Knockdown of CAVEOLIN-1 Sensitizes Human Basal-Like Triple-Negative Breast Cancer Cells to Radiation

Abstract

Background/Aims: Triple-negative breast cancer (TNBC) is a high-risk breast cancer phenotype without specific targeted therapy options and is significantly associated with increased local recurrence in patients treated with radiotherapy. CAVEOLIN-1 (CAV-1)-mediated epidermal growth factor receptor (EGFR) nuclear translocation following irradiation promotes DNA repair and thus induces radiation resistance. In this study, we aimed to determine whether knockdown of CAV-1 enhances the radiosensitivity of basal-like TNBC cell lines and to explore the possible mechanisms. Methods: Western blotting was used to compare protein expression in a panel of breast cancer cell lines. Nuclear accumulation of EGFR as well as DNA repair and damage at multiple time points following irradiation with or without CAV-1 siRNA pretreatment were investigated using western blotting and confocal microscopy. The radiosensitizing effect of CAV-1 siRNA was evaluated using a clonogenic assay. Flowcytometry was performed to analyse cell apoptosis and cell cycle alteration. Results: We found that CAV-1 is over-expressed in basal-like TNBC cell lines and barely expressed in HER-2-positive cells; additionally, we observed that HER-2-positive cell lines are more sensitive to irradiation than basal-like TNBC cells. Our findings revealed that radiation-induced EGFR nuclear translocation was impaired by knockdown of CAV-1. In parallel, radiation-induced elevation of DNA repair proteins was also hampered by pretreatment with CAV-1 siRNA before irradiation. Silencing of CAV-1 also promoted DNA damage 24 h after irradiation. Colony formation assays verified that cells could be radiosensitized after knockdown of CAV-1. Furthermore, G₂/M cell cycle arrest and apoptosis enhancement may also contribute to the radiosensitizing effect of CAV-1 siRNA. Conclusion: Our results support the hypothesis that CAV-1 knockdown by siRNA causes increased radiosensitivity in basal-like TNBC cells. The mechanisms associated with this effect are reduced DNA repair through delayed CAV-1-associated EGFR nuclear accumulation and induction of G₂/M arrest and apoptosis through the combined effects of CAV-1 siRNA and radiation.

Caveolin‐1, cancer and therapy resistance

“…86 Herein, CAV1 was found to be overexpressed in TNBC cell lines and CAV1 expression levels correlated with the sensitivity to IR. 86 The more radiosensitive low CAV1-expressing or CAV1-negative cells were characterized by an impaired RTinduced nuclear EGFR translocation, pronounced DNA damage and apoptosis. CAV1 silencing limited the radiationinduced elevation of DNA repair proteins, subsequently leading to sustained DNA damage and finally resulting in increased apoptosis.…”

Mining Prognostic Significance of MEG3 in Human Breast Cancer Using Bioinformatics Analysis

“…Breast cancer remains a leading cause of cancer-related death in women [1][2][3]. Despite increased screening and improved diagnosis and treatment of breast cancer, prognosis remains poor [4][5][6].…”

The Role of Canonical Wnt Signaling in Regulating Radioresistance

“…In phase 3 clinical trials, radiation in combination with the molecular-targeted epidermal growth factor receptor (EGFR) inhibitor cetuximab led to a survival benefit of 10% in patients with HNSCC [3]. Delayed EGFR nuclear accumulation by downregulation of caveolin-1 increased radiosensitivity in breast cancer [86]. In preclinical models, PI3K/mTOR inhibitor enhances HNSCC radiosensitivity [87].…”

“…It has been demonstrated that Wnt1 signaling inhibits cancer therapy-induced apoptosis by inhibiting cytochrome c release and activation of caspase-9 [84]. In addition, inhibition of β-catenin in head and neck squamous cell carcinoma (HNSCC) induced the activation of caspase-3, increased p53 and the proapoptotic protein Bax, and reduced the anti-apoptotic protein Bcl-2 [86]. Wnt-1-induced secreted protein, as an important downstream target gene of Wnt1/β-catenin signaling, prevents p53-mediated apoptosis, inhibits the mitochondrial release of cytochrome c, and elevates the expression of anti-apoptotic protein Bcl-X L in cancer [52].…”