Neutralizing the Systemic Toxicity of Co-Formulations of Chemotherapeuitcs Using Magneto-Electric Silica Nanocarriers for Specific Therapeutic Action Against Metastatic Cancer Cells

<b>Statement of Purpose:</b> The leading cause of fatalities in breast cancer is metastasis.¹ To increase the success rate of metastasis-free survival, there is a need to tackle therapy-resistant metastatic forms of the disease with novel, patient-friendly, combinatorial treatment regimens. At present, doxorubicin (Dox) regimens are standard of care for tumor debulking but do not stop metastatic recurrence and present cardiotoxicity. Vacuolar ATPase (V-ATPase) H+ pump inhibitors (e.g., diphyllins) prevent metastasis, but the ubiquitous occurrence of this target raises concerns about off-target toxicity.² A solution is targeted delivery to reduce off-target effects while also minimizing drug dose side effects.³ So, here we present the successful demonstration of targeted combinatorial-delivery of V-ATPase inhibitors (Diph) and standard chemotherapeutics (Dox) to the MDAMB231 triple-negative breast cancer metastatic cell model (2D and 3D) with positive cell clearance and affirmative inhibition of cancer cell invasion.<br/><b>Methods:</b> Recently developed magneto-silica nanoparticles (Mag-Si-Ns of ~5-8 nm) in our lab have been tuned to selectively permeabilize cancer cells in an external magnetic field, followed by a triggered release of a drug cocktail through an external oscillating AC electromagnetic field.⁴ The MagSiNs possess a cobalt ferrite core and a piezoelectric fused silica shell. Anticancer drugs (Dox and Diph) which are encapsulated on MagSiNs, are co-administered, to specifically inhibit cancer growth and metastasis in MDAMB231, while avoiding toxic side-effects on healthy control endothelial cells (HUVEC). The dosages of Dox and Diph tested were 20 nM, 500 nM, and 1000 nM. Dose-dependent cancer cell viability, cancer cell invasion capacity, MagSiNs uptake, and intracellular MagSiNs distribution were all assessed to ascertain cell clearing and anti-metastatic capabilities of our combinatorial chemotherapeutic regimen.<br/><b>Results:</b> A 7-fold drop in invasive capacity of metastatic MDAMB231 was achieved when a low dose of 20 nM of Diphyllins was released from MagSiNs formulations. The previously unusable super-toxic drug candidate (Diph) became highly biocompatible to normal endothelial cells (HUVEC) when encapsulated on MagSiNs formulations. Drug molecules (Dox and Diph) released from MagSiNs formulation retained their anti-cancer potency. MagSiNs formulation co-dispersed previously unmixable chemotherapeutic drug molecules into a single dose (hydrophilic Dox and hydrophobic Diph). MagSiNs formulations had a 16-fold increase in the efficacy of Doxorubicin as a standalone chemotherapeutic and achieved a 75% kill rate of MDAMB231, at 500 nM dose of Dox, 24h post-exposure.⁵ Magnetically directed MagSiNs formulation co-delivering Dox and Diph have achieved up to ~88% kill rate of MDAMB231with a 24h dose exposure, clearly demonstrating the synergistic anticancer effect between Dox and Diph. Magnetically directed MagSiNs were also localized in the cytosol of the cells and not sequestered in cytosolic lysosomes.<br/><b>Conclusion:</b> The drugs@MagSiNs formulations were magnetoelectrically permeabilized into the cancer cells, the active form of the drugs were released through a magnetic trigger, the drugs were selectively compartmentalized into the cancer cells, and the V-ATPase inhibitor worked synergistically with the doxorubicin to reduce cancer cell numbers and inhibit cancer metastasis. The results have been successfully replicated in other metastatic cancer cell variants of ovarian and prostate cancer (A2780, PC3).<br/><b>References:</b> [1] Dubey, A.K., et al. Asian Pac J Cancer Prev 16, 4237-45 (2015). [2] McHenry, P. et al. J Cell Biochem 109, 634-42 (2010). [3] Huang, T. et al. Anal Chem 79, 7708-18 (2007). [4] Guduru, R. et al. Sci Rep 3, 2953 (2013). [5] Pilco-Ferreto, N. et al International J. of Oncology 49, 753-762 (2016).