and regulates cell proliferation and survival. Recent studies in our laboratory showed that Ell3 induces the differentiation of mouse embryonic stem cells by protecting differentiating cells from apoptosis via the promotion of p53 degradation. In this study, we evaluated the function of Ell3 in breast cancer cell lines. MCF7 cell lines overexpressing Ell3 were used to examine cell proliferation and cancer stem cell properties. Ectopic expression of Ell3 in breast cancer cell lines induces proliferation and 5-FU resistance. In addition, Ell3 expression increases the cancer stem cell population, which is characterized by CD44 (+) or ALDH1 (+) cells. Mammosphere-forming potential and migration ability were also increased upon Ell3 expression in breast cancer cell lines. Through biochemical and molecular biological analyses, we showed that Ell3 regulates proliferation, cancer stem cell properties and drug resistance in breast cancer cell lines partly through the MEK-extracellular signal-regulated kinase signaling pathway. Murine xenograft experiments showed that Ell3 expression promotes tumorigenesis in vivo. The transcription elongation factor Ell3 induces chemosensitization of MCF7 cells to the chemotherapeutic agent cis-diamminedichloroplatinum (II) (CDDP) by stabilizing p53. Interestingly, Ell3 induced p53 stabilization in response to CDDP by promoting binding of p53 to NADH quinoneoxidoreductase 1 (NQO1), which is linked to an ubiquitin-independent degradation pathway, as well as by suppressing a MDM2 mediated ubiquitin-dependent degradation pathway. Furthermore, Ell3 enhanced interleukin-20 (IL-20) expression leading to the activation of the ERK1/2 signaling pathway. By analyzing the suppressive effects of IL-20 and ERK signaling in the Ell3 expressing MCF7 cells, we confirmed that the IL-20 mediated ERK1/2 signaling pathway is the main cause of p53 stabilization after CDDP exposure in MCF7 cells.

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Homo sapiens

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