Testosterone metabolites inhibit proliferation of castration- and therapy-resistant prostate cancer

Molecular Efficacy of Gnetin C as Dual-Targeted Therapy for Castrate-Resistant Prostate Cancer

SCOPE

Resistance of castrate-resistant prostate cancer (CRPC) to enzalutamide (Enz) involves the expression of constitutively active androgen receptor splice variant (AR-V7). In addition to altered AR pathways, CRPC is characterized by "non-AR-driven" signaling, which includes an overexpression of metastasis-associated protein 1 (MTA1). Combining natural compounds with anticancer drugs may enhance drug effectiveness while reducing adverse effects. In this study, the in vitro and in vivo anticancer effects of Gnetin C (GnC) alone and in combination with Enz against CRPC are examined.

METHODS AND RESULTS

The effects of GnC alone and in combination with Enz are assessed by cell viability, clonogenic survival, cell migration, and AR and MTA1 expression using 22Rv1 cells. The tumor growth in vivo is assessed by bioluminescent imaging, western blots, RT-PCR, and IHC. GnC alone and in combined treatment inhibit cell viability, clonogenic survival and migration, and AR and MTA1 expression in 22Rv1 cells. The underlying AR- and MTA1-targeted anticancer mechanisms of treatments in vivo involve inhibition of proliferation and angiogenesis, and induction of apoptosis.

CONCLUSION

The findings demonstrate that GnC alone and GnC combined with Enz effectively inhibits AR- and MTA1-promoted tumor-progression in advanced CRPC, which indicates its potential as a novel therapeutic approach for CRPC.

AKR1C2 Promotes Metastasis and Regulates the Molecular Features of Luminal Androgen Receptor Subtype in Triple Negative Breast Cancer Cells

PURPOSE

Patients with triple-negative breast cancer (TNBC) have an increased risk of distant metastasis compared to those with other subtypes. In this study, we aimed to identify the genes associated with distant metastasis in TNBC and their underlying mechanisms.

METHODS

We established patient-derived xenograft (PDX) models using surgically resected breast cancer tissues from 31 patients with TNBC. Among these, 15 patients subsequently developed distant metastases. Candidate metastasis-associated genes were identified using RNA sequencing. In vitro wound healing, proliferation, migration, and invasion assays and in vivo tumor xenograft and metastasis assays were performed to determine the functional importance of aldo-keto reductase family 1 member C2 (AKR1C2). Additionally, we used the METABRIC dataset to investigate the potential role of AKR1C2 in regulating TNBC subtypes and their downstream signaling activities.

RESULTS

RNA sequencing of primary and PDX tumors showed that genes involved in steroid hormone biosynthesis, including AKR1C2, were significantly upregulated in patients who subsequently developed metastasis. In vitro and in vivo assays showed that silencing of AKR1C2 resulted in reduced cell proliferation, migration, invasion, tumor growth, and incidence of lung metastasis. AKR1C2 was upregulated in the luminal androgen receptor (LAR) subtype of TNBC in the METABRIC dataset, and AKR1C2 silencing resulted in the downregulation of LAR classifier genes in TNBC cell lines. The androgen receptor (AR) gene was a downstream mediator of AKR1C2-associated phenotypes in TNBC cells. AKR1C2 expression was associated with gene expression pathways that regulate AR expression, including JAK-STAT signaling or interleukin 6 (IL-6). The levels of phospho-signal transducer and activator of transcription and IL-6, along with secreted IL-6, were significantly downregulated in AKR1C2-silenced TNBC cells.

CONCLUSION

Our data indicate that AKR1C2 is an important regulator of cancer growth and metastasis in TNBC and may be a critical determinant of LAR subtype features.

S-Adenosylmethionine affects ERK1/2 and STAT3 pathway in androgen-independent prostate cancer cells

Background

The most critical point in the treatment of prostate cancer is the progression towards a hormone-refractory tumour, making research on alternative therapies necessary. This study focused on the methyl donor S-adenosylmethionine (SAM), which is known to act as an antitumourigenic in several cancer cell lines. Though a genome-wide downregulation of proto-oncogenes in prostate cancer cell lines treated with SAM is obvious, the anticancer effects remain elusive. Thus, in this study, the impact of SAM treatment on the cell cycle, apoptosis and cancer-related pathways was investigated.

Methods and results

After performing SAM treatment on prostate cancer cell lines (PC-3 and DU145), a cell-cycle arrest during the S-phase, a downregulation of cyclin A protein levels and an upregulation of p21 cell cycle inhibitor were observed. The proapoptotic Bax/Bcl-2 ratio and the caspase-3 activity were elevated; additionally, the apoptosis rate of SAM treated cells increased significantly in a time-dependent manner. Moreover, immunoblots displayed a downregulation of Erk1/2 and STAT3 phosphorylation accompanied by a reduced expression of the STAT3 protein.

Conclusion

SAM caused changes in cancer-related pathways, probably leading to the effects on the cell cycle and apoptosis rate. These results provide deeper insights into the anticancer effects of SAM on prostate cancer cells.

Overview of human 20 alpha-hydroxysteroid dehydrogenase (AKR1C1): Functions, regulation, and structural insights of inhibitors

Human aldo-keto reductase family 1C1 (AKR1C1) is an important enzyme involved in human hormone metabolism, which is mainly responsible for the metabolism of progesterone in the human body. AKR1C1 is highly expressed and has an important relationship with the occurrence and development of various diseases, especially some cancers related to hormone metabolism. Nowadays, many inhibitors against AKR1C1 have been discovered, including some synthetic compounds and natural products, which have certain inhibitory activity against AKR1C1 at the target level. Here we briefly reviewed the physiological and pathological functions of AKR1C1 and the relationship with the disease, and then summarized the development of AKR1C1 inhibitors, elucidated the interaction between inhibitors and AKR1C1 through molecular docking results and existing co-crystal structures. Finally, we discussed the design ideals of selective AKR1C1 inhibitors from the perspective of AKR1C1 structure, discussed the prospects of AKR1C1 in the treatment of human diseases in terms of biomarkers, pre-receptor regulation and single nucleotide polymorphisms, aiming to provide new ideas for drug research targeting AKR1C1.

Modulating the Heat Sensitivity of Prostate Cancer Cell Lines In Vitro: A New Impact for Focal Therapies

Focal therapies such as high-intensity focused ultrasound (HiFU) are an emerging therapeutic option for prostate cancer (PCA). Thermal or mechanical effects mediate most therapies. Moreover, locally administered drugs such as bicalutamide or docetaxel are new focal therapeutic options. We assessed the impact of such focal medical treatments on cell viability and heat sensitivity by pre-treating PCA cell lines and then gradually exposing them to heat. The individual heat response of the cell lines tested differed largely. Vertebral-Cancer of the Prostate (VCaP) cells showed an increase in metabolic activity at 40-50 °C. Androgen receptor (AR)-negative PC3 cells showed an increase at 51.3 °C and were overall more resistant to higher temperatures. Pre-treatment of VCaP cells with testosterone (VCaPrev) leads to a more PC3-like kinetic of the heat response. Pre-treatment with finasteride and bicalutamide did not cause changes in heat sensitivity in any cell line. Mitoxantrone treatment, however, shifted heat-induced proliferation loss to lower temperature in VCaP cells. Further analysis via RNAseq identified a possible correlation of heat resistance with H3K27me3-dependent gene regulation, which could be related to an increase in the histone methyltransferase EZH2 and a possible neuroendocrine differentiation. Pre-treatment with mitoxantrone might be a perspective for HiFU treatment. Further studies are needed to evaluate possible combinations with Hsp90 or EZH2 inhibitors.

Clinical activity of abiraterone plus prednisone in docetaxel-naοve and docetaxel-resistant Chinese patients with metastatic castration-resistant prostate cancer

This study investigated the clinical activity of abiraterone plus prednisone in docetaxel-naïve and docetaxel-resistant Chinese patients with metastatic castration-resistant prostate cancer (mCRPC). A total of 146 patients with docetaxel-naïve group (103 cases) and docetaxel-resistant group (43 cases) were enrolled from the Shanghai Cancer Center (Shanghai, China) in this retrospective cohort study. The efficacy endpoints were prostate-specific antigen response rate, prostate-specific antigen progression-free survival, clinical/radiographic progression-free survival, and overall survival in response to abiraterone plus prednisone. Significantly higher prostate-specific antigen response rate was found in docetaxel-naïve group (54.4%, 56/103) compared to docetaxel-resistant group (34.9%, 15/43) (P = 0.047). In addition, significantly higher median prostate-specific antigen progression-free survival (14.0 vs 7.7 months, P = 0.005), clinical or radiographic progression-free survival (17.0 vs 12.5 months, P = 0.003), and overall survival (27.0 vs 18.0 months, P = 0.016) were found in docetaxel-naïve group compared to docetaxel-resistant group, respectively. The univariate and multivariate analyses indicated that lower albumin and visceral metastases were independent significant predictors for shorter overall survival. To sum up, our data suggested that abiraterone plus prednisone was efficient in both docetaxel-naïve and docetaxel-resistant Chinese patients. Moreover, higher PSA response rate and longer overall survival were observed in the docetaxel-naïve group, which suggested that abiraterone was more effective for docetaxel- naïve patients than for docetaxel failures.

Transcriptional repression by androgen receptor: roles in castration-resistant prostate cancer

Androgen receptor (AR), a hormonal transcription factor, plays important roles during prostate cancer progression and is a key target for therapeutic interventions. While androgen-deprivation therapies are initially successful in regressing prostate tumors, the disease ultimately comes back as castration-resistant prostate cancer (CRPC) or at the late stage as neuroendocrine prostate cancer (NEPC). CRPC remains largely dependent on hyperactive AR signaling in the milieu of low androgen, while NEPC is negative of AR expression but positive of many AR-repressed genes. Recent technological advances in genome-wide analysis of transcription factor binding sites have revealed an unprecedented set of AR target genes. In addition to its well-known function in activating gene expression, AR is increasingly known to also act as a transcriptional repressor. Here, we review the molecular mechanisms by which AR represses gene expression. We also summarize AR-repressed genes that are aberrantly upregulated in CRPC and NEPC and represent promising targets for therapeutic intervention.

Role of Estrogen in Androgen-Induced Prostate Carcinogenesis in NBL Rats

Androgens are thought to cause prostate cancer, but the underlying mechanisms are unclear. Data from animal studies suggest that for androgens to cause prostate cancer, they must be aromatized to estrogen and act in concert with estrogen metabolites. We tested the hypothesis that androgen-receptor and estrogen receptor-mediated effects of androgen and estrogen are necessary, as well as genotoxicity of estrogen metabolites. NBL rats were treated with androgenic and estrogenic compounds for 16-75 weeks through slow-release silastic implants or pellets. Testosterone alone induced cancer in the prostate of 37% of rats. 5α-Dihydrotestosterone, which cannot be converted to estradiol or testosterone, did not cause a significant prostate cancer incidence (4%). Addition of estradiol to 5α-dihydrotestosterone treatment did not markedly enhance prostate cancer incidence (14%), unlike adding estradiol to testosterone treatment which induced a 100% tumor incidence. Testosterone plus estradiol treatment induced a DNA adduct detectable by ³²P-postlabeling, oxidative DNA damage (8-hydroxyguanosine), and lipid peroxidation at the site within the prostate where this treatment causes cancers, preceding later cancer formation. The non-estrogenic 4-hydroxy metabolite of estradiol, when combined with testosterone, induced prostatic dysplasia within 16 weeks and, after long-term treatment, a very low incidence of prostate cancer (21%). When an estrogen that cannot be hydroxylated (2-fluoroestradiol) was added to this combined treatment with testosterone and 4-hydroxyestradiol, dysplasia frequency after 16 weeks was doubled. These results strongly support the hypothesis, but additional definitive studies are needed which may identify new targets to interfere with these mechanisms that are clinically feasible in humans.

Androgen receptor: what we know and what we expect in castration-resistant prostate cancer

Androgen deprivation therapy is an important therapy for prostate cancer (PCa) in aging men. Under the background of castration, it is inevitable that prostate cancer will develop into castration-resistant prostate cancer (CRPC), which has a high mortality rate, after 2-3 years. Androgen receptor (AR) plays a key role in PCa development and is essential to CRPC. More recent research studies have reported that the development of CRPC is largely due to altered mechanisms related to AR, so it is important for us to understand the roles of AR and detailed AR-related mechanisms in CRPC. The multiple AR-related mechanisms promoting the development of CRPC are as follows: (1) enhanced transformation and increased synthesis of intratumoral androgen; (2) AR overexpression, which enables CRPC to be hypersensitive to low levels of androgen; (3) AR cofactors, which enhanced AR transactivation; (4) AR-spliced variants, which mediated downstream gene expression without androgen; (5) the interaction between the AR pathway and classic tumor-related pathways; and» (6) AR mutations, which reduced AR specificity and enhanced AR transcription.