Overcoming Drug Resistance in Myeloma By Synchronized Delivery of Therapeutic and Bone Marrow Disrupting Agents By Nanoparticles Targeting Tumor-Associated Endothelium

• Published in: Blood 2018-11, Vol.132 (Supplement 1), p.1931-1931
• Main Authors: Federico, Cinzia, Muz, Barbara, Sun, Jennifer, Alhallak, Kinan, King, Justin, Kohnen, Daniel R., Fiala, Mark A., Roccaro, Aldo M., Vij, Ravi, Azab, Abdel Kareem
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2018-99-118251

Proteasome inhibitors (PIs) have improved the treatment of multiple myeloma (MM) and prolonged patient survival, but several challenges remain to overcome drug-resistance and toxicity. Bone marrow microenvironment (BMM) drives tumor progression and PIs-resistance in MM; and agents that inhibit the interaction between MM and BMM have been shown to re-sensitize MM cells to therapy. However, the synchronized in vivo delivery of BMM-targeting agents with PIs has been a challenge so far. Nanoparticles offer a valuable platform to encapsulate drugs, and if functionalized, they can facilitate specific delivery to tumor, thus improving treatment efficacy and reducing off-target effects. Within the BMM, the endothelium plays a relevant tumor promoting role. By analyzing the expression of an array of markers in normal and in MM-related endothelium, we found high levels of P-selectin expression on MM-activated endothelial cells (ECs) than normal cells and on ECs collected from the BM of either MM patients or MM-bearing mice compared to their respectively healthy BMMNCs. We next sought to develop lipid nanoparticles (LNPs) targeting the MM-related endothelium, loaded with both PI and BMM-targeting agent for synchronized delivery and reversal of the BMM-induced drug resistance. At this aim, we developed targeted LNPs towards P-selectin by decorating their surface with P-selectin-glycoprotein-ligand-1 (PSGL-1). PSGL-1-targeted LNPs showed specific binding to recombinant P-selectin than identically non-targeted particles, and to MM-associated endothelium compared to healthy endothelium, both in vitro and in vivo. To reverse BMM-induced resistance, LNPs were loaded with bortezomib (BTZ) together with a BMM disrupting agent, ROCK-inhibitor (Y-27632) that inhibits the downstream signaling of the RhoA GTPase pathway, known to be instrumental to the interaction of MM cells with BMM. Consequently, we tested the effect of synchronized delivery of BTZ and Y-27632 in the same LNP on MM cell survival in co-culture with the BMM in vitro. While Y-27632-loaded LNPs did not affect cell proliferation, LNPs loaded with both Y-27632 and BTZ enhanced responsiveness of MM cells to BTZ, compared to BTZ-loaded LNPs, thus overcoming the BMM-induced resistance. Mechanistically, we observed more significant inhibition of PI3K and MAPK signaling, decrease of pRb and up-regulation of p21 and induction of pro-apoptotic pathway (caspase-3, caspase-9 and PARP) by drug-loaded LNPs, compared to free d