A Novel Deep Learning Method for Identification of Cancer Genes From Gene Expression Dataset

Introduction

Bioinformatics is a multidisciplinary subject, related to area as diverse as Computer Science, Mathematics, Biology, Statistics and Information Technology. Cancer is featured by an irregular, unmanageable growth that may destroy and cause the neighboring healthy body tissues. In the past, cancer classification by medical practitioners and radiologists was based on clinical and morphological features and had limited diagnostic ability. It deals with different kinds of biological data. The dimension and complexity of raw gene expression data creates challenging data analysis and data management problems. The fundamental goal of microarray gene expression data analysis is to find the behaviourial patterns of genes.

Computational molecular biology deals with different kinds of biological data. Gene expression data is one among them. Hence Gene expression data are the basic data used in this paper. Gene expression is the process by which the information encoded in a gene is changed into an observable phenotype (protein). It is the degree to which a gene is active in certain tissues of the body, measured by the amount of Messenger Ribonucleic Acid (mRNA) in the tissue. Individual genes can be switched on (apply their effects) or switched off according to the needs and situations of the cell at a particular instance. Thus, abnormalities or deviations of gene expression may result in the death of cells, or their uncontrolled growth, such as cancer (Subramanian 2010).

Gene Expression Data

The gene expression matrix is a processed data obtained after the normalization. Each row in the matrix corresponds to a particular gene and each column could either correspond to an experimental condition or a specific time point at which expression of the genes has been measured (Tiwari et al. 2012). The expression level for a gene across different experimental conditions is cumulatively called the gene expression profile, and the expression level of each gene under an experimental condition is cumulatively called the sample expression profile (Androulakis et al. 2007). An expression profile of an experimental condition or a gene is thought of as a vector and can be represented in vector space. For example, an expression profile of a gene can be considered as a vector in n dimensional space where n is the number of conditions, and an expression profile of a condition with m genes can be considered as a vector in m dimensional space where m is the number of genes. Figure 1 shows the gene expression matrix A with m genes across n conditions is considered to be an m × n matrix. Each element a_ijof this matrix represents the expression level of a gene i under a specific condition j, and is represented by a real number.

Figure 1.

Gene expression matrix