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V C Jordan

Publications and source records attributed to V C Jordan.

At least 19 recordsLinked to original sources
PubMed1992

High-dose oral tamoxifen, a potential multidrug-resistance-reversal agent: phase I trial in combination with vinblastine.

BACKGROUND: P-glycoprotein mediates resistance to natural-product anti-neoplastic agents like vinblastine through an active transport process resulting in reduced intracellular concentration of these agents. The triphenylethylene antiestrogen tamoxifen and its major metabolite N-desmethyltamoxifen at concentrations of 4-6 microM enhance the intracellular concentration of natural-product antineoplastics and augment the cytotoxicity of such drugs three-fold to 10-fold in a variety of human and murine cell lines. PURPOSE: On the basis of these preclinical findings, we conducted a phase I clinical trial of high-dose, oral tamoxifen administered in conjunction with a 5-day continuous infusion of vinblastine. METHODS: We studied 53 patients with advanced epithelial tumors. Tamoxifen was given orally as a loading dose on day 1, followed by two doses a day on days 2-13. Vinblastine was given as a 120-hour continuous infusion (1.5 mg/m2 per day) on days 9-13 of each tamoxifen course. The starting dose of tamoxifen was 40 mg/m2 administered twice a day following a loading dose of 150 mg/m2. The maximum dose was 260 mg/m2 twice a day following a loading dose of 680 mg/m2. Treatment cycles were repeated every 28 days. RESULTS: The dose-limiting toxic effects of tamoxifen were neurologic and began within 3-5 days after the start of treatment. They consisted of tremor, hyperreflexia, dysmetria, unsteady gait, and dizziness. One patient experienced a grand mal seizure 24 hours after the last tamoxifen dose. Toxic effects were rapidly reversible. Asymptomatic prolongation of the QT interval on electrocardiogram occurred at doses of tamoxifen of 80 mg/m2 or higher given twice a day. No coagulation or ophthalmologic abnormalities occurred. Tamoxifen did not enhance the toxicity of vinblastine. Mean plasma concentrations of tamoxifen or N-desmethyltamoxifen at 260 mg/m2 tamoxifen given twice a day for 13 days were 6.04 and 6.56 microM, respectively. There was no relationship between plasma antiestrogen content and the development of neurotoxic effects. CONCLUSIONS: Tamoxifen at 150 mg/m2 given twice a day following a loading dose of 400 mg/m2 results in plasma levels of tamoxifen and N-desmethyltamoxifen of 4 and 6 microM, respectively, without dose-limiting toxicity. We recommend this dose for phase II trials of tamoxifen to modulate P-glycoprotein-mediated drug resistance. IMPLICATIONS: Our study demonstrates that high-dose tamoxifen can be safely administered and that plasma concentrations that may inhibit P-glycoprotein function can be achieved.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Estrogenic potential of progestins in oral contraceptives to stimulate human breast cancer cell proliferation.

Most oral contraceptives (OC) contain a progestin in combination with an estrogen, and the progestin component in OC includes one of the following 19-nortestosterone derivatives: norethynodrel; norethindrone; or norgestrel (levonorgestrel). It is well known that estrogens promote the growth of breast cancer. However, progestins have recently also been implicated in the development of breast cancer. We have compared and contrasted the ability of synthetic progestins to stimulate the proliferation of cultured human breast cancer cells and examined their possible mechanism of action. We found that some progestins used in OC were able to stimulate the growth of estrogen receptor-positive (ER+) MCF-7 and T47DA18 human breast cancer cells but not ER- MDA-MB-231, BT-20, and T47DC4 human breast cancer cells. However, two other progestins, MPA and R5020, which are not used in OC, were either not able to stimulate or only slightly stimulated growth. The potency of norethynodrel [median effective dose (EC50) = 4 x 10(-8) M] and norethindrone (EC50 = 3 x 10(-8) M) was greater than norgestrel (EC50 = 2 x 10(-7) M) in MCF-7 cells. E2 (EC50 = 8 x 10(-13) M) was an even more potent stimulator of growth. More importantly, the progestin-induced growth stimulation was blocked by the antiestrogens 4-hydroxytamoxifen and ICI 164,384 but not the antiprogestin 17 beta-hydroxy-11 beta-(4-dimethylaminophenyl)-17 alpha-(1-propynyl)-estra-4, 9-dien-3-one (RU486). To determine whether the proliferative action of progestins was mediated through the ER, cells were transfected with a chloramphenicol acetyltransferase reporter gene containing an estrogen response element derived from vitellogenin 2A gene. The progestins which stimulated the growth of breast cancer cells also increased chloramphenicol acetyltransferase activity. The induction of chloramphenicol acetyltransferase activity was blocked by the addition of the antiestrogens 4-hydroxytamoxifen and ICI 164,384 but not the antiprogestin RU486. This study provides direct evidence that the 19-nortestosterone derivatives in OC have estrogenic properties and suggests that activation of ER, but not progesterone receptor, is the growth-stimulatory mechanism for these synthetic progestins. Our results may help to explain the conflicting evidence linking OC and breast cancer risk. A rigorous evaluation of the "total" estrogenic potential of OC might produce a better correlation with breast cancer risk.

Amino Acid Sequence↗
PubMed1992

The strategic use of antiestrogens to control the development and growth of breast cancer.

Tamoxifen has become the endocrine treatment of choice for all stages of breast cancer. Its low incidence of side effects and proven survival advantage observed during adjuvant therapy in postmenopausal women with node-positive disease has encouraged the use of long-term treatment for patients to benefit fully from therapy. The drug has an appropriate level of estrogen-like effects that could be beneficial to maintain bone density and prevent development of coronary heart disease by lowering circulating cholesterol. These effects might be useful in all patients with estrogen receptor-positive breast cancer who currently are receiving no therapy. This antiestrogenic agent could be effective therapy to deter recurrence, and the estrogen-like side effects support the physiologic processes of the patient as hormone-replacement therapy. In the laboratory, a tamoxifen-stimulated breast cancer model has been described in vivo. This form of drug resistance may occur in patients after long-term or indefinite adjuvant therapy. Novel pure antiestrogenic drugs have been discovered that soon will become available as second-line therapy after tamoxifen failure. In addition, tamoxifen is being evaluated in the United Kingdom as chemosuppressive therapy to prevent the development of breast cancer in high-risk women. A similar clinical evaluation is underway in the United States.

Animals↗
PubMed1992

Growth regulation of estrogen receptor-negative breast cancer cells transfected with complementary DNAs for estrogen receptor.

BACKGROUND: The growth of estrogen receptor (ER)-positive breast cancer cells is hormonally regulated, but the majority of breast cancers are ER negative and unresponsive to hormonal therapy. PURPOSE AND METHODS: To test whether hormonal control over replication can be re-established in ER-negative cells, we transfected ER-negative MDA-MB-231 (clone 10A) cells with sense and antisense constitutive ER expression vectors containing the gene for either wild-type or mutant ER linked to the gene for neomycin resistance aminoglycoside phosphotransferase (neo). A Northern blot analysis was done on total RNA from eight of the 10 transfectant clones produced to detect messenger RNA coding for ER and neo, and a Western blot analysis was done on protein extracted from the cells of one mutant and two wild-type ER sense transfectant clones to determine the molecular weight of the ER in transfectants. Levels of ER in transfectants were measured both by enzyme immunoassay and by ligand-binding methods. To ascertain whether the ER in wild-type and mutant sense transfectants was functional, we tested the effects of 17 beta-estradiol (E2) and/or an antiestrogen, ICI 164,384, on 1) ER-activated gene regulation (by transient transfection of these cells a second time with a reporter plasmid containing an estrogen response element linked to the chloramphenicol acetyl transferase [CAT] gene), 2) induction of progesterone receptor, 3) DNA replication, and 4) cell cycle kinetics. RESULTS: Messenger RNA coding for ER and for neo was detectable in both sense and antisense transfectant clones. Sense transfectants (both mutant and wild-type) expressed ER protein with a molecular weight similar to that found in ER-positive control cells. By the ligand-binding method high levels of ER were detected in both wild-type and mutant transfectants, although by the enzyme immunoassay method lower levels were detected in mutant transfectants. ER from both wild-type and mutant sense transfectants appeared functional, since E2 stimulated the expression of reporter-linked CAT and of progesterone receptor in these transfectants. E2 inhibited DNA replication in wild-type sense transfectants at a concentration of 10(-10) M and mutant sense transfectants at a concentration of 10(-8) M, and ICI 164,384 blocked this effect. CONCLUSION: ER-negative breast cancer cells stably transfected with either a mutant or wild-type ER gene regain hormonal responsiveness; however, E2 inhibits rather than stimulates cell growth. IMPLICATION: Reactivation of quiescent ER may provide a novel therapeutic approach for controlling ER-negative breast cancers.

Base Sequence↗
PubMed1992

Effects of tamoxifen on bone mineral density in postmenopausal women with breast cancer.

BACKGROUND AND METHODS: Tamoxifen, a synthetic antiestrogen, increases disease-free and overall survival when used as adjuvant therapy for primary breast cancer. Because it is given for long periods, it is important to know whether tamoxifen affects the skeleton, particularly since it is used extensively in postmenopausal women who are at risk for osteoporosis. Using photon absorptiometry, we studied the effects of tamoxifen on the bone mineral density of the lumbar spine and radius and on biochemical measures of bone metabolism in 140 postmenopausal women with axillary-node-negative breast cancer, in a two-year randomized, double-blind, placebo-controlled trial. RESULTS: In the women given tamoxifen, the mean bone mineral density of the lumbar spine increased by 0.61 percent per year, whereas in those given placebo it decreased by 1.00 percent per year (P less than 0.001). Radial bone mineral density decreased to the same extent in both groups. In a subgroup randomly selected from each group, serum osteocalcin and alkaline phosphatase concentrations decreased significantly in women given tamoxifen (P less than 0.001 for each variable), whereas serum parathyroid hormone and 1,25-dihydroxyvitamin D concentrations did not change significantly in either group. CONCLUSIONS: In postmenopausal women, treatment with tamoxifen is associated with preservation of the bone mineral density of the lumbar spine. Whether this favorable effect on bone mineral density is accompanied by a decrease in the risk of fractures remains to be determined.

Alkaline Phosphatase↗
PubMed1992

Overview from the International Conference on Long-Term Tamoxifen Therapy for Breast Cancer.

The development of tamoxifen therapy to treat selected patients, with all stages of breast cancer, has provided the clinical community with an efficacious and safe drug for long-term therapy. Issues of safety are under constant review, but justified concerns about high doses of tamoxifen acting as a promoter of liver cancer in rats or as a promoter of endometrial cancer in women have not, as yet, proved to be of clinical relevance. The situation will continue to be reviewed during the development of the prevention studies in Europe and the United States because an improvement in women's health is the ultimate goal of these programs. The hallmark for the successful development of tamoxifen has been the close cooperation between the laboratory and the clinic. The clinical strategy of long-term tamoxifen therapy is a direct application of a laboratory concept. Furthermore, potential problems in the clinic have been identified in the laboratory, and the clinical community has responded quickly to evaluate the real risks to the patient population. This close cooperation will continue. Issues of drug resistance, new antiestrogen development, and the application of the knowledge about steroid receptors to develop targeted gene therapies are being addressed so that additional treatment approaches for breast cancer will be in place by the turn of the century.

Breast Neoplasms↗
PubMed1992

Gynecologic complications associated with long-term adjuvant tamoxifen therapy for breast cancer.

The antiestrogen tamoxifen was originally introduced as a therapy for advanced breast cancer. Today, tamoxifen is used to treat selected patients with all stages of breast cancer, and trials are underway to evaluate its effectiveness as a potential breast cancer preventive. When tamoxifen is used as an adjuvant or preventive, extended patient survival times can be expected, and concerns about iatrogenic complications arising from long-term treatment become important. This review discusses currently available laboratory and clinical data regarding the toxicology of tamoxifen and focuses in particular on the gynecologic complications potentially associated with long-term tamoxifen administration.

Breast Neoplasms↗
PubMed1992

An estrogen receptor positive MCF-7 clone that is resistant to antiestrogens and estradiol.

The antiestrogen tamoxifen has been successfully used to control estrogen receptor (ER) and progesterone receptor positive breast cancer. However, the development of antiestrogen resistance is frequently observed in patients following long term treatment. We have studied the development of antiestrogen resistance in vitro and established an antiestrogen resistant variant of MCF-7 cells (clone 5C) after long term culture in estrogen free medium. The growth of clone 5C cells was not altered by either estradiol-17 beta or the antiestrogens 4-hydroxytamoxifen and ICI 164,384. Estrogen-stimulated progesterone receptor and reporter gene expression were markedly reduced in 5C cells compared to wild type MCF-7 cells. Only minor alteration in the levels of ER and no alteration in the affinity of ER for ligand were found in 5C cells. No mutation of ER cDNA in 5C cells was detected by polymerase chain reaction and DNA sequencing. This study demonstrates that change(s) in ER-mediated gene expression rather than the amino acid sequence of the ER itself may be associated with the development of at least one form of antiestrogen resistance.

Breast Neoplasms↗
PubMed1992

Influence of estradiol and tamoxifen on susceptibility of human breast cancer cell lines to lysis by lymphokine-activated killer cells.

The design of combination hormonal and immunotherapeutic protocols for breast cancer patients may be facilitated by analysis of preclinical in vitro model systems. Estrogen receptor positive (ER+: MCF-7) and negative (ER-: MDA-MB-231) human breast cancer cell lines were utilized to evaluate the effects of tamoxifen (TAM) and estradiol (E2) on modulation of breast cancer target susceptibility to lysis by lymphokine-activated killer (LAK) cells. E2-stimulated ER+ cells were more susceptible to lysis by LAK cells than corresponding TAM-treated or control cells, while treatment of ER- cells with either E2 or TAM alone did not alter from control their susceptibility to this immune-mediated lysis. All ER+ and ER- cells tested remained sensitive after treatment with TAM to lysis by LAK cells. In addition, an adenocarcinoma reactive human-mouse chimeric monoclonal antibody (ING-1) was able to significantly boost in vivo generated LAK cell-mediated lysis of control, E2-treated, and TAM-treated ER+ and ER- cells. These in vitro results provide a preclinical rationale for in vivo testing of TAM, interleukin-2 (IL-2), and breast cancer reactive antibody-dependent cellular cytotoxicity facilitating antibody in patients with refractory or high risk breast cancer.

Antibodies, Monoclonal↗
PubMed1992

Point mutation of estrogen receptor (ER) in the ligand-binding domain changes the pharmacology of antiestrogens in ER-negative breast cancer cells stably expressing complementary DNAs for ER.

The antiestrogen tamoxifen is used in the treatment of hormone-responsive breast cancer. However, therapeutic failure has frequently been observed in both patients and animal models after long term treatment. We have studied the effect of a point mutation that leads to the substitution of Val for Gly at codon 400 in the ligand-binding domain of the estrogen receptor (ER) on estrogenic and antiestrogenic activities of 4-hydroxytamoxifen (4-OHT) and its derivatives. Stable ER transfectants derived from MDA-MB-231 CL10A, an ER-negative breast cancer cell line, have been used in these studies. 4-OHT and its fixed ring derivatives showed more estrogen-like activity in ER transfectants than in MCF-7, an ER-positive breast cancer cell line. In this study, 4-OHT was a partial agonist of cell growth in the transfectant S30 cells, which express the wild-type ER. However, it was a full agonist in the mutant ER transfectant ML alpha 2H, which expressed ER with Val at codon 400. The increased estrogenic activity of 4-OHT in ML alpha 2H cells was not due to the preferential isomerization of trans 4-OHT to cis 4-OHT, since the nonisomerizable fixed ring trans 4-OHT was a partial agonist for cell growth in S30 cells and was a full agonist in ML alpha 2H cells. Transient transfection using a reporter plasmid containing an estrogen response element demonstrated that fixed ring trans 4-OHT had estrogenic activity in ML alpha 2H cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Neoplasms↗
PubMed1992

A molecular strategy to control tamoxifen resistant breast cancer.

Our research goal is to develop possible strategies that could have therapeutic implications for the control of breast cancer. Although tamoxifen therapy is successful for some patients, it does not provide adequate benefit for the majority, who have ER negative disease. There is also both laboratory and clinical evidence to support the position that initially responsive tumours will eventually develop resistance to tamoxifen therapy. Since the ER mechanism is the key to the successful control of tumour growth with anti-oestrogens, we have taken the strategic step of determining whether the ER will reassert growth control in breast tumour cells. We have demonstrated that this is feasible, and it might now be appropriate to plan a "gene therapy" approach to cancer control that is based on reactivation of the ER or the development of a targeted vector. Since the concept of growth control in refractory breast cancer has become a reality, there can now be enthusiasm about developing a means to achieve this therapeutic goal. Indeed, the implications for cancer therapy could be enormous. There is every reason to suppose that other types of cancer cells transfected with steroid receptor genes will respond with growth suppression to the appropriate ligand. We have further broadened our studies of anti-oestrogens to describe a laboratory model to dissect the molecular pharmacology of hormone and anti-hormone action. In practical terms, the model has provided an insight into tamoxifen stimulated growth as a mechanism of tamoxifen resistance. The pharmacology of a model compound, fixed ring 4-hydroxytamoxifen, was changed by a mutant ER. It is possible to envisage the clonal selection of cells with mutated ER or ERE that will thrive on the partial agonist actions of tamoxifen. These cells would, as is observed in the MCF-7 TAM and EnCa101 laboratory models, also respond to oestradiol stimulation. Future studies of mutant receptors in the laboratory and clinic might provide support for a novel mechanism of tamoxifen resistance. What is most encouraging, though, is the finding that the pharmacology of new pure anti-oestrogens is not affected by the mutation in the ER and that the pure anti-oestrogens can control tamoxifen stimulated growth. These observations provide additional support for the development of pure anti-oestrogens as a therapy for breast cancer. A clinically acceptable compound could be used as a therapy after tamoxifen failure or perhaps the compound may prevent the development of receptor mutants if it is used as a first line therapy.

Breast Neoplasms↗
PubMed1991

Effects of tamoxifen on cardiovascular risk factors in postmenopausal women.

OBJECTIVE: To determine the effects of tamoxifen on risk factors for cardiovascular disease in disease-free postmenopausal women. DESIGN: Double-blind, placebo-controlled, randomized 2-year clinical trial. SETTING: University health sciences center. PATIENTS: Clinically postmenopausal women (140) with a diagnosis of axillary node-negative breast cancer, who were disease-free by laboratory and clinical evaluations. MEASUREMENTS: Levels of total cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, apolipoprotein A-I, apolipoprotein B, glucose, weight, blood pressure, and reported exercise and work activity were measured. MAIN RESULTS: Postmenopausal women receiving tamoxifen were evaluated at 3- or 6-month intervals during a 2-year assessment period and showed a mean decrease of 12% in total cholesterol levels (at 24 months -0.672 mmol/L; 95% CI, -0.839 to -0.505 mmol/L) and a mean decrease of 20% in calculated low-density lipoprotein (LDL) cholesterol levels (at 24 months, -0.725 mmol/L; 95% CI, -0.868 to -0.583 mmol/L) (P less than 0.001). Women with greater baseline cholesterol levels had greater decreases with tamoxifen treatment. Levels of HDL cholesterol decreased in patients treated with tamoxifen, but this decrease was only statistically significant at one of five measurement times. Apolipoprotein A-I levels increased significantly at the two time points at which it was measured (P = 0.02), and apolipoprotein B levels decreased significantly at these times (P less than 0.01) in patients treated with tamoxifen. Plasma glucose levels, reported exercise and work activity, reported smoking, weight, and systolic and diastolic blood pressures did not change with treatment. CONCLUSION: During 2 years of treatment, tamoxifen showed generally favorable effects on the lipid and lipoprotein profile of treated postmenopausal women. These effects may partially explain the decrease in adverse events and in mortality related to coronary heart disease seen in patients receiving adjuvant tamoxifen treatment.

Apolipoprotein A-I↗
PubMed1991

Alteration of endocrine parameters in premenopausal women with breast cancer during long-term adjuvant therapy with tamoxifen as the single agent.

Tamoxifen is used to treat selected patients at each stage of breast cancer. Although most clinical experience has been obtained with postmenopausal women, increasing numbers of premenopausal women will be treated with 5 or more years of adjuvant tamoxifen therapy following surgery. Indeed, the proposed use of tamoxifen to prevent breast cancer in high-risk women could result in its extended use during the childbearing years. We have monitored the changes in circulating hormone levels from the ovary and pituitary gland in premenopausal (41-47 years old) women with stage I or II breast cancer during adjuvant therapy with tamoxifen as the single agent for 4-72 months following a mastectomy. Each patient (total eight) continued to menstruate, and ovulation occurred. Circulating levels of luteinizing hormone and follicle-stimulating hormone (except in one woman) remained in the normal range (determined in 12 regularly menstruating women in a control group). The levels of estradiol, estrone, and progesterone were elevated onefold to threefold. Prolactin levels decreased by 30%-40%, but the levels of sex hormone binding-globulin were unaffected. These data demonstrate that premenopausal women taking tamoxifen are potentially at risk for pregnancy and must be counseled about barrier contraception. Furthermore, the impact of many years of ovarian stimulation by tamoxifen must be evaluated, especially in women with node-negative disease or in healthy women in whom tamoxifen is used to prevent breast cancer.

Adult↗
PubMed1991

Suppression of mouse mammary tumorigenesis by long-term tamoxifen therapy.

A sustained release of tamoxifen, which produced decreasing serum levels of this drug (24 to 4 ng/mL) over 6 months, suppressed mammary tumorigenesis in virgin or once pregnant C3H/OUJ female mice. Tamoxifen was consistently more effective than early ovariectomy, which only delayed tumorigenesis. Tamoxifen prevented the stimulatory action of cyclical (alternate-month) progesterone administration on mouse mammary tumorigenesis. However, when tamoxifen treatment (12 months) was stopped, progesterone treatment initiated tumorigenesis. In contrast, when long-term tamoxifen treatment was stopped in mice that had not undergone ovariectomy, and estrous cycle returned, the majority of these mice remained tumor free. A comparison of different durations (3, 6, and 12 months) of tamoxifen treatment of virgin mice, starting at approximately 4 months of age, showed an equivalent effect on mammary tumorigenesis. All virgin mice developed tumors by 18 months of age, whereas 80% of the tamoxifen-treated mice were tumor free. Nevertheless, cyclical progesterone administration caused rapid development of tumors after 3 months of tamoxifen treatment; only 15% of these mice were tumor free at 18 months. Cyclical progesterone administration caused an increase in tumorigenesis after 6 months of tamoxifen treatment; 50% of these mice were tumor free at 18 months of age. These data demonstrate the efficacy of tamoxifen to suppress mouse mammary tumorigenesis and demonstrate that continuous tamoxifen therapy is necessary to prevent the development of tumors by progesterone, a stimulatory hormone.

Animals↗
PubMed1991

Antiestrogen therapy for breast cancer: current strategies and potential causes for therapeutic failure.

There is an enormous literature that supports the use of tamoxifen as the treatment of choice for breast cancer. However, preliminary evidence suggests that long-term treatment with tamoxifen may expose the women to an increased risk of liver and endometrial cancer. This is probably only of concern to young women with stage I (node negative) disease. It remains to be seen whether any of the new strategies, including the new antiestrogens discussed here and novel endocrine therapies, will prove any better as an antitumor treatment. Treatments will probably be directed initially at treating patients after tamoxifen failure and ultimately at treating hormone-independent cancers. These therapies may involve the autocrine growth factors produced by breast cancer cells as potential targets. Such development of novel treatments will be extremely beneficial to these women, who face a worrying lack of therapeutic opportunities, with the exception of chemotherapy.

Breast Neoplasms↗
PubMed1991

Chemosuppression of breast cancer with long-term tamoxifen therapy.

The pharmacology of the antiestrogen tamoxifen is reviewed. The drug is currently used extensively in the treatment of all stages of breast cancer and is being considered as a preventive agent for women at high risk for breast cancer. Extensive laboratory studies demonstrate that tamoxifen is a tumoristatic agent in models of mammary carcinogenesis. Any clinical applications must therefore consider long-term (5-10 years) treatment strategies. Tamoxifen prevents rat mammary carcinogenesis. However, the timing of the carcinogenic insult is unknown among women. Tamoxifen must be considered to be a chemosuppressive agent to prevent the appearance of the primary tumor rather than to prevent the initial carcinogenic insult.

Animals↗