Discovery of ultrafast spontaneous spin switching in an antiferromagnet by femtosecond noise correlation spectroscopy.

Owing to their high magnon frequencies, antiferromagnets are key materials for future high-speed spintronics. Picosecond switching of antiferromagnetic spin systems has been viewed a milestone for decades and pursued only by using ultrafast external perturbations. Here, we show that picosecond spin switching occurs spontaneously due to thermal fluctuations in the antiferromagnetic orthoferrite Sm0.7Er0.3FeO3. By analysing the correlation between the pulse-to-pulse polarisation fluctuations of two femtosecond optical probes, we extract the autocorrelation of incoherent magnon fluctuations. We observe a strong enhancement of the magnon fluctuation amplitude and the coherence time around the critical temperature of the spin reorientation transition. The spectrum shows two distinct features, one corresponding to the quasi-ferromagnetic mode and another one which has not been previously reported in pump-probe experiments. Comparison to a stochastic spin dynamics simulation reveals this new mode as smoking gun of ultrafast spontaneous spin switching within the double-well anisotropy potential.

Metachronous hepatic resection for liver only pancreatic metastases.

BACKGROUND: The value of liver resection (LR) for metachronous pancreatic ductal adenocarcinoma (PDAC) metastases remains controversial. However, in light of increasing safety of liver resections, surgery might be a valuable option for metastasized PDAC in selected patients. METHODS: We performed a retrospective, multicenter study including patients undergoing hepatectomy for metachronous PDAC liver metastases between 2004 and 2015 to analyze postoperative outcome and overall survival. All patients were operated with curative intent. Patients with oligometastatic metachronous liver metastasis with definitive chemotherapy (n = 8) served as controls. RESULTS: Overall 25 patients in seven centers were included in this study. The median age at the time of LR was 63.8 years (56.9-69.9) and the median number of metastases in the liver was 1 (IQR 1-2). There were eight non-anatomical resections (32%), 15 anatomical minor (60%) and 2 major LR (8%). Postoperative complications occurred in eleven patients (eight Clavien-Dindo grade I complications (32%) and three grade IIIa complications (12%), respectively). The 30-day mortality was 0%. The median length of stay was 8.6 days (IQR 5-11). Median overall survival following LR was 36.8 months compared to 9.2 months in patients with metachronous liver metastasis with chemotherapy (p = 0007). DISCUSSION: Liver resection for metachronous PDAC metastasis is safe and feasible in selected patients. To address general applicability and to find factors for patient selection, larger trials are urgently warranted.

Varying ratios of wavelengths in dual wavelength LED photomodulation alters gene expression profiles in human skin fibroblasts.

BACKGROUND AND OBJECTIVE: LED photomodulation has been shown to profoundly influence cellular behavior. A variety of parameters with LED photomodulation can alter cellular response in vitro. The effects of one visible and one infrared wavelength were evaluated to determine the optimal ratio to produce a net increase in dermal collagen by altering the ratio of total energy output of each wavelength. The ratio between the two wavelengths (590 and 870 nm) was shifted in 25% increments. STUDY DESIGN/MATERIALS AND METHODS: Human skin fibroblasts in culture were exposed to a 590/870 nm LED array with total combined energy density fixed at 4.0 mW/cm.. The ratio of 590/870 nm tested parameters were: 100/0%, 75/25%, 50/50%, 25/75%, and 0/100%. These ratios were delivered using pulsed duty cycle of exposure (250 milliseconds "on" time/100 milliseconds "off" time/100 pulses) for a total energy fluence of 0.1 J/cm.. Gene expression was examined using commercially available extra cellular matrix and adhesion molecule RT PCR Arrays (SA Biosciences, Frederick, MD) at 24 hours post-exposure. RESULTS: Different expression profiles were noticed for each of the ratios studied. Overall, there was an average (in an 80 gene array) of 6% expression difference in up or downregulation between the arrays. The greatest increase in collagen I and decrease in collagenase (MMP-1) was observed with 75/25% ratio of 590/870 nm. The addition of increasing proportions of IR wavelengths causes alteration in gene expression profile. The ratios of the wavelengths caused variation in magnitude of expression. CONCLUSIONS: Cell metabolism and gene expression can be altered by simultaneous exposure to multiple wavelengths of low energy light. Varying the ratios of specific wavelength intensity in both visible and near infrared light therapy can strongly influence resulting fibroblast gene expression patterns.

Hierarchical protein folding: asymmetric unfolding of an insulin analogue lacking the A7-B7 interchain disulfide bridge.

The landscape paradigm of protein folding can enable preferred pathways on a funnel-like energy surface. Hierarchical preferences may be manifest as a nonrandom pathway of disulfide pairing. Stepwise stabilization of structural subdomains among on-pathway intermediates is proposed to underlie the disulfide pathway of proinsulin and related molecules. Here, effects of pairwise serine substitution of insulin's exposed interchain disulfide bridge (Cys(A7)-Cys(B7)) are characterized as a model of a late intermediate. Untethering cystine A7-B7 in an engineered monomer causes significantly more marked decreases in the thermodynamic stability and extent of folding than occur on pairwise substitution of internal cystine A6-A11 [Weiss, M. A., Hua, Q. X., Jia, W., Chu, Y. C., Wang, R. Y., and Katsoyannis, P. G. (2000) Biochemistry 39, 15429-15440]. Although substantially disordered and without significant biological activity, the untethered analogue contains a molten subdomain comprising cystine A20-B19 and a native-like cluster of hydrophobic side chains. Remarkably, A and B chains make unequal contributions to this folded moiety; the B chain retains native-like supersecondary structure, whereas the A chain is largely disordered. These observations suggest that the B subdomain provides a template to guide folding of the A chain. Stepwise organization of insulin-like molecules supports a hierarchic view of protein folding.

Novel treatment strategies in chronic lymphocytic leukemia.

The recent introduction of new active agents has led to a renaissance of clinical investigation in chronic lymphocytic leukemia (CLL). These agents include three purine analogues, (pentostatin, fludarabine, and cladribine) and two monoclonal antibodies (rituximab and CAMPATH I-H). Careful clinical studies have allowed for the development of novel combinations of two and even three non-cross- resistant agents. These preliminary studies indicate that such combinations can induce complete responses in a larger proportion of patients than can single-agent therapy. In CLL, survival is superior for patients achieving a complete response compared with patients achieving a partial response. Therefore, strategies designed to induce high-quality responses in the majority of patients may one day lead to improved survival or possibly even cure in patients with chronic lymphocytic leukemia.

A thermophilic mini-chaperonin contains a conserved polypeptide-binding surface: combined crystallographic and NMR studies of the GroEL apical domain with implications for substrate interactions.

A homologue of the Escherichia coli GroEL apical domain was obtained from thermophilic eubacterium Thermus thermophilus. The domains share 70 % sequence identity (101 out of 145 residues). The thermal stability of the T. thermophilus apical domain (Tm>100 degrees C as evaluated by circular dichroism) is at least 35 degrees C greater than that of the E. coli apical domain (Tm=65 degrees C). The crystal structure of a selenomethione-substituted apical domain from T. thermophilus was determined to a resolution of 1.78 A using multiwavelength-anomalous-diffraction phasing. The structure is similar to that of the E. coli apical domain (root-mean-square deviation 0.45 A based on main-chain atoms). The thermophilic structure contains seven additional salt bridges of which four contain charge-stabilized hydrogen bonds. Only one of the additional salt bridges would face the "Anfinsen cage" in GroEL. High temperatures were exploited to map sites of interactions between the apical domain and molten globules. NMR footprints of apical domain-protein complexes were obtained at elevated temperature using 15N-1H correlation spectra of 15N-labeled apical domain. Footprints employing two polypeptides unrelated in sequence or structure (an insulin monomer and the SRY high-mobility-group box, each partially unfolded at 50 degrees C) are essentially the same and consistent with the peptide-binding surface previously defined in E. coli GroEL and its apical domain-peptide complexes. An additional part of this surface comprising a short N-terminal alpha-helix is observed. The extended footprint rationalizes mutagenesis studies of intact GroEL in which point mutations affecting substrate binding were found outside the "classical" peptide-binding site. Our results demonstrate structural conservation of the apical domain among GroEL homologues and conservation of an extended non-polar surface recognizing diverse polypeptides.

Hierarchical protein "un-design": insulin's intrachain disulfide bridge tethers a recognition alpha-helix.

A hierarchical pathway of protein folding can enable segmental unfolding by design. A monomeric insulin analogue containing pairwise substitution of internal A6-A11 cystine with serine [[Ser(A6),Ser(A11),Asp(B10),Lys(B28),Pro(B29)]insulin (DKP[A6-A11](Ser))] was previously investigated as a model of an oxidative protein-folding intermediate [Hua, Q. X., et al. (1996) J. Mol. Biol. 264, 390-403]. Its structure exhibits local unfolding of an adjoining amphipathic alpha-helix (residues A1-A8), leading to a 2000-fold reduction in activity. Such severe loss of function, unusual among mutant insulins, is proposed to reflect the cost of induced fit: receptor-directed restoration of the alpha-helix and its engagement in the hormone's hydrophobic core. To test this hypothesis, we have synthesized and characterized the corresponding alanine analogue [[Ala(A6),Ala(A11),Asp(B10),Lys(B28), Pro(B29)]insulin (DKP[A6-A11](Ala))]. Untethering the A6-A11 disulfide bridge by either amino acid causes similar perturbations in structure and dynamics as probed by circular dichroism and (1)H NMR spectroscopy. The analogues also exhibit similar decrements in thermodynamic stability relative to that of the parent monomer as probed by equilibrium denaturation studies (Delta Delta G(u) = 3.0 +/- 0.5 kcal/mol). Despite such similarities, the alanine analogue is 50 times more active than the serine analogue. Enhanced receptor binding (Delta Delta G = 2.2 kcal/mol) is in accord with alanine's greater helical propensity and more favorable hydrophobic-transfer free energy. The success of an induced-fit model highlights the applicability of general folding principles to a complex binding process. Comparison of DKP[A6-A11](Ser) and DKP[A6-A11](Ala) supports the hypothesis that the native A1-A8 alpha-helix functions as a preformed recognition element tethered by insulin's intrachain disulfide bridge. Segmental unfolding by design provides a novel approach to dissecting structure-activity relationships.

Treatment of poikiloderma of Civatte with an intense pulsed light source.

BACKGROUND: Effective treatment of poikiloderma of Civatte combines elimination of both the vascular and pigmented components simultaneously. A broad spectrum, noncoherent, intense pulsed light (IPL) source delivers multiple wavelengths with software controlled pulse durations and sequencing, which permits treatment of both vascular and pigmented lesions simultaneously. OBJECTIVE: To determine response and side effects of poikiloderma of Civatte of the neck and chest when treated by IPL. METHODS: One hundred and thirty-five patients randomly selected with typical changes of poikiloderma of Civatte on the neck and/or upper chest were treated with one to five treatments using IPL. RESULTS: Clearance of more than 75% of telangiectasias and hyperpigmentation comprising poikiloderma was observed. The incidence of side effects was 5%, including pigment changes. In many cases, improved skin texture was noted both by physician and patient. CONCLUSION: IPL is an effective mode of therapy for poikiloderma of Civatte. It offers a reduction of pigment and telangiectasias with a low risk profile. Additional benefits include subjective changes of improvement in skin texture.

Consolidation therapy with high-dose cyclophosphamide improves the quality of response in patients with chronic lymphocytic leukemia treated with fludarabine as induction therapy.

Fludarabine is the most active agent in the treatment of chronic lymphocytic leukemia (CLL). Despite this activity only a minority of patients treated with fludarabine achieve a complete response. We evaluated a new treatment program of sequential therapy with fludarabine followed by high-dose cyclophosphamide in previously untreated patients with CLL. This report details the results in 25 patients with previously untreated CLL. Patients received fludarabine (25 mg/m2/day x 5 days every 4 weeks for six cycles) as induction followed by consolidation with high-dose cyclophosphamide at one of three dose levels 1.5 g/m2, 2.25 g/m2, or 3 g/m2 administered every 2 weeks for three doses. High-dose cyclophosphamide was given with G-CSF support (5 microg/kg/day days 3-12). Complete response (CR) required a normal physical examination, normal CBC, a normal bone marrow evaluation including no residual lymphoid nodules on biopsy. A nodular response was defined as a complete response with the exception of an occasional residual nodule seen on bone marrow biopsy. Flow cytometric analysis for CD5:CD19 dual staining and kappa/lambda clonal excess was performed in all patients as a sensitive measure of minimal residual disease (MRD). Selected patients had patient/tumor-specific oligonucleotides generated that were subsequently used in a polymerase chain reaction as an extremely sensitive measure of MRD. There were no treatment-related deaths and no patient encountered unacceptable toxicity. After completion of this sequential regimen 76% (95% confidence interval: 59-93%) of patients had a major response: eight (32%) achieved a CR, four (16%) a nodular response, seven (28%) a PR, and six patients (24%) failed. Four patients withdrew from study during induction with fludarabine and did not receive at least one cycle of cyclophosphamide. Of the 21 patients who received consolidation with cyclophosphamide 10 (48%) had an improved quality of response when compared to that achieved with fludarabine. Two patients (8%) had no disease detectable by flow cytometry ('flow cytometric' CR) after six cycles of fludarabine. This improved to nine patients (36%) after high-dose cyclophosphamide. Following consolidation with high-dose cyclophosphamide three patients (12%) tested negative by PCR. All of these patients had morphologic evidence of residual disease after six cycles of fludarabine. Consolidation with high-dose cyclophosphamide increased the fraction of patients achieving a nodular response or CR three-fold (16% to 48%). This appears to be clinically relevant because with a median follow-up of 52 (range 34-78) months the projected 6-year survival for patients achieving a CR or NR is 91% compared to 41% for all others (P = 0.012). We conclude that sequential therapy with fludarabine followed by high-dose cyclophosphamide in previously untreated patients with CLL is safe and can improve the quality of response in a large proportion of patients compared to therapy with fludarabine alone.

Sexual dimorphism in diverse metazoans is regulated by a novel class of intertwined zinc fingers.

Sex determination is regulated by diverse pathways. Although upstream signals vary, a cysteine-rich DNA-binding domain (the DM motif) is conserved within downstream transcription factors of Drosophila melanogaster (Doublesex) and Caenorhabditis elegans (MAB-3). Vertebrate DM genes have likewise been identified and, remarkably, are associated with human sex reversal (46, XY gonadal dysgenesis). Here we demonstrate that the structure of the Doublesex domain contains a novel zinc module and disordered tail. The module consists of intertwined CCHC and HCCC Zn(2+)-binding sites; the tail functions as a nascent recognition alpha-helix. Mutations in either Zn(2+)-binding site or tail can lead to an intersex phenotype. The motif binds in the DNA minor groove without sharp DNA bending. These molecular features, unusual among zinc fingers and zinc modules, underlie the organization of a Drosophila enhancer that integrates sex- and tissue-specific signals. The structure provides a foundation for analysis of DM mutations affecting sexual dimorphism and courtship behavior.

A phase I and II study of pentostatin (Nipent) with cyclophosphamide for previously treated patients with chronic lymphocytic leukemia.

Purine analogs and alkylating agents are the most active drugs in the treatment of patients with chronic lymphocytic leukemia (CLL). Although fludarabine is the most widely tested purine analog in CLL, myelosuppression has limited its use in combination chemotherapy regimens. Because pentostatin (Nipent; SuperGen, San Ramon, CA), a related purine analog with proven activity in CLL, has less myelosuppression, we postulated that it would prove advantageous and could be more readily combined with alkylating agents. We are conducting a phase I/II trial of combination chemotherapy with pentostatin and cyclophosphamide for previously treated patients with CLL. Patients need to have Rai high-risk disease or "active" intermediate-risk disease. The treatment regimen consists of a fixed dose of pentostatin (4 mg/m2) combined with an increasing dose of cyclophosphamide. We plan to treat cohorts of three patients each at cyclophosphamide dose levels of 600, 900, 1,200, 1,500, and 2,000 mg/m2. Cycles will be repeated every 21 days. If unacceptable toxicity is encountered at one dose level, then three additional patients (total of six patients) will be accrued to that dose level before further dose escalations will be permitted. A second instance of unacceptable toxicity will close that dose level and identify the preceding level as the phase II dose. Additional patients will be accrued to the phase II dose level to better assess response. Supportive measures include the use of granulocyte colony-stimulating factor (5 microg/kg/d) to limit neutropenia. Sulfamethoxazole/trimethoprim will be given as prophylaxis against Pneumocystis carinii pneumonia and acyclovir will be administered as prophylaxis for herpes zoster. Response will be assessed according to standard criteria, and flow cytometry and fluorescent in situ hybridization will be used to assess for minimal residual disease in patients with trisomy 12.

Acute myelogenous leukemia after exposure to strontium-89 for the treatment of adenocarcinoma of the prostate.

BACKGROUND: Strontium-89 is a pure Beta-emitting radioactive analogue of calcium that has been shown to be beneficial in the palliation of pain due to osseous metastases from adenocarcinoma of the prostate. The most significant reported toxicity is dose-related, reversible, myelosuppression characterized primarily by thrombocytopenia. METHODS: A report of two patients in whom acute myelogenous leukemia (AML) developed after treatment with strontium-89 and a review of the literature are presented. RESULTS: The two patients described in the current study developed AML 17 months and 26 months, respectively, after exposure to strontium-89 for the treatment of prostate carcinoma. To the authors' knowledge these patients represent the first two reported cases of AML after strontium-89 therapy for prostate carcinoma. CONCLUSIONS: The results of the current study suggest the leukemogenic potential of strontium-89 treatment in humans. To the authors' knowledge, the current study represents the first report of AML after therapeutic exposure to strontium-89. As this agent is used more frequently (and earlier in the disease course) in patients with prostate carcinoma, an increased incidence of secondary AML complicating the clinical management of patients with prostate carcinoma may be observed. [See editorial on pages 497-9, this issue.]

Early clinical results with a multiple synchronized pulse 1064 NM laser for leg telangiectasias and reticular veins.

BACKGROUND: The 1064 nm wavelength penetrates tissue and blood vessels with little absorption by melanin. OBJECTIVE: To perform a study examining the effects of 1064 nm laser used in pulses from 4 msec to 16 msec on leg telangiectasias ranging in size from 0.5 to 3 mm. METHOD: In this initial trial, 50 sites on 30 patients were enrolled and treated with a multiple synchronized pulse laser at 1064 nm. The primary parameter utilized was a single 10-16 msec pulse. Improvement was judged by comparison of digital images at 1 month, 2 months, and 3 months posttreatment. Improvement was judged, based on size and number of vessels remaining. Side effects were noted as present or absent at each visit. RESULTS: Immediate contraction or darkening followed by urtication and visible total vessel closure as indicated by absence of blanching and visual elimination of the vessel border occurred in most of the treated sites. Two 3 mm diameter vessels were confirmed to be closed without flow by Duplex ultrasound visualization, using a 10 MHz transducer. Bruising from vessel rupture was seen in approximately 50% of the cases. No epidermal injury was noted in any sites, even in Fitzpatrick skin Types IV. At 3 months follow-up, 75% improvement was noted at treatment sites. CONCLUSIONS: Initial clinical results with a new multiple synchronized pulsed 1064 nm laser indicate that this longer wavelength supplied at pulses of up to 16 msec appears to be a valuable modality for immediate closure and subsequent elimination of leg ectatic veins. Epidermal injury is unlikely, as the near infrared wavelength has minimal interaction with melanin.

Periorbital skin resurfacing using high energy erbium:YAG laser: results in 50 patients.

OBJECTIVE: To evaluate Erbium:YAG regional periorbital laser resurfacing clinically and histologically. STUDY DESIGN/MATERIALS AND METHODS: Photographic evaluation before and after Erbium:YAG resurfacing with histologic evaluation of depth of injury. SETTING: Group private single specialty practice. PATIENTS: Fifty patients in the age range of 35-62 years, Fitzpatrick skin types I-III were treated using Erbium:YAG for regional resurfacing of periorbital rhytides. OUTCOME MEASURES: Patients were seen at days 1, 2, 3, 7, 14, 28, and at six months and one year. Photographs were obtained prior to application of topical anesthesia and were utilized to judge improvement of rhytides at all time intervals. Additional photographs were taken at each follow-up visit and the results judged by an independent investigator. Results were graded into five categories at all treatment intervals: no improvement, mild (grade 1: up to 25%), moderate (grade 2: 25-50%), good (grade 3: 50-75%, or excellent (grade 4: 75-100%). For histologic evaluation of depth of ablation and thermal injury one, two, and three passes at 21.2 J/cm2 were performed on four patients. RESULTS: Re-epithelization in the periorbital region was rapid with a mean duration of 2.65 days. Erythema ranged from a longest of six weeks to the shortest of seven days with a mean duration of 15.4 days. Evaluation of clinical results revealed that at two weeks mean improvement was 2.15 (between moderate and good). At four weeks further improvement was noted with a mean of 2.62. By six months, mean improvement score increased to 2.94. Minimal further improvement was noted between six months and one year with a mean improvement score of 3.02 (good to excellent). Histology revealed complete removal of the epidermis with one to three passes. Dermal ablation of 5-10 microns accompanied by small increases (5-10 microns) in dermal thermal injury occurred with each subsequent pass. CONCLUSIONS: We conclude that high energy Erbium:YAG periorbital resurfacing is a safe and effective modality which achieves substantial therapeutic effect. Most patients achieve approximately 75% improvement. Erythema fades quickly, reepithelization is rapid and side effects are minimal.

Hair removal with a non-coherent filtered flashlamp intense pulsed light source.

BACKGROUND AND OBJECTIVE: To evaluate the effects on disruption of hair growth of the non-coherent filtered flashlamp intense pulsed light (IPL) source. MATERIALS AND METHODS: Twenty-eight sites on 23 patients with Fitzpatrick type I-III were enrolled using a single treatment IPL followed for three months post-treatment. Another 56 on 48 patients with Fitzpatrick skin types I-V randomly enrolled for two treatments one month apart and followed for six months. STUDY DESIGN: Prior to beginning treatment and at each follow-up visit hair counts were obtained by averaging three 1-cm2 areas on a clear acetate template placed over the skin. Repeat hair counts and photographs were obtained at 2, 4, 8, and 12 weeks for the single treatment protocol and at additional 4, 5, and 6 months for the double treatment protocol. Parameters utilized were a 2.8-3.2 millisecond pulse duration typically for three pulses with thermal relaxation intervals of 20-30 milliseconds with a total fluence of 40-42 J/cm2. RESULTS: For the double treatment protocol hair clearance of 64% was achieved immediately following the second treatment. By week 8 reduction of hair counts was 42%. At 6 months, hair counts were reduced by 33%. CONCLUSIONS: Non-coherent IPL is an effective modality for long-term hair removal. IPL is safe with minimal side effects of epidermal injury or pigmentation change.

Post-sclerotherapy compression: controlled comparative study of duration of compression and its effects on clinical outcome.

BACKGROUND: Although much has been published on the effects of compression on the venous system, relatively few studies address the duration of compression following sclerotherapy of telangiectatic webs associated with reticular veins. OBJECTIVE: To perform a controlled study comparing the effects of different durations of compression following sclerotherapy of reticular veins and telangiectasias in similar locations. METHOD: This study consisted of a total of 40 patients, 30 patients who received compression therapy and 10 control patients who did not receive compression therapy. The compression group consisted of 10 in each of three duration groups: 3 days, 1 week, and 3 weeks. Patients were evaluated at 1 week, 2 weeks, 6 weeks, 12 weeks, and 24 weeks for degree of improvement and side effects. RESULTS: The three compression groups showed significantly greater improvement at 6 weeks (p = .004). There was a strong correlation between the length of time compression was applied and degree of improvement at 6 weeks, 12 weeks, and 24 weeks of clinical follow-up; r = .74, p = .0006, r = .59, p = .006, r = .66, p = .0001, respectively. The patients treated with compression for 3 days and 1 week had more improvement than the control patients while the patients treated for 3 weeks of continuous compression had the most improvement. In terms of side effects, the 1 week and 3 week compression groups experienced the least amount of post-sclerotherapy hyperpigmentation. CONCLUSIONS: Compression enhances the results following sclerotherapy in a statistically significant way and is directly correlated with duration of compression. Three weeks of continuous compression leads to the best results, although even 3 days of compression results in greater improvement than no compression. Compression leads to a statistically significant reduction of post-sclerotherapy hyperpigmentation.

A phase I trial of a single high dose of idarubicin combined with high-dose cytarabine as induction therapy in relapsed or refractory adult patients with acute lymphoblastic leukemia.

Relapsed or refractory adult acute lymphoblastic leukemia (ALL) carries a grave prognosis. The most promising strategy for curing these patients is through re-induction chemotherapy followed by successful allogeneic transplant. We studied a new high-dose induction regimen in order to improve the outcome for these patients. Eighteen adult patients with relapsed/refractory ALL were treated on a phase I study of high-dose cytarabine combined with a single escalating dose of idarubicin. Five patients had primary refractory disease and 13 were treated in refractory relapse. Nine patients (50%) had Ph+ ALL. The induction regimen was cytarabine 3 g/m2/day intravenously days 1-5 and idarubicin as a single intravenous dose on day 3. G-CSF 5 microg/kg subcutaneously every 12 h was started on day 7. The initial idarubicin dose was 20 mg/m2 with dose escalations of 10 mg m2. Cohorts of three patients were treated at each idarubicin dose level. Unacceptable toxicity was encountered at 50 mg/m2 with one death from infection and one death from cardiotoxicity in a patient with significant prior anthracycline exposure. There were no instances of grade 4 non-hematologic toxicity encountered at idarubicin doses of 20 mg/m2, 30 mg/m2, or 40 mg/m2. The data suggest a dose-response relationship for increasing doses of idarubicin with 0/3 complete responses (CR) at 20 mg/m2, 1/3 CR at 30 mg/m2, and 7/12 (58%) CR at idarubicin doses > or = 40 mg/m2. We conclude that concomitant administration of cytarabine 3 g/m2/day x 5 and high-dose idarubicin at 40 mg/m2 as a single dose on day 3 can be administered safely to patients with refractory and relapsed ALL.

Transcriptional activator-coactivator recognition: nascent folding of a kinase-inducible transactivation domain predicts its structure on coactivator binding.

A model of transcriptional activator-coactivator recognition is provided by the mammalian CREB activation domain and the KIX domain of coactivator CBP. The CREB kinase-inducible activation domain (pKID, 60 residues) is disordered in solution and undergoes an alpha-helical folding transition on binding to CBP [Radhakrishan, I., Perez-Alvarado, G. C., Parker, D., Dyson, H. J., Montminy, M. R., and Wright, P. E. (1997) Cell 91, 741-752]. Binding requires phosphorylation of a conserved serine (RPpSYR) in pKID associated in vivo with the biological activation of CREB signaling pathways. The CBP-bound structure of CREB contains two alpha-helices (designated alphaA and alphaB) flanking the phosphoserine; the bound structure is stabilized by specific interactions with CBP. Here, the nascent structure of an unbound pKID domain is characterized by multidimensional NMR spectroscopy. The solubility of the phosphopeptide (46 residues) was enhanced by truncation of N- and C-terminal residues not involved in pKID-CBP interactions. Although disordered under physiologic conditions, the pKID fragment and its unphosphorylated parent peptide exhibit partial folding at low temperatures. One recognition helix (alphaA) is well-defined at 4 degreesC, whereas the other (alphaB) is disordered but inducible in 40% trifluoroethanol (TFE). Such nascent structure is independent of serine phosphorylation and correlates with the relative extent of engagement of the two alpha-helices in the pKID-KIX complex; whereas alphaA occupies a peripheral binding site with few intermolecular contacts, the TFE-inducible alphaB motif is deeply engaged in a hydrophobic groove. Our results support the use of TFE as an empirical probe of hidden structural propensities and define a correspondence between induced fit and the nascent structure of peptide fragments.