Bone Marrow Granulocyte-macrophage Colony-forming Units Research Articles

Genz-644282, a Novel Non-Camptothecin Topoisomerase I Inhibitor for Cancer Treatment

Genz-644282 [8,9-dimethoxy-5-(2-N-methylaminoethyl)-2,3-methylenedioxy-5H-dibenzo[c,h][1,6]naphthyridin-6-one] has emerged as a promising candidate for antitumor agents. This report describes the bone marrow colony-forming unit, granulocyte macrophage (CFU-GM) and tumor cell CFU activity of topoisomerase I (Top1) inhibitors, such as Genz-644282, topotecan, irinotecan/SN-38, and ARC-111, and examines their activity in several human tumor xenograft models. Colony-forming assays were conducted with mouse and human bone marrow and eight human tumor cell lines. In addition, 29 human tumor cell lines representing a range of histology and potential resistance mechanisms were assayed for sensitivity to Genz-644282 in a 72-hour exposure assay. The efficacy of Genz-644282 was compared with standard anticancer drugs (i.e., irinotecan, docetaxel, and dacarbazine) in human tumor xenografts of colon cancer, renal cell carcinoma, non-small cell lung cancer, and melanoma. Human bone marrow CFU-GM was more sensitive to the Top1 inhibitors than was mouse bone marrow CFU-GM. The ratio of mouse to human IC(90) values was more than 10 for the camptothecins and less than 10 for Genz-644282, which had more potency as a cytotoxic agent toward human tumor cells in culture than the camptothecins in the colony-forming and 72-hour proliferation assays. Genz-644282 has superior or equal antitumor activity in the human tumor xenografts than the standard drug comparators. On the basis of preclinical activity and safety, Genz-644282 was selected for development and is currently undergoing phase 1 clinical trial.

Abstract C217: Genz-644282, a novel non-camptothecin topoisomerase I inhibitor for cancer treatment

Abstract Topoisomerase I (Top1), a well-established anticancer target, is a nuclear enzyme producing a single-strand DNA break to allow transcription. Camptothecin Top1 inhibitors are important drugs for the treatment of a variety of cancers including colon cancer, leukemias and ovarian cancer. Potent non-camptothecin Top1 inhibitors were identified. One of these, Genz-644282, binds tightly and selectively to the DNA:Top1 complex. The effects of Genz-644282, topotecan and irinotecan/SN38 in cell-based assays were compared. The colony formation assay is the gold-standard for determination of the cytotoxicity of compounds toward bone marrow and malignant cells as it measures the survival/killing of cells capable of self-renewal. Mouse and human bone marrow were subjected to colony forming unit -granulocyte/macrophage (CFU-GM) assays over a 5-log concentration range with continuous exposure to the compounds for 13–15 days. The IC90s for topotecan and SN38 for mouse CFU-GM were 519 nM and 331 nM, respectively. For human CFU-GM, the IC90s for topotecan and SN38 were 19 nM and 26 nM, resulting in mouse to human differentials of 28- and 13-fold. Genz-644282 was more potent, with IC90s of 8.4nM for mouse CFU-GM and 1.2 nM for human CFU-GM; thus only a 7-fold differential between species. The cytotoxicities of topotecan, SN38 and Genz-644282 were compared in the ability of seven human tumor cell lines of varied histologies to form colonies after a week of exposure to a 5-log concentration range of each compound. Human bone marrow CFU-GM was much more sensitive to topotecan than were RPMI-8226 multiple myeloma, KBV-1 cervical carcinoma or NCI-H460 non-small cell lung carcinoma cells. The IC90s for topotecan ranged between 11 and 257 nM. SN38 cytotoxicity to human bone marrow CFU-GM and to several human tumor cell lines was very similar with IC90s in the cancer lines ranging between 2 and 55 nM. HT29 human colon cancer cells, however, were markedly sensitive to SN38 (IC90 = 2 nM). Genz-644282 was a more potent cytotoxic agent than topotecan or SN38 with IC90 values ranging between 0.7 and 9.1 nM across the seven cell lines. MDA-MB-231 human breast carcinoma, HT29 colon carcinoma and RPMI-8226 cells were most sensitive to Genz-644282 with IC90s ranging between 0.7 and 7.0 nM. The growth inhibition produced by 72-hr exposure to Genz-644282 was examined in 26 established human tumor cell lines representing pancreatic carcinoma, melanoma, non-small cell lung cancer, breast carcinoma, ovarian carcinoma and renal cell carcinoma using a Cell TiterGlo ATP content endpoint. The IC90s for Genz-644282 ranged between 0.054 micromolar and 5 micromolar in this assay. The most sensitive tumor lines were 4 of 6 pancreatic cancer lines and the least sensitive lines included 3 of 4 melanoma lines. Colony formation data were analyzed by non-linear regression using SAS version 8.2. Based upon these findings and other data, Genz-644282 was selected as a development candidate. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C217.

Anti-Ccl2 Spiegelmer Permits 75% Dose Reduction of Cyclophosphamide to Control Diffuse Proliferative Lupus Nephritis and Pneumonitis in MRL-Fas(lpr) Mice

Cyclophosphamide (CYC) can control diffuse proliferative lupus nephritis (DPLN) by potent immunosuppression but remains associated with serious and life-threatening complications. Drugs that specifically target mediators of DPLN may help to reduce CYC dose and side effects. Monocyte chemoattractant protein (MCP-1)/CCL2 mediates monocyte and T cell recruitment in DPLN and Ccl2-specific l-enantiomeric RNA Spiegelmer mNOX-E36 neutralizes the biological effects of murine Ccl2 in vitro and in vivo. We injected MRL(lpr/lpr) mice with DPLN from 14 weeks of age with vehicle, weekly 30 mg/kg CYC (full dose), monthly 30 mg/kg CYC (one-fourth full dose), pegylated control Spiegelmer, pegylated anti-Ccl2 Spiegelmer (3/week), pegylated anti-Ccl2 Spiegelmer plus CYC one-fourth full dose and mycophenolate mofetil. At week 24, DPLN and autoimmune lung injury were virtually abolished with CYC full dose but not with CYC one-fourth full dose. The CYC one-fourth full dose/Spiegelmer combination was equipotent to CYC full dose on kidney and lung injury. CD3(+)CD4(-)CD8(-) and CD3(+)CD4(+)CD25(+) T cells and serum interleukin-12p40 and tumor necrosis factor-alpha levels were all markedly affected by CYC full dose but not by CYC one-fourth full dose. No additive effects of anti-Ccl2 Spiegelmer were noted on bone marrow colony-forming unit-granulocyte macrophage counts and 7/4(high) monocyte counts, lymphoproliferation, and spleen T cell depletion. In summary, anti-Ccl2 Spiegelmer permits 75% dose reduction of CYC for controlling DPLN and pneumonitis in MRL-Fas(lpr) mice, sparing suppressive effects of full-dose CYC on myelosuppression and T cell depletion. We propose anti-Ccl2 Spiegelmer therapy as a novel strategy to reduce CYC toxicity in the treatment of severe lupus.

Bone marrow and tumor cell colony-forming units and human tumor xenograft efficacy of noncamptothecin and camptothecin topoisomerase I inhibitors

Topoisomerase I (TopoI), an established anticancer target, is an enzyme producing a single-strand DNA break during transcription. Several noncamptothecin TopoI inhibitors have been identified. One of these, ARC-111, was compared with two clinically used camptothecins, topotecan and irinotecan/SN-38. In mouse and human bone marrow colony formation [colony-forming units granulocyte-macrophage (CFU-GM)] assays, the IC(90) values were 519 and 331 nmol/L for topotecan and SN-38 mouse CFU-GM and were 19 and 26 nmol/L for human CFU-GM, giving mouse to human differentials of 28- and 13-fold. ARC-111 produced IC(90) values of 28 nmol/L in mouse and 6.2 nmol/L in human CFU-GM, thus only a 4.5-fold differential between species. Human bone marrow CFU-GM was more sensitive to topotecan than were several human cancer cell lines, but ARC-111 cytotoxicity was similar for human bone marrow CFU-GM and the seven human tumor cell lines tested. In HCT-116 xenografts, tumor growth delays (TGD) were 17 days for irinotecan and 20 days for ARC-111. In HT-29 xenografts, the TGD was 9 days for both irinotecan and ARC-111. Both ARC-111 and docetaxel had a TGD of 21 days in NCI-H460 xenografts, and both ARC-111 and gemcitabine had a TGD of 7 days in MiaPaCa2 xenograft. Current TopoI inhibitors have broad antitumor activity in human tumor xenografts that is not achieved in the clinic. This may be due to greater sensitivity of human bone marrow than mouse to the cytotoxicity of these agents. It may be possible to achieve similar levels of ARC-111 in patients as in mice allowing improved antitumor activity.

Mad2 is required for optimal hematopoiesis: Mad2 associates with c-Kit in MO7e cells

AbstractMitotic arrest deficiency 2 (Mad2) is a component of mitotic spindle checkpoint proteins and is essential for accurate chromosome segregation. We investigated a role for Mad2 in hematopoiesis using Mad2-haploinsufficient (Mad2+/−) mice. Mad2+/− bone marrow (BM) and spleen manifested decreased absolute numbers and cycling status of immature, but not mature, hematopoietic progenitor cells. Mad2+/− BM granulocyte-macrophage colony-forming units (CFU-GMs) did not manifest synergistic proliferation in response to stem cell factor (SCF) plus GM-CSF. The percentage of annexin V+ cells was higher in Mad2+/− than Mad2+/+c-Kit+lin− BM after culture with SCF and GM-CSF. However, no significant difference in phosphorylation of extracellular signal–related kinase (Erk1/2) at Thr202/Tyr204 and Akt at Ser473 between Mad2+/− and Mad2+/+BM c-Kit+lin− cells was observed. Immunoprecipitation assays performed in human MO7e cells demonstrated physical association of c-Kit with Mad2. Moreover, stimulation with SCF plus GM-CSF led to dissociation of Mad2 from c-Kit. Confocal microscopy demonstrated that Mad2 colocalized with c-Kit in the cytoplasm of MO7e cells. These results suggest that Mad2 is involved in synergistic growth of immature hematopoietic progenitor cells in response to SCF plus GM-CSF, effects that may be mediated via physical association of Mad2 with c-Kit.

The suppression of radiation-induced NF-κB activity by dexamethasone correlates with increased cell death in vivo

In this study, we show that dexamethasone treatment increases ionizing radiation-induced cell death by inducing the inhibitory κBα (IκBα) pathway in mice. The effect of dexamethasone on radiation-induced cell death was assessed by changes in total spleen cellularity and bone marrow colony-forming unit–granulocyte–macrophage (CFU–GM) contents after total body irradiation. While in vivo treatment of mice with dexamethasone alone (1 mg/kg/day, for 2 days) failed to elicit cell death in spleen cells, the combined treatment with dexamethasone (1 mg/kg/day, for 2 days) and γ-rays (1 or 5 Gy) caused a 50–80% reduction in total cellularity in spleen and CFU–GM contents in bone marrow. These results demonstrate that dexamethasone has a synergistic effect on radiation-induced cellular damages in vivo. Immunoblot analysis showed that dexamethasone treatment significantly increases IκBα expression in the spleens of irradiated mice. In addition, the dexamethasone treatment significantly reduced radiation-induced nuclear translocation of the nucleus factor-κB in the spleens of irradiated mice. These results indicate that dexamethasone treatment in vivo may increase radiation-induced cell damages by increasing IκBα expression in hematopoietic organs such as spleen and bone marrow.

Limits of stimulation of proliferation and differentiation of bone marrow cells of mice treated with swainsonine

The limits of stimulation of the immunomodulatory alkaloid swainsonine (8αβ-indolizidine-1α,2α,8β-triol) were studied in inbred C57BL/6 mice for potential support of intense high dose cancer chemotherapy and/or radiation because of its attractive pharmacologic profile on the hematopoietic system. Specifically, the effects of swainsonine on bone marrow cellularity and on in vitro progenitor cell proliferation to total colony forming units (CFU) and differentiation to different lineages were studied as a function of number of days post drug administration. The lineages evaluated were colony forming units-granulocyte-macrophage (CFU-GM), erythroid-burst forming units (BFU-e) and CFU-granulocyte-erythrocyte-monocyte-megakaryocyte (CFU-GEMM or CFU-Mix). Groups of mice were treated with swainsonine or plain vehicle, phosphate buffered saline for 10 consecutive days. The effects of these agents on the hematopoietic system were studied up to 60 days following their discontinuation. The magnitude of the effects of swainsonine on bone marrow system gradually declined with increasing duration of days following its discontinuation. Nevertheless, its residual stimulatory effects on bone marrow cellularity, total CFU, CFU-GM, BFU-e and CFU-Mix continued to be significant ( P<0.0001) up to 45, 50, 50, 55 and 50 days, respectively, compared to those of diluent buffer or untreated controls. Since cancer chemotherapeutic agents or radiation are normally given in schedules and/or cycles, these results strongly suggest that swainsonine effects are sustained long enough to potentially support and facilitate hematopoietic recovery during anti-cancer cytotoxic treatment.

Prevalidation of a model for predicting acute neutropenia by colony forming unit granulocyte/macrophage (CFU-GM) assay

This report describes an international prevalidation study conducted to optimise the Standard Operating Procedure (SOP) for detecting myelosuppressive agents by CFU-GM assay and to study a model for predicting (by means of this in vitro hematopoietic assay) the acute xenobiotic exposure levels that cause maximum tolerated decreases in absolute neutrophil counts (ANC). In the first phase of the study (Protocol Refinement), two SOPs were assessed, by using two cell culture media (Test A, containing GM-CSF; and Test B, containing G-CSF, GM-CSF, IL-3, IL-6 and SCF), and the two tests were applied to cells from both human (bone marrow and umbilical cord blood) and mouse (bone marrow) CFU-GM. In the second phase (Protocol Transfer), the SOPs were transferred to four laboratories to verify the linearity of the assay response and its interlaboratory reproducibility. After a further phase (Protocol Performance), dedicated to a training set of six anticancer drugs (adriamycin, flavopindol, morpholino-doxorubicin, pyrazoloacridine, taxol and topotecan), a model for predicting neutropenia was verified. Results showed that the assay is linear under SOP conditions, and that the in vitro endpoints used by the clinical prediction model of neutropenia are highly reproducible within and between laboratories. Valid tests represented 95% of all tests attempted. The 90% inhibitory concentration values (IC 90) from Test A and Test B accurately predicted the human maximum tolerated dose (MTD) for five of six and for four of six myelosuppressive anticancer drugs, respectively, that were selected as prototype xenobiotics. As expected, both tests failed to accurately predict the human MTD of a drug that is a likely protoxicant. It is concluded that Test A offers significant cost advantages compared to Test B, without any loss of performance or predictive accuracy. On the basis of these results, we proposed a formal Phase II validation study using the Test A SOP for 16–18 additional xenobiotics that represent the spectrum of haematotoxic potential.

Chronopharmacologic Effects of Recombinant Human Granulocyte Colony-Stimulating Factor (rhG-CSF) on Hematopoiesis in Mice

Chronopharmacologic effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) on circulating white blood cell and differential counts as well as bone marrow granulocyte-macrophage colony-forming units (CFU-GM) counts were investigated in B6D2F1 mice. The animals were synchronized with an alternation of 12 h of light (L) and 12 h of darkness (D) (LD 12:12) for 3 weeks prior to study, then received a daily subcutaneous injection of rhG-CSF (400 µg/kg/day) for 4 consecutive days at 3, 9, 15 or 21 h ours a fter l ight o nset (HALO). Samples were obtained on the fifth day at the same circadian stage as that of rhG-CSF injection. rhG-CSF significantly increased the 24-h mean of leukocyte, neutrophil, lymphocyte and CFU-GM counts. Maximum increase in leukocyte and neutrophil counts was observed when rhG-CSF was administered in the middle of the dark span, while maximum stimulatory effect on circulating lymphocytes or on CFU-GM counts was obtained with rhG-CSF administration near the middle of the light span. The results indicate that choosing the dosing time of this cytokine may selectively orient its pharmacologic action. Appropriate chronomodulated delivery schemes of rhG-CSF may further reduce hematological toxicity following chemotherapy.

Prolactin exerts hematopoietic growth-promoting effects in vivo and partially counteracts myelosuppression by azidothymidine

Prolactin (PRL) is a neuroendocrine hormone that influences immune and hematopoietic development. The mechanism of action of this hormone in vivo remains unclear; therefore, we assessed the effects of PRL on hematopoiesis in vivo and in vitro. Normal resting mice were treated with 0, 1, 10, or 100 μg of recombinant human prolactin (rhPRL) for 4 consecutive days and euthanized on the fifth day for analysis of myeloid and erythroid progenitors in the bone marrow and spleen. Both frequencies and absolute numbers of splenic colony-forming unit granulocyte-macrophage (CFU-GM) and burst-forming unit-erythroid (BFU-e) were significantly increased in mice receiving rhPRL compared to the controls that had received saline only. Bone marrow cellularities were not significantly affected by any dose of rhPRL, but the absolute numbers and frequencies of bone marrow CFU-GM and BFU-e were augmented by rhPRL. These results suggest that rhPRL can promote hematopoiesis in vivo. Because rhPRL augments myeloid development in vivo, we examined the potential of the hormone to reverse the anemia and myelosuppression induced by azidothymidine (AZT). Mice were given rhPRL injections concurrent with 2.5 mg/mL AZT in drinking water. rhPRL partially restored hematocrits in the animals after 2 weeks of treatment and increased CFU-GM and BFU-e in both spleens and bone marrow. The experiments with AZT and rhPRL support the conclusion that the hormone increases myeloid and erythroid progenitor numbers in vivo, and they suggest that the hormone is clinically useful in reversing myelosuppression induced by AZT or other myeloablative therapies.

Preclinical antitumor activity of XK469 (NSC 656889).

XK469 (NSC 656889) is a water-soluble member of the novel quinoxaline family of antitumor agents. In vitro, XK469 demonstrated selective cytotoxicity for several murine solid tumors including colorectal and mammary adenocarcinoma cell lines, when compared to both leukemia and normal epithelial cells. In vivo, XK469 was active against 7/7 murine tumors tested, including pancreatic ductal carcinomas #02 and #03, colon adenocarcinomas #38 and #51/A, mammary adenocarcinoma #16/C and the Adriamycin resistant mammary adenocarcinomas #16/C/ADR and #17/ADR. XK469 was efficacious both intravenously and orally. Regardless of dosing schedule, conventional mice tolerated higher total doses than SCID or nu/nu mice did. Despite these reduced doses, XK469 was active against xenografts of 4/6 human tumor lines including mammary adenocarcinoma MX-1, the small cell lung cancer DMS 273, the prostate model LNCaP and the CNS tumor SF295. The lower doses in the xenograft studies were below curative levels. The dose-limiting toxicity appeared to be myelosuppression with rapid host recovery (5-8 days), and in vitro assays of XK469 toxicity to murine bone marrow neutrophil progenitors CFU-GM (colony forming unit-granulocyte/macrophage) demonstrated concentration-dependent toxicity from 0.5-30 microg/mL. The difference in drug tolerance between BDF1 and SCID mice was detected in vitro as a 3-fold difference in the IC90 for CFU-GM, despite similar IC50 values. Comparative in vitro hematotoxicology studies revealed that human bone marrow CFU-GM tolerated XK469 as well as their SCID counterparts (IC90 values 5.7 vs. 7.4 microg/mL). Based on comparison with previously tested anti-cancer agents, these data suggest that humans will be able to tolerate XK469 doses that are efficacious against human tumor xenografts.

Kappa-Opioid receptors in marrow stroma mediate the hematopoietic effects of melatonin-induced opioid cytokines.

Melatonin exerts colony-stimulating activity and rescues myeloid progenitors from apoptosis, induced either in vivo or in vitro by cancer chemotherapy compounds in tumor-bearing mice. These effects are mediated mainly by T-helper cell-derived opioid cytokines with an apparent molecular mass of 15 kDa and 67 kDa that are recognized both by anti-interleukin-4 and anti-dynorphin B antibodies. These putative new cytokines were named melatonin-induced-opioid (MIO). The most active and naltrexone-sensitive MIO was the smaller molecule, which was called MIO15 and found to act on an opioid-binding site present in adherent bone marrow cells. However, the hematopoietic action of MIO15 was dependent on the presence of colony-stimulating factors (CSF). To investigate this point, we studied the ability of melatonin to rescue granulocyte/macrophage colony-forming units (GM-CFU) in the bone marrow of tumor-free animals treated with cancer chemotherapeutic compounds. We found that melatonin not only is unable to protect bone marrow GM-CFU unless the mice are transplanted with Lewis lung carcinoma (LLC), but also that melatonin seems to increase the myelotoxicity of cyclophosphamide in tumor-free mice. In both tumor-bearing or healthy mice, the effect of melatonin is negated by naltrexone, indicating the involvement of MIO15. Competition studies classified the target opioid-binding site as a kappa-opioid receptor with low affinity in tumor-free mice and high affinity in LLC-implanted mice. LLC is known to release CSF. Consistently, addition of CSF in the form of lung-conditioned medium (LCM) to adherent bone marrow cells increased the affinity of the kappa-opioid receptor. Addition of antigranulocyte/macrophage colony-stimulating factor (GM-CSF) mAbs neutralized the effect of LCM. In conclusion, the affinity state of the kappa-opioid receptors in stromal bone marrow cells seems to modulate the hematopoietic effect of melatonin and/or MIO15.

Influence of Photofrin® on the Hematopoietic Accessory Function of Murine Peritoneal Cells

The porphyrin photochemotherapeutic agent Photofrin® stimulates hematopoietic activity within the bone marrow (BM) and spleens of normal mice. We found that the intraperitoneal (i.p.) administration of Photofrin® also caused a 3–4 fold increase in peritoneal cell (PC) numbers, particularly cells bearing granulocyte surface antigens. Little granulocyte-macrophage progenitor activity was detectable within the PC population of control and Photofrin®-injected mice suggesting that Photofrin® had elicited an influx of inflammatory cells into the region. In contrast to cells from control animals, PC obtained 6 h to 168 h after the i.p. injection of Photofrin® exhibited a consistently inferior capacity to support the growth of BM colony forming units granulocyte-macrophage (CFU-GM). When PC from control or Photofrin®-treated mice were added to the BM culture system in the presence of defined growth factors there was no effect on the number of colonies formed. This finding indicated that negative regulatory elements were not responsible for the reduced hematopoietic accessory activity exhibited by PC from Photofrin®-treated mice. Supernatants conditioned by PC from Photofrin®-injected mice poorly supported BM CFU-GM growth in vitro and in contrast to PC supernatants prepared from control mice did not contain detectable amounts of granulocyte-macrophage colony stimulating factor (GM-CSF). The cellular changes which occur within the peritoneal cavity represent bystander events not directly related to the hematostimulatory action of Photofrin®.

Allergen-induced increase in bone marrow progenitors in airway hyperresponsive dogs: regulation by a serum hemopoietic factor.

We have previously reported that bone marrow progenitors in dogs, specifically granulocyte-macrophage colony-forming units (GM-CFU), increase developing airway hyperresponsiveness after inhalation of the allergen Ascaris suum. In the present study, we evaluated whether this increased marrow hemopoietic activity can be stimulated by a factor in serum after allergen challenge. Serum samples taken from dogs prior to and 20 min, 2 h, and 24 h after Ascaris or diluent challenge were added to bone marrow cells aspirated prior to challenge, and GM-CFU measured. A second bone marrow aspirate was performed 24 h after challenge. Nonadherent mononuclear bone marrow cells were incubated for 8 days in the presence of the serum and recombinant canine hemopoietic cytokines (stem cell factor, granulocyte colony-stimulating factor, GM colony-stimulating factor). Eight dogs that developed (airway responders) and eight dogs that did not develop (airway nonresponders) allergen-induced airway hyperresponsiveness were studied. Allergen inhalation increased bone marrow GM-CFU in response to all three growth media in vitro for the airway responder (P < 0.05) but not airway nonresponder dogs. The 24-h serum, taken from the airway responder but not the airway nonresponder dogs, produced a similar increase in granulocyte progenitors when added to the bone marrow taken before allergen inhalation (P < 0.05). These findings demonstrate that bone marrow-derived granulocyte progenitors are upregulated by a factor that can be shown to be present in serum 24 h after allergen challenge in dogs that develop allergen-induced airway hyperresponsiveness. Whether in vivo stimulation of bone marrow inflammatory cell production is necessary for the development of allergen-induced airway hyperresponsiveness remains to be proven.

Transforming growth factor-beta in in vivo resistance.

The potential role of transforming growth factor-beta in in vivo resistance was examined by administration of transforming growth factor-beta-neutralizing antibodies to animals bearing the EMT-6/Parent tumor or the antitumor alkylating resistance tumors, EMT-6/CTX or EMT-6/CDDP. Treatment of tumor bearing animals with anti-TGF-beta antibodies by intraperitoneal injection daily on days 0-8 post-tumor cell implantation increased the sensitivity of the EMT-6/Parent tumor to cyclophosphamide (CTX) and cisplatin (CDDP) and markedly increased the sensitivity of the EMT-6/CTX tumor to CTX and the EMT6/CDDP tumor to CDDP, as determined by tumor cell survival assay. Bone marrow granulocyte-macrophage colony-forming units (CFU-GM) survival was determined from these same animals. The increase in the sensitivity in the tumors upon treatment with the anti-TGF-beta antibodies was also observed in increased sensitivity of the bone marrow CFU-GM to CTX and CDDP. Treatment of non-tumor-bearing animals with the anti-TGF-beta regimen did not alter blood ATP or serum glucose level but did decrease serum lactate levels. This treatment also decreased hepatic glutathione, glutathione S-transferase, glutathione reductase, and glutathione peroxidase in non-tumor bearing animals by 40-60% but increased hepatic cytochrome P450 reductase in these normal animals. Animals bearing the EMT-6/CTX and EMT-6/CDDP tumors had higher serum lactate levels than normal or EMT-6/Parent tumor-bearing animals; these were decreased by the anti-TGF-beta regimen. Treatment of animals bearing any of the three tumors with the anti-TGF-beta regimen decreased by 30-50% the activity of hepatic glutathione S-transferase and glutathione peroxidase, and increased by 35-80% the activity of hepatic cytochrome P450 reductase. In conclusion, treatment with transforming growth factor-beta-neutralizing antibodies restored drug sensitivity in the alkylating agent-resistant tumors, altering both the tumor and host metabolic states.

Isolation and characterization of two monoclonal antibodies that recognize different epitopes of the human c-kit receptor.

After immunizing mice with a human megakaryoblastic leukemia cell line, M-MOK, we obtained two monoclonal antibodies which recognize the human c-kit receptor. The monoclonal antibodies, designated MTK1 and MTK2, were found to specifically recognize Balb/3T3 cells transfected with human c-kit cDNA and not parent Balb/3T3 cells while showing different immunological, biochemical and biological behaviors. Both allowed visualization of the 140 kDa c-kit protein by Western blot analysis, but MTK1 detected only positive band with non-reducing conditions for sodium dodecyl sulfate-polyacrylamide gel electrophoresis. MTK1 partially inhibited the stem cell factor (SCF) induced proliferation of M-MOK cells, whereas, MTK2 was without effect. MTK1 also inhibited the bone marrow derived colony forming unit granulocyte/macrophage (CFU-GM) formed by granulocyte-macrophage colony stimulating factor (GM-CSF) and SCF. Not only anti-CD34 antibodies (HPCA-1) but also MTK1 could be shown to concentrate bone marrow CFU-GM and burst forming unit erythroid (BFU-E) effectively. The presently described monoclonal antibodies may therefore be useful for functional analysis of the ligand binding domain of the human c-kit receptor, as well as for further classification of hematopoietic stem cells in addition to the CD34 positive cells.

Corticosteroid Alteration of Carboplatin-Induced Hematopoietic Toxicity in a Murine Model

AbstractCorticosteroids exhibit extensive hematopoietic effects both in vitro and in vivo. Some of the previously studied effects suggested that corticosteroids may alter hematopoietic toxicity of chemotherapeutic agents. In this study, we examined (1) the optimum dose and schedule of cortisone acetate (CA) to reduce hematopoietic toxicity of carboplatin (CB) and (2) possible mechanisms involved in this protective effect. CA given subcutaneously at 0.5 mg/d per mouse for 7 days before CB reduced CB-induced mortality due to neutropenia from 88% in controls to 14% in CA-treated mice (P < .05). Lower CA doses were not effective. Three days of pretreatment (but not 1 day) was as effective as 7 days. CA given after CB had no effect on mortality. Pharmacokinetic studies of CA at 0.5 mg per mouse demonstrated blood levels of Cortisol achievable in patients (peak level, 82 μg/dL). CA treatment markedly reduced spleen cell number and colony-forming units-granulocyte/macrophage (CFU-GM) as well as bone marrow CFU-GM. Bone marrow CFU-GM removed from CA-treated mice demonstrated increased resistance to platinum and increased resistance to high specific activity 3H-thymidine. These findings suggest that treatment of mice with CA induces cellular resistance of hematopoietic precursors to platinum and, thus, reduces CB hematotoxicity. CA or other corticosteroids may be useful in reducing clinical toxicity of CB.

Protection of bone-marrow granulocyte-macrophage colony-forming units in mice bearing in vivo alkylating-agent-resistant EMT-6 tumors.

The survival of bone-marrow granulocyte-macrophage colony-forming units (CFU-GM), an alkylating-agent-sensitive normal tissue, was assessed in mice bearing the EMT-6 parental tumor or the in vivo resistant EMT-6/CDDP, EMT-6/CTX, EMT-6/Thio, and EMT-6/Carbo tumors. The survival pattern of the bone-marrow CFU-GM recapitulated the survival of the tumor cells, mimicking the development of resistance and reversion to sensitivity upon removal of the selection pressure for each of the four alkylating agents. When the EMT-6 parental tumor was implanted in the opposite hind limb of animals bearing the EMT-6/CDDP or EMT-6/CTX tumor, the survival of the parental tumor cells after treatment of the animals with the appropriate antitumor alkylating agent was enhanced. The EMT-6/CDDP tumor was cross-resistant to CTX and high-dose L-PAM, whereas the EMT-6/CTX tumor was somewhat resistant to CDDP and markedly sensitive to VP-16. In each case, the survival pattern of the bone-marrow CFU-GM reflected the survival of the tumor cells. These results indicate that the presence of an alkylating-agent-resistant tumor in an animal can affect the drug response of tissues distal to that tumor.

Factors affecting blood stem cell collections following high-dose cyclophosphamide mobilization in lymphoma, myeloma and solid tumors

Sixty patients with malignancy were enrolled in a study of high dose chemotherapy and peripheral blood stem cell transplantation (PBSCT). The International Journal of Cell Cloning were harvested prior to PBSCT using 75 cycles of high-dose Cyclophosphamide (Cy) mobilization (4 or 7 G/m2) with collection of a median of 4.6 × 108/kg mononuclear cells (MNC) (range 0.2 - 9.5) and 21.6 × 104/kg colony forming unit - granulocyte /macrophage (CFU-GM) (range 0.1 -220). Forty seven patients were mobilized once, 11 required 2 cycles and 2 required 3 cycles. Eight patients (13%) failed to reach the optimim CFU-GM target (total of > 15 × 104 CFU-GM/kg) following Cy mobilization. In a multivariate regression analysis, a number of factors identified those patients who were likely to achieve optimum stem cell collections. These included the use of the higher Cy mobilization dose (P <0.02), a longer interval from last chemotherapy cycle to mobilization(P <0.01) and a higher pre-mobilization bone marrow CFU-GM level (P <0.005). Patient's age, the degree of bone marrow infiltration, the kind of disease or the number of premobillzation chemotherapeutic cycles did not affect the ability to collect adequate stem cell numbers. The mobilization procedure was associated with moderate non-hematologic toxicity and significant hematological morbidity was observed primarily in patients mobilized using the 7 G/m2 dose. Patients mobilized at the higher Cy dose experienced significantly prolonged median days with ANC < 500 (10 vs. 6.6) and platelets < 50,000 (7 vs. 1.4), deeper neutropenic and thrombocytopenic nadirs, more febrile days and bacteremic episodes (P for all < 0.0001). Refinements to the protocol, in particular the use of hematopoietic colony-stimulating growth factors, are currently under investigation.

Combination of etanidazole with cyclophosphamide and platinum complexes

In an effort to improve the therapeutic efficacy and selectivity of cyclophosphamide (CTX), cis-diamminedichloroplatinum(II) (CDDP), and carboplatin (Carbo), these antitumor alkylating agents were combined with the 2-nitroimidazole drug etanidazole (ETA). As revealed by tumor-cell survival assay in the FSaIIC murine fibrosarcoma, the addition of ETA (1 g/kg, i.p.) just prior to the i.p. injection of various doses of the alkylating agents resulted in increases in the tumor-cell kill produced by each drug (CTX, 10-fold; CDDP, 20-fold; and Carbo, 5- to 15-fold), whereas toxicity to bone marrow granulocyte-macrophage colony-forming units (CFU-GM) increased only about 0- to 3-fold. When CTX was combined with either CDDP or Carbo, striking increases in tumor-cell killing were observed (20- to 100-fold across the CDDP dose range and 5- to 20-fold across the dose range of Carbo), which were supra-additive for CDDP and additive for Carbo as revealed by isobologram analysis. The addition of ETA to these alkylating-agent combinations produced a further approx. 20-fold increase in tumor-cell kill for both CTX/CDDP and CTX/Carbo. This effect was greatest at the lowest dose of the platinum drug tested and was supra-additive in the case of CDDP and additive for Carbo. Following treatment with ETA/CTX/CDDP, bone marrow CFU-GM toxicity increased only about 5-fold over that of CTX/CDDP alone, but the injection of ETA/CTX/Carbo resulted in a 10- to 20-fold increase in bone marrow toxicity as compared with that obtained using CTX/Carbo alone. Tumor growth-delay studies revealed significant increases in the antitumor effect of the alkylating agents when these were given in combination with ETA. Both the ETA/CTX/CDDP and the ETA/CTX/Carbo combinations produced tumor growth delays of 23 days, which represented approx. 1.6-fold increases over those obtained using the alkylating-agent combinations alone. These results suggest that ETA could significantly improve the therapeutic efficacy of these alkylating agents, whether they are given individually or in combination.