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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.

Abstract Background The chorioallantoic membrane (CAM) assay is a well-established technique to evaluate tumor invasion and angiogenesis and may overcome the shortcoming of the patient-derived xenograft (PDX) mouse model. Currently, few reports have described lung cancer invasion and angiogenesis in the CAM assay. We therefore used the CAM assay in the evaluation of lung cancer. Method Lung cancer cell line-derived organoids or lung cancer cell lines were transplanted into the CAM on embryonic development day (EDD) 10, and an analysis was performed on EDD 15. Microscopic and macroscopic images and movies of the grafts on the CAM were captured and analyzed. The relationships between the graft and chick vessels were evaluated using immunohistochemistry. Results We transplanted lung cancer cell lines and cell line-derived organoid into a CAM to investigate angiogenesis and invasion. They engrafted on the CAM at a rate of 50–83%. A549-OKS cells showed enhanced cell invasion and angiogenesis on the CAM in comparison to A549-GFP cells as was reported in vitro. Next, we found that A549-TIPARP cells promoted angiogenesis on the CAM. RNA-seq identified 203 genes that were upregulated more than twofold in comparison to A549-GFP cells. A pathway analysis revealed many upregulated pathways related to degradation and synthesis of the extracellular matrix in A549-TIPARP cells. Conclusions The CAM assay can be used to evaluate and research invasion and angiogenesis in lung cancer. The elevated expression of TIPARP in lung cancer may induce angiogenesis by remodeling the extracellular matrix.

Abstract Background Cancer stem cells (CSCs) are considered to be responsible for tumor initiation, formation, and poor prognosis of cancer patients. However, the rarity of CSCs in clinical samples makes it difficult to elucidate characteristics of CSCs, especially in osteosarcoma (OS). The aim of this study is to verify whether it is possible to generate CSC-like cells by transducing defined factors into an OS cell line. Methods We retrovirally transduced the Octamer-binding transcription factor 3/4 (OCT3/4), Kruppel-like factor 4 (KLF4), and SRY-box transcription factor 2 (SOX2) genes into the MG-63 human OS cell line (MG-OKS). Parental and GFP-transduced MG-63 cells were used as negative control. We assessed the properties of the generated cells in vitro and in vivo. Multiple comparisons among groups were made using a one-way analysis of variance (ANOVA) followed by post hoc testing with Tukey’s procedure. Results MG-OKS cells in vitro exhibited the significantly increased mRNA expression levels of CSC markers (CD24, CD26, and CD133), decreased cell growth, increased chemoresistance and cell migration, and enhanced sphere formation. Notably, MG-OKS cells cultured under osteogenic differentiation conditions showed strongly positive staining for both Alizarin Red S and alkaline phosphatase, indicating osteogenesis of the cells. Gene ontology analysis of microarray data revealed significant upregulation of epidermal-related genes. Tumors derived from MG-OKS cells in vivo were significantly larger than those from other cells in μCT analysis, and immunohistochemical staining showed that Ki-67, osteocalcin, and HIF-1α-positive cells were more frequently detected in the MG-OKS-derived tumors. Conclusions In this study, we successfully generated OS CSC-like cells with significantly enhanced CSC properties following transduction of defined factors.