Spotlight on Volasertib: Preclinical and Clinical Evaluation of a Promising Plk1 Inhibitor

Considering the important side effects of conventional microtubule targeting agents, more and more research focuses on regulatory proteins for the development of mitosis-specific agents. Polo-like kinase 1 (Plk1), a master regulator of several cell cycle events, has arisen as an intriguing target in this research field. The observed overexpression of Plk1 in a broad range of human malignancies has given rise to the development of several potent and specific small molecule inhibitors targeting the kinase. In this review, we focus on volasertib (BI6727), the lead agent in category of Plk1 inhibitors at the moment. Numerous preclinical experiments have demonstrated that BI6727 is highly active across a variety of carcinoma cell lines, and the inhibitor has been reported to induce tumor regression in several xenograft models. Moreover, volasertib has shown clinical efficacy in multiple tumor types. As a result, Food and Drug Administration (FDA) has recently awarded volasertib the Breakthrough Therapy status after significant benefit was observed in acute myeloid leukemia (AML) patients treated with the Plk1 inhibitor. Here, we discuss both preclinical and clinical data available for volasertib administered as monotherapy or in combination with other anticancer therapies in a broad range of tumor types.

Preclinical and clinical studies on afatinib in monotherapy and in combination regimens: Potential impact in colorectal cancer

Targeting the epidermal growth factor receptor (EGFR) with monoclonal antibodies (mAbs) or tyrosine kinase inhibitors (TKI) has been an interesting therapeutic strategy because aberrant activation of this receptor plays an important role in the tumorgenesis of many cancer types, including colorectal cancer (CRC). After the initial promising results of EGFR-targeted therapies, therapeutic resistance is a major clinical problem. In order to overcome resistance to these EGFR-targeted therapies, new treatment options are necessary. In contrast to first generation EGFR inhibitors, afatinib (BIBW2992) is a second-generation irreversible ErbB family blocker that inhibits EGFR as well as HER2 and HER4. Consequently, treatment with afatinib may result in a distinct and more pronounced therapeutic benefit. Preclinical studies have reported promising results for afatinib in monotherapy as well as in combination with other drugs in CRC model systems. Furthermore, clinical studies examining afatinib as single agent and in combination therapy demonstrated manageable safety profile. Nevertheless, only limited antitumor activity has been observed in CRC patients. Although several combination treatments with afatinib have already been investigated, no optimal combination has been identified for CRC patients yet. As molecular tumor characteristics have gained increased importance in the choice of treatment, additional studies with biomarker-driven patient recruitment are required to further explore afatinib efficacy in CRC.

Circulating cell-free nucleic acids and platelets as a liquid biopsy in the provision of personalized therapy for lung cancer patients

Lung cancer is the predominant cause of cancer-related mortality in the world. The majority of patients present with locally advanced or metastatic non-small-cell lung cancer (NSCLC). Treatment for NSCLC is evolving from the use of cytotoxic chemotherapy to personalized treatment based on molecular alterations. Unfortunately, the quality of the available tumor biopsy and/or cytology material is not always adequate to perform the necessary molecular testing, which has prompted the search for alternatives. This review examines the use of circulating cell-free nucleic acids (cfNA), consisting of both circulating cell-free (tumoral) DNA (cfDNA-ctDNA) and RNA (cfRNA), as a liquid biopsy in lung cancer. The development of sensitive and accurate techniques such as Next-Generation Sequencing (NGS); Beads, Emulsion, Amplification, and Magnetics (BEAMing); and Digital PCR (dPCR), have made it possible to detect the specific genetic alterations (e.g. EGFR mutations, MET amplifications, and ALK and ROS1 translocations) for which targeted therapies are already available. Moreover, the ability to detect and quantify these tumor mutations has enabled the follow-up of tumor dynamics in real time. Liquid biopsy offers opportunities to detect resistance mechanisms, such as the EGFR T790M mutation in the case of EGFR TKI use, at an early stage. Several studies have already established the predictive and prognostic value of measuring ctNA concentration in the blood. To conclude, using ctNA analysis as a liquid biopsy has many advantages and allows for a variety of clinical and investigational applications.

Abstract P5-09-04: The effect of nuclear factor kappa B activation on cell proliferation of estrogen receptor positive breast cancer cell lines with different HER2-status

Introduction:Endocrine treatment is the mainstay of therapy for patients with Estrogen Receptor positive (ER+) breast cancer.Unfortunately, primary and secondary resistance to endocrine therapy are a major clinical problem. Previous studies have suggested a possible role for NFkB transcription factor family members in this resistance due to their effect on ER signaling. In this study, we aim to elucidate the interaction between both transcription factor families (ER and NFkB) and the consequence thereof on the growth pattern of ER+ cell lines.

Materials and methods:For this study, 2 ER+ breast cancer cell lines (i.e. MCF7 and MDA-MB-361) were selected based on a documented attenuated NFkB activity in these cell lines and a different ErbB2 status.Prior to treatment with estrogen (E2), TNFα (NFkB activation) and/or parthenolide (NFkB inhibition), cells were seeded in 48 well plates. Proliferation was measured by means of a crystal violet assay. ELISA experiments to measure NFkB DNA-binding in nuclear protein extracts and qRT-PCR for NFkB target genes was performed.

Results:Treatment of MCF7cells with different concentrations of TNFα initially increased cell proliferation, but after 48hrs, apoptosis occurred. Evaluation of NFkB DNA-binding showed a clear increase in RelA (p65), RelB (p62) and NFkB1 (p50) DNA-binding after 4hrs and up until but no longer than 24hrs of treatment. Results were confirmed by qRT-PCR for NFkB target genes.Due to the dynamics of NFkB activation secondary to TNFα treatment, we limited further experiments to 24hrs of treatment. Combination of E2and TNFα gave an additive effect in MCF7 cell proliferation compared to E2 alone, an effect counteracted by parthenolide in a concentration dependent manner. In the ErbB2+ cell line MDA-MB-361 our initial results suggest that addition of TNFα does not affect E2-driven cell proliferation.

Conclusion: Our results so far suggest a different, ErbB2-dependent role for NFkB on the proliferation of ER+ breast cancer cells. Interestingly, the effect of NFkB seems to depend on both RelA- and RelB-dependent pathways. Experiments are currently being performed to elaborate on the present results.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-09-04.

KRAS mutation detection and prognostic potential in sporadic colorectal cancer using high-resolution melting analysis

BACKGROUND

The development of targeted therapies has created a pressing clinical need for molecular characterisation of cancers. In this retrospective study, high-resolution melting analysis (HRMA) was validated and implemented for screening of 164 colorectal cancer (CRC) patients to detect KRAS hot-spot mutations and to evaluate its prognostic value. Direct sequencing was used to confirm and characterise HRMA results.

METHODS

After establishing its sensitivity, HRMA was validated on seven cell lines and inter- and intra-variation were analysed. The prognostic value of KRAS mutations in CRC was evaluated using survival analysis.

RESULTS

HRMA revealed abnormal melting patterns in 34.1% CRC samples. Kaplan-Meier survival curves revealed a significantly shorter overall (OS) and disease-free survival (DFS) for CRC patients harbouring a KRAS mutation. In the Cox regression analysis, only when colon and rectal cancer were analysed separately, KRAS mutation was a negative predictor for OS in patients with rectal cancer and DFS in those with stage II colon cancer.

CONCLUSIONS

HRMA was found to be a valid screening method for KRAS mutation detection. The KRAS mutation came forward as a negative predictive factor for OS in patients with rectal cancer and for DFS in stage II colon cancer patients.

In vitro interaction between ecteinascidin 743 (ET-743) and radiation, in relation to its cell cycle effects

Ecteinascidin 743 (ET-743) is a new marine-derived agent with promising activity against a number of solid tumours. In four human tumour cell lines, the interaction between ET-743 and radiation was investigated in relation to the effects of ET-743 on the cell cycle, in vitro. Cell survival was measured based on quantitative staining of cellular protein by sulforhodamine B. A 24 h treatment with ET-743 before radiation resulted in a moderate increase in radiosensitivity in three out of four cell lines. Dose enhancement factors > or =1.8 were observed for concentrations resulting in 52, 46 and 30% cell kill in ECV304, H292 and CAL-27, respectively, whereas in A549 no radiosensitisation was observed (no significant increase in radiosensitivity). According to the combination index analysis, synergism was observed only in ECV304 and CAL-27 cells. A 24 h incubation with ET-743 resulted in a concentration-dependent G2/M block, which might explain the moderate radiosensitising effects in ECV304 and H292. The lack of radiosensitisation in A549 might be due to the S phase delay preceding the G2/M block at the moment of radiation, which only occurred in this cell line. In conclusion, ET-743 has moderate cell line-dependent radiosensitising properties; however, only when cytotoxic concentrations of ET-743 are used. In one of the four cell lines tested, no radiosensitisation was observed.

The radiosensitising effect of gemcitabine and the influence of the rescue agent amifostine in vitro

In this study, the radiosensitising effect of different concentrations of gemcitabine and the combination of gemcitabine/radiotherapy with the rescue agent amifostine was investigated in different human tumour cell lines. The cells were treated with gemcitabine (0-8 nM) for 24 h prior to radiation (0-8 Gy). Amifostine (ami) and alkaline phosphatase (AP) were added 30 min before radiation. Cell survival was determined 7 or 8 days after radiation treatment by the sulforhodamine B (SRB) test. For ECV304 cells, the dose enhancement factor (DEF) varied from 1.39 to 2.98 after treatment with 1-6 nM gemcitabine. FaDu, H292, A549 and CAL-27 seemed to be less sensitive, with DEFs ranging from 1.02 to 2.67. These cells were also less sensitive to the cytotoxic effects of single-agent gemcitabine. Amifostine with AP clearly showed a protective effect in combination with gemcitabine/radiotherapy. In H292 cells, the protection factor (PF) of amifostine after treatment with gemcitabine and radiotherapy varied from 1.64 to 1.86. In ECV304 cells, the PF varied from 2.20 to 2.29. In conclusion, a clear concentration- and cell line-dependent radiosensitising effect of gemcitabine was observed in all cell lines. Amifostine with AP showed protection against the radiosensitising effect of gemcitabine. If the protection in vivo indeed occurs selectively in normal tissues, then amifostine could prevent or strongly minimise the increased toxicity resulting from the radiosensitising effect of the combination of gemcitabine and radiotherapy, without influencing the antitumour effect.

mRNA-electroporated mature dendritic cells retain transgene expression, phenotypical properties and stimulatory capacity after cryopreservation

Genetically modified dendritic cells (DC) are increasingly used in vitro to activate cytotoxic T lymphocyte (CTL) immune responses. Because T cell activation protocols consist of multiple restimulation cycles of peripheral blood lymphocytes with antigen-loaded mature DC, continuous generation of DC is needed throughout the experiment. Therefore, cryopreservation of DC loaded with antigen is a valuable alternative for weekly generation and modification of DC. Recently, we described an antigen loading method for DC based on electroporation of defined tumor antigen mRNA. In this study, we demonstrate that mRNA-electroporated DC can efficiently be prepared for cryopreservation. Using an optimized maturation and freezing protocol after mRNA electroporation, we obtained high transgene-expressing viable mature DC. In addition, we showed that these modified cryopreserved DC retain stimulatory capacity in an influenza model system. Therefore, cryopreservation of mature mRNA-electroporated DC is a useful method for continuous availability of antigen-loaded DC throughout T cell activation experiments.

Prevalence of human papillomavirus in elderly women with cervical cancer

To investigate the relation between the prevalence of human papillomavirus (HPV) and age in cervical cancer patients, material from 93 patients with Ia-IIb cervical carcinoma was analyzed for the presence of HPV by both type-specific and general primer polymerase chain reaction. Patients were divided into 2 groups: 64 years or younger, and 65 years and older. There was no statistically significant difference in either the prevalence of HPV DNA or distribution of genotypes amongst the 2 groups. Therefore, HPV detection can be equally well used in the management and follow-up of elderly cervical cancer patients.

Human papillomavirus infection in the female population of Antwerp, Belgium: prevalence in healthy women, women with premalignant lesions and cervical cancer

Worldwide there is a strong relation between the presence of human papillomavirus (HPV) and the development of cervical cancer. This study investigated the prevalence and genotype of HPV in women with normal smears, women with premalignant lesions and women with cervical cancer in Antwerp, Belgium. Type-specific polymerase chain reaction (PCR) for HPV types 16 and 18 and general primer PCR (GP5+/6+) was performed on DNA extracted from paraffin-embedded tissue from women with lesions or fresh material from controls. HPV was detected in 11% of controls, 61% of women with atypia, 77% of women with CIN lesions and 88% of women with cervical carcinoma (chi2 trend, 273, p<0.001). The odds ratio for high-risk HPV types was 9.3 for atypia (95%CI. 4.3-19.8), 33.6 for CIN lesions (95%CI, 19.3-58.6) and 78.8 for cervical cancer (95%CI, 39.2-158.3). In total, 19 different HPV genotypes were detected, including five low risk HPV types. Seven of the 14 high-risk HPV types were detected in cervical cancer patients. Based on our study it is suggested that a prophylactic vaccine based on a cocktail of a limited number of high-risk HPV types should be considered in order to protect most women from developing cervical cancer.

Highly efficient gene delivery by mRNA electroporation in human hematopoietic cells: superiority to lipofection and passive pulsing of mRNA and to electroporation of plasmid cDNA for tumor antigen loading of dendritic cells

Designing effective strategies to load human dendritic cells (DCs) with tumor antigens is a challenging approach for DC-based tumor vaccines. Here, a cytoplasmic expression system based on mRNA electroporation to efficiently introduce tumor antigens into DCs is described. Preliminary experiments in K562 cells using an enhanced green fluorescent protein (EGFP) reporter gene revealed that mRNA electroporation as compared with plasmid DNA electroporation showed a markedly improved transfection efficiency (89% versus 40% EGFP(+) cells, respectively) and induced a strikingly lower cell toxicity (15% death rate with mRNA versus 51% with plasmid DNA). Next, mRNA electroporation was applied for nonviral transfection of different types of human DCs, including monocyte-derived DCs (Mo-DCs), CD34(+) progenitor-derived DCs (34-DCs) and Langerhans cells (34-LCs). High-level transgene expression by mRNA electroporation was obtained in more than 50% of all DC types. mRNA-electroporated DCs retained their phenotype and maturational potential. Importantly, DCs electroporated with mRNA-encoding Melan-A strongly activated a Melan-A-specific cytotoxic T lymphocyte (CTL) clone in an HLA-restricted manner and were superior to mRNA-lipofected or -pulsed DCs. Optimal stimulation of the CTL occurred when Mo-DCs underwent maturation following mRNA transfection. Strikingly, a nonspecific stimulation of CTL was observed when DCs were transfected with plasmid DNA. The data clearly demonstrate that Mo-DCs electroporated with mRNA efficiently present functional antigenic peptides to cytotoxic T cells. Therefore, electroporation of mRNA-encoding tumor antigens is a powerful technique to charge human dendritic cells with tumor antigens and could serve applications in future DC-based tumor vaccines.

Prospective study of intratumoral microvessel density, p53 expression and survival in colorectal cancer

Adjuvant treatment of patients with colorectal cancer is hampered by a lack of reliable prognostic factors in addition to the clinicopathological staging system. A poorly defined but considerable fraction of Astler-Coller stage B patients will experience tumour recurrence, and some of the stage C patients will probably survive for a prolonged time after surgery without adjuvant treatment. Assessing parameters related to tumour angiogenesis has provided valuable prognostic information in different tumour types. The formation of new microvessels is part of the malignant phenotype in the majority of tumours. Alterations in tumour-suppressor genes, such as the p53 gene, or oncogenes, such as the ras gene, have been found to be responsible for changing the local balance of pro- and antiangiogenic factors in favour of the former. In this prospective study, intratumoral microvessel density (IMD) was assessed by immunostaining tissue sections for CD31 and counting individual microvessels in selected and highly vascular regions in specimens of 145 colorectal cancer patients. p53 protein overexpression was semiquantitatively determined after immunohistochemistry. In both uni- and multivariate analysis, high IMD was significantly associated with shorter survival in the patients undergoing surgery with curative intent (Astler-Coller stages A-C). p53 added prognostic power to IMD, both in Astler-Coller stage B and stage C patients. An association between IMD and mode of metastasis was also noted. High IMD was strongly associated with the incidence of haematogenous metastasis during follow-up, but not with the presence of lymphogenic metastasis observed at surgery. This study confirms the results of previous retrospective analyses of IMD and survival in colorectal cancer and warrants a clinical validation by randomizing stage B tumour patients with high IMD and p53 overexpression between adjuvant treatment or not.

CD34++ CD38- and CD34+ CD38+ human hematopoietic progenitors from fetal liver, cord blood, and adult bone marrow respond differently to hematopoietic cytokines depending on the ontogenic source

CD34++ CD38- and CD34+ CD38+ hematopoietic progenitor cells (HPCs) from human fetal liver (FL), cord blood (CB), and adult bone marrow (ABM) were isolated and investigated for their growth characteristics, cytokine requirements and response to two modulators of early hematopoiesis, interferon (IFN)-gamma and macrophage inflammatory protein (MIP)-1alpha. We observed first that a significantly lower percentage of CD34++ cells were CD38- in ABM than in FL and CB. Second, the functional differences between CD34++ CD38- and CD34+ CD38+ cells were less pronounced in FL and CB than in their ABM counterparts. Third, an inverse correlation was found between growth factor response and the ontogenic age of HPCs, and a direct correlation was noted between cytokine requirements and the ontogenic age of HPCs. Fourth, spontaneous colony formation in a classic semisolid culture system was reproducibly obtained only in the ontogenically earliest cells, that is, in FL but not in CB and ABM, in which no such spontaneous colony formation was observed. Fifth, the modulatory effects of IFN-gamma and MIP-1alpha were qualitatively different depending on the ontogenic age of the progenitor source: whereas IFN-gamma was only a selective inhibitor of primitive CD34++ CD38- ABM progenitor cells, it inhibited both CD34++ CD38- and CD34+ CD38+ FL and CB cells to the same extent. In contrast to the effects of MIP-1alpha on ABM, we could not find any consistently stimulatory or inhibitory effects on FL and CB progenitors. In conclusion, important functional and biologic differences exist between FL, CB, and ABM progenitor cells, and these differences could have major implications for the use of these cell populations in preparative protocols of ex vivo expansion, transplantation strategies, or gene transfer experiments.

Decrease in nucleoside diphosphate kinase (NDPK/nm23) expression during hematopoietic maturation

The nucleoside diphosphate kinase (NDPK/nm23) isoforms H1 and H2 were localized in hematopoietic tissues. Flow cytometric analysis and enzymatic assays were used to quantify the intracellular and extracellular concentrations of NDPK. Bone marrow CD34(+) progenitors contained the highest intracellular levels of both nm23-H1 and nm23-H2. Lower levels were measured in more mature bone marrow cells, whereas peripheral blood leukocytes had the lowest expression of nm23. These data suggest a function of NDPK in early hematopoiesis and a down-regulation of NDPK upon differentiation. In addition, an up-regulation of nm23 expression was observed in lymphocytes after induction of proliferation with phytohemagglutinin. Multiparameter flow cytometry demonstrated that this up-regulation occurred during the G0/G1-transition. Flow cytometric analysis also revealed a weak surface expression of nm23 on a number of hematopoietic cell lines, which was not detected on normal hematopoietic cells. Our data also demonstrated the presence of NDPK in human plasma, probably due to a limited in vivo lysis of red blood cells.

Nonviral transfection of distinct types of human dendritic cells: high-efficiency gene transfer by electroporation into hematopoietic progenitor- but not monocyte-derived dendritic cells

Human dendritic cells (DC) are highly professional antigen presenting cells for the priming of naive cytotoxic T cells. Gene transfer in DC would be a useful strategy to load DC with relevant de novo synthesized antigens for immunotherapeutical purposes. As a first step towards a DC-based gene therapy, we examined the efficiency of nonviral transfection in different types of cultured human dendritic cells with a humanized red-shifted green fluorescent protein reporter gene. Plasmid DNA transfection by electroporation or lipofection was used to transfect CD34+ progenitor cell-derived DC (PC-DC) and Langerhans' cells (PC-LC), as well as monocyte-derived DC (Mo-DC). While lipofection was unsuccessful in all types of DC, we obtained high-efficiency gene transfer by electroporation in PC-LC (16%) and PC-DC (12%). In contrast, electroporation was strikingly less efficient in Mo-DC (< or = 2%). The potent allostimulatory capacity of DC was still retained in electroporated PC-DC and PC-LC. In conclusion, electroporation of antigen expressing plasmid DNA is an efficient tool for nonviral gene transfer in PC-DC and PC-LC, but not in Mo-DC and could be useful for the development of DC-based tumor immunotherapy.

Effect of indomethacin on cell cycle dependent cyclic AMP fluxes in tobacco BY-2 cells

The evolution of adenosine 3',5'-cyclic monophosphate (cAMP) levels was investigated in synchronised tobacco BY-2 cells by virtue of a method based on immunoaffinity purification and analysis on electrospray tandem mass spectrometry. A transient peak in cAMP content was observed during the S and G1 phases of the cell cycle. Application of the prostaglandin inhibiting drug indomethacin at early S phase resulted in the loss of the cAMP peak in S phase and inhibited mitotic division. This inhibition of cAMP accumulation suggests the presence of a prostaglandin-dependent adenylyl cyclase activity, analogous to animal cyclases. A potential role for cAMP during the plant cell cycle is postulated.

Generation of dendritic cells from bone marrow progenitors using GM-CSF, TNF-alpha, and additional cytokines: antagonistic effects of IL-4 and IFN-gamma and selective involvement of TNF-alpha receptor-1

We report the generation of dendritic cells (DC) starting from CD34+ bone marrow (BM) progenitor cells, using a two-stage culture system in which, besides granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumour necrosis factor-alpha (TNF-alpha), stem-cell factor (SCF) was added during the first 5 days, while interleukin-4 (IL-4) and/or interferon-gamma (IFN-gamma) were added during the secondary culture period of 9 days. Addition of IL-4 favoured the outgrowth of CD1a+, HLA-DR+, CD4+, CD40+, CD80+ but CD14- cells with dendritic morphology and strong antigen-presenting capacity. Addition of IFN-gamma selectively induced HLA-DR and CD86 but did not up-regulate CD1a expression or antigen-presenting capacity of the differentiated cells. An antagonism between IL-4 and IFN-gamma could further be confirmed in that, as compared with IL-4 alone, the simultaneous addition of IL-4 and IFN-gamma to GM-CSF plus TNF-alpha during maturation reduced both the phenotypical (CD1a, CD4, CD40) and functional characteristics of DC. Using receptor-specific TNF-alpha mutants, we investigated the relative involvement of TNF-alpha receptors R1 and R2 in the generation of DC. The induction of CD1a and HLA-DR, as well as the increase in allostimulatory capacity were dependent on TNF-R1 triggering, whereas triggering through TNF-R2 had no measurable effect. We conclude first, that the expansion of DC from BM progenitors could most effectively be enhanced in a two-stage culture assay using SCF, GM-CSF, TNF-alpha and IL-4; second, that the effect of TNF-alpha in DC generation involves signalling via the TNF-R1 receptor; and third, that IFN-gamma counteracts some of the effects of IL-4 in DC generation.

The combined effects of all-trans retinoic acid and TGF-beta on the initial proliferation of normal human bone marrow progenitor cells

We investigated the cell kinetic effects of retinoic acid (RA) and the functional interaction between RA and TGF-beta on normal human bone marrow progenitor cells (CD34+). Cell cycle progression throughout the first three consecutive cell cycles and alterations in cell kinetic responses were measured using the BrdU-Hoechst quenching technique. RA stimulates the IL-3-induced growth by additionally recruiting quiescent stem and progenitor cells out of the G0/G1-phase and by increasing the cell cycle traverse rate. In contrast, TGF-beta addition resulted in a significant decrease in the number of proliferating cells. Simultaneous addition of RA and TGF-beta resulted in a stronger inhibition compared to addition of TGF-beta alone. Preincubation experiments further showed that RA is capable of sensitizing the progenitors to the inhibitory action of TGF-beta: the inhibitory effect of TGF-beta was significantly increased when cells were pretreated with RA. These data show that, in combination with IL-3, RA additionally stimulates quiescent bone marrow progenitors in a simultaneous way, and that it increases sensitivity of the progenitors to the inhibitory action of TGF-beta. The combination of RA and TGF-beta on normal and leukemic hematopoiesis has to be further investigated, since this combination may possibly provide additional therapeutic benefit.

TGF-beta and MIP-1 alpha exert their main inhibitory activity on very primitive CD34+2CD38- cells but show opposite effects on more mature CD34+CD38+ human hematopoietic progenitors

We investigated the effects of transforming growth factor-beta (TGF-beta) and macrophage inflammatory protein-1 alpha (MIP-1 alpha) on very primitive CD34++CD38- and on more mature CD34++CD38+ human hematopoietic progenitor cells by means of a two stage pre-colony-forming cell (pre-CFC) assay. The first (liquid) stage of this assay allows evaluation of the effects of TGF-beta and MIP-1 alpha on the "primary" proliferation of the progenitors under study and on the generation of "secondary" colony-forming cells (CFC, cells for which a second stage semisolid clonogenic assay was used as a read-out). TGF-beta inhibited the proliferation and CFC generation of CD34++CD38- and CD34+CD38+ cells, showing the strongest inhibitory activity on CD34++CD38- cells. MIP-1 alpha exerted a weaker inhibitory activity on CD34+2CD38- cells, whereas it enhanced the primary proliferation of CD34+CD38+ cells and generation of secondary CFC in this subpopulation. Thus, TGF-beta, and MIP-1 alpha both inhibit very primitive CD34+2)CD38- cells, but they are not equally potent. The effects of TGF-beta and MIP-1 alpha on more mature progenitor cells are more complex. Our results and data from the literature indicate that, as progenitor cells mature, they reach a "pivotal point" at a certain stage in their differentiation pathway, depending on the inhibitor, where they are no longer inhibited or where they may even be stimulated by the former inhibitor to proliferate.

Tumor necrosis factor alpha is a potent synergistic factor for the proliferation of primitive human hematopoietic progenitor cells and induces resistance to transforming growth factor beta but not to interferon gamma

Since tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, and transforming growth factor (TGF)-beta have all been shown to be specific inhibitors of early human hematopoiesis, we wanted to investigate the interactions of these three cytokines on very primitive human adult bone marrow CD34++CD38- hematopoietic progenitor cells, using a pre-colony-forming cell (pre-CFC) assay, which detects the effects of these cytokines on the initial phases of the differentiation of these primitive progenitors, which are unresponsive to interleukin (IL) 3 alone. Surprisingly, TNF-alpha was a very potent stimulator of the proliferation of CD34++CD38- cells and was the most potent synergistic factor for the IL-3-induced proliferation of these cells of all cytokines tested (IL-1, IL-6, granulocyte colony-stimulating factor, kit ligand). TNF-alpha was the only cytokine that, as a single added factor, induced substantial proliferation in CD34++CD38- cells in the presence of IL-3, except for kit ligand, which induced very limited proliferation. TNF-alpha, moreover, induced a high degree of resistance to the inhibitory effects of TGF-beta in a dose-dependent way. The inhibitory effects of IFN-gamma, however, were not affected by the presence of TNF-alpha. We hypothesize that in situations of the hematopoietic stress, TNF-alpha may abrogate the inhibitory effect of ambient TGF-beta in the bone marrow microenvironment to allow primitive stem cells to proliferate and differentiate in response to an increased demand for mature blood cells.

Interleukin 4 and interferon gamma costimulate the expansion of early human myeloid colony-forming cells. Proposal of a model for the regulation of myelopoiesis by interleukin 4 and interferon gamma and its integration with the regulation of the immune response

We have previously shown that interleukin 4 (IL-4) and interferon gamma (INF-gamma) reciprocally regulate the production of granulocytes and monocytes from mature monopotential hematopoietic progenitor cells, while at the level of the very primitive stem cells IFN-gamma is a selective inhibitor of proliferation and differentiation, and IL-4 has weak stimulatory effects. We investigated the effects of IL-4 and IFN-gamma on the expansion in suspension culture of myeloid colony-forming cells (CFCs) induced by either IL-3 or IL-1+IL-3, using on the one hand more differentiated CD34+HLA-DR strongly positive (HLA-DR++) and on the other hand more primitive Cd34+HLA-DR weakly positive (HLA-DR+/-) human bone marrow cells. It is shown that both IL-4 and IFN-gamma stimulate the IL-3- and IL-3+IL-1-induced expansion of the number of CFCs in the HLA-DR+/- population. In the presence, but not in the absence of IL-1, additive effects of IL-4 and IFN-gamma were seen. We could not demonstrate any IL-3-like effect by IL-4 on early human hematopoietic progenitors. No expansion of CFC number was seen in the HLA-DR++ population. Based on these data and on data which we have published previously, a model for the regulation of myelopoiesis by IL-4 and IFN-gamma is proposed. In this model, IL-4 and IFN-gamma, which are both immune recognition induced inflammatory cytokines, both stimulate the expansion and recruitment of early myeloid progenitors, whereas at the level of their terminal differentiation, the balance between both cytokines determines whether preferentially monocytes/macrophages (IFN-gamma) or granulocytes (IL-4) are being produced. At the level of the most primitive cells, the inhibitory action of IFN-gamma might prevent differentiative exhaustion of the stem cell compartment in situations of hematopoietic stress.

Interferon gamma selectively inhibits very primitive CD342+CD38- and not more mature CD34+CD38+ human hematopoietic progenitor cells

To assess the effects of interferon gamma (IFN-gamma) on very primitive hematopoietic progenitor cells, CD34(2+)CD38- human bone marrow cells were isolated and cultured in a two-stage culture system, consisting of a primary liquid culture phase followed by a secondary semisolid colony assay. CD34(2+)CD38- cells needed at least the presence of interleukin 3 (IL-3) and kit ligand (KL) together with either IL-1, IL-6, or granulocyte-colony-stimulating factor (G-CSF) in the primary liquid phase in order to proliferate and differentiate into secondary colony-forming cells (CFC). Addition of IFN-gamma to the primary liquid cultures inhibited cell proliferation and generation of secondary CFC in a dose-dependent way. This was a direct effect since it was also seen in primary single cell cultures of CD34(2+)CD38- cells. The proliferation of more mature CD34+CD38+ cells, however, was not inhibited by IFN-gamma, demonstrating for the first time that IFN-gamma is a specific and direct hematopoietic stem cell inhibitor. IFN-gamma, moreover, preserves the viability of CD34(2+)CD38- cells in the absence of other cytokines. IFN-gamma could, therefore, play a role in the protection of the stem cell compartment from exhaustion in situations of hematopoietic stress and may be useful as stem cell protecting agent against chemotherapy for cancer.

Transforming growth factor-beta regulates the cell cycle status of interleukin-3 (IL-3) plus IL-1, stem cell factor, or IL-6 stimulated CD34+ human hematopoietic progenitor cells through different cell kinetic mechanisms depending on the applied stimulus

The immediate cell kinetic response of highly purified human bone marrow progenitor cells (CD34+ sorted fraction) to the inhibitory effects of transforming growth factor-beta (TGF-beta) was studied using the BrdU-Hoechst flow-cytometric technique. The progenitor cells were stimulated with either interleukin-3 (IL-3) alone or with IL-3 in combination with IL-1, stem cell factor (SCF), or IL-6, and the inhibitory action of TGF-beta was evaluated in each phase of the first three consecutive cell cycles. Semisolid methylcellulose cultures were also performed to compare these initial events to the effects observed after 7, 14, and 21 days of incubation. Within the CD34+ compartment, the progenitor cells can be discriminated on a functional basis, i.e., in terms of TGF-beta sensitivity. Very primitive progenitors, recruited out of the G0 phase by IL-3 plus an early-acting factor (IL-1, SCF) are, upon addition of TGF-beta, arrested specifically in the G1 phase of the second cell cycle. In the clonogenic assays, the increased colony formation due to IL-1 or SCF was completely abolished by the counteracting effect of TGF-beta that diminished colony output back to the level of TGF-beta-plus-IL-3 supplemented colony growth. Addition of TGF-beta to CD34+ progenitors responding to IL-3 alone resulted in an overall retardation, but without an apparent specific accumulation of cells in any of the cell cycles. Finally, within the CD34+ compartment, there exists a subset of IL-3-responsive, but TGF-beta-insensitive, progenitor cells that were, upon addition of TGF-beta, not arrested at all. In conclusion, our results demonstrate that TGF-beta exerts different cell kinetic effects on CD34+ progenitor cell growth depending on the applied stimulus.

Differential regulation of the expression of CD38 and human leukocyte antigen-DR on CD34+ hematopoietic progenitor cells by interleukin-4 and interferon-gamma

We studied the effects of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) on the expression of CD38 and human leukocyte antigen (HLA)-DR on purified CD34+ bone marrow progenitor cells. CD34+CD38- and CD34+HLA-DR- cells are largely nonoverlapping populations. After culture for 4 days in IFN-gamma, the expression of CD38 and HLA-DR is significantly increased and the disappearance of the CD38- and HLA-DR- populations is virtually complete. Moreover, IFN-gamma induces a population of CD34+ cells with a very high expression of CD38 (CD34+CD38++ cells), which were absent in the initial CD34+ population. IL-4 has no effect on the expression of CD38, but induces a limited but significant increase in the expression of HLA-Dr. After culture in IFN-gamma, CD34+ cells show a higher cloning efficiency of the colony-forming unit-macrophage (CFU-M) and burst-forming unit-erythroid (BFU-E) compared to cells cultured in medium alone. After culture in IL-4, a limited increase in CFU-granulocyte (CFU-G) and BFU-E is seen, whereas CFU-G, CFU-M, and BFU-E are increased after culture in IL-4 plus IFN-gamma. We further investigated the functional properties of the CD34+CD38++ cells generated in the presence of IFN-gamma. This cell population is highly enriched for BFU-E but partially depleted of CFU-M. Most of the CFU-M were found in the CD34+CD38+/-(CD34+CD38- and CD34+CD38+ cells) population.

Quantitative cell-cycle progression analysis of the first three successive cell cycles of granulocyte colony-stimulating factor and/or granulocyte-macrophage colony-stimulating factor-stimulated human CD34+ bone marrow cells in relation to their colony formation

The bromodeoxyuridine (BrdU)-Hoechst flow cytometric technique was applied to study the immediate cell kinetic response of highly purified human (h) bone marrow progenitor cells (CD(34+)-sorted fraction) to h granulocyte colony-stimulating factor (G-CSF) and/or h granulocyte-macrophage colony-stimulating factor (GM-CSF). The technique permits us to differentiate cycling from noncycling cells and to make a quantitative assessment of cell cycles after stimulation. Semisolid agar and single-cell liquid cultures were also performed to compare these initial events to the effects observed after 14 days of culture. The combination of G-CSF plus GM-CSF, acting synergistically in day 14 cultures, was found to have a subadditive effect in the first cell cycles, thereby indicating partial overlap of the different target cells. However, this combination accelerated transit through the cell cycle, as could be seen from the higher number of cells in the third cell cycle after 72 hours of stimulation. We conclude that, apart from the unresponsive cells, the CD34+ compartment consists of cells responsive to both G-CSF and GM-CSF, and cells responsive to either one of the CSFs alone, and that the combination of the two CSFs speeds up the cell cycle traverse rate for a significant fraction of the target cells that are initially responsive for both G-CSF and GM-CSF. The latter supports the hypothesis of an overlapping signalling pathway of G-CSF and GM-CSF.

Effects of interleukin-4 on myelopoiesis: localization of the action of IL-4 in the CD34+HLA-DR++ subset and distinction between direct and indirect effects of IL-4

We compared the myelopoietic effects of interleukin-4 (IL-4) on CD34+HLA-DR+ and on CD34+HLA-DR++ bone marrow progenitor cells stimulated by either granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3). IL-4 stimulates G-CSF-induced colony-forming unit-granulocyte (CFU-G) and inhibits all colony types induced by GM-CSF and IL-3 in the HLA-DR++ population, but not in the HLA-DR+ population. In CD34+HLA-DR+ cells, however, a stimulation of G-CSF-supported CFU-G was also seen with sequential application of IL-4 in liquid cultures followed by G-CSF in agar cultures. In order to confirm that these are direct effects of IL-4, single-cell culture experiments were performed with CD34+HLA-DR++ cells. In these cultures IL-4 stimulates G-CSF-induced CFU-G and only inhibits colony-forming unit-macrophage (CFU-M) regardless of the CSF used to generate them.

Interferon-gamma and interleukin-4 reciprocally regulate the production of monocytes/macrophages and neutrophils through a direct effect on committed monopotential bone marrow progenitor cells

We studied the direct effects of interferon-gamma (IFN-gamma) in single cell colony assays of CD34+HLA-DR++ bone marrow progenitor cells stimulated by either granulocyte-colony-stimulating factor (G-CSF), interleukin(IL)-3, granulocyte/macrophage-colony-stimulating factor (GM-CSF), combinations of these CSF or medium conditioned by the 5637 human bladder carcinoma cell line. In this culture system IFN-gamma stimulated monocytic colonies (CFU-M) no matter which CSF or CSF combination was used to support them and inhibited granulocytic colonies (CFU-G) if they were generated in the presence of G-CSF. IL-4 antagonized the myelopoietic effects of IFN-gamma: the IFN-gamma-induced suppression of G-CSF-supported CFU-G, as well as the stimulation of CFU-M, were reversed by IL-4. In all cultures, IFN-gamma had a limited, but statistically non-significant, inhibitory effect on CFU-GM, which was not affected by the presence of IL-4. These data show that IFN-gamma and IL-4 reciprocally regulate the generation of myeloid cells involved in humoral (neutrophils) and cellular (macrophages) immune responses through a direct effect on monopotential myeloid progenitor cells.

Effects of interleukin-4 (IL4) on myelopoiesis: studies on highly purified CD34+ hematopoietic progenitor cells

We studied the effects of interleukin 4 (IL4) on myelopoiesis supported by either granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage CSF (GM-CSF) or IL3 on purified CD34+ bone marrow progenitor cells. IL4 stimulates the colony-forming unit granulocyte (CFU-G) induced by G-CSF and inhibits all colony types supported by either IL3 and GM-CSF, although inhibition of CFU-M (macrophage) was significantly stronger than that of CFU-G and CFU-GM. When the cells were first incubated in liquid culture for 4 days in IL4, followed by agar culture in G-CSF, there was a significant increase in the number of CFU-G compared to cells which had been incubated in medium alone for 4 days before plating out in agar containing G-CSF. The inhibitory effects of IL4 on GM-CSF or IL3 supported colony formation, however, disappear with sequential incubation in IL4 in liquid culture followed by culture in agar with either GM-CSF or IL3.

Direct effects of 13-cis and all-trans retinoic acid on normal bone marrow (BM) progenitors: comparative study on BM mononuclear cells and on isolated CD34+ BM cells

The effects of both 13-cis-and all-trans retinoic acid (RA) on colony formation of normal bone marrow (BM) progenitors were investigated in semi-solid (methylcellulose) assays, using either isolated CD34+ cells or BM mononuclear cells. Single cell liquid cultures were performed to further discriminate between direct and indirect effects. RA action results in significant decrease of colony forming units (CFUs). This effect is more pronounced starting from CD34+ progenitors than starting from total BM. This overall decrease in CFUs is due to selective inhibition of CFU-M (macrophage) and erythroid colonies (BFU-E). At the single cell level the CFU-M inhibition is confirmed with--in addition--a significant inhibition of CFU-GM (granulocyte-macrophage) and a marked stimulation of CFU-G (granulocyte)s. Both retinoids exert the above-mentioned effects. All-trans RA, however, is effective at a tenfold lower concentration (10(-7)M) than 13-cis RA (10(-6)M). Results on CD34+ BM fractions (substantially reduced in accessory cells) demonstrate that the described effects can probably be attributed to the direct action of RA on these progenitors; single progenitor (CD34+) cell liquid cultures further prove this point.