The combinatorial approach of laser-captured microdissection and reverse transcription quantitative polymerase chain reaction accurately determines HER2 status in breast cancer

Background

HER2 expression in breast cancer correlates with increased metastatic potential, higher tumor recurrence rates and improved response to targeted therapies. Fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) are two methods commonly used for the analysis of HER2 in the clinic. However, lack of standardization, technical variability in laboratory protocols and subjective interpretation are major problems associated with these testing procedures.

Methods

Here we evaluated the applicability of reverse-transcription quantitative polymerase chain reaction (RT-qPCR) for HER2 testing in breast cancer. We tested thirty formaldehyde-fixed and paraffin-embedded tumor samples by RT-qPCR, FISH and IHC and analysed and compared the data from the three methods.

Results

We found that laser-captured microdissection is essential for the accurate determination of HER2 expression by RT-qPCR. When isolating RNA from total tumor tissue we obtained a significant number of false negative results. However, when using RNA from purified cancer cells the RT-qPCR data were fully consistent with FISH and IHC. In addition we provide evidence that ductal carcinomas might be further classified by the differential expression of HER3 and HER4.

Conclusions

Laser-captured microdissection in combination with RT-qPCR is a precise and cost-effective diagnostic approach for HER2 testing in cancer. The PCR assay is simple, accurate and robust and can easily be implemented and standardized in clinical laboratories.

Nosocomial Staphylococcal scalded skin syndrome caused by intra-articular injection

BACKGROUND

The pathogenic role of nasal carriage as a source for cutaneous and soft-tissue Staphylococcus aureus (SA) infections, and Staphylococcal scalded skin syndrome (SSSS) in particular, is unclear.

OBSERVATION

We herein describe a nosocomial outbreak of SSSS in three orthopaedic patients who received intra-articular injections by a single orthopaedic surgeon. Bacteriological samples from the index patients and medical personnel involved in their care were assessed by phage typing, polymerase chain reaction for exfoliative toxin genes, SmaI macro-restriction analysis and molecular spa-typing. These studies first revealed SA cultural growth in synovial fluid of all three patients as well as nasal mucosa of one medical assistant. Moreover, all SA isolates had the same phage typing and antibiotic susceptibilities and were positive for exfoliative toxin ETa by polymerase chain reaction. SmaI macro-restriction and spa-typing further confirmed all proband isolates to be identical.

CONCLUSION

These findings provide evidence that SA nasal colonization of otherwise healthy carriers is a risk factor for SA infections, including SSSS, in predisposed individuals.

Cytokeratin-related loss of cellular integrity is not a major driving force of human intrinsic skin aging

The contribution of extracellular matrix components to intrinsic skin aging has been investigated thoroughly, however, there is little information as to the role of the cytoskeletal proteins in this process. Therefore, we compared the expression of the constituents of the cytoskeleton, keratins 1-23 (K1-K23) as well as junction-plakoglobin (JUP), alpha-tubulin (TUBA), and beta-actin (ACTB) in human foreskins of both young (mean 6.4 years) and aged (mean 54.3 years) individuals. By applying RNA expression analysis to intrinsically aged human skin, we demonstrated that the mRNA levels of the genes for K1, K3, K4, K9, K13, K15, K18, K19 and K20 are downregulated in aged skin, K5 and K14 are unchanged, and K2, K16 and K17 are upregulated in aged skin. The mRNA data were confirmed on the protein level. This diverse picture is in contrast to other cytoskeletal proteins including components of the desmosome (JUP), microtubuli (TUBA) and microfilaments (ACTB) - often regarded as house-keeping genes - that were all reduced in aged skin. These cytoskeletal features of intrinsic aging highlight the importance of the cellular compartment in this process and demonstrate that special attention has to be given to RNA as well as protein normalization in aging studies.

Ribosomal proteins Rpl10 and Rps6 are potent regulators of yeast replicative life span

The yeast ribosome is composed of two subunits, the large 60S subunit (LSU) and the small 40S subunit (SSU) and harbors 78 ribosomal proteins (RPs), 59 of which are encoded by duplicate genes. Recently, deletions of the LSU paralogs RPL31A and RPL6B were found to increase significantly yeast replicative life span (RLS). RPs Rpl10 and Rps6 are known translational regulators. Here, we report that heterozygosity for rpl10Delta but not for rpl25Delta, both LSU single copy RP genes, increased RLS by 24%. Deletion of the SSU RPS6B paralog, but not of the RPS6A paralog increased replicative life span robustly by 45%, while deletion of both the SSU RPS18A, and RPS18B paralogs increased RLS moderately, but significantly by 15%. Altering the gene dosage of RPL10 reduced the translating ribosome population, whereas deletion of the RPS6A, RPS6B, RPS18A, and RPS18B paralogs produced a large shift in free ribosomal subunit stoichiometry. We observed a reduction in growth rate in all deletion strains and reduced cell size in the SSU RPS6B, RPS6A, and RPS18B deletion strains. Thus, reduction of gene dosage of RP genes belonging to both the 60S and the 40S subunit affect lifespan, possibly altering the aging process by modulation of translation.

Relative Quantitation of Protein–Protein Interaction Strength Within the Yeast Two-Hybrid System via Fluorescenceβ-Galactosidase Activity Detection in a High-Throughput and Low-Cost Manner

The yeast two-hybrid (Y2H) method is capable of delivering vast amounts of interacting positive yeast colonies from a single library screen, particularly if a multifunctional protein is used as bait. However, the selection of definitive colonies for further molecular analysis is limited by both technical practicality and high costs. Here we demonstrate a cost-effective and simple method for the rapid selection and ranking of those Y2H-positive interaction clones that are suitable for further analysis. We performed a Y2H screen for the identification of human transforming growth factor beta2- interacting proteins in a human skin keratinocyte library. The identified clones were ranked by the amount of beta-galactosidase enzyme produced, as well as by the interaction strength of the positive colonies. The combination of high-throughput microplate fluorescence readers and specific fluorescence assays can be utilized for relative quantitation of protein-protein interaction strength of Y2H-positive colonies in crude yeast-cell lysates. We demonstrate here that the high sensitivity of the fluorescence approach can bypass cumbersome conventional methods of cell lysis used in beta-galactosidase assays, and still deliver accurate values for analysis of protein interaction data. Finally, we also achieved a better understanding of general aspects of beta-galactosidase measurements in the Y2H system, such as protein normalization, the influence of yeast culture incubation time on optimal beta-galactosidase detection, and the linearity of beta-galactosidase detection in crude cell lysates.

Haploinsufficiency due to deletion within the 3′-UTR of C1-INH-gene associated with hereditary angioedema

PURPOSE

Sequences within the non-coding 3'UTR (untranslated region) of genes were reported to be involved in the regulation of gene expression by modifying pathways of (co)transcription, post-transcriptional processing and RNA transport. However, direct biological evidence (i.e., knock-out models) is sparse. This report intends to correlate the first reported alteration within the 3'UTR of the C1 inhibitor (C1-INH) gene with clinical presentation of hereditary angioedema (HAE).

METHODS AND RESULTS

Direct sequencing of genomic DNA revealed in all affected members of a family suffering from HAE a heterozygous 155 bp deletion 100 bp downstream of the physiological stop-codon in exon 8. A substantial reduction of both mRNA as well as C1-INH protein expression was revealed by RT-PCR and nephelometry, respectively.

CONCLUSION

We suppose that the mutation within the 3'UTR interferes with integral pathways of gene expression leading to pathogenic haploinsufficiency in this family.

Introducing a fast and simple PCR-RFLP analysis for the detection of mutant thiopurine S-methyltransferase alleles TPMT*3A and TPMT*3C

BACKGROUND

Azathioprine, in combination with corticosteroids, is the first-line therapy of severe forms of pemphigus vulgaris. Patients with an impaired thiopurine S-methyltransferase (TPMT) activity are at risk of developing severe myelo-suppression upon treatment with thiopurines such as azathioprine. Analysis of the TPMT status prior to drug administration is therefore highly recommended. However, because of the limited availability of TPMT testing outside of specialized centres, pre-emptive TPMT testing is not widespread. To avoid laborious biochemical and sequencing assays, we evaluated a new restriction fragment length polymorphism (RFLP) analysis.

METHODS

We designed a rapid genetic polymerase chain reaction (PCR)-RFLP screen for the most prevalent mutant TPMT*3A and TPMT*3C alleles that are known to result in reduced TPMT enzyme activity.

RESULTS

Validating our fast system on 871 Caucasian DNA samples, we observed that 8.61% of our probands carried the TPMT*3A allele and 0.23% were heterozygous for the TPMT*3C allele, which is in concordance with previously reported allele frequencies.

CONCLUSION

This simple and low-cost PCR-RFLP TPMT polymorphism testing approach can be performed in a standard laboratory. It should be applied to all patients prior to receiving thiopurine drug therapy to avoid the severe, but predictable, haematopoietic side-effects of thiopurine drug administration.

Functional interaction in establishment of ribosomal integrity between small subunit protein rpS6 and translational regulator rpL10/Grc5p

Functional ribosomes synthesize proteins in all living cells and are composed of two labile associated subunits, which are made of rRNA and ribosomal proteins. The rRNA of the small 40S subunit (SSU) of the functional eukaryotic 80S ribosome decodes the mRNA molecule and the large 60S subunit (LSU) rRNA catalyzes protein synthesis. Recent fine structure determinations of the ribosome renewed interest in the role of ribosomal proteins in modulation of the core ribosomal functions. RpL10/Grc5p is a component of the LSU and is a multifunctional translational regulator, operating in 60S subunit biogenesis, 60S subunit export and 60S subunit joining with the 40S subunit. Here, we report that rpL10/Grc5p functionally interacts with the nuclear export factor Nmd3p in modulation of the cellular polysome complement and with the small subunit protein rpS6 in subunit joining and differential protein expression.

Translational regulator RpL10p/Grc5p interacts physically and functionally with Sed1p, a dynamic component of the yeast cell surface

Biogenesis of an active ribosome complement and a dynamic cell surface complement are two major determinants of cellular growth. In yeast, the 60S ribosomal subunit protein RpL10p/Grc5p functions during successive stages in ribosome biogenesis, specifically rRNA processing, nucle(ol)ar preribosomal subunit assembly, nucleo-cytoplasmic transport and cytoplasmic maturation of ribosomes. Here, we report that a two-hybrid screen identified yeast genes SED1, ACS2 and PLB3 as encoding proteins physically interacting with both ribosomal RpL10p/Grc5p and its human homologue hRpL10p/QMp. SED1 encodes a differentially expressed cell wall protein which is proposed to be first transiently secreted to the plasma membrane as a GPI (glycosylated derivative of phosphoinositol)-anchored form and to be then transferred to the glucan layer of the cell wall. Ectopic expression of SED1 rescues both the aberrant growth phenotype and the translation defect of grc5-1(ts) temperature-sensitive cells. Furthermore, we report that Sed1p associates with translating ribosomes suggesting a novel, cytoplasmic role for Sed1p. ACS2 encodes one of the two yeast acetyl-CoA synthases and represents a key enzyme in one of several metabolic routes to produce acetyl-CoA, which in turn is indispensable for lipid biosynthesis. PLB3 encodes a phospholipase, which is active in the breakdown of membrane lipids. Our results support the view that Grc5p/RpL10p links ribosome function to membrane turnover and cell surface biogenesis.