Resistance to hormone therapy in breast cancer cells promotes autophagy and EGFR signaling pathway.

Breast cancer is the leading cause of cancer deaths for women worldwide. Endocrine therapies represent the cornerstone for hormone-dependent breast cancer treatment. However, in many cases, endocrine resistance is induced with poor prognosis for patients. In the current study, we have developed MCF-7 cell lines resistant to fulvestrant (MCF-7Fulv) and tamoxifen (MCF-7Tam) aiming at investigating mechanisms underlying resistance. Both resistant cell lines exerted lower proliferation capacity in two-dimensional (2-D) cultures but retain estrogen receptor α (ERα) expression and proliferate independent of the presence of estrogens. The established cell lines tend to be more aggressive exhibiting advanced capacity to form colonies, increased expression of epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), and heterodimerization of ERBB family receptors and activation of EGFR downstream pathways like MEK/ERK1/2 and PI3K/AKT. Tyrosine kinase inhibitors tested against resistant MCF-7Fulv and MCF-7Tam cells showed moderate efficacy to inhibit cell proliferation, except for lapatinib, which concomitantly inhibits both EGFR and HER2 receptors and strongly reduced cell proliferation. Furthermore, increased autophagy was observed in resistant MCF-7Fulv and MCF-7Tam cells as shown by the presence of autophagosomes and increased Beclin-1 levels. The increased autophagy in resistant cells is not associated with increased apoptosis, suggesting a cytoprotective role for autophagy that may favor cells' survival and aggressiveness. Thus, by exploiting those underlying mechanisms, new targets could be established to overcome endocrine resistance.NEW & NOTEWORTHY The development of resistance to hormone therapy caused by both fulvestrant and tamoxifen promotes autophagy with concomitant apoptosis evasion, rendering cells capable of surviving and growing. The fact that resistance also triggers ERBB family signaling pathways, which are poorly inhibited by tyrosine kinase inhibitors might attribute to cells' aggressiveness. It is obvious that the development of endocrine therapy resistance involves a complex interplay between deregulated ERBB signaling and autophagy that may be considered in clinical practice.

Epidermal growth factor receptor status and Notch inhibition in non-small cell lung cancer cells.

BACKGROUND: Notch may behave as an oncogene or a tumor suppressor gene in lung cancer cells. Notch receptor undergoes cleavage by enzymes, including γ-secretase, generating the active Notch intracellular domain (NICD). The aim of the present study was to investigate the effect of DAPT, a γ-secretase inhibitor, in non-small cell lung cancer (NSCLC) cells, as well as the impact of epidermal growth factor (EGF) that is over-expressed by NSCLC cells, on Notch signaling. H23, A549, H661 and HCC827 human NSCLC cell lines were used, expressing various NICD and EGF receptor (EGFR) protein levels. RESULTS: DAPT decreased the number of H661 cells in a concentration-dependent manner, while it had a small effect on H23 and A549 cells and no effect on HCC827 cells that carry mutated EGFR. Notch inhibition did not affect the stimulatory effect of EGF on cell proliferation, while EGF prevented DAPT-induced NICD decrease in H23 and H661 cells. The type of cell death induced by DAPT seems to depend on the cell type. CONCLUSIONS: Our data indicate that inhibition of Notch cleavage may not affect cell number in the presence of EGFR mutations and that EGFR may affect Notch signalling suggesting that a dual inhibition of these pathways might be promising in NSCLC.

Anabolic androgenic steroids reverse the beneficial effect of exercise on tendon biomechanics: an experimental study.

BACKGROUND: The effect of anabolic androgenic steroids on tendons has not yet been fully elucidated. Aim of the present study was the evaluation of the impact of anabolic androgenic steroids on the biomechanical and histological characteristics of Achilles tendons. METHODS: Twenty-four male Wistar rats were randomized into four groups with exercise and anabolic steroids (nandrolone decanoate) serving as variables. Protocol duration was 12 weeks. Following euthanasia, tendons' biomechanical properties were tested with the use of a modified clamping configuration. Histological examination with light and electron microscopy were also performed. RESULTS: In the group of anabolic steroids and exercise the lowest fracture stress values were observed, while in the exercise group the highest ones. Histological examination by light and electron microscopy revealed areas of collagen dysplasia and an increased epitendon in the groups receiving anabolic steroids and exercise. CONCLUSIONS: These findings suggest that anabolic androgenic steroids reverse the beneficial effect of exercise, thus resulting in inferior maximal stress values.