Adult ; Female ; Humans ; Lupus Erythematosus, Systemic ; enzymology ; Male ; Middle Aged ; Peroxidase ; blood

PURPOSE: Although the interferon α (IFNα) signaling and the paired-like homeodomain transcription factor 2 (PITX2) have both been implicated in the progression of breast cancer (BCa), it remains obscure whether these two pathways act in a coordinated manner. We therefore aimed to elucidate the expression and function of PITX2 during the pathogenesis of endocrine resistance in BCa. MATERIALS AND METHODS: PITX2 expression was assessed in BCa tissues using quantitative reverse transcription polymerase chain reaction (RT-qPCR) and immunohistochemistry and in experimentally induced letrozole-resistant BCa cells using RT-qPCR and immunoblotting. Effects of PITX2 deregulation on BCa progression was determined by assessing MTT, apoptosis and xenograft model. Finally, using multiple assays, the transcriptional regulation of interferon-inducible transmembrane protein 1 (IFITM1) by PITX2 was studied at both molecular and functional levels. RESULTS: PITX2 expression was induced in letrozole-resistant BCa tissues and cells, and PITX2 induction by IFNα signaling powerfully protected BCa cells against letrozole insult and potentiated letrozole-resistance. Mechanistically, PITX2 enhanced IFNα-induced AKT activation by transactivating the transcription of IFITM1, thus rendering BCa cells unresponsive to letrozoleelicited cell death. Additionally, ablation of IFITM1 expression using siRNA substantially abolished IFNα-elicited AKT phosphorylation, even in the presence of PITX2 overexpression, thus sensitizing BCa cells to letrozole treatment. CONCLUSION: These results demonstrate that constitutive upregulation of PITX2/IFITM1 cascade is an intrinsic adaptive mechanism during the pathogenesis of letrozole-resistance, and modulation of PITX2/IFITM1 level using different genetic and pharmacological means would thus have a novel therapeutic potential against letrozole resistance in BCa.
Apoptosis ; Breast Neoplasms ; Breast ; Cell Death ; Heterografts ; Immunoblotting ; Immunohistochemistry ; Interferons ; Phosphorylation ; Polymerase Chain Reaction ; Reverse Transcription ; RNA, Small Interfering ; Transcription Factors ; Transcriptional Activation ; Up-Regulation

Among the types of lung cancer, lung adenocarcinoma accounts for the majority, and its overall survival rate is poor. B-cell translocation gene 2 (BTG2) is a member of the antiproliferative gene family, belonging to the BTG/TOB family. Many studies have shown that BTG2 was abnormally expressed in many types of tumors, but its regulatory role in the radiosensitivity of lung adenocarcinoma remained unclear. In this study, we explored the expression level of BTG2 in patients with lung adenocarcinoma and its correlation with clinical prognosis through online database and tissue samples of lung adenocarcinoma patient. The results indicated that the expression level of BTG2 decreased significantly in lung adenocarcinoma patient with radiation resistance. Bioinformatics analysis confirmed that BTG2 could respond to radiotherapy in lung adenocarcinoma cell lines, and its low expression in lung adenocarcinoma patients was associated with poor prognosis (P < 0.05). The lentivirus overexpressing BTG2 (OE-BTG2) was transfected into human lung adenocarcinoma cell lines to increase the expression level of BTG2 including A549 and H1299. And the effect of BTG2 overexpression on the radiosensitivity of lung adenocarcinoma cell lines was detected by clone formation assay. Clone formation experiment confirmed that overexpression of BTG2 could significantly enhance the radiosensitivity of A549 and H1299 cell lines (P < 0.05). The expression levels of BTG2 and apoptosis related protein-Bax were detected by Western blotting (WB) and immunohistochemistry (IHC). The effect of BTG2 on radiation sensitivity of lung adenocarcinoma was further detected via nude mouse in vivo. WB experiment confirmed that BTG2 upregulation could significantly increase the apoptosis level of A549 and H1299 cells after radiation. Moreover, BTG2 overexpression can markedly enhance the radiosensitivity of lung adenocarcinoma (P < 0.05) and increase the protein level of Bax after radiation in vivo. In conclusion, BTG2 had low expression in lung adenocarcinoma patients and its low expression level was closely related to the poor clinical prognosis. Overexpression of BTG2 can increase the radiosensitivity of lung adenocarcinoma cell lines and promote the process of apoptosis after radiation, indicating a new target for overcoming the radiation resistance of lung adenocarcinoma.