  Different aspects of a clinical sample can be revealed by multiple types of
omics data. Integrated analysis of multi-omics data provides a comprehensive
view of patients, which has the potential to facilitate more accurate clinical
decision making. However, omics data are normally high dimensional with large
number of molecular features and relatively small number of available samples
with clinical labels. The "dimensionality curse" makes it challenging to train
a machine learning model using high dimensional omics data like DNA methylation
and gene expression profiles. Here we propose an end-to-end deep learning model
called OmiVAE to extract low dimensional features and classify samples from
multi-omics data. OmiVAE combines the basic structure of variational
autoencoders with a classification network to achieve task-oriented feature
extraction and multi-class classification. The training procedure of OmiVAE is
comprised of an unsupervised phase without the classifier and a supervised
phase with the classifier. During the unsupervised phase, a hierarchical
cluster structure of samples can be automatically formed without the need for
labels. And in the supervised phase, OmiVAE achieved an average classification
accuracy of 97.49% after 10-fold cross-validation among 33 tumour types and
normal samples, which shows better performance than other existing methods. The
OmiVAE model learned from multi-omics data outperformed that using only one
type of omics data, which indicates that the complementary information from
different omics datatypes provides useful insights for biomedical tasks like
cancer classification.
