Table 5.

The top 20 keywords

Rank	Frequency	Keywords	Centrality
1	977	expression	0.12
2	761	cAMP	0.09
3	650	activation	0.07
4	514	cancer	0.07
5	482	gene expression	0.14
6	420	phosphorylation	0.03
7	400	apoptosis	0.13
8	368	cell	0.04
9	354	protein kinase a	0.12
10	334	proliferation	0.08
11	328	growth	0.03
12	320	pathway	0.04
13	299	in vitro	0.06
14	294	protein	0.04
15	290	breast cancer	0.05
16	274	receptor	0.02
17	252	inhibition	0.02
18	242	gene	0.07
19	233	cancer cell	0.06
20	222	CREB	0.08