[Endometrial cancer: what's new?]

OBJECTIVES

New and much debated data of the endometrial cancer concerning the preoperative assessment of myometrial invasion, the surgical staging, and the adjuvant treatment.

PATIENTS AND METHODS

Medline (1998-2002): searching for "endometrial carcinoma".

RESULTS

The pap smears are useful when it is difficult to have a transvaginal ultrasonography or an MRI. We can perform the pap smears and the endometrial biopsy in the clinic. If a patient has pap smears with malignant cells or elevated preoperative CA 125, it probably is a cancer with poor prognostic factors. Surgical staging with abdominal and node evaluation is necessary. The MRI seems to be the best preoperative imaging because we have information about adnexal and abdominal metastases, pelvic or aortic nodes and the invasion of the myometrium. So it gives us information on the surgical route, and provides indication for a lymphadenectomy. The surgical staging is a part of the treatment of the endometrial cancer: an exploration of the peritoneal cavity, a pelvic lymphadenectomy, a para-aortic lymphadenectomy if the pelvic nodes are positive or if there are factors of bad prognosis (deep stage IC, grade 3, adnexal or abdominal involvement, serous carcinoma of the endometrium). It can be performed if technical conditions are correct. The adjuvant teletherapy in the documented stage IpN0 (surgical staging with pelvic lymphadenectomy) does not seem to be necessary. But we can perform an adjuvant brachytherapy (high-dose rate if it is possible) in patients with a high local recurrence (stage IC, stage I with grade 3, stage IB grade 2).

CONCLUSION

The preoperative MRI is useful choosing the surgical approach, and the depth of the myometrial invasion, which can be an indication for a pelvic lymphadenectomy. The surgical staging must be a part of the treatment of the endometrial cancer. So the adjuvant teletherapy in patients with stage IpN0 documented should not be used.

Vaginal evisceration after hysterectomy: the repair by a laparoscopic and vaginal approach with a omental flap

BACKGROUND

Vaginal evisceration is generally repaired by vaginal or abdominal route. We describe two cases of vaginal evisceration using a combined laparoscopic and vaginal approach employing an omental flap.

CASES

Case 1: A radical abdominal hysterectomy was performed in a premenopausal patient for a FIGO IB1 cervical cancer. Four months later, she was found to have a vaginal cuff dehiscence which was repaired by a vaginal approach. Two months later, she had a vaginal cuff evisceration which was repaired using a combined laparoscopic and vaginal approach employing an omental flap with good success. Case 2: A postmenopausal woman who underwent an abdominal hysterectomy and pelvic lymphadenectomy for a FIGO IB endometrial cancer was noted to have a vaginal evisceration two months after primary surgery. This was also successfully repaired using a combined laparoscopic and vaginal approach employing an omental flap.

CONCLUSION

The combined laparoscopic and vaginal approach with omental flap is effective for repair of a vaginal cuff dehiscence with bowel evisceration. The addition of laparoscopy provides an opportunity for inspection of the small bowel, the peritoneal toilet, and mobilization of an omental flap.

Laparoscopic restaging of borderline ovarian tumours: results of 30 cases initially presumed as stage IA borderline ovarian tumours

OBJECTIVES

To review our experience with the laparoscopic restaging procedure of presumed early stage borderline ovarian tumours.

DESIGN

Retrospective study.

SETTING

Cancer centre.

POPULATION

Thirty patients with presumed stage I borderline ovarian tumours after limited initial surgery.

METHODS

From April 1991 to May 2001, the patients were laparoscopically reassessed. The procedure involved peritoneal cytology, exploration of the peritoneal cavity, infracolic omentectomy, directed or random peritoneal biopsies, and when appropriate, contralateral oophorectomy and hysterectomy and appendectomy. Medical records were reviewed for patients' age, interval time between procedures, tumour stage, histological type, operative time, hospital stay, peri-operative complications and follow up.

MAIN OUTCOME MEASURES

Seroperative and postoperative data, pathology and clinical follow up.

RESULTS

Laparoscopic restaging was completed in all 30 (100%) identified patients. The mean age was 34.8 (10.5) years; the delay between initial operation and restaging laparoscopy averaged 9.8 (6.6) weeks. The mean operative time was 165.4 (53.8) minutes, and the mean hospital stay was 2.7 (1.3) days. There were two (7.0%) major complications related directly to the procedure. Eight (26.6%) patients were upstaged. Mean follow up was 29.1 (6.6) months, all patients are alive and one (3.2%) recurrence was observed.

CONCLUSIONS

Laparoscopic approach of restaging for borderline ovarian tumours is an accurate safe procedure. It is associated with an acceptable rate of minor complications, it has similar morbidity associated with laparotomy and it minimises the incidence of infertility in the young patients. Whenever staging of borderline ovarian tumours is to be considered in an individual patient, laparoscopy provides a suitable alternative approach.

[Ultrastructural studies of hepatoblast junctions and liver hematopoiesis of the mouse embryo]

To clarify the morphological changes in hepatoblast connections during the development of fetal liver hematopoiesis, ICR mouse livers of 11 to 19 days of gestation were studied by means of three-dimensional reconstruction, immunohistochemistry, electron microscopy and freeze fracture replica method. Embryonic liver weight showed rapid increase until 19 days of gestation, and an initial steep increase, due to hematopoietic development, was observed at 13 to 15 days of gestation. Hepatoblast volume appeared to be constant until 13 days of gestation, and, thereafter, showed a gradual increase. An 11-day primitive hepatic cord contained a few immature hematopoietic cells among hepatoblasts, and the hepatoblasts made contact with one another by short cytoplasmic projections. The area of the contact surface had a diameter of 4-5 microns, where E-cadherin-mediated adherens junctions were found. At 12-13 days of gestation, hepatoblasts surrounded large ellipsoidal hematopoietic foci, with long cytoplasmic projections. In addition to the adherens junctions, small desmosomes appeared to bind hepatoblasts together, and biliary canaliculi could be recognized between hepatoblasts. At peak stage of liver hematopoiesis at 14 days of gestation, both tight junctions and gap junctions appeared around the biliary canaliculi, and four types of specialized junctions, i.e., adherens junctions, desmosomes, tight junctions and gap junctions, appeared to be fully developed. After 15 days of gestation, hepatocyte volume showed rapid increase, and the surface areas between adjacent hepatocytes were markedly enlarged. As a result, the involuted hematopoietic foci were forced to move from interhepatocytic spaces to perisinusoidal space at the end of the intrauterine life.

Simultaneous signalling through c-mpl, c-kit and CXCR4 enhances the proliferation and differentiation of human megakaryocyte progenitors: possible roles of the PI3-K, PKC and MAPK pathways

We assessed the effect of signalling through CXCR4 on the proliferation and differentiation of human megakaryocytic progenitor cells (CFU-Meg) in the presence or absence of stem cell factor (SCF) and/or thrombopoietin (TPO), using peripheral blood-derived CD34(+)IL-6R(-) cells as a target. TPO alone induced a significant number of CFU-Meg colonies. Although stromal cell-derived factor-1 (SDF-1) or SCF alone did not support CFU-Meg colony formation, these factors had a synergistic effect on CFU-Meg colony formation in the presence of TPO. The combination of SDF-1, SCF and TPO induced twice as many CFU-Meg colonies as TPO alone. To investigate the mechanism of this synergistic action, we examined the effects of various protein kinase inhibitors on CFU-Meg colony formation. LY294002 and GF109203X (inhibitors of PI3-K and PKC respectively) completely or partially inhibited this synergistic action. In contrast, a MEK inhibitor (PD98059) did not inhibit CFU-Meg colony formation. It significantly increased the higher ploidy classes (16N to 64N) of megakaryocytes supported by TPO, TPO + SCF, TPO + SDF-1, and TPO + SCF + SDF-1, whereas it abolished the effect of SDF-1 on the increase of higher ploidy classes of megakaryocytes supported by TPO. These results suggest that MAPK may negatively or positively regulate the nuclear maturation of megakaryocytes, known as endomitosis. In the presence of PD98059, proplatelet formation (PPF) was significantly augmented, suggesting that the MAPK pathway may also inhibit the initiation of PPF. In conclusion, simultaneous activation of three signals through c-mpl, c-kit and CXCR4 can induce the in vitro proliferation and differentiation of CFU-Meg, and SDF-1 is a potentiator of human megakaryocytopoiesis.

Akt pathway activation converts anaplastic astrocytoma to glioblastoma multiforme in a human astrocyte model of glioma

Human malignant gliomas are thought to develop as the result of stepwise accumulations of multiple genetic alterations. Recently, we showed that E6/E7-mediated inactivation of p53/pRb, ras pathway activation (initiated by expression of mutant H-Ras), and expression of human telomerase reverse transcriptase (hTERT) in combination converted normal human astrocytes into cells that formed intracranial tumors resembling human anaplastic astrocytoma (AA). In this study, we created human astrocytes that, in addition to expressing E6/E7, hTERT, and Ras, also expressed a constitutive activated form of Akt intended to mimic the Akt activation noted in grade IV glioblastoma multiforme (GBM). Although these cells grew no differently than astrocytes expressing E6, E7, and H-Ras in vitro or in the first 28 days following s.c. implantation, they ultimately formed tumors four to six times larger than those formed by the E6/E7/hTERT/Ras cells. Unlike the poorly vascularized, necrosis-free AA formed by E6/E7/hTERT/Ras cells, the tumors formed by s.c. or intracranial injection of Akt-expressing cells had large areas of necrosis surrounded by neovascularization and were consistent in appearance with grade IV human GBM. These results show that activation of the Akt pathway is sufficient to allow conversion of human AA to human GBM.

Formation of intracranial tumors by genetically modified human astrocytes defines four pathways critical in the development of human anaplastic astrocytoma

The formation of human malignant gliomas is thought to involve the accumulation of multiple genetic alterations. To define the function of specific alterations in glioma formation, we serially introduced genetic alterations functionally equivalent to those noted in human malignant gliomas into normal human astrocytes (NHAs). We then monitored the ability of each of these alterations to contribute to the growth of otherwise genetically stable NHAs into intracranial malignant gliomas. Using this model, we show that expression of human telomerase catalytic component (hTERT), but not E7-mediated inactivation of pRb or E6/E7-mediated inactivation of p53/pRb, was sufficient to initiate the tumorigenic process by circumventing cellular senescence in astrocytes. hTERT expression, even in combination with inactivation of p53/pRb, did not transform astrocytes. These alterations together, however, cooperated with ras pathway activation (initiated by expression of mutant H-Ras), but not with phosphatidylinositol 3-kinase pathway activation (initiated by expression of myristoylated Akt) or epidermal growth factor receptor activation, to allow for the formation of intracranial tumors strongly resembling p53/pRb pathway-deficient, telomerase-positive, ras-activated human grade III anaplastic astrocytomas. These results identify four pathways as key in the development of human anaplastic astrocytomas.

Immunogenicity of human amniotic membrane in experimental xenotransplantation

PURPOSE

The immunogenic characterization of amniotic membrane is still unknown. This study was designed to examine the immunogenicity of human amniotic membrane, by using experimental xenotransplantation models.

METHODS

Anti-human class I, class II, and Fas ligand monoclonal antibodies were used against cryopreserved amniotic membrane and cell viability tested for cryopreserved amniotic membrane. Amniotic membranes were then transplanted to the limbal area, intracorneal space, and under the kidney capsule. The scores of transparency and neovascularization after transplantation were recorded by slit lamp microscopy. Host cell infiltration was examined by hematoxylin-eosin or immunohistochemical staining. Control grafts were transplanted human cryopreserved skin grafts.

RESULTS

Strong class I expression was observed in amniotic epithelium, mesenchymal cells, and fibroblasts in cryopreserved amniotic membrane. Some fibroblast cells unexpectedly expressed class II antigen. Fas ligand-positive cells were also detected in mesenchymal cells of amniotic stroma. Approximately 50% of epithelial cells of amniotic membrane cryopreserved for several months were still viable. In limbal transplantation, although some CD4(+) and CD8(+) T cells surrounded the amniotic graft, the response was mild. In intracorneal transplantation, all grafted amniotic membranes were accepted and clear, without host cell infiltration. In contrast, all skin grafts were rejected within 3 weeks after intracorneal transplantation. In amniotic membrane transplantation under the kidney capsule, extremely few host vessels and cells infiltrated the amniotic membrane; however, more host cells infiltrated the skin tissues under the kidney capsule.

CONCLUSIONS

Amniotic membrane seems to be immune-privileged tissue and to contain some immunoregulatory factors, including HLA-G and Fas ligand. The amniotic membrane may be useful to supplement corneal collagen, and it may be applied not only to the ocular surface but also intracorneally.

slender rice, a constitutive gibberellin response mutant, is caused by a null mutation of the SLR1 gene, an ortholog of the height-regulating gene GAI/RGA/RHT/D8

The rice slender mutant (slr1-1) is caused by a single recessive mutation and results in a constitutive gibberellin (GA) response phenotype. The mutant elongates as if saturated with GAs. In this mutant, (1) elongation was unaffected by an inhibitor of GA biosynthesis, (2) GA-inducible alpha-amylase was produced by the aleurone layers without gibberellic acid application, and (3) endogenous GA content was lower than in the wild-type plant. These results indicate that the product of the SLR1 gene is an intermediate of the GA signal transduction pathway. SLR1 maps to OsGAI in rice and has significant homology with height-regulating genes, such as RHT-1Da in wheat, D8 in maize, and GAI and RGA in Arabidopsis. The GAI gene family is likely to encode transcriptional factors belonging to the GRAS gene superfamily. DNA sequence analysis revealed that the slr1-1 mutation is a single basepair deletion of the nuclear localization signal domain, resulting in a frameshift mutation that abolishes protein production. Furthermore, introduction of a 6-kb genomic DNA fragment containing the wild-type SLR1 gene into the slr1-1 mutant restored GA sensitivity to normal. These results indicate that the slr1-1 mutant is caused by a loss-of-function mutation of the SLR1 gene, which is an ortholog of GAI, RGA, RHT, and D8. We also succeeded in producing GA-insensitive dwarf rice by transforming wild-type rice with a modified SLR1 gene construct that has a 17-amino acid deletion affecting the DELLA region. Thus, we demonstrate opposite GA response phenotypes depending on the type of mutations in SLR1.

A MEK inhibitor, PD98059 enhances IL-1-induced NF-kappaB activation by the enhanced and sustained degradation of IkappaBalpha

Interleukin-1 (IL-1) mediates numerous host responses through rapid activation of nuclear factor-kappaB (NF-kappaB), but signal pathways leading to the NF-kappaB activation appear to be complicated and multiplex. We propose a novel regulatory system for NF-kappaB activation by the extracellular signal-related kinase (ERK) pathway. In a human glioblastoma cell line, T98G, IL-1-induced NF-kappaB activation was significantly augmented by the pretreatment of a specific MEK inhibitor, PD98059. In contrast, ectopic expression of a constitutive activated form of Raf (v-Raf) reduced IL-1-induced NF-kappaB activation, and this inhibition was completely reversed by PD98059. Interestingly, PD98059 sustained IL-1-induced NF-kappaB DNA binding activity by an electrophoretic mobility shift assay and also IkappaBalpha degradation, presumably by augmenting and sustaining the proteasome activation. Concomitantly, two NF-kappaB dependent genes, A20 and IkappaBalpha expression were prolonged with PD98059. These data suggested that MEK-ERK pathway exerts a regulatory effect on NF-kappaB activation, providing a novel insight on the role of MEK-ERK pathway.

High incidence of positive peritoneal cytology in low-risk endometrial cancer treated by laparoscopically assisted vaginal hysterectomy

OBJECTIVE

Laparoscopically assisted vaginal hysterectomy (LAVH) has evolved into an alternative form of surgical management in the treatment of low-risk endometrial cancer. The purpose of this study was to determine whether low-risk endometrial cancer patients are subject to a higher incidence of positive peritoneal cytology when treated with LAVH compared to total abdominal hysterectomy (TAH).

METHODS

We retrospectively reviewed the medical records of patients with low-risk endometrial cancer (grade 1--2 endometrioid type with no evidence of extrauterine spread or grade 3 with <50% myometrial invasion (MI), no cervical or adnexal involvement, and negative lymph nodes when sampled) treated at Memorial Sloan-Kettering Cancer Center from January 1993 to September 1999. We compared 131 patients treated with LAVH to 246 controls who underwent TAH. The two groups were compared for known prognostic factors including grade, MI, vascular space involvement, and lower uterine segment extension.

RESULTS

The mean age of patients who underwent LAVH (61 years) was similar to that of the controls (62 years). Fourteen (10.3%) of the patients treated with LAVH had positive peritoneal cytology compared to only 7 (2.8%) of the control population. Factors including FIGO grade, myometrial invasion, and preoperative hysteroscopy did not influence the final results. When stratifying for these factors, the odds ratios of having positive peritoneal washings in those patients treated by LAVH were 5.2, 5.2, and 3.7, respectively.

CONCLUSION

Treatment of low-risk endometrial cancer by LAVH is associated with a significantly higher incidence of positive peritoneal cytology. This may be due to the retrograde dissemination of cancer cells into the peritoneal cavity during uterine manipulation. The clinical significance of these findings is yet to be determined.

Differential involvement of p38 mitogen-activated protein kinase and phosphatidyl inositol 3-kinase in the IL-1-mediated NF-κB and AP-1 activation

Interleukin-1 (IL-1) is a central regulator of the immune and inflammatory responses by which various inflammatory genes are induced. Although IL-1 signaling is known to involve PI3-kinase, p38 mitogen-activated protein (MAP) kinase and extracellular signal-regulated kinase (ERK), the crosstalk of these kinases on the IL-1-mediated signal transduction is not clear. We used two specific inhibitors, SB203580 which selectively inhibits p38 MAP kinase and LY294002 which inhibits PI3-kinase, respectively, to explore the involvement of these kinases in the IL-1-induced NF-kappa B activation, using a human glioblastoma cell line, T98G. Two kinase inhibitors decreased IL-1-induced IL-8 mRNA and protein levels markedly. IL-1 caused phosphorylation of p38 MAP kinase with concomitant recruitment of PI3-kinase to IL-1 receptor I (IL-1RI) and its activation. In this context, pretreatment of LY294002, but not SB203580, inhibited IL-1-induced NF-kappa B activation significantly. While IL-1 induced-AP-1 activation was moderate, both LY294002 and SB203580 suppressed IL-1-induced AP-1 activation. These observations were prominent particularly in the TRAF6 transfection system, in which overexpression of wild type TRAF6 augmented the IL-1 mediated NF-kappa B and AP-1 activation, while dominant negative TRAF6 construct (delta TRAF6) suppressed these activation. Namely, LY294002 inhibited TRAF6-mediated IL-1-induced NF-kappa B and AP-1 activation markedly, while SB203580 inhibited TRAF6-induced AP-1 activation but not NF-kappa B activation. Above results indicated that both PI3-kinase and p38 MAP kinase are differentially involved in IL-1-induced NF-kappa B and AP-1 activation.

Signal through gp130 activated by soluble interleukin (IL)-6 receptor (R) and IL-6 or IL-6R/IL-6 fusion protein enhances ex vivo expansion of human peripheral blood-derived hematopoietic progenitors

This study was designed to investigate the effects of a combination of soluble interleukin (sIL)-6 receptor (R) and IL-6 on the ex vivo expansion of human peripheral blood (PB)-derived hematopoietic progenitor cells in a short-term serum-free liquid suspension culture system, using PB-derived CD34(+)IL-6R(+/-) cells as a target. In combination with stem cell factor (SCF), IL-3, and sIL-6R/IL-6, the expansion efficiency (EE) for granulocyte/macrophage colony-forming unit (CFU-GM) reached a peak level on day 10 of incubation. On the other hand, the EE for erythroid burst (BFU-E) and mixed colony-forming unit (CFU-Mix) reached a peak level on day 7 of incubation. Among the cytokine combinations tested, SCF + IL-3 + sIL-6R/IL-6 + flt3 ligand (FL) most effectively expanded CFU-GM and CFU-Mix. The maximum EEs for CFU-GM and CFU-Mix were 208-fold and 42-fold, respectively. While the EE for BFU-E was 70-90-fold in the presence of SCF + IL-3 + sIL-6R/IL-6, FL significantly augmented the EE for CFU-GM and CFU-Mix. In contrast, thrombopoietin (TPO) significantly augmented the EE for CFU-Mix. Interestingly, in combination with IL-3 and SCF, newly generated IL-6R/IL-6 fusion protein (FP) expanded PB-derived BFU-E and CFU-Mix twice more effectively than a combination of sIL-6R and IL-6. These results demonstrated that human PB-derived committed progenitors were effectively expanded in vitro using sIL-6R/IL-6 or FP, in combination with IL-3, SCF and/or FL or TPO, and that FP may transduce a stronger intracellular signal than a combination of sIL-6R and IL-6.

FTY720, a novel immunosuppressive agent, induces apoptosis in human glioma cells

FTY720, a metabolite from Isaria sinclairii, has been developed to be a potent immunosuppressive drug with induction of apoptosis in T cells and several cell lines. We investigated whether FTY720 induces apoptosis in human glioma cell lines, since they are relatively resistant to multiple apoptotic stimuli. In human glioma cells including T98G, FTY720 induced apoptosiswith ED50 between 1 to 10 microg/ml, while etoposidedid not induce apoptosis at the same doses. Among the caspase family proteases, mainly caspase-6 was activated during the apoptosis by FTY720 but not etoposide. In addition, FTY720 caused tyrosine dephosphorylation of FAK and did not activate a FAK-PI3-kinase survival pathway. This was confirmed also by the observation that orthovanadate prevented FTY720-induced dephosphorylation of FAK and inhibited FTY720-induced cell death. We assumed that FTY720 induced FAK dephosphorylation and cut off the FAK-PI3-kinase pathway resulting in the induction of apoptosis via caspase-6 activation in these glioma cells.

Functional evaluation of p53 and PTEN gene mutations in gliomas

We screened mutations of two major tumor suppressor genes, p53 and PTEN, in 66 human brain tumors using a yeast-based functional assay and cDNA-based direct sequencing, respectively. The frequency of p53 mutations was 28.8% (19 of 66) and was higher in anaplastic astrocytoma (9 of 14, 64.3%,) than in glioblastoma multiforme (GBM; 7 of 27, 25.9%,), supporting previous speculation that there are at least two genetic pathways leading to GBM, a de novo pathway without p53 mutation and a "progressive" pathway with p53 mutation. PTEN mutation was observed in 8 of 64 tumors (12.5%), mainly GBMs (7 of 26, 26.9%), both with and without p53 mutation. These results suggest that mutation of the PTEN gene is a later event than that of the p53 gene in glioma progression and is associated with both the genetic pathways. All of the detected PTEN missense mutations and an in-frame small deletion inactivated PTEN phosphoinositide phosphatase activity in vitro. Because the tumors containing PTEN mutations also showed loss of heterozygosity in the chromosome 10q23 region flanking the PTEN gene, our data clearly indicate that inactivation of both PTEN alleles occurs in a subset of high-grade gliomas, therefore confirming the previous idea that PTEN acts as a tumor suppressor gene.

Interleukin 6 receptor expression by human cord blood- or peripheral blood-derived primitive haematopoietic progenitors implies acquisition of different functional properties

The significance of interleukin 6 receptor (IL-6R) expression by cord blood (CB)- and peripheral blood (PB)-derived primitive haematopoietic progenitors was investigated. IL-6R was preferentially expressed by PB-derived myeloid progenitors. Most PB-derived erythroid bursts (BFU-E) and mixed colony-forming cells (CFU-Mix) did not express this receptor. However, CB-derived primitive progenitor cells possessed multipotentiality, irrespective of IL-6R expression. Interestingly, the long-term culture-initiating cell (LTC-IC) population was enriched in PB-derived CD34+ IL-6R+ cells, but the extended LTC-IC (ELTC-IC) population, which represents a less mature class of haematopoietic progenitors, seemed to be equally distributed in the IL-6R+ and IL-6R- cell populations. In contrast, the number of LTC-ICs and ELTC-ICs was similar in CB-derived CD34+ IL-6R+ or IL-6R- cells. It is noteworthy that the number of LTC-ICs and ELTC-ICs in CB-derived CD34+ cells was markedly higher than that in PB-derived CD34+ cells regardless of IL-6R expression. Telomerase activity was consistently lower in PB-derived CD34+ IL-6R- cells than in CD34+ IL-6R+ cells. In contrast, telomerase activity was similar in CB-derived CD34+ IL-6R+ or IL-6R- cells. The pattern of telomerase induction upon cytokine stimulation differed between CB- and PB-derived CD34+ IL-6R+ or IL-6R- cells. However, overall telomerase activity per dish was well correlated with the proliferative potential of both cell populations, suggesting that induction of telomerase plays an important role in the escape from replicative senescence of primitive haematopoietic progenitors. Collectively, these results suggest that CB-derived primitive progenitors are less mature than PB-derived progenitors and that the expression of IL-6R by primitive haematopoietic progenitors may have different implications for PB- and CB-derived CD34+ cells.