Avaliação do efeito da Uncaria tomentosa sob o sistema purinérgico em linhagens de câncer de mama

Abstract

The Uncaria tomentosa (UT), or cat's claw, is a perennial plant, native to Central and South America, rich in oxindole alkaloids and their precursors, indole alkaloids. For this plant have been assigned many biological activities such as: immunostimulating, anti-inflammatory, inducing apoptosis and inhibition of tumor proliferation in cancer cell lines. Breast cancer, the most common cancer among women, is usually treated by surgery, chemotherapy, hormone therapy or radiation. Among the treatment options, chemotherapy, which by their cytotoxic effects, result in some adverse effects. Considering the above, the objective of this study was to evaluate the effect of UT in the activity of ectonucleotidase, which are involved in tumor progression. To evaluate this purpose, we used two breast cancer cell lines: one that not express estrogen receptor (ER) and progesterone (PR), MDA-MB-231, characterized as poor prognosis and another line, the MCF-7 that expresses these receptors and, in most cases, responds well to treatment. First we proved the antiproliferative effect of alcoholic extract of hydro UT, by trypan blue and MTT methods. Next we evaluate the activities of ectonucleotidase, when we observed that the UT extracts in concentrations of 250 and 500 μg/mL did not alter the hydrolysis of ATP and ADP in MDA-MB-231 cells, already the MCF-7 cells, but no significant alterations in ATP hydrolysis, the extract UT 250 and 500 μg/mL significantly reduced the hydrolysis of ADP. However, the UT 500 μg/mL associated with doxorubicin group showed an increase in the activity of ecto-NTPDase using ATP and ADP as substrates, thereby reducing the levels of ATP in the extracellular medium. UT extracts, at both concentrations, were able to inhibit the activity of ecto-5'-nucleotidase in both cell lines (MDA-MB-231 and MCF-7). As well as, when were associated the UT (at both concentration) with doxorubicin on MDA-MB-231 cells, and UT 250 μg/mL associated with tamoxifen on MCF-7 cells observed a significant reduction of the activity of ecto-5'-nucleotidase. We found an increased expression of CD39 in UT 250 μg/mL and UT 250 μg/mL associated doxorubicin groups in MDA-MB-231 cells. While the expression of CD73 did not change in expression in any of the treatments applied to cell lines. The expression of A1 receptors increased with the extract UT treatments whereas decreased expression of P2X7 on MDA-MB-231 line after the treatment. We conclude that UT is capable of modulating the activity of purinergic system enzymes, especially ecto-5'-nucleotidase. This effect can reduce adenosine in the extracellular environment, this molecule favors tumor proliferation. Furthermore, the UT extract alters the expression of purinergic receptors which together with the modulation of enzymatic activity minimize the process of tumor invasion.