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Biomedical subjects

V C Jordan

Publications and source records attributed to V C Jordan.

At least 217 records · Page 12Linked to original sources
PubMed1990

Tamoxifen metabolites in patients on long-term adjuvant therapy for breast cancer.

Serum concentrations of tamoxifen, 4-OH-tamoxifen, N-desmethyltamoxifen, and metabolites E and Y were assayed to assess the variation of tamoxifen-metabolism during short-term and long-term endocrine treatment for breast cancer. Once steady-state was achieved, serum levels of tamoxifen and its metabolites in individual patients were stable in the short (10 weeks) and long term (over 7 years) (coefficient of variation [CV], 10-15%), but the variation between individuals (CV 50-70%) was high. Serum tamoxifen and N-desmethyltamoxifen levels were not correlated with indices of obesity. Thus this does not explain the large variation between individuals. In addition to the metabolites that were measured, 4-hydroxy-N-desmethyltamoxifen was tentatively identified in patients' serum. Overall, this study demonstrated that the metabolites of tamoxifen are stable (i.e. no metabolic tolerance) for up to 10 years of drug administration.

Breast Neoplasms↗
PubMed1990

Adjuvant antiestrogen therapy for breast cancer. Past, present, and future.

Laboratory investigations using animal models of breast cancer growth have indicated that the antiestrogenic compound tamoxifen is a tumoristatic agent. It is therefore effective in suppressing, rather than destroying, the breast tumor. Its use as an adjuvant in breast cancer management has been successful, with a proportion of women benefiting from long periods of tamoxifen treatment. All the initial studies recruited postmenopausal women, but tamoxifen is now proposed for the treatment of premenopausal women for an extended time. Naturally, there are many aspects of the toxicology of tamoxifen to consider; however, careful monitoring of clinical trials will determine the safety of the drug for the general patient population.

Animals↗
PubMed1990

Structure-function relationships of hydroxylated metabolites of tamoxifen that control the proliferation of estrogen-responsive T47D breast cancer cells in vitro.

Several hydroxylated derivatives of tamoxifen were tested for their effects on the growth of T47D human breast cancer cells in vitro. Compounds containing a fused seven-membered ring were used to prevent isomerization of the triphenyl-ethylenes at the double bond. This stable structure permitted the determination of the activity of the cis and trans forms of tamoxifen and the true activity of two of its metabolites, 4-hydroxytamoxifen and metabolite E. Estradiol stimulates the growth of T47D cells 3-4-fold over control after 6 days of treatment (EC50 = congruent to 3 x 10(-12) to 3 x 10(-11) M, depending upon the particular experiment). The fixed ring form of the trans isomer of tamoxifen is an antiestrogen, whereas the cis isomer is estrogenic. Fixed ring-trans-4-hydroxytamoxifen is a potent antiestrogen, and its cis isomer is a weak antiestrogen (IC50 congruent to 4 x 10(-8) to 2 x 10(-7) M). The fixed ring form of trans-metabolite E (tamoxifen without the dimethylaminoethane side chain) is only a weak partial estrogen agonist, whereas the fixed ring derivative of its cis isomer is a potent estrogen agonist (EC50 congruent to 4 x 10(-12) to 1 x 10(-11) M). These studies have determined the true biological activities of the hydroxylated derivatives of tamoxifen. This information will be valuable for the development of drug receptor models and will be particularly useful when the three-dimensional structure of the receptor complex is determined.

Breast Neoplasms↗
PubMed1989

Enhanced growth of an estrogen receptor-negative endometrial adenocarcinoma by estradiol in athymic mice.

The aim of this study was to investigate the effects of estradiol and tamoxifen (TAM) on the growth of human endometrial carcinomas in athymic mice. Tissues from primary tumors were implanted into estradiol-treated mice. In passage 2, animals were treated with (a) placebo, (b) estradiol, (c) estradiol plus TAM, and (d) TAM alone. The size of the tumors was measured weekly. Estrogen receptors (ER) were determined with the dextran-coated charcoal method and/or ER enzyme-linked immunoassay. Progesterone receptors were measured with the dextran-coated charcoal technique. Of 16 primary tumors, 2 grew in the athymic mice and were studied further. Tumor EL was positive for ER (145 fmol/mg protein) and progesterone receptors (993 fmol/mg protein). Tumor EL in passage 2 was not significantly stimulated by estradiol, but was stimulated by a combination of estradiol and TAM. Treatments (estradiol, estradiol plus TAM, or TAM) all increased tumor growth in passage 3. Tumor BR and a metastasis BR-MET were ER and progesterone receptor negative, applying dextran-coated charcoal, ER enzyme-linked immunoassay, and immunocytochemistry. The BR and BR-MET cells contain the complete ER gene but do not express any measurable amounts of ER mRNA as quantitated by Northern blot analysis, using a complete ER complementary DNA probe. In all animal passages the growth rate was significantly higher in estradiol-treated mice compared with the control. TAM alone had some growth stimulatory effect, but much smaller than observed in the estradiol group. TAM inhibited estradiol-stimulated growth. These results suggest that estradiol and possibly TAM are capable of stimulating tumor growth in the athymic mice independently from ER, potentially through a host-mediated mechanism.

Adenocarcinoma↗
PubMed1989

Differential ability of antiestrogens to stimulate breast cancer cell (MCF-7) growth in vivo and in vitro.

We have previously described an MCF-7 breast cancer cell variant, MCF-7TAM, which is stimulated to grow in athymic mice by tamoxifen (TAM) (M. M. Gottardis and V. C. Jordan, Cancer Res., 48:5183-5187, 1988). Earlier experiments have shown that TAM exhibits some profound estrogen-like effects in mice whereas TAM is less estrogenic in the rat. The aim in these studies was to compare the ability of MCF-7TAM to grow in different host environments and to determine whether the TAM-stimulated phenotype could be maintained in vitro. Ovariectomized athymic mice and rats were implanted with 1-mm3 pieces of MCF-7TAM tumor and treated with estradiol, TAM, or control silastic capsules. After 9 weeks of growth in either species, TAM or estradiol-treated groups both had sustained growth of MCF-7TAM compared with the control groups. To determine the effects of estradiol and TAM on immune function in athymic mice, splenocytes from treated or control athymic mice, challenged with poly(I:C), were assayed for natural killer (NK) cell activity against 51Cr-labeled YAC1 target cells. Both estradiol and TAM abolished lytic activity by 12 weeks of treatment. To evaluate the role of a decrease in NK-cell activity in the host on growth of MCF-7TAM xenografts we compared the growth effects in athymic and NK-cell deficient, ovariectomized beige mice. TAM stimulated MCF-7TAM in both beige and athymic mice; however, the tumor grew more rapidly in control beige mice than in control athymic mice. This study demonstrated that TAM-stimulated growth could occur in vivo. However, TAM or 4-hydroxytamoxifen did not cause a stimulation of MCF-7TAM compared with wild-type MCF-7 cells when experiments were conducted in vitro. These studies demonstrate that a suppression immune function can facilitate the growth of MCF-7TAM in athymic animals. However, additional components of the host environment contribute to TAM-stimulated growth in vivo.

Animals↗
PubMed1989

Inhibition of tamoxifen-stimulated growth of an MCF-7 tumor variant in athymic mice by novel steroidal antiestrogens.

This investigation examines the tamoxifen (TAM)-dependent growth in vivo of an MCF-7 tumor variant, MCF-7TAM, previously reported in this journal (M. M. Gottardis and V. C. Jordan, Cancer Res., 48: 5183-5187, 1988). Ovariectomized athymic mice were implanted with 1-mm3 pieces of MCF-7TAM and were treated with Silastic capsules of varying sizes containing TAM to demonstrate dose-dependent growth over a 10-wk experiment. TAM was necessary to maintain tumor growth. Animals whose capsules were removed at 6 wk showed complete tumor stasis after 20 wk of observation. Removal of TAM after 11 wk caused the rate of tumor growth to decrease compared with TAM-treated animals. Tumor areas were significantly different (P less than 0.03) at Wk 20. The growth of TAM-stimulated tumor, MCF-7TAM, was inhibited by the novel steroidal antiestrogens, ICI 164,384 and RU 39,411. TAM-stimulated growth (0.5-cm Silastic capsule) was maintained at control levels by 8 wk of treatment with ICI 164,384 (1 mg s.c. every other day). ICI 164,384 alone had no stimulatory activity. At the same dose, RU 39,411 inhibited TAM-stimulated growth of MCF-7TAM, although not to control levels. RU 39,411 was slightly stimulatory when administered alone. The growth of MCF-7TAM was stimulated by either TAM or 17 beta-estradiol. The antiestrogen, RU 39,411, effectively inhibited estradiol-stimulated tumor growth. Overall, these studies confirm and extend the previous observation on TAM-stimulated growth of breast cancer cells in vivo and demonstrate the possibility of developing novel antiestrogens to prevent this form of drug resistance should it occur in the clinic.

Animals↗
PubMed1989

Effects of type I and II interferons on cultured human breast cells: interaction with estrogen receptors and with tamoxifen.

The combined effects of tamoxifen, a competitive inhibitor of estrogen, and type I or II interferons on the proliferation of several human breast cancer cell lines in vitro were examined. Additive antiproliferative effects were observed with interferons and tamoxifen, in two estrogen receptor positive cell lines, MCF-7 and T-47D. In MCF-7 cells neither beta ser interferon, gamma interferon, nor alpha 6 interferon were able to significantly alter estrogen receptor levels. Antigrowth activities of beta ser interferon and gamma interferon in an estrogen receptor negative cell line, HS578T, were equivalent to those in estrogen receptor-positive cell lines. Consistent with the antiproliferative effects of interferons, high affinity beta ser interferon receptors and interferon inducible 2'5'-oligoadenylate synthetase were present in both MCF-7 and HS578T cell lines. Thus steroid hormone receptor status did not influence the antiproliferative effects of interferons on breast carcinoma cells in vitro.

2',5'-Oligoadenylate Synthetase↗
PubMed1989

Antiestrogenic action of toremifene on hormone-dependent, -independent, and heterogeneous breast tumor growth in the athymic mouse.

The antiestrogen toremifene has been used to study the growth control of hormone-dependent (MCF-7), -independent (MDA-MB-231), or mixed tumor cell populations in athymic mice. Maximal MCF-7 tumor growth was produced in ovariectomized athymic mice by circulating estradiol levels of approximately 200 pg/ml (produced by 0.5-cm silastic capsules implanted s.c.). The antiestrogen toremifene (77 +/- 4 micrograms/day from a 2-cm silastic capsule) inhibited estradiol (0.5-cm capsule)-stimulated growth by more than 70%. No tumor growth was observed in mice treated with toremifene alone, although toremifene acted as a weak partial agonist on the mouse uterus. The growth of hormone-independent MDA-MB-231 breast tumors implanted in athymic mice was not influenced by either estradiol (0.5-cm capsule) or toremifene (2-cm capsule) when administered alone or in combination. Furthermore, even very large doses of toremifene (5 mg/day p.o.) did not alter the rate of MDA-MB-231 tumor growth. Mixtures of MCF-7 and MDA-MB-231 cells in 9:1 and 99:1 ratios inoculated into athymic mice produced tumors which grew in the absence of estradiol but responded to estradiol supplementation (0.5-cm capsule) with a more rapid rate of tumor growth. Tumors grown from inoculated MCF-7:MDA-MB-231 cells (99:1 ratio) in the presence of estradiol had estrogen receptor levels of 33.2 +/- 9.2 fmol/mg of protein at Day 44 compared to 84.8 +/- 4.8 fmol/mg of protein in pure MCF-7 tumors. Toremifene (2-cm capsule) treatment inhibited the estrogen stimulation of these mixed tumors (99:1 starting ratio) to that of toremifene alone. However, toremifene-alone treatment produced a more rapid rate of tumor growth than control or tumors grown from irradiated MCF-7 cells mixed with viable MDA-MB-231 cells. Increasing the ratio of MCF-7:MDA-MB-231 cells (999:1) initially inoculated resulted in tumors which developed less rapidly than the lower ratio (99:1). Toremifene (2-cm capsule) again produced partial inhibition of 17 beta-estradiol-stimulated tumor growth while increasing tumor growth above control when the antiestrogen was administered alone. These results demonstrate that toremifene is effective in inhibiting estrogen stimulation of hormone-dependent tumors and partially successful at controlling mixed hormone-dependent/independent tumors; however, the antiestrogen cannot control the growth of a hormone-independent tumor in this model.

Animals↗
PubMed1989

Decrease in estradiol-stimulated progesterone receptor production in MCF-7 cells by epidermal growth factor and possible clinical implication for paracrine-regulated breast cancer growth.

These studies have evaluated the modulation by epidermal growth factor (EGF) of estrogen receptor (ER) levels and estradiol-stimulated progesterone receptor (PgR) synthesis. Short-term culture of MCF-7 cells in an "estrogen (phenol red indicator)-free" environment caused a rise in ER concentration that is inhibited by EGF at 10(-8) M and 10(-7) M. Estradiol at 10(-10) M induced a 5-fold increase of PgR over a 5-day assay period. However, the rise in PgR was diminished or prevented by increasing concentrations of EGF (10(-9) M to 10(-7) M). Similarly, the concentration-related rise in PgR caused by estradiol (10(-13) M to 10(-9) M) was abolished after a 7-day pretreatment with EGF (10(-7) M). For both the ER and PgR receptor, EGF treatment caused a decrease in receptor number without an apparent change in receptor affinity. Thus, EGF appears to down regulate the ER by approximately 50% and to diminish the ability of estradiol to induce PgR. In addition, a survey of ER+PgR+ and ER+PgR- values of primary breast tumors from women between the ages of 55 and 70 demonstrated significantly less (50%) (85 to 39 fmol/mg of cytosol protein) ER in ER+PgR- tumors (P = 0.0005). The median PgR values for the PgR-positive tumors were 139 fmol/mg of cytosol protein. We propose that ER+ breast cancer that has changed to a paracrine growth factor-driven system (from stromal cells or ER- breast cancer cells) is less responsive to gonadal steroids. The loss of PgR in these ER+ carcinomas may be an indicator of this type of hormone independence.

Breast Neoplasms↗
PubMed1989

Immune-deficient animals to study "hormone-dependent" breast and endometrial cancer.

Athymic (nu/nu) mice are T cell deficient and can accept xenografts of human tumor material. Hormone-dependent tumor growth can be demonstrated in ovariectomized athymic mice by estrogen administration. Estrogen receptor (ER) positive MCF-7 breast cancer cells implanted into the axillary mammary fat do not grow into palpable tumors unless sustained release preparations of estrogen are administered. The non-steroidal antiestrogen tamoxifen, though it exhibits estrogenic properties in the mouse, does not facilitate MCF-7 tumor growth (during short term, i.e. 8 weeks of therapy) and can prevent estradiol-stimulated growth. In contrast, ER negative MDA-MB-231 cells grow with or without estrogen administration and tamoxifen does not control tumor growth. These statements reflect current dogma concerning the value of athymic mice to confirm the hormone dependent growth of cancer cells in vivo. Our aim has been to define the limits of this dogma and to investigate the growth relationship of hormone-dependent and independent cells with their host environment. The potential endocrine or paracine effect of ER negative tumors on the growth of ER positive tumors was evaluated by transplantation on opposite sides of athymic mice or by the inoculation of different ratios of ER positive/negative cells (MCF-7:MDA-MB-231 9:1, 99:1, 999:1). MCF-7 cells could not be encouraged to grow by a rapidly growing MDA-MB-231 tumor on the opposite side of the animal. Similarly ER negative tumors grew out of the mixed tumor inoculates suggesting that ER positive tumors could not be encouraged to grow preferentially by the paracrine influences of ER negative cells. However, estrogen facilitates the growth of an ER positive tumor following inoculation of mixed cell populations. Antiestrogen treatment can blunt estrogen-stimulated growth but cannot control the growth of ER positive/negative containing tumors. ER positive endometrial tumors grow in response to estrogen treatment and some (EnCa101) have been shown to grow in response to tamoxifen or a combination of tamoxifen and estrogen. More unusual though is our recent observation that an ER negative primary endometrial tumor (BR) and its metastasis (BR-MET) grow more rapidly in estrogen-treated athymic mice. This finding seems to have far-ranging consequences for our view of hormone-dependent growth. Either our view of estrogen-stimulated growth needs to be modified or the host is specifically altered during estrogen treatment. We have taken the position that since natural killer cells (present in athymic mice) can be lowered by estrogen this may result in an increased tumor cell survival in the heterotransplant model.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Structural components necessary for the antiestrogenic activity of tamoxifen.

The biological activities of tamoxifen derivatives that contain various side chain alterations were studied using a T47D breast cancer cell growth assay in vitro. We studied the activity of various analogs to determine the important aspects of side chain composition and aryl ring positioning on antiestrogenic activity. Previous studies utilizing a rat pituitary cell prolactin synthesis assay have shown that substitution of the aminoethoxy side chain for an allyl side chain resulted in agonist activity, whereas the addition of a glyceryl side chain produced antiestrogenic activity. In the present study utilizing T47D cells, compounds with alkyl or allyl substitutions were partial agonists, as were compounds with bulky para-substituted benzyl group constituents. A tamoxifen derivative with a side chain containing an ethyl ester was antiestrogenic (IC50 = 2 x 10(-6) M) and effectively inhibited estradiol (10(-10) M) stimulation of growth. However, a compound with a short similar methyl ester-containing side chain did not possess any activity. Compounds with carbinol-containing side chains were antiestrogenic (IC50 = 2.8-3.5 x 10(-7) M). All of the compounds displaying antiestrogenic activity could be "rescued" by incubation with estradiol (10(-8) M) and therefore were not nonspecifically toxic to the cells. These results support the hypothesis that the presence of a lone pair of electrons within the side chain region of tamoxifen may be required for antiestrogenic activity. Also, nonplanar placement of the aryl ring of the triphenylethylene-type of compound is critical for potency.

Breast Neoplasms↗