Androgen-regulated microRNA-135a decreases prostate cancer cell migration and invasion through downregulating ROCK1 and ROCK2

Androgen signaling, via the androgen receptor (AR), is crucial in mediating prostate cancer (PCa) initiation and progression. Identifying new downstream effectors of the androgens/AR pathway will allow a better understanding of these mechanisms and could reveal novel biomarkers and/or therapeutic agents to improve the rate of patient survival. We compared the microRNA expression profiles in androgen-sensitive LNCaP cells stimulated or not with 1 nM R1881 by performing a high-throughput reverse transcriptase-quantitative PCR and found that miR-135a was upregulated. After androgen stimulation, we showed that AR directly activates the transcription of miR-135a2 gene by binding to an androgen response element in the promoter region. Our findings identify miR-135a as a novel effector in androgens/AR signaling. Using xenograft experiments in chick embryos and adult male mice, we showed that miR-135a overexpression decreases in vivo invasion abilities of prostate PC-3 cells. Through in vitro wound-healing migration and invasion assays, we demonstrated that this effect is mediated through downregulating ROCK1 and ROCK2 expression, two genes that we characterized as miR-135a direct target genes. In human surgical samples from prostatectomy, we observed that miR-135a expression was lower in tumoral compared with paired adjacent normal tissues, mainly in tumors classified with a high Gleason score (⩾8). Moreover, miR-135a expression is lower in invasive tumors, showing extraprostatic extension, as compared with intraprostatic localized tumors. In tumor relative to normal glands, we also showed a more frequently higher ROCK1 protein expression determined using a semi-quantitative immunohistochemistry analysis. Therefore, in tumor cells, the lower miR-135a expression could lead to a higher ROCK1 protein expression, which could explain their invasion abilities. The highlighted relationship between miR-135a expression level and the degree of disease aggressiveness suggests that miR-135a may be considered as a prognostic marker in human PCa.

Thyroid hormone signaling is highly heterogeneous during pre- and postnatal brain development

We have generated transgenic reporter mice to analyze the spatio-temporal distribution of thyroid hormone signaling during mouse brain development. The reporter system, utilizing a chimeric yeast Gal4 DNA-binding domain-thyroid hormone alpha ligand-binding domain fusion protein to drive lacZ expression, revealed that thyroid hormone signaling starts in the midbrain roof several days before the onset of thyroid gland function, and that it remains highly heterogeneous in the central nervous system throughout pre- and postnatal development. We speculate that this heterogeneity might provide neural cells with positional information during development.

HEMCAM/CD146 downregulates cell surface expression of (β)1 integrins

HEMCAM/gicerin, an immunoglobulin superfamily protein, is involved in homophilic and heterophilic adhesion. It interacts with NOF (neurite outgrowth factor), a molecule of the laminin family. Alternative splicing leads to mRNAs coding for HEMCAM with a short (HEMCAM-s) or a long cytoplasmic tail (HEMCAM-l). To investigate the cellular function of these two variants, we stably transfected murine fibroblasts with either form of HEMCAM. Expression of each isoform of this protein in L cells delayed proliferation and modified their adhesion properties to purified extracellular matrix proteins. Expression of either HEMCAM-s or HEMCAM-l inhibited integrin-dependent adhesion and spreading of fibroblasts to laminin 1, showing that this phenomenon did not depend on the cytoplasmic region. By contrast, L-cell adhesion and spreading to fibronectin depended on the HEMCAM isoform expressed. Flow cytometry and immunoprecipitation studies revealed that the expression of HEMCAM downregulated expression of the laminin-binding integrins (α)3 (β)1, (α)6 (β)1 and (α)7 (β)1, and fibronectin receptor (α)5 (β)1 from the cell surface. Semi-quantitative PCR and northern blot experiments showed that the expression of (α)6 (β)1 integrin modified by HEMCAM occurred at a translation or maturation level. Thus, our data demonstrate that HEMCAM regulates fibroblast adhesion by controlling (β)1 integrin expression. http://www.biologists.com/JCS/movies/jcs1886.html

Quantification of T-cell progenitors during ontogeny: thymus colonization depends on blood delivery of progenitors

An in vivo thymus reconstitution assay based on intrathymic injection of hematopoietic progenitors into irradiated chicks was used to determine the number of T-cell progenitors in peripheral blood, paraaortic foci, bone marrow (BM), and spleen during ontogeny. This study allowed us to analyze the regulation of thymus colonization occurring in three waves during embryogenesis. It confirmed that progenitors of the first wave of thymus colonization originate from the paraaortic foci, whereas progenitors of the second and the third waves originate from the BM. The analysis of the number of T-cell progenitors indicates that each wave of thymus colonization is correlated with a peak number of T-cell progenitors in peripheral blood, whereas they are almost absent during the periods defined as refractory for colonization. Moreover, injection of T-cell progenitors into the blood circulation showed that they homed into the thymus without delay during the refractory periods. Thus, thymus colonization kinetics depend mainly on the blood delivery of T-cell progenitors during embryogenesis.

Renewal of thymocyte progenitors and emigration of thymocytes during avian development

The avian thymus is colonized by three waves of hemopoietic progenitors during embryogenesis. An in vivo thymus reconstitution assay based on intrathymic injection of irradiated chicks showed that cells of para-aortic foci were able to differentiate into T lymphocytes, confirming their putative role in the first wave of thymus colonization. This assay was also used to detect and to characterize T cell progenitors from the bone marrow which are involved in the second and third wave of thymus colonization. In the bone marrow, progenitors that differentiated into T cells were found in a subpopulation that expressed the molecules HEMCAM, c-kit and c128. Engraftment of thymus lobes into thymectomized young chick recipients showed that T cell progenitors are replaced in the thymus by subsequent waves of progenitors after hatching. Finally, analysis of thymocyte differentiation suggested that gamma delta and alpha beta T cells migrate from the thymus to the periphery in alternating waves.

Use of retroviral vectors to introduce and express the beta-galactosidase marker gene in cultured chicken primordial germ cells

Three methods of isolating primordial germ cells (PGCs) from gonads of 5-day-old chick embryos were compared. PGCs were then cultured in vitro in DMEM/F12 medium containing 10% fetal calf serum. BrdU incorporation showed that at least 10% of the PGC population were dividing, under our culture conditions, during the 2nd day of in vitro culture. During this culture period, PGCs were exposed to avian leukosis sarcoma virus-based retroviral vector pseudotyped with subgroup A envelope, carrying the LacZ reporter gene. X-Gal staining showed that PGCs were permissive to infection, with more than 50% of PGCs expressing the beta-Gal protein. These data represent the first demonstration that PGCs, isolated from gonads of 5-day-old chick embryos, are able to divide in vitro and that it is possible to introduce and express exogenous DNA in chick PGCs maintained in vitro.

[Variations in the testicular response to HCG during the perinatal period in the rat: influence of estrogens]

The variations of the testicular responsiveness to hCG and the implication of the maternal estrogens in the functioning of the testes were studied in the perinatal male rat. Male rat fetuses treated with hCG at the end of gestation failed to show an increase in serum testosterone (T). The lack of testicular responsiveness to hCG in the fetus is neither due to anesthesia nor to a blocking effect of estrogens directly on the testes. On the other hand, hCG injected either at 4 h or at 48 h after birth increases serum T. The administration of 5 micrograms of estradiol 17 beta (E2) to the newborn male rat at the time of birth blocks the expression of the postpartum testosterone surge. The fall in the plasma estrogens and the increase of the testicular sensitivity to gonadotropic stimulation at the time of birth are factors which are very likely implicated in the determinism of the neonatal testicular hyperactivity.