Biomedical subjects

Lori A Worley

Publications and source records attributed to Lori A Worley.

6 recordsLinked to original sources

PubMed2006

Functional gene expression analysis uncovers phenotypic switch in aggressive uveal melanomas.

Microarray gene expression profiling is a powerful tool for generating molecular cancer classifications. However, elucidating biological insights from these large data sets has been challenging. Previously, we identified a gene expression-based classification of primary uveal melanomas that accurately predicts metastatic death. Class 1 tumors have a low risk and class 2 tumors a high risk for metastatic death. Here, we used genes that discriminate these tumor classes to identify biological correlates of the aggressive class 2 signature. A search for Gene Ontology categories enriched in our class-discriminating gene list revealed a global down-regulation of neural crest and melanocyte-specific genes and an up-regulation of epithelial genes in class 2 tumors. Correspondingly, class 2 tumors exhibited epithelial features, such as polygonal cell morphology, up-regulation of the epithelial adhesion molecule E-cadherin, colocalization of E-cadherin and beta-catenin to the plasma membrane, and formation of cell-cell adhesions and acinar structures. One of our top class-discriminating genes was the helix-loop-helix inhibitor ID2, which was strongly down-regulated in class 2 tumors. The class 2 phenotype could be recapitulated by eliminating Id2 in cultured class 1 human uveal melanoma cells and in a mouse ocular melanoma model. Id2 seemed to suppress the epithelial-like class 2 phenotype by inhibiting an activator of the E-cadherin promoter. Consequently, Id2 loss triggered up-regulation of E-cadherin, which in turn promoted anchorage-independent cell growth, a likely antecedent to metastasis. These findings reveal new roles for Id2 and E-cadherin in uveal melanoma progression, and they identify potential targets for therapeutic intervention.

Animals↗

PubMed2006

Prognostic testing in uveal melanoma by transcriptomic profiling of fine needle biopsy specimens.

Many uveal melanoma patients die of metastasis despite ocular treatment. Transcriptomic profiling of enucleated tumors can identify patients at high metastatic risk. Because most uveal melanomas do not require enucleation, a biopsy would be required for this analysis. Here, we establish the feasibility of transcriptomic analysis of uveal melanomas from fine needle aspirates. Transcriptomic profiles were analyzed from postenucleation "mock" needle biopsies and matching tumors from eight enucleated eyes and from fine needle aspirates in 17 uveal melanomas before radiotherapy. Predictive accuracy was assessed using a weighted voting classifier optimized for probe set selection using a minimal redundancy/maximum relevance algorithm. Transcriptomic profiles from mock biopsies were highly similar to those from their matching tumor samples (P < 0.0001). Transcriptomic profiles from fine needle aspirates clustered into two classes with discriminating probe sets that overlapped significantly with those for our published classification (P < 0.00001). No loss of predictive accuracy was identified among eight needle aspirates obtained from a distant location. Thus, it is feasible to obtain RNA of adequate quality and quantity to perform transcriptomic analysis on uveal melanoma samples obtained by fine needle biopsy. This method can be applied to specimens obtained from distant geographic locations and can stratify uveal melanoma patients based on metastatic risk.

Adult↗

PubMed2005

Loss of Rb-E2F repression results in caspase-8-mediated apoptosis through inactivation of focal adhesion kinase.

Molecular hardwiring of the cell cycle to the apoptotic machinery is a critical tumor suppressor mechanism for eliminating hyperproliferative cells. Deregulation of the Rb-E2F repressor complex by genetic deletion or functional inhibition of Rb triggers apoptosis through both the intrinsic (caspase-9 mediated) and extrinsic (caspase-8 mediated) death pathways. Induction of the intrinsic pathway has been studied extensively and involves release of free E2F and direct transcriptional activation of E2F-responsive apoptotic genes such as ARF, APAF1, and CASP9. In contrast, the mechanisms leading to activation of the extrinsic pathway are less well understood. There is growing evidence that Rb-E2F perturbation induces the extrinsic pathway, at least in part, through derepression (as opposed to transactivation) of apoptotic genes. Here, we explore this possibility using cells in which Rb-E2F complexes are displaced from promoters without stimulating E2F transactivation. This derepression of Rb-E2F-regulated genes leads to apoptosis through inactivation of focal adhesion kinase and activation of caspase-8. These findings reveal a new mechanistic link between Rb-E2F and the extrinsic (caspase 8-mediated) apoptotic pathway.

ADP-Ribosylation Factors↗

PubMed2005

Association between microarray gene expression signature and extravascular matrix patterns in primary uveal melanomas.

PURPOSE: To determine whether there is an association between gene expression profile and looping extravascular matrix patterns in primary uveal melanomas. DESIGN: Laboratory investigation. METHODS: Formalin-fixed, paraffin-embedded sections from 22 primary uveal melanomas that previously were analyzed by microarray gene expression profiling were stained for periodic acid-Schiff and scored in a masked fashion for the presence of looping extravascular matrix patterns. RESULTS: A strong association was observed between looping patterns and the unfavorable class 2 molecular prognostic signature (P < .001). CONCLUSIONS: Looping extravascular matrix patterns occur almost exclusively in class 2 uveal melanomas. This finding may provide new insights into the pathogenesis and management of uveal melanoma.

Gene Expression↗

PubMed2005

Functional analysis of the p53 pathway in response to ionizing radiation in uveal melanoma.

PURPOSE: Uveal melanomas are notoriously radioresistant and thus necessitate treatment with extremely high radiation doses that often cause ocular complications. The p53 tumor suppressor pathway is a major mediator of the cellular response to radiation-induced DNA damage, suggesting that this pathway may be defective in uveal melanoma. The current study was conducted to analyze the functional integrity of the p53 pathway in primary uveal melanoma cells. METHODS: The p53 gene was sequenced in three primary uveal melanoma cells lines. Cultured primary uveal melanoma cells (MM28, MM50, Mel202, Mel270, and Mel290), MCF7 breast carcinoma cells, normal uveal melanocytes (UM47), and normal human diploid fibroblasts (NHDFs) were irradiated at 250 kVp and 12 mA at a dose rate of 1.08 Gy/min for a total dose of up to 20 Gy. Cell viability was analyzed with trypan blue exclusion. Western blot analysis was used to analyze the expression of p53, p53-phospho-Ser15, p21, Bax, PUMA, and Bcl-x(L). RESULTS: No p53 gene mutations were found in MM28, MM50, or Mel270 cells. Upstream signaling to p53 was intact, with normal induction of p53 and phosphorylation of p53-Ser15, in all five cell lines. Radiation-induced downstream activation of p21 was defective in MM28 and MM50 cells, and activation of Bax was defective in MM50 and Mel290 cells. MM28, MM50, and Mel202 cells failed to deamidate Bcl-x(L) in response to radiation-induced DNA damage. Overall, four of the five uveal melanoma cell lines exhibited at least one downstream defect in the p53 pathway. CONCLUSIONS: Expression of p53 and upstream signaling to p53 in response to radiation-induced DNA damage appear to be intact in most uveal melanomas. In contrast, functional defects in the p53 pathway downstream of p53 activation appear to be common. Further elucidation of p53 pathway abnormalities in uveal melanoma may allow therapeutic interventions to increase the radiosensitivity of the tumors.

Apoptosis Regulatory Proteins↗

PubMed2004

Gene expression profiling in uveal melanoma reveals two molecular classes and predicts metastatic death.

Melanomas are notoriously difficult to classify because of a lack of discrete clinical and pathological stages. Here, we show that primary uveal melanomas surprisingly cluster into two distinct molecular classes based on gene expression profile. Genes that discriminate class 1 (low-grade) from class 2 (high-grade) include highly significant clusters of down-regulated genes on chromosome 3 and up-regulated genes on chromosome 8q, which is consistent with previous cytogenetic studies. A three-gene signature allows biopsy-size tumor samples to be assigned accurately to tumor classes using either array or PCR platforms. Most importantly, this molecular classification strongly predicts metastatic death and outperforms other clinical and pathological prognostic indicators. These studies offer new insights into melanoma pathogenesis, and they provide a practical foundation for effective clinical predictive testing.

Chromosome Aberrations↗