Could vertical mine tubes be adapted into missile cells?

Could specialist submarine minelaying tubes be modified into vertical-launch missile cells?

Potentially, but only with a new internal support and launch structure fitted inside the through-hull mine tube.

Dedicated mine tubes already passed vertically through the submarine's outer casing and opened at both ends. That geometry makes a missile conversion conceivable, although the original tube was built to let a mine fall. A supporting canister or cell structure would have to carry the weapon and manage launch loads safely. The conversion is technically plausible only with that additional structure.