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\title{\Rpackage{CancerMutationAnalysis} package} 
\author{Giovanni Parmigiani \\
  Dana-Farber Cancer Institute and \\
  Harvard School of Public Health \\ 
  email: \texttt{gp@jimmy.harvard.edu}, \\ \\
  Simina M. Boca \\
  Georgetown University Medical Center \\
  email: \texttt{smb310@georgetown.edu}}

\maketitle
\tableofcontents

\section{Overview}

This package contains software which implements a variety of
methods for gene and gene-set level analysis
in somatic mutation studies of cancer. 
The methods implemented are described in
\cite{SjoblomEtAl2006} and \cite{ParmigianiEtAl2007},
for the gene level analysis, and
\cite{BocaEtAl2010}, for the gene-set level analysis.
The gene level methods considered were developed to
distinguish between ``driver genes'' 
and ``passenger genes;'' the former play an
active role in tumorigenesis, having mutations which
are selected for in cancer, while the latter are mutated
in tumor samples, but have no role in tumorigenesis.
They incorporate the study design used in
\cite{SjoblomEtAl2006, WoodEtAl2007, JonesEtAl2008, ParsonsEtAl2008, ParsonsEtAl2011}:
The complete collection of coding exons (the exome) was
sequenced in several ``discovery samples,'' with
a smaller number of genes being further sequenced in
a larger number of ``prevalence samples,'' based on 
the results of the discovery screen, and possibly, on
prior knowledge about their role in cancer.

The gene-set methods implemented
carry out the ``patient-oriented'' approach, 
which calculates gene-set scores for each sample, then combines them
across samples. By comparison, gene-oriented methods calculate a score
for each gene across all samples, then combine them into gene-set scores.
The four patient-oriented methods described in \cite{BocaEtAl2010}
are included, as well as 
the gene-oriented method described in
\cite{MichaudEtAl2008} (see also \cite{SchaefferEtAl2008}), 
which is in the \Rpackage{limma} package and performs
a Wilcoxon test.
Data from several comprehensive studies are also
distributed with this package
\citep{SjoblomEtAl2006, WoodEtAl2007, JonesEtAl2008, ParsonsEtAl2008, ParsonsEtAl2011}.

This vignette represents an introduction to the 
\Rpackage{CancerMutationAnalysis} package. The primary functions are:
\Rfunction{cma.scores}, which calculates a variety of gene scores;
\Rfunction{cma.fdr}, which estimates passenger probabilities and
false discovery rates; and
\Rfunction{cma.set.stat}, which implements a number
of gene-set level methods.
The function
\Rfunction{cma.set.sim} performs gene-set simulations using either
the permutation null or the passenger null (see \cite{BocaEtAl2010}).
The functions \Rfunction{extract.sims.method} and \Rfunction{combine.sims}
are used to manipulate the objects resulting from 
\Rfunction{cma.set.sim}.

\section{Data objects}

We first load the data and look at them:
<<LoadData, eval=TRUE>>=
library(CancerMutationAnalysis)
data(WoodBreast07)
data(WoodColon07)
data(JonesPancreas08)
data(ParsonsGBM08)
data(ParsonsMB11)
@ 
The datasets are labelled according to the publication year of the 
study and the tumor type. Thus, data is available for
studies of breast cancer, colon cancer, pancreatic cancer,
glioblastoma multiforme (GBM), and medulloblastoma (MB).

The objects containing information on the somatic mutations are
labelled \texttt{GeneAlter*}. As an example, consider the 
\texttt{GeneAlterGBM} object:
<<GeneAlter, eval=TRUE>>=
head(GeneAlterGBM)
@ 
The columns represent the transcript, mutation type 
(\texttt{Mut}, \texttt{Amp}, \texttt{Del}, for point mutations,
amplifications, and deletions, respectively), sample ID,
screen (\texttt{Disc} or \texttt{Prev} for ``Discovery'' or
``Prevalence''), wild type nucleotype, context, and nucleotide 
after mutation. Only point mutations are used to calculate gene scores, estimate
passenger probabilities, and perform gene-set level analyses.
Only discovery samples are used to perform the set analyses.

The \texttt{GeneCov*} objects contain data on the number of
nucleotides of each type successfully sequenced for each transcript:
<<GeneCov, eval=TRUE>>=
head(GeneCovGBM)
@ 

The \texttt{GeneSamp*} objects store the number of discovery and
prevalence samples for each transcript:
<<GeneSamp, eval=TRUE>>=
head(GeneSampGBM)
@ 

The \texttt{BackRates*} objects contain estimated passenger probabilities
used in the original studies.

\section{Calculating gene scores}

Gene scores are obtained using the \texttt{cma.scores} function.
These scores include the Cancer Mutation Prevalence (CaMP) score
\citep{ParmigianiEtAl2007} and the
log Likelihood Ratio (logLRT) score \citep{GetzEtAl2007}.
They take into account
the mutation profile and the total
number of nucleotides successfully sequenced for each gene, as well as
an estimated ``background passenger rate'' of mutation:

<<CalcScores, eval=TRUE>>=
ScoresGBM <- cma.scores(cma.alter = GeneAlterGBM,
                        cma.cov = GeneCovGBM,
                        cma.samp = GeneSampGBM,
                        passenger.rates = BackRatesGBM["MedianRates",])

head(ScoresGBM)
@ 

\section{Estimating passenger probabilities}

Passenger probabilities for individual genes are estimated using the
\texttt{cma.fdr} function, which performs an empirical Bayes (EB)
analysis. 
The output of this function is a list,
each score having an entry which, for each gene, 
gives the corresponding score, the number of
genes with scores greater or equal in the dataset
(\texttt{F}), the average number of genes with scores
greater or equal in the simulated datasets
(\texttt{F0}), the estimated false discovery rate
(\texttt{Fdr}), the estimated local false discovery rate
(\texttt{fdr}), and the estimated value of the prior probability
of the gene being null (\texttt{p0}).
The estimated passenger probabilities for individual genes are the estimate
local false discovery rates.
If \texttt{showFigure=TRUE}, a plot is also generated for each score,
displaying the right tail of the density of null scores and
a 1-D ``rug plot'' histogram of the observed scores.
A cutoff is chosen so that the false discovery rate has the
largest possible value below it. See
Figure \ref{fig:Fdr} for an example.
<<FdrFig, height=8, width=8, echo=TRUE, include=FALSE>>=
set.seed(188310)
FdrGBM <-  cma.fdr(cma.alter = GeneAlterGBM,
                   cma.cov = GeneCovGBM,
                   cma.samp = GeneSampGBM,
                   scores = "logLRT",
                   passenger.rates = BackRatesGBM["MedianRates",],
                   showFigure=TRUE,
                   cutoffFdr=0.1,
                   M = 5)

head(FdrGBM[["logLRT"]])
@ 
\begin{figure}
  \caption{Example of figure obtained by setting \texttt{showFigure=TRUE}
in the \texttt{cma.fdr} function.}
\begin{center}
<<label=FdrFig-here, fig=TRUE, echo=FALSE>>=
<<FdrFig>>
@ 
\end{center}
  \label{fig:Fdr}
\end{figure}

\section{Performing gene-set analyses}

The function \Rfunction{cma.set.stat} returns a data-frame with 
p-values and q-values for all the methods selected. By default, all the
methods are implemented; however this takes several minutes.
Setting the \texttt{gene.method} parameter to \texttt{TRUE} implements
the gene-oriented method. The other method parameters refer to
the patient-oriented methods:
\texttt{perm.null.method} refers to the permutation null without heterogeneity,
\texttt{perm.null.het.method} to the permutation null with heterogeneity,
\texttt{pass.null.method} to the passenger null without heterogeneity, and
\texttt{pass.null.het.method} to the passenger null with heterogeneity.
See \cite{BocaEtAl2010} for more details on all these methods
and \cite{LinEtAl2007} for a related method.

We use gene-sets from KEGG \citep{KanehisaAndGoto2000} in this example through the \texttt{KEGG.db}
package \citep{CarlsonEtAl2007}:
<<loadKEGGsets, eval=TRUE>>=
library(KEGG.db)
KEGGPATHID2EXTID
@ 

Since the genes in the GBM datasets are annotated by gene names,
while \texttt{KEGGPATHID2EXTID} uses EntrezGene identifiers,
we also need to load the vector mapping the identifiers to the names,
which we obtained by using the \texttt{biomaRt} package \citep{DurinkEtAl}.
<<loadEntrezID2Name>>=
data(EntrezID2Name)
@ 

We now use the function \texttt{cma.set.stat} to perform the gene-set
analyses on three KEGG sets:
<<GeneSet, eval=TRUE>>=
as.character(KEGGPATHNAME2ID[c("Endometrial cancer", 
                               "Non-small cell lung cancer",
                               "Alanine, aspartate and glutamate metabolism")])

SetResultsGBM <-
  cma.set.stat(cma.alter = GeneAlterGBM,
               cma.cov = GeneCovGBM,
               cma.samp = GeneSampGBM,
               GeneSets = KEGGPATHID2EXTID[c("hsa05213", 
                 "hsa05223",  "hsa00250")],
               ID2name = EntrezID2Name,
               gene.method = FALSE,
               perm.null.method = TRUE,
               perm.null.het.method = FALSE,
               pass.null.method = TRUE,
               pass.null.het.method = FALSE)
@ 

The resulting object is a data-frame containing p-values and q-values
for the methods which were implemented:

<<showGBMSetResults, eval=TRUE>>=
SetResultsGBM
@ 

\section{Simulating data for gene-sets}

We now demonstrate the use of the \texttt{cma.set.sim} function,
which simulates datasets under either the permutation or passenger null
(see \cite{BocaEtAl2010}), depending on whether \texttt{pass.null} is set
to \texttt{TRUE} or \texttt{FALSE}, and calculates the p-values and q-values
for those datasets for the selected methods. The simulations may also
include spiked-in gene-sets, by using the \texttt{perc.samples} and
\texttt{spiked.set.sizes} options. For example, if one desires to have two 
spiked-in gene-sets, both having $50$ genes, but one having the probability 
of being altered in any given sample of $0.75$ and the other of $0.95$, then 
these parameters should be set to \texttt{perc.samples = c(75, 90)} and
\texttt{spiked.set.sizes = 50}. The spiked-in gene-sets are artificially created
with hypothetical genes (for more details on how they are generated, 
see \cite{BocaEtAl2010}). 
To simulate the data without spiked-in sets, under the permutation or
passenger null hypotheses, the parameters should be set as following:
\texttt{perc.samples = NULL, spiked.set.sizes = NULL}.
The object outputted by 
\texttt{cma.set.sim} is of the class \texttt{SetMethodsSims}.
Note that this code takes several minutes to run:

<<simDataSets, eval=TRUE>>=
set.seed(831984)

resultsSim <- 
    cma.set.sim(cma.alter = GeneAlterGBM,
                cma.cov = GeneCovGBM,
                cma.samp = GeneSampGBM,
                GeneSets = KEGGPATHID2EXTID[c("hsa05213", 
                  "hsa05223", "hsa00250")],
                ID2name = EntrezID2Name,
                nr.iter = 2,
                pass.null = TRUE,
                perc.samples = c(75, 95),
                spiked.set.sizes = c(50),
                show.iter = TRUE,
                gene.method = FALSE,
                perm.null.method = TRUE,
                perm.null.het.method = FALSE,
                pass.null.method = TRUE,
                pass.null.het.method = FALSE)

resultsSim

slotNames(resultsSim)

resultsSim@null.dist
@ 

\subsection{Manipulating the \texttt{SetMethodsSims} objects}

We provide $2$ functions to help manipulate the \texttt{SetMethodsSims} objects
which result from the \texttt{cma.set.sim} function:
\texttt{extract.sims.method} and \texttt{combine.sims}. The
\texttt{extract.sims.method} function is used to obtain a single data frame
with the p-values or q-values from one of the specific methods. For instance,
the command to get the p-values for the permutation null with no
heterogeneity method is:

<<extractSimMethod, eval=TRUE>>=
extract.sims.method(resultsSim,
                    "p.values.perm.null")

@ 

The function \texttt{combine.sims} may be used to combine $2$ simulations:

<<combineSims, eval=TRUE>>=
combine.sims(resultsSim, resultsSim)
@ 

\bibliographystyle{plain}
\bibliography{CancerMutationAnalysis}

\section{Acknowledgments}
We would like to thank Michael A. Newton and Luigi Marchionni for generously sharing their code and
Benjamin Langmead, Fernando Pineda, and Michael Ochs for some very
helpful discussions.



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