Potential biomarkers associated with prognosis and trastuzumab response in HER2+ breast cancer

Abstract

Abstract: Breast cancer (BC) is the most common malignancy among women worldwide. Around15–25% of BC overexpress the human epidermal growth factor receptor 2 (HER2), which is associatedwith a worse prognosis and shortened disease-free survival. Therefore, anti-HER2 therapies havebeen developed, such as monoclonal antibodies (trastuzumab, Tz), antibody–drug conjugates (adotrastuzumabemtansine, T-DM1), and pharmacological inhibitors of tyrosine kinase activity (lapatinib,Lp). Although Tz, the standard treatment, has significantly improved the prognosis of patients,resistance still affects a significant population of women and is currently a major challenge in clinicaloncology. Therefore, this study aims to identify potential biomarkers to predict disease progression(prognostic markers) and the efficacy of Tz treatment (predictive markers) in patients with HER2+BC. We hypothesize that proteins involved in cell motility are implicated in Tz-resistance. We aim toidentify alterations in Tz-resistant cells to guide more efficient oncologic decisions. By bioinformatics,we selected candidate proteins and determined how their expression, localization, and the processthey modulate were affected by anti-HER2 treatments. Next, using HER2+ BC patients’ data, weassessed these proteins as prognostic and predictive biomarkers. Finally, using Tz-resistant cells, weevaluated their roles in Tz response. We identified deregulated genes associated with cell motility inTz/T-DM1-resistant vs. -sensitive cells. We showed that Tz, T-DM1, and Lp decrease cell viability,and their effect is enhanced in combinations. We determined synergism between Tz/T-DM1 andLp, making possible a dose reduction of each drug to achieve the same therapeutic effect. We foundthat combinations (Tz/T-DM1 + Lp) efficiently inhibit cell adhesion and migration. Furthermore, wedemonstrated the induction of FAK nuclear and cortactin peri-nuclear localization after T-DM1, Lp,and Tz/T-DM1 + Lp treatments. In parallel, we observed that combined treatments downregulateproteins essential for metastatic dissemination, such as SRC, FAK, and paxillin. We found that lowvinculin (VCL) and cortactin (CTTN) mRNA expression predicts favorable survival rates and hasdiagnostic value to discriminate between Tz-sensible and Tz-resistant HER2+ BC patients. Finally, weconfirmed that vinculin and cortactin are overexpressed in Tz-resistance cells, SKBR3-RTz. Moreover,we found that Tz plus FAK/paxillin/cortactin-silencing reduced cell adhesion/migration capacityin Tz-sensitive and -resistant cells. In conclusion, we demonstrate that combined therapies areencouraging since low doses of Tz/T-DM1 + Lp inhibit metastatic processes by downregulatingcritical protein expression and affecting its subcellular localization. We propose that vinculin andcortactin might contribute to Tz-sensibility/resistance in BC cells. Finally, we identify potentialprognostic and predictive biomarkers that are promising for personalized BC management thatwould allow efficient patient selection in order to mitigate resistance and maximize the safety andefficacy of anti-HER2 therapies.