Objective:
We propose a novel method to compare directed networks by decomposing the network
into small modules, the so-called network subgraph approach, which is distinct from the network
motif approach because it does not depend on null model assumptions.
Method:
We developed an alignment-free algorithm called the Subgraph Identification Algorithm
(SIA), which could generate all subgraphs that have five connected nodes (5-node subgraph). There
were 9,364 such modules. Then, we applied the SIA method to examine 17 cancer networks and
measured the similarity between the two networks by gauging the similarity level using Jensen-
Shannon entropy (HJS).
Method:
We developed an alignment-free algorithm called the Subgraph Identification Algorithm
(SIA), which could generate all subgraphs that have five connected nodes (5-node subgraph). There
were 9,364 such modules. Then, we applied the SIA method to examine 17 cancer networks and
measured the similarity between the two networks by gauging the similarity level using Jensen-
Shannon entropy (HJS).
Results::
We identified and examined the biological meaning of 5-node regulatory modules and
pairs of cancer networks with the smallest HJS values. The two pairs of networks that show similar
patterns are (i) endometrial cancer and hepatocellular carcinoma and (ii) breast cancer and pathways
in cancer. Some studies have provided experimental data supporting the 5-node regulatory modules.
result:
We identify and examine the biological meaning of 5-node regulatory modules and pairs of cancer networks which have the smallest HJS values. These two pairs of networks that show similar patterns are (i) endometrial cancer and hepatocellular carcinoma, and (ii) breast cancer and pathways in cancer. Some literature studies provide experimental data to support the 5-node regulatory modules.
Conclusion:
Our method is an alignment-free approach that measures the topological similarity of
5-node regulatory modules and aligns two directed networks based on their topology. These modules
capture complex interactions among multiple genes that cannot be detected using existing
methods that only consider single-gene relations. We analyzed the biological relevance of the regulatory
modules and used the subgraph method to identify the modules that shared the same topology
across 2 cancer networks out of 17 cancer networks. We validated our findings using evidence from
the literature.