Role of HOX Genes in Stem Cell Differentiation and Cancer

Abnormally high expression of HOXA2 as an independent factor for poor prognosis in glioma patients

In recent years, studies have revealed HOXA2 as a new oncogene, but its function is unknown in gliomas. We aimed to reveal the relationship between HOXA2 and glioma based on the Chinese Glioma Genome Atlas(CGGA) and the cancer genome atlas (TCGA). HOXA2 expression data and clinically relevant information of glioma patients were obtained from the CGGA and TCGA containing 1447 glioma tissues and five non-tumor brain tissues. The Wilcox or Kruskal tests were used to detect the correlation between the HOXA2 expression level and clinical data of glioma patients. the Kaplan-Meier method were used to examine the relationship between HOXA2 and overall patient survival. Gene set enrichment analysis (GSEA) was conducted to indirectly reveal the signaling pathways involved in HOXA2, and RT-PCR was used to detect HOXA2 expression in gliomas and non-tumor brain tissues. High HOXA2 expression was found to be positively correlated with clinical grade, histological type, age, and tumor recurrence, but negatively correlated with 1p19 codeletion and isocitrate dehydrogenase mutation status.RT-PCR results showed that HOXA2 expression levels were significantly higher in tumor tissues than in non-tumor brain tissues. GSEA showed that HOXA2 promoted the activation of the activation of the JAK-STAT-signaling pathway, focal adhesion, cell-adhesion-molecules-CAMS pathway, cytosolic DNA sensing pathway, and natural killer cell-mediated cytotoxicity. This study revealed for the first time that the novel oncogene,HOXA2, leads to poor prognosis in gliomas, and can be used as a biomarker for the diagnosis and treatment of gliomas.

KRAS-retroviral fusion transcripts and gene amplification in arsenic-transformed, human prostate CAsE-PE cancer cells

CAsE-PE cells are an arsenic-transformed, human prostate epithelial line containing oncogenic mutations in KRAS compared to immortalized, normal KRAS parent cells, RWPE-1. We previously reported increased copy number of mutated KRAS in CAsE-PE cells, suggesting gene amplification. Here, KRAS flanking genomic and transcriptomic regions were sequenced in CAsE-PE cells for insight into KRAS amplification. Comparison of DNA-Seq and RNA-Seq showed increased reads from background aligning to all KRAS exons in CAsE-PE cells, while a uniform DNA-Seq read distribution occurred in RWPE-1 cells with normal transcript expression. We searched for KRAS fusions in DNA and RNA sequencing data finding a portion of reads aligning to KRAS and viral sequence. After generation of cDNA from total RNA, short and long KRAS probes were generated to hybridize cDNA and KRAS enriched fragments were PacBio sequenced. More KRAS reads were captured from CAsE-PE cDNA versus RWPE-1 by each probe set. Only CAsE-PE cDNA showed KRAS viral fusion transcripts, primarily mapping to LTR and endogenous retrovirus sequences on either 5'- or 3'-ends of KRAS. Most KRAS viral fusion transcripts contained 4 to 6 exons but some PacBio sequences were in unusual orientations, suggesting viral insertions within the gene body. Additionally, conditioned media was extracted for potential retroviral particles. RNA-Seq of culture media isolates identified KRAS retroviral fusion transcripts in CAsE-PE media only. Truncated KRAS transcripts suggested multiple retroviral integration sites occurred within the KRAS gene producing KRAS retroviral fusions of various lengths. Findings suggest activation of endogenous retroviruses in arsenic carcinogenesis should be explored.

Inhibition of urinary bladder cancer cell proliferation by silibinin

Silibinin, a natural compound extracted from milk thistle, has demonstrated antitumor properties in urinary bladder cancer cells; however, the role of TP53 gene in these effects is unclear. In order to better understand the molecular and antiproliferative mechanisms of this compound, urinary bladder cancer cells with different TP53 gene status, RT4 (low-grade tumor, wild TP53 gene), 5637 (high-grade tumor, Grade 2, mutated TP53 gene), and T24 (high-grade tumor, Grade 3, mutated TP53 gene) were treated with several concentrations of silibinin (1, 5, 10, 50, 100, and 150 μM). Cytotoxicity, prooxidant effect, morphological changes, cell migration, cell cycle progression, global methylation profile, and relative expression of HOXB3, c-MYC, PLK1, SMAD4, SRC, HAT, HDAC, and RASSF1A genes were evaluated. The silibinin presented cytotoxic and prooxidant effects in the three cell lines. In mutated TP53 cells, significant interference in cell migration and cell cycle arrest at the G2/M phase was observed. Additionally, silibinin induced global DNA hypomethylation in the highest grade tumor cells. For wild-type TP53 cells, a sub-G1 apoptotic population was present. Furthermore, there was modulation of gene expression responsible for cell growth (SMAD and c-MYC), migration (SRC), cell cycle kinetics (PLK1), angiogenesis (HOXB3), and of genes associated with epigenetic events such as DNA acetylation (HAT) and deacetylation (HDAC). In conclusion, the silibinin inhibited the urinary bladder tumor cell proliferation independently of TP53 status; however, cell cycle effects, gene expression changes, and alteration of cell migration are dependent on TP53 status. © 2020 Wiley Periodicals, Inc.

Forced expression of HOXA13 confers oncogenic hallmarks to esophageal keratinocytes

HOXA13 overexpression has been detected in human ESCC tissue and high HOXA13 protein expression is correlated with a shorter median survival time in ESCC patients. Although aberrant expression of HOXA13 in ESCC has thus been established, little is known regarding the functional consequences thereof. The present study aimed to examine to what extent aberrant HOXA13 might drive carcinogenesis in esophageal keratinocytes. To this end, we overexpressed HOXA13 in a non-transformed human esophageal cell line EPC2-hTERT, performed gene expression profiling to identify key processes and functions, and performed functional experiments. We found that HOXA13 expression confers oncogenic hallmarks to esophageal keratinocytes. It provides proliferation advantage to keratinocytes, reduces sensitivity to chemical agents, regulates MHC class I expression and differentiation status and promotes cellular migration. Our data indicate a crucial role of HOXA13 at early stages of esophageal carcinogenesis.

HOX genes function in Breast Cancer development

Breast cancer develops in the mammary glands during mammalian adulthood and is considered the second most common type of human carcinoma and the most incident and mortal in the female population. In contrast to other human structures, the female mammary glands continue to develop after birth, undergoing various modifications during pregnancy, lactation and involution under the regulation of hormones and transcription factors, including those encoded by the HOX clusters (A, B, C, and D). Interestingly, HOX gene deregulation is often associated to breast cancer development. Within the HOXB cluster, 8 out of the 10 genes present altered expression levels in breast cancer with an impact in its aggressiveness and resistance to hormone therapy, which highlights the importance of HOXB genes as potential therapeutic targets used to overcome the limitations of tamoxifen-resistant cancer treatments. Here, we review the current state of knowledge on the role of HOX genes in breast cancer, specially focus on HOXB, discussing the causes and consequences of HOXB gene deregulation and their relevance as prognostic factors and therapeutic targets.

HOXC11 functions as a novel oncogene in human colon adenocarcinoma and kidney renal clear cell carcinoma

AIMS

Accumulating evidence has confirmed the involvement of the homeobox (HOX) gene family in carcinogenesis. HOXC11, belongs to the homeobox-C (HOXC) gene cluster, has been reported to play important roles in the development of several cancers. However, its expression and clinical value in pan-cancer remain elusive.

MATERIALS AND METHODS

Bioinformatics analysis, CCK-8 assay, Flow cytometry and Western blot were used to analyze gene expression and patient survival, cell proliferation, cell apoptosis and protein level, respectively.

KEY FINDINGS

In this study, we comprehensively analyzed the expression profile and prognostic value of HOXC11 in human pan-cancer using online The Cancer Genome Atlas (TCGA) databases. HOXC11 was widely up-regulated in tumor tissues when compared with the normal tissues in pan-cancer across nine cancer types. In addition, high mRNA level of HOXC11 predicted poor overall survival (OS) of patients with adrenocortical carcinoma (ACC), colon adenocarcinoma (COAD), kidney renal clear cell carcinoma (KIRC), mesothelioma (MESO) and pancreatic adenocarcinoma (PAAD), respectively. By comparative analysis, we found that HOXC11 was up-regulated and closely correlated patient OS in COAD and KIRC. Functionally, down-regulation of HOXC11 inhibited cell proliferation but promoted apoptosis of COAD and KIRC in vitro. Mechanistically, HOXC11 promoted cell proliferation of COAD and KIRC might by inactivating the peroxisome proliferator-activated receptor gamma (PPARγ) signaling pathway.

SIGNIFICANCE

Our findings suggest that HOXC11 may act as a tumor driving gene in COAD and KIRC.

Bioinformatics analysis of the expression of HOXC13 and its role in the prognosis of breast cancer

The homeobox (HOX) genes, a class of transcription factors, are known to promote embryonic development and induce tumor formation. To date, the HOXA and HOXB gene families have been reported to be associated with breast cancer. However, the expression and exact role of homeobox C13 (HOXC13) in breast cancer has not yet been investigated. In the present study, the HOXC13 expression in human breast cancer was evaluated using the Oncomine database and Cancer Cell Line Encyclopedia (CCLE). Next, the Gene expression-based Outcome for Breast cancer online database, cBioportal, University of California Santa Cruz Xena browser and bc-GenExMinerv were used to explore the specific expression of HOXC13 in breast cancer. The methylation and mutation status of HOXC13 in breast cancer was then validated using the CCLE and cBioportal databases. Finally, the co-expression of HOX transcript antisense RNA (HOTAIR) and HOXC13 in breast cancer were analyzed and their impact on clinical prognosis determined. It was found that the expression of HOXC13 was high in breast cancer compared with other types of cancer, such as gastric cancer and colon cancer. Following co-expression analysis, a significant positive association was identified between HOTAIR and HOXC13. An association between HOTAIR and HOXC13, and lymph node and distant metastasis recurrence was also revealed during the development of breast cancer. Of note, survival analysis showed that high expression of HOTAIR and HOXC13 predicted poor prognosis. These findings revealed that HOXC13 plays an important role in the progression of breast cancer. However, the specific mechanism needs to be confirmed by subsequent experiments.

HOX family transcription factors: Related signaling pathways and post-translational modifications in cancer

HOX family transcription factors belong to a highly conserved subgroup of the homeobox superfamily that determines cellular fates in embryonic morphogenesis and the maintenance of adult tissue architecture. HOX family transcription factors play key roles in numerous cellular processes including cell growth, differentiation, apoptosis, motility, and angiogenesis. As tumor promoters or suppressors HOX family members have been reported to be closely related with a variety of cancers. They closely regulate tumor initiation and growth, invasion and metastasis, angiogenesis, anti-cancer drug resistance and stem cell origin. Here, we firstly described the pivotal roles of HOX transcription factors in tumorigenesis. Then, we summarized the main signaling pathways regulated by HOX transcription factors, including Wnt/β-catenin, transforming growth factor β, mitogen-activated protein kinase, phosphoinositide 3-kinase/Akt, and nuclear factor-κB signalings. Finally, we outlined the important post-translational modifications of HOX transcription factors and their regulation in cancers. Future research directions on the HOX transcription factors are also discussed.

Two Receptors, Two Isoforms, Two Cancers: Comprehensive Analysis of KIT and TrkA Expression in Neuroblastoma and Acute Myeloid Leukemia

Pediatric cancers represent a wide variety of different tumors, though they have unique features that distinguish them from adult cancers. Receptor tyrosine kinases KIT and TrkA functions in AML and NB, respectively, are well-characterized. Though expression of these receptors is found in both tumors, little is known about KIT function in NB and TrkA in AML. By combining gene enrichment analysis with multidimensional scaling we showed that pediatric AMLs with t(8;21) or inv16 and high KIT expression levels stand out from other AML subtypes as they share prominent transcriptomic features exclusively with KIT-overexpressing NBs. We showed that AML cell lines had a predominant expression of an alternative TrkAIII isoform, which reportedly has oncogenic features, while NB cell lines had dominating TrkAI-II isoforms. NB cells, on the other hand, had an abnormal ratio of KIT isoforms as opposed to AML cells. Both SCF and NGF exerted protective action against doxorubicin and cytarabine for t(8;21) AML and NB cells. We identified several gene sets both unique and common for pediatric AML and NB, and this expression is associated with KIT or TrkA levels. NMU, DUSP4, RET, SUSD5, NOS1, and GABRA5 genes are differentially expressed in NBs with high KIT expression and are associated with poor survival in NB. We identified HOXA10, BAG3, and MARCKS genes that are connected with TrkA expression and are marker genes of poor outcome in AML. We also report that SLC18A2, PLXNC1, and MRPL33 gene expression is associated with TrkA or KIT expression levels in both AML and NB, and these genes have a prognostic value for both cancers. Thus, we have provided a comprehensive characterization of TrkA and KIT expression along with the oncogenic signatures of these genes across two pediatric tumors.

Leveraging Biomaterial Mechanics to Improve Pluripotent Stem Cell Applications for Tissue Engineering

A primary goal in tissue engineering is to develop functional tissues by recapitulating salient features of complex biological systems that exhibit a diverse range of physical forces. Induced pluripotent stem cells (iPSCs) are promising autologous cell sources to execute these developmental programs and their functions; however, cells require an extracellular environment where they will sense and respond to mechanical forces. Thus, understanding the biophysical relationships between stem cells and their extracellular environments will improve the ability to design complex biological systems through tissue engineering. This article first describes how the mechanical properties of the environment are important determinants of developmental processes, and then further details how biomaterials can be designed to precisely control the mechanics of cell-matrix interactions in order to study and define their reprogramming, self-renewal, differentiation, and morphogenesis. Finally, a perspective is presented on how insights from the mechanics of cell-matrix interactions can be leveraged to control pluripotent stem cells for tissue engineering applications.

HOX genes as transcriptional and epigenetic regulators during tumorigenesis and their value as therapeutic targets

Several HOX genes are aberrantly expressed in a wide range of cancers interfering with their development and resistance to treatment. This seems to be often caused by alterations in the methylation profiles of their promoters. The role of HOX gene products in cancer is highly 'tissue specific', relying ultimately on their ability to regulate oncogenes or tumor-suppressor genes, directly as transcriptional regulators or indirectly interfering with the levels of epigenetic regulators. Nowadays, different strategies have been tested the use of HOX genes as therapeutic targets for cancer diagnosis and treatment. Here, we trace the history of the research concerning the involvement of HOX genes in cancer, their connection with epigenetic regulation and their potential use as therapeutic targets.

Dysregulation of DNA methylation patterns may identify patients with breast cancer resistant to endocrine therapy: A predictive classifier based on differentially methylated regions

Endocrine therapy (ET) is one of a number of targeted therapies for estrogen receptor-positive breast cancer (BRCA); however, resistance to ET has become the primary issue affecting treatment outcome. In the present study, a predictive classifier was created using a DNA methylation dataset to identify patients susceptible to endocrine resistance. DNA methylation and RNA sequencing data, and the clinicopathological features of BRCA, were obtained from The Cancer Genome Atlas. Stringent criteria were set to select and classify patients into two groups, namely those resistant to ET (n=11) and sensitive to ET (n=21) groups. Bump hunting analysis revealed that 502 out of 135,418 genomic regions were differentially methylated between these two groups; these regions were differentially methylated regions (DMRs). The majority of the CpG sites contained in the DMRs mapped to the promoter region. Functional enrichment analyses indicated that a total of 562 specific genes encompassing these DMRs were primarily associated with 'biological progress of organ morphogenesis and development' and 'cell-cell adhesion' gene ontologies. Logistic regression and Pearson's correlation analysis were conducted to construct a predictive classifier for distinguishing patients resistant or sensitive to ET. The highest areas under the curve and relatively low Akaike information criterion values were associated with a total of 60 DMRs; a risk score retained from this classifier was revealed to be an unfavorable predictor of survival in two additional independent datasets. Furthermore, the majority of genes (55/63) exhibited a statistically significant association between DNA methylation and mRNA expression (P<0.05). The association between the mRNA expression of a number of genes (namely calcium release activated channel regulator 2A, Schlafen family member 12, chromosome 3 open reading frame 18, zinc finger protein 880, dual oxidase 1, major histocompatibility complex, class II, DP β1, C-terminal binding protein 1, ALG13 UDP-N-acetylglucosaminyltransferase subunit and RAS protein activator like 2) and the prognosis of patients with estrogen receptor-positive BRCA and ET resistance was determined using Kaplan-Meier Plotter. In summary, the predictive classifier proposed in the present study may aid the identification of patients sensitive or resistant to ET, and numerous genes maybe potential therapeutic targets to delay the development of resistance to ET.

HOXA10 induces BCL2 expression, inhibits apoptosis, and promotes cell proliferation in gastric cancer

Homeobox A10 (HOXA10) has been implicated critical for the promotion of carcinogenesis, but the underlying mechanism between HOXA10 and malignant gastric cancer (GC) phenotype remains elusive. In the present study, we analyzed and validated that HOXA10 and BCL2 expressions were elevated both at the mRNA and protein levels in GC tissues. Upregulated HOXA10 promoted GC cell proliferation with reduced apoptosis in vitro and accelerated GC tumor growth in vivo. Bioinformatics analysis and quantitative real‐time polymerase chain reaction (qRT‐PCR) experiment inferred that HOXA10 might upregulate the expression of BCL2. By performing western blot, chromatin immunoprecipitation and quantitative PCR (ChIP‐qPCR), and rescue experiment, we found that HOXA10 might bind to BCL2 promoter region, induce its expression, and thus inhibit intrinsic apoptosis pathway. Moreover, higher expression of HOXA10 and BCL2 predicted poor overall survival (OS) in GC patients. In summary, our study indicated that HOXA10 was upregulated in GC, and that HOXA10 might promote cell proliferation by elevating BCL2 expression and inhibiting apoptosis.

Direct and Indirect Targeting of HOXA9 Transcription Factor in Acute Myeloid Leukemia

HOXA9 (Homeobox A9) is a homeotic transcription factor known for more than two decades to be associated with leukemia. The expression of HOXA9 homeoprotein is associated with anterior-posterior patterning during embryonic development, and its expression is then abolished in most adult cells, with the exception of hematopoietic progenitor cells. The oncogenic function of HOXA9 was first assessed in human acute myeloid leukemia (AML), particularly in the mixed-phenotype associated lineage leukemia (MPAL) subtype. HOXA9 expression in AML is associated with aggressiveness and a poor prognosis. Since then, HOXA9 has been involved in other hematopoietic malignancies and an increasing number of solid tumors. Despite this, HOXA9 was for a long time not targeted to treat cancer, mainly since, as a transcription factor, it belongs to a class of protein long considered to be an "undruggable" target; however, things have now evolved. The aim of the present review is to focus on the different aspects of HOXA9 targeting that could be achieved through multiple ways: (1) indirectly, through the inhibition of its expression, a strategy acting principally at the epigenetic level; or (2) directly, through the inhibition of its transcription factor function by acting at either the protein/protein interaction or the protein/DNA interaction interfaces.

A novel long non-coding RNA from the HOXA6-HOXA5 locus facilitates colon cancer cell growth

Background

Homeobox A5 (HOXA5), a member of the HOX family, plays an important role in tumor development and morphogenesis, although opposite effects on tumorigenesis have been observed, depending on the tissue type. In this study, we aimed to investigate the role of a novel transcript from the HOXA6-HOXA5 locus in colon cancer tumorigenesis.

Methods

Human colon cancer cell lines were analyzed using next generation sequencing-based targeted mRNA capture. The effects of overexpression and silencing of HOXA5 transcripts were evaluated in vitro and using a xenograft nude mouse model.

Results

We identified three novel transcripts (HOXA5 short, long 1, and long 2) transcribed from the HOXA6-HOXA5 locus in HCT116 colon cancer cells using next generation sequencing-based targeted mRNA capture. Knockdown of HOXA5 long 1 and long 2 transcripts did not affect cell growth, while selective silencing of HOXA5 short RNA inhibited cell growth independent of HOXA5 expression. Stable overexpression of HOXA5 short RNA promoted proliferation and migration of colon cancer cell lines HCT116, DLD1, and HT-29 and accelerated tumor growth in the xenograft mouse model. In vitro translation assays suggested HOXA5 short RNA was a functional long non-coding RNA (lncRNA). Consistent with these observations, expression of HOXA5 short RNA was upregulated in advanced colon cancer tissues. Ingenuity Pathway Analysis of differentially expressed genes between HOXA5 short RNA overexpressed and silenced HCT116 cells revealed that HOXA5 short RNA preferentially modified expression of epidermal growth factor (EGF) signal-related genes. Western blot analysis demonstrated that stable overexpression of HOXA5 short RNA increased EGF receptor levels and facilitated its phosphorylation in both HCT116 cells and xenograft tumors.

Conclusions

Our results suggested that HOXA5 short RNA, a novel lncRNA, may play a crucial role in colon tumor growth through activation of EGF signaling.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5715-0) contains supplementary material, which is available to authorized users.

MicroRNAs as regulators and effectors of hematopoietic transcription factors

Hematopoiesis is a highly-regulated development process orchestrated by lineage-specific transcription factors that direct the generation of all mature blood cells types, including red blood cells, megakaryocytes, granulocytes, monocytes, and lymphocytes. Under homeostatic conditions, the hematopoietic system of the typical adult generates over 10¹¹ blood cells daily throughout life. In addition, hematopoiesis must be responsive to acute challenges due to blood loss or infection. MicroRNAs (miRs) cooperate with transcription factors to regulate all aspects of hematopoiesis, including stem cell maintenance, lineage selection, cell expansion, and terminal differentiation. Distinct miR expression patterns are associated with specific hematopoietic lineages and stages of differentiation and functional analyses have elucidated essential roles for miRs in regulating cell transitions, lineage selection, maturation, and function. MiRs function as downstream effectors of hematopoietic transcription factors and as upstream regulators to control transcription factor levels. Multiple miRs have been shown to play essential roles. Regulatory networks comprised of differentially expressed lineage-specific miRs and hematopoietic transcription factors are involved in controlling the quiescence and self-renewal of hematopoietic stem cells as well as proliferation and differentiation of lineage-specific progenitor cells during erythropoiesis, myelopoiesis, and lymphopoiesis. This review focuses on hematopoietic miRs that function as upstream regulators of central hematopoietic transcription factors required for normal hematopoiesis. This article is categorized under: RNA in Disease and Development > RNA in Development Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs.

Targeting PRMT5 Activity Inhibits the Malignancy of Hepatocellular Carcinoma by Promoting the Transcription of HNF4α

Background: Liver cancer stem cells (LCSCs) are responsible for the initiation, progression and chemoresistance of liver cancer. However, no agent targeting LCSC is available in the clinic to date. Here, we investigated the effects of targeting protein arginine methyltransferase 5 (PRMT5), an epigenetic regulator, on LCSCs and HCC using a novel PRMT5 inhibitor DW14800. Methods: Tumor spheroid formation culture was used to enrich LCSCs and assess their self-renewal capability. Human alpha-1-antitrypsin (A1AT) ELISA, acetylated low-density lipoprotein (ac-LDL) uptake, periodic acid-Schiff (PAS) reactions and senescence associated β-galactosidase (SA-β-gal) activity assays were performed to examine the differentiation status of HCC cells. The effects of DW14800 on HCC malignancy were assessed in HCC cell lines and on an HCC xenograft model in mice. Chromatin immunoprecipitation was applied to clarify the transcriptional regulation of HNF4α by PRMT5-mediated Histone H4 arginine-3 symmetrical dimethylation (H4R3me2s). Results: Quantitative real-time PCR revealed that the expression of PRMT5 was upregulated in LCSCs. DW14800 specifically decreased the symmetrical dimethylation of arginine residues in HCC cells. Treatment of DW14800 suppressed the self-renewal capacity of LCSCs while re-establishing hepatocyte-specific characteristics in HCC cells. DW14800 displayed antitumor effects in HCC cells in vitro and in xenograft HCC in vivo. Importantly, ChIP assay showed that PRMT5 and H4R3me2s bound to the promoter region of HNF4α gene, and DW14800 increased the expression of HNF4α via reducing the H4R3me2s levels and enhancing the transcription of HNF4α. Conclusions: Our data revealed the significance of targeting PRMT5 activity in LCSC elimination and HCC differentiation, and proposed that DW14800 may represent a promising therapeutic agent for HCC in the clinic.

A Case of Identity: HOX Genes in Normal and Cancer Stem Cells

Stem cells are undifferentiated cells that have the unique ability to self-renew and differentiate into many different cell types. Their function is controlled by core gene networks whose misregulation can result in aberrant stem cell function and defects of regeneration or neoplasia. HOX genes are master regulators of cell identity and cell fate during embryonic development. They play a crucial role in embryonic stem cell differentiation into specific lineages and their expression is maintained in adult stem cells along differentiation hierarchies. Aberrant HOX gene expression is found in several cancers where they can function as either oncogenes by sustaining cell proliferation or tumor-suppressor genes by controlling cell differentiation. Emerging evidence shows that abnormal expression of HOX genes is involved in the transformation of adult stem cells into cancer stem cells. Cancer stem cells have been identified in most malignancies and proved to be responsible for cancer initiation, recurrence, and metastasis. In this review, we consider the role of HOX genes in normal and cancer stem cells and discuss how the modulation of HOX gene function could lead to the development of novel therapeutic strategies that target cancer stem cells to halt tumor initiation, progression, and resistance to treatment.

HOXA10 expression profiling in prostate cancer

BACKGROUND

HOX genes encode transcription factors that play key roles in modulating normal tissue morphogenesis, differentiation and homeostasis. Disruption of normal HOX gene expression occurs frequently in human cancers and is associated with both tumor promoting and suppressing activities. Among these is, HOXA10, a pleiotropic gene that is critical for normal prostate development. In this study we characterized HOXA10 expression in human and mouse PCa to gain insights into its clinical significance.

METHODS

A meta-analysis of HOXA10 mRNA expression was carried out across several publicly available data sets. Expression of HOXA10 protein expression was assessed by immunohistochemistry (IHC) using human radical prostatectomy (RP) cases. We correlated HOXA10 expression to clinicopathological features and investigated its relationship to biochemical recurrence (BCR) after RP by the Kaplan-Meier method. HOXA10 mRNA and IHC protein expression was also examined in a mouse model of Pten-null PCa.

RESULTS

A meta-analysis of HOXA10 gene expression indicated dysregulated expression of HOXA10 in human PCa. IHC profiling of HOXA10 revealed inverse correlations between HOXA10 expression and Gleason pattern, Gleason score, and pathological stage (P < 0.01). Patients with low expression profiles of HOXA10 were associated with a higher risk of BCR, (OR, 3.54; 95%CI, 1.21-16.14; P = 0.049) whereas patients with high HOXA10 expression experienced longer times to BCR (P = 0.045). However, HOXA10 was not an independent predictor of BCR (OR, 1.52; 95%CI, 0.42-5.54; P = 0.52). Evaluation of expression patterns of HOXA10 in mouse prostate tumors mimicked that of humans.

CONCLUSIONS

Our findings show that HOXA10 expression is inversely associated with tumor differentiation and high HOXA10 expression is associated with improved BCR-free survival. This study provides human and mouse evidence to suggest tumor suppressive roles for HOXA10 in the context of prostate cancer.

NUP214 in Leukemia: It's More than Transport

NUP214 is a component of the nuclear pore complex (NPC) with a key role in protein and mRNA nuclear export. Chromosomal translocations involving the NUP214 locus are recurrent in acute leukemia and frequently fuse the C-terminal region of NUP214 with SET and DEK, two chromatin remodeling proteins with roles in transcription regulation. SET-NUP214 and DEK-NUP214 fusion proteins disrupt protein nuclear export by inhibition of the nuclear export receptor CRM1, which results in the aberrant accumulation of CRM1 protein cargoes in the nucleus. SET-NUP214 is primarily associated with acute lymphoblastic leukemia (ALL), whereas DEK-NUP214 exclusively results in acute myeloid leukemia (AML), indicating different leukemogenic driver mechanisms. Secondary mutations in leukemic blasts may contribute to the different leukemia outcomes. Additional layers of complexity arise from the respective functions of SET and DEK in transcription regulation and chromatin remodeling, which may drive malignant hematopoietic transformation more towards ALL or AML. Another, less frequent fusion protein involving the C terminus of NUP214 results in the sequestosome-1 (SQSTM1)-NUP214 chimera, which was detected in ALL. SQSTM1 is a ubiquitin-binding protein required for proper autophagy induction, linking the NUP214 fusion protein to yet another cellular mechanism. The scope of this review is to summarize the general features of NUP214-related leukemia and discuss how distinct chromosomal translocation partners can influence the cellular effects of NUP214 fusion proteins in leukemia.

Hematopoietic Differentiation of Human Pluripotent Stem Cells: HOX and GATA Transcription Factors as Master Regulators

Numerous human disorders of the blood system would directly or indirectly benefit from therapeutic approaches that reconstitute the hematopoietic system. Hematopoietic stem cells (HSCs), either from matched donors or ex vivo manipulated autologous tissues, are the most used cellular source of cell therapy for a wide range of disorders. Due to the scarcity of matched donors and the difficulty of ex vivo expansion of HSCs, there is a growing interest in harnessing the potential of pluripotent stem cells (PSCs) as a de novo source of HSCs. PSCs make an ideal source of cells for regenerative medicine in general and for treating blood disorders in particular because they could expand indefinitely in culture and differentiate to any cell type in the body. However, advancement in deriving functional HSCs from PSCs has been slow. This is partly due to an incomplete understanding of the molecular mechanisms underlying normal hematopoiesis. In this review, we discuss the latest efforts to generate human PSC (hPSC)-derived HSCs capable of long-term engraftment. We review the regulation of the key transcription factors (TFs) in hematopoiesis and hematopoietic differentiation, the Homeobox (HOX) and GATA genes, and the interplay between them and microRNAs. We also propose that precise control of these master regulators during the course of hematopoietic differentiation is key to achieving functional hPSC-derived HSCs.

Gene expression signatures for HOXA4, HOXA9, and HOXD10 reveal alterations in transcriptional regulatory networks in colon cancer

We previously reported that HOXA4, HOXA9, and HOXD10 are selectively expressed in colonic stem cells (SCs) and their overexpression contributes to colorectal cancer (CRC). Our goals here were to determine how these HOX genes are transcriptionally regulated and whether transcriptional dysregulation of HOX genes occurs in CRC. Accordingly, we used correlation analysis to identify genes that are expression-correlated or anticorrelated with HOXA4, HOXA9, and HOXD10. We then used Gene Ontology (GO) analysis to functionally classify these genes. The GO results for both HOXA4 and HOXD10 correlated gene sets for normal colon and CRC show functions mostly classified as developmental, transcriptional regulation, and DNA binding. This raised the question: Are these gene sets regulated by the same transcription factors (TFs)? Consequently, we used promoter analysis and interaction network toolset (PAINT) to identify commonly shared transcription response elements. The results indicated that completely different sets of TFs coregulate HOXA4 and HOXD10 (but not HOXA9) and their expression-correlated genes. And predicted TFs are altered in CRC compared with normal colon. Taken together, analysis of gene signatures correlated with expression of HOXA4 and HOXD10 indicates how these HOX genes are: (a) transcriptionally regulated in the normal colon; (b) dysregulated in CRC. This discovery provides a mechanism for targeting CRC SCs.

Increased Musashi-2 and Decreased NUMB Protein Levels Observed in Human Colorectal Cancer are reverted to Normal Levels by ATRA-Induced Cell Differentiation

Background:

Musashi stem cell (SC) proteins (MSI-1 & MSI-2) are known to become over expressed during colorectal tumorigenesis in humans and mice. MSI-1 overexpression induces tumorigenesis through Notch activation via inactivation of NUMB. Previous studies also show that MSI-2 overexpression in mice induces intestinal tumorigenesis but the mechanism is independent of NUMB. However, whether the MSI-2/NUMB pathway contributes to colorectal cancer (CRC) development in humans is still undetermined.

Methods:

We evaluated expression of MSI-2 and NUMB proteins in matched normal and CRC patient samples, as well as in human CRC cell lines. We also determined whether induction of cellular differentiation by all-trans retinoic acid (ATRA) influences MSI-2 and NUMB expression.

Results:

Analysis of matched patient tissue samples and CRC cell lines showed that MSI-2 protein expression is significantly increased and NUMB expression is decreased in CRCs compared to the normal colonic tissue. Immunostaining of normal and adenomatous colonic epithelium revealed that MSI-1+ andMSI-2+ SCs reside in the SC niche and they become overpopulated during colon tumorigenesis. Moreover, promoting cellular differentiation by ATRA reduces MSI-2 protein levels, while increasing NUMB protein levels in human CRC cell lines.

Conclusions:

MSI-2/NUMB protein expression is altered during colon tumorigenesis, and indicates that MSI-2/NUMB signaling in human colonic stem cells is closely linked to normal colonic epithelial homeostasis.

Implications:

The ability to normalize MSI-2/NUMB signaling by inducing differentiation of cancer SCs suggests a novel therapeutic approach for CRC treatment.