New developments in chemotherapy of advanced breast cancer

Anthracyclines and taxanes are the two most active classes of chemotherapy for the treatment of advanced breast cancer. Recent studies have investigated combination therapy including doxorubicin (Dox) and paclitaxel. The efficacy of this combination has been established in a phase III study conducted by ECOG, comparing Dox/paclitaxel versus Dox versus paclitaxel. The combination is superior to Dox or paclitaxel with respect to response rate and time to disease progression, indicating that the combination provides a new standard for the first line treatment of metastatic breast cancer [1]. Phase II studies using higher doses of Dox and using shorter infusions of paclitaxel have suggested the combination can be further optimized; Gianni reported a 94% objective response rate using Dox 60 mg/m2 followed by paclitaxel 175 mg/m2 given over three hours [2]. The more active regimens are associated with enhanced cardiotoxicity; this toxicity can be avoided, however, by limiting the exposure to doxorubicin. The newer regimens have now been moved into phase III studies. Future progress for this disease will depend on the introduction of new agents. Two novel drugs are currently being investigated in randomised phase III trials as potentiators of Dox and/or paclitaxel. One is a monoclonal antibody from Genentech (Herceptin, trastuzumab) directed at the HER-2/neu oncogene, which is overexpressed in > 25% of breast cancers [3]. Recent results indicate that Herceptin in combination with paclitaxel (or with a Dox plus cyclophosphamide regimen) induces a higher response rate (RR) and prolongs the time to disease progression when compared to chemotherapy alone. The second agent N,N-diethyl-2[4-(phenylmethyl)-phenoxy] ethanamine.HCl (DPPE, BMS-217380-01), when combined with Dox, was associated with a higher RR than previously observed with Dox alone [4]. A randomized trial of Dox versus Dox plus DPPE is ongoing. The possible mechanisms underlying chemo-potentiation by these agents are discussed. As new anthracycline/taxane combinations establish themselves in earlier stages of the disease, the need for effective, non-cross resistant salvage regimens will emerge.

Radiopotentiation by the oral platinum agent, JM216: role of repair inhibition

PURPOSE

To test for in vitro radiopotentiation by the orally-administered platinum (IV) complex, JM216; to compare these results to cisplatin and carboplatin; and to investigate whether the mechanism of radiopotentiation involves repair inhibition of radiation-induced DNA damage.

METHODS AND MATERIALS

H460 human lung carcinoma cells were incubated with the drugs for 1 h at 37 degrees C, irradiated at room temperature, and returned to 37 degrees C for 20 min. Cells were then rinsed and colony forming ability was assessed. Wild-type V79 Chinese hamster cells and radiosensitive, DNA repair-deficient mutant cells (XR-V15B) were also studied along with H460 cells. Ku86 cDNA, which encodes part of a protein involved in DNA repair, was transfected into XR-V15B cells as previously described. The effect of JM216 on sublethal damage repair (SLDR) was also assessed using split-dose recovery.

RESULTS

Using equally cytotoxic doses of JM216, cisplatin, and carboplatin, the radiation dose enhancement ratios (DER) were 1.39, 1.31, and 1.20, respectively; the DER with 20 microM JM216 was 1.57. JM216 (20 microM) did not significantly change the final slope of radiation survival curves, but greatly reduced the survival curve shoulder. V79 cells also showed radioenhancement using 20 microM JM216, but no enhancement occurred using XR-V15B cells. Transfection of Ku86 cDNA into XR-V15B cells restored radiopotentiation by JM216 to wild-type V79 levels. In addition, 20 microM JM216 completely inhibited sublethal damage repair in H460 cells.

CONCLUSION

Our results show that JM216 can potentiate the effects of radiation in human lung cancer cells, and that the mechanism of this effect is probably inhibition of DNA repair by JM216.

Phase II and pharmacologic study of docetaxel as initial chemotherapy for metastatic breast cancer

PURPOSE

Because docetaxel (Taxotere, RP 56976; Rhone-Poulenc Rorer, Antony, France) appeared to be active against breast cancer in phase I trials, we performed this phase II study.

PATIENTS AND METHODS

Thirty-seven patients with measurable disease were enrolled. Only prior hormone therapy was allowed, as was adjuvant chemotherapy completed > or = 12 months earlier. Docetaxel 100 mg/m2 was administered over 1 hour every 21 days. Diphenhydramine hydrochloride and/or corticosteroid premedication was added after hypersensitivity-like reactions (HSRs) were seen in two of the first six patients. Pharmacokinetic studies were performed during cycle 1 for correlation with toxicity.

RESULTS

Thirty-seven patients were assessable. Nineteen (51%) required dose reductions, usually for neutropenic fever. The median nadir WBC count was 1.4 x 10(3)/microL. HSRs were noted in 20 patients (54%). At a median cumulative dose of 297 mg/m2 (range, 99.6 to 424.5 mg/m2), 30 patients (81%) developed fluid retention, for which 11 (30%) subsequently stopped treatment. The first-cycle plasma area under the concentration-time curve (AUC) did not correlate with toxicity, although an ineligible patient with hepatic metastases (pretreatment bilirubin level 1.8 mg/dL) had an elevated AUC and died of toxicity. Responses were seen at all sites. On an intent-to-treat basis, there were two (5%) complete responses (CRs) and 18 (49%) partial responses (PRs). The overall response proportion (CRs plus PRs) was 54% (95% confidence interval, 37% to 71%). The median time to response was 12 weeks (range, 3 to 15) and the median duration was 26 weeks (range, 10 to 58+).

CONCLUSION

Docetaxel is active for metastatic breast cancer. Neutropenia and fluid retention are dose-limiting. The AUC did not predict toxicity, but caution is warranted when treating patients with liver dysfunction. An understanding of the pathophysiology of the fluid retention may facilitate prevention. Frequent HSR may warrant prophylactic premedication.

Insulin-like growth factors modulate the growth inhibitory effects of retinoic acid on MCF-7 breast cancer cells

Retinoids are currently being tested for the treatment and prevention of several human cancers, including breast cancer. However, the anti-cancer and growth inhibitory mechanisms of retinoids are not well understood. All-trans retinoic acid (RA) inhibits the growth of the estrogen receptor-positive (ER+) breast cancer cell line, MCF-7, in a reversible and dose-dependent manner. In contrast, insulin-like growth factors (IGF-I, IGF-II) and insulin are potent stimulators of the proliferation of MCF-7 and several other breast cancer cell lines. Pharmacologic doses of RA (> or = 10(-6) M) completely inhibit IGF-I-stimulated MCF-7 cell growth. Published data suggest that the growth inhibitory action of RA on IGF-stimulated cell growth is linear and dose-dependent, similar to RA inhibition of unstimulated or estradiol-stimulated MCF-7 cell growth. Surprisingly, we have found that IGF-I or insulin-stimulated cell growth is increased to a maximum of 132% and 127%, respectively, by cotreatment with 10(-7) M RA, and that 10(-9) - 10(-7) M RA increase cell proliferation compared to IGF-I or insulin alone. MCF-7 cells that stably overexpress IGF-II are also resistant to the growth inhibitory effects of 10(-9) - 10(-7) M RA. Treatment with the IGF-I receptor blocking antibody, alpha IR-3, restores RA-induced growth inhibition of IGF-I-treated or IGF-II-overexpressing MCF-7 cells, indicating that the IGF-I receptor is mediating these effects. IGFs cannot reverse all RA effects since the altered cell culture morphology of RA-treated cells is similar in growth-inhibited cultures and in IGF-II expressing clones that are resistant to RA-induced growth inhibition. These results indicate that RA action on MCF-7 cells is biphasic in the presence of IGF-I or insulin with 10(-9) - 10(-7) M RA enhancing cell proliferation and > or = 10(-6) M RA causing growth inhibition. As IGF-I and IGF-II ligands are frequently detectable in breast tumor tissues, their potential for modulation of RA effects should be considered when evaluating retinoids for use in in vivo experimental studies and for clinical purposes. Additionally, the therapeutic use of inhibitors of IGF action in combination with RA is suggested by these studies.

Herbimycin A induces the 20 S proteasome- and ubiquitin-dependent degradation of receptor tyrosine kinases

Herbimycin A is an ansamycin antibiotic isolated as an agent that reverses morphological transformation induced by v-src. Although herbimycin A is widely used as a tool for inhibiting multiple tyrosine protein kinases and tyrosine kinase-activated signal transduction, its mechanism of action is not well defined and includes a decrease in both tyrosine kinase protein levels and activity (Uehara, Y., Murakami, Y., Sugimoto, Y., and Mizuno, S. (1989) Cancer Res. 49, 780-785). We now show that herbimycin A induces a profound decrease in the total cellular activity of transmembrane tyrosine kinase receptors, such as insulin-like growth factor, insulin, and epidermal growth factor receptors. A substantial proportion of the in vivo inhibition could be explained by an increase in the rate of degradation. The enhanced degradation of insulin-like growth factor-insulin receptor was prevented by inhibitors of the 20S proteasome, whereas neither lysosomotropic agents nor general serine- and cysteine-protease inhibitors were active in preventing receptor degradation induced by herbimycin A. Moreover, in a temperature-sensitive mutant cell line defective in the E1-catalyzed activation of ubiquitin, herbimycin A treatment at the restrictive temperature did not result in the degradation of insulin receptor. These results suggest that herbimycin A represents a novel class of drug that targets the degradation of tyrosine kinases by the 20S proteasome. The ubiquitin dependence of this process indicates that this degradation of tyrosine kinases might involve the 20S proteasome as the proteolytic core of the ubiquitin-dependent 26S protease.

Taxol (paclitaxel) plus recombinant human granulocyte colony-stimulating factor in the treatment of metastatic breast cancer

We treated 28 patients who had no prior chemotherapy for stage IV breast cancer and 51 patients with extensive prior exposure to other chemotherapeutic agents with a 24-hour infusion of Taxol (paclitaxel) as a single agent. Prophylactic recombinant human granulocyte colony-stimulating factor was administered routinely to ameliorate the anticipated dose-limiting toxicity of neutropenia. Nonhematologic toxicity was mild to moderate in most cases. Taxol was more active in patients with chemotherapy-naive stage IV disease, but activity was also observed in extensively treated patients as well. There is a strong clinical suggestion of at least partial noncross-resistance with doxorubicin. Taxol is a very promising agent for the treatment of metastatic breast cancer; its optimal application in this disease will be the subject of future trials.

Insulin and insulin-like growth factor signaling are defective in the MDA MB-468 human breast cancer cell line

Polypeptide growth factors including the insulin-like growth factors (IGFs), insulin, and transforming growth factor-alpha are mitogens for many breast cancer cell lines and may act as regulators of cancer cell growth. In a human breast cancer cell line MCF-7, which expresses IGF-I receptor (IGF-IR), stimulation with insulin or IGFs resulted in autophosphorylation of the IGF-IR in an increased proportion of ras bound to GTP and in the association of phosphatidylinositol 3'-kinase (PI3K) activity and of p85-PI3K with M(r) 185,000 phosphotyrosinylated proteins corresponding in size to insulin/IGF-IR substrates. These events were associated with enhanced proliferation. MDA MB-468 is a human breast cancer cell line which expresses insulin receptor and high levels of epidermal growth factor/transforming growth factor alpha receptor but low levels of IGF-IR. In this cell line, insulin stimulated autophosphorylation of IR at physiological concentrations and promoted the association of PI3K activity and of p85 with phosphotyrosine-containing proteins. Insulin did not, however, induce increased ras.GTP, and the cells exhibited minimal proliferation in response to insulin. Unlike insulin treatment, epidermal growth factor stimulation of MDA MB-468 cells is mitogenic and resulted in increased ras.GTP content, suggesting that the failure of insulin to induce these changes is not due to alterations in these signaling molecules. We conclude that there is a postreceptor defect in insulin signaling in MDA MB-468 which prevents the activation of ras and the induction of mitogenesis. Activation of PI3K by insulin is not sufficient to mediate mitogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Tamoxifen administration is associated with a high rate of treatment-limiting symptoms in male breast cancer patients

BACKGROUND

Although an uncommon disease, male breast cancer (MBC) will be responsible for 300 deaths in 1993 in the United States. Because of the high rate of estrogen receptor positivity in males, adjuvant hormonal therapy with tamoxifen in the adjuvant setting has been used widely. Little is known about the side effects of this estrogen receptor blocker in males.

METHODS

The authors evaluated the side effects of adjuvant tamoxifen treatment in 24 patients (19 of whom were estrogen receptor positive) treated at the authors' institution between 1990 and 1993.

RESULTS

Fifteen (62.5%) patients reported at least one side effect. The most common side effect was a decrease in libido, which occurred in 7 (29.2%) patients; followed by weight gain, which occurred in 6 (25%) patients; hot flashes, which occurred in 5 (20.8%); mood alterations, which occurred in 5 (20.8%); depression, which occurred in 4 (16.6%); insomnia, which occurred in 3 (12.5%); and deep venous thrombosis, which occurred in 1 (4.2%). Five (20.8%) patients terminated treatment with tamoxifen in less than 1 year because of these side effects. Two of these patients had decreased libido, two had hot flashes, and one suffered deep venous thrombosis.

CONCLUSIONS

In contrast to female breast cancer patients, who have a 4% attrition rate to adjuvant tamoxifen treatment, MBC patients have a 20.8% attrition rate related to side effects of tamoxifen treatment.

A truncated cyclin D1 gene encodes a stable mRNA in a human breast cancer cell line

The G1 cyclin D1 is amplified in approximately 20% of human breast cancers and is frequently overexpressed as part of an amplicon in these tumors, suggesting a potential role for this gene in the pathogenesis of breast cancer. Although amplification of cyclin D1 occurs in human breast cancer, it is possible that another gene in the amplicon is the relevant oncogene in these cancers. We now report a truncation of the cyclin D1 gene in a human breast cancer cell line, associated with overexpression of a short cyclin D1 mRNA. In a survey of breast cancer cell lines and tumors by Southern blot hybridization, using a 1.2 kb human cyclin D1 cDNA, we observed that genomic DNA derived from the MDA MB-453 cell line contains an extra band in the Bg1II and BamHI digests, suggesting that one allele of gene is altered. Moreover, the altered allele is amplified three-fold relative to the normal allele, and contains a 3' deletion. On Northern analysis, the MDA MB-453 line has a marked increase in 1.1 to 1.3 kb transcripts, which are truncated at the 3' end, in contrast to the normally predominant 4.2 kb transcript. The 1.1-1.3 kb cyclin D1 mRNA has a longer half-life than the 4.2 kb mRNA, indicating that the 3' truncation may contribute an increased stability and therefore an elevated steady-state level of the short mRNA. These alterations in the cyclin D1 gene and mRNA suggest that altered expression of cyclin D1 may be important in the malignant transformation of this cell line, and support the identification of cyclin D1 as a dominant oncogene at 11q13 in human breast cancer.

Paclitaxel and recombinant human granulocyte colony-stimulating factor as initial chemotherapy for metastatic breast cancer

PURPOSE

A phase II study of Taxol (paclitaxel; Bristol-Myers Squibb Co, Princeton, NJ) as initial chemotherapy for metastatic breast cancer was conducted. Recombinant human granulocyte colony-stimulating factor (rhG-CSF) was used to ameliorate myelosuppression, the anticipated dose-limiting toxicity.

PATIENTS AND METHODS

Twenty-eight patients with bidimensionally measurable breast cancer who had not received prior chemotherapy for metastatic disease were treated. Taxol was administered at 250 mg/m2 as a continuous 24-hour intravenous (i.v.) infusion every 21 days. rhG-CSF was administered at 5 micrograms/kg/d subcutaneously on days 3 through 10.

RESULTS

Objective responses were observed in 16 of 26 assessable patients (62%; 95% confidence interval, 41% to 80%). There were three (12%) complete responses (CRs) and 13 (50%) partial responses (PRs). Ten of 16 patients (63%) who had received prior adjuvant chemotherapy responded, which included one CR and four PRs among eight patients who had received prior doxorubicin-containing therapy. Responses were observed in all sites of metastatic disease. The median time to first objective response was 5 weeks (range, 1 to 14). Administration of rhG-CSF was associated with a short duration of neutropenia (median, 2 days with absolute neutrophil count < 500 cells/microL). Eight of 26 patients (31%) who received more than one course received subsequent therapy without dose reduction. One hundred seventy-eight cycles of treatment were administered, with a median of six cycles per patient (range, one to 19). Eight courses (4.5%) were associated with admissions for neutropenic fever. Twenty-two patients (79%) did not require admission for neutropenic fever. Treatment was well tolerated. Adverse effects included generalized alopecia in all patients. Myalgias, arthralgias, and peripheral neuropathy were mild. No hypersensitivity reactions and no cardiac toxicity were observed.

CONCLUSION

Taxol is highly active as initial chemotherapy for metastatic breast cancer. Administration of rhG-CSF reduced the incidence, depth, and duration of neutropenia, compared with published prior experience. Further studies of Taxol in breast cancer, including combinations with other active agents, are clearly warranted.

Preliminary experience with paclitaxel (Taxol) plus recombinant human granulocyte colony-stimulating factor in the treatment of breast cancer

Single-agent paclitaxel (TAXOL) was administered to 79 patients with stage IV breast cancer. Twenty-eight patients had no prior chemotherapy (for metastatic disease), and 51 patients had extensive exposure to other chemotherapeutic agents before beginning the 24-hour paclitaxel infusion. Routine use of recombinant human granulocyte colony-stimulating factor helped to ameliorate neutropenia, the dose-limiting toxicity, in some cases. Other toxicity was generally mild to moderate. Paclitaxel was more active in patients whose stage IV disease had not yet been exposed to chemotherapy, but activity was seen in the patients previously treated extensively as well. There is a strong clinical suggestion of non-cross-resistance with doxorubicin. In one case, an excellent response in previously irradiated skin was seen. Paclitaxel is a very promising agent for the treatment of metastatic breast cancer.

Expression of inducible membrane-anchored insulin receptor kinase enhances deoxyglucose uptake

We have transfected mouse L cells with a recombinant membrane-anchored insulin receptor kinase (called MARK), under the transcriptional control of a glucocorticoid-responsive element. The transfected construct includes only 15 extracellular residues, with the transmembrane and intracellular kinase domains of the human insulin receptor cDNA (amino acid residues -27 to 12 and 915 to 1343 (see Ullrich, A., Bell, J. R., Chen, E. Y., Herrera, R., Petruzzelli, L. M., Dull, T. J., Gray, A., Coussens, L., Liao, Y. C., Tsubokawa, M., Mason, A., Seeburg, P. H., Grunfeld, C., Rosen, O. M., and Ramachandran, J. (1985) Nature 313, 756-761), predicted Mr = 56,000 with signal sequence, 53,000 without). Transfected cells which are exposed to dexamethasone express two proteins of approximate Mr = 54,000 which (a) react with anti-peptide antisera raised to human insulin receptor sequences, (b) localize to the membrane fraction, and (c) possess ligand (insulin)-independent tyrosine kinase activity. In extracts of steroid-treated MARK cells, a phosphotyrosine-containing protein of Mr = 185,000 is detected, which corresponds in size to a known endogenous substrate for the insulin receptor. Control studies were performed with the nontransfected parent line, and with L cells transfected with an inactive human insulin receptor protein tyrosine kinase. Dexamethasone induced no change in the proteins detected by an anti-phosphotyrosine antibody in the two control lines. In studies of deoxyglucose uptake, dexamethasone stimulated increase in deoxyglucose uptake 2-fold in the MARK cells compared to the same cells studied in the absence of dexamethasone. Dexamethasone had no effect in the control cell lines. These studies demonstrate that a membrane-anchored insulin receptor kinase, devoid of virtually the entire extracellular domain of the insulin receptor, is sufficient to induce enhanced deoxyglucose uptake.

Polylysine activates and alters the divalent cation requirements of the insulin receptor protein tyrosine kinase

Protamine and poly(Lys) activate the protein tyrosine kinase of both the human placental insulin receptor and its purified recombinant cytoplasmic domain. Spermidine, poly(Arg) (average molecular mass 15 kDa), poly(Glu), Arg or Lys are not effective. Activation is stable, reversible, and optimal when the enzyme is preincubated with activator, divalent cation and ATP prior to the addition of exogenous protein substrates. The most striking feature of the activation is that it results in 20-30-fold stimulation of the kinase in the presence of 0.2-0.4 mM Mn2+ and induces equivalent activity in the presence of Mg2+ alone (0.4-4.0 mM). The activated protein tyrosine kinase has a specific activity (0.25-0.5 mumol/mg protein) that approaches that of well characterized protein serine kinases.