Hi!
I think you might want to enable this option: http://i.imgur.com/YXrnIYX.png
Because all of the checkboxes are unchecked, by default it tells the search to everything that is not unchecked. Once you turn that option on, it will ignore the filter until at least one checkbox is selected.
The second is not possible unfortunately, because these tags are from the same taxonomy. If the ‘Anoikis-resistant breast cancer’ and the ‘antiestrogenic’ were in different taxonomies, then this might be possible, I think.