1. Introduction
Various diseases have different molecular network dynamics. Signaling pathways are activated or inactivated in diffuse- and intestinal-type gastric cancer (GC) [
1,
2,
3]. For instance, epithelial-mesenchymal transition (EMT) regulation pathway is altered in diffuse- and intestinal-type GC [
1,
2]. EMT is involved in the acquisition of anti-cancer drug resistance, recurrence, and metastasis of cancer. EMT and cancer stem cells (CSCs) share some properties in terms of anti-cancer drug resistance, whereas the precise mechanism of how CSCs arise and the condition of EMT appearance is not well understood.
The drug resistance is closely related to EMT and CSCs that have high expression of transporters such as ATP binding cassette (ABC) transporters [
4,
5,
6]. EMT, itself is related to the development process, induced by TGF-β [
7] and shares some properties in CSCs in terms of cancer malignancy as metastasis, recurrence, and drug resistance [
8].
The metastatic GC is characterized with EMT and resistance toward therapeutics [
9]. The molecular pathways related to EMT in metastatic and resistant GC have been identified, however, the causal networks in GC with poor prognosis are not well understood [
10,
11,
12]. The diffuse-type GC has a much poorer prognosis compared to intestinal-type GC, and it has been revealed that a significant difference exists in the spread patterns of intestinal- and diffuse-type GC [
13]. The identification of the regulators of molecular networks in diffuse- and intestinal-type GC is crucial for understanding drug resistance and finding therapeutic targets of diffuse-type GC [
14].
In this study, we investigated the master regulators of the causal networks in diffuse- and intestinal-type GC and found some interactions of molecular networks in diffuse- and intestinal-type GC. The study elucidated an interesting relationship between molecular networks of diffuse- and intestinal-type GC. These findings may be useful for targeting the new therapeutics in treatment-resistant cancer.
3. Discussion
Two distinct molecular subtypes, mesenchymal and epithelial phenotype in GC have been identified [
15]. The mesenchymal-like type includes diffuse-type with poor prognosis [
16]. The tumor protein 53 (TP53)-active and TP53-inactive types include patients with an intermediate prognosis, which arises an important issue that the subtypes with molecular hallmarks are risk factors of prognosis [
16].
Lenvatinib, pyrotinib, HDAC1, mir-196, and ERBB2 have been identified as master regulators of causal networks in diffuse- and intestinal-type GC in the analysis. Since diffuse-type GC has relatively stable genomic features, the development of the targeting therapies has been challenging [
17]. The combination of focal adhesion kinase inhibitor and mitogen-activated protein kinase (MAPK) kinase inhibitor was effective to inhibit the tumor growth of human diffuse-type GC xenograft [
17]. Lenvatinib, a multi-kinase inhibitor to inhibit vascular endothelial growth factor receptor (VEGFR), fibroblast growth factor receptor (FGFR), platelet-derived growth factor receptor (PDGFR0 alpha, KIT, and rearranged during transfection (RET), showed an effect in progression-free survival and response rate in patients with radioiodine-refractory thyroid cancer [
18]. Pyrotinib is an inhibitor of EGFR (ERBB1) and HER2/4 (ERBB2/4), which is approved for the treatment of breast cancer in China [
19]. Since both lenvatinib and pyrotinib-oriented causal networks in diffuse-type GC were activated, it may be targeted in the treatment of diffuse-type GC as well. The effects of the combination therapy with sorafenib and lenvatinib were limited in hepatocellular carcinoma, careful examination in terms of drug resistance and effectiveness is required [
20].
Histone modification is involved in drug resistance in lung cancer [
21]. Long non-coding RNA HRCEG which is regulated by HDAC1 inhibited cell proliferation and EMT in GC [
22]. Silencing of HDAC1 inhibited the proliferation of GC, which suggested the role of HDAC1 as a target for the treatment of GC [
23]. HDAC expression determines the sub-type of GC and is involved in tumor microenvironment characteristics and immunotherapy efficacy in GC [
24]. Class I HDAC inhibitor-induced lipid peroxidation and ferroptosis which inhibit tumor cell growth [
25]. HDAC inhibitors demonstrate the anti-cancer effect via the production of reactive oxygen species, of which dampening renders the resistance to HDAC inhibitors in cancer cells, which requires future investigation to reveal the mechanism of resistance acquisition of cancer [
26,
27].
The causal network of mir-196, a master regulator of the network, was activated in intestinal-type GC and inactivated in diffuse-type GC. Inhibitor of growth (ING)5, a class II tumor suppressor, is translationally targeted by miR-196, miR-196a, miR-196b-5p, miR-193a-3p and miR-27-3p [
28]. ING5 promotes autoacetylation of p53 and histone H3 and H4 to induce the transcription of Bax, GADD45, p21, and p27 [
28]. miRNAs are involved in linking obesity and cancer [
29]. The investigation of miRNA-miRNA and miRNA-long non-coding RNA interaction revealed the link between PPARγ cell signaling regulated by miR-130, miR-4663, miR-375, miR-494-3p, and miR-128-3p, and MAPK cell signaling regulated by miR-143, miR-375, miR-196, and miR-128-3p [
29]. miR-196 is overexpressed in the intestinal epithelium of Crohn’s disease patients, for which the relationship between cancer and Crohn’s disease is unknown [
30]. miR-196 is up-regulated in pancreatic cancer cells and activates the AKT signaling pathway, which is involved in the development of type 2 diabetes [
31]. The expression level of miR-196b was higher in pancreatic cancer cells than in cancer stroma and the high expression of miR-196b decreased the overall survival rate, which suggested the role of miR-196b as a prognosis biomarker for pancreatic cancer [
32]. The relationship between miRNAs and causal networks may need to be further elucidated for revealing the malignancy.
Regulator effect network analysis in diffuse-type GC revealed the relationship between the network of infection and let-7, mir-15, mir-17, mir-34, mir-8, mir-497, miR-136-3p (miRNAs w/seed AUCAUCG), miR-3529-3p (miRNAs w/seed ACAACAA), miR-3680-3p (miRNAs w/seed UUUGCAU), and miR-7215-5p (miRNAs w/seed CUCUUUA). let-7 plays a crucial role in the development of virus and cancer-associated virus infection [
33]. Since let-7 serves as a regulator of a number of cellular processes [
33], it may be challenging to target let-7 in general to treat diseases, some specific targeting for disease-associated cells would be valuable. let-7 regulates self-renewal and tumorigenicity of breast cancer cells [
34]. let-7 was decreased in breast tumor-initiating cells and increased with differentiation [
34]. let-7 may be involved in reducing cancer cell resistance to chemotherapy by silencing the target molecules to inhibit self-renew [
34]. let-7 has been identified as a starting point of the RNA revolution and a potential target for cancer and immune therapy [
35]. These various roles of let-7 are crucial for considering cancer therapeutics.
In conclusion, several causal networks in diffuse- and intestinal-type GC have been identified in the study. The master regulators of the causal network included lenvatinib, pyrotinib, HDAC1, mir-196, and ERBB2. Signaling pathways regulated by the master regulators may be targeted for therapeutics in treatment-resistant cancer.
Author Contributions
Conceptualization, S.T.; methodology, S.T.; formal analysis, S.T.; investigation, S.T.; writing—original draft preparation, S.T.; writing—review and editing, S.T., S.Q., H.C., H.Y., E.J.P. and H.S.; visualization, S.T.; project administration, S.T.; funding acquisition, S.T. All authors have read and agreed to the published version of the manuscript.
Figure 1.
Master regulators of 1099 causal networks in diffuse- and intestinal-type GC included ERBB2, lenvatinib, pyrotinib, mir-196, and HDAC1 (As of July 2023). (a) Biological drug and chemical drug of molecule type; (b) Growth factor and transcription regulator of molecule type; (c) microRNA of molecule type; (d) Kinase of molecule type.
Figure 1.
Master regulators of 1099 causal networks in diffuse- and intestinal-type GC included ERBB2, lenvatinib, pyrotinib, mir-196, and HDAC1 (As of July 2023). (a) Biological drug and chemical drug of molecule type; (b) Growth factor and transcription regulator of molecule type; (c) microRNA of molecule type; (d) Kinase of molecule type.
Figure 2.
The causal network regulated by HDAC1 with depth 2. (a) Regulators of the HDAC1-regulated causal network in diffuse-type GC are shown with activation prediction; (b) Regulators of the HDAC1-regulated causal network in intestinal-type GC are shown with activation prediction.
Figure 2.
The causal network regulated by HDAC1 with depth 2. (a) Regulators of the HDAC1-regulated causal network in diffuse-type GC are shown with activation prediction; (b) Regulators of the HDAC1-regulated causal network in intestinal-type GC are shown with activation prediction.
Figure 3.
The analysis of the HDAC1-interacting network identified the involvement of regulation of EMT by growth factors pathway, coronavirus pathogenesis pathway, and vorinostat. (a) The HDAC1-interacting network in diffuse-type GC; (b) The HDAC1-interacting network in intestinal-type GC.
Figure 3.
The analysis of the HDAC1-interacting network identified the involvement of regulation of EMT by growth factors pathway, coronavirus pathogenesis pathway, and vorinostat. (a) The HDAC1-interacting network in diffuse-type GC; (b) The HDAC1-interacting network in intestinal-type GC.
Figure 4.
The HDAC1-regulated causal network with depth 3 had RNA-RNA interactions with microRNAs such as mir-10, mir-15, mir-17, mir-19, mir-21, mir-223, mir-25, mir-27, mir-29, and mir-34. (a) The regulators of the HDAC1-regulated causal network with depth 3 in diffuse-type GC are shown; (b) The regulators of the HDAC1-regulated causal network with depth 3 in intestinal-type GC are shown.
Figure 4.
The HDAC1-regulated causal network with depth 3 had RNA-RNA interactions with microRNAs such as mir-10, mir-15, mir-17, mir-19, mir-21, mir-223, mir-25, mir-27, mir-29, and mir-34. (a) The regulators of the HDAC1-regulated causal network with depth 3 in diffuse-type GC are shown; (b) The regulators of the HDAC1-regulated causal network with depth 3 in intestinal-type GC are shown.
Figure 5.
Gene expression of HDAC family genes in normal stomach and gastric cancer organoid in a public database (GSE112369); (a) Gene expression of HDAC family genes (HDAC1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11); (b) The result of cluster analysis of HDAC gene expression (HDAC1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11) in normal stomach and gastric cancer organoid (NCSS2023).
Figure 5.
Gene expression of HDAC family genes in normal stomach and gastric cancer organoid in a public database (GSE112369); (a) Gene expression of HDAC family genes (HDAC1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11); (b) The result of cluster analysis of HDAC gene expression (HDAC1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11) in normal stomach and gastric cancer organoid (NCSS2023).
Figure 6.
Regulator effect network of diffuse-type GC (Infection of cells, ID25)
Figure 6.
Regulator effect network of diffuse-type GC (Infection of cells, ID25)
Figure 7.
Causal networks of lenvatinib in diffuse- and intestinal-type GC. (a) The causal network (depth 3) of lenvatinib in diffuse-type GC; (b) The causal network (depth 3) of lenvatinib in intestinal-type GC.
Figure 7.
Causal networks of lenvatinib in diffuse- and intestinal-type GC. (a) The causal network (depth 3) of lenvatinib in diffuse-type GC; (b) The causal network (depth 3) of lenvatinib in intestinal-type GC.
Table 1.
Causal networks of HDAC molecules as master regulators in diffuse- and intestinal-type gastric cancer (GC).
Table 1.
Causal networks of HDAC molecules as master regulators in diffuse- and intestinal-type gastric cancer (GC).
Master Regulator |
Analysis |
Depth |
Predicted Activation |
Activation z-score |
p-value of overlap |
Network bias- corrected p-value |
Causal network |
Target-connected regulators |
HDAC1 |
TCGA GS |
3 |
|
0.405 |
2.87E-26 |
2.00E-04 |
878 (117) |
115 |
TCGA CIN |
3 |
|
1.08 |
2.87E-26 |
2.00E-04 |
878 (117) |
115 |
HDAC5 |
TCGA GS |
3 |
Inhibited |
-4.321 |
2.01E-25 |
1.00E-04 |
733 (80) |
78 |
TCGA CIN |
3 |
|
0.85 |
2.01E-25 |
1.00E-04 |
733 (80) |
78 |
Hdac1/2 |
TCGA GS |
3 |
Inhibited |
-4.33 |
2.53E-25 |
1.00E-03 |
820 (95) |
95 |
TCGA CIN |
3 |
|
1.606 |
2.53E-25 |
1.00E-03 |
820 (95) |
95 |
HDAC1 |
TCGA GS |
2 |
Inhibited |
-2.011 |
7.62E-19 |
1.00E-04 |
457 (15) |
15 |
TCGA CIN |
2 |
Activated |
2.199 |
7.62E-19 |
1.00E-04 |
457 (15) |
15 |
HDAC10 |
TCGA GS |
3 |
|
-0.089 |
1.43E-15 |
1.70E-02 |
508 (37) |
37 |
TCGA CIN |
3 |
|
-1.509 |
1.43E-15 |
1.70E-02 |
508 (37) |
37 |
HDAC2 |
TCGA GS |
1 |
|
1.528 |
3.55E-03 |
2.24E-02 |
21 (1) |
1 |
TCGA CIN |
1 |
|
-0.655 |
3.55E-03 |
2.24E-02 |
21 (1) |
1 |
Table 2.
microRNAs which have a direct relationship between regulator effect network of diffuse-type gastric cancer.
Table 2.
microRNAs which have a direct relationship between regulator effect network of diffuse-type gastric cancer.
let-7 |
miR-136-3p (miRNAs w/seed AUCAUCG) |
mir-15 |
miR-3529-3p (miRNAs w/seed ACAACAA) |
mir-17 |
miR-3680-3p (miRNAs w/seed UUUGCAU) |
mir-34 |
miR-7215-5p (miRNAs w/seed CUCUUUA) |
mir-8 |
mir-497 |