EphrinA1 inhibits malignant mesothelioma tumor growth via let-7 microRNA-mediated repression of the RAS oncogene

Our plain-English summary of EphrinA1 inhibits malignant mesothelioma tumor growth via let-7 microRNA-mediated repression of the RAS oncogene, by N. Khodayari, K.A. Mohammed, E.P. Goldberg, et al (Cancer Gene Therapy, 2011).

The study

• Authors: N. Khodayari, K.A. Mohammed, E.P. Goldberg, N. Nasreen
• Journal: Cancer Gene Therapy
• Published: 2011;18(11):806-16
• Cited by: 41 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

EphrinA1 binding with receptor EphA2 suppresses malignant mesothelioma (MM) growth. The mechanisms whereby EphrinA1 attenuates the MM cell (MMC) growth are not clear. In this study, we report that the activation of MMCs with EphrinA1 leads to an induction of let-7 microRNA (miRNA) expression, repression of RAS proto-oncogene and the attenuation of MM tumor growth. The expression of miRNAs was determined by reverse transcription-quantitative polymerase chain reaction and in situ hybridization. RAS expression was determined by q-PCR, western blotting and immunofluorescence. MMC proliferation and tumor growth were determined by WST-1 and Matrigel assay, respectively. EphrinA1 activation induced several fold increases in let-7a1, let-7a3, let-7f1 and let-7f2 miRNA expression in MMCs. In contrast, EphrinA1 activation significantly downregulated H-RAS, K-RAS and N-RAS expression and inhibited MMC proliferation and tumor growth. In MMCs transfected with 2'-O-methyl antisense oligonucleotides to let-7 miRNA, EphrinA1 activation failed to inhibit the proliferative response and tumor growth. In mismatch antisense oligonucleotide-treated MMCs, the proliferation and tumor growth were comparable to untreated proliferating cells. Furthermore, the transfection of MMCs with let-7a miRNA precursor inhibited RAS expression and attenuated MMC tumor growth. Our data revealed that EphrinA1 signaling induces let-7 miRNA expression and attenuates MM tumor growth by targeting RAS proto-oncogene in MMCs.

In plain English

This was a laboratory study of two human malignant mesothelioma cell lines, CRL-2081 (biphasic) and CRL-5830 (epithelioid), obtained from a cell collection. It did not study patients or asbestos exposure. The authors treated the cells with a laboratory-made form of the protein EphrinA1, which binds a receptor called EphA2. They then measured a small regulatory RNA called let-7, the RAS cancer genes, cell growth, and the growth of tumor colonies in a gel. EphrinA1 treatment raised let-7 levels, with let-7a1 reported as fivefold higher than the other let-7 forms. It also lowered RAS levels and slowed cell and colony growth. When the cells' let-7 was blocked with an antisense molecule, EphrinA1 no longer lowered RAS or slowed cell and colony growth. Adding a let-7a precursor alone lowered RAS protein by about 65% at 50 nM and 88% at 100 nM, and it reduced colony growth. The authors concluded that EphrinA1's tumor-suppressive effect in these cells works through let-7a acting on RAS. They said further studies are needed.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) experiments on cultured human malignant mesothelioma cell lines
• Who was studied: Two commercially obtained human mesothelioma cell lines: CRL-2081 (biphasic, fibroblast morphology) and CRL-5830 (epithelioid, epithelial morphology), from the American Type Culture Collection. No patients were studied.
• Exposure: No asbestos or fiber exposure was studied. Cells were treated with recombinant EphrinA1 (Ephrin-A1/Fc chimera), and some were also given an antisense molecule blocking let-7, a mismatch control, a let-7a precursor, or a scrambled control sequence.
• Main results:
  • EphrinA1 treatment increased let-7 levels compared with untreated control cells.
  • In EphrinA1-treated cells, let-7a1 expression was reported as fivefold higher than the other let-7 forms.
  • EphrinA1 treatment lowered RAS protein in both cell lines, significantly at 24 hours.
  • In cells where let-7 was blocked with the antisense molecule before EphrinA1 treatment, RAS levels were restored to those of unstimulated cells.
  • Blocking let-7 fully restored H-RAS but only partly restored K-RAS and N-RAS.
  • Adding a let-7a precursor lowered RAS protein by about 65% at 50 nM and about 88% at 100 nM.
  • In cells where let-7 was blocked, EphrinA1 no longer reduced cell growth.
  • Cells given the let-7a precursor showed the lowest growth, whether or not they were also given EphrinA1.
  • In the gel colony test, EphrinA1 failed to reduce colony growth in cells where let-7 was blocked.
  • In the MMC1 cell line, the let-7a precursor significantly reduced colony growth. Similar results in MMC2 were reported but not shown.
• The authors' conclusion: The authors concluded that this was the first report showing that EphrinA1's tumor-suppressive properties in mesothelioma cells are due to let-7a expression targeting the RAS oncogene.
• Limitations the authors state:
  • The authors stated that the relationship between EphrinA1 and let-7a signaling needs further study.
  • The authors stated that more work is needed on how EphrinA1 acts against tumors in these cells.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma.

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