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We found that cells expressDLX2, but neitherDLX5norDLX6(Physique1). The expression ofDLX2andDLX5was evaluated in 408 primary human breast cancers examining theGSE1456andGSE3494microarray datasets. Kaplan-Meier estimates for disease-free survival were calculated for the patients grouped on OBSCN the basis ofDLX2/DLX5expression. == Results == Before injection, or after subcutaneous growth, MDA-MB-231 cells expressedDLX2but neitherDLX5norDLX6. Instead, in bone and lung metastases resulting from intravenous injection we detected expression ofDLX5/6but not ofDLX2, suggesting thatDLX5/6are activated during metastasis formation, and that their expression is alternative to that ofDLX2. Thein vitrotreatment of MDA-MB-231 cells with ET1, resulted in switch fromDLX2toDLX5expression. By data mining in microarray datasets we found that expression ofDLX2occurred in 21.6% of patients, and was significantly correlated with prolonged disease-free survival and reduced incidence of relapse. Instead,DLX5was expressed in a small subset of cases, 2.2% of total, displaying reduced disease-free survival and high incidence of relapse which was, however, nonsignificantly different from the other groups due to the small size of theDLX+cohort. In all cases, we found mutually exclusive expression ofDLX2andDLX5. == Conclusions == Our studies indicate thatDLXgenes are involved in human breast cancer progression, and thatDLX2andDLX5genes might serve as prognostic markers. == Background == The abnormal expression of homeobox genes in many solid tumors and hematological malignancies [1,2] has reinforced the notion that these key regulators of embryogenesis can also play a role in neoplastic processes.DLXgenes, the vertebrate homologues ofDrosophila distal-less (dll), constitute a family of homeobox transcription factors involved in control of cell differentiation and morphogenesis. The mouse and humanDLXgene system is formed by three bi-gene clusters:DLX1 andDLX2;DLX5 andDLX6;DLX3 andDLX4. AllDLXgenes are expressed by embryonic stem cells and play a role in the control Dihydromyricetin (Ampeloptin) of craniofacial embryogenesis [3], of neurogenesis [4], and of formation of the distal regions of extending Dihydromyricetin (Ampeloptin) appendages [5]. Furthermore,DLX5andDLX6are expressed in all developing bones and control osteoblastogenesis and osteoblast/osteoclast coupling AlthoughDLXgenes are expressed in several adult tissues, including bone, brain and epithelia, little is known about their possible involvement in neoplastic process. We have previously exhibited [6,7] thatDlxgenes participate Dihydromyricetin (Ampeloptin) to the regulatory cascade initiated by acute lymphoblastic leukemia(ALL)-1gene, a grasp regulator gene whose disruption is usually implicated in human acute leukemias [8].DLXgenes respond differently to the t(4;11)(q21;q23) chromosomal abnormality: while the expression ofDLX2,DLX3, andDLX4 is virtually abrogated, that ofDLX5andDLX6is increased [8]. These data indicate that different members of theDLXgene family could play diverse roles in predisposing cells to leukemic transformation. Furthermore, evidences have been found onDLX5involvement in T-cell lymphomas both in mouse models and in humans [9]. In non-hematological malignancies most of the available information concernsDLX4.DLX4overexpression by ovarian cancer is strongly associated with high tumor grade and advanced disease stage [10]. This gene, when overexpressed in the breast cancer cell line MCF7, inhibits apoptosis [11]. However, recently published microarray Dihydromyricetin (Ampeloptin) studies exhibited the upregulation ofDLX5in several human solid tumors, suggesting that overexpression ofDLX5could contribute to tumor progression and represent a novel prognostic marker [12,13]. The analysis of factors involved inDlxgene regulation has evidenced thatEndothelin1(ET1) is usually directly involved in the activation ofDlx5andDlx6and inhibits the expression ofDlx2[14-16]. It is of note that ET1 expression has been directly associated to the invasive phenotype of breast tumor cells [17]. == Methods == == 2.1. Cell culture and ET1 treatment == MDA-MB-231 cells were obtained from Dr. Paola Manduca (Dipartimento di Oncologia, Biologia e Genetica, Universit di Genova, Italy). Cells were produced in DMEM supplemented with 10% Fetal Calf Serum (FCS), 1% glutamine and 1% penicillin/streptomycin (all from Biochrom Seromed, Berlin, Germany) at 37C in 5% CO2atmosphere. For ET1 treatment, adherent sub-confluent MDA-MB-231 cells were starved for 24 h in serum-free medium, trypsinized and centrifuged. Pellets were resuspended in serum-free medium either made up of or not 100.