Cell-Penetrating Doxorubicin Released from Elastin-Like Polypeptide Kills Doxorubicin-Resistant Cancer Cells in In Vitro Study

Elastin-like polypeptides (ELPs) undergo a characteristic phase transition in response to ambient temperature. Therefore, it has been be used as a thermosensitive vector for the delivery of chemotherapy agents since it can be used to target hyperthermic tumors. This novel strategy introduces unprecedented options for treating cancer with fewer concerns about side effects. In this study, the ELP system was further modified with an enzyme-cleavable linker in order to release drugs within tumors. This system consists of an ELP, a matrix metalloproteinase (MMP) substrate, a cell-penetrating peptide (CPP), and a 6-maleimidocaproyl amide derivative of doxorubicin (Dox). This strategy shows up to a 4-fold increase in cell penetration and results in more death in breast cancer cells compared to ELP-Dox. Even in doxorubicin-resistant cells (NCI/ADR and MES-SA/Dx5), ELP-released cell-penetrating doxorubicin demonstrated better membrane penetration, leading to at least twice the killing of resistant cells compared to ELP-Dox and free Dox. MMP-digested CPP-Dox showed better membrane penetration and induced more cancer cell death in vitro. This CPP-complexed Dox released from the ELP killed even Dox-resistant cells more efficiently than both free doxorubicin and non-cleaved ELP-CPP-Dox.

Cell-penetrating doxorubicin released from Elastin-like polypeptide kills doxorubicin-resistant cancer cells in vitro study

Background: Elastin-like polypeptide (ELP) undergoes its characteristic of phase transitioning in response to ambient temperature. ELP therefore has been be used as a thermosensitive vector for the delivery of chemotherapy agents since it can be targeted to hyperthermic tumors. This novel strategy introduces unprecedented options for treating cancer, with fewer concerns about side effects. In this study, the ELP system was further modified with an enzyme-cleavable linker in order to release drugs within tumors. This system consists of ELP, a matrix metalloproteinase (MMP) substrate, a cell penetrating peptide (CPP), and 6-maleimidocaproyl amide derivative of doxorubicin (Dox). This construct may be initially targeted to the tumor by application of mild heat after administration. Within the hyperthermic tumor, then this construct is cleaved by MMP, releasing CPP-Dox, which can infiltrate tumor tissues and penetrate cell membranes.Methods: We produced the construct in E.coli and examined its cleavage by MMP enzymes in vitro. Flow cytometry and confocal analysis were used to verify the facilitated uptake of the digested cell-penetrating Dox by breast cancer cells and Dox-resistant cells. Cytotoxicity tests further demonstrated improvements in bioavailability of cell-penetrating Dox following the enhanced cellular uptake of the cancer cells. Comparisons with the non-cleavable ELP counterpart were paralleled.Results: This strategy shows up to a 4-fold increase in cell penetration and results in more death in breast cancer cells than the ELP-Dox. Even in doxorubicin-resistant cells (NCI/ADR and MES/ADR), ELP-released, cell-penetrating doxorubicin demonstrated better membrane penetration, leading to at least twice the killing of resistant cells than ELP-Dox and free Dox. Conclusion: MMP-digested CPP-Dox shows better membrane penetration and induces more cancer cell death in vitro. This CPP-complexed Dox released from ELP kills even dox-resistant cells more efficiently than both free doxorubicin and non-cleaved ELP-CPP-Dox.