Primary brain tumor representation in the post-traumatic growth literature: A scoping review

Background

Post-traumatic growth (PTG) has been extensively explored within general oncology, yet little is known about the experience of PTG in neuro-oncology. This study aimed to determine the representation of patients with primary brain tumors (PBT) in the PTG literature.

Methods

PsycINFO, PubMed, and CINAHL were systematically searched from inception to December 2022. Search terms were related to personal growth and positive reactions to cancer. Articles were first screened by titles and abstracts, then full texts were reviewed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses method.

Results

A total of 382 articles met the inclusion criteria. Of those, 13 included patients with PBT. Over 100 000 cancer patients were represented, with 0.79% having a PBT. Most research focused on low-grade gliomas. PTG negatively correlated with post-traumatic stress symptoms and avoidant coping. In the sole longitudinal study, patients with PBT demonstrated improved PTG after 1 year. Three quasi-experimental studies investigated the effect of mindfulness-based interventions with mixed-cancer samples and demonstrated improvement in PTG.

Conclusions

The inclusion rate of patients with PBT in the PTG literature was significantly lower than the population prevalence rate (1.3% of cancer diagnoses). Relatively few studies focused exclusively on how patients with PBT experience PTG (k = 5), and those that did only included low-grade glioma. The experience of PTG in those with high-grade glioma remains unknown. Patients with PBT are scarcely included in research on PTG interventions. Few studies examined the relationship between PTG and medical, cognitive, or psychological characteristics. Our understanding of the PTG experience in neuro-oncology remains extremely limited.

Measuring and understanding death anxiety in caregivers of patients with primary brain tumor

OBJECTIVE

Caregivers of patients with primary brain tumor (PBT) describe feeling preoccupied with the inevitability of their loved one's death. However, there are currently no validated instruments to assess death anxiety in caregivers. This study sought to examine (1) the psychometric properties of the Death and Dying Distress Scale (DADDS), adapted for caregivers (DADDS-CG), and (2) the prevalence and correlates of death anxiety in caregivers of patients with PBT.

METHODS

Caregivers (N = 67) of patients with PBT completed the DADDS-CG, Patient Health Questionnaire (PHQ-9), Generalized Anxiety Disorder (GAD-7), Fear of Cancer Recurrence (FCR-7), and God Locus of Health Control (GLHC). Caregivers' sociodemographic information and patients' medical characteristics were also collected. Preliminary examination of the psychometric properties of the DADDS-CG was conducted using exploratory factor analysis, Cronbach's alpha, and correlations. The prevalence and risk factors of death anxiety were assessed using frequencies, pair-wise comparisons, and correlations.

RESULTS

Factor analysis of the DADDS-CG revealed a two-factor structure consistent with the original DADDS. The DADDS-CG demonstrated excellent internal consistency, convergent validity with the PHQ-9, GAD-7, and FCR-7, and discriminant validity with the GLHC. Over two-thirds of caregivers reported moderate-to-severe symptoms of death anxiety. Death anxiety was highest in women and caregivers of patients with high-grade PBT.

SIGNIFICANCE OF RESULTS

The DADDS-CG demonstrates sound psychometric properties in caregivers of patients with PBT, who report high levels of death anxiety. Further research is needed to support the measure's value in clinical care and research - both in this population and other caregivers - in order to address this unmet, psychosocial need.

A constructivist grounded theory exploration of Mindfulness for Healthcare Professional students

BACKGROUND AND PURPOSE

To better understand the effects of an intervention, Mindfulness for Healthcare Professional (MIHP), and how it may improve healthcare professional student (HCP) functioning, a constructivist grounded theory exploration was conducted.

MATERIALS AND METHODS

Ten participants with the lowest or highest changes on quantitative measures of burnout and perceived stress at the end of MIHP were interviewed at a long-term follow-up. A theoretical framework was developed from the resultant themes to describe the mechanisms by which MIHP had effects on work-relevant functioning.

RESULTS

Three overarching themes emerged as mechanisms of change both from their presence in those participants reporting an improvement in stress and their missingness from those participants who reported no change: developing a mindfulness practice, integrating practice into daily life, and enhanced awareness. These mechanisms led to optimized work-relevant functioning: 1) emotional competencies, including nonjudgement, emotion regulation, and burnout prevention; and 2) patient-centered care, including improved listening, patience, and efficiency at work.

CONCLUSION

The resultant framework is discussed in the context of previous literature on MIHP and mindfulness theory more broadly. Implications for future disseminations of MIHP encourage the use of group interventions with emphasis on developing at-home practice and informal mindfulness integrated into daily work.

Maintenance of Effects and Correlates of Changes Following Mindfulness for Interdisciplinary Health Care Professional Students

OBJECTIVES

To evaluate long-term outcomes after an 8-week mindfulness intervention, Mindfulness for Interdisciplinary Health Care Professionals (MIHP), and investigate relationships between outcomes overtime.

DESIGN/METHODS

In this single-arm study, 35 participants received MIHP and completed measures of burnout, perceived stress, activity impairment, and dispositional mindfulness at baseline, post-MIHP, and a 3-month follow-up. Changes over time were evaluated using repeated-measures analysis of variance (ANOVA) and reliable change indices (RCIs). Then, correlations between dispositional mindfulness and distress/impairment outcomes were evaluated.

RESULTS

At follow-up, aspects of burnout and several mindfulness skills demonstrated maintained improvements. RCIs showed that a higher percentage of participants improved on all outcomes at each time period than declined-all outcomes showed little to no deterioration. However, most participants did not reliably change, and this was more pronounced at the follow-up. Changes in two mindfulness skills (acting with awareness and nonjudging of inner experience) were consistently negatively correlated with distress and impairment outcomes.

CONCLUSIONS

Acquired mindfulness skills during MIHP were maintained at the follow-up. RCI analyses demonstrated that MIHP may protect against worsening stress and burnout during training. Two mindfulness skills, acting with awareness and nonjudging of inner experience, showed potential mechanistic effects on work-relevant outcomes. Booster sessions to encourage maintained mindfulness practices and skills should be investigated in future trials. This study was registered on clinicaltrials.gov (#NCT03403335) on January 11, 2018.

Introducing FCR 6 – Brain: Measuring Fear of Cancer Recurrence in Brain Tumor Patients and Their Caregivers

Background

Fear of cancer recurrence (FCR) is a psychological consequence of cancer diagnosis that impacts quality of life in neuro-oncology. However, the instruments used to assess FCR have not been tested for validity in patients with brain tumors. The present study explored the psychometric properties of a brief FCR scale in patients with primary brain tumor (PBT) and their caregivers.

Methods

Adult patients with PBT (n = 165) and their caregivers (n = 117) completed the FCR–7-item scale (FCR7) and measures of psychological functioning. Exploratory factor analyses (EFA) were conducted for both patient and caregiver FCR7. Convergent validity, prevalence, the difference between FCR in patients and caregivers, and relationships with relevant medical and demographic variables were explored.

Results

EFAs revealed a single factor with one item demonstrating poor loading for both patients and caregivers. Removal of the item measuring hypervigilance symptoms (checking for physical signs of tumor) greatly improved the single factor metrics. The amended scale (FCR6-Brain) demonstrated good convergent validity. Caregiver FCR was significantly higher than patient. Clinical guidance to identify clinically significant FCR was introduced. Age, gender, and time since diagnosis were related to FCR, with higher FCR in younger women more recently diagnosed.

Conclusions

The FCR6-Brain is the first validated instrument to assess FCR in this population and should be used to identify individuals at risk for FCR and guide development of future psychotherapeutic interventions. This study highlights the distinct characteristics of FCR in neuro-oncology. Symptoms of hypervigilance in PBT patients need further investigation.

Managing cancer and living meaningfully (CALM) in adults with malignant glioma: a proof-of-concept phase IIa trial

BACKGROUND

Managing Cancer and Living Meaningfully (CALM) is an evidence-based, brief, semi-structured psychotherapy designed to help patients with advanced cancer cope with the practical and profound challenges of their illness. However, no study to date has investigated its feasibility, acceptability, and preliminary effectiveness in adults with malignant glioma, despite the well-documented incidence of psychological distress in this vulnerable and underserved population.

METHODS

Fourteen patients with glioma and elevated symptoms of depression and/or death anxiety enrolled in the trial: 83% glioblastoma, 75% female, M_age = 56 years (SD = 15.1; range = 27-81). Feasibility was assessed based on established metrics. Acceptability was measured by post-session surveys and post-intervention interviews. Preliminary intervention effects were explored using paired t-tests, comparing psychological distress at baseline and post-intervention.

RESULTS

Of the 14 enrolled patients, 12 were evaluable. Nine completed the study (75% retention rate). Three patients withdrew due to substantial disease progression which affected their ability to participate. Participants reported high perceived benefit, and all recommended the program to others. Baseline to post-intervention assessments indicated reductions in death anxiety, generalized anxiety, and depression, and increases in spirituality. Quality of life and fear of cancer recurrence remained stable throughout the study period.

CONCLUSIONS

CALM appears feasible for use with adults with malignant glioma. Enrollment and retention rates were high and comparable to psychotherapy trials for patients with advanced cancer. High perceived benefit and reductions in symptoms of death anxiety, generalized anxiety, and depression were reported by participants. These findings are extremely encouraging and support further study of CALM in neuro-oncology.

TRIAL REGISTRATION NUMBER

NCT04646213 registered on 11/27/2020.

Comparison of conventional and actuarial neuropsychological criteria for mild cognitive impairment in a clinical setting

INTRODUCTION

Evidence-based practice in neuropsychology involves the use of validated tests, cutoff scores, and interpretive algorithms to identify clinically significant cognitive deficits. Recently, actuarial neuropsychological criteria (ANP) for identifying mild cognitive impairment were developed, demonstrating improved criterion validity and temporal stability compared to conventional criteria (CNP). However, benefits of the ANP criteria have not been investigated in non-research, clinical settings with varied etiologies, severities, and comorbidities. This study compared the utility of CNP and ANP criteria using data from a memory disorders clinic.

METHOD

Data from 500 non-demented older adults evaluated in a Veterans Affairs Medical Center memory disorders clinic were retrospectively analyzed. We applied CNP and ANP criteria to the Repeatable Battery for the Assessment of Neuropsychological Status, compared outcomes to consensus clinical diagnoses, and conducted cluster analyses of scores from each group.

RESULTS

The majority (72%) of patients met both the CNP and ANP criteria and both approaches were susceptible to confounding factors such as invalid test data and mood disturbance. However, the CNP approach mislabeled impairment in more patients with non-cognitive disorders and intact cognition. Comparatively, the ANP approach misdiagnosed patients with depression at a third of the rate and those with no diagnosis at nearly half the rate of CNP. Cluster analyses revealed groups with: 1) minimal impairment, 2) amnestic impairment, and 3) multi-domain impairment. The ANP approach yielded subgroups with more distinct neuropsychological profiles.

CONCLUSIONS

We replicated previous findings that the CNP approach is over-inclusive, particularly for those determined to have no cognitive disorder by a consensus team. The ANP approach yielded fewer false positives and better diagnostic specificity than the CNP. Despite clear benefits of the ANP vs. CNP, there was substantial overlap in their performance in this heterogeneous sample. These findings highlight the critical role of clinical interpretation when wielding these empirically-derived tools.

Subjective executive dysfunction in patients with primary brain tumors and their informants: relationships with neurocognitive, psychological, and daily functioning

OBJECTIVE

We assessed agreement between patient- and informant-report on the Behavior Rating Inventory of Executive Function - Adult (BRIEF-A) in patients with primary brain tumors (PBT) and differences on BRIEF-A in neurocognitive (intact v. impaired), psychological (asymptomatic v. distressed), and functional (independent v. dependent) categories using both patient- and informant-report.

METHOD

PBT patients (n = 102) completed neuropsychological evaluations including the BRIEF-A, clinical interview, neurocognitive tests, and mood questionnaires. Correlations between the BRIEF-A and Informant (n = 39) were conducted. Differences in patient and informant BRIEF-A indices were investigated across five classifications: neurocognitive functioning, psychological functioning, medication management, appointment management, and finance management.

RESULTS

Patient and informant BRIEF were correlated. There was no difference on BRIEF-A or Informant indices for intact v. impaired neurocognitive status. Higher BRIEF-A and Informant indices were observed among psychologically distressed v. asymptomatic patients. Results showed higher BRIEF indices among those requiring assistance with medication, appointments, and finances.

CONCLUSIONS

Patients and informants agreed in their reports of executive function (EF). These reports, while not different in neurocognitive classification, were different in psychological functioning and in those needing assistance with instrumental activities of daily living (IADL). Patient- and informant-reported EF may provide important data regarding psychological and IADL functioning in this population.

Death anxiety in patients with primary brain tumor: Measurement, prevalence, and determinants

OBJECTIVE

This study investigated death anxiety in patients with primary brain tumor (PBT). We examined the psychometric properties of two validated death anxiety measures and determined the prevalence and possible determinants of death anxiety in this often-overlooked population.

METHODS

Two cross-sectional studies in neuro-oncology were conducted. In Study 1, 81 patients with PBT completed psychological questionnaires, including the Templer Death Anxiety Scale (DAS). In Study 2, 109 patients with PBT completed similar questionnaires, including the Death and Dying Distress Scale (DADDS). Medical and disease-specific variables were collected across participants in both studies. Psychometric properties, including construct validity, internal consistency, and concurrent validity, were investigated. Levels of distress were analyzed using frequencies, and determinants of death anxiety were identified using logistic regression.

RESULTS

The DADDS was more psychometrically sound than the DAS in patients with PBT. Overall, 66% of PBT patients endorsed at least one symptom of distress about death and dying, with 48% experiencing moderate-severe death anxiety. Generalized anxiety symptoms and the fear of recurrence significantly predicted death anxiety.

SIGNIFICANCE OF RESULTS

The DADDS is a more appropriate instrument than the DAS to assess death anxiety in neuro-oncology. The proportion of patients with PBT who experience death anxiety appears to be higher than in other advanced cancer populations. Death anxiety is a highly distressing symptom, especially when coupled with generalized anxiety and fears of disease progression, which appears to be the case in patients with PBT. Our findings call for routine monitoring and the treatment of death anxiety in neuro-oncology.

Demographic differences in performance validity test failure

OBJECTIVE

The present study investigated demographic differences in performance validity test (PVT) failure in a Veteran sample.

METHOD

Data were extracted from clinical neuropsychological evaluations. Only veterans who identified as men, as either European American/White (EA) or African American/Black (AA) were included (n = 1261). We investigated whether performance on two frequently used PVTs, the Test of Memory Malingering (TOMM), and the Medical Symptom Validity Test (MSVT), differed by age, education, and race using separate logistic regressions.

RESULTS

Veterans with younger age, less education, and Veterans Affairs (VA) service-connected disability were significantly more likely to fail both PVTs. Race was not a significant predictor of MSVT failure, but AA patients were significantly more likely than EA patients to fail the TOMM. For all significant demographic predictors in the models, effects were small. In a subsample of patients who were given both PVTs (n = 461), the effects of race on performance remained.

CONCLUSIONS

Performance on the TOMM and MSVT differed by age and level of education. Performance on the TOMM differed between EA and AA patients, whereas performance on the MSVT did not. These results suggest that demographic factors may play a small but measurable role in performance on specific PVTs.

Examining fear of cancer recurrence in primary brain tumor patients and their caregivers using the Actor-Partner Interdependence Model

OBJECTIVE

Fear of cancer recurrence (FCR) is related to psychological distress and poor quality of life in cancer patients and their caregivers. However, no studies have investigated FCR in neuro-oncology. Given the varied prognosis, treatment, and disease trajectory of brain cancer, FCR may affect patients and their caregivers differently.

METHODS

Eighty adult primary brain tumor (PBT) patients and 52 caregivers completed questionnaires assessing FCR and psychological distress (depressive symptoms, generalized anxiety, and death anxiety). Differences in patient and caregiver FCR by demographic and medical characteristics were examined. Using multilevel modeling, the Actor-Partner Interdependence Model (APIM) was used to investigate the interrelationship between patient and caregiver FCR with demographics and psychological distress measures.

RESULTS

Caregivers reported significantly higher FCR than patients. There were no effects of demographic or medical characteristics on patient FCR. Time since diagnosis was negatively related to caregiver FCR. All measures of psychological distress exerted a significant actor effect on FCR among both patients and caregivers. Two partner effects were found: caregiver depressive symptoms and death anxiety negatively predicted patients' FCR.

CONCLUSIONS

This is the first investigation of FCR in PBT patients and their caregivers. Most demographic and medical characteristics were not related to patient or caregiver FCR. Caregiver FCR may be higher at the time of diagnosis and decrease over time. APIMs revealed actor effects on patient and caregiver FCR for all measures of psychological distress. Results demonstrated the dyadic effects of a brain tumor diagnosis, emphasizing the need to include caregivers in psychotherapy for neuro-oncology patients.

Brief Yoga Intervention for Dental and Dental Hygiene Students: A Feasibility and Acceptability Study

The present study investigated whether a brief yoga intervention would be feasible and acceptable for dental students. Based on empirical evidence about state mindfulness (SM), change in self-reported SM was assessed as a measure of the intervention's feasibility and acceptability. A repeated-measures within-subjects design was used. Participants were third- and fourth-year dental and dental hygiene students (76% female). The State Mindfulness Scale (SMS), a validated self-report measure of SM with 2 subscales, Mind and Body, was used. Students (n = 132) completed the SMS immediately prior to and following a 1-hour yoga intervention. Dispositional mindfulness, burnout, perceived stress, and depressive symptoms were also investigated as moderators of changes in state mindfulness to determine whether psychological variables had an effect on feasibility in this sample. Total SM significantly increased from pre- to post-intervention, t(46) = 10.26, P < .001. An analysis of covariance showed a significant interaction effect in the relationship between pre-/post-intervention SM of Mind (β = 0.51, P = .048), such that higher levels of stress saw greater increases in SM of Mind. No other psychological variables were significant moderators. A brief yoga intervention for dental students significantly increased SM, suggesting that yoga interventions may be feasible and acceptable in this population. The results of moderation analyses suggest that a brief yoga intervention may be especially effective at increasing SM for those with high levels of stress. Future research should use a randomized control group to test group differences in SM after a brief yoga intervention for dental students.

Can mindfulness in health care professionals improve patient care? An integrative review and proposed model

Mindfulness in health care professionals (HCPs) is often discussed as a tool for improving patient care outcomes, yet there has not been a critical evaluation of the evidence, despite a growing body of research on mindfulness-based interventions (MBIs). Numerous mechanisms exist by which mindfulness in HCPs may have an effect on patient care, and the field lacks an integrated model to guide future investigations into how MBIs may exert effects. The primary goals of this integrative review are to evaluate the evidence for the impact of MBIs in HCPs on patient care outcomes and to propose a causal model to guide future research. Databases were systematically searched for eligible studies investigating either an MBI or a measure of dispositional mindfulness in HCPs on patient care outcomes. Studies were critically evaluated using a previously developed tool. Twenty-six studies were identified (N = 1,277), which provide strong support for effects of mindfulness on HCP-reported patient care. Moderate support was found for patient safety, patient treatment outcomes, and patient-centered care. There was overall weak evidence to support a relationship between HCP-mindfulness on patient satisfaction. Mindfulness in HCPs may be related to several aspects of patient care.

Being Mindful: A Long-term Investigation of an Interdisciplinary Course in Mindfulness

Background

Burnout and work-related stress in health-care professionals (HCPs) is a growing concern to the optimal functioning of the health-care system. Mindfulness-based interventions may be well-suited to address burnout in HCPs.

Objective

The purpose of this study was (1) to quantitatively evaluate the effect of a mindfulness-based intervention for interdisciplinary HCPs over time and at a long-term follow-up and (2) to explore perceived benefits, facilitators, and barriers to the practice of mindfulness at the long-term follow-up.

Design

A mixed-method, repeated measures, within-subjects design was used to investigate Mindfulness for Interdisciplinary HCPs (MIHP) at baseline, post-MIHP, and a follow-up (6 months to 1.5 years after MIHP). MIHP is an 8-week, group-based course for interdisciplinary HCPs and students, with weekly meditation training, gentle yoga, and discussions on the application of mindfulness to common stressors faced by HCPs. Main outcome measures were the Maslach Burnout Inventory—Health Services Survey and the Five Facet Mindfulness Questionnaire. A semistructured interview was used to explore participants’ perceptions of sustained effects and practice in the context of HCP work at the long-term follow-up. The study protocol was registered with ClinicalTrials.gov (NCT02736292).

Results

Eighteen HCPs (88% female) participated in the study. Significant reductions were found after the intervention for 2 subscales of burnout: depersonalization, F(2, 17) = 5.98, P = .01, and emotional exhaustion, F(2, 17) = 2.64, P = .10. Three facets of dispositional mindfulness showed significant increases at long-term follow-up, act aware: F(2, 15) = 4.47, P = .03, nonjudge: F(2, 15) = 4.7, P = .03, and nonreactivity: F(2, 15) = 3.58, P = .05. Continued practice of skills long term was facilitated by the use of informal practice and perceived improvement in work and personal life.

Conclusion

In sum, MIHP improved subscales of burnout and mindfulness. These findings should be further explored with a larger, controlled study. Interventions should focus on developing mindfulness practice that can be integrated into the work of HCPs.

Larval Bradysia impatiens (Diptera: Sciaridae) potential for vectoring Pythium root rot pathogens

A series of laboratory experiments were conducted to investigate the capacity of Bradysia impatiens (Johannsen) larvae to ingest propagules from two strains each of Pythium aphanidermatum (Edson) Fitzp. and P. ultimum Trow and transmit the pathogens to healthy geranium seedlings on a filter-paper substrate in petri dishes. The capacity of fungus gnat larvae to transmit P. aphanidermatum to seedlings rooted in a commercial peat-based potting mix and germination of Pythium oospores and hyphal swellings before and after passage through the guts of larval fungus gnats were also examined. Assays revealed that Pythium spp. transmission by larval fungus gnats varied greatly with the assay substrate and also with the number and nature of ingested propagules. Transmission was highest (65%) in the petri dish assays testing larvae fed P. aphanidermatum K-13, a strain that produced abundant oospores. Transmission of strain K-13 was much lower (<6%) in plug cells with potting mix. Larvae were less efficient at vectoring P. ultimum strain PSN-1, which produced few oospores, and no transmission was observed with two non-oospore-producing strains: P. aphanidermatum Pa58 and P. ultimum P4. Passage of P. aphanidermatum K-13 through larval guts significantly increased oospore germination. However, decreased germination of hyphal swellings was observed following larval gut passage for strains of P. ultimum. These results expand previous studies suggesting that larval fungus gnats may vector Pythium spp.

Fungus gnat feeding and mechanical wounding inhibit Pythium aphanidermatum infection of geranium seedlings

ABSTRACT A series of laboratory tests were conducted to investigate potential effects of fungus gnat (Bradysia impatiens) feeding damage on susceptibility of geranium seedlings (Pelargonium x hortorum) to infection by the root rot pathogen Pythium aphanidermatum. Effects were compared with those from similar tests in which the seedlings were mechanically wounded by severing the root tip with a scalpel. Assays of geranium seedlings in petri dishes revealed a pronounced negative fungus gnat-Pythium interaction, with exposure to fungus gnat larvae 24 h prior to inoculation with P. aphanidermatum zoospores resulting in up to 47% fewer seedling deaths than would have been expected if the two agents had acted independently. Similar results were observed when seedlings were subjected to mechanical wounding 24 h prior to zoospore inoculation. In contrast, no interaction occurred when seedlings were mechanically wounded immediately prior to inoculation. The degree of plant damage inflicted by the feeding activities of the larval fungus gnats had no significant effect on the combined damage from fungus gnats and Pythium in petri dishes. Ancillary studies showed that Pythium development on V8 agar was not inhibited by the presence of fungus gnat-associated microorganisms, nor were seedlings inoculated with these microbes less susceptible to Pythium infection. The precise mechaism or mechanisms underlying the observed interactions were not elucidated; however, the results strongly suggest that both fungus gnat feeding and mechanical wounding activated systemic defenses that made the seedlings more resistant to Pythium infection.

The interphase microtubule damage checkpoint defines an S-phase commitment point and does not require p21(waf-1)

Cell cycle checkpoints ensure orderly progression of events during cell division. A microtubule damage (MTD)-induced checkpoint has been described in G(1) phase of the cell cycle (G(1)MTC) for which little is known. The present study shows that the G(1)MTC is intact in activated T lymphocytes from mice with the p21(waf-1) gene deleted. However, p21(waf-1) gene deletion does affect the ratio of cells that arrest at the G(1)MTC and the spindle checkpoint after MTD. The G(1)MTC arrests T lymphocytes in G(1) prior to cdc2 up-regulation and prior to G(1) arrest by p21(waf-1). Once cells have progressed past the G(1)MTC, they are committed to chromosome replication and metaphase progression, even with extreme MTD. The G(1)MTC is also present in a human myeloid cell line deficient in p21(waf-1) gene expression. The p21-independent G(1)MTC may be important in cellular responses to MTD such as those induced by drugs used to treat cancer.

Transcriptional and ERK1/2-dependent synergistic upregulation of p21(cip1/waf1) associated with steel factor synergy in MO7e

Steel factor (SLF) plus GM-CSF induces proliferative synergy in myeloid progenitors and factor-dependent cell line MO7e. We previously reported that the protein level of cyclin-dependent kinase inhibitor p21(cip1/waf1) (p21) increased synergistically when MO7e cells were stimulated with SLF plus GM-CSF and that p21 induction was required for SLF synergistic responses. Here we show that this p21 induction is regulated at the transcriptional level. Based on use of a multiprobe RNase protection assay, the synergistic increase of p21 mRNA was unique among many cell cycle regulators. While STAT5A and 5B were activated after stimulation with GM-CSF alone or SLF plus GM-CSF, there was no difference in activation between the groups. p44/42 MAP kinase (ERK1/2) was synergistically activated by SLF plus GM-CSF, but SAPK/JNK and p38 MAP kinase were not. Synergistic induction of p21 was significantly decreased with a MEK1 inhibitor, suggesting that the ERK1/2 pathway is involved in the synergistic increase of p21 after GM-CSF plus SLF stimulation.

Co-transduction of cDNAs for c-kit and steel factor into single CD34+ cord blood cells further enhances the growth of erythroid and multipotential progenitors

Previous studies have demonstrated that the c-kit encoded tyrosine kinase receptor and its ligand, steel factor (SLF), are critical for normal blood cell development. We have reported that transduction of the c-kit gene into single hematopoietic progenitor cells (HPC), CD34(+++) cells, from cord blood (CB) enhances erythroid colony formation via a SLF-dependent mechanism. We therefore decided to evaluate the impact on cell proliferation of co-transducing c-kit and SLF cDNAs into these cells. CD34(+++) cells were sorted as a population or as 1 cell/well for cells expressing the highest levels of CD34 and different levels of c-kit. Cells were then prestimulated with granulocyte macrophage (GM)-colony stimulating factor (CSF), interleukin (IL)-3, IL-6, erythropoietin (Epo) in the presence and absence of various concentrations of SLF. Cells were then transduced with SLF and/or c-kit cDNAs, and then assayed for colony formation with the same cytokine combination. At a single cell level, co-transduction with c-kit and SLF genes significantly enhanced colony formation compared with individual gene transduction, especially by erythroid and multipotential progenitors that responded to stimulation by added cytokines. Little or no growth was seen with the c-kit- and/or SLF-transduced cells without addition of cytokines. The degree of enhancement effected by co-transduction inversely correlated with the degree of expression of c-kit protein before transduction. Optimal enhancing effects were noted in CD34(+++) kit(Lo/-) cells co-transduced with both c-kit and SLF cDNAs. Reverse transcriptase-polymerase chain (RT-PCR) analysis of SLF mRNA expression in CD34(+++) cells and enzyme-linked immunoadsorbent assay (ELISA) measurement of secreted SLF protein demonstrated that the transduced SLF cDNA was expressed and soluble SLF was released in medium cultured with SLF gene transduced MACS-separated CD34(+) cells in the presence, but not in the absence, of IL-3, GM-CSF, IL-6, and Epo. These results demonstrate the enhancement of the proliferation of growth factor responsive HPC that express transduced c-kit and SLF genes.

Comparative effects of retroviral-mediated gene transfer into primary human stromal cells of Flt3-ligand, interleukin 3 and GM-CSF on production of cord blood progenitor cells in long-term culture

The effects of different cytokines on growth of human cord blood CD34 cells was studied by performing long-term culture (LTC) with primary human stromal cells transduced with genes for either Flt3-ligand (L) (human transmembrane, murine soluble or murine membrane-bound forms), human interleukin 3 (IL-3) or human GM-CSF. Molecular analysis of genomic DNA from transduced stromal cells using neo-specific polymerase chain reaction demonstrated gene transfer of G418-selected stromal cell populations. Enzyme-linked immunosorbent assay and biological assays of conditioned media from transduced stromal cells indicated expression and release of soluble cytokines. Numbers of both immature and more mature progenitors (colony-forming unit-granulocyte, erythroid, macrophage, megakaryocyte; CFU-GEMM, BFU-E, CFU-GM) were increased threefold compared to control in the Flt3-L (transmembrane) LTC throughout five weeks of culture. IL-3 and GM-CSF feeders increased progenitor cell output also, but these effects were significantly lower than Flt3-L feeders. The two Flt3-L isoform engineered feeders, Ex6 (soluble isoform) and 5H (membrane-bound isoform), showed a decreased effect compared to the transmembrane Flt3-L feeders and, in particular, Ex6 feeders were similar to control feeders and 5H feeders were comparable to Flt3-L feeders only in the first two weeks of LTC. These results were apparent also by limiting dilution assays that showed a higher frequency of pre-CFU in the transmembrane Flt3-L feeders compared to control and the other cytokine feeders. Exogenous addition of soluble growth factors to suspension cultures without feeder layers, while superior to stromal feeders for short-term expansion of early progenitors, were inferior to the long-term maintenance/output on stromal feeders. Pre-CFU analysis supported these data. These results may be of some significance to understanding the actions of Flt3-L on blood cell production.

"Supercharged Cells" for delivery of recombinant human iduronate-2-sulfatase

Expression of iduronate-2-sulfatase (IDS) from three different promoters in four retroviral vectors was studied in peripheral blood lymphocytes from patients with Hunter syndrome (PBL(MPS)), i.e., the LTR in vectors L2SN and L2, avian beta-actin promoter in LB2, and the CMV early promoter in LNC2. PBL(MPS) were exposed to packaging cell supernatant resulting in transduction frequencies ranging 10-fold from 5 to 49%. Surprisingly, IDS activities were equally high in all transduced lymphocyte populations: 515 U/mg/h in PBL(MPS)-L2SN, 734 in PBL(MPS)-LB2, 352 in PBL(MPS)-L2, and 389 in PBL(MPS)-LNC2 compared to controls (<10 in PBL(MPS)-LXSN or PBL(MPS)). The half-life of endocytosed IDS in PBL(MPS) was 1.9 days. However, the level of lymphocyte IDS activity from proviral expression was found to be only a fraction of the total, a large portion being derived from reuptake of enzyme from murine packaging cells, i.e., a "second source" of enzyme. Therefore, measurement of transgene lysosomal enzyme soon after exposure of target cells to vector supernatant may yield a gross overestimate of long-term transgene expression by transduced cells. Nevertheless, patient fibroblasts cocultured with transduced PBL(MPS) had reduced (35)SO(4)-GAG accumulation, levels similar to those of normal fibroblasts. These studies revealed a broadly applicable phenomenon: cells can be charged with a lysosomal enzyme to levels much higher than those found in nature. By "supercharging" cells with a lysosomal protein (or other molecule bearing the mannose-6-phosphate ligand), such cells may be exploited as vehicles for systemic delivery of therapeutic or diagnostic agents.

The CC chemokine CK beta-11/MIP-3 beta/ELC/Exodus 3 mediates tumor rejection of murine breast cancer cells through NK cells

CK beta-11 chemoattracts T cells, B cells, dendritic cells, macrophage progenitors, and NK cells and facilitates dendritic cell and T cell interactions in secondary lymphoid tissues. We hypothesized that expression of CK beta-11 in tumor cells may generate antitumor immunity through these interactions. After transduction with the retroviral vector L(CK beta 11)SN, the murine breast cancer cell line C3L5 (C3L5-CK beta 11) showed expression of retroviral mRNA by Northern analysis and production of functional CK beta-11 by chemotaxis of human NK cells to C3L5-CK beta 11 supernatant. Only 10% of mice injected with C3L5-CK beta 11 developed tumors, compared with 100% of mice injected with a transduced control C3L5 line (C3L5-G1N). Importantly, the in vitro growth characteristics of the CK beta-11-transduced cell line were unaffected, suggesting the difference in growth in vivo was a result of chemokine production. Vaccination with C3L5-CK beta 11 partially protected animals from parental C3L5 challenge. Immunodepletion with anti-asialo-GM1 or anti-CD4 during C3L5-CK beta 11 vaccination significantly reduced CK beta-11 antitumor activity compared with control and anti-CD8-treated groups. Splenocytes from NK-depleted animals transferred the acquired immunity generated with C3L5-CK beta 11 vaccination, while splenocytes from the CD4-depleted animals did not. These results indicate, for the first time, that expression of CK beta-11 in a breast cancer cell line mediates rejection of the transduced tumor through a mechanism involving NK and CD4+ cells. Furthermore, CK beta-11-transduced tumor cells generate long-term antitumor immunity that requires CD4+ cells. These studies demonstrate the potential role of CK beta-11 as an adjuvant in stimulating antitumor responses.

Antileukemic activity of Flt3 ligand in murine leukemia

Flt3-ligand (Flt3-L) is an early acting costimulatory cytokine that has been shown to possess antitumor properties in murine solid tumor models. Flt3-L is a trans-membrane protein (tm) but can be proteolytically cleaved to a soluble form, which is also biologically active. In this study, the antitumor effect of both soluble and tmFlt3-L was evaluated in a mouse leukemia model. To mimic the multiorgan involvement characteristic of human leukemia, a factor-dependent cell line FDC.P1 was made leukemogenic by transfection with the human BCR/ABL gene. The resulting cell line, AW, expresses BCR/ABL RNA and protein. It maintains a similar in vitro growth rate as the parent cell line, but unlike the parent cell line, AW cells are factor independent and tumorigenic. Growth of FDC.P1 and AW cells are unaffected by the addition of soluble human Flt3-L to the culture medium. Also, AW growth is unaltered after transduction with a retroviral vector expressing the tm isoform of human Flt3-L (AW/tmFlt3-L). When 10(5) AW cells were i.v. injected into syngeneic DBA/2 mice, fatal leukemia developed in nine of nine (100%) mice within 4-6 weeks with involvement of the blood, bone marrow, spleen, and thymus. Systematic administration of soluble human Flt3-L (500 microg/kg/day) for 10 days protected mice from leukemia, with 11 of 17 mice tumor free at week 8 (64.7%) The tm isoform of Flt3-L also was protective. When 10(4) AW/tmFlt3-L cells were injected i.v. into mice, only 35.7% (5 of 14) developed leukemia versus 100% in control groups. Adoptive transfer of immunity was also demonstrated; T cells obtained from tumor-free animals conferred protection to 87% (seven of eight) naive mice challenged with AW cells. These results demonstrate that both soluble and membrane-bound human Flt3-L has antitumor activity in this leukemia model.

Differential in vitro maturation of hematopoietic stem cells from wild-type and immunoglobulin transgenic mice

During B-cell lymphopoiesis, hematopoietic stem cells commit to the B-cell lineage as monitored by the expression of phenotypic cell surface antigens and the production of immunoglobulin chains. Two cytokines, interleukin-7 (IL-7) and Flt-3 ligand (FL), appear to act in conjunction to drive this development process. Using an in vitro, stroma-free culture system and these cytokines, the commitment of murine Sca+ Lin- bone marrow cells to the B-cell lineage was examined with stem cells from immunoglobulin (Ig) transgenic and wild-type mice. After 12 days of culture in IL-7 and FL, stem cells from wild-type animals had matured to express surface B220, CD19, CD43, BP-1 and heat-stable antigen (HSA). These cells lacked detectable intracellular mu chains while exhibiting partial D-J rearrangement. In contrast, Sca+Lin- cells from Ig transgenic mice that were cultured similarly expressed B220, CD19, IgD, intracellular and surface mu, HSA but not CD43 or BP-1. These results suggest that expression of the Ig transgene during in vitro development overcame a block in B-cell lymphopoiesis and recapitulated in vivo events. Thus, IL-7 and FL treatment allowed uncommitted stem cells to progress to the early pre-B-cell stage while similarly treated Ig transgenic cells progressed completely to the mature B-cell stage.

Flt3 ligand antitumor activity in a murine breast cancer model: a comparison with granulocyte-macrophage colony-stimulating factor and a potential mechanism of action

We have shown that Flk2/Flt3 ligand (Flt3L)-transduced tumor vaccine induces transferable T cell protection against a murine breast cancer cell line, but a direct comparison with the potent effector GM-CSF, the activity against preestablished tumors, and the mechanism of antitumor response in this breast cancer model are not known. We compared vaccination with C3L5 cells expressing Flt3L (C3Lt-Flt3L) and GM-CSF (C3L5-GMCSF) by injecting 1 x 10(4) cells subcutaneously into the chest wall and then, after 4 weeks, challenging the contralateral chest of tumor-free mice with parental C3L5 cells. C3L5-Flt3L and C3L5-GMCSF had reduced in vivo growth rates (25% tumor formation each) compared with 100% tumor formation of C3L5 cells expressing only neomycin phosphotransferase (C3L5-G1N). However, when tumor-free animals were challenged with parental C3L5 cells, C3L5-Flt3L vaccination was significantly better at preventing tumor growth (p < 0.05) than C3L5-GMCSF vaccination (33% of C3L5-Flt3L-vaccinated animals developed tumor compared with 77% of C3L5-GMCSF-vaccinated animals). Adoptive transfer of immunity for both vaccines was demonstrated; splenic T cells from tumor-free mice protected naive mice from parental tumor challenge. To simulate minimal disease, parental C3L5 cells at two concentrations (high, 5 x 10(3) cells; or low, 1 x 10(3) cells) were injected into the contralateral chest wall 4 days prior to treatment with C3L5-G1N or C3L5-Flt3L. C3L5-Flt3L treatment decreased contralateral parental tumor formation (high, 67% tumor free; low, 90% tumor free) compared with C3L5-G1N treatment (high and low, 0% tumor free). Immunodepletion of activated natural killer cells with anti-asialo-GM1 blocked C3L5-Flt3L- and C3L5 plus soluble Flt3L-mediated antitumor activity. Thus, Flt3L-transduced tumor cells manifest potent antitumor activity, apparently mediated, at least partially, by natural killer cells.

H-Ras is involved in the inside-out signaling pathway of interleukin-3-induced integrin activation

The proto-oncogene product, p21(ras), has been implicated in the cellular mechanism of adhesion, although its precise role has been controversial. Numerous cytokines and growth-factors activate Ras, which is an important component of their growth-promoting signaling pathways. On the other hand, the role of Ras in cytokine-induced adhesion has not been elucidated. We therefore investigated the function of H-Ras in the inside-out signaling pathway of interleukin-3 (IL-3)-induced integrin activation in the murine Baf3 cell line after transfection of cells with either constitutively active, dominant-negative, or wild-type H-Ras cDNAs. Adhesion of Baf3 cells to fibronectin was induced by IL-3 in a dose-dependent manner via very late antigen-4 (VLA-4; alpha4beta1 integrins) and VLA-5 (alpha5beta1 integrins) activation. On the other hand, IL-4 did not induce the adhesion of Baf3 cells to fibronectin, although IL-4 did stimulate the cell proliferation of Baf3 cells. Constitutively active H-Ras-transfected Baf3 cells adhered to fibronectin without IL-3 stimulation through VLA-4 and VLA-5, whereas dominant-negative H-Ras-transfected Baf3 cells showed significantly less adhesion induced by IL-3 compared with wild-type and constitutively active H-Ras-transfected Baf3 cells. Anti-beta1 integrin antibody (clone; 9EG7), which is known to change integrin conformation and activate integrins, induced the adhesion of dominant-negative H-Ras-transfected Baf3 cells as much as the other types of H-Ras-transfected Baf3 cells. 8-Br-cAMP, Dibutyryl-cAMP, Ras-Raf-1 pathway inhibitors, and PD98059, a MAPK kinase inhibitor, suppressed proliferation and phosphorylation of MAPK detected by Western blotting with anti-phospho-MAPK antibody, but not adhesion of any type of H-Ras-transfected Baf3 cells, whereas U-73122, a phospholipase C (PLC) inhibitor, suppressed adhesion of these cells completely. These data indicate that H-Ras and PLC, but not Raf-1, MAPK kinase, or the MAPK pathway, are involved in the inside-out signaling pathway of IL-3-induced VLA-4 and VLA-5 activation in Baf3 cells.

Thrombopoietin-induced conformational change in p53 lies downstream of the p44/p42 mitogen activated protein kinase cascade in the human growth factor-dependent cell line M07e

Thrombopoietin is a cytokine with potent megakaryocytopoietic and thrombopoietic activities in vivo. Wild-type p53 is a conformationally flexible, anti-oncogenic transcription factor that plays a principal role in mediating growth factor withdrawal-induced apoptosis in factor-dependent hematopoietic cells. We recently reported that Tpo induces a conformational change in and functional inactivation of p53, coincident with its anti-apoptotic effects, in the human factor-dependent cell line M07e. In an effort to identify potential signaling cascades through which Tpo illicits these effects on p53, we report here that treating M07e cells with MAPK kinase inhibitor PD98059 dramatically suppressed Tpo-induced conformational change in p53 as well as Tpo-enhanced viability in M07e cells in a p53-dependent manner. Furthermore, the expression of constitutively active Raf1 in M07e cells induced conformational change in p53 independent of Tpo stimulation. Inhibition of the JAK/STAT pathway revealed that JAK/STAT signaling plays an insignificant role in conformational modulation of p53 and apoptosis suppression. Inhibition of phosphatidylinositol-3 kinase did not have a significant effect on p53 conformation but did have a weak but significant effect on Tpo-enhanced viability. Cytokine-induced activation of the MAPK pathway and the subsequent functional neutralization of p53, may be an event by which apoptosis is commonly suppressed in hematopoiesis.

p21(cip-1/waf-1) deficiency causes deformed nuclear architecture, centriole overduplication, polyploidy, and relaxed microtubule damage checkpoints in human hematopoietic cells

A recent hypothesis suggests that tumor-specific killing by radiation and chemotherapy agents is due to defects or loss of cell cycle checkpoints. An important component of some checkpoints is p53-dependent induction of p21(cip-1/waf-1). Both p53 and p21 have been shown to be required for microtubule damage checkpoints in mitosis and in G1 phase of the cell cycle and they thus help to maintain genetic stability. We present here evidence that p21(cip-1/waf-1) deficiency relaxes the G1 phase microtubule checkpoint that is activated by microtubule damage induced with nocodazole. Reduced p21(cip-1/waf-1) expression also results in gross nuclear abnormalities and centriole overduplication. p53 has already been implicated in centrosome regulation. Our findings further suggest that the p53/p21 axis is involved in a checkpoint pathway that links the centriole/centrosome cycle and microtubule organization to the DNA replication cycle and thus helps to maintain genomic integrity. The inability to efficiently upregulate p21(cip-1/waf-1) in p21(cip-1/waf-1) antisense-expressing cells in response to microtubule damage could uncouple the centrosome cycle from the DNA cycle and lead to nuclear abnormalicies and polyploidy. A centrosome duplication checkpoint could be a new target for novel chemotherapy strategies.

A positive effect of p21cip1/waf1 in the colony formation from murine myeloid progenitor cells as assessed by retroviral-mediated gene transfer

p21cip1/waf1 is a cyclin dependent kinase inhibitor. We have previously reported stimulation of p21cip1/waf1 by steel factor and GM-CSF in a factor dependent cell line and of p21cip1/waf1 involvement in hematopoiesis in vivo in p21cip1/waf1 gene knockout (-/-) mice. To further assess a role for increased p21cip1/waf1 in hematopoietic progenitor cells, we developed the retroviral vector L(p21cip1)SN to transcriptionally regulate p21cip1/waf1 from the Mo-MLV LTR. L(p21cip1)SN and the control vector LXSN were used to transduce murine bone marrow progenitor cells from p21cip1/waf1 (-/-) and littermate control (+/+) mice, as well as from other mouse strains. Hematopoietic colony formation by transduced cells was assessed in semi-solid culture medium with multiple growth factors. Myeloid colony formation by bone marrow cells from p21cip1/waf1 (-/-) mice was significantly lower than that by (+/+) mouse cells. Transduction of cells with LXSN had no effect on colony formation: however, (-/-) cells transduced with L(p21cip1)SN formed significantly greater numbers of colonies than either LXSN-transduced (-/-) or (+/-) cells. Moreover, L(p21cip1)SN-transduced (+/+) cells formed significantly more colonies than LXSN-transduced (+/+) cells. Increased cloning efficiency of progenitors from normal strains of mice induced by L(p21cip1)SN compared to LXSN-transduced cells was seen whether unseparated or highly purified populations of Sca1+ Lin- marrow cells were used. Gene transfer of L(p21cip1)SN increased the size and number of cells per colony, as well as the number of colonies compared to LXSN gene transfer. No colonies grew from non-transduced, LXSN-, or L(p21cip1)SN-transduced cells when no growth factors were added to the cultures. These results document the positive effect of p21cip1/waf1 in the proliferation and/or differentiation of the murine myeloid progenitor cells that lead to colony formation.

Thrombopoietin upregulates the promoter conformation of p53 in a proliferation-independent manner coincident with a decreased expression of Bax: potential mechanisms for survival enhancing effects

Thrombopoietin (Tpo) has proliferative and maturational effects on immature and more committed cells, respectively. We previously reported a role for Tpo as a survival factor in the factor-dependent human cell line M07e by demonstrating that Tpo suppresses apoptosis in the absence of induced proliferation. Wild-type p53 is a tumor suppressor gene that can play a vital role in mediating growth factor withdrawal-induced apoptosis in factor-dependent hematopoietic cells. Wild-type p53 can switch from a suppressor conformation, with an antiproliferative, pro-apoptotic phenotype, to a promoter conformation that has a diminished ability to mediate cell cycle arrest and apoptosis. In an effort to elucidate the mechanisms through which Tpo suppresses apoptosis, we investigated the effects of Tpo treatment on p53-mediated apoptosis in M07e cells. Tpo upregulated the expression of the promoter conformation of p53 in M07e cells coincident with a downregulation of Bax and Mdm2 protein levels. Protein levels of Bcl-2 and Bcl-xL did not significantly vary as a function of growth-factor stimulation. Conversely, the levels of suppressor conformation p53 were maximal when M07e was in a growth arrested state and decreased during factor stimulation. Furthermore, Tpo treatment induced an extranuclear buildup and greatly weakened the DNA binding capacity of p53. p53-specific antisense oligonucleotide treatment recapitulated the effects of Tpo treatment on the levels of Bax, Mdm-2, and Bcl-2. These results suggest that Tpo is suppressing growth factor withdrawal induced-apoptosis, at least in part, by downregulating the expression of pro-apoptotic Bax protein levels, through modulating the conformation of p53, which results in a functional inactivation of its pro-apoptotic abilities.

Gene therapy strategies for leukemia

A number of diverse gene therapy strategies are being evaluated in the search for novel therapeutic approaches to leukemia. Antisense oligonucleotides, ribozymes and retroviral vectors are approaches directed at the molecular mechanisms of cancer. Transfer of genes encoding cytokines and human leukocyte antigens (HLAs) could also be used to elicit immunity against tumor cells. Gene marking strategies have been useful in elucidating the biology of disease relapse after autologous bone marrow transplantation. Suicide genes, such as the herpes simplex thymidine kinase gene, have been used to modulate graft-versus-host disease after allogeneic bone marrow transplantation. Although gene delivery remains a major challenge to gene therapy, some modifications have been implemented to overcome this issue. This review will summarize these gene therapy strategies aimed at increasing the survival of patients with leukemia.

Retrovirally mediated gene transfer of Arg22 and Tyr22 forms of dihydrofolate reductase into the hematopoietic cell line K562: a comparison of methotrexate resistance

Mutations in the enzyme dihydrofolate reductase (DHFR) can confer resistance to the inhibitory effects of folate analogs such as methotrexate (Mtx) and trimetrexate (Ttx). Retroviral vectors expressing the DHFR-Arg22 mutants and the newly described DHFR-Tyr22 mutant were used to transduce the hematopoietic cell line K562. In vitro selection of vector-containing cells was documented via polymerase chain reaction and Southern analysis. When proliferation of selected vector-containing cells was evaluated over a range of Mtx concentrations (0.01 to 10 micromol/L), both Arg22 and Tyr22 provided protection from Mtx, but Tyr22 proved superior to Arg22 in conferring Mtx resistance at low concentrations. Ttx proved to be 10- to 100-fold more potent than Mtx in inhibiting proliferation of nontransduced K562, but the relative effectiveness of individual mutants in conferring drug resistance was similar to that of Mtx. Decreasing the amount of folate in the culture medium to more physiological concentrations increased the potency of administered Mtx and Ttx. Drug resistance in retrovirally transduced K562 cells is consistent with the enzymatic characteristics of the individual mutants. Our findings suggest that the new Tyr22 form of DHFR may prove better in conferring drug resistance than the previously reported Arg22 mutant.

Retroviral mediated gene transfer of Flt3 ligand enhances proliferation and MAP kinase activity of AML5 cells

Flt3/flk-2 ligand (Flt3-L) co-stimulates and synergizes with cytokines such as granulocyte-macrophage colony stimulating factor, granulocyte colony stimulating factor (G-CSF), interleukin-3 (IL-3), and erythropoietin in the proliferation of bone marrow and cord blood hematopoietic stem and progenitor cells. To study the biological effects of Flt3-L on the Flt3-L responsive AML5 cell line, the retroviral vector L(Flt3-L)SN was constructed based on the vector LXSN, but containing the human Flt3-L cDNA transcriptionally regulated by the Mo-MLV LTR. High-titer amphotropic producer cells that generated 10(6) cfu/mL after shuttle packaging through ecotropic packaging cells were isolated. AML5 cells were cultured overnight with L(Flt3-L)SN retroviral supernatant, 8 micrograms/mL polybrene, and 100 U/mL G-CSF, and expanded 1 week in medium with G-CSF. Transduced cells were selected in medium containing 0.4 mg/mL G418 and then in medium with 1.0 mg/mL G418. Retroviral mediated gene transfer in G418-resistant cells was confirmed after amplification by PCR of neo-specific sequences in genomic DNA. Northern blot analysis demonstrated L(Flt3-L)SN mRNA expression. Soluble Flt3-L was undetectable (< 100 pg/mL) by ELISA assay of conditioned medium from transduced cells, but Flt3-L was detected on the surface of AML5 cells by FACS analysis. Cells were plated in colony assay with and without 100 ng/mL Flt3-L, 100 U/mL G-CSF, and the combination. Gene transfer or growth factor treatment increased somewhat the clonogenicity of the nontransduced AML5 cells. More strikingly, L(Flt3-L)SN and each growth factor combination greatly increased the size of the resultant colonies such that the size of colonies from AML5/Flt3-L cells without added growth factor approximated that of the AML5 cells stimulated by exogenous soluble Flt3-L. Moreover, MAP kinase activity in L(Flt3-L)SN-transduced cells cultured without soluble Flt3-L was increased to the level induced in control cells by soluble Flt3-L. These results indicate that retroviral mediated gene transfer and autologous expression of the Flt3-L enhances growth and intracellular signaling of AML5 cells, information that should be of value for studying the effects of Flt3-L on immature subsets of primary hematopoietic stem and progenitor cells.

Flt3-ligand production by human bone marrow stromal cells

Bone marrow stromal cells are important sources of cytokines and growth factors which participate in regulation of proliferation and differentiation of hematopoietic stem and progenitor cells. Recently flt3/flk-2-ligand (flt3-L), a new growth factor which uses a membrane tyrosine kinase receptor, was cloned. It is expressed in transmembrane and soluble forms and stimulates/co-stimulates proliferation and colony formation of hematopoietic stem/progenitor cells. It has not been reported whether flt3-L is produced by cells of the hematopoietic bone marrow microenvironment. We demonstrate the expression of flt3-L in bone marrow fibroblasts (BMF) and in stromal cells of adherent layers of long-term bone marrow cultures by RT-PCR, Northern blot, immunocytochemistry and FACS analysis. The latter two methods localized flt3-L intracellularly and on cell membranes. Treatment with interleukin-1 alpha increased the expression of flt3-L in BMF. This demonstrates production and modulation of flt3-L in stromal cells of human bone marrow.

Preclinical studies of lymphocyte gene therapy for mild Hunter syndrome (mucopolysaccharidosis type II)

To explore the feasibility of ex vivo lymphocyte gene therapy for mild Hunter syndrome (mucopolysaccharidosis type II), we evaluated retrovirus-mediated gene transfer of the iduronate-2-sulfatase (IDS) coding sequence into peripheral blood lymphocytes from enzyme-deficient individuals (PBLMPS). Moloney murine leukemia virus-derived retroviral vectors were constructed by inserting the IDS cDNA under transcriptional regulation of the long terminal repeat (LTR) (in vector L2SN) or the cytomegalovirus (CMV) early promoter (vector LNC2). High-titer virus-producer cells were generated using amphotropic PA317 packaging cells. After 3 days of in vitro stimulation of T lymphocytes with anti-CD3 antibody and interleukin-2 (IL-2), PBLMPS were transduced once on each of the next 3 days. Seven to 21 days later, cultured PBLMPS were evaluated for gene transfer and IDS specific activity. Heterogeneous populations of L2SN-transduced PBLMPS had high levels of IDS enzyme activity (456 U/mg per hr +/- SD 292) despite a gene transfer efficiency of 5% or less. Owing to overexpression of IDS in that percentage of PBLMPS successfully transduced, IDS activity was increased above the deficiency found in patients with Hunter syndrome (< 20 U/mg per hr) to a level comparable with that of normal individuals (mean activity of uncultured normal leukocytes 807 U/mg per hr; SD 252). Reduced 35SO4-glucosaminoglycan (GAG) accumulation was observed in PBLMPS that had been transduced with L2SN, or when PBLMPS were grown in medium that had been "conditioned" by growth of L2SN-transduced cells. This latter result indicated that metabolic cross-correction occurred by means of intercellular enzyme transfer. These studies of retrovirus-mediated expression and metabolic correction, finding near-normal levels of IDS in cultured PBLMPS and metabolic correction, demonstrate the potential for treatment of mild, nonneuropathic Hunter syndrome by means of ex vivo lymphocyte gene therapy.

Molecular diagnosis of mucopolysaccharidosis type II (Hunter syndrome) by automated sequencing and computer-assisted interpretation: toward mutation mapping of the iduronate-2-sulfatase gene

Virtually all mutations causing Hunter syndrome (mucopolysaccharidosis type II) are expected to be new mutations. Therefore, as a means of molecular diagnosis, we developed a rapid method to sequence the entire iduronate-2-sulfatase (IDS) coding region. PCR amplicons representing the IDS cDNA were sequenced with an automatic instrument, and output was analyzed by computer-assisted interpretation of tracings, using Staden programs on a Sun computer. Mutations were found in 10 of 11 patients studied. Unique missense mutations were identified in five patients: H229Y (685C-->T, severe phenotype); P358R (1073C-->G, severe); R468W (1402C-->T, mild); P469H (1406C-->A, mild); and Y523C (1568A-->G, mild). Non-sense mutations were identified in two patients: R172X (514C-->T, severe) and Q389X (1165C-->T, severe). Two other patients with severe disease had insertions of 1 and 14 bp, in exons 3 and 6, respectively. In another patient with severe disease, the predominant (> 95%) IDS message resulted from aberrant splicing, which skipped exon 3. In this last case, consensus sequences for splice sites in exon 3 were intact, but a 395 C-->G mutation was identified 24 bp upstream from the 3' splice site of exon 3. This mutation created a cryptic 5' splice site with a better consensus sequence for 5' splice sites than the natural 5' splice site of intron 3. A minor population of the IDS message was processed by using this cryptic splice site; however, no correctly spliced message was detected in leukocytes from this patient. The mutational topology of the IDS gene is presented.

Metabolic correction and cross-correction of mucopolysaccharidosis type II (Hunter syndrome) by retroviral-mediated gene transfer and expression of human iduronate-2-sulfatase

To explore the possibility of using gene transfer to provide iduronate-2-sulfatase (IDS; EC 3.1.6.13) enzyme activity for treatment of Hunter syndrome, an amphotropic retroviral vector, L2SN, containing the human IDS coding sequence was constructed and studied for gene expression in vitro. Lymphoblastoid cell lines (LCLs) from patients with Hunter syndrome were transduced with L2SN and expressed high levels of IDS enzyme activity, 10- to 70-fold higher than normal human peripheral blood leukocytes or LCLs. Such L2SN-transduced LCLs failed to show accumulation of 35SO4 into glycosaminoglycan (35SO4-GAG), indicating that recombinant IDS enzyme participated in GAG metabolism. Coculture of L2SN-transduced LCLs with fibroblasts from patients with Hunter syndrome reduced the accumulation of 35SO4-GAG. These results demonstrated retroviral-mediated IDS gene transfer into lymphoid cells and the ability of such cells to provide recombinant enzyme for intercellular metabolic cross-correction.