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Targeting JARID1B's demethylase activity blocks a subset of its functions in oral cancer
Nicole D Facompre1, Kayla M Harmeyer1, Varun Sahu1
1Department of Otorhinolaryngology, Head and Neck Surgery, The University of Pennsylvania, Philadelphia, PA, USA.
Abstract:
Upregulation of the H3K4me3 demethylase JARID1B is linked to acquisition of aggressive, stem cell-like features by many cancer types. However, the utility of emerging JARID1 family inhibitors remains uncertain, in part because JARID1B's functions in normal development and malignancy are diverse and highly context-specific. In this study, responses of oral squamous cell carcinomas (OSCCs) to catalytic inhibition of JARID1B were assessed using CPI-455, the first tool compound with true JARID1 family selectivity. CPI-455 attenuated clonal sphere and tumor formation by stem-like cells that highly express JARID1B while also depleting the CD44-positive and Aldefluor-high fractions conventionally used to designate OSCC stem cells. Silencing JARID1B abrogated CPI-455's effects on sphere formation, supporting that the drug acted through this isoform. To further delineate CPI-455's capacity to block JARID1B's functions, its biologic effects were compared against those indicated by pathway analysis of the transcriptional profile produced by JARID1B knockdown. Downregulation of multiple gene sets related to stem cell function was consistent with the drug's observed actions. However, strong E-Cadherin upregulation seen upon silencing JARID1B surprisingly could not be reproduced using CPI-455. Expressing a demethylase-inactive mutant of JARID1B demonstrated suppression of this transcript to be demethylase-independent, and the capacity of mutant JARID1B but not CPI-455 to modulate invasion provided a functional correlate of this finding. These results show that JARID1B catalytic inhibition effectively targets some stem cell-like features of malignancy but also reveal demethylase-independent actions refractory to inhibition. Future application of JARID1 inhibitors in combinatorial use for cancer therapy may be guided by these findings.
Insights
JARID1B inhibition targets cancer stem cell traits in oral squamous cell carcinoma. However, some JARID1B functions, like E-Cadherin regulation, are independent of its demethylase activity and unaffected by inhibitors.
Area of Science:
- Oncology
- Epigenetics
- Cancer Stem Cell Biology
Background:
- JARID1B, an H3K4me3 demethylase, is upregulated in aggressive cancers, promoting stem cell-like features.
- The therapeutic utility of JARID1 family inhibitors is unclear due to JARID1B's context-specific roles.
Purpose of the Study:
- To assess the effects of JARID1B catalytic inhibition on oral squamous cell carcinoma (OSCC) using the selective inhibitor CPI-455.
- To differentiate between demethylase-dependent and -independent functions of JARID1B in OSCC.
Main Methods:
- Utilized CPI-455, a selective JARID1 family inhibitor, to treat OSCC cells.
- Assessed effects on stem-like cell populations (CD44-positive, Aldefluor-high) and clonal formation.
- Performed JARID1B knockdown and analyzed transcriptional profiles.
- Compared CPI-455 effects with JARID1B knockdown and utilized a demethylase-inactive JARID1B mutant.
Main Results:
- CPI-455 reduced sphere and tumor formation in stem-like OSCC cells expressing JARID1B.
- JARID1B silencing confirmed the drug's on-target effects on sphere formation.
- Transcriptional analysis revealed downregulation of stem cell-related gene sets by CPI-455.
- CPI-455 did not replicate E-Cadherin upregulation observed upon JARID1B silencing, indicating a demethylase-independent function.
Conclusions:
- JARID1B catalytic inhibition effectively targets certain cancer stem cell properties in OSCC.
- JARID1B possesses demethylase-independent functions in OSCC, such as E-Cadherin regulation, which are not targeted by current inhibitors.
- Findings guide the potential use of JARID1 inhibitors in combination cancer therapy.