Rapid hematopoietic recovery after coinfusion of autologous-blood stem cells and culture-expanded marrow mesenchymal stem cells in advanced breast cancer patients receiving high-dose chemotherapy

PURPOSE

Multipotential mesenchymal stem cells (MSCs) are found in human bone marrow and are shown to secrete hematopoietic cytokines and support hematopoietic progenitors in vitro. We hypothesized that infusion of autologous MSCs after myeloablative therapy would facilitate engraftment by hematopoietic stem cells, and we investigated the feasibility, safety, and hematopoietic effects of culture-expanded MSCs in breast cancer patients receiving autologous peripheral-blood progenitor-cell (PBPC) infusion.

PATIENTS AND METHODS

We developed an efficient method of isolating and culture-expanding a homogenous population of MSCs from a small marrow-aspirate sample obtained from 32 breast cancer patients. Twenty-eight patients were given high-dose chemotherapy and autologous PBPCs plus culture-expanded MSC infusion and daily granulocyte colony-stimulating factor.

RESULTS

Human MSCs were successfully isolated from a mean +/- SD of 23.4 +/- 5.9 mL of bone marrow aspirate from all patients. Expansion cultures generated greater than 1 x 10(6) MSCs/kg for all patients over 20 to 50 days with a mean potential of 5.6 to 36.3 x 10(6) MSCs/kg after two to six passages, respectively. Twenty-eight patients were infused with 1 to 2.2 x 10(6) expanded autologous MSCs/kg intravenously over 15 minutes. There were no toxicities related to the infusion of MSCs. Clonogenic MSCs were detected in venous blood up to 1 hour after infusion in 13 of 21 patients (62%). Median time to achieve a neutrophil count greater than 500/microL and platelet count >/= 20,000/microL untransfused was 8 days (range, 6 to 11 days) and 8.5 days (range, 4 to 19 days), respectively.

CONCLUSION

This report is the first describing infusion of autologous MSCs with therapeutic intent. We found that autologous MSC infusion at the time of PBPC transplantation is feasible and safe. The observed rapid hematopoietic recovery suggests that MSC infusion after myeloablative therapy may have a positive impact on hematopoiesis and should be tested in randomized trials.

Phenotypic and functional comparison of cultures of marrow-derived mesenchymal stem cells (MSCs) and stromal cells

Mesenchymal stem cells (MSCs) are a population of pluripotent cells within the bone marrow microenvironment defined by their ability to differentiate into cells of the osteogenic, chondrogenic, tendonogenic, adipogenic, and myogenic lineages. We have developed methodologies to isolate and culture-expand MSCs from human bone marrow, and in this study, we examined the MSC's role as a stromal cell precursor capable of supporting hematopoietic differentiation in vitro. We examined the morphology, phenotype, and in vitro function of cultures of MSCs and traditional marrow-derived stromal cells (MDSCs) from the same marrow sample. MSCs are morphologically distinct from MDSC cultures, and flow cytometric analyses show that MSCs are a homogeneous cell population devoid of hematopoietic cells. RT-PCR analysis of cytokine and growth factor mRNA in MSCs and MDSCs revealed a very similar pattern of mRNAs including IL-6, -7, -8, -11, -12, -14, and -15, M-CSF, Flt-3 ligand, and SCF. Steady-state levels of IL-11 and IL-12 mRNA were found to be greater in MSCs. Addition of IL-1alpha induced steady-state levels of G-CSF and GM-CSF mRNA in both cell preparations. In contrast, IL-1alpha induced IL-1alpha and LIF mRNA levels only in MSCs, further emphasizing phenotypic differences between MSCs and MDSCs. In long-term bone marrow culture (LTBMC), MSCs maintained the hematopoietic differentiation of CD34+ hematopoietic progenitor cells. Together, these data suggest that MSCs represent an important cellular component of the bone marrow microenvironment.

Hematopoietic engraftment and survival in adult recipients of umbilical-cord blood from unrelated donors

BACKGROUND

Umbilical-cord blood from unrelated donors who are not HLA-identical with the recipients can restore hematopoiesis after myeloablative therapy in children. We studied the use of transplantation of umbilical-cord blood to restore hematopoiesis in adults.

METHODS

Sixty-eight adults with life-threatening hematologic disorders received intensive chemotherapy or total-body irradiation and then transplants of HLA-mismatched umbilical-cord blood. We evaluated the outcomes in terms of hematologic reconstitution, the occurrence of acute and chronic graft-versus-host disease (GVHD), relapses, and event-free survival.

RESULTS

Of the 68 patients, 48 (71 percent) received grafts of umbilical-cord blood that were mismatched for two or more HLA antigens. Of the 60 patients who survived 28 days or more after transplantation, 55 had neutrophil engraftment at a median of 27 days (range, 13 to 59). The estimated probability of neutrophil recovery in the 68 patients was 0.90 (95 percent confidence interval, 0.85 to 1.0). The presence of a relatively high number of nucleated cells in the umbilical-cord blood before it was frozen was associated with faster recovery of neutrophils. Severe acute GVHD (of grade III or IV) occurred in 11 of 55 patients who could be evaluated within the first 100 days after transplantation. Chronic GVHD developed in 12 of 33 patients who survived for more than 100 days after transplantation. The median follow-up for survivors was 22 months (range, 11 to 51). Of the 68 patients, 19 were alive and 18 of these (26 percent) were disease-free 40 months after transplantation. The presence of a high number of CD34+ cells in the graft was associated with improved event-free survival (P=0.05).

CONCLUSIONS

Umbilical-cord blood from unrelated donors can restore hematopoiesis in adults who receive myeloablative therapy and is associated with acceptable rates of severe acute and chronic GVHD.

Cotransplantation of HLA-identical sibling culture-expanded mesenchymal stem cells and hematopoietic stem cells in hematologic malignancy patients

Mesenchymal stem cells (MSCs) are found in a variety of tissues, including human bone marrow; secrete hematopoietic cytokines; support hematopoietic progenitors in vitro; and possess potent immunosuppressive properties. We hypothesized that cotransplantation of culture-expanded MSCs and hematopoietic stem cells (HSCs) from HLA-identical sibling donors after myeloablative therapy could facilitate engraftment and lessen graft-versus-host disease (GVHD); however, the safety and feasibility of this approach needed to be established. In an open-label, multicenter trial, we coadministered culture-expanded MSCs with HLA-identical sibling-matched HSCs in hematologic malignancy patients. Patients received either bone marrow or peripheral blood stem cells as the HSC source. Patients received 1 of 4 study-specified transplant conditioning regimens and methotrexate (days 1, 3, and 6) and cyclosporine as GVHD prophylaxis. On day 0, patients were given culture-expanded MSCs intravenously (1.0-5.0 x 10(6)/kg) 4 hours before infusion of either bone marrow or peripheral blood stem cells. Forty-six patients (median age, 44.5 years; range, 19-61 years) received MSCs and HLA-matched sibling allografts. MSC infusions were well tolerated, without any infusion-related adverse events. The median times to neutrophil (absolute neutrophil count > or = 0.500 x 10(9)/L) and platelet (platelet count > or = 20 x 10(9)/L) engraftment were 14.0 days (range, 11.0-26.0 days) and 20 days (range, 15.0-36.0 days), respectively. Grade II to IV acute GVHD was observed in 13 (28%) of 46 patients. Chronic GVHD was observed in 22 (61%) of 36 patients who survived at least 90 days; it was extensive in 8 patients. Eleven patients (24%) experienced relapse at a median time to progression of 213.5 days (range, 14-688 days). The probability of patients attaining disease- or progression-free survival at 2 years after MSC infusion was 53%. Cotransplantation of HLA-identical sibling culture-expanded MSCs with an HLA-identical sibling HSC transplant is feasible and seems to be safe, without immediate infusional or late MSC-associated toxicities. The optimal MSC dose and frequency of administration to prevent or treat GVHD during allogeneic HSC transplantation should be evaluated further in phase II clinical trials.

Prolonged granulocytopenia: the major risk factor for invasive pulmonary aspergillosis in patients with acute leukemia

A case-control study of patients with acute leukemia was done to identify significant risk factors for invasive pulmonary aspergillosis by reviewing the medical histories of 15 cases of pathologically proven invasive pulmonary aspergillosis and 45 controls. A history of lung or sinus disease, smoking, and multiple recurrences of leukemia did not increase the risk of invasive pulmonary aspergillosis. Cases and controls received similar chemotherapeutic regimens, and exposure to aminoglycosides, carbenicillin, trimethoprim-sulfamethoxazole, or corticosteroids was not significantly associated with development of invasive pulmonary aspergillosis. Among the factors tested, only granulocytopenia was associated with development of invasive pulmonary aspergillosis. Early in the course of granulocytopenia, patients developed signs of invasive pulmonary aspergillosis at a rate of approximately 1% per day. As the duration of granulocytopenia increased, the rate increased, approximating 4.3% per day between the 24th and 36th days. Of the 13 patients remaining granulocytopenic at 28 days, 7 had developed signs of invasive pulmonary aspergillosis. For patients with acute leukemia, granulocytopenia persisting longer than three weeks is the major risk factor for developing invasive pulmonary aspergillosis.

Allogeneic mesenchymal stem cell infusion for treatment of metachromatic leukodystrophy (MLD) and Hurler syndrome (MPS-IH)

Patients with Hurler syndrome (mucopolysaccharidosis type-IH) and metachromatic leukodystrophy (MLD) develop significant skeletal and neurologic defects that limit their survival. Transplantation of allogeneic hematopoietic stem cells results in partial correction of the clinical manifestations. We postulated that some of these defects may be corrected by infusion of allogeneic, multipotential, bone marrow-derived mesenchymal stem cells (MSC). Patients with Hurler syndrome (n = 5) or MLD (n = 6) who previously underwent successful bone marrow transplantation from an HLA-identical sibling were infused with 2-10 x 10(6)/kg MSCs, isolated and expanded from a bone marrow aspirate of the original donor. There was no infusion-related toxicity. In most recipients culture-purified MSCs at 2 days, 30-60 days and 6-24 months after MSC infusion remained of host type. In two patients the bone marrow-derived MSCs contained 0.4 and 2% donor MSCs by FISH 60 days after MSC infusion. In four patients with MLD there were significant improvements in nerve conduction velocities after MSC infusion. The bone mineral density was either maintained or slightly improved in all patients. There was no clinically apparent change in patients' overall health, mental and physical development after MSC infusion. We conclude that donor allogeneic MSC infusion is safe and may be associated with reversal of disease pathophysiology in some tissues. The role of MSCs in the management of Hurler syndrome and MLD should be further evaluated.

Human marrow-derived mesenchymal stem cells (MSCs) express hematopoietic cytokines and support long-term hematopoiesis when differentiated toward stromal and osteogenic lineages

Human mesenchymal stem cells (MSCs), bone marrow-derived pluripotent adherent cells of mesenchymal origin can differentiate along the osteogenic, chondrogenic, adipogenic, and tendonogenic lineages. In this report we characterize cytokine and growth factor gene expression by MSCs and investigate the modulation of cytokine expression that occurs during osteogenic and stromal differentiation. MSCs constitutively expressed mRNA for interleukin (IL)-6, IL-11, leukemia inhibitory factor (LIF), macrophage colony-stimulating factor (M-CSF), and stem cell factor (SCF). MSCs treated with IL-1alpha upregulated mRNA levels of IL-6, IL-11, and LIF, and began to express detectable levels of granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF). mRNA levels of M-CSF and SCF did not change. MSCs cultured in osteogenic medium differentiated along the osteogenic lineage and downregulated mRNA levels of IL-6, IL-11 and LIF whereas, M-CSF and SCF expression were unchanged and G-CSF and GM-CSF remained undetectable. IL-3 was not detected in MSC culture under any conditions. MSCs precultured in control medium, IL-1alpha, or osteogenic medium maintained similar capacity to support long-term culture initiating cell (LT-CIC). Thus, primary and osteogenic differentiated MSCs produce important hematopoietic cytokines and support hematopoiesis in long-term cultures, suggesting that these cells may provide an excellent ex vivo environment for hematopoiesis during progenitor cell expansion and may be important for in vivo cell therapy.

Clinical relevance of MGMT in the treatment of cancer

Anumber of DNA-damaging chemotherapeutic agents attack the O(6) position on guanine, forming the most potent cytotoxic DNA adducts known. The DNA repair enzyme O(6)-alkylguanine DNA alkyltransferase (AGT), encoded by the gene MGMT, repairs alkylation at this site and is responsible for protecting both tumor and normal cells from these agents. Cells and tissues vary greatly in AGT expression, not only between tissues but also between individuals. AGT activity correlates inversely with sensitivity to agents that form O(6)-alkylguanine DNA adducts, such as carmustine (BCNU), temozolomide, streptozotocin, and dacarbazine. The one exception is those tumors lacking mismatch repair, which renders them resistant to methylating agents. A recent study in patients with gliomas confirmed the correlation between low-level expression of the MGMT gene and response and survival after BCNU. An inhibitor to AGT, O(6)-benzylguanine (BG), depletes AGT in human tumors without associated toxicity and is now in phase II clinical trials. Finally, mutations within the active site region of the MGMT gene render the AGT protein resistant to BG inactivation. As a result, mutant MGMT gene transfer into hematopoietic stem cells has been shown to selectively protect the marrow from the combination of an alkylating agent and BG, while at the same time sensitizing tumor cells. MGMT remains a paradigm for development of new agents that modulate known mechanisms of drug resistance in cancer cells and raise the spectra of combinatorial therapies that encompass known drug resistance mechanisms.

Hematologic effects of linezolid: summary of clinical experience

Linezolid has been associated with reversible myelosuppression. Clinical trial data were evaluated for anemia, thrombocytopenia, and neutropenia. Thrombocytopenia and a slight increased risk for anemia were evident at > or =2 weeks of linezolid treatment. Hematologic abnormalities were consistent with mild, reversible, duration-dependent myelosuppression. Appropriate monitoring is warranted with linezolid use.

Marked inactivation of O6-alkylguanine-DNA alkyltransferase activity with protracted temozolomide schedules

Temozolomide, an oral DNA methylator that inactivates the DNA repair enzyme O(6)-alkylguanine-DNA alkyltransferase (AGAT), has demonstrated anticancer activity on protracted schedules. Protracted schedules may lead to an 'autoenhancement' of temozolomide's inherent cytotoxic potential by cumulative reduction of the cell's capacity for AGAT-mediated DNA repair and resistance. This study was undertaken to characterise AGAT inactivation and regeneration in the peripheral blood mononuclear cells (PBMCs) of patients treated on two protracted temozolomide schedules. O(6)-alkyl guanine-DNA alkyltransferase activity was measured in the PBMCs of patients treated on two phase I protracted temozolomide studies. Patients were treated daily for either 7 days every 2 weeks (Schedule A) or 21 days every 4 weeks (Schedule B). The effects of various temozolomide doses (75-175 mg m(-2)), treatment duration (7-21 days), and temozolomide plasma levels on AGAT inactivation and regeneration, as well as the relation between AGAT inactivation and toxicity, were studied. O(6)-alkyl guanine-DNA alkyltransferase activity in PBMCs was measured serially in 52 patients. Marked inactivation of AGAT occurred following 7 days of temozolomide treatment, with mean AGAT activity decreasing by 72% (P<0.0001). Similarly, mean AGAT activity decreased by 63 and 73% after 14 and 21 days of treatment, respectively (P<0.001 for both comparisons). O(6)-alkyl guanine-DNA alkyltransferase inactivation was greater after 7 days of treatment with higher doses of temozolomide than lower doses and remained markedly reduced 7 days post-treatment. However, AGAT inactivation following temozolomide treatment for 14 and 21 days was similar at all doses. On the continuous 21-day schedule, AGAT inactivation was significantly greater in patients who experienced severe thrombocytopenia than those who did not (90.3+/-5.5 vs 72.5+/-16.1%, P<0.045). In conclusion, protracted administration of temozolomide, even at relatively low daily doses, leads to significant and prolonged depletion of AGAT activity, which may enhance the antitumour activity of the agent.

Metabolic regulation by the mitochondrial phosphatase PTPMT1 is required for hematopoietic stem cell differentiation

The regulation and coordination of mitochondrial metabolism with hematopoietic stem cell (HSC) self-renewal and differentiation is not fully understood. Here we report that depletion of PTPMT1, a PTEN-like mitochondrial phosphatase, in inducible or hematopoietic-cell-specific knockout mice resulted in hematopoietic failure due to changes in the cell cycle and a block in the differentiation of HSCs. Surprisingly, the HSC pool was increased by ∼40-fold in PTPMT1 knockout mice. Reintroduction of wild-type PTPMT1, but not catalytically deficient PTPMT1 or truncated PTPMT1 lacking mitochondrial localization, restored differentiation capabilities of PTPMT1 knockout HSCs. Further analyses demonstrated that PTPMT1 deficiency altered mitochondrial metabolism and that phosphatidylinositol phosphate substrates of PTPMT1 directly enhanced fatty-acid-induced activation of mitochondrial uncoupling protein 2. Intriguingly, depletion of PTPMT1 from myeloid, T lymphoid, or B lymphoid progenitors did not cause any defects in lineage-specific knockout mice. This study establishes a crucial role of PTPMT1 in the metabolic regulation of HSC function.

TISSUE REGENERATION. Inhibition of the prostaglandin-degrading enzyme 15-PGDH potentiates tissue regeneration

Agents that promote tissue regeneration could be beneficial in a variety of clinical settings, such as stimulating recovery of the hematopoietic system after bone marrow transplantation. Prostaglandin PGE2, a lipid signaling molecule that supports expansion of several types of tissue stem cells, is a candidate therapeutic target for promoting tissue regeneration in vivo. Here, we show that inhibition of 15-hydroxyprostaglandin dehydrogenase (15-PGDH), a prostaglandin-degrading enzyme, potentiates tissue regeneration in multiple organs in mice. In a chemical screen, we identify a small-molecule inhibitor of 15-PGDH (SW033291) that increases prostaglandin PGE2 levels in bone marrow and other tissues. SW033291 accelerates hematopoietic recovery in mice receiving a bone marrow transplant. The same compound also promotes tissue regeneration in mouse models of colon and liver injury. Tissues from 15-PGDH knockout mice demonstrate similar increased regenerative capacity. Thus, 15-PGDH inhibition may be a valuable therapeutic strategy for tissue regeneration in diverse clinical contexts.

Cancer stem cells: targeting the roots of cancer, seeds of metastasis, and sources of therapy resistance

With the goal to remove the roots of cancer, eliminate metastatic seeds, and overcome therapy resistance, the 2014 inaugural International Cancer Stem Cell (CSC) Conference at Cleveland, OH, convened together over 320 investigators, including 55 invited world-class speakers, 25 short oral presenters, and 100 poster presenters, to gain an in-depth understanding of CSCs and explore therapeutic opportunities targeting CSCs. The meeting enabled intriguing discussions on several topics including: genetics and epigenetics; cancer origin and evolution; microenvironment and exosomes; metabolism and inflammation; metastasis and therapy resistance; single cell and heterogeneity; plasticity and reprogramming; as well as other new concepts. Reports of clinical trials targeting CSCs emphasized the urgent need for strategically designing combinational CSC-targeting therapies against cancer.

Comparison of O6-alkylguanine-DNA alkyltransferase activity based on cellular DNA content in human, rat and mouse tissues

O6-Alkylguanine-DNA alkyltransferase (alkyltransferase) is the repair protein for O6-alkylguanine, a pre-mutagenic adduct formed by a variety of alkylating agents. Previous comparisons of the repair capacity of O6-alkylguanine in different tissues have expressed the alkyltransferase activity relative to total protein, and have asserted that tissues with low levels of activity were at greater risk for mutagenic damage than tissues with higher levels of activity. Because the alkyltransferase uses DNA as substrate, and because tissues vary greatly in protein content, comparisons of tissue alkyltransferase activity may be more appropriately based on cellular DNA content. We compared alkyltransferase activity relative to tissue DNA content with the activity related to protein content in human, rat and mouse tissues. In each species, liver containing the highest level of activity using either method. In agreement with the findings of others, low levels of alkyltransferase activity relative to protein were seen in human brain, rat brain and small intestine, and mouse kidney. However, based on alkyltransferase activity relative to DNA content, low levels of activity were seen in human bone marrow myeloid precursors, rat bone marrow, brain and intestine, and mouse spleen and bone marrow. The range of activity between tissues was 18-fold in human, 15-fold in rat and 8-fold in mouse. In general, the rank of alkyltransferase activity relative to DNA for each tissue was human greater than rat greater than mouse. These results suggest that the mouse is more susceptible to nitrosoureas than rat or human. In each species, the organs with low levels of alkyltransferase activity relative to tissue DNA content would appear to be targets for mutagenic damage following nitrosourea exposure.

Targeted Modulation of MGMT: Clinical Implications: Fig. 1

O(6)-Methylguanine DNA methyltransferase (MGMT) has been studied for >20 years as a gene that is associated with the mutagenicity and cytotoxicity induced by either methylating carcinogens or alkylating (methylating and chloroethylating) therapeutic agents. Pioneering studies of alkylating agents identified alkylated guanine at the O(6) position, the substrate of MGMT, as a potentially promutagenic and lethal toxic DNA lesion. MGMT plays a prominent role in DNA adduct repair that limits the mutagenic and cytotoxic effect of alkylating agents. Because of its role in cancer etiology and chemotherapy resistance, MGMT is of particular interest. In this article, the clinical effect of MGMT expression and targeted modulation of MGMT will be summarized.

Endothelial Kruppel-like factor 4 protects against atherothrombosis in mice

The endothelium regulates vascular homeostasis, and endothelial dysfunction is a proximate event in the pathogenesis of atherothrombosis. Stimulation of the endothelium with proinflammatory cytokines or exposure to hemodynamic-induced disturbed flow leads to a proadhesive and prothrombotic phenotype that promotes atherothrombosis. In contrast, exposure to arterial laminar flow induces a gene program that confers a largely antiadhesive, antithrombotic effect. The molecular basis for this differential effect on endothelial function remains poorly understood. While recent insights implicate Kruppel-like factors (KLFs) as important regulators of vascular homeostasis, the in vivo role of these factors in endothelial biology remains unproven. Here, we show that endothelial KLF4 is an essential determinant of atherogenesis and thrombosis. Using in vivo EC-specific KLF4 overexpression and knockdown murine models, we found that KLF4 induced an antiadhesive, antithrombotic state. Mechanistically, we demonstrated that KLF4 differentially regulated pertinent endothelial targets via competition for the coactivator p300. These observations provide cogent evidence implicating endothelial KLFs as essential in vivo regulators of vascular function in the adult animal.

Bone marrow-derived mesenchymal stem cells remain host-derived despite successful hematopoietic engraftment after allogeneic transplantation in patients with lysosomal and peroxisomal storage diseases

Human bone marrow contains mesenchymal stem cells (MSCs) that can differentiate into various cells of mesenchymal origin. We developed an efficient method of isolating and culture expanding a homogenous population of MSCs from bone marrow and determined that MSCs express alpha-L-iduronidase, arylsulfatase-A and B, glucocerebrosidase, and adrenoleukodystrophy protein. These findings raised the possibility that MSCs may be useful in the treatment of storage disorders. To determine if donor derived MSCs are transferred to the recipients with lysosomal or peroxisomal storage diseases by allogeneic hematopoietic stem cell (HSC) transplantation, we investigated bone marrow derived MSCs of 13 patients 1-14 years after allogeneic transplantation. Highly purified MSCs were genotyped either by fluorescence in situ hybridization using probes for X and Y-chromosomes in gender mis-matched recipients or by radiolabeled PCR amplification of polymorphic simple sequence repeats. Phenotype was determined by the measurement of disease specific protein/enzyme activity in purified MSCs. We found that MSCs isolated from recipients of allogeneic HSC transplantation are not of donor genotype and have persistent phenotypic defects despite successful donor type hematopoietic engraftment. Whether culture expanded normal MSCs can be successfully transplanted into patients with storage diseases and provide therapeutic benefit needs to be determined.

The prevention of thymic lymphomas in transgenic mice by human O6-alkylguanine-DNA alkyltransferase

Nitrosoureas form O6-alkylguanine-DNA adducts that are converted to G to A transitions, the mutation found in the activated ras oncogenes of nitrosourea-induced mouse lymphomas and rat mammary tumors. These adducts are removed by the DNA repair protein O6-alkylguanine-DNA alkyltransferase. Transgenic mice that express the human homolog of this protein in the thymus were found to be protected from developing thymic lymphomas after exposure to N-methyl-N-nitrosourea. Thus, transgenic expression of a single human DNA repair gene is sufficient to block chemical carcinogenesis. The transduction of DNA repair genes in vivo may unravel mechanisms of carcinogenesis and provide therapeutic protection from known carcinogens.

Quantitative H2S-mediated protein sulfhydration reveals metabolic reprogramming during the integrated stress response

The sulfhydration of cysteine residues in proteins is an important mechanism involved in diverse biological processes. We have developed a proteomics approach to quantitatively profile the changes of sulfhydrated cysteines in biological systems. Bioinformatics analysis revealed that sulfhydrated cysteines are part of a wide range of biological functions. In pancreatic β cells exposed to endoplasmic reticulum (ER) stress, elevated H2S promotes the sulfhydration of enzymes in energy metabolism and stimulates glycolytic flux. We propose that transcriptional and translational reprogramming by the integrated stress response (ISR) in pancreatic β cells is coupled to metabolic alternations triggered by sulfhydration of key enzymes in intermediary metabolism.

LacZ and interleukin-3 expression in vivo after retroviral transduction of marrow-derived human osteogenic mesenchymal progenitors

Human marrow-derived mesenchymal progenitor cells (hMPCs), which have the capacity for osteogenic and marrow stromal differentiation, were transduced with the myeloproliferative sarcoma virus (MPSV)-based retrovirus, vM5LacZ, that contains the LacZ and neo genes. Stable transduction and gene expression occurred in 18% of cells. After culture expansion and selection in G418, approximately 70% of neo(r) hMPCs co-expressed LacZ. G418-selected hMPC retain their osteogenic potential and form bone in vivo when seeded into porous calcium phosphate ceramic cubes implanted subcutaneously into SCID mice. LacZ expression was evident within osteoblasts and osteocytes in bone developing within the ceramics 6 and 9 weeks after implantation. Likewise, hMPCs transduced with human interleukin-3 (hIL-3) cDNA, adhered to ceramic cubes and implanted into SCID mice, formed bone and secreted detectable levels of hIL-3 into the systemic circulation for at least 12 weeks. These data indicate that genetically transduced, culture-expanded bone marrow-derived hMPCs retain a precursor phenotype and maintain similar levels of transgene expression during osteogenic lineage commitment and differentiation in vivo. Because MPCs have been shown to differentiate into bone, cartilage, and tendon, these cells may be a useful target for gene therapy.

DNA repair defects in stem cell function and aging

Cellular DNA is under constant challenge by exogenous and endogenous genotoxic stress, which results in both transient and accumulated DNA damage and genomic instability. All cells are equipped with DNA damage response pathways that trigger DNA repair, cell cycle arrest, and, if need be, apoptosis, to eliminate DNA damage or damaged cells. The consequences of these processes for stem cells can be profound: diminution in stem cell pools, or, because of altered gene expression, an increased chance for stem cell differentiation or malignant transformation. Furthermore, a number of DNA repair abnormalities are linked to premature aging syndromes, and these are associated with defects in the stem cell population. The specific DNA repair systems for which there are data regarding the impact of repair defects on stem cell function include O(6)-alkylguanine DNA alkyltransferase, nucleotide excision repair, base excision repair, mismatch repair, non-homologous DNA end-joining Fanconi's anemia protein complex, and homologous recombination. It has recently become clear that deficiencies of these processes are associated not only with cancer and/or aging but also with stem cell defects. This discovery raises the possibility of a link between aging and stem cell dysfunction. In this review, we provide evidence for a link between DNA repair systems and the maintenance and longevity of stem cells.

Human bone marrow-derived mesenchymal (stromal) progenitor cells (MPCs) cannot be recovered from peripheral blood progenitor cell collections

The purpose of this study was to compare the ability to collect human bone marrow-derived mesenchymal (stromal) progenitor cells (MPC) from bone marrow versus peripheral blood hematopoietic progenitor cell (PBPC) collections using in vitro and in vivo assays. Ten milliliter samples of PBPC collections mobilized from 11 patients undergoing autotransplants using chemotherapy followed by G-CSF 5-10 micrograms/kg were evaluated using in vitro and in vivo assays for hematopoietic progenitors and MPCs. Additionally, 10 ml samples of unstimulated bone marrow aspirates as well as PBPC collected after mobilization using G-CSF 10 micrograms/kg obtained from 3 normal, histocompatible allogeneic donors were analyzed for hematopoietic progenitors and MPCs. The MPCs were isolated and culture-expanded as adherent cells in vitro and subsequently tested for the capacity to differentiate into mesenchymal phenotypes in vivo using calcium hydroxyapatite porous ceramic cubes implanted s.c. in athymic mice. Demineralized sections of these cubes were analyzed histologically for the appearance of bone and cartilage. Seven autotransplant subjects with cancer received G-CSF after chemotherapy administration, whereas 4 cancer patients and all 3 normal donors received G-CSF alone as the mobilizing regimen. For the autologous PBPC collections and the normal marrow aspirations, median hematopoietic progenitor content was in the normal range for our institution. MPCs were detected in in vitro cultures and as bone-positive ceramic cubes in samples of all 3 allogeneic donor bone marrows but in none of the 14 autologous and 6 allogeneic PBPC collections. In conclusion, MPCs could not be recovered in PBPC collections obtained from either normal donors or patients who underwent PBPC collections after mobilization therapy but could be obtained routinely from bone marrow samples. Although the role of transplanted MPCs is an area of clinical investigation, this study points out a fundamental differences in the population of cells transplanted after collection from bone marrow versus peripheral blood.

Concise Reviews: Cancer Stem Cell Targeted Therapies: Toward Clinical Success

Cancer stem cells (CSCs) are a subpopulation of cells within tumors that possess the stem cell characteristics of self-renewal, quiescence, differentiation, and the ability to recapitulate the parental tumor when transplanted into a host. CSCs are correlated with poor clinical outcome due to their contribution to chemotherapy resistance and metastasis. Multiple cell surface and enzymatic markers have been characterized to identify CSCs within a heterogeneous tumor, and here we summarize ongoing preclinical and clinical efforts to therapeutically target these cells and improve patient outcomes. Stem Cells Translational Medicine 2019;8:75-81.