How can I invoke Drush command inside hook_cron? I have module that provides drush integration.

Now I want to create modules with hook_cron where I want to launch drush command. 

How can I run Drush command programmatically?
You should not call drush from inside a Drupal module.  Instead, factor out the functionality of your Drush commands into separate functions that can be called from module code and drush commandfiles alike.  Your module code should do all user access / permissions checks before calling the API functions (usually via the access checks provided by Drupal's menu system); the Drush commands should call the API functions directly, without access checks.