Mechanistic Study of RGD Cyclic Peptide-modified Albumin-arsenic Trioxide Targeting the Pancreatic Cancer Tumor Microenvironment

OBJECTIVE To construct an arginine-glycine-aspartic acid(RGD) cyclic peptide-modified human serum albumin(HSA)-arsenic trioxide(ATO) nanomedicine, characterize its physicochemical properties, and evaluate its in vitro anti-pancreatic cancer efficacy and transport mechanisms.

METHODS HSA was conjugated with ATO via arsenic-sulfur bonds to form HSA-ATO, which was further modified with RGD peptides to create RGD-HSA-ATO. The particle size, Zeta potential, and polydispersity index(PDI) of HSA-ATO and RGD-HSA-ATO were assessed using transmission electron microscopy(TEM) and Malvern particle size analyzer. The arsenic content in HSA-ATO and RGD-HSA-ATO was determined using an inductively coupled plasma spectrometer(ICP), and the drug loading capacity was calculated. An in vitro co-culture AsPC-1 mCherry/HPSC CMFDA tumor spheroid model was established, and the efficacy and transport of the nanomedicines were evaluated by treating with HSA-ATO and RGD-HSA-ATO, with ATO as a control. Further, the transport mechanism of RGD-HSA-ATO uptake by tumor spheroids was investigated using transport inhibitors.

RESULTS HSA-ATO and RGD-HSA-ATO nanomedicines were successfully constructed in this study. Test result showed particle sizes of HSA-ATO and RGD-HSA-ATO were uniform with good distribution, measuring (33.20±1.80)nm and (34.80±2.30)nm, respectively, and both showed negative Zeta potentials. ICP results revealed drug loading capacities of (3.00±0.04)% for HSA-ATO and (2.99±0.06)% for RGD-HSA-ATO. In vitro release studies showed pH and glutathione responsiveness. Results of the co-culture model showed that, RGD and HSA modifications significantly enhanced drug transport within the tumor spheroids and anti-tumor efficacy. After 144 h of RGD-HSA-ATO treatment, the tumor cell viability was (57.33±1.88)%, significantly lower than the ATO-treated group. Transport mechanism studies indicated that RGD-HSA-ATO entered tumor cells via macropinocytosis.

CONCLUSION  RGD-HSA-ATO significantly enhances the efficacy and transport of ATO into pancreatic tumor cells. This study provides a foundation for overcoming the dense stromal barrier in pancreatic cancer, allowing traditional Chinese medicine-derived hydrophilic small molecule anti-tumor drugs to penetrate deeper tumor tissues and exert their therapeutic effects.