Detailed analysis of a randomized phase III trial: can the tolerability of capecitabine plus docetaxel be improved without compromising its survival advantage?

BACKGROUND: In a phase III trial, 3-weekly capecitabine (1250 mg/m(2) twice daily days 1-14) plus docetaxel (75 mg/m(2) day 1) demonstrated significantly superior overall survival to 3-weekly docetaxel (100 mg/m(2) day 1). We report a retrospective analysis of the impact of capecitabine/docetaxel dose reduction on safety and efficacy. PATIENTS AND METHODS: Safety and efficacy data were analyzed retrospectively according to the actual doses of capecitabine and docetaxel administered. RESULTS: More patients receiving capecitabine/docetaxel (65%) had dose reductions for adverse events than docetaxel alone (35%). In most patients requiring dose reduction with the combination (80%), capecitabine and docetaxel were simultaneously reduced to 950 mg/m(2) and 55 mg/m(2), respectively. Subsequently, there were fewer cycles (17%) with grade 3/4 adverse events than with the full doses (34%). Time to progression and overall survival appeared to be similar in patients starting the second cycle with reduced doses of capecitabine/docetaxel and those who continued to receive full doses of capecitabine/docetaxel for at least the first four cycles. CONCLUSIONS: Capecitabine/docetaxel dosing flexibility allows management of side-effects without compromising efficacy. This retrospective analysis, as well as multiple phase II studies of taxanes with reduced-dose capecitabine, shows that reducing the starting dose of capecitabine with docetaxel is a reasonable strategy for the treatment of patients with metastatic breast cancer. In addition, reducing the dose of both agents may be appropriate.

Differential immunohistochemical staining for DNA topoisomerase II alpha and beta in human tissues and for DNA topoisomerase II beta in non-Hodgkin's lymphomas.

Topoisomerase II (Topo II) is the target for several chemotherapeutic agents, including doxorubicin and etoposide, termed Topo II poisons. Previous studies from cancer cell lines and clinical specimens attempted to correlate expression of Topo II with drug sensitivity. Mammalian cells, however, contain two isoforms of Topo II, termed Topo II alpha (subunit molecular weight, 170 kDa) and Topo II beta (subunit molecular weight, 180 kDa), both of which are sensitive to Topo II poisons. Studies of Topo II alpha in normal cells and tissues are limited, and few studies have begun to characterize the beta isoform. This study employed in situ immunohistochemical staining to characterize the tissue distribution of Topo II alpha in formalin-fixed, paraffin-embedded human tissues. A new antibody, confirmed by Western blot, specific to the beta isoform, was also used to characterize its distribution in non-neoplastic, formalin-fixed, paraffin-embedded human tissues and 33 cases of non-Hodgkin's lymphomas. Topo II alpha was identified in normal tissues with proliferating cells, especially in spermatocytes, germinal centers, and proliferative endometrium. Some terminally differentiated tissues, e.g., cerebral cortex, skeletal muscle, and nerve, showed no detectable Topo II alpha, whereas others, e.g., breast, salivary gland, and kidney, showed rare positive cells. In contrast, Topo II beta was present in all tissues, including fully differentiated tissues, e.g., cerebellum, myometrium, pancreas, as well as in tissues with cell turnover, e.g., endometrium, skin, and bowel mucosa. In non-Hodgkin's lymphomas, Topo II beta was uniformly present with no change in the intensity or staining pattern among the tumor subtypes. Topo II alpha may be distinguished from the beta isoform using immunohistochemical techniques, which permit precise localization of the enzyme in individual cells. Detection of this differential expression between the alpha and beta isoform of Topo II suggests distinct physiologic roles and might allow better therapeutic targeting for tumors.

An electrical impedance tomography microscope.

A circular array of 16 electrodes has been constructed for use as an electrical impedance tomography (EIT) microscope. The electrodes were made from 60 microns diameter gold wires anchored to a printed circuit board. The internal diameter of the array was 0.9 mm giving a theoretical spatial resolution of about 100 microns. For EIT imaging, the array was connected to an imaging system operating at 82 kHz. Static images of conducting and insulating filaments (cooper wire and human hair) in saline solution were obtained as well as dynamic imaging sequences of glass microspheres migrating through the array. The interelectrode impedance was typically 5 k omega and the transimpedances ranged from 14 to 210 omega.

Selective use of an alternative stop codon and polyadenylation signal within intron sequences leads to a truncated topoisomerase II alpha messenger RNA and protein in human HL-60 leukemia cells selected for resistance to mitoxantrone.

Topoisomerase II alpha is an essential nuclear enzyme involved in DNA replication and a target for many of the clinically useful antineoplastic agents. In a mitoxantrone-selected human leukemia cell line, HL-60/MX2, cellular topoisomerase II (topo II) catalytic activity is decreased, in association with the finding of reduced nuclear topo II alpha and beta protein levels. In addition, HL-60/MX2 cells contain a novel M(r) 160,000 topo II alpha-related protein that localizes predominantly to the cell cytoplasm (W. G. Harker et al., Biochemistry, 30: 9953-9961, 1991). In these studies, we have investigated the molecular mechanisms underlying the altered expression of the topo II alpha protein(s) in these cells. Three topo II alpha mRNAs, 7.2, 6.3, and 4.8 kb, were identified in the HL-60/MX2 cells, with the 6.3 and 4.8 kb transcripts being present in roughly equivalent amounts, while the 7.2-kb mRNA represents < 7% of the total topo II alpha-specific mRNA. Portions of the 3'-coding and 3'-untranslated regions were found to be missing from the 7.2- and 4.8-kb topo II alpha mRNAs by Northern blot analysis. Sequences encoding the 3' regions of the normal and truncated forms of the topo II alpha enzyme were obtained from the HL-60/MX2 cells through the use of a 3'-rapid amplification of cDNA ends strategy. Approximately 1321 nucleotides are missing from the 3'-coding and 3'-untranslated regions of the 4.8-kb mRNA and are replaced by 122 nucleotides that contain an in-frame stop codon and consensus polyadenylation signal. The translation product of the truncated 4388-bp topo II alpha transcript would have a predicted M(r) of 157,850, with 108 COOH-terminal amino acids being replaced by 13 novel residues. Immunoblot analysis confirmed that amino acids in the COOH-terminal region of topo II alpha were missing from the M(r) 160,000 HL-60/MX2 protein, and antisera generated to a synthetic peptide representing the 13 unique amino acids identified a M(r) 160,000 protein in nuclear extracts from these cells. PCR evaluation of the organization of the 3' region of the topo II alpha gene revealed that the 4.8-kb mRNA found in HL-60/MX2 cells diverges from that of the 6.3-kb mRNA at a consensus exon-intron splice donor site. The 122-bp novel nucleotides identified in the truncated transcript appear to originate from an adjacent intron as a result of altered RNA processing. These studies suggest that as a result of the disruption of the carboxy terminus of the topo II alpha protein and the putative nuclear targeting sequences identified therein, cellular localization of the protein is altered, which may confer a growth advantage for the HL-60/MX2 cells in the presence of mitoxantrone.

Adjusting the dose of intravenous ondansetron plus dexamethasone to the emetogenic potential of the chemotherapy regimen.

PURPOSE: This pilot, open-label study evaluates the antiemetic efficacy and safety of a single 20-mg intravenous (IV) dose of dexamethasone combined with a single IV dose of ondansetron (32, 24, or 8 mg) in patients receiving highly emetogenic (HE), moderately high emetogenic (MHE), or moderately emetogenic (ME) chemotherapy, respectively. PATIENTS AND METHODS: One hundred forty-six patients received a single 20-mg IV dose of dexamethasone over 15 minutes beginning 45 minutes before chemotherapy and either a single 32-, 24-, or 8-mg IV dose of ondansetron over 15 minutes beginning 30 minutes before chemotherapy. Patients were evaluated for emetic episodes, extent of nausea, and adverse events for 24 hours after chemotherapy. RESULTS: Complete response (no emetic episodes) was noted in 72% (95% confidence interval [CI], 60% to 84%), 88% (95% CI, 79% to 97%), and 77% (95% CI, 63% to 92%) of patients in the HE, MHE, and ME categories, respectively. The proportion of patients who experienced no nausea on the posttreatment assessment was 51% (95% CI, 37% to 64%), 69% (95% CI, 56% to 81%), and 47% (95% CI, 29% to 65%), respectively. The antiemetic regimens were all well tolerated. The proportion of patients with any drug-related adverse events did not vary across the three study groups despite the range of ondansetron doses and variety of chemotherapy regimens. Mild headache was noted in 28% of patients. Other adverse events, all of which were noted in fewer than 10% of patients, included lightheadedness, fatigue, dizziness, and constipation. CONCLUSION: A single IV dose of either 8, 24, or 32 mg of ondansetron combined with a single 20-mg IV dose of dexamethasone resulted in good control of acute emesis across a wide spectrum of chemotherapy regimens. Nausea control proved somewhat more difficult, with approximately 50% of patients in the HE and ME emetogenic categories experiencing some degree of nausea. The results of our pilot study suggest that adjusting the dose of ondansetron to the intrinsic emetogenicity of the chemotherapy regimen permits a more efficient use of ondansetron while maintaining good antiemetic control. Such an approach appears worthy of further investigation.

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.

Mutation at the catalytic site of topoisomerase I in CEM/C2, a human leukemia cell line resistant to camptothecin.

We developed previously a resistant cell line, CEM/C2, from the human leukemia cell line CCRF-CEM by stepwise selection in camptothecin. This cell line is 974-fold more resistant to camptothecin than parental cells. Resistance is only partially explained by 2-fold reductions in topoisomerase I protein and mRNA levels. We further investigated biochemical and molecular features of topoisomerase I in the resistant cell line. Sequence analyses of the top1 cDNA from CEM/C2 identified mutations corresponding to two amino acid substitutions, Met370Thr and Asn722Ser. Asn722Ser is next to the catalytic Tyr723 in a region highly conserved among type I eukaryotic DNA topoisomerases. Recombinant top1 with the corresponding substitution was found to be catalytically active and resistant to camptothecin. These results indicate that camptothecin resistance of CEM/C2 is due to the mutation Asn722Ser and strongly suggest that the asparagine immediately flanking the catalytic tyrosine is important for the camptothecin action.

Altered topoisomerase I expression in two subclones of human CEM leukemia selected for resistance to camptothecin.

Two camptothecin-resistant variants of the CEM human leukemia cell line were developed by stepwise selection in camptothecin (CPT) in vitro. The two lines, named CEM/C1 and CEM/C2, were found to be approximately 31- and 970-fold less sensitive to CPT, respectively, than the CEM parental line and variably cross-resistant to the CPT analogs 9-amino-CPT, 10,11-methylenedioxy-CPT, and topotecan. Levels of DNA-protein complex formation resulting from cell exposure to CPT were found to be progressively reduced in the CPT-resistant cells, despite equivalent CPT accumulation in the drug-sensitive and -resistant cells. Nuclear extracts (1.0 M NaCl) prepared from the CEM/C1 and CEM/C2 lines contained 1.5- to 2-fold less DNA topoisomerase I catalytic activity per microgram of protein than did extracts from the drug-sensitive CEM line, in association with altered sensitivity of the enzyme in the CEM/C1 and CEM/C2 extracts to the inhibitory activity of CPT. Only minor differences were noted in the CPT IC50s for the topoisomerase I activity in extracts from the two CPT-resistant cell lines, however, despite the marked differences in cellular sensitivity to CPT. There were notable differences in the level of CPT-induced cleavage of DNA oligonucleotides by topoisomerase I in nuclear extracts from CEM cells compared with the drug-resistant cell extracts, with very little oligonucleotide cleavage induced by enzyme in either drug-resistant cell type, despite the use of very high (100 microM) CPT concentrations. The alterations in topoisomerase I catalytic activity were associated with reduced cellular levels of both immunoreactive topoisomerase I protein (representing 59 +/- 19% [CEM/C1] and 49 +/- 12% [CEM/C2] of that in CEM, respectively) and mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

A randomized, double-blind comparison of intravenous ondansetron alone and in combination with intravenous dexamethasone in the prevention of high-dose cisplatin-induced emesis.

PURPOSE: This study compares the efficacy and safety of ondansetron alone with that of ondansetron plus dexamethasone in the prevention of emesis induced by high-dose cisplatin (> or = 100 mg/m2). PATIENTS AND METHODS: This multicenter study used a randomized, double-blind, parallel-group design. Chemotherapy-naive patients were randomized to receive intravenous (IV) ondansetron (Zofran, Cerenex Pharmaceuticals, Research Triangle Park, NC) 0.15 mg/kg for three doses every 4 hours beginning 30 minutes before cisplatin administration either alone or in combination with dexamethasone 20 mg administered 45 minutes before cisplatin. Cisplatin (> or = 100 mg/m2) was administered as a single infusion (< or = 3 hours). Patients were monitored for emetic episodes (EEs), adverse events, and laboratory safety parameters for 24 hours after cisplatin administration. RESULTS: A total of 275 patients were enrolled. Of these, 245 were assessable for efficacy. Patients who received ondansetron plus dexamethasone had a higher complete antiemetic response rate (61% v 46%, P = .02) and less nausea (posttreatment visual analog scale mean 18.2 v 32.8, P < .001) than did those who received ondansetron alone. The time to the first EE was longer for patients in the group that received ondansetron plus dexamethasone (P = .005). Headache (12%), diarrhea (2%), and abdominal colic (1%) were the most common antiemetic-related adverse events reported. The incidence of adverse events was similar between the treatment groups. CONCLUSION: IV ondansetron in combination with dexamethasone is safe and more effective than ondansetron alone in the prevention of emesis induced by high-dose cisplatin.

Peripherally inserted central venous catheters. Low-risk alternatives for ongoing venous access.

We prospectively evaluated the use of peripherally inserted central venous catheters to provide ongoing venous access in general medical and surgical patients in a Department of Veterans Affairs medical center. Between 1985 and 1988 trained nurses successfully inserted 393 catheters in 460 suitable patients (an 85.4% success rate). Correct catheter tip placement in the superior vena cava was documented in 359 of the 393 (91.3%) catheter insertions, but an additional 30 catheters were in a position deemed adequate for the intended use. The mean duration of catheter use was 27.6 +/- 5.2 (1 standard deviation) days (median 20 days, range 1 to 370 days). A total of 65 patients left the hospital with catheters in place, with the mean length of catheter use at home being 36.2 +/- 6.0 days (range 2 to 266). In all, 79% of the catheters were in use until the successful completion of therapy or patient death; catheter-related complications led to premature catheter removal in the remaining 21%. Catheter-related complications included bland phlebitis (8.2%), occlusion (8.2%), local infection (3.6%), bacteremia or fungemia (2.1%), mechanical failure or rupture (2.6%), venous thrombosis (0.7%), and other (3.3%). One patient required vein excision for the management of suppurative phlebitis, but no deaths were attributed to catheter use. This study illustrates the use and safety of peripherally inserted central venous catheters to provide reliable vascular access over prolonged periods in an elderly veteran population. At our facility, percutaneous central venous catheters and surgically implanted (Hickman or Broviac) catheters are now reserved for use in patients in whom peripherally inserted catheters cannot be placed.

Single-strand conformational polymorphism analysis of the M(r) 170,000 isozyme of DNA topoisomerase II in human tumor cells.

Five cell lines selected for resistance to the cytotoxicity of inhibitors of DNA topoisomerase II have point mutations in the gene that codes for the M(r) 170,000 form of this enzyme. In each case, the mutation results in an amino acid change in or near an ATP binding sequence of the M(r) 170,000 isozyme of topoisomerase II. We used single-strand conformational polymorphism analysis to screen for similar mutations in other drug-resistant cell lines or in leukemic cells from patients previously treated with etoposide or teniposide. We also analyzed the region of the gene that codes for amino acids adjacent to the tyrosine at position 804 of topoisomerase II which binds covalently to DNA. CEM/VM-1, CEM/VM-1-5, and HL-60/AMSA human leukemic cell lines were used as controls; 3 of 3 known mutations were detected by migration differences of polymerase chain reaction products from the RNA extracted from these three lines. A previously unknown mutation was found in the tyrosine 804 region of the M(r) 170,000 topoisomerase II expressed by CEM/VM-1 and CEM/VM-1-5 cells. Sequence analysis showed that substitution of a T for a C at nucleotide 2404 resulted in an amino acid change of a serine for a proline at amino acid 802. No mutations in any of the ATP binding sequences or in the tyrosine 804 region were detected in polymerase chain reaction products from RNA extracted from human leukemia HL-60/MX2 or CEM/MX1 cells (both cell lines selected for resistance to mitoxantrone) or in human myeloma 8226/Dox1V cells (selected for resistance by simultaneous exposure to doxorubicin and verapamil). No mutations were detected in polymerase chain reaction products from RNA extracted from blasts of 15 patients with relapsed acute lymphocytic leukemia, previously treated with etoposide or teniposide. We conclude that: (a) single-strand conformational polymorphism analysis is useful for screening for mutations in topoisomerase II; (b) resistance to the cytotoxicity of inhibitors of DNA topoisomerase II is not always associated with mutations in ATP binding sequences or the active site tyrosine region of M(r) 170,000 topoisomerase II; and (c) mutations similar to those detected in drug resistant cells selected in culture have not been identified in blast cells from patients with relapsed acute lymphocytic leukemia, previously treated with etoposide or teniposide.

Phase II trial of mitotane and cisplatin in patients with adrenal carcinoma: a Southwest Oncology Group study.

PURPOSE: Previous reports of chemotherapy in patients with adrenal cancer have described responses to cisplatin (CDDP). Because of these reports of good results, a phase II trial that used CDDP with and without mitotane (o,p'DDD) was initiated. PATIENTS AND METHODS: Patients with metastatic or residual adrenocortical carcinoma with objectively measurable disease or biochemical abnormalities were divided into good-risk and poor-risk categories. The latter received CDDP 100 mg/m2 intravenously, and the former received 75 mg/m2. o,p'DDD was administered at a 1,000-mg dose orally four times a day along with cortisone acetate and Florinef (fludrocortisone acetate; Bristol-Myers Squibb Co, Princeton, NJ). RESULTS: Of a total of 42 patients entered onto the study, 37 were eligible. Twenty-nine patients received good-risk and eight received poor-risk doses of CDDP. Functioning tumors were present in 45% of patients. Objective responses were noted in 30% (11 of 37) patients (95% confidence interval, 16% to 50%). Response duration was 7.9 months, and the median time to response was 76 days. The median survival of the 37 eligible patients was 11.8 months, and a significant survival advantage was found for patients who underwent prior surgical removal of their primary tumor or bulky disease, who had a performance status of 0 or 1, or who had synchronous metastatic disease. Toxicity of the CDDP and o,p'DDD combination was moderate to severe, and the most common side effects were gastrointestinal, renal, and neurologic. CONCLUSION: The regimen of CDDP and o,p'DDD has activity in patients with adrenocortical carcinoma; however, the toxicity of this treatment was moderate to severe.

Isolation, purification, and characterization of two new chemical decomposition products of methylazoxyprocarbazine.

We have previously reported that the antineoplastic agent, procarbazine, in aqueous solutions was chemically oxidized to its azoxy metabolites (methylazoxy and benzylazoxy). To determine if there was additional metabolism of the most active metabolite, methylazoxyprocarbazine, it was incubated in the presence and absence of CCRF-CEM human leukemia cells. Incubations were extracted, and potential metabolites were detected by HPLC with UV detection and by combined HPLC and thermospray mass spectrometric analysis. The major metabolite identified by HPLC with UV detection of the extracts was N-isopropyl-p-formylbenzamide; this was identified by comparison of its retention time with that of a synthesized standard. This identification was further corroborated by HPLC/thermospray mass spectrometry (LC/MS). Analysis of the extracts by LC/MS also showed the presence of a closely eluting peak that had a protonated molecular ion at m/z 207. This new metabolite was identified as N-isopropyl-(benzene-1,4-bis-carboxamide) by 1H NMR and gas chromatography/ion trap mass spectrometry. This metabolite is postulated to arise from breakage of the N-N bond in the hydrazine portion of the molecule. Reconstructed ion (m/z 236) current profiles from the analysis of the cell extracts indicated that there was only a trace amount of methylazoxyprocarbazine left after a 72-hr incubation. Interestingly, a peak with the same molecular weight as the parent compound (methylazoxyprocarbazine) was observed in the cellular incubations and also in extracts of control incubations in which methylazoxyprocarbazine was incubated in medium without cells. This unknown was silylated and identified as a hydroxyazo compound by an ion trap mass spectrometer operated under both single and multiple-stage mass analysis. Formation of this decomposition product appears to involve a novel intramolecular rearrangement of methylazoxyprocarbazine in solution. This pathway may be responsible for the formation of the ultimate cytotoxic species by chemical decomposition of procarbazine.

Non-enzymatic activation of procarbazine to active cytotoxic species.

The cellular cytotoxicity of procarbazine is thought to result from bioactivation of the parent compound through reactive intermediates to an ultimate alkylating species. Procarbazine is converted initially to azoprocarbazine, which is then N-oxidized through a cytochrome P-450-mediated process to a mixture of the positional isomers, benzylazoxyprocarbazine and methylazoxyprocarbazine. In order to define the bioactivation events that lead to the cytotoxic species, the in vitro cytotoxicities of the purified azoxy isomers as well as of the parent compound, procarbazine, were evaluated with the human leukemia cell line, CCRF-CEM. The methylazoxy isomer was found to be the most active species. Procarbazine inhibited the growth of CCRF-CEM cells but at a concentration much higher than that required for the methylazoxy isomer. Since procarbazine must be metabolized to form the cytotoxic species, we sought to determine if the active metabolite, methylazoxyprocarbazine, was being formed in the incubations. Solutions of procarbazine incubated with and without cells at 37 degrees C were analyzed by combined liquid chromatography-mass spectrometry with a thermospray interface. The azoxy metabolites of procarbazine appeared rapidly in cellular incubations and in the aqueous solutions without cells. More of the methylazoxy isomer was formed initially, but by 72 hr the benzylazoxy isomer was the predominant species. Thus, in these studies it appears that procarbazine was benzylazoxy isomer was the predominant species. Thus, in these studies it appears that procarbazine was non-enzymatically oxidized to the two azoxyprocarbazine isomers and that the methylazoxy compound was the most cytotoxic to CCRF-CEM cells.

Mitoxantrone resistance in HL-60 leukemia cells: reduced nuclear topoisomerase II catalytic activity and drug-induced DNA cleavage in association with reduced expression of the topoisomerase II beta isoform.

Mitoxantrone-resistant variants of the human HL-60 leukemia cell line are cross-resistant to several natural product and synthetic antineoplastic agents. The resistant cells (HL-60/MX2) retain sensitivity to the Vinca alkaloids vincristine and vinblastine, drugs that are typically associated with the classical multidrug resistance phenotype. Mitoxantrone accumulation and retention are equivalent in the sensitive and resistant cell types, suggesting that mitoxantrone resistance in HL-60/MX2 cells might be associated with an alteration in the type II DNA topoisomerases. We discovered that topoisomerase II catalytic activity in 1.0 M NaCl nuclear extracts from the HL-60/MX2 variant, as measured by the decatenation of Crithidia fasciculata kinetoplast DNA, was reduced 4- to 5-fold compared to that in the parental HL-60 cells. Total cellular topoisomerase II activity in HL-60/MX2 cells was only 50% lower than that in HL-60 cells, however, because the "cytosolic fraction" of the HL-60/MX2 nuclear preparation contained high levels of decatenating activity. Antisera to calf thymus topoisomerase II defined a distinctive immunoreactive pattern of topoisomerase II proteins in crude nuclear extracts from the HL-60/MX2 cells. Both alpha (170 kDa) and beta (180 kDa) forms of topoisomerase II were detected in the HL-60 cell extracts, but only the alpha form was detected in extracts from HL-60/MX2 cells. This finding was associated with the appearance of a new 160-kDa immunoreactive species in nuclear extracts from HL-60/MX2 but not HL-60 cells. Studies were designed to minimize the proteolytic degradation of the topoisomerase II enzymes by extraction of whole cells with hot SDS.(ABSTRACT TRUNCATED AT 250 WORDS)

Human tumor cell line resistance to chemotherapeutic agents does not predict resistance to natural killer or lymphokine-activated killer cell-mediated cytolysis.

Cancer cells selected for resistance to natural product chemotherapeutic agents typically display cross-resistance to a variety of structurally and mechanistically diverse agents, a phenomenon known as multidrug resistance. Preliminary studies involving cells selected for multidrug resistance in vitro have suggested that the development of resistance to these agents might simultaneously confer resistance to some forms of immunotherapy. Using human tumor cell line models, we have investigated the relationship between either intrinsic or selected multidrug resistance and sensitivity to natural killer (NK) or lymphokine-activated killer (LAK) cell-mediated cytolysis. We compared the NK and LAK cell susceptibility of three human tumor cell lines displaying distinct mechanisms of selected drug resistance with that of the parental drug-sensitive lines. We also evaluated the NK and LAK susceptibility of five established renal cell carcinoma lines, all of which were found to be intrinsically resistant to doxorubicin and vinblastine. The drug-resistant cell lines were variably sensitive to NK-mediated lysis. In contrast, all drug-resistant cell lines tested were LAK cell sensitive. The NK and LAK cell-mediated cytolytic sensitivities of the drug-resistant cell lines correlated well with those of the drug-sensitive parental lines, suggesting that susceptibility to lysis was related intrinsically to each tumor type, and not to the resistance phenotype. We attempted to correlated the NK sensitivity of these cells with the cell surface expression of Class I or II histocompatibility antigens, or the presence or absence of the membrane inhibitor of complement-mediated reactive lysis. None of these phenotypic markers were found to predict NK resistance. We therefore conclude that these cells, which are either spontaneously resistant to commonly utilized antitumor agents or are multidrug resistant as a result of drug exposure in vitro, remain sensitive to LAK cell-mediated cytolysis. Our studies suggest that interleukin 2-induced LAK cells may be useful in the therapy of some chemotherapy-resistant cancers.

Multidrug resistance in mitoxantrone-selected HL-60 leukemia cells in the absence of P-glycoprotein overexpression.

A multidrug-resistant variant of the human HL-60 promyelocytic leukemia cell line (HL-60/MX2) has been isolated in vitro by subculturing these cells in progressively increasing concentrations of mitoxantrone. The MX2 cells are cross-resistant to etoposide, teniposide, bisantrene, dactinomycin, 4'-(9-acridinylamino)methanesulfon-m-anisidide, and the anthracyclines daunorubicin and doxorubicin but retain sensitivity to the Vinca alkaloids melphalan and mitomycin C. In addition, the MX2 cells display slight collateral sensitivity to bleomycin. Despite being 30-35-fold less sensitive to mitoxantrone, net [14C]mitoxantrone accumulation at 60 min was reduced by only 10% in the mitoxantrone-resistant cells compared to the parental line. Furthermore, at later time points, e.g., 120 and 180 min, mitoxantrone accumulation in the MX2 cells exceeded that in HL-60 cells by 8.5 and 6.4%, respectively. No significant differences were observed between the sensitive and resistant cell lines in the initial (first 60 s) accumulation of mitoxantrone, and only minor (3-6%) enhancement of mitoxantrone efflux was detected in the resistant cell type. Monoclonal antibodies to P-glycoprotein had no detectable reactivity with membrane vesicles from either the sensitive or resistant cell types as determined by standard immunoblotting techniques. The mitoxantrone-resistant cells displayed a reciprocal translocation [rcpt(1;3)-(q21;p23)] not found in the sensitive parent, but there were no demonstrable double minute chromosomes or homogeneous staining regions in cells from either line. Thus, these mitoxantrone-resistant human leukemia cells display many features which are atypical for the "classic" multidrug resistance phenotype and should provide a useful model for the study of multidrug resistance which is not mediated by P-glycoprotein.

Methylazoxyprocarbazine, the active metabolite responsible for the anticancer activity of procarbazine against L1210 leukemia.

Procarbazine is a 1,2-disubstituted hydrazine derivative that is used to treat human leukemias. The anticancer activity of procarbazine results from bioactivation to reactive intermediates. It is first oxidized to azoprocarbazine and further N-oxidized to a mixture of methylazoxyprocarbazine and benzylazoxyprocarbazine isomers. In this study the azoxyprocarbazine isomers were synthesized and purified. The cytotoxic effect of the metabolites on the L1210 murine leukemia cell line were then evaluated in vitro by use of a colorimetric assay using 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide. The results of this study showed that the methylazoxyprocarbazine isomer was the most cytotoxic metabolite (IC50, 0.2 mM). The benzylazoxy isomer had an insignificant cytotoxic effect, and a mixture of the two isomers was intermediate in effectiveness. This assay, however, could not be used to determine the cytotoxicity of procarbazine since the drug itself (not the live cells) reduced the dye. A soft-agar clonogenic assay demonstrated that procarbazine was cytotoxic only at higher concentrations (IC50, 1.5 mM) than methylazoxyprocarbazine (IC50, 0.15 mM). The effect of procarbazine and its metabolites on the survival of L1210 tumor-bearing mice was determined, and methylazoxyprocarbazine was again the most effective compound. These studies demonstrate that the methylazoxyprocarbazine metabolite is probably the major cytotoxic intermediate involved in the mechanism of anticancer action of procarbazine.

Verapamil-mediated sensitization of doxorubicin-selected pleiotropic resistance in human sarcoma cells: selectivity for drugs which produce DNA scission.

The effects of verapamil on the cytotoxicity and accumulation of multiple drugs were studied in a model of pleiotropic resistance generated by doxorubicin (DOX) selection of the human sarcoma cell line MES-SA. The in vitro sensitivity of the DOX-resistant variant (named Dx5), which is 50- to 100-fold resistant to DOX compared to MES-SA, was enhanced approximately 7-fold by verapamil (3 micrograms/ml). In addition, the cytotoxicity of several agents to which the Dx5 line displays cross-resistance, i.e., daunorubicin, dactinomycin, mitoxantrone, and etoposide, was also enhanced 2- to 14-fold by verapamil. These agents share the properties of DNA intercalation and/or interaction with topoisomerase II. In contrast, verapamil did not alter the sensitivity of Dx5 to several other agents to which cross-resistance had been demonstrated, i.e., vincristine, vinblastine, colchicine, mitomycin C, and melphalan; nor did verapamil enhance the cytotoxicity of DOX or other agents against the DOX-sensitive parent, MES-SA. The sensitizing effect of verapamil did not correlate well with its effects on intracellular drug accumulation. [14C]DPX accumulation was increased by 30-40% in Dx5 but not in MES-SA cells in the presence of verapamil. [3H]Vinblastine accumulation was increased by 24-72% in both MES-SA and Dx5 cells in the presence of verapamil, although cytotoxicity of the Vinca alkaloids was not affected. In this human sarcoma model of DOX-selected pleiotropic resistance, verapamil partially reversed the resistance to DOX, as well as four of the nine drugs for which cross-resistance had been demonstrated in Dx5. The potentiation by verapamil of the cytotoxicity of some but not all of these antitumor agents suggests that factors other than altered drug transport may be responsible. The pattern of sensitization, restricted to agents which produce DNA strand scission by interaction with topoisomerase II, suggests that verapamil may be acting to promote the formation or inhibit the repair of such DNA strand breaks.

Cisplatin, methotrexate, and vinblastine (CMV): an effective chemotherapy regimen for metastatic transitional cell carcinoma of the urinary tract. A Northern California Oncology Group study.

Fifty-eight patients with metastatic transitional cell carcinoma of the urinary tract received cisplatin, methotrexate, and vinblastine (CMV) combination chemotherapy. Complete responses (CRs) were noted in 14 of the 50 (28%) evaluable patients and partial responses (PRs) in 14 patients for an overall response rate of 56% (95% confidence limits of 42% to 70%). The median duration of the 14 CRs was 9 months. Six of the 14 CRs (43%) remain in unmaintained remission from 6 + to 35 + months from onset of treatment. The median survival of evaluable patients receiving CMV was 8 months. Median survival for CRs was 11 months v 7 months for PRs (P less than .05) and 6 months for nonresponders. Renal and hematologic toxicities with this regimen were moderate. CMV is an effective regimen for patients with metastatic transitional cell carcinoma of the bladder. Prolonged disease-free survival may result from a CR to this regimen.