Low CYP expression in patients with HCC
The transcription and protein levels of the 12 CYPs members were evaluated using the ONCOMINE, UALCAN, and Human Protein Atlas databases. As shown in Figure 1, the mRNA expression levels of the 12 CYPs were significantly downregulated in HCC compared with those in normal liver according to the ONCOMINE database. The detailed results of p value and fold change are shown in Table 1. The p value ranged from −1.512 to −63.196, whereas fold change ranged from 0.001 to 1.5E-131. For example, the mRNA expression level of CYP1A2 in HCC remarkably decreased in the three datasets compared with that in normal liver. In the Roessler liver dataset, the expression of CYP1A2 in HCC was low compared with that in normal liver, with a fold change of −63.196 (p = 4.58E-21). In Roessler liver 2, the mRNA expression level of CYP1A2 in HCC decreased by 18.872-fold (p = 1.5E-131). In Wurmbach liver, the mRNA expression level of CYP1A2 in HCC samples decreased by 23.814-fold (p = 1.69E-09). The mRNA expression levels of the other CYPs in HCC tissues were substantially lower in at least two datasets (Table 1). The transcriptional levels of the 12 CYP members were further determined in the UALCAN database, which is quite different from the ONCOMINE database. With the exception of CYP2A7 and CYP3A5, the mRNA expression levels of the CYP members considerably decreased in HCC samples compared in normal liver samples (p < 0.001). The protein expression levels of the 12 CYP members in HCC were explored using the Human Protein Atlas database. Most immunohistochemical staining of CYP members can be found in the database, except for that of CYP2J2, CYP3A5, and CYP4A11. The protein expression levels of CYP1A2, CYP2A6, CYP2A7, CYP2B6, CYP2C8, CYP2C9, and CYP2E1 were high in normal liver tissues, whereas these proteins were not detected in HCC tissues. Additionally, the protein expression level of CYP27A1 was medium and that of CYP3A4 was high in normal liver tissues, but no proteins were detected or their expression levels were low in HCC tissues. Based on the results of analyses using these three databases, the transcription and protein expression levels of the 12 CYP members were low in patients with HCC patients.
Table 1. The significant changes of CYPs expression in transcription level between hepatocellular carcinoma and normal liver tissues (ONCOMINE database)
|
Types of HCC VS. Liver
|
Fold Change
|
P value
|
t-test
|
Reference
|
CYP1A2
|
Hepatocellular Carcinoma
|
-63.196
|
4.58E-21
|
-22.801
|
Roessler Liver[27]
|
Hepatocellular Carcinoma
|
-18.872
|
1.50E-131
|
-35.521
|
Roessler Liver 2[27]
|
Hepatocellular Carcinoma
|
-23.814
|
1.69E-09
|
-8.942
|
Wurmbach Liver[28]
|
CYP27A1
|
Hepatocellular Carcinoma
|
-1.936
|
2.21E-26
|
-11.77
|
Roessler Liver 2[27]
|
Hepatocellular Carcinoma
|
-2.345
|
7.42E-05
|
-4.467
|
Roessler Liver[27]
|
CYP2A6
|
Hepatocellular Carcinoma
|
-11.335
|
7.21E-72
|
-23.859
|
Roessler Liver 2[27]
|
Hepatocellular Carcinoma
|
-6.534
|
6.56E-15
|
-8.617
|
Chen Liver[29]
|
Hepatocellular Carcinoma
|
-7.586
|
1.75E-08
|
-7.611
|
Roessler Liver[27]
|
Hepatocellular Carcinoma
|
-9.301
|
9.69E-04
|
-3.563
|
Wurmbach Liver[28]
|
CYP2A7
|
Hepatocellular Carcinoma
|
-6.674
|
5.03E-79
|
-25.133
|
Roessler Liver 2[27]
|
Hepatocellular Carcinoma
|
-5.337
|
6.86E-10
|
-8.241
|
Roessler Liver[27]
|
Hepatocellular Carcinoma
|
-9.49
|
6.55E-04
|
-3.733
|
Wurmbach Liver[28]
|
CYP2B6
|
Hepatocellular Carcinoma
|
-13.569
|
7.56E-18
|
-14.541
|
Roessler Liver[27]
|
Hepatocellular Carcinoma
|
-10.802
|
3.59E-100
|
-29.077
|
Roessler Liver 2[27]
|
Hepatocellular Carcinoma
|
-2.955
|
9.51E-27
|
-12.67
|
Chen Liver[29]
|
Hepatocellular Carcinoma
|
-7.529
|
1.15E-04
|
-4.63
|
Wurmbach Liver[28]
|
CYP2C8
|
Hepatocellular Carcinoma
|
-5.766
|
2.32E-20
|
-10.515
|
Chen Liver[29]
|
Hepatocellular Carcinoma
|
-3.561
|
2.69E-05
|
-5.393
|
Wurmbach Liver[28]
|
CYP2C9
|
Hepatocellular Carcinoma
|
-4.874
|
2.89E-95
|
-27.301
|
Roessler Liver 2[27]
|
Hepatocellular Carcinoma
|
-5.164
|
2.15E-13
|
-10.51
|
Roessler Liver[27]
|
Hepatocellular Carcinoma
|
-5.606
|
1.33E-19
|
-10.216
|
Chen Liver[29]
|
Hepatocellular Carcinoma
|
-4.438
|
3.38E-08
|
-6.534
|
Wurmbach Liver[28]
|
CYP2E1
|
Hepatocellular Carcinoma
|
-1.512
|
2.06E-06
|
-5.172
|
Mas Liver[30]
|
Hepatocellular Carcinoma
|
-8.697
|
3.46E-38
|
-15.287
|
Roessler Liver 2[27]
|
Hepatocellular Carcinoma
|
-3.825
|
2.48E-05
|
-4.613
|
Wurmbach Liver[28]
|
CYP2J2
|
Hepatocellular Carcinoma
|
-3.11
|
1.16E-49
|
-17.655
|
Roessler Liver 2[27]
|
Hepatocellular Carcinoma
|
-2.112
|
1.50E-11
|
-7.105
|
Chen Liver[29]
|
Hepatocellular Carcinoma
|
-1.982
|
2.05E-05
|
-4.897
|
Wurmbach Liver[28]
|
Hepatocellular Carcinoma
|
-3.209
|
3.54E-06
|
-5.653
|
Roessler Liver[27]
|
CYP3A4
|
Hepatocellular Carcinoma
|
-4.23
|
1.27E-12
|
-11.406
|
Roessler Liver[27]
|
Hepatocellular Carcinoma
|
-7.094
|
3.85E-71
|
-23.668
|
Roessler Liver 2[27]
|
Hepatocellular Carcinoma
|
-2.53
|
3.17E-10
|
-6.543
|
Chen Liver[29]
|
CYP3A5
|
Hepatocellular Carcinoma
|
-2.771
|
4.63E-40
|
-14.932
|
Roessler Liver 2[27]
|
Hepatocellular Carcinoma
|
-2.516
|
8.02E-07
|
-5.918
|
Roessler Liver[27]
|
Hepatocellular Carcinoma
|
-1.809
|
5.67E-08
|
-5.531
|
Chen Liver[29]
|
CYP4A11
|
Hepatocellular Carcinoma
|
-5.733
|
2.29E-80
|
-24.804
|
Roessler Liver 2[27]
|
Hepatocellular Carcinoma
|
-3.806
|
1.82E-09
|
-7.533
|
Roessler Liver[27]
|
Hepatocellular Carcinoma
|
-2.655
|
1.91E-08
|
-5.769
|
Chen Liver[29]
|
Hepatocellular Carcinoma
|
-3.398
|
0.001
|
-3.537
|
Wurmbach Liver[28]
|
CYP: cytochrome P450, HCC: hepatocellular carcinoma
Relationship between mRNA expressionlevels of the 12 CYP members and clinicopathological parameters of patients with HCC
Using the UALCAN database (http://ualcan.path.uab.edu), we compared the mRNA expression levels of the 12 CYP members in normal liver tissues and HCC tissues at specific cancer stages and tumor grades. Except for that of CYP3A5, the mRNA expression levels of the CYP members were negatively correlated with individual cancer stages (Figure 4). Patients with HCC at advanced stages were presented lower mRNA expression levels of the CYPs than those with HCC at early stages. The mRNA expression levels of CYP 1A2, 2A7, 2C9, 2E1, and 3A4 were the lowest at stage 4. By comparison, the mRNA expression levels of CYP27A1, 2A6, 2B6, 2C8, 2J2, and 4A11 were the lowest at stage 3. Given that only six patients had stage 4 HCC, the mRNA expression levels of CYP 27A1, 2A6, 2B6, 2C8, 2J2, and 4A11 between stages 4 and 3 did not considerably differ. In addition, only the mRNA expression level of CYP3A5 significantly varied between stages 1 and 3. Similarly, the mRNA expression levels of the 12 CYP members (except for that of CYP2A7 and CYP3A5) negatively correlated with tumor grades (Figure 5), indicating that the mRNA expression levels of the CYP members decreased as tumor grades increased. The mRNA expression levels of CYP2A7 and CYP3A5 did not substantially differ between normal and different grades. These findings indicated that the mRNA expression levels of the 12 CYP members strongly associated with the clinicopathological parameters of patients with HCC.
Association of mRNA expression levels of the 12 CYP members and prognosis of patients with HCC
The Kaplan–Meier plotter database (http://kmplot.com/analysis/) was utilized to determine the relationship between the mRNA expression levels of the 12 CYP members and the survival of patients with HCC. The high mRNA expression levels of CYP27A1 (HR = 0.42, P = 4.1E-07), CYP2A6 (HR = 0.54, P = 7E-04), CYP2A7 (HR = 0.57, P = 0.0016), CYP2C8 (HR = 0.54, P = 0.00048), CYP2C9 (HR = 0.42, P = 3.2E-07), CYP2E1 (HR = 0.57, P = 0.0037), CYP3A4 (HR = 0.57 , P = 0.0017), CYP3A5 (HR = 0.43, P = 1.4E-05), and CYP4A11 (HR = 0.59, P = 0.0025) were significantly correlated with long overall survival of patients with HCC. However, the differences in the mRNA expression levels of CYP1A2 (HR = 0.71, P = 0.074), CYP2B6 (HR = 0.71, P = 0.061), and CYP2J2 (HR = 0.75, P = 0.11) and survival of patients with HCC were not significant. Thus, the mRNA expression levels of CYP27A1, CYP2A6, CYP2A7, CYP2C8, CYP2C9, CYP2E1, CYP3A4, CYP3A5, and CYP4A11 were significantly correlated with the OS of patients with HCC. These CYPs may be developed as valuable biomarkers to predict the prognosis of patients with HCC.
Among the 364 patients with HCC found in the Kaplan–Meier plotter database, 29 received sorafenib for HCC treatment. The relationship between the mRNA expression levels of the 12 CYPs and OS of the 29 patients with HCC was explored. As shown in Figure 7, only the high mRNA expression levels of CYP27A1, CYP2A7, CYP2B6, CYP2C9, and CYP3A5 were significantly correlated with favorable OS in the 29 patients with HCC (p < 0.05). Notably, the mRNA expression level of CYP2B6 (HR = 0.14, P = 0.00076) was markedly related to long OS of the 29 patients. This result was inconsistent with that of CYP2B6 (HR = 0.71, P = 0.061) in 364 patients with HCC. These results suggested that the mRNA expression level of CYP2B6 may be developed into a unique biomarker to predict the prognosis of patients with HCC who received sorafenib therapy.
Genetic alterations in the 12 CYP members and their relationship with OS and DFS of patients with HCC
The cBioPortal (https://www.cbioportal.org/) database was used to explore genetic mutations and their relevance to OS and DFS of patients with HCC. The genes of the 12 CYP members were altered in 144 out of 366 queried patients at a rate of 39% (Figure 8a). The rate of genetic alteration of individual CYP members varied from 5% to 9%. Moreover, no significant correlation was observed between genetic alteration in the 12 CYP members and OS (Figure 8b, Logrank p = 0.0955) or DFS (Figure 8c, Logrank p = 0.652). Thus, the genetic alterations in the 12 CYP members did not seem to remarkably influence the prognosis of patients with HCC.
PPI network construction of the 12 CYP members and analysis of their GO and KEGG pathways in patients with HCC
The PPI network of the 12 CYP members and 50 target genes that they closely interact with was analyzed using the STRING database (https://string-db.org/). The CYP1A1 (degree = 24), AOX1 (degree = 18), CYP2C19 (degree = 15), CYP2D6 (degree = 13), and EPHX1 (degree = 12) of these 50 genes were significantly related to the 12 CYP members in the PPI network (Figure 9a). Subsequently, the GO and KEGG pathways of the 12 CYP members and 50 target genes that they closely interact with were analyzed using the DAVID database (http://david.abcc.ncifcrf.gov). The top 10 terms of GO and KEGG analysis are displayed in Figure 9. As shown in Figures 9b–9d, the biological processes strongly concerned with alterations in the 12 CYPs were xenobiotic metabolic process (GO: 0006805), drug metabolic process (GO: 0017144), oxidation–reduction process (GO: 0055114), epoxygenase P450 pathway (GO: 0019373), and steroid metabolic process (GO: 0008202). The cellular components substantially regulated by alterations in the 12 CYPs were organelle membrane (GO: 0031090), endoplasmic reticulum membrane (GO: 0005789), intracellular membrane-bounded organelle (GO: 0043231), endoplasmic reticulum (GO: 0005783), and integral component of membrane (GO: 0016021). The molecular functions notably influenced by the 12 CYP members were heme binding (GO: 0020037), monooxygenase activity (GO: 0004497), iron ion binding (GO: 0005506), steroid hydroxylase activity (GO: 0008395), and oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen (GO: 0016705). KEGG analysis was conducted to explore the altered pathways related to the 12 CYP members and their neighboring genes. As depicted in Figure 9e, the pathways chemical carcinogenesis (hsa05204), drug metabolism - cytochrome P450 (hsa00982), metabolism of xenobiotics by cytochrome P450 (hsa00980), retinol metabolism (hsa00830), and metabolic pathways (hsa01100) were involved in the functions of the 12 CYP and the target genes they closely interact with in HCC.
Network pharmacology analysis of sorafenib administration for HCC treatment
The flowchart of network pharmacology analysis of sorafenib administration for HCC treatment is shown in Figure 10. Four human protein targets and 10 human protein targets of sorafenib were obtained from the Therapeutic Target Database (http://db.idrblab.net/ttd/) and the Drugbank database (https://www.drugbank.ca/), respectively. Sorafenib acted as a substrate or inhibitor for 11 metabolic enzymes and six drug transporters that were regarded as targets of sorafenib. Afterward, 100 human targets (probability ≥ 0.9) and 20 targets (confident ≥ 0.9) were predicted from the Swiss Target Prediction database (http://www.swisstargetprediction.ch/) and the Stitch database (http://stitch.embl.de/), respectively. After removing the overlaps, a total of 123 protein targets (28 identifiable targets and 95 predictive targets) were obtained for further analysis (Additional file 1). A previous study [31] screened 566 HCC-related genes from both the OncoDB.HCC and Liverome databases (Additional file 2). Subsequently, human targets of sorafenib were mapped with HCC-related targets, and 25 targets (12 validated targets and 13 predicted targets) were harvested as candidate targets of sorafenib for HCC treatment (Additional file 3).
The PPI network of the 25 candidate targets of sorafenib was analyzed using the String database. Results showed that CCNA2 (degree = 24), SRC (degree = 23), MAPK1 (degree = 22), MAPK3 (degree = 21), AURKA (degree = 18), and EGFR (degree = 16) were the key potential targets in the network (Figure 11a). In addition, a group of candidate target CYPs, namely, CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP3A4, and CYP3A5, was included. The GO and KEGG pathways of the 25 candidate targets and their 50 closely related genes were analyzed using the David database (Figures 11b–11e and Additional file 4). GO covered three parts, namely, biological process, cellular component, and molecular function terms. The biological processes significantly regulated by the 25 candidate targets of sorafenib for HCC treatment were MAPK cascade (GO: 0000165), epidermal growth factor receptor signaling pathway (GO: 0007173), negative regulation of apoptotic process (GO: 0043066), cell division (GO: 0051301), and positive regulation of fibroblast proliferation (GO: 0048146) (Figure 11b). The 25 candidate targets and their 50 frequently associated genes were primarily located in the cellular components cytosol (GO: 0005829), nucleus (GO: 0005634), nucleoplasm (GO: 0005654), membrane raft (GO: 0045121), and cyclin-dependent protein kinase holoenzyme complex (GO: 0000307). The candidate targets exerted their molecular functions through Ras guanyl-nucleotide exchange factor activity (GO: 0005088), ATP binding (GO: 0005524), protein binding (GO: 0005515), protein kinase activity (GO: 0004672), and kinase activity (GO: 0016301). Most notably, the primary pathways affected by the candidate targets were hepatitis B (hsa05161), cell cycle (hsa04110), pathways in cancer (hsa05200), FoxO signaling pathway (hsa04068), and ErbB signaling pathway (hsa04012).