20The HOX genes are a highly conserved family of homeodomain-containing 21 transcription factors that specify cell identity in early development and, subsequently,

Alzheimer's disease is characterized by the histopathological presence of amyloid-β plaques and tau-containing neurofibrillary tangles. Microglial activation is also a recognized pathological component. The relationship between microglial activation and protein aggregation is still debated. We investigated the relationship between amyloid plaques, tau tangles and activated microglia using PET imaging. Fifty-one subjects (19 healthy controls, 16 mild cognitive impairment and 16 Alzheimer's disease subjects) participated in the study. All subjects had neuropsychometric testing, MRI, amyloid (18F-flutemetamol), and microglial (11C-PBR28) PET. All subjects with mild cognitive impairment and Alzheimer's disease and eight of the controls had tau (18F-AV1451) PET. 11C-PBR28 PET was analysed using Logan graphical analysis with an arterial plasma input function, while 18F-flutemetamol and 18F-AV1451 PET were analysed as target:cerebellar ratios to create parametric standardized uptake value ratio maps. Biological parametric mapping in the Statistical Parametric Mapping platform was used to examine correlations between uptake of tracers at a voxel-level. There were significant widespread clusters of positive correlation between levels of microglial activation and tau aggregation in both the mild cognitive impairment (amyloid-positive and amyloid-negative) and Alzheimer's disease subjects. The correlations were stronger in Alzheimer's disease than in mild cognitive impairment, suggesting that these pathologies increase together as disease progresses. Levels of microglial activation and amyloid deposition were also correlated, although in a different spatial distribution; correlations were stronger in mild cognitive impairment than Alzheimer's subjects, in line with a plateauing of amyloid load with disease progression. Clusters of positive correlations between microglial activation and protein aggregation often targeted similar areas of association cortex, indicating that all three processes are present in specific vulnerable brain areas. For the first time using PET imaging, we show that microglial activation can correlate with both tau aggregation and amyloid deposition. This confirms the complex relationship between these processes. These results suggest that preventative treatment for Alzheimer's disease should target all three processes.

Although PBX proteins are known to increase DNA-binding/transcriptional activity of HOX proteins through their direct binding, the functional importance of their interaction in leukemogenesis is unclear.We recently reported that overexpression of a 4-homeobox-gene signature (ie, PBX3/HOXA7/HOXA9/HOXA11) is an independent predictor of poor survival in patients with cytogenetically abnormal acute myeloid leukemia (CA-AML). Here we show that it is PBX3, but not PBX1 or PBX2, that is consistently coexpressed with HOXA9 in various subtypes of CA-AML, particularly MLL-rearranged AML, and thus appears as a potential pathologic cofactor of HOXA9 in CA-AML. We then show that depletion of endogenous Pbx3 expression by shRNA significantly inhibits MLL-fusion-mediated cell transformation, and coexpressed PBX3 exhibits a significantly synergistic effect with HOXA9 in promoting cell transformation in vitro and leukemogenesis in vivo. Furthermore, as a proof of concept, we show that a small peptide, namely HXR9, which was developed to specifically disrupt the interactions between HOX and PBX proteins, can selectively kill leukemic cells with overexpression of HOXA/PBX3 genes. Collectively, our data suggest that PBX3 is a critical cofactor of HOXA9 in leukemogenesis, and targeting their interaction is a feasible strategy to treat presently therapy resistant CA-AML (eg, MLL-rearranged leukemia) in which HOXA/PBX3 genes are overexpressed.

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. [Cancer Res 2007;67(12):5806-13]

Purpose: Prostate cancer (PC) is the second most common cause of cancer related death in men. A number of key limitations with prostate specific antigen (PSA), currently the standard detection test, has justified evaluation of new biomarkers. We have assessed the diagnostic potential of Engrailed-2 (EN2) protein, a homeodomain-containing transcription factor expressed in PC cell lines and secreted into the urine by PC in men.Experimental Design: EN2 expression in PC cell lines and prostate cancer tissue was determined by semi-quantative RT-PCR and immunohistochemistry. First pass urine [without prior digital rectal examination (DRE)] was collected from men presenting with urinary symptoms (referred to exclude/confirm the presence of prostate cancer) and from controls. EN2 protein was measured by ELISA in urine from men with PC (n ¼ 82) and controls (n ¼ 102).Results: EN2 was expressed and secreted by PC cell lines and PC tissue but not by normal prostate tissue or stroma. The presence of EN2 in urine was highly predictive of PC, with a sensitivity of 66% and a specificity of 88.2%, without requirement for DRE. There was no correlation with PSA levels. These results were confirmed independently by a second academic center.Conclusions: Urinary EN2 is a highly specific and sensitive candidate biomarker of prostate cancer. A larger multicenter study to further evaluate the diagnostic potential of EN2 is justified.

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. The HOX genes are a family of homeodomain-containing transcription factors that determine the identity of cells and tissues in early development (Iimura and Pourquié, 2007), and also have key regulatory roles in adult haematopoietic stem cells and their descendants (Abramovich and Humphries, 2005). In addition, HOX genes are often overexpressed in malignant cells and are known to act as oncogenes in some haematopoietic malignancies (Eklund, 2007).Repeated duplication events have given rise to 39 HOX genes in mammals, divided into four groups (A -D) in tightly linked clusters on different chromosomes (Hoegg and Meyer, 2005). The HOX genes are also divided into paralogue groups -genes that have the equivalent position in each cluster (1 -13) -thus HOXA1, for example, is the 3 0 most gene in cluster A (Scott, 1993). Whereas some HOX genes have distinct functions in specific contexts, many others have overlapping or redundant functions, both during early development (McIntyre et al, 2007) and in malignant cells (Eklund, 2007). This redundancy in HOX function is based in part upon the binding of similar DNA sequences and also on the interaction of HOX proteins with a common set of co-factors including PBX and MEIS. PBX and MEIS modify the DNA-binding specificity of HOX proteins, influence the regulation of transcription and are required for many aspects of HOX function (Moens and Selleri, 2006).In addition to haematological malignancies, the HOX genes are also expressed at high levels in many other solid malignancies, although with the exception of melanoma (Morgan et al, 2007), they are not known to have an oncogenic function. A number of studies, focusing on small groups of HOX genes, have shown that some are upregulated in lung cancer (Abe et al, 2006), but the functional significance of this is unknown. Here we present a comprehensive analysis of HOX expression in non-small-cell lung cancer (NSCLC) that reveals that many of the HOX genes have strongly elevated expression in malignant cells. Further, we show that antagonising HOX/PBX binding in the NSCLC cell lines A549 (Lieber et al, 1976) and H23 (Little et al, 1983) induces apoptosis in vitro and causes significant tumour shrinkage in A549 nude mouse models.

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

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