[1] After studying civil law, Castiglione became a protonotary apostolic, gaining a reputation as a great canonist and sacred orator.
[1] He served as the papal legate of Pope Nicholas V and Pope Callixtus III to Germany, in which capacity he was present at the Diet of Regensburg of April 1454 and the Diet of Frankfurt of October 1454.
[1] On 8 September 1455 he was present in St Mark's Basilica in Venice for the ceremony of the departure of the Crusade.
[1] At the request of Francesco I Sforza, Pope Callixtus III made Castiglione a cardinal in the consistory of 17 December 1456.
[1] Cardinal Castiglione participated in the papal conclave of 1458 that elected Pope Pius II.