Determinants for dental visit behavior among Hong Kong Chinese in a longitudinal study

OBJECTIVES

The aim of this research was to study the major determinants for dental services utilization among middle-aged Hong Kong Chinese in a longitudinal study using an expanded Andersen and Newman model as the theoretical framework.

METHODS

A random sample of 372 middle-aged Hong Kong Chinese were interviewed and clinically examined in an oral health survey. The findings were explained to the subjects and they were advised to seek care from their own dentist as appropriate.

RESULTS

A total of 322 subjects were interviewed over the telephone after 12 months. About half had visited a dentist within the study period. Results of the bivariate analysis showed that proportionally more subjects who had dental benefit coverage, had prevention-oriented attitudes, were regular users of dental services, had received counseling from a dentist, or had more filled teeth at the baseline examination had visited a dentist within the study period. Logistic regression analysis produced a final model consisting of seven factors and three interaction terms that was able to classify 68 percent of the subjects into the correct user category.

CONCLUSION

The expanded Andersen and Newman model was useful as a theoretical framework in studying the dental services utilization behaviors of the Hong Kong adults.

DNA plasmid that codes for human Bcl-2 gene preserves axotomized Clarke's nucleus neurons and reduces atrophy after spinal cord hemisection in adult rats

Spinal cord injury in adult mammals causes atrophy or death of some axotomized neurons. The product of the antiapoptotic gene Bcl-2 prevents neuron death in vivo. We delivered Bcl-2 by intraspinal injection of a DNA plasmid encoding this gene to determine if axotomized neurons destined to undergo retrograde death could be rescued. Axons of the right side Clarke's Nucleus (CN) were cut unilaterally in adult Sprague-Dawley rats by T8 hemisection, leaving the contralateral (left) CN as an intact control. Two months postoperatively, there was approximately 35% loss of total CN neurons in the right L1 segment. Only 15% of large CN neurons (>400 microm2), whose axons project to the cerebellum, survived--indicating atrophy and/or death of 85% of these cells. We injected a DNA plasmid encoding the human Bcl-2 gene and the bacterial reporter gene LacZ, which was complexed with cationic lipids, into the right side of segment T8 of the normal spinal cord, or just caudal to the hemisection site. The reporter gene was expressed in the perikarya of right CN neurons at L1 for up to 7 days, but not 14 days. Two months following T8 hemisection and Bcl-2/LacZ DNA injection, there was no significant loss of CN neurons ipsilateral to the lesion. Surprisingly, 61% of large neurons survived, indicating partial protection from atrophy. In contrast, a DNA plasmid that codes for the LacZ reporter gene, but not Bcl-2, did not prevent CN neuron death or atrophy. Administration of the Bcl-2 gene in adult rats and its expression in these CNS neurons prevents retrograde cell death, and also minimizes atrophy. These results may serve as the basis for developing novel gene therapy strategies for patients with spinal cord injury.

Oral health status of southern Chinese following head and neck irradiation therapy for nasopharyngeal carcinoma

OBJECTIVE

To investigate the oral health status of patients with nasopharyngeal carcinoma (NPC) after completion of radiotherapy.

METHODS

Thirty-three NPC patients (mean age 53 +/- 10 years) who had completed head and neck radiotherapy (3.6 +/- 3.1 years post-operation) were examined. Dental caries, periodontal status and oral mucosal lesions were recorded. Stimulated whole saliva (SWS) flow rate, pH, buffer capacity and carriage rate of carcinogenic micro-organisms were assessed. Jaw opening was measured.

RESULTS

Xerostomia was present in all patients, while 42% had candidiasis and 21% had limited jaw opening. The mean number of teeth present was 22, mean DMFT was 8.0, mean number of untreated root caries lesions was 1.4. Both saliva pH and buffering capacity were low while Streptococcus mutans and Lactobacillus spp. carriage were high. 52% of the patients had no dental care following radiotherapy. Although few patients expressed direct dissatisfaction, perceived level of information and of post-operative dental care was insufficient.

CONCLUSIONS

Post-irradiated NPC patients constitute a high-risk group for dental root caries and oral candidiasis. The carriage rate of Streptococcus mutans and Lactobacillus spp. in this NPC patient group was the highest among findings of other similar studies. This may be related to the inadequacy of dental care after radiotherapy. Head and neck radiotherapy was not associated with periodontal disease.

Arresting dentine caries in Chinese preschool children

OBJECTIVES

To investigate the incidence of rehardening of caries lesions in children in Southern China taking part in a preventive programme.

DESIGN

Longitudinal study.

SAMPLE AND METHODS

A prevention programme was established for 168 3-6-year-old children in a kindergarten (KG1), which included regular oral health education sessions and a daily toothbrushing exercise using fluoridated toothpaste (1000 ppm F). A group of 121 children studying in two other kindergartens without a preventive programme formed the controls. Due to lack of resources and dental personnel, restorative and other curative treatments were not provided.

RESULTS

Rehardening of dentine caries (arrested caries) was found in children in both test and control groups. At the third annual examination, 45% of the caries lesions on the proximal surfaces of primary anterior teeth in KG1 children found at the baseline and previous annual examinations had become arrested. A multiple linear regression analysis indicated that baseline ds score and its interactions with the prevention programme, gender and the child's oral hygiene all had significant effect on the number of tooth surfaces with arrested caries at the third annual examination.

CONCLUSION

Results from this study support the use of simple prevention programmes to stabilize the caries situation in communities where intensive use of trained dental personnel is not feasible.

Advances in refolding of proteins produced in E. coli

Inclusion body production is a common theme in recombinant protein technology. Hence, renaturation of these inclusion body proteins is a field of increasing interest for gaining large amounts of proteins. Recent developments of renaturation procedures include the inhibition of aggregation during refolding by the application of low molecular weight additives and matrix-bound renaturation techniques.

Prevention of early childhood caries--results of a fluoride toothpaste demonstration trial on Chinese preschool children after three years

OBJECTIVES

This field demonstration trial evaluates the long-term effects of introducing daily toothbrushing with fluoride toothpaste in a Chinese kindergarten (test group) compared to caries development in children who had no organized preventive program (control group).

METHODS

In the test group teacher-supervised toothbrushing was initiated with 1,000 ppm MFP toothpaste in addition to oral health education activities. Test and control children were examined at baseline (n = 289, aged 3 years) and annually thereafter.

RESULTS

After three years, 251 children (87%) were still in the trial. Caries development (dmfs) calculation included only those children who were present at both baseline and subsequent annual examinations. At baseline the mean dmfs was 4.8 in the test group and 6.5 in the control group (NS). After three years the caries increment was 6.2 and 8.4 in the test group and the control group, respectively (P < .05). Adjusting for reversals, the net caries increment was 3.6 and 6.3, respectively (P < .01). Additionally, multiple linear regression analysis indicated that both baseline dmfs, the program and plaque level had a significant effect on the net caries increment. The use of hierarchical caries severity zones was useful for the identification of those children most at risk for further caries development.

CONCLUSIONS

We conclude that a daily toothbrushing with limited involvement of professional staff was feasible in a Chinese kindergarten and that caries development was significantly slowed in the test children. Caries severity zones may possibly assist in determining levels of intervention.

Is caries prevention cost-effective? Does anybody care?

The aim of this article is to review current issues concerning the cost-effectiveness of caries prevention. Several decades after considerable improvements in the oral disease situation were documented in Scandinavia, doubts are still expressed about whether preventive measures are cost-effective. An analytic model is suggested to explore the relationships between the dental profession, which provides the prevention, the research and development activities, which provide the material and data basis for prevention, and political/societal responses to the professional input. The four elements considered were the definition of prevention, the practical perception of effective prevention, the appropriateness of traditional cost-effectiveness analysis, and the time factor with regard to when a preventive effect should be evaluated. The main arguments of the discussion are that caries prevention is not uniformly defined by the profession, that dental research is casting doubt on the effectiveness of traditionally accepted preventive measures, that political pressures on health care are motivated by economic pressures, but that traditional cost benefit/effectiveness analyses have not been able to help the decision-makers choose wisely. Often the time perspective for the real effects of prevention lies beyond the interests of decision-makers. Although caries prevention may be viewed as an investment in health by the profession, this contention may not be acceptable to a society with very short-term perspectives.

Nuclear matrix attachment regions of human papillomavirus type 16 point toward conservation of these genomic elements in all genital papillomaviruses

The gene functions, transcriptional regulation, and genome replication of human papillomaviruses (HPVs) have been extensively studied. Thus far, however, there has been little research on the organization of HPV genomes in the nuclei of infected cells. As a first step to understand how chromatin and suprachromatin structures may modulate the life cycles of these viruses, we have identified and mapped interactions of HPV DNAs with the nuclear matrix. The endogenous genomes of HPV type 16 (HPV-16) which are present in SiHa, HPKI, and HPKII cells, adhere in vivo to the nuclear matrixes of these cell lines. A tight association with the nuclear matrix in vivo may be common to all genital HPV types, as the genomes of HPV-11, HPV-16, HPV-18, and HPV-33 showed high affinity in vitro to preparations of the nuclear matrix of C33A cells, as did the well-known nuclear matrix attachment region (MAR) of the cellular beta interferon gene. Affinity to the nuclear matrix is not evenly spread over the HPV-16 genome. Five genomic segments have strong MAR properties, while the other parts of the genome have low or no affinity. Some of the five MARs correlate with known cis-responsive elements: a strong MAR lies in the 5' segment of the long control region (LCR), and another one lies in the E6 gene, flanking the HPV enhancer, the replication origin, and the E6 promoter. The strongest MAR coincides with the E5 gene and the early-late intergenic region. Weak MAR activity is present in the E1 and E2 genes and in the 3' part of L2. The in vitro map of MAR activity appears to reflect MAR properties in vivo, as we found for two selected fragments with and without MAR activity. As is typical for many MARs, the two segments with highest affinity, namely, the 5' LCR and the early-late intergenic region, have an extraordinarily high A-T content (up to 85%). It is likely that these MARs have specific functions in the viral life cycle, as MARs predicted by nucleotide sequence analysis, patterns of A-T content, transcription factor YY1 binding sites, and likely topoisomerase II cleavage sites are conserved in similar positions throughout all genital HPVs.

Mam33p, an oligomeric, acidic protein in the mitochondrial matrix of Saccharomyces cerevisiae is related to the human complement receptor gC1q-R

Mam33p (mitochondrial acidic matrix protein) is a soluble protein, located in mitochondria of Saccharomyces cerevisiae. It is synthesized as a precursor with an N-terminal mitochondrial targeting sequence that is processed on import. Mam33p assembles to a homo-oligomeric complex in the mitochondrial matrix. It can bind to the sorting signal of cytochrome b2 that directs this protein into the intermembrane space. Mam33p is encoded by an 801 bp open reading frame. Gene disruption did not result in a significant growth defect. Mam33p exhibits sequence similarity to gC1q-R, a human protein that has been implicated in the binding of complement factor C1q and kininogen.

APM-1, a novel human gene, identified by aberrant co-transcription with papillomavirus oncogenes in a cervical carcinoma cell line, encodes a BTB/POZ-zinc finger protein with growth inhibitory activity

Integration of human papillomavirus (HPV) DNA into the host cell genome is an important step in cervical carcinogenesis. In tumour cells with integrated HPV DNA, transcription of viral oncogenes E6 and E7 continues into the flanking cellular sequences thereby producing viral-cellular fusion transcripts. Analysis of cellular sequences flanking the integrated HPV68 DNA in the cervical carcinoma cell line ME180 revealed homozygosity of the mutant allele in ME180 cells. We speculated that this could indicate the existence of a cellular tumour suppressor gene in the integration region. We report here the identification of a novel human gene, named APM-1, which is co-transcribed with the HPV68 E6 and E7 genes and is present in the 3'-cellular part of the ME180 viral-cellular fusion transcripts. The APM-1 gene encodes a protein with a BTB/POZ domain and four zinc fingers, and is located at chromosome 18q21. APM-1 transcripts are detected in normal cervical keratinocytes, but not in the majority of cervical carcinoma cell lines analysed. The APM-1 gene caused a reduction of clonal cell growth in vitro of HeLa and CaSki tumour cells. These characteristics make APM-1, the first novel human gene identified in a HPV integration region, a likely candidate for the postulated tumour suppressor gene.

Reduced gene expression of E-cadherin and associated catenins in human cervical carcinoma cell lines

Cell-cell adhesion mediated by E-cadherin is often lost or disturbed in human carcinomas. For regular adhesive function, E-cadherin has to form complexes with peripheral cytoplasmic catenins which are multifunctional proteins that are also involved in signal transduction and growth regulation. We have analyzed the expression levels of the genes encoding alpha-catenin, beta-catenin and plakoglobin in correlation to the E-cadherin expression levels in cell lines derived from human cervical carcinomas. Reduced mRNA and protein levels were detected for plakoglobin, whereas alpha- and beta-catenin showed only reduced protein (but not mRNA) levels. The alterations in catenin gene expression were often associated with absent or reduced E-cadherin. The findings indicate that a reduction of catenin gene expression may contribute to the development of cervical carcinomas.

Major histocompatibility complex (MHC) class III genetics in two Amerindian tribes from southern Brazil: the Kaingang and the Guarani

Population genetic studies of the major histocompatibility complex (MHC) class III region, comprising C2, BF and C4 phenotypes, and molecular genetic data are rarely available for populations other than Caucasoids. We have investigated three Amerindian populations from Southern Brazil: 131 Kaingang from Ivaí (KIV), 111 Kaingang (KRC) and 100 Guarani (GRC) from Rio das Cobras. Extended MHC haplotypes were derived after standard C2, BF, C4 phenotyping and restriction fragment length polymorphism (RFLP) analysis with TaqI, together with HLA data published previously by segregation analysis. C2 and BF frequencies corresponded to other Amerindian populations. C4B*Q0 frequency was high in the GRC (0.429) but low in the Kaingang. Unusual C4 alleles were found, viz. C4A*58, A*55 and C4B*22 (presumably non-Amerindian) and aberrant C4A*3 of Amerindian origin occurring with a frequency of 0.223 in the GRC. C4A*3 bands of homo- and heterozygous individuals carrying this variant were Rodgers 1 positive and Chido 1,3 positive, showed a C4A specific lysis type and a C4A like alpha-chain. Polymerase chain reaction studies and sequencing showed that this is based on a C4A*3 duplication with a regular C4A*3 and a partially converted C4A*0304 carrying the C4B specific epitopes Ch 6 and Ch 1,3. Associations of class III haplotypes with particular RFLP patterns were similar to those reported for Caucasoids. The previously described association between combined C4A and CYP21P deletions and the 6.4 kb TaqI fragment was not seen in these Amerindians. This fragment occurred within a regular two locus gene structure in the Kaingang, representing a "short" gene at C4 locus I. C4 and CYP21 duplications were frequently observed. The distribution of extended MHC haplotypes provides evidence for a close relationship between the KIV and KRC and a larger genetic distance between the two Kaingang groups and the GRC.

Patterns of dental caries severity in Chinese kindergarten children

The dental caries status of a population group is traditionally described by mean values of decayed, missing and filled teeth or surfaces (DMFT or S). Because of the limitations of the DMF values alone, additional measures of dental caries become important. A system of describing the pattern of dental caries attack hierarchically according to severity of caries was suggested by Poulsen & Horowitz (Community Dent Oral Epidemiol 1974;2:7-11). The purpose of the present study was to analyze caries data from a group of 3-6-year-old Chinese kindergarten children according to this hierarchical system, assess the hierarchical assumptions of the system with deciduous teeth and evaluate its usefulness as an additional caries description for a kindergarten population. As part of a longitudinal field trial, baseline caries data were collected from 452 children. Caries was registered by tooth surface without the use of radiographs. Each child was assigned to one of six mutually exclusive zones of increasing caries severity, from zone 0=caries free through zone 5, the most severe, assuming that once a child was classified into a given zone it automatically belonged to all zones of lesser severity (except zone 0). On the basis of the original six zones, 61% of the children were classified correctly according to the hierarchical concept, but different alternative models which merged one or more zones together demonstrated varying percentages of correct classification, the cariologically most acceptable one placing 83% correctly. For each age group there was a close correlation between mean dmfs and increasing severity. The hierarchical model provides a valuable additional description of the caries status in deciduous teeth and is consistent with professional and epidemiological knowledge of caries attack patterns.

N-terminal hydrophobic sorting signals of preproteins confer mitochondrial hsp70 independence for import into mitochondria

The requirement of mitochondrial hsp70 (mt-hsp70) for the import of a series of preproteins containing hydrophobic sorting signals into isolated yeast mitochondria was investigated. Here we demonstrate that the presence of such a sorting signal in proximity to the N-terminal matrix-targeting sequence of a preprotein can secure a translocating polypeptide chain in the import channel in a manner that does not require mt-hsp70 activity. Trapping the translocating chain in this fashion leads to efficient processing by the mitochondrial processing peptidase and to complete translocation across the outer mitochondrial membrane into the intermembrane space. These mt-hsp70-independent effects appear to be exerted at the level of the inner membrane through an interaction of the hydrophobic core of the sorting signal with component(s) of the translocase of the inner membrane. Hydrophobic sorting signals of inner membrane proteins inserted into the membrane from the matrix, as well as those of intermembrane space proteins, are capable of causing this mt-hsp70-independent stabilization, demonstrating that this phenomenon is not unique to those preproteins normally sorted to the intermembrane space.

[Integration of young goats into a herd of adult goats]

The female offsprings of a goat farm were observed to establish what effects the introduction of these goats to the older animals has on behaviour, physical development, fertility and milk yield. The 32 young goats were divided into two groups. Shortly after group 1 had been mounted, they were introduced to the older goats. From group 2 those who had already given birth were introduced to the older goats the following spring. The following results could be ascertained: In group 1 there were significantly more twin births and the weight of the newborn kids was greater than that of group 2. The weight gain of the two groups differed only marginally. This was also the case for the milk yield. After having integrated them into the herd of older goats, the young goats developed a strategy for avoiding, to a large extent, being pursued by older goats and to achieve almost undisturbed fodder intake. Amongst the young goats there is a marked sense of group cohesion. When the shed is well structured, a useable area of 1.2 m2/animal for hornless goats seems to be enough to ensure species specific husbandry conditions.

High-level expression of the retinoic acid receptor beta gene in normal cells of the uterine cervix is regulated by the retinoic acid receptor alpha and is abnormally down-regulated in cervical carcinoma cells

Retinoic acid (RA) is essential for regulation of epithelial cell differentiation. The intracellular effects of RA are mediated by RA-binding nuclear receptors, including the RA receptors (RARs) alpha, beta, and gamma. The ligand-activated receptors induce the transcription of target genes by binding to RA-responsive elements in the promoter regions. One target gene is the RAR beta gene, which encodes a potential tumor suppressor. Loss of RA inducibility of RAR beta gene expression is assumed to play a role in the development of several types of human carcinomas, including carcinomas of the uterine cervix. We have analyzed RAR beta gene expression in normal cervical cells and in cervical carcinoma cell lines. The results show that the RAR beta mRNA levels are high and RA inducible in the primary keratinocytes, whereas they are low and not inducible or only slightly inducible by RA in all of the cervical carcinoma cell lines analyzed. The basal and the RA-induced RAR beta mRNA levels tend to increase with senescence of the normal cells. Fusion of primary ectocervical keratinocytes with HeLa cervical carcinoma cells revealed that the characteristics of RAR beta gene expression of the normal cells are dominant over that of the tumor cells. Using synthetic retinoids with receptor-preferential agonist activities and a RAR alpha-specific antagonist, we show that RAR alpha is the major endogenous RAR subtype for induction of RA-dependent RAR beta gene expression. Taken together, our results indicate that abnormal downregulation of RAR beta gene expression may be an important step in the multifactorial process of cervical carcinogenesis.

Molecular biology in diagnosis and epidemiology of Helicobacter pylori: PCR for the detection and AP-PCR for characterization of patient isolates

Infection with Helicobacter pylori causes chronic active gastritis and has been associated with gastric and duodenal ulcer disease. In biopsy samples of 110 patients with clinical symptoms of active gastritis, H. pylori was detected by means of the polymerase chain reaction (PCR), using species-specific primers defining a 858 bp DNA fragment of H. pylori urease beta-subunit. Sensitivity and specificity of the PCR was compared with culture, histology and Warthin-Starry stain (WSs), detection of H. pylori urease antibodies in serum and urease testing with the Campylobacter-like organism (CLO) test. PCR yielded specific amplification products in 53 cases, whereas culture of the organisms was positive in a subset of 50 cases. Only direct detection in histological sections of biopsy specimens had a higher sensitivity, with 65 positive samples. In contrast, the CLO test was negative in eleven culture-positive and PCR-positive cases. Significant urease antibody titres were found in 39 patients with histologically confirmed diagnosis. These results placed the sensitivity of PCR between tat of the Warthin-Starry stain (WSs) and that of culture. Therefore, PCR can be proposed as a useful rapid and time-saving technique for the detection of H.pylori in gastritis. For epidemiological purposes, fingerprinting with arbitrarily chosen primers by AP-PCR was evaluated. Strain-specific patterns with up to 13 fragments were achieved with 10-nucleotide or longer primers (21-nt) with a G + C content > or = 55%. Thirty-five of 40 strains investigated by this method were distinguishable with a single primer. These results suggest a high level of DNA sequence diversity within this species with the possibility of confirming the clonality in consecutive isolates from a single individual. Alternatively, an increased in-vivo mutation rate could be responsible for DNA divergence, resulting in specific strains for each individual patient.

Role of the mitochondrial DnaJ homolog Mdj1p as a chaperone for mitochondrially synthesized and imported proteins

Mdj1p, a DnaJ homolog in the mitochondria of Saccharomyces cerevisiae, is involved in the folding of proteins in the mitochondrial matrix. In this capacity, Mdj1p cooperates with mitochondrial Hsp70 (mt-Hsp70). Here, we analyzed the role of Mdj1p as a chaperone for newly synthesized proteins encoded by mitochondrial DNA and for nucleus-encoded proteins as they enter the mitochondrial matrix. A series of conditional mutants of mdj1 was constructed. Mutations in the various functional domains led to a partial loss of Mdj1p function. The mutant Mdj1 proteins were defective in protecting the tester protein firefly luciferase against heat-induced aggregation in isolated mitochondria. The mitochondrially encoded var1 protein showed enhanced aggregation after synthesis in mdj1 mutant mitochondria. Mdj1p and mt-Hsp70 were found in a complex with nascent polypeptide chains on mitochondrial ribosomes. Mdj1p was not found to interact with translocation intermediates of imported proteins spanning the two membranes and exposing short segments into the matrix, in accordance with the lack of requirement of Mdj1p in the mt-Hsp70-mediated protein import into mitochondria. On the other hand, precursor proteins in transit which had further entered the matrix were found in a complex with Mdj1p. Our results suggest that Mdj1p together with mt-Hsp70 plays an important role as a chaperone for mitochondrially synthesized polypeptide chains emerging from the ribosome and for translocating proteins at a late import step.

Small-angle X-ray scattering reveals differences between the quaternary structures of oxygenated and deoxygenated tarantula hemocyanin

Small-angle X-ray scattering (SAXS) curves have been recorded for the oxygenated and deoxygenated states of the 4 x 6-meric hemocyanin from the tarantula Eurypelma californicum. A comparison of the curves shows that the quaternary structures of the two states are different by three criteria, which all indicate that the hemocyanin is less compact in the oxygenated compared to the deoxygenated form: (a) The radius of gyration is 8.65 +/- 0.05 nm for the deoxy- and 8.80 +/- 0.05 nm for the oxy-form. (b) The maximum particle dimension amounts to 25.0 +/- 0.5 nm for the deoxy- and to 27.0 +/- 0.5 nm for the oxy-form. (c) A dip in the intramolecular distance distribution function p(r) is more pronounced and shifted to larger distances in the oxy-form. The p(r) functions based on SAXS measurements were compared to p(r) functions deduced from published electron microscopical images of three different 4 x 6-meric hemocyanins from closely related species. The p(r) functions of SAXS and electron microscopy were similar in one case, whereas in the other two cases the distance between the two 12-meric half-molecules had to be changed by 1-1.5 nm to obtain good agreement. The differences between the p(r) functions of oxygenated and deoxygenated 4 x 6-meric tarantula hemocyanin are much larger than one would expect from a comparison of X-ray structures of the oxygenated and deoxygenated states of a closely related 6-meric hemocyanin. Thus, the conformational changes upon oxygenation occur at various levels of the quaternary structure, as postulated by hierarchical theories of allosteric interactions.

Different ligand responsiveness of human retinoic-acid-receptor beta-gene transcription in tumorigenic and non-tumorigenic cervical-carcinoma-derived cell lines is mediated through a large retinoic-acid-response domain

The retinoic-acid-receptor beta gene (RAR-beta) encodes a suspected tumor suppressor for several types of human carcinomas. RAR-beta transcription is induced by retinoic acid (RA) through retinoid receptors which bind as heterodimers of a RA-activated RA receptor (RAR) and a retinoid X receptor to the RA-responsive element in the RAR-beta promoter region (beta RARE). RA inducibility of RAR-beta gene expression is often lost or reduced in human carcinoma cells. As previously shown, the RAR-beta gene is highly RA-inducible in nontumorigenic HeLa x fibroblast hybrid cells, but neither in HeLa cervical carcinoma cells nor in a tumorigenic hybrid segregant line. We report here that severe reduction of RA-induced RAR-beta mRNA levels is a general feature of tumorigenic HeLa x fibroblast segregants. To study the molecular basis of differential RA inducibility, we have performed transient transfection assays in HeLa and nontumorigenic 444 hybrid cells using reporter constructs with different 5' and internal deletions of the RAR-beta transcription-control region. Remarkably, maximal RA inducibility in 444 cells required the integrity of the complete RAR-beta upstream region. In HeLa cells, all reporter constructs showed only low RA inducibility levels. The differential RA inducibility in 444 and HeLa cells could be conferred by the RAR-beta upstream region, but not by subfragments of it, on a heterologous RA-responsive promoter. The data indicate that maximal RA inducibility of RAR-beta gene transcription in nontumorigenic 444 cells depends on the cooperation of the beta RARE with additional upstream elements. All elements together constitute a large RA response domain as the higher-order transcription control unit. The communication between the upstream elements and the beta RARE seems to be disturbed in HeLa cells. Similar defects may be responsible for the loss of RA responsiveness of RAR-beta gene expression in other human tumors.