p300 activity and cellular location track breast cancer aggressiveness

Blocking the activity of the transcriptional cofactor p300 reduced the survival and metastatic spread of triple-negative breast cancer cells in laboratory models, according to a study that also identified the protein’s location inside tumor cells as a potential indicator of clinical outcome. The researchers focused on p300, an epigenetic regulator with histone acetyltransferase activity, because its functional role and intracellular distribution had not been fully characterized in this aggressive, hormone-independent form of breast cancer.

In cell-based experiments and animal models, genetic depletion of p300 or pharmacological inhibition of its histone acetyltransferase activity reduced tumor-cell viability, promoted apoptosis and impaired metastatic dissemination. These experimental effects were accompanied by changes in markers associated with epithelial–mesenchymal transition, a process linked to tumor-cell plasticity and invasion, as well as changes in cytoskeletal organization. The findings support a role for p300 activity in maintaining the growth and metastatic behavior of triple-negative breast cancer models, although they do not establish that p300 inhibition would produce the same benefits in patients.

Analysis of human triple-negative breast cancer specimens showed that p300 was predominantly located in the cytoplasm of tumor cells. Within that clinical cohort, tumors in which p300 was found exclusively in the cytoplasm were associated with lower tumor stage and improved overall survival. This association remained evident independently of mutations affecting p300’s histone acetyltransferase domain, suggesting that the protein’s location may carry prognostic information not explained by mutations in that functional region alone.

The results distinguish two related but nonidentical features of p300: its biochemical activity and its subcellular localization. Experimental interference with p300 activity was linked to reduced viability and dissemination in preclinical models, while the distribution of p300 in human tumors was associated with stage and survival. The study therefore presents p300 as both a potential regulator of triple-negative breast cancer aggressiveness and a candidate biomarker whose interpretation may require attention to where the protein resides within tumor cells. Because the clinical findings are associations, they do not show that cytoplasmic localization causes better outcomes, and the experimental results do not demonstrate clinical efficacy or establish a treatment recommendation for people with the disease.

Subject of Research: p300 activity and localization in triple-negative breast cancer

Article Title: p300 activity and subcellular localization associate with tumor aggressiveness and clinical outcome in triple-negative breast cancer

Article References: Fermento, M. E., Clemente, V., Gallardo, G. A., Masciovecchio, M. V., Villegas, M. E., Alonso, E. N., Ferronato, M. J., Coló, G. P., Arévalo, J., Juri, M. A. Q., Jung, M., Facchinetti, M. M., & Curino, A. C. (2026). p300 activity and subcellular localization associate with tumor aggressiveness and clinical outcome in triple-negative breast cancer. Scientific Reports. https://doi.org/10.1038/s41598-026-69778-8

Image Credits: AI Generated

DOI: 10.1038/s41598-026-69778-8

Keywords: p300, triple-negative breast cancer, histone acetyltransferase, tumor aggressiveness, cancer metastasis, subcellular localization, tumor stage, overall survival, epigenetic regulation, activity, subcellular, localization