Retinoblastoma protein directly interacts with and activates the transcription factor NF-IL6

The biological function of the retinoblastoma protein (RB) in the cell division cycle has been extensively documented, but its apparent role in differentiation remains largely unexplored. To investigate how RB is involved in differentiation, the U937 large-cell lymphoma line was induced to differentiate along a monocyte/macrophage lineage. During differentiation RB was found to interact directly through its simian virus 40 large tumor antigen (T antigen)-binding domain with NF-IL6, a member of the CAAT/enhancer-binding protein (C/EBP) family of transcription factors. NF-IL6 utilizes two distinct regions to bind to the hypophosphorylated form of RB in vitro and in cells. Wild-type but not mutant RB enhanced both binding activity of NF-IL6 to its cognate DNA sequences in vitro and promoter transactivation by NF-IL6 in cells. These findings indicate a novel biochemical function of RB: it activates, by an apparent chaperone-like activity, specific transcription factors important for differentiation. This contrasts with its sequestration and inactivation of other transcription factors, such as E2F-1, which promote progression of the cell cycle. Such disparate mechanisms may help to explain the dual role of RB in cell differentiation and the cell division cycle.

Grafted cerebellar cells in a mouse model of hereditary ataxia express IGF-I system genes and partially restore behavioral function

Fetal grafts of normal cerebellar tissue were implanted into the cerebellum of Purkinje cell degeneration mutant mice (pcd/pcd), a model of adult-onset recessively inherited cerebello-olivary atrophy, in an attempt at correcting their cellular and motor impairment. Donor cerebellar cells engrafted in the appropriate sites, as evidenced by the pattern of expression of insulin-like growth factor-I (IGF-I) system genes. Bilateral cerebellar grafts led to an improvement of motor behaviors in balance rod tests and in the open field, providing evidence for functional integration into the atrophic mouse cerebellum and underscoring the potential of neural transplantation for counteracting the human cerebellar ataxias.

Aberrant subcellular localization of BRCA1 in breast cancer

The BRCA1 gene product was identified as a 220-kilodalton nuclear phosphoprotein in normal cells, including breast ductal epithelial cells, and in 18 of 20 tumor cell lines derived from tissues other than breast and ovary. In 16 of 17 breast and ovarian cancer lines and 17 of 17 samples of cells obtained from malignant effusions, however, BRCA1 localized mainly in cytoplasm. Absence of BRCA1 or aberrant subcellular location was also observed to a variable extent in histological sections of many breast cancer biopsies. These findings suggest that BRCA1 abnormalities may be involved in the pathogenesis of many breast cancers, sporadic as well as familial.

Life and death by p53

p53 is a multifunctional protein which plays a role in modulating gene transcription, policing cell cycle checkpoints, activating apoptosis, controlling DNA replication and repair, maintaining genomic stability and responding to genetic insults. Mutation of the p53 gene confers the single greatest known selective advantage favoring cancer formation. Point mutations result not only in the loss of tumor suppressor functions, but also in the gain of tumor promotion functions. These dual circumstances may be unique to p53 and, in part, could explain the relatively powerful force behind this selection pressure. General mechanisms of gain of function by mutated p53 may include alteration in transcriptional modulation and newly acquired targets for transcriptional regulation and protein binding. Despite the direct significance of p53 mutations, loss of the remaining wild-type allele is usually required for the formation of tumors in the natural setting. Novel applications of the basic scientific knowledge of p53 could lead to an improvement in cancer treatment, hopefully in the not so distant future.

Analysis of insulin-like growth factors (IGF)-I, and -II, type II IGF receptor and IGF-binding protein-2 mRNA and peptide levels in normal and nephrectomized rat kidney

Immunocytochemistry, in situ hybridization, and radioimmunoassay were employed to examine the cellular distribution of mRNAs and proteins for IGF-I, II, IGF-II/M6P receptor, IGFBP2 as well as the levels of IGF-I and II in normal and unilaterally nephrectomized (Nx) adult rat kidneys. A similar distribution of immunoreactive IGF-I, and -II as well as IGF-II/M6P receptor was found in the principal cells of the cortical collecting duct and in all cells of the inner medullary collecting duct. In addition, immunostainable IGF-I and IGF-II/M6P receptor were noted in some inner medullary loops of Henle, while IGFBP2 was seen in the collecting ducts and loops of Henle of the inner medullar and the renal vasculature of all animals. By comparison, in situ hybridization revealed IGF-I mRNA only in the medullary thick ascending limbs while IGF-II mRNA was localized to the wall of the renal microvasculature in all kidneys. IGFBP2 mRNA was localized to the renal corpuscle and to inner medullary interstitial cells of all kidneys. These data suggest that renal IGF-I and IGFBP2 are synthesized at upstream sites along the nephron and then transported downstream for interaction with IGF receptors. Following nephrectomy, the renal levels of IGF-I peptide and mRNA were elevated at both 5 and 33 days post-nephrectomy, supporting a potential functional role for IGF-I in stimulating the structural and functional recovery in compensatory hypertrophy.

Detection of apoptosis in weaver cerebellum by electron microscopic in situ end-labeling of fragmented DNA

Massive degeneration of granule cell precursors occurs perinatally in the cerebellum of weaver mutant mice. We have studied the electron microscopic (EM) features of granule cell death in weaver and control mice, using an in situ end-labeling (ISEL) technique for detecting DNA fragmentation, a hallmark of apoptosis. In all animals, EM-ISEL revealed the pattern of apoptosis, with an enhanced expression in weaver mice. The weaver gene appears to accelerate the death program, most likely through potassium channel-mediated signals.

Association of human Pur alpha with the retinoblastoma protein, Rb, regulates binding to the single-stranded DNA Pur alpha recognition element

The retinoblastoma protein, Rb, is detected in extracts of monkey CV-1 cells complexed with Pur alpha, a sequence-specific single-stranded DNA-binding protein implicated in control of gene transcription and DNA replication. These complexes can be immunoextracted from cell lysates using monoclonal antibodies to either Pur alpha or Rb. The Pur alpha-Rb complexes contain a form of Pur alpha with extensive post-synthetic modification, as demonstrated following expression of Pur alpha cDNA fused to a 9-amino acid epitope tag. Human Pur alpha, expressed as a glutathione S-transferase fusion protein, specifically binds to the hypophosphorylated form of Rb with an affinity as high as that of SV40 large T-antigen. In the absence of DNA, glutathione S-transferase-Pur alpha binds to p56RB, an NH2-terminal-truncated Rb protein purified from Escherichia coli, containing the T-antigen binding domain, to form multimeric complexes. The single-stranded DNA Pur alpha recognition element disrupts these complexes. Conversely, high concentrations of p56RB prevent Pur alpha binding to DNA. Through use of a series of deletion mutants, the DNA binding activity of Pur alpha is localized to a series of modular amino acid repeats. Rb binding involves a Pur alpha region with limited homology to the Rb-binding region of SV40 large T-antigen. Binding of Pur alpha to p56RB, the COOH-terminal portion of Rb, is inhibited by a synthetic peptide containing the T-antigen Rb-binding motif.

Graft-induced restoration of function in hereditary cerebellar ataxia

Fetal cerebellar cell suspensions, prepared from wild-type (+/+) mice, were implanted bilaterally into the cerebellum of Purkinje cell degeneration' (pcd) mutant mice, a model of adult-onset recessively inherited cerebellar ataxia, to study the functional effects of the grafts on motor coordination and fatigue resistance in a rotating rod treadmill paradigm. The viability of transplanted Purkinje cells was verified with immunocytochemistry for calbindin-D28k and for glutamate receptor 2/3 subunits and with in situ hybridisation histochemistry for insulin-like growth factor I mRNA, biochemical markers normally expressed by Purkinje cells in the cerebellum. Sham injections of vehicle did not appreciably modify the performance of pcd mutants in the rota-rod tests. On the other hand, bilateral cerebellar grafts led to a 3.5-fold increase in the time period that recipient pcd mice were able to stay on the rotating drum based on the comparison of mean scores (of three trials) or a 5.5-fold increase based on the comparison of maximum scores (of the three trials). These findings provide evidence for a motor enhancement in the pcd mouse model of hereditary cerebellar ataxia following intracerebellar transplantation of primordial Purkinje cells.

Isolation and properties of a blood coagulation factor X activator from the venom of king cobra (Ophiophagus hannah)

A specific blood coagulation factor X activator was purified from the venom of Ophiophagus hannah by gel filtration and two steps of FPLC Mono-Q column ion-exchange chromatography. It showed a single protein band both in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and alkaline polyacrylamide gel electrophoresis. The mol. wt was estimated to be 62,000 in non-reducing conditions and 64,500 in reducing conditions by SDS-PAGE. The isoelectric point was found to be pH 5.6. The enzyme had weak amidolytic activities toward CBS 65-25, but it showed no activities on S-2266, S-2302, thrombin substrate S-2238, plasmin substrate S-2251 or factor Xa substrate S-2222. It had no arginine esterase activity toward substrate benzoylarginine ethylester (BAEE). The enzyme activated factor X in vitro and the effect was absolutely Ca2+ dependent, with a Hill coefficient of 6.83. It could not activate prothrombin nor had any effect on fibrinogen and thus appeared to act specifically on factor X. The procoagulant activity of the enzyme was almost completely inhibited by serine protease inhibitors like PMSF, TPCK and soybean trypsin inhibitor; partially inhibited by L-cysteine. Metal chelator EDTA did not inhibit its procoagulant activity. These results suggest that the factor X activator from O. hannah venom is a serine protease.

The CD45RA+ (quiescent) cellular phenotype is overabundant relative to the CD45RA- phenotype within the involuted splenic T cell population of weanling mice subjected to wasting protein-energy malnutrition

The objective of this investigation was to determine whether an imbalance between naive- and memory-phenotype cells occurs within CD4+ and/or CD8+ splenic T cell subsets in models of protein-energy malnutrition (PEM) which produce wasting disease (loss of approximately 1.6% of body weight per day for 14 d) and profound depression in thymus-dependent immunity. Male and female weanling mice of disparate inbred strains, CBA/J and C57BL/6J, were allocated to the following groups: zero-time control (23 d old and 19 d old, respectively), ad libitum intake of a complete purified diet (19% crude protein, 17 kJ/g gross energy), restricted intake of the complete diet, and (C57BL/6J, only) ad libitum intake of an isocaloric low protein diet (0.6% crude protein). Surface expression of isoforms of CD45, a component of the T cell receptor complex, as well as of the accessory molecule, CD2, were assessed by flow cytometry of splenic mononuclear cell suspensions. Both major T cell subsets in the malnourished groups contained a significantly higher proportion of cells expressing the surface marker, CD45RA, than was found in the spleen cells of the control groups. CD45RA+ (naive-phenotype) T cells represent the extreme of quiescence and stringent activation requirements among thymic lymphocytes. The results provide the first clear evidence of a T cell subset imbalance in PEM which is consistent with depression in acquired immunity and which occurs, apart from antigenic challenge, in a site wherein immune responses take place. The T cell receptor complex may emerge as a focal point of the depressive influence of PEM on the competence of thymic lymphocytes.

Mitochondrial alterations of skeletal muscle in a heat stress rat model

The morphological and ultrastructural alterations of skeletal muscle in experimental rats with heat stress were investigated. Fifteen male Sprague-Dawley rats were exposed in a 42 degrees C constant temperature oven, resulting in a heat stress state; ten rats were used as controls. All treated rats had weakness of the 4 limbs associated with increased serum creatine kinase levels (p < 0.01). Soleus muscles were submitted to histological, histochemical, ultrastructural and quantitative-morphometric analysis. The group receiving heat stress showed many ragged-red fibers in Gomori trichrome stain and appeared hyper-reactive in succinate dehydrogenase and cytochrome C oxidase stains. The ultrastructure of ragged-red fibers showed increased mitochondrial aggregation as multiple small nests, which were particularly located in the subsarcolemmal space. The mitochondrial area was significantly increased in heat stress rats (p < 0.001). The consistently increased mitochondrial area and histochemical alterations of mitochondria are early pathological abnormalities in muscles with heat stress and indicate fundamental impairment of energy metabolism.

Molecular evidence that in situ-transduced fetal liver hematopoietic stem/progenitor cells give rise to medullary hematopoiesis in adult rats

We exploited the ability to transduce fetal liver hematopoietic stem/progenitor cells in situ with recombinant retrovirus, together with the ability to analyze proviral integration patterns into chromosomal DNA, to detect the cellular and organ fate of hematopoietic stem and progenitor-derived progeny in tissues and in the circulation of neonatal and adult rats. Two hundred seventeen fetuses were injected with retrovirus supernatant on day 16 of gestation, before the development of the bone marrow cavity. The progeny of 41 stem and progenitor cells from 97 liveborn rats were clonally identified. Pluripotent and lineage-restricted stem/progenitor clones derived from the fetal liver consistently gave rise to progeny in the marrow of newborn and adult rats. Patterns of differentiation of transduced stem and progenitor cells fell into distinct subsets. Blood cells derived from in situ transduced cells that originated in the fetal liver circulated throughout the life span of the adult animals. These data provide molecular evidence of the origin of medullary cavity hematopoiesis by cells derived from the fetal liver that were transduced in vivo, homed to the developing medullary cavity and proliferated in a normal medullary hematopoietic microenvironment.

Rhabdomyosarcoma of the vagina in a postmenopausal woman: report of a case and review of the literature

Most rhabdomyosarcomas (RMSs) of the female genital tract occur in infants and young children as sarcoma botryoides. Vaginal RMS occurring in a postmenopausal woman is extremely rare. To our knowledge, only three vaginal RMSs have been reported in patients who were over 50 years of age. Herein, the first case in Taiwan and the fourth case in the world is reported, and the pertinent literature is briefly reviewed. A 63-year-old woman complained of a few days of abnormal vaginal bleeding. Vaginal examination demonstrated two black polypoid tumors located at the left-lateral and posterior wall of the vagina. The patient had previously undergone a vaginal total hysterectomy for rectocele and urine incontinence, so surgical treatment including local wide excision and bilateral salpingo-oophorectomy were performed under the diagnosis of malignant vaginal tumor. The clinical, histopathological, and immunohistochemical studies revealed a group Ia pleomorphic RMS. Postoperative radiotherapy was performed. The patient remains alive and well 12 months after a combined therapy.

Characterization of a novel 350-kilodalton nuclear phosphoprotein that is specifically involved in mitotic-phase progression

A gene assigned to human chromosome 1q32-41 encodes a novel protein of 3,113 amino acids containing an internal tandem repeat of 177 amino acids. The protein, which we have named "mitosin," was identified by direct binding to purified retinoblastoma protein in vitro with a region distantly related to the retinoblastoma protein-binding site of E2F-1. Mitosin is expressed throughout S, G2, and M phases of the cell cycle but is absent in G1. Its localization is dramatically reorganized from a rather homogeneous nuclear distribution in S phase to paired dots at the kinetochore/centromere region, to the spindle apparatus, and then to the midbody during M-phase progression. This spatial reorganization coincides closely with the temporal phosphorylation patterns of mitosin. Overexpression of N-terminally truncated mutants blocks cell cycle progression mainly at G2/M. These results suggest that mitosin may play an important role in mitotic-phase progression.

The C terminus of mitosin is essential for its nuclear localization, centromere/kinetochore targeting, and dimerization

Mitosin is a novel 350-kDa nuclear phosphoprotein that dramatically relocates from the evenly nuclear distribution in S phase to the centromere/kinetochore and mitotic apparatus in M phase. The dynamic relocalization of mitosin is accompanied by the phosphorylation of itself, suggesting that mitosin plays a role in mitotic progression. The molecular basis of nuclear localization and targeting of mitosin to the centromere/kinetochore were characterized using a set of epitope-tagged deletion mutants. The data indicate that the extreme C terminus (amino acids 2,487-3,113) of mitosin has both an independent centromere/kinetochore targeting domain and an unusually spaced bipartite nuclear localization signal. Moreover, the same centromere/kinetochore targeting domain was shown to be essential for the ability of mitosin to bind to itself or other putative mitosin-associated proteins through use of the yeast two-hybrid system. These results suggest that the C terminus of the mitosin is essential for its role in influencing cell cycle progression.

Detection of human papillomavirus DNA in colorectal carcinomas by polymerase chain reaction

Human papillomaviruses (HPVs) are associated with a number of benign and malignant neoplasms. To substantiate the relationship between HPV DNA and colorectal carcinomas, 70 carcinomas and 37 adenomas were analysed in this study. Specific types of HPV DNA in colorectal tumours were detected by polymerase chain reaction (PCR) and Southern blot hybridisation. HPV DNA was detected in 11 of 37 (29.7%) adenomas and in 52.9% 37 of 70 (52.9%) of carcinomas. The expression of HPV DNA in adenomas and carcinomas, especially that of HPV 16 in HPV positive cases (4 of 11 v 26 of 37), was significantly different (p < 0.05). There was no correlation, however, between HPV and the location, differentiation, stage, or survival of malignant neoplasms. These data suggest that HPV DNA, especially type 16, is associated with colorectal carcinogenesis.

Identification and localization of secretin and secretin receptor mRNAs in rat testis

Secretin is a well-conserved member of the growth hormone-releasing hormone (GHRH) family of peptides expressed in brain, gut and gonads. To determine whether secretin may also play a physiological role in testis, we examined the level and cellular distribution of secretin and secretin receptor gene expression in rat testis. RNAs from total testis, Sertoli, germ and Leydig cells were amplified by comparative reverse transcription-polymerase chain reaction (RT-PCR). Southern blot analysis of the PCR products indicated secretin and secretin receptor mRNA expression primarily in germ cells. Sequence comparisons of cloned secretin and secretin receptor PCR products showed 100% identity with the previously reported sequences. To localize secretin and secretin receptor mRNAs at the cellular level within testis,in situ hybridization was performed. Specific hybridization to secretin mRNA was observed in low abundance in many germ cell types, but was heaviest over step 19 spermatids in stages VII and VIII tubules. Secretin receptor mRNA was detected in approximately the same cell types as was secretin mRNA, except that labeling was greatest in round spermatids (steps 6-8). Since the patterns of gene expression of secretin and its receptor overlap, these data suggest that there may be an intrinsic secretin system in testis.

Culture media and methods for the isolation of Listeria monocytogenes

The recovery of low numbers of Listeria monocytogenes from foods and environmental samples requires the use of enrichment cultures followed by selective plating and, where injured organisms are likely to be present, a pre-enrichment step. The development of selective and enrichment media for L. monocytogenes is traced and currently used media are discussed. Comparisons of media and methods for the culture of L. monocytogenes are reported but no single method can be recommended for all situations. Guidance is given on the choice of media and methods which is governed by the type of sample, number and nature of competing flora and cost.

Media used in the detection and enumeration of Staphylococcus aureus

Over the years a range of selective and diagnostic media have been developed to assist in the detection and enumeration of Staphylococcus aureus in routine food surveillance programmes and food poisoning investigations and these are reviewed here. Baird-Parker agar remains, however, the medium of choice for direct plating and enumeration of S. aureus in both Europe and the US. This paper also reports on a comparison of the productivity and selectivity of trypticase soy broth with 10% NaCl and 1% sodium pyruvate (PTSBS) with trypticase soy broth (TSB) for the isolation of S. aureus. Using three strains of S. aureus and a strain of S. hyicus the productivity ratio of PTSBS to TSBS ranged from -0.17 to 0.57. In the recovery of heat-injured cells of S. aureus, PTSBS offered little or no improvement over TSB with sodium chloride but no pyruvate in a three-tube MPN assessment. Of the seven other bacterial cultures tested, none grew well on the PTSBS. Selectivity ratios of 4.4-7 were found.

Altered IGFBP5 gene expression in the cerebellar external germinal layer of weaver mutant mice

The IGF system components play important roles in cerebellar development as demonstrated by their specific spatial-temporal expression. IGF-I, type I IGF receptor (IGFR-I), IGFBP2 and IGFBP5 mRNA are localized in distinct cell populations, and all are expressed at the highest levels at the peak of Purkinje cell growth, active synaptogenesis and dendritic formation. To understand IGF-I's action at the cellular level, in situ hybridization was employed to investigate the distribution of IGF system gene transcripts in the cerebellum of weaver mutant mice (wv/wv). Although located ectopically, the surviving Purkinje cells express IGF-I mRNA at the same level in wv/wv as in +/+. No alteration in the cellular distribution or mRNA levels was observed with IGFBP2, or IGFR-I mRNAs. However, the pattern of IGFBP5 expression is altered in the external germinal layer of wv/wv mice. Not only is IGFBP5 expressed by more granule cell precursors of wv/wv cerebellum, but its mRNA level is 2.3 fold that of +/+. The altered IGFBP5 gene expression in granule cell precursors may modulate the interaction of IGF-I with IGFR-I in ways that contribute to their massive death occurring in the development of wv/wv cerebellum.

The aetiology of postmenopausal bleeding--a study of 163 consecutive cases in Singapore

OBJECTIVE

To study the aetiology and pattern of Postmenopausal Bleeding (PMB) in the local population.

DESIGN

A retrospective study

SUBJECTS

163 consecutive patients who presented with postmenopausal bleeding (PMB) SETTING: Kandang Kerbau Hospital, Singapore

RESULTS

Malignant causes were found in 42 (25.7%) patients. Cervical carcinoma was the most common malignancy (12.9% of the patients) followed by endometrial carcinoma (11%). Important benign causes are cervicitis (12.9%), atrophic vaginitis (12.3%) and cervical polyp (6.7%). Other benign causes include endometrial hyperplasia (3.1%), urethral caruncle (2.5%) and estrogen replacement therapy (1.8%).

CONCLUSION

PMB is a symptom of varied aetiologies. The associated incidence of malignancy is high and a thorough diagnostic evaluation is mandatory.

Regulatory networks of the retinoblastoma protein

Studies of the retinoblastoma (RB) gene product suggest that it may work as a fundamental regulator to coordinate pathways of cellular growth and differentiation. One known function of retinoblastoma (Rb) protein is its ability to suppress tumorigenesis. In many different cultured tumor cells, replacement of a normal RB gene and expression of normal Rb protein results in suppression of neoplastic properties. Moreover, in humans or experimental mice, germ line mutation of the RB gene leads particularly to retinoblastomas or pituitary tumors, respectively, which demonstrates that the role of RB in tumor predisposition is specific to certain tissues. In addition to suppressing tumor formation, Rb apparently also has roles in normal development and cellular differentiation. Recent characterizations of Rb-associated proteins and proteins within the Rb family may provide some clues to exploring the complex networks in which Rb is involved.

Differential expression of the human metastasis adhesion molecule CD44V in normal and carcinomatous stomach mucosa of Chinese subjects

BACKGROUND

CD44 is a cell surface adhesion molecule involved in cell-cell and cell-matrix interactions. Tumor cells transfected to overexpress the isoform CD44V readily gain access to lymph nodes and form distant metastases.

METHODS

Monoclonal antibodies directed at epitopes common to known CD44 isoforms were used to investigate CD44V expression in 30 normal gastric mucosa tissues, 64 different gastric adenocarcinomas, 20 metastatic adenocarcinoma lymph nodes and 4 established gastric carcinoma cell lines. In addition, CD44V gene expression in six gastric adenocarcinoma tissues and four gastric cancer cell lines were investigated by northern blotting.

RESULTS

Immunohistochemistry screening of 30 subjects with normal gastric mucosa did not reveal expression of CD44 variants. Areas of intestinal metaplasia, a precancerous lesion, were stained with antibodies against either V5- or V6-containing isoforms of CD44. Tubular and signet-ring cell types of adenocarcinoma were strongly positive for epitopes encoded by CD44 variants containing exons V5 (41/49 and 10/10, respectively). Some tubular type adenocarcinomas (15/49) also expressed CD44 variants containing the V6 epitope. Tumor differentiation was closely related to CD44 V5 expression (P < 0.001). In addition, 18 of 20 gastric adenocarcinomas metastatic to lymph nodes expressed the V5 epitope of CD44 and 4 of 20 expressed the V6 epitope. Analysis of four established gastric adenocarcinoma cell lines revealed that two had moderate to strong expression of exons V5 and V6 of CD44. An antibody directed against CD44 variants containing exons V8 to V10 strongly stained all gastric adenocarcinoma cell lines. Northern blotting demonstrated that all four tumor cell lines and six gastric carcinoma mucosa tissues expressed CD44V.

CONCLUSIONS

Generation of CD44 splice variants may be closely linked with gastric carcinoma tumorigenesis and differentiation. In addition, expression of CD44 variants containing exons V5 and V6 may be used as an indicator of evolving gastric cancer.

Differential expression of the human metastasis adhesion molecule CD44V in normal and carcinomatous stomach mucosa of Chinese subjects

BACKGROUND

CD44 is a cell surface adhesion molecule involved in cell-cell and cell-matrix interactions. Tumor cells transfected to overexpress the isoform CD44V readily gain access to lymph nodes and form distant metastases.

METHODS

Monoclonal antibodies directed at epitopes common to known CD44 isoforms were used to investigate CD44V expression in 30 normal gastric mucosa tissues, 64 different gastric adenocarcinomas, 20 metastatic adenocarcinoma lymph nodes and 4 established gastric carcinoma cell lines. In addition, CD44V gene expression in six gastric adenocarcinoma tissues and four gastric cancer cell lines were investigated by northern blotting.

RESULTS

Immunohistochemistry screening of 30 subjects with normal gastric mucosa did not reveal expression of CD44 variants. Areas of intestinal metaplasia, a precancerous lesion, were stained with antibodies against either V5- or V6-containing isoforms of CD44. Tubular and signet-ring cell types of adenocarcinoma were strongly positive for epitopes encoded by CD44 variants containing exons V5 (41/49 and 10/10, respectively). Some tubular type adenocarcinomas (15/49) also expressed CD44 variants containing the V6 epitope. Tumor differentiation was closely related to CD44 V5 expression (P < 0.001). In addition, 18 of 20 gastric adenocarcinomas metastatic to lymph nodes expressed the V5 epitope of CD44 and 4 of 20 expressed the V6 epitope. Analysis of four established gastric adenocarcinoma cell lines revealed that two had moderate to strong expression of exons V5 and V6 of CD44. An antibody directed against CD44 variants containing exons V8 to V10 strongly stained all gastric adenocarcinoma cell lines. Northern blotting demonstrated that all four tumor cell lines and six gastric carcinoma mucosa tissues expressed CD44V.

CONCLUSIONS

Generation of CD44 splice variants may be closely linked with gastric carcinoma tumorigenesis and differentiation. In addition, expression of CD44 variants containing exons V5 and V6 may be used as an indicator of evolving gastric cancer.