The relative biological effectiveness of antiprotons

BACKGROUND AND PURPOSE

Aside from the enhancement of physical dose deposited by antiprotons annihilating in tissue-like material compared to protons of the same range a further increase of biological effective dose has been demonstrated. This enhancement can be expressed in an increase of the relative biological effectiveness (RBE) of antiprotons near the end of range. We have performed the first-ever direct measurement of the RBE of antiprotons both at rest and in flight.

MATERIALS AND METHODS

Experimental data were generated on the RBE of an antiproton beam entering a tissue-like target consisting of V79 cells embedded in gelatin with an energy providing a range of approximately 10cm.

RESULTS

The RBE in the entrance channel (the "plateau") is only slightly above the value for a comparable proton beam, and remains low until the proximal edge of the spread-out Bragg peak (SOBP). A steep increase of RBE is seen starting from the onset of the SOBP.

CONCLUSIONS

This paper reports the final results of the experiment AD-4/ACE at CERN on the first-ever direct measurement of RBE of antiprotons and constitutes the first step toward developing treatment plans.

Direct measurement of the formation length of photons

We report the first observation of a shoulder in the radiation spectrum from GeV electrons in a structured target consisting of two thin and closely spaced foils. The position of the shoulder depends on the target spacing and is directly connected to the finite formation length of a low-energy photon emitted by an ultrarelativistic electron. With the present setup it is possible to control the separation of the foils on a μm scale and hence measure interference effects caused by the macroscopic dimensions of the formation length. Several theoretical groups have predicted this effect using different methods. Our observations have a preference for the modified theory by Blankenbecler but disagree with the results of Baier and Katkov.

Target structure induced suppression of the ionization cross section for very low energy antiproton-hydrogen collisions

Low energy antiprotons have been used previously to give benchmark data for theories of atomic collisions. Here we present measurements of the cross section for single, nondissociative ionization of molecular hydrogen for impact of antiprotons with kinetic energies in the range 2-11 keV, i.e., in the velocity interval of 0.3-0.65 a.u. We find a cross section which is proportional to the projectile velocity, which is quite unlike the behavior of corresponding atomic cross sections, and which has never previously been observed experimentally.

V-79 Chinese hamster cells irradiated with antiprotons, a study of peripheral damage due to medium and long range components of the annihilation radiation

PURPOSE

Radiotherapy of cancer carries a perceived risk of inducing secondary cancer and other damage due to dose delivered to normal tissue. While expectedly small, this risk must be carefully analysed for all modalities. Especially in the use of exotic particles like pions and antiprotons, which annihilate and produce a mixed radiation field when interacting with normal matter nuclei, the biological effective dose far out of field needs to be considered in evaluating this approach. We describe first biological measurements to address the concern that medium and long range annihilation products may produce a significant background dose and reverse any benefits of higher biological dose in the target area.

MATERIALS AND METHODS

Using the Antiproton Decelerator (AD) at CERN (Conseil Européen pour la Recherche Nucléaire) we irradiated V-79 Chinese Hamster cells embedded in gelatine using an antiproton beam with fluence ranging from 4.5 x 10(8) to 4.5 x 10(9) particles, and evaluated the biological effect on cells located distal to the Bragg peak using clonogenic survival and the COMET assay.

RESULTS

Both methods show a substantial biological effect on the cells in the entrance channel and the Bragg Peak area, but any damage is reduced to levels well below the effect in the entrance channel 15 mm distal to the Bragg peak for even the highest particle fluence used.

CONCLUSIONS

The annihilation radiation generated by antiprotons stopping in biological targets causes an increase of the penumbra of the beam but the effect rapidly decreases with distance from the target volume. No major increase in the biological effect is found in the far field outside of the primary beam.

Impact of BCL2 and p53 on postmastectomy radiotherapy response in high-risk breast cancer. A subgroup analysis of DBCG82 b&c

PURPOSE

To examine p53 and BCL2 expression in high-risk breast cancer patients randomized to postmastectomy radiotherapy (PMRT).

PATIENTS AND METHODS

The present analysis included 1 000 of 3 083 high-risk breast cancer patients randomly assigned to PMRT in the DBCG82 b&c studies. Tissue microarray sections were stained with immunohistochemistry for p53 and BCL2. Median potential follow-up was 17 years. Clinical endpoints were locoregional recurrence (LRR), distant metastases (DM), overall mortality, and overall survival (OS). Statistical analyses included Kappa statistics, chi(2) or exact tests, Kaplan-Meier probability plots, Log-rank test, and Cox univariate and multivariate regression analyses.

RESULTS

p53 accumulation was not significantly associated with increased overall mortality, DM or LRR probability in univariate or multivariate Cox regression analyses. Kaplan-Meier probability plots showed reduced OS and improved DM and LRR probabilities after PMRT within subgroups of both p53 negative and p53 positive patients. Negative BCL2 expression was significantly associated with increased overall mortality, DM and LRR probability in multivariate Cox regression analyses. Kaplan-Meier probability plots showed a significantly improved overall survival after PMRT for the BCL2 positive subgroup, whereas practically no survival improvement was seen after PMRT for the BCL2 negative subgroup. In multivariate analysis of OS, however, no significant interaction was found between BCL2 and randomization status. Significant reductions in LRR probability after PMRT were recorded within both the BCL2 positive and BCL2 negative subgroups.

CONCLUSION

p53 was not associated with survival after radiotherapy in high-risk breast cancer, but BCL2 might be.

Tissue microarrays compared with whole sections and biochemical analyses. A subgroup analysis of DBCG 82 b&c

INTRODUCTION

The tissue microarray (TMA) technique comprises the potential of significantly reducing time and tissue spent on slicing and performing immunohistochemical (IHC) stainings of paraffin-embedded tumor tissue. Tissue heterogeneity is an argument against using TMAs, which has been dealt with by increasing the size and number of cores punched from each tumor. No consensus exists on the most optimal size, number, and position of TMA cores in the donor paraffin block and no information exist regarding agreement between TMA cores from two different paraffin blocks from the same tumor or between TMA cores and biochemical analyses.

PATIENTS AND METHODS

A central and a peripheral 1mm core and a whole section from each of 54 paraffin blocks from 27 breast cancers included in a one-institution cohort, and a single 1mm central TMA core, from each breast tumor from 1000 patients included in the DBCG82 b&c trials, were IHC stained for ER, PgR and HER2. In addition, ER and PgR were measured in the DBCG82 b&c trials by a biochemical analysis. Statistical analyses included Kappa statistics, Kaplan-Meier survival curves, Log-rank tests, and Cox regression hazards analyses.

RESULTS AND CONCLUSION

IHC stainings for ER, PgR, and HER2 showed a substantial agreement between a single 1mm TMA core and the corresponding whole section, between central and peripheral cores, and between cores from two different paraffin blocks from the same tumor. In addition, a fine agreement was found for ER and PgR between IHC stainings of TMA cores and biochemical analyses. Divergence between IHC and biochemical analyses was predominantly due to the chosen thresholds. IHC staining of one 1mm core from each tumor revealed a significant independent prognostic value of PgR and HER2 on overall survival. In conclusion, IHC stainings for ER, PgR, and HER2 of just a single 1mm TMA core seems to be sufficient, as no significant heterogeneity was noticed.

Ionization of helium and argon by very slow antiproton impact

The total cross sections for single ionization of helium and single and double ionization of argon by antiproton impact have been measured in the kinetic energy range from 3 to 25 keV using a new technique for the creation of intense slow antiproton beams. The new data provide benchmark results for the development of advanced descriptions of atomic collisions and we show that they can be used to judge, for the first time, the validity of the many recent theories.

TOP2A aberrations as predictive and prognostic marker in high-risk breast cancer patients. A randomized DBCG Trial (DBCG89D)

532

Background: The primary objective of the study was to evaluate TOP2A as predictive marker for adjuvant treatment with epirubicin in high-risk breast cancer patients. As a secondary objective the prognostic characteristics of TOP2A gene aberrations was investigated. The data presented on the predictive properties is a follow-up to the data previously published (Knoop et al, J Clin Oncol 2005; 23: 7483–90). Methods: 962 pre- and postmenopausal high-risk Danish patients were enrolled in the DBCG89D protocol. The patients were randomly allocated to either 9 × CMF (cyclophosphamide, methotrexate, 5-flurouracil) (n=495) or 9 × CEF (cyclophosphamide, epirubicin, 5-flurouracil) (n=467) every 3 weeks. Tumor-tissue was available from 806 patients (84%). The tumors were analyzed for TOP2A copy number changes with the TOP2A FISH pharmDx Kit (Dako, Glostrup). Recurrence-free survival (RFS) was used as primary end-point. Univariate and multivariate statistics were used to assess the predictive and prognostic properties of the TOP2A gene aberrations. Results: The TOP2A test was successful in 96% of the patients. Ninety-two (12.0%) patients were found to have TOP2A amplified tumors, and 86 (11.1%) to have TOP2A deleted tumors. For the primary study endpoint (RFS) a significant predictive value of TOP2A gene amplifications was found (HR=0.39; CI: 0.22–0.70; p=0.0017). A similar trend was seen with respect to TOP2A deletions (HR=0.61; CI: 0.35–1.07; p=0.082). TOP2A gene aberrations were significantly associated with several established prognostic factors and had independent prognostic value, associated with a significant worse prognosis both for RFS (p=0.036) and overall survival (p=0.012). Conclusions: The DBCG89D study has shown that TOP2A amplifications are associated with a favorable outcome of adjuvant treatment with epirubicin in primary breast cancer. Further, TOP2A aberrations demonstrated an independent prognostic value.

[Table: see text]

Stopping power in insulators and metals without charge exchange

The slowing-down process of pointlike charged particles in matter has been investigated by measuring the stopping power for antiprotons in materials of qualitatively very different nature. Whereas the velocity-proportional stopping power observed for metal-like targets such as aluminum over a wide energy range of 1-50 keV is in agreement with expectations, it is surprising that the same velocity dependence is seen for a large band-gap insulator such as LiF. The validity of these observations is supported by several measurements with protons and several checks of the target properties. The observations call for both a qualitative explanation and a quantitative theoretical model.

Food safety on the slaughterline: inspection of pig heads

This paper summarises information on the current inspection procedures for pig heads on the slaughterline and their impact on food safety, and considers the implications for food safety of certain lesions. It is argued that although a modified slaughter and inspection technique would decrease the contamination of the carcase with pathogenic microorganisms, leaving lesions in the head undiscovered would be of little or no importance either for human health or for the overall supervision of animal health.

Expanded bed adsorption in the purification of monoclonal antibodies: a comparison of process alternatives

Expanded bed adsorption (EBA) was examined as the initial capture/purification step in the purification of monoclonal antibodies from Chinese hamster ovary (CHO) cultures. Two process alternatives each using EBA were compared to a conventional Protein A process without EBA. One alternative used Protein A affinity EBA followed by packed-bed cation and anion-exchange steps. The other alternative used cation-exchange EBA as the capture step followed by packed-bed Protein A and anion-exchange steps. The process using Protein A EBA produced comparable purity (host cell protein, DNA, Protein A, antibody aggregate) to the conventional process. However, the Protein A EBA column showed a significant decrease in dynamic capacity with a limited number of cycles. The process using cation EBA achieved comparable levels of host cell proteins (HCP) and DNA but not antibody aggregate or leached Protein A compared to the conventional process.

Antiproton stopping at low energies: confirmation of velocity-proportional stopping power

The stopping power for antiprotons in various solid targets has been measured in the low-energy range of 1-100 keV. In agreement with most models, in particular free-electron gas models, the stopping power is found to be proportional to the projectile velocity below the stopping-power maximum. Although a stopping power proportional to velocity has also been observed for protons, the interpretation of such measurements is difficult due to the presence of charge exchange processes. Hence, the present measurements constitute the first unambiguous support for a velocity-proportional stopping power due to target excitations by a pointlike projectile.

Electromagnetically induced nuclear-charge pickup observed in ultrarelativistic Pb collisions

A strong increase of inclusive nuclear-charge pickup cross sections, forming 83Bi from 158A GeV 82Pb ions, is observed in comparison to similar measurements at 10.6A GeV. From the dependence of these cross sections on target atomic number, this increase is attributed to the electromagnetic process of pion production by equivalent photons. The observed cross sections can be reproduced quantitatively using the recently developed RELDIS code.

A case of lymphoblastoid natural killer (NK)-cell lymphoma: association with the NK-cell receptor complex CD94/NKG2 and TP53 intragenic deletion

The clinical, histological, phenotypic and genotypic features of a lymphoblastoid natural killer (NK)-cell lymphoma presenting in the skin in a young caucasian woman are described. The disease behaved aggressively, but long-lasting remission was obtained by combination chemotherapy followed by autologous bone marrow transplantation. The blastoid cells were positive for terminal deoxynucleotidyl transferase, CD34, CD56 and CD4. Furthermore, the NK-cell receptor complex CD94/NKG2 was strongly expressed, as shown by examination with reverse transcription-polymerase chain reaction. The T-cell receptor (TCR)-gamma genes were in germline, and with the exception of CD4 all T-cell antigens were negative, including CD3, TCR-beta, TCR-delta, TIA-1, granzyme B and perforin. Epstein-Barr virus was negative, and no expression was seen of myeloid cell-associated markers. Molecular analysis showed no abnormalities of the CDKN2A (p16), CDKN2B (p15) or TNFRSF6 (Fas) genes. By contrast, a 34-bp deletion in exon 7 of the TP53 (p53) gene was detected. It is suggested that lymphoblastoid NK-cell lymphoma, which is a rare but distinctive disease, originates from NK cell precursors and may be associated with and possibly caused by alterations in the TP53 gene. Experience is too limited to warrant therapeutic suggestions. However, stem cell transplantation may be a useful option in younger patients.

Cellular uptake of adamantyl conjugated peptide nucleic acids

Peptide nucleic acids (PNA) (15-mers) conjugated to adamantyl acetic acid and labeled with fluorescein have been prepared, and their (liposome mediated) uptake in human cells in culture (HeLa, IMR-90 and MDA-MB-453) has been studied by confocal fluorescence microscopy. It is found that adamantyl-PNAs show greatly improved (endosomal) cellular uptake, but that this uptake is dependent on the cell line. Cellular uptake of such lipophilic PNAs is further mediated by cationic liposomes, and in some cases, the intracellular localization is diffuse cytoplasmic or nuclear, again cell-type dependent. The results show that this simple PNA modification can indeed greatly improve cellular uptake, but the effect appears strongly cell-type as well as PNA-sequence dependent.

CD34+ megakaryoblastic leukaemic cells are CD38-, but CD61+ and glycophorin A+: improved criteria for diagnosis of AML-M7?

The aim of this flow cytometry study in acute megakaryoblastic leukaemia (AML-M7) was to describe the membrane phenotype of CD34+ progenitor subsets and compare these with the phenotypes expressed by other AML FAB types. Following conventional histopathological diagnosis mononuclear cells from bone marrow and blood were examined in seven patients with AML-M7 and compared with results from 26 sequential patients with AML-M0 to AML-M6. The CD34+ subsets in AML-M7 patients differed from that of patients with AML-M0 to AML-M6 as the CD34+ CD61+ and the CD34+ Glycophorin A+ subsets were median 31% and 20%, respectively, compared to 4% and 2% in the AML-M0 to AML-M6 (P = 0.0005). Only 1% of the CD34+ progenitors were CD34+ CD38+ in AML-M7 compared to 72% in other AML subtypes (P < 0.000). These findings suggest that the CD34+ cell compartment in AML-M7 consists of early lineage-specific progenitors. In conclusion, flow cytometry analysis of CD34+ subsets may improve the diagnostic safety in AML-M7 and consequently the prognostic significance of immunophenotyping in acute leukaemia.

Application of peptide nucleic acid in cancer therapy

Peptide nucleic acid (PNA) is a DNA mimic with a pseudopeptide backbone composed of aminoethyl glycine units. Several features of PNA, such as superior hybridization affinities to RNA and DNA, high biological stability, and convenient solid-phase synthesis, make it a promising candidate for use as a gene targeting drug. Here we review the chemical and biological properties of PNA in relation to its potential as an anti-cancer drug.

Antisense properties of duplex- and triplex-forming PNAs

The potential of peptide nucleic acids (PNAs) as specific inhibitors of translation has been studied. PNAs with a mixed purine/pyrimidine sequence form duplexes, while homopyrimidine PNAs form (PNA)2/RNA triplexes with complementary sequences on RNA. We show here that neither of these PNA/RNA structures are substrates for RNase H. Translation experiments in cell-free extracts showed that a 15mer duplex-forming PNA blocked translation in a dose-dependent manner when the target was 5'-proximal to the AUG start codon on the RNA, whereas similar 10-, 15- or 20mer PNAs had no effect when targeted towards sequences in the coding region. Triplex-forming 10mer PNAs were efficient and specific antisense agents with a target overlapping the AUG start codon and caused arrest of ribosome elongation with a target positioned in the coding region of the mRNA. Furthermore, translation could be blocked with a 6mer bisPNA or with a clamp PNA, forming partly a triplex, partly a duplex, with its target sequence in the coding region of the mRNA.

Short-term in vivo priming of bone marrow haematopoiesis with rhG-CSF, rhGM-CSF or rhIL-3 before marrow harvest expands myelopoiesis but does not improve engraftment capability

In an attempt to optimize bone marrow grafts for autologous transplantation 37 sequential patients suffering from various haematological diseases were treated with either recombinant human granulocyte colony-stimulating factor (rhG-CSF) (n = 23) or granulocyte-macrophage CSF (rhGM-CSF) (n = 8) for 5 days or interleukin 3 (rhIL-3) (n = 6) for 10 days before marrow harvest. All patients were in marrow remission at study entry. In contrast to rhIL-3, the administration of rhG-CSF or rhGM-CSF caused a significant (P < 0.01) increase in blood absolute neutrophil count. An increased marrow cellularity and a rise in the myeloid:-erythroid ratio was seen in the majority of patients during therapy, and in the rhIL-3 treated group a rise in the number of megakaryocytes and increased marrow fibrosis was seen in most patients. Moreover, a median of 2-, 5- and 10-fold increase in myeloid progenitors was the result of short-term administration of rhIL-3, rhGM-CSF and rhG-CSF, respectively. However, transplantation performed with primed expanded marrow grafts did not significantly reduce the time to myeloid regeneration when compared to historical controls. In conclusion, the results demonstrate that short-term priming with haematopoietic cytokines before autologous bone marrow stem cell harvest is a safe procedure which effectively expands marrow haematopoisis without enhanced engraftment capability.

Expression of the intercellular adhesion molecule-3 (ICAM-3) in human renal tissue with relation to kidney transplants and various inflammatory diseases

Adhesion molecules are important for immune regulatory mechanisms concerning antigen presentation, lymphocyte activation, localisation and migration as well as effector-target cell interactions in inflammatory processes. The immunohistochemical expression of ICAM-3, a recently cloned new member of the immunoglobulin family which also binds leucocyte function antigen 1 (LFA-1), was examined in 80 needle core biopsies from 35 renal allografts, 7 patients with mesangioproliferative glomerulonephritis, 5 patients with extracapillary glomerulonephritis, 4 patients with interstitial nephritis and 5 patients with diabetic nephropathy and 20 normal kidneys. In all types of lesions ICAM-3 was constitutively expressed on the majority of infiltrating leucocytes without detectable upregulation or presentation on possible target structures during inflammation indicating its possible role to be mainly in initiation of the inflammatory response.

A common response element mediates differential effects of phorbol esters and forskolin on type-1 plasminogen activator inhibitor gene expression in human breast carcinoma cells

We have characterized regulation of type-1 plasminogen activator inhibitor (PAI-1) gene expression by phorbol 12-myristate 13-acetate (PMA) and the cAMP-inducing agent forskolin in the human breast carcinoma cell line MCF-7. PMA caused a strong induction of PAI-1, while forskolin suppressed the PMA response. Transfection experiments with fusion genes showed that sequences mediating PMA induction as well as forskolin suppression were present between base pairs -100 and -30 of the 5'-flanking region of the PAI-1 gene. The region was found to contain two Sp1 binding sites. A proximal sequence in the region, TGAGTTCA (P box), with sequence similarity to phorbol ester response elements (TRE) as well as to cAMP response elements (CRE), bound a low-abundance, as yet unidentified nuclear protein in MCF-7 cells. This sequence had a higher affinity to purified c-jun homodimer than to c-jun/c-fos heterodimer in MCF-7 nuclear extracts; it had no affinity to the proteins binding to CRE consensus sequences in these extracts. A distal TRE-like sequence, TGAGTGG (D box), had a weak affinity to c-jun/c-fos heterodimer and c-jun homodimer; binding of proteins to this sequence was facilitated by binding of proteins to the P box. Both the P box and the D box were necessary for PMA responsiveness, suggesting a cooperativity between the two binding sites. A mutation of the P box removing the CRE similarity abolished the forskolin suppression of the PMA response. We propose that the protein kinase C and the protein kinase A signal-transduction pathways, with opposite effects on PAI-1 gene expression converge by modulating differently P-box-binding proteins.

[Multiple personality--a phenomenon also in Norway?]

Dissociative disorders are little known and seldom referred to in the Norwegian medical literature. Our paper describes signs and criteria for multiple personality and dissociative syndromes, and reviews the recent literature. Three cases are briefly presented.