Richard Morgan

HOX transcription factors are potential therapeutic targets in non-small-cell lung cancer (targeting HOX genes in lung cancer)

The HOX genes are a family of homeodomain-containing transcription factors that determine the identity of cells and tissues during embryonic development. They are also known to behave as oncogenes in some haematological malignancies. In this study, we show that the expression of many of the HOX genes is highly elevated in primary non-small-cell lung cancers (NSCLCs) and in the derived cell lines A549 and H23. Furthermore, blocking the activity of HOX proteins by interfering with their binding to the PBX co-factor causes these cells to undergo apoptosis in vitro and reduces the growth of A549 tumours in vivo. These findings suggest that the interaction between HOX and PBX proteins is a potential therapeutic target in NSCLC.

Targeting HOX and PBX transcription factors in ovarian cancer

BackgoundOvarian cancer still has a relatively poor prognosis due to the frequent occurrence of drug resistance, making the identification of new therapeutic targets an important goal. We have studied the role of HOX genes in the survival and proliferation of ovarian cancer cells. These are a family of homeodomain-containing transcription factors that determine cell and tissue identity in the early embryo, and have an anti-apoptotic role in a number of malignancies including lung and renal cancer.MethodsWe used QPCR to determine HOX gene expression in normal ovary and in the ovarian cancer cell lines SK-OV3 and OV-90. We used a short peptide, HXR9, to disrupt the formation of HOX/PBX dimers and alter transcriptional regulation by HOX proteins.ResultsIn this study we show that the ovarian cancer derived line SK-OV3, but not OV-90, exhibits highly dysregulated expression of members of the HOX gene family. Disrupting the interaction between HOX proteins and their co-factor PBX induces apoptosis in SK-OV3 cells and retards tumour growth in vivo.ConclusionHOX/PBX binding is a potential target in ovarian cancer

Antagonism of HOX/PBX dimer formation blocks the in vivo proliferation of melanoma

Malignant melanoma is a cancer that arises from melanocyte cells in a complex but well-studied process, and which can only be successfully treated prior to metastasis as it is highly resistant to conventional therapies. A number of recent reports have indicated that members of the HOX family of homeodomain-containing transcription factors are deregulated in melanoma, and may actually be required to maintain proliferation. In this report, we describe the use of a novel, cell-permeable antagonist of the interaction between HOX proteins and PBX, a second homeodomain-containing transcription factor that modifies HOX activity. This antagonist can block the growth of murine B16 cells and trigger apoptosis both in vitro and in vivo when administered to mice with flank tumors.

Disrupting the Interaction Between HOX and PBX Causes Necrotic and Apoptotic Cell Death in the Renal Cancer Lines CaKi-2 and 769-P

PURPOSEnThe HOX genes are a family of homeodomain containing transcription factors that determine embryonic tissue identity and also have regulatory and oncogenic roles in adult cells. We quantified the expression of HOX genes in normal kidney tissue, primary tumors and derived cell lines, and examined their role in renal cancer cell survival.nnnMATERIALS AND METHODSnQuantitative polymerase chain reaction was used to evaluate HOX gene expression in cells and tissues. HOX gene function was disrupted using a peptide that blocks the interaction between HOX proteins and their PBX cofactor. Apoptosis was assessed by annexin/propidium iodide staining and direct measurement of caspase activity.nnnRESULTSnPrimary renal tumors and derived cell lines showed abnormal HOX gene expression. Furthermore, blocking HOX activity by targeting the interaction between HOX and its cofactor PBX caused apoptotic and necrotic cell death in the renal cancer cell lines CaKi-2 and 769-P, while sparing normal adult kidney cells.nnnCONCLUSIONSnOur findings suggest that the HOX/PBX dimer is a potential therapeutic target in renal cancer.

HOX Genes in Pancreatic Development and Cancer

The HOX genes are a family of homeodomain-containing transcription factors that determine cellular identity during development and which are subsequently re-expressed in many types of cancer. Some recent studies have shown that HOX genes may have key roles both in pancreatic development and in adult diseases of the pancreas, including cancer. In this review we consider recent advances in elucidating the role of HOX genes in these processes, how they may connect early developmental events to subsequent adult disease, and their potential both as diagnostic markers and therapeutic targets.

Disruption of HOX activity leads to cell death that can be enhanced by the interference of iron uptake in malignant B cells

The HOX genes encode a family of transcription factors that are dysregulated in several malignancies and have been implicated in oncogenesis and cancer cell survival. Disruption of HOX protein function using the peptide HXR9 has shown anti-tumor effects against melanoma, lung cancer and renal cancer. In this report, we evaluated the expression of all 39 HOX genes in a panel of six malignant B-cell lines, including multiple myeloma cells and found different levels of expression of HOX family members suggesting that they also have a role in malignant B-cell survival. We show that disrupting HOX function using the peptide HXR9 induces significant cytotoxicity in the entire panel of cell lines. Importantly, we found that the cytotoxic effects of HXR9 can be enhanced by combining it with ch128.1Av, an antibody-avidin fusion protein specific for the human transferrin receptor 1 (CD71). Iron starvation induced by the fusion protein contributes to the enhanced effect and involves, at least in part, the induction of a caspase-independent pathway. These results show the relevance of HOX proteins in malignant B-cell survival and suggest that our therapeutic strategy may be effective in the treatment of incurable B-cell malignancies such as multiple myeloma.

A conserved 30 base pair element in the Wnt-5a promoter is sufficient both to drive its' early embryonic expression and to mediate its' repression by otx2

We have characterised a short (30 base pair) element from the Xenopus Wnt-5a promoter which is nearly identical to one located in the human Wnt-5a promoter, and has the same position relative to the transcription start site. When placed in front of a LacZ gene, this element can reproduce the same expression pattern observed for Wnt-5a at the late gastrula stage. Further we show that gastrula stage Wnt-5a expression is repressed by otx2, something which is reflected by the mutually exclusive expression patterns of these two genes. The isolated promoter sequence contains an OTX- consensus binding site and its activity in embryos is repressed by ectopically expressed otx2.

A novel guanine exchange factor increases the competence of early ectoderm to respond to neural induction

Inductive interactions between different cell layers have an extremely important role in early embryogenesis. One of the most intensively studied and best characterised of these is the induction of neural tissue from ectodermal cells by the dorsal mesoderm. The competence of ectodermal cells to respond to neural induction varies according to dorsal-ventral position; with dorsal ectoderm (much of which forms the neural plate) having a far higher competence. Here we show that overexpression of the nucleotide exchange factor lfc increases ectodermal competence for neural induction as well as the amount of neural tissue in the whole embryo. Lfc is expressed pan ectodermally soon after gastrulation and may respond to an early determinant of dorsal ectoderm.

Computer simulation of genetic pathways

The early development of the vertebrate embryo requires a greater level of transcriptional activity than at any other stage in the life cycle. The specification of numerous cell types in the correct spatial and temporal pattern demands a very fine control over this transcription. As a result, the overall complexity of genetic interactions in development are vast, and might always defy a complete algorithmic description. However, a number of developmental processes occur relatively independently of others, and this has allowed them to be modelled by computers, a process referred to as in silico modelling.Jason Kastner and his colleagues at The California Institute of Technology have used this approach to study the genetic interactions that help pattern the early hindbrain [1xModeling a Hox gene network in silico using a stochastic simulation algorithm. Kastner, J. et al. Dev. Biol. 2002; 246: 122–131Crossref | PubMed | Scopus (21)See all References][1]. Development of the vertebrate hindbrain is relatively well understood, and involves a physical subdivision into a number of segmental compartments, or rhombomeres. Each rhombomere expresses a distinctive set of transcription factors, membrane receptors and ligands that define its identity and determine its function in the adult brain. Kastner and his colleagues have concentrated on two rhombomeres in particular, r4 and r5. Embryological and genetic experiments in mice and chicks reveal that these rhombomeres express the transcription factors Hoxb1 and Krox20, respectively. Hoxb1 expression is maintained in r4 by a cofactor-dependant, autoregulatory loop, and Hoxb1 is thought to repress Krox20 expression. A further transcription factor, Hoxb2, is required in both r4 and r5. Its expression is maintained by different mechanisms in each rhombomere, requiring Hoxb1 in r4 and Krox20 in r5.The authors have used a stochastic algorithm to mimic these genetic interactions in silico. This algorithm incorporates the known promoter and enhancer elements in Hoxb1, Hoxb2 and Krox20, and uses starting values that represent the conditions at a very early stage in hindbrain development. It also takes into account cell division and random changes in gene expression known to occur in a few cells at early developmental stages.It is very encouraging that the results of this analysis match closely those obtained in live embryos. This also holds true with experimental manipulations of gene expression. For example, a Hoxb1?/? background can be simulated by simply removing Hoxb1 from the algorithm. In this case Hoxb2 expression is lost from r4, something which is known to occur in real Hoxb1?/? embryos. Intriguingly, the in silico simulation also suggests that the Krox20 gene is strongly expressed in r4 of Hoxb1?/? embryos, a novel finding that still awaits experimental confirmation in vivo.The in silico model also predicts the ‘misfiring’ of a small number of cells, whereby they stop expressing the developmental genes of their neighbours and deviate from their normal fate. The model shows that if this occurs at an early stage in hindbrain development some cells can recover and express the right genes again. This recovery is not possible if it occurs at a later stage though, and the cells fail to adopt any specific developmental fate. The success of this simple in silico model is highly encouraging, and suggests that this approach could yield new biological insights.