Differential Expression of Long Non-Coding RNA IGF2-AS in Tamoxifen-Resistant Breast Cancer Cells

Background: Breast cancer, particularly the luminal subtype, often responds to endocrine therapies. However, 20-30% of patients develop resistance, resulting in more aggressive disease. Long non-coding RNAs (lncRNAs) are implicated in cancer progression and treatment resistance. Objective: This study aimed to evaluate the role of the lncRNA insulin-like growth factor 2 antisense (IGF2-AS) in tamoxifen-resistant breast cancer and assess its potential as a therapeutic target. Methods: Two tamoxifen-resistant breast cancer cell lines (TAMR-V and TAMR-H) were used to assess IGF2-AS expression via qPCR. Knockdown experiments with siRNA evaluated the role of IGF2-AS in cell proliferation, invasion, and migration. Next-generation sequencing (NGS) analyzed gene expression differences between the cell lines. Kaplan-Meier survival analysis determined the clinical significance of IGF2-AS expression in breast cancer patients. Results: IGF2-AS expression was significantly upregulated in TAMR-V and TAMR-H cell lines compared to control MCF-7 cells. Knockdown of IGF2-AS reduced cell proliferation and invasion in TAMR-V cells but did not significantly affect TAMR-H cells, indicating a cell line-specific role in tamoxifen resistance. NGS revealed differential gene expression profiles between TAMR-V and TAMR-H cells, suggesting variability in resistance mechanisms. Survival analysis demonstrated that higher IGF2-AS expression was associated with poorer prognosis in breast cancer patients, including those with hormone-positive and triple-negative subtypes. Conclusions: IGF2-AS is upregulated in tamoxifen-resistant breast cancer and promotes cell proliferation and invasion in a cell line-specific manner. Its differential expression in TAMR-V and TAMR-H cells highlights the complexity of resistance mechanisms, suggesting IGF2-AS as a potential therapeutic target for overcoming tamoxifen resistance.