In breast cancer, the tumor suppressor gene TP53 plays a pivotal role in regulating cell cycle arrest, apoptosis, and DNA repair, with dysregulation frequently observed in aggressive subtypes such as triple-negative breast cancer (TNBC) and HER2-positive tumors. In vitro models provide a controlled environment to dissect the complex cross-talk between TP53 and estrogen receptor (ER) signaling pathways, critical for understanding subtype-specific tumor biology and therapy resistance. This review consolidates evidence from cellular studies utilizing diverse breast cancer cell lines, including MCF-7 and MDA-MB-231, employing assays such as MTT viability, wound-healing migration, and Western blot analysis to assess TP53 inhibition effects and downstream signaling alterations. Furthermore, network pharmacology approaches that predict phytochemical modulators targeting the TP53-ER axis are explored, highlighting compounds like curcumin and resveratrol with potential therapeutic synergy. Integrating in vitro assay results with computational predictions advances our understanding of TP53-driven signaling networks and aids in identifying novel agents for tailored breast cancer treatment. The review concludes by emphasizing the translational prospects of these findings, advocating for the development of advanced in vitro models and multi-omics integration to refine targeted therapies in breast cancer subtypes, ultimately improving clinical outcomes.