No abstract

Androgen receptor (AR) targeting remains the gold standard treatment for advanced prostate cancer (PCa); however, treatment resistance remains a major clinical problem. To study the therapeutic effects of clinically used anti-androgens we characterized herein a tissue-mimetic three-dimensional (3D) in vitro model whereby PCa cells were cultured alone or with PCa-associated fibroblasts (CAFs). Notably, the ratio of PCa cells to CAFs significantly increased in time in favor of the tumor cells within the spheroids strongly mimicking PCa in vivo. Despite this loss of CAFs, the stromal cells, which were not sensitive to androgen and even stimulated by the anti-androgens, significantly influenced the sensitivity of PCa cells to androgen and to the anti-androgens bicalutamide and enzalutamide. In particular, DuCaP cells lost sensitivity to enzalutamide when co-cultured with CAFs. In LAPC4/CAF and LNCaP/CAF co-culture spheroids the impact of the CAFs was less pronounced. In addition, 3D spheroids exhibited a significant increase in E-cadherin and substantial expression of vimentin in co-culture spheroids, whereas AR levels remained unchanged or even decreased. In LNCaP/CAF spheroids we further found increased Akt signaling that could be inhibited by the phosphatidyl-inositol 3 kinase (PI3K) inhibitor LY294002, thereby overcoming the anti-androgen resistance of the spheroids. Our data show that CAFs influence drug response of PCa cells with varying impact and further suggest this spheroid model is a valuable in vitro drug testing tool.

In this study three major subtypes of nicotinic acetylcholine receptors were characterized pharmacologically using the calcium influx through the ion channel as a robust functional assay system. Human alpha3beta4 receptors and alpha4beta2 receptors were cloned and stably expressed in HEK293 cells. [(125)I]epibatidine saturation binding yielded a B(max) of 4420+/-840 fmol/mg protein for the alpha4beta2 receptor ( n=4) and 518+/-15 fmol/mg protein for the alpha3beta4 receptor ( n=4). As a source for muscle type of nicotinic receptor, the TE671 cell line was used which expresses endogenously the human fetal alpha1beta1gammadelta subtype of nicotinic receptor. Stimulation of these nicotinic receptor subtypes in the different cell lines led to calcium transients that peaked 5-10 s after agonist application and declined thereafter. Eleven agonists were tested in this study and their efficacy and potency at the three nicotinic receptor subtypes were determined (epibatidine, ABT594, anatoxin, ABT418, nicotine, DMPP, cytisine, ABT089, choline, GTS21, AAR17779). This pharmacological characterization of agonist-induced elevation of intracellular free Ca(2+) revealed a distinct rank order of agonist potency for each receptor subtype. Epibatidine showed at all three subtypes the highest potency and was a full agonist. The agonist-elicited response could be blocked by co-incubation of different antagonists from which mecamylamine did not display a strong subtype specificity. These data illustrate that the assessment of calcium transients upon receptor stimulation is a powerful tool for rapid examination of the functional properties of nicotinic receptors.

Background: Androgen receptor targeted therapies have emerged as an effective tool to manage advanced prostate cancer (PCa). Nevertheless, frequent occurrence of therapy resistance represents a major challenge in the clinical management of patients, also because the molecular mechanisms behind therapy resistance are not yet fully understood. In the present study, we therefore aimed to identify novel targets to intervene with therapy resistance using gene expression analysis of PCa co-culture spheroids where PCa cells are grown in the presence of cancer-associated fibroblasts (CAFs) and which have been previously shown to be a reliable model for antiandrogen resistance. Methods: Gene expression changes of co-culture spheroids (LNCaP and DuCaP seeded together with CAFs) were identified by Illumina microarray profiling. Real-time PCR, Western blotting, immunohistochemistry and cell viability assays in 2D and 3D culture were performed to validate the expression of selected targets in vitro and in vivo. Cytokine profiling was conducted to analyze CAF-conditioned medium. Results: Gene expression analysis of co-culture spheroids revealed that CAFs induced a significant upregulation of cholesterol and steroid biosynthesis pathways in PCa cells. Cytokine profiling revealed high amounts of proinflammatory, pro-migratory and pro-angiogenic factors in the CAF supernatant. In particular, two genes, 3-hydroxy-3-methylglutaryl-Coenzyme A synthase 2 (HMGCS2) and aldo-keto reductase family 1 member C3 (AKR1C3), were significantly upregulated in PCa cells upon co-culture with CAFs. Both enzymes were also significantly increased in human PCa compared to benign tissue with AKR1C3 expression even being associated with Gleason score and metastatic status. Inhibiting HMGCS2 and AKR1C3 resulted in significant growth retardation of co-culture spheroids as well as of various castration and enzalutamide resistant cell lines in 2D and 3D culture, underscoring their putative role in PCa. Importantly, dual targeting of cholesterol and steroid biosynthesis with simvastatin, a commonly prescribed cholesterol synthesis inhibitor, and an inhibitor against AKR1C3 had the strongest growth inhibitory effect.