MMP1 expression in HCC and other carcinomas
MMP1 expression inhibition would ultimately contribute to prevention of HCC progression, according to a previous study[41]. In order to confirm the carcinogenesis of MMP1 in HCC, we utilized the Oncomine database to evaluate the levels of MMP1 expression in both tumor and normal tissues of various cancers. Except kidney cancer as well as brain and central nervous system cancer which have a reduced expression of MMP1, together with leukemia, liver cancer and myeloma with censored data, the expression levels of MMP1 gene were upregulated significantly in other types of tumor tissues compared to their respective adjacent normal tissues; including bladder, breast, cervical, colorectal, esophageal, gastric, head and neck, lung, lymphoma, melanoma, ovarian, pancreatic, prostate, and sarcoma cancer tissues (Fig. 1A). Although no discernible relationship between MMP1 expression and HCC was observed using Oncomine, further assessment of MMP1 RNA-seq expression in HCC using TIMER 2.0 based on the TCGA database, indicated that a high expression of MMP1 in 22 types of cancers was detected, including HCC, p-value < 0.001 (Fig. 1B). These results strongly suggested that the overexpression of MMP1 might play a positive role in the progression of different neoplasms, especially in HCC.
Evaluation of MMP1 expression and HCC prognosis
The Kaplan-Meier plotter and GEPIA database were used to evaluate the prognostic potential of MMP1 transcriptional levels in HCC tissues. Interestingly, we found that higher expression of MMP1 was associated with poorer prognosis in patients with HCC (Fig. 2A, disease-specific survival (DSS): HR = 2.41, 95% CI = 1.55–3.76, p = 6.1e-05, n = 357; Fig. 2B, overall survival (OS): HR = 2.1, 95% CI = 1.49–2.98, p = 1.7e-05, n = 364; Fig. 2C, progression free survival (PFS): HR = 1.96, 95% CI = 1.46–2.63, p = 5.9e-06, n = 366; Fig. 2D, relapse free survival (RFS): HR = 1.79, 95% CI = 1.27–2.5, p = 0.00065, n = 313). Additionally, we got consistent results with statistical significance in the GEPIA database (Fig. 2E, disease free survival (DFS): HR = 1.4, p = 0.018; Fig. 2F, OS: HR = 2, p = 0.00023).
Next, we investigated the relationship between the levels of MMP1 expression and the related prognostic in other cancers through the Kaplan-Meier plotter analysis. Similarly, the survival curves showed that high expression of MMP1 in tumor tissues was relevant to poor prognosis in different cancers. For example, poor OS, RFS, post progression survival (PPS) and distant metastasis-free survival (DMFS) in breast cancer were observed to be highly correlated with strong expression of MMP1 (Fig. 3A, OS: HR = 1.54, 95% CI = 1.27–1.86, p = 7.6e-06; PPS: HR = 1.37, 95% CI = 1.08–1.73, p = 0.0084; RFS: HR = 1.7, 95% CI = 1.54–1.88, p < 1e-16; DMFS: HR = 1.67, 95% CI = 1.43–1.95, p = 1.1e-10). On the other hand, only poor OS in gastric cancer (Fig. 3B, HR = 0.75, 95% CI = 0.63–0.9, p = 0.0021), ovarian cancer (Fig. 3C, HR = 1.15, 95% CI = 1.01–1.31, p = 0.04) and lung cancer (Fig. 3D, HR = 1.16, 95% CI = 1-1.35, p = 0.047) respectively, was related to high expression of MMP1.
As a supplement, we assessed the relationship between MMP1 transcriptional level and the other tumor tissues via GEPIA database. The high expression of MMP1 was associated with poor OS in head and neck squamous cell carcinoma (HNSC), cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC), pancreatic adenocarcinoma (PAAD) (Fig. 4B, E, F), poor DFS in glioblastoma multiforme (GBM) (Fig. 4A), and both in kidney chromophobe (KICH) and kidney renal papillary cell carcinoma (KIRP) (Fig. 4C, D).
Correlation analysis between MMP1 expression and clinical characteristics of patients with HCC
Furthermore, we evaluated the correlation between MMP1 expression levels and clinicopathological factors in HCC using STATA based on the data of Kaplan-Meier plotter database (Table.1). The characteristics were classified into several subgroups based on stage, grade, ACJJ-T, gender, vascular invasion, race, alcohol consumption, and hepatitis virus. Almost all were independent risk factors for the prognosis of HCC patients with high expression of MMP1 (Fig. 5A-D). In particular, the higher expression of MMP1 was closely associated with worse OS, PFS, RFS and DSS rates in relation to the following factors: grades II (OS: HR = 1.98, 95% CI = 1.18–3.33, p = 0.0082; PFS: HR = 2.57, 95% CI = 1.66–3.98, p = 1.2e-05; RFS: HR = 2.39, 95% CI = 1.4–4.06, p = 9.3e-04; DSS: HR = 3.14, 95% CI = 1.54–6.39, p = 8.9e-04), male (OS: HR = 2.9, 95% CI = 1.86–4.52, p = 8.3e-07; PFS: HR = 1.86, 95% CI = 1.29–2.67, p = 6.8e-04; RFS: HR = 1.75, 95% CI = 1.17–2.61, p = 0.0057; DSS: HR = 3.4, 95% CI = 1.92–6.02, p = 7.9e-06), Asian (OS: HR = 3.88, 95% CI = 2.14–7.06, p = 1.7e-06; PFS: HR = 2.28, 95% CI = 1.41–3.68, p = 5.4e-04; RFS: HR = 2.11, 95% CI = 1.26–3.52, p = 0.0038; DSS: HR = 4.27, 95% CI = 1.93–9.46, p = 1e-04), non-vascular invasion (OS: HR = 2.09, 95% CI = 1.24–3.55, p = 0.005; PFS: HR = 1.77, 95% CI = 1.13–2.77, p = 0.011; RFS: HR = 1.84, 95% CI = 1.08–3.15, p = 0.023; DSS: HR = 2.16, 95% CI = 1.04–4.5, p = 0.035), non-alcoholics (OS: HR = 2.59, 95% CI = 1.47–4.58, p = 6.7e-04; PFS: HR = 1.93, 95% CI = 1.28–2.9, p = 0.0013; RFS: HR = 1.91, 95% CI = 1.14–3.21, p = 0.013; DSS: HR = 4.1, 95% CI = 1.72–9.78, p = 5.8e-04), patients with hepatitis virus infection (OS: HR = 3.33, 95% CI = 1.73–6.39, p = 1.3e-04; PFS: HR = 2.02, 95% CI = 1.27–3.22, p = 0.0026; RFS: HR = 1.75, 95% CI = 1.06–2.87, p = 0.026; DSS: HR = 3.54, 95% CI = 1.55–8.08, p = 0.0014) and those without it (OS: HR = 1.76, 95% CI = 1.1–2.8, p = 0.017; PFS: HR = 2.19, 95% CI = 1.41–3.39, p = 3.3e-04; RFS: HR = 1.99, 95% CI = 1.2–3.31, p = 0.0066; DSS: HR = 2.41, 95% CI = 1.31–4.44, p = 0.0037). These findings indicated that high expression of MMP1 might be one of the contributing factors to poor prognosis in HCC patients with different clinical characteristics.
MMP1 expression levels and TIICs in HCC
Tumor infiltrating immunocytes have been shown to influence the progression of patients with different cancers. Thus, it’s necessary for us to investigate any relationship between MMP1 expression and TIICs in HCC via TIMER database. Consistent with previous survival results, a high expression level of MMP1 was positively related with a number of TIICs and notable outcomes (Fig. 6). It was associated with high infiltration levels of B cells (Rho = 0.268, p = 4.31e-07), dendritic cells (Rho = 0.432, p = 4.01e-17), macrophages (Rho = 0.263, p = 7.39e-07), neutrophils (Rho = 0.268, p = 4.52e-07), CD4 + T cells (Rho = 0.116, p = 3.07e-02), and CD8 + T cells (Rho = 0.108, p = 4.57e-02) (Fig. 6). On the contrary, MMP1 expression was not correlated with tumor purity (Rho = 0.056, p = 3.00e-01), indicating that perhaps it originates from the cells in the tumor-immunity microenvironment.
Gene analysis for MMP1 and Immune cell subset biomarkers
Besides verifying the positive correlation between MMP1 expression and several TIICs, we proceeded to test the correlation of MMP1 expression with levels of specific biomarker genes in the select TIICs or their subsets in HCC tissues vias TIMER database and explore MMP1-involved carcinogenic mechanisms and filtrate promising therapeutic targets in the future. In detail, the correlation analysis was conducted with with/without adjustment by purity, indicating significantly positive correlation of co-expression of MMP1 and biomarker genes of TIICs or subsets of them (Fig. 7). What we found was that almost all the biomarker genes we investigated were positively related to MMP1 expression, including CD19 (B cell biomarker, R = 0.147, p = 6.35e-03), CD79A (B cell biomarker, R = 0.155, p = 3.8e-03) (Fig. 7A), CD8A (CD8 + T cell biomarker, R = 0.209, p = 9.55e-05), CD8B (CD8 + T cell biomarker, R = 0.239, p = 7.09e-06) (Fig. 7B), CD86 (Monocyte biomarker, R = 0.377, p = 4.03e-13), CSF1R (Monocyte biomarker, R = 0.29, p = 4.06e-08) (Fig. 7C), IRF5 (M1 Macrophage biomarker, R = 0.168, p = 1.69e-03), PTGS2 (M1 Macrophage biomarker, R = 0.201, p = 1.65e-04) (Fig. 7D), CD163 (M2 Macrophage biomarker, R = 0.158, p = 3.18e-03), VSIG4 (M2 Macrophage biomarker, R = 0.173, p = 1.25e-03), MS4A4A (M2 Macrophage biomarker, R = 0.196, p = 2.51e-04) (Fig. 7E), ITGAM (Neutrophils biomarker, R = 0.364, p = 2.84e-12) (Fig. 7F), CCL2 (tumor-associated macrophage (TAM) biomarker, R = 0.189, p = 4.15e-04), CD68 (TAM biomarker, R = 0.325, p = 6.6e-10), IL10 (TAM biomarker, R = 0.326, p = 5.7e-10) (Fig. 7H), HLA-DPB1 (Dendritic cell biomarker, R = 0.227, p = 2.11e-05), HLA-DQB1 (Dendritic cell biomarker, R = 0.237, p = 8.36e-06), HLA-DRA (Dendritic cell biomarker, R = 0.251, p = 2.37e-06), HLA-DPA1 (Dendritic cell biomarker, R = 0.219, p = 4.02e-05), CD1c (Dendritic cell biomarker, R = 0.12, p = 2.57e-02), NRP1 (Dendritic cell biomarker, R = 0.218, p = 4.29e-05), and ITGAX (Dendritic cell biomarker, R = 0.419, p = 4.38e-16) (Fig. 7I), as well as the biomarker genes of subsets of T cells, such as FOXP3 (Tregs biomarker, R = 0.172, p = 1.33e-03), CCR8 (Tregs biomarker, R = 0.311, p = 3.53e-09), TGFB1 (Tregs biomarker, R = 0.277, p = 1.67e-07), IL2RA (Tregs biomarker, R = 0.356, p = 1.02e-11), CD4 (Tregs biomarker, R = 0.247, p = 3.34e-06) (Fig. 7G), PDCD-1 (T cell exhaustion biomarker, R = 0.268, p = 4.55e-07), CTLA4 (T cell exhaustion biomarker, R = 0.386, p = 1.02e-13), LAG3 (T cell exhaustion biomarker, R = 0.2, p = 1.86e-04), HAVCR2 (T cell exhaustion biomarker, R = 0.436, p = 1.8e-17), BTLA (T cell exhaustion biomarker, R = 0.121, p = 2.49e-02), TIGIT (T cell exhaustion biomarker, R = 0.348, p = 3.14e-11), and GZMB (T cell exhaustion biomarker, R = 0.206, p = 1.12e-04) (Fig. 7J).
Expression levels of MMP1 related to TMB and MSI in HCC
Studies have increasingly reported that TMB[42] and MSI[43] could be used as predictive biomarkers for cancer immunotherapy, which might be the one of most popular methods to predict the therapeutic efficiency of immunotherapy on carcinomas. Therefore, we investigated the correlation between MMP1 expression and TMB/MSI in 32 types cancers via SangerBox. Contrary to what would be expected, there was no significant correlation between MMP1 expression and TMB/MSI in HCC patients. It was only positively related to TMB in lung adenocarcinoma (LUAD) (p = 0.0024), prostate adenocarcinoma (PRAD) (p = 0.046), sarcoma (SARC) (p = 0.013), breast invasive carcinoma (BRCA) (p = 7.3e-05), colon adenocarcinoma (COAD) (p = 0.0017) (Fig. 8A) and MSI in testicular germ cell tumors (TGCT) (p = 0.00095), kidney renal clear cell carcinoma (KIRC) (p = 6e-04), and COAD (p = 3.2d-07) (Fig. 8B). In addition, negative correlation was only observed between MMP1 expression and TMB in head and neck squamous cell carcinoma (HNSC) (p=-0.0079) (Fig. 8A) and MSI in pancreatic adenocarcinoma (PAAD) (p=-0.023). This might indicate that HCC patients with neither high nor low expression of MMP1 could equally benefit from TMB/MSI targeted immunotherapy.