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Retinoblastoma. Interphotoreceptor retinoid binding protein mRNA analysis by polymerase chain reaction
S Rajagopalan1, M M Rodrigues, B Wiggert
1Laboratory of Ophthalmic Pathology, University of Maryland, Baltimore.
Abstract:
The authors used the polymerase chain reaction (PCR) to detect the mRNA for interphotoreceptor retinoid-binding protein (IRBP/RBP3), a photoreceptor specific protein, in small samples. They carried out these experiments to assess the feasibility of applying this technique to small tumor samples. Surgically excised tumor samples from four enucleations were analyzed. Messenger RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction was followed by phenol-chloroform purification, reverse-transcription and amplification. The primers used were 5' TGATGACTCTGTCAGTG 3' in exon 3 (sense) and 5' TTGTGCTGGAGCATCTC 3' in exon 4 (antisense). Controls included an IRBP cDNA pIRBP 20-700 and RNA from normal human retina. All samples amplified the same size band if detected. Three tumor samples contained IRBP mRNA as indicated by amplified 234 bp band. These three samples showed a high IRBP protein level by slot blot and RNA for IRBP detected by northern blot. Hematoxylin-eosin staining of one of these samples revealed a well differentiated tumor with numerous Flexner-Wintersteiner rosettes. In the fourth tumor, a poorly differentiated neoplasm, no IRBP mRNA was detected. The authors' results showed a qualitative variation of IRBP mRNA levels, usually related to the histologic differentiation, with IRBP expressed in well differentiated tumors as well as in the normal human retina in contrast to a poorly differentiated tumor with no detectable IRBP. The feasibility of the reverse transcriptase-PCR (RT-PCR) technique to detect IRBP mRNA in small retinoblastoma tumors, was demonstrated.
Insights
Reverse transcriptase-polymerase chain reaction (RT-PCR) successfully detected interphotoreceptor retinoid-binding protein (IRBP) mRNA in small retinoblastoma tumor samples. IRBP mRNA levels correlated with tumor differentiation, being present in well-differentiated tumors but absent in poorly differentiated ones.
Area of Science:
- Ophthalmology
- Molecular Biology
- Oncology
Background:
- Interphotoreceptor retinoid-binding protein (IRBP/RBP3) is a photoreceptor-specific protein.
- Assessing IRBP mRNA in small tumor samples is crucial for understanding retinoblastoma.
- Polymerase chain reaction (PCR) offers potential for detecting specific mRNA in limited tissue.
Purpose of the Study:
- To evaluate the feasibility of using reverse transcriptase-polymerase chain reaction (RT-PCR) to detect IRBP mRNA in small retinoblastoma samples.
- To correlate IRBP mRNA expression with histological differentiation in retinoblastoma tumors.
- To assess the utility of RT-PCR for molecular diagnostics in ocular oncology.
Main Methods:
- Messenger RNA (mRNA) was isolated from four surgically excised retinoblastoma tumor samples.
- RT-PCR was performed using specific primers targeting IRBP mRNA.
- Controls included IRBP cDNA and normal human retina RNA; results were validated by slot blot and northern blot.
Main Results:
- Three out of four retinoblastoma samples showed detectable IRBP mRNA via a 234 bp amplified band.
- These three samples also exhibited high IRBP protein levels and were histologically well-differentiated.
- The fourth sample, a poorly differentiated tumor, lacked detectable IRBP mRNA.
Conclusions:
- RT-PCR is a feasible technique for detecting IRBP mRNA in small retinoblastoma samples.
- IRBP expression in retinoblastoma correlates with histological differentiation.
- This method holds promise for molecular analysis of small tumor biopsies in ophthalmology.