Cancer Res Treat.  2016 Apr;48(2):715-726. 10.4143/crt.2015.227.

Caveolin-1 Modulates Docetaxel-Induced Cell Death in Breast Cancer Cell Subtypes through Different Mechanisms

• Kang J
• Park JH
• Lee HJ
• Jo U
• Park JK
• Seo JH
• Kim YH
• Kim I
• Park KH

• KMID: 2454350
• DOI: http://doi.org/10.4143/crt.2015.227

Abstract

PURPOSE
Caveolin-1 (CAV-1) expression is more associated with basal-like cancers than estrogen receptor- or ErbB-2-expressing breast cancers. However, the biological relevance of different levels of CAV-1 expression according to subtype in the epithelial compartment of breast cancer remains unclear.
MATERIALS AND METHODS
We investigated whether CAV-1 functions as a tumor suppressor and/or modulator of the cytotoxic activity of docetaxel (DTX) in subtypes of breast cancer using in vitro and xenograft models.
RESULTS
The levels of CAV-1 expression were closely associated with DTX sensitivity in triple-negative breast cancer cells. In addition, CAV-1 significantly inhibited cell proliferation and modulated DTX-induced apoptosis through cell cycle arrest in the G2/M phase. The mechanisms underlying DTX-induced apoptosis differed in breast cancers according to the levels of CAV-1 expression. DTX robustly enhanced Bcl-2 inactivation by CAV-1 in MDA-MB-231 cells, while p53-mediated cell cycle arrest by DTX was more pronounced in CAV-1-low but p53-functional MCF-7 cells. In parallel with the data from breast cancer cell lines, CAV-1-transfected MCF-7 cells showed higher efficacy of DTX treatment in a xenograft model.
CONCLUSION
We clearly demonstrated cooperative effects between CAV-1 and DTX in mediating apoptosis, suggesting that the levels of CAV-1 expression might be an important indicator for DTX use in breast cancer.

Keyword

Caveolin-1; Breast neoplasm; Apoptosis; Docetaxel

MeSH Terms

Apoptosis
Breast Neoplasms*
Breast*
Caveolin 1*
Cell Cycle Checkpoints
Cell Death*
Cell Line
Cell Proliferation
Estrogens
Heterografts
In Vitro Techniques
MCF-7 Cells
Negotiating
Triple Negative Breast Neoplasms
Caveolin 1
Estrogens

Figure

• 

  Fig. 1. Caveolin-1 (CAV-1)-expressing breast cancer cells are more sensitive to docetaxel (DTX). (A) The levels of expression of the estrogen receptor (ER), ErbB-2, and CAV-1 were evaluated by western blot analyses according to subtype of breast cancer cells. β-Actin was used as an internal control. (B) ZR75-1, T47D, MCF-7, SKBR3, HCC1954, BT474, Hs578T, MDA-MB-231, and MDA-MB-468 cells were treated with the indicated concentrations of DTX, and the mean percentage of survival in the MTT assay is shown. TN, triple negative; MTT, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium. *p < 0.05 compared to MCF-7 cells.

• 

  Fig. 2. Caveolin-1 (CAV-1) enhances the antiproliferative activity of docetaxel (DTX). Associations between the status of CAV-1 expression and the DTX-induced antiproliferative activity were analyzed by [3H]thymidine incorporation in MDA-MB-231 cells (A), MCF-7 cells (B), and ZR75-1 cells (C) after transfection with an empty vector (EV) or a CAV-1 expression vector (CAV-1), respectively. The bars show the mean value of [3H]thymidine incorporation, and the error bars indicate standard deviation. *p < 0.05 in Student’s t tests.

• 

  Fig. 3. Caveolin-1 (CAV-1) induces cell cycle arrest in the G2/M phase. Changes in the cell cycle were analyzed with propidium iodide staining in MDA-MB-231 cells (A) and CAV-1-transfected MCF-7 (CAV-1/MCF-7) or empty vector-transfected MCF-7 (EV/MCF-7) cells (B). The bars show the mean percentages of the different phases of the cell cycle. Changes in cell cycle-related proteins were examined by western blot analyses in MDA-MB-231 (C) and CAV-1/MCF-7 or EV/MCF-7 (D) cells. β-Actin was used as an internal control. PBS, phosphate buffered saline; DTX, docetaxel.

• 

  Fig. 4. Caveolin-1 (CAV-1) expression increases docetaxel (DTX)-induced apoptotic cell death. (A) Changes in the apoptotic cell population were evaluated by annexin V staining in CAV-1-transfected MCF-7 (CAV-1/MCF-7) or empty vector-transfected MCF-7 (EV/MCF-7) cells. The bars show the mean percentage of annexin V-positive cells. (B) Changes in the expression of apoptosis-related proteins were examined by western blot analyses in CAV-1/MCF-7 or EV/MCF-7 cells. β-Actin was used as an internal control. PBS, phosphate buffered saline; PARP, poly(ADP-ribose) polymerase. *p < 0.05 in Student's t tests.

• 

  Fig. 5. Silencing of caveolin-1 (CAV-1) expression dampened the docetaxel (DTX)-induced phosphorylation of Bcl-2 and cytotoxicity in triple-negative breast cancer cells. The phosphorylation status was evaluated by western blot analyses in CAV-1 siRNA-transfected MDA-MB-231 (A) and MCF-7 (B) cells. β-Actin was used as an internal control. The mean percentages of survival in the MTT assay in CAV-1 siRNA-transfected MDA-MB-231 and Hs578T cells are shown (C). PTX, paclitaxel. *p < 0.05 compared to siRNA controls.

• 

  Fig. 6. Caveolin-1 (CAV-1) enhances docetaxel (DTX)-induced inhibition of tumor growth in vivo. (A) Images of the mice,tumors, and the mean tumor volume from each group: empty vector-transfected MCF-7 (EV/MCF-7) (phosphate buffered saline [PBS] control and DTX) and CAV-1-transfected MCF-7 (CAV-1/MCF-7) (PBS control and DTX). The error bars represent the standard error. ***p < 0.001. (B) Representative staining results from hematoxylin and eosin (H&E) and immunohistochemical staining for CAV-1, p53, and Ki-67 in tissues isolated from EV/MCF-7 or CAV-1/MCF-7 cells. Tissues isolated from mice induced by MDA-MB-231 cells were used as a control for the expression of these proteins.

Reference

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