Sensitization of prostate cancer to radiation therapy: Molecules and pathways to target.

Radiation therapy is used to treat cancer by radiation-induced DNA damage. Despite the best efforts to eliminate cancer, some cancer cells survive irradiation, resulting in cancer progression or recurrence. Alteration in DNA damage repair pathways is common in cancers, resulting in modulation of their response to radiation. This article focuses on the recent findings about molecules and pathways that potentially can be targeted to sensitize prostate cancer cells to ionizing radiation, thereby achieving an improved therapeutic outcome.

Radio-223 en la secuencia terapéutica del cáncer de próstata resistente a la castración metastásico / Radium-223 in the therapeutic sequence of metastatic castration-resistant prostate cancer

Contexto: El radio-223 es un emisor de partículas □ con acción específica sobre las metástasis óseas. El estudio ALSYMPCA demostró que el radio-223 prolonga la supervivencia global y retrasa la aparición de eventos óseos en pacientes con cáncer de próstata resistente a la castración con metástasis óseas (CPRCm) sintomáticas y sin metástasis viscerales, con un buen perfil de seguridad. Objetivo: Revisión de la nueva evidencia científica de radio-223 a partir de análisis preespecificados y post hoc del estudio ALSYMPCA y de programas de acceso precoz posteriores a la publicación del estudio ALSYMPCA, con el fin de aportar nuevos datos en el manejo de pacientes con CPRCm. Adquisición de la evidencia: Búsqueda de evidencia en PubMed y en abstracts de congresos de urología y oncología internacionales, así como ensayos clínicos en marcha (ClinicalTrials.gov). Síntesis de la evidencia: Los resultados de los estudios revisados ofrecen resultados prometedores que ampliarían el beneficio terapéutico de radio-223 a pacientes con síntomas leves e incluso asintomáticos. También aportan evidencia preliminar acerca del beneficio del tratamiento con radio-223 tras el fracaso a docetaxel o a enzalutamida o abiraterona o la combinación de radio-223 con estos u otros agentes terapéuticos como los dirigidos al hueso o inmunoterapia. Conclusión: El radio-223 puede ser una opción de tratamiento en pacientes con síntomas leves y aportar un beneficio terapéutico tras el fracaso a tratamientos disponibles en la actualidad o en combinación con estos. Esta evidencia ha de ser corroborada en ensayos clínicos antes de ser incorporados en la práctica clínica

Context: Radium-223 is an -particle transmitter with specific action on bone metastases. The Alpharadin in Symptomatic Prostate Cancer Patients (ALSYMPCA) study showed that radium-223 extended overall survival and delayed the onset of bone events in patients with symptomatic castration-resistant prostate cancer with bone metastases (mCRPC) and without visceral metastases, with a good safety profile. Objective: To review the new scientific evidence on radium-223 based on prespecified and post-hoc analyses of the ALSYMPCA study and on early-access programs after the publication of the ALSYMPCA study, thereby providing new data on the management of patients with mCRPC. Acquisition of evidence: We searched for evidence on PubMed and in the abstracts of international urology and oncology congresses, as well as ongoing clinical trials (ClinicalTrials.gov). Synthesis of the evidence: The results of the reviewed studies offer promising results that will broaden the therapeutic benefits of radium-223 to patients with mild symptoms and those with no symptoms. The results also provide preliminary evidence on the benefit of radium-223 treatment after the failure of docetaxel, enzalutamide or abiraterone or the combination of radium-223 with these agents or other therapeutic agents such as bone-targeted agents and immunotherapy. Conclusion: Radium-223 can be a treatment option for patients with mild symptoms and can provide a therapeutic benefit after failure of currently available treatments or in combination with these treatments. This evidence should be corroborated in clinical trials before being added to clinical practice

Calmodulin-androgen receptor (AR) interaction: calcium-dependent, calpain-mediated breakdown of AR in LNCaP prostate cancer cells.

Chemotherapy of prostate cancer targets androgen receptor (AR) by androgen ablation or antiandrogens, but unfortunately, it is not curative. Our attack on prostate cancer envisions the proteolytic elimination of AR, which requires a fuller understanding of AR turnover. We showed previously that calmodulin (CaM) binds to AR with important consequences for AR stability and function. To examine the involvement of Ca(2+)/CaM in the proteolytic breakdown of AR, we analyzed LNCaP cell extracts that bind to a CaM affinity column for the presence of low molecular weight forms of AR (intact AR size, approximately 114 kDa). Using an antibody directed against the NH(2)-terminal domain (ATD) of AR on Western blots, we identified approximately 76-kDa, approximately 50-kDa, and 34/31-kDa polypeptides in eluates of CaM affinity columns, suggesting the presence of CaM-binding sites within the 31/34-kDa ATD of AR. Under cell-free conditions in the presence of phenylmethylsulfonyl fluoride, AR underwent Ca(2+)-dependent degradation. AR degradation was inhibited by N-acetyl-leu-leu-norleu, an inhibitor of thiol proteases, suggesting the involvement of calpain. In intact cells, AR breakdown was accelerated by raising intracellular Ca(2+) using calcimycin, and increased AR breakdown was reversed with the cell-permeable Ca(2+) chelator bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetra-(acetoxymethyl)-ester. In CaM affinity chromatography studies, the Ca(2+)-dependent protease calpain was bound to and eluted from the CaM-agarose column along with AR. Caspase-3, which plays a role in AR turnover under stress conditions, did not bind to the CaM column and was present in the proenzyme form. Similarly, AR immunoprecipitates prepared from whole-cell extracts of exponentially growing LNCaP cells contained both calpain and calpastatin. Nuclear levels of calpain and calpastatin (its endogenous inhibitor) changed in a reciprocal fashion as synchronized LNCaP cells progressed from G(1) to S phase. These reciprocal changes correlated with changes in AR level, which increased in late G(1) phase and decreased as S phase progressed. Taken together, these observations suggest potential involvement of AR-bound CaM in calcium-controlled, calpain-mediated breakdown of AR in prostate cancer cells.

[Kinetic parameters of androgen receptor complexes and the activities of the glycolysis and oxidative pentose phosphate pathway key enzymes in rat testis cytosol after whole body 60-min exposure to high frequency electromagnetic field (39.5 Ghz)]. / Vliianie vysokochastotnogo élektromagnitnogo izlucheniia millimetrovogo diapazona na kineticheskie parametry retseptsii androgenov, aktivnosti kliuchevykh fermentov glikoliza i oksidativnogo pentozofosfatnogo puti v semennikakh krys..

The effect of electromagnetic field of millimeter range on biochemical indices of testicles of totally exposed rats at various periods of observation (day 1, 10, 30, 90) was studied. The following functional shifts were revealed: the 6-phosphogluconate dehydrogenase activities enforced approximately up to 130% on 30th day in comparison with the controls, but in three months (90th day) the activity returned to normal values: glucose-6-phosphate dehydrogenase an puruvate kinase did not show obvious changes of activities. On the contrary, there were surprising differences in behavior of androgen-receptor system: the number of androgen-receptor sites in cytosol was increased significantly on 1st day after exposure (114%); on 10th day concentration of RA was quite oppositely 1.68-fold reduced in relation to the control; through 1-month after exposure the rising of [RA] (123%) was registered; however, to 3-month term the significant fall (1.42 times) of the RA contents in testicular cytosol persisted.

Photoperiod and testosterone regulate androgen receptor immunostaining in the Siberian hamster brain.

Day length regulates the effects of gonadal steroids on gonadotropin secretion and behavior in seasonal breeders. To determine whether this influence of photoperiod results from changes in androgen receptor expression in Siberian hamster brain regions that regulate neuroendocrine function, androgen receptor immunostaining was examined in castrated animals given either no androgen replacement or one of three doses of testosterone (T) resulting in physiological serum concentrations. Half of the animals were housed under inhibitory photoperiod conditions, and immunostaining was quantified 11 days later. Measurement of serum gonadotropin and prolactin concentrations confirmed that androgen exerted graded effects on pituitary function but that the animals were killed before photoperiodic influences had fully developed. T significantly increased the numbers of androgen receptor-immunoreactive cells in every brain region examined. Photoperiod exerted no significant influence on androgen receptor-immunoreactive cell number in the arcuate nucleus, bed nucleus of the stria terminalis (BNST), medial preoptic nucleus, or in medial amygdala. An interaction between T and photoperiod was observed in the BNST and in the rostral and middle portions of the arcuate nucleus. Although increasing concentrations of T resulted in more intense cellular immunostaining in the BNST and arcuate, this effect was not influenced by day length. These results indicate that relatively short-duration (11 days) exposure to inhibitory photoperiod triggers localized and regionally specific changes in androgen receptor expression.

[Effects of prolonged low-dose gamma irradiation on testes of rats]. / Posledstviia prolongirovannogo nizkodozovogo gamma-oblucheniia v semennikakh krys.

Dose-dependent characteristics of rat testicular cytosol androgen reception at varied terms after prolonged whole-body gamma-irradiation (0.1, 0.25 and 0.5 Gy at dose rate of 5.83 x 10(-7) Gy/s) coupled with an electron microscopy morphological characteristics of Sertoli cells. Leydig's cells and other populations of testicular cells, were examined. Analysis of the data obtained suggests the existence of gamma-sensor in brain of mammals, that involved on hypothalamic-pituitary-testicular levels in realisation of radiation stress suppression of Sertoli cell functions at a relatively "low" (0.1-0.5 Gy) doses by means of hypothalamic releasing factors and, therefore pituitary gonadotropins hypersecretion.

Substitution of Cys-560 by Phe, Trp, Tyr, and Ser in the first zinc finger of human androgen receptor affects hormonal sensitivity and transcriptional activation.

We have established and characterized four human androgen receptor (AR) mutants, AR C560F, C560W, C560Y, C560S). To assess the functional significance of these substitutions, we compared the transcriptional activation, hormone binding affinity, receptor-DNA interaction, and the subcellular distribution of the hormone-receptor complexes. Binding studies showed that all mutants bound methyltrienolone (R1881) with wild type affinity (Kd = 0.5 nM). Transactivation efficiency, as compared to wild type AR, increased 150% with C560F and decreased to 70% with C560W and C560Y and to 40% with mutant C560S. Subcellular receptor distribution showed that 85% of C560F bound with hormone was extracted from the nuclear fraction and 15% in the cytosol. Gel mobility shift assays showed that C560F expressed in CV-1 cells bound to an androgen responsive element (ARE) with equal efficiency as the wild type human AR. The mutants C560W and C560Y demonstrated a lower ability to bind to ARE, whereas C560S showed a significantly lower ability to interact with ARE. We propose that the change in polarity introduced into the loop structure by C560S leads to a shorter period of contact between the mutant receptor and DNA resulting in decreased transcriptional activation levels.

Radiation-inactivation size of transformed and non-transformed androgen receptors.

The nucleic acid sequence of the androgen receptor (AR) gene predicts that the protein structure possesses DNA- and steroid-binding domains that show high degrees of sequence similarity with those of other steroid receptors. Since the steroid-binding domain of the AR corresponds to a 30 kDa portion of the protein, and the AR structure may be monomeric or hetero-oligomeric depending on its transformation state, we have herein determined the AR radiation-inactivation size (RIS) in relation to the molecular structure whose binding activity toward methyltrienolone (R1881) is abolished by a radiation 'hit'. Soluble fractions from whole canine prostatic tissue were used as a source of non-transformed AR. The AR transformation was induced by the addition of 0.6 M-KCl, and these preparations were used together with high-salt nuclear extracts as a source of transformed AR. To maximize the binding activity, molybdate and dithiothreitol were included during AR extraction. Receptor transformation was verified by modifications of both the sedimentation coefficients (from 7.5 S to 4.1 S on sucrose gradients) and molecular masses (from 260 kDa to 115 kDa by gel filtration). The RIS values of the non-transformed and transformed ARs were not statistically different: 92 +/- 19 kDa and 110 +/- 25 kDa respectively. In addition, the inactivation of AR binding activity by radiation was attributed to a loss of binding sites, with no significant change in the Kd. When benzoic acid, a free-electron scavenger, was added together with dithiothreitol before and after irradiation, no change in the RIS value was observed. Thus, in the canine prostate, the RIS value of the AR represents the monomeric protein, independently of its association with other proteins, and this value corresponds to that predicted by cloning studies and photoaffinity-labelling of AR.

Influence of photoinhibition, photostimulation and prolactin on pituitary and hypothalamic nuclear androgen receptors in the male hamster.

Testosterone (T) feedback sensitivity is markedly altered in adult male golden hamsters following exposure to short photoperiods (SD). Using a technique which measures total androgen receptors within the cell nucleus, the present study examined pituitary and hypothalamic nuclear androgen receptor levels in animals exposed to (1) long days (LD) or SD in the presence and absence of a constant T level supplied via a Silastic implant, (2) photostimulation following SD-induced testicular regression and (3) short-term prolactin injections following SD-induced testicular regression. Short photoperiods were associated with a drop in nuclear androgen receptor levels which was correlated with a decline in circulating T. When constant T was supplied to gonadectomized hamsters, those exposed to SD possessed higher pituitary and similar hypothalamic nuclear androgen receptor levels than those exposed to LD. As expected, plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were greatly reduced in SD-exposed, castrated, T-treated hamsters as compared to LD-exposed, castrated, T-treated animals. Photostimulation of intact SD-exposed hamsters for 5 or 10 days was associated with a decline in pituitary nuclear androgen receptors. Prolactin treatment caused no noticeable change in pituitary or hypothalamic androgen receptors even though plasma LH and FSH levels were significantly increased. These results support the hypothesis that altered T feedback mechanisms controlling LH and FSH release following chronic exposure to SD may be related to an alteration in the amount of androgen receptors present in the anterior pituitary.