Cloning and characterization of a specific coactivator, ARA70, for the androgen receptor in human prostate cells

The androgen receptor (AR) is a member of the steroid receptor superfamily that plays an important role in male sexual differentiation and prostate cell proliferation. Mutations or abnormal expression of AR in prostate cancer can play a key role in the process that changes prostate cancer from androgen-dependent to an androgen-independent stage. Using a yeast two-hybrid system, we were able to isolate a ligand-dependent AR-associated protein (ARA70), which functions as an activator to enhance AR transcriptional activity 10-fold in the presence of 10(-10) M dihydrotestosterone or 10(-9) M testosterone, but not 10(-6) M hydroxyflutamide in human prostate cancer DU145 cells. Our data further indicated that ARA70 Will only slightly induce the transcriptional activity of other steroid receptors such as estrogen receptor, glucocorticoid receptor, and progesterone receptor in DU145 cells. Together, these data suggest that AR may need a specific coactivator(s) such as ARA70 for optimal androgen activity.

From HER2/Neu signal cascade to androgen receptor and its coactivators: a novel pathway by induction of androgen target genes through MAP kinase in prostate cancer cells

Overexpression of the HER2/Neu protooncogene has been linked to the progression of breast cancer. Here we demonstrate that the growth of prostate cancer LNCaP cells can also be increased by the stable transfection of HER2/Neu. Using AG879, a HER2/Neu inhibitor, and PD98059, a MAP kinase inhibitor, as well as MAP kinase phosphatase-1 (MPK-1), in the transfection assay, we found that HER2/Neu could induce prostate-specific antigen (PSA), a marker for the progression of prostate cancer, through the MAP kinase pathway at a low androgen level. Reporter assays and mammalian two-hybrid assays further suggest this HER2/Neu-induced androgen receptor (AR) transactivation may function through the promotion of interaction between AR and AR coactivators, such as ARA70. Furthermore, we found this HER2/Neu --> MAP kinase --> AR-ARAs --> PSA pathway could not be blocked completely by hydroxyflutamide, an antiandrogen used in the treatment of prostate cancer. Together, these data provide a novel pathway from HER2/Neu to AR transactivation, and they may represent one of the reasons for the PSA re-elevation and hormone resistance during androgen ablation therapy in prostate cancer patients.

Akt suppresses androgen-induced apoptosis by phosphorylating and inhibiting androgen receptor

Whereas several apoptosis-related proteins have been linked to the antiapoptotic effects of Akt serine-threonine kinase, the search continues to explain the Akt signaling role in promoting cell survival via antiapoptotic effects. Here, we demonstrate that Akt phosphorylates the androgen receptor (AR) at Ser-210 and Ser-790. A mutation at AR Ser-210 results in the reversal of Akt-mediated suppression of AR transactivation. Activation of the phosphatidylinositol-3-OH kinase/Akt pathway results in the suppression of AR target genes, such as p21, and the decrease of androgen/AR-mediated apoptosis, which may involve the inhibition of interaction between AR and AR coregulators. Together, these findings provide a molecular basis for cross-talk between two signaling pathways at the level of Akt and AR-AR coregulators that may help us to better understand the roles of Akt in the androgen/AR-mediated apoptosis.

Cloning and characterization of androgen receptor coactivator, ARA55, in human prostate

Androgen receptor (AR) is a hormone-activated transcriptional factor that can bind to androgen response elements and that regulates the transcription of target genes via a mechanism that presumably involves cofactors. We report here the cloning of a novel AR coactivator ARA55 using a yeast two-hybrid system. ARA55 consists of 444 amino acids with the predicted molecular mass of 55 kDa and its sequence shows very high homology to mouse hic5, a TGF-beta1-inducible gene. Yeast and mammalian two-hybrid systems and co-immunoprecipitation assays all prove ARA55 can bind to AR in a ligand-dependent manner. Transient transfection assay in prostate cancer DU145 cells further demonstrates that ARA55 can enhance AR transcriptional activity in the presence of 1 nM dihydrotestosterone or its antagonists such as 100 nM 17beta-estradiol or 1 microM hydroxyflutamide. Our data also suggest the C-terminal half of ARA55, which includes three LIM motifs, is sufficient to interact with AR. Northern blot and polymerase chain reaction quantitation showed ARA55 can be expressed differently in normal prostate and prostate tumor cells. Together, our data suggests that ARA55 may play very important roles in the progression of prostate cancer by the modulation of AR transactivation.

Androgen receptor: an overview

The action of androgens in regulating development and growth is mediated by androgen receptor (AR). AR is a member of the steroid hormone receptor superfamily, a class of receptors that function through their ability to regulate the transcription of specific genes. The AR is located in various target tissues, with its levels and activity altered with the onset of various cellular events (e.g., sexual development, malignant transformation). The modulation of AR levels occurs through a number of mechanisms, including transcription, and is regulated by various factors (e.g., androgens). The ability of AR to modulate gene transcription is through its interaction with specific DNA sequences located near or within the target gene promoter. The importance of the AR in reproductive physiology has been emphasized by the finding of AR mutations, leading to a variety of disorders, including testicular feminization syndrome. In this article, we review the structure and function of AR and the role AR plays in the function of the mammalian system.

From estrogen to androgen receptor: a new pathway for sex hormones in prostate

While all three coactivators ARA70, steroid receptor coactivator 1, and RAC3/ACTR can enhance androgen receptor (AR) transcriptional activity at 1 nM dihydrotestosterone, we here demonstrate that only ARA70 can induce AR transcriptional activity >30-fold in the presence of 10 nM 17beta-estradiol (E2), but not diethylstilbestrol. The significance of this newly described E2-induced AR transcriptional activity in DU145 human prostate cancer cells was further strengthened by finding patients with Reifenstein partial-androgen-insensitive syndrome that fail in the E2-AR-ARA70 pathway. Together, our data suggest, for the first time, testosterone/dihydrotestosterone may not be the only ligands for the AR. E2 represents another important natural ligand for AR that may play an essential role for the AR function and the development of the male reproductive system.

Androgen receptor (AR) differential roles in hormone-related tumors including prostate, bladder, kidney, lung, breast and liver

The androgen receptor (AR) is expressed in many cell types and the androgen/AR signaling has been found to have important roles in modulating tumorigenesis and metastasis in several cancers including prostate, bladder, kidney, lung, breast and liver. However, whether AR has differential roles in the individual cells within these tumors that contain a variety of cell types remains unclear. Generation of AR knockout (ARKO) mouse models with deletion of AR in selective cells within tumors indeed have uncovered many unique AR roles in the individual cell types during cancer development and progression. This review will discuss the results obtained from various ARKO mice and different human cell lines with special attention to the cell type- and tissue-specific ARKO models. The understanding of various results showing the AR indeed has distinct and contrasting roles in each cell type within many hormone-related tumors (as stimulator in bladder, kidney and lung metastases vs as suppressor in prostate and liver metastases) may eventually help us to develop better therapeutic approaches by targeting the AR or its downstream signaling in individual cell types to better battle these hormone-related tumors in different stages.

The interaction between Toxoplasma gondii and mammalian cells. I. Mechanism of entry and intracellular fate of the parasite

Macrophage, fibroblast, and HeLa cell cultures have been infected with Toxoplasma gondii, and observations have been made on parasite entry and fate. A special procedure was devised for studying the entry of toxoplasmas by electron microscopy. Toxoplasmas were centrifuged onto the cells in the cold; fixation 1-3 min after warming yielded specimens showing numerous examples of parasites in the process of entering cells. The mechanism of entry into macrophages, fibroblasts, and HeLa cells was in all cases by phagocytosis. Micropseudopods were extended by the cells to envelop the attached parasites in a typical phagocytic vacuole. Apparently the toxoplasmas stimulated this response of HeLa cells and fibroblasts, cell types not usually phagocytic. No instance was seen of penetration of toxoplasmas through the cell membrane, or of parasites located free in the cytoplasm. Essentially all of the toxoplasmas that entered HeLa cells divided with a generation time of 9 hr; the parasites formed large rosettes situated in vacuoles, eventually leading to host cell rupture. Macrophages took in larger numbers of toxoplasmas than did HeLa cells, but approximately half of the parasites inside of macrophages degenerated within a few hours. The surviving toxoplasmas in macrophages divided every 8 hr, forming rosettes and eventually rupturing the cells.

Cloning and characterization of human prostate coactivator ARA54, a novel protein that associates with the androgen receptor

Androgen receptor (AR) is a member of the steroid receptor superfamily that may require coactivators for proper or maximal transactivation. Using a yeast two-hybrid screening followed by mammalian cell analyses, we identified a novel ligand-dependent AR-associated protein, ARA54, which consists of 474 amino acids with a molecular mass of 54 kDa. We demonstrated that ARA54 might function as a preferential coactivator for AR-mediated transactivation in human prostate cancer DU145 cells. Interestingly, our data also showed that ARA54 could significantly enhance the transcriptional activity of LNCaP mutant AR (ARt877a) but not wild type AR or another mutant AR (ARe708k) in the presence of 10 nM 17beta-estradiol or 1 microM hydroxyflutamide. These results imply that both ARA54 and the positions of the AR mutation (877 versus 708) might contribute to the specificity of AR-mediated transactivation. Our findings further demonstrated that the C-terminal domain of ARA54 can serve as a dominant negative inhibitor and exogenous full-length ARA54 can reverse this squelching effect on AR transcriptional activity. Co-expression of ARA54 with other AR coactivators, such as ARA70 or SRC-1, showed additive stimulation of AR-mediated transactivation, which indicates that these cofactors may function individually as AR coactivators to induce AR target gene expression. Through our findings, we have identified and characterized a novel AR coactivator, ARA54, which may play an important role in the AR signaling pathway in human prostate.

Promotion of agonist activity of antiandrogens by the androgen receptor coactivator, ARA70, in human prostate cancer DU145 cells

Although hormone therapy with antiandrogens has been widely used for the treatment of prostate cancer, some antiandrogens may act as androgen receptor (AR) agonists that may result in antiandrogen withdrawal syndrome. The molecular mechanism of this agonist response, however, remains unclear. Using mammalian two-hybrid assay, we report that antiandrogens, hydroxyflutamide, bicalutamide (casodex), cyproterone acetate, and RU58841, and other compounds such as genistein and RU486, can promote the interaction between AR and its coactivator, ARA70, in a dose-dependent manner. The chloramphenicol acetyltransferase assay further demonstrates that these antiandrogens and related compounds significantly enhance the AR transcriptional activity by cotransfection of AR and ARA70 in a 1:3 ratio into human prostate cancer DU145 cells. Our results suggest that the agonist activity of antiandrogens might occur with the proper interaction of AR and ARA70 in DU145 cells. These findings may provide a good model to develop better antiandrogens without agonist activity.

Isoprene increases thermotolerance of fosmidomycin-fed leaves

Isoprene is synthesized and emitted in large amounts by a number of plant species, especially oak (Quercus sp.) and aspen (Populus sp.) trees. It has been suggested that isoprene improves thermotolerance by helping photosynthesis cope with high temperature. However, the evidence for the thermotolerance hypothesis is indirect and one of three methods used to support this hypothesis has recently been called into question. More direct evidence required new methods of controlling endogenous isoprene. An inhibitor of the deoxyxylulose 5-phosphate pathway, the alternative pathway to the mevalonic acid pathway and the pathway by which isoprene is made, is now available. Fosmidomycin eliminates isoprene emission without affecting photosynthesis for several hours after feeding to detached leaves. Photosynthesis of fosmidomycin-fed leaves recovered less following a 2-min high-temperature treatment at 46 degrees C than did photosynthesis of leaves fed water or fosmidomycin-fed leaves in air supplemented with isoprene. Photosynthesis of Phaseolus vulgaris leaves, which do not make isoprene, exhibited increased thermotolerance when isoprene was supplied in the airstream flowing over the leaf. Other short-chain alkenes also improved thermotolerance, whereas alkanes reduced thermotolerance. It is concluded that thermotolerance of photosynthesis is a substantial benefit to plants that make isoprene and that this benefit explains why plants make isoprene. The effect may be a general hydrocarbon effect and related to the double bonds in the isoprene molecule.

Anti-androgen receptor ASC-J9 versus anti-androgens MDV3100 (Enzalutamide) or Casodex (Bicalutamide) leads to opposite effects on prostate cancer metastasis via differential modulation of macrophage infiltration and STAT3-CCL2 signaling

Despite androgen deprivation therapy (ADT) suppression of prostate cancer (PCa) growth, its overall effects on PCa metastasis remain unclear. Using human (C4-2B/THP1) and mouse (TRAMP-C1/RAW264.7) PCa cells–macrophages co-culture systems, we found currently used anti-androgens, MDV3100 (enzalutamide) or Casodex (bicalutamide), promoted macrophage migration to PCa cells that consequently led to enhanced PCa cell invasion. In contrast, the AR degradation enhancer, ASC-J9, suppressed both macrophage migration and subsequent PCa cell invasion. Mechanism dissection showed that Casodex/MDV3100 reduced the AR-mediated PIAS3 expression and enhanced the pSTAT3-CCL2 pathway. Addition of CCR2 antagonist reversed the Casodex/MDV3100-induced macrophage migration and PCa cell invasion. In contrast, ASC-J9 could regulate pSTAT3-CCL2 signaling using two pathways: an AR-dependent pathway via inhibiting PIAS3 expression and an AR-independent pathway via direct inhibition of the STAT3 phosphorylation/activation. These findings were confirmed in the in vivo mouse model with orthotopically injected TRAMP-C1 cells. Together, these results may raise the potential concern about the currently used ADT with anti-androgens that promotes PCa metastasis and may provide some new and better therapeutic strategies using ASC-J9 alone or a combinational therapy that simultaneously targets androgens/AR signaling and PIAS3-pSTAT3-CCL2 signaling to better battle PCa growth and metastasis at castration-resistant stage.

Human and rat TR4 orphan receptors specify a subclass of the steroid receptor superfamily

We have identified a member of the steroid receptor superfamily and cloned it from human and rat hypothalamus, prostate, and testis cDNA libraries. The open reading frame between first ATG and terminator TGA can encode 615 (human) and 596 (rat) amino acids with calculated molecular mass of 67.3 (human) and 65.4 (rat) kDa. The amino acid sequence of this protein, called TR4 orphan receptor, is closely related to the previously identified TR2 orphan receptor. The high homology between TR2 and TR4 orphan receptor suggests that these two orphan receptors constitute a unique subfamily within the steroid receptor superfamily. These two orphan receptors are differentially expressed in rat tissues. Unlike TR2 orphan receptors, the TR4 orphan receptor appears to be predominantly located in granule cells of the hippocampus and the cerebellum, suggesting that it may play some role(s) in transcriptional regulation in these neurons.

Highly effective induction therapy for stage 4 neuroblastoma in children over 1 year of age

PURPOSE

To test the efficacy of a protocol for poor-risk neuroblastoma that builds on the following: (1) our favorable previously reported results with dose-intensive use of cyclophosphamide; (2) our retrospective analysis of neuroblastoma chemotherapy reports, which supported the value of high-dose cisplatin and etoposide (VP-16); and (3) the Goldie-Coldman hypothesis that rapid cytoreduction plus the use of non-cross-resistant chemotherapy combinations will decrease the risk of drug resistance.

PATIENTS AND METHODS

The N6 protocol included seven courses of high-dose chemotherapy plus surgical resection of bulk disease. Courses 1, 2, 4, and 6 consisted of 6-hour intravenous infusions of cyclophosphamide 70 mg/kg/d on days 1 and 2 (ie, 140 mg/kg per course), a 72-hour intravenous infusion of doxorubicin 75 mg/m2 and vincristine 0.1 mg/kg beginning day 1, and vincristine 1.5 mg/m2 intravenous bolus on day 9. Courses 3, 5, and 7 consisted of 2-hour intravenous infusions of VP-16 200 mg/m2/d on days 1 to 3 (ie, 600 mg/m2 per course), and 1-hour intravenous infusions of cisplatin 50 mg/m2/d on days 1 to 4 (ie, 200 mg/m2 per course). Courses were to start after neutrophil counts reached 500/microL and platelet counts reached 100,000/microL. Response was defined by international criteria.

RESULTS

Among 24 consecutive previously untreated patients diagnosed with stage 4 neuroblastoma at more than 1 year of age, 21 patients achieved a complete or very good partial remission; one patient had no evidence of disease except by iodine-131-metaiodobenzylguanidine (MIBG) scan, which was markedly improved; and one patient had resolution of extensive metastatic disease, but still had an incompletely resected primary tumor. The sole patient to have a poor response had clinical features at diagnosis that are atypical for neuroblastoma, namely, 8 years of age and an unknown primary tumor. Severe toxicities included myelosuppression, mucositis, and hearing deficits.

CONCLUSION

The N6 approach reliably achieves significant cytoreduction against stage 4 neuroblastoma. This may eventuate in an improved cure rate, since consolidative treatments using myeloablative therapy, immunotherapy, or biologic response modifiers such as cis-retinoic acid are most likely to be effective against minimal residual disease.

From transforming growth factor-beta signaling to androgen action: identification of Smad3 as an androgen receptor coregulator in prostate cancer cells

Although transforming growth factor-beta (TGF-beta) has been identified to mainly inhibit cell growth, the correlation of elevated TGF-beta with increasing serum prostate-specific antigen (PSA) levels in metastatic stages of prostate cancer has also been well documented. The molecular mechanism for these two contrasting effects of TGF-beta, however, remains unclear. Here we report that Smad3, a downstream mediator of the TGF-beta signaling pathway, functions as a coregulator to enhance androgen receptor (AR)-mediated transactivation. Compared with the wild-type AR, Smad3 acts as a strong coregulator in the presence of 1 nM 5alpha-dihydrotestosterone, 10 nM 17beta-estradiol, or 1 microM hydroxyflutamide for the LNCaP mutant AR (mtAR T877A), found in many prostate tumor patients. We further showed that endogenous PSA expression in LNCaP cells can be induced by 5alpha-dihydrotestosterone, and the addition of the Smad3 further induces PSA expression. Together, our findings establish Smad3 as an important coregulator for the androgen-signaling pathway and provide a possible explanation for the positive role of TGF-beta in androgen-promoted prostate cancer growth.

Delta5-androstenediol is a natural hormone with androgenic activity in human prostate cancer cells

It is known that androst-5-ene-3beta,17beta-diol (Adiol), a precursor of testosterone (T), can activate estrogen target genes. The androgenic activity of Adiol itself, however, is poorly understood. Using a transient transfection assay, we here demonstrate in human prostate cancer cells that Adiol can activate androgen receptor (AR) target genes in the presence of AR, and that AR coactivator ARA70 can further enhance this Adiol-induced AR transcriptional activity. In contrast to this finding, an active metabolite of dehydroepiandrosterone, 7-oxo-dehydroepiandrosterone, does not activate AR target gene in the absence or presence of ARA70. Thin layer chromatography analysis reveals that T, dihydrotestosterone, and 17beta-estradiol are undetectable in human prostate cancer DU145 cells after treatment with Adiol. Additionally, a proteolysis assay shows that a distinct ligand-receptor conformational difference exists between T-AR and Adiol-AR. Together, the above findings and the fact that T, but not Adiol, can induce transcriptional activity in a mutant AR (mtAR708), suggest that, without being metabolized into T, Adiol itself may represent a natural hormone with androgenic activity in human prostate cancer cells. Because two potent antiandrogens, hydroxyflutamide (Eulexin), and bicalutamide (casodex), that are widely used for the treatment of prostate cancer, fail to block Adiol-mediated induction of AR transcriptional activity in prostate cancer cells, the effectiveness of so-called "total androgen blockage," a standard treatment for prostate cancer, may need to be reevaluated.

Increase of androgen-induced cell death and androgen receptor transactivation by BRCA1 in prostate cancer cells

Although mutations of the breast cancer susceptibility gene 1 (BRCA1) may play important roles in breast and prostate cancers, the detailed mechanism linking the functions of BRCA1 to these two hormone-related tumors remains to be elucidated. Here, we report that BRCA1 interacts with androgen receptor (AR) and enhances AR target genes, such as p21((WAF1/CIP1)), that may result in the increase of androgen-induced cell death in prostate cancer cells. The BRCA1-enhanced AR transactivation can be further induced synergistically with AR coregulators, such as CBP, ARA55, and ARA70. Together, these data suggest that the BRCA1 may function as an AR coregulator and play positive roles in androgen-induced cell death in prostate cancer cells and other androgen/AR target organs.

Chitinase genes responsive to cold encode antifreeze proteins in winter cereals

Antifreeze proteins similar to two different chitinases accumulate during cold acclimation in winter rye (Secale cereale). To determine whether these cold-responsive chitinases require post-translational modification to bind to ice, cDNAs coding for two different full-length chitinases were isolated from a cDNA library produced from cold-acclimated winter rye leaves. CHT9 is a 1,193-bp clone that encodes a 31.7-kD class I chitinase and CHT46 is a 998-bp clone that codes for a 24.8-kD class II chitinase. Chitinase-antifreeze proteins purified from the plant were similar in mass to the predicted mature products of CHT9 and CHT46, thus indicating that there was little chemical modification of the amino acid sequences in planta. To confirm these results, the mature sequences of CHT9 and CHT46 were expressed in Escherichia coli and the products of both cDNAs modified the growth of ice. Transcripts of both genes accumulated late in cold acclimation in winter rye. Southern analysis of winter rye genomic DNA indicated the presence of a small gene family homologous to CHT46. In hexaploid wheat, CHT46 homologs mapped to the homeologous group 1 chromosomes and were expressed in response to cold and drought. We conclude that two novel cold-responsive genes encoding chitinases with ice-binding activity may have arisen in winter rye and other cereals through gene duplication.

Identification of ARA70 as a ligand-enhanced coactivator for the peroxisome proliferator-activated receptor gamma

In an effort to understand transcriptional regulation by the peroxisome proliferator-activated receptor gamma (PPARgamma), we have investigated its potential interaction with coregulators and have identified ARA70 as a ligand-enhanced coactivator. ARA70 was initially described as a coactivator for the androgen receptor (AR) and is expressed in a range of tissues including adipose tissue (Yeh, S., and Chang, C. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 5517-5521). Here we show that ARA70 and PPARgamma specifically interact by coimmunoprecipitation and in a mammalian two-hybrid assay. PPARgamma and ARA70 interact in the absence of the PPARgamma ligand 15-deoxy-Delta12,14-prostaglandin J2, although the addition of exogenous ligand enhances this interaction. Similarly, in transient transfection of DU145 cells, cotransfection of PPARgamma and ARA70 induces transcription from reporter constructs driven by either three copies of an isolated PPAR response element or the natural promoter of the adipocyte fatty acid-binding protein 2 in the absence of exogenous 15-deoxy-Delta12,14-prostaglandin J2. However, this PPARgamma-ARA70 transactivation is enhanced by the addition of ligand. Thus, ARA70 can function as a ligand-enhanced coactivator of PPARgamma. Finally, we show that AR can squelch PPARgamma-ARA70 transactivation, which suggests that cross-talk may occur between PPARgamma- and AR-mediated responses in adipocytes.

Clinical pharmacologic and therapeutic studies of bleomycin given by continuous infusion

The clinical toxicology, clinical pharmacology, and therapeutic effects of bleomycin given by continuous intravenous infusion were studied in patients with far-advanced unresectable cancer. The toxicity of bleomycin given by that schedule was qualitatively and quantitatively the same as when it was given by daily intravenous "push"; mucocutaneous toxicity occurred regularly after 7-11 days of infusion. Careful monitoring of pulmonary function revealed minor changes in Total Lung Capacity and Pulmonary Diffusion Capacity in nearly all patients; however, overt pulmonary toxicity occurred in only six patients (5%). 111Indium-labeled bleomycin was used to follow blood levels of bleomycin; it correlated well with the levels determined by microbiologic assay and could be measured at levels lower than could be determined by bioassay. Useful therapeutic responses were seen in a variety of tumors; 30% patients with very far-advanced carcinoma of the cervix demonstrated CR or PR, an incidence higher than has been seen with other regimens. Sixty-nine percent of patients with disseminated germ cell neoplasms of the testis, refractory to bleomycin given by conventional dose schedules, have attained partial remission through the continuous infusion of bleomycin.

N7: a novel multi-modality therapy of high risk neuroblastoma (NB) in children diagnosed over 1 year of age

BACKGROUND

The N7 protocol for poor-risk neuroblastoma uses dose-intensive chemotherapy (as in N6 protocol [Kushner et al.: J Clin Oncol 12:2607-2613, 1994] but with lower dosing of vincristine) for induction, surgical resection and 2100 cGy hyperfractionated radiotherapy for local control, and for consolidation, targeted radioimmunotherapy with 131I-labeled anti-GD2 3F8 monoclonal antibody and immunotherapy with unlabeled/unmodified 3F8 (400 mg/m2).

PROCEDURE

The chemotherapy consists of: cyclophosphamide 70 mg/kg/d x 2 and a 72-hr infusion of doxorubicin 75 mg/m2 plus vincristine 2 mg/m2, for courses 1, 2, 4, and 6; and cisplatin 50 mg/m2/d x 4 and etoposide 200 mg/m2/d x 3, for courses 3, 5, and 7. 131I-3F8 is dosed at 20 mCi/kg, which is myeloablative and therefore necessitates stem-cell support.

RESULTS

Of the first 24 consecutive previously untreated patients more than 1 year old at diagnosis, 22 were stage 4 and two were unresectable stage 3 with MYCN amplification. Chemotherapy achieved CR/VGPR in 21 of 24 patients. Twenty patients to date have completed treatment with 131I-3F8, and 15 patients have completed all treatment. With a median follow-up of 19 months, 18 of 24 patients remain progression-free.

CONCLUSIONS

Major toxicities were grade 4 myelosuppression and mucositis during chemotherapy, and self-limited pain and urticaria during antibody treatment. Late effects include hearing deficits and hypothyroidism.

Retinoblastoma, a tumor suppressor, is a coactivator for the androgen receptor in human prostate cancer DU145 cells

The retinoblastoma protein may function as a tumor suppressor by controlling the progression of the normal cell cycle. Inactivation of Rb has been regarded as an important event in prostate carcinogenesis. However, the detailed mechanism of how Rb is linked to androgen-androgen receptor (A-AR), the major factor in promotion of prostate tumor growth, remains unclear. Using GST-Rb pull down assay and mammalian two-hybrid system, we report here that Rb can bind specifically to AR in an androgen-independent manner. Transient transfection assay demonstrates that cotransfection of AR and Rb can further induce AR transcriptional activity 4-fold in the presence of 1 nM dihydrotestosterone in DU145 cells. Interestingly, cotransfection of Rb and ARA70, the first identified AR coactivator, with AR can additively induce AR transcriptional activity 13-fold (from 5-fold to 64-fold). In conclusion, our discovery that Rb can function as a coactivator to induce AR transcriptional activity in prostate cells may represent the first data to link a negative growth regulatory protein function in a positive manner, by inducing the transcriptional activity of AR.

Isolation of Ku70-binding proteins (KUBs)

DNA-dependent protein kinase (DNA-PK) plays a critical role in resealing DNA double-stand breaks by non-homologous end joining. Aside from DNA-PK, XRCC4 and DNA ligase IV, other proteins which play a role(s) in this repair pathway remain unknown; DNA-PK contains a catalytic subunit (DNA-PKcs) and a DNA binding subunit (Ku70 and Ku80). We isolated Ku70-binding proteins (KUB1-KUB4) using yeast two-hybrid analyses. Sequence analyses revealed KUB1 to be apolipoprotein J (apoJ), also known as X-ray-inducible transcript 8 (XIP8), testosterone-repressed prostate message-2 (TRPM-2) and clusterin. KUB2 is Ku80. KUB3 and KUB4 are unknown, >10 kb trans-cripts. Interactions of apoJ/XIP8 or KUB3 with Ku70 were confirmed by co-immunoprecipitation analyses in MCF-7:WS8 breast cancer or IMR-90 normal lung fibroblast cells, respectively. The interaction of apoJ/XIP8 with Ku70 was confirmed by far-western analyses. Stable over-expression of full-length apoJ/XIP8 in MCF-7:WS8 caused decreased Ku70/Ku80 DNA end binding that was restored by apoJ/XIP8 monoclonal antibodies. The role of apoJ/XIP8 in ionizing radiation resistance/sensitivity is under investigation.