Heinemann, Luca; Möllers, Klara Maria; Mohammed Ahmed, Helal Mohammed; Wei, Lanying ; Sun, Kaiyan; Nimmagadda, Subbaiah Chary; Frank, Daria; Baumann, Anja; Poos, Kathrin ; Dugas, Martin ; Varghese, Julian ; Raab, Marc-Steffen ; Khandanpour, Cyrus: Inhibiting PI3K–AKT–mTOR Signaling in Multiple Myeloma-Associated Mesenchymal Stem Cells Impedes the Proliferation of Multiple Myeloma Cells