MicroRNA-15b is induced with E2F-controlled genes in HPV-related cancer

Background:

MicroRNAs (miRNAs) are important regulators of cellular processes and are found to be deregulated in many cancers. We here analysed the miRNA expression in anal carcinomas. In a previous study, we found that our anal carcinoma tumours were divided into two groups based on the expression of E2F-regulated genes. Therefore, we searched for miRNAs that could reproduce this grouping.

Methods:

A global screen of the miRNA population was performed using real-time quantitative PCR (RT–qPCR) array methods and differentially expressed miRNAs were identified. Real-time–qPCR was used to verify the expression levels of selected miRNAs and genes in a larger collection of biopsies. A siRNA-mediated knockdown of human papilloma virus (HPV)16 E7 in a cervical cell line was performed to assess the effect of E7 on miR-15b.

Results:

The grouping of tumours into two groups based on the expression of E2F-controlled genes was confirmed in a larger collection of anal carcinoma tumours. The expression of miR-15b was shown to be highly correlated with that of five selected E2F-induced genes (CCNA2, CCNB1, CCNB2, MSH6 and MCM7). A knockdown of HPV16 E7 resulted in decreased levels of miR-15b in Ca Ski cells.

Conclusion:

MiR-15b expression correlates with E2F-regulated genes in anal carcinoma and appears to be part of the E2F-regulatory network.

AIRE variations in Addison's disease and autoimmune polyendocrine syndromes (APS): partial gene deletions contribute to APS I

Autoimmune Addison's disease (AAD) is often associated with other components in autoimmune polyendocrine syndromes (APS). Whereas APS I is caused by mutations in the AIRE gene, the susceptibility genes for AAD and APS II are unclear. In the present study, we investigated whether polymorphisms or copy number variations in the AIRE gene were associated with AAD and APS II. First, nine SNPs in the AIRE gene were analyzed in 311 patients with AAD and APS II and 521 healthy controls, identifying no associated risk. Second, in a subgroup of 25 of these patients, AIRE sequencing revealed three novel polymorphisms. Finally, the AIRE copy number was determined by duplex quantitative PCR in 14 patients with APS I, 161 patients with AAD and APS II and in 39 healthy subjects. In two Scandinavian APS I patients previously reported to be homozygous for common AIRE mutations, we identified large deletions of the AIRE gene covering at least exon 2 to exon 8. We conclude that polymorphisms in the AIRE gene are not associated with AAD and APS II. We further suggest that DNA analysis of the parents of patients found to be homozygous for mutations in AIRE, always should be performed.

Ectopic expression of Bcl-2 switches over nuclear signalling for cAMP-induced apoptosis to granulocytic differentiation

The IPC-81 myeloid leukaemia cells undergo apoptosis rapidly after cAMP stimulation (6 h) and cell death is prevented by early over-expression of the cAMP-inducible transcription repressor ICER, that blocks cAMP-dependent nuclear signalling. Therefore, the expression of specific genes controlled by CRE-containing promoters is likely to determine cell fate. We now show that cAMP-induced cell death also is abrogated by the over-expression of the anti-apoptotic gene, Bcl-2. Contrary to ICER, Bcl-2 does not affect cAMP-signalling and allows the analysis of cAMP responses in death rescued cells. The Bcl-2 transfected cells treated with 8-CPT-cAMP were growth-arrested and thereafter cells embarked in granulocytic differentiation, with no additional stimulation. Neutrophilic polynuclear granulocytes benefited from a long life span in G0-G1 and remained functional (phagocytosis). This work demonstrates that, using anti-apoptosis regulators, 'death signals' could be exploited to trigger distinct biological responses. Indeed, cAMP signal can trigger several simultaneously developing biological programs, in the same cell, i.e., growth regulation, apoptosis and differentiation. This cell system should prove useful to determine how a tumour cell can be re-programmed for either apoptosis or functional maturation by physiological signals.

Dose distribution measurements by MRI of a phantom containing lung tissue equivalent compartments made of ferrous sulphate gel

Gel dosimetry based on magnetic resonance imaging (MRI) has previously been shown to provide verification of calculated dose distributions in soft tissue equivalent homogeneous phantoms. This study demonstrates how measurements of dose distribution can also be achieved in a phantom containing porous, lung-equivalent, Fricke gel. A phantom was made of Fe2+ infused low-density gel and conventional ferrous sulphate gel, filled in separate compartments in a Perspex container. Absorbed dose measurements were accomplished by MR imaging and by calibrating the proton spin-lattice relaxation rate (R1) versus absorbed dose by means of TLD measurements. This study shows that the production of lung-equivalent low-density (LD) dosimeter gel (mean CT number of -610 HU) is feasible. The MR signal detected in the LD gel dosimeter was substantially more noisy (i.e. displayed larger random fluctuations) than the signal from conventional gel, as expected. A deviation between calculated (TPS) and measured dose of about 3% (6 MV) and 4-7% (15 MV) was found in the LD region of the phantom. These results correspond well with data from other studies of dose distribution in lung-equivalent phantoms. The Fe2+ infused LD gel therefore seems suitable for measurement of absorbed dose distribution in phantoms that contain lung tissue compartments.

Expression of a peptide binding to receptor for activated C-kinase (RACK1) inhibits phorbol myristoyl acetate-stimulated phospholipase D activity in C3H/10T1/2 cells: dissociation of phospholipase D-mediated phosphatidylcholine breakdown from its synthesis

The C3H/10T1/2 Cl8 HAbetaC2-1 cells used in this study express a peptide with a sequence shown to bind receptor for activated C-kinase (RACK1) and inhibit cPKC-mediated cell functions. Phorbol myristoyl acetate (PMA) strongly stimulated phosphatidylcholine (PtdCho)-specific phospholipase D (PLD) activity in the C3H/10T1/2 Cl8 parental cell line, but not in Cl8 HAbetaC2-1 cells, indicating that full PLD activity in PMA-treated Cl8 cells is dependent on a functional interaction of alpha/betaPKC with RACK1. In contrast, the PMA-stimulated uptake of choline and its subsequent incorporation into PtdCho, were not inhibited in Cl8 HAbetaC2-1 cells as compared to Cl8 cells, indicating a RACK1-independent but PKC-mediated process. Increased incorporation of labelled choline into PtdCho upon PMA treatment was not associated with changes of either CDP-choline: 1,2-diacylglycerol cholinephosphotransferase activity or the CTP:phosphocholine cytidylyltransferase distribution between cytosol and membrane fractions in Cl8 and Cl8 HAbetaC2-1 cells. The major effect of PMA on the PtdCho synthesis in C3H/10T1/2 fibroblasts was to increase the cellular uptake of choline. As a supporting experiment, we inhibited PMA-stimulated PtdH formation by PLD, and also putatively PtdH-derived DAG, in Cl8 cells with 1-butanol. Butanol did not influence the incorporation of [(14)C]choline into PtdCho. The present study shows: (1) PMA-stimulated PLD activity is dependent on a functional interaction between alpha/betaPKC and RACK1 in C3H/10T1/2 Cl8 fibroblasts; and (2) inhibition of PLD activity and PtdH formation did not reduce the cellular uptake and incorporation of labelled choline into PtdCho, indicating that these processes are not directly regulated by PtdCho-PLD activity in PMA-treated C3H/10T1/2 Cl8 fibroblasts.

Accurate determination of the number of CAG repeats in the Huntington disease gene using a sequence-specific internal DNA standard

We have developed a sequence-specific internal DNA size standard for the accurate determination of the number of CAG repeats in the Huntington disease (HD) gene by cloning key fragments (between 15 and 64 CAG repeats) of the HD gene. These fragments, pooled to produce a sequence-specific DNA ladder, enabled us to observe the true number of CAG repeats directly, with no need for calculations. Comparison of the calculated numbers of CAG repeats in the HD gene using this sequence-specific DNA standard with a commercially available standard (GENESCAN-500 TAMRA) showed that the latter underestimated the number of CAG repeats by three when analyzed by capillary electrophoresis on the ABI 310 Genetic Analyzer (POP4 polymer). In contrast, the use of the same standard overestimated the number of CAG repeats by one when the samples were analyzed by denaturing polyacrylamide electrophoresis on ABI 377 DNA Sequencer (6% denaturing polyacrylamide gel). This suggests that our sequence-specific standard provides greater accuracy for the determination of the true number of CAG repeats in the HD gene than commercially available standards. The sequence-specific standard can be radioactively labeled and successfully replace conventional DNA size standards when analyzing polymerase chain reaction (PCR)-amplified HD alleles by denaturing polyacrylamide electrophoresis.

Choline derived from the phosphatidylcholine specific phospholipase D is not directly available for the CDP choline pathway in phorbol ester-treated C3H10T1/2 Cl 8 fibroblasts

We have shown that 12-O-tetradecanoylphorbol 13-acetate (TPA) increases protein kinase C (PKC)-mediated choline transport, incorporation of choline into phosphatidylcholine (PtdCho) and PtdCho degradation by phospholipase D (PLD) in C3H10T1/2 Cl 8 cells. Dual prelabeling experiment using [3H]/[14C]choline indicated that intracellular choline generated from the PLD reaction was not directly recycled to PtdCho synthesis within the cell, and that a large fraction of the choline was transported out of the TPA-treated cells. In contrast, medium derived choline was preferably channeled to PtdCho synthesis. These results indicate that in TPA-treated cells, the choline derived from the PKC-mediated increased PLD activity and the choline newly taken up by the cell behave as two distinctly different metabolic pools.

Uptake, penetration, and binding of monoclonal antibodies with increasing affinity in human osteosarcoma multicell spheroids

BACKGROUND

Multicell spheroids from the human osteosarcoma cell line, OHS, were incubated with increasing concentrations of the monoclonal antibodies TP-1, TP-3 and 9.2.27 having different affinities (Ka = 8.5 x 10(8) M-1, 3.4 x 10(9) M-1 and 1.4 x 10(11) M-1, respectively).

MATERIALS AND METHODS

Uptake and penetration of the fluorescein labelled antibodies were studied using confocal laser scanning fluorescence microscopy, and antibodies bound per cell were measured using flow cytometry.

RESULTS

The antibody with highest affinity, 9.2.27, bound to all available binding sites in one cell-layer before reaching the next, whereas TP-3 and TP-1 gradually bound to an increasing number of epitopes of all cells throughout the spheroids. The penetration rate and antibody uptake increased with increasing antibody concentration up to saturating concentrations. 9.2.27 required saturation concentrations to reach the center of the spheroids, whereas TP-1 and TP-3 penetrated the centre when concentrations below saturation were applied.

CONCLUSION

The antibodies might be useful in radioimmunotherapy of micrometastases.

Penetration and binding of monoclonal antibody in human osteosarcoma multicell spheroids. Comparison of confocal laser scanning microscopy and autoradiography

Penetration and binding of monoclonal antibody (MAb) in multicell osteosarcoma spheroids have been studied by autoradiography and confocal laser scanning microscopy (CLSM). Optical sectioning of the 3-dimensional spheroids was performed by CLSM. Owing to attenuation of fluorescence intensity, FITC-labelled MAb could not be detected at depths greater than 60 microm within the spheroids. The antibody uptake seen in autoradiographs and CLSM images 60 microm within the spheroids were essentially identical. MAb had reached all parts of the spheroids within 6 h. Quantitative measurements of the fluorescence intensity of FITC-labelled MAb seen in confocal images and measurements of MAb bound per cell using flow cytometry, showed that maximum uptake was reached after 6 h. The possibility to perform both quantitative and qualitative measurements makes CLSM a promising method for studying antibody uptake in thick tissue samples.

PKU mutation (D143G) associated with an apparent high residual enzyme activity: expression of a kinetic variant form of phenylalanine hydroxylase in three different systems

We have used three complementary in vitro systems to express the human phenylalanine hydroxylase (PAH) gene at high levels. Recombinant PAH was expressed in Escherichia coli (as a fusion protein), in human kidney cells and in a cell-free in vitro transcription-translation system. These systems were used to characterize a novel kinetic variant form (D143G) of the enzyme. The recombinant D143G mutant enzyme had the same physicochemical properties as the wild-type PAH and was stable when expressed in eukaryotic cells. Enzyme activity studies of the D143G mutant enzyme, produced in the three expression systems, revealed a kinetic variant form with reduced affinity for L-Phe (about 2.4-fold increase in the S0.5 value) as well as reduced affinity for tetrahydrobiopterin (BH4) (about 2-fold increase in the apparent Km). At standard assay conditions (1 mM L-Phe, t5 microM BH4) the residual activity of the mutant enzyme was high and variable (52%, 33%, and 102%) when analysed in the three different systems. The high residual activities of the mutant enzyme obtained at these conditions were not in agreement with the classical PKU phenotype found in a patient compound heterozygous for the termination mutation G272X and the novel D143G mutation. However, when the D143G mutant enzyme was assayed at lower concentrations of L-Phe (100-300 microM) and BH4 (10 microM) the residual activities were compatible with severely reduced hydroxylation of L-Phe and the classical PKU phenotype.

Proliferative activity of synovial sarcoma: an immunohistochemical evaluation of Ki-67 labeling indices of 52 primary and recurrent tumors

The relationship between cell differentiation and proliferation in biphasic synovial sarcoma (BSS) and the connection between the two components of these tumors and monophasic synovial sarcoma (MSS) are still unknown. In this study we specifically compared the Ki-67 labeling indices (Ki-67-LI) in the solid/glandular and spindle cell components of primary BSS (n = 8) as well as the values thus obtained in primary BSS both outside clear-cut biphasic areas (n = 7) and in primary MSS (n = 23). We also compare the Ki-67-LI of primary tumors (seven BSS, seven MSS) and their respective first recurrences. We observed that the cells of the solid/glandular component of BSS proliferate significantly faster (p = 0.007) than those of spindle cell areas. No significantly different Ki-67-LI were observed in the comparison of the solid/glandular areas of BSS with the spindle/epithelioid component of BSS without clear-cut biphasia and MSS. No significant differences of Ki-67-LI were observed in the comparison of primary tumors of both subtypes with their respective first recurrences. The implications of the low proliferative activity of the spindle cell component of BSS exhibiting clear-cut biphasia, which was also confirmed in a concurrent study using anti-proliferating cell nuclear antigen/Cyclin PC10, remains to be clarified.

Validity and usefulness of human tumor models established by intratibial cell inoculation in nude rats

Intratibial injection in nude rats of 1 x 10(6) OHS, MHMX, and LOX human tumor cells resulted in each case in progressively growing bone tumors. When the diameter of the affected leg had increased by 2-3 mm, the animals were examined for uptake of 99mTc-methylenediphosphonate. The OHS osteosarcoma tumors caused sclerotic lesions with high and uniform isotope uptake, and the MHMX unclassified sarcoma showed a mixed pattern with both sclerotic and lytic areas, whereas the LOX melanoma caused lytic bone lesions with low uptake of the radionuclide. These findings were compared with the results of analogous investigations previously performed in the patients from whom the tumor lines originated. Striking similarities in both the morphology and the scintigraphic images were observed between corresponding tumors in rats and humans, with results supporting the clinical relevance of the model systems. When the LOX model was used for therapy experiments, doxorubicin had no effect on the growth of the tibial tumors, which in the control group appeared after a latency of 13.5 days. The alkylating agent mitozolomide increased the median tumor-free latency to 47 days in 7 rats, and 5 animals did not develop tumors within the observation period of 60 days. Doxorubicin was ineffective also against the OHS tumor, whereas ifosfamide and the radionuclide 89Sr-chloride showed significant antitumor activity. The disease-free latency increased from 20 days, in the control animals, to 45 and 28.5 days, respectively, in the 2 treated groups, in which 2 of 7 and 2 of 10 rats were without tumors at 60 days. The data demonstrate that the tibial models discriminated between the action of the different therapeutic agents, and suggest that they may be useful in selecting compounds with clinical activity against skeletal tumors.

Immunohistochemical profile of synovial sarcoma with emphasis on the epithelial-type differentiation. A study of 49 primary tumours, recurrences and metastases

The relationship between biphasic (BSS) and monophasic (MSS) subtypes of synovial sarcoma (SS) as well as the relationship between cells of solid/glandular areas and the spindle cells of BSS remain controversial. In order to further evaluate the immunohistochemical phenotype of SS we studied 34 primary tumours (15 BSS; 19 MSS), 7 recurrences (4 from primary BSS; 3 from primary MSS) and 8 metastases (7 BSS; one MSS), using several antibodies (EMA, CEA, keratins 1, 4, 5/6, 7, 8, 13, 18, 19, 20, vimentin, collagen IV and laminin) that work in paraffin-embedded material. Spindle cells outside solid/glandular areas of BSS and in MSS showed immunoreactivity for keratins 5/6, 7, 8, 18 and 19. The transition of solid/glandular areas to surrounding spindle cells also showed keratin staining and failed to show a distinct separation regarding the immunoreactivity for laminin and collagen IV. Peripheral cells of solid/glandular areas were immunoreactive for vimentin. No major differences were observed between immunophenotypical cell profiles of BSS and MSS, apart from the exclusive immunostaining of solid/glandular areas of BSS for keratin 13 and CEA. Downgrading of keratin and extracellular matrix antigens immunoreactivity was observed when primary tumours were compared to recurrent and/or metastatic tumours of both subtypes (MSS and BSS). We conclude that SS should be regarded as carcinomas of soft tissues with an immunohistochemical phenotype depending on the degree of epithelial differentiation: spindle cells (MSS and BSS) predominantly expressing simple keratins, and poorly differentiated (solid/glandular) as well as well-differentiated (glandular) areas (BSS) expressing, in addition, complex epithelial-type keratins.

Therapeutic efficacy of the alpha-emitter 211At bound on microspheres compared with 90Y and 32P colloids in a murine intraperitoneal tumor model

alpha-Emitting radionuclides such as 211At have a number of physical characteristics which make them attractive for the treatment of micrometastases. 211At was bound to polymer microspheres and its efficacy was compared with the beta-emitting 32P and 90Y colloids for the treatment of intraperitoneally growing K13 hybridoma tumors in mice. Single graded doses of 0.1-2.5 MBq 211At microspheres injected intraperitoneally 24 hr after inoculation of the hybridoma cells improved survival and produced higher cure rates than 32P colloid, 90Y colloid, or no treatment. One of the most striking contrasts between 211At microspheres and 90Y or 32P colloids was the ability of relatively low doses 211At to affect cures. When comparing the groups with the highest survival rate for each radionuclide (0.1-1 MBq 211At, 2.5 MBq 90Y, and 2.5 MBq 32P), 211At treatment resulted in an improved survival over that with 32P therapy, but the difference was not significant between 211At and 90Y. Toxicity studies with 211At microspheres showed that dosages up to 17 MBq per mouse were not lethal. In conclusion, the present study suggests that the high-energy transfer and the short-range cytotoxicity of the alpha-emitter 211At might be of benefit for intracavitary radiotherapy.

Selective localisation of two radiolabelled anti-sarcoma monoclonal antibodies in human osteosarcoma xenografts

Two mouse monoclonal antibodies (MoAbs), TP-1 and TP-3, previously shown in immunohistochemical studies to react with osteosarcomas, were labelled with 125I or 131I and evaluated for their ability to localise to human osteogenic sarcoma xenografts after intravenous injection. The radiolabelled TP-1 and TP-3 MoAbs had immunoreactive fractions of 70% and 67%, respectively, and bound to target cells with binding constants of 8.5 X 10(8) M-1 and 4.0 X 10(9) M-1, respectively. After injection of labelled TP-3 IgG, approximately 16% of the dose X g-1 tissue was found in the tumour after 24 hours. Maximum tumour/blood radioactivity ratios of 6-7 were achieved 3-4 days after antibody injection, while the ratios for the normal tissues were less than 1. The tumours could be clearly visualised by whole-body gamma scintigraphy without the need for subtraction techniques. The TP-1 IgG accumulated to a large extent also in the spleen. Hence, with this antibody the tumour was less well delineated from the adjacent normal tissues. However, the F(ab')2 fragments, derived from the TP-1 IgG, gave tumour/blood ratios up to approximately 40 after 3-4 days and yielded sharp gamma scintigrams of the tumour. Specificity of the antibody localisation was indicated by the lack of accumulation in a contralateral melanoma xenograft and the failure of 2 isotype-matched irrelevant MoAbs to localise to the sarcomas. With the F(ab')2 fragments satisfactory images could be obtained already after 16 hours. The results suggest that this preparation may be useful in clinical radioimmunodetection of osteogenic sarcomas.

Characteristics of a cell line established from a patient with multiple osteosarcoma, appearing 13 years after treatment for bilateral retinoblastoma

An osteosarcoma cell line, OHS, was established from a patient with multiple skeletal manifestations of osteosarcoma, developing after bilateral retinoblastoma. The tumor cells expressed sarcoma-associated antigens and showed rapid growth in monolayers and as multicellular spheroids. They formed distinct colonies in soft agar, and subcutaneous tumors in nude mice. Morphological studies indicated that OHS cells had retained important characteristics of the cells of origin. No deletion of the retinoblastoma genes on chromosome 13q14 could be demonstrated with the banding techniques used. However, cytogenetic studies revealed double minute chromosomes, as evidence of gene amplification, as well as translocations involving chromosomes 1,6,11 and 13. The OHS line can be used to study the genetic basis of tumor initiation and growth, and to elucidate factors predisposing for second primary cancers in retinoblastoma patients.

New monoclonal antibodies specific for human sarcomas

Monoclonal antibodies (MAbs) against sarcoma-associated cell membrane antigens were prepared by immunizing BALB/c mice with tumor cells from a human osteosarcoma, TPX, grown as a xenograft in athymic BALB/c nude mice. Spleen cells from immunized mice were hybridized with X-63 Ag. 8.653 mouse myeloma cells which yielded 260 growing hybridomas. Seven of these produced antibodies that bound to TPX cells and to cells from another osteosarcoma, but not to autologous skin fibroblasts. MAbs from 2 (TP-1 and TP-3) of these 7 clones did not cross-react with non-sarcomatous tumor cells or peripheral blood lymphocytes. Immunohistochemical studies on frozen tissue sections showed that the TP-1 (IgG-2a) and TP-3 (IgG-2b) antibodies had characteristic and identical specificity profiles. Binding of TP-1 (TP-3) was demonstrated to 15/15 (15/15) osteosarcomas, 3/3 (2/2) synovial sarcomas, 7/9 (6/8) malignant fibrous histiocytomas, 2/2 (1/1) malignant hemangiopericytomas, 1/2 (1/2) chondrosarcomas and 3/6 (1/3) unclassified sarcomas. The antibodies did not bind to any of 16 sarcomas belonging to other histological subtypes, including liposarcomas and leio- and rhabdomyosarcomas. Moreover, they failed to bind to sections of 66 different non-sarcomatous malignancies, or to any of a range of normal adult and fetal tissues, although some weak staining of proximal kidney tubules was seen. The restricted specificity of these antibodies to some major subtypes of human sarcomas makes them promising tools for identification and subclassification of sarcomas.

Unexpected expression of the 250 kD melanoma-associated antigen in human sarcoma cells

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The use of multicellular spheroids in establishing human sarcoma cell lines in vitro

By a new procedure stable monolayer cultures were derived from spheroids in 8 out of 17 different human sarcomas (16 soft-tissue and I osteogenic sarcoma). Eleven of the sarcomas were obtained from patients undergoing surgery, and 6 from BALB/c nude mice carrying s.c. growing xenografts. The new procedure involves aggregation of single-cell suspensions into spheroids and cultivation of these in agar-coated flasks until the growth rate levels off, at which time the spheroids are transferred to uncoated flasks. Cells proliferating from the rim of adhering spheroids are trypsinized and aggregated to form new spheroids. By 3 to 5 such alternations, monolayer cultures were obtained that have now been subcultured for about 6 months. The cell lines all gave rise to colonies in a clonogenic soft-agar system, and upon s.c. injection into athymic nude mice 3 lines tested formed growing tumors. The histology of spheroids formed from late monolayer passages closely resembled that of the original tumors. That the new procedure is superior to other methods of establishing sarcoma cell lines is indicated by the fact that a stable monolayer culture could be obtained directly from the tumors in only 1/8 cases where the above procedure was successful, and in only 2 instances from soft-agar colonies derived from the tumors.

The protein synthesis inhibitors from wheat, barley, and rye have identical antigenic determinants

We have purified the protein synthesis inhibitors from wheat (tritin) and investigated their antigenic relationship to inhibitors from other grains and more distantly related plants. Three forms of tritin (tritin 1, 2, and 3) indistinguishable with regards to their molecular weight and enzymatic properties were found. Antiserum against the most abundant tritin, tritin 2, cross reacted with tritin 1, tritin 3, and with the translation inhibitors from barley and rye, but not with other plant-derived translational inhibitors. The results indicate that only closely related plants contain antigenically similar protein synthesis inhibitors.

Dianthin 30 and 32 from Dianthus caryophyllus: two inhibitors of plant protein synthesis and their tissue distribution

The ability of dianthin 30 and 32 to inhibit translation in reticulocyte lysates and wheat germ extracts has been studied. The dianthins, like the A chains of the toxins abrin and ricin, inhibited protein synthesis in reticulocyte lysates by inactivating the 60S ribosomal subunit. They also inhibited, at concentrations of 10 ng/ml, a protein-synthesizing system from wheat germ and inactivated isolated wheat germ ribosomes. The concentration of the dianthins in different tissues of the plant was determined by rocket immunoelectrophoresis and by the dianthin's ability to inhibit protein synthesis. Dianthin 32 was found only in the leaves and in growing shoots, while dianthin 30 was present throughout the plant. In the older parts of the plant, the dianthins constituted between 1 and 3% of the total extractable protein whereas much less was found in the younger parts.