LS-1-P-6077  The importance of PTEN-PI3K-AKT Signaling Pathway on Invasive Breast Cancer Cell Lines MDA-MB-231

Breast cancer in women, is the second most common cancer after lung cancer. MDA-MB-231 cells which are isolated from pleural effusion of women who are diagnosed as invasive epithelial breast adenocarcinoma is a useful model for studying in vitro treatments of metastatic breast cancer. These cell lines are also used for modelling cell migration, proliferation and invasion of breast cancer. PTEN-PI3K-AKT signaling pathway plays a role on cell proliferation, growth, metabolism and apoptosis. The aim of this study was to determine the effects of Rapamycine which is mTORC1 inhibitor and PTEN-PI3K-AKT pathway using indirect immunohistchemistry method on invasive MDA-MB 231 breast cancer cell lines.

MDA-MB-231 cells were cultured in RPMI-1640 medium; containing 10% fetal bovine serum, 1% L-glutamine and 1% penicilline/streptomycine solution in a humidity incubator at 37°C, containing 5% CO₂. The study was carried out as the control group (MDA-MB-231 cells) and the Rapamycine group (MDA-MB-231 + IC₅₀ Rapamycine). The effects of Rapamycine on MDA-MB 231 cells were evaluated at 24^th  hours. The cells were fixed with 4% paraformaldehyde and prepared for immunohistochemical analysis with anti-PTEN, anti-PI3K and anti-AKT by using indirect avidin-biotin peroxidase method. Positively stained cells were counted and the H-score was determined according to the severity of immunoreactivity which were evaluated minimal (1), moderate (2), strong (3) and very strong (4).The results were compared with One way- ANOVA statistical test.

The immunoreactivity of anti-PI3K  (Figure 1) and anti-AKT (Figure 2) antibodies were observed as moderate/strong (2/3) and the immunoreactivity of anti-PTEN was observed as strong/very strong (3/4) in the Control group. Decreased immunoreactivities were detected on anti-PI3K (Figure 3) and anti-AKT (Figure 4) on MDA-MB-231 cells in Rapamycine treated group, compared with the Control group (p<0.05). The immunorecativity of anti-PTEN was observed as unchanged (p>0.05).

In this study, Rapamycine has been shown to be effective on PI3K-AKT signaling pathway on invasive breast cancer cell lines MDA-MB-231. PTEN is a dual effective protein/lipid phosphatase which plays an important role in human cancer because of the decreased activity caused by mutation, deletion and methylation. Several cellular systems have different tumor growth properties such as Ras, PIP3; so it was thought that mTOR inhibitors might be beneficial for additional therapy and new drug development on cancer treatment.

References :

1. Figlin RA, et al.. JNCCN 2008; 6: 1-20

2. Zhang HY, et al.. Oncology Letters 2013; 6: 161-168

3. Zaytseva YY, et al.. Cancer Letters 2012; 319: 1-7