Recombinant human interferon alpha increases oestrogen receptor expression in human breast cancer cells (ZR-75-1) and sensitizes them to the anti-proliferative effects of tamoxifen

Effects of natural beta-interferon and recombinant alpha-2B-interferon on proliferation, glucocorticoid receptor content, and antigen expression in cultured HL-60 cells

In the current study, we investigated the effects of natural beta-interferon (beta-IFN) and recombinant alpha-2b-interferon (alpha-IFN) on the growth of the HL-60 cell line. Cells cultured in a medium that contains various concentrations (from 10 to 1000 IU/ml) of interferons showed a growth inhibition, which reaches the maximum after a 6-day treatment, at the highest dose used. Furthermore, we studied the effect of both beta-IFN and alpha-IFN on the level of glucocorticoid receptors. This was enhanced more than 30% with respect to control in HL-60 cells exposed for 24 hours to concentrations of beta-IFN that ranged from 100 to 1000 IU/ml. The increase of the receptor amount was seen even if cells were treated for 5 days, and was not accompanied by a modification of antigen expression of HL-60 cells. alpha-IFN did not modify the glucocorticoid receptor level substantially in our experimental conditions. Our data indicate that both beta-IFN and alpha-IFN regulate HL-60 cell proliferation. Additional studies are required to clarify if modifications of the receptor level induced by beta-IFN could be related to the modulation of hormone-sensitivity in this model.

Inhibition of hormone-dependent and independent breast cancer cell growth in vivo and in vitro with the antiestrogen toremifene and recombinant human interferon-alpha 2

The antiproliferative action of the antiestrogen toremifene and recombinant human interferon-alpha 2a (IFN-alpha 2a) were examined on human breast cancer cell lines grown in culture and in the athymic mouse. Solid tumors grew from an inoculation of a 99:1 ratio of hormone dependent (MCF-7) and hormone independent (MDA-MB-231) breast cancer cells without estrogen administration. However, estradiol supplementation significantly increased the rate of tumor growth. The daily administration of 1.35 x 10(6) U of recombinant human IFN-alpha 2a resulted in a marked rduction of tumor growth in both estradiol-treated and non-treated mice. Toremifene administration (130 micrograms/day from a sustained release preparation) markedly inhibited estradiol stimulation of mouse uterine weight and partially reduced estradiol-stimulated tumor growth. The combination of IFN-alpha 2a (1.35 x 10(6) u/day) with toremifene (130 micrograms/day) reduced estradiol-stimulated growth much below that of toremifene alone but not below that seen with interferon alone. Toremifene (10(-10)-10(-6) M) did not inhibit the growth of hormone-independent MDA-MB-231 breast cancer cells in vitro whereas it did inhibit the growth of hormone-dependent MCF-7 cells in phenol red containing media. IFN-alpha 2a (1-10,000 u) inhibited the growth of both MCF-7 and MDA-MB-231 cells in culture; however, MCF-7 cells were approximately 10-fold more sensitive to interferon inhibition. This was consistent with the MCF-7 cells showing a greater sensitivity to interferon than MDA-MB-231 cells in the induction of 2'5'-oligoadenylate synthetase.(ABSTRACT TRUNCATED AT 250 WORDS)

Rationale for combining tamoxifen and interferon in the treatment of advanced breast cancer

Several investigators have discussed the possible combination of tamoxifen and interferon (IFN) in the treatment of breast cancer patients. The rationale in combining these drugs is that IFN induces the expression of estrogen receptors and therefore increases the sensitivity of breast cancer cells toward the growth-inhibitory activity of tamoxifen. In this paper we review the literature on the IFN-mediated expression of estrogen receptors and the postulated synergism of tamoxifen and IFN in the growth inhibition of breast cancer cell lines. Our results indicate that neither type I nor type II IFN increases the expression of estrogen receptors in MCF-7 cells. Together with tamoxifen both type I and type II IFN mediate additive but not synergistic growth inhibition of MCF-7 cells. On the basis of these results it is feasible to test tamoxifen and IFN as combined therapy in breast cancer patients. Preliminary clinical data show that the combination of 30 mg tamoxifen and 2 x 10(6) IU IFN-alpha as daily doses may induce WHO grade 3 leukopenia and thrombopenia in patients who are pretreated with polychemotherapy.

Progression of human breast cancer cells from hormone-dependent to hormone-independent growth both in vitro and in vivo

We have isolated a series of sublines of the hormone-dependent MCF-7 human breast cancer cell line after selection both in vivo and in vitro for growth in the presence of subphysiological concentrations of estrogens. These sublines represent a model system for study of the processes leading to hormonal autonomy. The cells form growing tumors in ovariectomized athymic nude mice in the absence of estrogen supplementation but retain some responsivity to estrogen as determined by stimulation of the rate of tumor growth in vivo and by induction of progesterone receptor. An ovarian-independent but hormone-responsive phenotype may occur early in the natural progression to hormone-independent and unresponsive growth in breast cancer. We observed no change in the affinity or decrease in the level of expression of estrogen receptors and progesterone receptors among the sublines and the parental cells. Epidermal growth factor receptors are not overexpressed in ovarian-independent cells. Thus, altered hormone receptor expression may be a late event in the acquisition of a hormone-independent and unresponsive phenotype. Sublines isolated by in vivo but not in vitro selection are more invasive than the parental cells both in vivo and across an artificial basement membrane in vitro. Thus, as yet unknown tumor-host interactions may be important in the development of an invasive phenotype. Furthermore, acquisition of the ovarian-independent and invasive phenotypes can occur independently.

Characterisation of a tamoxifen-resistant variant of the ZR-75-1 human breast cancer cell line (ZR-75-9a1) and ability of the resistant phenotype

A 6-month exposure of ZR-75-1 human breast cancer cells to tamoxifen (1 microM rising to 2 microM). resulted in a fall in oestrogen receptor (ER) levels from 225 fmol mg protein-1 to 56 fmol mg protein-1 while progesterone receptor (PGR) concentration fell from 63 fmol mg protein-1 to undetectable levels. Sensitivity to the anti-proliferative effects of tamoxifen was unchanged. A further 6 months' exposure to 4 microM tamoxifen resulted in loss of detectable ER and PGR and development of resistance to tamoxifen. Resistant cells, designated ZR-75-9a1, displayed morphological changes consistent with the acquisition of a less well differentiated phenotype. Flow cytometric studies demonstrated that the cell cycle distribution pattern of the resistant variant growing in the presence of 8 microM tamoxifen was identical to that of the untreated parent line, which showed marked accumulation of cells in G0/G1 when exposed to 8 microM tamoxifen. The resistant phenotype was not stable if cells were transferred to complete drug-free medium, but remained stable for at least 3 months in the presence of medium lacking oestrogenic activity. ZR-75-9a1 cells differ from previously reported tamoxifen-resistant variants of the MCF-7 line which retain ER and may prove a valuable model for the study of the development and stability of tamoxifen resistance in human breast cancer.

Rats with mammary cancer treated with toremifene and interferon: morphometry and needle aspiration biopsy for determination of ATP and 14C-fluorodeoxyglucose content

The combined and separate action of the antiestrogen toremifene (TOR) and recombinant rat gamma interferon (RIF) was studied in rat mammary cancer induced by dimethylbenzanthracene (DMBA). The content of ATP and 14C-fluorodeoxyglucose (FDG) was also determined from fine needle aspiration biopsies (FNAB). RIF alone had no antitumor activity, when measured as the average number of new tumors appearing in RIF and control animals (2.4 vs 2.4 new tumors per animal), while TOR and TOR + RIF had a significant effect (1.2, P less than 0.05 and 0.6, P less than 0.01). Morphometrically, there was a significant decrease in the amount of epithelium in the tumors of the RIF + TOR animals (65% vs 82% in the controls, P less than 0.05); there was conversely an increase in the stromal component (25% vs 14%, NS). It appears that an increase of the stromal compartment is part of the healing process. The feasibility of the FNAB-technique was shown by the finding that there was a close correlation between FDG and ATP content in almost all the groups before and after treatment. Thus, FDG and ATP measure the same phenomenon, i.e., energy content. There was a large variation in the contents of ATP and FDG within and among the groups, which invalidated considerations regarding the predictive value of ATP and FDG content in tumors subject to treatment.

Auto-tumor recognition following in vitro induction of MHC antigen expression on solid human tumors: stimulation of lymphocytes and generation of cytotoxicity against the original MHC-antigen-negative tumor cells

Expression of major histocompatibility complex (MHC) class I antigens was induced in eight out of nine freshly prepared tumor cell suspensions by exposure to interferon (IFN gamma) and tumor necrosis factor (TNF alpha) in vitro. The untreated, class-I-antigen-negative, and the treated, antigen-positive, cells of three tumors (one breast carcinoma, one plasmocytoma and one ovarian carcinoma) were compared for the capacity to stimulate autologous and allogeneic blood lymphocytes, to generate auto-tumor cytotoxicity and for sensitivity to the lytic effect induced in autologous mixed lymphocyte tumor cell culture (MLTC). The MHC class I-negative cells did not stimulate, while the cells induced for expression of antigens did. On the other hand, when the autologous cytotoxic cells were generated in the MLTC by the class I antigen-positive tumor cells the class I-negative tumor cells were also damaged. Lysis of the class-I-positive tumor cells was abrogated by the W6/32 monoclonal antibody directed against the monomorphic part of the class I molecules.

Divergent effects of interferons on the growth of human benign prostatic hyperplasia cells in primary culture

Epithelial cells from human benign prostatic hyperplasia tissues were grown in primary cultures for up to 21 days and the effects of interferons on the growth of the cells were investigated. Interferon-alpha (Wellferon) showed growth inhibition both in the presence and in the absence of 3 x 10(-10)M testosterone propionate (TP) whereas interferon-gamma stimulated growth in a dose dependent manner under similar conditions. Interferon-beta had little effect on growth at the dose levels used in the study. The growth inhibition by interferon-alpha can be induced after stimulation of growth is achieved either with TP or with interferon-gamma. Implications of these findings for clinical use of these lymphokines is discussed.

Combined effects of interferon alpha and interleukin 2 on the induction of a vascular leak syndrome in mice

Immunotherapy with interleukin 2 (IL-2) alone or in combination with lymphokine-activated killer cells can mediate tumor regression in mice and in man. Further dose escalation of IL-2 along with lymphokine-activated killer cells has been prevented by the development of a vascular leak syndrome produced by IL-2. Because we have found that interferon alpha (IFN-alpha) or tumor necrosis factor (TNF-alpha) has synergistic antitumor effects when administered together with IL-2, we have tested the vascular leakage induced by these lymphokine combinations. We used a murine model to quantify vascular leakage by measuring the extravasation of 125I-albumin from the intravascular space as well as the wet and dry lung weights after treatment with different cytokines. Cytokines (or Hanks balanced salt solution) were administered to C57BL/6 mice and 4 h after the last injection the vascular leak was quantified. IFN-alpha alone did not cause extravasation of radiolabel or increase in wet lung weights, though when given in combination with IL-2, significantly greater extravasation (P less than 0.01) as well as increase in lung water weights (P less than 0.05) was observed compared to the response in mice treated with IL-2 alone. IFN-alpha in combination with IL-2 induced significant vascular leakage earlier than the response induced by IL-2 alone. For example treatment with IFN-alpha and IL-2 induced accumulation of 14,674 +/- 605 cpm in the lungs at day 1 while IL-2 alone induced 12,340 +/- 251 cpm. The degree of vascular leakage was highly related to the dose of IFN-alpha administered along with IL-2 and increased vascular leak syndrome was evident even at low doses (5000 units) of IFN-alpha. Immunosuppression of mice by pretreatment irradiation (500 rad) markedly decreased the development of vascular leak syndrome induced by IL-2 and IFN-alpha. Interestingly IFN-gamma and TNF-alpha did not induce vascular leakage in the lungs when given alone, and did not add or synergize with IL-2 in causing the syndrome. Thus the administration of IFN-alpha in combination with IL-2 produces a dose-limiting vascular leakage that is more severe than that caused by IL-2 alone, and may be mediated, directly or indirectly by host radiosensitive cells.