Transcriptome analysis of an AKT inhibitor-resistant endometrial cancer cell line.

BACKGROUND: Drug resistance in endometrial cancer (EC) is a serious problem and a barrier to improving prognosis. The PI3K/AKT/mTOR pathway is highly activated in EC and can serve as a potential therapeutic target. Inhibitors against AKT have been developed, but resistance to these inhibitors is a concern. This study aimed to establish AKT inhibitor resistant cell lines and identify differentially expressed genes (DEGs) between parental and AKT inhibitor resistant cell lines to understand the mechanism of drug resistance to AKT inhibitors in EC. METHODS: The sensitivity of eight EC cell lines to AKT inhibitor was analyzed. One of them was used to establish a drug-resistant cell line. DEGs were examined using RNA sequencing (RNA-seq). Furthermore, DEGs were comprehensively analyzed to identify hub genes. Hub genes were evaluated using quantitative real-time polymerase chain reaction. RESULTS: RNA-seq identified 617 DEGs. Hub genes were selected using bioinformatics analysis. The top 10 hub genes were TNF, CDH1, CCND1, COL1A1, CDH2, ICAM1, CAV1, THBS1, NCAM1, and CDKN2A. Relative mRNA expression was significantly upregulated for TNF, CDH1, CCND1, THBS1, p16INK4a, and p14ARF and significantly downregulated for CDH2, ICAM1, and NCAM1 in borussertib-resistant EC cell line. CONCLUSIONS: Drug resistance to AKT inhibitors may depend on genes related to cell adhesion-mediated resistance and transforming growth factor ß signaling.

Acquired AKT-inhibitor Resistance Is Mediated by ATP-binding Cassette Transporters in Endometrial Carcinoma.

BACKGROUND/AIM: Endometrial cancer is increasing in prevalence worldwide. It is treated with chemotherapy and radiotherapy, in addition to surgery, but the presence of treatment-resistant tumor cells remains a barrier to effective tumor control. The purpose of this study was to develop drug-resistant cell lines using triciribine, an AKT inhibitor, and investigate the mechanism of acquired resistance. MATERIALS AND METHODS: Triciribine sensitivity assays were performed using Cell Counting Kit-8 (CCK-8) on eight endometrial cancer cell lines. The chosen cell lines were highly sensitive to chemotherapy and radiotherapy. A new triciribine-resistant cell line was established and found to be highly resistant to chemotherapy. Properties of the resistant cell line were identified using molecular and cell biological techniques including CCK-8 and quantitative PCR analysis. RESULTS: HEC-151 had the highest triciribine sensitivity (IC50 value of 0.7±0.1 µM) of the endometrial cancer cell lines tested. We established a triciribine-resistant cell line from HEC-151 by growing cells in the presence of increasing concentrations of triciribine up to 66.6 µM. The resistant HEC-151 cells changed to spindle-shaped morphology and importantly reduced triciribine sensitivity compared to the parental cell line. ABC transporters involved in drug efflux had significantly higher expression levels in ABCB1 (1.4±0.10 times higher), ABCC1 (11.4±0.22 times higher), and ABCC4 (4.5±0.42 times higher). CONCLUSION: In this study, we established a triciribine-resistant cell line from HEC-151 cells. Our data suggest that the mechanism of drug resistance in endometrial cancer cells is attributed to the increased expression of ABC transporters.

Proliferation of poorly differentiated endometrial cancer cells through autocrine activation of FGF receptor and HES1 expression.

Patients with poorly differentiated endometrial cancer show poor prognosis, and effective molecular target-based therapies are needed. Endometrial cancer cells proliferate depending on the activation of HES1 (hairy and enhancer of split-1), which is induced by several pathways, such as the Notch and fibroblast growth factor receptor (FGFR) signaling pathways. In addition, aberrant, ligand-free activation of the FGFR signaling pathway resulting from mutations in FGFR2 was also reported in endometrial cancer. However, a clinical trial showed that there was no difference in the effectiveness of FGFR inhibitors between patients with and without the FGFR2 mutation, suggesting a presence of another signaling pathway for the FGFR activation. Here, we investigated the signaling pathway regulating the expression of HES1 and proliferation of poorly and well-differentiated endometrial cancer cell lines Ishikawa and HEC-50B, respectively. Whereas Ishikawa cells proliferated and expressed HES1 in a Notch signaling-dependent manner, Notch signaling was not involved in HES1 and proliferation of HEC-50B cells. The FGFR inhibitor, NVP-BGJ398, decreased HES1 expression and proliferation of HEC-50B cells; however, HEC50B cells had no mutations in the FGFR2 gene. Instead, HEC-50B cells highly expressed ligands for FGFR2, suggesting that FGFR2 is activated by an autocrine manner, not by ligand-free activation. This autocrine pathway activated Akt downstream of FGFR for cell proliferation. Our findings suggest the usefulness of HES1 as a marker for the proliferation signaling and that FGFR inhibitor may be effective for poorly differentiated endometrial cancers that harbor wild-type FGFR.

Isolation of side population cells from endometrial cancer cells using a violet laser diode.

Cancer stem cells (CSCs) possess the ability for self-renewal, differentiation, and tumorigenesis and play a role in cancer recurrence and metastasis. CSCs are usually sorted in analysis into side population (SP) cells using ultraviolet (UV) laser (350 nm) excitation; they cannot be stained with Hoechst 33342 because of their efflux ability. However, it is difficult to avoid cell damage using a UV laser. Therefore, we attempted to isolate CSCs using a violet laser (407 nm) excitation to avoid cellular DNA damage. We sorted SP cells and main population (MP) cells from a human endometrial cancer cell line using the FACSAria system equipped with a violet laser and analyzed the biological properties of these cells. SP cells exhibited drug efflux, self-renewal, differentiation abilities, and tumorigenicity. It was found that v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) expression was significantly higher in SP cells than in MP cells. Our results suggest that CSCs exist in the SP fraction sorted using the FACSAria system equipped with a violet laser, which presents a useful tool to isolate small populations of viable putative CSCs from solid tumors and can be used to identify and characterize CSCs.

Tumorigenesis in cells derived from induced pluripotent stem cells.

Induced pluripotent stem (iPS) cells are an attractive source for potential cell-replacement therapy. However, transplantation of differentiated products harbors the risk of teratoma formation, presenting a serious health risk. Thus, we characterized Nanog-expressing (undifferentiated) cells remaining after induction of differentiation by cytological examination. To induce differentiation of iPS cells, we generated embryoid bodies (EBs) derived from iPS cells carrying a Nanog­green fluorescent protein(GFP) reporter and then injected GFP-positive and GFP negative EBs into nude mice. GFP-positive EB transplantation resulted in the formation of immature teratoma grade 3, but no tumors were induced by GFP-negative EB. GFP positive cells revealed significantly lower cytoplasmic area and higher nucleus/cytoplasm ratio than those of GFP negative cells. Our results suggest that morphological analysis might be a useful method for distinguishing between tumorigenic and nontumorigenic iPS cells.

Diagnostic utility of notch-1 immunocytochemistry in endometrial cytology.

OBJECTIVE: It was the aim of this study to evaluate the diagnostic utility of Notch-1 immunocytochemistry in distinguishing endometrial glandular and stromal breakdown (EGBD) from endometrial adenocarcinoma in endometrial cytology. STUDY DESIGN: Samples of normal endometrium, EGBD and endometrial adenocarcinoma were subjected to immunocytochemical staining for Notch-1, and we examined the labeling index (LI) of Notch-1 (the ratio of intranuclear Notch-1-positive cells to total cells). We compared (1) the Notch-1 LI in normal endometrium, (2) the Notch-1 LI between normal endometrium and endometrial adenocarcinoma, and (3) the Notch-1 LI in normal endometrium, EGBD and endometrial adenocarcinoma. RESULTS: In analysis item 1, the LI of Notch-1 was 32.9 ± 8.4, 19.4 ± 8.2 and 12.5 ± 7.5% in proliferative endometrium, secretory endometrium and atrophic endometrium, respectively. In analysis item 2, the LI of Notch-1 in endometrial adenocarcinoma was 45.2 ± 7.4%, which was significantly higher than that in normal endometrium. In analysis item 3, the LI of Notch-1 in EGBD was 31.3 ± 8.3%, which was significantly lower than that in endometrial adenocarcinoma. CONCLUSION: In conclusion, Notch-1 immunocytochemistry is a useful method for distinguishing between EGBD and endometrial carcinoma in endometrial cytology.

Effects of N-[N-(3, 5-difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester (DAPT) on cell proliferation and apoptosis in Ishikawa endometrial cancer cells.

Endometrial cancer is one of the most common gynecological malignancies in Japan, where the disease shows an increasing morbidity. However, surgical therapy remains the treatment of choice for endometrial cancers that tend to be insensitive to radiation therapy and chemotherapy. Therefore, novel therapeutic strategies are required. The Notch signaling pathway regulates embryogenesis and cellular development, but deregulated Notch signaling may contribute to tumorigenesis in several cancers. Moreover, γ-secretase inhibitors have been shown to be potent inhibitors of the Notch signaling pathway; they suppress cellular proliferation and induce apoptosis in several cancer cells. In the present study, we investigated the effect of N-[N-(3, 5-difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester (DAPT, γ-secretase inhibitor) on the cell proliferation and apoptosis in Ishikawa endometrial cancer cells. Real-time PCR detected mRNA derived from NOTCH1 and HES1, which are target genes of the Notch signaling pathway, in Ishikawa endometrial cancer cells. After blocking Notch signaling, cellular proliferation decreased, accompanied by increased expression of p21 mRNA and decreased expression of the cyclin A protein. Furthermore, blockade of Notch signaling induced apoptosis. These results suggest that the Notch signaling pathway may be involved in cell proliferation through cell cycle regulation and apoptosis in Ishikawa endometrial cancer cells. Inhibition of the Notch signaling pathway by γ-secretase inhibitors is expected to be a potential target of novel therapeutic strategies for endometrial cancer.