Effects of testosterone and 17β‑estradiol on angiotensin‑induced changes in tyrosine kinase activity in the androgen‑independent human prostate cancer cell line, DU145

Angiotensin II (AngII), the main peptide of the renin‑angiotensin system (RAS), is involved in the proliferation of different types of cells, normal and pathological as well. The protein tyrosine kinases (PTKs) play an important role in the growth, differentiation and apoptosis of cells. AngII action depends on the hormonal milieu of the cell, and on sex steroid influence. Angiotensin 1‑7 (Ang1‑7), metabolite of AngII, shows opposite action to AngII in cells. The present study aimed to examine the influence of 17β‑estradiol and testosterone on AngII and Ang1‑7 action on PTK activity in androgen‑independent humane prostate cancer cell line DU145. Cell cultures of human prostate cancer DU145 cells were used as a source of PTKs. Cultures were exposed to different concentrations of AngII (5x10‑11 to 5x10‑9 M). The incubation with hormones lasted 15 min to limit the genomic effects of steroids. In the phosphorylation reaction, we used γ32P‑ATP as a donor of phosphate and a synthetic peptide, Poly(Glu, Tyr) (4:1), as a substrate. The specific activities of PTKs were defined as pmol of 32P incorporated into 1 mg of exogenous Poly(Glu, Tyr) per minute (pmol/mg/min). Our findings suggest that testosterone and 17β‑estradiol may change the effects of angiotensins in a rapid non‑genomic way, probably via membrane‑located receptors. The most significant change was caused by testosterone, whose effect was most significant on changes caused by Ang1‑7. AngII‑induced changes in phosphorylation appeared to be insensitive to the presence of testosterone, but were modified by 17β‑estradiol.

Angiotensin II as a factor modulating protein tyrosine kinase activity in two breast cancer lines - MCF-7 and MDA-MB-231

INTRODUCTION

Angiotensin II (AngII), a peptide that regulates the water-electrolytic balance and blood pressure, is also known to influence cell proliferation. It can either induce cell growth, when binding to angiotensin type-I receptor, or trigger growth inhibition via angiotensin type-II receptor. AngII stimulates proliferation of some normal and tumour cell lines, e.g. pituitary, adrenal glands and breast cancer.

MATERIAL AND METHODS

The aim of this study was to evaluate possible AngII effect on the growth of two breast cancer cell lines - hormone-dependent MCF-7 and hormone-independent MDA-MB-231. We measured tyrosine kinase activity as a potential proliferation marker. We also estimated the influence of 17b-oestradiolon AngII-induced changes.

RESULTS

In the MDA-MB-231 line, AngII radically slowed the activity of tyrosine kinases and 17b-oestradiol only at a concentration of 10⁻⁶ M, while it enhanced the effect of angiotensin II at a concentration of 10⁻⁹ M. In MCF-7, Ang II had a strong inhibitory effect in the presence of oestradiol (10⁻⁶ M). Oestradiol alone decreased the activity of examined enzymes in both cell lines. AngII receptor type 1 was found in both studied lines, but type 2 only in MDA-MB-231.

CONCLUSIONS

Our results show that AngII can modulate tyrosine kinase activity in breast tumour cell lines.