EC is one of the most frequent gynecological cancer worldwide[1]. The incidence and mortality of EC are rising throughout the developed world with a tendency for onset at younger age, and this trend is expected to continue mainly due to the increasing prevalence of obesity, hypertension, diabetes, and prolonged life expectancy[23]. For purpose of improving treatment and follow-up of EC patients, the importance of various prognostic factors had been extensively studied over the past few decades, including pathological stage, histological type and grade, age, tumor size, and lymphovascular space involvement[5, 24–26]. In addition, some tumor biomarkers also had been studied for their potential clinical value in patients with EC, including HE4, chaperonin 10, CA125, CA15.3, CA19.9, CA72.4, CEA, OVX1, and M-CSF[23, 27]. However, no good marker was routinely recommended for patients with EC. A study on large sample is probably needed to validate the independent connection of above-mentioned variables and biomarkers with prognosis.
EC typically spreads by invasion of the myometrium into the cervix, or via the fallopian tubes to the ovaries or trans-serosal spread to bladder or bowel[28]. The role of preoperative staging is aiming to establish a recurrence risk group to inform surgical management decisions, mainly based on tumor histology, tumor grade, MI depth and lymph node metastasis[29]. The tumor histology and grade may be evaluated preoperatively by endometrial biopsy, but it is difficult to determine the extent of MI accurately using the techniques in clinical practices. MI by the EC was associated with lymph node involvement, and both prognostic significance for EC patients were well documented[30, 31]. Thus, methods to assess the extent of MI are important. Clinically, TVS is excellent in determining the endometrial thickens, but it is limited in the evaluation of the depth of MI by the EC[32]. MRI is considered the most accurate imaging technique for preoperative assessment of EC due to its excellent soft tissue contrast resolution. However, there are some limitations including the uterine anatomy distorted by leiomyomas, presence of adenomyosis and when the tumor involved a cornu of the uterus[33]. Recent meta-analyses[34] had shown that estimated sensitivity and specificity for diagnosing deep MI were 75% (95% confidence interval [CI] = 67%-82%) and 82% (95% CI = 75%-93%) for TVS, and 83% (95% CI = 76%-89%) and 82% (95% CI = 72%-89%) for MRI, respectively. However, all studies included in this systematic review were both high and low risk patients for deep MI, which may affect the clinical applicability of both techniques. Therefore, it is necessary to develop new methods to assist in evaluating the extent of MI for a precise determination of prognosis and accurate tailoring of adjuvant therapy.
To date, there are no molecular markers could help to assess the depth of MI by the EC. CCT7, also known as the TCP1 ring complex, consists of two identical stacked rings and folds various proteins, which is involved in the folding of cytoskeletal proteins in an ATP dependent approach[16, 35, 36]. Based on our results, CCT7 may have a critical role in the processes of muscle invasion and distant/nodal metastasis in EC development. Our previous proteomics experiments had shown that the CCT7 gene was differentially expressed between EC and adjacent normal tissues[18], which was re-verified in the present study (p = 0.033). Of note, we found that the rate of CCT7 strongly positive cells differed significantly between the two groups, i.e., patients with and without deep MI (p = 0.039). Along with the ROC (AUC = 0.8502, p < 0.0001) between CCT7 expression and MI depth, suggesting that CCT7 was related to MI and it could be a valuable biomarker to evaluate the extent of MI by the EC. Better prognosis of EC patients related to lower pathological stages had been suggested[5], additional analyses confirmed that CCT7 expression also had an obvious correlation with pathological stage of patients, for advanced stage (III/IV) EC patients had higher CCT7 strongly positive cells rates and CCT7 protein level compared to lower stage (I/II) (p = 0.029 and Fig. 1e), same as the ROC (AUC = 0.8694, p < 0.0001) between CCT7 expression and FIGO stage, which demonstrated the patients with higher CCT7 expression would be an unfavorable prognosis. Notably, corresponding with the survival analysis based on TCGA data, which showed that the EC patients with lower level CCT7 expression had better OS (p = 0.0081) and CCT7 had a potential prognostic value for EC patients.
Subsequently work, we attempted to validate the potential function and predict the potential molecular pathways involved of CCT7 in EC development, the siRNAs method to knockdown CCT7 expression in Ishikawa and RL95-2 cell lines was performed. We found a diminished proliferation activity, invasion abilities and colony capacity in both Ishikawa and RL95-2 cells after CCT7 knockdown. At the same time, further studies revealed that loss of CCT7 significantly stimulated the cell apoptosis and induced G2/M cell cycle arrest in EC cells. Collectively, CCT7 expression were considerably correlated to EC cells function, which could affect multiple aspects of tumor cell development. For the bioinformatic analysis, based on TCGA, there were no significance about CCT7 expression between UCEC and normal samples, but the imbalance between the tumor and normal data may cause inefficiency for analysis. In addition, GO enrichment indicated that “RNA binding”, “Mitochondrion”, “Translation”, and “Spliceosome” were most significantly enriched potential pathways. In addition, five hub genes were analyzed from PPI network, PSMA5, PSMD14, SNRPB, SNRPG and TXNL4A, which were all significantly upregulated in UCEC compared to adjacent healthy controls. PSMA5 and PSMD14 are the core components of the proteasome complex participates in numerous cellular processes, including cell cycle progression, apoptosis, or DNA damage repair[37, 38]. It was reported that PSMA5 and PSMD14 could promote the tumorigenic process and tumor metastasis in various cancers[39, 40]. SNRPB, SNRPG and TXNL4A are the core components of spliceosome and play a major role in regulating alternative splicing of the pre-mRNA[41, 42]. SNRPB was reported that promoted the non-small cell lung cancer tumorigenesis[43]. These five genes were positively correlated with CCT7 in UCEC, which revealed that CCT7 may have similar potential tumorigenic function.
In our present work, we first provided a new method based on CCT7 to assess the extent of MI by EC, and CCT7 could also be a potential biomarker to predict the prognosis. However, there are some limitations we have to acknowledge. In this retrospective study, we only investigated the CCT7 expression in EC and adjacent normal endometrium tissues, but healthy patients were not included, which may affect the clinical utility of this biomarker. And the potential molecular pathway was predicted but further confirmed experiments were needed.