Regulation of breast cancer growth by insulin-like growth factors

The IGFs may be important autocrine, paracrine or endocrine growth factors for human breast cancer. IGF-I and II stimulate growth of cultured human breast cancer cells. IGF-I is slightly more potent, paralleling its higher affinity for the IGF-I receptor. Antibody blockade of the IGF-I receptor inhibits growth stimulation induced by both IGFs, suggesting that this receptor mediates the growth effects of both peptides. However, IGF-I receptor blockade does not inhibit estrogen (E2)-induced growth suggesting that secreted IGFs are not the major mediators of E2 action. Several breast cancer cell lines express IGF-II mRNA by both Northern analysis and RNase protection assay. IGF-II activity is found in conditioned medium by radioimmuno and radioreceptor assay, after removal of somatomedin binding proteins (BP) which are secreted in abundance. IGF-I is undetectable. BPs of congruent to 25 and 40 K predominate in ER-negative cell lines while BPs of 36 K predominate in ER-positive cells. Blockade of the IGF-I receptor inhibits anchorage-independent and monolayer growth in serum of a panel of breast cancer cell lines. Growth of one line (MDA-231) was also inhibited in vivo by receptor antibody treatment of nude mice. The antibody had no effect on growth of MCF-7 tumors. These data suggest that IGFs are important regulators of breast cancer cell proliferation and that antagonism of this pathway may offer a new treatment strategy.

Insulin-like growth factor binding protein secretion by breast carcinoma cell lines: correlation with estrogen receptor status

Breast tumor cell lines have been shown to secrete several distinct polypeptide growth factors, although conflicting results exist for the insulin-like growth factors (IGFs). In contrast a limited number of breast tumor cell lines have definitely been shown to secrete the high affinity IGF binding proteins (IGFBPs) that modify IGF actions. To characterize the types of IGFBPs that are secreted by breast tumor cell lines, conditioned medium was collected from seven separate tumor cell lines, three of which were estrogen receptor (ER) negative, and four of which were ER positive. All three of the ER negative cell lines, MDA-231, MDA-330, and HS578T, secreted binding proteins of 49,000 and 43,000 Mr (IGFBP-3) as well as 29,000 (IGFBP-1) and 24,000 Mr. In contrast, all four ER positive cell lines secreted 34,000 (IGFBP-2) or 24,000 Mr forms, and none secreted the 49,000 and 43,000 or 29,000 Mr forms. BT-20, a cell line that is positive for ER messenger RNA (mRNA) but negative for ER protein, secreted predominantly a 34,000 Mr protein. The amount of total IGFBP activity released in 24 h ranged between 0.4 and 5.6 nM equivalents of IGFBP-1, and there was no significant difference between the ER positive and negative cell lines. The MCF-7 cells that produced predominantly 34,000 and 24,000 Mr forms showed a 1.8-fold increase in IGFBP secretion after estrogen stimulation. Immunoblotting and a specific RIA for IGFBP-1 showed that only the ER negative lines MDA-330, MDA-231, and HS578T secreted this form. Northern blotting analysis for the mRNA encoding this protein showed that both MDA-330 and MDA-231 contained a single 1.6 kilobase mRNA species that hybridized with an IGFBP-1 complementary DNA (cDNA) probe. Immunoblotting analysis of the other cell lines showed that only the 34,000 Mr form secreted by the ER positive cell lines reacted with IGFBP-2 antisera. Exposure of the conditioned media from the three ER negative cell lines to N-glycanase revealed that the 49,000 and 43,000 Mr forms of IGFBP were glycosylated and therefore probably represent IGFBP-3. We conclude that ER negative cell lines secrete three forms of IGFBPs, IGFBP-1, IGFBP-3, and a 24,000 Mr form. In contrast, the ER positive cell lines secrete predominantly IGFBP-2 and the 24,000 Mr form but do not secrete IGFBP-3 or 1.(ABSTRACT TRUNCATED AT 400 WORDS)

Combined versus sequential chemo-endocrine therapy in advanced prostate cancer: final results of a randomized Southwest Oncology Group study

Cytotoxic chemotherapy has not provided survival benefit in metastatic prostate cancer, although it has been used most frequently in patients with far-advanced, refractory disease. To evaluate the effects of chemotherapy given earlier in the course of the disease, the Southwest Oncology Group (SWOG) performed a randomized trial between September 1982 and October 1986 comparing endocrine therapy (diethylstilbestrol [DES] or orchiectomy) alone followed by cyclophosphamide-Adriamycin (doxorubicin; Adria Laboratories, Columbus, OH) chemotherapy at progression versus initial combined chemo-endocrine therapy. One hundred forty-three patients were registered, and only six were declared ineligible. Patients on the combined chemo-endocrine therapy arm had a slightly higher response rate (63%) compared with endocrine therapy alone (48%). A log-linear model of tumor response and treatment arm adjusted for the stratification factors favored the combination arm (P = .059). Only three of 27 patients on the endocrine therapy alone arm had an objective partial response when crossed over to chemotherapy, while two others had stable disease. Despite the difference in initial response rate, time to treatment failure and survival were identical in the two treatment arms. Seventy-seven percent of patients on the initial endocrine therapy alone arm have died (median survival, 25.6 months) compared with 78% on the chemo-endocrine therapy arm (median survival, 22.0 months). No significant effect of treatment on survival was observed even after adjustment for the stratification variables in a Cox regression model. Exploratory survival analyses with patients on both arms combined did show a marginally significant time to treatment failure and survival advantage for patients treated with DES rather than orchiectomy as initial endocrine therapy. Eighty-six percent of patients treated by orchiectomy have died compared with only 65% of those treated with DES. These data do not support the addition of cytotoxic chemotherapy to initial endocrine therapy in patients with metastatic prostate cancer.

Autocrine and paracrine growth regulation of breast cancer: clinical implications

Research using experimental models of human breast cancer has broadened our understanding of the possible biochemical pathways regulating breast cancer growth. Breast cancer cells express receptors for and respond to a variety of steroid and polypeptide hormones and growth factors. Specific oncogenes are also expressed in breast cancer cells, and levels of expression may relate to tumor growth and aggressiveness. Recent studies have shown that breast cancer cells can even synthesize and secrete various growth factors that could stimulate tumor growth through autocrine and/or paracrine mechanisms. Secretion of some of these growth factors is regulated by estrogen, providing a possible mechanism for estrogen induced growth. Knowledge of these growth regulatory pathways has potentially important clinical implications. Blockade of these pathways offers new possible treatment strategies, much as antiestrogens have been used to inhibit tumor growth. Quantification of the expression of certain oncogenes, growth factor receptors, or the growth factors themselves, may provide prognostic information for the individual patient. Finally, it is plausible that measurement of these tumor products in body fluids might provide tumor markers that are useful in the diagnosis and treatment of breast cancer.

Prognostic factors in breast cancer

A variety of tumor characteristics can provide prognostic information useful in managing the patient with primary breast cancer. Some of these characteristics are firmly established, whereas others are observer dependent or require prospective validation. No single characteristic, however, is likely to fully define which patient with primary breast cancer is destined to relapse. This clinical dilemma--recognition of the high-risk patient--is particularly important in the management of women with node-negative breast cancer. Because most women with this early stage of disease will be cured by surgery alone, the use of adjuvant chemotherapy must be limited to high-risk subsets. Tumor size and ER status are established prognostic factors. Histologic and nuclear grade may be important, but problems of interobserver variability remain. Some studies have shown that aneuploidy or a high S-phase fraction may be independent, high-risk characteristics. Flow cytometric DNA content analysis must be applied with caution, however, because the calculation of S-phase fraction has not been standardized and because the prognostic utility of this approach has not been prospectively confirmed. For now, a prudent approach might be to gather as much prognostic information about each patient's tumor as possible. Those with several of the high-risk characteristics listed in Table 2 should receive strongest consideration for adjuvant treatment. Some of these same prognostic factors, along with several others, can be used to characterize the high-risk node-positive patient. The number of involved axillary nodes is the most important established predictor. Progesterone-receptor status is associated with both disease-free and overall survival, whereas ER status is independently related only to overall survival. Histologic grade, DNA ploidy, and S-phase fraction can also be used to help define the high-risk patient. Finally, tumors that amplify or overexpress the HER-2 gene may have a higher risk of relapse, although this finding has been questioned. Management of patients with breast cancer requires an individualized approach that is based on a careful weighing of a variety of prognostic considerations. The relative importance of these factors will require further large-scale, prospective, multiparameter studies. Although results from such studies are awaited, an understanding of the clinical heterogeneity of breast cancer must be based on a multiplicity of observations, each of which characterizes, in a limited way, the biology of this disease.

Growth inhibition of human breast cancer cells in vitro with an antibody against the type I somatomedin receptor

Insulin and insulin-like growth factors (IGFs) stimulate the growth of human breast cancer cells in vitro. The type I somatomedin receptor (SR), expressed in these cells, may mediate the mitogenic effects of these peptides. We have examined the effect of type I SR blockade on human breast cancer growth with a monoclonal antibody (alpha-IR3) that blocks the receptor binding domain. alpha-IR3 inhibited binding of 125I-IGF-I in all breast cancer cell lines tested. Binding affinity of alpha-IR3 was 2 to 5 times higher than that of IGF-I in MDA-231 (Kd 2.1 nM) and MCF-7 cells (Kd 0.6 nM), respectively. In the presence of 10% calf serum, the antibody inhibited anchorage-independent growth of six of seven breast cancer cell lines. This inhibition was reversible with excess IGF-I. In serum-free medium, alpha-IR3 blocked IGF-I-stimulated DNA synthesis in four of four breast cancer cell lines (MCF-7, ZR75-1, MDA-231, and HS578T). However, the antibody did not inhibit basal growth of any of the breast cancer cell lines in serum-free conditions. In three estrogen receptor-positive, estrogen-responsive breast cancer cell lines (MCF-7, ZR75-1, and T47D), type I SR blockade with alpha-IR3 failed to block estrogen-stimulated DNA synthesis or cell proliferation, indicating that secreted IGF activity is not the sole mediator of the growth effects of estrogen. In conclusion, antibody-mediated type I SR blockade does not inhibit basal growth of breast cancer cells under serum-free conditions, arguing against a critical autocrine role of endogenously secreted IGF activity in vitro. However, type I SR blockade inhibits breast cancer cell growth in the presence of serum, suggesting that serum IGFs might be critical endocrine or paracrine regulators of human breast cancer.

Insulin-like growth factor-II (IGF-II): a potential autocrine/paracrine growth factor for human breast cancer acting via the IGF-I receptor

Insulin-like growth factor-II (IGF-II) is a potent mitogen for several types of cultured cells and tissues. We have studied the interaction of IGF-II with a panel of cultured human breast cancer cell lines, examining the possibility that these cells synthesize and secrete IGF-II activity which could have autocrine/paracrine functions. Synthetic IGF-II was mitogenic in five of seven cell lines tested, including the estrogen receptor-positive lines MCF-7L, ZR75-1, and T47D and the estrogen receptor (ER)-negative lines Hs578T and MDA-231. IGF-II was slightly less potent than IGF-I in stimulating DNA synthesis in MCF-71 cells, an effect that paralleled its ability to compete for [125I]IGF-I binding in these cells. Affinity labeling studies revealed that IGF-II could also compete for binding to the 130,000 mol wt alpha-subunit of the IGF-I receptor. A monoclonal antibody to the IGF-I receptor inhibited the mitogenic effects of IGF-II in MCF-7L and MDA-231 cells, suggesting that this receptor mediates the growth effects of IGF-II in these breast cancer cells. Using a RIA and a RRA, IGF-II-like activity was detected in conditioned medium extracts processed to remove IGF-binding proteins from several breast cancer cell lines, with the highest levels found in conditioned medium from MCF-7L and T47D cell lines. IGF-II mRNA transcripts in MCF-7L and T47D cells were identified by Northern blot analysis and were confirmed by RNase protection assay. IGF-II mRNA was increased by estrogen in MCF-7L cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Blockade of the type I somatomedin receptor inhibits growth of human breast cancer cells in athymic mice

Insulin and insulin-like growth factors (IGIs) stimulate the growth of human breast cancer cells in vitro. The type I somatomedin receptor (SR) expressed in these cells may mediate the growth effects of these peptides. We have examined the role of this receptor on human breast cancer growth with a monoclonal antibody (alpha-IR-3) that blocks the receptor binding domain and inhibits IGF-I-induced growth. alpha-IR-3 inhibited clonal growth in vitro and blocked the mitogenic effect of exogenous IGF-I in both MCF-7 and MDA-231 breast cancer cell lines. Antibody-induced blockade of the type I SR also inhibited the estrogen-independent MDA-231 cells growing in vivo in nude mice, but growth of the estrogen-dependent MCF-7 cells was unaffected. IGIs are important growth regulators of MDA-231 breast cancer cells. Blockade of this growth stimulatory pathway may provide a new treatment strategy.

Megestrol acetate in breast cancer--a panel discussion

Physicians have been using hormonal manipulation to treat advanced breast cancer for almost a century. Surgical ablation of the ovaries, adrenals, and pituitary glands has achieved remarkable tumor regression in sensitive patients. Alternatively, large doses of estrogens, progestins, and androgens have achieved similar results. More recently, the emergence of new therapies, such as antiestrogens, LHRH agonists, and chemical blockade of adrenal steroid biosynthesis offer additional choices. Within limits, all of these therapies are equally effective in sensitive patients. The trend at the present time is to select a therapy that will produce a good response with minimal toxicity. Here the participating physicians will discuss one such therapy-Megace (megestrol acetate). They will consider the role of Megace in the treatment of advanced breast cancer along with issues such as toxicity, dose response, etc.

Adjuvant CMFVP versus melphalan for operable breast cancer with positive axillary nodes: 10-year results of a Southwest Oncology Group Study

Four hundred forty-one women with operable breast cancer with histologically positive axillary nodes were randomized to receive either combination cyclophosphamide (60 mg/m2 orally everyday for 1 year); fluorouracil (300 mg/m2 intravenously [IV] weekly for 1 year); methotrexate (15 mg/m2 IV weekly for 1 year); vincristine (0.625 mg/m2 IV for 10 weeks); prednisone (30 mg/m2 orally days 1 to 14, 20 mg/m2 days 15 to 28, 10 mg/m2 days 29 to 42) (CMFVP) or single-agent melphalan (L-PAM) (5 mg/m2 orally every day for 5 days every 6 weeks for 2 years) chemotherapy after a modified or radical mastectomy between January 1975 and February 1978. Patients were stratified according to menopausal status and number of positive nodes (one to three, more than three nodes) before randomization. Seventy-eight patients were ineligible, most (56) because they were registered more than 42 days from surgery. Maximum duration of follow-up is 12 years, with a median of 9.8 years. The treatment arms were balanced with respect to age, menopausal status, and number of positive nodes. Among eligible patients, disease-free survival and survival were superior with CMFVP (P = .002, .005, respectively). At 10 years, 48% of patients treated with CMFVP remain alive and disease-free and 56% remain alive, compared with 35% alive and disease-free and 43% alive on the L-PAM arm. Disease-free survival and survival were significantly better with CMFVP compared with L-PAM only in premenopausal patients and patients with four or more positive nodes. Both regimens were well tolerated, although toxicity was more severe and more frequent with CMFVP. We conclude that after 10 years of follow-up, adjuvant combination chemotherapy with CMFVP is superior to single-agent L-PAM in patients with axillary node-positive primary breast cancer. The major advantage is in premenopausal women and in patients with more than three positive axillary nodes.

Effects of c-myc overexpression on the growth characteristics of MCF-7 human breast cancer cells

Amplification and overexpression of the c-myc protooncogene have been observed in 22 to 32% of primary human breast cancers, yet the exact role of this gene in mammary tumor progression is unclear. We sought to elucidate this role by overexpressing cloned myc genes in the human breast carcinoma cell line MCF-7. We found that augmented myc RNA levels were associated with slower in vitro growth rates, but that estrogen receptor levels, the requirement for estrogen for in vivo growth in castrated athymic nude mice, and sensitivity to the antiestrogen, tamoxifen were not altered. Furthermore, chemosensitivity to the cytotoxic agent, Adriamycin, was not affected. Lastly, overexpression of a transfected myc gene did not suppress endogenous myc levels unlike the findings in lymphoma cells. Thus our data suggest that the effect of augmented myc expression in human breast cancer cells is complex and may not induce more malignant patterns of growth as has been suggested for other human cancers.

Phase II trial of a new biological response modifier (ImuVert) in advanced prostate cancer

ImuVert, a new biological response modifier of bacterial origin, was evaluated in a Phase II trial of patients with metastatic prostate cancer. Sixteen patients with hormone refractory measurable or evaluable disease were treated with ImuVert 1.0 mg subcutaneously once weekly for 5 weeks. After a 1 week rest period, the dose was escalated to 3.0 mg weekly for 5 additional weeks. Eleven patients received the full 10 weeks of therapy. Toxicity consisted of mild transient flu-like symptoms as well as the development of tenderness and induration at injection sites. No patient responded to treatment. ImuVert at this dose and schedule is inactive in advanced prostate cancer.

Antagonism of chemotherapy-induced cytotoxicity for human breast cancer cells by antiestrogens

In a prior National Surgical Adjuvant Breast and Bowel Project (NSABP) adjuvant study, the addition of the antiestrogen tamoxifen to chemotherapy with melphalan and fluorouracil adversely affected survival in several patient subsets, suggesting an antagonistic drug interaction. To investigate this possibility, we studied the interaction of tamoxifen and other antiestrogens with several cytotoxic drugs in cultured human breast cancer cell lines. Clinically relevant concentrations of tamoxifen and melphalan reduced colony survival of estrogen receptor (ER)-positive breast cancer cells when used alone in a colony-forming assay. However, pretreatment of cells with tamoxifen followed by exposure to melphalan resulted in antagonism, with more colonies surviving treatment with the combination than with melphalan alone. Identical effects were seen using several other triphenylethelene antiestrogens. An antagonistic interaction was observed even with a brief preincubation with tamoxifen that had no effect on cell proliferation, indicating that antagonism was not due to tamoxifen's known cell kinetic effects. Tamoxifen even antagonized melphalan cytotoxicity in ER-negative breast cancer cells and in cultured liver cells. An additive drug interaction occurred when melphalan was combined with pharmacologic concentrations of estradiol or medroxyprogesterone acetate, but antagonism was also observed with dexamethasone. Tamoxifen also antagonized the cytotoxicity of fluorouracil in these cells. However, an additive interaction occurred when the antiestrogen was combined with doxorubicin or 4-hydroxy-cyclophosphamide, an alkylating agent that is transported into the cell by a different carrier-mediated mechanism than melphalan. To avoid potential antagonism in the clinic, combinations of tamoxifen with melphalan and/or fluorouracil should be avoided.

Efficacy of adjuvant chemotherapy in high-risk node-negative breast cancer. An intergroup study

We randomly assigned 536 women who had undergone either a modified radical mastectomy or a total mastectomy with low axillary-node dissection for potentially curable breast carcinoma to receive adjuvant chemotherapy or no-treatment observation. The patients were considered at high risk for recurrence because they had either an estrogen-receptor-negative tumor of any size or an estrogen-receptor-positive tumor at least 3 cm in diameter with no histopathological evidence of axillary-node involvement. The chemotherapy consisted of six four-week cycles of cyclophosphamide (100 mg per square meter of body-surface area orally on days 1 through 14), methotrexate (40 mg per square meter intravenously on days 1 and 8), fluorouracil (600 mg per square meter intravenously on days 1 and 8), and prednisone (40 mg per square meter orally on days 1 through 14). Treatments were balanced with respect to patients' characteristics. The analysis included 406 eligible patients who were entered in the study before October 1, 1987. The overall disease-free survival among patients treated with the four-drug regimen was 84 percent, as compared with 69 percent for the control group, at a median follow-up of three years (P = 0.0001). A treatment benefit was also observed in premenopausal and postmenopausal patients as well as in patients with estrogen-receptor-positive or with estrogen-receptor-negative tumors. Severe or life-threatening hematologic toxicity was encountered in 33 percent of the treated patients, with one death. Our results indicate that adjuvant chemotherapy with six cycles of cyclophosphamide, methotrexate, fluorouracil, and prednisone is effective in improving three-year disease-free survival among high-risk patients with axillary-node-negative, operable breast cancer. An analysis of the effect of treatment on survival awaits a longer follow-up.

Tumor and serum tamoxifen concentrations in the athymic nude mouse

The athymic nude mouse has been used as an in vivo model for pharmacologic studies of the antiestrogen, tamoxifen. Serum and tumor tamoxifen and metabolite concentrations were examined during and after 100 and 1000 micrograms/day doses injected s.c. Tamoxifen and tamoxifen metabolites were quantitated by high-performance liquid chromatography. Tamoxifen was detected in tumors after a dose of 100 micrograms/day, although serum concentrations were not detected. At a dose of 1000 micrograms/day, tumor tamoxifen and its active metabolites were detected in high concentrations ranging up to greater than 6 mmol/g tissue. Serum tamoxifen metabolites were not detected at either dose. In summary, high doses of tamoxifen were required in the nude mouse to obtain clinically relevant serum concentrations, and significant tumor levels were achieved at doses that resulted in undetectable serum levels. The relationship between serum tamoxifen concentrations, tumor tamoxifen levels, and the biologic activity of the drug requires further study.

Antitumor activity and murine pharmacokinetics of parenteral acronycine

The lipophilic antitumor alkaloid acronycine (ACRO) was solubilized in the cosolvent system used for etoposide. ACRO in this etoposide diluent (VPD) was found to be cytotoxic (less than or equal to 50% colony formation in soft agar) in fresh human tumors from patients with renal cell cancer, ovarian cancer, uterine cancer, and metastatic tumors of unknown primary. In P-glycoprotein-positive, multidrug-resistant (MDR) cell lines, ACRO in VPD was active in MDR Chinese hamster ovary cells but not against MDR L1210 murine leukemia cells, 8226 human myeloma cells, or human CCRF-CEM lymphoblasts. In mice, ACRO in VPD was active in two solid tumor models and an i.p. MOPC-315 plasmacytoma model. ACRO i.p. in 10% VPD (v/v%) produced significant tumor growth delays in (a) nude mice bearing human MCF-7 breast cancer xenografts and (b) C57BL mice bearing colon 38 tumor. In MOPC-315-bearing mice, a single i.p. ACRO dose of 25 mg/kg was as effective as melphalan (15 mg/kg) at prolonging life span. Finally, ACRO pharmacokinetics was evaluated in mice given single 25-mg/kg doses i.p. or p.o. The oral bioavailability of an ACRO solution in VPD was only 50% but both i.p. and p.o. regimens achieved plasma levels greater than 1.0 micrograms/ml. The plasma half-life was just under 2 h. These results show that parenteral ACRO in VPD comprises a cytotoxic antitumor agent with improved bioavailability over p.o. administration. ACRO is active in vitro against several human solid tumors but is cross-resistant in 3 of 4 MDR tumor cell lines. The prior clinical activity of p.o. ACRO in myeloma and the new results in MOPC-315 plasmacytomas in mice suggest that ACRO in VPD could have activity against human multiple myeloma.

Pain control in breast cancer. A panel discussion

Pain can be a prominent finding in breast cancer patients. It may occur in the setting of the postmastectomy period, related to the disruption of normal neural pathways or the development of lymphedema. In advanced disease, the management of pain from nerve compression or bone metastases requires special approaches. In this panel discussion, the participating physicians will discuss these topics and provide an up-to-date approach to pain control in breast cancer patients.

Therapy in premenopausal women with advanced, oestrogen positive or/and progesterone positive breast cancer: surgical oophorectomy versus the LHRH analogue, Zoladex

The basis and design of a trial that will compare surgical oophorectomy with the LHRH analogue, Zoladex, in the treatment of premenopausal women with advanced, oestrogen receptor-positive or progesterone receptor-positive breast cancer, is described.

Cell proliferative indices and DNA content as prognostic factors in primary breast cancer

Cumulative data from several studies suggest that indices of cell proliferation, including tritiated thymidine labelling index, S-phase fraction and DNA ploidy are among the most powerful prognostic factors in patients with breast cancer. If the prospective trials currently in progress confirm these findings, then DNA flow cytometry may become standard in the management of breast cancer patients, particularly in selecting those node-negative patients who have a relatively high risk of relapse and who may benefit from adjuvant systemic therapy.

Adjuvant treatment of node-negative breast cancer

About half of all breast cancer patients do not have axillary nodal involvement at the time of diagnosis, and this fraction will become even larger as more women participate in screening mammography programs. Recently completed trails of limited surgery have changed the primary management of node-negative disease for many women. Now, early results from a number of carefully controlled clinical trails suggest ways in which the approach to adjuvant treatment of this disease can be improved.