Sjögren syndrome successfully treated with oxygen-ozone auto-hemotherapy (O2-O3-AHT). a case report.

OBJECTIVE: Sjögren syndrome (SS) is an autoimmune disorder, affecting about 16,000 individuals in Italy, yet lacking a standardized therapy protocol and a plain inclusion in the reimbursed healthcare services. This raises many controversial issues about how managing the SS patient, to relief pain and discomfort and improve patients' health and social life. The ozone therapy resulted successful in previous reports, and therefore, it was used in this case report. CASE PRESENTATION: A 69-years old female outpatient, showing positivity to Schirmer's test, was previously diagnosed as a primary Sjögren syndrome, who later developed an autoimmune thyroiditis and showed the presence of rheumatoid factors. The patient suffered from a marked ocular dryness, subsequently to a purported endothelitis, alongside with fatigue and pain. Laboratory tests showed a positive ANA 1:320 in a speckled pattern with negative anti-SSA and anti-SSB tests. From December 2020 to January 2021 she underwent 2 routes of three sessions of oxygen-ozone autohemotherapy (O2-O3 AHT), as described below and improved, with only 2 sessions, her symptomatology and clinical outcome, as ocular dryness, fatigue and pain, rapidly disappeared. CONCLUSIONS: The use of ozone in the therapy of SS is a straightforward, affordable and feasible approach to treat primary Sjögren syndrome without significant side effects.

An atypical occurrence of Aspergillosis in leukemic patient: Brief description of a clinical case.

Herein we describe a 43 year-old Caucasian female patient with acute myeloid leukemia that developed an unconventional form of invasive Aspergillosis. For therapeutic reasons, a Groshong-type central venous catheter was positioned. Monitoring the patient's clinical conditions, positive values for C-reactive protein and galactomannan were correlated with a probably Aspergillosis. Surprisingly no pulmonary evidences were observed. Due to worsening conditions, she was re-hospitalized and a blood culture was performed, whom positivity resulted as the first clinical evidence of Aspergillus fumigatus. Further evidence about species identification was obtained by sequencing the fungal ITS region. We support the clinical value of blood culture as a decisive factor to improve the diagnosis of catheter-related Aspergillosis.

Hematologic improvement and response in elderly AML/RAEB patients treated with valproic acid and low-dose Ara-C.

The histone deacetylase inhibitor (HDACi) valproic acid (VPA) has been shown to be active on acute myeloid leukemia (AML) and refractory anemia with excess of blasts (RAEB). Thirty-one elderly AML/RAEB patients (AML n=25; RAEB n=6) with a high rate of comorbidity were entered in a phase II study with low-dose cytarabine (Ara-C) and VPA. Fitness was evaluated by means of the Comprehensive Geriatric Assessment (CGA), including the Cumulative Illness Rating Scale (CIRS) score, the self-sufficiency scores of Activity of Daily Living (ADL) and Instrumental Activity of Daily Living (IADL). Eight patients obtained a lasting complete remission and 3 other patients obtained hematologic improvement for a total response rate of 35%. Five of 11 responding patients were relapsed or resistant after a previous treatment with Ara-C. Seven of 11 responding patients were assessed as frail at enrollment and/or had IADL impairment. Grades 3 and 4 toxicities were mainly hematological. Low-dose Ara-C and VPA is a relatively non-toxic combination with good therapeutic activity in elderly patients with AML/RAEB. This therapeutic approach represents an alternative treatment for patients who cannot undergo standard induction therapy.

Safety and efficacy of STI-571 (imatinib mesylate) in patients with bcr/abl-positive chronic myelogenous leukemia (CML) after autologous peripheral blood stem cell transplantation (PBSCT).

We examined safety and efficacy of STI-571 in 24 bcr/abl-positive patients with CML post PBSCT. At start of STI-571 therapy, nine patients presented in blast crisis (BC) or in accelerated phase (AP), and 15 in chronic phase (CP). Patients were evaluated for hematologic, cytogenetic and molecular response, survival and toxicity. In general, STI-571 was well tolerated in this heavily pretreated group of patients with a non-hematologic and hematologic toxicity profile similar to that observed in a previous phase I trial at comparable doses. Five of nine patients with CML in transformation (AP, BC) were evaluable for hematologic response. Two of five patients had transient reductions in WBC and blasts, and three patients achieved a sustained hematologic response (>4 weeks). Cytogenetic analysis in these patients revealed numerical and/or structural responses. In CML chronic phase, STI-571 induced complete hematologic responses in all patients and major cytogenetic responses in 61% of patients with a complete cytogenetic response rate of 46%. This report indicates that STI-571 is a safe and effective drug in heavily pretreated patients. No apparent additional side-effects were noted in this patient cohort. The high rate of complete hematologic and complete cytogenetic responses in CP patients is remarkable, as intensive treatment approaches plus IFN-alpha failed to be efficient in achieving long-term stabilization of CML in this patient cohort.

Autografting followed by nonmyeloablative immunosuppressive chemotherapy and allogeneic peripheral-blood hematopoietic stem-cell transplantation as treatment of resistant Hodgkin's disease and non-Hodgkin's lymphoma.

PURPOSE: To investigate the use of a nonmyeloablative fludarabine-based immunosuppressive regimen to allow engraftment of HLA-sibling donors' mobilized stem cells and induction of a graft-versus-lymphoma effect for patients with advanced resistant Hodgkin's disease and non-Hodgkin's lymphoma. PATIENTS AND METHODS: Fifteen patients with Hodgkin's disease (n = 10) and non-Hodgkin's lymphoma (n = 5) were studied. All patients received cyclophosphamide and granulocyte colony-stimulating factor to mobilize autologous hematopoietic stem cells (HSCs). Subsequently, they received high-dose therapy with carmustine, etoposide, cytarabine, and melphalan and reinfusion of HSCs. At a median of 61 days after engraftment, patients were given fludarabine 30 mg/m(2) with cyclophosphamide 300 mg/m(2) daily for 3 days. Donor-mobilized HSC collections were prepared for fresh infusion and were not T-cell depleted. Methotrexate and cyclosporine were used to prevent graft rejection and as graft-versus-host disease (GVHD) prophylaxis. RESULTS: Combined treatment was well tolerated. After mini-allografting, hematologic recovery was prompt. Thirteen patients had 100% donor cell engraftment. Eleven patients achieved complete remission (CR) after the combined procedure. Nine patients, who were in partial remission after autografting, achieved CR after mini-allografting. Seven patients developed >/= grade 2 acute GVHD (aGVHD) and two developed extensive chronic GVHD (cGVHD). Three patients who received the highest number of donor lymphocyte infusions (DLIs) developed grade 3 GVHD (two patients) and extensive cGVHD (one patient). Ten patients are currently alive, and five are in continuous CR. Seven patients received DLI, with five CRs. Five patients died: one of progressive disease, two of progressive disease combined with aGVHD or cGVHD, one of extensive cGVHD, and one of infection. CONCLUSION: Fludarabine/cyclophosphamide was well tolerated and allowed consistent engraftment in lymphoma allografted patients. Response rates were high in this group of refractory and heavily pretreated patients. This dual procedure seems to be most promising in patients with end-stage malignant lymphomas.

Cytogenetic response to autografting in chronic myelogenous leukemia correlates with the amount of BCR-ABL positive cells in the graft.

OBJECTIVE: An important step in successful autografting of patients with chronic myelogenous leukemia is the delivery of a leukemia-free graft. We conducted this study to determine whether the cytogenetic response after autografting was correlated with the number of BCR ABL-positive cells present within the stem cell grafts. MATERIALS AND METHODS: By BCR-ABL mRNA quantification, we studied the serial pheresis products from 40 Philadelphia (Ph)-positive patients who received ICE/mini-ICE mobilization therapy and underwent autologous stem cell transplantation. We correlated the residual disease within the graft reinfused with the cytogenetic response following transplantation, taking into consideration those responses that lasted 12 months or more. RESULTS: Thirty-two patients received a graft with 0-35% Ph-metaphases and 19 received a graft with BCR-ABL/ABL ratio < or =0.01. After a median of 27 months (range, 12-50) from transplant, 18 patients achieved complete or major cytogenetic response lasting at least 12 months, and 14 of them (78%) received a graft with BCR-ABL/ABL ratio < or =0.01 (range, 0.0003-0.01). Twenty-two patients experienced short-lived responses or had >35% Ph-positive cells in the marrow after transplant, but only 5 of them (23%) had a graft with BCR-ABL/ABL ratio < or =0.01 (range, 0.001-0.01). Therefore, we found a strong association between a BCR-ABL/ABL ratio less than or =0.01 and the achievement of complete or major cytogenetic remission after autografting (chi(2) test, p = 0.0001). Patients reinfused with grafts contaminated at low levels with leukemic cells also showed a longer duration of the response (log-rank test, p = 0.0009). Eleven patients were reinfused with the lowest level of contaminated stem cell collections, according to the BCR-ABL/ABL ratio. None of these patients experienced prolonged neutropenia or thrombocytopenia following stem cell reinfusion and nine of them had long-lasting complete or major cytogenetic responses after transplant. CONCLUSION: This study demonstrates that the number of BCR-ABL positive cells present in a stem cell graft is an important predictive factor for the achievement and the duration of cytogenetic response after autografting. [corrected]

Quantitative competitive reverse transcriptase-polymerase chain reaction for BCR-ABL on Philadelphia-negative leukaphereses allows the selection of low-contaminated peripheral blood progenitor cells for autografting in chronic myelogenous leukemia.

The Philadelphia (Ph) translocation t(9;22) results in the creation of the BCR-ABL gene, which is now regarded as central to the mechanism that underlies the chronic phase of chronic myelogenous leukemia (CML). From a clinical point of view, BCR-ABL mRNA detection has become the basis for the study of minimal residual disease in CML, particularly when a complete cytogenetic remission is achieved after interferon-alpha (IFN-alpha) therapy or allogeneic stem cell transplantation. We have recently demonstrated that it is possible to mobilize normal peripheral blood progenitor cells (PBPC) in higher rates if this procedure is performed during the early chronic phase. In an attempt to monitor the leukemic cell content of PBPC collections, we used quantitative-competitive RT-PCR (QC-RT-PCR). Thirty consecutive Philadelphia (Ph) chromosome positive patients were enrolled in this study. After chemotherapy and G-CSF, 14 patients achieved 100% Ph-negative metaphases, nine patients had < or =34% and seven patients >34% leukemic metaphases. A total of 116 collection samples were studied. For each sample, BCR-ABL transcript numbers and BCR-ABL/ABL ratio were evaluated. A highly significant correlation between Ph-positive metaphases and BCR-ABL transcript numbers (r = 0.84, P < 0.0001) or BCR-ABL/ABL ratio (r = 0.86, P < 0.0001) was found. For patients that underwent the procedure in early chronic phase, Ph-negative collections showed different levels of BCR-ABL expression. BCR-ABL transcript numbers varied from a median of 100/microg RNA in the first and second leukaphereses, to 500/microg RNA in the third and fourth leukaphereses, and 1500/microg RNA in the fifth leukapheresis (P = 0.002). BCR-ABL/ABL ratio values showed similar kinetics. We have also demonstrated that there is a correlation between low values in BCR-ABL/ABL ratio (< or =0.01) in the reinfused PBPC and the achievement of cytogenetic remission after autografting (chi2 test, P = 0.01). In conclusion, this study demonstrates that QC-RT-PCR for BCR-ABL is a reliable and helpful method for monitoring residual leukemic load in mobilized PBPC, particularly in Ph-negative collections. Moreover, QC-RT-PCR allows selection of the best available collections for reinfusion into patients after myeloablative therapy.

Autografting with philadelphia chromosome-negative mobilized hematopoietic progenitor cells in chronic myelogenous leukemia.

Intensive chemotherapy given in early chronic phase of chronic myelogenous leukemia (CML) has resulted in high numbers of circulating Philadelphia (Ph) chromosome-negative hematopoietic progenitor cells (HPC). We have autografted 30 consecutive patients with CML in chronic phase with HPC collected in this way to facilitate restoration of Ph-negative hematopoiesis in bone marrow after high-dose therapy. Hematopoietic recovery to greater than 0.5 x10(9)/L neutrophils and to greater than 25 x 10(9)/L platelets occurred in all patients, a median of 13 (range, 9 to 32) days and 16 (range, 6 to 106) days postautograft, respectively. Regenerating marrow cells were Ph-negative in 16 (53%) patients and greater than 66% Ph-negative in 10 (33%) patients. Twenty-eight patients are alive 6 to 76 months (median, 24 months) after autografting. Three patients have developed blast crisis from which 2 have died. Eight patients are in complete cytogenetic remission at a median of 20 (range, 6 to 44) months with a median ratio BCR-ABL/ABL of 0.002 (range, <0.001 to 0.01). Eight patients are in major cytogenetic remission at a median of 22 (range, 6 to 48) months. No patient died as a consequence of the treatment. All patients had some degree of stomatitis that was severe in 15 (50%) patients. Gastrointestinal and hepatic toxicities were observed in about one fourth of patients. Thus, autografting with Ph-negative mobilized HPC can result in prolonged restoration of Ph-negative hematopoiesis for some patients with CML; moreover, most autograft recipients report normal or near normal activity levels, suggesting that this procedure need not to be associated either with prolonged convalescence or with chronic debility.

Autologous peripheral blood haematopoietic stem cell transplantation for chronic myelogenous leukaemia.

In these last four decades there has been extraordinary progress in our understanding of the biology of, and therapeutic approach to, chronic myelogenous leukaemia (CML). During these decades new observations arising from studies of the biological behaviour of diploid and leukaemic stem cells and, recently, from clinical investigations have received the most attention. From a clinical point of view, allografting is still the only procedure which is able to cure CML. For patients without HLA-compatible donors, current therapeutic options include conventional chemotherapy (hydroxyurea), interferon-alpha (IFN-alpha) and autografting. While IFN-alpha (+/- low-dose ARA-C) must be considered the first-line therapy, autografting, according to our approach, or other procedures, raises the question of an ideal sequential strategy in the management of CML patients (diploid stem cell mobilization, autografting, IFN-alpha). Because it seems that the diploid haematopoietic reservoir declines with time, it may be desirable to mobilize and collect diploid stem cells in order to store them as soon as diagnosis is possible when the WBC count has been controlled by hydroxyurea.

Evidence of cytogenetic and molecular remission by allogeneic cells after immunosuppressive therapy alone.

An immunosuppressive but not myeloablative regimen followed by HLA-matched donor mobilized haemopoietic stem cell transplantation was employed in two high-risk patients. The first patient had refractory anaemia with excess blasts (RAEB) and cytogenetic evidence of translocation 1;3(p36;q21). The second patient had Philadelphia-negative but p190 BCR-ABL chimaeric gene positive chronic myelogenous leukaemia in accelerated phase (AP-CML). The conditioning regimen consisted of fludarabine (30 mg/m2/d, days 1-3) with cyclophosphamide (300 mg/m2/d, days 1-3). Cyclosporine and methotrexate were employed for acute graft-versus-host disease (aGVHD) prophylaxis. In both cases the engraftment of donor cells was demonstrated by cytogenetics and short tandem repeat polymorphisms via PCR. Both patients are alive with normal cytogenetic (RAEB) and molecular (AP-CML) remissions, 100 and 150 d after allografting, respectively. In particular, in the AP-CML patient, the BCR-ABL became undetectable and the BCR-ABL/ABL ratio was <0.0001.

Engraftment of HLA-matched sibling hematopoietic stem cells after immunosuppressive conditioning regimen in patients with hematologic neoplasias.

BACKGROUND AND OBJECTIVE: The main objective of this pilot study was to assess the possibility of achieving engraftment of HLA-matched sibling donor mobilized hematopoietic stem cells after immunosuppressive non-myeloablative therapy. The second objective was to verify whether high-dose therapy with autologous stem cells rescue followed by allografting conditioned by only an immunosuppressive regimen, can be combined in order to achieve the reduction of tumor burden after autografting and the control of residual disease with immune-mediated effects after allografting. DESIGN AND METHODS: To enter the pilot study the patients had to fulfil the following criteria: advanced resistant disease, presence of an HLA matched sibling donor, no general contraindications to stem cell transplantation. Our data refers to 9 patients: Hodgkin's disease (n = 4), non-Hodgkin's lymphoma (n = 2), advanced chronic myelogenous leukemia (n = 2) (one patient with accelerated phase Ph-negative but p190 BCR-ABL gene positive by RT-PCR and one with Ph-positive blastic phase), refractory anemia with excess of blasts t(1;3) (p36;q21) (n = 1). All patients but one received the combined approach. At a median of 40 days (range 30-96), after high-dose therapy and autologous stem cell engraftment, the patients were treated with immunosuppressive therapy consisting of fludarabine and cyclophosphamide (Flu-Cy protocol) and then HLA matched donor mobilized stem cells were infused into the patients. GvHD prophylaxis consisted of cyclosporin and methotrexate. RESULTS: To date, with a median observation period of 4 months (range, 2-10), complete chimerism (100% donor cells) has been achieved in 6 patients. Three patients did not achieve complete chimerism: one patient died of progressive Hodgkin's disease when he reached 55% of donor cells, another patient is now in increasing phase of donor cell engraftment and the last patient (blastic phase-CML) was the only case who appears to have had autologous recovery. Two of the Hodgkin's disease patients, who were in partial remission after autografting, achieved complete remission after allografting and both are disease free 2 and 6 months after. Another Hodgkin's disease patient is alive at 10 months but she has progressive disease. One of the two patients with non-Hodgkin's lymphoma, who achieved partial remission after autografting, obtained complete remission and he is disease free 2 months after allografting. The other patient maintains partial remission obtained after autografting. The accelerated phase-CML patient obtained hematologic and molecular remission; the RAEB patient achieved hematologic and cytogenetic remission. In two patients severe aGVHD (grade II-III) was the single major complication but neither patient died of it. Mild aGVHD was seen in another patient. In only one patient did the ANC decrease to below 1 x 10(9)/L and in no case did platelets decrease below 20 x 10(9)/L. No patients required a sterile room or any red cell or platelet transfusions. INTERPRETATION AND CONCLUSIONS: Immunosuppressive therapy with a Flu-Cy protocol allowed engraftment of HLA-matched sibling donor stem cells without procedure-related deaths; moreover, we have demonstrated that this combined procedure can be pursued in safety in a serious ill population and some of these patients achieved a complete remission. This procedure is not likely to be curative, but a fascinating step along the path to curing these diseases. Of course, the follow-up is too short to document the incidence of cGvHD.

Effective mobilization of Philadelphia-chromosome-negative cells in chronic myelogenous leukaemia patients using a less intensive regimen.

To determine if reducing the intensity of the mobilizing chemotherapy protocol used would alter the number and/or quality of the progenitors mobilized in patients with chronic myelogenous leukaemia (CML), we undertook a pilot study. 36 consecutive CML patients previously treated only with hydroxyurea were given mobilization therapy within 12 months of diagnosis. 17 patients were treated by the ICE protocol and 19 patients received the mini-ICE protocol. The leukapheresis product collected from 22/36 patients (62%) was entirely Ph-negative. The cytogenetic results between ICE and mini-ICE-treated protocols were not significant, although the reduction in median days of hospitalization required for the mini-ICE versus the ICE protocol was highly significant (P < 0.0001). There was no significant difference in the yield of CD34+ cells and CFU-GM collected. No patient in the mini-ICE protocol experienced high-grade oral mucositis and GI toxicity whereas three such cases occurred with the ICE protocol. No patient died of the mobilization procedure in either group.

Lineage- and stage-specific expression of runt box polypeptides in primitive and definitive hematopoiesis.

Translocations involving the human CBFA2 locus have been associated with leukemia. This gene, originally named AML1, is a human homologue of the Drosophila gene runt that controls early events in fly embryogenesis. To clarify the role of mammalian runt products in normal and leukemic hematopoiesis, we have studied their pattern of expression in mouse hematopoietic tissues in the adult and during ontogeny using an anti-runt box antiserum. In the adult bone marrow, we found expression of runt polypeptides in differentiating myeloid cells and in B lymphocytes. Within the erythroid lineage, runt expression is biphasic, clearly present in the erythroblasts of early blood islands and of the fetal liver, but absent in the adult. Biochemical analysis by Western blotting of fetal and adult hematopoietic populations shows several runt isoforms. At least one of them appears to be myeloid specific.

Expression of runtB is modulated during chondrocyte differentiation.

The runt locus in Drosophila encodes a nuclear protein involved in embryo segmentation, sex determination/X dosage compensation, and neurogenesis. runt homologues have been identified in higher vertebrates. The encoded proteins share a domain of 128 amino acids called the runt domain. It has been reported that this domain mediates DNA binding and heterodimerization. Here, we analyze runtB expression during chondrocyte differentiation "in vitro" and "in vivo." We have first isolated, from a chondrocyte library, a cDNA clone coding for a runtB chicken homologue and containing a complete open reading frame. The predicted protein product is 84% identical to the mouse PEBP2alphaB2 isoform. By RT-PCR analysis we have also cloned the chicken cDNA fragment coding for delta alphaB2, the exon sequence included in the B1 isoform mRNA. On Northern blot analysis of cultured chondrocytes, runtB mRNA levels increase dramatically with the transition from stage 0 (dedifferentiated) to stages I and II (hypertrophic chondrocytes). Moreover, runt polypeptides were demonstrated in chondrocytes both in vivo and in vitro. These results suggest that runt plays a role in chondrogenic differentiation.

Expression of HOXC4 homeoprotein in the nucleus of activated human lymphocytes.

We have analyzed the expression of homeoproteins of the HOX family in resting and activated lymphoid cells and in neoplastic lymphoid cell lines by the use of monoclonal antibodies (MoAbs) already shown to react with the homeoproteins HOXA10, HOXC6, and HOXD4, respectively. Anti-HOXA10 and C6 MoAbs DIDi not show any reactivity with the lymphoid cells tested, whereas anti-HOXD4 MoAb stained few resting peripheral blood lymphocytes (PBLs) and most phytohemagglutinin (PHA)-stimulated PBLs as early as 6 hours after stimulation. The pattern of staining of PHA-activated PBLs is reminiscent of the stages of nucleolar fragmentation in different phases of the cell cycle. The MoAb reacted also with activated or Epstein-Barr virus-transformed B cells, with clonal or polyclonal T and natural killer (NK) cells, with leukemic T-cell lines, and with a Burkitt's lymphoma cell line. RNAse protection experiments, per formed with probes specific for HOXD4 or for the highly homologous HOXA4, HOXB4, and HOXC4, belonging to the same paralogy group, indicated that only HOXC4 mRNA is present in resting or activated PBLs. Northern blot analysis on polyA+ RNA from activated PBLs or Raji cells showed the presence of two different HOXC4 transcripts of 2.8 and 1.9 kb. Gel retardation and Southwestern blot assays showed the presence of a 32-kD homeoprotein with DNA-binding properties typical of a HOX4 homeoprotein in nucleolar extracts of PHA-activated, but not of resting, lymphocytes. Taken together, these data indicate that the HOXC4 homeoprotein is expressed in activated and/or proliferating lymphocytes of the T-, B-, or NK-cell lineage, whereas it is weakly expressed in a minority of resting cells. The early expression and the nucleolar localization suggest an involvement of HOXC4 in the regulation of genes controlling lymphocyte activation and/or proliferation.

Nucleolar localisation of three Hox homeoproteins.

Homeoproteins encoded by genes of the Hox family are nuclear proteins believed to act as transcription factors and to participate in the determination of the body plan. Here we show that in several vertebrate cells, they exhibit a subnuclear localisation associated with the nucleolus. We used monoclonal antibodies to study the distribution of three homeoproteins, namely HOXB7, HOXC6 and HOXD4. The immunoreactivity to antibodies against HOXC6 protein in Xenopus laevis embryonic tissues is restricted to one or two spots within the nucleus; this distribution partially overlaps that of fibrillarin, a protein of the fibrillar zone of the nucleoli. Indirect immunofluorescence analysis of the distribution of HOXB7 protein in 3T3 cells, and of HOXD4 protein in human neuroblastoma and Raji lymphoma cell lines and activated lymphocytes, results invariably in a nucleolar localisation. Purified nucleoli from stimulated T lymphocytes, and Raji cells contain an activity capable of binding, in a gel retardation assay, to an oligonucleotide specifically recognised by the HOXD4 homeoprotein. This activity is specifically removed by anti-HOXD4 antibodies and is found associated in southwestern blots with a single band with an apparent M(r) of 30,000, corresponding to that of recombinant HOXD4. The functional significance of the nucleolar localisation of Hox proteins remains to be determined.

Changes in the prevalence of an homeobox gene product during muscle differentiation.

We have studied by immunohistofluorescence and confocal microscopy the localization of the XlHbox-1 protein, the product of a Xenopus class 1 homeobox gene corresponding to the human HOX 3C, during the development of Xenopus laevis mesodermal derivatives. The protein, not present at early stages of embryonic development, can first be detected in the neurula where it is weakly expressed in the rostral part of the spinal cord and in the nuclei of the corresponding somites. At later stages of mesodermal development, very high levels of the molecule are present in the nuclei of a small group of myogenic cells in the most dorsal aspect of the myotome, while the nuclei of differentiated muscle fibers within the myotome are either stained weakly or completely negative. A similar transient expression of XlHbox-1 gene product during myogenesis occurs during muscle differentiation in the limb bud and during differentiation of visceral smooth muscles from the lateral plate mesoderm. In both cases the nuclei of precursor cells contain high level of this protein which is rapidly down regulated during further muscle differentiation. In myogenic areas the modulation of XlHbox-1 expression invariably parallels that of the neural cell adhesion molecule N-CAM. These data are the first evidence that a homeobox gene belonging to the Antennapedia-Bithorax complex is transiently expressed in early phases of muscle differentiation. The transient expression of homeobox genes in early phases of embryonic development could act synergistically with the expression of other myogenic transcriptional factors to specify a fine level of differentiation of the muscle cells along the body axis.