Downregulation of FTL decreases proliferation of malignant mesothelioma cells by inducing G1 cell cycle arrest

Our plain-English summary of Downregulation of FTL decreases proliferation of malignant mesothelioma cells by inducing G1 cell cycle arrest, by T. Kambara, V.J. Amatya, K. Kushitani, et al (Oncology Letters, 2022).

The study

• Authors: T. Kambara, V.J. Amatya, K. Kushitani, Y. Fujii, I. Endo, Y. Takeshima
• Journal: Oncology Letters
• Published: 2022;23(6):174
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Pleural malignant mesothelioma is a malignant tumor with a poor prognosis that is strongly associated with asbestos exposure during its development. Because there is no adequate treatment for malignant mesothelioma, investigation of its molecular mechanism is important. The ferritin light chain (FTL) is a subunit of ferritin, and its high expression in malignant tumors, including malignant mesothelioma, has recently been reported; however, its role in malignant mesothelioma is unclear. The purpose of the present study was to clarify the function of FTL in malignant mesothelioma. The expression levels of FTL in malignant mesothelioma were examined using the Cancer Cell Line Encyclopedia database and our previous data. The short interfering (si)RNA against FTL was transfected into two mesothelioma cell lines, ACC-MESO-1 and CRL-5915, and functional analysis was performed. Expression of p21, p27, cyclin-dependent kinase 2 (CDK2) and phosphorylated retinoblastoma protein (pRb) associated with the cell cycle were examined as candidate genes associated with FTL. The expression levels of the FTL mRNA were higher in malignant mesothelioma compared with other tumors in the Cancer Cell Line Encyclopedia database, and among other genes in our previous study. Reverse transcription-quantitative PCR and western blotting demonstrated suppression of FTL expression in two cell lines transfected with FTL siRNA compared with cells transfected with negative control (NC) siRNA. In the two cell lines transfected with FTL siRNA, proliferation was significantly suppressed, and cell cycle arrest was observed in the G1 phase. The levels of p21 and p27 were increased, while those of CDK2 and pRb were decreased compared with NC. However, no significant differences in invasion and migration ability were revealed between FTL siRNA-transfected cells and NC. In conclusion, FTL may increase the proliferative capacity of malignant mesothelioma cells by affecting p21, p27, CDK2 and pRb, and promoting the cell cycle at the G1 phase.

Copyright: © Kambara et al.

In plain English

This laboratory study used mesothelioma cells grown in culture; it did not examine asbestos exposure or test patients. The authors examined a gene called ferritin light chain (FTL). Public cell-line databases showed higher FTL mRNA expression in mesothelioma than in other cancers. The authors' earlier gene data from six epithelioid mesotheliomas and six lung adenocarcinomas showed high FTL in both. They then lowered FTL in two mesothelioma cell lines, ACC-MESO-1 and CRL-5915, and compared them with control cells. FTL protein fell by 85% and 87%. Growth fell by 11.0% at 48 hours and 19.5% at 72 hours in ACC-MESO-1, and by 4.02% and 8.96% in CRL-5915. More cells stalled in an early growth phase (G1): from 65.6 to 76.4% and from 65.3 to 93.9%. The cell-cycle proteins p21 and p27 rose; CDK2 and pRb fell. Invasion, migration, apoptosis and necrosis did not change significantly. The authors concluded that FTL increases mesothelioma cell proliferation through the cell cycle and expected it to become a treatment target or diagnostic marker. They noted that only epithelioid cell lines were used and that no animal experiments were done.

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 experiment, together with analysis of public gene-expression databases and a reanalysis of the authors' earlier gene-expression data
• Who was studied: Two human mesothelioma cell lines: ACC-MESO-1 (from RIKEN BioResearch Center, Japan) and CRL-5915 (from the American Type Culture Collection). The study also used the Cancer Cell Line Encyclopedia and DepMap Portal databases, and the authors' earlier gene-expression data from six epithelioid mesotheliomas and six lung adenocarcinomas.
• Exposure: No asbestos exposure was studied. The cells were treated with short interfering RNA (siRNA) that lowers FTL, and were compared with cells given a negative control siRNA.
• Main results:
  • In the Cancer Cell Line Encyclopedia database, FTL mRNA expression was higher in mesothelioma than in other malignant tumors.
  • In the reanalysis of the authors' earlier data, the six lung adenocarcinomas also showed high FTL mRNA expression, as the six epithelioid mesotheliomas did.
  • Compared with control cells, FTL siRNA lowered FTL mRNA by 75.5% in ACC-MESO-1 and 98.2% in CRL-5915. It lowered FTL protein by 85% in ACC-MESO-1 and 87% in CRL-5915.
  • Compared with control cells, proliferation of ACC-MESO-1 cells fell by 11.0% at 48 hours and 19.5% at 72 hours. Proliferation of CRL-5915 cells fell by 4.02% at 48 hours and 8.96% at 72 hours.
  • Compared with control cells, the share of cells in the G1 phase of the cell cycle rose from 65.6 to 76.4% in ACC-MESO-1 and from 65.3 to 93.9% in CRL-5915.
  • Compared with control cells, p21 increased by 113% in ACC-MESO-1 and 37% in CRL-5915, and p27 increased by 148% and 74%. CDK2 decreased by 48% and 60%, and pRb decreased by 29% and 50%, in the same order of cell lines.
  • Lowering FTL had no significant effect on invasion, migration, apoptosis or necrosis in either cell line.
• The authors' conclusion: The authors concluded that FTL increases proliferation of malignant mesothelioma cells by suppressing p21 and p27, and through effects on CDK2 and Rb that promote the cell cycle. They stated that FTL is expected to be a new therapeutic target or diagnostic marker, and that further investigation is required. The abstract states this more cautiously, saying FTL "may" increase proliferative capacity.
• Limitations the authors state:
  • The experiments used epithelioid mesothelioma cell lines. The authors said the function of FTL in sarcomatoid and biphasic mesothelioma is worth examining.
  • The work was done only in cell culture. The authors said in vivo experiments would be needed to see whether FTL acts the same way in living organisms.

Topics

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Prognosis, Asbestos Exposure, Ferritin, Mesothelioma.

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