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Quantitative analysis of tyrosinase transcripts in blood
Linköping University, Department of Biomedicine and Surgery, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
AB Sangtec Medical, Bromma, Sweden..
AB Sangtec Medical, Bromma, Sweden..
Linköping University, Department of Biomedicine and Surgery, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
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2000 (English)In: Clinical Chemistry, ISSN 0009-9147, E-ISSN 1530-8561, Vol. 46, no 7, 921-927 p.Article in journal (Refereed) Published
Abstract [en]

Background: Tyrosinase is an enzyme unique to pigment-forming cells. Methods using this transcript for detection of melanoma cells in blood have given divergent results. Quantitative analytical procedures are therefore needed to study the analytical performance of the methods.

Methods: Mononucleated cells were isolated by Percoll centrifugation. RNA was isolated by each of three methods: UltraspecTM-II RNA isolation system, FastRNATM GREEN Kit, and QIAamp RNA Blood Mini Kit. cDNA was synthesized using random hexamer primers. A tyrosinase-specific product of 207 bp was amplified by PCR. As an internal standard (and competitor) we used a 207-bp cDNA with a base sequence identical to the tyrosinase target except for a 20-bp probe-binding region. The PCR products were identified by 2,4-dinitrophenol (DNP)-labeled probes specific for tyrosinase (5′DNP-GGGGAGCCTTGGGGTTCTGG-3′) and internal standard (5′DNP-CGGAGCCCCGAAACCACATC-3′) and quantified by ELISA.

Results: The calibration curves were linear and had a broad dynamic measuring range. A detection limit (2 SD above zero) of 48 transcripts/mL of blood was obtained from a low control. The analytical imprecision was 50% and 48% at concentrations of 1775 and 17 929 transcripts/mL (n = 12 and 14, respectively). With the cell line SK-Mel 28 added to blood and RNA extracted with the Ultraspec, Fast RNA, and QIAamp RNA methods, we found (mean ± SD) 1716 ± 1341, 2670 ± 3174, and 24 320 ± 5332 transcripts/mL of blood. Corresponding values were 527 ± 497, 2497 ± 1033, 14 930 ± 1927 transcripts/mL of blood when the cell line JKM86-4 was added. One high-risk patient was followed by repeated analysis of tyrosinase transcripts in blood. The melanoma marker 5-S-cysteinyldopa in serum and urine was within reference values, but tyrosinase mRNA was slightly increased (120–168 transcripts/mL of blood). The tyrosinase mRNA increased to 1860 transcripts/mL concomitant with the increase in 5-S-cysteinyldopa; later a spleen metastasis was found.

Conclusions: The results obtained with different RNA extraction methods illustrate the importance of quantitative methods for validation of methods. The use of QIAamp RNA improved the extraction efficiency considerably. Data from a case study suggest the assay is suitable in the follow-up of patients with high risk of developing metastases.

Place, publisher, year, edition, pages
2000. Vol. 46, no 7, 921-927 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-25119Local ID: 9552OAI: oai:DiVA.org:liu-25119DiVA: diva2:245445
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2012-10-30
In thesis
1. Quantitative analysis of melanoma transcripts: with emphasis on methodological and biological variation
Open this publication in new window or tab >>Quantitative analysis of melanoma transcripts: with emphasis on methodological and biological variation
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The introduction of RT-PCR made it possible to detect circulating tumor cells in melanoma patients by analysis of melanoma-associated transcripts, especially tyrosinase. Since the development of the first PCR method for tyrosinase mRNA, several studies have presented varying results. In the present thesis I have developed and used quantitative PCR methods in order to evaluate methodological and biological factors which may explain the disparity in the literature.

Two methods were developed for tyrosinase, one competitive PCR and one real-time PCR method. With the real-time PCR technique, quantitative methods were also developed for tyrosinase related protein (TRP)-1, TRP-2, MART-1/Melan-A, S-100, GD2 synthase, MAGE-A3 and MAGE-A12. Methodological studies on the RNA extraction showed that the silica based RNA extraction method QIAamp gave considerably higher yields compared with the phenol-chloroform based extraction methods Ultraspec and FastRNA. Further studies showed that yields comparable with the QIAamp method could be obtained with the mRNA extraction method GenoPrep. Optimization of the cDNA synthesis procedure revealed that the reverse transcriptase and factors in the RNA sample inhibited the following PCR. This was avoided by diluting the cDNA sample before PCR.

The stability of the tumor cell RNA in the samples is of great concern when it comes to transporting samples from distant hospitals to the laboratory. It was found that blood collected in ACD was best, although insufficiently, stabilized when stored at +4 °C compared with room temperature. Similar stability was also obtained for PAXgene tubes stored at room temperature, however the stability of RNA was much improved when the PAXgene tubes were frozen.

Studies on the biological variation in cultured melanoma cell lines and tissue sections from melanoma metastases showed that the expression of melanoma associated transcripts varied widely. In melanoma cell lines the expression of the transcripts tyrosinase, TRP-1, TRP-2 and MART-1/Melan-A was related to the pigmentation of the cell lines. The pigment-related transcripts and S-100 were expressed at higher levels than GD2 synthase, MAGE-A3 and MAGE-A12 in the melanoma metastases. The expressions of TRP-2 and GD2 synthase appeared to be influenced by therapy. In metastases from patients treated with a combination of cisplatinum, DTIC and interferon-α2b, TRP-2 was expressed at higher levels and GD2 synthase at lower levels compared with untreated patients.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2004. 61 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 843
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-24062 (URN)3621 (Local ID)91-7373-816-6 (ISBN)3621 (Archive number)3621 (OAI)
Public defence
2004-04-07, Aulan, Administrationshuset, Hälsouniversitetet, Linköping, 09:00 (Swedish)
Opponent
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2012-10-30Bibliographically approved

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Johansson, MalinÅrstrand, KerstinKågedal, Bertil

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