Abstract 908
Background
Romidepsin (FK228), a histone deacetylase inhibitor (HDACi), has anti-tumor effects against several types of solid tumors. Studies have suggested that HDACi could upregulate PD-L1 expression in tumor cells, changing the state of anti-tumor immune responses. However, the influence of enhanced PD-L1 expression in tumor cells induced by romidepsin on anti-tumor immune responses are still under debate. So, the purpose of this study was to explore the anti-tumor effects and influence on immune responses of romidepsin in colon cancer.
Methods
The effects of romidepsin on proliferation, cell cycle and apoptosis in the murine colon cancer cell lines CT26 and MC38 were evaluated. PD-L1 expression levels were examined before and after treatment with romidepsin. To analyze the mechanisms through which romidepsin regulates PD-L1 expression, the acetylation of histones H3 and H4 and transcription factor BRD4 was measured. The influence of romidepsin on FOXP3+ regulatory T cells (Tregs), Th1/Th2 balance and IFN-γ+CD8+ T cells was evaluated in a subcutaneous transplanted tumor model and a colitis-associated cancer (CAC) model.
Results
The results indicated that romidepsin inhibited proliferation, induced G0/G1 cell cycle arrest and increased apoptosis in CT26 and MC38 cells. Romidepsin treatment increased PD-L1 expression in CT26 and MC38 cells via increasing the acetylation levels of histones H3 and H4 and regulating the transcription factor BRD4. In subcutaneous transplant tumor mice and CAC mice, romidepsin increased the percentage of FOXP3+ Tregs, decreased the ratio of Th1/Th2 cells and decreased the percentage of IFN-γ+CD8+ T cells in the peripheral blood and the tumor microenvironment. Upon combination with an anti-PD-1 antibody, the anti-tumor effects were enhanced, and the influence on CD4+ and CD8+ T cells was partially reversed.
Conclusions
Although romidepsin had direct anti-tumor effects in murine colon cancer, it increased PD-L1 expression in tumor cells and the percentage of immune-suppressive cells. Combination with anti-PD-1 antibody augmented the anti-tumor effects by reversing the influence of romidepsin on immune cells.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The author.
Funding
National Natural Science Foundation of China.
Disclosure
The author has declared no conflicts of interest.
Resources from the same session
1619 - Meta-analysis of KRAS Mutation as prognostic factor in patients (pts.) with resection of colorectal (CRC) liver metastases: Tumor burden and Sideness analysis.
Presenter: Maria Romina Luca
Session: Poster Display session 2
Resources:
Abstract
2104 - Clinical implications of regorafenib-induced hypothyroidism in metastatic colorectal cancer refractory to standard therapies: A prospective evaluation
Presenter: Jwa Hoon Kim
Session: Poster Display session 2
Resources:
Abstract
2143 - Clinical impact of BRAF V600E mutations in patients (pts) with resectable solitary colorectal liver metastases (CRLM)
Presenter: Shin Kobayashi
Session: Poster Display session 2
Resources:
Abstract
3136 - Trifluridine/tipiracil in metastatic colorectal cancer: an updated multicentre real-world analysis on efficacy, safety and predictive factors.
Presenter: Chara Stavraka
Session: Poster Display session 2
Resources:
Abstract
4234 - Correlation between p53 expression and clinical outcome in RAS/BRAF wild type metastatic colorectal cancer patients receiving later-line irinotecan-cetuximab
Presenter: Eleonora Lai
Session: Poster Display session 2
Resources:
Abstract
4287 - Safety and effectiveness of aflibercept + FOLFIRI for the treatment of patients with metastatic colorectal cancer (mCRC): OZONE secondary analyses
Presenter: Ian Chau
Session: Poster Display session 2
Resources:
Abstract
1820 - A Phase Ib study of the safety and efficacy of atezolizumab (atezo) + bevacizumab (bev) + cobimetinib (cobi) in patients (pts) with metastatic colorectal cancer (mCRC)
Presenter: Johanna Bendell
Session: Poster Display session 2
Resources:
Abstract
5644 - Development and validation of a metastasis-associated immune prognostic model for concurrent metastatic colorectal cancer
Presenter: Zhiwen Luo
Session: Poster Display session 2
Resources:
Abstract
5697 - Prognostic role of blood cell count-based immuno-inflammatory parameters in the Valentino trial
Presenter: Giovanni Fuca
Session: Poster Display session 2
Resources:
Abstract
4704 - Evaluation of safety, immunogenicity and preliminary efficacy of PolyPEPI1018 vaccine in subjects with metastatic colorectal cancer (mCRC) with a predictive biomarker
Presenter: Joleen Hubbard
Session: Poster Display session 2
Resources:
Abstract