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Because of recent advances in the molecular diagnosis of cancer patients, tissue quality has become more important in daily practice.
To evaluate the effects of fixative, duration of fixation, decalcification, and storage periods on nucleic acid integrity, DNA and RNA were extracted from gastrointestinal cancer tissue. The yield and purity were analyzed, and polymerase chain reaction (PCR) for glyceraldehyde 3-phosphate dehydrogenase (GAPDH; 60 bp), β-actin (148 bp), and human growth hormone (hGH; 434 bp) and real-time reverse transcription-PCR for β-actin (97 bp) were performed.
All formalin-fixed paraffin-embedded (FFPE) and methacarn-fixed paraffin-embedded (MFPE) samples tested positive for GAPDH and β-actin by PCR. hGH was successfully detected in all MFPE samples, but in only 46.7% of the FFPE samples. Prolonged formalin fixation resulted in fewer GAPDH and β-actin PCR products, and amplification of hGH was not successful. The PCR and reverse transcription-PCR results were significantly affected by the duration of decalcification. The yield, purity, and integrity of mRNA progressively decreased with increased storage periods of paraffin blocks.
Fixation and storage should therefore be standardized in order to improve the quality of molecular pathologic diagnosis.
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Glioblastomas may develop
We evaluated the immunohistochemical expression of epidermal growth factor receptor (EGFR), p53, and isocitrate dehydrogenase 1 (IDH-1) in 150 glioblastoma cases.
According to clinical history, the glioblastomas analyzed in this study consisted of 146 P-GBLs and 4 S-GBLs. Immunohistochemical expression of EGFR, p53, and IDH-1 was observed in 62.6%, 49.3%, and 11.1%, respectively. Immunohistochemical profiles of EGFR(+)/p53(-), IDH-1(-)/EGFR(+)/p53(-), and EGFR(-)/p53(+) were noted in 41.3%, 40.2%, and 28.7%, respectively. Expression of IDH-1 and EGFR(-)/p53(+) was positively correlated with young age. The typical immunohistochemical features of S-GBLs comprised IDH-1(+)/EGFR(-)/p53(+), and were noted in 3.6% of clinically P-GBLs. The combination of IDH-1(-) or EGFR(+) was the best set of immunohistochemical stains for identifying P-GBLs, whereas the combination of IDH-1(+) and EGFR(-) was best for identifying S-GBLs.
We recommend a combination of IDH-1 and EGFR for immunohistochemical classification of glioblastomas. We expect our results to be useful for determining treatment strategies for glioblastoma patients.
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