High serum miR-19a levels are associated with inflammatory breast cancer and are predictive of favorable clinical outcome in patients with metastatic HER2+ inflammatory breast cancer

Abstract

Introduction: Altered serum microRNA (miRNA) levels may be correlated with a dysregulated expression pattern in parental tumor tissue and reflect the clinical evolution of disease. The overexpression of miR-21, miR-10b, and miR-19a is associated with the acquisition of malignant characteristics (increased tumor cell proliferation, migration, invasion, dissemination, and metastasis); thus, we determined their utility as serum biomarkers for aggressive breast cancer (HER2-overexpressed or -amplified [HER2(+)] and inflammatory breast cancer [IBC]).

Experimental design: In this prospective study, we measured miR-21, miR-10b, and miR-19a levels using quantitative reverse transcriptase-polymerase chain reaction in the serum of 113 breast cancer patients and determined their association with clinicopathologic factors and clinical outcome. Thirty healthy donors with no history of cancer were enrolled as controls.

Results: Patients with non-metastatic HER2(+) breast cancer had higher serum miR-21 median levels than patients with non-metastatic HER2(-) disease (p = 0.044); whereas patients with metastatic HER2(+) breast cancer had higher serum miR-10b median levels than patients with metastatic HER2(-) disease (p = 0.0004). There were no significant differences in serum miR-19a median levels between HER2(+) and HER2(-) groups, regardless of the presence of metastases. High serum miR-19a levels were associated with IBC (p = 0.039). Patients with metastatic IBC had significantly higher serum miR-19a median levels than patients with metastatic non-IBC (p = 0.019). Finally, high serum miR-19a levels were associated with longer progression-free survival time (10.3 vs. 3.2 months; p = 0.022) and longer overall survival time (median not reached vs. 11.2 months; p = 0.003) in patients with metastatic HER2(+) IBC.

Conclusion: High levels of miR-21 and miR-10b were present in the serum of patients with non-metastatic and metastatic HER2(+) breast cancer, respectively. High levels of serum miR-19a may represent a biomarker for IBC that is predictive for favorable clinical outcome in patients with metastatic HER2(+) IBC.

Figure 1. Mean threshold cycle values of miR-192± standard deviation in the serum of breast cancer patients and healthy donors.

No significant differences in mean threshold cycle (Ct) values of miR-192 were observed among the serum of different groups (Kruskal–Wallis test, p = 0.785).

Figure 2. Serum miRNA levels in patients with M0 HER2⁺, M0 HER2⁻, M1 HER2⁺, M1 HER2⁻ breast cancer and HDs.

The box plots show: a) relative serum miR-21 and miR-19a levels in patients with M0 HER2⁺ and M0 HER2⁻ breast cancer; and b) relative serum miR-21 and miR-10b levels in patients with M1 HER2⁺ and M1 HER2⁻ breast cancer. Thirty HDs were included as a control group. The differences in serum levels were evaluated using the Mann-Whitney U test, and the p values are indicated above the plots.

Figure 3. Serum miR-19a levels in patients with MIBC and MNIBC.

The box plots show: a) relative serum miR-19a levels in patients with MNIBC and MIBC; and b) relative serum miR-19a levels in patients with MNIBC HER2⁻, MIBC HER2⁻, MNIBC HER2⁺ and MIBC HER2⁺. Thirty HDs were included as controls. The differences in serum miR-19a levels were evaluated using the Mann-Whitney U test, and the p values are indicated above the plots.

Figure 4. MiR-19a expression in breast cancer cell lines.

The expression of miR-19a was evaluated in 5 breast cancer cell lines. The two IBC cell lines SUM-149 (TN) and KPL-4 (HER2⁺) expressed significantly higher levels of miR-19a than the non-IBC cell lines MCF-7 (ER⁺), SKBR-3 (HER2⁺), and MDA-231 (TN) (mean ± standard deviation; 2-tailed Student's t-test; p<0.05 is indicated with: *; p<0.01 is indicated with: **; p<0.001 is indicated with: ***).

Figure 5. Kaplan-Meier plots of breast cancer patients according to serum miR-19a levels.

The Kaplan-Meier plots show the survival time of breast cancer patients according to serum miR-19a levels. In a) patients with MIBC HER2⁺ and high serum miR-19a levels had longer PFS time (10.3 vs. 3.2 months; p = 0.022) and OS time (median not reached vs. 11.2 months; p = 0.003) than patients with MIBC HER2⁺ and with low serum miR-19a levels; in b) patients with MNIBC HER2⁺ and high serum miR-19a levels had longer PFS time (7.7 vs. 5.1 months; p = 0.061) and OS time (32.9 vs. 13.3 months; p = 0.015) than patients with MNIBC HER2⁺ and low serum miR-19a levels. High and low serum miR-19a levels were defined according to a cut-off corresponding to the mean values of miR-19a in the serum of HDs plus 2 standard deviations. A log-rank test was used to analyze the differences in the survival times between patients with high and low serum miR-19a levels. Characteristics of patients with MIBC HER2⁺ and high serum miR-19a levels: median age (48.3); trastuzumab-treated (12/17 = 70.6%); treatment-naïve (3/17 = 17.6%); no trastuzumab-treated (2/17 = 11.8%). Characteristics of patients with MIBC HER2⁺ and low serum miR-19a levels: median age (53.2); trastuzumab-treated (5/10 = 50.0%); treatment-naïve (0/10 = 0.0%); no trastuzumab-treated (5/10 = 50.0%). Characteristics of patients with MNIBC HER2⁺ and high serum miR-19a levels: median age (53.8); trastuzumab-treated (5/10 = 50.0%); treatment-naïve (2/10 = 20.0%), no trastuzumab-treated (3/10 = 30.0%). Characteristics of patients with MNIBC HER2⁺ and low serum miR-19a levels: median age (54.1); trastuzumab-treated (11/14 = 78.6%); treatment-naïve (1/14 = 7.1%); no trastuzumab-treated (2/14 = 14.3%).