Targeting ROR1 in combination with pemetrexed in malignant mesothelioma cells

Our plain-English summary of Targeting ROR1 in combination with pemetrexed in malignant mesothelioma cells, by N. Miyake, N. Ochi, H. Yamane, et al (Lung Cancer, 2020).

The study

• Authors: N. Miyake, N. Ochi, H. Yamane, T. Fukazawa, T. Ikeda, E. Yokota, M. Takeyama, N. Nakagawa, H. Nakanishi, H. Kohara, Y. Nagasaki, T. Kawahara, N. Ichiyama, T. Yamatsuji, Y. Naomoto, N. Takigawa
• Journal: Lung Cancer
• Published: 2020;139:170-178
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is overexpressed in a subset of malignant cells. However, it remains unknown whether ROR1 is targetable in malignant mesothelioma (MM). Therefore, in this study, we investigated the effects of ROR1 inhibition in mesothelioma cells.

Materials And Methods: Growth inhibition, colony formation, apoptosis, and mRNA/protein levels using siRNA-transfected MM cells were evaluated. Cluster analysis using Gene Expression Omnibus repository of transcriptomic information was also performed.

Results: Our results indicated that in three (H2052, H2452, and MESO-1) among four MM cell lines, ROR1 inhibition had anti-proliferative and apoptotic effects and suppressed the activation of AKT and STAT3. Although growth inhibition by siROR1 was minimal in another mesothelioma cell line (H28), colony formation was significantly suppressed. Microarray, quantitative polymerase chain reaction, and Western blot analyses showed that there were differences in the suppression of mRNA and proteins between H2452 and H28 cells transfected with siROR1 compared with those transfected with control siRNA. Cluster analysis further showed that MM tumors had relatively high ROR1 expression, although the cluster in them was different from that in MM cell lines. Thymidylate synthase, a target of pemetrexed, was downregulated in H2452 cells transfected with siROR1. Accordingly, a combination of pemetrexed with siROR1 was found to be effective in the three MM cell lines we studied.

Conclusion: Our findings may provide novel therapeutic insight into the treatment of advanced MM.

Copyright © 2019 Elsevier B.V. All rights reserved.

In plain English

This was a laboratory study of human malignant mesothelioma cells grown in dishes. No patients were treated. The authors used small interfering RNA (siRNA) to lower levels of ROR1, a protein found in some cancers, in four mesothelioma cell lines (H2052, H2452, MESO-1 and H28). They also analysed a public gene-expression dataset that included 40 surgically removed mesothelioma tumors. Lowering ROR1 significantly reduced cell numbers, although H28 cells responded poorly. It also significantly reduced colony formation in all four lines. Apoptosis (programmed cell death) increased in H2052, H2452 and MESO-1 cells but was not confirmed in H28 cells. Lowering ROR1 reduced thymidylate synthase (TYMS), a target of the chemotherapy drug pemetrexed, in H2452 and H28 cells. Some pemetrexed concentrations combined with ROR1 reduction lowered cell viability significantly more than pemetrexed with a control siRNA. Response to cisplatin in H2452 cells did not change. In the dataset, the tumors had relatively high ROR1. The authors concluded that suppressing ROR1 increased mesothelioma cells' sensitivity to pemetrexed. They noted that they did no animal experiments.

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) cell-line experiments, plus a cluster analysis of a public gene-expression dataset
• Who was studied: Four human malignant mesothelioma cell lines: H2452, H2052 and H28 from the American Type Culture Collection, and ACC-MESO-1 from RIKEN. The public dataset (GSE2549) included 40 surgically resected mesothelioma tumors, 4 normal lung specimens, 5 normal pleura specimens and 5 cell lines.
• Exposure: Not an asbestos exposure study. Cells were treated with siRNA targeting ROR1 (10 to 40 nM) or a control siRNA, alone or combined with the chemotherapy drugs pemetrexed or cisplatin.
• Main results:
  • Lowering ROR1 significantly reduced cell numbers. H28 cells responded poorly compared with the other cell lines.
  • Colony formation was significantly suppressed in all cell lines. The MESO-1 line showed at most a 20% reduction. H28 colonies were reduced by about half by siROR1#1.
  • Apoptosis increased in H2052, H2452 and MESO-1 cells. It was not confirmed in H28 cells.
  • Activated AKT and STAT3 (cell-survival signalling proteins) were reduced in H2052, H2452 and MESO-1 cells. They were unchanged in H28 cells.
  • TYMS (thymidylate synthase, a pemetrexed target) mRNA was significantly reduced in both H2452 and H28 cells after ROR1 knockdown. TYMS protein was also reduced in both lines.
  • Several pemetrexed concentrations combined with siROR1#1 significantly reduced cell viability compared with pemetrexed plus control siRNA. The IC50 of pemetrexed fell from 16.8 to 0.15. The unit symbol is lost in the text, and the cell line for this figure is not stated.
  • In H2452 cells, lowering ROR1 did not change the growth suppression caused by cisplatin.
  • In the cluster analysis, mesothelioma tumor specimens had relatively high ROR1 with variable TYMS. The cell lines had high TYMS with comparatively low ROR1.
• The authors' conclusion: The authors concluded that TYMS seems to be downregulated when ROR1 is suppressed, at least in mesothelioma cell lines, and that this increased the cells' sensitivity to pemetrexed. They said this may give therapeutic insight for mesothelioma.
• Limitations the authors state:
  • No experiments in living animals (in vivo) were performed.
  • The effect of reducing ROR1 may differ between H2452 and H28 cells.
  • Microarray results for TYMS were inconsistent with the RT-PCR and Western blot results. The two microarrays were run on different platforms at different times (2013 and 2017).
  • The authors judged the growth inhibition from ROR1 knockdown alone not satisfactory.

Topics

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

Medical terms in this study, explained in our Lexicon: Pemetrexed (Alimta), Malignant Mesothelioma, Mesothelioma, Apoptosis.

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