Transcription-mediated chimeric RNAs in prostate cancer: time to revisit old hypothesis?

Chromosomal rearrangements and fusion genes play important roles in tumor development and progression. Four high-frequency prostate cancer-specific fusion genes were recently reported in Chinese cases. We attempted to confirm one of the fusion genes, USP9Y-TTTY15, by reverse transcription PCR, but detected the presence of the USP9Y-TTTY15 fusion transcript in cancer samples, nonmalignant prostate tissues, and normal tissues from other organs, demonstrating that it is a transcription-induced chimeric RNA, which is commonly produced in normal tissues. In 105 prostate cancer samples and case-matched adjacent nonmalignant tissues, we determined the expression level of USP9Y-TTTY15 and a previously reported transcription-induced chimeric RNA, SLC45A3-ELK4. The expression levels of both chimeric RNAs vary greatly in cancer and normal cells. USP9Y-TTTY15 expression is neither higher in cancer than adjacent normal tissues, nor correlated with features of advanced prostate cancer. Although the expression level of SLC45A3-ELK4 is higher in cancer than normal cells, and a dramatic increase in its expression from normal to cancer cells is correlated with advanced disease, its expression level in cancer samples alone is not correlated with any clinical parameters. These data show that both chimeric RNAs contribute less to prostate carcinogenesis than previously reported.

Identification of a neuronal transcription factor network involved in medulloblastoma development.

BACKGROUND: Medulloblastomas, the most frequent malignant brain tumours affecting children, comprise at least 4 distinct clinicogenetic subgroups. Aberrant sonic hedgehog (SHH) signalling is observed in approximately 25% of tumours and defines one subgroup. Although alterations in SHH pathway genes (e.g. PTCH1, SUFU) are observed in many of these tumours, high throughput genomic analyses have identified few other recurring mutations. Here, we have mutagenised the Ptch+/- murine tumour model using the Sleeping Beauty transposon system to identify additional genes and pathways involved in SHH subgroup medulloblastoma development. RESULTS: Mutagenesis significantly increased medulloblastoma frequency and identified 17 candidate cancer genes, including orthologs of genes somatically mutated (PTEN, CREBBP) or associated with poor outcome (PTEN, MYT1L) in the human disease. Strikingly, these candidate genes were enriched for transcription factors (p=2x10-5), the majority of which (6/7; Crebbp, Myt1L, Nfia, Nfib, Tead1 and Tgif2) were linked within a single regulatory network enriched for genes associated with a differentiated neuronal phenotype. Furthermore, activity of this network varied significantly between the human subgroups, was associated with metastatic disease, and predicted poor survival specifically within the SHH subgroup of tumours. Igf2, previously implicated in medulloblastoma, was the most differentially expressed gene in murine tumours with network perturbation, and network activity in both mouse and human tumours was characterised by enrichment for multiple gene-sets indicating increased cell proliferation, IGF signalling, MYC target upregulation, and decreased neuronal differentiation. CONCLUSIONS: Collectively, our data support a model of medulloblastoma development in SB-mutagenised Ptch+/- mice which involves disruption of a novel transcription factor network leading to Igf2 upregulation, proliferation of GNPs, and tumour formation. Moreover, our results identify rational therapeutic targets for SHH subgroup tumours, alongside prognostic biomarkers for the identification of poor-risk SHH patients.

Ethnical disparities of prostate cancer predisposition: genetic polymorphisms in androgen-related genes.

Prostate cancer (PCa) is the most commonly diagnosed male malignancy and the second biggest cause of cancer death in men of the Western world. Higher incidences of PCa occur in men from North America, Oceania and Western countries, whereas men from Asia and North Africa have a much lower PCa incidence rate. Investigations into this population disparity of PCa incidence, in order to identify potential preventive factors or targets for the therapeutic intervention of PCa, have found differences in both environmental and genetic variations between these populations. Environmental variations include both diet and lifestyle, which vary widely between populations. Evidence that diet comes into play has been shown by men who immigrate from Eastern to Western countries. PCa incidence in these men is higher than men in their native countries. However the number of immigrants developing PCa still doesn't match native black/white men, therefore genetic factors also contribute to PCa risk, which are supported by familial studies. There are a number of genetic polymorphisms that are differentially presented between Western and Eastern men, which are potentially associated with PCa incidence. Androgen and its receptor (AR) play a major role in PCa development and progression. In this study, we focus on genes involved in androgen biosynthesis and metabolism, as well as those associated with AR pathway, whose polymorphisms affect androgen level and biological or physiological functions of androgen. While many of the genetic polymorphisms in this androgen/AR system showed different frequencies between populations, contradictory evidences exist for most of these genes investigated individually as to the true contribution to PCa risk. More accurate measurements of androgen activity within the prostate are required and further studies need to include more African and Asian subjects. As many of these genetic polymorphisms may contribute to different steps in the same biological/physiological function of androgen and AR pathway, an integrated analysis considering the combined effect of all the genetic polymorphisms may be necessary to assess their contribution to PCa initiation and progression.

Vascular targeting agents enhance chemotherapeutic agent activities in solid tumor therapy.

The utility of combining the vascular targeting agents 5,6-dimethyl-xanthenone-4 acetic acid (DMXAA) and combretastatin A-4 disodium phosphate (CA4DP) with the anticancer drugs cisplatin and cyclophosphamide (CP) was evaluated in experimental rodent (KHT sarcoma), human breast (SKBR3) and ovarian (OW-1) tumor models. Doses of the vascular targeting agents that led to rapid vascular shutdown and subsequent extensive central tumor necrosis were identified. Histologic evaluation showed morphologic damage of tumor cells within a few hours after treatment, followed by extensive hemorrhagic necrosis and dose-dependent neoplastic cell death as a result of prolonged ischemia. Whereas these effects were induced by a range of CA4DP doses (10-150 mg/kg), the dose response to DMXAA was extremely steep; doses < or = 15 mg/kg were ineffective and doses > or = 20 mg/kg were toxic. DMXAA also enhanced the tumor cell killing of cisplatin, but doses > 15 mg/kg were required. In contrast, CA4DP increased cisplatin-induced tumor cell killing at all doses studied. This enhancement of cisplatin efficacy was dependent on the sequence and interval between the agents. The greatest effects were achieved when the vascular targeting agents were administered 1-3 hr after cisplatin. When CA4DP (100 mg/kg) or DMXAA (17.5 mg/kg) were administered 1 hr after a range of doses of cisplatin or CP, the tumor cell kill was 10-500-fold greater than that seen with chemotherapy alone. In addition, the inclusion of the antivascular agents did not increase bone marrow stem cell toxicity associated with these anticancer drugs, thus giving rise to a therapeutic gain.