Xevinapant combined with pembrolizumab in patients with advanced, pretreated colorectal and pancreatic cancer: results of the phase 1b/2 CATRIPCA trial

PURPOSE

Xevinapant is an orally available inhibitor of apoptosis proteins (IAP) inhibitor. Preclinical data suggest that IAP antagonism may synergize with immune checkpoint blockers (ICB) by modulating the NF-KB pathway in immune cells.

PATIENTS AND METHODS

Adult patients (pts) with non MSI-H advanced/metastatic PDAC or CRC were enrolled in this phase 1b/2 and received pembrolizumab 200mg q3w, IV and ascending doses of oral xevinapant (100, 150 and 200mg daily for 14 days on/7 days off). Dose escalation followed a 3+3 design with a 21-day dose-limiting toxicity (DLT) evaluation period. Following the determination of the recommended phase II dose (RP2D), 14 patients with PDAC and 14 patients with CRC were enrolled in expansion cohorts to assess preliminary efficacy.

RESULTS

Forty-one pts (26 males) with a median age of 64 years were enrolled: 13 in the dose escalation and 28 in the two expansion cohorts. No DLT was observed during dose-escalation. The RP2D was identified as xevinapant 200mg/d + pembrolizumab 200mg q3w. The most common adverse events (AE) were fatigue (37%), gastrointestinal AE (decreased appetite in 37%, nausea in 24%, stomatitis in 12 % and diarrhea and vomiting in 10% each), and cutaneous AE (pruritus, dry skin and rash seen in 20, 15 and 15% of patients respectively). The best overall response according to RECIST1.1 was partial response (PR, confirmed) in one (3%) , stable disease (SD) in four (10%) and progressive disease in 35 (88%).

CONCLUSIONS

Xevinapant combined with pembrolizumab was well tolerated with no unexpected adverse events. However, anti-tumor activity was low.

Pembrolizumab in Lymphopenic Metastatic Breast Cancer Patients Treated with Metronomic Cyclophosphamide: A Clinical and Translational Prospective Study

Purpose

Metastatic endocrine-resistant breast cancer (MBC) is a disease with poor prognosis and few treatment options. Low lymphocyte count is associated with limited overall survival. In a prospective cohort of lymphopenic patients with HER-2 negative MBC, we assessed the clinical and biological impact of pembrolizumab combined with metronomic cyclophosphamide.

Experimental Design

This multicenter Phase II study evaluated the safety and clinical activity of pembrolizumab (intravenous (IV), 200mg, every 3 weeks) combined with metronomic cyclophosphamide (50mg/day, per os) in lymphopenic adult patients with HER2-negative MBC previously treated by at least one line of chemotherapy in this setting according to a Simon's minimax two-stage design. Blood and tumor samples were collected to assess the impact of the combined treatment on circulating immune cells and the tumor immune microenvironment through multiparametric flow cytometry and multiplex immunofluorescence analyses. Primary endpoint was the clinical benefit rate at 6 months of treatment (CBR-6M). Secondary endpoints were objective response rate (ORR), duration of response, progression free survival (PFS), and overall survival (OS).

Results

Two out of the twenty treated patients presented clinical benefit (one Tumor Mutational Burden (TMB)-high patient with complete response (CR) and one patient with objective response (OR) per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST V1.1) associated with a strong increase of cytokine-producing and proliferating CD4⁺ T cells and higher CD8⁺ T cells to macrophage ratios in the tumor. This impact on CD4⁺ and CD8⁺ T cell polyfunctionality was still observed more than one year for the patient with CR. A decreased in their absolute number of CD4⁺ and CD8⁺ memory T cells was observed in other patients.

Conclusion

Pembrolizumab combined with metronomic cyclophosphamide was well tolerated, and displayed limited anti-tumoral activity in lymphopenic MBC. Correlative translational data of our trial advocates for additional studies with other chemotherapy combinations.

OS4.1 MEVITEM: A European, randomized, open-label, Phase I/II study of vismodegib in combination with temozolomide versus temozolomide alone in adult patients with recurrent or refractory medulloblastoma presenting an activation of the Sonic Hedgehog (SHH) pathway

BACKGROUND

Vismodegib (V) suppresses sonic hedgehog (SHH) signaling. We postulated that vismodegib together with chemotherapy may be more efficient than chemotherapy alone in patients (pts) relapsing of a SHH-activated medulloblastoma (MB).

MATERIAL AND METHODS

Adult pts with recurrent SHH-MB not previously exposed to temozolomide (T) were randomly assigned (2:1 ratio) to Arm A (V daily 150mg/d, po) + T (D1-5: 150 mg/m2 for cycle 1 and 200 mg/m2 thereafter; n=up to 25pts) or Am B (T alone; n=up to 13pts). Identification of SHH activation was performed centrally by IHC (GAB1, β-catenin, filamin A, and YAP1). NGS analyses were performed to identify the mutations responsible for SHH activation. Primary objectives were to assess the incidence of severe toxicities (safety run-in based on a 3 + 3 design) and the 6-month non-progression rate (NPR-6m) according to WHO criteria and based on central read tumor assessment (Phase II). A Minimax Simon’s two-stage design was used to detect NPR-6m of 55% (p0: 30%, type I error rate of 5%, power of 80%). At first stage, ≥ 3/9 pts without progression at 6m were required for the accrual of 16 additional pts in Arm A. A 3rd independent and parallel arm with V as single agent (Arm C, n= up to15pts) was added for pts previously treated by T.

RESULTS

24 SHH-MB pts were enrolled (Arm A: 10, Arm B: 5 and Arm C: 9; median age: 37 y [21–55]). At the end of the safety run-in; no major safety concerns were reported. At the end of Stage I: no objective response were reported and 2 pts among 10 were free of progression at 6m among in Arm A. According to statistical rules, the study was definitively closed to enrolment. NGS analyses showed a PTCH1 inactivating mutation in 6 pts (n=4 in arm A; n= 2 in arm B); a SMO activating mutation in 4 pts (n= 3 in Arm A; n=1 in Arm B). For 1 pt in each arm, no tumor sample was available for analysis, for 1 pt in Arm A DNA quality was insufficient, and for 1 patient in each arm no mutations of SMO, PTCH1, SUFU or SHH were found. Out of the 4 pts in Arm A with an inactivating PTCH1 mutation, only 1 was progression free at 6m. PFS and OS data will be presented at the meeting.

CONCLUSION

The combination of vismodegib with monthly T failed to demonstrate superior activity as compared with T alone. Further studies are warranted to refine therapeutic indication for vismodegib

Molecular screening program to select molecular-based recommended therapies for metastatic cancer patients: analysis from the ProfiLER trial

BACKGROUND

Antitumor activity of molecular-targeted agents is guided by the presence of documented genomic alteration in specific histological subtypes. We aim to explore the feasibility, efficacy and therapeutic impact of molecular profiling in routine setting.

PATIENTS AND METHODS

This multicentric prospective study enrolled adult or pediatric patients with solid or hematological advanced cancer previously treated in advanced/metastatic setting and noneligible to curative treatment. Each molecular profile was established on tumor, relapse or biopsies, and reviewed by a molecular tumor board (MTB) to identify molecular-based recommended therapies (MBRT). The main outcome was to assess the incidence rate of genomic mutations in routine setting, across specific histological types. Secondary objectives included a description of patients with actionable alterations and for whom MBRT was initiated, and overall response rate.

RESULTS

Four centers included 2579 patients from February 2013 to February 2017, and the MTB reviewed the molecular profiles achieved for 1980 (76.8%) patients. The most frequently altered genes were CDKN2A (N = 181, 7%), KRAS (N = 177, 7%), PIK3CA (N = 185, 7%), and CCND1 (N = 104, 4%). An MBRT was recommended for 699/2579 patients (27%), and only 163/2579 patients (6%) received at least one MBRT. Out of the 182 lines of MBRT initiated, 23 (13%) partial responses were observed. However, only 0.9% of the whole cohort experienced an objective response.

CONCLUSION

An MBRT was provided for 27% of patients in our study, but only 6% of patients actually received matched therapy with an overall response rate of 0.9%. Molecular screening should not be used at present to guide decision-making in routine clinical practice outside of clinical trials.This trial is registered with ClinicalTrials.gov, number NCT01774409.

Abstract P3-13-08: Preclinical validation of a new tumor imaging agent targeting αvβ3 to detect breast tumor using NIR-light imaging

Surgery is still a essential step for breast cancer treatment. Complete tumor removal during surgery rely on surgeon's ability to differentiate tumor from normal tissue. To date, no intra operative method is available and reliable enough to help the surgeon delineate precisely tumor extension in the adjacent normal tissue. Thus, surgeons rely solely on pre operative imaging techniques to delineate tumor margins. Recent advances made in the field of non-invasive imaging and vectorized nano-size particles have revealed a remarkable potential for improved tumor-margin detection. AngiostampTM is a new fluorescent agent for intra operative imaging. This system provides strong binding on αvβ3 integrin-rich tumor neoangiogenesis. Our general hypothesis is that targeting αvβ3 integrin-rich breast carcinoma neoangiogenesis should provide improved delivery of diagnostic compounds and assist surgeons intra operatively using near-infrared imaging techniques.

We conducted preclinical studies to evaluate the distribution of angiostampTM in vivo in murine breast tumor model and to determine the expression of αvβ3 integrin on human breast specimens.

The capacity of AngiostampTM to target αvβ3 integrin was assessed in 4T1 breast tumor model. After tumor implantation, mices were injected with AngiostampTM or a saline solution. Detection of the tumors was performed at different timepoints (early, progressive and established tumors, N= 24 mices/timepoint) using near infrared (NIR) imaging system (FluobeamTM) to detect fluorescence in tumor tissue.

In parallel, the expression of αvβ3 integrins in normal breast tissue, benign lesions (N=20) and various tumors subtypes (N=120) was assessed by immunohistochemistry.

In mice injected with AngiostampTM, fluorescence was observed only within the tumors with low background. AngiostampTM labeled tumors at all timepoint. No false negative fluorescence was found as confirmed by histopathological analyses.

In humans, the αvβ3 integrin are expressed in normal breast epithelial cells and benign metaplastic or proliferative epithelial lesions. However, due to the density of carcinomatous cells, the level of expression was much higher in breast cancer: 94% of invasive ductal carcinomas and 100% of invasive lobular carcinomas had a membranous staining (moderate to high intensity). Expression in breast cancer was not restricted to tumor subtypes neither hormone receptor expression nor SBR grade.

Based on this preclinical demonstration, AngiostampTM could allow a better intra-operative detection of tumor bed in breast cancer, increasing the efficiency of surgical procedure especially for infraclinic disease and decreasing the rate of second surgery. Preclinical development is ongoing and the first clinical trial is expected in 2017.

Citation Format: Beurrier F, Dutour A, Chen Y, Froc E, Gayet P, Guillermet S, Rizo P, Chopin N, Faure C, Dammaco MA, Klinger S, Ferraioli D, Garin G, Treilleux I. Preclinical validation of a new tumor imaging agent targeting αvβ3 to detect breast tumor using NIR-light imaging [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-13-08.

Immune cell dysfunctions in breast cancer patients detected through whole blood multi-parametric flow cytometry assay

Monitoring functional competence of immune cell populations in clinical routine represents a major challenge. We developed a whole-blood assay to monitor functional competence of peripheral innate immune cells including NK cells, dendritic and monocyte cell subsets through their ability to produce specific cytokines after short-term stimulation, detected through intra-cytoplasmic staining and multi-parametric flow-cytometry. A PMA/ionomycin T cell activation assay complemented this analysis. Comparing cohorts of healthy women and breast cancer (BC) patients at different stages, we identified significant functional alteration of circulating immune cells during BC progression prior to initiation of treatment. Of upmost importance, as early as the localized primary tumor (PT) stage, we observed functional alterations in several innate immune populations and T cells i.e. (i) reduced TNFα production by BDCA-1⁺ DC and non-classical monocytes in response to Type-I IFN, (ii) a strong drop in IFNγ production by NK cells in response to either Type-I IFN or TLR7/8 ligand, and (iii) a coordinated impairment of cytokine (IL-2, IFNγ, IL-21) production by T cell subpopulations. Overall, these alterations are further accentuated according to the stage of the disease in first-line metastatic patients. Finally, whereas we did not detect functional modification of DC subsets in response to TLR7/8 ligand, we highlighted increased IL-12p40 production by monocytes specifically at first relapse (FR). Our results reinforce the importance of monitoring both innate and adaptive immunity to better evaluate dysfunctions in cancer patients and suggest that our whole-blood assay will be useful to monitor response to treatment, particularly for immunotherapeutic strategies.

Abstract CT333: Elypse-7: A randomized, placebo-controlled, Phase 2a evaluating the impact of IL-7 immunotherapy on CD4 count, risks of severe haematological toxicity and tumor progression in metastatic breast cancer patients

Background: Total and CD4 lymphopenia is observed in 25% of advanced cancers patients and is a predictive factor of chemotherapy (CT)-induced death, febrile neutropenia, thrombocytopenia, anemia, as well as an independent prognostic factor for survival and tumor progression. CYT107 is a glycosylated recombinant human IL-7 (CYTHERIS, France) emerging as a promising immuno-restorative agent well tolerated in Phase 1 trials. To date, it is unknown whether IL-7 can correct lymphopenia during CT and whether this could translate into clinical benefit in advanced cancer patients.

Methods: A placebo-controlled, monocentric, Phase 2a (NCT01368107) was conducted in lymphopenic metastatic breast cancer (MBC) patients to be treated by capecitabine (2500mg/m2/d, pers os, 21-day cycle from D21 after randomization). Using a 2x2 factorial design, patients were randomly allocated to 4 arms to receive 1) before the 1st cycle of CT : r-hIL-7 (CYT107:10µg/kg, subcutaneously, weekly at D0, D7, D14, groups 2 & 4) or placebo (groups 1 & 3), then 2) during the 3rd cycle of CT: r-hIL-7 (weekly at D57, D64, D71, groups 3 & 4) or placebo (groups 1 & 2). The primary endpoint, CD4 count evolution, was evaluated before (D0 to D21) and during CT (D57 to D78). Secondary endpoints include risks of severe hematological AE, safety and progression free survival (PFS). An ancillary study has evaluated the quantitative and functional changes in circulating immune cells (see abstract Ménétrier-Caux).

Results: From Nov. 2011 to Jun. 2013, 20 patients (median age [range]: 60 [39-76 y.]; median CD4 count on D0: 242 [22-522 cells/µL]) with MBC (mainly with bone and liver metastasis) were enrolled. Before CT (n=20), r-hIL-7 treatment induced a significant increase of CD4 count (median relative evolution: +148.1% [41.8-763.9 cells/µL] in r-hIL-7 groups vs +9.9% [-50.3-102.2 cells/µL] in placebo [Wilcoxon, p=0.002]). During CT (n=11), r-hIL-7 treatment also increased CD4 count (+58.6%[-15.2-281.5 cells/µL] in r-hIL-7 groups vs -2.4% [-27.6-112.5 cells/µL] in placebo [p=0.121]). Overall, r-hIL-7 was well tolerated with reactions related to injection as the main specific AE, no binding or neutralizing antibodies, and no r-hIL-7-related ≥ Grade 3 AE except 1 fatal SAE for which one a relationship to r-hIL-7 cannot be ruled out. Interestingly, r-hIL-7 treatment during CT reduced the incidence of Grade 3 hematological AE compared to placebo (0 vs 5 events, respectively). PFS data will be available by Feb. 2014.

Conclusion: In this exploratory trial, r-hIL-7 treatment was safe at biologically active dose, able to correct CD4 lymphopenia and associated with lower incidence of severe hematological toxicity during CT. These early results are encouraging and warrant further investigations of IL-7 clinical applications in the oncology field.

Citation Format: Ray-Coquard Isabelle, Olivier Tredan, Gwenaele Garin, Christine Ménétrier-Caux, Sylvie Chabaud, Thomas Bachelot, Claire Cropet, Pierre-Etienne Heudel, Paul Rebattu, Patricia Dupont, Estelle Verronese, Anne-claire Cadore, Valérie Fouillat, Olfa Derbel, Nathalie Bonnin, Thérèse Croughs, Michel Morre, Nicolas Pasqual, Manuari Manuel, Gilles Clapisson, Christophe Caux, David Pérol, Jean-Yves Blay. Elypse-7: A randomized, placebo-controlled, Phase 2a evaluating the impact of IL-7 immunotherapy on CD4 count, risks of severe haematological toxicity and tumor progression in metastatic breast cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT333. doi:10.1158/1538-7445.AM2014-CT333

Flow-Mediated Signaling Modulates Endothelial Cell Phenotype

The focal development of atherosclerosis in the vascular tree may be explained in part by the local nature of blood flow. Bifurcations and branching points, prone to early atherogenesis, experience disturbed and oscillatory flow, whereas straight vascular regions, resistant to atherosclerosis, are exposed to steady laminar flow. A large number of studies suggest that the antiatherosclerotic effects of laminar flow are in part due to the ability of flow to modulate endothelial cell phenotype. Under steady laminar flow, endothelial cells generate molecules that promote a vasoactive, anticoagulant, anti-inflammatory, and growth-inhibitory surface. In contrast, disturbed flow induces a proliferative, prothrombotic, and adhesive phenotype. Endothelial cells are able to sense the variations of flow via mechanosensitive cell surface proteins and to transduce these signals via intracellular pathways to transcription factors in the nucleus leading to phenotypic changes. This review summarizes the "outside-in" signaling events initiated by flow that modulate endothelial cell phenotype.

Flow Antagonizes TNF-α Signaling in Endothelial Cells by Inhibiting Caspase-Dependent PKCζ Processing

Unidirectional laminar flow is atheroprotective, in part by inhibiting cytokine-mediated endothelial cell (EC) inflammation and apoptosis. Previously, we showed that flow inhibited TNF-α signaling by preventing activation of JNK. Recently, PKCζ was identified as the PKC isoform most strongly regulated by flow pattern, with increased PKCζ activity in regions of disturbed flow versus unidirectional flow. Interestingly, PKCζ is cleaved by caspases after TNF-α stimulation to generate a 50-kDa truncated form (CATζ, catalytic domain of PKCζ) with a higher kinase activity than the full-length protein. We hypothesized that flow would inhibit TNF-α–mediated PKCζ cleavage and thereby CATζ formation. We found that PKCζ activity was required for TNF-α–mediated JNK and caspase-3 activation in ECs. PKCζ was rapidly cleaved to generate CATζ in cultured bovine and human aortic ECs and in intact rabbit vessels stimulated with TNF-α. This truncated form of PKCζ enhanced JNK and caspase-3 activation. Interestingly, PKCζ cleavage was prevented by inhibitors of PKCζ, JNK, and caspase activities, suggesting that these enzymes, via regulating CATζ formation, modulate caspase-3 activity in ECs. Finally, we found that flow reduced caspase-dependent processing of PKCζ and caspase-3 activation. These results define a novel role for PKCζ as a shared signaling mediator for flow and TNF-α, and important for flow-mediated inhibition of proinflammatory and apoptotic events in ECs.

6A3-5/Osa2 is an early activated gene implicated in the control of vascular smooth muscle cell functions

Vascular smooth muscle cells (VSMC) growth plays a key role in the pathophysiology of vascular diseases. However, the molecular mechanisms controlling gene transcription in VSMC remain poorly understood. We previously identified, by differential display, a new gene (6A3-5) overexpressed in proliferating rat VSMC. In this study, we have cloned the full-length cDNA by screening a rat foetal brain cDNA library and investigated its functions. The 6A3-5 protein shows 4 putative conserved functional motifs: a DNA binding domain called ARID (AT-rich interaction domain), two recently described motifs (Osa Homology Domain), and a nuclear localization signal. The deduced protein sequence was observed to be 85% identical to the recently described human Osa2 gene. Immunolabelling, using an anti-6A3-5/Osa2 monoclonal antibody, showed a nuclear localization of the 6A3-5/Osa2 protein. In addition, PDGF upregulated 6A3-5/Osa2 expression at both the transcript and protein levels in a dose and time-dependent fashion. The pattern of upregulation by PDGF was reminiscent of the early responsive gene c-fos. The PDGF-induced upregulation of 6A3-5/Osa2 and proliferation of VSMC were significantly inhibited in a dose and sequence-dependent fashion by an antisense, but not by sense, scrambled or mismatched oligonucleotides directed against 6A3-5/Osa2. In VSMC of aortas derived from hypertensive (LH) rats, 6A3-5/Osa2 is overexpressed as compared to that in normotensive (LL) rats. The 6A3-5/Osa2-gene expression is downregulated by an ACE inhibitor and upregulated by exogenous AngiotensinII in LH rats. In summary, these results indicate that 6A3-5/Osa2 is an early activated gene that belongs to a new family of proteins involved in the control of VSMC growth.

Vascular shear stress and activation of inflammatory genes

Atherosclerotic lesions form preferentially at distinct sites in the arterial tree, especially at or near branch points, bifurcations, and curvatures where there is disturbed or oscillatory blood flow. In contrast, straight regions of the vasculature exhibit uniform laminar shear stress, which is atheroprotective. The ability of laminar flow to exert an anti-inflammatory effect on the endothelial cell lining of the blood vessel is revealed by preventing monocyte adhesion, proliferation, and apoptosis. Changes in endothelial cell gene expression in response to laminar shear stress reflect these changes in cell physiology with the demonstration that physiologic flow inhibits the expression of inflammatory genes. Thus, shear stress is critically important in regulating vascular physiology and pathobiology of the vessel wall via the modulation of endothelial cell gene expression.

BMK1/ERK5 is a novel regulator of angiogenesis by destabilizing hypoxia inducible factor 1alpha

Big MAP kinase 1 (BMK1 or ERK5) is a key mediator of endothelial cell (EC) function as shown by impaired embryonic angiogenesis and vascular collapse in BMK1 knockout mice. Hypoxia inducible factor 1alpha (HIF1alpha), a potent mediator of angiogenesis, is positively regulated by the MAP kinases, ERK1/2. Because BMK1 deficiency is associated with impaired angiogenesis we hypothesized that BMK1 might regulate HIF1alpha. To test this hypothesis, bovine lung microvascular ECs (BLMECs) were transfected with HIF1alpha and BMK1 cDNAs, and stimulated by hypoxia. HIF1alpha activity was measured by a reporter gene assay in which luciferase expression was driven by HIF1alpha activation. Hypoxia (1% O2, 24 hours) stimulated HIF1alpha activity by 5.1+/-0.6 fold. In the presence of dominant negative (DN)-BMK1, which inhibited BMK1 activity, hypoxia induced HIF1alpha activity was enhanced significantly to 6.4+/-0.4 fold. BMK1 activation by constitutively active (CA)-MEK5 inhibited HIF1alpha activity by 46+/-4%, suggesting BMK1 functions as a negative regulator of HIF1alpha activation. Activation of BMK1 reduced HIF1alpha protein levels. Ubiquitination inhibitors (30 micromol/L ALLN, 2 micromol/L lactacystin, or 100 nmol/L MG132) reduced the BMK1-mediated effect on HIF1alpha expression by >80%, suggesting that BMK1 stimulated HIF1alpha proteolysis. The negative effect of BMK1 on HIF1alpha was functionally important because transfection with CA-MEK5 significantly decreased EC migration by 68+/-10%, and inhibited angiogenesis (in vitro Matrigel assay) by 76+/-7%. In summary, BMK1 is a novel negative regulator of HIF1alpha and angiogenesis by increasing HIF1alpha ubiquitination and inhibiting HIF1alpha activity in endothelial cells.

Calcium-dependent interaction of S100B with the C-terminal domain of the tumor suppressor p53

In vitro, the S100B protein interacts with baculovirus recombinant p53 protein and protects p53 from thermal denaturation. This effect is isoform-specific and is not observed with S100A1, S100A6, or calmodulin. Using truncated p53 proteins in the N-terminal (p53(1-320)) and C-terminal (p53(73-393)) domains, we localized the S100B-binding region to the C-terminal region of p53. We have confirmed a calcium-dependent interaction of the S100B with a synthetic peptide corresponding to the C-terminal region of p53 (residues 319-393 in human p53) using plasmon resonance experiments on a BIAcore system. In the presence of calcium, the equilibrium affinity of the S100B for the C-terminal region of p53 immobilized on the sensor chip was 24 +/- 10 nM. To narrow down the region within p53 involved in S100B binding, two synthetic peptides, O1(357-381) (residues 357-381 in mouse p53) and YF-O2(320-346) (residues 320-346 in mouse p53), covering the C-terminal region of p53 were compared for their interaction with purified S100B. Only YF-O2 peptide interacts with S100B with high affinity. The YF-O2 motif is a critical determinant for the thermostability of p53 and also corresponds to a domain responsible for cytoplasmic sequestration of p53. Our results may explain the rescue of nuclear wild type p53 activities by S100B in fibroblast cell lines expressing the temperature-sensitive p53val135 mutant at the nonpermissive temperature.

Central nervous system prophylaxis. Studies showing impairment in verbal skills and academic achievement

School attendance and school achievement were the parameters studied to assess the pediatric cancer patient's ability to learn and keep pace with their peers. Effects of CNS prophylaxis, as either intrathecal methotrexate (IT) alone or intrathecal methotrexate given in addition to cranial radiation (CRT), were studied in two groups. A third group of cancer patients who received no CNS prophylaxis, and two comparison groups, siblings and a matched sample of children, also participated in the study. Impairment in central nervous system function was measured by means of psychological testing, neurological examination, and computer-assisted tomography. Patients who received central nervous system prophylactic treatments at an early age had poorer performance on verbal IQ scores, with comprehension and arithmetic subscores being most affected. Patients who received both cranial radiotherapy plus intrathecal methotrexate showed a decrease in six out of seven categories of instruction when grades from the year prior to diagnosis were compared to those obtained 3 years after diagnosis. The combined groups of patients with leukemia had a lower grade point average and poorer school attendance than did the comparison groups.