Androgen hypersensitivity in prostate cancer: molecular perspectives on androgen deprivation therapy strategies

YB-1 variant and androgen receptor axis-targeted agents in metastatic castration-resistant prostate cancer patients

Aim: To evaluate the influence of YB-1 rs10493112 variant as a genetic marker for response to second-generation androgen receptor axis-target agents. Methods: A hospital-based cohort study of 78 patients with metastatic castration-resistant prostate cancer was conducted. Genotyping was performed by TaqMan^® allelic discrimination technology. Main results: In abiraterone-treated and high-risk patients, YB-1 rs10493112 AA genotype carriers showed lower progression-free survival than C allele genotype patients (4 vs 17 months; p = 0.009). For carriers of AA genotype, multivariate Cox regression analysis revealed a fivefold increased risk of progression (p = 0.035). Conclusion: The study findings suggest that, for metastatic and castration-resistant prostate cancer patients, this polymorphism might be a putative marker for the clinical outcome.

The cAMP phosphodiesterase-4D7 (PDE4D7) is downregulated in androgen-independent prostate cancer cells and mediates proliferation by compartmentalising cAMP at the plasma membrane of VCaP prostate cancer cells

Background:

Isoforms of the PDE4 family of cAMP-specific phosphodiesterases (PDEs) are expressed in a cell type-dependent manner and contribute to underpinning the paradigm of intracellular cAMP signal compartmentalisation. Here we identify the differential regulation of the PDE4D7 isoform during prostate cancer progression and uncover a role in controlling prostate cancer cell proliferation.

Methods:

PDE4 transcripts from 19 prostate cancer cell lines and xenografts were quantified by qPCR. PDE4D7 expression was further investigated because of its significant downregulation between androgen-sensitive (AS) and androgen-insensitive (AI) samples. Western blot analysis, PDE activity assay, immunofluorescent staining and cAMP responsive FRET assays were used to investigate the sub-plasma membrane localisation of a population of PDE4D7 in VCaP (AS) and PC3 (AI) cell lines. Disruption of this localisation pattern using dominant-negative protein expression and siRNA knockdown showed that PDE4D7 acts in opposition to proliferative signalling as assessed by electrical impedance-based proliferation assays.

Results:

Here we identify the differential regulation of the PDE4D7 isoform during prostate cancer progression. PDE4D7 is highly expressed in AS cells and starkly downregulated in AI samples. The significance of this downregulation is underscored by our finding that PDE4D7 contributes a major fraction of cAMP degrading PDE activity tethered at the plasma membrane and that displacement of PDE4D7 from this compartment leads to an increase in the proliferation of prostate cancer cells. PDE4D7 mRNA expression is not, however, directly regulated by the androgen receptor signalling axis despite an overlapping genomic structure with the androgen responsive gene PART1. PDE4D7, which locates to the plasma membrane, acts to supress aberrant non-steroidal growth signals within the prostate or AS metastasis.

Conclusions:

PDE4D7 expression is significantly downregulated between AS and AI cell phenotypes. This change in expression potentially provides a novel androgen-independent biomarker and manipulation of its activity or its expression may provide therapeutic possibilities and insights into contributory aspects of the complex molecular pathology of prostate cancer.

Polymorphisms of the androgen transporting gene SLCO2B1 may influence the castration resistance of prostate cancer and the racial differences in response to androgen deprivation

BACKGROUND

Organic anion-transporting polypeptides (OATPs) encoded by SLCO mediate the cellular uptake of many compounds, including androgens. SLCO1B3 and SLCO2B1 are polymorphic, and single-nucleotide polymorphisms of those genes alter androgen transport efficiency. We aimed to investigate the association between genetic variations in SLCOs and the progression to castration-resistant prostate cancer (CRPC).

METHODS

We studied the progression to CRPC for the SLCO1B3 rs4149117 and SLCO2B1 rs12422149 genotypes in 87 prostate cancer patients who received androgen deprivation therapy (ADT). Data were analyzed using the χ(2) test, Kaplan-Meier survival analysis and Cox proportional hazard model.

RESULTS

SLCO3B1 genotypes were not significantly associated with the time to progression (TTP); however, patients carrying the active androgen transport SLCO2B1 genotype (GG allele) exhibited a median TTP that was 7 months shorter than that of patients with impaired androgen-transporting activity SLCO2B1 polymorphisms (GA/AA alleles) (10.0 vs 17.0 months, P=0.004). Active androgen transport genotypes of SLCO2B1 (GG allele) occurred more frequently in African and Caucasian populations than in Japanese and Han Chinese populations (P<0.001).

CONCLUSIONS

These data suggest that SLCO2B1 rs12422149 variants could provide prognostic value for prostate cancer patients treated with ADT and influence ethnic differences in response to ADT. Active androgen import may be one of the underlying mechanisms of resistance to ADT, and androgen-transporting systems could provide novel biomarkers and targets for CRPC treatment.

The present and future of prostate cancer urine biomarkers

In order to successfully cure patients with prostate cancer (PCa), it is important to detect the disease at an early stage. The existing clinical biomarkers for PCa are not ideal, since they cannot specifically differentiate between those patients who should be treated immediately and those who should avoid over-treatment. Current screening techniques lack specificity, and a decisive diagnosis of PCa is based on prostate biopsy. Although PCa screening is widely utilized nowadays, two thirds of the biopsies performed are still unnecessary. Thus the discovery of non-invasive PCa biomarkers remains urgent. In recent years, the utilization of urine has emerged as an attractive option for the non-invasive detection of PCa. Moreover, a great improvement in high-throughput “omic” techniques has presented considerable opportunities for the identification of new biomarkers. Herein, we will review the most significant urine biomarkers described in recent years, as well as some future prospects in that field.

Circulating sex steroids and prostate cancer: introducing the time-dependency theory

PURPOSE

We sought whether serum total testosterone (tT), estradiol (E2), tT/E2 ratio, and sex hormone-binding globulin (SHBG) significantly fluctuate throughout time in men with prostate cancer (PCa).

METHODS

Circulating hormones were measured in a cohort of 631 candidates for radical prostatectomy. Hormone levels were analyzed according to either patient age, stratified into quartiles, or body mass index (BMI). Linear regression analyses tested the association between sex steroids and continuously coded patient age and BMI values.

RESULTS

No significant differences were found among age quartiles regarding serum tT levels and tT/E2 ratio. Conversely, E2 and SHBG levels significantly increased throughout time (all, p ≤ 0.001). Total T did not linearly change according to continuously coded patient age; in contrast, E2 and SHBG linearly increased (all, p ≤ 0.001), whereas tT/E2 decreased (p = 0.016) with aging. Rate of hypogonadism significantly increased with aging (p = 0.04). Total T, T/E2 ratio, and SHBG linearly decreased along with BMI increases (all p ≤ 0.02), whereas serum E2 did not significantly change. Rate of hypogonadism significantly increased with BMI increases (p < 0.001).

CONCLUSIONS

In contrast with longitudinal studies in the general male population, these data indirectly suggest that serum tT levels could be stable over time in PCa patients. This finding led to formulation of a "time-dependency theory", which postulates that the endocrine biology of prostate tissue is dependent on the exposure time at a given concentration of sex steroid, which, in turn, fluctuates throughout the lifespan of the individual.

Angiotensin-(1-7) attenuates metastatic prostate cancer and reduces osteoclastogenesis

BACKGROUND

Angiotensin-(1-7) [Ang-(1-7)] is an endogenous, heptapeptide hormone with anti-proliferative and anti-angiogenic properties. The primary objective of this study was to determine whether Ang-(1-7) effectively reduces prostate cancer metastasis in mice.

METHODS

Human PC3 prostate cancer cells were injected into the aortic arch via the carotid artery of SCID mice pre-treated with Ang-(1-7) or injected into the tibia of athymic mice, administered Ang-(1-7) for 5 weeks beginning 2 weeks post-injection. Tumor growth and volume were determined by bioluminescent and magnetic resonance imaging. The presence of tumors was confirmed by hematoxylin and eosin staining; TRAP histochemistry was used to identify osteolytic lesions. The effect of Ang-(1-7) on osteoclastogenesis was assessed in differentiated bone marrow cells.

RESULTS

Pre-treatment with Ang-(1-7) prevented metastatic tumor formation following intra-aortic injection of PC3 cells, while 83% of untreated mice developed tumors in metastatic sites. Circulating VEGF was significantly higher in control mice compared to mice administered Ang-(1-7). A 5-week regimen of the heptapeptide hormone attenuated intra-tibial tumor growth; Ang-(1-7) was significantly higher in the tibia of treated mice than in control animals. Osteoclastogenesis was reduced by 50% in bone marrow cells differentiated in the presence of Ang-(1-7), suggesting that the heptapeptide hormone prevents the formation of osteolytic lesions to reduce tumor survival in the bone microenvironment.

CONCLUSIONS

These findings suggest that Ang-(1-7) may serve as an anti-angiogenic and anti-metastatic agent for advanced prostate cancer. By extension, the heptapeptide hormone may provide effective therapy for bone metastasis produced from primary tumors of the lung and breast.

Cancer/testis antigens and urological malignancies

Cancer/testis antigens (CTAs) are a group of tumour-associated antigens (TAAs) that display normal expression in the adult testis--an immune-privileged organ--but aberrant expression in several types of cancers, particularly in advanced cancers with stem cell-like characteristics. There has been an explosion in CTA-based research since CTAs were first identified in 1991 and MAGE-1 was shown to elicit an autologous cytotoxic T-lymphocyte (CTL) response in a patient with melanoma. The resulting data have not only highlighted a role for CTAs in tumorigenesis, but have also underscored the translational potential of these antigens for detecting and treating many types of cancers. Studies that have investigated the use of CTAs for the clinical management of urological malignancies indicate that these TAAs have potential roles as novel biomarkers, with increased specificity and sensitivity compared to those currently used in the clinic, and therapeutic targets for cancer immunotherapy. Increasing evidence supports the utilization of these promising tools for urological indications.