Oestradiol enhances doxorubicin uptake and cytotoxicity in human breast cancer cells (MCF-7)

Tidal chemotherapy in premenopausal patients with hormone receptor positive breast cancer

Neoadjuvant chemotherapy remains an inseparable part of systemic therapy for hormone receptor positive (HR+) advanced breast cancer. However, efficacy of neoadjuvant chemotherapy in this subtype of patients is inferior to its hormone receptor negative counterpart. Several preclinical and clinical studies have suggested that it was growth rate rather than hormone receptor status that determined sensitivity to chemotherapy. In addition, estrogen was proved to recruit more HR+ breast cancer cells into actively dividing phase according to various studies. For premenopausal females, sexual hormone like estradiol fluctuates with menstrual cycle. When menstruation occurs, women have the lowest level of estradiol, which is resemble to pharmaceutical effect of endocrine therapy. If chemotherapy is given to females during menstruation, it's almost equal to concurrent use of chemotherapy and endocrine therapy, which is not recommended by guideline. Accordingly, chemotherapy would attain best efficacy applied at the peak of estradiol, because more tumor cells being in actively dividing phase recruited by comparatively high level of estradiol would help cytotoxic agents function better given that majority of chemotherapeutic drugs are cellular phase dependent. We name this rhythmic mode of chemotherapy for premenopausal HR+breast cancer females, giving chemotherapy to patients when estradiol rises and avoiding prescription at menstruation, tidal chemotherapy. It's postulated that tidal chemotherapy would improve efficacy of neoadjuvant chemotherapy for premenopausal HR+breast cancer females, achieve more pathologic complete response and in the long run improve prognosis.

Binding and inhibition of drug transport proteins by heparin: a potential drug transporter modulator capable of reducing multidrug resistance in human cancer cells

A major problem in cancer treatment is the development of resistance to chemotherapeutic agents, multidrug resistance (MDR), associated with increased activity of transmembrane drug transporter proteins which impair cytotoxic treatment by rapidly removing the drugs from the targeted cells. Previously, it has been shown that heparin treatment of cancer patients undergoing chemotherapy increases survival. In order to determine whether heparin is capable reducing MDR and increasing the potency of chemotherapeutic drugs, the cytoxicity of a number of agents toward four cancer cell lines (a human enriched breast cancer stem cell line, two human breast cancer cell lines, MCF-7 and MDA-MB-231, and a human lung cancer cell line A549) was tested in the presence or absence of heparin. Results demonstrated that heparin increased the cytotoxicity of a range of chemotherapeutic agents. This effect was associated with the ability of heparin to bind to several of the drug transport proteins of the ABC and non ABC transporter systems. Among the ABC system, heparin treatment caused significant inhibition of the ATPase activity of ABCG2 and ABCC1, and of the efflux function observed as enhanced intracellular accumulation of specific substrates. Doxorubicin cytoxicity, which was enhanced by heparin treatment of MCF-7 cells, was found to be under the control of one of the major non-ABC transporter proteins, lung resistance protein (LRP). LRP was also shown to be a heparin-binding protein. These findings indicate that heparin has a potential role in the clinic as a drug transporter modulator to reduce multidrug resistance in cancer patients.

Neo-endocrinochemotherapy: a novel approach for enhancing chemotherapeutic efficacy in clinic?

Chemosensitization means enhancing the sensitivity of tumor cells to chemotherapy with certain methods for better efficacy. Tumor progression depends on stimulation of multiple hormones, decrease in hormones during chemotherapy induces G0/G1 arrest of tumor cells, which may be the main cause for chemoresistance. Some of the choriocarcinoma and testicular tumors are curable with chemotherapy only, underlying mechanism may refer high level of human chorionic gonadotropin, which has thyroid stimulating hormone like effect and even induce hyperthyroidism in these patients. Some of these patients usually have high levels of thyroid hormones or suffer thyroid crisis during chemotherapy. Possibly owning to the proliferative or metabolic promotion effect of thyroid hormones and/or other endocrine hormones, which can promote tumor cells in G0 phase metabolizing actively or stepping into division cycle again, tumors are more sensitive to chemotherapy. Both endocrinotherapy and chemotherapy are major therapies for tumor, traditional endocrinotherapy suppresses tumor progression through decreasing tumor-dependent hormones or competitively combining and blocking hormone receptors. While, chemotherapy mostly killed tumor cells that proliferate actively, because tumor cells retardant in G0 phase by endocrinotherapy are no more sensitive to chemotherapy, endocrinotherapy cannot be concurrently used with chemotherapy. Nevertheless, decrease in hormones during chemotherapy is similar to concurrently using endocrinotherapy and chemotherapy. It has been found in some basic researches that some chemotherapeutics concurrently combined with endocrine hormones can achieve better efficacy compared with chemotherapy only. It is therefore hypothesized in this article that decrease in hormones during chemotherapy causes cell cycle arrest and renders tumor cells insensitive to chemotherapy; addition of endocrine hormones to mimic the hormones and microenvironment changes during chemotherapy for patients with choriocarcinoma or testicular tumor-curable with chemotherapy only, will rescue tumor cells from cell cycle arrest rendering them sensitive to chemotherapy. This new combinative therapy of concurrently using endocrine hormones and chemotherapy is defined as choriocarcinoma-mimic chemotherapy or neo-endocrinochemotherapy to distinguish the routine term of endocrinochemotherapy and is expected to be a novel approach to enhance chemotherapeutic efficacy in clinic.

Value of estrogenic recruitment before chemotherapy: first randomized trial in primary breast cancer

PURPOSE

Several preclinical studies showed that short-term pretreatment of breast cancer cells with estrogens can increase the antitumor efficacy of different cytotoxic drugs. Some early clinical studies in patients with advanced breast cancer did seem to support these findings. Therefore, the efficacy of estrogenic recruitment followed by chemotherapy was compared with that of chemotherapy alone in a randomized phase III study in women with lymph node-positive primary breast cancer.

PATIENTS AND METHODS

Three hundred twenty-eight patients with stage II/IIIA breast cancer who were younger than 66 years of age were randomly allocated to chemotherapy with fluorouracil, doxorubicin, and cyclophosphamide (FAC) or FAC plus pretreatment with ethinyl estradiol (EE(2)). FAC (500, 50, and 500 mg/m(2), respectively) was administered intravenously once every 4 weeks for four cycles. EE(2) (0.5 mg) was administered orally, both 24 hours and immediately preceding FAC chemotherapy.

RESULTS

Patient and tumor characteristics and chemotherapy dosages were comparable in both treatment groups. Of 318 assessable patients, with a median follow-up of 6.8 years, 177 patients had a relapse and 127 died. No significant differences were observed between the two treatment groups with respect to relapse-free, local recurrence-free, and overall survival according to univariate and multivariate analyses adjusted for age, menopausal status, tumor size, grade, number of positive nodes, and steroid-receptor status. The power for the detection of an increase of 50% in the median relapse-free survival was 80%.

CONCLUSION

Estrogenic recruitment of breast cancer cells before FAC chemotherapy did not influence the efficacy of adjuvant chemotherapy in stage II/IIIA breast cancer patients after a follow-up of 6.8 years.

Uptake and distribution of doxorubicin in hormone-manipulated human breast cancer cells in vitro

BACKGROUND

Kinetic resistance to cytotoxic drugs may account for the moderate responsiveness of breast cancer to chemotherapy. In the present study the in vitro effects of estradiol-mediated DNA stimulation on the cellular uptake of the DNA intercalating drug doxorubicin (DOX) were examined in MCF-7 human breast cancer cells.

METHODS

Using the fluorescent properties of the drug, the cellular uptake was investigated by high performance liquid chromatography (HPLC), and by flow cytometry.

RESULTS

The uptake of DOX (0.01-2 microg/ml) by MCF-7 cells in suspension, incubated for 1 and 6 h, showed a strong correlation between the incubation concentration of DOX and the cellular uptake of the drug as measured by HPLC and flow cytometry. Simultaneous exposure of MCF-7 cells, in monolayer culture, to DOX (0.04-0.2 microg/ml) and estradiol (1 nM) for 1-24 h showed no significant difference in uptake of the drug compared to control cultures exposed to DOX in the absence of estradiol. Neither was there a significant difference in uptake of DOX when MCF-7 cells were pretreated with estradiol (1 nM) for 16-24 h followed by a 0.5, 1, 6, and 21/23 h incubation with DOX (0.01-2 microg/ml). Pretreatment with estradiol did not affect the retention of DOX as measured 24 h after a 0.5 h incubation with DOX (2 microg/ml). Furthermore, fluorescence microscopy revealed no difference in the cellular DOX distribution pattern of estradiol-stimulated MCF-7 cultures compared to unstimulated cultures.

CONCLUSION

From this study we can conclude that, for the human MCF-7 breast cancer cells in vitro, the uptake, retention, and cellular distribution of DOX are not influenced by estrogenic manipulation.

Novel endocrine therapies in breast cancer

Endocrine therapy of breast cancer consists of a variety of both medical and surgical ablative treatment modalities, but ablative therapy is increasingly replaced by medical treatment. Most endocrine therapies have more than one endocrine effect, frequently together with direct growth inhibitory actions via receptors. Endocrine therapy can be effective in all phases of the disease, but curative only in early disease while in advanced cancer it can only prolong survival. In the past decade the number of available endocrine agents has been drastically increased. Novel approaches in the endocrine therapy of breast cancer are application of new antiestrogens, antiprogestins, new potent aromatase inhibitors, analogues of luteinizing hormone-releasing hormone (LHRH-A) and somatostatin, inhibitors of prolactin secretion, vitamin A and D analogues, bisphosphonates, growth factor antagonists, tyrosine protein kinase inhibitors, protease inhibitors, inhibitors of angiogenesis, radiolabeled hormones and monoclonal antibodies. New cell biological factors such as oncogenes and suppressorgenes, secretory proteins and membrane receptors can be used not only as prognostic factors but also for prediction of type of response to endocrine and chemotherapy. Thus, these cell biological parameters can be used to select high and low risk patients, type of systemic treatment, and can also be used as targets for new treatment modalities. Future studies on treatment of all stages of disease will increasingly focus on promising combined treatment modalities.

Cell biological factors associated with the response of breast cancer to systemic treatment

A large number of cell biological parameters are currently available to predict the prognosis of patients with breast cancer, but it is still difficulty accurately to predict the response to treatment. A valuable prognostic factor can be a poor predictive factor for response, and vice versa. High tumor levels of ER, PgR, AR and pS2 predict a relatively good response to endocrine therapy, while EGF-R positively, HER2/neu positivity, aneuploidy, high proliferation indices and possibly high uPA levels indicate a high chance of poor response to endocrine therapy in metastatic breast cancer. With respect to chemotherapy, a high proliferation rate and HER2/neu amplification predict a good response to therapy in metastatic disease, while MDR gene expression and possibly c-myc amplification are related to a worse response. In conclusion, the newer cell biological parameters can be used to select high and low-risk patients, type of systemic treatment, and as targets for new treatment modalities.

Clinical breast cancer, new developments in selection and endocrine treatment of patients

Breast cancer is the most common malignant tumor among women, comprising an estimated 24% of all cancer cases and 18% of all cancer deaths. At least half of the patients with primary breast cancer will ultimately die by metastatic disease. The tumor characteristics, the natural course of the disease and the response to therapy vary strongly. A number of recently detected cell biological parameters such as oncogenes/suppressor genes, growth factors and secretory proteins are more or less important prognostic factors, because they influence the characteristics and behavior of a tumor with respect to metastatic pattern, extent of cellular differentiation, growth rate and response to treatment. However, there is no clear consensus how best to identify patients at high or low risk. In our experience c-myc amplification and pS2 protein are strong prognosticators for relapse rate, while in advanced disease (apart from a negative estrogen/progesterone receptor/pS2 status) amplification of HER2/neu is a good prognosticator for failure to endocrine therapy. In the diagnosis of breast cancer, in vivo imaging of tumors by labeled hormones or other factors also forms a new development which might have implications for treatment too. With respect to treatment both endocrine and chemotherapy can cure a minority of patients with micrometastases, but in patients with advanced disease only a prolongation of (progression-free) survival can be reached. Response rates decrease with increasing tumor load. In the past decade a number of interesting new endocrine agents has been developed such as new (pure) (anti)steroidal agents, vitamins, aromatase inhibitors, analogs of peptide hormones, prolactin inhibitors and growth factor antagonists. However, less is known on the (potential) interaction between hormones, chemotherapeutic agents, retinoids, cytokins, growth factor antagonists and irradiation. Rapid detection of new powerful combination therapies are needed to improve treatment results during the nineties.

In vitro sensitivity testing of human breast cancer cells to hormones and chemotherapeutic agents

The sensitivities of human breast cancer cells to hormones and chemotherapeutic agents were measured using a new in vitro assay. Tumor cells from individual patients were cultured on collagen-coated dishes in medium containing the patient's serum. The rationale for use of the patient's serum is that the components of this serum interact with the cells and therapeutic agents in vivo. Cells were incubated for the length of the assay in the presence or absence of estrogen (E2) with or without tamoxifen (TAM) or in the presence or absence of cortisol (F). At 1 day after cell seeding, cells were exposed to a chemotherapeutic agent, Adriamycin, melphalan, or 5-fluorouracil, for 24 h. After a 48-h recovery period, [3H]-thymidine ([3H]-TdR) was added to the cultures for 24 h. Depending on the concentration, E2 generally stimulated or inhibited incorporation of [3H]-TdR into the DNA of cells from estrogen-receptor (ER)-positive tumors. TAM eliminated the effects of E2. F generally stimulated or inhibited incorporation in cells with no correlation to ER status. Stimulation of [3H]-TdR incorporation by hormones increased cell sensitivity to Adriamycin. In contrast, hormone inhibition of [3H]-TdR incorporation decreased cell responsiveness to this drug. This rapid assay, which can measure the sensitivities of breast carcinoma cells to hormones and drugs and identify effective combinations of therapeutic agents, should lead to a rational selection of treatment for the individual patient.

Effect of hormonal manipulation and doxorubicin administration on cell cycle kinetics of human breast cancer cells

Dual-parameter flow cytometry, following bromodeoxyuridine (BrdUrd) incorporation and propidium iodide (PI) uptake into DNA, was used to study the effects of oestradiol and/or insulin on cell cycle kinetics of human breast cancer cells in vitro. After a lag-period of 6-12 h, an optimum in the percentage of S-phase cells was reached between 18 and 24 h after hormone administration. A 1 h pulse of oestradiol was as effective as the continuous presence of oestradiol in pushing the cells from quiescent growing cultures into the cell cycle. A 1 h pulse of insulin was less effective than continuous administration. The addition of doxorubicin resulted in an accumulation of the cells in the late S/G2M-phases. It is concluded that dual-parameter flow cytometry allows accurate assessment of the effects of hormones and chemotherapy on the cell cycle. Therefore this method is very suitable for studying the interaction of hormones and chemotherapy on cell growth.

Adriamycin action on human breast cancer cells: enhancement by medroxyprogesterone acetate

Exposure of cultured human breast cancer cells (MCF-7) to medroxyprogesterone acetate (MPA) prior to treatment with adriamycin (ADR) enhanced the effect of the cytotoxic drug on cell yield after further growth of viable cells. Pretreatment with oestradiol (E2) produced similar synergism, but no such effect was observed using dexamethasone. Exposure to ADR before MPA led to an additive effect, but not to synergism. When cells resistant to the growth-inhibitory action of MPA were examined, progestogen/drug synergism could still be demonstrated. We conclude that the effects of ADR, like those of methotrexate and vincristine, can be enhanced by pre-treatment with MPA and that further clinical trials of such a regimen are needed.

Actions of medroxyprogesterone acetate on the efficacy of cytotoxic drugs: studies with human breast cancer cells in culture

Human breast cancer cells (MCF-7) showed increased responses to methotrexate and vincristine after a 48-hr pre-treatment with medroxyprogesterone acetate. The effect of the hormone, which was detectable at concentrations of between 10 and 100 nM, was independent of its growth-inhibitory action. These findings confirm a previous clinical study and have important implications with regard to the management of advanced breast cancer.