No, Visual Studio does not support that. For a reference of the regular expressions capabilities in VS check:
Regular Expressions (Visual Studio)
(Original answer, given due to misinterpreting the original question)
Assuming Visual Studio C# Default key bindings.
There are different ways you can achieve this.
If it's a (variable, method, property, etc) you can use the Rename refactoring to change all instances. This refactoring is invoked by pressing F2 key while on the instance you want to rename.
If you perform the change on the definition itself you can also use SHIFT+ALT+F10 to invoke the active refactorings popup and then do the rename all instances.
If it's a string literal you can use the shortcut CTRL+U (lowercase) and CTRL+SHIFT+U (uppercase) to rapidly switch the case of the selection. This is valid for all text shown in the editor, but most useful for string literals.