3.1 Single-cell transcription mapping and cell typing of the CC matrix
To understand the cellular diversity and molecular features of cervical tissues in patients with CC, we analyzed scRNA-seq datasets of 20,938 cells from patients with CC and healthy control individuals. Of these cells, 10,395 were obtained from the tumor samples that comprised seven cell types, including Myeloid cells, lymphocytes, endothelial cells, endometrial stromal cells, fibroblasts, smooth muscle cells, and CC cells, which were compared with those of the normal group and annotated using classical marker genes (Fig. 1a, and S1a). The heatmap showed marker genes (Figure S1b and S1c). To understand the proportion of MMP molecules in each cell type, we used the bar graph to reveal the percentage of MMPs gene expression in each cell type. We found that MMP-1, MMP-7, MMP-13 and MMP-14 had a high proportion of diverse cell types (Fig. 1b). We also made conclusion that MMP-3, MMP-7, MMP-13 and MMP-14 were up-regulated in CC cells in individuals and MMP-9, MMP-14 and MMP-19 were up-regulated in Myeloid cells by employing the heatmap(Fig. 1c). To elucidate the mechanism of MMP regulation in diverse cell types in CC, we identified DEGs in individuals between MMPs high-expression and low-expression groups, finally it was found MMP-1, MMP-12, MMP-13 and MMP-7 were upregulated, but MMP-14, MMP-19, MMP-2, and MMP-21 were downregulated in diverse cell types (Fig. 1d), suggesting biochemically redundant members of the MMP family may have intricate interplay in tumor progression. To further explain the relationship between the expression of five MMPs in diverse cell types, we performed the re-clustering and Uniform Manifold Approximation and Projection (UMAP) dimensionality reduction profiles of MMPs in the CC and control groups. We found that the expressions of MMP-14, MMP-19 and MMP-2 were upregulated in normal individuals compared to CC (Fig. 1f–h), during which fibroblasts and myeloid cells displayed abundant MMP expression, indicating that the MMPs gene set could participate in inhibits tumor progression of CC. To identify whether MMP molecules can be linked to an favorable prognosis in CC, we then put MMPs as a gene module to calculate the score using AddModuleScore methods. The violin plot illustrated the fibroblasts, CC, and Mye cell had a higher score than the other cell types, consistently showing that the MMPscore was associated with immune responses in CC (Fig. 1e).
To investigate the association between the classical CC pathways and MMPscore more accurately, we analyzed another scRNA-seq datasets from 3 normal and 3 CC (Fig. 1i, Fig. 1j), which encompassed 50,014 cells from patients with CC and healthy control individuals that consisted of seven cell types, including macrophage, lymphocytes, Neutrophils, endothelial cells, fibroblasts, smooth muscle cells, and epithelial cells (CC cells) (Fig. 1l). The CC patient group had more abundant epithelial cells, macrophage and lymphocytes (Figure S1d). To understand the proportion of MMP molecules in each cell type, the bar graph showed the percentage of MMP-1, MMP-2, MMP-7, MMP-13 and MMP-14 had a high proportion of diverse cell types (Fig. 1n). By identifying DEGs between MMP high-expression and low-expression groups, MMP-1, MMP-3, MMP-12, MMP-13 and MMP-7 were upregulated, but MMP-2, MMP-14 and MMP-19 were downregulated in diverse cell types (Figure S1e-g). We also put MMPs as a gene module to calculate the score using AddModuleScore methods and to define scores separately. Then we found that fibroblasts, CC, and Mye cell also had a higher score, suggesting that MMP-related genes played function more in these cell types (Fig. 1k). A higher score for CC patients than for normal may indicate a potential association of MMP-related genes and CC. To probe the association between the MMP-regulation and progression of CC, we used the functional enrichment analyses based on the GSEA database, and we performed the correlation between MMPscore by AUCell and classical pathways in CC to explore the influence of MMP regulators on CC pathways. Notably, we found MMPscore was upregulating TGF-β pathway (R > 0.6) and epithelial cell proliferation (R > 0.8), but downregulating PD-1 (R < -0.8), HPV copy number (R < -0.4), Wnt pathway (R < -0.8) and CC cell proliferation (R < -0.2) in CC patients (Fig. 1m). To explore whether MMPs were associated with Wnt pathway in regulation of cell proliferation, with defense to virus by host and epithelial-mesenchymal transition (EMT). A correlation analysis combined with the MetaCell algorithm ( K = 30 ) revealed that MMP-1 (R = -0.79), MMP-7 (R = -0.69) and MMP-13 (R = -0.73)were negatively associated with EMT in CC. MMP-1 (R = -0.8), and MMP-7 (R = -0.81) and MMP-13 (R = -0.76)were negatively associated with Wnt pathway in regulation of cell proliferation. Scatter plot showed that MMP-7 (R= -0.57) and MMP-13 (R = -0.55) were negatively associated with positive regulation of defense response to virus by host in CC (Fig. 1m and Figure S1h-k). These results indicated that cell-type-specific up-regulation of MMP molecules was in normal cervical epithelial cell proliferation and inhibition to HPV infection, Wnt signaling, CC cell proliferation, EMT and PD1 in tumor proteins which controlled CC progression.
3.2 MMP genetic variation and expression landscape in CC
In this study, we first summarized the prevalence of MMP CNV and somatic mutations in CC. Investigating CNV alteration frequency showed prevalent CNV alteration in 21 regulators of three MMPs, mostly focusing on copy number amplification (Fig. 2a2). The chromosomal locations of MMP CNV alterations were shown in Fig. 2a1. By investigating MMP mRNA expression levels in normal and CC samples to determine whether the above genetic variations influenced MMP expression in patients with CC, we found that CNV change may be the main factor leading to abnormal MMP expression. Compared with normal cervical tissues, MMP-9 with amplified CNV demonstrated markedly higher expression in CC tissues (Figure S2e). There were significant differences in the expression of ten MMPs between patients with CC and normal controls (Fig. 2b). The correlation network diagram in Fig. 2c depicted MMP interactions and further confirmed the ubiquitous correlation of the ten MMPs. We then examined the Pearson correlation between ten MMPs associated with CC by Spearman’s correlation analyses, which observed a positive correlation among MMPs (Fig. 2d). In TCGA cohort, we used the R package “ConsensusClusterPlus” to categorize a series of patients with different MMP expression patterns according to the expression of the ten MMPs. With final identification of two distinct modification patterns by unsupervised clustering (Fig. 2e), we named these patterns MMPclusterA and -B that were supported by the principal component analysis results (Fig. 2f, Figure S2f-h, Figure S3a-b). Prognostic analysis of the two MMP expression subtypes revealed a prominent survival advantage within the MMPcluster-B expression pattern (p < 0.05) (Fig. 2g). We further explored the different clinicopathological features and prognoses between the two groups (Fig. 2h). The assessment of these data showed ten highly expressed MMPs in MMPcluster-A (Fig. 2i). In addition, we also examined the different expression of four MMP types, and a significant correlation with overall survival prediction was seen in patients with CC (Figure S2a-d).
3.3 Immune cell infiltration characteristics in the TME under different MMP expression patterns
The biological behaviors of various MMP expression patterns were analyzed by Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment. MMPcluster-A was significantly enriched in the matrix and carcinogenic activation pathways, like ECM receptor interactions, small cell lung cancer signaling pathways, cell adhesion, and MAPK signaling pathways, exhibiting significant aggregation during cell matrix catabolism. MMPcluster-B was mainly enriched in gene mutations, encompassing activation of homologous recombinant signaling pathways and RNA degradation signaling pathways (Fig. 2k). Furthermore, MMP expression patterns greatly differed in terms of cell composition, molecular function, and biological processes. MMPcluster-A presented a generally enriched result, especially in collagen catabolism, metabolism, ECM catabolism, and constituent components, unlike MMPcluster-B (Fig. 2l). Subsequent analyses indicated a higher degree of immune cell infiltration in the TME of MMPcluster-A, including activated T cells, CD56 + NK cells, MDSC, and plasmacytoid dendritic cells, while infiltration of CD56- NK cells, dendritic cells, and monocytes exhibited no clear difference between MMPcluster-A and -B (Fig. 2j). Combination of KEGG, GO, and TME immune cell infiltration analysis showed that MMP expression patterns had obvious immune cell infiltration characteristics. Despite the significant immune cell infiltration, MMPcluster-A did not show a matching survival advantage (Fig. 2g).
3.4 Generation of MMP gene signatures and functional annotations
To further investigate the potential biological behavior of each MMP expression pattern, we identified two expression patterns (MMPcluster-A and MMPcluster-B) by unsupervised clustering. To prepare for the establishment of the MMPscore and visualize the heatmap of DEGs between MMPclusterA and -B, we obtained a total of 350 genes using DEG analyses (Fig. 3a). Furthermore, through unsupervised clustering, DEGs were once again divided into three gene clusters: MMP gene cluster A-C (Fig. 3b), representing the genetic differences in MMPs. To quantify the MMP landscape and facilitate the identification of key genes, PCA was used to compute the aggregate score of feature genes from three different MMP genome phenotypes, respectively. We obtained the sum of scores and defined them as the MMPscore. All TCGA patients were stratified into two groups with high or low MMPscore. As indicated from the prognostic analyses, the prognosis of the high score was better than that of the low score, 27 of 253 patients with CC clustered in gene cluster B, which was shown to be associated with a better prognosis. In contrast, 94 patients in gene cluster A exhibited poorer prognosis. An intermediate prognosis was observed in gene cluster C with 132 clustered patients (Fig. 3c). In addition, we found that younger patients and patients with advanced diseases were significantly associated with lower MMPscore, implying that these patients were characterized by a poorer clinical outcome in the MMPcluster-A modification pattern (p < 0.05) (Fig. 3d), which suggested the two distinct MMP expression patterns in CC. We observed that MMP gene clusters A and B were consistent with the above expression patterns, whereas tumors in MMP gene cluster C exhibited poorer differentiation. Patients with clinically advanced diseases were characteristic of MMP gene cluster A, consistent with the above results (Fig. 3e). By performing ontology enrichment analyses of different MMP gene clusters, we found that they were significantly enriched in ECM, collagen, and extracellular structural tissues. Considering the individual heterogeneity of MMP expression (Fig. 3f), we quantified MMP expression in individual tumor cells by calculating the MMPscore. Compared with the other clusters, MMPcluster-A showed a significantly lower MMPscore, while MMPcluster-B displayed a high median score (p < 0.05) (Figure S3c). The Kruskal-Wallis test implied crucial differences in MMPscore between MMP gene clusters (p < 0.05). Gene cluster A had the lowest median score, while gene cluster B had the highest median score (Fig. 3d). Consistent with the above analysis, this suggested that a high MMPscore may be strongly associated with immune activation, whereas a low MMPscore may be linked to stromal activation. Next, we sought to further determine the importance of the MMPscore in predicting patient prognosis. Patients were divided into low and high MMPscore groups. Patients with high MMPscore showed a significant survival benefit (p < 0.001), approximately twice that of patients with low MMPscore (Fig. 3g). Besides, we found extremely different immune cell infiltration in the three gene clusters (Fig. 3h). Further single-sample GSEA revealed that different MMPscore were significantly associated with high and low levels of immune infiltration in tumor tissues (Fig. 3i, Fig. 4a). The high MMPscore group was dominated by immune cell activation that was closely correlated with prognosis (Fig. 3i). The above results strongly displayed that a high MMPscore was associated with increased immune activation. The MMPscore allowed for a better assessment of the MMP expression patterns of individual tumors and further assessed the TME infiltration characteristics of tumors to distinguish between true and false TME immune infiltration.
3.5 Role of MMP expression patterns in immunotherapy
To better characterize the MMP immune profile and test the correlation between immune cells and MMPscore, we examined the specific correlation between each TME-infiltrating cell type and high and low MMP expression, which showed a tight correlation (Fig. 3j). Our study implied that TME immune cell infiltration was significantly increased in tumors with high MMPscore, which meant a more significant positive correlation with T cell subsets, mast cells and B cells (p < 0.05) (Fig. 3k-m, Figure S3e-m). The investigation about the correlation between MMPscore and adhesion molecules, as well as between HLA molecules and interleukins, showed that MMPscore correlated significantly with immune checkpoints (Fig. 4a-c) with the most significant correlation of CD44 and TNFSF9 (Fig. 4d-f, Figure S3n-p). MMPscore can predict the strength and weakness of immune function with immunotherapy performed and evaluated for immune checkpoints. In addition, we found that different types of HLA also correlated with MMPscore (Fig. 4b), with HLA-E and HLA-C the most prominent (Fig. 4e, Figure S3p). For immune regulation, we found a correlation between MMPscore and interleukins (Fig. 4c), with TLSP and IL-33 of more value (Fig. 4f, Figure S3o). MMPscore also had predictive value in evaluating immune escape. The mRNA transcriptome showed differences with various MMPscore and correlated importantly with immune-related biological pathways (Fig. 4g). The expression of MMP may be involved in immune pathways and activation or inhibition. CD47 increased immune escape, and a high MMPscore was associated with low immune escape in a study examining the effect of MMPscore on immune checkpoint blockade therapy (Figure S4a). These results showed that tumors with high MMP expression showed significantly correlated immune activation pathways.
3.6 Characterization of MMP expression in TCGA molecular subtypes and tumor somatic cell mutations
TCGA constructed a comprehensive molecular landscape for CC and investigated the predictive ability of MMPscore in CC prognosis in patients with different tumor loads, revealing better survival prognosis in the high MMPscore group than in the low MMPscore group (Fig. 4h), which was not significantly related to high or low tumor loads (Fig. 4i). We counted 179 MMP mutations in 208 CC samples with a mutation frequency of 86.06%, of which TTN showed the highest mutation frequency followed by PIK3CA, and other genes also displayed varying degrees of mutation (Fig. 4j). The somatic mutation distribution differed between high and low MMPscore in the cohort (Fig. 4j, k): the low MMPscore group exhibited a wider range of tumor mutations, compared with the high MMPscore group. The rates of the 2nd and 14th most significant mutated genes were 27% and 7%, and 9% and 28%, respectively. The above analyses indicated that a high MMPscore was associated with long-term survival and durable clinical benefit. The combination of MMPscore and tumor mutation load could more accurately determine prognosis in different patient cohorts, and the predictive advantage of ROC curve assessment was reflected in the survival prognosis of patients with CC (Figure S3d).
3.7 Clinical features of MMP expression patterns
Consistent with the above findings (Fig. 5a), gene clusters B and C both showed high MMP expression and better survival outcomes, while gene cluster A, containing both high and low MMP expression cases, exhibited poorer survival outcomes, approximately 50% of patients with a prognosis of death. The above results again suggested that MMP expression profiles played a non-negligible role in shaping different TMEs. Next, we used MMPscore to systematically evaluate CC in terms of its clinical characteristics, including age, weight, smoking, clinical stage, and prognosis (Fig. 5b-k, Figure S4c-l). Once again, the high MMPscore was dominated by survival outcomes in the Fustat survival prognosis (Fig. 5b, d, h). In addition, high MMPscore also correlated significantly with TNM stage, especially in patients with Nx, T2, and G3 stages of better survival prognosis (Fig. 5e-g, 5i-k), which showed better assessment in tumor infiltration and metastasis. We also found that the MMPscore could indicate sensitivity to more than ten drugs, including nilotinib and Adriamycin. It can be inferred that high MMPscore can make drug response more sensitive (p < 0.05) (Fig. 5l-o, Figure S2i-p).
3.8 MMP expression is generally increased in CC tissue
By verifying the expression of the MMP gene set in CC tissues using immunohistochemistry, we found that MMP expression in normal cervical tissue showed low or no expression, demonstrating the effectiveness of the MMPscore (Fig. 6k-n). To confirm whether the expression of the MMP gene set was generalized at the molecular level in tissues of patients with CC, we conducted HE and qRT-PCR experiments on cervical tissues from three cases of CC and three healthy individuals. As listed in Table s1, the six subjects enrolled in this study were divided into the CC group (three patients with CC receiving surgery or other treatments) and the non-CC group (three subjects receiving abdominal hysterectomy for uterine leiomyoma or prolapse of uterus). The age distribution, the parity, and times of pregnancy showed no significant group differences. HE staining revealed cell polarity disorder, increased mitotic Figures, and abnormal cells breaking through the basal layer in CC tissues, which was consistent with the diagnosis of CC. HE staining of cervical tissue in the control group conformed to normal cervical pathological characteristics (Fig. 6a-b). We observed that the expression of MMP-2, MMP-3, MMP-7, MMP-9, MMP-12, MMP-13, MMP-14, and MMP-19 genes in CC tissue was generally higher than that in normal cervical tissue (Fig. 6c-j). qRT-PCR analysis displayed that the mRNA expression of MMP-2, MMP-3, MMP-7, and MMP-9 in the cervical tissue of patients with cancer was significantly greater than that in the normal group (p = 0.005, p < 0.001, p < 0.001, and p = 0.038, respectively). mRNA expression levels of MMP-12, MMP-13, MMP-14, and MMP-19 in the cervical tissue of patients with cancer were greater than that observed in the normal group (p = 0.045, p = 0.025, p = 0.003, and p = 0.025, respectively).