Intratumoral Gene Electrotransfer of Plasmid DNA Encoding shRNA against Melanoma Cell Adhesion Molecule Radiosensitizes Tumors by Antivascular Effects and Activation of an Immune Response.

Simona Kranjc Brezar,Monika Savarin,Valter Mrak,Masa Bosnjak,Maja Cemazar,Gregor Sersa

doi:10.3390/vaccines8010135

Simona Kranjc Brezar, Monika Savarin + Show 4 more

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https://doi.org/10.3390/vaccines8010135

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Journal: Vaccines	Publication Date: Mar 19, 2020
Citations: 12	License type: CC BY 4.0

Affiliation: Institute of Oncology Ljubljana

Abstract

In this study, radiotherapy was combined with the gene electrotransfer (GET) of plasmid encoding shRNA against melanoma cell adhesion molecule (pMCAM) with dual action, which was a vascular-targeted effect mediated by the silencing of MCAM and an immunological effect mediated by the presence of plasmid DNA in the cytosol-activating DNA sensors. The effects and underlying mechanisms of therapy were evaluated in more immunogenic B16F10 melanoma and less immunogenic TS/A carcinoma. The silencing of MCAM potentiated the effect of irradiation (IR) in both tumor models. Combined therapy resulted in 81% complete responses (CR) in melanoma and 27% CR in carcinoma. Moreover, after the secondary challenge of cured mice, 59% of mice were resistant to challenge with melanoma cells, and none were resistant to carcinoma. Combined therapy reduced the number of blood vessels; induced hypoxia, apoptosis, and necrosis; and reduced cell proliferation in both tumor models. In addition, the significant increase of infiltrating immune cells was observed in both tumor models but more so in melanoma, where the expression of IL-12 and TNF-α was determined as well. Our results indicate that the combined therapy exerts both antiangiogenic and immune responses that contribute to the antitumor effect. However, tumor immunological status is crucial for a sufficient immune system contribution to the overall antitumor effect.

Highlights

Melanoma cell adhesion molecule (CD146/MCAM), which was originally discovered in melanoma cells [1], is a transmembrane glycoprotein of the immunoglobulin superfamily that is present in many tumors, such as melanoma, the pancreas, prostate, breast, kidney, ovarian cancer, mesothelioma, and small cell lung cancer [1,2,3,4,5,6,7]
In this study, radiotherapy was combined with the gene electrotransfer (GET) of plasmid encoding short hairpin RNA (shRNA) against melanoma cell adhesion molecule with dual action, which was a vascular-targeted effect mediated by the silencing of MCAM and an immunological effect mediated by the presence of plasmid DNA in the cytosol-activating DNA sensors
This study indicates a radiosensitization of two radioresistant tumor models, B16F10 melanoma and TS/A carcinoma, expressing high and low levels of MCAM, after silencing MCAM using the GET

Summary

Introduction

Melanoma cell adhesion molecule (CD146/MCAM), which was originally discovered in melanoma cells [1], is a transmembrane glycoprotein of the immunoglobulin superfamily that is present in many tumors, such as melanoma, the pancreas, prostate, breast, kidney, ovarian cancer, mesothelioma, and small cell lung cancer [1,2,3,4,5,6,7]. The in vitro targeting MCAM using antibodies altered the biological properties of endothelial, melanoma, breast, ovarian, adenoid cystic carcinoma, and osteosarcoma cells, such as the proliferation or survival, migration, and invasion [3,15,16,17,18,19,20,21,22,23]. Treating cells with antibodies against MCAM reduced proliferation for approximately 60%, migration for 75%, and tube formation in human umbilical vein endothelial cells (HUVEC), and invasion in melanoma and osteosarcoma cells, while the proliferation of melanoma, hepatocarcinoma, osteosarcoma, ovary, and cervix tumor cells was not affected [21,22,23,24]

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