Cracking melanoma's armor: Supramolecular dual-strike on XPO1 and β-catenin to overcome resistance.

Introduction: XPO1 plays a crucial role in the nuclear export machinery, making it an attractive target for inhibiting nuclear-cytoplasmic transport in melanoma, where its overexpression is linked to unfavorable prognosis. However, XPO1 monotherapy has not demonstrated sufficient efficacy to be considered a first-line treatment option for melanoma.

Objectives: This research aimed to delve into the resistance mechanism of XPO1-targeting therapy in melanoma and fabricate a proteinoid microsphere which could target XPO1 and β-catenin to maximize the effect of XPO1 inhibitors.

Methods: Transcriptome sequencing was used to analyze the effects of XPO1 interference on the signaling pathways of melanoma. Nuclear-cytoplasmic protein separation, co-immunoprecipitation, and confocal microscopic analyses were conducted to clarify the resistance mechanism of XPO1 targeting therapy. A proteinoid microsphere named XPinβ was developed by co-assembling a specially designed XPO1 antagonistic peptide (XPin) and a β-catenin antagonist (Carnosic acid/CA). Cell model, mouse allograft and patient-derived xenograft (PDX) models were used to evaluate the antitumor effect of XPinβ.

Results: In our study, inhibition of XPO1 led to the nuclear accumulation of β-catenin, altered the nuclear-cytoplasmic localization of APC, and activated the Wnt/β-catenin signaling pathway. XPinβ was efficiently internalized into melanoma cells via macropinocytosis, achieving simultaneous inhibition of both XPO1 and β-catenin. As expected, XPinβ demonstrated robust anti-tumor efficacy in an allograft melanoma mouse model, with significantly superior therapeutic effects compared to monotherapy targeting XPO1 or CA treatment alone. Moreover, XPinβ effectively inhibited growth of patient-derived xenograft (PDX) tumors overexpressing XPO1, outperforming both CA and the commercially available XPO1 inhibitor KPT-330. Most importantly, XPinβ significantly suppressed pulmonary metastasis of melanoma while maintaining excellent biosafety.

Conclusions: This study demonstrates the enhanced efficacy of XPO1-targeted therapy through the inhibition of the Wnt/β-catenin signaling pathway and introduces XPinβ, a proteinoid microsphere with promising clinical translational potential for dual targeting therapy against melanoma involving both XPO1 and β-catenin.