I would like to add the contents of a cell to the Scrip message

Question

I created a script that when a certain date arrives it sends a merge, only in this message I would like to add the contents of a cell of the spreadsheet where the script is running this

function EnviaEmail(){
  var resultado,linha,data;
  var assunto = "XXXXXXXXXXX<conteudo da célula> ";
  var mensagem = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"<conteudo da celula>;
  var aba = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(nomeAba);
  var colunas = aba.getLastColumn();