17 beta-Hydroxysteroid dehydrogenase activity in endometrial cancer cells: different metabolic pathways of estradiol in hormone-responsive and non-responsive intact cells.

In this paper we report that two human long-term endometrial cancer cell lines, Ishikawa and HEC-1A, exhibit quite different abilities in metabolizing estrogens. As a matter of fact, incubation of Ishikawa cells with close-to-physiological concentrations of estradiol (E2) as precursor resulted in: (1) elevated formation (up to 90%) of E2-sulphate (E2-S), using lower precursor concentrations; (2) very limited conversion to estrone (E1) (< 10% at 24 h incubation), as either free or sulphate; and (3) low but consistent production of other estrogen derivatives, such as 2-hydroxy-estrogens and estriol. Conversely, scant amounts (if any) of E2-S were found in HEC-1A cells, while no detectable formation of other estrogen metabolites could be observed after 24 h. On the other hand, E1 production was significantly greater (nearly 60% at 24 h) than in Ishikawa cells, a large proportion of E1 (over 50% of the total) being formed after only 6 h incubation using time-course experiments. The hypothesis that E2 metabolism could be minor in Ishikawa cells as a consequence of the high rate of E2-S formation encountered is contradicted by the evidence that conversion to E1 also remains limited in the presence of much lower E2-S amounts, seen using higher molar concentrations of precursor. Overall, we observe that 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity diverges significantly in intact Ishikawa and HEC-1A endometrial cancer cells. This difference could not merely be accounted for by the diverse amounts of substrate (E2) available to the cells, nor may it be imputed to different levels of endogenous estrogens. It should rather be sought in different mechanisms controlling 17 beta-HSD activity or, alternatively, in the presence of distinct isoenzymes in the two different cell types.

Oxidative and reductive pathways of estrogens in hormone responsive and non-responsive human breast cancer cells in vitro.

In order to measure the formation and degradation rates of estradiol by human breast cancer cells, after assessing the biochemical basis of hormone responsiveness and growth response to estrogens, we considered both responsive, estrogen receptor (ER) positive, and non-responsive, ER-negative, breast cancer cell lines, i.e. MCF7, ZR75-1 and MDA-MB231. To this end, we employed a novel "intact cell" approach which allows us, after 24 h incubation, to analyze several enzyme activities in sequence, concurrently with the monitoring of labeled precursor degradation. Our investigations led to the following evidence: (a) the reductive activity of the 17 beta-hydroxysteroid oxoreductase (17 beta-HSOR) appears to be higher than the oxidative only in responsive, ER-rich MCF7 and ZR75-1 cells, as also previously observed by others; (b) this activity is, on the contrary, much lower in MDA-MB231 cells and other unresponsive, ER-poor breast cancer cell lines; (c) conversely, the oxidative activity shows an opposite pattern, being limited in MCF7 and ZR75-1 cells and much higher in MDA-MB231 cells. Overall, a 17 beta-HSOR reductive pathway prevails in both MCF7 and ZR75-1 cells, whilst the oxidative pathway is prevalent in MDA-MB231 cells, leading to a large formation of estrone that is no further metabolized, at least in the experimental conditions used. Our results may provide a likely explanation of previous data on the different estrogen content of breast tumor tissues.

Sex steroids up-regulate E-cadherin expression in hormone-responsive LNCaP human prostate cancer cells.

There is convincing evidence that a reduced expression of the E-cadherin cell-cell adhesion molecule associates with low tumor grade and poor prognosis in prostate cancer patients. However, little is known on how E-cadherin levels are regulated in human prostate cancer cells. We have inspected the effect of both androgens and estrogen on the expression of E-cadherin in the hormone-responsive LNCaP prostate tumor cell line, which is endowed with both androgen and estrogen receptors. Using both Dot Blot analysis and immunocytochemistry we have observed that either steroid significantly increased E-cadherin levels in these cells; this effect was not reversed by the simultaneous addition of the relevant antagonist, hydroxyflutamide or ICI-182,780.