Many prostate cancer cell line, such LnCap, Vcap and LAPC4, are androgen-dependent. While studying drug resistance mechanism especially Enzalutamide resistancen, many literature are using charcoal-stripped serum to support their cell line. How will this impact the outcome? I calculated testosterone concentration in normal 10% FBS-supported medium and find it's actually similar to castrated patient whose testosterone are at 20 ng/dl.
Think of this: clinically defined castrated testosteron level is about 5% to 10% of normal male testosteron level, since some of them are synthesized by adrenal gland and cannot be antagonized by GnRH therapy. And we are adding 5% ~ 10% FBS to medium, actually diluted androgen just like castrated patient.
This is a slightly complex question.
Essentially you are correct. The cells are growing at levels which would be thought of as castrate in humans. It is more of a question of the 'norms' used for growing these cells lines.
The cells in culture will have adapted their growth to the level they have since they were originally derived, and 10% serum is the recommended growth medium from ATCC, even though it may be lower than human levels. These cells may be considered as being already somewhat androgen independent or adapted compared to normal tissue.
Androgen levels can have a range of concentrations in humans and mammals, and animal sera will also differ - so its important to batch test the serum. Also human patients will have very different levels dependent on being in puberty or elderly - so there is no ideal level - just a 'normal' range. The main thing is to keep it constant for your experiments, and to keep it in line with all other research. It would be impossible and / or very expensive to grow them in pure human serum. Such cells may actually stop growing or die if they were suddenly given the full maximum human level of androgens.
Using charcoal stripped serum will help in measuring androgen - anti-androgen interactions in a controlled system where you can remove all androgens and then add the compounds in a controlled manner, and measure an output - growth or PSA levels are good.
Remember that stripping serum with activated charcoal will remove all small lipophilic compounds - including estrogens, androgens, adrenal androgens, corticosteroids etc. So you may want to take that into account.