You sure can. Wort is wort, it's how you ferment it determines whether it is a lager or an ale, and there is a blurry line.
There are always exceptions but most people think of lagers as being crisp (high attenuating yeast) and clean.
You may find the yeast you are using for your lager can be brewed reasonably warm without producing any of the esters associated with ales.
I haven't done it but I have heard of people taking the classic Weihenstephan 34/70 up to 20C and it still is neutral.
For my lagers I am using Novalager yeast which can also go to 20C and above and not throw any fruity esters, meaning I can brew pseudo-lagers all year around with it.
If you want to use an ale yeast, choose a neutral flavoured ale yeast, most of them are listed as "American" such as US-05, BRY-97, M42, M44 etc.
If you were to use a British style strain you probably going to get a lot of that ale character. Perfectly delicious beer but not be as as crisp and clean as a traditional lager. The exception is Nottingham, that is pretty neutral. Anyway, talk to your local shop and find out what they have.