Cloning human enamelin cDNA, chromosomal localization, and analysis of expression during tooth development

Enamelin is the largest protein in the enamel matrix of developing teeth. In the pig, enamelin is secreted as 186-kDa phosphorylated glycoprotein, which is rapidly processed by enamel proteinases into smaller cleavage products. During the secretory stage of enamel formation, enamelin is found among the crystallites in the rod and interrod enamel and comprises roughly 5% of total matrix protein. Although the function of enamelin is unknown, it is thought to participate in enamel crystal nucleation and extension, and the regulation of crystal habit. Here we report the results of enamelin in situ hybridization in a day 1 mouse developing incisor that shows that enamelin is expressed by ameloblasts, but not by odontoblasts or other cells in the dental pulp. The restricted pattern of enamelin expression makes the human enamelin gene a prime candidate in the etiology of amelogenesis imperfecta (AI), a genetic disease in which defects of enamel formation occur in the absence of non-dental symptoms. We have cloned and characterized a full-length human enamelin cDNA and determined by radiation hybrid mapping and fluorescent in situ hybridization (FISH) that the gene is located on chromosome 4q near the ameloblastin gene in a region previously linked to local hypoplastic AI in six families. These findings will facilitate the search for specific mutations in the enamelin gene in kindreds suffering from amelogenesis imperfecta.

Localization of EMSP1 expression during tooth formation and cloning of mouse cDNA

Enamel matrix serine proteinase 1 (EMSP1) is a proteolytic enzyme that has been isolated from the developing enamel of pig teeth. Its apparent function is to degrade the organic matrix in preparation for enamel maturation. The expression of EMSP1 has never been investigated in another organism besides the pig, and EMSP1 expression in the enamel organ has never been specifically demonstrated in ameloblasts. Here we report the expression of recombinant pig EMSP 1 (rpEMSP 1), the generation of rabbit polyclonal antibodies against rpEMSP1, the characterization of the antibodies and EMSP1 expression by Western blot and immunohistochemical analyses, the cloning and characterization of a full-length cDNA encoding mouse EMSP1, and the localization of EMSP1 expression in ameloblasts in mouse day 14 first and second molars by in situ hybridization. The full-length mouse EMSP1 cDNA clone has 1,237 nucleotides, excluding the poly(A+) tail, and encodes a preproprotein of 255 amino acids. Mouse EMSP1 shares 75% amino acid identity with pig EMSP1 and has three potential N-linked glycosylation sites, two of which are conserved in the pig homologue. Western blot analysis shows that the polyclonal antibodies are specific for EMSP1 and do not cross-react with trypsin. Immunohistochemistry of pig incisors shows discrete staining in the surface enamel at the earliest part of the maturation stage. In mouse molars, in situ hybridization gives a distinct and specific signal in maturation-stage ameloblasts, and in the junctional epithelium following tooth eruption. We conclude that EMSP1 is expressed by pig and mouse ameloblasts during the early maturation stage of amelogenesis.

Near-cognate peptidyl-tRNAs promote +1 programmed translational frameshifting in yeast

Translational frameshifting is a ubiquitous, if rare, form of alternative decoding in which ribosomes spontaneously shift reading frames during translation elongation. In studying +1 frameshifting in Ty retrotransposons of the yeast S. cerevisiae, we previously showed that unusual P site tRNAs induce frameshifting. The frameshift-inducing tRNAs we show here are near-cognates for the P site codon. Their abnormal decoding induces frameshifting in either of two ways: weak codon-anticodon pairing allows the tRNA to disengage from the mRNA and slip +1, or an unusual codon-anticodon structure interferes with cognate in-frame decoding allowing out-of-frame decoding in the A site. We draw parallels between this mechanism and a proposed mechanism of frameshift suppression by mutant tRNAs.

[Experimental study of the anti-tumor effects of directly administered packaging cell line of retroviral vector carrying IL-12 gene on hepatoma]

OBJECTIVE

To study the inhibitory effects of vivo directly administered packaging cell line of retroviral vector carrying mouse interleukin-12(mIL-12) on the growth of the vivo established hepatoma and to explore a new way for hepatoma gene therapy.

METHODS

Retroviral vector carrying mIL-12 gene was constructed. The vector was transfected to retroviral packaging cell line. Then the cell was injected intra-peritoneally and locally into hepatoma tissues or intrasplenally to observe its effects on the growth of hepatoma and the changes of immunological function in rats. Its toxic effects were also documented.

RESULTS

In treatment group, the rats survived permanently with the ratio of the packaging cell to hepatoma cell being less than 1:10, while the survival time of rats was only prolonged when the ratio was more than 1:10. In groups treated locally in the hepatoma tissue or intrasplenally, the rats survived permanantly with the packaging cell line given on the first or the third day, while the rats survived only longer with the packaging cell line given on the fifth or the seventh day. The immunological study showed that the number of hepatoma infiltrating lymphocytes, mainly composed of NK cell and cytotoxic T cell, was increased in the treatment group. The pathological study showed thicking of the vascular wall and sternosis of vascular cavity in hepatoma tissue in the treatment group.

CONCLUSION

The directly injected packaging cell line in vivo carrying mIL-12 gene via retroviral vector inhibits the growth of hepatoma. The therapeutical effects of early administration are superior to later one. Direct injection via spleen is a new, safe and effective way for hepatoma therapy with.

Effective use of polymerase chain reaction for diagnosis of central nervous system infections

Polymerase chain reaction (PCR)-based testing of cerebrospinal fluid (CSF) specimens has become standard for confirmatory diagnosis of central nervous system (CNS) infections; however, these tests increase health care costs. We reviewed 3-year data from 974 consecutive CSF specimens submitted for detection of seven pathogens by PCR. In 1997, 237 of 367 specimens (64.6%) were submitted for multiple tests, compared with 203 of 522 (38.9%) in 1996 and 18 of 85 (21.2%) in 1995. In each year the arrival of new house officers coincided with a peak in multiple testing. Among 732 specimens submitted for herpesvirus detection, results were positive for 24 (4.6%) of 523 specimens with increased leukocyte counts or protein levels. None of 209 specimens with normal leukocyte and protein levels were positive for herpesviruses. None of 471 CSF specimens submitted for Borrelia burgdorferi detection were PCR-positive. Use of protein and leukocytes to screen CSF specimens before employing PCR for herpesvirus detection would save almost one-third of costs without reducing sensitivity.

[Determination of 14 elements in chromium-rich brewer's yeast by ICP-AES]

An ICP-AES method was established for the determination of 14 elements in chromium-rich and normal brewer's yeast. The RSDs of two standard reference materials were 0. 5%-3.2% and 0.4%-3.4%, respectively. The results showed that chromium contents could affect the concentrations of other elements in chromium-rich brewer's yeast. The concentrations of K, Mn, P, V, Mg and Ca in chromium-rich brewer's yeast were significantly lower than those in normal brewer's yeast.

Transfer RNA modification: influence on translational frameshifting and metabolism

Transfer RNA modification improves the rate of aa-tRNA selection at the A-site and the fitness in the P-site and thereby prevents frameshifting according to a new model how frameshifting occurs [Qian et al. (1998) Mol. Cell 1, 471-482]. Evidence that the presence of various modified nucleosides in tRNA also influences central metabolism, thiamine metabolism, and bacterial virulence is reviewed.

[IL-12 gene treatment of hepatocellular carcinoma: experimental study]

OBJECTIVE

To investigate the inhibitory effects of retrovirus vector containing IL-12 gene on hepatoma growth in vivo and to explore a new approach of gene therapy to hepatocellular carcinoma (HCC).

METHODS

Retrovirus vector containing IL-12 gene was constructed and transfected into packaged cell PA317. Positive PA317 was injected into the rat which suffered from experimental HCC and its anti-tumor effects and immunity changes were recorded.

RESULTS

The packaged cell PA317 containing IL-12 gene could inhibit the proliferation of hepatocellular cell line CBRH3. The rats injected at day 1 or 3 can survive permanently, while those injected at day 5 or 7 can survive longer than those not injected. However, tumor generated in rats injected with blank control or package cells containing retroviral vector without IL-12 gene (P < 0.01).

CONCLUSIONS

Package cells transfected with retroviral vector containing IL-12 either injected to the hepatoma tissue locally or given splenic exercises anti-hepatoma effects efficiently. The direct intrasplenic injection route is new, safe and effective.

Characterization of recombinant pig enamelysin activity and cleavage of recombinant pig and mouse amelogenins

Enamelysin (MMP-20) is a tooth-specific matrix metalloproteinase that is initially expressed by ameloblasts and odontoblasts immediately prior to the onset of dentin mineralization, and continues to be expressed throughout the secretory stage of amelogenesis. During the secretory stage, enamel proteins are secreted and rapidly cleaved into a large number of relatively stable cleavage products. Multiple proteinases are present in the developing enamel matrix, and the precise role of enamelysin in the processing of enamel proteins is unknown. We have expressed, activated, and purified the catalytic domain of recombinant pig enamelysin, and expressed a recombinant form of the major secreted pig amelogenin rP172. These proteins were incubated together, and the digestion products were analyzed by SDS-PAGE and mass spectrometric analyses. We assigned amelogenin cleavage products by selecting among the possible polypeptides having a mass within 2 Daltons of the measured values. The polypeptides identified included the intact protein (amino acids 2-173), as well as 2-148, 2-136, 2-107, 2-105, 2-63, 2-45, 46-148, 46-147, 46-107, 46-105, 64-148, 64-147, and 64-136. These fragments of rP172 include virtually all of the major amelogenin cleavage products observed in vivo. We propose that enamelysin is the predominant proteinase that processes enamel proteins during the secretory phase of amelogenesis.

Serum beta-hydroxybutyrate measurement in patients with uncontrolled diabetes mellitus

OBJECTIVE

To assess whether routinely measuring serum beta-hydroxybutyrate (beta-OHB) concentration might help judge the severity of or assist in treating patients with suspected ketoacidosis.

METHODS

Serum beta-OHB level was estimated by a standard enzymatic method in 64 episodes in adults admitted to a municipal hospital. Of the 85 specimens analyzed, 60 were taken before treatment from a nearly consecutive group of diabetic patients with ketosis, 21 were follow-up specimens, and 4 were from nondiabetic patients with ketosis.

RESULTS

In the 85 specimens, the correlation between serum carbon dioxide and beta-OHB levels was -0.69, and that between anion gap and beta-OHB level was 0.75. For just the initial specimens, the respective correlation coefficients were -0.60 and 0.52.

CONCLUSIONS

The correlations between serum beta-OHB and carbon dioxide levels and the anion gap were close, but not sufficiently so for the beta-OHB measurements to be routinely useful alone to assess the severity of the ketoacidosis. Full laboratory assessment of the severity and characteristics of ketoacidosis also requires knowledge of serum carbon dioxide level, anion gap, often blood pH, and ideally serum acetoacetate and lactate concentrations as well as serum beta-OHB concentration.

A concise promoter region of the heart fatty acid-binding protein gene dictates tissue-appropriate expression

The heart fatty acid-binding protein (HFABP) is a member of a family of binding proteins with distinct tissue distributions and diverse roles in fatty acid metabolism, trafficking, and signaling. Other members of this family have been shown to possess concise promoter regions that direct appropriate tissue-specific expression. The basis for the specific expression of the HFABP has not been previously evaluated, and the mechanisms governing expression of metabolic genes in the heart are not completely understood. We used transient and permanent transfections in ventricular myocytes, skeletal myocytes, and nonmyocytic cells to map regulatory elements in the HFABP promoter, and audited results in transgenic mice. Appropriate tissue-specific expression in cell culture and in transgenic mice was dictated by 1.2 kb of the 5'-flanking sequence of FABP3, the HFABP gene. Comparison of orthologous murine and human genomic sequences demonstrated multiple regions of near-identity within this promoter region, including a CArG-like element close to the TATA box. Binding and transactivation studies demonstrated that this element can function as an atypical myocyte enhancer-binding factor 2 site. Interactions with adjacent sites are likely to be necessary for fully appropriate, tissue-specific, developmental and metabolic regulation.

[The influences of interleukin-1 beta converting enzyme expression on the biologic characteristics of ovarian cancer cells]

OBJECTIVE

To investigate the effects of interleukin-1 beta converting enzyme (ICE) gene on the biologic characteristics of ovarian cancer cells.

METHODS

A 1.3 Kilobase human ICE cDNA with 5' and 3' untranslated sequences was cloned into the EcoR I site of pLXSN retrovirus vector in sense orientation. After that, the recombinant plasmid pLXSN-ICE was transferred to virus-packing cell PA317 by electroporation method. And then the retrovirus containing human ICE cDNA generated by these PA317 cells were used to transfect human ovarian cancer cell lines, AO and 3AO.

RESULTS

After being transfected with these retrovirus, the number of the clones obtained after G418 resistance selection is far less than that of controlled groups with plasmid pLXSN. The growth rate of these transfected cells was significantly suppressed in comparison with the parental cell line. Apoptosis was also found in these cells. After the transfection cancer cells were inoculated subcutaneously in nude mice, the tumor growth was significantly inhibited.

CONCLUSION

It suggest that human ICE gene can suppress the phenotype and tumorigenicity in nude mice of ovarian cancer cell lines AO and 3AO.

Comparison of the chromium distribution in organs and subcellular fractions of normal and diabetic rats by using enriched stable isotope Cr-50 tracer technique

The enriched stable isotope 50Cr(III) tracer technique combined with neutron activation analysis was used to examine the intracellular distribution of Cr(III) in the liver, pancreas, testes, and kidney homogenates of both normal and diabetic rats. Our new results showed that the nucleic fraction has the highest Cr concentration in the liver cell of both normal and diabetic rats. The diabetic rats retain more Cr in the mitochondrial and lysosomal fractions of liver homogenate than the normal. This is likely an indication of chromium participating in the glucose or lipid metabolism to compensate the low level of insulin in the body of diabetic rats. The concentrations of Cr in the subcellular fractions of pancreas, testes, and kidney in the normal rats are higher than those in the diabetic rats, which favor the hypothesis that Cr(III) plays its biological function via interaction with the insulin-sensitive tissues or enhancement of the sensitivity of the insulin receptor.

Cloning, characterization, and tissue expression pattern of mouse tuftelin cDNA

Tuftelin is a protein that has been suggested to function during enamel crystal nucleation. Published sequences for bovine tuftelin cDNA and genomic clones proposed different reading frames that radically affected the derived amino acid sequence of the tuftelin carboxyl-terminus. We have isolated and characterized a full-length mouse cDNA clone and a partial porcine cDNA clone that include the region of the proposed frame-shift. The mouse tuftelin clone is 2572 nucleotides in length, exclusive of the poly(A+) tail. Translation from the 5'-most ATG yields a protein of 390 amino acids with an isotope-averaged molecular mass of 44.6 kDa and an isoelectric point of 5.9. Comparison of the bovine, mouse, and porcine cDNAs supports the revised bovine tuftelin amino acid sequence and suggests that the bovine tuftelin translation initiation codon be re-assigned to a more 5' ATG. Re-assigning the translation initiation codon lengthens the tuftelin protein by 52 amino acids, 51 of which are identical between bovine and mouse. At the carboxyl-terminus, the revised bovine and the mouse sequences match at 39 of the final 42 amino acid positions, compared with 2 identities with the originally published bovine reading frame. Northern blot analysis reveals that tuftelin is not ameloblast-specific but is expressed in multiple tissues, including kidney, lung, liver, and testis. Two tuftelin RNA messages, of 2.6 and 3.2 kb, were detected. DNA sequence characterization of an RT-PCR amplification product confirmed expression of tuftelin in kidney, and identified an alternatively spliced mouse tuftelin mRNA lacking exon 2.

[Genetic analysis on a new sterile locus discovered in hybrids between indica and japonica rice (Oryza sativa L.)]

Japonica line 02428, possessing wide compatibility gene S-5n, showed semi-sterility as crossed with indica variety IR24. Genetic analysis was conducted on the spikelet fertility in segregation generations from the crosses of 02428 with IR24, Pecos and Akihikara. The results indicated that the sterility in hybrids between 02428 and IR24 was controlled by a single non-allelic to S-5 gene and its inheritance fitted to one-locus sporo-gametophytic interaction model. Pecos, an American variety, has a neutral allele. The new sterility locus was preliminarily located near G24 marker on chromosome 11 detected by RFLP. The non-allelic S-locus in the study is named tentatively S-p(t). It was found that the sterility caused by the cross of Akihikara and IR24 was controlled by two S-loci, S-5 and S-p(t), and its genetical effect was additive.

Reparative dentin formation in rat molars after direct pulp capping with growth factors

Growth factors involved in normal wound healing may promote tissue repair when applied as a direct pulp capping medication. A minimal pulp exposure was made in rat molars, a pulp capping medication was placed, and the cavity was sealed. Epidermal growth factor, basic fibroblast growth factor, insulin-like growth factor II, platelet-derived growth factor-BB, and transforming growth factor-beta 1 (TGF-beta 1)--each absorbed onto a sterile collagen membrane (BioMend; Calcitek, Carlsbad, CA)--were used separately as pulpal medicaments. Dycal, unimpregnated collagen membrane, and no medication were used as controls. Eight samples from each treatment regimen were collected 2 and 3 weeks after surgery. Pulpal soft and hard tissue responses were graded. Data were analyzed by one-way ANOVA and Tukey-Kramer tests. No significant differences were detected after 2 wk. Pulp treated with TGF-beta 1 showed significantly improved soft and hard tissue healing at week 3, compared with the procedure control. We conclude that TGF-beta 1 as a pulp-capping medication enhances reparative dentin formation in rat molars.

Serum and urine chromium concentrations in elderly diabetics

The serum and urine chromium concentrations of 57 diabetics and 55 normal fasting subjects were determined by atomic absorption spectrometry (AAS). Our results indicate that the chromium concentration ranges of serum and urine for diabetics are 0.22-0.36 and 4.54-5.90 microg/L, respectively, significantly lower than 0.66-0.84 7.80-9.68 microg/L for the normal (P<0.001), which implies that the elderly diabetics probably lack chromium. Further, it was found that the urine chromium level of the female diabetics was substantially higher than that of the male in the same age group (P<0.01), whereas the serum chromium level was almost the same. However, the urine chromium concentration increases with aging, no matter who the diabetics or the controls are. The serum chromium concentrations of the 24 cases patients with 2-h oral glucose tolerance test (OGTT) were significantly lower than that of those with empty stomach, whereas the urine chromium exhibits a contrary tendency. Our data indicate that the chromium lost and excreted from human body increases with aging and is related to the diabetics. Thus, it is recommended to supplement a certain amount of chromium to the elderly diabetics according to their nutritional level.

Use of the enriched stable isotope Cr-50 as a tracer to study the metabolism of chromium (III) in normal and diabetic rats

The activable enriched stable isotope Cr-50 compound Cr2O3 was used as a tracer to study the metabolism of chromium(III) [CR(III)] intragastrically administered in normal and diabetic rats. The comparison of absorption, distribution, and excretion in organs and tissues of the two groups do not show much alteration, but some differences exist indeed. The contents of 51Cr radioactivity of the diabetic rats appear to be of higher retention than in most studied organisms. The urinary 51Cr excretion of diabetics is significantly higher than that of normal rats. Therefore, a conclusion can be drawn that the insulin-dependent rats generally absorb and excrete more chromium (Cr) than the normal rats.

[Construction and application of retroviral vector carrying green fluorescent protein]

OBJECTIVE

To construct retroviral vector carrying rapidly selective marker.

METHODS

The recombination retroviral vector GCGFPPXSN was constructed by cloning the green fluorescent protein (GFP) cDNA into the retroviral vector containing putative internal ribosome entry sites GCXPXSN and transferred in ecotropic packaging cell line PE501 by electroporation method. The supernatants of the PE501GCGFPPXSN were used to infect the amphotropic packaging cell line PA317. The G418 resistant clones were selected in 4 weeks and were detectable by fluorescence microscopy or by fluorescence-activated cell sorting(FACS).

RESULTS

A recombination retroviral vector GCGFPPXSN carrying rapidly selective marker GFP was constructed. GFP expression in packaging cell line PA317-GCGFPPXSN transferred by GCGFPPXSN was detected by fluorescence microscopy of FACS. PA317-GCGFPPXSN grew to a titer of 1.2 x 10(5) cpu/ml. By cocultivating retroviral vector producing cells and T lymphocytes, expression of GFP was observed in T lymphocytes 2 days after the end of the cocultivation. T lymphocytes expressing GFP were separated.

CONCLUSION

The mammalian cell can be efficient gene transfected by retroviral vector carrying GFP. The use of GFP for cell marking represents an important advantage over conventional strategies which typically involve the use of neomycin resistance. GFP, in fact, allows a rapid in vitro selection of transduced cell by FACS. The selection requires only two-day culture with this retroviral vector, compared with 10-14 day culture with a classical retroviral vector.

Correlation of mercury with selenium in human hair at a typical mercury-polluted area in China

The levels of mercury (Hg) and selenium (Se) and their correlation in human scalp hair of 29 pairs of pregnant women and their newborns living at a high-Hg and low-Se area, the Second Song-Hua-Jiang River System, have been studied by instrumental neutron activation analysis. Our results indicate that the Hg level in infant hair samples are roughly close to that in their mothers, whereas the Se level in infants is much higher. Furthermore, the molar ratios of Se/Hg in newborns are also 40% higher than those in mothers. It demonstrates that infants are able to absorb more selenium from their mothers' bodies to protect against or alleviate the intoxication of Hg. This "autoprotective mechanism" likely plays a critical role during fetal development. The possible chemical species of Hg and Se in hair is also discussed.

[Fas mediated apoptosis inhibited by human bcl-2 gene in lymphoma cell line Jurkat]

OBJECTIVE

To understand the mechanism of bcl-2 gene in escaping the immune surveillance in the development of lymphoma.

METHODS

A recombinant retroviral vector pLXSN-bcl-2 was constructed by cloning bcl-2 cDNA into the replication defective retroviral vector pLXSN, and transferred to packaging cell line PA317 by electroporation. The G418 resistant colonies were selected, and the supernatants of the colony cultures were used to infect the human lymphoma cell line Jurkat. Cells in G418 resistant Jurkat colonies were characterized by immunohistochemistry. Anti-Fas monoclonal antibody (McAb) was applied to Jurkat cells for inducing apoptosis which mimicked the cytotoxic activity of T lymphocyte.

RESULTS

Expression of bcl-2 in pLXSN-bcl-2 transfected Jurkat cell (Jurkat-bcl-2) increased, while there was no change of Fas gene expression. Apoptosis was blocked in Jurkat-bcl-2 by anti-Fas McAb treatment.

CONCLUSION

Overexpression of bcl-2 in lymphoma cell line could inhibit cell apoptosis induced by anti Fas McAb, suggesting that overexpression of bcl-2 is one of the mechanisms in escaping immune surveillance in the development of lymphoma.

[The development of computer-assisted gastric function testing system]

This paper introduces a system consisting of the PC computer, sensing device, the card for electro-gastric signals amplifier and analog-digital converter. By using only one piece of 1.2 M 3" diskette, the system can realize the dialogue between human and the computer to sample, process, store and display the electro-gastric signals, and print the auxiliary analysis and diagnostic results for doctors to refer to. When the computer is more and more popular today, it is one of the convenient, painless and effective method to check up the gastric functional disease.

The methyl group of the N6-methyl-N6-threonylcarbamoyladenosine in tRNA of Escherichia coli modestly improves the efficiency of the tRNA

tRNA species that read codons starting with adenosine (A) contain N6-threonylcarbamoyladenosine (t6A) derivatives adjacent to and 3' of the anticodons from all organisms. In Escherichia coli there are 12 such tRNA species of which two (tRNA(Thr1)GGU and tRNA(Thr3)GGU) have the t6A derivative N6-methyl-N6-threonylcarbamoyladenosine (m6t6A37). We have isolated a mutant of E. coli that lacks the m6t6A37 in these two tRNA(Thr)GGU species. These tRNA species in the mutant are likely to have t6A37 instead of m6t6A37. We show that the methyl group of m6t6A37 originates from S-adenosyl-L-methionine and that the gene (tsaA) which most likely encodes tRNA(m6t6A37)methyltransferase is located at min 4.6 on the E. coli chromosomal map. The growth rate of the cell, the polypeptide chain elongation rate, and the selection of Thr-tRNA(Thr)GGU to the ribosomal A site programmed with either of the cognate codons ACC and ACU were the same for the tsaA1 mutant as for the congenic wild-type strain. The expression of the threonine operon is regulated by an attenuator which contains in its leader mRNA seven ACC codons that are read by these two m6t6A37-containing tRNA(Thr)GGU species. We show that the tsaA1 mutation resulted in a twofold derepression of this operon, suggesting that the lack of the methyl group of m6t6A37 in tRNA(Thr)GGU slightly reduces the efficiency of this tRNA to read cognate codon ACC.

[Perforin and Fas-ligand expression of tumor infiltrating lymphocytes in human hepatocellular carcinoma]

OBJECTIVE

To investigate perforin and Fas-ligand (Fas-L) expression of tumor infiltrating lymphocytes (TIL) in human hepatocellular carcinoma (HCC).

METHODS

Expression of perforin and Fas-L of TIL was studied in 20 HCC cases using in situ hybridization and immunohistochemistry.

RESULTS

Expression of perforin and Fas-L gene were detected in TIL in 80% of the cases studied. Among them, one patient (no. 14) in whom expression of perforin and Fas-L were noticed in the majority of the TIL, had no recurrence of HCC for one and one half (1.5) year after tumor resection. It indicates that presence of large number of activated T cells might be beneficial for the tumor therapy. In the remaining cases, only 10% of TIL were obtained able to express perforin and Fas-L indicating that only a few TIL were activated and cytotoxic to HCC.

CONCLUSIONS

Even there were a multitude of T cells infiltrating in HCC, only few of them were immunoactived and to be cytotoxic to HCC. It seems important to adopt measures in order to promote further proliferation of these activated T cells either in vitro or in vivo.

A new model for phenotypic suppression of frameshift mutations by mutant tRNAs

According to the prevailing model, frameshift-suppressing tRNAs with an extra nucleotide in the anticodon loop suppress +1 frameshift mutations by recognizing a four-base codon and promoting quadruplet translocation. We present three sets of experiments that suggest a general alternative to this model. First, base modification should actually block such a four-base interaction by two classical frameshift suppressors. Second, for one Salmonella suppressor tRNA, it is not mutant tRNA but a structurally normal near cognate that causes the +1 shift in-frame. Finally, frameshifting occurs in competition with normal decoding of the next in-frame codon, consistent with an event that occurs in the ribosomal P site after the translocation step. These results suggest an alternative model involving peptidyl-tRNA slippage at the classical CCC-N and GGG-N frameshift suppression sites.