Abstract P3-06-04: Tumor specific cargo release in ex vivo patient samples and murine models of triple negative breast cancer by a pH-targeted nanoparticle: V3-RUBY
Authors: Thomas Alexandra , Chiba Akiko , Samykutty Abhilash , McNally Molly W. , McNally Lacey R. 
Published: March 2020

Background: Triple negative breast cancer (TNBC), unlike other breast cancer subtypes, lacks a specific targetable receptor. As such tumor specific delivery, which can limit off-target effects of anti-neoplastic therapies, has been an unmet clinical need in treating this aggressive breast cancer subtype. To address this need, we exploited the tumor hallmark of an acidic microenvironment and developed a pH targeted nanoparticle by conjugation of the V3 pH specific peptide on a wormhole pore mesoporous silica nanoparticles (V3-RUBY) and assessed the ability of V3-RUBY to specifically release cargo in ex vivo patient samples and in orthotopically implanted TNBC tumors as detect by multispectral optoacoustic imaging technology (MSOT).

Methods: The silica nanoparticles with wormhole pore architecture were synthesized by sol-gel chemistry and characterized by transmission electron microscopy (TEM), zeta potential, and dynamic light scattering (DLS). The surface base particle was crosslinked with a gatekeeper molecule, chitosan. Further targeting of the particle using V3 pHLIP (low insertion peptide), resulted in the V3-RUBY nanoparticle which allows for pH-sensitive cargo release. The particle was loaded with imaging dye to assess tumor specificity. Fresh ex vivo TNBC patient tumor tissues were resected and rapidly treated with V3-RUBY containing propodium iodide (PI) to evaluate tumor uptake of V3-RUBY and cargo release within the tumor cells, as measured by the red fluorescence of PI when bound to nucleic acids. (PI independently cannot cross cell membranes.) In vivo, female athymic mice were implanted with MDA-MB-468 breast cancer cells by the mammary fat pad injection. Once the tumor reached 3mm in size, athymic mice were intravenously injected with V3-RUBY nanoparticles carrying IR780 infrared imaging dye and were imaged with MSOT inVision 512TF.

Results: The RUBY nanoparticle with wormhole pores was 27 nm diameter. The dual targeting approach of a nanoparticle with V3 targeting peptide and chitosan demonstrated pH specificity around tumor pH. In ex vivo patient TNBC samples, V3-RUBY demonstrated active targeting and dye release at pH 6.8, which approximated the pH measured at surgical tumor removal, in 10 fresh patient samples compared to pH 7.4 controls (p&lt;0.0001, N=10) (Table). There was a non-significant trend towards lower uptake in histological grade 2 tumors, relative to grade 3 tumors. In the murine models, IR780 uptake in the MDA-MB-468 tumors measured 23.2 a.u (arbitrary units) and was 3.1, a.u. in the liver and 0.9 a.u. in the kidneys (p &lt;0.0001, N=5). Tumor accumulation in the MDA-MB-468 model was significantly increased compared to both liver and kidneys (p=0.0002 and p=0.0003).

Conclusion: The tumor-specific release of payload by V3-RUBY suggests the potential of a pH specific target in TNBC, with such a nanoparticle holding promise to deliver both diagnostic and therapeutic cargo directly to the tumor and limit off-target toxicity. Future translation of these technologies could have promise in TNBC, as well as other high-grade breast cancer subtypes and expand treatment options in this challenging area of oncology.

TablePatientBreast Cancer SubtypeTumor GradePathologic StagePI Uptake (a.u.) pH 6.8PI Uptake (a.u.) 7.41TNBC3ypT3N3a33.20.82TNBC3ypT2N038.41.53TNBC3ypT4bN1a36.81.74TNBC3T1bN022.40.85TNBC2T1cN021.80.86TNBC2ypT0N021.50.67TNBC3ypT1aN2a22.00.48TNBC3ypT4dN239.52.19TNBC3T2N2a31.52.210TNBC3T2N1a32.21.8

Citation Format: Alexandra Thomas, Akiko Chiba, Abhilash Samykutty, Molly W. McNally, Lacey R. McNally. Tumor specific cargo release in ex vivo patient samples and murine models of triple negative breast cancer by a pH-targeted nanoparticle: V3-RUBY [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-06-04.