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Gail M Seigel, Dhavalkumar Shah, Pia Mendoza, Hans E Grossniklaus, Yinghui Song, Jidong Shan; Her2 expression in retinoblastoma and adjacent "normal" retina detected by in situ hybridization. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2318. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Retinoblastoma (RB) is a potentially blinding ocular malignancy of early childhood. Recent emphasis has been on vision-preserving chemotherapy treatments that spare the eye and preserve visual function, but may also spare chemoresistant tumor cells. One potential therapeutic target for RB is HER2, (ERBB2), a member of the epidermal growth factor family that is expressed in RB cell lines and tumors, as we have shown previously. Since RB appears to express a truncated form of the HER2 protein, questions have persisted regarding Her2 expression in situ. To address this issue, we tested the hypothesis that Her2 DNA and RNA are expressed in human RB tumors in situ.
We examined 24 different cases of paraffin-embedded human RB tumors (Groups B-D; TNM Stages T1-T4), along with normal adjacent retinal tissues (and control tissues) for Her2 expression by fluorescent and colorimetric in situ hybridization (FISH and CISH). The FISH method utilized a Her2 BAC clone, with Spectrum orange (552 nm) and Aqua (415 nm) for immunofluorescence detection of Her2 DNA. For the CISH method, we employed a highly specific RNAScope Fast Red kit (Advanced Cell Diagnostics) and Her2/Erbb2 human probe to detect Her2 RNA.
A total of 21/22 RB tumors expressed some Her2 DNA detected by FISH and 14/19 tumors expressed some Her2 RNA as detected by CISH. In 17 paired RB cases tested for both FISH and CISH, there were three cases in which Her2 DNA was detected, but not RNA. Interestingly, we also saw Her2 RNA signal in six separate cases of “normal” adjacent retinal tissue, particularly in the inner nuclear and outer nuclear layers.
Our results with both FISH (DNA) and CISH (RNA) show that Her2 (Erbb2) is expressed not only in many RB tumors, but also in some adjacent "normal" retinal tissues. The expression of Her2 in both tumor and adjacent retina may have implications for RB tumor progression, as well as drug targeting approaches designed to spare the eye, preserve vision and improve quality of life for RB patients.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Her2 RNA detected in retinal tissue adjacent to retinoblastoma tumor by RNAScope colorimetric in situ hybridization (CISH). Red dots indicate Her2 signals. ONL= outer nuclear layer; INL = inner nuclear layer.
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