Can spaghetti noodles replace lo mein noodles?
Round lo mein noodles look veeeeery similar to spaghetti:

Spaghetti


Lo mein


The biggest difference, ingredient-wise is that dried pasta (mostly?) does not contain eggs and lo mein noodles do.

I know that at least once shopping mall food court chinese food place I've eaten from uses spaghetti for their lo mein. It's kind of obvious, but it's not bad. I feel that lo mein typically has a denser, chewier bite than spaghetti. In a pinch, spaghetti will make a tasty noodle dish. It won't quite be lo mein, though.

My advice would be to try it and see what you think. Be careful to not over-cook your spaghetti.