Essential role of the histone lysine demethylase KDM4A in the biology of malignant pleural mesothelioma (MPM)

Our plain-English summary of Essential role of the histone lysine demethylase KDM4A in the biology of malignant pleural mesothelioma (MPM), by M. Lapidot, A.E. Case, E.L. Weisberg, et al (British Journal of Cancer, 2021).

The study

• Authors: M. Lapidot, A.E. Case, E.L. Weisberg, C. Meng, S.R. Walker, S. Garg, W. Ni, K. Podar, Y.P. Hung, R.D. Carrasco, A. Knott, P.C. Gokhale, S. Sharma, A. Pozhitkov, P. Kulkarni, D.A. Frank, R. Salgia, J.D. Griffin, S.V. Saladi, R. Bueno, M. Sattler
• Journal: British Journal of Cancer
• Published: 2021;125(4):582-592
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Malignant pleural mesothelioma (MPM) is a highly aggressive cancer with a dismal prognosis. There is increasing interest in targeting chromatin regulatory pathways in difficult-to-treat cancers. In preliminary studies, we found that KDM4A (lysine-specific histone demethylase 4) was overexpressed in MPM.

Methods: KDM4A protein expression was determined by immunohistochemistry or immunoblotting. Functional inhibition of KDM4A by targeted knockdown and small molecule drugs was correlated to cell growth using cell lines and a xenograft mouse model. Gene expression profiling was performed to identify KDM4A-dependent signature pathways.

Results: Levels of KDM4A were found to be significantly elevated in MPM patients compared to normal mesothelial tissue. Inhibiting the enzyme activity efficiently reduced cell growth in vitro and reduced tumour growth in vivo. KDM4A inhibitor-induced apoptosis was further enhanced by the BH3 mimetic navitoclax. KDM4A expression was associated with pathways involved in cell growth and DNA repair. Interestingly, inhibitors of the DNA damage and replication checkpoint regulators CHK1 (prexasertib) and WEE1 (adavosertib) within the DNA double-strand break repair pathway, cooperated in the inhibition of cell growth.

Conclusions: The results establish a novel and essential role for KDM4A in growth in preclinical models of MPM and identify potential therapeutic approaches to target KDM4A-dependent vulnerabilities.

© 2021. The Author(s).

In plain English

This was a laboratory study; asbestos was mentioned only as background. The authors examined a protein called KDM4A in malignant pleural mesothelioma (MPM). KDM4A was found in all 53 MPM tissue samples but not in 8 normal mesothelial samples, which the article describes both as from normal donors and as from MPM donors. In MPM cell lines, lowering KDM4A by genetic knockdown significantly suppressed cell growth. Two experimental KDM4A-blocking drugs reduced MPM cell growth at lower concentrations than they needed in a non-cancerous mesothelial cell line. In mice with implanted MPM tumours, final average tumour volume was 625.1 cubic millimetres in 6 treated mice versus 867.2 in 10 control mice. Two patient-derived cell lines that responded poorly to cisplatin did respond to KDM4A inhibitors. Gene studies linked KDM4A to cell growth and DNA repair pathways. The authors concluded that KDM4A has an essential role in growth in preclinical models of MPM. They noted that highly specific drugs exclusively targeting KDM4A and suitable for clinical trials are not yet available, and that a larger patient group with matching normal tissue should be evaluated.

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 (preclinical) study: tissue staining of patient samples, cell line experiments, and a xenograft mouse experiment
• Who was studied: Tissue microarrays with samples from 53 MPM patients (31 epithelioid, 19 biphasic, 3 sarcomatoid) and 8 normal tissue samples, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Boston. The Methods describe the normal samples as from normal donors, but the Results describe them as normal pleural tissue from MPM donors. The study also used MPM cell lines (MSTO, H28, H2804, H2052), eight patient-derived MPM cell lines (MS1 to MS8), a non-cancerous mesothelial cell line (LP9), and female SCID hairless mice implanted with MSTO cells (6 treated, 10 control).
• Exposure: Asbestos exposure was not studied. The experimental treatments were KDM4A knockdown by RNA interference and the KDM4A inhibitors PKF118–310 and ML324. In some experiments these were compared or combined with cisplatin, pemetrexed, BH3 mimetics (venetoclax, navitoclax, S63845), the CHK1 inhibitor prexasertib and the WEE1 inhibitor adavosertib.
• Main results:
  • In the tissue samples, KDM4A was not detected in the 8 normal mesothelial samples but was found in all 53 MPM samples: weak staining 9.4% (5/53), moderate 52.8% (28/53), strong 37.7% (20/53). The difference was reported as p = 4.74 times 10 to the power of minus 10.
  • KDM4A knockdown significantly suppressed cell growth in the MSTO and H28 cell lines (p < 0.0005) and in patient-derived MPM cells after four days (p < 0.01), compared with control-vector cells.
  • The KDM4A inhibitors were more potent against MPM cell lines than against LP9 control cells. For PKF118–310, IC50 was 0.2–0.7 μM in MPM lines versus 0.9 μM in LP9. For ML324, IC50 was 7.6–17.9 μM in MPM lines versus more than 30 μM in LP9.
  • In the mouse xenograft experiment, tumours in PKF118–310-treated mice (n = 6) were smaller than in vehicle-treated mice (n = 10), with p < 0.03 on days 18 and 23. Final average volume was 625.1 plus or minus 83.4 mm3 in treated mice versus 867.2 plus or minus 52.0 mm3 in control mice. Body weight was not altered.
  • Patient-derived cell lines MS4 and MS8 were insensitive to cisplatin but sensitive to both KDM4A inhibitors.
  • In H28 and MSTO cells, combining ML324 with navitoclax inhibited growth more than either drug alone.
  • Gene expression analysis after KDM4A knockdown in MSTO and H28 cells showed depletion of pathways associated with cell growth or viability and with DNA repair.
  • The WEE1 inhibitor adavosertib and the CHK1 inhibitor prexasertib cooperated in inhibiting growth of MPM cell lines.
• The authors' conclusion: The authors concluded that KDM4A has a novel and essential role in growth in preclinical models of MPM. They also concluded that their findings identify potential therapeutic approaches to target KDM4A-dependent vulnerabilities.
• Limitations the authors state:
  • A larger group of MPM patients with matching normal tissue is needed to judge the extent of the expression differences.
  • Highly specific small molecule drugs that exclusively target KDM4A and are suitable for clinical trials are not yet available.
  • Sensitivity to KDM4A inhibitors differed among cell lines and patient-derived cells, and KDM4A expression alone may not predict response.
  • Differences in drug sensitivity between MPM and control cells were smaller for some models than for others.
  • No control primary mesothelial cells were available for comparison with the patient-derived MPM cell lines.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Prognosis, Immunohistochemistry, Apoptosis.

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