Proteína αKlotho: da associação in vitro com o ERβ ao perfil antitumoral no soro de pacientes com câncer de mama

Abstract

αKlotho, a cellular anti-senescence protein, is related to antitumor actions, regulating the growth, proliferation and invasiveness in several types of tumors, including breast cancer. The diagnosis and prognosis of breast cancer are based on intrinsic characteristics of the tumor, such as the presence of estrogen receptors, especially ERα. In turn, ERβ despite demonstrating antitumor actions, remains with an uncertain role in breast carcinogenesis and its clinical use is limited. The aim of the study was to analyze the relationship between αKlotho and estrogen receptors, as well as to evaluate the serum levels of this protein in patients with breast cancer according to histopathological and immunohistochemical characteristics of the tumor. The luminal and triple-negative lineages of breast cancer, MCF-7 and MDA MB-231, were cultured and exposed to the agonists of ER, E2 and DPN, to determine the expression of αKlotho, then proliferation and EMT evaluation trials were performed on MCF-7 cells treated with the same agonists. For the soluble αKlotho assays, serum samples from 75 breast cancer patients and 63 healthy controls were randomized and serum levels were assessed by sandwich ELISA. Clinical and diagnostic data were obtained from hospital records and databases. In MCF-7 cells there was a considerable increase in αKlotho expression after stimulation of ERβ with PND (p<0.01). Activation of ERβ also led to decreased proliferation and cell cycle arrest, as well as inhibition of the epithelial-mesenchymal transition (EMT). In serum analyzes, healthy women had higher levels of soluble αKlotho than patients (p=0.04). Among the patients, those with initial tumor (p=0.02), ER positivity (p=0.03), and luminal subtype (p=0.04) had higher serum levels of soluble αKlotho. Furthermore, αKlotho production in low or high levels (p=0.04 and p=0.03) was associated with higher rates of proliferation by Ki67. Finally, patients with no lymph node metastasis also had higher levels of α Klotho (p=0.03). These data suggest that soluble αKlotho was related to factors of better prognosis in breast cancer and confirm the relationship between αKlotho and ERβ with the positive regulation of αKlotho expression by this receptor and its antitumor profile in breast lumen.