Localization of human ERBA2 to the 3p22----3p24.1 region of chromosome 3 and variable deletion in small cell lung cancer

Triiodothyronine lowers the potential of colorectal cancer stem cells in vitro

Cancer stem cells (CSCs) play a key role in the development and progression of colorectal cancer (CRC), but the influence of triiodothyronine (T3) on the biological regulation of CSCs remains unclear. In the present study, it was reported that T3 exerts significant impact on CSCs of two CRC cell lines cultured in the form of colonospheres. It was observed that the incubation of colonospheres with T3 decreased the viability, proliferative and spherogenic potential of cancer cells (P<0.05). In addition, increased apoptotic rate of CRC cells treated with T3 was revealed. Furthermore, T3‑treated colonospheres were more likely to move into silenced pool in G0/G1 phase of the cell cycle. The smaller sizes of colonospheres observed after the treatment with T3 confirmed this conclusion. T3 could lower the proportion of primitive cells which supply the pool of proliferating cells within spheres. Thyroid receptors THRα1 and THRβ1 and two deiodinases (DIO2 and DIO3) were affected by T3 in manner depended on clinical stage of cancer and CRC cell line used for analysis. In summary, the present study uncovered a novel function of thyroid hormones signaling in the regulation of the CSCs of CRC, and these findings may be useful for developing novel therapies by targeting thyroid hormone functions in CRC cells.

Age-associated increase of thyroid hormone receptor β gene promoter methylation coexists with decreased gene expression

PURPOSE

It is not established if healthy aging of the thyroid axis is associated with alterations other than changes in hormone secretion.

METHODS

The expression of thyroid hormone receptor β gene (THRB) was analyzed in peripheral blood mononuclear cells (PBMC) obtained from young, elderly, and long-lived individuals. The interaction between the 3'UTR of TRβ1 mRNA and selected miRNAs was measured using pmirGLO reporter vector. Methylation of the THRB CpG island was analyzed using methylation-sensitive restriction/RT-PCR and bisulfite sequencing methods.

RESULTS

Old age was associated with a significantly lower amount of total TRβ mRNA (p = 0.033) and of TRβ1 mRNA (p = 0.02). Older age was also associated with significantly higher methylation of the THRB promoter (restriction/RT-PCR: p = 0.0023, bisulfite sequencing: p = 0.0004). Higher methylation corresponded to a lower expression of the THRB mRNA, but this correlation did not reach the level of significance. miR-26a interacted with two sites in the 3'UTR of the TRβ1 mRNA leading to the decrease of the reporter protein activity (p < 0.0001 and p = 0.0005), and miR-496 interacted with one of the two putative binding sites which also decreased the reporter protein activity (p < 0.0001). Analysis of the expression of miR-21, miR-26a, miR-146a, miR-181a, miR-221, and miR-496 showed that the expression of miR-26a was significantly decreased in old subjects (p = 0.017), while the levels of other miRNAs were unaffected.

CONCLUSIONS

Age-related decrease of THRB expression in PBMC of elderly and long-lived humans might be, in part, a result of the increased methylation of its promoter, but is unrelated to the activity of the miRNAs analyzed here.

Genomic Alterations in Human Breast Cancer: A Review

We review and discuss data on the genetic alterations documented in human breast carcinomas at the molecular level. These alterations may result in: 1) deletion of genetic material (chromosome 11p, 13q, 3p, 1q, 17p); 2) amplification of genes or entire chromosomal segments (c-myc, c-erb-B2, locus DF3/PUM, loci on 11q13); 3) rearrangements (c-myc); 4) point mutations (c-ras). Presently available informations do not allow the development of cohesive pathogenetic models but indicate that the molecular basis of human breast cancer is heterogeneous.

Emerging role of thyroid hormone metabolites

Thyroid hormones (THs) are essential for the regulation of development and metabolism in key organs. THs produce biological effects both by directly affecting gene expression through the interaction with nuclear receptors (genomic effects) and by activating protein kinases and/or ion channels (short-term effects). Such activations can be either direct, in the case of ion channels, or mediated by membrane or cytoplasmic receptors. Short-term-activated signalling pathways often play a role in the regulation of genomic effects. Several TH intermediate metabolites, which were previously considered without biological activity, have now been associated with a broad range of actions, mostly attributable to short-term effects. Here, we give an overview of the physiological roles and mechanisms of action of THs, focusing on the emerging position that TH metabolites are acquiring as important regulators of physiology and metabolism.

Mineralocorticoid receptor suppresses cancer progression and the Warburg effect by modulating the miR-338-3p-PKLR axis in hepatocellular carcinoma

Hormones and their corresponding receptors are vital in controlling metabolism under normal physiologic and pathologic conditions, but less is known about their roles in the metabolism of cancer. Using a small interfering RNA screening approach, we examined the effects of silencing 20 well-known hormone receptors on the Warburg effect, specifically by measuring the production of lactate in four established hepatocellular carcinoma (HCC) cell lines. We found that silencing a variety of hormone receptors had effects on the production of this metabolite. Unexpectedly silencing of mineralocorticoid receptor (MR) significantly increased lactate production in all these HCC cell lines. Subsequent in vitro and in vivo studies showed that gain- and loss-of-function of MR significantly influenced HCC cellular proliferation, cell cycle distribution, and apoptosis. Furthermore, mechanistic studies revealed that MR as a transcriptional factor directly regulated the expression of miR-338-3p, suppressing the Warburg effects of HCC cells by targeting a key enzyme of glycolysis: pyruvate kinase, liver and red blood cells. Moreover, MR expression was significantly down-regulated in 81% of HCC patient tissues, caused by both chromosome deletion and histone deacetylation. Low expression of MR in tumor tissues was associated with poor patient prognosis. The expression level of miR-338-3p was found to positively correlate with the expression of MR in HCC tissues and to inversely correlate with expression of the enzyme pyruvate kinase, liver and red blood cells.

CONCLUSION

MR affects HCC development by modulating the miR-338-3p/pyruvate kinase, liver and red blood cells axis with an ability to suppress the Warburg effect.

Genetic features of thyroid hormone receptors

Thyroid hormone receptors (TR) are prototypes of nuclear transcription factors that regulate the expression of target genes. These receptors play an important role in many physiological processes. Moreover, a dysfunction of these proteins is often implicated in several human diseases and malignancies. Here we report genetic variations and alterations of the TRs that have been described in the literature as well as their potential role in the development of some human diseases including cancers. The functional effects of some mutations and polymorphisms in TRs on disease susceptibility, especially on cancer risk, are now established. Therefore, further investigations are needed in order to use these receptors as therapeutic targets or as biological markers to decide on appropriate forms of treatment.

Thyroid hormone actions in liver cancer

The thyroid hormone 3,3',5-triiodo-L-thyronine (T3) mediates several physiological processes, including embryonic development, cellular differentiation, metabolism, and the regulation of cell proliferation. Thyroid hormone receptors (TRs) generally act as heterodimers with the retinoid X receptor (RXR) to regulate target genes. In addition to their developmental and metabolic functions, TRs have been shown to play a tumor suppressor role, suggesting that their aberrant expression can lead to tumor transformation. Conversely, recent reports have shown an association between overexpression of wild-type TRs and tumor metastasis. Signaling crosstalk between T3/TR and other pathways or specific TR coregulators appear to affect tumor development. Since TR actions are complex as well as cell context-, tissue- and time-specific, aberrant expression of the various TR isoforms has different effects during diverse tumorigenesis. Therefore, elucidation of the T3/TR signaling mechanisms in cancers should facilitate the identification of novel therapeutic targets. This review provides a summary of recent studies focusing on the role of TRs in hepatocellular carcinomas (HCCs).

Aberrant methylation of the THRB gene in tissue and plasma of breast cancer patients

The thyroid hormone receptors (TR) have three major isoforms, TRalpha1, TRalpha2, and TRbeta1; these are ligand-dependent nuclear transcription factors. THRB, the gene encoding TRbeta1, is considered a potential cancer suppressor. The mechanism of its inactivation is not yet clear. Aberrant silencing of THRB in breast cancer tissue and plasma by promoter hypermethylation was investigated in the present study. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to examine THRB mRNA expression in the breast cancer tissues. Methylation-specific polymerase chain reaction (MSP) combined with nested PCR was used to determine the methylation status of the THRB gene promoter region in 40 cancer tissue and 40 plasma samples from breast cancer patients. Methylation status of MSP product in plasma was also evaluated by direct sequencing. The expression of THRB mRNA in breast cancer tissues was lower than that in the normal tissues; hypermethylation was found in 32 of 40 breast cancer tissues (80%) and in 28 of 40 plasma samples (70%). Loss of THRB gene expression was associated with the CpG island hypermethylation of promoter regions. THRB gene CpG island methylation was not related to clinical pathologic parameters. Sequencing results were identical to agarose gel electrophoresis results. The present results indicate that hypermethylation of THRB as an alternative gene silencing mechanism is highly prevalent in breast cancer. Methylated tumor-specific DNA may serve as a plasma biomarker for prognosis in patients with breast cancer.

Hypothyroidism enhances tumor invasiveness and metastasis development

BACKGROUND

Whereas there is increasing evidence that loss of expression and/or function of the thyroid hormone receptors (TRs) could result in a selective advantage for tumor development, the relationship between thyroid hormone levels and human cancer is a controversial issue. It has been reported that hypothyroidism might be a possible risk factor for liver and breast cancer in humans, but a lower incidence of breast carcinoma has been also reported in hypothyroid patients

METHODOLOGY/PRINCIPAL FINDINGS

In this work we have analyzed the influence of hypothyroidism on tumor progression and metastasis development using xenografts of parental and TRbeta1-expressing human hepatocarcinoma (SK-hep1) and breast cancer cells (MDA-MB-468). In agreement with our previous observations tumor invasiveness and metastasis formation was strongly repressed when TRbeta-expressing cells were injected into euthyroid nude mice. Whereas tumor growth was retarded when cells were inoculated into hypothyroid hosts, tumors had a more mesenchymal phenotype, were more invasive and metastatic growth was enhanced. Increased aggressiveness and tumor growth retardation was also observed with parental cells that do not express TRs.

CONCLUSIONS/SIGNIFICANCE

These results show that changes in the stromal cells secondary to host hypothyroidism can modulate tumor progression and metastatic growth independently of the presence of TRs on the tumor cells. On the other hand, the finding that hypothyroidism can affect differentially tumor growth and invasiveness can contribute to the explanation of the confounding reports on the influence of thyroidal status in human cancer.

The thyroid hormone receptor is a suppressor of ras-mediated transcription, proliferation, and transformation

The thyroid hormone triiodothyronine (T3) has a profound effect on growth, differentiation, and metabolism in higher organisms. Here we demonstrate that T3 inhibits ras-induced proliferation in neuroblastoma cells and blocks induction of cyclin D1 expression by the oncogene. The hormone, at physiological concentrations, strongly antagonizes the transcriptional response mediated by the Ras/mitogen-activated protein kinase/ribosomal-S6 subunit kinase (Rsk) signaling pathway in cells expressing thyroid hormone receptors (TRs). T3 blocks the response to the oncogenic forms of the three ras isoforms (H-, K-, and N-ras) and both TRalpha and TRbeta can mediate this action. The main target for induction of cyclin D1 transcription by oncogenic ras in neuroblastoma cells is a cyclic AMP response element (CRE) located in proximal promoter sequences, and T3 represses the transcriptional activity of b-Zip transcription factors such as CREB (CRE-binding protein) or ATF-2 (activation transcription factor 2) that are direct targets of Rsk2 and bind to this sequence. The hormone also blocks fibroblast transformation by oncogenic ras when TR is expressed. Furthermore, TRs act as suppressors of tumor formation by the oncogene in vivo in nude mice. The TRbeta isoform has stronger antitransforming properties than the alpha isoform and can inhibit tumorigenesis even in hypothyroid mice. These results show the existence of a previously unrecognized transcriptional cross talk between the TRs and the ras oncogene which influences relevant processes such as cell proliferation, transformation, or tumorigenesis.

Allelic loss of chromosome 3p24 correlates with tumor progression rather than with retinoic acid receptor beta2 expression in breast carcinoma

A tumor suppressor gene. retinoic acid receptor (RAR) beta2, has been mapped to chromosome 3p24, a region where loss of heterozygosity (LOH) has been observed commonly in carcinomas of various tumor tissues. RAR beta2 expression is reduced or lost in many malignant tumors including breast cancer, however, whether LOH accounts for the loss of expression of RAR beta2 in breast cancer is unknown. We, therefore, assessed LOH on chromosome band 3p24 to correlate it with RAR beta2 expression and other established prognostic parameters in 52 breast carcinomas. Based on three microsatellites, D3S 1283, D3S 1293 and D3S 1286. all of the tumors were informative, of these, 12 (23%) exhibited LOH. RAR beta2 expression was lost in 42% (19/45) of these samples. We found that LOH on chromosome band 3p24 was not correlated with loss of RAR beta2, but correlated with higher histological grade, p53-positivity, and loss of estrogen and progesterone receptors. Our findings suggest that LOH of the RAR beta2 gene does not account for the frequent loss of RAR beta2 expression in breast cancer but the genomic structural alteration at or close to the RAR beta2 gene locus are likely to be associated with tumor progression and/or loss of hormonal dependency.

Loss of heterozygosity at 3p23 is correlated with poor survival in patients with colorectal carcinoma

BACKGROUND

Loss of heterozygosity (LOH) of chromosome 3p has been observed commonly in carcinomas of various tumor tissues, including colorectal carcinoma (CRC). Because there is no report analyzing 3p deletions in relation to patient prognosis in CRC, the authors investigated the prognostic value of LOH on 3p in 87 patients with sporadic CRC.

METHODS

DNA samples from tumor and nontumor tissues were amplified by using polymerase chain reaction (PCR) and were analyzed for LOH on 3p using four different polymorphic human dinucleotide repeat DNA markers that map on this chromosome arm. The correlations with prognosis were established by the Kaplan-Meier method, and the Cox proportional hazards model was used to identify which independent factors jointly had a significant influence on patient survival.

RESULTS

Overall, allelic losses were detected in 19.5% of the patients evaluated. Only considering informative tumors, the data indicated that LOH was observed in 17 of 71 (29.4%) informative cases. Results from survival analysis showed a significant correlation between this molecular abnormality and both overall survival and disease free survival (P = 0.02 and P = 0.0005, respectively). The worst prognosis was found for the group of patients with LOH at 3p23: This alteration was an independent prognostic factor according to Cox multivariate analysis.

CONCLUSIONS

This study is the first to demonstrate the prognostic significance of LOH at chromosome arm 3p for patients CRC and may help to identify patients who need an intensive postoperative follow-up protocol.

Expression of thyroid hormone receptors is disturbed in human renal clear cell carcinoma

Human renal clear cell carcinoma (RCCC) accounts for up to 2% of human cancers. To find out if thyroid hormone (T3) and its receptors (TRs) play a role in tumorigenesis of RCCC, the expression of TRs was evaluated on mRNA and protein level. It was found that TRalpha (both alpha1 and alpha2) mRNA amount was significantly decreased in tumors while compared with healthy kidney tissue, and this decrease was deepest in G1 (well differentiated) RCCCs. In contrast, TRalpha1 protein was 1.6x overexpressed in tumors. TRbeta1 mRNA amount was overexpressed in 30% and significantly decreased in 70% of examined tumors. On the protein level, TRbeta1 amount was 1.7x lower in tumors than in healthy controls.

The localization of thyroid hormone receptor mRNAs in human bone

Thyroid hormones have well-documented effects on the skeleton although the mechanism of their action on bone is poorly understood. We have recently reported the presence of different thyroid hormone receptor isoforms in human bone. However, there is evidence to suggest that the expression of thyroid hormone receptor (TR) protein may not necessarily correlate with its mRNA. In this study, we used specific digoxigenin-labeled ribo probes to investigate the expression of TRalpha1, variant TRalpha2, TRbeta1, and in particular TRbeta2 mRNA in human osteophytic bone and osteoclastoma tissue in situ. The number of positive cells was expressed as the percentage of the total number of cells of the same phenotype. In osteophytes, at sites of endochondral ossification, TRalpha1, variant TRalpha2, TRbeta1, and TRbeta2 mRNA were widely distributed in undifferentiated, proliferating, mature and hypertrophic chondrocytes. At sites of bone remodeling, TRalpha1 mRNA was expressed in the majority (> 90%) of osteoblasts. TRbeta1 and the variant TR-alpha2 mRNA were moderately expressed in approximately 75% of cells with only a few osteoblasts (< 25%) expressing TRbeta2 mRNA. All the TR transcripts were highly expressed in multinucleated osteoclasts in osteoclastoma tissue. The distribution of TR mRNAs was similar to TR receptor protein expression (as we have previously reported) in both osteophytic bone and osteoclastoma tissue except TRalpha1 mRNA that was highly expressed in osteoclasts and in undifferentiated, proliferating, mature, and hypertrophic chondrocytes in contrast to its receptor protein expression. This study highlights the importance of studying both TR mRNA and receptor proteins in triiodothyronine (T3) responsive tissues. This is also the first demonstration of the presence of TRbeta2 mRNA in bone. The role of TRbeta2 in mediating the actions of thyroid hormones in bone is not known and requires further investigation.

A new locus for late-onset, progressive, hereditary hearing loss DFNA20 maps to 17q25

We report the localization of DFNA20, a gene causing dominant, nonsyndromic, progressive hearing loss in a three-generation Midwestern family, to chromosome 17q25. Affected family members show a bilateral, sloping, progressive, sensorineural hearing loss, first evident at 6000 and 8000 Hz, that can be identified in some family members in the early teens and is clearly evident by the early twenties. As age increases, the degree of hearing loss increases with threshold shifts seen at all frequencies. Linkage to known hereditary hearing loss loci was excluded. A genome-wide screen detected positive linkage to D17S784 (LOD(Z) = 6.62; &theta; = 0). Haplotype analysis refines the DFNA20 critical region to 12 cM between D17S1806 and D17S668. Radiation hybrid mapping with Stanford G3 and TNG panels was used to evaluate the genes ACTG1, GRIN2C, FKHL13, P4HB, SPARC, and ARHGDIA as candidates for DFNA20.

Deletions of the short arm of chromosome 3 in solid tumors and the search for suppressor genes

The concept that cells can become malignant upon the elimination of parts of chromosomes inhibiting cell division dates back to Boveri in 1914. Deletions occurring in tumor cells are therefore considered a first indication of possible locations of tumor suppressor gene. Approaches used to localize and identify the paradigm of tumor suppressors, RB1, have also been applied to localize tumor suppressor genes on 3p, the short arm of chromosome 3. This review discusses the methodological advantages and limitations of the various approaches. From a review of the literature on losses of 3p in different types of solid tumors it appears that some tumor types show involvement of the same region, while between others the regions involved clearly differ. Also discussed are results of functional assays of tumor suppression by transfer of part of chromosome 3 into tumor cell lines. The likelihood that a common region of deletions would contain a tumor suppressor is strongly enhanced by coincidence of that region with a chromosome fragment suppressing tumorigenicity upon introduction in tumor cells. Such a situation exists for a region in 3p21.3 as well as for one or more in 3p12-p14. The former region is considered the location of a lung cancer suppressor. The same gene or a different one in the same region may also play a role in the development of other cancers including renal cell cancer. In the latter cancer, there may be additional roles of the VHL region and/or a 3p12-p14 region. The breakpoint region of a t(3;8) originally found to be constitutively present in a family with hereditary renal cell cancer now seems to be excluded from such a role. Specific genes on 3p have been suggested to act as suppressor genes based on either their location in a common deletion region, a markedly reduced expression or presence of aberrant transcripts, their capacity to suppress tumorigenicity upon transfection in to tumor cells, the presumed function of the gene product, or a combination of several of these criteria. A number of genes are evaluated for their possible role as a tumor suppressor according to these criteria. General agreement on such a role seems to exist only for VHL. Though hMLH1 plays an obvious role in the development of specific mismatch repair-deficient cancers, it cannot revert the tumor phenotype and therefore cannot be considered a proper tumor suppressor. The involvement of VHL and MLH1 also in some specific hereditary cancers allowed to successfully apply linkage analysis for their localization. TGFBR2 might well have a tumor suppressor function. It does reduce tumorigenicity upon transfection. Other 3p genes coding for receptor proteins THRB and RARB, are unlikely candidates for tumor suppression. Present observations on a possible association of FHIT with tumor development leave a number of questions unanswered, so that provisionally it cannot be considered a tumor suppressor. Regions that have been identified as crucial in solid tumor development appear to be at the edge of synteny blocks that have been rearranged through the chromosome evolution which led to the formation of human chromosome 3. Although this may merely represent a chance occurrence, it might also reflect areas of genomic instability.

Effect of thyroid hormone on growth. Lessons from the syndrome of resistance to thyroid hormone

Thyroid hormone deprivation results in deleterious effects on bone growth. The delayed bone development is mediated by a direct effect of thyroid hormone on bone and an indirect effect of the hormone on GH release and IGF-1 action. Both TR alpha and TR beta are expressed in bone cells. To examine the role of TR beta on bone, we have reviewed the growth abnormalities in the human syndrome of RTH caused by mutations in the TR beta gene. The mutant TR beta reduces the tissue responsiveness to thyroid hormone, producing in some tissues variable degrees of thyroid hormone deprivation. With regard to bone, relative thyroid hormone deficiency caused by the mutant TR beta produces short stature and delayed bone growth but does not attenuate growth to the extent that absolute thyroid hormone deficiency does. These observations indicate that an intact TR beta is required for normal bone development and growth.

Submicroscopic deletions of 3p sequences in pleomorphic adenomas with t(3;8)(p21;q12)

A subgroup of benign pleomorphic adenomas of the salivary glands is characterized by translocations, or on rare occasions deletions, with breakpoints at 3p21. We have applied restriction fragment length polymorphism (RFLP) analysis to assess the frequency of allelic losses at four different loci located within 3p21-->p25 in 35 pleomorphic adenomas, 18 of which were also karyotyped. Parallel analysis of constitutional and tumor DNAs in informative tumors revealed that all patients retained heterozygosity in their tumor DNA at the D3S2 and RAF1 loci. Among the 29 tumors informative for THRB three showed loss of heterozygosity (LOH). All three tumors had a t(3;8)(p21;q12). Of the 23 tumors informative for D3F15S2, one showed LOH. This tumor also had a t(3;8)(p21;q12). To further map the deletions in relation to the 3p21 translocation breakpoint, we also sublocalized the THRB locus. Using in situ hybridization we assigned the gene to 3p24.1-3. The fact that none of the tumors with loss of 3p alleles showed cytogenetic evidence of deletions indicates that the losses are submicroscopic, probably interstitial, and in most cases distal to the 3p21 breakpoint. This was confirmed in one case with loss of a THRB allele where both proximal (D3F15S2) and distal (RAF1) markers retained heterozygosity. Our results suggest that deletion of 3p sequences might be of progressional importance in a subset of pleomorphic adenomas with t(3;8)(p21;q12).

Differential expression of mutant and normal beta T3 receptor alleles in kindreds with generalized resistance to thyroid hormone

Thyroid hormone resistance (THR) is primarily an autosomal dominant inherited disease characterized by resistance of pituitary and peripheral tissues to the action of thyroid hormone. We investigated whether the heterogeneous phenotypic features that occur not only among kindreds but also within the same kindred might be due to the expression of differing ratios of mutant and normal receptors in tissues. Using an allele-specific primer extension method, we determined the relative expression of normal and mutant mRNAs from the fibroblasts of affected and unaffected members of two kindreds with TRH: A-H and N-N. While two affected members of A-H, as expected, had nearly equal amounts of normal and mutant hTR beta mRNA, two other members had mutant mRNA levels that accounted for at least 70% of the hTR beta mRNA. Phenotypic variability within and between kindreds with generalized resistance to thyroid hormone GRTH may be due to this differential expression of the mutant and wild type mRNA. Furthermore, when several clinical parameters of THR were compared in several affected members from two kindreds with GRTH, we found that two cases in one kindred exhibited a high mutant-to-normal hTR beta ratio and had considerably more bone resistance during their development. In certain kindreds with THR, differing ratios of normal and mutant hTR receptors may be age and growth related and may account for the reported attenuation of phenotypic symptoms with age.

Identification of a novel mutation in the gene encoding the beta-triiodothyronine receptor in a patient with apparent selective pituitary resistance to thyroid hormone

OBJECTIVE

We investigated whether the first patient (L-F3) reported as having selective pituitary resistance had a mutation in the hTR beta gene. We compared the clinical parameters of this case with those of patients with generalized resistance to thyroid hormone.

DESIGN

The patient, L-F3, was part of a study at the NIH to identify mutations by sequencing the hTR beta gene in kindreds with thyroid hormone resistance. The clinical data of L-F3 as well as patients with generalized resistance to thyroid hormone were compared and analysed retrospectively.

MEASUREMENT

We amplified by the polymerase chain reaction and then sequenced exons 5 to 10 of the hTR beta gene in L-F3 and a normal control. Upon finding the mutation in L-F3, we measured the affinity constant of this mutated hTR beta receptor. Criteria developed previously were used to assess tissue responsiveness to thyroid hormone of L-F3.

RESULTS

We identified a C to T transition at base 1297 in codon 333 of the hTR beta gene in the first patient (L-F3) reported as having apparent selective pituitary resistance. This base substitution resulted in more than a four-fold decrease in T3-binding affinity for the hTR beta 1 receptor. The mutation of L-F3 occurred in the dimerization domain of exon 9, a region where the majority of mutations of kindreds with generalized thyroid hormone resistance have been found. Furthermore, the nucleotide substitution at base 1297 found in the apparent selective pituitary resistant case, L-F3, was the same as in an unrelated patient (K-T3) with generalized resistance to thyroid hormone. As a result, we compared the clinical parameters of both patients and found that they had similar patterns of resistance in several tissues. Besides the bone resistance present in both kindreds, the apparent selective pituitary resistance case also had liver and neuromuscular resistance.

CONCLUSIONS

These findings suggest that apparent selective pituitary resistance and generalized resistance to thyroid hormone are not qualitatively different syndromes. Nevertheless, identification of selective pituitary resistance is a useful clinical distinction since such patients with clinical and biochemical features of hyperthyroidism appear to benefit from reduction in serum thyroid hormone concentrations. In contrast, patients with more conventional forms of thyroid hormone resistance require no treatment or may benefit from increased concentrations of thyroid hormone.

Oncogenes in human lung cancer

The rapid pace of research in the genetics of human cancer will predictably render any review of the topic out of date by the time of its publication. Prospects for the near future will likely include the identification of a chromosome 3p gene(s) linked with the development of familial renal cancer and, perhaps, also lung cancer. In addition, the availability from the Human Genome Project of an increasing number of well-characterized markers will accelerate the search for additional human recessive oncogenes. Many questions still remain about the etiology of lung cancer and how to apply this information for patient care. For example, identification of the cell of origin for small cell and non-small cell lung cancers will facilitate our understanding of the development of these tumors and improve the possibilities for future preventive strategies. In addition, we now realize that these cancers arise from the sequential accumulation of multiple genetic mutations (Table 3; Fig. 1). Therefore, a central question is which of these targets are essential for the process of carcinogenesis, and whether there is a critical temporal order for this process with a defined premalignant phase in a discrete field of bronchial tissue. In addition, are there genetically inherited susceptibilities to the development of lung cancer (either directly or via variabilities in carcinogen metabolism) that could be accurately identified in the general population? Finally, is there a rate-limiting mutation and will the genetic correction of this defect suffice to restore growth regulation, or will the replacement of multiple gene products be required for tumor suppression? We are already witnessing the beginnings of the use of molecular diagnostic markers as a research tool for assigning prognostic information. The expression of neuroendocrine markers in non-small cell lung cancer has recently been applied as an indicator of the potential response to combination chemotherapy [15]. Similar methods are being applied to the expression of tumor suppressor genes or the presence of somatic mutations in dominant oncogenes such as the ras gene. However, the clinical benefit of this prognostic information with currently available treatment programs is still uncertain.(ABSTRACT TRUNCATED AT 400 WORDS)

Thyroid hormone regulation of thyrotropin gene expression

Thyroid hormones suppress the synthesis and release of thyrotropin from thyrotropes in the anterior pituitary gland, a feature that is critical in the classic negative-feedback loop of the pituitary-thyroid endocrine axis. The major effect of thyroid hormones in this system is exerted at the transcriptional level. The molecular mechanisms by which there is negative regulation of TSH subunit gene expression by thyroid hormone have been elucidated. The TSH subunit genes have isolated and characterized. Structure-function analyses using fusion genes and DNA transfection approaches have defined the putative negative TREs among the promoters of the rat, mouse, and human alpha and TSH beta genes. These sequences are either largely overlapping direct TRE half-sites, TRE half-sites as direct repeats gapped by two nucleotides, or single TRE half-sites. These arrangements are distinct from those seen in positive TREs. Recent knowledge regarding the molecular mechanisms of thyroid action in general forces consideration of multiple TR isoforms, TR heterodimer partners (TRAPs), and thyroid hormones in the ultimate mechanisms of negative action. Several models have been proposed, but none has yet been proved. In addition, the role of thyroid hormone in the regulation of gene expression at the posttranscriptional level is beginning to be addressed. Future work should continue to illuminate these important facets of gene regulation.

Two hereditary defects related to vitamin D metabolism map to the same region of human chromosome 12q13-14

We have localized the locus for the vitamin D receptor (VDR) responsible for hypocalcemic vitamin D-resistant rickets (HVDRR), close to the pseudovitamin D-deficient rickets (PDDR) locus, another disorder related to impaired vitamin D metabolism. PDDR (formerly vitamin D dependency type I, VDD1) was recently mapped to human chromosome 12q14 by linkage analysis. Here we report on the assignment of VDR to 12q13-14 by in situ hybridization and by linkage analysis. Linkage analysis between VDR, PDDR, and several RFLP markers show close linkage, with no recombination (theta = 0) between VDR and PDDR (Z = 1.94), a COL2A1 haplotype (Z = 4.03), ELA1 (Z = 0.98), and D12S15 (Z = 4.17). The analysis of extended haplotypes in one of the PDDR families provides evidence for recombination between VDR and PDDR and localizes VDR together with COL2A1 proximal to PDDR. Complete allelic association detected between VDR and COL2A1 loci on PDDR chromosomes and lower association between VDR and PDDR suggests a VDR location very close to COL2A1 and one more distant to PDDR. We propose the following order of loci: (VDR, COL2A1), (PDDR, ELA1, D12S15), D12S4, (D12S14, D12S17), D12S6. Thus, two clearly distinct loci involved in the control of vitamin D activity map close to each other in the region 12q13-14.

Ordering of six polymorphic DNA markers important in the delineation of 3p deletions in neoplasia

Using fluorescence in situ hybridisation (FISH) the chromosomal location and relative order of six human chromosome 3 probes has been determined. The sensitivity of the technique has enabled the relative mapping of probes carrying inserts as small as 500 basepairs (bp), thus allowing the following proximal-distal probe order to be proposed: D3S30 (3p13-14), D3S4 (3p13-14), D3S2 (distal 3p14), D3S32 (3p21), D3S48E (3p21-23), and D3S11 (3p22-23). These data combined with the deletion mapping data of other researchers raise the possibility that the loss of more than one region of the short arm of chromosome 3 may be important in the development of small cell lung cancer.

Expression of the thyroid hormone receptor, the oncogenes c-myc and H-ras, and the 90 kD heat shock protein in normal, hyperplastic, and neoplastic human thyroid tissue

Expression of the thyroid hormone receptor (TR beta), the 90 KD heat shock protein (HSP 90), and the oncogenes H-ras and c-myc mRNA in normal hyperplastic, and neoplastic human thyroid tissue was investigated by Northern blot and slot blot analyses. The TR beta mRNA was present in all normal and neoplastic thyroid tissue samples. The levels were significantly higher in normal and hyperplastic tissues (7.91 +/- 0.48 and 7.60 +/- 0.68 arbitrary units, respectively) than in neoplastic tissues (3.82 +/- 0.67) (p < 0.001). H-ras and c-myc mRNA were also detected in glandular tissue specimens, but no significant difference was observed in their expression levels. Furthermore, there was a tendency to a negative correlation between the level of TR beta and c-myc mRNA (p = 0.06). In normal thyroid tissue, HSP 90 mRNA levels were significantly higher than in hyperplastic and papillary carcinoma tissue specimens (p < 0.001). These results indicate that mRNA of TR beta and HSP 90 (the latter only in papillary thyroid carcinoma) are expressed in relation to the degree of cellular differentiation. Furthermore, the presence of TR beta in normal thyroid tissue implies that T3 and T4 may be involved in the regulation of their own production via TR beta activated feedback mechanism(s).

BglI RFLP for the human erb-A beta locus on chromosome 3p22-3p24.1 (THRB)

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Involvement of the RAF1 locus, at band 3p25, in the 3p deletion of small-cell lung cancer

The ability to establish long-term cell lines of small-cell lung cancer (SCLC) has provided an in vitro model for the disease. We report on the characterization of 10 new human SCLC cell lines established from 34 cytopathologically positive specimens. Based on morphologic and biochemical characterization, growth properties, and expression of MYC and neuroendocrine properties, eight cell lines were categorized as "classic" and two cell lines as "variant". Cytogenetic examination revealed loss of all or part of 3p in all nine SCLC cell lines analyzed. The smallest deletion in common was found at 3p21-3p25. Restriction fragment length polymorphism (RFLP) analyses with probes for 3p were performed for correlation with karyotypic data and supported the cytogenetic findings. In 21 SCLC specimens (cell lines and tumor tissue) with normal DNA, used for comparison, we observed loss of heterozygosity at RAF1 (3p25) in ten of ten informative pairs by using two RFLPs from the RAF1 locus. In addition, loss of heterozygosity was noted in nine of 10 pairs examined with DNF15S2 (3p21) and four of four with D3S3 (3p14). Analysis of cell lines and tumor specimens that lacked paired normal tissue showed a homozygous pattern with the RAF1 probes in all 18 cases. Northern blots revealed significant expression of RAF1 in all cell lines tested. The transcript size was normal. The cytogenetic and RFLP data suggest that the RAF1 locus at 3p25 is involved in the chromosomal deletion of SCLC.

Isolation and regional localization of a large collection (2,000) of single-copy DNA fragments on human chromosome 3 for mapping and cloning tumor suppressor genes

A collection of 2,000 lambda phage-carrying human single-copy inserts (greater than 700 bp) were isolated from two chromosome-3 flow-sorted libraries. The single-copy DNA fragments were first sorted into 3p and 3q locations and about 700 3p fragments were regionally mapped using a deletion mapping panel comprised of two human-hamster and two-human-mouse cell hybrids, each containing a chromosome 3 with different deletions in the short arm. The hybrids were extensively mapped with a set of standard 3p markers physically localized or ordered by linkage. The deletion mapping panel divided the short arm into five distinct subregions (A-E). The 3p fragments were distributed on 3p regions as follows: region A, 26%; B, 31%; C, 4%; D, 4% and E, 35%. We screened 300 single-copy DNA fragments from the distal part of 3p (regions A and B) with ten restriction endonucleases for their ability to detect restriction fragment length polymorphisms (RFLPs). Of these fragments 110 (36%) were found to detect useful RFLPs; 35% detected polymorphisms with frequency of heterozygosity of 40% or higher, and 25% with frequency of 30% or higher. All polymorphisms originated from single loci and most of them were of the base pair substitution type. These RFLP markers make it possible to construct a fine linkage map that will span the distal part of chromosome 3p and encompasses the von Hippel-Lindau disease locus. The large number of single-copy fragments (2,000) spaced every 100-150 kb on chromosome 3 will make a significant contribution to mapping and sequencing the entire chromosome 3. The 300 conserved chromosome 3 probes will increase the existing knowledge of man-mouse homologies.

Advances in molecular biology. Potential impact on diagnosis and treatment of disorders of the thyroid

Advances in molecular biology research continue to have a major impact on clinical medicine. These advances have provided a means to produce proteins previously available in limited supply and allow for the production of novel proteins that are improved agonists or else antagonists with greater specificity for therapeutic targets. Newer drug delivery systems should facilitate delivery of these proteins. By combining the capabilities to produce drug targets in acceptable quantities with improved methods for determining the three-dimensional structures of these targets, novel organic therapeutic molecules that act on these targets will be designed. Gene transfer therapy using genes that express important proteins or that encode "antisense" RNAs that inhibit the translation of specific mRNAs will soon become a reality. The use of RFLPs and PCR methodologies promises increased means to diagnose specific genetic diseases and infections. Most importantly, molecular biology is helping to understand the mechanisms of disease such that novel diagnostic and therapeutic approaches can be described. These advances are providing an understanding of the mechanisms involved in cancers of the thyroid gland. They have already led to an enhanced understanding of (1) the growth factors that control proliferation of the thyroid gland, (2) the potential steps in thyroid nodule and neoplasia development, (3) particular mutations that may occur as thyroid cancers develop, (4) oncogenes that are expressed in thyroid cancers, and (5) the genetic defects that are responsible for thyroid gland malignancies in the multiple endocrine neoplasia (MEN) syndromes. With the latter, the RFLP technology has already provided an enhanced means to diagnose the disorder. With further progress, enhanced means for diagnosis and treatment should emerge. Molecular biology techniques are contributing to an increased understanding of the mechanisms of development of autoimmune thyroid disease as with Graves' disease and Hashimoto's thyroiditis. The potential role of infections, histocompatibility antigens, thyroid gland and extraglandular antigens, immune modulators, subpopulations of T-cells such as suppressor and helper cells, other cells involved in immune responses, and a combination of influences of several different functions on the thyroid gland are being defined. This knowledge should soon suggest improved means for diagnosis and treatment. Understanding of the function of the thyroid hormone receptors should have clinical importance. This knowledge suggests a means to develop thyroid hormone antagonists that may be used to more rapidly ameliorate the effects of hyperthyroidism and could be useful in nonthyroidal disorders such as cardiac arrhythmias.(ABSTRACT TRUNCATED AT 400 WORDS)

The 11q13 amplicon of a mammary carcinoma cell line

Fifteen to 20% of breast carcinomas show amplification of genes located at 11q13. The HST/FGFK and INT2 fibroblast growth factor (FGF)-related genes and the BCL1 locus are usually present in the amplification units. We have investigated the structure and chromosomal location of the 11q13 amplicon of the MDA-MB-134 mammary carcinoma cell line by using in situ chromosomal and pulsed field gel hybridizations. The results indicate that a limited number of amplification units are involved in the constitution of an extended chromosomal region located on 11q. These units do not show any important rearrangement over rather large distances around the HST/INT2 and BCL1 loci.

Cytogenetics of non-small cell lung cancer: analysis of consistent non-random abnormalities

Cytogenetic analysis of ten primary non-small cell lung carcinomas (NSCLC), including five adenocarcinomas (ADC), three squamous cell (SQC), and two large cell (LCC) carcinomas has been carried out in an attempt to determine karyotype changes involved in the early stage of disease. The tumors were all aneuploid and exhibited complex karyotypes with multiple structural and numerical abnormalities. Clonal structural rearrangements were identified and in particular loss of material from the short arm of chromosome 9 had a 90% incidence. This loss was due to non-reciprocal translocation, deletion, or chromosome loss. Breakpoints were in the region 9q13 to p22. Other chromosome regions that were non-randomly involved are as follows: I cen to p13, 3p, 5q11 to q13, 6p, 6q15 to q27, 7p, 8p, 11q12 to q23, 13p, 14p, 15p, 17p, and 19p. While a primary cytogenetic change in NSCLC has not been identified conclusively, our findings implicate loss of material from 9p as a potentially important event.

Molecular analysis of the short arm of chromosome 3 in five renal oncocytomas

Renal oncocytomas were tested for loss of alleles at loci on the short arm of chromosome 3, a genetic change characteristic of human renal cell carcinoma. Five renal oncocytomas did not show loss of alleles at loci on 3p supporting the view that renal oncocytoma is a distinct form of renal neoplasia.

Molecular mapping of deletion sites in the short arm of chromosome 3 in human lung cancer

We used 10 restriction fragment length polymorphism (RFLP) probes spanning the length of the short arm of chromosome 3 (3p) to map deletion sites in human lung cancer. Two approaches were used. 1) When a patient's tumor and normal tissue were available, loci with allelic heterozygosity in the normal tissue were tested for loss of alleles at 3p. 2) When the corresponding normal tissue was not available, the frequency of heterozygosity at each locus in a panel of tumors was compared to the corresponding published frequencies in nontumor tissue of healthy individuals or patients with lung cancer. In 14 small cell lung carcinomas (SCLC) with normal DNA for comparison, allele loss was found at all heterozygous loci, with one exception at a locus near the 3p centromere (D3S4). In the total of 53 SCLCs, which included tumors without paired normal tissue, frequency of heterozygosity was significantly reduced in all 10 3p loci. Three loci, DNF 15S2, RAF1, and D3S18, were homozygous in all tumors in the SCLC panel. These loci, which are in regions 3p21 and 3p25, may thus be involved in the origin or evolution of SCLC. We also investigated 24 non-SCLC tumors. In this panel, frequency of heterozygosity was significantly reduced at seven of the 10 loci tested. Comparison of the results shows that the pattern of allele loss on 3p is different in SCLC and non-SCLC, suggesting a difference in pathogenesis at the genetic level.

A base mutation of the C-erbA beta thyroid hormone receptor in a kindred with generalized thyroid hormone resistance. Molecular heterogeneity in two other kindreds

Generalized thyroid hormone resistance (GTHR) is a disorder of thyroid hormone action that we have previously shown to be tightly linked to one of the two thyroid hormone receptor genes, c-erbA beta, in a single kindred, A. We now show that in two other kindreds, B and D, with differing phenotypes, there is also linkage between c-erbA beta and GTHR. The combined maximum logarithm of the odds score for all three kindreds at a recombination fraction of 0 was 5.77. In vivo studies had shown a triiodothyronine (T3)-binding affinity abnormality in nuclear receptors of kindred A, and we therefore investigated the defect in c-erbA beta in this kindred by sequencing a major portion of the T3-binding domain in the 3'-region of fibroblast c-erbA beta cDNA and leukocyte c-erbA beta genomic DNA. A base substitution, cytosine to adenine, was found at cDNA position 1643 which altered the proline codon at position 448 to a histidine. By allelic-specific hybridization, this base substitution was found in only one allele of seven affected members, and not found in 10 unaffected members of kindred A, as expected for a dominant disease. Also, this altered base was not found in kindreds B or D, or in 92 random c-erbA beta alleles. These results and the fact that the mutation is predicted to alter the secondary structure of the crucial T3-binding domain of the c-erbA beta receptor suggest this mutation is an excellent candidate for the genetic cause of GTHR in kindred A. Different mutations in the c-erbA beta gene are likely responsible for the variant phenotypes of thyroid hormone resistance in kindreds B and D.

Expression of the ErbA-beta class of thyroid hormone receptors is selectively lost in human colon carcinoma

Members of the erbA gene family are involved both in control of differentiation and in neoplasia. V-erbA, a retroviral oncogene, blocks avian erythroid differentiation. V-erbA-related transcripts are physiologically expressed in multiple normal tissues. They encode a family of transcriptional regulatory factors, some of which are thyroid hormone receptors. In man, two genes, erbA-alpha and erbA-beta, are transcriptionally active. We examined expression of erbA-related transcripts in normal and neoplastic colon. In normal colon mucosa, as well as in a colon polyp and in a colon polyp cell line, three characteristic erbA-related transcripts were consistently found. One transcript of 6 kb was erbA-beta related. Two transcripts of 2.7 and 5.2 kb were erbA-alpha related. In eight patients' colon carcinomas expression of the 6-kb erbA-beta transcript was absent or markedly diminished when compared with the same patients' noninvolved mucosa. In contrast, expression of the two erbA-alpha transcripts was the same in both colon carcinoma and noninvolved mucosa. No evidence was found of erbA-beta gene deletion in any of the tumors lacking erbA-beta expression. These data suggest that selective loss of normally present erbA-beta gene expression accompanies malignant transformation of the colonic epithelial cell.