Intracellular nanoparticle delivery by oncogenic KRAS-mediated macropinocytosis

Abstract

Background

The RAS family of oncogenes (KRAS, HRAS, NRAS) are the most frequent mutations in cancers and regulate key signaling pathways that drive tumor progression. As a result, drug delivery targeting RAS-driven tumors has been a long-standing challenge in cancer therapy. Mutant RAS activates cancer cells to actively take up nutrients, including glucose, lipids, and albumin, via macropinocytosis to fulfill their energetic requirements to survive and proliferate.

Purpose

We exploit macropinocytosis pathway to deliver nanoparticles (NPs) in cancer cells harboring activating KRAS mutations.

Methods

NPs were synthesized by the desolvation method. The physicochemical properties and stability of NPs were characterized by dynamic light scattering and transmission electron microscopy. Uptake of fluorescently labelled NPs in wild-type and mutant KRAS cells were quantitively determined by flow cytometry and qualitatively by fluorescent microscopy. NP uptake by KRAS-driven macropinocytosis was confirmed by pharmacological inhibition and genetic knockdown. 

Results

We have synthesized stable albumin NPs that demonstrate significantly greater uptake in cancer cells with activating mutations of KRAS than monomeric albumin (ie, dissociated form of clinically used nab-paclitaxel). From pharmacological inhibition and semi-quantitative fluorescent microscopy studies, these NPs exhibit significantly increased uptake in mutant KRAS cancer cells than wild-type KRAS cells by macropinocytosis.

Conclusions

The uptake of albumin nanoparticles is driven by KRAS. This NP-based strategy targeting RAS-driven macropinocytosis is a facile approach toward improved delivery into KRAS-driven cancers.

Keywords:

• albumin nanoparticles
• KRAS mutation
• macropinocytosis

Supplementary material

Figure S1 Macropinocytosis of TMR-dextran (red) in cells (nuclei in blue) observed by fluorescence microscopy. (A) MDA-MB-231 cells without EIPA treatment; (B) MDA-MB-231 cells treated with 25 µM EIPA; (C) MDA-MB-468 cells without EIPA treatment; (D) MDA-MB-468 cells treated with 25 µM EIPA. (E) Relative macropinocytotic index of cells. (n=10, **p<0.05, n.s. is no significant difference)

Abbreviations: TMR, tetramethylrhodamine; EIPA, 5-(N-ethyl-N-isopropyl)amiloride.

Acknowledgment

This work was supported by startup funds generously provided by The University of Texas at Austin College of Pharmacy.

Disclosure

The authors report no conflicts of interest in this work.