Arginine methylation-dependent LSD1 stability promotes invasion and metastasis of breast cancer.

Histone lysine demethylase 1 (LSD1), the first identified histone demethylase, is overexpressed in multiple tumor types, including breast cancer. However, the mechanisms that cause LSD1 dysregulation in breast cancer remain largely unclear. Here, we report that protein arginine methyltransferase 4 (PRMT4 or CARM1) dimethylates LSD1 at R838, which promotes the binding of the deubiquitinase USP7, resulting in the deubiquitination and stabilization of LSD1. Moreover, CARM1- and USP7-dependent LSD1 stabilization plays a key role in repressing E-cadherin and activating vimentin transcription through promoter H3K4me2 and H3K9me2 demethylation, respectively, which promotes invasion and metastasis of breast cancer cells. Consistently, LSD1 arginine methylation levels correlate with tumor grade in human malignant breast carcinoma samples. Our findings unveil a unique mechanism controlling LSD1 stability by arginine methylation, also highlighting the role of the CARM1-USP7-LSD1 axis in breast cancer progression.

Phosphorylation of LSD1 at Ser112 is crucial for its function in induction of EMT and metastasis in breast cancer.

PURPOSE: LSD1 is overexpressed in various cancers including breast cancer, but its functional roles in tumourigenesis are not fully understood. This study aims at revealing the role of LSD1 in breast cancer development. In addition, it has been reported that phosphorylation of the Serine 112 residue of LSD1 by PKCα is crucial for its function in gene regulation. We also explored whether this phosphorylation affects LSD1's role in breast cancer development. METHODS: This study includes LSD1 IHC data generated with tissue microarrays of 163 cases of breast cancer samples and 72 normal tissues. In vitro, role of LSD1, LSD1 S112D mutant (a phosphorylation simulation) and LSD1 S112A mutant (an unphosphorylation simulation) in induction of EMT is evaluated. Mechanismly, we checked the role of LSD1 and its mutant on E-cadherin promoter histone modifications. We also investigated the role of LSD1 and its mutants in metastasis with a nude mice model. RESULTS: We found LSD1 is expressed at a higher level in breast cancer tissues compared with that in normal tissues, and LSD1 expression is closely linked to breast cancer metastasis. LSD1 potentiates EMT in breast epithelia cells by repressing E-cadherin expression through demethylating H3K4me at gene's promoter, during which phosphorylation of LSD1 Ser112 is crucial for its binding and demethylation activity. In vivo, knockdown of LSD1 impairs the metastatic ability of MDA-MB-231 breast cancer cells in nude mice. Ectopic overexpression of either LSD1 or LSD1 S112D mutant (a phosphorylation simulation) facilitates metastasis, whereas the LSD1 S112A mutant (an unphosphorylation simulation) fails to affect the metastasis. CONCLUSIONS: Data presented in this report indicate that LSD1 is able to induce EMT and to promote metastasis in breast cancer, and phosphorylation at LSD1 Ser112 is crucial for these functions.

SHON, a novel secreted protein, regulates epithelial-mesenchymal transition through transforming growth factor-ß signaling in human breast cancer cells.

The epithelial-mesenchymal transition (EMT) is one of the main mechanisms contributing to the onset of cancer metastasis, and has proven to be associated with breast cancer progression. SHON is a novel secreted hominoid-specific protein we have previously identified; it is specifically expressed in all human cancer cell lines tested and is oncogenic for human mammary carcinoma cells. Here, we show that ectopic overexpression of SHON in immortalized human mammary epithelial cells is sufficient for cells to acquire the mesenchymal traits, as well as the enhanced cell migration and invasion, along with the epithelial stem cell properties characterized by increased CD44(high) /CD24(low) subpopulation and mammosphere-forming ability. Moreover, we demonstrate that SHON positively activates the autocrine transforming growth factor-ß (TGF-ß) pathway to contribute to EMT, while SHON itself is induced by TGF-ß in mammary epithelial cells. These data are in favor of a SHON-TGFß-SHON-positive feedback loop that regulates EMT program in breast cancer progression. Finally, examination of the human clinic breast cancer specimens reveals that tumor cells may extracellularly release SHON protein to promote the cancerization of surrounding cells. Together, our findings define an important function of SHON in regulation of EMT via TGF-ß signaling, which is closely associated with the invasive subtypes of human breast cancer.

p53 Attenuates the oncogenic Ras-induced epithelial-mesenchymal transition in human mammary epithelial cells.

Inactivation of the tumor suppressor p53 and activation of the oncogene Ras are the two most pivotal events in tumor development. However, potential intersection between p53 and Ras activity during an EMT process, which plays a crucial role during malignant tumor progression, remains elusive. Here, we report that increased expression of wild type p53 suppressed H-Ras(V12)-induced EMT phenotypes and restrained stem cell properties, through downregulation of MEK-ERK signaling pathways. In vivo experiments showed that p53 was able to inhibit H-Ras(V12)-induced tumor growth of human mammary epithelial cells. This study elucidates a novel correlation between the tumor suppressor gene p53 and the oncogene Ras in regulating EMT program, and expands the knowledge about the function of p53 in EMT process.

Antisense transcription from lentiviral gene targeting linked to an integrated stress response in colorectal cancer cells.

Advances in gene therapy research have resulted in the successful development of new therapies for clinical use. Here, we explored a gene targeting approach to deplete ephrinB2 from colorectal cancer cells using an inducible lentiviral vector. EphrinB2, a transmembrane ephrin ligand, promotes colorectal cancer cell growth and viability and predicts poor patient survival when expressed at high levels in colorectal cancer tissues. We discovered that lentiviral vector integration and expression in the host DNA frequently drive divergent host gene transcription, generating antisense reads coupled with splicing events and generation of chimeric vector/host transcripts. Antisense transcription of host DNA was linked to development of an integrated stress response and cell death. Despite recent successes, off-target effects remain a concern in genetic medicine. Our results provide evidence that divergent gene transcription is a previously unrecognized off-target effect of lentiviral vector integration with built-in properties for regulation of gene expression.

Bone marrow niches in myelodysplastic syndromes.

Genetic and epigenetic lesions within hematopoietic cell populations drive diverse hematological malignancies. Myelodysplastic syndromes (MDS) are a group of myeloid neoplasms affecting the hematopoietic stem cells characterized by recurrent genetic abnormalities, myelodysplasia (a pathological definition of abnormal bone marrow structure), ineffective hematopoiesis resulting in blood cytopenia, and a propensity to evolve into acute myelogenous leukemia. Although there is evidence that the accumulation of a set of genetic mutations is an essential event in MDS, there is an increased appreciation of the contribution of specific microenvironments, niches, in the pathogenesis of MDS and response to treatment. In physiologic hematopoiesis, niches are critical functional units that maintain hematopoietic stem and progenitor cells and regulate their maturation into mature blood cells. In MDS and other hematological malignancies, altered bone marrow niches can promote the survival and expansion of mutant hematopoietic clones and provide a shield from therapy. In this review, we focus on our understanding of the composition and function of hematopoietic niches and their role in the evolution of myeloid malignancies, with an emphasis on MDS.

Targeting the SHP2 phosphatase promotes vascular damage and inhibition of tumor growth.

The tyrosine phosphatase SHP2 is oncogenic in cancers driven by receptor-tyrosine-kinases, and SHP2 inhibition reduces tumor growth. Here, we report that SHP2 is an essential promoter of endothelial cell survival and growth in the remodeling tumor vasculature. Using genetic and chemical approaches to inhibit SHP2 activity in endothelial cells, we show that SHP2 inhibits pro-apoptotic STAT3 and stimulates proliferative ERK1/2 signaling. Systemic SHP2 inhibition in mice bearing tumor types selected for SHP2-independent tumor cell growth promotes degeneration of the tumor vasculature and blood extravasation; reduces tumor vascularity and blood perfusion; and increases tumor necrosis. Reduction of tumor growth ensues, independent of SHP2 targeting in the tumor cells, blocking immune checkpoints, or recruiting macrophages. We also show that inhibiting the Angiopoietin/TIE2/AKT cascade magnifies the vascular and anti-tumor effects of SHP2 inhibition by blocking tumor endothelial AKT signaling, not a target of SHP2. Since the SHP2 and Ang2/TIE2 pathways are active in vascular endothelial cells of human melanoma and colon carcinoma, SHP2 inhibitors alone or with Ang2/TIE2 inhibitors hold promise to effectively target the tumor endothelium.

CDK5 is essential for TGF-ß1-induced epithelial-mesenchymal transition and breast cancer progression.

Epithelial-mesenchymal transition is a change of cellular plasticity critical for embryonic development and tumor metastasis. CDK5 is a proline-directed serine/threonine kinase playing important roles in cancer progression. Here we show that CDK5 is commonly overexpressed and significantly correlated with several poor prognostic parameters of breast cancer. We found that CDK5 participated in TGF-ß1-induced EMT. In MCF10A, TGF-ß1 upregulated the CDK5 and p35 expression, and CDK5 knockdown inhibited TGF-ß1-induced EMT. CDK5 overexpression also exhibited a potential synergy in promoting TGF-ß1-induced EMT. In mesenchymal breast cancer cells MDA-MB-231 and BT549, CDK5 knockdown suppressed cell motility and tumorigenesis. We further demonstrated that CDK5 modulated cancer cell migration and tumor formation by regulating the phosphorylation of FAK at Ser-732. Therefore, CDK5-FAK pathway, as a downstream step of TGF-ß1 signaling, is essential for EMT and motility in breast cancer cells. This study implicates the potential value of CDK5 as a molecular marker for breast cancer.

SOX4 induces epithelial-mesenchymal transition and contributes to breast cancer progression.

Epithelial-mesenchymal transition (EMT) is a developmental program, which is associated with breast cancer progression and metastasis. Here, we report that ectopic overexpression of SOX4 in immortalized human mammary epithelial cells is sufficient for acquisition of mesenchymal traits, enhanced cell migration, and invasion, along with epithelial stem cell properties defined by the presence of a CD44(high)/CD24(low) cell subpopulation. SOX4 positively regulated expression of known EMT inducers, also activating the TGF-ß pathway to contribute to EMT. SOX4 itself was induced by TGF-ß in mammary epithelial cells and was required for TGF-ß-induced EMT. Murine xenograft experiments showed that SOX4 cooperated with oncogenic Ras to promote tumorigenesis in vivo. Finally, in clinical specimens of human breast cancer, we found that SOX4 was abnormally overexpressed and correlated with the triple-negative breast cancer subtype (ER(-)/PR(-)/HER2(-)). Our findings define an important function for SOX4 in the progression of breast cancer by orchestrating EMT, and they implicate this gene product as a marker of poor prognosis in this disease.

SOX7 is involved in aspirin-mediated growth inhibition of human colorectal cancer cells.

AIM: To confirm the role of sex-determining region Y-box 7 (Sox7) in aspirin-mediated growth inhibition of COX-independent human colorectal cancer cells. METHODS: The cell survival percentage was examined by MTT (Moto-nuclear cell direc cytotoxicity) assay. SOX7 expression was assessed by using reverse transcription-polymerase chain reaction and Western blotting. SB203580 was used to inhibit the p38MAPK signal pathway. SOX7 promoter activity was detected by Luciferase reporter assay. RESULTS: SOX7 was upregulated by aspirin and was involved in aspirin-mediated growth inhibition of SW480 human colorectal cancer cells. The p38MAPK pathway played a role in aspirin-induced SOX7 expression, during which the AP1 transcription factors c-Jun and c-Fos upregulated SOX7 promoter activities. RESULTS: SOX7 is upregulated by aspirin and is involved in aspirin-mediated growth inhibition of human colorectal cancer SW480 cells.