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Preeclampsia (PE) remains a leading cause of maternal and perinatal mortality and morbidity worldwide. Its pathogenesis has not been fully elucidated and no causal therapy is currently available. It is of clinical relevance to decipher novel molecular biomarkers. RITA (RBP-J (recombination signal binding protein J)-interacting and tubulin-associated protein) has been identified as a negative modulator of the Notch pathway and as a microtubule-associated protein important for cell migration and invasion. In the present work, we have systematically studied RITA’s expression in primary placental tissues from patients with early- and late-onset PE as well as in various trophoblastic cell lines. RITA is expressed in primary placental tissues throughout gestation, especially in proliferative villous cytotrophoblasts, in the terminally differentiated syncytiotrophoblast, and in migrating extravillous trophoblasts. RITA’s messenger RNA (mRNA) level is decreased in primary tissue samples from early-onset PE patients. The deficiency of RITA impairs the motility and invasion capacity of trophoblastic cell lines, and compromises the fusion ability of trophoblast-derived choriocarcinoma cells. These data suggest that RITA may play important roles in the development of the placenta and possibly in the pathogenesis of PE.
Adaptation of wild-type p53 expressing UKF-NB-3 cancer cells to the murine double minute 2 inhibitor nutlin-3 causes de novo p53 mutations at high frequency (13/20) and multi-drug resistance. Here, we show that the same cells respond very differently when adapted to RITA, a drug that, like nutlin-3, also disrupts the p53/Mdm2 interaction. All of the 11 UKF-NB-3 sub-lines adapted to RITA that we established retained functional wild-type p53 although RITA induced a substantial p53 response. Moreover, all RITA-adapted cell lines remained sensitive to nutlin-3, whereas only five out of 10 nutlin-3-adapted cell lines retained their sensitivity to RITA. In addition, repeated adaptation of the RITA-adapted sub-line UKF-NB-3rRITA10 μM to nutlin-3 resulted in p53 mutations. The RITA-adapted UKF-NB-3 sub-lines displayed no or less pronounced resistance to vincristine, cisplatin, and irradiation than nutlin-3-adapted UKF-NB-3 sub-lines. Furthermore, adaptation to RITA was associated with fewer changes at the expression level of antiapoptotic factors than observed with adaptation to nutlin-3. Transcriptomic analyses indicated the RITA-adapted sub-lines to be more similar at the gene expression level to the parental UKF-NB-3 cells than nutlin-3-adapted UKF-NB-3 sub-lines, which correlates with the observed chemotherapy and irradiation sensitivity phenotypes. In conclusion, RITA-adapted cells retain functional p53, remain sensitive to nutlin-3, and display a less pronounced resistance phenotype than nutlin-3-adapted cells.
RITA, the RBP‐J interacting and tubulin‐associated protein, has been reported to be related to tumor development, but the underlying mechanisms are not understood. Since RITA interacts with tubulin and coats microtubules of the cytoskeleton, we hypothesized that it is involved in cell motility. We show here that depletion of RITA reduces cell migration and invasion of diverse cancer cell lines and mouse embryonic fibroblasts. Cells depleted of RITA display stable focal adhesions (FA) with elevated active integrin, phosphorylated focal adhesion kinase, and paxillin. This is accompanied by enlarged size and disturbed turnover of FA. These cells also demonstrate increased polymerized tubulin. Interestingly, RITA is precipitated with the lipoma‐preferred partner (LPP), which is critical in actin cytoskeleton remodeling and cell migration. Suppression of RITA results in reduced LPP and α‐actinin at FA leading to compromised focal adhesion turnover and actin dynamics. This study identifies RITA as a novel crucial player in cell migration and invasion by affecting the turnover of FA through its interference with the dynamics of actin filaments and microtubules. Its deregulation may contribute to malignant progression.