PFS by blinded independent central review (BICR) in the VELIA trial of veliparib (V) plus carboplatin/paclitaxel (CP) and as monotherapy in newly diagnosed patients (pts) with high-grade serous ovarian cancer (HGSC)

6077

Background: The phase III VELIA trial (NCT02470585) demonstrated statistically significant improvement in PFS per investigator (INV) for V added to CP and continued as maintenance (CPV-V) vs. CP alone in pts with newly diagnosed HGSC in the BRCA mutated ( BRCAm), homologous recombination deficient (HRD), and whole populations. Here we present pre-specified analyses of PFS per BICR. Methods: Pts with Stage III-IV HGSC received V or Placebo (PL) with CP (6 cycles) and as maintenance (30 additional cycles). Primary analysis of PFS by INV compared CPV-V to CP alone in the BRCAm, HRD, and whole populations. Exploratory analyses of PFS in BRCA wildtype (wt) and non-HRD HGSC were performed. Radiologic tumor assessments were also prospectively submitted to an independent central reviewer for blinded assessment per RECIST v 1.1. PFS per BICR and rates of concordance between INV and BICR for determination of disease progression were analyzed. Safety data from the primary analysis were previously reported. Results: 1140 total pts were enrolled (CPV-V 382; CP 375). In the whole population, 26% of HGSCs were BRCAm and 55% were HRD. Concordance rates between INV and BICR were 68-85% by arm for each population. Analyses of PFS per BICR and per INV were consistent (Table). PFS was prolonged in the CPV-V vs. CP arm in all primary and exploratory populations assessed. Conclusions: Analyses of PFS per BICR supported the primary analysis of PFS per INV in the BRCAm, HRD, and whole populations, as well as exploratory BRCAwt and non-HRD populations. Median PFS per BICR was longer compared to PFS per INV assessments in all populations and in both arms. These findings support the reliability of PFS by INV in ovarian cancer trials. Alternate strategies like audits may be appropriate to support PFS by INV with less time and expense than full BICR. Clinical trial information: NCT02470585. [Table: see text]

Breast conservation after neoadjuvant chemotherapy for triple-negative breast cancer: Surgical results from an international randomized trial (BrighTNess)

514

Background: Neoadjuvant systemic therapy (NST) increases the frequency of breast-conserving therapy (BCT) in stage II-III breast cancer, but there is little data on how often it converts patients (pts) from BCT-ineligible (BCT-I) to BCT-eligible (BCT-E) and on the impact of other factors on surgical choices. We collected surgical assessment and management data from an international randomized trial of NST in triple-negative breast cancer (TNBC). Methods: Women with operable TNBC were randomized to veliparib (V) with carboplatin (C) and paclitaxel (P), placebo with C and P or placebo with P followed by doxorubicin and cyclophosphamide. The surgeons assessed BCT candidacy by clinico-radiographic criteria before and after NST; surgical management was at surgeon and patient discretion. We assessed interactions between BCT eligibility pre- and post-NST, germline BRCA mutation ( gBRCA) status, continent of treatment and achievement of pathologic complete response(pCR) and percentage of pts who underwent BCT versus mastectomy. Results: Pre- and post-NST surgical assessments were available for 604 pts who underwent surgery. BCT rates are listed in the Table. The BCT rate was 68% among pts deemed BCT-E after NST. pCR rates were identical between BCT-E pts who chose BCT (55%) vs. mastectomy (53%). Of 141 pts deemed BCT-I at baseline, 75 (53%) converted to BCT-E but only 42 (56%) of these opted for BCT. pCR rates were 49% in BCT-E converts vs. 36% in those remained BCT-I. gBRCA pts (n = 84) were less likely to choose BCT even if they were BCT-E. Pts treated in North America (NA) were less likely to choose BCT (55% vs. 80% for Europe and Asia P<0.0001) even among non- gBRCA considered BCT-E post-NST (61% vs. 85% P<0.0001). Conclusions: This largest prospective analysis of the impact of NST in TNBC demonstrates a conversion rate from BCT-I to BCT-E of 53%. BCT rates were lower in pts with gBRCA; the much higher mastectomy rate among BCT-E pts in NA merits investigation. Clinical trial information: NCT02032277. [Table: see text]

Phase 3 study evaluating efficacy and safety of veliparib (V) plus carboplatin (Cb) or Cb in combination with standard neoadjuvant chemotherapy (NAC) in patients (pts) with early stage triple-negative breast cancer (TNBC)

520

Background: Clinical studies suggest that TNBC is sensitive to DNA-damaging agents, including Cb. V is a potent PARP inhibitor that may enhance the antitumor activity of such agents. We present primary response data from a phase 3 randomized, placebo-controlled study (NCT02032277) evaluating the addition of V + Cb or Cb to neoadjuvant paclitaxel (P) followed by doxorubicin + cyclophosphamide (AC). Methods: Pts with histologically confirmed, invasive TNBC (T2–T4 N0–2 or T1 N1–2) amenable to surgical resection were randomized 2:1:1 to (Arm A) P 80 mg/m2 weekly + Cb AUC 6 mg/mL/min q3 weeks + V 50 mg PO BID; (Arm B) P + Cb + PO placebo; or (Arm C) P + IV placebo + PO placebo, for 12 weeks followed by AC (60 mg/m2 or 600 mg/m2 q2 or 3 weeks) × 4. Primary endpoint was pathologic complete response (pCR) in breast and nodes with > 80% power at 2-sided α of 0.05 using pair-wise comparisons for A vs B and A vs C to detect significant treatment effects using Χ2 test; secondary endpoint was rate of conversion to eligibility for breast conservation surgery (BCS). Adverse events (AEs) were assessed with NCI CTCAE V4.0. Results: Six hundred thirty-four pts (median age 50 years; range 22–79) were randomized to Arms A (n = 316), B (n = 160), or C (n = 158). Baseline characteristics were well balanced. No pCR difference was observed between Arms A and B (53.2% vs 57.5% p = 0.36), but pCR in Arm A was higher than Arm C (53.2% vs 31.0% p < 0.001). In non-prespecified analysis, pCR in Arm B was also higher than Arm C (57.5% vs 31.0% p < 0.001). Among pts ineligible for BCS at screening (n = 141), 62% were eligible after NAC in Arm A vs 44% each in Arms B (p = 0.13) and C (p = 0.14). Grade 3–4 AEs (Arms A/B/C, 86%/85%/45%) and serious AEs (30%/27%/14%) neutropenia, thrombocytopenia, anemia, nausea, and vomiting were increased with the addition of Cb; V did not impact toxicity. Median cycles of NAC were not reduced with V + Cb + P or Cb + P vs P. Conclusions: Addition of V to neoadjuvant Cb + P followed by AC did not increase pCR rate in breast and nodes in stage II–III TNBC, while addition of V + Cb or Cb alone to P followed by AC did. Cb (+/– V) increased toxicity but did not impact delivery of NAC. Clinical trial information: NCT02032277.

Topoisomerase II beta levels are a determinant of melphalan-induced DNA crosslinks and sensitivity to cell death

The role of topoisomerase (topo) II in DNA repair has yet to be fully elucidated. Current evidence suggesting a role for topo II in the repair of DNA damage has been obtained by using in vitro model systems or inferred from correlative data in drug resistant cell lines. In this study we directly examined the role of topo IIalpha and beta in mediating the repair of melphalan-induced crosslinks in cellular DNA. To accomplish this, we used siRNA technology to knock down either topo IIalpha or beta in human chronic myelogenous leukemia K562 and histiocytic lymphoma U937 cell line. Our data demonstrate that topo IIbeta levels, (but not alpha), are a determinant of melphalan-induced crosslinks and sensitivity to melphalan. Furthermore, we show that knocking down topo IIbeta inhibits the repair of melphalan-induced crosslinks in K562 cells. These studies represent the first direct evidence that topo IIbeta participates in the repair of DNA damage induced by an alkylating agent in cellular DNA. Finally, these results suggest non-redundant roles for these two isoforms in mediating repair of DNA crosslinks.

Characterization of fresh yard trimmings for agricultural use

Direct application of yard trimmings to agricultural land can benefit soils and crop production, while providing an outlet for handling high volumes of materials at compost facilities. Variability in the composition of yard trimmings can make it difficult to determine appropriate application rates. Our objective was to characterize the chemical composition and variability of yard trimmings generated throughout the spring and summer season at facilities in the Puget Sound region of Washington State. Yard trimmings were sampled from four composting facilities on five dates between April and August 1999. One material contained mostly grass clippings and had higher mean total N (3.2%) than mixed grass and woody materials (1.5-2%). Mean C:N was lower in the grass-rich material (12:1 vs. 15 to 21:1), while mean ammonium concentrations were similar (0.18-0.28%). Variation among facilities was greater than variation over time. The amount of variation observed with other nutrients, pH, EC, or trace elements would not affect use of the yard trimmings in agriculture. Our results suggest that it is possible to characterize yard trimmings adequately for agricultural use.

Seven years of biosolids versus inorganic nitrogen applications to tall fescue

Repeated applications of municipal wastewater biosolids is cost effective for biosolids managers, but may lead to undesirable accumulations of nutrients or contaminants. We evaluated the effects of seven years of biosolids applications on tall fescue (Festuca arundinacea Schreb.) production and nutrient availability. We compared two types of Class A biosolids applied to tall fescue on a sandy loam in western Washington. Mean annual biosolids rates of 290, 580, and 870 kg total N ha(-1) yr(-1) were compared with inorganic N and zero-N controls using a randomized complete block design. We measured yield and N uptake for each forage harvest, plant tissue metals at selected harvests, soil nitrate each fall, diethylenetriaminepentaacetic acid (DTPA)-extractable metals after five years of applications, and soil pH, available P, and organic C after seven years. Forage yields increased with biosolids rate. Apparent nitrogen recovery (ANR) for biosolids averaged 18% in 1993 (Year 1), 35% in 1994, and 46% in 1999. The ANR for inorganic N averaged 62% from 1994-1999. Residual soil nitrate was less than 25 kg ha(-1) for all treatments through 1995, but increased beginning in 1996 for the high biosolids rate. Biosolids increased soil organic C levels by 2 to 5 g kg(-1) and Bray-1 P levels by 300 to 600 mg kg(-1) (0-15 cm depth). Plant tissue Zn increased from 24 to 66 mg kg(-1) at the highest application rate. Nearly all of the DTPA-extractable metals remained in the 0- to 8-cm soil depth.

Reduction in drug-induced DNA double-strand breaks associated with beta1 integrin-mediated adhesion correlates with drug resistance in U937 cells

We previously showed that adhesion of myeloma cells to fibronectin (FN) by means of beta1 integrins causes resistance to certain cytotoxic drugs. The study described here found that adhesion of U937 human histiocytic lymphoma cells to FN provides a survival advantage with respect to damage induced by the topoisomerase (topo) II inhibitors mitoxantrone, doxorubicin, and etoposide. Apoptosis induced by a topo II inhibitor is thought to be initiated by DNA damage. The neutral comet assay was used to determine whether initial drug-induced DNA damage correlated with cellular-adhesion-mediated drug resistance. Cellular adhesion by means of beta1 integrins resulted in a 40% to 60% reduction in mitoxantrone- and etoposide-induced DNA double-strand breaks. When the mechanisms regulating the initial drug-induced DNA damage were examined, a beta1 integrin-mediated reduction in drug-induced DNA double-strand breaks was found to correlate with reduced topo II activity and decreased salt-extractable nuclear topo IIbeta protein levels. Confocal studies showed changes in the nuclear localization of topo IIbeta; however, alterations in the nuclear-to-cytoplasmic ratio of topo IIbeta in FN-adhered cells were not significantly different. Furthermore, after a high level of salt extraction of nuclear proteins, higher levels of topo IIbeta-associated DNA binding were observed in FN-adhered cells than in cells in suspension. Together, these data suggest that topo IIbeta is more tightly bound to the nucleus of FN-adhered cells. Thus, FN adhesion by means of beta1 integrins appears to protect U937 cells from initial drug-induced DNA damage by reducing topo II activity secondarily to alterations in the nuclear distribution of topo IIbeta.

Biventricular cardiac dysfunction after acute massive pulmonary embolism in the rat

Cardiac dysfunction has been documented in vivo after acute massive pulmonary embolism (AMPE). The present study tests whether intrinsic ventricular dysfunction occurs in rat hearts isolated after AMPE. AMPE was induced in spontaneously breathing ketamine-xylazine-anesthetized rats by thrombus infusion until mean arterial blood pressure (MAP) was approximately 40% of basal measurement. A hypotensive control group underwent controlled blood withdrawal to produce MAP approximately 40% of basal levels. Shams underwent identical surgical and anesthesia preparation but without pulmonary embolization. Hearts were perfused in isovolumetric mode, and simultaneous right ventricular (RV) and left ventricular (LV) pressures were measured. AMPE caused arterial hypotension with hypoxemia (PO(2) = 50 +/- 14 Torr), acidemia (pH = 7.26 +/- 0.11), and high lactate concentration (6.9 +/- 1.7 mM). Starling curves from both ventricles demonstrated that AMPE significantly reduced ex vivo systolic contractile function in the RV (P = 0.031) and LV (P = 0.008) compared with both the hypotensive control and sham hearts. AMPE did not alter coronary flow or compliance in either ventricle. Soluble tumor necrosis factor-alpha decreased in the RV (P = 0.043) and LV (P = 0.005) tissue. These data support the hypothesis that AMPE produces intrinsic biventricular dysfunction and suggest that arterial hypotension is not the principal mechanism of this dysfunction.

Identifying dementia in the primary care practice

BACKGROUND

The purpose of this study was to evaluate the utility (i.e., positive and negative predictive value) of the 7 Minute Screen in identifying patients with probable Alzheimer's disease (AD) in a primary care practice. A second objective was to estimate the number of undiagnosed AD patients in a typical primary care practice.

METHODS

One hundred thirty-seven successive admissions (96%) of patients over the age of 60 to a primary care practice over a 53-day period who completed informed consent documents were administered the 7 Minute Screen. All patients who screened positive (n = 13) and a random sample of those who screened negative (n = 26) returned for full diagnostic evaluation. Positive predictive value (PPV) and negative predictive value (NPV) of the 7 Minute Screen were determined using the criterion standard of clinical diagnosis established by examination, history, and laboratory studies. Test-retest reliability and time for administration were also determined.

RESULTS

Of the 137 patients evaluated, 13 screened positive and 124 screened negative. Eleven of the 13 patients who screened positive were willing to return to the primary care practice for follow-up evaluation. A random sample of 26 patients who screened negative all agreed to return for follow-up evaluation. Of the 11 patients who screened positive and who returned for evaluation, 10 were subsequently diagnosed with probable AD. The remaining patient was diagnosed with mixed dementia. The caregivers of the two patients who refused to return were contacted and both indicated that the patients were having significant cognitive problems as verified by an activities of daily living scale. Of the 26 patients who screened negative, 25 were judged to be cognitively normal and the 26th was judged to have mild cognitive impairment.

DISCUSSION

In successive admissions of patients over the age of 60 in a primary care practice, the 7 Minute Screen showed a PPV of 91% and an NPV of 96% in identifying patients who were subsequently identified with AD or other dementing disorder. These data suggest that this may be a useful instrument in identifying patients who should undergo diagnostic evaluation for AD and other dementing disorders. Additionally, extrapolation from the data in this practice suggests that there may be between 75 and 100 AD patients in the typical primary care practice, many of whom may not be diagnosed.

Identification of oxidant-sensitive proteins: TNF-alpha induces protein glutathiolation

Reactive oxygen species are thought to play a role in a variety of physiologic and pathophysiological processes. One possible mediator of oxidant effects at the molecular level is a subset of proteins containing reactive cysteine thiols that can be readily oxidized. The transient incorporation of glutathione into cellular proteins is an established response to oxidant stress and could provide a mechanism for reversible covalent modification in response to reactive oxygen species. To better understand the function of protein S-glutathiolation in vivo, a biotinylated membrane-permeant analogue of glutathione, biotinylated glutathione ethyl ester, was developed and used to detect proteins into which glutathione is incorporated under oxidant stress. Oxidant stress from exogenous hydrogen peroxide or generated in response to TNF-alpha was found to increase incorporation of biotinylated glutathione ethyl ester into several HeLa cell proteins. The identity of two of these proteins was determined by peptide sequencing and mass spectrometric peptide mapping. A 23 kDa S-glutathiolated protein was identified as thioredoxin peroxidase II, a member of the peroxiredoxin family of peroxidases known to play a role in redox-dependent growth factor and cytokine signal transduction. A second, 36 kDa, protein was identified as annexin II. Further investigation revealed a single reactive cysteine in the annexin II tail domain. Deletion of the identified cysteine was found to abolish S-glutathiolation of annexin II. These findings demonstrate a specific posttranslational modification associated with an endogenously generated oxidant stress and suggest a mechanism by which TNF-alpha might selectively regulate protein function in a redox-dependent fashion.

Gutta-percha: a look at the need for sterilization

Many have argued that the prevention of contamination becomes a problem when gutta-percha cones are used to obturate the root canal space. This study evaluated the extent of contamination of commercially available gutta-percha cones taken directly from the manufacturer's box. Results show that if gutta-percha is not intentionally contaminated, there is no need for chemical decontamination before obturation.

Cell density-dependent VP-16 sensitivity of leukaemic cells is accompanied by the translocation of topoisomerase IIalpha from the nucleus to the cytoplasm

The resistance of several leukaemic and myeloma cell lines (CCRF, L1210, HL-60, KG-1a and RPMI 8226) to VP-16 was found to increase with cell density and to be maximal (3.5- to 39-fold) in plateau phase cell cultures, as measured by clonogenic and MTT assays. Non-transformed confluent Flow 2000 human fibroblasts and Chinese hamster ovary (CHO) cells were also five- and 15-fold resistant to VP-16 respectively. The transition from log to plateau phase was accompanied by a drastic decrease in topoisomerase (topo) IIalpha content in CHO cells and human fibroblasts, while the leukaemic cells maintained constant cellular levels of topo IIalpha and topo IIbeta. However, the nuclear topo IIalpha content was found to decrease as a result of translocation of the enzyme to the cytoplasmic compartment in the leukaemic cells. This was confirmed by subcellular fractionation experiments, Western blotting analyses and immunocytochemistry studies. The quantity of topo IIalpha in plateau phase cytoplasmic fractions ranged from 18% in L1210 cells to 50% in HL-60 and 8226 cells, as measured by both immunoblotting and quantification of the label in immunofluorescent images. The cytoplasmic fraction from plateau phase cells retained topo II catalytic activity, as measured by the decatenation of kinetoplast DNA. The nuclear-cytoplasmic ratio of topo IIalpha may be critical in determining the sensitivity of leukaemic cells to topo II inhibitors. Cytoplasmic trafficking of topo IIalpha was observed in plasma cells obtained from patients with multiple myeloma, and perhaps contributes to drug resistance in this disease.

Current Clinical Practice: Application of Resistance Reversal Agents in Hematologic Malignancies

The clinical application of resistance reversal drugs for patients with hematologic malignancies is reviewed. The phenomenon of multidrug resistance versus other mechanisms are discussed. The pump-like mechanisms of P-glycoprotein, multidrug resistance associated protein, lung resistance protein and of other ATP binding cassette transporter proteins are reviewed briefly, as well as the important substrate drugs and pump-blocking compounds. The problems associated with resistance protein assays in clinical samples and the concept of prognostic versus therapeutic clinical relevance are described, within the context of selected hematologic malignancies. Toxicities and treatment outcomes of phase II and III trials of reversal agents in lymphoma, multiple myeloma, myelodysplastic syndromes, acute myeloid leukemia and blast phase of chronic myeloid leukemia are reviewed. Finally, current options for on-study management of relapsed or refractory hematologic malignancy patients are discussed.

Effects of wild-type p53 expression on the quantity and activity of topoisomerase IIalpha and beta in various human cancer cell lines

The p53 null HL-60 cell line was transfected with plasmids coding for either the wild-type p53 or mutant p53 gene. The stable expression of wild-type p53 resulted in a significant increase in sensitivity to the topoisomerase II poisons etoposide and doxorubicin, but not to the topoisomerase II inhibitors razoxane and ADR-529. HL-60 cells expressing wild-type p53 demonstrated 8- to 10-fold more VP-16 induced DNA breaks by the alkaline elution assay. The effect of inducible expression of wild-type p53 was also studied in the p53 null erythroblastoid cell line K562 and in the human squamous carcinoma cell line SqCC. The inducible expression of wild-type p53 in the K562 cell line resulted in a 3-fold increase in sensitivity to VP-16. The quantity of topoisomerase IIalpha was not altered by the transfection as determined by immunoblotting, while the amount of the beta isoform was increased 2.5-fold in HL-60 cells. The topo II catalytic activity present in nuclear extracts was measured as the decatenation of kinetoplast DNA, and found to be unaltered by p53 expression. Immunostaining for topoisomerase IIalpha was substantially diminished in both stable and inducible wild-type p53 expressing cells when three different antibodies were used (two polyclonal and one monoclonal). However, the addition of VP-16 resulted in a rapid appearance of nuclear fluorescence for topoisomerase IIalpha. No changes in topoisomerase IIbeta immunostaining were observed. These results suggest that an epitope for topoisomerase IIalpha is concealed in cells expressing wild-type p53 and that a complex between topoisomerase IIalpha and p53 may be disrupted by the addition of antitumor drugs.

Carbamate analogues of amsacrine active against non-cycling cells: relative activity against topoisomerases IIalpha and beta

PURPOSE

Methyl N-(4'-(9-acridinylamino)-phenyl)carbamate hydrochloride (AMCA) and methyl N-(4'-(9-acridinylamino)-2-methoxyphenyl)carbamate hydrochloride (mAMCA) are analogues of the topoisomerase II (topo II) poison amsacrine, and are distinguished from amsacrine by their high cytotoxicity towards non-cycling cells. Since mammalian cells contain two forms (alpha and beta) of topo II and the alpha isoform is down-regulated in non-cycling cells, we have considered whether these carbamate analogues target topo IIbeta selectively.

METHODS

A drug permeable yeast strain (JN394 top2-4) was transformed using a shuttle vector containing either human top2alpha, human top2alpha or yeast top2 under the control of a GAL1 promoter. The strain was analysed at a non-permissive temperature, where only the plasmid-borne topo II was active.

RESULTS

AMCA and mAMCA produced comparable levels of cell killing with human DNA topo IIalpha, human DNA topo IIbeta and yeast DNA topo II. Two other acridine derivatives N-[2-(dimethylamino)ethyl]acridine-4-carboxamide (DACA) and its 7-chloro derivative, which like AMCA and mAMCA are able to overcome multidrug resistance mechanisms, were much more active against human DNA topo IIalpha than against human DNA topo IIbeta and yeast DNA topo II. A series of mutant Chinese hamster and human lines with defined topo lesions, including the HL60/MX2 line that lacks topo IIbeta expression, was also used to compare resistance to amsacrine, AMCA and etoposide. Loss of topo IIbeta activity had a greater effect on amsacrine and AMCA than on etoposide. Resistance of murine Lewis lung cultures in exponential and plateau phase was also measured. Loss of topo IIalpha activity, as measured in both mutant cells expressing lower amounts of enzyme and in cells in plateau phase, resulted in concomitant acquisition of resistance that was greatest for etoposide and least for AMCA.

CONCLUSION

We conclude that the carbamate analogues of amsacrine recognize both topo IIalpha and beta in cells.

Regulation of endothelial cell adherens junctions by a Ras-dependent signal transduction pathway

Adherens junctions, consisting of transmembrane cadherin molecules and their associated cytoplasmic alpha-, beta-, and gamma-catenin proteins, are thought to be critical for the development of stable cell adhesion and subsequent 3-dimensional tissue organization. In human endothelial cells there is a marked induction of gamma-catenin levels when cells reach confluence. We demonstrate that expression of a dominant negative ras gene product (N17ras) via adenoviral mediated gene transfer inhibits the confluent-dependent rise in gamma-catenin mRNA and protein levels. Consistent with its effects on overall gamma-catenin levels, expression of N17ras also reduces the amount of gamma-catenin associated with the adherens junction. Finally, although expression of N17ras under normal culture conditions produces no clear morphological phenotype, endothelial cells expressing a dominant negative ras gene product fail to form 3-dimensional, vascular-like structures when plated on reconstituted extracellular matrix.

Multiple DNA repair mechanisms and alkylator resistance in the human medulloblastoma cell line D-283 Med (4-HCR)

PURPOSE

We have previously reported preferential repair of DNA interstrand crosslinks in the 4-hydroperoxycyclophosphamide-resistant human medulloblastoma cell line D-283 Med (4-HCR). We now report further studies that explored the potential mechanisms underlying this repair.

METHODS

Limiting dilution assays and Western, Southern, and Northern blots were used to compare specific differences between D-283 Med (4-HCR) and its parental line D-283 Med.

RESULTS

D-283 Med (4-HCR) was cross-resistant to melphalan and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), with O6-alkylguanine-DNA alkyltransferase (AGT) levels of 466+/-164 fmol/mg protein; AGT levels in the parental line, D-283 Med, were 76+/-96 fmol/mg. The increase in AGT activity was not a result of gene amplification. Depleting AGT with O6-benzylguanine partially restored sensitivity to BCNU. Both cell lines were deficient in the human mismatch protein MutLalpha. ERCC4 mRNA and poly(ADP-ribose) polymerase levels were similar in both cell lines, and ERCC1 mRNA levels were 2- to 2.5-fold lower in D-283 Med (4-HCR). Topoisomerase I levels were 2- to 2.5-fold higher in D-283 Med compared with D-283 Med (4-HCR).

CONCLUSION

These results, while illustrating the multiple differences between D-283 Med and D-283 Med (4-HCR), do not explain the enhanced DNA interstrand crosslink repair seen in D-283 Med (4-HCR).

A large PEST-like sequence directs the ubiquitination, endocytosis, and vacuolar degradation of the yeast a-factor receptor

The yeast a-factor receptor (encoded by STE3) is subject to two modes of endocytosis, a ligand-dependent endocytosis as well as a constitutive, ligand-independent mode. Both modes are associated with receptor ubiquitination (Roth, A.F., and N.G. Davis. 1996. J. Cell Biol. 134:661-674) and both depend on sequence elements within the receptor's regulatory, cytoplasmically disposed, COOH-terminal domain (CTD). Here, we concentrate on the Ste3p sequences required for constitutive endocytosis. Constitutive endocytosis is rapid. Receptor is synthesized, delivered to the cell surface, endocytosed, and then delivered to the vacuole where it is degraded, all with a t1/2 of 15 min. Deletion analysis has defined a 36-residue-long sequence mapping near the COOH-terminal end of the Ste3p CTD that is the minimal sequence required for this rapid turnover. Deletions intruding into this interval block or severely slow the rate of endocytic turnover. Moreover, the same 36-residue sequence directs receptor ubiquitination. Mutants deleted for this sequence show undetectable levels of ubiquitination, and mutants having intermediate endocytosis defects show a correlated reduced level of ubiquitination. Not only necessary for ubiquitination and endocytosis, this sequence also is sufficient. When transplanted to a stable cell surface protein, the plasma membrane ATPase Pma1p, the 36-residue STE3 signal directs both ubiquitination of the PMA1-STE3 fusion protein as well as its endocytosis and consequent vacuolar degradation. Alanine scanning mutagenesis across the 36-residue-long interval highlights its overall complexity-no singular sequence motif or signal is found, instead required sequence elements distribute throughout the entire interval. The high proportion of acidic and hydroxylated amino acid residues in this interval suggests a similarity to PEST sequences-a broad class of sequences which have been shown to direct the ubiquitination and subsequent proteosomal degradation of short-lived nuclear and cytoplasmic proteins. A likely possibility, therefore, is that this sequence, responsible for both endocytosis and ubiquitination, may be first and foremost a ubiquitination signal. Finally, we present evidence suggesting that the true signal in the wild-type receptor extends beyond the 36-residue-long sequence defined as a minimal signal to include contiguous PEST-like sequences which extend another 21 residues to the COOH terminus of Ste3p. Together with sequences identified in two other yeast plasma membrane proteins, the STE3 sequence defines a new class of ubiquitination/endocytosis signal.

Grapefruit juice and the response to warfarin

The effect if any of prepared frozen grapefruit juice on prothrombin times (PTs) in patients undergoing stabilized warfarin therapy was studied. Patients receiving low-intensity warfarin therapy (targeted International Normalized Ratio [INR], 2-3) who had two consecutive baseline PTs within 10% of each other were recruited. Patients who regularly consumed grapefruit juice or alcohol or who were taking drugs known to interact with grapefruit juice were excluded. A one-week supply of freshly prepared frozen grapefruit juice in individual 8-oz containers was given to all the subjects, who were told to drink the entire contents of on container three times a day for one week. PTs were measured and INRs calculated on the day before grapefruit juice ingestion began (day 0) and a days 2, 6, and 8. Ten men (mean age, 66 years) were enrolled; one withdrew because of diarrhea. Compliance in consuming the juice was reported to range from 85.7% to 100% among patients. There was no significant difference among PT or INR values over the course of the study in any of the nine subjects. Ingestion of grapefruit juice prepared from frozen concentrate did not change PTs in patients treated with warfarin.

Broadened clinical utility of gene gun-mediated, granulocyte-macrophage colony-stimulating factor cDNA-based tumor cell vaccines as demonstrated with a mouse myeloma model

Effective immunization against the murine B16 melanoma by a nonviral approach in which a gene gun is used to transfer GM-CSF cDNA into tumor cells has been described. We have extended this nonviral approach by using the poorly immunogenic murine myeloma MPC11 model. Vaccination with the transfected, GM-CSF-expressing MPC11 cells induced a potent antitumor cytotoxic T lymphocyte response associated with tumor rejection in the majority of the test mice. Furthermore, nearly 100% (27 of 28) of the tumor-free mice were able to reject a tumor rechallenge. While this approach is clinically attractive because of minimal tissue manipulation/culturing and the absence of infectious agents, a number of tested human primary tumors, including myeloma cells, have failed to produce high levels of GM-CSF after gene gun transfection. To circumvent the low transfection efficiency in certain human tumor cells, we showed that combining irradiated tumor cells to provide tumor antigens together with gene gun-transfected fibroblasts to provide GM-CSF induced effective tumor rejection. We also report that normal human skin fibroblasts transfected by the gene gun produce high levels of human GM-CSF (250 ng/10(6) cells/24 hr). These results suggest that combining irradiated tumor cells with gene gun-transfected fibroblasts results in antitumor immune responses and may allow for a wider application of this approach to cancer immunotherapy.

Defining the role of novel high-dose chemotherapy regimens for the treatment of high-risk breast cancer

We have explored several novel high-dose combinations in an attempt to increase antitumor activity while decreasing treatment-related toxicity. From October 1989 through June 1997, we performed phase I/II dose-escalation trials exploring novel high-dose regimens including ifosfamide/carboplatin/etoposide, mitoxantrone/thiotepa, and paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ)/mitoxantrone/thiotepa. We have also evaluated busulfan/cyclophosphamide and cyclophosphamide/thiotepa/carboplatin in phase II trials. Three hundred ninety-three patients have been treated in these trials and followed for a minimum of 3 months. Event-free survival (including relapses and treatment-related mortality; +/-SE) at 3 years by stage and chemosensitivity is as follows: stage II, four to nine positive nodes (n=16), 52%+/-17%; stage II, greater than nine nodes (n=30), 46%+/-11%; stage III (n=59), 50%+/-8%; inflammatory stage III (n=15), 27%+/-17%; stage IV, anthracycline responsive (n=69), 19%+/-5%; stage IV, anthracycline refractory but responsive to salvage therapy with ifosfamide, carboplatin, and etoposide or paclitaxel (n=53), 12%+/-6%; stage IV, refractory (n=128), 5%+/-2%; and stage IV, not evaluable for response (n=23), 10%+/-8%. Treatment-related mortality was 4% for both phase I and II studies involving stage II breast cancer patients, 5% for stage III breast cancer, 15% for inflammatory breast cancer, and 18% for all stage IV breast cancers, responsive and refractory. We conclude that high-dose therapy for the treatment of high-risk early stage breast cancer or metastatic breast cancer results in durable remissions. Chemosensitivity to induction regimens remains the most important prognostic indicator, although long-term survival has been seen even in patients with highly refractory disease. Further studies are necessary to define optimal high-dose strategies based on stage and chemosensitivity of disease.

Retrovirus-mediated gene transfer of ornithine-delta-aminotransferase into keratinocytes from gyrate atrophy patients

Gyrate atrophy is a progressive blindness associated with deficiency of ornithine aminotransferase (OAT). The strategy of using an autologous keratinocyte graft, modified to express high levels of OAT as an ornithine-catabolizing skin-based enzyme sink, is investigated. Two OAT-containing retroviral vectors were constructed with or without a resistance gene. When packaged in a retroviral vector particle generated with the gibbon ape leukemia (GALV) virus envelope (PG13), these vectors could readily transduce >50% of target keratinocytes. The transduced keratinocytes in culture expressed up to 75-fold more OAT than normal control keratinocytes and these gene-modified cells extracted [14C]ornithine more efficiently than controls. The vector prepared without neo transduced cells more efficiently and led to higher levels of OAT expression than the neo-containing vector. Ornithine catabolism was maintained at high levels when the transduced patient keratinocytes were differentiated in vitro as a multilayered cutaneous organoid.

High-dose chemotherapy and autologous peripheral blood stem cell transplantation in patients with multiple myeloma and renal insufficiency

Six patients with multiple myeloma and chronic renal insufficiency (serum creatinine >3.0 mg/dl), including four on dialysis, received high-dose busulfan and cyclophosphamide (BUCY) followed by autologous peripheral stem cell transplantation. Peripheral blood stem cells were collected after priming with cyclophosphamide, etoposide and G-CSF. Patterns of engraftment and toxicities were not apparently different from those seen in myeloma patients with normal renal function. There was one toxicity-related death, resulting from a massive spontaneous subdural hematoma. One patient died of disease progression 6 months after transplant, while the remaining four patients are alive and free of myeloma progression 6 to 39 months after high-dose therapy. Two of these patients have remained in complete remission for 28 and 39 months. Our experience suggests that high-dose therapy with BUCY and autologous peripheral blood stem cell rescue is feasible in patients with multiple myeloma and renal failure.

Drug resistance to DNA topoisomerase I and II inhibitors in human leukemia, lymphoma, and multiple myeloma

Several antineoplastic agents used in the treatment of hematologic malignancies exert their cytotoxic effects by inhibiting the activity of nuclear DNA topoisomerase (topo) I or II. Mechanisms of drug resistance to topoisomerase inhibitors have been defined at the molecular level from in vitro studies using model cell lines, and include quantitative and qualitative changes in topo I and II. The possible roles of these mechanisms in clinical drug resistance and clinical outcomes for patients with hematologic malignancies are now under investigation. Available data indicate that the blast content of topo II does not correlate with clinical outcome in acute myeloid leukemia (AML), and this may also be true in acute lymphocytic leukemia (ALL). Chronic lymphocytic leukemia (CLL) cells are resistant to topo II inhibitors because they express low levels of topo II. Further studies using sequential biopsy samples and assays of topoisomerase activity should establish the role that changes in topo I and II activity play in the development of drug resistance in hematologic malignancies.

Ornithine-delta-aminotransferase expression and ornithine metabolism in cultured epidermal keratinocytes: toward metabolic sink therapy for gyrate atrophy

There is now strong evidence that the chorioretinal degeneration associated with ornithine-delta-aminotransferase (OAT) deficiency is a consequence of hyperornithinemia. Therefore development of a metabolic system for clearing ornithine from the circulation is being pursued as a potential treatment. The skin is considered an attractive location for such a metabolic system because autologous cells can be safely and easily utilized. This study was undertaken to determine the ornithine metabolizing capacity of epidermal keratinocytes expressing normal and superphysiologic amounts of OAT. The data show that overexpression of OAT in keratinocytes cultured from a gyrate atrophy patient restores ornithine metabolism and results in a rate of ornithine disappearance from the medium that is significantly higher than the rate of disappearance from the medium bathing normal keratinocytes. In addition, OAT activity determined in soluble protein prepared from sonicates suggests that the capacity to maintain plasma ornithine within the normal range is contained within an accomplishable graft of keratinocytes overexpressing OAT. However, the actual rate of ornithine disappearance from the media was significantly less than predicted from enzyme activity assays. Following ornithine metabolite production by intact cells suggests that ornithine metabolism is limited primarily by clearance of downstream metabolites, as opposed to substrate delivery.

Quantitative immunofluorescence and immunoelectron microscopy of the topoisomerase II alpha associated with nuclear matrices from wild-type and drug-resistant chinese hamster ovary cell lines

Topo II alpha is considered an important constituent of the nuclear matrix, serving as a fastener of DNA loops to the underlying filamentous scaffolding network. To further define a mechanism of drug resistance to topo II poisons, we studied the quantity of topo II alpha associated with the nuclear matrix in drug-resistant SMR16 and parental cells in the presence and absence of VP-16. Nuclear matrices were prepared from nuclei isolated in EDTA buffer, followed by nuclease digestion with DNase II in the absence of RNase treatment and extraction with 2 M NaCl. Whole-mount spreading of residual structures permits, by means of isoform-specific antibody and colloidal-gold secondary antibodies, an estimate of the amount of topo II alpha in individual nuclear matrices. There are significant variations in topo II alpha amounts between individual nuclear matrices due to the cell cycle distribution. The parental cell line contained eight to ten times more nuclear matrix-associated topo II alpha than the resistant cell line matrices. Nuclear matrix-associated topo II alpha from wild-type and resistant cell lines correlated well with the immunofluorescent staining of the enzyme in nuclei of intact cells. The amount of DNA associated with residual nuclear structures was five times greater in the resistant cell line. This quantity of DNA was not proportional to the quantity of topo II alpha in the same matrix; in fact they were inversely related. In situ whole-mount nuclear matrix preparations were obtained from cells grown on grids and confirmed the results from labeling of isolated residual structures.

Identification and characterization of P2Y2 nucleotide receptors in human retinal pigment epithelial cells

P2 nucleotide receptor expression in cultured human retinal pigment epithelial (RPE) cells was investigated using the photoaffinity ATP analog BzATP, polymerase chain reaction of reverse-transcribed RNA (RT-PCR) and fura-2 fluorescence measurement of changes in intracellular free calcium concentration ([Ca2+]i). In experiments carried out in RPE cells at passage 10-15, addition of micromolar concentrations of ATP, UTP, and ATPgammaS to RPE cells resulted in a rapid, transient 3.5-fold increase in [Ca2+]i followed by a prolonged elevation that was twofold above the original baseline. Similar results were obtained from cells at passage 2. Characteristics of nucleotide-stimulated calcium mobilization in RPE cells, including partial inhibition by pertussis toxin, suggest that a G protein-coupled receptor mediates this response. Consistent with the expression of a P2Y2 nucleotide receptor subtype in RPE cells, [alpha-32P]BzATP labeled a 53-kDa protein in plasma membranes, and RT-PCR revealed the presence of P2Y2 receptor RNA. Adenosine had no effect on [Ca2+]i in RPE cells, indicating that the A2 subtype of P1 receptor described previously in human RPE is not involved in the response to nucleotides. Together the results indicate that human RPE cells express functional P2Y2 nucleotide receptors.

Interleukin-10 immunoadhesin production by a replication-defective adenovirus

The present study examined the use of replication-defective adenovirus for in vitro production of an immunoadhesin. A recombinant adenovirus, rendered replication defective by deletion of the E1 gene, was constructed to contain the murine interleukin-10 gene fused in frame with the hinge, CH2, and CH3 domains of the murine immunoglobulin gamma 1 heavy chain constant region gene under the control of the human cytomegalovirus promoter. The resultant recombinant virus, Ad5.hCMV.mIL-10:HFc, was used to transduce several cell types. The expressed protein, mIL-10:HFc, is secreted as a disulfide-bonded homodimer. In vitro, a murine pro-B-cell line expressing transfected recombinant murine interleukin-10 receptor proliferated in response to purified mIL-10:HFc. The results obtained demonstrate the relative ease of production of an immunoadhesin using replication-defective adenovirus.

Potentiation of etoposide-induced apoptosis by staurosporine in human tumor cells is associated with events downstream of DNA-protein complex formation

Protein kinase inhibitors have demonstrated potential for use in the therapy of human cancers, in particular leukemia. Staurosporine, a protein kinase inhibitor with broad specificity, enhances the cytotoxic effects of various antitumor agents with different modes of action. The topoisomerase II inhibitor, etoposide, has shown clinical activity against a wide range of tumor types.

PURPOSE

The purpose of this study was to assess the effects of staurosporine on etoposide-induced cell death processes in a human tumor of epithelial origin.

METHODS

Modulation of etoposide-induced apoptosis by staurosporine in HeLa cells was assessed by cell morphology, extraction of low molecular weight DNA, quantitation of DNA-protein complexes, and measurements of rates of DNA synthesis. The effects on cellular genes implicated in apoptosis were determined by Northern and Western blotting, along with assays of cyclin-dependent kinase activities.

RESULTS

Staurosporine exhibited a two- to three-fold potentiation of apoptosis caused by etoposide in HeLa cells when applied concurrently, or immediately following etoposide removal, but did not alter the quantity of DNA-protein complexes produced by etoposide. Etoposide-induced apoptosis, and its potentiation by staurosporine, were associated with reduced c-myc expression, and a moderate increase in p21WAF1/CIP1 mRNA and protein levels. Inhibitors of cyclic AMP-dependent protein kinase and protein kinase C, which exhibit greater specificity than staurosporine, were without effect on apoptosis caused by etoposide, whereas use of the tyrosine phosphatase inhibitor, vanadate, resulted in its abrogation. The potentiation of etoposide-induced apoptosis by staurosprine was associated with a significant increase in cyclin A-dependent kinase activity. In addition, etoposide caused substantial inhibition of DNA synthesis.

CONCLUSION

These results indicate that staurosporine potentiates apoptosis through events which occur downstream of DNA damage, and implicate unscheduled activation of cyclin A-dependent kinase during inhibition of DNA synthesis as a possible cause.

Verapamil suppresses the emergence of P-glycoprotein-mediated multi-drug resistance

Selection protocols were designed to determine whether non-cytotoxic chemomodifiers can influence the evolution of the drug-resistant phenotype. To this end, the human multiple myeloma cell line RPMI 8226 (8226/S) was selected with either doxorubicin, verapamil or doxorubicin plus verapamil. Using this approach low-level multi-drug-resistant (MDR) cell lines were obtained when 8226/S was selected with doxorubicin only or doxorubicin plus verapamil but not with verapamil only. The MDR phenotypes obtained were mechanistically distinct. In doxorubicin only-selected cells (8226/dox4), drug resistance was mediated by over-expression of the MDR1 gene and its cognate protein P-glycoprotein. In contrast, the drug resistance seen in the doxorubicin plus verapamil-selected cells was mediated through decreases in topoisomerase II protein levels and catalytic activity and not by P-glycoprotein over-expression. Cells selected with verapamil alone did not become resistant to any of the drugs tested. None of the 3 selected cell lines showed any changes in MRP gene expression when compared with 8226/S. Our results indicate that the inclusion of verapamil during drug selection with doxorubicin influences the drug-resistant phenotype by preventing the selection of MDR1/P-glycoprotein-positive cells.

Adenovirus-mediated gene transfer of ornithine aminotransferase in cultured human retinal pigment epithelium

PURPOSE

To evaluate the efficacy of adenovirus mediated transfer of ornithine delta-aminotransferase (OAT) into human retinal pigment epithelial (RPE) cells.

METHODS

Adenovirus-mediated gene transfer into primary cultures of human RPE was evaluated by measurement of enzyme activity in whole cell extracts and by Western blot analysis. To assess mitochondrial integrity, succinate dehydrogenase activity was measured in transduced RPE cells. Expression of adenovirus early genes was evaluated using reverse transcription-polymerase chain reaction.

RESULTS

OAT activity, which was 65 nmol/mg.hour in untransduced cells, could be increased to levels in excess of 20,000 nmol/mg.hour using an adenovirus vector carrying the OAT cDNA. There was, however, a significant reduction in succinate dehydrogenase activity associated with OAT activity greater than 12,000 nmol/mg.hour. Transduced human RPE displayed an altered morphology that appears to be a response to the vector because similar changes could be induced by an adenovirus vector that does not carry the OAT cDNA. Adenovirus early gene expression was detected in transduced RPE.

CONCLUSIONS

This study represents a first step in the development of intraocular gene replacement therapy for the treatment of gyrate atrophy. The authors demonstrate that adenovirus is an efficient vehicle for the delivery of OAT into human RPE and that RPE will tolerate greater than a 150-fold increase in OAT-specific activity. Evidence for disruption of mitochondria when OAT activity exceeds 12,000 nmol/mg.hour and vector-induced toxicity indicate that more controlled transgene expression and refinement of the vector systems is needed.

A regulatory role in mammalian salivary glands for 5-hydroxytryptamine receptors coupled to increased cyclic AMP production

Although a functional role for serotonin (5-hydroxytryptamine, 5-HT) has been defined in the salivary glands of some lower species, relatively few data supporting a role for 5-HT in the regulation of mammalian salivary glands have been presented. Our initial results from polymerase chain reaction studies in cells of mammalian submandibular gland origin using consensus sequence primers from G protein-coupled receptors suggested the presence of mRNA for a 5-HT receptor in these cells. Based on this observation, the question of a role for 5-HT in mammalian submandibular gland function was re-addressed, using isolated, perfused rat submandibular glands and dispersed-cell aggregates from this gland. In perfused glands, 5-HT decreased the rate of saliva flow initiated by acetylcholine by about 50% and increased the amount of protein in the saliva two-fold. In dispersed-cell aggregates, 5-HT elicited a concentration-dependent increase in the accumulation of adenosine 3',5' monophosphate (cyclic AMP; EC50 = 660 +/- 110 nM). In addition, functional studies, as well as radioligand binding experiments, indicated that the effects of 5-HT are independent of beta-adrenoceptors. Accumulation of cAMP in gland cells was consistent with a direct action of 5-HT on adenylyl cyclase. Similar cyclic AMP responses to 5-HT were observed in cells isolated from mouse and opossum submandibular glands and rat sublingual and parotid glands. Our findings suggest the presence of a 5-HT receptor in mammalian salivary glands coupled to the stimulation of adenylyl cyclase and, at least in rat submandibular gland, involved in modifying the volume and protein content of saliva.

Preservation of amplitude modulation coding in the presence of background noise by chinchilla auditory-nerve fibers

Sound envelope temporal fluctuations are important for effective processing of biologically relevant acoustic information including speech, animal vocalizations, sound-source location, and pitch. Amplitude modulation (AM) of sound envelopes can be encoded in quiet with high fidelity by many auditory neurons including those of the auditory nerve (AN) and cochlear nucleus. From both neurophysiological and clinical perspectives, it is critical to understand the effects of background masking noise on the processing of AM. To further this goal, single-unit recordings were made from AN fibers in anesthetized chinchillas. Units were classified according to spontaneous firing rate (SR) and threshold. Best frequency (BF) pure-tone bursts and AM (10-500 Hz) tone bursts were employed as stimuli at several sound levels, both in quiet and in the presence of a continuous wideband noise. It was found that (1) in quiet, low SR AN fibers show the strongest AM coding, followed in order by medium SR and high SR fibers, respectively. (2) AN units of all three classes generally preserve their AM coding even in the presence of loud (0 or +6 dB S/N) background noise and at high sound levels (over 75 dB SPL). (3) This preservation is usually achieved by lowering the average firing rate proportionately to decreases in the synchronous (fundamental frequency) response. (4) For a few AN fibers, the AM coding increases or is reduced in the presence of the background noise. These findings suggest that AN preservation of AM coding in the presence of a continuous masking noise results from shifts in the operating ranges and firing rates of AN fibers resulting from cochlear nonlinearities and adaptive mechanisms.

Alterations in the topoisomerase II alpha gene, messenger RNA, and subcellular protein distribution as well as reduced expression of the DNA topoisomerase II beta enzyme in a mitoxantrone-resistant HL-60 human leukemia cell line

A human HL-60 leukemia cell line selected for resistance to mitoxantrone, HL-60/MX2, displays cross-resistance only to agents whose cytotoxicities result from interaction with the nuclear enzyme DNA topoisomerase II (topo II). The topo II catalytic activity is reduced 2-fold in the drug-resistant cell line in association with the absence of the M(r) 180,000 isoform of topo II and the finding of novel M(r) 160,000 topo II alpha-related immunoreactive protein in these cells by immunoblot. The topo II alpha (M(r) 170,000) protein levels in nuclear extracts from the HL-60/MX2 cells were noted on average to be approximately 40% lower than in comparable HL-60 nuclei. Studies of the subcellular localization of topo II by immunohistochemical and fractional extraction techniques demonstrated that the M(r) 160,000 topo II alpha-related protein is primarily localized in the cytoplasm. Levels of the 6.3-kilobase topo II alpha mRNA were noted to be reduced 2-fold in the HL-60/MX2 cells in association with the finding of a novel 4.8-kilobase topo II alpha-related mRNA transcript that was present in HL-60/MX2 but not HL-60 cells. The absence of topo II beta protein in nuclear and whole cell extracts from the HL-60/MX2 cells was associated with the virtual absence of detectable topo II beta mRNA in those cells by Northern blot analysis. Using a reverse transcription-PCR assay we were able to demonstrate the presence of very low levels of topo II beta mRNA in HL-60/MX2 cells, representing < 1% of that found in the HL-60 cells. In contrast, the nuclear catalytic activity and cellular mRNA levels of the related nuclear enzyme DNA topoisomerase I were nearly identical in the two cell types. Southern blot analysis of DNA extracted from the drug-sensitive and drug-resistant cells revealed a structural alteration in one topo II alpha allele in the HL-60/MX2 cells, but there was no evidence of rearrangement or hypermethylation of the topo II beta locus. These results indicate that the reduced levels of topo II alpha and beta isoenzymes observed in mitoxantrone-resistant HL-60/MX2 cells are related to changes in the levels of their respective mRNA transcripts. The identification of structural changes in one topo II alpha allele in the HL-60/MX2 cell line suggests that the altered allele may serve as the source of the unique 4.8-kilobase topo II alpha-related mRNA transcript and the M(r) 160,000 protein discovered in those cells.

Phosphorylation of the alpha- and beta-isoforms of DNA topoisomerase II is qualitatively different in interphase and mitosis in Chinese hamster ovary cells

Qualitative differences between interphase and mitotic topoisomerase II were studied in Chinese hamster ovary cells. Differences in sites of phosphorylation of in vivo 32P-labeled topoisomerase II alpha were observed between mitosis and interphase by one-dimensional phosphopeptide mapping of partial tryptic digests. Two-dimensional phosphopeptide mapping of complete trypsin digests revealed two phosphopeptides unique to interphase and three phosphopeptides unique to mitosis. A reduced electrophoretic mobility on denaturing gels (approximately 190 kDa) was observed for the beta-isoform of topoisomerase II in mitosis relative to interphase. Treatment of lysates with alkaline phosphatase demonstrated that this was due to phosphorylation of mitotic topoisomerase II beta. The existence of interphase- and mitosis-specific sites of phosphorylation of topoisomerase II alpha, along with the electrophoretic mobility shift caused by phosphorylation of topoisomerase II beta in mitosis, demonstrates qualitative differences between interphase and mitosis in the phosphorylation state of both isoforms of topoisomerase II.

D2 dopamine receptor response to endophyte-infected tall fescue and an antagonist in the rat

Effects on rat brain D2 dopamine receptors by endophyte-infected tall fescue seed consumption and antagonist injection were characterized. Forty-eight male Wistar rats (225 g) in three separate trials were exposed to either 22 or 32 degrees C. Diets, to maintain similar concentrations of ergovaline, contained 10% (Trial 1) or 15% (Trials 2 and 3) endophyte-infected (E+; 325 average ppb of ergovaline) or uninfected (E-; 0 ppb of ergovaline) tall fescue seed. Rats were injected i.p. daily with either placebo (PL) or an experimental D2 dopamine antagonist (DA, .0375 mg/kg BW). No effects (P > .10) on diet DM intake by E+ ingestion or DA injection were detected at 22 degrees C. However, ingestion of E+ reduced (P < .01) and injection of DA improved (P < .05) DM intake of rats housed in 32 degrees C (11.1 vs 15.4 g of DM/d for E+ vs E-, respectively). Whole brain D2 dopamine receptor density (Bmax) and mRNA were reduced (P < .05) by E+ and increased (P < .05) by DA in Trial 1. No treatment effects (P > .10) on cerebral cortex alpha 1- and alpha 2-adrenergic or striatal D2 dopamine receptor Bmax were measured in Trials 2 and 3. In summary, dietary E+ reduced whole brain D2 dopamine mRNA and Bmax, whereas injection of DA increased D2 dopamine mRNA. Thus, long-term regulation of monoamine receptors seems to be affected by E+ ingestion or DA injection.

Cloning and expression of a human P2U nucleotide receptor, a target for cystic fibrosis pharmacotherapy

The Cl- secretory pathway that is defective in cystic fibrosis (CF) can be bypassed by an alternative pathway for Cl- transport that is activated by extracellular nucleotides. Accordingly, the P2 receptor that mediates this effect is a therapeutic target for improving Cl- secretion in CF patients. In this paper, we report the sequence and functional expression of a cDNA cloned from human airway epithelial (CF/T43) cells that encodes a protein with properties of a P2U nucleotide receptor. With a retrovirus system, the human airway clone was stably expressed in 1321N1 astrocytoma cells, a human cell line unresponsive to extracellular nucleotides. Studies of inositol phosphate accumulation and intracellular Ca2+ mobilization induced by extracellular nucleotides in 1321N1 cells expressing the receptor identified this clone as the target receptor in human airway epithelia. In addition, we independently isolated an identical cDNA from human colonic epithelial (HT-29) cells, indicating that this is the same P2U receptor that has been functionally identified in other human tissues. Expression of the human P2U receptor (HP2U) in 1321N1 cells revealed evidence for autocrine ATP release and stimulation of transduced receptors. Thus, HP2U expression in the 1321N1 cell line will be useful for studying autocrine regulatory mechanisms and in screening of potential therapeutic drugs.

Altered subcellular distribution of topoisomerase II alpha in a drug-resistant human small cell lung cancer cell line

A drug-resistant human small cell lung cancer cell line, H209/V6, selected in the presence of increasing concentrations of 9-(4,6-O-ethylidene-beta-D-glucopyranosyl)-4'-demethylepipodophylloto xin (VP-16) from parental H209 cells, is 22-, 9-, and 4-fold resistant to VP-16, 4'-(9-acridinyl-amino)methanesulfon-m-anisidide, and doxorubicin, respectively, but not cross-resistant to 1,4-dihydroxy-5,8-bis((2-[(2-hydroxyethyl)amino] ethyl]-amino)-9,10-anthracenedione. These cells do not overexpress P-glycoprotein or the multidrug resistance-associated protein. Immunoblotting demonstrates that H209 cells contain the M(r) 170,000 isoform of topoisomerase II (topo II), while H209/V6 cells have a M(r) 160,000 enzyme but none of the M(r) 170,000 isoform. The cell lines have equal amounts of topo II beta. The H209/V6 cells have a 5-fold decrease in total immunoreactive topo II alpha. The catalytic and VP-16-induced DNA cleavage activities of the topo II present in 0.35 M NaCl nuclear extracts are decreased 2- to 3-fold in the drug-resistant cell line. This decrease in enzymatic activity is not consistent with either the 22-fold VP-16 resistance of the H209/V6 cell line or the approximately 5-fold decrease in immunoreactive topo II alpha in the cells. The M(r) 160,000 isoform from the H209/V6 cell line and the M(r) 170,000 enzyme from the parental cell line were purified so that the enzymatic activity of the 2 isoforms could be evaluated. The catalytic activities of the purified isoforms were found to be very similar. The drug-induced DNA cleavage activity of the M(r) 160,000 enzyme was reduced compared to the M(r) 170,000 enzyme. However, as with the nuclear extracts, the differences in enzymatic activity of the purified enzymes are considerably less than the level of drug resistance. Investigations of the subcellular localization of topo II by immunocytochemical techniques and cytoplasm/nuclear fractionation studies demonstrated that the M(r) 160,000 topo II alpha-related enzyme is primarily localized in the cytoplasm, while the M(r) 170,000 topo II alpha enzyme and topo II beta are located in the nucleus. These data imply that the deleted sequence in the M(r) 160,000 enzyme is not necessary for catalytic activity but is required to facilitate nuclear localization.

Functional expression and photoaffinity labeling of a cloned P2U purinergic receptor

ATP and UTP can function as extracellular signaling molecules by activating plasma membrane receptors termed P2 purinergic receptors. In the present study a P2U receptor cDNA has been expressed in K-562 human leukemia cells, one of the few available mammalian cell lines that lacks an endogenous P2U receptor. In stably transfected cells, low micromolar concentrations of ATP or UTP activated the receptor, resulting in the mobilization of intracellular calcium but not the influx of extracellular calcium. A photoaffinity agonist of the P2U receptor, 3'-O-(4-benzoylbenzoyl)adenosine 5'-[alpha-32P]triphosphate ([alpha-32P]BzATP), photolabeled several proteins in plasma membranes from the stable transfectant or from untransfected K-562 cells. The photolabeling of a 53-kDa protein was significantly greater in plasma membranes from the stable transfectant than from untransfected cells. A mutant receptor containing six consecutive histidine residues at its carboxyl terminus was constructed and used to verify that this 53-kDa protein was the P2U receptor. In plasma membranes from cells expressing the histidine-tagged P2U receptor, but not from cells expressing the wild-type receptor, a single [alpha-32P]BzATP-labeled protein with a molecular mass of 53 kDa was retained on a Ni(2+)-charged Sepharose column, which binds many proteins containing a polyhistidine tag. Photolabeling of the 53-kDa protein by [alpha-32P]BzATP was inhibited by ATP but not by UTP, raising the possibility that the P2U receptor may have distinct binding sites for each nucleotide.

Stanford 3D hyperthermia treatment planning system. Technical review and clinical summary

In the field of deep regional hyperthermia cancer therapy the Sigma 60 applicator of the BSD-2000 Hyperthermia System is one of the most widely used devices. This device employs four independent sources of radiofrequency electromagnetic energy to heat tumour sites deep within the body. The difficulty in determining the input parameters for the four sources has motivated the development of a computer-based three-dimensional (3D) treatment planning system. The Stanford 3D Hyperthermia Treatment Planning System has been in clinical use at Stanford Medical Center for the past 2 years. It utilizes a patient-specific, three-dimensional computer simulation to determine safe and effective power deposition plans. An optimization programme for the selection of the amplitudes, phases and frequency for the sources has been developed and used in the clinic. Examples of the application of the treatment planning for hyperthermia treatment of pulmonary, pelvic, and mediastinal tumours are presented. Methods for quantifying the relative effectiveness of various treatment plans are reviewed.

Cell-cycle-dependent phosphorylation and activity of Chinese-hamster ovary topoisomerase II

Cell-cycle-dependent protein levels and phosphorylation of DNA topoisomerase II in relation to its catalytic and cleavage activities were studied in Chinese-hamster ovary cells. Immunoreactive topoisomerase II protein levels were maximal in G2-phase cells, intermediate in S- and M-phase cells, and minimal in a predominantly G1-phase population. When the phosphorylation of topoisomerase II in vivo was corrected for differences in specific radioactivity of intracellular ATP, the apparent phosphorylation of S- and M-phase topoisomerase II was altered significantly. Relative phosphorylation in vivo was found to be greatest in M-phase cells and decreased in the other populations in the order: S > G2 > asynchronous. Phosphoserine was detected in every phase of the cell cycle, with a minor contribution of phosphothreonine demonstrated in M-phase cells. Topoisomerase II activity measured in vivo as 9-(4,6-O-ethylidene-beta-D-glucopyranosyl)-4'-demethylepipodophylloto xin (VP-16)-induced DNA double-strand breaks (determined by neutral filter elution) increased in the order: asynchronous < S < G2 < M. Topoisomerase II cleavage activity, assayed in vitro as the formation of covalent enzyme-DNA complexes, was lowest in S phase, intermediate in asynchronous and G2-phase cells, and maximal in M phase. Topoisomerase II decatenation activity was 1.6-1.8-fold greater in S-, G2- and M-phase populations relative to asynchronous cells. Therefore DNA topoisomerase II activity measured both in vivo and in vitro is maximal in M phase, that phase of the cell cycle with an intermediate level of immunoreactive topoisomerase II but the highest level of enzyme phosphorylation. The discordance between immunoreactive topoisomerase II protein levels, adjusted relative phosphorylation, catalytic activity, cleavage activity and amino acid residue(s) modified, suggests that the site of phosphorylation may be cell-cycle-dependent and critical in determining catalytic and cleavage activity.

Long-term intravenous hydroxyurea infusions in patients with advanced cancer. A phase I trial

BACKGROUND

Hydroxyurea is an S-phase specific drug. Constant exposure of tumor cells with a low S-phase fraction to the agent may result in improved cell kill. Because of its short half-life, a continuous intravenous infusion may result in better tumor exposure than intake by mouth. The goal of this trial was to find the longest tolerable duration of a continued intravenous infusion of hydroxyurea (HU) given at escalating doses.

METHODS

Eligible patients had histologically confirmed cancer without effective alternate therapy, normal blood counts, liver and kidney function. After giving informed consent, the infusion began via a permanent indwelling catheter utilizing a portable pump. Dose levels (in g/m2/d) were 0.5 for level I, 1.0 for level II, 1.66 for level III, and 2.5 for level IV.

RESULTS

Fourteen patients were entered. Five were men. Median age was 56 years of age (range: 32-67), median performance status 1 (range: 0-2). Diagnoses were as follows: colorectal cancer, seven; unknown primary site, three; breast cancer, two; melanoma, one; and adenoid-cystic carcinoma, one. Nine patients were pretreated with chemotherapy. Three patients were entered per dose level, except on level I, were five were entered. The mean duration of infusion was 12 weeks on level I, 5 weeks on II, 3 on III, 1 on IV. Toxicity included leukopenia below 2.0 K/mm3 in one patient each on levels III and IV, thrombocytopenia below 100 K/mm3 in one patient each on levels II and IV, and stomatitis in three patients (one on level II and two on IV). This toxicity was dose limiting. One patient on level III, with an unknown primary, had an objective response. HU levels were measured by a modification of the Fabricius-Rajewsky method. Mean plasma levels in micrograms per milliliter (SEM) were as follows: level I, 3.6 (0.23); level II, 5.1 (0.57); level III, 10.1 (1.55); and level IV, 16.7 (one point). Fetal hemoglobin rose two-fold and five-fold in two patients on level I after 9 and 16 weeks on therapy, respectively.

CONCLUSIONS

HU as a continuous intravenous infusion is well tolerated; the maximum duration of therapy is related inversely with the dose given. No major antitumor activity was seen. The greatest interest in the drug rests in its future use as a modulator and radiation potentiator. The increase in hemoglobin F was of interest and may be important in the treatment of sickle cell disease.