Steroid hormone receptors as targets for the therapy of breast and prostate cancer--recent advances, mechanisms of resistance, and new approaches

Design, synthesis, molecular docking and biological evaluation of 1,3,5-trisubstituted-1H-pyrazole derivatives as anticancer agents with cell cycle arrest, ERK and RIPK3- kinase activities

The need for new ERK and RIPK3 kinase modulators arises from their central roles in cellular processes, especially in diseases like cancer. This research focused on a ligand-based strategy, incorporating previously documented 1,3,5-trisubstituted-1H-pyrazole derivatives, to craft innovative inhibitors specifically targeting ERK and RIPK3 kinases. Compounds 6, 7, 10a, 10c, and 10d exhibited significant cytotoxicity against PC-3 and MCF-7 cancer cell lines, with IC50 values ranging from 21.9 to 28.6 µM and 3.90-35.5 µM, respectively values surpassing those of the reference compound Doxorubicin. Additionally, cell cycle analysis revealed intriguing results, particularly with 10d inducing cell cycle arrest at the S phase in treated PC-3 cells, indicating potential DNA replication phase inhibition. Moreover, compounds 6, 10a, and 10d exhibited promising results in the in vitro kinase assay supported by molecular docking studies. The core scaffold of these compounds established interactions with vital amino acids within the active pockets of ERK and RIPK3 kinases, thereby securely anchoring them in place. These findings underscore the development of promising modulators for ERK and RIPK3 kinases, suggesting their potential for future contributions to cancer treatments.

Pentafluoroethylation of Carbonyl Compounds Using HFC-125 in a Flow Microreactor System

The protocol of micro-flow nucleophilic pentafluoroethylation using pentafluoroethane (HC₂F₅, HFC-125), a nontoxic, inexpensive, and commercially available greenhouse gas, is described. The micro-flow pentafluoroethylation by HFC-125 proceeded smoothly at room temperature or at -10 °C in DMF or toluene in the presence of a potassium base, namely, t-BuOK or KHMDS. A broad range of ketones, aldehydes, and chalcones with various substituted benzene rings were successfully converted to the corresponding pentafluoroethyl carbinols instantly with good to high yields.

Discovery of Vilaprisan (BAY 1002670): A Highly Potent and Selective Progesterone Receptor Modulator Optimized for Gynecologic Therapies

Progesterone plays an important role in the female reproductive system. However, there is also evidence that gynecologic disorders/diseases such as uterine fibroids and endometriosis are progesterone-dependent. Steroidal and non-steroidal selective progesterone receptor modulators (SPRMs) have shown potential for the treatment of such diseases. Steroidal SPRMs, including mifepristone and ulipristal acetate, have proven effective in clinical trials. However, several steroidal SPRMs containing a dimethylamino substituent have been associated with elevated liver enzymes in patients. An earlier drug discovery program identified lonaprisan as a highly selective SPRM that did not show drug-related change in liver enzyme activity. Building on data obtained from that work, here we describe the research program that culminated in the discovery of a novel steroidal SPRM, vilaprisan, which combines an extremely high potency with very favorable drug metabolism and pharmacokinetic properties. Vilaprisan has entered clinical development and is currently undergoing phase 3 clinical trials.

MED23 in endocrinotherapy for breast cancer

We investigated the role of the transcriptional mediator subunit 23 (MED23) in everolimus drug resistance, invasion and metastasis during breast cancer treatment and its molecular mechanism. We also evaluated the endocrinotherapy and prevention method for breast cancer. Breast cancer cell strains were established that can continuously express MED23, as well as inducible MED23-shRNA expression plasmids. The inductive agent, doxycycline (Dox), was added to the water for long-term silencing of MED23 in intratumoral cells. We conducted experiments on the role of MED23 in the regulation of invasion and metastasis of breast cancer using cell culture, western blotting, MTT proliferation experiment, fluorescent quantitative PCR and chromatin immunoprecipitation (ChIP). The silencing of MED23 significantly inhibited cellular growth and proliferation as well as soft agar cloning. Silencing of MED23 strengthened the sensitivity of the everolimus-resistant breast cancer cell strains BT474 and MCF-7/ADM cells to everolimus medication. The silencing of MED23, in combination with everolimus, inhibits the cell cycle progress of breast cancer cells. ChIP indicated that the mutual regulation of HER2 and MED23 also participates in the formation of the everolimus drug resistance mechanism. Therefore, MED23 plays an important role in everolimus drug resistance, invasion, and metastasis of breast cancer. As a potential molecular therapeutic target of breast cancer, MED23 overcomes drug resistance in clinical endocrinotherapy and controls the distal relapse and metastasis in breast cancer by the targeted silencing of MED23.

Association analysis between MDR1 genetic variant and breast cancer risk factors in Chinese Han population

The multidrug resistance 1 gene (MDR1) is an important candidate gene for influencing breast cancer susceptibility. This study aimed to evaluate the association between MDR1 genetic variants and breast cancer susceptibility. A total of 340 breast cancer patients and 348 cancer-free controls were enrolled in this study. The patients' general characteristics and related risk factors of breast cancer were collected by questionnaires. The c.4125A>C genetic variant was genotyped through created restriction site polymerase chain reaction method. Our data suggest that there are no significant differences in the allelic and genotypic frequencies between breast cancer patients and cancer-free controls. Moreover, the distribution of breast cancer patients' risk factors is not different among AA, AC, and CC genotypes. These preliminary results suggest that the c.4125A>C genetic variant is not significantly associated with breast cancer susceptibility.

Investigation on MDR1 gene polymorphisms and its relationship with breast cancer risk factors in Chinese women

The human multidrug resistance 1 gene (MDR1) is an important candidate gene influencing the susceptibility to various diseases, including breast cancer. The object of this study was to investigate on MDR1 gene polymorphisms and its relationship with the susceptibility to breast cancer. A total of 271 patients with breast cancer and 225 healthy controls were enrolled in this study. Data about the risk factors for breast cancer were collected using questionnaires. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing methods were used to investigate the c.3073A > C polymorphisms. We observed no significant differences in the allelic and genotypic frequencies of c.3073A > C polymorphisms between patients and control subjects. Furthermore, there were no significant differences about the distribution of the breast cancer patients' risk factors among AA, AC and CC genotype. Results from this study suggested that c.3073A > C polymorphism was not associated with the susceptibility to breast cancer in the studied population. Future studies evaluating the association between c.3073A > C variant and breast cancer risks are essential to reach to more reliable results on larger populations.

Human infertility: are endocrine disruptors to blame?

Over recent decades, epidemiological studies have been reporting worrisome trends in the incidence of human infertility rates. Extensive detection of industrial chemicals in human serum, seminal plasma and follicular fluid has led the scientific community to hypothesise that these compounds may disrupt hormonal homoeostasis, leading to a vast array of physiological impairments. Numerous synthetic and natural substances have endocrine-disruptive effects, acting through several mechanisms. The main route of exposure to these chemicals is the ingestion of contaminated food and water. They may disturb intrauterine development, resulting in irreversible effects and may also induce transgenerational effects. This review aims to summarise the major scientific developments on the topic of human infertility associated with exposure to endocrine disruptors (EDs), integrating epidemiological and experimental evidence. Current data suggest that environmental levels of EDs may affect the development and functioning of the reproductive system in both sexes, particularly in foetuses, causing developmental and reproductive disorders, including infertility. EDs may be blamed for the rising incidence of human reproductive disorders. This constitutes a serious public health issue that should not be overlooked. The exposure of pregnant women and infants to EDs is of great concern. Therefore, precautionary avoidance of exposure to EDs is a prudent attitude in order to protect humans and wildlife from permanent harmful effects on fertility.

Steroid-coupled liposomes for targeted delivery to tumor

The steroidal receptors play a key role in protein synthesis and maintain the homeostasis in normal and diseased state, including tumorigenesis at the target tissues when overactivated. Thus steroidal receptors may act as potential targets for selective delivery of different therapeutic agents as they are overexpressed by a number of endocrinal tumors. The selective delivery of these agents may be a better treatment strategy for endocrinal cancer as it may also result in cytosolic and nuclear delivery of cytotoxic agents. In this review, the targeting potential of steroidal receptors for the drug or bioactive(s) delivery is discussed. The ligands that have been proven to be effective for specific steroidal receptors can be used as vectors for carrying the drug or drug-delivery system to the desired site of drug action in an optimum concentration. This strategy will not only minimize the undesired side effects associated with nonspecific delivery of drug, but will also maximize the drug utilization. Ligand-conjugated liposomes as a carrier of bioactives prevent passive diffusion of the encapsulated drug to normal cells, increase the time of circulation and reduce the undesirable side effects of a drug.

ETAR antagonist ZD4054 exhibits additive effects with aromatase inhibitors and fulvestrant in breast cancer therapy, and improves in vivo efficacy of anastrozole

Endothelin-1 (ET-1) and endothelin A receptor (ETAR) contribute to the development and progression of breast carcinomas by modulating cell proliferation, angiogenesis, and anti-apoptosis. We investigated antitumoral effects of the specific ETAR antagonist ZD4054 in breast cancer cells and xenografts, and assessed antitumoral efficacy of the combinations of ZD4054 with aromatase inhibitors and fulvestrant. Gene expression changes were assessed by quantitative real-time PCR. Cell proliferation was measured using alamarBlue; migration and invasion assays were performed using modified Boyden chambers. Evaluating the antitumoral efficacy of ZD4054 in vivo, different breast cancer models were employed using nude mice xenografts. ZD4054 reduced ET-1 and ETAR expression in MCF-7, MDA-MB-231, and MDA-MB-468 breast cancer cells in a concentration-dependent manner. ZD4054 inhibited invasion by up to 37.1% (P = 0.022). Combinations of ZD4054 with either anastrozole or letrozole produced significant reductions in migration of aromatase-overexpressing MCF-7aro cells (P < 0.05). Combination of ZD4054 with fulvestrant reduced MCF-7 cell migration and invasion by 36.0% (P = 0.027) and 56.7% (P < 0.001), respectively, with effects significantly exceeding those seen with either compound alone. Regarding tumor volume reduction in vivo, ZD4054 (10 mg/kg) was equipotent to fulvestrant (200 mg/kg) and exhibited additive effects with anastrozole (0.5 mg/kg). These data are the first indicating that selective ETAR antagonism by ZD4054 displays antitumoral activity on breast cancer cells in vitro and in vivo. Our data strongly support a rationale for the clinical use of ZD4054 in combination with endocrine therapies.

Association of C3435T single-nucleotide polymorphism of MDR1 gene with breast cancer in an Iranian population

The human multidrug resistance gene 1 (MDR1) encodes a plasma membrane, P-glycoprotein (Pgp), which functions as the transmembrane efflux pump for various structurally unrelated anticancer agents and toxins. Polymorphisms in the MDR1 gene may have an impact on the expression and function of Pgp, thereby influencing the susceptibility to various diseases, including cancer. Recently, a silent C3435T polymorphism in exon 26 of MDR1 has been reported to be associated with decreased expression of Pgp in TT genotype carriers and thus it may alter the physiological protective role of Pgp and influence disease risk. To evaluate the association of this polymorphism with breast cancer, 106 patients with breast cancer and 77 healthy controls were enrolled in this study. They were visited at two centers during a 1-year period (2006-2007). Data about the risk factors of breast cancer were collected using questionnaires. DNA of the whole-blood sample was extracted, and the polymorphic fragment was amplified by polymerase chain reaction using specific primers. The C3435T polymorphism was detected by the restriction fragment length polymorphism method. There were no significant differences in genotype (p = 0.744) and allele (p = 0.590) frequencies between patients and control subjects. Moreover, distribution of the breast cancer patients' risk factors was not different among CC, CT, and TT genotypes. Our results suggest that C3435T MDR1 polymorphism was not associated with the susceptibility to breast cancer in the population studied.

Positive correlation of steroid hormones and EGF in canine mammary cancer

There are no published studies focused on the potential crosstalk between steroid hormones and EGF in canine mammary tumourigenesis. The objective was to investigate the role of EGF in canine mammary tumours (CMT) and the relationship with steroid hormones. Sixty-three CMT (39 malignant including 10 inflammatory mammary carcinomas (IMC); 19 benign and 5 dysplasias), and 13 normal mammary glands from dogs without history of neoplastic disease were analysed. Levels of EGF and steroid hormones [progesterone (P4); 17beta-estradiol (E2); androstenedione (A4) and dehydroepiandrosterone (DHEA)], were analysed by EIA in CMT homogenates. Levels of EGF were significantly higher in malignant compared with benign tumours, dysplasias and normal mammary glands (p<0.001). IMC presented the highest EGF levels, with statistical significant difference between IMC and non-IMC cases (p<0.05). Steroid hormone levels were also significantly higher in malignant tumours compared with benign tumours, dysplasias and normal mammary glands (p<0.001). In malignant tumours (non-IMC and IMC), a strong correlation was observed between EGF and: P4 (r=0.452; p=0.003); E2 (r=0.624; p=0.023); A4 (r=0.496; p=0.038); DHEA (r=0.431; p=0.005). These results suggest that EGF is implicated in canine mammary tumourigenesis. The positive correlation observed, opens an interesting perspective of interaction that should be further investigated.

The CYP19 TTTA repeat polymorphism is related to the prognosis of premenopausal stage I-II and operable stage III breast cancers

PURPOSE

Given the critical role of the CYP19 gene, encoding aromatase, in estrogen synthesis and the association of the estrogen level with its TTTA repeat polymorphism, the potential influence of this polymorphism on breast cancer survival, and hence management, deserves further study.

METHODS

Genotyping for the CYP19 TTTA repeat polymorphism was performed on 482 stage I-II and operable stage III Taiwanese breast cancer patients. Patients with more than seven TTTA repeats in either allele of CYP19 were defined as having the long allele. We correlated clinical variables and CYP19 genotypic polymorphism with outcome.

RESULTS

In hormone receptor (HR)-positive breast cancers, premenopausal patients with the long allele of the CYP19 polymorphism had a significantly higher overall survival (OS) rate (8-year, 89% versus 68%; p= .003) than those without it. This difference was further demonstrated by a multivariate analysis (OS hazard ratio, 1.53; p= .041). In postmenopausal women or patients with HR-negative breast cancer, there was no significant difference in OS between patients with or without the long allele. In premenopausal women with HR-positive cancers, adequate intensity adjuvant chemotherapy did not achieve a greater OS rate than suboptimal chemotherapy in patients with the long allele, but it resulted in a significantly higher OS rate (p= .011) than suboptimal chemotherapy in women without the long allele.

CONCLUSIONS

The CYP19 TTTA repeat polymorphism is associated with survival in premenopausal women, but not in postmenopausal women, with HR-positive breast cancers. Premenopausal women with the long allele have a greater survival rate and may not gain benefit from adjuvant chemotherapy.

Investigational developments for the treatment of progesterone-dependent diseases

BACKGROUND

Clinical evidence has shown that conditions such as uterine fibroids, endometriosis and breast cancer are progesterone-dependent diseases. Therefore, progesterone receptor (PR) antagonists and selective PR modulators (SPRMs) are under development for the treatment of these conditions. However, the first PR antagonists that became available exhibit insufficient selectivity or tolerability for the chronic administration required to treat these conditions. Despite initial setbacks, development of second-generation PR antagonists with better selectivity continues forward.

OBJECTIVE

In this review we would like to summarise prospects for using PR antagonists for the treatment of uterine fibroids, endometriosis and breast cancer, and to give an overview of the development of new steroidal and non-steroidal PR antagonists.

METHOD

Available preclinical and clinical data and publications have been reviewed with the focus on scientific background and use in the three mentioned indications.

RESULTS/CONCLUSION

Preclinical and clinical evidence demonstrated that PR antagonists and SPRMs are effective for the treatment of progesterone-dependent diseases. Future development will demonstrate if they can become important drugs.

MDR1 C3435T polymorphism in patients with breast cancer

BACKGROUND

The human multidrug-resistant gene (MDR1) encodes P-glycoprotein (Pgp), a membrane-bound efflux transporter conferring resistance to a number of natural cytotoxic drugs and potentially toxic xenobiotics. Single-nucleotide polymorphisms (SNPs) in MDR1 gene are associated with phenotypic variation in Pgp expression levels of tissue. SNPs may alter the physiological protective role of Pgp and, therefore, influence disease risk.

METHODS

In our study we identified the MDR1 C3435T polymorphism in breast cancer patients (n = 57) and healthy subjects (n = 50). DNA was extracted from peripheral blood samples by standard phenol/chloroform extraction method. Polymerase chain reaction-restriction fragment length polymorphism was used for the detection of C3435T single nucleotide polymorphism.

RESULTS

We obtained CC, CT and TT genotype frequencies in breast cancer patients as 12.3%, 57.9% and 29.8%, respectively. In the control group, frequencies of genotypes were found as 36% for CC, 46% for CT and 18% for TT. We observed difference in SNPs in MDR1 gene C3435T polymorphism between breast cancer patients and healthy controls (chi(2) = 8.66, df = 2, p = 0.013). The C allele frequency was found in 41.2% and the T allele frequency was found in 58.8%. C3435T MDR1 gene allele frequencies in breast cancer patients as compared to results in control group were as follows: [OR = 1.5 (95% CI: 1.09-1.96)]. In the patient group, T allele frequency was significantly higher than controls (p <0.01). Clinicopathological parameters of patients with breast cancer were compared for C3435T polymorphism. We did not find any significant difference between clinicopathological parameters and MDR1 phenotype of breast cancer patients. The progression-free survival rate in a subgroup analysis based on MDR1 genotypes with CC genotype was 71.4%, CT genotype was 75.7%, and TT genotype was 88.2%, respectively. This difference was not statistically significant (log rank p = 0.63).

CONCLUSIONS

Results of the present study demonstrated a 1.5-fold increased risk for development of breast cancer in T allele carriers.

Pus3p- and Pus1p-Dependent Pseudouridylation of Steroid Receptor RNA Activator Controls a Functional Switch that Regulates Nuclear Receptor Signaling

It was previously shown that mouse Pus1p (mPus1p), a pseudouridine synthase (PUS) known to modify certain transfer RNAs (tRNAs), can also bind with nuclear receptors (NRs) and function as a coactivator through pseudouridylation and likely activation of an RNA coactivator called steroid receptor RNA activator (SRA). Use of cell extract devoid of human Pus1p activity derived from patients with mitochondrial myopathy and sideroblastic anemia, however, still showed SRA-modifying activity suggesting that other PUS(s) can also target this coactivator. Here, we show that related mPus3p, which has a different tRNA specificity than mPus1p, also serves as a NR coactivator. However, in contrast to mPus1p, it does not stimulate sex steroid receptor activity, which is likely due to lack of binding to this class of NRs. As expected from their tRNA activities, in vitro pseudouridylation assays show that mPus3p and mPus1p modify different positions in SRA, although some may be commonly targeted. Interestingly, the order in which these enzymes modify SRA determines the total number of pseudouridines. mPus3p and SRA are mainly cytoplasmic; however, mPus3p and SRA are also localized in distinct nuclear subcompartments. Finally, we identified an in vivo modified position in SRA, U206, which is likely a common target for both mPus1p and mPus3p. When U206 is mutated to A, SRA becomes hyperpseudouridylated in vitro, and it acquires dominant-negative activity in vivo. Thus, Pus1p- and Pus3p-dependent pseudouridylation of SRA is a highly complex posttranscriptional mechanism that controls a coactivator-corepressor switch in SRA with major consequences for NR signaling.

Tamoxifen effect on L-DOPA induced response complications in parkinsonian rats and primates

The contribution of striatal protein kinase C (PKC) isoform changes in levodopa (L-DOPA) induced motor response complications in parkinsonian rats was investigated and the ability of tamoxifen, an antiestrogen with a partial PKC antagonist property, to prevent these response alterations in 6-hydroxydopamine (6-OHDA) lesioned rats as well as in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treated cynomologous monkeys was studied. Following treatment of adult male rats with L-DOPA twice daily for 3 weeks, protein levels of left (lesioned) and right (intact) striatal PKC isoforms were measured. Western blot analysis showed increased protein expression of both the novel PKC epsilon isoform and the atypical PKC lambda isoform ipsilateral to the lesion (174+/-17% for epsilon, 140+/-9% for lambda, of intact striatum in 6-OHDA lesioned plus chronic L-DOPA treated animals) in acute L-DOPA treated rats. No enhancement was observed in PKC immunoreactivity for other isoforms. Tamoxifen (5.0 mg/kg p.o.) significantly attenuated the L-DOPA induced augmentation of protein expression of PKC epsilon and PKC lambda, but had no effect on immunoreactivity for other PKC isoforms. In chronic L-DOPA treated parkinsonian rats, tamoxifen prevented (5.0 mg/kg p.o.) as well as ameliorated (5.0 mg/kg p.o.) the characteristic shortening in duration of motor response to L-DOPA challenge. In MPTP lesioned primates, similar to the ameliorative effect seen in rats, tamoxifen (1 and 3 mg/kg p.o) reduced the appearance of L-DOPA induced dyskinesia by 61% and 55% respectively (p<0.05). These results suggest that changes in specific striatal PKC isoforms contribute to the pathogenesis of L-DOPA induced motor complications and further that drugs able to selectively inhibit these signaling kinases might provide adjunctive benefit in the treatment of Parkinson's disease.

Redistribution of androgen receptors in acquired hormone-refractory prostate cancer cells

The dynamic translocation of androgen receptors (ARs) in prostate cancer cells after hormone conversion was studied. The prostate cancer cell line LNCaP was converted into androgen-independent sublines after long-term treatment with 5alpha-reductase inhibitor and steroid-depleted medium. Immunohistochemical, immunofluorescent staining and laser scanning microscopy were used to observe the redistribution and serial translocation of ARs in these tumor cells. The androgen-independent tumor cells (LNCaP/Fin and LNCaP/HR) grew slower than native cells with fibroblastic-like characteristics. On immunohistochemical and immunofluorescent double staining, translocation and exocytosis of ARs were noted in androgen- independent tumor cells much more markedly than in native cells. Furthermore, laser-scanning microscopy revealed serial image changes of AR vesicle shifting and exocytosis in androgen-converted tumor cells. Translocation and exocytosis processes were observed in androgen-independent prostate cancer cells. ARs lose partly normal cellular biologic role during hormone manipulation.

Hic-5/ARA55, a LIM Domain–Containing Nuclear Receptor Coactivator Expressed in Prostate Stromal Cells

Prostate gland development and growth requires both androgen action and epithelial-stromal communications. In fact, androgen signaling through the androgen receptor (AR) may be important in both stromal and epithelial cells of the prostate. Because interaction of AR with the coactivator, Hic-5/ARA55, results in enhanced androgen-induced transcription, we analyzed Hic-5/ARA55 expression in prostate tissue sections from normal human donors and prostate cancer patients. In each sample, Hic-5/ARA55 expression was confined to the stromal compartment of the prostate. Furthermore, a prostate stromal cell line, WPMY-1 cells, expresses Hic-5/ARA55, which is localized both at focal adhesion complexes and within the soluble cytoplasmic compartment. The ability of Hic-5/ARA55 to shuttle between the nuclear and cytoplasmic compartments was revealed on inhibition of nuclear export with leptomycin B. Small interfering RNA ablation experiments established endogenous Hic-5/ARA55 as a coactivator for both viral and endogenous cellular AR-regulated genes. Finally, the mechanism of Hic-5/ARA55 coactivator activity in WPMY-1 cells was revealed by chromatin immunoprecipitation analysis that showed its androgen-dependent recruitment to the promoter of the stromal androgen-responsive keratinocyte growth factor gene. These data provide the first demonstration of a stromal-specific AR coactivator that has an effect on an androgen-regulated growth factor that is essential for stromal/epithelial cell communication in the prostate.

Novel mechanisms of resistance to endocrine therapy: genomic and nongenomic considerations

Selective estrogen receptor (ER) modulators have been the most commonly used neoadjuvant therapy for hormone-dependent breast cancer. However, resistance to endocrine therapy, either inherent or acquired during treatment, presents a major challenge in disease management. The causes of resistance to hormone therapy are not well understood and are the subject of active investigation. It is increasingly clear that decreasing sensitivity of ER-positive breast cancer cells to antiestrogens is caused by several factors. Cross talk between ER and growth factor signaling has emerged as a critical factor in endocrine resistance. Here, we present evidence that receptor tyrosine kinase signaling also plays a role in resistance by controlling the subcellular localization of ER signaling components. Localization of ER in either the nuclear or cytoplasmic compartments has functional implications. Recent work suggests that dynein light chain 1, a recently identified substrate of p21-activated kinase 1, modulates ER transactivation functions through a novel ER coactivator function. Likewise, receptor tyrosine kinase signaling can also alter the expression of ER coregulators such as metastasis-associated antigen 1, leading to hormonal independence. Furthermore, proline-, glutamic acid-, leucine-rich protein 1, an ER coactivator involved in both genomic and nongenomic signaling pathways, is activated by epidermal growth factor receptor and plays a prominent role in resistance to tamoxifen. These recent advances suggest new targeted therapeutic approaches that may lead to either reversion or prevention of endocrine resistance in breast tumors.

Recent advances on multiple tumorigenic cascades involved in prostatic cancer progression and targeting therapies

Recent advances on differently-expressed gene products and their functions during the progression from localized androgen-dependent states into androgen-independent and metastatic forms of prostate cancer are reported. The expression levels of numerous oncogenes and tumor suppressor genes in distinct prostatic cancer epithelial cell lines and tissues relative to normal prostate cells are described. This is carried out to identify the signaling elements that are altered during the initiation, progression and metastatic process of prostate cancer. Additional information on the interactions between certain deregulated signaling pathways such as androgen receptor (AR), estrogen receptors, epidermal growth factor receptor (EGFR), hedgehog and Wnt/beta-catenin cascades in controlling the proliferation, survival and invasion of tumor prostate epithelial cells during the disease progression is described. The emphasis is on the critical functions of the AR and EGF-EGFR systems at all stages during prostate carcinogenesis. Of therapeutic interest, new strategies for the diagnosis and treatment of localized and metastatic forms of prostate cancer by targeting multiple tumorigenic signaling elements are also reported.