Resistance to cisplatin in human lung adenocarcinoma cells: effects on the glycophenotype and epithelial to mesenchymal transition markers.

The characteristics that grant the most malignancy to cancer cells are the ability to evade apoptotic mechanisms and the capacity to migrate beyond the boundaries of the original tissue. Studies by our own group and others show that changes in glycosylation are now considered hallmarks of cancer cells and are also able to impact tumor malignancy. This study aims to evaluate changes in the glycosylation profile of the A549 lung cancer cells brought about by the induction of a MDR phenotype as well as investigate the relationship between drug resistance, the cell glycophenotype and EMT. We induced resistance by employing a continuous treatment with cisplatin. Our results demonstrate overexpression of ABC transporters as well as anti-apoptotic members of the Bcl-2 family, leading to a MDR phenotype. The cells also undergo a classic EMT process, displaying the iconic cadherin switch and increased of both total and oncofetal fibronectin, coupled with increased cell motility. We also managed to show changes in the expression of both glycosyltransferases and the glycan epitopes they are responsible for building. We also suggest that perhaps not only changes in cell sialylation are common during resistance induction but are essential to it.

Glycosylation in Cancer: Interplay between Multidrug Resistance and Epithelial-to-Mesenchymal Transition?

The expression of unusual glycan structures is a hallmark of cancer progression, and their functional roles in cancer biology have been extensively investigated in epithelial-to-mesenchymal transition (EMT) models. EMT is a physiological process involved in embryonic development and wound healing. It is characterized by loss of epithelial cell polarity and cell adhesion, permitting cell migration, and thus formation of new epithelia. However, this process is unwanted when occurring outside their physiological limit, resulting in fibrosis of organs and progression of cancer and metastasis. Several studies observed that EMT is related to the acquisition of multidrug resistance (MDR) phenotype, a condition in which cancer cells acquire resistance to multiple different drugs, which has virtually nothing in common. However, although some studies suggested interplay between these two apparently distinct phenomena, almost nothing is known about this possible relationship. A common pathway to them is the need for glycosylation, a post-translational modification that can alter biological function. Thus, this review intends to compile the main facts obtained until now in these two areas, as an effort to unravel the relationship between EMT and MDR.

Modulation of ABCC1 and ABCG2 proteins by ouabain in human breast cancer cells.

ABCC1 and ABCG2 are two transporters associated with multi-drug resistance to cancer chemotherapy. Ouabain is a cardiotonic steroid, currently considered as a hormone associated with arterial hypertension. Previous studies have suggested that ouabain can modulate ABCB1 and ABCC1 expression in cancer and renal cell lines. The present study investigated the effects of physiological concentrations of ouabain on the expression and activity of ABCC1 and ABCG2 in two human breast cancer cell lines, MCF7 and MDA-MB-231, the first known to be responsive to estrogens. Cell viability and proliferation assays showed that 1 µM ouabain reduced proliferation of MCF7, but not if MDA-MB-231 cells. On the other hand, 10 nM ouabain increased proliferation of MDA-MB-231, but not of MCF7 cells. Ouabain (10 nM) prevented the cytotoxic effects of doxorubicin in MCF7 cells, but not in MDA-MB-231 cells. Treatment of cells under different ouabain concentrations for 24 h did not cause any significant effects in the expression of ABCG2 or ABCC1 in either cell line. However, the activity of ABCC1 was increased when MCF7 and MDA-MB-231 cells were treated with 10 mM and 1 nM ouabain respectively. These results claim attention to the possibility that breast cancer patients with high levels of endogenous ouabain may have different responses to chemotherapy.