LIM domain only 2 induces glioma invasion via cytosolic p27KIP1

SLUG and Truncated TAL1 Reduce Glioblastoma Stem Cell Growth Downstream of Notch1 and Define Distinct Vascular Subpopulations in Glioblastoma Multiforme

Simple Summary

Glioblastoma multiforme is the most aggressive form of brain tumor and is still incurable. These neoplasms are particularly difficult to treat efficiently because of their highly heterogeneous and resistant characteristics. Advances in genomics have highlighted the complex molecular landscape of these tumors and the need to further develop effective and targeted therapies for each patient. A specific population of cells with enriched stem cell properties within tumors, i.e., glioblastoma stem cells (GSC), drives this cellular heterogeneity and therapeutical resistance, and thus constitutes an attractive target for the design of innovative treatments. However, the signals driving the maintenance and resistance of these cells are still unclear. We provide new findings regarding the expression of two transcription factors in these cells and directly in glioblastoma patient samples. We show that these proteins downregulate GSC growth and ultimately participate in the progression of gliomas. The forthcoming results will contribute to a better understanding of gliomagenesis.

Abstract

Glioblastomas (GBM) are high-grade brain tumors, containing cells with distinct phenotypes and tumorigenic potentials, notably aggressive and treatment-resistant multipotent glioblastoma stem cells (GSC). The molecular mechanisms controlling GSC plasticity and growth have only partly been elucidated. Contact with endothelial cells and the Notch1 pathway control GSC proliferation and fate. We used three GSC cultures and glioma resections to examine the expression, regulation, and role of two transcription factors, SLUG (SNAI2) and TAL1 (SCL), involved in epithelial to mesenchymal transition (EMT), hematopoiesis, vascular identity, and treatment resistance in various cancers. In vitro, SLUG and a truncated isoform of TAL1 (TAL1-PP22) were strongly upregulated upon Notch1 activation in GSC, together with LMO2, a known cofactor of TAL1, which formed a complex with truncated TAL1. SLUG was also upregulated by TGF-β1 treatment and by co-culture with endothelial cells. In patient samples, the full-length isoform TAL1-PP42 was expressed in all glioma grades. In contrast, SLUG and truncated TAL1 were preferentially overexpressed in GBMs. SLUG and TAL1 are expressed in the tumor microenvironment by perivascular and endothelial cells, respectively, and to a minor extent, by a fraction of epidermal growth factor receptor (EGFR) -amplified GBM cells. Mechanistically, both SLUG and truncated TAL1 reduced GSC growth after their respective overexpression. Collectively, this study provides new evidence for the role of SLUG and TAL1 in regulating GSC plasticity and growth.

LMO2 upregulation due to AR deactivation in cancer-associated fibroblasts induces non-cell-autonomous growth of prostate cancer after androgen deprivation

The androgen receptor (AR) is expressed in prostate fibroblasts in addition to normal prostate epithelial cells and prostate cancer (PCa) cells. Moreover, AR activation in fibroblasts dramatically influences prostate cancer (PCa) cell behavior. Androgen deprivation leads to deregulation of AR downstream target genes in both fibroblasts and PCa cells. Here, we identified LIM domain only 2 (LMO2) as an AR target gene in prostate fibroblasts using ChIP-seq and revealed that LMO2 can be repressed directly by AR through binding to androgen response elements (AREs), which results in LMO2 overexpression after AR deactivation due to normal prostate fibroblasts to cancer-associated fibroblasts (CAFs) transformation or androgen deprivation therapy. Next, we investigated the mechanisms of LMO2 overexpression in fibroblasts and the role of this event in non-cell-autonomous promotion of PCa cells growth in the androgen-independent manner through paracrine release of IL-11 and FGF-9. Collectively, our data suggest that AR deactivation deregulates LMO2 expression in prostate fibroblasts, which induces castration resistance in PCa cells non-cell-autonomously through IL-11 and FGF-9.

LIM domain only 2 over-expression in prostate stromal cells facilitates prostate cancer progression through paracrine of Interleukin-11

Mechanisms of stromal-epithelial crosstalk are essential for Prostate cancer (PCa) tumorigenesis and progression. Peripheral zone of the prostate gland possesses a stronger inclination for PCa than transition zone. We previously found a variety of genes that differently expressed among different prostate stromal cells, including LIM domain only 2 (LMO2) which highly expressed in peripheral zone derived stromal cells (PZSCs) and PCa associated fibroblasts (CAFs) compared to transition zone derived stromal cells (TZSCs). Studies on its role in tumors have highlighted LMO2 as an oncogene. Herein, we aim to study the potential mechanisms of stromal LMO2 in promoting PCa progression. The in vitro cells co-culture and in vivo cells recombination revealed that LMO2 over-expressed prostate stromal cells could promote the proliferation and invasiveness of either prostate epithelial or cancer cells. Further protein array screening confirmed that stromal LMO2 stimulated the secretion of Interleukin-11 (IL-11), which could promote proliferation and invasiveness of PCa cells via IL-11 receptor α (IL11Rα) – STAT3 signaling. Moreover, stromal LMO2 over-expression could suppress miR-204-5p which was proven to be a negative regulator of IL-11 expression. Taken together, results of our study demonstrate that prostate stromal LMO2 is capable of stimulating IL-11 secretion and by which activates IL11Rα – STAT3 signaling in PCa cells and then facilitates PCa progression. These results may make stromal LMO2 responsible for zonal characteristic of PCa and as a target for PCa microenvironment-targeted therapy.