Molecular analysis of the androgen receptor in ten prostate cancer specimens obtained before and after androgen ablation

Plasma-Free Amino Acid Profiling of Nasal Polyposis Patients

AIM AND OBJECTIVE

To determine the mechanisms present in the etiopathogenesis of nasal polyposis. It is not clear whether amino acids contribute in a causal way to the development of the disease. Therefore, the aim of this study was to determine the plasma-free amino acid profile in patients with nasal polyposis and to compare the results with a healthy control group.

MATERIALS AND METHODS

This was a prospective controlled study that took place in the Otolaryngology Department at the Harran University Faculty of Medicine between April 2017 and April 2018. Plasmafree amino acid profile levels were studied in serum samples taken from a patient group and a healthy control group. Patients who were diagnosed with bilateral diffuse nasal polyposis and were scheduled for surgical interventions were included in this study. Individuals whose age, gender, and body mass index values were compatible with that of the patient group and who did not have any health problems were included in the control group. All the participants whose levels of plasma-free amino acid were thought to be affected by one or more of the following factors were excluded from the study: smoking and alcohol use, allergic rhinitis presence, the presence of acute or chronic sinusitis, a history of endoscopic sinus surgery, unilateral nasal masses, a history of chronic drug use, systemic or topical steroid use in the last three months for any reason, and liver, kidney, hematological, cardiovascular, metabolic, neurological, or psychiatric disorders or malignancies.

RESULTS

In patients with nasal polyposis, 3-methyl histidine (3-MHIS: nasal polyposis group (ng) = 3.22 (1.92 - 6.07); control group (cg) = 1.21 (0.77 - 1.68); p = 0.001); arginine (arg: ng = 98.95 (70.81 - 117.75); cg = 75.10 (54.49 - 79.88); p = 0.005); asparagine (asn: ng = 79.84 (57.50 - 101.44); cg = 60.66 (46.39 - 74.62); p = 0.021); citrulline (cit: ng = 51.83 (43.81 - 59.78); cg = 38.33 (27.81 - 53.73); p = 0.038); cystine (cys: ng = 4.29 (2.43 - 6.66); cg = 2.41 (1.51 - 4.16); p = 0.019); glutamic acid (glu: ng = 234.86 (128.75 - 286.66); cg = 152.37 (122.51 - 188.34); p = 0.045); histidine (his: ng = 94.19 (79.34 - 113.99); cg = 74.80 (62.76 - 98.91); p = 0.018); lysine (lys: ng = 297.22 (206.55 - 371.25); cg = 179.50 (151.58 - 238.02); p = 0.001); ornithine (ng = 160.62 (128.36 - 189.32); cg = 115.91 (97.03 - 159.91); p = 0.019); serine (ser: ng = 195.15 (151.58 - 253.07); cg = 83.07 (67.44 - 92.44); p = 0.001); taurine (tau: ng = 74.69 (47.00 - 112.13); cg = 53.14 (33.57 - 67.31); p = 0.006); tryptophan (trp: ng = 52.31 (33.81 - 80.11); cg = 34.44 (25.94 - 43.07); p = 0.005), homocitrulline (ng = 1.75 (1.27 - 2.59); cg = 0.00 (0.00 - 0.53); p = 0.001); norvaline (ng = 6.90 (5.61 - 9.18); cg = 4.93 (3.74 - 7.13); p = 0.021); argininosuccinic acid (ng = 14.33 (10.06 - 25.65); cg = 12.22 (5.77 - 16.87) p = 0.046); and plasma concentrations were significantly higher than in the healthy control group (p <0.05). However, the gamma-aminobutyric acid (gaba: ng = 0.16 (0.10 - 0.24); cg = 0.21 (0.19 - 0.29); p = 0.010) plasma concentration was significantly lower in the nasal polyposis group than in the healthy control group.

CONCLUSION

In this study, plasma levels of 15 free amino acids were significantly higher in the nasal polyposis group than in the healthy control group. A plasma level of 1 free amino acid was found to be significantly lower in the nasal polyposis group compared to the healthy control group. Therefore, it is important to determine the possibility of using the information obtained to prevent the recurrence of the condition and to develop effective treatment strategies. This study may be a milestone for studies of this subject. However, this study needs to be confirmed by further studies conducted in a larger series.

Advances in genetics: widening our understanding of prostate cancer

Prostate cancer is a leading cause of cancer-related death in Western men. Our understanding of the genetic alterations associated with disease predisposition, development, progression, and therapy response is rapidly improving, at least in part, owing to the development of next-generation sequencing technologies. Large advances have been made in our understanding of the genetics of prostate cancer through the application of whole-exome sequencing, and this review summarises recent advances in this field and discusses how exome sequencing could be used clinically to promote personalised medicine for prostate cancer patients.

The impact of point mutations in the human androgen receptor: classification of mutations on the basis of transcriptional activity

Androgen receptor mediated signaling drives prostate cancer cell growth and survival. Mutations within the receptor occur infrequently in prostate cancer prior to hormonal therapy but become prevalent in incurable androgen independent and metastatic tumors. Despite the determining role played by the androgen receptor in all stages of prostate cancer progression, there is a conspicuous dearth of comparable data on the consequences of mutations. In order to remedy this omission, we have combined an expansive study of forty five mutations which are predominantly associated with high Gleason scores and metastatic tumors, and span the entire length of the receptor, with a literature review of the mutations under investigation. We report the discovery of a novel prevalent class of androgen receptor mutation that possesses loss of function at low levels of androgen yet transforms to a gain of function at physiological levels. Importantly, mutations introducing constitutive gain of function are uncommon, with the majority of mutations leading to either loss of function or no significant change from wild-type activity. Therefore, the widely accepted supposition that androgen receptor mutations in prostate cancer result in gain of function is appealing, but mistaken. In addition, the transcriptional outcome of some mutations is dependent upon the androgen receptor responsive element. We discuss the consequences of these findings and the role of androgen receptor mutations for prostate cancer progression and current treatment options.

Physical chemistry of polyglutamine: intriguing tales of a monotonous sequence

Polyglutamine (polyQ) sequences of unknown normal function are present in a significant number of proteins, and their repeat expansion is associated with a number of genetic neurodegenerative diseases. PolyQ solution structure and properties are important not only because of the normal and abnormal biology associated with these sequences but also because they represent an interesting case of a biologically relevant homopolymer. As the common thread in expanded polyQ repeat diseases, it is important to understand the structure and properties of simple polyQ sequences. At the same time, experience has shown that sequences attached to polyQ, whether in artificial constructs or in disease proteins, can influence structure and properties. The two major contenders for the molecular source of the neurotoxicity implicit in polyQ expansion within disease proteins are a populated toxic conformation in the monomer ensemble and a toxic aggregated species. This review summarizes experimental and computational studies on the solution structure and aggregation properties of both simple and complex polyQ sequences, and their repeat-length dependence. As a representative of complex polyQ proteins, the behavior of huntingtin N-terminal fragments, such as exon-1, receives special attention.

Androgen receptor signaling and mutations in prostate cancer

Normal and neoplastic growth of the prostate gland are dependent on androgen receptor (AR) expression and function. Androgenic activation of the AR, in association with its coregulatory factors, is the classical pathway that leads to transcriptional activity of AR target genes. Alternatively, cytoplasmic signaling crosstalk of AR by growth factors, neurotrophic peptides, cytokines or nonandrogenic hormones may have important roles in prostate carcinogenesis and in metastatic or androgen-independent (AI) progression of the disease. In addition, cross-modulation by various nuclear transcription factors acting through basal transcriptional machinery could positively or negatively affect the AR or AR target genes expression and activity. Androgen ablation leads to an initial favorable response in a significant number of patients; however, almost invariably patients relapse with an aggressive form of the disease known as castration-resistant or hormone-refractory prostate cancer (PCa). Understanding critical molecular events that lead PCa cells to resist androgen-deprivation therapy is essential in developing successful treatments for hormone-refractory disease. In a significant number of hormone-refractory patients, the AR is overexpressed, mutated or genomically amplified. These genetic alterations maintain an active presence for a highly sensitive AR, which is responsive to androgens, antiandrogens or nonandrogenic hormones and collectively confer a selective growth advantage to PCa cells. This review provides a brief synopsis of the AR structure, AR coregulators, posttranslational modifications of AR, duality of AR function in prostate epithelial and stromal cells, AR-dependent signaling, genetic changes in the form of somatic and germline mutations and their known functional significance in PCa cells and tissues.

Pleiotropic functional properties of androgen receptor mutants in prostate cancer

The androgen receptor (AR) signaling pathway plays an important role during the development of the normal prostate gland, but also during the progression of prostate cancer on androgen ablation therapy. Mutations in the AR gene emerge to keep active the AR signaling pathway and to support prostate cancer cells growth and survival despite the low levels of circulating androgens. Indeed, mutations affecting the ligand binding domain (LBD) of the AR have been shown to generate so-called "promiscuous" receptors that present widened ligand specificity and allow the stimulation of these receptors by a larger spectrum of endogenous hormones. Another class of mutations, arising in the amino-terminal domain (NTD) of the receptor, modulate AR interactions with coregulators involved in cell proliferation regulation. Besides characteristics of these well-known types of mutations, the properties of other classes of AR mutants recently described in prostate cancer are currently under investigation. Most interestingly, in addition to their potential role in the mechanisms which allow prostate cancer cells to escape androgen ablation therapy, data suggest that certain AR mutations are present early in the natural history of the disease and may play a role in many aspects of prostate cancer progression. Surprisingly, singular truncated AR devoid of their carboxy-terminal end (CTE) region seem to exert specific paracrine effects and to induce a clonal cooperation with neighboring prostate cancer cells, which may facilitate both the invasion and metastasis processes. In this article, we review the functional properties of different classes of AR mutants and their potential impact on the natural history of prostate cancer. Hum Mutat 0, 1-14, 2008. (c) 2008 Wiley-Liss, Inc.

Herbal/hormonal dietary supplement possibly associated with prostate cancer progression

BACKGROUND

Patients seek herbal/hormonal dietary supplements (HHDS) to prevent and/or solve health and aging issues. After two men developed an unusual course of clinically aggressive prostate cancer within months of starting daily consumption of the same HHDS product, we investigated the effect of this product on prostate cancer progression.

METHODS

We evaluated serum levels of total testosterone, luteinizing hormone, and follicle-stimulating hormone and screened prostate biopsy and metastatic specimens for androgen receptor protein expression and mutations. We did hormone analyses and capillary electrophoresis. We tested the effect of the HHDS product on androgen receptor-negative (DU-145 and PC-3) and androgen receptor-positive (LNCaP) human prostate cancer cell lines.

RESULTS

Both patients had low hormone levels. The androgen receptor was expressed in all primary and metastatic prostate cancer tissues and no mutations were identified. Hormone analysis revealed that the HHDS contained testosterone and estradiol. The HHDS product was a more potent dose-dependent stimulator of cancer cell growth than testosterone both in androgen receptor-negative and receptor-positive cell lines. Blocking experiments with increasing concentrations of bicalutamide did not prevent the HHDS product-stimulated growth. We filed an adverse event report with the Food and Drug Administration who issued a warning letter. The manufacturer responded by removing this HHDS product from the market.

CONCLUSIONS

The HHDS product contained one or more endocrinologically active tumor-promoting components that had cellular androgen receptor status-independent activity. The HHDS product exhibited potent prostate cancer growth stimulatory activity that was more powerful than that of testosterone, independent of the androgen-receptor status of prostate cancer cells, and resistant to antiandrogen blockade.

Plasma free amino acid profile in cancer patients

Redistribution or translocation of plasma free amino acids (PFAAs) to support visceral or tumor protein synthesis is an essential feature in cancer patients. An abnormal PFAA profile might be presented via the total reflection of cancer-induced protein metabolism in tumors, skeletal muscle and the liver in cancer patients. Clinical data from 13 studies have demonstrated a cancer-related PFAA profile, especially in digestive organ cancers. The PFAA profile can differ between the early and late stages of cancer. The profile is also affected by the type of cancer. Therefore, it is postulated that a detailed analysis of the PFAA profile may serve as one of the biological markers for cancer patients.

Mutation of histidine 874 in the androgen receptor ligand-binding domain leads to promiscuous ligand activation and altered p160 coactivator interactions

The androgen receptor (AR) signaling pathway is a major therapeutic target in the treatment of prostate cancer. The AR functions as a ligand-activated transcription factor in the presence of the cognate hormone ligands testosterone and dihydrotestosterone (DHT). We have characterized a highly conserved sequence at the C-terminal end of helix 10/11 in the ligand-binding domain (LBD), which is prone to receptor point mutations in prostate cancer. This sequence includes threonine 877 that is involved in hydrogen bonding to the D ring of the steroid molecule and leads to promiscuous ligand activation of the AR when mutated to alanine or serine. A second mutation in this region, H874Y, also results in a receptor protein that has broadened ligand-binding specificity, but retains an affinity for DHT (K(d) = 0.77 nm) similar to that of the wild-type receptor. The structure of the mutant LBD, expressed in Escherichia coli, is not dramatically altered compared with the wild-type AR-LBD in the presence of DHT, but shows a modestly increased sensitivity to protease digestion in the absence of hormone. This mutant AR showed wild-type AR-LBD/N-terminal domain interactions, but significantly enhanced binding and transactivation activity with all three members of the p160 family of coactivator proteins. Together, these phenotypic changes are likely to confer a selective advantage for tumor cells in a low androgen environment resulting from hormone therapy.

Alterations of androgen receptor in prostate cancer

The significance of androgens in the development of prostate cancer has been known for more than half century. During the last decade, a lot of effort has been put to study the significance of the specific nuclear receptor of the hormone, androgen receptor (AR). It has been suggested that polymorphisms, especially the length of CAG repeat in exon 1 of the gene, are associated with the risk of prostate cancer. However, not all studies have confirmed the association. Most surprisingly, it has now become clear that prostate carcinomas emerging during the androgen withdrawal therapy (i.e. hormone-refractory tumors) are capable of reactivating the AR-mediated signalling despite of the low levels of androgens. In addition, it has been shown that AR gene itself is genetically targeted. One-third of the hormone-refractory prostate carcinomas contains amplification of the gene. In addition, 10-30% of prostate carcinomas treated by antiandrogens acquire point mutation in the AR gene. The genetic alterations in AR indicate that receptor should be considered as putative treatment target. Evidently, the currently available antiandrogens are not capable to abolish the AR-mediated signalling efficiently enough.