The present invention discloses methods and materials for delivering a cargo compound into a brain cancer cell and/or across the blood-brain barrier. Delivery of the cargo compound is accomplished by the use of protein transport peptides derived from Neisseria outer membrane proteins, such as Laz. The invention also provides synthetic transit peptides comprised of the pentapeptide AAEAP (SEQ ID NO: 25). The invention further discloses methods for treating cancer, and specifically brain cancer, as well as other brain-related conditions. Further, the invention provides methods of imaging and diagnosing cancer, particularly brain cancer.