Bioinformatics analysis of MMP7 expression in gastric cancer
Gastric adenocarcinoma represents the primary form of gastric cancer, with metastasis in gastric adenocarcinoma patients being a critical determinant of their quality of life and survival. Our analysis of gene expression profiles in gastric adenocarcinoma, utilizing data from the TCGA database, revealed elevated expression levels of MMP11 and MMP7, members of the MMPs family (as depicted in Fig. 1). MMP7, specifically, is secreted by cancer cells and possesses the ability to degrade the extracellular matrix, facilitating the breach of the initial defensive barrier during cancer cell metastasis.
Subsequent to this, we conducted an analysis of MMP7 RNA expression levels in different types of tumors. As illustrated in Fig. 2A-B, the results indicate a significant elevation in MMP7 expression within gastric adenocarcinoma. When compared to normal tissue samples (n = 34), the transcription levels of MMP7 in gastric adenocarcinoma tissue samples (n = 415) were notably higher, as demonstrated in Fig. 2C. Furthermore, the survival prognosis curve reveals that heightened levels of MMP7 expression are associated with unfavorable survival outcomes for patients, as depicted in Fig. 2D.
Next, we delved into an analysis of MMP7 expression levels in gastric adenocarcinoma tissues across various stages. In comparison to normal tissues (n = 34), MMP7 expression exhibited a significant increase in Grade 1 (n = 12), Grade 2 (n = 148), and Grade 3 (n = 246) with strong statistical significance. Nevertheless, there were no statistically significant disparities in MMP7 expression levels among gastric adenocarcinoma tissues at different stages, as depicted in Fig. 3A.
Furthermore, we investigated MMP7 expression levels in gastric adenocarcinoma tissues across different grades. Contrasting with normal tissues (n = 34), MMP7 expression displayed a marked rise in Stage 1 (n = 18), Stage 2 (n = 123), Stage 3 (n = 169), and Stage 4 (n = 41), all exhibiting significant statistical significance. Notably, there were no discernible distinctions in MMP7 expression levels among gastric adenocarcinoma tissues of various grades, as illustrated in Fig. 3B.
Subsequent to these analyses, we examined the disparities in MMP7 levels within gastric adenocarcinoma tissues of male and female patients. The results indicated that in comparison to normal tissues (n = 34), MMP7 expression was elevated in both male (n = 268) and female (n = 147) patients, but no notable differences were observed in MMP7 expression levels between male and female patients, as shown in Fig. 3C.
Crucially, we also compared MMP7 expression differences in gastric adenocarcinoma patients with lymph node metastasis. The findings highlighted that, when compared to normal tissues (n = 34), MMP7 expression increased significantly in N0 (n = 123), N1 (n = 112), N2 (n = 79), and N3 (n = 82), without any statistically significant disparities in MMP7 expression levels between gastric adenocarcinoma tissues from patients with varying degrees of lymph node metastasis, as depicted in Fig. 3D.
These observations underscore the pivotal role of MMP7 in the metastasis process of gastric adenocarcinoma, emphasizing the clinical significance of selecting MMP7 as a target for further exploration and potential intervention.
Bioinformatics analysis of EGFR expression in gastric cancer
The transcription level expression of MMP7 is regulated by upstream signaling pathways. Research reports have shown that EGFR can regulate the expression of MMP7 in diabetic kidney disease24. We analyzed the differential expression of EGFR in normal and gastric adenocarcinoma tissues using the TCGA database, and the results showed that EGFR was highly expressed in gastric adenocarcinoma (Fig. 4A). More importantly, we analyzed the impact of EGFR on survival and prognosis in gastric adenocarcinoma, and the results showed that overexpression of EGFR in gastric adenocarcinoma is not conducive to the survival and prognosis of patients (Fig. 4B).
The expression of MMP7 and EGFR is higher in metastatic gastric adenocarcinoma tissues
A total of 32 clinical samples, comprising gastric adenocarcinoma and corresponding normal tissue samples, were collected. Among these, 17 samples were derived from metastatic cases, and 15 from non-metastatic cases. Immunohistochemical staining for EGFR and MMP7, along with HE staining, was performed on these samples. Here, we present the representative findings from two non-metastatic cases (Patients 1 and 2) and two metastatic cases (Patients 3 and 4).
Upon analyzing the correlation between EGFR and MMP7 in gastric adenocarcinoma tissues with and without metastasis using Graphpad Prism, the results unveiled higher expression levels of both EGFR and MMP7 in metastatic tissues when compared to non-metastatic tissues. These findings align with the results obtained from our prior bioinformatics analysis, underscoring the crucial role of EGFR and MMP7 in the metastatic progression of gastric adenocarcinoma (Fig. 5A-C). This collective evidence reaffirms the significance of these proteins in the metastasis process of gastric adenocarcinoma.
EGFR and MMP7 are positively correlated in gastric adenocarcinoma tissue
Subsequently, we examined the expression levels of EGFR and MMP7 in 17 metastatic patients, categorized into low to moderately high MMP7 expression levels, as illustrated in Fig. 6A. Patient 5 exhibited low immunohistochemical staining of MMP7, Patient 6 displayed moderate immunohistochemical staining of MMP7, and Patient 7 showcased high immunohistochemical staining of MMP7 (Fig. 6A).
We further scrutinized the immunohistochemical staining levels of EGFR and MMP7 in the 32 gastric adenocarcinoma tissue samples and their corresponding normal tissue counterparts. The results demonstrated elevated expression levels of both EGFR and MMP7 in gastric adenocarcinoma tissue samples compared to normal tissue samples, as delineated in Fig. 6B-C.
Notably, from Fig. 6A, it becomes evident that as the MMP7 expression level decreases (as seen in Patient 5), the EGFR expression is also lower. Conversely, when MMP7 expression is high (as observed in Patient 7), EGFR expression levels increase correspondingly. Consequently, we performed a correlation analysis between EGFR and MMP7 in the 32 gastric adenocarcinoma tissue samples, revealing a positive correlation between EGFR and MMP7 expression (r^2 = 0.6219, P < 0.0001), as represented in Fig. 6D. This correlation underscores the association between EGFR and MMP7 in gastric adenocarcinoma, reinforcing their potential significance in the disease process.