Genes Frequently Coexpressed with Hoxc8 Provide Insight into the Discovery of Target Genes

Tipifarnib Reduces Extracellular Vesicles and Protects From Heart Failure

BACKGROUND

Heart failure (HF) is one of the leading causes of mortality worldwide. Extracellular vesicles, including small extracellular vesicles or exosomes, and their molecular cargo are known to modulate cell-to-cell communication during multiple cardiac diseases. However, the role of systemic extracellular vesicle biogenesis inhibition in HF models is not well documented and remains unclear.

METHODS

We investigated the role of circulating exosomes during cardiac dysfunction and remodeling in a mouse transverse aortic constriction (TAC) model of HF. Importantly, we investigate the efficacy of tipifarnib, a recently identified exosome biogenesis inhibitor that targets the critical proteins (Rab27a [Ras associated binding protein 27a], nSMase2 [neutral sphingomyelinase 2], and Alix [ALG-2-interacting protein X]) involved in exosome biogenesis for this mouse model of HF. In this study, 10-week-old male mice underwent TAC surgery were randomly assigned to groups with and without tipifarnib treatment (10 mg/kg 3 times/wk) and monitored for 8 weeks, and a comprehensive assessment was conducted through performed echocardiographic, histological, and biochemical studies.

RESULTS

TAC significantly elevated circulating plasma exosomes and markedly increased cardiac left ventricular dysfunction, cardiac hypertrophy, and fibrosis. Furthermore, injection of plasma exosomes from TAC mice induced left ventricular dysfunction and cardiomyocyte hypertrophy in uninjured mice without TAC. On the contrary, treatment of tipifarnib in TAC mice reduced circulating exosomes to baseline and remarkably improved left ventricular functions, hypertrophy, and fibrosis. Tipifarnib treatment also drastically altered the miRNA profile of circulating post-TAC exosomes, including miR 331-5p, which was highly downregulated both in TAC circulating exosomes and in TAC cardiac tissue. Mechanistically, miR 331-5p is crucial for inhibiting the fibroblast-to-myofibroblast transition by targeting HOXC8, a critical regulator of fibrosis. Tipifarnib treatment in TAC mice upregulated the expression of miR 331-5p that acts as a potent repressor for one of the fibrotic mechanisms mediated by HOXC8.

CONCLUSIONS

Our study underscores the pathological role of exosomes in HF and fibrosis in response to pressure overload. Tipifarnib-mediated inhibition of exosome biogenesis and cargo sorting may serve as a viable strategy to prevent progressive cardiac remodeling in HF.

HOXC8/TGF-β1 positive feedback loop promotes liver fibrosis and hepatic stellate cell activation via activating Smad2/Smad3 signaling

Liver fibrosis occurs in any chronic liver disease, where extraordinary increase of extracellular matrix components is caused by the hepatic stellate cell (HSC) activation. HOXC8 has been disclosed to participate inregulating cell proliferation and fibrosis in tumors. However, the role of HOXC8 in liver fibrosis and the underlying molecular mechanisms has not yet been investigated. In this study, we founded that HOXC8 mRNA and protein was elevated in a carbon tetrachloride (CCl₄)-induced liver fibrosis mouse model and transforming growth factor-β (TGF-β)-treated human (LX-2) HSC cells. Importantly, we observed that downregulating HOXC8 alleviates liver fibrosis and suppressed the fibrogenic gene induction induced by CCl₄ in vivo. In addition, inhibition of HOXC8 suppressed the HSC activation and the expression of fibrosis-associated genes (α-SMA and COL1a1) induced by TGF-β1 in LX-2 cells in vitro, while HOXC8 overexpression had the opposite effects. Mechanistically, we demonstrated HOXC8 activates TGFβ1 transcription and enhanced the phosphorylated Smad2/Smad3 levels, suggesting a positive feedback loop between HOXC8 and TGF-β1 that facilitates TGF-β signaling and subsequent HSCs activation. Collectively, our data strongly indicated that a HOXC8/TGF-β1 positive feedback loop plays as a critical role in controlling the HSC activation and in the liver fibrosis process, suggesting that inhibition of HOXC8 may serve as a promoting therapeutic strategy for diseases characterized by liver fibrosis.

Dual Role of the PTPN13 Tyrosine Phosphatase in Cancer

In this review article, we present the current knowledge on PTPN13, a class I non-receptor protein tyrosine phosphatase identified in 1994. We focus particularly on its role in cancer, where PTPN13 acts as an oncogenic protein and also a tumor suppressor. To try to understand these apparent contradictory functions, we discuss PTPN13 implication in the FAS and oncogenic tyrosine kinase signaling pathways and in the associated biological activities, as well as its post-transcriptional and epigenetic regulation. Then, we describe PTPN13 clinical significance as a prognostic marker in different cancer types and its impact on anti-cancer treatment sensitivity. Finally, we present future research axes following recent findings on its role in cell junction regulation that implicate PTPN13 in cell death and cell migration, two major hallmarks of tumor formation and progression.

Homeobox C8 inhibited the osteo-/dentinogenic differentiation and migration ability of stem cells of the apical papilla via activating KDM1A

Enhancing the functions of mesenchymal stem cells (MSCs) is considered a potential approach for promoting tissue regeneration. In the present study, we investigate the role of HOXC8 in regulating differentiation and migration by using stem cells of the apical papilla (SCAPs). Our results showed that overexpression of HOXC8 suppressed the osteo-/dentinogenic differentiation, as detected by measuring alkaline phosphatase activity, in vitro mineralization, and the expressions of dentin sialophosphoprotein, dentin matrix acidic phosphoprotein 1, bone sialoprotein, runt-related transcription factor 2, and osterix in SCAPs, and inhibited in vivo osteo-/dentinogenesis of SCAPs. In addition, knockdown of HOXC8 promoted the osteo-/dentinogenic differentiation potentials of SCAPs. Mechanically, HOXC8 enhanced KDM1A transcription by directly binding to its promoter. HOXC8 and KDM1A also inhibited the migration and chemotaxis abilities of SCAPs. To sum up, HOXC8 negatively regulated the osteo-/dentinogenic differentiation and migration abilities of SCAPs by directly enhancing KDM1A transcription and indicated that HOXC8 and KDM1A could serve as potential targets for enhancing dental MSC mediated tissue regeneration.

HOXC8: a predictive glioma biomarker that induces epithelia-mesenchymal transition

BACKGROUND

The transcription factor Homeobox C8 (HOXC8) is overexpressed and regulates many important genes involved in the proliferation and invasion of many malignant tumors. However, the function of HOXC8 in gliomas remains unclear.

METHOD

Based on the Chinese Glioma Genome Atlas (CGGA) set, HOXC8 expression is negatively correlated with overall survival (OS). Small interfering RNA (si-HOXC8) was used to downregulate the mRNA and protein expression levels of HOXC8 to assess glioma cell proliferation, migration and invasion.

RESULTS

Patients with higher HOXC8 levels showed poorer prognosis. DAVID analysis results indicated that HOXC8 was related to cell cycle, cell adhesion and immune response. In U251 and LN229 glioma cells treated with small interfering RNA for HOXC8 (si-HOXC8) for gene knockdown, significantly lower cell capacity of growth, migration and invasion was observed. Moreover, HOXC8 knockdown could reduce the protein expression of classical epithelial mesenchymal transition (EMT) related markers.

CONCLUSION

HOXC8 may play an important role in glioma proliferation, migration and invasion. These findings indicated that HOXC8 may constitute a novel target for glioma treatment.

HOXC8 regulates self-renewal, differentiation and transformation of breast cancer stem cells

BACKGROUND

Homeobox genes are master regulators of cell fate during embryonic development and their expression is altered in cancer. By regulating the balance between cell proliferation and differentiation, they maintain homeostasis of normal tissues. Here, we screened the expression of homeobox genes in mammary stem cells to establish their role in stem cells transformation in breast cancer.

METHODS

Using a Homeobox Genes PCR array, we screened 83 homeobox genes in normal cancer breast stem/progenitor cells isolated by flow cytometry. The candidate gene HOXC8 epigenetic regulation was studied by DNA methylation and miRNA expression analyses. Self-renewal and differentiation of HOXC8-overexpressing or knockdown cells were assessed by flow cytometry and mammosphere, 3D matrigel and soft agar assays. Clinical relevance of in vitro findings were validated by bioinformatics analysis of patient datasets from TCGA and METABRIC studies.

RESULTS

In this study we demonstrate altered expression of homeobox genes in breast cancer stem/progenitor cells. HOXC8 was consistently downregulated in stem/progenitor cells of all breast molecular subtypes, thus representing an interesting tumour suppressor candidate. We show that downregulated expression of HOXC8 is associated with DNA methylation at the gene promoter and expression of miR196 family members. Functional studies demonstrated that HOXC8 gain of function induces a decrease in the CD44⁺/CD24^-/low cancer stem cell population and proportion of chemoresistant cells, with a concomitant increase in CD24⁺ differentiated cells. Increased HOXC8 levels also decrease the ability of cancer cells to form mammospheres and to grow in anchorage-independent conditions. Furthermore, loss of HOXC8 in non-tumorigenic mammary epithelial cells expands the cancer stem/progenitor cells pool, increases stem cell self-renewal, prevents differentiation induced by retinoic acid and induces a transformed phenotype.

CONCLUSIONS

Taken together, our study points to an important role of homeobox genes in breast cancer stem/progenitor cell function and establishes HOXC8 as a suppressor of stemness and transformation in the mammary gland lineage.