A phase I study of sequential versus concurrent interleukin-3 and granulocyte-macrophage colony-stimulating factor in advanced breast cancer patients treated with FLAC (5-fluorouracil, leucovorin, doxorubicin, cyclophosphamide) chemotherapy

Cumulative thrombocytopenia is a dose-limiting toxicity of dose-intensive chemotherapy for advanced breast cancer. In this phase I study, we have studied the hematologic toxicity associated with sequential interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF; molgramostim) administration after multiple cycles of FLAC (5-fluorouracil, leucovorin, doxorubicin, cyclophosphamide) chemotherapy compared with that after concurrent cytokine administration or to each cytokine administered alone. Ninety-three patients with advanced breast cancer were treated with five cycles of FLAC chemotherapy and either IL-3 alone, GM-CSF alone, sequential IL-3 and GM-CSF administered by schedule A (5 days of IL-3 followed by 10 days of GM-CSF) or schedule B (9 days of IL-3 followed by 6 days of GM-CSF), or concurrent administration of IL-3 and GM-CSF for 15 days. Cohorts of patients were treated with one of four dose levels of IL-3 (1,2.5, 5, and 10 micrograms/kg) administered subcutaneously for each schedule of cytokine administration. The GM-CSF dose in all schedules was 5 micrograms/kg/day. Sequential IL-3 and GM-CSF (schedule B) was associated with higher platelet nadirs, shorter durations of platelet counts less than 50,000/microL, and the need for fewer platelet transfusions over five cycles of FLAC chemotherapy compared with concurrent cytokines, sequential IL-3 and GM-CSF schedule A, and GM-CSF alone. Concurrent IL-3 and GM-CSF was associated with unexpected platelet toxicity. The duration of granulocytopenia after FLAC chemotherapy was significantly worse with IL-3 alone compared with each of the GM-CSF-containing cytokine regimens. Although no cycle 1 maximum tolerated dose for IL-3 was defined in this study, 5 micrograms/kg was well tolerated over multiple cycles of therapy and is recommended for future studies. The data from this phase I study suggest that sequential IL-3 and GM-CSF with IL-3 administered for 9 days before beginning GM-CSF may be superior to shorter durations of IL-3 administered sequentially with GM-CSF, to concurrent IL-3 and GM-CSF, and to either colony-stimulating factor alone in ameliorating the cumulative hematologic toxicity associated with multiple cycles of FLAC chemotherapy. Additional studies of sequential IL-3 and GM-CSF are warranted.

Effects of a recombinant adenovirus expressing WAF1/Cip1 on cell growth, cell cycle, and apoptosis

To evaluate the effects of a p53-inducible gene WAF1/Cip1 on cell proliferation and apoptosis, a recombinant adenovirus vector (E1 minus) expressing WAF1/Cip1 cDNA (AdWAF1) was constructed and compared with a previously studied recombinant adenovirus vector expressing wild-type p53 (AdWTp53). Infection of normal and tumor cells of lung and mammary epithelial origin with AdWAF1 resulted in high levels of WAF1/Cip1 gene expression, which was comparable to that induced by AdWTp53. AdWAF1 and AdWTp53 inhibited growth of all cells studied; tumor cells devoid of endogenous p53 (H-358) or cells expressing endogenous mutant p53 (MDA-MB-231) were more sensitive to the inhibitory effect than tumor (MCF-7) or normal mammary epithelial cells expressing endogenous wild-type p53. Cell cycle analysis of AdWTp53-infected cells indicated a decline in the cell number in S phase and a significant increase in cell number in G2-M phase. AdWAF1 infection also led to a decline in the percentage of cells in S phase and a significant accumulation of cells in G1. AdWAF1 failed to induce apoptosis in any of the cells tested. In contrast, AdWTp53 induced apoptosis in H-358 and in MDA-MB-231 cells. These data suggest that AdWTp53-mediated WAF1/Cip1 induction and cytotoxicity are likely to be associated with WAF1/Cip1-mediated cell cycle arrest. However, because overexpression of WAF1/Cip1 protein failed to induce apoptosis, AdWTp53 effects on apoptosis apparently require cellular factors in addition to WAF1/Cip1 induction.

Cross-resistance to camptothecin analogues in a mitoxantrone-resistant human breast carcinoma cell line is not due to DNA topoisomerase I alterations

We have previously described a mitoxantrone-resistant human breast carcinoma cell line, MCF7/MX, in which resistance was associated with a defect in the energy-dependent accumulation of mitoxantrone in the absence of P-glycoprotein overexpression (M. Nakagawa et al., Cancer Res. 52: 6175-6181, 1992). We now report that this cell line is highly cross-resistant to the camptothecin analogues topotecan (180-fold), 9-aminocamptothecin (120-fold), CPT-11 (56-fold), and SN38 (101-fold), but is only mildly cross-resistant to the parent compound camptothecin (3.2-fold) and 10,11-methylenedioxy-camptothecin (2.9-fold). Topotecan accumulation was decreased in MCF7/MX cells compared to parental MCF7/WT cells, and there was a corresponding reduction in topotecan-mediated stimulation of the enzyme/DNA complex formation in MCF7/MX cells compared to MCF7/WT cells. No overexpression of the multidrug resistance-associated protein was detected compared to parental MCF7/WT cells. Furthermore, both sensitive MCF7/WT and mitoxantrone-resistant MCF7/MX cells contain equal amounts of DNA topoisomerase I protein, and DNA relaxation activities were equal in both cell lines and inhibited to the same extent by topotecan and camptothecin. Thus, these results suggest a novel mechanism of resistance to topoisomerase I inhibitors in cancer cells.

Isolation of a gene encoding a human reduced folate carrier (RFC1) and analysis of its expression in transport-deficient, methotrexate-resistant human breast cancer cells

Our laboratory has previously reported the isolation of a murine cDNA which restores reduced folate carrier (RFC) activity and methotrexate (MTX) sensitivity to a MTX-resistant, transport-deficient human breast cancer cell line (MTXR ZR-75-1) (K. H. Dixon et al., J. Biol. Chem., 269: 17-20, 1994). Using this murine cDNA as a probe, we have isolated two homologous overlapping partial cDNAs from a human testis cDNA library. In addition, using human cDNA as a probe, we have isolated a 20-kb human genomic fragment which contains RFC coding regions. Analysis of the nucleotide sequence of these clones revealed that the human RFC gene, RFC1, is approximately 65% homologous to the murine and hamster genes. Using a human genomic P1 plasmid clone containing RFC1, we mapped the location of RFC1 by fluorescence in situ hybridization to the end of the long arm of chromosome 21 (21q22.2-q22.3). Fluorescence in situ hybridization analysis also showed that two copies of RFC1 were present in MTXR ZR-75-1 cells, and showed no evidence of rearrangement of this gene. Northern blot analysis of MTXR ZR-75-1 cells demonstrated a marked decrease in the level of the 3-kb RFC1 transcript relative to the parental cell line, and Western blot analysis using a polyclonal antibody raised against a peptide generated from the RFC1 sequence showed decreased expression of an approximately M(r) 56,000 protein in MTXR ZR-75-1 cells. Finally, MTXR ZR-75-1 cells transfected with an RFC1 gene showed increased MTX uptake, which was more sensitive to competition by folinic acid than by folic acid. Therefore, decreased RFC1 expression appears to be the molecular mechanism of decreased MTX uptake in this MTX-resistant cell line.

Markedly decreased expression of glutathione S-transferase pi gene in human cancer cell lines resistant to buthionine sulfoximine, an inhibitor of cellular glutathione synthesis

Buthionine sulfoximine (BSO) is a synthetic amino acid that irreversibly inhibits an enzyme, gamma-glutamylcysteine synthetase (gamma-GCS), which is a critical step in glutathione biosynthesis. We isolated three BSO-resistant sublines, KB/BSO1, KB/BSO2, and KB/BSO3, from human epidermoid cancer KB cells. These cell lines showed 10-to 13-fold higher resistance to BSO, respectively, and had collateral sensitivity to cisplatin, ethacrynic acid, and alkylating agents such as melphalan and nitrosourea. Cellular levels of glutathione S-transferase pi (GST-pi) and its mRNA in BSO-resistant cell lines were less than 10% of the parental cells. Nuclear run-on assay showed that the transcriptional activity of GST-pi was decreased in BSO-resistant cells, and transient transfection of GST-pi promoter-chloramphenicol acetyltransferase constructs revealed that the sequences between -130 and -80 base pairs of the 5'-flanking region wer at least partially responsible for the decreased expression of the GST-pi gene. By contrast, gamma-GCS mRNA levels were 3-to 5-fold higher in resistant cell lines than in KB cells, and the gamma-GCS gene was found to be amplified in the BSO-resistant cells lines. GST-pi mRNA levels appeared to be inversely correlated with gamma-GCS mRNA levels in BSO-resistant cells. We further established the transfectants, KB/BSO3-pi1 and KB/ BSO2-pi2, that overexpressed GST-pi, from KB/BSO3, after introducing a GST-pi expression plasmid. These two transfectants had similar levels in gamma-GCS mRNA, drug sensitivity to alkylating agents, and glutathione content at those of KB cells. These findings suggest that the cellular levels of GST-pi and gamma-GCS might be co-regulated in these novel BSO-resistant cells.

Effect of R-verapamil on the pharmacokinetics of paclitaxel in women with breast cancer

PURPOSE

To study the effect of the multidrug-resistance reversal agent R-verapamil on the pharmacokinetic behavior of paclitaxel.

METHODS

Six women with breast cancer who received paclitaxel as a 3-hour infusion with and without R-verapamil were monitored with frequent plasma sampling up to 24 hours postinfusion. Paclitaxel concentrations were measured using a reverse-phase high-pressure liquid chromatography assay.

RESULTS

Concomitant administration of R-verapamil resulted in a decrease in mean (+/- SD) paclitaxel clearance from 179 +/- 67 mL/min/m2 to 90 +/- 34 mL/min/m2 (P < .03) and in a twofold increase in paclitaxel exposure (area under the curve [AUC]). The mean end-infusion paclitaxel concentration was also twofold higher: 5.1 +/- 1.8 mumol/L versus 11.3 +/- 4.1 mumol/L (P < .03).

CONCLUSION

The alteration in paclitaxel pharmacokinetics when paclitaxel and R-verapamil are coadministered complicates the interpretation of response and toxicity data from clinical trials of this drug combination.

Cytotoxic effects of adenovirus-mediated wild-type p53 protein expression in normal and tumor mammary epithelial cells

To evaluate the effects of the wild-type p53 expression in normal and tumor cells, we have constructed a recombinant adenovirus vector (E1 minus) expressing human wild-type p53 cDNA (AdWTp53). Infection of normal and tumor cells of lung and mammary epithelial origin with AdWTp53 resulted in high levels of wild-type p53 expression. Production of p53 protein following infection was dependent on the dose of AdWTp53 with maximum amounts of p53 produced following infection with 50 plaque-forming units/cell. AdWTp53 infection inhibited the growth of all human cell lines studied. However, tumor cells that were null for p53 prior to infection (H-358 and MDA-MB-157) and tumor cells that expressed mutant endogenous p53 protein (MDA-MB-231 and MDA-MB-453) were more sensitive to AdWTp53 cytotoxicity than cells that contained the wild-type p53 (MCF-7, MCF-10, 184B5, and normal mammary epithelial cells). All cells exhibited WAF1/Cip1 mRNA and protein induction following AdWTp53 infection. AdWTp53-induced cytotoxicity of human tumor cell lines expressing mutant p53 was mediated by apoptosis as revealed by nucleosomal DNA fragmentation analysis. No detectable nucleosomal DNA fragmentation was observed following AdWTp53 infection of human cells expressing wild-type p53. These data suggest that endogenous p53 status is a determinant of AdWTp53-mediated cell killing of human tumor cells.

Effects of cell cycle, wild-type p53 and DNA damage on p21CIP1/Waf1 expression in human breast epithelial cells

In this study we examine the relationship between p21CIP1/Waf1 (CIP1), a 21 kDa protein that binds to and modulates the activity of several cyclin dependent kinases and expression of wild-type (WT) p53 in human breast epithelial cells. Basal CIP1 protein, but not CIP1 mRNA levels correlated well with expression of WT p53 in human breast epithelial cells. To obtain more direct evidence that WT p53 regulated the level of CIP1 protein, the Human Papilloma Virus (HPV) E6 protein was introduced into immortalized 184B5 breast cells. Residual WT p53 levels correlated well with CIP1 protein but not CIP1 mRNA levels in isolated clones of transfected cells. CIP1 protein was increased at early times after growth factor arrested cells were stimulated to proliferate. The rise in CIP1 protein was due to a concomitant increase in CIP1 mRNA levels in MCF10, but not in normal mammary epithelial cells. DNA damage induced by ionizing radiation resulted in a transient increase in WT p53 levels but a prolonged induction of CIP1 protein. The sustained increase in CIP1 protein 24 h after radiation could not be attributed to a concomitant increase in CIP1 mRNA levels. Although the half-life of the CIP1 protein was not altered following irradiation, a fourfold increase in the amount of radioactivity incorporated into CIP1 protein was detected. When considered together these data suggest that wild-type p53 affects CIP1 protein accumulation at a posttranscriptional level in human breast epithelial cells under different physiologic and stress conditions.

Ca2+/Mg(2+)-dependent endonuclease activation is an early event in VP-16-induced apoptosis of human breast cancer MCF7 cells in vitro

Apoptosis is now recognized as one of the major processes regulating the size of cell populations. However, despite intensive investigations the biochemical and enzymological mechanisms involved in apoptosis remain unclear. In the present study we demonstrate activation of a Ca2+/Mg(2+)-dependent endonuclease during VP-16-induced apoptosis in MCF7 cells. Nuclease activation occurred prior to the appearance of internucleosomal DNA fragmentation, suggesting that this activation may be an early and possibly critical step in drug-induced apoptosis. Analysis of the internucleosomal DNA fragments showed that they contained phosphorylated 5'-ends, indicating that they were produced by a Ca2+/Mg(2+)-dependent endonuclease.

Characterization of cross-resistance to methotrexate in a human breast cancer cell line selected for resistance to melphalan

We have demonstrated previously decreased melphalan accumulation in a human breast cancer cell line selected for resistance to melphalan (MelR MCF-7). Cross-resistance studies of MelR MCF-7 cells revealed that this cell line was 6.7-fold cross-resistant to methotrexate, but only 2-fold resistant to trimetrexate. Methotrexate transport studies in MelR MCF-7 cells showed a 2-fold decrease in initial methotrexate uptake and a 2-fold decrease in the Vmax for methotrexate uptake in the resistant cells. Methotrexate resistance in MelR MCF-7 cells was also associated with a decrease in non-effluxable methotrexate following incubation with radiolabeled drug for 24 hr. Characterization of intracellular methotrexate after accumulation for 24 hr demonstrated decreased levels of free methotrexate in MelR MCF-7 cells. Analysis of methotrexate polyglutamate formation in MelR MCF-7 cells indicated that the decrease in non-effluxable, non-protein-bound methotrexate was associated with a 3-fold decrease in higher order methotrexate polyglutamate formation. No difference was noted in folylpolyglutamate synthetase activity between the resistant and parental cell lines. Therefore, the observed decrease in methotrexate polyglutamate formation in MelR MCF-7 cells appeared to result from decreased availability of substrate. There was no evidence of any alteration in the amount of the catalytic activity of dihydrofolate reductase in MelR MCF-7 cells compared with parental MCF-7 (WT MCF-7) cells; moreover, the binding affinity of dihydrofolate reductase for methotrexate and the percentage of protein-bound methotrexate were similar in both cell lines. In addition, the total amounts of thymidylate synthase protein and thymidylate synthase catalytic activity in MelR MCF-7 cells were unchanged. Thus, acquired methotrexate resistance in MCF-7 cells selected for resistance to melphalan appears to result from down-regulation of methotrexate uptake.

Ten-year results of a comparison of conservation with mastectomy in the treatment of stage I and II breast cancer

BACKGROUND

Breast-conservation therapy for early-stage breast cancer is now an accepted treatment, but there is still controversy about its comparability with mastectomy. Between 1979 and 1987, the National Cancer Institute conducted a randomized, single-institution trial comparing lumpectomy, axillary dissection, and radiation with mastectomy and axillary dissection for stage I and II breast cancer. We update the results of that trial after a median potential follow-up of 10.1 years.

METHODS

Two hundred forty-seven patients with clinical stage I and II breast cancer were randomly assigned to undergo either modified radical mastectomy or lumpectomy, axillary dissection, and radiation therapy. The 237 patients who actually underwent randomization have been followed for a median of 10.1 years. The primary end points were overall survival and disease-free survival.

RESULTS

At 10 years overall survival was 75 percent for the patients assigned to mastectomy and 77 percent for those assigned to lumpectomy plus radiation (P = 0.89). Disease-free survival at 10 years was 69 percent for the patients assigned to mastectomy and 72 percent for those assigned to lumpectomy plus radiation (P = 0.93). The rate of local regional recurrence at 10 years was 10 percent after mastectomy and 5 percent after lumpectomy plus radiation (P = 0.17) after recurrences successfully treated by mastectomy were censored from the analysis.

CONCLUSIONS

In the management of stage I and II breast cancer, breast conservation with lumpectomy and radiation offers results at 10 years that are equivalent to those with mastectomy.

Buthionine sulphoximine-mediated sensitisation of etoposide-resistant human breast cancer MCF7 cells overexpressing the multidrug resistance-associated protein involves increased drug accumulation

Preincubation of etoposide-resistant human MCF7 breast cancer cells (MCF7/VP) with buthionine sulphoximine (BSO) resulted in their sensitisation to etoposide and vincristine. Chemosensitisation was accompanied by elevated intracellular drug levels. In contrast, simultaneous exposure to BSO did not result in increased drug accumulation. Similar, but quantitatively smaller, effects were also observed when sensitive wild-type MCF7/WT cells were treated with BSO. In agreement with its effect on drug accumulation, BSO pretreatment also increased VP-16-stimulated cleavable complex formation between DNA topoisomerase II and cellular DNA. BSO treatment also led to a significant increase in acid-precipitable VP-16 levels in MCF7/VP, but not MCF7/WT cells. In contrast, no clear effects of BSO on drug efflux were observed and drug retention was only minimally increased after BSO treatment of both MCF7/WT and MCF7/VP cells and no difference between the two cell lines was detected. Thus, chemosensitisation by BSO appeared to be mediated through increased intracellular drug concentrations and/or protein binding.

Wild type p53 stimulates expression from the human multidrug resistance promoter in a p53-negative cell line

The effect of human wild type and mutant p53 proteins on the human multidrug resistance (MDR1) promoter was studied in a p53-negative human cell line. Transient expression of MDR1 promoter-chloramphenicol acetyltransferase reporter gene constructs (MDRCAT) cotransfected with p53 expression vectors was analyzed in H358 lung carcinoma cells. Cotransfection with a wild type p53 expression vector stimulated MDRCAT activity, while cotransfection with mutant p53 expression vectors altered at amino acid positions 181, 252, 258, or 273 failed to stimulate expression. Wild type p53 stimulation of MDRCAT activity was time dependent with maximal expression occurring 24-30 h following transfection and correlating with high p53 protein levels. MDR1 promoter deletion analysis suggested that the sequences involved in wild type p53 stimulation of MDRCAT activity were contained within the region from -39 to +53 relative to the start of transcription at +1. This region contains no TATA or p53 consensus binding sequence but does contain an initiator sequence. Wild type p53 stimulation of MDRCAT expression also occurred in parental and doxorubicin-resistant SW620 colon and parental 2780 ovarian cancer cell lines, indicating that wild type p53-mediated simulation of the MDR1 promoter is not restricted to a single cell line.

Posttranscriptional regulation of the c-myb proto-oncogene in estrogen receptor-positive breast cancer cells

We have determined that expression of the c-myb proto-oncogene is associated with estrogen receptor (ER) status and not with tumor progression in human breast epithelial cells. Analysis of normal, immortalized, nontumorigenic, and tumorigenic mammary epithelial cells showed that only ER+ tumor cell lines expressed readily detectable levels of c-myb mRNA and a Mr 75,000 protein that was the same size as the c-myb transcripts and protein products present in hematopoietic cells. In this report we show that c-myb mRNA and protein levels are down-regulated during estrogen withdrawal. A 20-fold increase in c-myb mRNA and protein expression was observed upon addition of beta-estradiol to the culture medium. Nuclear run-on transcription analyses showed that c-myb was transcribed at the same rate in the presence and absence of estrogen, suggesting that c-myb mRNA accumulation was regulated at a posttranscriptional level. To provide additional evidence that c-myb mRNA was dependent on ER expression, we examined c-myb mRNA levels in MCF-7 cells selected for resistance to antineoplastic drugs. c-myb expression was decreased only in cell lines that showed concomitant loss of ER expression. Moreover, c-myb mRNA was expressed and modulated by estrogen in ER-, MDA-MB-231 cells stably transfected with a human ER gene. When considered together, these data indicate that c-myb mRNA levels are regulated by estrogens and further suggest that this proto-oncogene plays a role in the biology of ER+ breast tumor cells.

Arterial thrombosis associated with granulocyte-macrophage colony-stimulating factor (GM-CSF) administration in breast cancer patients treated with dose-intensive chemotherapy: a report of two cases

The occurrence of arterial thrombosis reported in other breast cancer series has largely been confined to the upper extremities, ipsilateral to a previous mastectomy site and clinically manifest as cerebral vascular accidents. This case report describes 2 patients who experienced iliac artery thrombosis temporally related to receiving granulocyte-macrophage colony-stimulating factor (GM-CSF) and dose-intensive chemotherapy for metastatic breast cancer. A review of the literature concerning arterial thrombosis as relevant to breast cancer treatment and GM-CSF is included.

Increased expression of the multidrug resistance-associated protein gene in relapsed acute leukemia

Quantitative reverse transcriptase polymerase chain reaction (RT-PCR) was used to determine relative levels of transcripts for MDR1 and the recently described multidrug resistance-associated protein (MRP) in normal lymphohematopoietic cells and in 62 bone marrow aspirates of newly diagnosed and recurrent acute leukemia. Levels of MRP expression in newly diagnosed AML samples were similar to those observed in normal bone marrow cells (CD34-negative and CD34-positive) and in unselected HL60 human promyelocytic leukemia cells, which were used as an internal control throughout this study. In contrast, samples of AML obtained at the time of relapse contained approximately twofold higher levels of MRP RNA (P < .01). Analysis of paired samples, the first obtained at diagnosis and the second at relapse, from 13 acute myelogenous leukemia (AML) and four acute lymphocytic leukemia (ALL) patients showed that MRP expression was increased at the time of relapse in greater than 80% of patients. In contrast, no consistent changes of MDR1 expression at relapse were observed. These results raise the possibility that increased MRP expression might contribute to leukemic relapse.

Transforming growth factor-beta1 circulates in normal human plasma and is unchanged in advanced metastatic breast cancer

A method has been developed to determine true plasma transforming growth factor beta (TGF-beta) levels by using the platelet alpha granule-specific marker, platelet factor 4, to correct for the TGF-beta contributed by platelets degranulated ex vivo. TGF-beta levels were measured on acid-ethanol extracts of human plasma using isoform-specific sandwich enzyme-linked immunosorbent assays. Normal human subjects had 4.1 +/- 2.0 ng/ml TGF-beta1 (range, 2.0-12.0; n = 42), <0.2 ng/ml TGF-beta2, and <0.1 ng/ml TGF-beta3 in their plasma. There were no significant changes with age or with hormonal status, but any given individual showed fluctuations of up to 3-fold in measured plasma TGF-beta levels due to unknown factors. Of 28 patients with advanced metastatic breast cancer, 2 had greatly elevated TGF-beta1 levels, while the rest were in the normal range. The presence of physiologically significant levels of TGF-beta1 in the plasmas of normal human subjects may indicate previously unsuspected endocrine roles for this peptide, while TGF-beta2 and TGF-beta3 appear to act only in a local autocrine/paracrine fashion.

Differential expression of multiple MDM2 messenger RNAs and proteins in normal and tumorigenic breast epithelial cells

The MDM2 gene is a nuclear phosphoprotein that is regulated by p53 and functions, in one capacity, to inhibit the transcriptional activity of the wild-type p53 protein. Multiple MDM2 transcripts were detected in human breast epithelial cells. In estrogen receptor-negative normal, immortal, and tumorigenic breast epithelial cells, we found a good correlation between MDM2 mRNA levels and expression of wild-type p53. When wild-type p53 was overexpressed in estrogen receptor-negative tumor cells containing a mutant or no endogenous p53, MDM2 mRNA levels increased significantly, indicating that wild-type p53 positively influences MDM2 mRNA levels in these tumor cells. Because all estrogen receptor-positive breast tumor cells had high MDM2 mRNA levels regardless of the status of their endogenous p53 protein, other factors likely influence MDM2 expression in these cells. Distinct MDM2 proteins (range, Mr 54,000-68,000 and 90,000-100,000, respectively) were differentially expressed in human breast epithelial cells. The lower molecular weight MDM2 proteins were most abundant in the normal mammary cells but present at varying levels in many of the tumor cells examined. MDM2 was a nuclear protein; however, nuclear staining intensity did not always correlate with the amount of MDM2-immunoreactive protein as determined by Western blot analysis. This discrepancy suggests that MDM2 interacts with novel cellular proteins in different kinds of breast epithelial cells.

Current status of paclitaxel in the treatment of breast cancer

Paclitaxel is a highly active single agent as therapy for previously untreated as well as doxorubicin-refractory metastatic breast cancer, with associated response rates of 62% and 20-48%, respectively. Complete responses with paclitaxel occur chiefly in breast cancer patients whose metastatic disease has not been previously treated with chemotherapy. Early data suggest a possible dose-response relationship for paclitaxel in metastatic breast cancer, but the optimal dose has not yet been defined. The optimal duration of infusional paclitaxel treatment is also not yet known. A study of 96-hour infusional paclitaxel in the treatment of doxorubicin- or mitoxantrone-refractory metastatic breast cancer patients has demonstrated a 48% response rate suggesting that prolonged exposures to paclitaxel may offer a therapeutic advantage. Randomized trials of 3- vs 96-hour paclitaxel are ongoing or planned. The relative efficacy of paclitaxel versus standard chemotherapy as front-line or salvage therapy for metastatic breast cancer is currently under study. In addition, two randomized trials are under way in node positive breast cancer patients to study whether treatment with paclitaxel following standard or high dose doxorubicin and cyclophosphamide adjuvant therapy results in improved patient benefit. Combining paclitaxel with other active agents in the treatment of metastatic breast cancer is an area of active investigation. Combined paclitaxel and doxorubicin, administered concurrently or sequentially, is associated with modest complete response rates in metastatic breast cancer patients. Sequential paclitaxel-->doxorubicin administration is associated with more mucositis than is doxorubicin-->paclitaxel when paclitaxel is administered over 24 hours. High doses of cyclophosphamide can be combined with 24- or 72-hour infusional paclitaxel, and phase II studies of this combination are warranted. Early data suggest that administering biweekly paclitaxel and cisplatin to previously untreated metastatic breast cancer patients is associated with high response rates, and confirmatory studies of this combination and schedule are planned. Preclinical data suggest that cell cycle considerations may be important in combining doxorubicin and possibly other agents with paclitaxel. Paclitaxel is an excellent substrate for P-glycoprotein, the protein product of the multidrug resistance-1 (mdr-1) gene, and phase I trials are under way combining paclitaxel with several known blockers of Pgp function. Finally, pilot studies are under way to determine whether the radiation sensitizing effects of paclitaxel can be exploited as part of radiation therapy for patients with locally advanced breast cancer.

Loss of heterozygosity of the human cytosolic glutathione peroxidase I gene in lung cancer

The consistent deletion of 3p21 in lung cancer has led to intensive efforts to identify a lung tumor suppressor gene at this locus. We recently mapped the gene for the selenium-dependent drug-detoxifying enzyme glutathione peroxidase 1 (GPX1) to this location by in situ hybridization. We developed a polymerase chain reaction-based assay which demonstrated the existence of three GPX1 alleles characterized by the number of alanines in a polyalanine coding sequence in exon 1. These three alleles produced a heterozygote frequency of 70% in two separate populations: normal tissue DNA taken from Centre d'Etude du Polmorphisme Humain (CEPH) parents and normal tissue taken from cancer patients. In contrast, 10 heterozygote tumors were detected out of 64 lung cancer specimens. Linkage analysis of GPX1 to Genethon 3p markers in CEPH pedigrees demonstrated that GPX1 was located between the two microsatellite markers believed to flank the lung cancer deletion site. Nucleotide sequence analysis of GPX1 alleles did not reveal any mutations of this gene in lung tumors. However, sequence analysis did reveal that the three GPX1 alleles were characterized by three nucleotide substitutions in addition to the polyalanine polymorphism, including a substitution at codon 198 which results in either a proline or leucine at that position. Therefore, the different GPX1 alleles encode structurally different hGPx1 subunits. In addition, analysis of allele frequency suggests that the GPX1*ALA7 allele may occur less frequently in tumors with 3p21 deletions.

Combination paclitaxel (Taxol) and doxorubicin therapy for metastatic breast cancer

Paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) is a very active agent for the treatment of breast cancer, with associated complete response rates of 12% in patients with minimally pretreated metastatic disease. Simultaneous paclitaxel and doxorubicin administration by 72-hour continuous infusion in patients with previously untreated metastatic breast cancer has yielded an overall response rate of 72% with 8% complete responses. No alterations in paclitaxel or doxorubicin pharmacokinetics were observed when the drugs were administered alone versus in combination. Two phase I studies from the M.D. Anderson Cancer Center (Houston, TX) and the University of Indiana (Indianapolis, IN) have shown that administration of a 24-hour paclitaxel infusion prior to doxorubicin results in a significantly higher incidence of mucositis than the reverse sequence. Preliminary pharmacokinetic studies from M.D. Anderson suggest that peak plasma concentration and clearance of doxorubicin are altered by pretreatment with 24-hour paclitaxel. In contrast, in an ongoing phase I study at the Istituto Nazionale Tumori in Milan, Italy, no differences in toxicities have been observed with the combination of intravenous bolus doxorubicin and 3-hour infusional paclitaxel administered by either sequence. Preclinical in vitro and in vivo studies suggest that the combination of paclitaxel and doxorubicin is associated with no or minimal additive antitumor effects. The modest complete response rates that have been observed in patients with metastatic breast cancer to date are in agreement with these observations. A randomized study of paclitaxel versus doxorubicin versus intravenous bolus doxorubicin followed by 24-hour paclitaxel is now being conducted by the Eastern Cooperative Oncology Group.

Utilization of multiple polyadenylation signals in the human RHOA protooncogene

Little is known regarding the regulation of expression of the RHOA protooncogene, a member of the family of genes encoding Ras-related GTP-binding proteins. We have previously reported that the 3' untranslated region (UTR) of RHOA was contained within a genomic sequence which flanked the 5' end of the human glutathione peroxidase 1-encoding gene [J.A. Moscow et al., J. Biol. Chem. 267 (1992) 5949-5958]. Our previous studies revealed the presence of multiple (1.8 and 1.5 kb) RHOA mRNA species in breast cancer cell lines and of three putative polyadenylation signals in the RHOA 3' UTR. In this report, we have isolated several RHOA cDNAs from a multidrug-resistant MCF-7 human breast cancer cell line. Sequence analyses of these RHOA cDNA clones indicate that multiple polyadenylation signals are used to terminate RHOA transcripts. RNase-protection analysis demonstrated that all three polyadenylation signals are utilized in breast cancer cell lines and RNA stability studies demonstrated that RHOA RNA species with different 3' ends have equivalent stability. Since little is known about the RNA expression of RHOA in human tumors, and since both activated and non-activated RHOA genes possess transformation potential, we analyzed RHOA mRNA in lung and colon tumors by Northern blot and RNase-protection analyses. In all eight lung tumors examined, RHOA RNA levels were decreased relative to the level in normal surrounding tissue, whereas RHOA expression was decreased in only two of six colon tumors. We also found that lovastatin-induced cell cycle arrest resulted in increased RHOA RNA expression in breast cancer cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)

Retroviral mediated transfer of the human multidrug resistance gene (MDR-1) into hematopoietic stem cells during autologous transplantation after intensive chemotherapy for metastatic breast cancer

Patients with metastatic breast cancer will receive 4-5 cycles of induction chemotherapy on one of the ongoing Medicine Branch protocols. Patients achieving at least a partial response, and who do not have evidence of bone marrow involvement and who do not have metastatic bone disease, will undergo PBSC and bone marrow harvest when hematologic recovery has occurred. Patients who have not achieved a PR, but who are responding to therapy, may be treated with additional cycles of therapy in an attempt to achieve a PR. Such patients will be eligible for transplant if a PR is obtained. 70% of the bone marrow and PBSC will be cryopreserved. The CD34+ subpopulation from the remaining 30% of the bone marrow and PBSC harvest will be obtained using an anti-CD34+ antibody and immunoabsorption column. The bone marrow and peripheral blood CD34 cells will be transduced with a retroviral vector expressing the human MDR-1 cDNA. Patients with positive bone scans or histologic evidence of bone marrow involvement will be excluded from the gene transfer component of the protocol. The MDR-1 transduced CD34 cells will be reinfused along with the non-transduced bone marrow and PBSC into patients following high dose ICE chemotherapy. Serial peripheral blood and bone marrow samples will be obtained to study hematopoietic reconstitution with MDR-1 transduced cells. Patients with residual or progressive disease after ABMT will be treated with taxol or vinblastine. In these relapsed patients, peripheral blood and bone marrow samples will be obtained to study whether chemotherapy amplifies the proportion of hematopoietic cells containing the MDR-1 provirus. We will monitor the nadir blood counts of each patient receiving salvage chemotherapy for evidence of myeloprotection and correlate this data with changes in the mean proviral copy number. Sites of relapsed tumor will be biopsied to test for the presence of the MDR-1 provirus.

Reversible transcriptional activation of mdr1 by sodium butyrate treatment of human colon cancer cells

We investigated the mechanism of sodium butyrate (NaB)-mediated induction of mdr1 mRNA in parental (wild type) and multidrug-resistant (Ad1000) SW620 colon cancer cell lines. NaB treatment resulted in reversible, time-dependent increases in nuclear run-on transcription of endogenous mdr1 in these cell lines that paralleled the reversible increases of mdr1 mRNA in both timing and magnitude. In contrast, NaB treatment had no effect on mdr1 mRNA stability. Thus, the effects of NaB on mdr1 mRNA levels are fully attributable to altered mdr1 transcription. Furthermore, NaB induces the expression of transiently transfected chloramphenicol acetyltransferase reporter plasmids that are under the transcriptional control of the mdr1 promoter (mdrCAT vectors). Transfections using mdrCAT vectors modified by deletion and site-directed mutagenesis of the mdr1 promoter indicate that NaB-mediated induction of these vectors is at least partially dependent upon sequences present in the basal mdr1 promoter between -89 and +11 relative to the start site of transcription. The Y-box motif located between -82 and -73 contributes to NaB inducibility of mdrCAT vector expression in Ad1000 SW620 cells.