Not really. Your best bet is to have a good keyword density for those words (probably between 3 - 5%, though experts may differ). You can also try section targeting if you have lengthy content. I've seen some neat tricks done wit URL structure, but I'm not knowledgeable enough to explain that.
It is possible ut it is not allowed. It's possible if you insert this tag into your adsense code google_page_url = "keyword1, keyword2, keyword3..."; Code (markup): but AdSense TOS say you are not allowed to change your code. You can use it only if you get written permission from google and they can give it to you only if you are getting unrelated ads on your page, but if you are getting unrelated ads you have to add more content with your keywords, put your keywords in title tag, etc.