Here is another pic.

{{!gwi}}

Well, It certainly looks nasty and painful. I would get it out of there before it get so big you can't. I have found that desirable plants usually do not volunteer like weeds do. You might try taking a piece of it to your county extension if you really want to salvage it. Take care that it doesn't injure you.
Good luck

Smilax.

It probably won't pull, Smilax usually need to be dug out.

Possibly Smilax rotundifolia (confusingly, the thorniness can vary considerably). If so, it has rhizomes/tubers which make it difficult to kill. Try Roundup concentrate; you may need to use it more than once.