47P - miR-18a and miR-18b expression in ERα negative breast cancers by chromogenic in situ hybridization (CISH)
|Date||08 May 2014|
|Session||Welcome reception and Poster Walk|
|Topics|| Breast Cancer
|Citation||Annals of Oncology (2014) 25 (suppl_1): i8-i16. 10.1093/annonc/mdu066|
K. Jonsdottir, N.G. Egeland, I. Skaland, E. Gudlaugsson, J.P.A. Baak, E. Janssen
Our previous results showed that miR-18a and miR-18b were strongly associated to proliferation and inversely correlated to the expression of oestrogen receptor alpha (ERα) in 204 lymph node-negative breast cancer tumours As proliferation and ERα- expression have great impact on tumour development and progression, further investigation of these microRNAs is warranted. Our previous results were obtained through analysing total RNA isolated from both fresh frozen and formalin fixed paraffin embedded material. By using in situ hybridization with LNA microRNA probes we want to investigate which cells show expression of miR-18a and miR-18b.
The expression of miR-18a and miR-18b were analysed by using in situ hybridization with LNA microRNA probes in 20 Erα-positive and 20 Erα-negative breast cancer tumours. For identification of the cells that express miR-18a and miR18b, parallel sections were stained by immunohistochemistry with antibodies for actin, CD4, CD8, CD20, CD68, CD138 and PAX-5.
Independent T-test showed that miR-18a and miR-18b were significantly higher expressed in Erα-negative breast cancer tumours than Erα-positive tumours, as seen by in situ hybridization. Furthermore, in situ hybridization showed that miR-18a and miR-18b were expressed only in the stroma near the tumour cells or the stroma in the tumour. Little or no expression was found in the tumour cells or outside the tumour area. Immunohistochemistry staining for CD20 and CD68, showed similar patterns as miR-18a and miR18b, but without full overlap with the microRNAs.
This study confirms our previous results that the expression of miR-18a and miR-18b are strongly associated to ERα expression. Expression of these microRNAs was mostly shown in the tumour stroma. The amount of infiltrating leucocytes in ERα -egative tumours might explain the higher level of expression of both microRNAs. On the other hand, none of the antibodies used could identify or correlated with the cell-type that shows the expression for these microRNAs, so the question still remains whether these cells are leucocytes or tumour-associated fibroblasts.
All authors have declared no conflicts of interest.