Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:TNFalso upregulated several growth factors and proteins associated with cell cycle progression, but downregulated proteins associated with cell cycle inhibition, including CEBP- (Table 1) (18), cyclin-dependent kinase inhibitor 1C, cyclin-dependent kinase inhibitor 2C (p18), growtharrest specific 1 (19,20), and growth-arrest and DNAdamage–inducible- gene (21).
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