Radiation responses of stem cells: targeted and not-targeted effects

Stem cells are fundamental to the development of any tissue or organism via their ability to self-renew, which is aided by their unlimited proliferative capacity and their ability to produce fully differentiated offspring, often from multiple lineages. Stems cells are long lived and have the potential to accumulate mutations, including in response to radiation exposure. It is thought that stem cells have the potential to be induced into a cancer stem cell phenotype and that these may play an important role in resistance to radiotherapy. For radiation-induced carcinogenesis, the role of targeted and non-targeted effects is unclear with tissue or origin being important. Studies of genomic instability and bystander responses have shown consistent effects in haematopoietic models. Several models of radiation have predicted that stem cells play an important role in tumour initiation and that bystander responses could play a role in proliferation and self-renewal.

The prognostic value of the stem-like group in colorectal cancer using a panel of immunohistochemistry markers

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths in the Western world. It is becoming increasingly clear that CRC is a diverse disease, as exemplified by the identification of subgroups of CRC tumours that are driven by distinct biology. Recently, a number of studies have begun to define panels of diagnostically relevant markers to align patients into individual subgroups in an attempt to give information on prognosis and treatment response. We examined the immunohistochemical expression profile of 18 markers, each representing a putative role in cancer development, in 493 primary colorectal carcinomas using tissue microarrays. Through unsupervised clustering in stage II cancers, we identified two cluster groups that are broadly defined by inflammatory or immune-related factors (CD3, CD8, COX-2 and FOXP3) and stem-like factors (CD44, LGR5, SOX2, OCT4). The expression of the stem-like group markers was associated with a significantly worse prognosis compared to cases with lower expression. In addition, patients classified in the stem-like subgroup displayed a trend towards a benefit from adjuvant treatment. The biologically relevant and poor prognostic stem-like group could also be identified in early stage I cancers, suggesting a potential opportunity for the identification of aggressive tumors at a very early stage of the disease.

Hemopoietic chimerism following stem cell transplantation

Hematopoietic chimerism is a measure of the number of donor and recipient cells in the host following stem cell transplantation (SCT). The type of conditioning therapy prior to SCT has a major impact on the chimeric status in the recipient. Different techniques of measurement have varying sensitivities. The use of polymerase chain reaction (PCR) of short tandem repeats (STR) using fluorescent amplification permits quantification using Genescan analysis. When SCT is used for malignant haematological disorders, measurement of chimeric status may indicate early relapse and in aplastic anemia graft rejection. Reduced intensity or T-cell depletion is associated with mixed haemopoietic chimerism. SCT for benign haematological disorders does not require complete donor chimerism for a successful outcome.

Marrow aplasia developing 13 years after HLA-identical sibling allogeneic transplantation for chronic myeloid leukaemia:successful treatment with antithymocyte globulin and peripheral blood stem cell infusion from the original donor

Secondary or late graft failure has been defined as the development of inadequate marrow function after initial engraftment has been achieved. We describe a case of profound marrow aplasia occurring 13 years after sibling allogeneic bone marrow transplantation for chronic myeloid leukaemia (CML) in first chronic phase. Although the patient remained a complete donor chimera, thereby suggesting that an unselected infusion of donor peripheral blood stem cells (PBSC) or bone marrow might be indicated, the newly acquired aplasia was thought to be immune in aetiology and some immunosuppression was therefore considered appropriate. Rapid haematological recovery was achieved after the infusion of unselected PBSC from the original donor following conditioning with anti-thymocyte globulin (ATG).

Treatment of relapse after allogeneic bone marrow transplantation with reduced intensity conditioning (FLAG +/- Ida) and second allogeneic stem cell transplant

Acute leukaemias in relapse after allogeneic stem cell transplantation (SCT) respond poorly to donor leucocyte infusions (DLI) compared with chronic myeloid leukaemia (CML), at least in part because of faster disease kinetics. Fludarabine-containing 'non-myeloablative' chemotherapy followed by further allo SCT may offer more rapid and effective disease control. We report 14 patients with relapse after allo SCT for acute leukaemia [seven acute myeloid leukaemia (AML), five acute lymphoblastic leukaemia (ALL)] or refractory anaemia with excess blasts in transformation (RAEB-t, n = 2) treated with fludarabine, high-dose cytosine arabinoside (ara-C) and granulocyte colony-simulating factor (G-CSF) with (n = 10) or without (n = 2) idarubicin (FLAG +/- Ida) or DaunoXome (FLAG-X) (n = 2) and second allo SCT from the original donor. Donors were fully human leucocyte antigen (HLA) -matched in 13 cases with a single class A mismatch in one. Actuarial overall survival was 60% and disease-free survival was 26% at 58 months. Remissions after the second SCT were longer than those after the first bone marrow transplantation (BMT) in eight of the 13 assessable patients to date. Haematopoietic recovery was rapid. Transplants were well tolerated with no treatment-related deaths. The major complication was graft-versus-host disease (GvHD, acute >/= grade II-2 cases, chronic - eight cases, two limited, six extensive) although there have been no deaths attributable to this. FLAG +/- Ida and second allo SCT is a safe and useful approach and may be more effective than DLI in the treatment of acute leukaemias relapsing after conventional allo SCT.

Short Report:Engraftment of T-cell-depleted allogeneic haematopoietic stem cells using a reduced intensity conditioning regimen

Graft-versus-host disease (GVHD) remains a significant complication in patients undergoing allogeneic stem cell transplantation (SCT) using a reduced intensity conditioning regimen. Although T-cell depletion (TCD) reduces the risk of GVHD after a myeloablative conditioning regimen, it is associated with an increased risk of graft failure. We have therefore examined whether TCD compromises engraftment using a fludarabine-based conditioning regimen. Fifteen patients have been transplanted using such a regimen of whom 13 underwent ex vivo TCD. All but one patient demonstrated durable engraftment and no patient receiving a TCD product developed severe GVHD. Thus, TCD may play a role in GvHD prophylaxis using such regimens.

FLAG-idarubicin and allogeneic stem cell transplantation for Ph-positive ALL beyond first remission

We describe a single centre experience of eight consecutive patients with relapsed or refractory Ph+ ALL treated with the FLAG/idarubicin regimen followed by BMT or PBSCT. Following FLAG/idarubicin, one achieved a partial response and seven CR. All patients subsequently received allogeneic transplants: one sibling BMT, three matched unrelated (MUD) BMT and four sibling PBSCT. Two patients received second transplants with PBSC from their original BM donors following FLA/Ida with no further conditioning. Three patients are alive in CR 9, 24 and 32 months after transplant. Seven of eight patients had a cytogenetic response following FLAG/Ida induction and one of seven became bcr-abl negative. All eight patients had a complete cytogenetic response following transplant. Four of five assessable patients became p190 bcr-abl negative after transplant; three of these subsequently relapsed. Both patients with the p210 bcr-abl transcript remained bcr-abl positive in CR after transplant. FLAG/Ida was well tolerated and appears to be effective in inducing remission in relapsed Ph+ ALL. The use of FDR-containing chemotherapy without further conditioning prior to PBSCT deserves further study in heavily pre-treated patients and, in patients with relapsed ALL following BMT, may be a safer option than DLI (donor lymphocyte infusion) by avoiding the associated risk of aplasia.

Effect of ultraviolet-B light on lymphocyte activity at doses at which normal bone marrow stem cells are preserved

Ultraviolet B (UVB) light is known to be immunosuppressive, but, probably because of a small UVC component in the emission spectra of some of the UVB lamps used, reports vary on effective dose levels. To prevent potentially lethal graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation, alloreactive donor T-cell activity must be suppressed. In this study, a narrow wavelength UVB lamp (TL01, 312 nm peak emission) was used to determine what doses of UVB were required to abolish rat lymphocyte proliferation while simultaneously preserving rat bone marrow progenitor cell and primitive hematopoietic stem cell viability. Lymphocyte proliferation, as measured by 3H-Thymidine incorporation, in response to lectin stimulation was abolished below detection at doses greater than 3,500 J/m2. When T-cell clonogenicity was measured in a limiting dilution assay, a small fraction (0.6%) was maintained at doses up to 4,000 J/m2. Cytotoxic T-lymphocyte (CTL) activity was reduced after treatment with 4,000 J/m2, but a significant level of cytotoxicity was still maintained. Natural killer cell cytolytic activity was not affected by doses up to 4,000 J/m2. At 4,000 J+m2 there was a 10% survival of colony-forming units-granulocyte-macrophage; a 1% and 4% survival of day-8 and day-12 colony-forming units-spleen, respectively; and 11% survival of marrow repopulating ability cells. Up to 25% of late cobblestone area forming cells (4 to 5 weeks), reflecting the more immature hematopoietic stem cells, were preserved in bone marrow treated with 4,000 J/m2, indicating that early stem cells are less sensitive to UVB damage than are more committed progenitor cells. Thus, a potential therapeutic window was established at approximately 4,000 J/m2 using this light source, whereby the potentially GVHD-inducing T cells were suppressed, but a sufficient proportion of the cells responsible for engraftment was maintained.