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Predictive sub-typing of subjects Retrospective and prospective studies Exploration of clinico-genomic data Identify relevant gene expression patterns Issues in Bayesian Tree Modeling of Clinical and Gene Expression Data
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Current Areas of Application Breast Cancer lymph node status disease recurrence Ovarian Cancer tumor location
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Lymph Node Involvement Is a Key Breast Cancer Risk Factor But -- lymph node dissection also carries morbidity and inaccuracy
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Identifying Metagenes Associated With Lymph Node Status Tumor Sample Gene
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Metagenes/ Expression Signatures Dimension reduction: Signal improvement Clustering Singular value decomposition Empirical or model-based factor analysis Characterize patterns in data
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Gene Clustering
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Gene Clustering (cont’d)
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Factor extraction (SVD)
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Differential Gene Expression
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Differential Gene Expression (Threshold 1)
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Differential Gene Expression (Threshold 2)
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Differential Gene Expression (Threshold 3)
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Nonlinear Expression
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Nonlinear Expression (Threshold 1)
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Nonlinear Expression (Threshold 2)
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Lymph Node Metastasis Metagenes
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Ovarian Tumor Site Genes
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Statistical Tree Models for Clinico-Genomic Prediction Regression trees: Non-linear, interactions Recursive partitioning Retrospective studies Many trees: Model uncertainty Predictions average across trees
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Binary Outcomes Retrospective Sampling LN +
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Binary Outcomes: Prospective Inference from Retrospective Model
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Binary Outcomes: Retrospective Model Model conditionals for predictors Nonparametric Bayes: Dirichlet model Modeling in x space – joint structure Implies Beta priors on
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Growing Binary Trees Node split: Each candidate predictor:threshold pair 2x2 table: 2 Bernoulli’s, fixed columns (Y=0/1) Assess and select split, or stop Conservative Bayesian tests Multiple trees: Multiple splits at any node
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Inference with Many Binary Trees Within-tree inference & prediction: Sequences of beta posteriors for Simulate: Impute Pr(Y=1|leaf) Multiple trees: Likelihood across trees Average predictions across trees Model (predictor:threshold)s uncertainty “Smoothing” classification boundaries
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Binary Outcome: Lymph Node Metastasis Tumor Sample Gene Predictive trees: Nonparametric Bayes’ Metagene expression Retrospective sampling Lancet 2003 (Huang, West et al) Lancet 2003 (Huang, West et al)
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Predicting Lymph Node Status With Metagenes LN+ LN- Probability of LN+ Out-of-sample cross validation Sample
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Forests of Clinico-Genomic Trees Select from potential clinical and genomic predictor variables multiple trees variable combination – co-occurrence multiple subtypes
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… With Metagenes and Clinical Predictors LN+ LN- Probability of LN+ Out-of-sample cross validation Sample
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Lymph Node Clinico-Genomic Predictors
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Predicting Ovarian Tumor Site Omentum Ovary Probability of Omentum Out-of-sample cross validation Sample
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Gene Identification Implicated metagenes – gene subsets Genes correlated with key metagenes Breast Cancer – nodal metastasis: Interferon pathway/inducible gene subset Interferons mediate anti-tumor response Evidence of dysfunction of normal anti-tumor response? Ovarian Cancer – tumor site: Growth regulatory pathway/inducible gene subset Evidence of dysfunction of normal cell growth?
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Ongoing Research Stochastic search (sequential,annealing) Representation of tree ‘forest’ Metagene definition/ creation Cluster implementation of tree models
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Computational & Applied Genomics Program Joseph Nevins Mike West Erich Huang Ed Iversen Holly Dressman Duke University Koo Foundation-Sun Yat Sen Cancer Center Andrew Huang, Skye Cheng, Mei-Hua Tsou http://www.isds.duke.edu/~jennifer/ Department of Obstetrics and Gynecology John Lancaster Andrew Berchuck
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Growing Binary Trees (2x2) ?
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