Sequential azacitidine and carboplatin induces immune activation in platinum-resistant high-grade serous ovarian cancer cell lines and primes for checkpoint inhibitor immunotherapy

Michelle W Wong-Brown,Andre Van Der Westhuizen,Nikola A Bowden

doi:10.1186/s12885-022-09197-w

Abstract

BackgroundPlatinum chemoresistance results in high-grade serous ovarian cancer (HGSOC) disease recurrence. Recent treatment advances using checkpoint inhibitor immunotherapy has not benefited platinum-resistant HGSOC. In ovarian cancer, DNA methyltransferase inhibitors (DNMTi) block methylation and allow expression of silenced genes, primarily affecting immune reactivation pathways. We aimed to determine the epigenome and transcriptome response to sequential treatment with DNMTi and carboplatin in HGSOC.MethodsIn vitro studies with azacitidine or carboplatin alone and in sequential combination. Response was determined by cell growth, death and apoptosis. Genome-wide DNA methylation levels and transcript expression were compared between untreated and azacitidine and carboplatin sequential treatment.ResultsSequential azacitidine and carboplatin significantly slowed cell growth in 50% of cell lines compared to carboplatin alone. The combination resulted in significantly higher cell death in 25% of cell lines, and significantly higher cell apoptosis in 37.5% of cell lines, than carboplatin alone. Pathway analysis of upregulated transcripts showed that the majority of changes were in immune-related pathways, including those regulating response to checkpoint inhibitors.ConclusionsSequential azacitidine and carboplatin treatment slows cell growth, and demethylate and upregulate pathways involved in immune response, suggesting that this combination may be used to increase HGSOC response to immune checkpoint inhibitors in platinum-resistant patients who have exhausted all currently-approved avenues of treatment.

Highlights

Platinum chemoresistance results in high-grade serous ovarian cancer (HGSOC) disease recurrence
Combination of azacitidine and carboplatin decreases ovarian cancer cell growth Cellular confluence was measured to determine if ovarian cancer cell growth is affected by combined azacitdine and carboplatin
Cells treated with azacitidine or carboplatin only grew at a non-significant slower rate compared to untreated control

Summary

Introduction

Platinum chemoresistance results in high-grade serous ovarian cancer (HGSOC) disease recurrence. DNA methyltransferase inhibitors (DNMTi) block methylation and allow expression of silenced genes, primarily affecting immune reactivation pathways. It is increasingly being recognised that progression to platinum chemoresistance in ovarian cancer is associated with epigenetic changes, including increased DNA methylation and subsequent transcriptional silencing of genes [8]. These alterations affect genes implicated in treatment resistance, such as the DNA repair pathways [9], regulation of cell cycle, and of other genes associated with recognition of chemotherapy damage and apoptotic responses [10, 11]. The results provided evidence that the combination can produce small incremental gains in overall survival, but not enough to be adopted into routine clinical practice [13]

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