Yes, they can be expressed in all cases, theoreticly spoken.
Although an apposition to a vocative is mostly replaced by a relative clause, or frequently stands in the nominative.
And when you want to put an apposition to a pronomen possessivum, it is in the genitive.
E. G.: liber tuus, fratris Quinti: the book of you, the brother of Quintus ...
= Your book, being the brother of Quintus ....
Hope I served you well,
Philippus Moerus Lovaniensis