Blockage of retinoic acid signaling via RARγ suppressed the proliferation of pancreatic cancer cells by arresting the cell cycle progression of the G1-S phase

Kohei Yamakawa; Michiyo Koyanagi-Aoi; Akihito Machinaga; Nobuyuki Kakiuchi; Tomonori Hirano; Yuzo Kodama; Takashi Aoi

doi:10.1186/s12935-023-02928-4

Blockage of retinoic acid signaling via RARγ suppressed the proliferation of pancreatic cancer cells by arresting the cell cycle progression of the G1-S phase

Cancer Cell Int. 2023 May 17;23(1):94. doi: 10.1186/s12935-023-02928-4.

Authors

Kohei Yamakawa^{1

2

3}, Michiyo Koyanagi-Aoi^{1

2

4}, Akihito Machinaga⁵, Nobuyuki Kakiuchi^{6

7

8}, Tomonori Hirano^{6

7}, Yuzo Kodama³, Takashi Aoi^{9

10

11}

Affiliations

¹ Division of Stem Cell Medicine, Graduate School of Medicine, Kobe University, 7-5-1 Kusunoki-Cho, Chuo-Ku, Kobe, Hyogo, 650-0017, Japan.
² Division of Advanced Medical Science, Graduate School of Science, Technology and Innovation, Kobe University, Kobe, Hyogo, Japan.
³ Division of Gastroenterology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan.
⁴ Center for Human Resource Development for Regenerative Medicine, Kobe University Hospital, Kobe, Hyogo, Japan.
⁵ Oncology Tsukuba Research Department, Discovery, Medicine Creation, DHBL, Eisai Co., Ltd, Tsukuba, Ibaraki, Japan.
⁶ Department of Pathology and Tumour Biology, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, Japan.
⁷ Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, Japan.
⁸ The Hakubi Center for Advanced Research, Kyoto University, Sakyo-ku, Kyoto, Japan.
⁹ Division of Stem Cell Medicine, Graduate School of Medicine, Kobe University, 7-5-1 Kusunoki-Cho, Chuo-Ku, Kobe, Hyogo, 650-0017, Japan. takaaoi@med.kobe-u.ac.jp.
¹⁰ Division of Advanced Medical Science, Graduate School of Science, Technology and Innovation, Kobe University, Kobe, Hyogo, Japan. takaaoi@med.kobe-u.ac.jp.
¹¹ Center for Human Resource Development for Regenerative Medicine, Kobe University Hospital, Kobe, Hyogo, Japan. takaaoi@med.kobe-u.ac.jp.

Abstract

Background: Our study and several studies have reported that in some cancers, including pancreatic ductal adenocarcinoma (PDAC), the expression of squamous lineage markers, such as esophagus-tissue-specific genes, correlated with a poor prognosis. However, the mechanism by which the acquisition of squamous lineage phenotypes leads to a poor prognosis remains unclear. We previously reported that retinoic acid signaling via retinoic acid receptor γ (RARγ signaling) determines the differentiation lineage into the esophageal squamous epithelium. These findings hypothesized that the activation of RARγ signaling contributed to acquiring squamous lineage phenotypes and malignant behavior in PDAC.

Methods: This study utilized public databases and immunostaining of surgical specimens to examine RARγ expression in PDAC. We evaluated the function of RARγ signaling by inhibitors and siRNA knockdown using a PDAC cell line and patient-derived PDAC organoids. The mechanism of the tumor-suppressive effects by blocking RARγ signaling was examined by a cell cycle analysis, apoptosis assays, RNA sequencing and Western blotting.

Results: RARγ expression in pancreatic intraepithelial neoplasia (PanIN) and PDAC was higher than that in the normal pancreatic duct. Its expression correlated with a poor patient prognosis in PDAC. In PDAC cell lines, blockade of RARγ signaling suppressed cell proliferation by inducing cell cycle arrest in the G1 phase without causing apoptosis. We demonstrated that blocking RARγ signaling upregulated p21 and p27 and downregulated many cell cycle genes, including cyclin-dependent kinase 2 (CDK2), CDK4 and CDK6. Furthermore, using patient-derived PDAC organoids, we confirmed the tumor-suppressive effect of RARγ inhibition and indicated the synergistic effects of RARγ inhibition with gemcitabine.

Conclusions: This study clarified the function of RARγ signaling in PDAC progression and demonstrated the tumor-suppressive effect of selective blockade of RARγ signaling against PDAC. These results suggest that RARγ signaling might be a new therapeutic target for PDAC.

Keywords: Cell cycle; Cell proliferation; Pancreatic ductal adenocarcinoma; Retinoic acid receptor γ; Retinoic acid signaling.

Abstract

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