Selective Androgen Receptor Modulator S42 Suppresses Prostate Cancer Cell Proliferation

In vitro anti-carcinogenic effect of andarine as a selective androgen receptor modulator on MIA-PaCa-2 cells by decreased proliferation and cell-cycle arrest at G0/G1 phase

Pancreatic cancer (PC) continues to be devastating due to its highly malignant nature and poor prognosis. The limited benefits of the chemotherapeutic drugs and increasing resistance pose a critical challenge to overcome and warrant investigations for new therapeutic agents. Several preclinical and clinical studies have suggested a possible role of the androgen receptor (AR) signaling pathway in PC development and progression. Nevertheless, the studies are limited and inconclusive in explaining the molecular link between AR signaling and PC. Selective androgen receptor modulators (SARMs) are small molecule drugs with high affinity for the androgen receptor. SARMs elicit selective anabolic activities while abrogating undesired androgenic side effects. There is no study focusing on the utility of SARMs as inhibitors of PC. Here, we report the first study evaluating the possible anti-carcinogenic influences of andarine, a member of the SARMs, on PC. The data we presented here has illustrated that andarine repressed PC cell growth and proliferation via cell cycle arrest at G₀/G₁ phase. Gene expression analysis revealed that it downregulates CDKN1A expression level accordingly. Furthermore, we established that the anti-carcinogenic activity of andarine is not mediated by the PI3K/AKT/mTOR signaling pathway, a crucial regulator of cell survival. Our findings suggest that andarine might be considered as a prospective drug for PC.

Activation of overexpressed glucagon-like peptide-1 receptor attenuates prostate cancer growth by inhibiting cell cycle progression

AIMS/INTRODUCTION

Incretin therapy is a common treatment for type 2 diabetes mellitus. We have previously reported an anti-prostate cancer effect of glucagon-like peptide-1 receptor (GLP-1R) agonist exendin-4. The attenuation of cell proliferation in the prostate cancer cell line was dependent on GLP-1R expression. Here, we examined the relationship between human prostate cancer severity and GLP-1R expression, as well as the effect of forced expression of GLP-1R using a lentiviral vector.

MATERIALS AND METHODS

Prostate cancer tissues were extracted by prostatectomy and biopsy. GLP-1R was overexpressed in ALVA-41 cells using a lentiviral vector (ALVA-41-GLP-1R cells). GLP-1R expression was detected by immunohistochemistry and quantitative polymerase chain reaction. Cell proliferation was examined by growth curves and bromodeoxyuridine incorporation assays. Cell cycle distribution and regulators were examined by flow cytometry and western blotting. In vivo experiments were carried out using a xenografted model.

RESULTS

GLP-1R expression levels were significantly inversely associated with the Gleason score of human prostate cancer tissues. Abundant GLP-1R expression and functions were confirmed in ALVA-41-GLP-1R cells. Exendin-4 significantly decreased ALVA-41-GLP-1R cell proliferation in a dose-dependent manner. DNA synthesis and G1-to-S phase transition were inhibited in ALVA-41-GLP-1R cells. SKP2 expression was decreased and p27Kip1 protein was subsequently increased in ALVA-41-GLP-1R cells treated with exendin-4. In vivo experiments carried out by implanting ALVA-41-GLP-1R cells showed that exendin-4 decreased prostate cancer growth by activation of GLP-1R overexpressed in ALVA41-GLP-1R cells.

CONCLUSIONS

Forced expression of GLP-1R attenuates prostate cancer cell proliferation by inhibiting cell cycle progression in vitro and in vivo. Therefore, GLP-1R activation might be a potential therapy for prostate cancer.

Selective androgen receptor modulators: the future of androgen therapy?

Selective androgen receptor modulators (SARMs) are small molecule drugs that function as either androgen receptor (AR) agonists or antagonists. Variability in AR regulatory proteins in target tissues permits SARMs to selectively elicit anabolic benefits while eschewing the pitfalls of traditional androgen therapy. SARMs have few side effects and excellent oral and transdermal bioavailability and may, therefore, represent viable alternatives to current androgen therapies. SARMs have been studied as possible therapies for many conditions, including osteoporosis, Alzheimer’s disease, breast cancer, stress urinary incontinence (SUI), prostate cancer (PCa), benign prostatic hyperplasia (BPH), male contraception, hypogonadism, Duchenne muscular dystrophy (DMD), and sarcopenia/muscle wasting/cancer cachexia. While there are no indications for SARMs currently approved by the Food and Drug Administration (FDA), many potential applications are still being explored, and results are promising. In this review, we examine the literature assessing the use of SARMS for a number of indications.

Selective androgen receptor modulator, S42 has anabolic and anti-catabolic effects on cultured myotubes

We previously identified a novel selective androgen receptor modulator, S42, that does not stimulate prostate growth but has a beneficial effect on lipid metabolism. S42 also increased muscle weight of the levator ani in orchiectomized Sprague–Dawley rats. These findings prompted us to investigate whether S42 has a direct effect on cultured C2C12 myotubes. S42 significantly lowered expression levels of the skeletal muscle ubiquitin ligase (muscle atrophy-related gene), atrogin1 and Muscle RING-Finger Protein 1(MuRF1) in C2C12 myotubes, as determined by real time PCR. Phosphorylation of p70 S6 kinase (p70S6K), an essential factor for promoting protein synthesis in skeletal muscle, was significantly increased by S42 to almost the same extent as by insulin, but this was significantly prevented by treatment with rapamycin, an inhibitor of mechanistic target of rapamycin complex 1 (mTORC1). However, phosphorylation of Akt, upstream regulator of mTORC1, was not changed by S42. S42 did not increase insulin-like growth factor 1 (Igf1) mRNA levels in C2C12 myotubes. These results suggest that S42 may have an anabolic effect through activation of mTORC1–p70S6K signaling, independent of IGF-1-Akt signaling and may exert an anti-catabolic effect through inhibition of the degradation pathway in cultured C2C12 myotubes.

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A SARM, S42 lowered expression levels of atrogin1 and MuRF1 mRNA in C2C12 myotubes.

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S42 increased phosphorylation of p70S6K through activation of mTORC1 in C2C12 myotubes.

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S42 may have anti-catabolic and anabolic effect in vitro.