J Cancer Prev 2021; 26(4): 250-257
Published online December 30, 2021
© Korean Society of Cancer Prevention
1Department of Radiation Oncology, Yantai Yuhuangding Hospital, Qingdao University, Yantai, 2Department of Oncology, School of Medicine, Qingdao University, Qingdao, 3Department of Otorhinolaryngology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
Correspondence to :
Yipeng Song, E-mail: firstname.lastname@example.org, https://orcid.org/0000-0002-5030-9159
Rukun Zang, E-mail: email@example.com, https://orcid.org/0000-0002-1852-8220
*These authors are co-first authors and contributed equally to this work.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Mitochondrial fission regulator 2 (MTFR2) is associated with mitochondrial fission, while few studies have assessed the associations between MTFR2 expression and clinical characteristics or prognosis of esophageal squamous cell carcinoma (ESCC). In this study, we compared the expression of MTFR2 in 6 ESCC tumors and relative normal tissues by immunohistochemistry (IHC). To assess the effect of MTFR2 expression on clinicopathologic characteristics and survival, 115 paraffin embedded ESCC tissue samples were assessed by IHC staining. Furthermore, the association between clinicopathological properties and MTFR2 expression in patients with ESCC was examined. The survival analysis was performed using the Cox regression models. We found that MTFR2 expression was significantly increased in ESCC tumors compared with normal esophageal epithelial cells. IHC analysis of 115 paraffin embedded ESCC tumor specimens of the patients showed that the expression of MTFR2 was significantly associated with clinical stage (
Keywords: MTFR2, Esophageal squamous cell carcinoma, Immunohistochemistry, Prognosis
Esophageal cancer is one of the most common malignant tumors in the upper digestive tract of the chest [1,2]. Esophageal squamous cell carcinoma (ESCC) is among the most common types of upper gastrointestinal cancer [3,4]. Approximately 300,000 people die of esophageal cancer annually worldwide, with more than half in China . Moreover, the mortality of esophageal cancer is ranked fourth in China . Recurrence and metastasis of ESCC are still the main causes for death and treatment failure, and have crucial impact on the prognosis of ESCC [6,7]. Although considerable progress has been made in diagnosis and treatment, the relevant predictors for early diagnosis and prognosis remain lacking. Therefore, identification of molecular biomarkers will promote the development of new diagnostic and prognostic predictors for early diagnosis and personalized treatment of patients with ESCC.
Mitochondrial fission regulator 2 (MTFR2), also known as similarity 54 family member A (FAM54A), belongs to the MTFR1/FAM54 family [8,9]. It has two subtypes and is produced by selective shearing. MTFR2 plays important roles in mitochondrial division and aerobic respiration , while few studies have assessed the effects of MTFR2 expression on clinicopathological characteristics and prognosis of ESCC. Some previous studies found that the high expression of MTFR2 was correlated with lymph node metastasis, age and prognosis of breast cancer [11,12]. Currently, some studies have shown that MTFR2 is overexpressed in glioblastoma (GBM) and lung cancer, and this was correlated with sex, age, smoking history, cancer stage, histological subtype, and TP53 mutation status of lung cancer [9,13]. However, the role of MTFR2 expression in ESCC remains unclear.
In this study, we analyzed the expression of MTFR2 in six paired ESCC and normal specimens and 115 paraffin embedded ESCC tumor samples by immunohistochemistry (IHC). We evaluated the associations of MTFR2 expression with clinicopathological characteristics of ESCC patients, and further explored the effect of MTFR2 expression on clinical outcome of ESCC.
Besides the 6-pairs of ESCC patients, additional 115 paraffin-embedded tumor specimens from patients, pathologically, diagnosed with ESCC between 2005 and 2010 at Yantai Yuhuangding Hospital, were included in this study. Detailed clinical information of the patients is shown in Table 1. Written informed consents were given to all patients before undertaking the study which was approved by the ethic committee of Yantai Yuhuangding Hospital (IRB No. 2017-204).
All procedures performed in studies involving human participants were in accordance with the ethical standards of the Ethics Committee of the Yantai Yuhuangding Hospital Affiliated Hospital of Qingdao University and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
MTFR2 expression was measured in 115 paraffin embedded ESCC specimens and 6 pairs of ESCC and normal tissue samples by IHC, as previously described . In IHC, we used rabbit monoclonal antibody targeting MTFR2 (1:200, Sigma® Life Science). Samples without any antibody were used as the corresponding blank control . In qualitative analysis, we selected 6 samples, which contained cancer and adjacent normal tissues, for comparison . Two independent pathologists who were not aware of the relevant clinical information evaluated the results of IHC staining of tumor sections . The positive staining score of cancer cells was divided into the following five grades: 0 (0), 1 (< 10%), 2 (11% to 50%), 3 (51% to 75%), and 4 (> 75%). The staining intensity was graded as follows: 0 (negative = no staining), 1 (weak = light yellow), 2 (moderate = yellow brown), and 3 (strong = brown). The staining index (SI) was defined as the staining intensity score × the proportion of positive staining tumor cells (ranging from 0 to 12). Simultaneously, we defined SI ≥ 6 as high expression and SI < 6 as low expression.
The relationships between MTFR2 expression levels and sex, age, T stage, lymphatic metastasis, distant metastasis (tumor-node-metastasis [TNM] stage) and clinical stage were analyzed using the Spearman correlation method. The effect of MTFR2 expression on clinicopathological characteristics was assessed using the χ2 test or the Fisher’s exact test. For survival analysis, the effect of clinicopathological characteristics and MTFR2 expression on prognosis of ESCC were examined by the Kaplan–Meier analysis and the log rank test, and further evaluated by univariate and multivariate Cox regression analyses. All statistical analyses were performed using SPSS software version 20 (SPSS Inc., Chicago, IL, USA). Statistical significance was set at
After IHC in 115 specimens, we found that MTFR2 was highly expressed in ESCC tissues. To validate the expression of MTFR2 in ESCC, we further analyzed the expression of MTFR2 in 6 pairs of ESCC tumor and adjacent normal tissues. Compared to that in normal tissues, the expression of MTFR2 in ESCC tissues was significantly upregulated as shown in Figure 1. In addition, to evaluate the association between MTFR2 expression and clinicopathological characteristics of patients with ESCC, we analyzed such associations in remaining 115 ESCC patients. These included 25 patients with stage I, 53 patients with stage II, 32 patients with stage III, and 5 patients with stage IV. The IHC staining showed that 38 cases (33.00%) had high MTFR2 protein expression and 77 cases (67.00%) had low or no expression (Table 1).
As shown in Table 2, there was no significant difference in MTFR2 expression for age and sex (
In the patients with low MTFR2 expression, the rate of cumulative 5-year survival was 61.0% (95% CI, 60.6%, 75.9%), while that was only 15.8% (95% CI, 15.2%, 28.1%) in patients with high MTFR2 expression.
Furthermore, we found that the survival time of ESCC patients was negatively correlated with MTFR2 expression (r = –0.580,
Finally, we performed both univariate and multivariate Cox regression analyses to assess the associations between MTFR2 expression and survival of patients with ESCC. Our results showed that the expression of MTFR2 was a significantly independent prognostic predictor for ESCC (adjusted hazard ratio [aHR], 3.04, 95%CI, 1.75 to 5.30;
In this study, MTFR2 expression was relatively higher in tumor lesions than that in normal tissues. MTFR2 was highly expressed in ESCC tumor specimens, and it was significantly correlated with clinical stage, T, N, M classification, histological differentiation, and metastasis of ESCC. The expression of MTFR2 increased with the progression of ESCC. Our current findings demonstrate that MTFR2 is an independent prognostic factor for the prognosis of patients with ESCC, and the patients with high MTFR2 expression have worse survival than those with corresponding low expression. Therefore, it is likely that MTFR2 expression may have a significant clinical value as a new prognostic predictor and one of potential novel targets for future targeted treatment of ESCC.
As a mitochondrion fission factor, MTFR2 participates in aerobic respiration and has antioxidant effects [8,17]. In addition, MTFR2 may play a key role in the induction of intrinsic apoptosis [18,19]. Compared to its role in normal cells, mitochondrion induces tumor-related programming and accelerates growth of tumor cells and blood vessels [20,21]. Some studies have shown that MTFR2 may transcriptionally regulate dual specificity protein kinase TTK .
TTK depletion might seriously impair the viability and clonogenic capability of triple-negative breast cancer cell lines . Thus, TTK might be an independent predictor of prognosis, and it appears biologically plausible that MTFR2 might play important roles in regulation of TTK in ESCC as well as occurrence and development of ESCC. However, the exact mechanisms underlying such associations require further exploration.
Dastsooz et al.  showed that the expression of MTFR2 was related to poor prognosis, suggesting that MTFR2 might be involved in the progression and invasion of several cancers [28,29]. In recent studies [11,12], MTFR2 was highly expressed in breast cancer tissue. Its altered expression affected the proliferation and metastasis of breast cancer and inhibited epithelial mesenchymal transition. Other similar studies found that the high expression of MTFR2 was related to the clinicopathology, diagnosis and prognosis, and promoted the occurrence and cancer development through p53-dependent cell cycle, DNA replication, and homologous recombination in lung cancer . Such findings may highlight the potential role of MTFR2 in ESCC as a novel therapeutic target for treatment.
Although we found that MTFR2 was overexpressed in ESCC, and was significantly associated with advanced disease and prognosis, which was consistent with the research on glioma , our research has some limitations. First, we only analyzed the expression levels of cell protein, while we did not specifically analyze other aspects of genetic alterations. Second, our sample size is relatively small, and all study patients are from a single hospital. Moreover, the selection bias may also exist. Nevertheless, the current preliminary findings from this pilot study might serve as a basis for future hypothesis generation and testing as well as validation in large well-designed prospective studies. Finally, more studies are needed to explore the exact molecular mechanisms underlying such associations.
In conclusion, in the current study, we found that MTFR2 is overexpressed in ESCC and correlated with ESCC progression. MTFR2 overexpression was inversely associated with survival of patients with ESCC, particularly in aggressive tumors. Thus, our current findings might support that MTFR2 could be an independent biomarker for prognosis and exploited as a potential new therapeutic target for ESCC.
This article is one of the results of the Key Research and Development Plan of Yantai City (2018SFGY110).
No potential conflicts of interest were disclosed.
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