PI3K/AKT and MAPK1 molecular changes preceding matrix metallopeptidases overexpression during tamoxifen-resistance development are correlated to poor prognosis in breast cancer patients.

BACKGROUND: Metastasis and drug resistance remain a persistent key clinical obstacle to the success of breast cancer treatments. Recent years have seen an increased focus on understanding the factors that influence metastasis and drug resistance. METHODS: In this study, the changes in MMPs gene expression were investigated together with their regulatory pathways-PI3K, MAPK and NFKß pathways-during the process of developing tamoxifen resistance in MCF7 cell line. Gene correlation maps and Kaplan-Meier survival plots among all breast cancer patients and patients treated with tamoxifen were evaluated. RESULTS: MMPs gene expression was found to be up regulated in MCF7 cell line treated with tamoxifen during the development of tamoxifen resistance using two approaches. Up-regulation of gene expression of AKT1 and MAPK1 started in cells treated with 10 µM tamoxifen that was followed with up-regulation of other genes in these pathways and MMPs in cells treated with 35 µM tamoxifen. MMPs and genes from PI3K, MAPK and NFKß pathways showed highly significant increase of expression at 50 µM or when cells were treated sequentially six times with 35 µM. Furthermore, increased genes expression was associated with aggressive pattern, clear morphological changes, higher growth rate, increased migration and adhesion potential and tamoxifen insensitivity. Breast cancer distant metastasis-free survival, and survival among tamoxifen treated patients had high expression levels of MAPK1, AKT1, TIMP2, MMP1, and MMP9 showed poor prognosis. CONCLUSION: Early changes of MAPK1, AKT1 gene expression upon tamoxifen treatment could possibly be used as an early marker of resistance and future poor prognosis.

Upregulation of PI3K/AKT/PTEN pathway is correlated with glucose and glutamine metabolic dysfunction during tamoxifen resistance development in MCF-7 cells.

Tamoxifen resistance is emerging as a big challenge in endocrine therapy of luminal A breast cancer patients. In this study, we aimed to determine the molecular changes of PI3K/AKT/PTEN signaling pathway during tamoxifen-resistance development using gradually increased doses of tamoxifen in one model, while fixing tamoxifen treatment dose at 35 µM for several times in the second model. An upregulation of AKT/PI3K genes was noticed at 30 µM tamoxifen concentration in cells treated with a gradual increase of tamoxifen doses. In the second model, significant upregulation of AKT1 was seen in cells treated with 35 µM tamoxifen for three times. All genes studied showed a significant increase in expression in resistant cells treated with 50 µM and 35 µM six times tamoxifen. These genes' upregulation was accompanied by PTEN and GSK3 ß genes' down-regulation, and it was in correlation to the changes in the metabolic rate of glucose in tamoxifen-resistant models. A significant increase in glucose consumption rate from culture media was observed in tamoxifen resistant cells with the highest consumption rate reported in the first day of culturing. Increased glucose consumption rates were also correlated with GLUL significant gene expression and non-significant change in c-MYC gene expression that may lead to increased endogenous glutamine synthesis. As a result, several molecular and metabolic changes precede acquired tamoxifen resistance could be used as resistance biomarkers or targets to reverse tamoxifen resistance.