This idea means that the problem is not the gene or the epigenome but the proteins after it. It could very well tie into the methlyation idea as both are very much linked. Truth is there is SO MUCH that modifies androgen function.
The AR is built in a modular fashion and composed of a long N-terminal region with transactivation functions, a central DNA-binding domain, an intermediate hinge region and a C-terminal ligand-binding domain with additional transactivation functions. In its inactive form, the AR is complexed to heat-shock proteins, and mainly cytoplasmic. Following activation, the AR enters the nucleus, binds to its cognate DNA response elements as a homodimer and stimulates gene transcription. Various cofactors directly interact with the AR to modulate gene transcription. In addition, cross-talk between the AR and other signalling pathways has been proven for several prostate-expressed genes. Understanding the intricate networks underlying androgen-selective gene regulation represents a formidable challenge but might also offer the chance to identify new drug targets for the treatment of prostate carcinoma.
en.wikipedia.org/wiki/Posttranslational_modification
Other modifications, like phosphorylation, are part of common mechanisms for controlling the behavior of a protein, for instance activating or inactivating an enzyme.
Androgen increases androgen receptor protein while decreasing receptor mRNA in LNCaP cells*1
We have examined the effect of androgen treatment on androgen receptor mRNA and protein expression in the LNCaP human prostate carcinoma cell line. Incubation with androgen caused a decrease in cellular androgen receptor mRNA content that was concentration and time dependent. Maximal suppression to approximately 35% of control level was observed after 49 h of exposure to androgen. By contrast, incubation of LNCaP cells with androgen resulted in a 2-fold increase in the cellular content of androgen receptor protein at 24 h. At 49 h androgen receptor protein increased 30% as assayed by immunoblots and 79% as assayed by ligand binding. These results suggest that ligand-induced changes in androgen receptor stability and/or the translational efficiency of androgen receptor mRNA account for the phenomenon of androgen receptor upregulation observed in cultured LNCaP cells. Furthermore, the suppression of androgen mRNA and protein that is caused by prolonged incubation with androgen is incomplete and is reversible upon removal of ligand.
onlinelibrary.wiley.com/doi/10.1111/j.1464-410X.2005.05526.x/full - makes an interesting read
The androgen receptor and signal-transduction pathways in hormone-refractory prostate cancer. Part 1: modifications to the androgen receptor
It is now apparent that the control of AR function involves post-translational modification, generally via phosphorylation by various kinase cascades.
Current published evidence suggests that the dominant pathways involved in the development of androgen escape are the MAPK and PI3K pathways (Fig. 3). These pathways act to directly modify the AR, altering its sensitivity to both androgens and antiandrogens. The pluripotency of these pathways suggests that molecular targeting of specific kinases (e.g. AKT or MAPK) within these pathways could reverse hormone resistance by several mechanisms. Further research into the role of these pathways in clinical samples should be the immediate focus for future research.
However, despite the current shift away from molecular targeting of the AR, one in five hormone-resistant prostate cancers show AR gene amplification; this may lead to screening of patients for AR amplification before implementing therapies.
AR gene amplification has been associated with hormone escape [18] and recently amplification rates were shown to rise significantly in the transition from hormone-sensitive to -resistant disease (0–5% in the former and 20–30% in the latter) [19]. Evidence from several sources suggests that, unlike chromosomal duplication (aneusomy), gene amplification results in greater protein expression via gene dysregulation. We showed recently that there was AR gene amplification in 20% of hormone-escaped prostate cancers and most tumours had a corresponding increase in AR protein expression (80%). However, the remaining tumours in the cohort that acquired AR gene amplification on the transition to hormone escape had no increase in AR protein expression. Therefore AR gene amplification does not always result in increased AR protein expression [19]. In the same study we identified a further 22% of tumours that had increased AR expression, in the absence of AR amplification [19]. Although first impressions suggest that the significant event in the development of hormone escape is an increase in AR expression and not AR amplification, further analysis suggests this might not be the case. It is AR amplification and not AR protein expression levels that influenced patient survival in our cohort (Fig. 2). This may be a result of gene amplification, and being able to detect those cases with marked protein over-expression more accurately than by immunohistochemistry, supporting the hypothesis that AR over-expression is important in androgen-insensitive prostate cancer. In studies of HER2 in breast cancer, HER2 gene amplification is a better predictor of survival and is linked to marked increases in protein expression (over 100-fold). One study using xenograft models showed that increasing AR protein expression induced androgen escape independent of AR amplification [20] but this does not reflect the mechanism of AR up-regulation in clinical prostate cancers. More significantly, that study also showed that high AR protein expression sensitizes prostate cancer cells to low circulating levels of androgens, and enables the AR to be activated. This suggests that by increasing the dose of antiandrogen therapy it may be possible to inhibit progression to androgen escape. However, animal experiments show that increased AR expression levels may allow antiandrogens to function as weak agonists, resulting in activation of the AR [20].
In conclusion, although the significant event in the development of androgen escape is an increase in AR protein expression, it appears that only cases with AR amplification can express AR protein at levels high enough to have functional relevance. Increased AR expression may explain the development of hormone-escaped prostate cancer in only 20–30% of cases, i.e. those who develop AR amplification, requiring the existence of alternative mechanisms to explain the 70–80% of patients with no AR gene amplification. Conversely, AR gene amplification may provide a powerful diagnostic tool for targeting AR over-expression.
In this idea for reasons I do not know the AR protein expression has changed in a way that has inhibited AR’s function. It is most probable that this does tie into the epigenetic thread but thought it needed its own thread.
The way i see it is that we have AR’s and they are semi functional. However, increasing testosterone which should upregulate androgen receptors and expression (toxsci.oxfordjournals.org/content/early/2011/03/21/toxsci.kfr063.abstract) does not appear to help which hints that the problem lies after this. This means the problem must lie after testosterone binds to the androgen receptor. The likely thing is that a protein is being produced that inhibits its function. Also the balance of co-regulators could be out and awors idea of AR hypersensitivity with subsequent downregulation and silencing still stands as a strong contender.