A phase I study of carboplatin and etoposide administered in conjunction with dipyridamole, prochlorperazine and cyclosporine A

PURPOSE

In recognition of the variety of available chemotherapeutic modulating agents and their potential to enhance the efficacy of platinum-based therapy, we embarked upon a phase I study to investigate the feasibility of combining fixed doses of carboplatinum (CBDCA) and etoposide (VP-16) with 24-h concurrent infusions of dipyridamole (DP), prochlorperazine (PCZ) and cyclosporine A (CSA) administered in escalating doses.

METHODS

Patients received intravenous VP-16 (200 mg/m2) and CBDCA (300 mg/m2), each over 30 min, starting at hour 6 of the modulator infusions. Resistance modulators were escalated sequentially to determine their respective maximally tolerated doses (MTDs). The pharmacokinetics (PK) of VP-16, CBDCA, and the three drug resistance (DR) modifiers were studied in eight patients.

RESULTS

A total of 59 patients were entered on study. The MTD was established at DP 5 mg/kg per day, PCZ 24 mg/h, and CSA 9.5 mg/kg per day. Dose-limiting toxicities included hypotension and severe sedation, presumably related to PCZ. No objective responses were seen. PK studies were performed when PCZ and DP doses were 24 mg/h and 3.3 mg/kg, and the CSA dose was either 8.5 mg/kg (five patients) or 9.5 mg/kg (three patients). The median clearance of VP-16 was 0.96 l/h per m2 (range 0.8-1.5 l/h per m2), which is lower than for VP-16 alone and similar to previously reported effects of CSA on VP-16 elimination. The median measured CBDCA AUC was 3.0 mg/ml x min (range 2.4-4.8 mg/ml x min). CBDCA AUC predicted by the Calvert formula using measured creatinine clearance underestimated the actual AUC in seven of the eight patients, in one case by as much as twofold. The median end of infusion PCZ and total DP plasma concentrations were 1.2 microM (range 0.5-2.2 microM) and 4.4 microM (range 1.3-5.9 microM), respectively, consistent with in vitro resistance modulatory levels. However, free DP was only 0.02 microM (range 0.004-0.04 microM). The median CSA level at 24 h of 1450 microg/l (range 1075-1640 microg/l) is in agreement with concentrations required for partial DR reversal in vitro, although it is much lower than levels achieved in our previous phase I study of CBDCA + CSA alone using similar doses of CSA. The CSA dose on the current trial was escalated beyond the MTD for the previous phase I study, suggesting that there may be an interaction between CSA and one of the other modulators.

CONCLUSION

These results demonstrate that in vitro DR-reversing levels of two of the three agents used in this study can be achieved in vivo, and that this combination of DR modulators has significant effects on the pharmacokinetics of VP-16.

A simple and sensitive ribonucleotide reductase assay

Ribonucleotide reductase (RR) is a key regulatory enzyme in the DNA synthesis pathway and is the target of the cancer chemotherapeutic agent hydroxyurea. The study of RR is significantly hindered by the tedious and labor-intensive nature of enzymatic assay. In this report, we present a novel RR assay in which detection of the deoxyribonucleotides produced by RR occurs via coupling to the DNA polymerase reaction, and is enhanced by using RNase to degrade endogenous RNA. Cell extracts from various cell lines were treated with RNase and then reacted with ATP and radioactive ribonucleotide diphosphate as the substrate. Incorporation of the radioactive substrate [14C]CDP into DNA was linear over 30 min and was linear with the amount of extract, which provided RR activity. The reaction was inhibited by hydroxyurea and required Mg2+ and ATP, suggesting that the assay is specific to RR activity. While RR activities determined by our method and by a conventional method were comparable, this novel method proved to be simpler, faster, more sensitive and less expensive. In addition, assay of the RR activity for multiple samples can easily be performed simultaneously. It is superior to other RR assays in all aspects.

Electrochemical treatment of human KB cells in vitro

Electrochemical treatment (ECT) of cancer is a promising new method by which direct current is delivered into tumor tissue to induce tumor regression. The purpose of this study is to evaluate the effectiveness of ECT on human cancer cells and to investigate the factors that affect ECT. The biological mechanisms of ECT in cancer treatment were also explored. Using human KB cells, ECT was found to delay cell growth by using 0.3 coulombs (C)/ml (1.5 C in 5 ml of culture medium; 3 V, 400 microA for 62.5 min). From the results of a colony-forming assay, it was clearly demonstrated that increasing the ECT dose decreases tumor cell survival. A cytotoxicity study, in which a methylene blue assay was used, determined that, for 2.5 x 10(5) cells in culture, the 1D50 was 0.68 C/ml. For a fixed dose of 0.6 C/ml (3 C in 5 ml), using higher current and shorter treatment time resulted in better cell survival. Time, therefore, is an important factor. When cell concentration was altered, the survival was higher for increased cell concentrations. A thymidine incorporation assay indicated that the amount of [3H]thymidine incorporated into DNA decreased as the ECT dose increased. After treatment with 1 C/ml (5 C in 5 ml; 3 V, 400 microA for 208.4 min), pH at the anode decreased to 4.53 and at the cathode increased to 10.46. These results indicate that ECT is effective for killing human KB cells in vitro and that the toxicity effect is related to charge, current, and treatment time. The effect of pH alteration on cells is one of the mechanisms of ECT.

Inhibition of human cancer cell growth by inducible expression of human ribonucleotide reductase antisense cDNA

Ribonucleotide reductase (RR) is a rate-limiting enzyme in DNA synthesis and repair. The enzyme consists of two dissimilar subunits, M1 and M2. It is known that the M2 subunit plays a role in tumorgenicity and metastasis. In this study, we transfected human oropharyngeal KB cancer cells with human RR M1 and M2 antisense cDNA expressed by an inducible vector system. The transfectants were double-selected with hygromycin and G418. The clones, designated KB-M1AS, KB-M2AS and KB-CAT, represented transfectant clones that contained M1 antisense cDNA, M2 antisense cDNA, and a CAT reporter gene, respectively. In a colony-forming assay, colony formation for the KB-M2AS clone decreased approximately 50% when M2 antisense mRNA expression was induced by isopropylthiogalactose (IPTG). However, the KB-M1AS clone revealed no significant inhibition under IPTG induction. RR enzyme activity, as measured by 14CDP reduction assay, revealed a 30% decrease in the IPTG-induced KB-M2AS clone relative to non-IPTG-induced samples at 144 hours. As shown by Northern blot, expression of the M2 antisense mRNA showed peaks at 48 hours and 144 hours after induction by IPTG. M2 antisense mRNA expression induced by IPTG was 33-fold greater than the uninduced control at 144 hours. Western blot analysis showed that the M2 subunit protein level decreased in the KB-M2AS clone beginning at 72 hours after induction and continued to decrease to 50% of the uninduced control at 144 hours, then showed a slight recovery at 168 hours. In conclusion, M2 antisense mRNA expression by an inducible system can effectively decrease RR M2 protein expression, reduce enzyme activity, and inhibit growth. Furthermore, this approach can be employed in future antisense investigations.

Overexpression of ribonucleotide reductase as a mechanism of resistance to 2,2-difluorodeoxycytidine in the human KB cancer cell line

In this study, human oropharyngeal epidermoid carcinoma KB cells that were resistant to 2,2-difluorodeoxycytidine (dFdCyd) were selected and designated the KB-Gem clone. The KB parental cell line IC50 was 0.3 microM dFdCyd, as compared with the KB-Gem clone IC50 of 32 microM dFdCyd. The KB-Gem clone demonstrated overexpression of ribonucleotide reductase (RR) M2 subunit mRNA (9-fold) and overexpression of M2 protein (2-fold); RR activity was 2.3-fold higher than the KB parental cell line. Both the dATP and dCTP pools of the KB-Gem clone increased 2-fold over the parental cell line, with no change in the dGTP and dTTP pools. Reverse transcriptase-PCR was used to clone the cDNA of deoxycytidine kinase (DCK). Resulting sequences revealed two silent mutations in the KB-Gem clone. The amino acid sequence of the DCK protein and mRNA expression remained unchanged. The KB-Gem clone's DCK enzyme activity was 56% of that of the parental cell line. After the endogenous dNTPs were removed with a G-25 column, no difference was evident between the enzyme activities of the KB-Gem clone and parental cells. Thus, contrary to previous hypotheses, DCK deficiency does not play the primary role in the resistance mechanism of dFdCyd, accepting a secondary role to the overexpression of the target gene, RR, and pool expansion.

Ethnic differences in the behavior of hepatocellular carcinoma

BACKGROUND

The purpose of this study was to examine the clinical presentation, prognostic factors, and survival rates of patients with hepatocellular carcinoma (HCC) and to examine differences between Asian and non-Asian patients with HCC.

METHODS

A review of the clinical characteristics and laboratory evaluations for 76 patients in two different broad ethnic groups (Asians [Group 1] and non-Asians [Group 2]) who underwent treatment for HCC from 1977-1995 was performed. Chi-square and Cox regression analyses were performed to assess factor interaction and association with survival.

RESULTS

A total of 24 patients in Group 1 and 52 patients in Group 2 were reviewed. Of the clinical variables examined, a higher rate of a history of hepatitis B positivity was observed in Group 1 compared with Group 2 (32% vs. 6%; P=0.001). Among the 76 patients with HCC, a 1-year survival estimate of 41.4% was found. There was a borderline significant difference in survival between Group 1 and Group 2 with a 1-year survival estimate of 29.5% versus 46.9%, respectively (P=0.08). Better overall survival was found in patients who had tumors that were resectable (P=0.0001), had an alpha-fetoprotein level <10 ng/mL (P=0.02), or were a younger age at the time of diagnosis (P=0.01). There was a trend for Asian race (P=0.08) to be associated with poorer survival. When these risk factors were entered into a multivariate analysis, tumor resectability and non-Asian race were most predictive of improved survival (model P value = 0.007). When controlling for the multiple variables most often reported to be associated with HCC, Asians had a significantly lower survival than non-Asians (P<0.01).

CONCLUSIONS

In this study it appears that the outcome for Asian patients with hepatoma is worse than for non-Asian patients, even when controlling for factors commonly associated with HCC. Biologic or social factors that are not appreciated currently may be involved in Asian patients with HCC, contributing to a poorer clinical outcome.

Ethnic differences in the behavior of hepatocellular carcinoma

BACKGROUND

The purpose of this study was to examine the clinical presentation, prognostic factors, and survival rates of patients with hepatocellular carcinoma (HCC) and to examine differences between Asian and non-Asian patients with HCC.

METHODS

A review of the clinical characteristics and laboratory evaluations for 76 patients in two different broad ethnic groups (Asians [Group 1] and non-Asians [Group 2]) who underwent treatment for HCC from 1977-1995 was performed. Chi-square and Cox regression analyses were performed to assess factor interaction and association with survival.

RESULTS

A total of 24 patients in Group 1 and 52 patients in Group 2 were reviewed. Of the clinical variables examined, a higher rate of a history of hepatitis B positivity was observed in Group 1 compared with Group 2 (32% vs. 6%; P=0.001). Among the 76 patients with HCC, a 1-year survival estimate of 41.4% was found. There was a borderline significant difference in survival between Group 1 and Group 2 with a 1-year survival estimate of 29.5% versus 46.9%, respectively (P=0.08). Better overall survival was found in patients who had tumors that were resectable (P=0.0001), had an alpha-fetoprotein level <10 ng/mL (P=0.02), or were a younger age at the time of diagnosis (P=0.01). There was a trend for Asian race (P=0.08) to be associated with poorer survival. When these risk factors were entered into a multivariate analysis, tumor resectability and non-Asian race were most predictive of improved survival (model P value = 0.007). When controlling for the multiple variables most often reported to be associated with HCC, Asians had a significantly lower survival than non-Asians (P<0.01).

CONCLUSIONS

In this study it appears that the outcome for Asian patients with hepatoma is worse than for non-Asian patients, even when controlling for factors commonly associated with HCC. Biologic or social factors that are not appreciated currently may be involved in Asian patients with HCC, contributing to a poorer clinical outcome.

Recombinant human thrombopoietin in combination with granulocyte colony-stimulating factor enhances mobilization of peripheral blood progenitor cells, increases peripheral blood platelet concentration, and accelerates hematopoietic recovery following high-dose chemotherapy

Lineage-specific growth factors mobilize peripheral blood progenitor cells (PBPC) and accelerate hematopoietic recovery after high-dose chemotherapy. Recombinant human thrombopoietin (rhTPO) may further increase the progenitor-cell content and regenerating potential of PBPC products. We evaluated the safety and activity of rhTPO as a PBPC mobilizer in combination with granulocyte colony-stimulating factor (G-CSF) in 29 breast cancer patients treated with high-dose chemotherapy followed by PBPC reinfusion. Initially, patients received escalating single doses of rhTPO intravenously (IV) at 0.6, 1.2, or 2.4 micrograms/kg, on day 1. Subsequent patients received rhTPO 0.6 or 0.3 micrograms/kg on days -3, -1, and 1, or 0.6 micrograms/kg on days -1 and 1. G-CSF, 5 micrograms/kg IV or subcutaneously (SC) twice daily, was started on day 3 and continued through aphereses. Twenty comparable, concurrently and identically treated patients (who were eligible and would have been treated on protocol but for the lack of study opening) mobilized with G-CSF alone served as comparisons. CD34(+) cell yields were substantially higher with the first apheresis following rhTPO and G-CSF versus G-CSF alone: 4.1 x 10(6)/kg (range, 1.3 to 17.6) versus 0.8 x 10(6)/ kg (range, 0.3 to 4.2), P =.0003. The targeted minimum yield of 3 x 10(6) CD34(+) cells/kg was procured following a single apheresis procedure in 61% of the rhTPO and G-CSF-mobilized group versus 10% of G-CSF-mobilized patients (P =.001). In rhTPO and G-CSF mobilized patients, granulocyte (day 8 v 9, P =.0001) and platelet recovery (day 9 v 10, P =.07) were accelerated, and fewer erythrocyte (3 v 4, P =.02) and platelet (4 v 5, P =.02) transfusions were needed compared with G-CSF-mobilized patients. Peripheral blood platelet counts, following rhTPO and G-CSF, were increased by greater than 100% and the platelet content of PBPC products by 60% to 110% on the first and second days of aphereses (P <.0001) with the greatest effect seen with repeated dosing of rhTPO at 0.6 microgram/kg. rhTPO is safe and well tolerated as a mobilizing agent before PBPC collection. Mobilization with rhTPO and G-CSF, in comparison to a comparable, nonrandomized G-CSF-mobilized group of patients, decreases the number of apheresis procedures required, may accelerate hematopoietic recovery, and may reduce the number of transfusions required following high-dose chemotherapy for breast cancer.

Effects of oxyhemoglobin on vasoconstriction in response to 5-hydroxytryptamine in isolated, perfused canine basilar arteries

OBJECTIVE

Oxyhemoglobin (OxyHb) is thought to be a critical trigger in the pathogenesis of cerebral vasospasm after aneurysmal subarachnoid hemorrhage. We investigated whether extraluminally applied OxyHb influenced vascular responses to intraluminally applied vasoactive agents in isolated, perfused, canine basilar arteries.

METHODS

The steel cannula insertion method was used to examine vascular responses to intraluminally applied 5-hydroxytryptamine (5-HT) receptor agonists, i.e., 5-HT, 5-carboxamidotryptamine (selective for 5-HT1 receptors), and alpha-methyl-5-hydroxytryptamine (selective for 5-HT2 receptors), potassium chloride, and acetylcholine, before and after extraluminal treatment with OxyHb.

RESULTS

Extraluminal application of 2.5 x 10(-5) mol/L OxyHb immediately induced a transient elevation of the basal perfusion pressure, which gradually decreased and then stabilized at a level slightly higher than the control level. Each 5-HT agonist induced dose-dependent vasoconstriction. The potencies of the agonists were not very different, but the efficacies varied, i.e., alpha-methyl-5-hydroxytryptamine > 5-HT > 5-carboxamidotryptamine. Each response was strongly inhibited by ketanserin (a selective 5-HT2 receptor antagonist), indicating that each agonist induces vasoconstriction mediated by 5-HT2 receptors. The vasoconstriction in response to each 5-HT receptor agonist was consistently potentiated by treatment with OxyHb (2.5 x 10(-5) mol/L). 5-HT receptor agonist-induced constrictions after OxyHb treatment were much more markedly inhibited by ketanserin, compared with those before OxyHb treatment. Acetylcholine-induced constrictions were enhanced by OxyHb, but KCl-induced constrictions were significantly decreased by OxyHb.

CONCLUSION

It is suggested that OxyHb enhancement of constrictions in response to 5-HT receptor agonists may be mediated by increased sensitivity of 5-HT2 receptors, in addition to actions in the endothelium, in canine basilar arteries. This potentiated vasoconstrictor mechanism may be partially implicated in cerebral vasospasm after subarachnoid hemorrhage.

Role of the M2 subunit of ribonucleotide reductase in regulation by hydroxyurea of the activity of the anti-HIV-1 agent 2',3'-dideoxyinosine

The ribonucleotide reductase inhibitor hydroxyurea exhibits potent synergism, even at low, non-cytotoxic concentrations, with the anti-HIV-1 dideoxynucleoside 2',3'-dideoxyinosine, bringing about failure of HIV DNA synthesis and, thus, of HIV replication. To elucidate the incompletely defined role of hydroxyurea in the hydroxyurea/dideoxyinosine interaction and, in particular, to identify the reasons for the unusual selective inhibitory action of the combination on retroviral rather than on cellular DNA synthesis, we prepared specific cDNA probes to determine the effects of low-level hydroxyurea on mammalian cell ribonucleotide reductase M1 and M2 subunit mRNA, while simultaneously quantitating the effects of the drug on cell cycle and on deoxynucleoside triphosphate pools. While dTTP, dCTP, and dGTP pools changed little or even increased in the presence of low-level hydroxyurea, there took place a rapid and specific inhibition of M2-subunit-catalyzed generation of dATP, with consequent slowing of cellular DNA synthesis and prolongation of S phase. However, the latter effect, in turn, resulted in increased M2 subunit mRNA transcription (a process blocked in Go/G1-phase cells, with full-length functional M2 transcripts being generated only during S phase) and, hence, in a return to normal levels of dATP and to a normal rate of cellular DNA synthesis. Because of this self-regulating mechanism, hydroxyurea-induced host-cell toxicity was obviated under conditions where HIV DNA synthesis, a process sensitive to both dATP depletion and the chain-terminating properties of the other inhibitory component of the combination (ddATP derived from dideoxyinosine), was unable to recover.

Phase I trial of intraperitoneal iododeoxyuridine with and without intravenous high-dose folinic acid in the treatment of advanced malignancies primarily confined to the peritoneal cavity: flow cytometric and pharmacokinetic analysis

In this Phase I study, the maximally tolerated doses (MTDs) of i.p. iododeoxyuridine (IdUrd) alone and in combination with i.v. calcium leucovorin (LV) were determined. The pharmacokinetics and pharmacological advantage of IdUrd were evaluated, and flow cytometric analysis allowed examination of the extent of incorporation of IdUrd into tumor cells with and without the addition of i.v. LV. Thirty-nine patients with advanced neoplasms primarily confined to the peritoneal space were enrolled in a dose-escalation trial using 4-h dwells of IdUrd administered i.p. daily for 4 days with and without an i.v. infusion of LV 500 mg/m2/day for 4.5 days. Twenty-three patients received single-agent therapy, and 13 patients received i.p. IdUrd in combination with i.v. LV. The MTD of single-agent IdUrd administered on this schedule was 4125 mg/m2/day for 4 days; and that of the IdUrd in combination was 3438 mg/m2/day. Dose-limiting toxicities were myelosuppression and stomatitis. During the period of the dwell, the peritoneal AUC (area under the curve) of IdUrd exceeded the plasma AUC of IdUrd by one or two orders of magnitude in all patients at all doses tested; there was a possible effect of LV on peritoneal AUC. The geometric mean pharmacological advantage (AUCperitoneal/ AUCplasma) was 181 at 625 mg/m2/day and 90 at 4538 mg/m2/day. Flow cytometric analysis suggests saturation of IdUrd measured in DNA at the 2500-3125 mg/m2 dose level, without an increase after the addition of LV. Twelve patients received 4-12 courses of therapy. One patient with recurrent ovarian cancer who received 16 courses of therapy experienced complete resolution of her ascites, near normalization of CA-125 levels, and improved quality of life; two patients with high-risk tumors receiving "adjuvant" therapy are disease-free at 3 and 6 years after treatment; other patients experienced transient clearing of ascites. The recommended Phase II dose of i.p. IdUrd using a 4-h dwell daily for 4 days is 3750 mg/m2/day alone or 3125 mg/m2/day in combination with continuous i.v. LV at 500 mg/m2/day for 4.5 days. Although flow cytometric data suggest that DNA incorporation of IdUrd is not affected by the addition of LV, the cytotoxicity of the combination regimen may be increased due to LV-enhanced, IdUrd-related inhibition of thymidylate synthase. For this reason, we recommend that efficacy studies of the combination continue in parallel with studies of IdUrd alone.

Determination of deoxyribonucleoside triphosphate pool sizes in ribonucleotide reductase cDNA transfected human KB cells

Ribonucleotide reductase (RR) is a rate-limiting enzyme in DNA synthesis, which is responsible for controlling deoxyribonucleoside triphosphate (dNTP) pool size. It has been shown that transfection of RR M2 cDNA in human KB cells (M2-D clone) results in overexpression for the M2 subunit and resistance to hydroxyurea (HU). In this study, dNTP pool assays were performed to measure the pool sizes in six cell lines: two controls, three transfectants, and drug-induced HU-resistant (HUR) cells. Total dNTP levels among the six cell lines rose in the following order: KB wild-type, KB vector-only transfectant, M1 cDNA transfectant, M2 cDNA transfectant, M1/M2 cDNA transfectant, and HU-induced resistant clone. The dCTP levels of the cells mimicked the total dNTP pools on a smaller scale. The significant increases in the dCTP pool sizes of the M2-D, X-D, and HUR clones were proportional to their respective increases in RR activity. Relative to all other transfectants, the M1-D clone demonstrated lower dCTP levels but increased dATP pools. The M1-D clone demonstrated a significant resistance to dNTP inhibition of RR activity compared with the control KB wild-type cells. In contrast, a profound inhibition of dCTP and a decreased sensitivity to dATP inhibition was observed in M2-D, X-D, and HUR clones. In summary, M2 cDNA transfectants and HUR clones had increased RR activity as well as expanded dNTP pools, particularly dCTP, when compared with wild-type KB cells. These data provide evidence for the intertwined relationship between RR activity and dNTP pools.

Reversal of hydroquinone-mediated suppression of T cell proliferation by transfection of the M2 subunit of ribonucleotide reductase

Hydroquinone (HQ) is a benzene derivative that is found in large quantities in cigarette tar as a result of the pyrolysis of tobacco flavinoids. HQ is a potent inhibitor of T cell proliferation, causing an immediate and complete cessation of DNA synthesis in IL-2-dependent human T lymphoblasts and Jurkat T cells without loss of cell viability. Previous studies from our laboratory demonstrated that the antiproliferative effects of RQ could be partially reversed by the addition of deoxyribonucleosides, but not by the corresponding ribonucleosides, suggesting that HQ might inhibit ribonucleotide reductase. In the present study, the molecular mechanism behind this observation was further investigated. Jurkat T cells were stably transfected with a pMEP4 expression vector containing the gene for the M2 subunit of ribonucleotide reductase under transcriptional control of the human metallothionein IIA promoter. M2-transfected Jurkat T cells exhibited a greater than three-fold increase in resistance to HQ compared to untransfected cells or cells transfected with the M2 gene in the reverse orientation. HQ resistance was associated with an increased level of M2 protein detected by Western blot. These results suggest that the benzene derivative inhibits lymphocyte proliferation by inhibiting ribonucleotide reductase.

Overexpression of transfected human ribonucleotide reductase M2 subunit in human cancer cells enhances their invasive potential

The ribonucleotide reductase (RR) gene has been associated with malignant transformation and metastatic potential. In this report, the significance of the expression of RR mRNA and enzymatic activity to the invasive potential was examined by Boyden chamber invasion assay. Our results suggest that overexpression of RR M2 mRNA and RR enzymatic activity correlates to an increase in cell invasive potential. The drug-induced HURs clone expressed a higher level RR M2 mRNA and enzyme activity which contributes significantly to the 3-fold increase in invasive potential of the cells observed relative to the KB wild-type control. On the contrary, the HUr revertant clone decreased the RR M2 mRNA level and enzymatic activity, concomitantly decreasing their invasive potential. This phenomenon is most likely due to the return of RR to levels comparable to that of the KB wild-type cells. To confirm that this observation was not of a drug-resistance phenotype associated with multiple gene alterations, the panel of RR transfectants (M1-D transfected M1 subunit cDNA, M2-D transfected M2 subunit cDNA, X-D transfected M1/M2 cDNA) characterized in a previous study were also tested in the invasion assay. The M2-D clone expressed 6-fold higher RR M2 mRNA and RR activity and also demonstrated 6-fold higher invasive potential in vitro than either the parental or vector only transfected cell line (KB-V). The X-D clone demonstrated 3-fold higher M2 mRNA expression and revealed 4-fold higher invasive potential than control cells. The M1-D clone, in contrast, expressed a baseline level of RR M2 mRNA and higher M1 mRNA. In contrast to the X-D and M2-D cells, the invasive potential of M1-D reached an even lower level in the invasive assay than the control. These results, therefore, suggest that RR M2 overexpression plays an important role in a tumor's invasiveness.

Root tip cell cycle synchronization and metaphase-chromosome isolation suitable for flow sorting in common wheat (Triticum aestivum L.)

An efficient procedure for cell-cycle synchronization in meristematic root tips was achieved in common wheat. Treatment parameters for synchronizing the cell cycle of root tip meristem cells, such as time-course and applied concentrations of various chemicals, were systematically tested and optimized by flow cytometric analysis of isolated nuclei. High mitotic indices (69.5% in the root tip meristematic area) were routinely obtained by treating germinating seeds with 1.25 mM hydroxyurea for 16 h, followed by incubation in a hydroxyurea-free solution for 2 h, and treatment with 1 μM trifluralin for 4 h. Uniform seed germination prior to treatment is very important for achieving consistently high metaphase indices in the root tips. Large numbers of metaphase chromosomes, suitable for flow cytometric analysis and sorting, were isolated from synchronized root tip cells. Flow sorted wheat chromosomes, via univariate and bivariate analysis, showed four major chromosome peaks. Each discrete peak may represent wheat chromosome types with similar DNA content. Bivariate flow karyotyping based on AT and GC content did not improve the separation of wheat chromosomes.Key words: flow cytometry, trifluralin, hydroxyurea, univariate analysis, bivariate analysis.

High-dose chemotherapy and stem-cell rescue in the treatment of high-risk breast cancer: prognostic indicators of progression-free and overall survival

PURPOSE

To examine the predictive value of tumor- and treatment-specific prognostic indicators of relapse-free survival (RFS) and overall survival (OS) in patients with high-risk breast cancer (HRBC) treated with high-dose chemotherapy (HDCT) and stem-cell rescue.

PATIENTS AND METHODS

Between June 1989 and September 1994, 114 patients with HRBC (stage II with > or = 10 axillary lymph nodes involved, stage IIIA, and stage IIIB inflammatory carcinoma) received adjuvant chemotherapy followed by HDCT with etoposide, cyclophosphamide, and either doxorubicin (CAVP) or cisplatin (CCVP). Variables analyzed included stage, tumor size, number of axillary nodes involved, grade and receptor status, and types of adjuvant chemotherapy and radiation therapy and HDCT.

RESULTS

With a median follow-up time of 46 months (range, 23 to 93), Kaplan-Meier estimates of 3.5-year OS for stage II, IIIA, and IIIB HRBC are 82% (95% confidence interval [CI], 67% to 97%), 79% (95% CI, 67% to 91%), and 72% (95% CI, 53% to 91%); RFS estimates are 71% (95% CI, 56% to 85%), 57% (95% CI, 43% to 72%), and 50% (95% CI, 29% to 71%) irrespective of the HDCT regimen. In univariate analysis, the risk of relapse was lower for patients with progesterone receptor (PR)-positive tumors (risk ratio [RR], 0.43; 95% CI, 0.22 to 0.81; P = .01) and higher for patients with inflammatory carcinoma (RR, 2.20; 95% CI, 1.02 to 4.76; P = .05). OS was better for patients with PR (RR, 0.16; 95% CI, 0.05 to 0.55; P = .003) and estrogen receptor (ER)-positive tumors (RR, 0.42; 95% CI, 0.17 to 1.02; P = .05); OS was worse for patients with high-grade primary tumors (RR, 4.08; 95% CI, 1.21-13.7; P = .02). In multivariate analysis, PR positivity was associated with improved RFS (P = .01) and OS (P = .001).

CONCLUSION

HDCT in selected patients with HRBC is safe and warrants further evaluation. Patients with receptor-negative, high-grade, or inflammatory tumors require improvement in their therapeutic options. Better assessment of the role of HDCT awaits completion of ongoing randomized trials.

Pharmacokinetics and toxicity of 120-hour continuous-infusion hydroxyurea in patients with advanced solid tumors

A group of 18 patients with advanced cancer were entered on a phase I study of a 120-h continuous intravenous infusion of hydroxyurea. The dose of hydroxyurea was escalated in cohorts of patients from 1 to 2 to 3.2 g/ m2 per day. The primary dose-limiting toxicity was neutropenia, often accompanied by leukopenia, thrombocytopenia and generalized skin rash. Prophylactic treatment of patients with dexamethasone and diphenhydramine hydrochloride prevented the skin rash, but not the hematopoietic toxicities. The pharmacokinetics of hydroxyurea were studied in all patients. The steady-state concentrations of hydroxyurea were linearly correlated with the dose (R2 = 0.71, n = 18, P < 0.0001). The mean +/- SE concentrations were 93 +/- 16, 230 +/- 6 and 302 +/- 27 microM at 1, 2 and 3.2 g/m2 per day, respectively. The mean +/- SE renal and nonrenal clearances of hydroxyurea were 2.14 +/- 0.18 and 3.39 +/- 0.28 l/h per m2 (n = 16), neither of which correlated with the dose. The concentration of hydroxyurea in plasma decayed monoexponentially with a mean +/- SE half-life of 3.25 +/- 0.18 h (n = 17). The steady-state concentration of hydroxyurea was > 200 microM in all nine patients treated at 2 g/m2 per day, a dose which was well tolerated for 5 days. We recommend this dose for phase II trials in combination with other antineoplastic agents.

Chromosomal locations of genes that control major RNA-degrading activities in common wheat (Triticum aestivum L.)

Seventeen RNA-degrading enzymes of common wheat, with apparent molecular masses from 42.2 kDa to 16.3 kDa, were observed by the RNA-SDS-PAGE assay. To determine their chromosome locations, all chromosome arms of common wheat except 4BS were assayed in their null condition by using a set of ditelosomic or nullitetrasomic lines of the cultivar Chinese Spring. Our results showed that only one chromosome location each was identified for the 22.8-kDa and the 21.2-kDa enzymes, as well as for the 21.6 kDa enzyme, and they are on chromosome arms 2AS and 2DS, respectively. Loci controlling the 20.1 kDa activity were on chromosome arms 2AL, 4BS, 4DS and 6BS. The locus or loci coding for the gene(s) of the 42.2-kDa, 40.9-kDa and 39.2-kDa enzymes were probably ocated on chromosome arm 5AS, and their expression, in agreement with most other RNA-degrading enzyme activities were stimulated when chromosome arm 5AL was missing, indicating a inhibiting locus on 5AL. Our data suggested that the 31.9-kDa, 30.6-kDa and 29.6-kDa enzymes were possibly products of a common precursor which might be coded by a gene(s) on chromosome arm 6BS, and that the processing is co-regulated by loci on chromosome arms 2BS, 3DS, 6AL, 6BL and 7BS. The remaining of the enzyme activities were consistently found in all of the lines tested, and thus are presumably encoded by multiple loci. The only other possibility is that, their loci may be on chromosome arm 4BS which we have not assayed in its null condition.

Pseudoleukemia after granulocyte colony-stimulating factor therapy

Therapy with myeloid colony-stimulating factors has been safely and effectively used in a wide variety of situations associated with neutropenia. We present a case of pseudoleukemia occurring in a patient with lymphoma and pancytopenia after 2 days of treatment with granulocyte colony-stimulating factor (G-CSF). Bone marrow aspirate and flow cytometry study results were consistent with acute myelomonocytic leukemia but were normal after G-CSF was discontinued for 4 days. As previous phase I studies of bone marrow morphology after G-CSF use have not described the extreme myeloid immaturity seen in this patient, it seems likely that the action of G-CSF was enhanced by factors associated with the patient's illness. We emphasize the clinical importance of this case in light of the widespread use of G-CSF.

Overexpression of ribonucleotide reductase in transfected human KB cells increases their resistance to hydroxyurea: M2 but not M1 is sufficient to increase resistance to hydroxyurea in transfected cells

Ribonucleotide reductase (RR) is a rate-limiting enzyme in DNA synthesis. The enzyme consists of two subunits, M1 and M2. Hydroxyurea (HU) is an M2-specific inhibitor. It has been shown that a HU-resistant clone derived from stepwise exposure to HU overexpresses the M2 mRNA and the RR protein (Y. Yen et al., Cancer Res., 54: 3868-3691, 1994). In this study, we established stable clones by transfecting human KB cells with the cDNA of human wild-type RR in which each subunit was overexpressed by a SV40 promoter. The mammalian cell expression vector ph beta APr-1 was used for constructing M1, M2, and M1/M2 subunit cDNA. The transfected cells were selected with G418. The clones designated M2-D, M1-D, X-D, and KB-V represent transfectant clones which contain M2 cDNA, M1 cDNA, M1/M2 cDNA, and vector alone, respectively. The parental KB cells and clones containing vector plasmid KB-V express equally low amounts of M2 and M1 mRNA from the endogenous genes. The expression of M2 mRNA and M1 mRNA is elevated 2-3 fold in the X-D transfectants. M2-D clone demonstrated a 6-fold higher M2 mRNA level although the M1 mRNA expression remains the same as parental cells. M1-D transfectants have a 3-fold increase in M1 mRNA expression relative to parental cells, but reveal no alteration of M2 mRNA. Southern analysis of genomic DNA suggested the incorporation of the plasmid into the genome. The X-D clone revealed both integration of the M2 and M1 gene while the M2-D clone only showed M2 gene integration. The M1-D clone revealed M1 gene integration relative to the parental cells. The Western blot of M2 protein showed a 3-fold increase in the X-D and M2-D clones whereas the M2 protein level in M1-D was the same as it was in parental cells. The M1 protein was increased 3-fold in X-D and 1.5-fold in M1-D over that of parental cells. However, lower M1 protein levels were identified in the M2-D clone. The specific activity of the RR enzyme from each transfectant showed a 3-fold increase in both the X-D and M2-D clones and slightly increased in M1-D clone over that of parental cells. However, X-D and M2-D both demonstrated a 3-fold increase in resistance to HU as compared to M1-D which showed the same sensitivity as the parental enzyme.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization of a hydroxyurea-resistant human KB cell line with supersensitivity to 6-thioguanine

Hydroxyurea (HU) is currently used in the clinic for the treatment of chronic myelogenous leukemia, head and neck carcinoma, and sarcoma. One of its drawbacks, however, is the development of HU resistance. To study this problem, we developed a HU-resistant human KB cell line which exhibits a 15-fold resistance to HU. The characterization of this HU-resistant phenotype revealed a gene amplification of the M2 subunit of ribonucleotide reductase (RR), increased levels of M2 mRNA and protein, and a 3-fold increase of RR activity. This HU-resistant cell line also expressed a "collateral sensitivity" to 6-thioguanine (6-TG), with a 10-fold decrease in the dose inhibiting cell growth by 50% as compared to the KB parental line. The mechanism responsible for this supersensitivity to 6-TG is believed to be related to an increasingly efficient conversion of 6-TG to its triphosphate form, which is subsequently incorporated into DNA. After passage of the resistant cells in the absence of HU, the cell line reverts. The revertant cells lose their resistance to HU and concomitantly their sensitivity to 6-TG. This phenomenon is due to the return of RR to levels comparable to that of the KB parental cell line. These observations and their relevance to cancer chemotherapy will be discussed in this paper. Our results suggest that a clinical protocol could be designed which would allow for a lower dose of 6-TG to be used by taking advantage of the increased RR activity in HU-refractory cancer patients. Two drugs which display collateral sensitivity are known as a "Ying-Yang" pair. Alternate treatment with two different Ying-Yang pairs is the rationale for the "Ying-Yang Ping-Pong" theory in cancer treatment. This rationale allows for effective cancer chemotherapy with reduced toxicity.

Wheat chromosome 2D carries genes controlling the activity of two DNA-degrading enzymes

DNA-degrading enzymes of 24.0 kDa and 27.0 kDa were observed to have different activities in two common wheat (Triticum aestivum L.) cultivars, 'Wichita' and 'Cheyenne'. A substrate-based SDS-PAGE assay revealed that these two enzymes were much more active in 'Wichita' than in 'Cheyenne'. Genes controlling the activities of these two enzymes were localized on chromosome 2D by testing DNA-degrading activities in reciprocal chromosome substitution lines between 'Wichita' and 'Cheyenne'. While the allele on 'Wichita' chromosome 2D stimulated the activities of the 24.0- and 27.0-kDa enzymes in Cheyenne, the allele on 'Cheyenne' chromosome 2D did not reduce the activities of the 24-kDa and 27-kDa enzymes in 'Wichita'. Whether these genes code for the DNA-degrading enzymes themselves or for factors that regulate the enzyme activities remains unknown.

The lupus anticoagulant. High incidence of 'negative' mixing studies in a human immunodeficiency virus-positive population

We identified 100 patients (51 males and 49 females) as having the lupus anticoagulant. The following diagnoses were found in the patient population: human immunodeficiency virus positivity, 20%; systemic lupus erythematosus, 10%; prolonged preoperative activated partial thromboplastin time (APTT), 10%; procainamide hydrochloride-induced inhibitor, 9%; deep vein thrombosis, 6%; seizure disorders/epilepsy, 5%; and miscellaneous conditions, 40%. Identification was based on a prolonged APTT (> 40 seconds) that normalized with increased phospholipid concentrations and/or a prolonged Russell viper venom clotting time patient-control ratio of 1.20 or greater. In 68 cases (group 1), patient plasma prolonged the APTT of normal plasma in a 1:1 mixing study. However, in 32 cases (group 2), no such prolongation was observed. There was a significant difference between presenting APTTs in patients from group 1 (mean +/- SD, 58.29 +/- 13.30 seconds) compared with that in group 2 (mean +/- SD, 47.93 +/- 5.09 seconds). Furthermore, 66% of group 1 patients had elevated anticardiolipin antibody titers compared with only 41% in group 2. Of the 32 patients in group 2, 16 (50%) were positive for human immunodeficiency virus. We concluded that the investigation of a lupus anticoagulant should not be abandoned because patient plasma does not prolong the APTT of normal plasma in a mixing study, especially in a human immunodeficiency virus-positive population.