Phase 1 study of selinexor in combination with salvage chemotherapy in Adults with relapsed or refractory Acute myeloid leukemia

Selinexor, an oral inhibitor of the nuclear transport protein Exportin-1, shows promising single-agent activity in clinical trials of relapsed/refractory (R/R) acute myeloid leukemia (AML) and preclinical synergy with topoisomerase (topo) IIα inhibitors. We conducted a phase 1, dose-escalation study of selinexor with mitoxantrone, etoposide, and cytarabine (MEC) in 23 patients aged < 60 years with R/R AML. Due to dose-limiting hyponatremia in 2 patients on dose level 2 (selinexor 40 mg/m2), the maximum tolerated dose was 30 mg/m2. The most common grade ≥ 3 treatment-related non-hematologic toxicities were febrile neutropenia, catheter-related infections, diarrhea, hyponatremia, and sepsis. The overall response rate was 43% with 6 patients (26%) achieving complete remission (CR), 2 (9%) with CR with incomplete count recovery, and 2 (9%) with a morphologic leukemia-free state. Seven of 10 responders proceeded to allogeneic stem cell transplantation. The combination of selinexor with MEC is a feasibile treatment option for patients with R/R AML.

Longitudinal Survival Outcomes in Allogeneic Stem Cell Transplantation: An Institutional Experience

Allogeneic hematopoietic stem cell transplantation (allo-SCT) is a potentially curative treatment for many hematological disorders, but is often complicated by relapse of the underlying disease, graft-versus-host disease (GVHD), and infectious complications. We conducted a retrospective analysis on patients undergoing allo-SCT from 1984 to 2018 to better understand how survival has changed longitudinally with therapeutic advancements made to mitigate these complications. Method: We analyzed data from 1943 consecutive patients who received allo-SCT. Patients were divided into groups (gps) based on the year (yr) of transplant. Primary endpoints were overall survival (OS), progression free survival (PFS), and GVHD-free relapse-free survival (GRFS). Secondary endpoints were the cumulative incidences of grade II−IV and grade III−IV acute GVHD (aGVHD), chronic GVHD (cGVHD), and non-relapse mortality (NRM). Results: Our study found statistically significant improvements in OS, PFS, and GRFS. Five-year PFS among the groups increased from 24% to 48% over the years. Five-year OS increased from 25% to 53%. Five-year GRFS significantly increased from 6% to 14%, but remained relatively unchanged from 2004 to 2018. Cumulative incidences of grade II−IV aGVHD increased since 2009 (p < 0.001). However, cumulative incidence of NRM decreased since 2004 (p < 0.001). Conclusions: Our data show improved OS, PFS, and GRFS post allo-SCT over decades. This may be attributed to advances in supportive care and treatments focused on mitigation of GVHD and relapse.

PP2A is a therapeutically targetable driver of cell fate decisions via a c-Myc/p21 axis in human and murine acute myeloid leukemia

Dysregulated cellular differentiation is a hallmark of acute leukemogenesis. Phosphatases are widely suppressed in cancers but have not been traditionally associated with differentiation. In this study, we found that the silencing of protein phosphatase 2A (PP2A) directly blocks differentiation in acute myeloid leukemia (AML). Gene expression and mass cytometric profiling revealed that PP2A activation modulates cell cycle and transcriptional regulators that program terminal myeloid differentiation. Using a novel pharmacological agent, OSU-2S, in parallel with genetic approaches, we discovered that PP2A enforced c-Myc and p21 dependent terminal differentiation, proliferation arrest, and apoptosis in AML. Finally, we demonstrated that PP2A activation decreased leukemia-initiating stem cells, increased leukemic blast maturation, and improved overall survival in murine Tet2-/-Flt3ITD/WT and human cell-line derived xenograft AML models in vivo. Our findings identify the PP2A/c-Myc/p21 axis as a critical regulator of the differentiation/proliferation switch in AML that can be therapeutically targeted in malignancies with dysregulated maturation fate.

Impact of Race and Geographic Area of Residence on Outcomes After Allogeneic Stem Cell Transplant

Background

Allogeneic hematopoietic stem cell transplant (allo-HCT) is a potential curative therapy for a variety of hematologic disorders. However, it requires highly specialized care that is only available at select centers across the country. Thus, minority populations are at risk for healthcare disparities in access to and outcomes of allo-HCT. Our study aimed to assess the impact of race and location of residence on outcomes of allo-HCT.

Methods

We performed a retrospective analysis of all patients who underwent allo-HCT at the Ohio State University from 1984 to 2018. Patients were divided by race (Caucasian, African American, and other) and grouped by zip code into rural, suburban, and urban groups. Primary endpoints included progression-free survival (PFS) and overall survival (OS).

Results

Of the 1,943 patients included in the study, 94.3% self-identified as Caucasian, 4.6% African American, and 1.1% other. In total, 63.4% lived in rural areas, 22.9% suburban, and 13.8% urban. There was no significant difference in OS or PFS by race (p = 0.15, 0.21) or place of residence (p = 0.39, 0.17). In addition, no difference in nonrelapse mortality, acute and chronic graft-versus-host disease (GVHD), and GVHD-free relapse-free survival (GRFS) was seen among the race or place of residence.

Conclusion

Our study suggests that when appropriate access to HCT is given, there is no difference in outcomes based on race, ethnicity or place of primary residence. Further research is needed to further evaluate barriers for these patients to undergo transplant and help mitigate these barriers.

Outcomes of Bone Marrow Compared to Peripheral Blood for Haploidentical Transplantation

Allogeneic hematopoietic cell transplantation (allo-HCT) from a haploidentical (haplo) donor has emerged as a suitable alternative in the absence of a matched donor. However, haplo-HCT patients have a higher risk of graft-versus-host disease (GVHD). Hence, bone marrow (BM) stem cell source and post-transplant cyclophosphamide (PTCy) have been routinely used to help mitigate this. Due to ease of collection, peripheral blood (PB) stem cells are increasingly being considered for haplo-HCT. We retrospectively analyzed 74 patients (42 BM and 32 PB) who underwent haplo-HCT at Ohio State University from 2009 to 2018. Median age at transplant was 60 years (yrs) for BM and 54 yrs for PB, (p = 0.45). There was no difference in OS (p = 0.13) and NRM (p = 0.75) as well as PFS (p = 0.10) or GRFS (p = 0.90) between the groups. The BM cohort showed a 3-year OS rate of 63% (95% confidence interval (CI): 46–76), and 3-year PFS of 49% (95% CI: 33–63). For the PB group, 3-year OS and PFS were 78% (95% CI: 59–89) and 68% (95% CI: 49–82), respectively. There were no differences in the incidence of acute GVHD (grade II-IV) (p = 0.31) and chronic GVHD (p = 0.18). Patients receiving BM had a significantly higher risk for relapse with relapse rates by 2 years at 36% (95% CI: 22–50) vs. 16% (95% CI: 6–31) for PB (p = 0.03). The findings from this study suggest that PB is an excellent alternative to BM for haplo-HCT.

Comparison of fixed dose reduced-intensity conditioning with fludarabine and busulfan to PK-guided busulfan AUC (FluBu4K) in hematopoietic stem cell transplant for AML/MDS

A retrospective cohort study was conducted to assess differences in efficacy and tolerability between a busulfan AUC target of 16.4 mg × Hr/L per day (FluBu4K) and a conventional RIC regimen (FluBu2). Adult patients with a diagnosis of AML or MDS who received fludarabine + busulfan conditioning with or without antithymocyte globulin between 2015 and 2018 were included. The primary outcome was relapse free survival. Overall, 74 patients received conditioning with either FluBu4K or FluBu2. At 18 months, relapse-free survival was not significantly different, at 63.9% with FluBu4k compared to 57.5% with FluBu2 (p = 0.49). There was a statistically significant difference in the cumulative incidence of relapse at 18 months in favor of the FluBu4K regimen, at 12.0% vs 32.5% (p = 0.047). The results of this study indicate that for select patients, there may be benefit in choosing targeted FluBu4K over FluBu2. Adverse effects other than mucositis were not significantly different.

A phase I study of lenalidomide plus chemotherapy with idarubicin and cytarabine in patients with relapsed or refractory acute myeloid leukemia and high-risk myelodysplastic syndrome

Patients with relapsed/refractory (R/R) acute myeloid leukemia (AML) have poor outcomes and hematopoietic cell transplantation (HCT) is the only curative treatment. New targeted therapies improved survival in select patients with specific mutations, however management of patients without these molecular alterations is an unmet need. We conducted a phase one study of lenalidomide in combination with cytarabine/idarubicin salvage chemotherapy in patients with R/R AML and high‐risk myelodysplastic syndromes. A total of 33 patients were enrolled in the study (30 AML, 3 MDS), and treated at three dose levels with 3 + 3 design. Dose‐limiting toxicity (DLT) was seen in eight patients, including four hematologic DLTs. The most commonly observed non‐hematologic serious adverse events were febrile neutropenia, rash, sepsis and renal injury. Dose level −1, consisting of 25 mg/d lenalidomide D1‐21, 1 g/m² cytarabine D5‐8, and 8 mg/m² idarubicin D5‐7 was determined to be the maximum tolerated dose. Note, 15/33 (45%) of patients were able to receive pre‐planned 21 days of lenalidomide. Overall, 18 patients achieved complete remission (CR) (n = 14) or CR with incomplete count recovery (CRi) (n = 4) with total CR/CRi rate of 56%. The 1‐year and 2‐year overall survival (OS) were 24% and 10%, respectively. Among responders, 10/18 underwent allogeneic HCT and had a 1‐year OS of 40%. There was no molecular pattern associated with response. These data demonstrate that the combination had clinical activity in R/R AML. This regimen should be further investigated for patients who relapsed after HCT, and as a bridge therapy to HCT. (ClinicalTrials.gov identifier: NCT01132586).

The Incidence of Invasive Fungal Infections in Patients With AML Treated With a Hypomethylating Agent

BACKGROUND

Newly diagnosed patients with acute myeloid leukemia (AML) who receive induction with a hypomethylating agent (HMA) are often neutropenic with an increased risk for invasive fungal infections (IFIs). This study analyzed the incidence and risk factors for IFIs in these patients, evaluated clinical patterns in antifungal prophylaxis, and assessed the diagnostic utility of tests in this setting.

PATIENTS AND METHODS

We studied 117 newly diagnosed patients with AML treated with HMAs at our center, divided into groups based on concern for IFI (cIFI: all possible, probable, and proven IFIs) versus no concern for IFI. The Fisher exact test compared patients with cIFI versus without, and a multivariable logistic regression model estimated odds for cIFI.

RESULTS

Sixty-seven (57%) patients had cIFI, with 48 possible IFIs, 17 probable, and 2 proven cases. There was no difference in incidence based on home zip code, but the presence of chronic obstructive pulmonary disease was highly associated with cIFI (P = .001), as was male gender (P = .01). Neutropenia at treatment initiation was borderline in significance (P = .08). In diagnostics, 9% of patients had positive serum fungal markers, and 30 patients underwent bronchoscopy, with only 27% of cases yielding positive results. There was a difference in treatment regimens between patients receiving antifungal prophylaxis with mold coverage versus without mold coverage with respect to cIFI (P = .04).

CONCLUSIONS

cIFI in patients with AML treated with HMAs remains significant, especially in males and those with chronic obstructive pulmonary disease, who were found to be at higher risk. This may prompt clinicians to consider anti-mold prophylaxis in this setting.

Transducin β-like protein 1 controls multiple oncogenic networks in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common non- Hodgkin lymphoma and is characterized by a remarkable heterogeneity with diverse variants that can be identified histologically and molecularly. Large-scale gene expression profiling studies have identified the germinal center B-cell (GCB-) and activated B-cell (ABC-) subtypes. Standard chemo-immunotherapy remains standard front-line therapy, curing approximately two thirds of patients. Patients with refractory disease or those who relapse after salvage treatment have an overall poor prognosis highlighting the need for novel therapeutic strategies. Transducin b-like protein 1 (TBL1) is an exchange adaptor protein encoded by the TBL1X gene and known to function as a master regulator of the Wnt signaling pathway by binding to β-CATENIN and promoting its downstream transcriptional program. Here, we show that, unlike normal B cells, DLBCL cells express abundant levels of TBL1 and its overexpression correlates with poor clinical outcome regardless of DLBCL molecular subtype. Genetic deletion of TBL1 and pharmacological approach using tegavivint, a first-in-class small molecule targeting TBL1 (Iterion Therapeutics), promotes DLBCL cell death in vitro and in vivo. Through an integrated genomic, biochemical, and pharmacologic analyses, we characterized a novel, β-CATENIN independent, post-transcriptional oncogenic function of TBL1 in DLBCL where TBL1 modulates the stability of key oncogenic proteins such as PLK1, MYC, and the autophagy regulatory protein BECLIN-1 through its interaction with a SKP1-CUL1-F-box (SCF) protein supercomplex. Collectively, our data provide the rationale for targeting TBL1 as a novel therapeutic strategy in DLBCL.

Incidence of venous thrombosis after peg-asparaginase in adolescent and young adults with acute lymphoblastic leukemia

AIM

There are limited data describing incidence of symptomatic venous thromboembolism (VTE) in adolescent and young adult (AYA) acute lymphoblastic leukemia (ALL) patients receiving peg-asparaginase.

MATERIALS & METHODS

Single-institution retrospective analysis of 44 AYA ALL patients treated with peg-asparaginase. Rates of VTE and proposed risk factors were assessed.

RESULTS

18 patients (41%) had a symptomatic VTE following peg-asparaginase. The cumulative incidence rate was 25% (95% CI: 13-38%) within 30 days of the initial dose. Personal history of thrombosis was statistically significantly associated with an increased risk of VTE with HR of 2.73 (95% CI: 1.40-5.33, p = 0.003) after adjusting for gender.

CONCLUSION

These data indicate a high rate of VTE in the AYA ALL population following treatment with peg-asparaginase.

Knowledge of Australian primary education providers towards dental avulsion injuries: a cross-sectional study

BACKGROUND/AIM

The aim of this study was to evaluate the knowledge of school professionals regarding the emergency management of dental avulsion.

METHODS

This cross-sectional study utilised a self-administered, pilot-tested questionnaire for school staff from primary schools. Descriptive statistics were used for the analysis - the prevalence and univariate associations between a categorical outcome and the variables under consideration, were evaluated using Pearson's Chi-squared test.

RESULTS

This survey yielded a response rate of 43.5% (n = 313). Approximately 60% of participants held valid first-aid certificates and 23% had received avulsion advice previously. Over 80% of participants expressed an unwillingness to replant an avulsed tooth, and over 90% believed that there should be greater awareness in this area. This unwillingness to replant was influenced by respondents' age (x2 = 8.13 df = 3, P = 0.043) and receiving advice previously (x2 = 13.15, df = 1, P < 0.001). Under-preparedness was related to years of experience (x2 = 15.03, df = 5, P = 0.010), first-aid training (x2 = 6.41, df = 1, P = 0.011) and receiving advice previously (x2 = 43.47, df = 1, P < 0.001). It was also evident that first-aid training positively influenced appropriate dental referral in the management pathway (x2 = 10.49, df = 1, P = 0.001).

CONCLUSION

This study suggests that there is an inadequate level of knowledge on the appropriate management of dental avulsion injuries amongst primary school professionals in Australia.

Selinexor in combination with decitabine in patients with acute myeloid leukemia: results from a phase 1 study

Current treatment options for older and relapsed or refractory (R/R) acute myeloid leukemia (AML) patients are limited and represent an unmet need. Based on preclinical studies showing strong anti-leukemic effects in vivo, this phase I dose-escalation study assessed the safety and preliminary clinical activity of the oral exportin-1 inhibitor, selinexor, in combination with the hypomethylating agent, decitabine 20 mg/m², in adults with R/R AML and in older (age ≥ 60) untreated AML patients. There were no protocol-defined dose limiting toxicities. The recommended phase 2 dose of selinexor was 60 mg (∼35 mg/m²) given twice-weekly. Notable grade ≥3 toxicities included asymptomatic hyponatremia (68%), febrile neutropenia (44%), sepsis (44%), hypophosphatemia (36%), and pneumonia (28%). In 25 patients, the overall response rate was 40%. Modification of selinexor to a flat dose of 60 mg, twice-weekly for two weeks after decitabine, improved tolerability of the regimen and demonstrated preliminary clinical activity in poor-risk patients with AML.

MicroRNA-29b mediates altered innate immune development in acute leukemia

Natural killer (NK) cells can have potent antileukemic activity following haplo-mismatched, T cell-depleted stem cell transplantations for the treatment of acute myeloid leukemia (AML), but they are not successful in eradicating de novo AML. Here, we have used a mouse model of de novo AML to elucidate the mechanisms by which AML evades NK cell surveillance. NK cells in leukemic mice displayed a marked reduction in the cytolytic granules perforin and granzyme B. Further, as AML progressed, we noted the selective loss of an immature subset of NK cells in leukemic mice and in AML patients. This absence was not due to elimination by cell death or selective reduction in proliferation, but rather to the result of a block in NK cell differentiation. Indeed, NK cells from leukemic mice and humans with AML showed lower levels of TBET and EOMES, transcription factors that are critical for terminal NK cell differentiation. Further, the microRNA miR-29b, a regulator of T-bet and EOMES, was elevated in leukemic NK cells. Finally, deletion of miR-29b in NK cells reversed the depletion of this NK cell subset in leukemic mice. These results indicate that leukemic evasion of NK cell surveillance occurs through miR-mediated dysregulation of lymphocyte development, representing an additional mechanism of immune escape in cancer.

Novel therapies in AML: reason for hope or just hype?

We have entered the genomic sequencing era in the treatment of acute myeloid leukemia (AML); our patients increasingly and justifiably demand personalized treatment based on aberrations of their own leukemia. Except in rare cases we are not yet able to provide truly personalized therapy, so the question of "hope or hype?" posed by the American Society for Clinical Oncology (ASCO) for this educational topic is quite timely. The answer based solely on advances in genomic sequencing is "both". There is an element of expectation among the public that we are "almost there" in solving the genetic cancer puzzle, an expectation indeed based on hype. However, there is no question that ultimate success lies in understanding the genetic underpinnings of disease. When decades of research in molecular biology and immunology are combined with transformative advances in cancer genetics, the answer is undeniably that our patients finally have reason for hope. Here, we review selected novel therapies for AML in areas such as immunotherapeutics, epigenetics, kinase inhibition/pathway inhibition, and the marrow microenvironment.

Antagonizing ClpP: A New Power Play in Targeted Therapy for AML

In this issue of Cancer Cell, Cole and colleagues report a non-mutant mitochondrial protein (ClpP) that is overexpressed in a wide range of acute myeloid leukemia (AML) cases, but not in normal hematopoietic precursors. This finding suggests a potentially unique therapeutic targeting opportunity for this difficult-to-treat disease.

Restricting oxygen supply to the prospective dorsal side does not reverse axis polarity in embryos of Xenopus laevis

During the first cell cycle, the prospective dorsal side of the embryo of Xenopus laevis becomes enriched in mitochondria relative to the ventral side. This differential distribution of mitochondria persists throughout early development, but it is not known if it is of functional significance, since there do not appear to be dorsal-ventral differences in metabolic rate. However, the unilateral anaerobiosis experiments of Landström and Løvtrup do suggest a role for energy metabolism in determining axis polarity. These experiments apparently show that restricting oxygen supply to the prospective dorsal side causes a reversal of dorsal-ventral axis polarity. We have reinvestigated this point using cell-marking techniques. We find that although gastrulation is initiated at the open end of the tube, the polarity of neural plate development is unaffected. Thus, definitive dorsal-ventral polarity is not affected by the experimental treatment, and it is unlikely that gradients of energy metabolism have a role in specifying axis polarity in X. laevis.

Male offspring production by asexual Potamopyrgus antipodarum, a New Zealand snail

As only females contribute directly to population growth, sexual females investing equally in sons and daughters experience a two-fold cost relative to asexuals producing only daughters. Typically, researchers have focused on benefits of sex that can counter this 'cost of males' and thus explain its predominance. Here, we instead ask whether asexuals might also pay a cost of males by quantifying the rate of son production in 45 experimental populations ('lineages') founded by obligately asexual female Potamopyrgus antipodarum. This New Zealand snail is a powerful model for studying sex because phenotypically similar sexual and asexual forms often coexist, allowing direct comparisons between sexuals and asexuals. After 2 years of culture, 23 of the 45 lineages had produced males, demonstrating that asexual P. antipodarum can make sons. We used maximum-likelihood analysis of a model of male production in which only some lineages can produce males to estimate that ~50% of lineages have the ability to produce males and that ~5% of the offspring of male-producing lineages are male. Lineages producing males in the first year of the experiment were more likely to make males in the second, suggesting that some asexual lineages might pay a cost of males relative to other asexual lineages. Finally, we used a simple deterministic model of population dynamics to evaluate how male production affects the rate of invasion of an asexual lineage into a sexual population, and found that the estimated rate of male production by asexual P. antipodarum is too low to influence invasion dynamics.

Myotonic dystrophy--a multigene disorder

Myotonic dystrophy (DM1) is the most common form of adult muscular dystrophy with an estimated incidence of 1/8000 births. The mutation responsible for this condition is an expanded CTG repeat within the 3' untranslated region of the protein kinase gene DMPK. Strong nucleosome positioning signals created by this expanded repeat cause a reduction in gene expression within the region. This "field effect" is further confounded by the retention of DMPK expansion containing transcripts, which acquire a toxic gain of function. Thus, the various manifestations exhibited by DM1 patients can be explained as a result of gene silencing, nuclear retention and sequestration of nuclear factors by the CUG containing transcript.

A self-calibrating phase-shifting algorithm based on the natural demodulation of two-dimensional fringe patterns

A new method of estimating the phase-shift between interferograms is introduced. The method is based on a recently introduced two-dimensional Fourier-Hilbert demodulation technique. Three or more interferogram frames in an arbitrary sequence are required. The first stage of the algorithm calculates frame differences to remove the fringe pattern offset; allowing increased fringe modulation. The second stage is spatial demodulation to estimate the analytic image for each frame difference. The third stage robustly estimates the inter-frame phase-shifts and then uses the generalised phase-shifting algorithm of Lai and Yatagai to extract the offset, the modulation and the phase exactly. Initial simulations of the method indicate that high accuracy phase estimates are obtainable even in the presence of closed or discontinuous fringe patterns.

In vivo co-localisation of MBNL protein with DMPK expanded-repeat transcripts

Myotonic dystrophy (DM1) is the most common form of adult muscular dystrophy and is inherited as an autosomal dominant trait. The genetic basis of DM1 is the expansion of a CTG repeat in the 3' untranslated region of a protein kinase gene (DMPK). The molecular mechanism by which this expanded repeat produces the pathophysiology of DM1 remains unknown. Transcripts from the expanded allele accumulate as foci in the nucleus of DM1 cells and it has been suggested that these transcript foci sequester cellular proteins that are required for normal nuclear function. We have investigated the role of three RNA-binding proteins, CUG-BP, hnRNP C and MBNL, as possible sequestered factors. Using a combination of indirect immunofluorescence to detect endogenous proteins and overexpression of proteins with green fluorescent protein (GFP) tags we have shown that CUG-BP and hnRNP C do not co-localise with expanded repeat foci in DM1 cell lines. However, GFP-tagged MBNL does itself form foci in DM1 cell lines and co-localises with the foci of expanded repeat transcripts. GFP-tagged MBNL does not appear as foci in non-DM1 cell lines. This work provides further support for the involvement of MBNL in DM1.

Three-dimensional Analysis of Laser Scanning Confocal Microscope Sections Reveals an Array of Microtubules in the Cleavage Furrow of Sea Urchin Eggs

Our recent observation that microtubules (MTs) are required for completion of division (abscission) led us to analyze MT organization during cytokinesis. Although many studies of MTs in sea urchin eggs have been done, computer-aided analysis of optical sections described herein reveals a new MT assemblage, which we call furrow MTs. This assemblage comprises bundles of MTs that lie in the cleavage furrow. Furrow MTs become apparent when the furrow has progressed approximately one-third of the way through the egg and persist to abscission. Furrow MTs are 8-24-&mgr;m long and arc across the base of the cleavage furrow. Acetylated tubulin is localized primarily in the furrow suggesting a distinct MT population. Three-dimensional analysis of optical sections suggests that furrow MTs are spatially distinct from midbody and astral MTs.

Ventral cell rearrangements contribute to anterior-posterior axis lengthening between neurula and tailbud stages in Xenopus laevis

Studies of morphogenesis in early Xenopus embryos have focused primarily on gastrulation and neurulation. Immediately following these stages is another period of intense morphogenetic activity, the neurula-to-tailbud transition. During this period the embryo is transformed from the spherical shape of the early stages into the long, thin shape of the tailbud stages. While gastrulation and neurulation depend largely on active cell rearrangement and cell shape changes in dorsal tissues, we find that the neurula-to-tailbud transition depends in part on activities of ventral cells. Ventral explants of neurula lengthen autonomously as much as the ventral sides of intact embryos, while dorsal explants lengthen less than the dorsal sides of intact embryos. Analyses of cell division, cell shapes, and cell rearrangement by transplantation of labeled cells and by time lapse recordings in live intact embryos concur that cell rearrangements in ventral mesoderm and ectoderm contribute to the autonomous anterior-posterior axis lengthening of ventral explants between neurula and tailbud stages.

Microtubules are required for completion of cytokinesis in sea urchin eggs

Completion of cytokinesis, abscission, has been studied little despite the intensive studies of the onset and contractile mechanism of the earlier phases of division. It has been well documented that microtubule (MT) disruption before furrow stimulation prevents furrowing, while MT disruption after furrow stimulation allows division to proceed. We have confirmed those findings using the MT inhibitors, nocodazole and demecolcine. In addition, we have found that MT disruption after furrow stimulation but before completion of division prevents abscission as evidenced by the observation that prospective daughter cells in MT-disrupted eggs maintain electrical continuity. Continued observation of eggs revealed that the furrow in MT-disrupted eggs did not result in abscission, but rather held steady until the time when controls underwent second cleavage, at which point the furrows regressed. These findings extend the recent reports that MTs are required for completion of division in mammalian tissue culture cells and frog eggs, to invertebrates, suggesting a common mechanism of abscission for animal cells.

Development of a yeast-based assay system for monitoring microsatellite instability

Simple sequence repeats (microsatellites) are found in all eukaryotic genomes. Instabilities within these sequences have been associated with several human disorders including Huntington's chorea and myotonic dystrophy. Further studies have identified links between microsatellite instability, faulty mismatch repair and certain human cancers, in particular a form of hereditary colorectal cancer. The assay system described here consists of a congenic set of yeast strains mutated in DNA replication and mismatch repair genes and assay plasmids with which it is possible to measure differences in microsatellite stability in the range of 5-850-fold. The development of this technology will allow monitoring of environmental and dietary influences on the genomic stability in the context of human disease.

Metal binding to the HIV nucleocapsid peptide

Co(II) and Zn(II) binding constants have been measured for binding to the HIV-1 nucleocapsid N-terminal metal binding domain (residues 1-18), using competition titration methods and monitoring Co(II) binding by visible absorbance spectroscopy. Enthalpies for binding were directly measured by isothermal titration colorimetry. The results are compared with recent studies of related systems, including a study of Zn(II) binding by the full length protein.

Requirement for microtubules in new membrane formation during cytokinesis of Xenopus embryos

In cleaving Xenopus eggs, exposure to nocodazole or cold shock prevents the addition of new plasma membrane to the cleavage plane and causes furrows to recede, suggesting a specific role for microtubules in cytokinesis. Whole-mount confocal immunocytochemistry reveals a ring of radially arranged, acetylated microtubule bundles at the base of all advancing cleavage furrows, from the first cleavage through the midblastula stage. We hypothesize that this novel microtubular structure is involved in transporting maternal stores of membrane in the subcortex to a site of membrane addition near the leading edge of the furrow.

Five newly established oesophageal carcinoma cell lines: phenotypic and immunological characterization

The derivation of permanent cell lines from 40 resected oesophageal carcinomas has been attempted. Five long-term lines have been established from three adenocarcinomas, one mixed carcinoma and one squamous carcinoma. Molecular and cellular analyses have been carried out on the lines and clones derived from them. Karyotype analysis indicates genetic variation among the clones. HLA-A, -B and -C is expressed constitutively, but not HLA-DR. ICAM-1-expressing phenotypes may have arisen during adaptation to long-term culture. All lines are capable of response to interferon-gamma (IFN-gamma) and all produce transforming growth factor beta 1 (TGF-beta 1). Two lines are resistant to the inhibitory growth effects of the latter, possibly contributing to malignancy. It is anticipated that these lines, originating from histologically different carcinomas, will provide a valuable, continuous resource for the investigation and treatment of these aggressive tumours.

Regulative development of Xenopus laevis in microgravity

To test whether gravity is required for normal amphibian development, Xenopus laevis females were induced to ovulate aboard the orbiting Space Shuttle. Eggs were fertilized in vitro, and although early embryonic stages showed some abnormalities, the embryos were able to regulate and produce nearly normal larvae. These results demonstrate for the first time that a vertebrate can ovulate in the virtual absence of gravity, and that the eggs can develop to a free-living stage.

Emotional and cardiovascular responses to adults' angry behavior and to challenging tasks in children of hypertensive and normotensive parents

Cardiovascular, overt-motor, and verbal-reported responses to interadult emotional expressions, including anger, and to challenging task situations were examined in a sample of 49 10-14-year-old children of hypertensive (EH) and normotensive parents (NT). Sons of EH parents showed greater systolic blood pressure reactivity to interadult anger and to the digit span task than sons of NT parents. A consistent pattern was not found for girls. Marital distress and overt maternal anger expression predicted verbal-reported and overt-motor responses to interadult anger. Family history of EH and sex did not predict these responses. Implications include (a) heightened systolic blood pressure response to stress may be found in sons of EH parents before they are diagnosed to have EH disorders, (b) relations between family history of EH and cardiovascular response may be sex moderated, and (c) vulnerability to stress may be related to specific familial histories and backgrounds.