Basal Protein Expression Is Associated With Worse Outcome and Trastuzamab Resistance in HER2+ Invasive Breast Cancer.

Abstract

BACKGROUND:

We investigated the effect of basal protein expression on trastuzamab response in patients with HER2-positive (HER2(+)) breast cancer who received trastuzamab (T) and in HER2(+) breast cancer cell lines.

PATIENTS AND METHODS:

Expression of cytokeratin (CK) 5/6, CK14, and epidermal growth factor receptor (EGFR) was evaluated after immunohistochemical staining in paraffin-embedded tissue of 97 patients with stage I to III HER2(+) breast cancer treated with chemotherapy/T. Groups with and without basal protein expression were compared with respect to clinicopathologic parameters and survival. We treated 4 cell lines (2 basal-HER2 [HCC1569, HCC1954] and 2 nonbasal HER2 [BT474, SKBR3]) each with vehicle, T 20 μg/mL, paclitaxel 0.01 μM (P), and T with P (T + P). Cell viability was assessed and HER2 pathway suppression was compared between groups using immunoblot analysis. Mammosphere formation was used to assess breast cancer stem cell properties.

RESULTS:

EGFR expression was significantly associated with cancer-specific survival (CSS) (P = .05). CK5/6 expression strongly correlated with overall and disease-free survival, and CSS (P = .03, P = .04, and P = .03, respectively). Statistical significance was maintained for EGFR and CK5/6 after adjustment for covariates. CK14 was not associated with survival. All cell lines expressed similar levels of HER2. T and P alone inhibited proliferation of nonbasal cell lines; T + P had an additive cytotoxic effect. Basal cells were resistant to T, P inhibited proliferation, but T + P had no additive cytotoxic effect on cell growth in basal cells. Immunoblot analysis showed a significant decrease in phosphorylated Akt levels after treatment with T or T + P in nonbasal cells but not in basal cells. Akt blockade suppressed growth of basal and nonbasal HER2(+) cells. Furthermore, basal HER2 cell lines had increased mammosphere formation, which suggests increased stem cell properties compared with nonbasal HER2 cell lines.

CONCLUSION:

CK5/6 and EGFR expression are predictive of worse prognosis in HER2(+) breast cancer patients treated with T. Basal HER2 breast cancer cell lines are resistant to trastuzamab, which is mediated through the Akt pathway; AKT inhibition abrogates this resistance. Basal HER2 cell lines also have increased stem cell properties, which might play a role in the resistance pathway.

• Authors: Alice Chung, Michael Choi, Bing-chen Han, Shikha Bose, Xiao Zhang, Lali Medina-Kauwe, Jessica Sims, Ramachandran Murali, Michael Taguiam, Marian Varda, Rachel Schiff, Armando Giuliano, Xiaojiang Cui
• Journal: Clinical breast cancer (Clin Breast Cancer) Vol. 15 Issue 6 Pg. 448-457.e2 (Dec 2015) ISSN: 1938-0666 [Electronic] United States
• PMID: 26248960 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015 Elsevier Inc. All rights reserved.

Chemical References

• Antineoplastic Agents
• Biomarkers, Tumor
• Keratins
• EGFR protein, human
• ERBB2 protein, human
• ErbB Receptors
• Receptor, ErbB-2
• Trastuzumab

Topics

• Adult
• Aged
• Aged, 80 and over
• Antineoplastic Agents (therapeutic use)
• Biomarkers, Tumor (analysis)
• Breast Neoplasms (metabolism, mortality, pathology)
• Disease-Free Survival
• Drug Resistance, Neoplasm (physiology)
• ErbB Receptors (analysis, biosynthesis)
• Female
• Humans
• Immunoblotting
• Immunohistochemistry
• Kaplan-Meier Estimate
• Keratins (analysis, biosynthesis)
• Middle Aged
• Neoplasm Invasiveness
• Phenotype
• Proportional Hazards Models
• Receptor, ErbB-2 (antagonists & inhibitors)
• Trastuzumab (therapeutic use)
• Treatment Outcome