Immuno-Oncology Signatures Explorer (IOSig) is an interactive Shiny application
meant to facilitate the investigation of immune checkpoint inhibitor (ICI)
treated datasets with gene expression biomarker signatures for prediction of responder / non-responder.
Previously published gene expression signatures have been collected in addition to publicly available ICI
treated RNA-seq cohorts to allow for query their own datasets or signatures against. In addition, it also possible to
explore the data within the application without providing your own.
The Dataset Analysis tab is meant for users to upload their own RNA-seq expression
datasets coupled with the necessary clinical data. The RNA-seq data is expected to
be in a comma or tab separated format with the columns containing the sample ids and
rows containing genes. The genes should be in HUGO format. Additionally the samples
cannot start with a number. If your samples start with a numerical value, add a
character, like 'X' at the start.
It is also necessary for the uploaded clinical data to have specific column names.
These column names are: 'Sample_ID' (sample name), 'response' (ICI response),
'os' (overall survival time), and 'os_event' (overall survival event).
'reponse' and 'os_event' should be binary columns where 1 represents
responder to ICI treatment and censoring in os_event.
Example RNA-seq and Clinical files can be downloaded from the left
side panel on the Dataset Analysis page. Additionally, the datasets
used for comparison in the AUROC portion can be filtered and selected
in the left side panel.
User Signature Analysis
The User Signature Analysis tab allows a user to upload a list of genes in HUGO format
to query against the datasets within IOSig. The genes should be separated by a new line
and pasted into the left side panel. A unique name for the uploaded gene signature is
also required. An example gene signature file can be downloaded from the left
side panel as well.
Published Signature Analysis
The 'Published Signature Analysis' tab is similar to the 'User Signature Analysis' tab except that
you can select from a variety of previously published gene signatures to query the IOSig datasets.
AUROC Analysis
Area under the receiver operating characteristic curve (AUROC)
is a performance measurement metric for a binary classifier. In IOSig,
AUROC is utilized to assess the ability of gene signature to distinguish
responder and non-responder based on the gene expression values for a sample.
The curve is plotted with the true positive rate on the y-axis and false
positive rate on the x-axis. A higher area under the curve (AUC) value the better
the gene signature is at predicting responder / non-responder. An AUC value of 0.5
signifies the gene signature has no ability to separate responder / non-responder while 1
is a perfect classifier.
Three AUROC analyses are calculated:
AUROC Overview
The individual AUROC plots for each dataset / signature (depending on analysis method).
AUROC Comparison
A graphical representation of the AUROC values of the selected datasets over all signatures.
AUROC Correlation
A correlation heatmap created from the AUROC values of all gene signatures.
Mann Whitney
The Mann Whitney U test provides a way to test for differences between two groups (responder, non-responder).
In this case, the metric used to compare responders and non-responders is the score calculated for each
sample from each gene signature. For this analysis, a box plot to demonstrate the distribution of responder
and non-responder samples is generated in addition to a table with basic summary information. For uploaded datasets,
response information should have a column title of 'response' with 1 signifying responder and 0 signifying non-responder.
Survival
A Survival analysis is available for datasets that have the necessary included information. Using
the overall survival information, a Kaplan-Meier graph is generated. When uploading new clinical data,
the column representing time should be 'os' with the column signifying an event labeled 'os_event'.
Gene Set Enrichment Analysis
Gene Set Enrichment Analysis (GSEA) is a method which analyzes gene expression data and focuses on
finding changes at the level of gene sets as opposed to individual genes. This allows for the
detection of changes which may be insignificant at the gene level, but significant across a summation of
genes that encompass a biological process or network. Normalized enrichment score (NES) is the
primary result of a GSEA analysis. This statistic reflects the level of which a gene set is overrepresented
at the top or bottom of the ranked list of genes. In IOSig, the GSEA analysis and plots are generated with
responders or high category samples at the top (dependent on dataset or signature analysis).
We would be grateful if you cite IOSig in your work:
Samuel Coleman, Caroline Wheeler, Rebecca Hoyd, Louis Denko, Ching-Nung Lin,
Muhammad Zaki Hidayatullah Fadlullah, Siwen Hu-Lieskovan, Christine H. Chung, Ahmad A. Tarhini,
Daniel Spakowicz and Aik Choon Tan, 2024