Human Tumor Cloning Assay Research Articles

Activating adaptive cellular mechanisms of resistance following sublethal cytotoxic chemotherapy: Implications for diagnostic microdosing

As Phase 0 studies have proven to be reasonably predictive of therapeutic dose pharmacokinetics, the application of microdosing has expanded into metabolism, drug-drug interactions and now diagnostics. One potentially serious issue with this application of microdosing that has not been previously discussed is the possibility of activating cellular mechanisms of drug resistance. Here, we provide an overview of Phase 0 microdosing and drug resistance, with an emphasis on cisplatin resistance, followed by a discussion of the potential for inducing acquired resistance to platinum-based or other types of chemotherapy in cancer patients participating in Phase 0 diagnostic microdosing studies. A number of alternative approaches to diagnostic microdosing, such as the human tumor cloning assay and the use of peripheral blood mononuclear cells as a surrogate for measuring DNA adducts, are discussed that would avoid exposing cancer patients to low doses of first-line chemotherapy and the possible risk of triggering cellular mechanisms of acquired resistance. Until it has been established that diagnostic microdosing in cancer patients poses no risk of acquired drug resistance, such studies should be approached with caution.

The gallium complex KP46 exerts strong activity against primary explanted melanoma cells and induces apoptosis in melanoma cell lines

The antineoplastic properties of gallium are well documented. Owing to their robust accumulation of gallium, melanoma cells should be amenable to gallium-based anticancer drugs. With the aim of improving the disappointingly low activity of inorganic gallium salts, we have developed the orally bioavailable gallium complex KP46 [tris(8-quinolinolato)gallium(III)] that had already been successfully studied in a phase I clinical trial. To assess its therapeutic potential in malignant melanoma, its antiproliferative effects were investigated in series of human cell lines and primary explanted melanoma samples by means of the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and the Human Tumor Cloning Assay, respectively. When compared with other cell lines, the majority of melanoma cells rank among the KP46-sensitive cell lines (50% inhibitory concentration values: 0.8-3.7 micromol/l). Clinically achievable concentrations of KP46 proved to be highly effective in melanoma cells from primary explants of cutaneous and lymph node metastases. Colony growth was inhibited in 10 of 10 specimens by 5 micromol/l KP46 (corresponding to the steady-state plasma concentration measured earlier in a study patient) and in four of 10 specimens by 0.5 micromol/l KP46. In-vitro potency of KP46 is higher than that of dacarbazine or fotemustine and comparable with that of cisplatin. The effects induced by KP46 in melanoma cell lines involve cell-cycle perturbations (S-phase arrest) and apoptosis (activation of caspase-9, PARP [poly(ADP-ribose) polymerase] cleavage, formation of apoptotic bodies). No effects on DNA secondary structure could be observed in an electrophoretic mobility shift assay using double-stranded plasmid DNA. Thus, further studies on the therapeutic applicability of KP46 in malignant melanoma are warranted.

Antitumor activity of irofulven against human ovarian cancer cell lines, human tumor colony-forming units, and xenografts.

The objective of this study was to investigate the cytotoxic activity of irofulven (HMAF, MGI 114), a unique chemotherapeutic agent currently under clinical investigation, in various preclinical models of ovarian cancer. Antiproliferative effects of irofulven in ovarian cancer cell lines and ovarian tumor specimens were characterized in vitro using sulforhodamine B and human tumor colony-forming assays, respectively. Irofulven demonstrated marked activity against a panel of ovarian tumor cell lines, including IGROV1, OVCAR-3, OVCAR-4, OVCAR-5, OVCAR-8, and SK-OV-3, all of which exhibit various drug resistance mechanisms. In human tumor cloning assays, irofulven inhibited colony formation in surgically derived ovarian tumors at concentrations as low as 0.001 micro g /ml and indicated superior activity in comparison with paclitaxel when tested against the same tumor specimens. The antitumor activity of irofulven compared to that of paclitaxel was also examined using the SK-OV-3 xenograft model. In mice bearing subcutaneously implanted SK-OV-3 tumors, treatment with paclitaxel failed to inhibit tumor growth; whereas mice treated with maximum tolerated doses of irofulven had a 25% partial shrinkage rate, and the remaining animals had a mean tumor growth inhibition of 82%. The potent activity of irofulven against ovarian tumors in vitro and in vivo supports the evaluation of its clinical activity in ovarian cancer.

Antitumor activity of irofulven against human ovarian cancer cell lines, human tumor colony-forming units, and xenografts

The objective of this study was to investigate the cytotoxic activity of irofulven (HMAF, MGI 114), a unique chemotherapeutic agent currently under clinical investigation, in various preclinical models of ovarian cancer. Antiproliferative effects of irofulven in ovarian cancer cell lines and ovarian tumor specimens were characterizedin vitrousing sulforhodamine B and human tumor colony-forming assays, respectively. Irofulven demonstrated marked activity against a panel of ovarian tumor cell lines, including IGROV1, OVCAR-3, OVCAR-4, OVCAR-5, OVCAR-8, and SK-OV-3, all of which exhibit various drug resistance mechanisms. In human tumor cloning assays, irofulven inhibited colony formation in surgically derived ovarian tumors at concentrations as low as 0.001 μg /ml and indicated superior activity in comparison with paclitaxel when tested against the same tumor specimens. The antitumor activity of irofulven compared to that of paclitaxel was also examined using the SK-OV-3 xenograft model. In mice bearing subcutaneously implanted SK-OV-3 tumors, treatment with paclitaxel failed to inhibit tumor growth; whereas mice treated with maximum tolerated doses of irofulven had a 25% partial shrinkage rate, and the remaining animals had a mean tumor growth inhibition of 82%. The potent activity of irofulven against ovarian tumorsin vitroandin vivosupports the evaluation of its clinical activity in ovarian cancer.

Activity of the multitargeted antifolate LY231514 in the human tumor cloning assay.

This study was performed to evaluate the activity of the multitargeted antifolate (MTA or LY231514) against a broad range of human tumors taken directly from patients. Human tumor colony-forming units were treated with MTA at concentrations of 0.1, 1.0, and 10 microg/ml in 1-h exposure studies. The responses of a limited number of specimens were also evaluated concurrently in 1-h exposures to cisplatin, fluorouracil, irinotecan, and/or paclitaxel. Of 358 specimens plated in the 1-h exposure studies, 148 (41%) were evaluable. Overall, responses were observed in 3% of specimens (4/144) at 0.1 microg/ml, 11% (17/148) at 1.0 microg/ml, and 23% (33/141) at 10 microg/ml. In this range of concentrations achievable clinically, there was a significant concentration-response relationship. At 10 microg/ml in the 1-h exposure studies, the response rate in colorectal cancer specimens was 32% (9/28), and the response rate in non-small-cell lung cancer was 25% (6/24). Responses were also observed in several chemoresistant tumors, including renal cell carcinoma, hepatocellular carcinoma, mesothelioma, and pancreatic carcinoma. The activity of MTA was not completely cross-resistant with that of cisplatin, fluorouracil, irinotecan, and paclitaxel. MTA demonstrated in vitro activity against a spectrum of tumors, including several tumors generally considered chemoresistant.

Activity of SCH 66336, a tricyclic farnesyltransferase inhibitor, against human tumor colony-forming units

The ras gene product regulates transduction of growth-proliferative signals from the membrane to the nucleus. Mutationally-activated Ras is the oncogene most frequently found in human tumors. In order to perform its function in cell signaling, Ras must be farnesylated on the CAAX motif present on the carboxyl terminus of the ras protein. This reaction is catalysed by farnesyl protein transferase. In the present study, SCH 66336, an orally bioavailable nonpeptide tricyclic farnesyltransferase inhibitor, was tested against a large variety of human tumors to define its preclinical activity profile, utilizing the human tumor cloning assay. A soft agar cloning assay was used to determine the in vitro effects of SCH 66336 against primary human tumor specimens taken directly from patients. A total of 70 evaluable specimens were exposed to SCH 66336 for 14-day continuous exposure at concentrations ranging from 0.1 to 2.5 microM. In vitro responses were defined as an inhibition > or = 50% of human tumor colony forming units at a given concentration. There was a positive relationship between concentration and response to SCH 66336. With the highest concentration (2.5 microM), response was demonstrated in 50% (three of six) of breast tumors, 40% (6 of 15) of ovarian tumors, and 38% (5 of 13) of non-small-cell lung tumor colony forming units. Among the 69 specimens tested at the concentration of 2.5 microM, SCH 66336 had activity in 27% of tumor specimens that were resistant to doxorubicin, 38% of tumor specimens resistant to cisplatin, 33% of tumor specimens resistant to paclitaxel, and 27% of tumor specimens resistant to etoposide. The broad spectrum of soft agar growth inhibition by SCH 66336 in the human tumor cloning assay, and its efficacy at physiologically relevant concentrations in animal models, suggest that SCH 66336 may deserve future clinical trials in patients with ovarian, breast and non-small-cell lung cancer.

Significant activity of a novel cytotoxic agent, LY295501, against a wide range of tumors in the human tumor cloning system

The diarylsulfonylureas (DSUs) are a novel class of cytotoxic agents with high potential for activity. LY295501 is one of the most active DSUs. In this study, we evaluated the cytotoxicity of LY295501 utilizing the human tumor cloning assay. LY295501 was tested at 10, 50 and 100 microg/ml using either 1 h or continuous exposure schedules. The majority of common solid tumors were evaluated including breast, colorectal, non-small cell lung and ovarian carcinomas. LY295501 demonstrated significant activity against all tumor types tested. Antitumor activity was noted after either 1 h or continuous exposure schedules at all concentrations tested. A concentration-response relationship was noted, with increasing concentrations of LY295501 leading to more cytotoxicity. Cytotoxicity, on the continuous exposure schedule, was noted in 38% of tumors exposed to LY295501 at 10 microg/ml, 58% of tumors exposed at 50 microg/ml (p=0.002 for 10 versus 50 microg/ml) and 72% of tumors exposed at 100 microg/ml (p=0.008 for 50 versus 100 microg/ml). In addition, more cytotoxicity was observed on the continuous exposure schedule compared to the 1 h schedule at all concentrations tested (p<0.01). The substantial activity of LY295501 in the human tumor cloning assay coupled with its clinical activity in phase I studies supports further clinical development of this agent.

Activity of pivaloyloxymethyl butyrate, a novel anticancer agent, on primary human tumor colony-forming units.

The anti-proliferative effects of pivaloyloxymethyl butyrate (AN-9), a butyric acid (BA) derivative with potent tumor-differentiating properties both in vitro and in vivo, was evaluated against colorectal, breast, lung, ovarian, renal cell, bladder, and other types of tumor colony-forming units in a human tumor cloning assay. A total of 76 evaluable specimens were exposed to AN-9 continuously, 48 of these were also exposed to BA continuously for direct comparison of the two agents, and 20 specimens were exposed to AN-9 for two hours. An in vitro inhibitory response was defined as a > or = 50% decrease in tumor colony formation in treated cells compared to untreated controls. Superior anti-tumor activity was observed with the continuous exposure to AN-9 (39% in vitro response at 100 microM and 70% at 200 microM) than with the two-hour exposure (20% at 100 microM and 25% at 200 microM). At a continuous concentration of 200 microM, AN-9 demonstrated greater tumor-specific activity than BA against melanoma (100% vs. 67%), ovarian (67% vs. 40%), breast (63% vs. 0%), non-small cell lung (60% vs. 10%), and colorectal tumor colony-forming units (62% vs. 20%). AN-9 is a novel differentiating agent with activity against colony-forming units derived from a variety of primary human tumors, including those that are considered relatively chemoresistant, and may thus provide a therapeutic alternative or addition to standard cytotoxic agents, if appropriate drug concentrations can be achieved in patients.

The efficiency of tumor cell purging using immunomagnetic CD34+ cell separation systems.

Immunomagnetic separation with anti-CD34 monoclonal antibodies and paramagnetic microbeads has been used to enrich hematopoietic stem cells from human bone marrow (BM) or mobilized peripheral blood mononuclear cells (PBMNC). The introduction of this technique also constitutes a new principle of tumor cell purging. The efficiency in terms of purging tumor cells from PBMNC was evaluated in seven different experiments. Mobilized (chemotherapy and G-CSF) PBMNC were collected from patients with solid tumors (n = 6) and multiple myeloma (n = 1) by leukapheresis using an automated MNC separation system and contaminated with 1% (n = 5) or 10% (n = 2) tumor cells from different epithelial cell lines being CD34-negative. The cell mixture was sensitized with anti-CD34 (9C5) antibodies and sheep anti-mouse IgG1 paramagnetic microspheres and enriched for CD34+ cells using an Isolex 50 magnetic separator. Purify of CD34+ cells was studied by flow cytometry (FACScan) and tumor cell depletion was evaluated by comparative human tumor cloning assays (HTCA) containing methylcellulose and agar. We achieved a median purity of CD34+ cells of 85.9% (range 69.8-92.9%) and a median yield of 48.1% (range 21.0-85.2%). From these data in each case the estimated log depletion of tumor cells was calculated and compared with the experimentally achieved (HTCA) log depletion (log delta depletion = log experimental depletion--log calculated depletion). In our experiments we achieved a median depletion of 2.75 log (range 1.55-3.69 log). When corrected for CD34+ cell yield of each experiment we observed a median 'yield corrected depletion' of 2.38 log (range 1.48-3.15 log). The following delta depletion values were obtained: +0.32 log (HTB 129, breast), +0.21 log (HTB 26, breast), +0.04 log (HTB 26) for experiments with higher experimental depletion, and -0.23 log (HTB 26), -0.9 log (HTB 26, PBMNC from patient with multiple myeloma), -0.82 log (HTB 131, breast) and -1.66 log (HTB 131) for lower depletion efficacy than calculated. These data suggest that depletion may depend on specific cell surface characteristics of tumor cells. Moreover, plasma factors (eg paraprotein) may also have some impact. In summary, the Isolex 50 provides a high purity of CD34+ cells and depletion of tumor cells was efficient. However, calculated and experimental purging efficiencies are not necessarily identical.

Activity of gemcitabine in a human tumor cloning assay as a basis for clinical trials with gemcitabine

2',2'-difluorodeoxycytidine (LY 188011, Gemcitabine, Gemzar) has recently been approved both in Europe for the treatment of patients with non-small cell lung cancer and in the United States for patients with pancreatic cancer. Since the initial discovery of the compound, we have been evaluating the in vitro activity of gemcitabine against human tumor colony-forming units taken directly from patients and growing in soft agar (in the human tumor cloning assay-HTCA). A total of 315 specimens have had gemcitabine tested against them with 44% giving evaluable results. Gemcitabine has been found to be active against colony-forming units from patients with non-small cell lung, breast, ovarian, and pancreatic cancers. A concentration-dependent in vitro response was noted with a higher in vitro response rate noted at 20 micrograms/ml than at 2.0 micrograms/ml. Based on subsequent clinical phase II data, the HTCA correctly predicted the wide spectrum of the clinical activity of gemcitabine.

Automated imaging and quantitation of tumor cells and CFU-GM colonies in microcapillary cultures: toward therapeutic index-based drug screening.

Human colony forming units (CFUs) from both malignant and hematopoietic tissues can be assayed in vitro in microcapillary cultures, an alternative cloning system to the Petri dish methodology. For technical reasons, microcapillary culture may be ideally suited for new drug screening by therapeutic index. To achieve the high output required by screening programs, automated quantitation of CFUs is required. Toward this end, this paper reports the development of a prototype CapScan, an image analysis system that uses a novel axial laser illumination system to detect tumor cell colonies and, with technical modifications, CFU-granulocyte-macrophage (CFU-GM) colonies in microcapillary cultures. As currently configured, the CapScan can quantify colonies grown in a rack of 18 microcapillary cultures in 30 minutes or less. The sensitivity and detection specificity of tumor cell colonies is >90% with a coefficient of variance of 5-40%, dependent upon colony number. Over a range of colony numbers, CapScan and manual colony counts showed a linear correlation > -0.9, and yielded identical results in assays of doxorubicin inhibition of clonogenic P388 cells. As an additional advantage, the growth kinetics of individual colonies can also be monitored with the CapScan, making distinctions between cytotoxic and cytostatic drugs possible; colonies of freshly isolated human tumor cells can also be quantified. Thus, a microcapillary-based human tumor cloning assay that tests for resistance and/or sensitivity to chemotherapeutic agents may be useful in drug development programs and may also facilitate the development of chemotherapy for individual patient tumors, especially when tumor availability is limited.

Effects of the hematopoietic growth factors GM-CSF, IL-3, and IL-6 on human tumor colony-forming units taken directly from patients

One concern regarding the use of hematopoietic growth factors (e.g., GM-CSF, IL-3, and IL-6) to accelerate hematologic recovery after treatment of solid tumors with high doses of chemotherapy is that these factors may stimulate tumor growth. We tested the effects of GM-CSF, IL-3 or IL-6 (continuous exposure to 1, 10, and 100 ng/ml of each cytokine) on tumor cells taken directly from patients with solid tumors using the human tumor cloning assay. The range of concentrations of the cytokines used in our study included the concentrations that appear to be clinically relevant. Of the evaluable samples, stimulation of tumor growth was noted in 0/16 exposed to GM-CSF, in 3/72 (4%) exposed to IL-3, and in 1/65 (2%) exposed to IL-6. Inhibition of tumor proliferation was noted in no sample exposed to GM-CSF, in 7 (10%) exposed to IL-3 and in 7 (10%) exposed to IL-6. The use of GM-CSF, IL-3 or IL-6 to reduce myelosuppression after high dose chemotherapy appears unlikely to result in stimulation of the growth of the most common solid tumors. It is also unlikely that either IL-3 and IL-6 alone will be useful as antitumor agents against solid tumors.

Antiproliferative effect of human interleukin-4 in human cancer cell lines: studies on the mechanism.

Interleukin-4 (IL-4) plays an important role in activating the immune system against malignant cells. The human interleukin-4 receptor (hIL-4R) is not only expressed by hematopoietic cells but also on a large number of tissue specimens which include colon, breast and lung carcinomas. In this study we report that rhIL-4 has an antiproliferative effect on 2 out of 3 non-small cell lung carcinoma (NSCLC) cell lines in vitro as measured by human tumor cloning assays (HTCA). In comparison, rhIL-4 had no effect on the growth of small cell lung carcinoma cell lines (SCLC) in vitro. The response towards the cytokine is correlated with expression of at least 1500 high affinity receptors/cell for hIL-4 on the responsive cell lines. Xenotransplanting the human lung tumor cell lines into nude mice followed by 12 days of systemic treatment of the mice with rhIL-4 revealed a significant growth retardation of the IL-4R positive NSCLC cell lines when compared with the controls, whereas the growth of the IL-4R negative SCLC cell lines was unaffected also in vivo. Studies of possible mechanisms involved in the antiproliferative effect of rhIL-4 showed that rhIL-4 does not induce apoptosis or modulation of the transcription factor c myc in the responsive NSCLC cell lines. Additionally, the expression of the epidermal growth factor receptor (EGFR), which is discussed as mediating autocrine/paracrine growth stimulation of NSCLC, is unaffected by rhIL-4. However, we have observed that rhIL-4 inhibited G1-S-phase cell cycle progression. We conclude that rhIL-4 has an antiproliferative effect on the growth of some NSCLC in vitro and in vivo. The mechanisms involved remain to be further elucidated.

INTERLEUKIN-1 RECEPTOR ANTAGONIST INHIBITS GROWTH MODULATION OF HUMAN TUMOR-CELL LINES BY INTERLEUKIN-1 IN-VITRO

In this study we report that recombinant human (rh) interleukin-1alpha (IL-1alpha) has direct and dose-dependent growth-modulating effects on human tumor cell lines in vitro as measured by a human tumor cloning assay (HTCA). Colony formation of the melanoma cell line A 375 was inhibited by rhIL-1alpha, whereas colony formation of the glioblastoma cell line HTB 14 was enhanced by this cytokine. Both growth-modulating effects were dose-dependent, however with some saturation. Subsequently, we have tested the activity of recombinant human IL-1 receptor antagonist (rhIL-1ra) on the tumor growth modulation by rhIL-1alpha. Tumor cells were incubated with increasing concentrations of rhIL-1ra and then added to the cultures containing rHIL-1alpha. Concentrations of rhIL-1ra were chosen to achieve a range between 0.01 and 100 ng/ml which includes a 1000-fold molar excess over IL-1alpha. The receptor antagonist was able to block both the inhibition and the stimulation of clonal growth of the respective tumor cell line by rhIL-1alpha. Furthermore, there was a direct dose dependent relationship revealing higher IL-1 antagonism of rhIL-1ra at higher concentrations with maximum efficacy at 1000-molar excess concentrations over IL-1alpha. In addition, rhIL-1ra alone did not reveal major modulation of the growth of A 375, but significantly decreased colony formation of HTB 14. We conclude that rhIL-1ra can counteract modulation of clonal growth of human tumor cells by IL-1alpha in vitro. Since our report provides first evidence that the stimulation of clonal tumor cell growth by IL-1alpha can be blocked by rhIL-1ra, this member of the IL-1 cytokine network should be further studied as a possible candidate for experimental cancer treatment.

Sensitivity of multiple myeloma to imexon in the human tumor cloning assay.

Sensitivity of multiple myeloma to imexon in the human tumor cloning assay.

MACROPHAGE INFLAMMATORY PROTEIN (MIP)-1-ALPHA STEM-CELL INHIBITOR (SCI) DOES NOT AFFECT CLONAL GROWTH OF HUMAN SOLID TUMOR-CELL LINES IN-VITRO

MIP-1alpha is a member of a family of proinflammatory cytokines produced by activated macrophages which has been shown to be a negative regulator of early hematopoietic stem cell progenitors. We report on results testing recombinant human (rh) MIP-1alpha on the clonal growth of different human nonhematopoietic tumor cell lines in vitro. Cell lines tested included the following histologies: 7 glioblastomas, 1 neuroblastoma, 2 head and neck carcinomas, 4 lung carcinomas, 3 colorectal carcinomas, 1 gastric carcinoma, 1 pancreatic carcinoma, 1 breast carcinoma, 1 prostate carcinoma, 1 choriocarcinoma, 1 ovary carcinoma, 1 osteosarcoma, and 3 melanomas. MIP-1alpha (0, 2, 20, 200 ng/ml) was tested in human tumor cloning assays (HTCA) in agar-containing capillaries (HTCAcap) and in mixtures of methylcellulose and agar (HTCAmix), representing assay systems with different plating efficiencies (PE). Tumor cells were continuously exposed to the cytokine for the complete assay period. Clonal growth of none of the cell lines was significantly and reproducibly stimulated or inhibited by MIP-1alpha.

Recombinant Human Interleukin-4 Inhibits Growth of Some Human Lung Tumor Cell Lines In Vitro and In Vivo

AbstractCytokines play an important role in activating the immune system against malignant cells. One of these cytokines, interleukin-4 (IL-4) has entered clinical phase I trials because of its immunoregulatory potency. In the present study we report that recombinant human (rh) IL-4 has major direct antiproliferative effects on one human lung cancer cell line (CCL 185) in vitro as measured by a human tumor cloning assay (HTCA), tritiated thymidine uptake, and counting cell numbers and marginal activity in a second cell line (HTB 56) in the HTCA. This activity could be abolished by neutralizing antibody against rhlL-4. The biological response of the tumor cells to the cytokine is correlated with expression of receptors for human IL-4 on both the mRNA level and the protein level. The responsive cell line, CCL 185, secretes IL-6 after being incubated with rhlL-4. On the other hand, neutralizing antibodies against IL-6 showed no influence on the growth modulatory efficacy of rhlL-4 in this cell line. Furthermore, CCL 185 does not show detectable production of IL-1, tumor necrosis factor alpha or interferon gamma after incubation with rhlL-4. Thus, the response to rhlL-4 is not mediated through autocrine production of these cytokines triggered by rhlL-4. In a next series of experiments some of the cell lines were xenotransplanted to BALB/c nu/nu mice. Subsequently, the mice were treated for 12 days with two doses of 0.5 mg/m2 rhlL-4 or control vehicle subcutane-ously per day. Treatment with rhlL-4 yielded a significant inhibition of tumor growth versus control in two of the non-small cell lung cancer cell lines being responsive in vitro (CCL 185, HTB 56). Histology of the tumors in both groups showed no marked infiltration of the tumors with murine hematopoietic and lymphocytic cells consistent with the species specificity of IL-4. In contrast, no tumor growth inhibition was found in the small cell lung cancer cell lines (HTB 119, HTB 120) being nonresponsive in vitro. We conclude that rhlL-4 has direct antiproliferative effects on the growth of some human non-small cell lung cancer cell lines in vitro and in vivo, which together with its regulatory effects on various effector cell populations makes this cytokine an interesting candidate for further investigation in experimental cancer treatment.

Recombinant human interleukin-4 inhibits growth of some human lung tumor cell lines in vitro and in vivo

Cytokines play an important role in activating the immune system against malignant cells. One of these cytokines, interleukin-4 (IL-4) has entered clinical phase I trials because of its immunoregulatory potency. In the present study we report that recombinant human (rh) IL- 4 has major direct antiproliferative effects on one human lung cancer cell line (CCL 185) in vitro as measured by a human tumor cloning assay (HTCA), tritiated thymidine uptake, and counting cell numbers and marginal activity in a second cell line (HTB 56) in the HTCA. This activity could be abolished by neutralizing antibody against rhIL-4. The biological response of the tumor cells to the cytokine is correlated with expression of receptors for human IL-4 on both the mRNA level and the protein level. The responsive cell line, CCL 185, secretes IL-6 after being incubated with rhIL-4. On the other hand, neutralizing antibodies against IL-6 showed no influence on the growth modulatory efficacy of rhIL-4 in this cell line. Furthermore, CCL 185 does not show detectable production of IL-1, tumor necrosis factor alpha or interferon gamma after incubation with rhIL-4. Thus, the response to rhIL-4 is not mediated through autocrine production of these cytokines triggered by rhIL-4. In a next series of experiments some of the cell lines were xenotransplanted to BALB/c nu/nu mice. Subsequently, the mice were treated for 12 days with two doses of 0.5 mg/m2 rhIL-4 or control vehicle subcutaneously per day. Treatment with rhIL-4 yielded a significant inhibition of tumor growth versus control in two of the non-small cell lung cancer cell lines being responsive in vitro (CCL 185, HTB 56). Histology of the tumors in both groups showed no marked infiltration of the tumors with murine hematopoietic and lymphocytic cells consistent with the species specificity of IL-4. In contrast, no tumor growth inhibition was found in the small cell lung cancer cell lines (HTB 119, HTB 120) being nonresponsive in vitro. We conclude that rhIL-4 has direct antiproliferative effects on the growth of some human non-small cell lung cancer cell lines in vitro and in vivo, which together with its regulatory effects on various effector cell populations makes this cytokine an interesting candidate for further investigation in experimental cancer treatment.

INTERLEUKIN-4 INHIBITS GROWTH OF A HUMAN LUNG-TUMOR CELL-LINE IN-VITRO AND HAS THERAPEUTIC ACTIVITY AGAINST XENOGRAFTS OF THIS CELL-LINE IN-VIVO

In the present study we report that recombinant human (rh) interleukin 4 (IL-4) has direct, dose-dependent antiproliferative effects on the human lung cancer cell line CCL 185 in vitro as measured by a human tumor cloning assay (HTCA). The biological response of the tumor cells to rhIL-4 is correlated with expression of specific binding sites for human (h) IL-4 on the cell surface. Furthermore, we have xenotransplanted CCL 185 into BALB/c nu/nu mice. Subsequently, the mice were treated for 17 days with twice 0.5 mg/m2 rhIL-4 or control vehicle subcutaneously per day. Treatment with rhIL-4 yielded a significant inhibition of tumor growth versus control. Histology of the tumors in both groups showed no marked infiltration of the tumors with murine hematopoietic and lymphocytic cells consistent with the species specificity of IL-4. We conclude that rhIL-4 has direct antiproliferative effects on the growth of a human lung tumor cell line in vitro and in vivo which together with its regulatory effects on various effector cell populations makes this cytokine a possible candidate for experimental cancer treatment.

In vitro evaluation of the antineoplastic activity of combretastatin A-4, a natural product from Combretum caffrum (arid shrub)

Combretastatin A-4 is a natural product which was isolated from the South African tree Combretum caffrum. In this study, the cytotoxic activity of combretastatin A-4 was tested in radiometric and human tumor cloning assays against eight different tumor cell lines and against 15 patient tumors in the human tumor cloning assay. To test the preferential cytotoxicity of combretastatin A-4 against tumor cells versus non-tumor cells, it was also tested in the radiometric assay against both normal human diploid fibroblasts and human bone marrow cells. Of the eight cell lines used, combretastatin A-4 showed preferential cytotoxicity for six of them. In addition, combretastatin A-4 showed a concentration-dependent cytotoxicity against a variety of human tumors. Based on the data generated in this study, combretastatin A-4 should be further tested in in vivo preclinical models.