Schematic drawing of the experimental protocol. The weekly dosing of MXT in mice was intended to mimic the monthly dosing of MXT in human cancer patients [13,14]. The order of the weekly injections for the Saline Group was saline, saline, saline, and saline; the order of the weekly injections for the PACAP Group was PACAP, saline, PACAP, and PACAP; the order of the weekly injections for the MXT Group was saline, MXT, saline, and saline; and the order of the weekly injections for the PACAP+MXT Group was PACAP, MXT, PACAP, and PACAP.