Potential Association of EEF1A Dimethylation at Lysine 55 in the Basal Area of Helicobacter Pylori-Eradicated Gastric Mucosa with the Risk of Gastric Cancer: A Retrospective Observational Study

doi:10.21203/rs.3.rs-1072695/v1

Background

Although eradication therapy for chronic Helicobacter pylori reduces the risk of gastric cancer (GC), its effectiveness is incomplete. Therefore, it is critically important to identify those patients who remain at high risk after H. pylori eradication therapy. Accumulation of protein methylation is strongly implicated in cancer, and a recent study showed that dimethylation of eEF1A lysine 55 (eEF1AK55me2) promotes carcinogenesis in vivo. We aimed to investigate the relationship between eEF1A dimethylation and H. pylori status in gastric mucosa and to reveal potential downstream molecules of eEF1A dimethylation in H. pylori-eradicated mucosa.

Methods

Records of 115 patients (11 H. pylori-negative, 29 H. pylori-positive, 75 post-eradication patients) who underwent upper gastrointestinal endoscopy were retrospectively reviewed. The eEF1A dimethyl level was evaluated in each functional cell type of gastric mucosa by immunofluorescent staining. We also investigated the relationship between eEF1AK55me2 downregulation by CRISPR/Cas9-mediated deletion of Mettl13, which is known as a dimethyltransferase of eEF1AK55me2.

Results

The level of eEF1A dimethylation significantly increased in the surface and basal areas of H. pylori-positive mucosa compared with -negative mucosa (surface, p=0.0031; basal, p<0.0001). The eEF1A dimethyl levels in the surface area were significantly reduced by eradication therapy (p=0.005), but those in the basal area were maintained even after eradication therapy. Multivariate analysis revealed that high dimethylation of eEF1A in the basal area of the mucosa was the independent factor related to GC incidence (odds ratio=3.6611, 95% confidence interval=1.0350–12.949, p=0.0441). We also showed the relationship between eEF1A dimethylation and expressions of reprogramming factors Oct4 and Nanog by immunohistochemistry and in vitro genome editing experiments.

Conclusions

The results indicated that H. pylori infection potently induced eEF1A dimethylation in gastric mucosa. The accumulation of dimethyl-eEF1A in the basal area of the mucosa might contribute to GC risk via regulation of reprograming factors in H. pylori-eradicated gastric mucosa.

Gastroenterology & Hepatology

Atrophic gastritis

Gastric cancer

Risk factor

Methylation

Helicobacter pylori infection, which causes atrophic gastritis, has been defined as a sequence of histological events that confers an increasing risk of malignant transformation [1, 2]. Reductions in primary and metachronous gastric cancer (GC) are expected with H. pylori eradication, whereas eradication alone does not completely eliminate GC risk in patients with atrophic gastric mucosa as precancerous lesions [3, 4]. Therefore, even after eradication therapy, identification of patients with high risk of GC is necessary to improve patient outcomes via an effective follow-up strategy.

In previous studies, accumulations of methylation in gastric mucosa after H. pylori eradication therapy were correlated with GC risk [5–7]. Most of these reports addressed only epigenetic biomarkers, such as DNA or histone methylation, in regard to the risk of GC in patients with chronic gastritis [8, 9]. However, it was recently revealed that hundreds and likely thousands of proteins are also methylated at lysine, which leads to upregulation of cellular pathways such as those for growth signaling and response to damage from chronic inflammation [10–12]. Eukaryotic elongation factor 1A (eEF1A) is one of the evolutionarily conserved and fundamental non-ribosomal components of the translational machinery [13]. The expression or upregulation of eEF1A has been reported to be associated with cancer development and invasion in ovarian, breast, lung, prostate, hepatic, and pancreatic cancers [14–16, 17]. Additionally, a recent study showed that dimethylation of eEF1Al lysine 55 (eEF1AK55me2) leads to its activation and utilization to increase translational output and promote carcinogenesis in vivo [12].

Although methylation is recognized as a key mechanism in cancer development in atrophic gastric mucosa [5, 18], how lysin methylation is maintained in atrophic gastric mucosa and contributes to GC development remains mostly unclear.

The aim of this study was to clarify the association between the dimethylation of eEF1A, an active GTPase form, and H. pylori infection status and GC incidence in gastric mucosa. Additionally. we investigated how dimethylated eEF1A contributes to GC development after eradication in gastric mucosa by focusing on the reprogramming factors Oct4 and Nanog.

Study subjects

We retrospectively investigated the mucosa of the middle portion of the greater curvature of the gastric corpus, approximately 8 cm from the gastric cardia, in patients who underwent upper gastrointestinal endoscopy with biopsy at Oita University Hospital, Japan, between January 2001 and December 2018. The biopsy site “B2”, which is recommended by the Updated Sydney System, is assumed to be best suited for evaluating the histological status of the fundic glands [19]. H. pylori infection was determined by culture, histology, and rapid urease test. In H. pylori-negative patients, we additionally confirmed the lack of endoscopic atrophy and histologic gastritis.

Histological analysis

Specimens were collected endoscopically from the greater curvature of the gastric middle bodies. Biopsy specimens were immediately fixed in 10% neutral buffered formalin for 24 h and embedded in paraffin wax blocks. Fixed samples were sliced into 3-μm-thick sections and stained with hematoxylin and eosin. Degrees of inflammation, activity, atrophy, and intestinal metaplasia were scored according to the Updated Sydney System (0, none; 1, weak; 2, moderate; 3, marked) [19].

Immunofluorescent staining

Anti-MUC5AC (1:50, Leica Biosystems), H⁺/K⁺ATPase (1:100; Medical & Biological Laboratories), MUC6 (1:200; BioRad), and PG1 (1:200; Abnova) antibodies were used for immunostaining to differentiate between cell types in the fundic glands. We performed immunohistochemistry using anti-dimethyl-eEF1AK55me2 antibody (1:400; ABclonal Technology), Nanog (1:10000; Cell Signaling Technology), and Oct4 (1:100; Santa Cruz Biotechnology, Santa Cruz, CA, USA). All biopsy materials were fixed in 10% buffered formalin for 24 h and then embedded in paraffin. After deparaffinization and subsequent rehydration to remove xylene, endogenous peroxidases were inactivated with 3% hydrogen peroxide solution (Wako, Osaka, Japan). Antigen retrieval was performed at pH 6.0. Next, the sections were incubated overnight with monoclonal anti-MUC5AC, MUC6, H⁺/K⁺ATPase, PG1, and dimethyl-eEF1A primary antibodies, followed by incubation with secondary antibodies (1:1000; Alexa Fluor R488 and 594) at room temperature for 2 h. After washing, images were captured with a Keyence BZ-9000 microscope (Keyence, Osaka, Japan).

Evaluation of dimethyl eEF1A level

Dimethylation levels of eEF1A were evaluated on surface, middle, and basal areas of gastric glands, which were identified by morphological appearance or immunostaining with antibodies for specific markers MUC5AC, H+/K+ ATPase, and PG1, respectively. After immunofluorescence staining with anti-dimethyl-eEF1A antibody, the mean fluorescent intensities of these areas were quantified using the region of interest (ROI) tool in ImageJ software. Multiple ROIs were set for each area based on marker immunofluorescence in one image, and several images at 4× magnification were used for each patient. Then, the dimethylation level of eEF1A for each area in each patient was expressed as an average of multiple mean fluorescent intensities from the ROIs.

Statistical analysis

We investigated the relationship between the clinical factors and dimethyl-eEF1A level of atrophic gastritis mucosa using univariate and multivariate analysis. All variables are expressed as means ± standard deviation for continuous data (Table 2). Prior to analysis, continuous data were divided into two groups using average values. Levels of eEF1A dimethylation were compared between groups using analysis of variance or analysis of covariance (for age-adjusted data), followed by the Tukey test. Univariate analyses were performed using the Student t-test or the Tukey test for continuous variables and chi-squared test for categorical variables. The results of the multivariate logistic regression analysis are expressed as adjusted odds ratios (aOR) with 95% confidence intervals (CI). A p-value <0.05 was considered to indicate statistical significance. All statistical analyses were performed using with JMP^® 11 (SAS Institute Inc, Cary, NC, USA).

Cell culture and CRISPR/Cas9

TMK-1 was provided by Dr. H. Ito (Tottori Prefectural Kousei Hospital, Tottori, Japan) with permission from an original provider, Dr. A. Ochiai (National Cancer Center, Kashiwa, Japan). Cells were cultured in RPMI1640 (Sigma) with 10% fetal bovine serum. We established Mettl13-knockout TMK-1 cells using the CRISPR-Cas9 genome editing system and generated stable Mkettl13 knockdown TMK-1 cells. Briefly, a single guide (sgRNA) targeting Mettl13 (5′-AAGAAAGCTTTCGAGTGGTATGG -3′) was cloned into a Cas9-expressing plasmid (pSpCas9(BB)-2A-Puro(PX450); Addgene plasmid #62988), and the plasmid was transfected into TMK-1 cells, which was subsequently cloned after a 2-day treatment with 2 µg/mL puromycine. Knockout of Mettl13 was confirmed by Western blotting.

Western blotting

Western blotting was performed as described previously [20]. Cells were lysed on ice for 20 min in SDS-modified RIPA buffer containing protease and phosphatase inhibitor cocktails (cOmplete Mini; Roche Diagnostics, Mannheim, Germany) (PhosSTOP EASYpack; Roche Diagnostics) and then centrifuged at 4℃ at 15,000 rpm for 20 min. The resulting cell lysates (20 µg each) were boiled with Laemmli sample buffer and subjected to SDS-PAGE. The samples were transferred to a polyvinylidene difluoride membrane (Merk Millipore, Darmstadt, Germany), which was blocked for 1 h in Block Ace (DS Pharma, Osaka, Japan) at room temperature and then incubated overnight at 4℃ with primary antibodies against METTL13 (1:1000; Bethyl Laboratories), dimethyl-eEF1A (1:1000; ABclonal Technology), eEF1A(1:1000; ABclonal Technology), Nanog (1:1000; Abcam), Oct4 (1:1000, Abcam), and GAPDH (1:1000, Santa Cruz Biotechnology). After washing with TBS containing 0.1% Tween 20, the membranes were incubated for 1 h at room temperature with appropriate secondary antibodies, followed by rewashing [20]. Finally, the signals were detected using an ECL Western blotting analysis system (GE Healthcare, Piscataway, NJ, USA) in accordance with the manufacturer’s instructions.

We retrospectively investigated the gastric corpus mucosa from 115 subjects (11 H. pylori-negative, 29 H. pylori-positive, and 75 post-eradication patients). The characteristic of the patients are provided in Table 1. Updated Sydney System scores for inflammation, activity, atrophy, and intestinal metaplasia (IM) are shown in Table 2. The dimethyl level of eEF1A of each gland area identified morphologically or by immunostaining for specific markers (surface, MUC5A; middle, H+/K+ATPase; and basal, PG1) was evaluated (Suppl. Figure 1 and Table 2). In the middle area, dimethyl-eEF1A was not detected in MUC6-positive cells but only in H+/K+ ATPase-positive cells (Suppl. Figure 1).

Difference in eEF1A dimethylation of gastric mucosa by H. pylori infection status

To investigate the association between H. pylori infection/eradication and eEF1A dimethylation in gastric mucosa, we first compared the dimethylation levels of eEF1A in each area (MUC5AC-, H^+/K⁺ATPase-, and PG1-positive cells) between the three groups: H. pylori-negative, H. pylori- positive, and post-eradicated patients (Figure 1a). H. pylori-positive patients showed higher eEF1A dimethylation than H. pylori-negative patients in the surface and basal areas of the gastric mucosa (surface: 16.91±6.42 vs. 27.95±10.95, p=0.0003 ; basal: 14.03±4.88 vs. 29.31±6.19, p<0.0001). These results suggested that dimethylation of eEF1A is associated with H. pylori infection in gastric mucosa.

The dimethylated eEF1A that was caused by H. pylori infection was effectively reduced in the surface area (MUC-5AC-positive area) of post-eradicated mucosa (p=0.0050) (Figure 1b). However, H. pylori eradication therapy did not affect eEF1A dimethylation in the basal area (PG-1-positive area) (Figure 1b). Because there were age differences between these three groups (Table 1), we also calculated the age-adjusted levels of eEF1A dimethylation and compared them between the groups using analysis of covariance with the Tukey test. We found the same tendency in both the crude and age-adjusted models, indicating that age-related differences in methylation did not account for the results (Figure 1b). These results suggested that the dimethylation of eEF1A in the basal level remained high in atrophic gastric mucosa even after H. pylori eradication therapy.

Univariate and multivariate analyses of GC and eEF1A dimethylation in basal area of gastric mucosa

As the accumulation of methylation is known to be one of the important factors in gastric carcinogenesis [21, 22], we investigated whether dimethylation of eEF1A in the basal area could cause a risk of cancer in post-eradicated atrophic gastritis mucosa. The influence of known potential risk factors for GC (age, sex, period after eradication therapy, and histological features) and eEF1A dimethyl level in basal mucosa were analyzed in 75 H. pylori eradication patients, which included in part those with a history of GC treatment. Univariate analyses showed that severe histological atrophy and high eEF1A dimethylation of the basal mucosal area were the risk factors for GC (Figure 2 and Table 3). Multivariate analysis revealed that not only histological atrophic levels (aOR=9.9493, 95% CI=1.7096–57.901, p=0.0106) but also high dimethylation of eEF1A in basal mucosal areas (aOR=3.6611, 95% CI=1.0350–12.949, p=0.0441) were the independent factors related to GC incidence (Table 3).

Accumulation of eEF1A dimethylation and metaplasia in gastric mucosa

Metaplastic lineages have been associated with various injurious scenarios in atrophic gastritis mucosa. We investigated eEF1A dimethylation in the area of IM (n=11) of eradicated mucosa. There was no significant accumulation in eEF1A dimethylation in the IM area compared with other gastric gland cells (mean: 22.01±8.86, Table 2). Although IM is considered an important step in the pathogenesis of GC in atrophic gastric mucosa, there was no significant increase in eEF1A dimethylation in the IM area in eradicated patients with GC incidence (GC(-), n=7 and GC(+), n=4) (Figure 3).

Association of eEF1A dimethylation with the expressions of reprogramming factors Oct4 and Nanog

In recent reports, chief cells have been identified as a cell capable of reprogramming and metaplastic response to parietal cell damage in atrophic gastric mucosa [23, 24]. Octamer-binding transcription factor 4 (OCT4), and Nanog lie in the core of the transcriptional network that controls stem cell pluripotency [25]. Therefore, we investigated whether the expressions of Oct4 and Nanog correlate with dimethylated eEF1A in post-eradicated mucosa. As shown in Figure 4a and b, the proportion of Oct4- or Nanog-positive cells in eradicated mucosa was significantly higher in patients with high eEF1A dimethylation. To investigate whether dimethylated eEF1A contributes to the expressions of Oct4 and Nanog in gastric cells, we next deleted Mettl13, which is the physiologic eEF1A lysine 55 dimethyltransferase [12], in a TMK-1 cell using the CRISPR/Cas9 system and analyzed the effect on the expressions of Oct4 and Nanog. As shown in Figure 4c, knockout of Mettl13 led to a decrease in the eEF1A dimethylation level in TMK-1 cells. Interestingly, reduction of dimethylated eEF1A downregulated the expressions of Oct4 and Nanog in TMK-1 cells (Figure 4d). These results suggest that accumulation of dimethylated eEF1A in the basal area of eradicated mucosa is associated with the expression of Oct4 and Nanog, which control reprogramming of various types of differentiated cells in response to chronic damage induced by H. pylori infection.

The presence of H. pylori, a well-known inducer of chronic inflammation and atrophy, is reported to be associated with aberrant DNA methylation in gastric mucosa [5]. However, it remains unknown whether H. pylori infection also induces aberrant methylation at the protein level, except for histone modification. In this study, we immunohistochemically analyzed the association of H. pylori status with the distribution of dimethylated eEF1A, whose function in tumorigenicity has been characterized recently by Liu et al. [12]. This is first report, to our knowledge, to spatially show the impact of H. pylori infection on the level of eEF1A dimethylation in gastric mucosa.

Our results showed that the levels of eEF1A dimethylation in gastric mucosa were different according to H. pylori status (negative, positive, and post-eradication therapy). eEF1A dimethylation of surface and basal cell areas was higher in H. pylori-positive than H. pylori-negative patients, suggesting that H. pylori infection induces eEF1A dimethylation of surface and basal cells in gastric mucosa. Indeed, eEF1A dimethylation in H. pylori-negative mucosa with adenocarcinoma of the fundic gland type, which is known to be unrelated to H. pylori infection, was comparable to that in H. pylori-negative and cancer-free mucosa (data not shown), further supporting our hypothesis that H. pylori infection might cause aberrant protein methylation.

Eradication of H. pylori infection has been reported to reduce the risk of GC among asymptomatic patients in high-risk countries [4]. However, long-term studies from Japan revealed that eradication therapy cannot reduce the risk of GC completely [2, 26, 27]. In the present study, we focused on a subset of atrophic gastritis patients who showed high dimethylation of eEF1A in the basal area of H. pylori-eradicated mucosa and found that highly dimethylated eEF1A in PG1-positive cells, chief cells in the basal area of the gastric mucosa, correlated with GC incidence in the post-eradicated gastric mucosa. Unlike the basal area of H. pylori-eradicated gastric mucosa, the eEF1A dimethylation occurring in the surface area (MUC5AC-positive cells) was strongly associated with H. pylori eradication therapy, i.e., the level of eEF1A dimethylation in the surface area were significantly reduced after eradication regardless of the incidence of GC. Considering that the cell lineages in gastric mucosa are known to vary greatly in their life spans, from 3 to 5 days for surface cells to several months for basal chief cells [28], these different life spans among gastric-cell lineages might cause specific accumulation of dimethylated eEF1A in the basal area even after eradication therapy. In our results, eEF1A dimethylation in the basal area of eradicated mucosa did not show significant reduction even after long-term monitoring following H. pylori eradication therapy in patients with GC incidence (follow-up periods of <3.5 versus ≥3.5 years, p=0.3908). Although data from further long-term monitoring after eradication therapy is needed, the level of dimethylated eEF1A could be a potential marker for GC risk during the follow-up of H. pylori-eradicated patients.

Although the severity of atrophic damage is already known to be strongly associated with carcinogenesis in gastric mucosa [29], the pathogenic mechanism of how H. pylori infection induces GC has remained a challenging question for decades. Consistent with previous studies, the present study also showed that the patients with severe atrophic change have GC incidence (Table 3). Additionally, we confirmed that eEF1A dimethylation in the basal area of the gastric mucosa is also an independent factor of GC incidence. Previous studies have also shown that damage to the gastric mucosa, including H. pylori-induced oxyntic atrophy, initiates mucosal metaplasia and the reprogramming and proliferation of basal cells, and these responses are associated with carcinogenesis in atrophic gastric mucosa [23, 30, 31]. Although our results indicated no significant increase in dimethylated eEF1A in the metaplasia area in eradicated gastric mucosa with GC incidence, we showed an association between the expressions of Oct4 and Nanog, which are known as crucial reprogramming factors, and eEF1A dimethylation in the basal area of eradicated gastric mucosa. Additionally, we also created a dimethyl-eEF1A-induced increase in the expression of Oct4 and Nanog in TMK-1 cells. Self-renewing progenitor and differentiating cells expressing reprograming factors may be a target for cancer initiation and progression through the induction of symmetrical cell division [32]. These results suggest that high eEF1A dimethylation in the basal area of eradicated mucosa could not only be a useful marker for GC risk but also might contribute to the development of gastric lesions, such as metaplasia and cancer, via regulation of Oct4 and Nanog. Further molecular functional analysis of eEF1A dimethylation will lead to elucidation of the mechanism of carcinogenesis in H. pylori-eradicated gastric mucosa.

The present study has several limitations. First, this was a retrospective observational study performed at a single center and only included patients who underwent upper gastrointestinal endoscopy for abdominal symptoms or other medical problems reported. Most participants had primary disease; therefore, bias may have occurred. Next, our study contained only 11 patients with IM, 4 of whom had a history of GC treatment (Table 3). Dimethyl-eEF1A was not detected in the MUC6-positive cells, so we therefore focused only on the fundic gland area. Because a recent study showed that alterations in methylation were observed in regions of IM [33], further prospective studies with larger numbers of samples including IM regions in the antrum area of the gastric mucosa may lead to the discovery of new pathological mechanisms of carcinogenesis in eradicated gastric mucosa.

In conclusion, the present results indicated that H. pylori infection induces dimethylation of eEF1A in the surface and basal areas of gastric mucosa. Especially, the dimethylation level of eEF1A in the basal area of gastric mucosae may be associated with the expression of reprogramming factors and GC risk in post-H. pylori-eradicated mucosa.

Acknowledgments

We would like to thank Mr. Yoshiyuki Tsukamoto, Ms. Kanako Ito, and Ms. Yoko Kudo for their excellent assistance with the experiments.

Author contributions

All authors have approved the final version of the article. Conceptualization: YH; Formal analysis and investigation: YH, MF, and MK; Writing - original draft preparation: YH; Writing - review and editing: KMizukami, YT, KH, TO, MK; Resources: YK, YW, KT, KF, KO, RO, and OM; Supervision: KMurakami.

Corresponding author

Correspondence to Yuka Hirashita.

Ethic approval and consent to participate

This study was approved by the ethics committee of Oita University Faculty of Medicine (approval number: 1541). All procedures were carried out according to the principles outlined in the Declaration of Helsinki. Written informed consent was obtained from the patients prior to study participation.

Consent for publication

Not applicable.

Conflict of interest

The authors declare that they have no conflict of interest.

Availability of data and materials

The datasets in this study available from the corresponding author on reasonable request.

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Table 1 Patient Characteristics (n=115)

Characteristics	Value
**HP-negative patients(n=11)**
Age (years)	45.36 ± 16.64
Sex(female/male)	3(27%)/8 (73%)
Endoscopic atrophy* (Close/Open)	8 (100%)/0 (0%)
HP-positive patients (n=29)
Age (years) Sex (female/male) History of gastric cancer (-/+) Endoscopic atrophy* (Close/Open)	68.76±10.33 7(24%)/22(76%) 16(55%)/13(45%) 6 (21%)/23(79%)
Post-HP-eradication patients (n=75)
Age (years) Sex (female/male) Incidence of gastric cancer (-/+) HP eradication therapy ** (1^st/2^nd) Period after eradication therapy (years) Endoscopic atrophy* (Close/Open)	69.52 ± 9.24 26 (35%)/49 (65%) 54 (72%)/21 (28%)/5 60(80%)/15(20%) 3.58±3.34 23 (35%)/52 (65%)

, *Kimura-Takemoto classification , **1^st line treatment (PPI, [proton pump inhibitor] clarithromycin, and amoxicillin), 2^nd line treatment (PPI, metronidazole, and amoxicillin)
HP, Helicobacter pylori

Table 2 Mean Pathological Features and Levels of eEF1A Dimethylation in Gastric Mucosa

HP-negative patients (n=11)	Mean (SD)
Histological features*
Activity	0
Inflammation	1.00 (0.000)
Atrophy	0
Intestinal metaplasia	0
eEF1A dimethyl level**
Surface	16.91 (6.423)
Middle	27.68 (6.010)
Basal	14.03 (4.882)
HP-positive patients (n=29)	Mean (SD)
Histological features*
Activity	0.79 (0.774)
Inflammation	1.76 (0.786)
Atrophy	0.55 (0.736)
Intestinal metaplasia	0.07 (0.371)
eEF1A dimethylation level**
Surface	27.95(10.954)
Middle	34.08 (9.658)
Basal	29.31 (6.187)
post eradicated patients (n=75)	Mean (SD)
Histological features*
Activity	0.04 (0.256)
Inflammation	1.20 (0.637)
Atrophy	0.44 (0.793)
Intestinal metaplasia	0.25 (0.660)
eEF1A dimethylation level**
Surface	22.52 (6.334)
Middle	32.59 (7.437)
Basal	25.26 (9.700)
Intestinal metaplasia	22.01 (8.86)

*scored using the Updated Sydney System, ** immunofluorescent intensity

Table 3. Univariate and multivariate analyses of the association between dimethyl eEF1A level and GC

No competing interests reported.

Suppfigure1.tif
Supplemental Figure 1 The study profile and immunofluorescent staining of H. pylori-eradicated gastric mucosa. (a) All patients received eradication therapy and were enrolled at least 6 months after establishment of successful H. pylori eradication (n=75). (b) Schematic model of a fundic gland. (c) Representative images of immunofluorescent staining for MUC5AC, MUC6, H+/K+ATPase, PG1, and dimethyl-eEF1A of gastric mucosa are shown. Merging was not detected in the MUC6 and dimethyl-eEF1A cell.
Suppfigure2.tif
Supplemental Figure 2 Full-length Western blot images.

Potential Association of EEF1A Dimethylation at Lysine 55 in the Basal Area of Helicobacter Pylori-Eradicated Gastric Mucosa with the Risk of Gastric Cancer: A Retrospective Observational Study

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Abstract

Background

Methods

Results

Conclusions

Figures

Introduction

Materials And Methods

Results

Discussion

Declarations

References

Tables

Additional Declarations

Supplementary Files

Status:

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