1:Marmara University, Istanbul; 2:Hacettepe University; 3:Inonu University

Tenascin-C (TN-C) is a matricellular protein that is expressed in embryo with a very limited expression in the postnatal life. However, TN-C expression increases dramatically in some tumors. Clinically, this high expression is correlated with bad prognosis and metastasis in many solid tumors, including breast cancer. Even though improvements in survival have been made in early-stage breast cancer, the prognosis of the metastasized breast cancer has only improved negligibly. High TN-C expression is correlated with lower lung-metastasis free survival in breast cancer patients. It has been shown that the autocrine TN-C prepares the metastatic niche in the lungs, and also aids in the invasion into the pulmonary blood vessels in animal models. Therefore, in this study we investigated the in vitro effect of TN-C silencing by CRISPR/Cas9 system on the metastatic capacity of the most aggressive subtype of breast cancer, triple negative breast cancer (TNBC). Our study has shown that the TN-C CRISPR/Cas9 treated human cell line had a significantly lower metastatic capacity and had slower migration in the wound healing assay. To specifically target the lung metastatic niche, we used chitosan-based carrier system, which has previously been shown to aid in lung accumulation. The biodistribution study by near-infrared fluorescence imaging for the intravenous injection of oxytocin-grafted chitosan, a peptide-polymer conjugate system, has shown that the carrier system accumulated primarily in liver and then in the lungs. Considering the results herein, we developed a non-viral vector for TN-C editing by CRISPR/Cas9 in the lungs to decrease lung metastasis in TNBC.