Aims To analyse microRNA (miR)-21 distribution and expression at the cellular level in non-small cell lung cancer (NSCLC). MiR-21 is an oncogenic microRNA overexpressed in NSCLC. In previous studies, overexpression of miR-21 was evaluated from the tumour bulk by quantitative reverse transcription PCR with results expressed on average across the entire cell population.
Methods We used in situ hybridisation and immunohistochemistry to assess the correlation between miR-21 levels and the expression of markers that may be possible targets (epidermal growth factor reaction) or may be involved in its upregulation (phosphatase and tensin homolog (PTEN), p53). The Pearson’s χ2 tests was used to assess correlation with clinicopathological data and with miR-21 expression both in tumour and tumour stroma.
Results Cytoplasmic staining and expression of Mir-21 were detected in the tumours and in associated stromal cells. Expression was highest in the stroma immediately surrounding the tumour cells and decreased as the distance from the tumour increased. No expression of miR-21 was found in normal lung parenchyma and a significant association was found between tumour localised miR-21 and PTEN.
Conclusions Presence of miR-21 in both cell tumour and stromal compartments of NSCLC and the relationship with PTEN confirms miR-21 as a microenvironment signalling molecule, possibly inducing epithelial mesenchymal transition and invasion by targeting PTEN in the stromal compartment possibly through exosomal transport. In situ immunohistochemical studies such as ours may help shed light on the complex interactions between miRNAs and its role in NSCLC biology.
- lung cancer
- in situ hybridisation
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Handling editor Runjan Chetty.
IM, EO and JB contributed equally.
Contributors All authors contributed substantially either to the conception or design of the work; or to the acquisition, analysis or interpretation of data for the work; they also helped either draft the work or revised it critically for important intellectual content; they gave their final approval of the version to be published and they agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Pr Barshack and Pr Katz supervised equally.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The study was approved by the Human Investigations (Helsinki) Committee of the Sheba Medical Center.
Provenance and peer review Not commissioned; internally peer reviewed.
Data availability statement Data are available upon reasonable request: All data relevant to the study are included in the article or uploaded as supplementary information.