Abstract
Background/Aim: Endometrial cancer (EC) is a frequent gynecological cancer. Studies have demonstrated that the sensitivity of EC toward 5-fluorouracil (5-FU) chemotherapy has decreased, leading to unsatisfactory treatment effects. There is an urgent need to investigate the reasons for the unsatisfactory treatment of EC with 5-FU. The purpose of the study was to investigate the effect of RAD51AP1 after being transcriptionally activated by E2F7 on the sensitivity of EC cells to 5-FU chemotherapy via the fatty acid metabolic pathway. Materials and Methods: mRNA expression data on EC were downloaded from The Cancer Genome Atlas database, subjected to differential expression analysis, and the target genes were determined based on the bioinformatics analysis and literature consulting. The regulatory transcription factor upstream of RAD51AP1 in EC was predicted using the hTFtarget database. The expression of E2F7 and RAD51AP1 was measured by qRT-PCR and western blot. Then, the transcriptional activation relationship between E2F7 and RAD51AP1 was verified by chromatin immunoprecipitation (ChIP) and dual luciferase assays. The IC50 values of EC cells toward 5-FU were determined by the CCK-8 assay, and cell apoptosis was detected by flow cytometry. The expression of apoptosis-related and fatty acid metabolism-related proteins was evaluated by western blot. Results: Bioinformatics analysis showed that both E2F7 and RAD51AP1 were highly expressed in EC, and the possible binding sites between RAD51AP1 promoter and E2F7 were predicted. ChIP assay and dual luciferase assay confirmed the binding of E2F7 to RAD51AP1 promoter region. Cell experiments showed that overexpressing RAD51AP1 could facilitate the growth and fatty acid metabolism of EC cells, and suppress cell sensitivity to 5-FU, while silencing of E2F7 could reduce the effect of RAD51AP1 overexpression on EC cell growth and sensitivity toward 5-FU. Conclusion: The E2F7/RAD51AP1 axis can promote the growth of EC cells and inhibit cell sensitivity to 5-FU by regulating fatty acid metabolism, suggesting that E2F7/RAD51AP1 axis may be a novel pathway for EC treatment.
Endometrial cancer (EC) is a common gynecological cancer, ranking second among all female malignancies worldwide (1). In recent years, EC incidence has been on the rise (2). With unsatisfactory treatment effects, prognosis of advanced or recurrent EC is extremely poor (3). Chemotherapy remains the main treatment method for EC. Currently, commonly used chemotherapy drugs for EC include cisplatin (DDP), doxorubicin (DOX), gemcitabine, and 5-fluorouracil (5-FU) (4). Among these drugs, 5-FU is an antitumor drug that affects pyrimidine synthesis (5). As a first-line drug in cancer treatment, 5-FU application has achieved significant results in the treatment of multiple cancers, such as breast cancer and EC (4-6). However, the drug resistance of tumor towards 5-FU limits the efficacy. Under current circumstance, it is necessary to clarify the mechanism related to 5-FU chemotherapy resistance in EC, as this can provide new therapeutic guidance for EC treatment.
In recent years, reprogramming of cell energy metabolism has been gradually emphasized and accepted as a new indicator for cancer (7), which plays a crucial role in cancer progression and chemotherapy resistance (8, 9). Various experimental and clinical studies have shown that metabolic reprogramming of cancer cells involves dysregulated glucose metabolism, glutamine metabolism, and fatty acid metabolism, which may be beneficial to the growth and chemotherapy resistance of tumor cells (10-12). Currently, studies on fatty acid metabolism in EC have attracted wide attention. For example, LPCAT1 is a key enzyme that regulates phospholipid metabolism. With LPCAT1 overexpression, the contents of phospholipids, such as phosphatidyl ethanolamine (PE), phosphatidyl choline (PC) and triglyceride (TG) change significantly. LPCAT1 promotes stemness and metastasis of EC by activating the TGF/β-Smad2/3 signaling pathway (13). Estrogen-associated receptor α (ERRα) regulates cellular oxidative phosphorylation and liposome metabolism, and transcription factors TFEB and ERRα regulate lipid metabolism through signal transduction to promote EC invasion and metastasis (14). In addition, alteration in fatty acid metabolism can affect tumor chemotherapy resistance. For example, in colorectal cancer, 6-shogaol down-regulates SREBP-1 to inhibit fat metabolism to enhance tumor cell sensitivity to 5-FU (15). However, the role of fatty acid metabolism in regulating EC sensitivity toward 5-FU has not been reported. Thus, this study aimed to explore the mechanism related to fat metabolism and 5-FU chemotherapy resistance in EC.
First, we identified the high expression of RAD51AP1 in EC tissues and cells. Later, we found that highly-expressed RAD51AP1 promoted EC cell growth and inhibited EC cell sensitivity to 5-FU through the fatty acid metabolism pathway. RAD51AP1 was found to be regulated by upstream transcription factor E2F7, which activated RAD51AP1 to promote cell growth and hamper cell sensitivity to 5-FU via fatty acid metabolism pathway. These results facilitated the understanding of EC malignant progression and the mechanism of genes affecting 5-FU resistance, suggesting that E2F7 and RAD51AP1 may be promising targets for EC treatment.
Materials and Methods
Bioinformatics analyses. EC mRNA expression data were downloaded from The Cancer Genome Atlas (TCGA)-UCEC dataset (normal:35, tumor:552) and subjected to differential expression analysis (|logFC|>2, FDR<0.05), which was performed by ‘edgeR’ package (16). The differentially expressed mRNAs (DEmRNAs) between normal and tumor groups were obtained, and the target genes were determined by consulting literature (17) and bioinformatics database. Further, the regulatory transcription factors upstream of EC target gene were searched in the hTFtarget database (18). Finally, the upstream gene was identified by Pearson correlation analysis. The binding sites of the target gene and the regulatory gene were predicted in JASPAR. Kaplan-Meier (KM) survival analysis predicted the relationship between RAD51AP1 expression and survival rate.
Cell culture and transfection. Human EC cell lines RL95-2 (ATCC, Rockefeller, MD, USA), Ishikawa (ATCC), HEC-1-A (ATCC, Rockefeller), HEC-1B (ATCC), human endometrial epithelial cell line hEEC (Xiamen Immocell Biotechnology Co., Ltd., Xiamen, PR China), and human embryonic kidney cell lines 293T (Cobioer Biosciences Co., Ltd., Nanjing, PR China), RL95-2, hEEC and 293T were all maintained in DMEM containing 10% fetal bovine serum (FBS). Ishikawa cells and HEC-1B cells were kept in MEM containing 10% FBS, 1% MEM non-essential amino acid (NEAA) and 1 mM sodium pyruvate (NaP). HEC-1-A cells were cultured in McCoy’s 5A medium with 10% FBS. All the above cells were cultured in a 37°C incubator containing 5% CO2.
According to the specification of Lipofectamine 2000 kit (GenePharma, Shanghai, PR China), EC cells were transfected with purchased sh-E2F7, oe-E2F7, oe-RAD51AP1, sh-RAD51AP1 or their corresponding controls (GenePharma). After 48 h, transfected cells were collected for subsequent experiments.
qRT-PCR. Total RNA from normal and cancer cells was extracted by the Trizol method (Invitrogen, Carlsbad, CA, USA). cDNA was obtained through reverse transcription, and qRT-PCR was performed by SYBR Green Master (Roche, Basel, Switzerland). With β-actin as the loading reference, the relative expression of genes was calculated by the 2−ΔΔCT method. Detailed information of primers is listed in Table I.
Primers used for qRT-PCR.
Western blot. Western blot operations were performed by referring to literature (19). Proteins were transferred onto membrane after electrophoresis and blocked at room temperature for 1 h. The membrane was then incubated overnight with SCD, SREBF1, E2F7 and RAD51AP1 rabbit anti-human primary antibody (Abcam, Cambridge, UK), followed by 2 h incubation with goat anti-rabbit IgG secondary antibody (Abcam). Finally, the membrane was photographed for color development.
Chromatin immunoprecipitation (ChIP). Briefly, the assay was performed using the IP-level anti-E2F7 antibody (Invitrogen) and the corresponding simple ChIP enzymatic chromatin IP kit according to the method described in literature (20). Detailed information of primers is mentioned in Table II.
Primers used for the ChIP-qPCR assay.
Dual-luciferase assay. First, the luciferase reporter vectors (Promega, Madison, WI, USA) of pGL3-RAD51AP1-promoter-WT (RAD51AP1-WT) and pGL3-RAD51AP1-promoter-MUT (RAD51AP1-MUT) were constructed. Then, human embryonic kidney cell line 293T was inoculated into 96-well plates (1×105 cells/well) and co-transfected with the plasmids RAD51AP1-WT/RAD51AP1-MUT and oe-NC/oe-E2F7. After 48 h of culture, luciferase activity was measured using the dual luciferase reporting system (Promega) according to the kit instructions. The experiment was repeated three times.
Cell counting kit-8 (CCK-8) assay. According to a previous study (21), CCK-8 (Beyotime, Shanghai, PR China) was used to detect EC cell proliferation and sensitivity to 5-FU. The cells were inoculated into 96-well plates at a density of 5×103 cells/well. After 0, 24, 48 or 72 h of culture, the cells were added with 10 μl CCK-8 solution (Sigma, St Louis, MO, USA) and cultured for 4 h. The absorbance at 450 nm was measured with a microplate reader. The IC50 value was tested as per the manufacturer’s instructions. Briefly, EC cells were seeded at a density of 5×103 per well in 96-well plates. Finally, the absorbance at 450 nm was measured. After treating EC cells in each group with 5-FU (Sigma; 0, 10, 20, 30, 40, 50, and 60 μg/ml) for 24 h, IC50 values were detected.
Lipid metabolism measurement. Orlistat lipase inhibitor (ChemeGen, Shanghai, PR China) was purchased and used with a concentration of 100 μM. Free fatty acids were quantified by free fatty acid quantitative assay kit (BioAssay Systems, Northern California Bay Area, CA, USA). The quantification of triglyceride was performed with a Glycerol Cell-Based assay kit (Cayman Chemical, Ann Arbor, MI, USA). BODIPY 493/503 (Invitrogen) was employed to detect neutral lipid accumulation in EC cells as per manufacturer’s instructions (22).
Statistical analysis. All data in this study were presented as mean±standard deviation (SD). Analysis of variance was adopted to test the significance of the differences between multiple groups, followed by Tukey’s test, and Student’s t-test was for that between two groups. Survival analysis was performed using the “Survival” package. p<0.05 was considered to be statistically significant.
Results
RAD51AP1 is highly expressed in EC tissues and cells. EC mRNA expression data were downloaded from TCGA database and subjected to differential expression analysis. Compared to normal tissues, EC tissues showed significantly higher RAD51AP1 expression (Figure 1A). The KM curve showed that patients with high RAD51AP1 expression had a poor survival rate (Figure 1B). Numerous studies have demonstrated that RAD51AP1 is up-regulated in a variety of cancer tissues and related to tumor malignant progression (23, 24). Therefore, it is speculated that RAD51AP1 is involved in the malignant progression of EC. The expression level of RAD51AP1 in EC cell lines (RL95-2, Ishikawa, HEC-1-A, HEC-1B) and human endometrial epithelial cells hEEC was detected by qRT-PCR. It turned out that RAD51AP1 was markedly overexpressed in EC cell lines (Figure 1C). The expression level of RAD51AP1 was higher in RL95-2 and lower in Ishikawa. Thus, RL95-2 and Ishikawa cell lines were selected for subsequent knockdown and overexpression experiments, respectively. The above results demonstrated a high-expression of RAD51AP1 in EC tissues and cells.
RAD51AP1 is highly expressed in EC tissues and cells. (A) Bioinformatics analysis of RAD51AP1 expression in normal and EC tissues. (B) The relationship between RAD51AP1 expression and survival rate of EC patients was analyzed by Kaplan Meier (KM) survival curve. (C) qRT-PCR analysis of RAD51AP1 expression in EC cell lines (RL95-2, Ishikawa, HEC-1-A, HEC-1B) and endometrial epithelial cells (hEEC). *p<0.05 vs. hEEC. EC: Endometrial cancer; RAD51AP1: RAD51-associated protein 1; qRT-PCR: real-time quantitative reverse transcription PCR.
Effects of RAD51AP1 on viability and 5-FU chemoresistance of EC cells. To further investigate the role of RAD51AP1 in EC progression, sh-NC, sh-RAD51AP1, oe-NC and oe-RAD51AP1 were transfected into RL95-2 and Ishikawa cell lines separately, and the transfection efficiency was detected by qRT-PCR. As the results displayed, RAD51AP1 expression was significantly decreased in sh-RAD51AP1 treatment group, while it was significantly up-regulated in oe-RAD51AP1 treatment group (Figure 2A-B). Subsequently, cell viability in each treatment group was detected. Overexpressing RAD51AP1 promoted the growth of EC cells, while knockdown of RAD51AP1 significantly inhibited the viability of EC cells (Figure 2C-D). Next, the IC50 value of 5-FU treated EC cells was detected by CCK-8. Down-regulated expression of RAD51AP1 significantly decreased the 5-FU IC50, while its up-regulation substantially increased the 5-FU IC50 (Figure 2E). These results indicated that RAD51AP1 expression was closely related to the sensitivity of EC cells to 5-FU.
Effects of RAD51AP1 on the viability and 5-FU chemoresistance of EC cells. (A-B) qRT-PCR analysis of RAD51AP1 expression in EC cells (RL95-2 and Ishikawa) in each group; (C-D): CCK-8 analysis of cell viability after RAD51AP1 silencing or overexpression; (E): CCK-8 analysis of IC50 value of EC cells after RAD51AP1 silencing or overexpressing (5-FU treatment concentrations were 0, 10, 20, 30, 40, 50, and 60 μg/ml); (F): GSEA analysis of RAD51AP1; (G): Pearson analysis of the correlation between RAD51AP1 and lipid metabolism related genes; (H): CCK-8 assay of the cell viability in oe-NC+PBS, oe-RAD51AP1+PBS, and oe-RAD51AP1+Orlistat treatment groups; (I): Neutral lipid accumulation in oe-NC+PBS, oe-RAD51AP1+PBS and oe-RAD51AP1+Orlistat treatment groups; (J): The contents of triglyceride in oe-NC+PBS, oe-RAD51AP1+PBS, oe-RAD51AP1+Orlistat treatment groups; (K): Relative content of free fatty acids in the oe-NC+PBS, oe-RAD51AP1+PBS and oe-RAD51AP1+Orlistat treatment groups; (L): Western blot results of lipid metabolism-related proteins; (M): The cell viability and IC50 value after 24 h of 5-FU treatment were detected by the CCK-8 assay; *p<0.05 vs. oe-NC+PBS. EC: Endometrial cancer; RAD51AP1: RAD51-associated protein 1; qRT-PCR: real-time quantitative reverse transcription PCR; GSEA: gene set enrichment analysis; PBS: phosphate buffered saline; CCK-8: cell counting kit-8.
Then, we conducted gene set enrichment analysis (GSEA) for RAD51AP1 and found a difference in the regulation of fatty acid metabolic pathway between RAD51AP1 high- and low-expression groups (Figure 2F). Pearson correlation analysis found that RAD51AP1 was positively correlated with the expression of key lipid synthesis genes (FASN, SCD and ACAA2) (Figure 2G). Thus, we speculated that RAD51AP1 was involved in the regulation of fatty acid metabolism in EC. Thereafter, to study the effect of fatty acid metabolic pathway on cancer cells, cells were divided into oe-NC+PBS, oe-RAD51AP1+PBS, oe-RAD51AP1+Orlistat (lipase inhibitor) groups, and cell viability was detected by CCK-8. According to the results, RAD51AP1 overexpression enhanced cell viability, as compared with the control group; however, the addition of lipase inhibitor reversed the effect of RAD51AP1 overexpression (Figure 2H). To further investigate the mechanism of the influence of lipase inhibitor, the lipophilic fluorescent dye BODIPY 493/503 was used to detect the neutral lipids in cells. As the results demonstrated, the content of neutral lipids increased after RAD51AP1 overexpression (Figure 2I), and the levels of free fatty acids and triglycerides increased evidently. However, the contents of free fatty acids and triglycerides were reduced after the addition of orlistat (Figure 2J-K). Western blot experiment showed similar trend (Figure 2L). Finally, CCK-8 assay measured the IC50 value of EC cells toward 5-FU. RAD51AP1 overexpression hampered the sensitivity of cancer cells to 5-FU, while orlistat treatment offset the inhibitory effect of RAD51AP1 overexpression on cell sensitivity (Figure 2M). To sum up, RAD51AP1 could hamper the sensitivity of EC cells to 5-FU through the fatty acid metabolism pathway.
E2F7 is the upstream regulator of RAD51AP1. The next step was to probe the regulatory mechanism of RAD51AP1 in EC progression. The potential transcription factors upstream of RAD51AP1 were predicted by bioinformatics analysis. Then, the predicted results were intersected with the up-regulated DEmRNAs in EC to generate a Venn diagram, and 9 potential transcription factors were obtained (Figure 3A). Correlation analysis showed that RAD51AP1 was positively correlated with E2F7 (Figure 3B-C) and that they had a binding site (Figure 3D). Therefore, it was preliminarily inferred that E2F7 was the upstream transcription factor of RAD51AP1. Bioinformatics analysis demonstrated the up-regulation of E2F7 in EC, and qRT-PCR verified the significant up-regulation of E2F7 in EC cell lines (Figure 3E-F). Then, ChIP experiment results showed that anti-E2F7 could significantly enrich RAD51AP1, indicating the binding relationship between E2F7 and RAD51AP1 promoter (Figure 3G). Regarding dual luciferase assay, overexpression of E2F7 enhanced the luciferase activity of wild-type RAD51AP1, but did not affect that of mutant RAD51AP1, further confirming the targeted binding relationship between E2F7 and RAD51AP1 (Figure 3H). Taken together, these results suggested that E2F7 can transcriptionally activate RAD51AP1.
E2F7 is an upstream regulator of RAD51AP1. (A): Venn diagram of predicted transcription factors upstream of RAD51AP1 and up-regulated DEmRNAs in EC; (B, C): Pearson correlation analysis between E2F7 and RAD51AP1; (D): Binding site of E2F7 and RAD51AP1 promoter analyzed by the JASPAR database; (E): Expression of E2F7 in normal and EC tissues; (F): Expression levels of hEEC of E2F7 in EC cell lines (RL95-2, Ishikawa, HEC-1-A, HEC-1B) and human endometrial epithelial cells measured by qRT-PCR; (G, H): Binding relationship between E2F7 and RAD51AP1 promoter analyzed by the ChIP assay and dual luciferase assay; *p<0.05 vs. oe-NC, ns: no significant difference. EC: Endometrial cancer; RAD51AP1: RAD51-associated protein 1; qRT-PCR: real-time quantitative reverse transcription PCR; E2F7: E2F transcription factor 7; ChIP: chromatin immunoprecipitation.
E2F7-activated RAD51AP1 inhibits EC cell sensitivity to 5-FU via fatty acid metabolism. To further explore the role of E2F7/RAD51AP1 axis in EC progression, we set the following experimental groups: sh-NC+oe-NC, sh-E2F7+oe-NC, sh-E2F7+oe-RAD51AP1. First, RAD51AP1 expression in RL95-2 cells in each treatment group was evaluated by qRT-PCR. Relative to the control group, the E2F7 knockdown group showed lower RAD51AP expression level, but this was reversed after RAD51AP1 overexpression (Figure 4A). Second, cell viability in each group was measured. Knockdown of E2F7 inhibited the growth of EC cells. However, simultaneous RAD51AP1 overexpression restored EC cell viability to the level of sh-NC+oe-NC group (Figure 4B). Third, lipid content in EC cells was detected. The neutral lipid content decreased after E2F7 knockdown, but it was increased to the level of sh-NC+oe-NC group after RAD51AP1 overexpression (Figure 4C). Similarly, silenced E2F7 resulted in a substantial decrease in the levels of intracellular free fatty acids and triglycerides, but they were recovered to the levels in the sh-NC+oe-NC group after RAD51AP1 overexpression (Figure 4D-E). Western blot showed similar results. The levels of intracellular SCD and SREBF1 proteins decreased after E2F7 silencing, while further overexpressing RAD51AP1 could reverse the effect of E2F7 silencing on these lipid metabolism-related proteins (Figure 4F). Finally, the viability of EC cells in each group was assayed after treating with different concentrations of 5-FU. The IC50 value decreased and the sensitivity to 5-FU increased after E2F7 knockdown, while RAD51AP1 overexpression reversed the effect of E2F7 knockdown on IC50 (Figure 4G). In conclusion, E2F7/RAD51AP1 axis inhibited the sensitivity of EC cells to 5-FU chemotherapy through fatty acid metabolism.
E2F7-activated RAD51AP1 inhibits EC cell sensitivity to 5-FU via fatty acid metabolism. (A): Expression of RAD51AP1 in EC cells analyzed by qRT-PCR; (B): EC cell activity was detected by CCK-8; (C): Neutral lipid accumulation; (D): Triglyceride content was detected; (E): Relative content of free fatty acids was tested; (F): Expression levels of fatty acid metabolism-related proteins in EC cells were examined by western blot; (G): Cell viability and IC50 values after treatment with 5-FU for 24 h were tested by CCK-8 assay; The treatment groups were sh-NC+oe-NC, sh-E2F7+oe-NC, and sh-E2F7+oe-RAD51AP1; *p<0.05. EC: Endometrial cancer; RAD51AP1: RAD51-associated protein 1; qRT-PCR: real-time quantitative reverse transcription PCR; E2F7: E2F transcription factor 7; CCK-8: cell counting kit-8.
Discussion
Occurrence and development of EC is a complicated process. It has been found that the development of resistance to chemotherapy drugs can further complicate the progression of EC. Data showing the mechanism of chemotherapy sensitivity of EC have recently emerged. In the current study, we demonstrated in vitro a novel E2F7/RAD51AP1 axis that inhibited the chemotherapy sensitivity of EC cells to 5-FU.
RAD51AP1, an auxilin of RAD51, plays an important role in DNA damage repair (25). RAD51AP1 overexpression was found to promote cancer development. For example, RAD51AP1 overexpression can activate TGF-β signaling and promote development of ovarian cancer (23). RAD51AP1 is highly expressed in non-small cell lung cancer tissues, and after silencing RAD51AP1 inhibits the epithelial-mesenchymal transition of cancer cells (26). RAD51AP1 knockdown inhibits the growth of breast cancer tumors (27). It has also been shown that this gene is involved in tumor cell resistance to chemotherapy drugs. As in colorectal cancer, cell resistance to 5-FU can be promoted by modulating RAD51AP1 expression (28). Similarly, the present study confirmed that RAD51AP1 with high expression can substantially enhance cell vitality and inhibit EC cell sensitivity to 5-FU chemotherapy, resulting in worse drug efficacy. It is concluded that RAD51AP1 may be a new target for EC treatment and that reducing RAD51AP1 expression can enhance cell sensitivity to 5-FU chemotherapy and thus improve the therapeutic effect.
We then identified E2F7 as the upstream regulator of RAD51AP1. Studies have shown that E2F7 can affect the proliferation and metastasis of tumor cells or lead to poor prognosis by interacting with different downstream targets in a variety of malignant tumors. For example, E2F7 transcriptionally activates QKI in esophageal cancer cells, and QKI positively regulates CircBCAR3, which promotes the proliferation and migration of esophageal cancer cells through miR-27a-3p (29). Another study found that increased expression of E2F7 in glioma patients leads to poor prognosis (30). Similarly, the results of the current study also support that if E2F7 is highly expressed in EC, it can activate the transcription of RAD51AP1 and promote EC progression and hinder EC sensitivity to 5-FU chemotherapy through the fatty acid metabolism pathway. Our results suggested that inhibiting the E2F7/RAD51AP1 axis may be an effective means to improve cell sensitivity to 5-FU in EC.
In recent years, many studies have confirmed that excess lipids can promote tumor cell proliferation and metastasis. Cancer cells can also regulate their own stroma and the activity of immune cells through lipid metabolism, thereby resisting treatment and promoting cancer recurrence (31). As some recent studies revealed, fatty acid metabolism plays a vital regulatory role in chemotherapy sensitivity of malignant tumors, such as colorectal cancer (15) and pancreatic cancer (32). For example, cell resistance to temozolomide can be effectively reduced by controlling cholesterol and lipid changes in glioblastoma (33). Our results suggested that RAD51AP1 expression is closely related to fatty acid metabolism and sensitivity to 5-FU chemotherapy of EC cells. Thus, it is of great significance to influence fatty acid metabolism by targeting RAD51AP1 to change tumor cell sensitivity toward chemotherapy drugs.
In summary, this study identified the molecular mechanism by which E2F7-activated RAD51AP1 affects cell sensitivity to 5-FU through fatty acid metabolism in EC in vitro. Our results confirmed that RAD51AP1 might promote chemotherapy resistance to 5-FU through the fatty acid metabolic pathway. This study also has some shortcomings. For example, Belen Martin-Salamanca et al. (34) showed that the ki67 and E-cadherin can be used to predict the survival of endometrial cancer in clinical practice, but our findings were not validated in combination with in vivo experiments in tumor setting, and the specific regulatory mechanisms that influence EC progression also need to be explored in more depth. In addition, further clinical studies are needed to determine the fatty acid metabolism mediated effect of E2F7-activated RAD51AP1 on cell sensitivity toward 5-FU in EC. We expect to provide more promising reference and reliable basis for the clinical treatment of EC.
Acknowledgements
This study was sponsored by the Research and Practice on Constructing Regional Security Information Network Integration Platform (No. 2019L09).
Footnotes
Authors’ Contributions
Xiaoyan Huang contributed to the study design. Xi Chen performed the experiments. Zaixin Wu performed data analysis. Chunhong Xiao wrote the article. Xiaoyan Huang, Xi Chen and Zaixin Wu revised the article. All Authors read and approved the final manuscript.
Conflicts of Interest
No conflicts of interest relevant to the submitted manuscript exist.
- Received June 7, 2023.
- Revision received October 5, 2023.
- Accepted October 9, 2023.
- Copyright © 2023 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.
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