High affinity of sigma1-binding sites for sterol isomerization inhibitors: evidence for a pharmacological relationship with the yeast sterol C8–C7 isomerase

1. The sigma-drug binding site of guinea-pig liver is carried by a protein which shares significant amino acid sequence similarities with the yeast sterol C₈–C₇ isomerase (ERG2 protein). Pharmacologically - but not structurally - the sigma₁-site is also related to the emopamil binding protein, the mammalian sterol C₈–C₇ isomerase. We therefore investigated if sterol C₈–C₇ isomerase inhibitors are high affinity ligands for the (+)-[³H]-pentazocine labelled sigma₁-binding site.
2. Among the compounds which bound with high affinity to native hepatic and cerebral as well as to yeast expressed sigma₁-binding sites were the agricultural fungicide fenpropimorph (K_i 0.005 nM), the antihypocholesterinaemic drugs triparanol (K_i 7.0 nM), AY-9944 (K_i 0.46 nM) and MDL28,815 (K_i 0.16 nM), the enantiomers of the ovulation inducer clomiphene (K_i 5.5 and 12 nM, respectively) and the antioestrogene tamoxifen (K_i 26 nM).
3. Except for tamoxifen these affinities are essentially identical with those for the [³H]-ifenprodil labelled sterol C₈–C₇ isomerase of S. cerevisiae. This demonstrates that sigma₁-binding protein and yeast isomerase are not only structurally but also pharmacologically related. Because of its affiliations with yeast and mammalian sterol isomerases we propose that the sigma₁-binding site is localized on a sterol isomerase related protein, involved in postsqualene sterol biosynthesis.

     

Flow cytometry: Potential utility in monitoring drug effects in breast cancer

Summary Flow cytometric analysis of DNA ploidy and S-phase fraction are well recognized prognostic indicators in breast cancer. The present paper deals with the widening of the applications of flow cytometry to monitoring the effectiveness of antiestrogen therapy, detecting clonal selection and emergence of drug resistance, and monitoring chemosensitizing properties of drugs. Antiestrogen activity can be studied by DNA flow cytometry to address clinical research problems such as patient-specific pharmacokinetics, dosing compliance, and acquired antiestrogen resistance. Patient plasma specimens containing various concentrations of triphenylethylenes can be monitored for drug-induced effects using cell cycle measurements and correlated toin vivo drug levels. DNA flow cytometry has also been instrumental in the study of the effects of prolonged low-dose (0.5 µM for > 100 days) tamoxifen treatment on human estrogen receptor negative MDA-MB-231 cells, where it was shown that tamoxifen may significantly alter cell cycle kinetics and tumorigenicity of these cells, selecting a new, more aggressive, and rapidly growing clone. Lastly, it has been shown that the chemosensitizing properties of another triphenylethylene antiestrogen, toremifene, on estrogen receptor negative, multidrug resistant MDA-MB-231-A1 human breast cancer cells can be studied using flow cytometric analysis. Toremifene (and its metabolites N-desmethyltoremifene and toremifene IV) are able to resensitize MDA-MB-231-A1 cells to vinblastine and doxorubicin, as reflected in a marked shift of cells to G₂/M phase of the cell cycle. Flow cytometry is a widely available technique that might be applied clinically to monitor, at the cellular level, drug effects on tumors, including the modulators of drug resistance.     

异搏定和三苯氧胺合并化疗治疗42例恶性肿瘤观察

目的：探索异搏定和三苯氧胺作为耐药调变剂与化疗联合应用治疗恶性肿瘤的作用。方法：对８２例恶性肿瘤患者进行随机分组对照实验,４２例化疗同时加用异搏定和三苯氧胺,４０例单纯化疗,两组化疗方案相同。结果：两组总有效率分别为６１．９％和４０．０％,治疗组与对照组疗效相比有显著性差异（Ｐ＜０．０５）,毒副作用两组无明显差别。结论：异搏定和三苯氧胺与化疗合用有助于改善化疗效果。     

The effects of cyclosporin A,tamoxifen, and medroxyprogesterone acetate on the enhancement of Adriamycin cytotoxicity in primary cultures of human breast epithelial cells

Summary Adriamycin (Adr), the single most active agent used in the treatment of breast cancer, may become ineffective as treatment progresses due to the development of multidrug resistant (MDR) tumors. A major mechanism associated with MDR is increased P-glycoprotein (Pgp) expression. This study examined the abilities of the anti-estrogen tamoxifen (TAM) and the progestin medroxyprogesterone acetate (MPA) as well as cyclosporin A (CsA), a known resistance modifier, to enhance the cytotoxic effects of Adr on human breast epithelial cells (HBEC) in primary culture. Pgp and estrogen receptor (ER) expression were determined in each of the cultures by immunocytochemical assays using the monoclonal antibodies C219 and H222 Sp, respectively. The Adr-sensitive, Pgp-, ER+ MCF-7 cell line and the Adr-resistant, Pgp+, ER-MCF7-AdrR cell line were used as controls. Primary cultures were categorized as HBEC from tissues with or without previous chemotherapy. Pgp was detected in 1 of the 15 cell cultures from tissues without previous chemotherapy and in 5 of the 6 cell cultures from tissues previously exposed to chemotherapy. Incubation with either CsA or MPA plus Adr enhanced Adr toxicity in Pgp+ but not Pgp- cell cultures, whereas TAM had no effect on the sensitivity of any of the cultures. Of the 21 primary cultures of HBEC, 3 were ER+. There was no correlation between the enhancement of Adr cytotoxicity and ER status. The data suggest that MPA as well as CsA may be useful as modifying agents in overcoming Pgp-associated multidrug resistance.     

Cellular uptake and concentrations of tamoxifen upon administration in poly(ε-caprolactone) nanoparticles

Purpose: In an attempt to increase the local concentration of tamoxifen in estrogen receptor positive breast cancer cells, we have prepared and characterized poly (ε-caprolactone) (PCL) nanoparticle formulation. Methods: PCL (mol wt 14,800 daltons) nanoparticles were prepared by the solvent displacement method in acetonewater system in the presence of Pluronic F-68. PCL nanoparticles, labeled with rhodamine 123, were incubated with MCF-7 estrogen receptor positive breast cancer cells to determine uptake, intracellular distribution, and localization as a function of time. Intracellular drug concentrations over a specified period of time using different initial doses were examined using tritiated [³H]-tamoxifen. Results: A significant fraction of the administered rhodamine 123-loaded PCL nanoparticles was found in the perinuclear region of the MCF-7 cells, where estrogen receptors are also localized, after 1 hour of incubation. Measurements of the intracellular concentrations revealed that most of the administered nanoparticle dose was internalized within the first 30 minutes of incubation, and the uptake followed saturable transport kinetics. Conclusion: Results of this study show that PCL nanoparticles were rapidly internalized in MCF-7 cells and intracellular tamoxifen concentrations followed a saturable process. This approach may provide better therapeutic benefit by delivering the drug locally, near the tumor cells, for a longer period of time.     

Biomarker investigations from the ATAC trial: the role of TA01

cDNA arrays and proteomic analyses have allowed the rapid identification of specific genes and proteins implicated in multiple tumor types. These molecules must then be validated as clinically relevant prognostic and predictive markers, and this translational research is best conducted in the context of clinical trials. Outcomes data and clinical specimens collected in the ‘Arimidex’, Tamoxifen, Alone or in Combination (ATAC) study, for example, can now be used to compare the expression of biomarkers with clinical outcomes. In this study, adjuvant tamoxifen and anastrozole (‘Arimidex’) were compared alone and in combination in more than 9000 women with breast cancer. Anastrozole was found to be superior to tamoxifen in terms of disease-free survival, time to recurrence, and reduction in the incidence of contralateral tumors. Importantly, tissue specimens from surgical excision, local relapse, and contralateral breast cancer were collected and paraffin-embedded for storage. In the TA01 (TransATAC) program, these specimens will be studied (after obtaining patient consent) using tissue microarrays; tissue biopsy cores 0.6 mm in diameter will be removed from donor blocks and placed on recipient blocks, which will be sectioned to allow the simultaneous analysis of the same samples for multiple biomarkers. These analyses can help determine differential benefits of treatment with anastrozole or tamoxifen, depending on the expression of particular biomarkers in tumor cells. This research also should clarify de novo and acquired resistance mechanisms, and the validation of relevant molecular pathways could guide the development of new drugs. Ultimately, the TA01 program has the potential to favorably impact treatment choices for breast cancer. This revised version was published online in August 2006 with corrections to the Cover Date.     

A trial-based cost-effectiveness analysis of letrozole followed by tamoxifen versus tamoxifen followed by letrozole for postmenopausal advanced breast cancer.

BACKGROUND: Third-generation aromatase inhibitors are being considered as an alternative to tamoxifen as first-line therapy for advanced breast cancer. These newer therapies are more expensive, and will gain greater acceptance if they can demonstrate cost-effectiveness. METHODS: Life table analyses are used to compare the costs and benefits [life years gained and quality-adjusted life years (QALYs) gained] of treating postmenopausal women with advanced breast cancer with first-line letrozole (with the option of second-line tamoxifen) compared with first-line tamoxifen (with the option of second-line letrozole). Patient-level data from a large clinical trial describes the effectiveness of the therapy options, clinicians estimate resource usage and utility values are obtained from the literature. RESULTS: The mean cost of providing first- and second-line hormonal therapy is pound 4765 if letrozole is the first-line therapy and pound 3418 if tamoxifen is provided first (a difference of pound 1347). However, patients receiving letrozole as first-line therapy gain an additional 0.228 life years, or 0.158 QALYs. The cost-effectiveness analysis found that first-line hormonal therapy with letrozole gains additional life years at a cost of pound 5917, whilst the cost per additional QALY gained is pound 8514. CONCLUSION: The strategy of letrozole as first-line hormonal therapy not only provides an opportunity for extending and improving patient's quality of life, but also is highly cost-effective compared with other generally accepted medical treatments.     

胃癌的雌孕激素受体检测及应用三苯氧胺治疗的研究

目的　探讨胃癌的雌激素受体 (ER)、孕激素受体 (PR)表达情况及其对预后的影响 ,观察三苯氧胺 (TAM)在胃癌治疗中的作用。方法　从 1993年 2月到 2 0 0 0年 12月 ,用免疫组化SP法 ,对 12 3例胃癌术后标本进行了ER、PR检测 ,并将TAM应用于胃癌的内分泌治疗 ,追踪随访 5年。结果　①胃癌的ER、PR阳性率均为 36 5 9% ( 45 / 12 3) ;②分化好 (高、中分化 )的胃癌ER、PR阳性率18.5 7% ( 13/ 70 ) ,分化差 (低分化腺癌 ,粘液腺癌和印戒细胞癌 )的胃癌ER、PR阳性率 60 38% ( 32 / 5 3) ,统计学处理有显著差异 (P <0 .0 5 ) ;③ER、PR阳性表达与临床分期呈正相关 ,分期越晚阳性率越高 ,但统计学无显著差异 (P >0 .0 5 ) ;④接受化疗 34例 ,化疗同时辅以TAM内分泌治疗 31例 ,5年生存率分别为 2 6.47% ( 9/ 34 )、5 1.61% ( 16/ 31) ,二者有显著差异 (P <0 .0 5 )。结论　本研究表明 ,ER、PR阳性表达的胃癌是一种雌、孕激素依赖性肿瘤 ,化疗联合TAM内分泌治疗 ,可抑制胃癌细胞的生长 ,提高 5年生存率     

Spinal chondrosarcoma following adenocarcinoma of the breast: case report

BACKGROUND

Chest wall chondrosarcomas have been reported rarely in breast cancer patients treated with chest wall radiation therapy. However, there are no prior reports of spinal chondrosarcomas arising in patients with a history of breast adenocarcinoma.

CASE DESCRIPTION

A neurologically intact 53-year-old woman with breast adenocarcinoma and new onset back pain was evaluated. Magnetic resonance imaging of the spine revealed a tumor of the posterior elements of T7, impinging upon the spinal cord. A computed tomography guided needle biopsy of the spinal mass failed to yield diagnostic results. The patient underwent an open surgical biopsy and complete excision of a low-grade chondrosarcoma. The patient’s thoracic pain resolved after surgical excision of her thoracic tumor. She remained neurologically intact. Pathological examination of the tumor revealed a low-grade chondrosarcoma.

CONCLUSION

We present the first reported case of chondrosarcoma of the spine arising in a patient with a history of breast adenocarcinoma without prior irradiation. Solitary spinal tumors in patients with breast adenocarcinoma should not be assumed to be metastatic lesions, and chondrosarcoma should be included in the differential diagnosis of spinal lesions in this patient population. Experimentally, chondrosarcomas have been shown to be sensitive to circulating levels of estrogens, and this might explain an association with adenocarcinoma of the breast treated with tamoxifen.