Targeting hormone-resistant breast cancer cells with docetaxel: a look inside the resistance.

Aim: The study aims to analyze the effect of long-term incubation of ERα-positive MCF7 breast cancer cells with 4-hydroxytamoxifen (HT) on their sensitivity to tubulin polymerization inhibitor docetaxel. Methods: The analysis of cell viability was performed by the MTT method. The expression of signaling proteins was analyzed by immunoblotting and flow cytometry. ERα activity was evaluated by gene reporter assay. To establish hormone-resistant subline MCF7, breast cancer cells were treated with 4-hydroxytamoxifen for 12 months. Results: The developed MCF7/HT subline has lost sensitivity to 4-hydroxytamoxifen, and the resistance index was 2. Increased Akt activity (2.2-fold) and decreased ERα expression (1.5-fold) were revealed in MCF7/HT cells. The activity of the estrogen receptor α was reduced (1.5-fold) in MCF7/HT. Evaluation of class III ß-tubulin expression (TUBB3), a marker associated with metastasis, revealed the following trends: higher expression of TUBB3 was detected in triple-negative breast cancer MDA-MB-231 cells compared to hormone-responsive MCF7 cells (P < 0.05). The lowest expression of TUBB3 was found in hormone-resistant MCF7/HT cells (MCF7/HT < MCF7 < MDA-MB-231, approximately 1:2:4). High TUBB3 expression strongly correlated with docetaxel resistance: IC50 value of docetaxel for MDA-MB-231 cells was greater than that for MCF7 cells, whereas resistant MCF7/HT cells were the most sensitive to the drug. The accumulation of cleaved PARP (a 1.6-fold increase) and Bcl-2 downregulation (1.8-fold) were more pronounced in docetaxel-treated resistant cells (P < 0.05). The expression of cyclin D1 decreased (2.8-fold) only in resistant cells after 4 nM docetaxel treatment, while this marker was unchanged in parental MCF7 breast cancer cells. Conclusion: Further development of taxane-based chemotherapy for hormone-resistant cancer looks highly promising, especially for cancers with low TUBB3 expression.

The expression and clinical significance of ERß/ERα in ovarian cancer: can we predict the effectiveness of platinum plus taxane therapy?

Estrogens play an extremely important role in regulating the proliferation of ovarian cancer. The estrogen receptor alpha (ERα) stimulates cell growth, whereas ERß can be attributed to tumor suppressors. The study aims to assess the relationship between the expression of estrogen receptors in tumors and the efficacy of front-line platinum plus taxane chemotherapy in ovarian cancer patients. MATERIALS AND METHODS: ERα and ERß tumor expression was evaluated quantitatively by flow cytometry in a narrowly defined group (31 patients): stage III high-grade serous ovarian carcinoma (HGSOC), suboptimal surgical cytoreduction, front-line platinum plus taxane chemotherapy (front-line, six cycles). RESULTS: The median of progression-free survival (PFS) was 2 times greater (18 vs 8 months, p = 0.04) and the recurrence risk (HR) was 2.2 times (95 % CI: 1.1-6.2, p = 0.04) lower in the group with high (in more than 40% of the cells) vs low level of ERß tumor expression. The statistically significant difference between PFS in the groups with high vs low tumor ERα expression was not revealed. CONCLUSION: A high level of ERß and not ERα expression can predict the efficacy of front-line platinum plus taxane chemotherapy in stage III HGSOC patients. The status of estrogen receptor beta can be considered as one of the possible predictors for evaluating the effectiveness of ovarian cancer therapy.

A new approach to epithelial-mesenchymal transition diagnostics in epithelial tumors: double immunofluorescent staining and flow cytometry.

A new method of double immunofluorescent staining for flow cytometry has been created to evaluate quantitative expression of mesenchymal protein vimentin only in epithelial cells of a solid tumor that is a mix of different origin cells. De novo vimentin expression is strongly associated with epithelial-mesenchymal transition and therefore is a metastatic potential marker of epithelial tumor cells. In comparison with semiquantitative available methods, the proposed one has several advantages, such as the accurate measurement of the marker's expression, and minimization of spatial and temporal tumor heterogeneity. Clinical validation of the method has revealed inverse correlation between the quantitative index of epithelial-mesenchymal transition level and progression-free survival using Kaplan-Meier curves and the COX proportional hazards ratio in 32 ovarian cancer patients.