Coupling assembly of the E-cadherin/beta-catenin complex to efficient endoplasmic reticulum exit and basal-lateral membrane targeting of E-cadherin in polarized MDCK cells

The E-cadherin/catenin complex regulates Ca++-dependent cell-cell adhesion and is localized to the basal-lateral membrane of polarized epithelial cells. Little is known about mechanisms of complex assembly or intracellular trafficking, or how these processes might ultimately regulate adhesion functions of the complex at the cell surface. The cytoplasmic domain of E-cadherin contains two putative basal-lateral sorting motifs, which are homologous to sorting signals in the low density lipoprotein receptor, but an alanine scan across tyrosine residues in these motifs did not affect the fidelity of newly synthesized E-cadherin delivery to the basal-lateral membrane of MDCK cells. Nevertheless, sorting signals are located in the cytoplasmic domain since a chimeric protein (GP2CAD1), comprising the extracellular domain of GP2 (an apical membrane protein) and the transmembrane and cytoplasmic domains of E-cadherin, was efficiently and specifically delivered to the basal-lateral membrane. Systematic deletion and recombination of specific regions of the cytoplasmic domain of GP2CAD1 resulted in delivery of <10% of these newly synthesized proteins to both apical and basal-lateral membrane domains. Significantly, >90% of each mutant protein was retained in the ER. None of these mutants formed a strong interaction with beta-catenin, which normally occurs shortly after E-cadherin synthesis. In addition, a simple deletion mutation of E-cadherin that lacks beta-catenin binding is also localized intracellularly. Thus, beta-catenin binding to the whole cytoplasmic domain of E-cadherin correlates with efficient and targeted delivery of E-cadherin to the lateral plasma membrane. In this capacity, we suggest that beta-catenin acts as a chauffeur, to facilitate transport of E-cadherin out of the ER and the plasma membrane.

Cadherin function in junctional complex rearrangement and posttranslational control of cadherin expression

The role of E-cadherin, a calcium-dependent adhesion protein, in organizing and maintaining epithelial junctions was examined in detail by expressing a fusion protein (GP2-Cad1) composed of the extracellular domain of a nonadherent glycoprotein (GP2) and the transmembrane and cytoplasmic domains of E-cadherin. All studies shown were also replicated using an analogous cell line that expresses a mutant cadherin construct (T151) under the control of tet repressor. Mutant cadherin was expressed at approximately 10% of the endogenous E-cadherin level and had no apparent effect on tight junction function or on distributions of adherens junction, tight junction, or desmosomal marker proteins in established Madin-Darby canine kidney cell monolayers. However, GP2-Cad1 accelerated the disassembly of epithelial junctional complexes and delayed their reassembly in calcium switch experiments. Inducing expression of GP2-Cad1 to levels approximately threefold greater than endogenous E-cadherin expression levels in control cells resulted in a decrease in endogenous E-cadherin levels. This was due in part to increased protein turnover, indicating a cellular mechanism for sensing and controlling E-cadherin levels. Cadherin association with catenins is necessary for strong cadherin-mediated cell-cell adhesion. In cells expressing low levels of GP2-Cad1, protein levels and stoichiometry of the endogenous cadherin-catenin complex were unaffected. Thus effects of GP2-Cad1 on epithelial junctional complex assembly and stability were not due to competition with endogenous E-cadherin for catenin binding. Rather, we suggest that GP2-Cad1 interferes with the packing of endogenous cadherin-catenin complexes into higher-order structures in junctional complexes that results in junction destabilization.

Productivity and some properties of immunoglobulin specific against Streptococcus mutans serotype c in chicken egg yolk (IgY)

Hens were immunized on thighs by using whole cells of Streptococcus mutans MT8148 serotype c strain as antigen through intramuscular (im) and subcutaneous (sc) routes to investigate the difference of immunization reactions and the changes in yolk antibody activities against antigen after initial immunization. Several properties of crude IgY were examined to evaluate the stability during food processing. Results showed that the specificity of IgY of im treated hens was nearly 10 times as high as those of sc treated antibody. IgY from the hens immunized with the serotype c strain showed significant cross-reactions against serotypes e and f, while minor reactions against serotypes a, b, d, and g were observed. In thermal stability tests, IgY activity in both yolk and crude IgY decreased with the increasing temperature, from 70 to 80 degrees C, but the thermal denaturation rates between those two samples were not significantly different. The addition of high levels sucrose, maltose, glycerol, or 2% glycine displayed effective protection against thermal denaturation of IgY. Lyophilized yolk-5% gum arabic powder showed better stability against proteases.

A prognostic rule for elderly patients admitted with community-acquired pneumonia

PURPOSE

We sought to identify admission characteristics predicting mortality in elderly patients hospitalized with community-acquired pneumonia and to develop a prognostic staging system and discriminant rule.

PATIENTS AND METHODS

We retrospectively analyzed data from 2,356 patients aged > or = 65 years admitted with community-acquired pneumonia. Multivariable analyses of a derivation cohort (n = 1,000) identified characteristics associated with hospital mortality. A staging system and discriminant rule based on these characteristics were tested in a validation cohort (n = 1,356). Our discriminant rule was compared with a rule formulated from a heterogeneous adult population with community-acquired pneumonia.

RESULTS

Hospital mortality rates were 9% (derivation cohort) and 12% (validation cohort). We identified five independent predictors of mortality: age > or = 85 years [odds ratio 1.8 (95% confidence interval 1.1-3.1)], comorbid disease [odds ratio 4.1 (2.1-8.1)], impaired motor response [odds ratio 2.3 (1.4-3.7)], vital sign abnormality [odds ratio 3.4 (2.1-5.4)], and creatinine level > or = 1.5 mg/dL [odds ratio 2.5 (1.5-4.2)]. These variables stratified patients into four distinct stages with increasing mortality in the derivation cohort (Stage 1, 2%; Stage 2, 7%; Stage 3, 22%; Stage 4, 45%; P = 0.001) as well as in the validation cohort (Stage 1, 4%; Stage 2, 11%; Stage 3, 23%; Stage 4, 41%; P = 0.001). The discriminant rule developed from the derivation cohort had greater overall accuracy (77.1%) in the validation cohort than a rule formulated from a heterogeneous adult population (68.0%, P = 0.001).

CONCLUSION

Elderly patients with community-acquired pneumonia have characteristics at admission that can predict mortality. Our staging system and discriminant rule improve prognostic stratification of these patients.

Improving cephalogram analysis through feature subimage extraction

An MLP with a GA was proposed to extract feature subimages containing orthodontic landmarks. Simulated images and cephalograms were used to investigate its performance in comparison with the cross-correlation method. From the results of simulated image containing shapes with different geometrical conditions, it was shown that the fault tolerance of the MLP for rotation, scaling, brightness variety, and other anomalous deformations is good enough to overcome the clinical application problems. It was also shown that the stability, accuracy, and speed of this proposed algorithm are very promising. Moreover, the performance of the MLP can be significantly improved by collecting, more "representative" false patterns. The GA is a good approach to speed up the process of feature subimage extraction based on the fitness evaluated using the MLP.

Trends in costs of percutaneous transluminal coronary angioplasty

OBJECTIVE

To evaluate recent trends in the cost of percutaneous transluminal coronary angioplasty (PTCA), particularly the impact of newer technology and changing patient profile.

STUDY DESIGN

Retrospective study with a 6-month follow up.

PATIENTS AND METHODS

We compared the data on two groups of 100 consecutive patients admitted for elective PTCA at Yale-New Haven Hospital in 1995 and 1996. Hospital records, cineangiograms, and hospital cost accounting system were reviewed, and 6-month clinical outcomes were obtained from telephone interviews and medical chart review.

RESULTS

Demographic and clinical characteristics did not differ between the 1995 and 1996 groups of patients, nor was a difference detected in in-hospital and 6-month clinical outcomes between 1995 and 1996. Angiographic features of treated lesions were different between the two groups, with a significantly higher frequency of type C and totally occluded lesions in 1996 (p = 0.002 and p = 0.04, respectively). The total hospital costs were higher in 1996 compared with 1995 ($11,799 +/- $6189 vs $10,087 +/- $5608; p = 0.04). This difference persisted after adjustment for changes in patient population. The major factor responsible for escalating costs was a 45% increase in catheterization laboratory costs ($8575 +/- $4524 in 1996 vs $5916 +/- $3030 in 1995; P < 0.0001). In contrast, the noncatheterization costs decreased substantially during this period, largely as a result of an approximately 33% decrease in length of stay (3.75 +/- 2.66 days in 1995 vs 2.57 +/- 1.99 days in 1996; P = 0.0005). In a multiple linear regression model, the most important determinants of cost were lesion characteristics, stent use, and radiographic contrast volume.

CONCLUSIONS

Despite cost reduction efforts, the costs of PTCA are rising because of increased consumption of resources in the catheterization laboratory.

Factors related to delayed treatment and posttreatment symptom severity in Taiwanese patients with benign prostatic hyperplasia

We evaluated the sociodemographic and clinical factors of delayed treatment and posttreatment symptom severity in outpatients with benign prostatic hyperplasia (BPH). The study included 146 BPH patients treated at the National Taiwan University Hospital in early 1997. All patients were treated with alpha-adrenergic antagonists or finasteride for at least 2 weeks. A questionnaire based on Andersen's Health Behavior Model was used to assess various sociodemographic features, while the pre- and posttreatment symptoms severity was rated according to the International Prostate Symptom Score (IPSS). Multiple logistic regression was used to assess the associations of these factors with delayed treatment and posttreatment symptom severity. Subjects who had recently quit smoking or were blue-collar workers tended to delay treatment, while those who chose a medical center as the care provider for chronic diseases tended to be less likely to delay treatment. However, none of these associations were statistically significant. No enabling factors (income, insurance) or need factors (symptom scores) evaluated were associated with delayed treatment. Predisposing factors associated with higher posttreatment symptom severity were delayed treatment (over 12 months) (adjusted odds ratio [OR]: 2.67, 95% confidence interval [CI]: 1.16-6.16), quitting smoking (adjusted OR: 4.47, 95% CI: 1.34-14.94), and having never smoked (adjusted OR: 3.73, 95% CI: 1.15-12.11). Subjects with severe pretreatment symptoms were far more likely than subjects with mild pretreatment symptoms to have severe symptoms after treatment (adjusted OR: 52.69, 95% CI: 54.46-621.90). Our findings, though based on a limited number of subjects, suggest sociodemographic factors rather than objective clinical attributes (prostate specific antigen level, prostate volume, and urodynamic results) are associated with delayed treatment in Taiwanese men with BPH. Both pretreatment symptom severity and sociodemographic factors are related to posttreatment symptom severity.

Mutational analysis of the conserved cationic residues of Bacillus stearothermophilus 6-phosphoglucose isomerase

The importance in catalysis of the conserved arginine (R207) and lysine residues (K144, K294, K356, and K425) of 6-phosphoglucose isomerase from Bacillus stearothermophilus was assessed by site-directed mutagenesis and kinetic analysis. In general mutations had minor effects on the Km for fructose 6-phosphate. More dramatic effects were seen on kcat. The R207A mutant had a five orders of magnitude decrease in kcat relative to the wild-type enzyme. There was a significant recovery, by three orders of magnitude, in the kcat for the R207K mutant. The results suggest that the positive charge provided by R207 plays a critical role in the isomerization reaction. K425 was substituted with alanine, valine, phenylalanine, tryptophan and aspartate. All mutant enzymes at position 425 had kcat decreased in the range of several-hundred-fold. For the other mutants, K294A and K144A, the kcat values were 3.5% and 27% of the wild-type enzyme, respectively. No effects on catalysis were observed for the K356A mutant. The results suggest that R207, K144, K294, and K425 are located in the active site of the enzyme. The active-site location and the catalytic roles of K425 and K294 are supported further by the inhibitory effects of pyridoxal 5'-phosphate on enzymatic activities. The data also confirm the importance of K425 and K144 anticipated by the affinity labeling studies of the corresponding residues by pyridoxal 5'-phosphate in pig muscle phosphoglucose isomerase.

Diagnostic red herring in an infant with stridor

Foreign body aspiration in children may present with a variety of symptoms. We report here an unusual case of laryngeal foreign body in an infant masquerading as laryngeal web in its clinical presentation as well as radiological findings. The diagnosis was only made at endoscopy, thus emphasising the limited sensitivity of radiographic studies in identifying this condition.

Sunlamp use and the risk of cutaneous malignant melanoma: a population-based case-control study in Connecticut, USA

BACKGROUND

The relationship between cutaneous malignant melanoma and sunlamp use is examined in a Caucasian population in Connecticut, United States.

METHODS

Cases were diagnosed between 15 January 1987 and 15 May 1987 with a first primary cutaneous melanoma. Controls were obtained from the general population, frequency matched to cases by sex and age, through random digit dialling of Connecticut telephone numbers.

RESULTS

Of all study subjects, 141 (23%) cases and 95 (19%) controls reported ever having used sunlamps. The crude odds ratio (OR) for developing malignant melanoma after ever having used sunlamps was 1.30 (95% confidence interval [CI]: 0.97-1.74). This was reduced to 1.13 (95% CI: 0.82-1.54) after further adjusting for cutaneous phenotype and recreational sun exposure. Those who used more than one type of sunlamp had a threefold higher risk for melanoma compared to never users. Subgroup analyses showed that sunlamp use was associated with a greater increase in risk for melanoma among those who used sunlamps at home and those who were first exposed to sunlamps prior to 1971. The first use of sunlamps before the age of 25 showed somewhat higher risk for melanoma compared to first use later in life.

CONCLUSION

The current study provides limited evidence that use of sunlamps increases the risk of melanoma. For future studies, it is crucial that type of sunlamp, year of first use and amount of exposure are all taken into account. The association between melanoma and tanning with both UV-A and UV-B lamps and tanning under sunlamps early in life merits further investigation.

A gene on chromosome 11q23 coding for a putative glucose- 6-phosphate translocase is mutated in glycogen-storage disease types Ib and Ic

Glycogen-storage diseases type I (GSD type I) are due to a deficiency in glucose-6-phosphatase, an enzymatic system present in the endoplasmic reticulum that plays a crucial role in blood glucose homeostasis. Unlike GSD type Ia, types Ib and Ic are not due to mutations in the phosphohydrolase gene and are clinically characterized by the presence of associated neutropenia and neutrophil dysfunction. Biochemical evidence indicates the presence of a defect in glucose-6-phosphate (GSD type Ib) or inorganic phosphate (Pi) (GSD type Ic) transport in the microsomes. We have recently cloned a cDNA encoding a putative glucose-6-phosphate translocase. We have now localized the corresponding gene on chromosome 11q23, the region where GSD types Ib and Ic have been mapped. Using SSCP analysis and sequencing, we have screened this gene, for mutations in genomic DNA, from patients from 22 different families who have GSD types Ib and Ic. Of 20 mutations found, 11 result in truncated proteins that are probably nonfunctional. Most other mutations result in substitutions of conserved or semiconserved residues. The two most common mutations (Gly339Cys and 1211-1212 delCT) together constitute approximately 40% of the disease alleles. The fact that the same mutations are found in GSD types Ib and Ic could indicate either that Pi and glucose-6-phosphate are transported in microsomes by the same transporter or that the biochemical assays used to differentiate Pi and glucose-6-phosphate transport defects are not reliable.

Mechanisms of epithelial cell-cell adhesion and cell compaction revealed by high-resolution tracking of E-cadherin-green fluorescent protein

Cadherin-mediated adhesion initiates cell reorganization into tissues, but the mechanisms and dynamics of such adhesion are poorly understood. Using time-lapse imaging and photobleach recovery analyses of a fully functional E-cadherin/GFP fusion protein, we define three sequential stages in cell-cell adhesion and provide evidence for mechanisms involving E-cadherin and the actin cytoskeleton in transitions between these stages. In the first stage, membrane contacts between two cells initiate coalescence of a highly mobile, diffuse pool of cell surface E-cadherin into immobile punctate aggregates along contacting membranes. These E-cadherin aggregates are spatially coincident with membrane attachment sites for actin filaments branching off from circumferential actin cables that circumscribe each cell. In the second stage, circumferential actin cables near cell-cell contact sites separate, and the resulting two ends of the cable swing outwards to the perimeter of the contact. Concomitantly, subsets of E-cadherin puncta are also swept to the margins of the contact where they coalesce into large E-cadherin plaques. This reorganization results in the formation of a circumferential actin cable that circumscribes both cells, and is embedded into each E-cadherin plaque at the contact margin. At this stage, the two cells achieve maximum contact, a process referred to as compaction. These changes in E-cadherin and actin distributions are repeated when additional single cells adhere to large groups of cells. The third stage of adhesion occurs as additional cells are added to groups of >3 cells; circumferential actin cables linked to E-cadherin plaques on adjacent cells appear to constrict in a purse-string action, resulting in the further coalescence of individual plaques into the vertices of multicell contacts. The reorganization of E-cadherin and actin results in the condensation of cells into colonies. We propose a model to explain how, through strengthening and compaction, E-cadherin and actin cables coordinate to remodel initial cell-cell contacts to the final condensation of cells into colonies.

Expression of melan-A (MART1) in benign melanocytic nevi and primary cutaneous malignant melanoma

The Melan-A (MART1) gene encodes an antigen recognized by cytotoxic T cells. Although its expression in metastatic melanoma has been documented in the literature by several investigators, little is known about its distribution in primary melanomas and benign melanocytic nevi. In this study, we evaluated Melan-A expression immunohistochemically on sections from paraffin-embedded material of 50 benign nevi and 40 primary cutaneous melanomas using the monoclonal antibody A103. To evaluate a potential role of A103 in the differential diagnosis of melanocytic from nonmelanocytic tumors, we also analyzed a number of benign and malignant peripheral nerve sheath tumors, fibrohistiocytic tumors, and leiomyosarcomas. Immunoreactivity with A103 was present in all "nonneurotized" nevi and in all nondesmoplastic primary melanomas, both in the intraepidermal and the dermal component. Only two nevi that underwent prominent neurotization showed no staining with A103. Although all melanomas with epithelioid cells tended to be strongly positive with A103, only 4 of 13 spindle cell and desmoplastic melanomas (all positive with anti-S-100 and negative with HMB-45) were immunoreactive with A103 (two focally, two diffusely). None of the nonmelanocytic lesions expressed Melan-A. Our results confirm that Melan-A protein is broadly expressed in the majority of benign and malignant melanocytic lesions and suggest that A103 can be helpful diagnostically, not only for metastatic tumors, but also for primary skin lesions. Its use in distinguishing between melanocytic and peripheral nerve sheath tumors, however, is limited because of the low or absent expression of Melan-A in nevi that underwent neurotization and spindle cell and desmoplastic melanomas.

Expression of SSX genes in human tumors

The HOM-MEL-40 antigen which is encoded by the SSX-2 gene was originally detected as a tumor antigen recognized by autologous IgG antibodies in a melanoma patient. Expression analysis demonstrated that SSX-2 is a member of the recently described cancer/testis antigen (CTA) class as it is expressed in a variety of different human neoplasms, but not in normal tissues with the exception of testis and a weak expression in the thyroid. Further studies demonstrated that SSX-2 belongs to a gene family consisting of at least 5 homologous genes. We now report the analysis of the expression of all 5 SSX genes in 325 specimens of human neoplasms from various histological origins, using reverse transcription polymerase chain reaction (RT-PCR). SSX-1, -2, and -4 were found to be expressed in 8%, 15% and 15%, of the tumors, respectively, while the expression of the SSX-5 gene was rare (7/325), and SSX-3 expression was not detected. For defined tumor types, expression of at least one of the SSX family members was most frequently observed in head and neck cancer (75%), followed by ovarian cancer (50%), malignant melanoma (43%), lymphoma (36%), colorectal cancer (27%) and breast cancer (23%), while leukemias and the few cases of leiomyosarcomas, seminomas and thyroid cancers were found not to express any SSX gene.

Expression of SSX genes in human tumors

The HOM-MEL-40 antigen which is encoded by the SSX-2 gene was originally detected as a tumor antigen recognized by autologous IgG antibodies in a melanoma patient. Expression analysis demonstrated that SSX-2 is a member of the recently described cancer/testis antigen (CTA) class as it is expressed in a variety of different human neoplasms, but not in normal tissues with the exception of testis and a weak expression in the thyroid. Further studies demonstrated that SSX-2 belongs to a gene family consisting of at least 5 homologous genes. We now report the analysis of the expression of all 5 SSX genes in 325 specimens of human neoplasms from various histological origins, using reverse transcription polymerase chain reaction (RT-PCR). SSX-1, -2, and -4 were found to be expressed in 8%, 15% and 15%, of the tumors, respectively, while the expression of the SSX-5 gene was rare (7/325), and SSX-3 expression was not detected. For defined tumor types, expression of at least one of the SSX family members was most frequently observed in head and neck cancer (75%), followed by ovarian cancer (50%), malignant melanoma (43%), lymphoma (36%), colorectal cancer (27%) and breast cancer (23%), while leukemias and the few cases of leiomyosarcomas, seminomas and thyroid cancers were found not to express any SSX gene.

Expression of SSX genes in human tumors

The HOM-MEL-40 antigen which is encoded by the SSX-2 gene was originally detected as a tumor antigen recognized by autologous IgG antibodies in a melanoma patient. Expression analysis demonstrated that SSX-2 is a member of the recently described cancer/testis antigen (CTA) class as it is expressed in a variety of different human neoplasms, but not in normal tissues with the exception of testis and a weak expression in the thyroid. Further studies demonstrated that SSX-2 belongs to a gene family consisting of at least 5 homologous genes. We now report the analysis of the expression of all 5 SSX genes in 325 specimens of human neoplasms from various histological origins, using reverse transcription polymerase chain reaction (RT-PCR). SSX-1, -2, and -4 were found to be expressed in 8%, 15% and 15%, of the tumors, respectively, while the expression of the SSX-5 gene was rare (7/325), and SSX-3 expression was not detected. For defined tumor types, expression of at least one of the SSX family members was most frequently observed in head and neck cancer (75%), followed by ovarian cancer (50%), malignant melanoma (43%), lymphoma (36%), colorectal cancer (27%) and breast cancer (23%), while leukemias and the few cases of leiomyosarcomas, seminomas and thyroid cancers were found not to express any SSX gene.

Expression of SSX genes in human tumors

The HOM-MEL-40 antigen which is encoded by the SSX-2 gene was originally detected as a tumor antigen recognized by autologous IgG antibodies in a melanoma patient. Expression analysis demonstrated that SSX-2 is a member of the recently described cancer/testis antigen (CTA) class as it is expressed in a variety of different human neoplasms, but not in normal tissues with the exception of testis and a weak expression in the thyroid. Further studies demonstrated that SSX-2 belongs to a gene family consisting of at least 5 homologous genes. We now report the analysis of the expression of all 5 SSX genes in 325 specimens of human neoplasms from various histological origins, using reverse transcription polymerase chain reaction (RT-PCR). SSX-1, -2, and -4 were found to be expressed in 8%, 15% and 15%, of the tumors, respectively, while the expression of the SSX-5 gene was rare (7/325), and SSX-3 expression was not detected. For defined tumor types, expression of at least one of the SSX family members was most frequently observed in head and neck cancer (75%), followed by ovarian cancer (50%), malignant melanoma (43%), lymphoma (36%), colorectal cancer (27%) and breast cancer (23%), while leukemias and the few cases of leiomyosarcomas, seminomas and thyroid cancers were found not to express any SSX gene.

Angiotensinogen gene polymorphism is associated with insulin resistance in nondiabetic men with or without coronary heart disease

BACKGROUND

Variants of the angiotensinogen gene may increase the risk of having arterial hypertension and coronary heart disease (CHD), but their effect on insulin resistance remains unknown.

METHODS

We determined M235 and T174 allele status and fasting plasma glucose, insulin, and lipids values in nondiabetic men with CHD documented on angiography (n = 102) and in a control group (n = 145). Plasma glucose and insulin responses to 75 gm oral glucose tolerant test and insulin resistance as measured by an insulin suppression test were also carried out in 46 (45%) patients with CHD and in 73 (50%) members of a control group.

RESULTS

We found no association between M235T status and blood pressure, fasting plasma glucose, insulin, most of the lipids values, and insulin resistance in patients with CHD and normal subjects. Nevertheless, compared with individuals with homozygotes T174, subjects with heterozygotes T174M were associated with greater glucose and insulin response to the oral glucose tolerance test and insulin resistance indicated by higher steady state plasma glucose concentrations in patients with CHD (14.7+/-0.9 vs 11.3+/-0.7 mmol/L, p < 0.04). Similar findings were found in the control group, with higher steady-state plasma glucose values in individuals with heterozygotes T174M than in those with homozygotes T174 (10.1+/-1.4 vs 7.7+/-0.4 mmol/L, p < 0.05).

CONCLUSION

We suggest that the angiotensinogen T174M allele might be associated with insulin resistance in nondiabetic men with and without CHD.

Characterization of human colon cancer antigens recognized by autologous antibodies

The screening of cDNA expression libraries derived from human tumors with autologous antibody (SEREX) has proven to be a powerful method for defining the structure of tumor antigens recognized by the humoral immune system. In the present study, 48 distinct antigens (NY-CO-1-NY-CO-48) reactive with autologous IgG were identified by SEREX analysis in 4 patients with colon cancer. Sequencing analysis showed that 17 of the cDNA clones were previously uncharacterized molecules and 31 represented known gene products. The individual cDNA clones were analyzed in the following manner: a search for mutations or other structural changes; an analysis of mRNA expression in a panel of normal tissues; and a frequency analysis of the antibody response to the expressed product in the sera of colon cancer patients and normal individuals. The initial analysis showed NY-CO-13 to be a mutated version of the p53 tumor suppressor gene. Three of the 48 antigens showed a differential pattern of mRNA expression, with NY-CO-27 (galectin-4) expressed primarily in gastrointestinal tract, and NY-CO-37 and -38 showing a pattern of tissue-specific isoforms. With regard to immunogenicity, 20 of the 48 antigens were detected by allogeneic sera; 14 of these were reactive with sera from both normal donors and cancer patients, and 6 other clones (NY-CO-8, -9, -13, -16, -20 and -38) reacted exclusively with sera from colon cancer patients (ranging from 14% to 27%). Our results on colon cancer illustrate both the complexity and the potential of the SEREX approach for analysis of the humoral immune response against human cancer.