I have the following AutoCompleteBox defined inside DataTemplate:

<Window.Resources>
  <DataTemplate x:key="PaneTitleTemplate">
    <Grid>
      <Grid.ColumnDefinitions>
        <ColumnDefinition />
        <ColumnDefinition />
      </Grid.ColumnDefinition>
      <ContentPresenter Content="{Binding}" />
      <toolkit:AutoCompleteBox x:Name="InsertBox" ItemsSource="{???}" />
    </Grid>
  </DataTemplate>
</Window.Resources>
...
<radRock:RadPane x:Name="pane1" TitleTemplate="{StaticResource PaneTitleTemplate}"/>

Now I'd like to fill it with a list of strings, but I don't know which Binding should I use. The list of strings is an instance variable from the Window. What should I do?